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Chem. Soc. Rev.最新综述：有序介孔碳材料的直接合成

Cite this:DOI:10.1039/c2cs35301f Direct synthesis of ordered mesoporous carbons w

Tian-Yi Ma,Lei Liu and Zhong-Yong Yuan*

Received 31st July 2012DOI:10.1039/c2cs35301f

Ordered mesoporous carbon materials have recently aroused great research interest because of their

widespread applications in many areas such as adsorbents,catalysts and supports,gas storage hosts,and electrode materials.The direct synthesis strategy from organic–organic self-assembly involving the

combination of polymerizable precursors and block copolymer templates is expected to be more ?exible in preparing mesoporous carbons,compared with the traditional nanocasting strategy of complicated and high-cost procedures using mesoporous silica materials as the hard template.In this review,we present the fundamentals and recent advances related to the ?eld of ordered mesoporous carbon materials from the direct synthesis strategy of block copolymer soft-templating,with a focus on their controllable

preparation,modi?cation and potential applications.Under the guidance of their formation mechanism,the preparation of ordered mesoporous carbons are discussed in detail by consulting di?erent

experimental conditions,including synthetic pathways,precursors,catalysts and templates.Both the mesopore size and morphology control are introduced.The potential applications of pure mesoporous carbons,nonmetallic-and metallic-modi?ed mesoporous carbons,and some interpenetrating carbon-based composites are demonstrated.Furthermore,remarks on the challenges and perspectives of research directions are proposed for further development of the ordered mesoporous carbons (232references).

1.Introduction

Porous materials are of great importance for fundamental research and practical applications ranging from catalysis,

adsorption,separation,sensing to biotechnology.1–3Notice-ably,ever since the exciting discovery of the novel family of M41S was reported by the researchers at Mobil Research and Development Corporation in 1992,4,5mesoporous materials have attracted more and more attention and shown great potentials in many ?elds,due to outstanding properties,including high surface areas,periodically arranged monodis-persed mesopore space,tunable pore sizes,alternative pore shapes,uniform nanosized frameworks,large particle sizes,and abundant compositions.6,7Besides typical silica-based

Institute of New Catalytic Materials Science,Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education),College of Chemistry,Nankai University,Tianjin 300071,China.E-mail:zyyuan@https://www.wendangku.net/doc/546538459.html,;Fax:+86-22-23502604;Tel:+86-22-23509610

w Part of the mesoporous materials themed

issue.

Tian-Yi Ma

Tian-Yi Ma received his BSc degree in Chemistry at Nankai University in 2008.He is cur-rently a PhD candidate in Phy-sical Chemistry under the supervision of Prof.Zhong-Yong Yuan.He won the Top-Ten Youth of Nankai Univer-sity and the YANG Shixian Scholarship in 2010,and the Academic Award for Doctoral Students by the Ministry of Education in 2011.His current research is focused on the rational synthesis and applica-tion exploration of mesoporous

materials with complex compositions from carbon,organic poly-mer to metal–organic

frameworks.

Lei Liu

Lei Liu received her BSc degree in Chemistry in 2006at Liao-cheng University,and obtained her MSc and PhD degrees in Physical Chemistry at Nankai University in 2009and 2012,respectively,under the supervi-sion of Prof.Zhong-Yong Yuan.Her work was focused on nano-porous carbon-based materials for applications in heterogeneous catalysis,gas storage and elec-trode materials.She is currently working in the Shandong University of Science and Tech-nology as a Lecturer.

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D o w n l o a d e d b y U n i v e r s i t y o f S c i e n c e a n d T e c h n o l o g y o f C h i n a o n 08 N o v e m b e r 2012P u b l i s h e d o n 07 N o v e m b e r 2012 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 2C S 35301F

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mesoporous materials,such as the M41S family,4,5SBA series 8,9and their related mesostructures,10–12ordered mesoporous materials with di?erent compositions from pure inorganic or pure organic frameworks to organic–inorganic hybrid frame-works have been widely reported in the past two decades.For example,mesoporous metal oxides and mixed oxides with semicrystalline frameworks,such as TiO 2,Ta 2O 5and ZrTiO 4,13,14mesoporous metal phosphates,borates and chalcogenides,15and other mesoporous non-oxide materials,such as SiC 16and BCN,17were successfully prepared by a direct synthesis strategy using amphiphilic copolymer templates.For organic–inorganic hybrid mesoporous materials with more complex compositions,periodic mesoporous organosilicas (PMOs)containing various bridged organic groups inside the hybrid network have been the most widely investigated.18,19Mesoporous metal phosphonates with organically bridged polyphosphonates were reported,consisting of di?erent functional groups inside the hybrid framework,with tunable mesoporosity from the hexagonal 20to cubic phase.21Periodic hexagonal mesoporous metal sulfonates were synthesized by the coupling of naphthalenedisulfonic acid or ethanedisulfonic acid with metal centers like Cd,La,Cu or Sr in the presence of surfactant templates and crown ether.22These two classes of non-silica-based hybrid mesoporous materials were proved to be useful in heavy metal ion and protein adsorption,CO 2capture,photocatalysis,acid catalysis and catalytic oxidation reactions.23

Porous carbon materials,as another huge family of porous materials,have also been widely studied due to their applications in water and air puri?cation,shape-selective catalysts,gas hosts,templates and components of electrodes for electrochemical double-layer capacitors.24,25The widespread applications of porous carbons are attributed to their remarkable physico-chemical properties,including the hydrophobicity of their surfaces,high corrosion resistance,good thermal stability,high surface area,large pore volume,good mechanical stability,easy handling and low cost of manufacture.26,27Thus the designed synthesis of porous carbon materials with controlled surface properties and structural ordering is important from a fundamental and application point of view.Porous carbons

with di?erent nanoscaled pores were investigated.The most representative method for the synthesis of disordered microporous carbons is the pyrolysis of appropriate carbon precursors.28,29Ordered microporous carbon materials were mainly synthesized using zeolites as templates,30,31and the resultant materials with a high surface area could retain the structural regularity of zeolite templates.For the synthesis of ordered macroporous carbons,various hard templates were utilized,such as a silica colloidal crystal,polymer microsphere,anodic aluminum oxide (AAO)and some mixed hard templates.32,33However,as to a number of other potential uses,such as large molecule separation and recognition,dye adsorption and catalyst supports for biomolecules,the presence of mesopores would be more preferable than micropores and macropores.Mesoporous carbons with disordered pores were obtained through various methods,including catalytic activation using a metal species,34carbonization of polymer/polymer blends 35and carbonization of organic aerogels.36Ordered mesoporous carbons can be synthesized by the nanocasting strategy using mesoporous silicas as the hard template.Ryoo and co-workers 37and Hyeon and colleagues 38were the ?rst to independently report the synthesis of ordered mesoporous carbons using cubic mesoporous silica MCM-48as the hard template in 1999.Subsequently,many other mesoporous silicas,such as the SBA series,39,40MSU-H 41and HMS,42were employed as the hard template.Based on this nanocasting strategy,some more cost-e?ective methods were also invented by making use of as-synthesized mesoporous silica/surfactant meso-phases as starting materials,followed by the introduction of extra carbon precursors.43,44By carbonization of phenyl-bridged meso-porous organosilica/surfactant mesophases without extra carbon precursors,mesoporous carbon with an average pore size of 2.5nm was reported by Lu et al.45To synthesize mesoporous carbons with larger pore sizes,colloid silica particles and silica gels have been explored as hard templates.46Mesocellular carbon foam,with uniform large mesopores,has been produced by partially impregnating mesocellular aluminosilicate foam with phenol/formaldehyde.47

However,some limitations have already emerged for the nanocasting strategy to prepare ordered mesoporous carbons.As shown in Fig.1,many experimental steps were

usually

Fig.1Two typical methods for the preparation of ordered mesoporous carbon materials:the nanocasting strategy from mesoporous silica hard templates and the direct synthesis from block copolymer soft

templates.

Zhong-Yong Yuan

Zhong-Yong Yuan received his BSc degree from Zhejiang Normal University in 1990,and obtained his MSc and PhD degrees from Nankai University in 1996and 1999,respectively.After his post doctoral research at the Insti-tute of Physics,Chinese Acad-emy of Sciences,he joined the Laboratory of Inorganic Materials Chemistry at the University of Namur,Belgium in 2001.In 2005,he was engaged as a Professor at Nankai University.In 2006,

he was awarded the ‘‘Program for New Century Excellent Talents in University’’by the Ministry of Education.He is coauthor of 170ISI publications,3book chapters and 9patents.

involved:(a)the preparation of ordered mesophase silica/surfactant composites;(b)the removal of surfactant molecules by calcination,extraction or other techniques (for the cost-e?ective method,surfactant molecules were preserved);(c)?lling of suitable carbon precursors into the template pores by either wet impregnation,chemical vapour deposition,or a combination of these two;(d)the carbonization of the carbon precursors inside the pore system of mesoporous silicas;(e)the removal of silica templates by etching.The nanocasting mechanism could lead to a relatively precise negative replica of the template and the syntheses are easy to control due to the ?xed template structure.However,the pore size distribution of the synthesized mesoporous carbons is relatively wider than the mother silica template;and the use of mesoporous silica as a sca?old makes the process expensive,complicated,and time-consuming,and consequently unsuitable for large-scale production and industrial applications.Meanwhile,much progress has been achieved on the direct synthesis of ordered mesoporous carbon materials by self-assembly of copolymer molecular arrays and carbon precursors,which is pioneered by the work of Dai et al.,48,49Nishiyama et al.,50and Zhao et al.51,52This opens a new way for the preparation of ordered mesoporous carbon materials with many advantages com-pared with the previous methods.First,fewer steps are needed in the preparation process (Fig.1):(a)the self-assembly of phenolic resin and block copolymer surfactants into three-dimensional ordered mesostructures according to corres-ponding symmetries (up to now only certain block copolymers could be utilized as the templates);(b)removal of the surfac-tants leaving mesoporous polymers and opened pores with the dimension,shape and topology depending on the size and structure of the supramolecular aggregates;(c)carbonization of the mesoporous polymers to give the ?nal mesoporous carbon materials.The directly synthesized carbon architec-tures via soft templates are more varied and mechanically stable due to the continuous framework.Their formation is dependent on the temperature,type of solvent and ionic strength,which makes the pore structure and surface properties easy to adjust.53–55The entire procedure is low-cost,simple,convenient,and suitable for large-scale industrial production.A comparison between the direct synthesis and nanocasting strategies is summarized in Fig.2.

Due to many advantages of this speci?c strategy and the resultant materials,the present review focuses mainly on the preparation of ordered mesoporous carbon materials by the direct strategy.The synthesis mechanism and the experimental condi-tions that a?ect the mesoporous structure will be discussed,including di?erent carbon precursors and block copolymers,the acidity of the reaction process,the use of various catalysts,and the di?erent preparation pathways [including evaporation-induced self-assembly (EISA)],aqueous route,macroscopic phase separa-tion process and hydrothermal synthesis through autoclaving treatment.Then the pore size and morphology control,the further functionalization and potential applications of the directly synthe-sized mesoporous carbons are presented.Finally we o?er some concluding remarks on the development and challenge of meso-porous carbon materials by direct synthesis.

There are some review articles on porous carbon materials.Lee et al.25and Xia et al.26independently reviewed carbon materials with micropores,mesopores and macropores synthe-sized from hard or soft templates.Liang et al.reviewed the mesoporous carbons obtained from both nanocasting and direct synthesis strategies,as well as some applications of carbons synthesized by hard templates.24Wan et al.presented a short review on the ordered mesoporous carbons and phenolic resin polymers from soft templates,mainly based on their contribution to this area;the history and development of the mechanism with supramolecular aggregates as the directing agent was clari?ed.54The present review highlights the direct-synthesized mesoporous carbons by combining the excellent work from worldwide researchers.The key elements in the preparation are discussed in detail,which aims at guiding the designed synthesis of mesoporous carbons and enlightening the future work in this speci?c ?eld.Moreover,the modi?cation and application of direct-synthesized carbons are elaborated,in an attempt to attract more attention and determine the real value of these materials.

2.Synthesis

2.1Synthesis mechanism

There were ?rst some attempts for mesoporous carbon preparation,consulted by the synthesis of ordered mesoporous silicates,in which the electrostatic interaction between the silicate precursor and the positively charged surfactant micelle leads to a supramolecular assembly.6,56However,by using phenol-fomaldehyde,57resorcinol-formaldehyde 58,59or oxidized polycondensed aromatic hydrocarbons 60as the precursors and cationic quaternary ammonium (e.g.,hexadecyl trimethyl ammonium bromide)as the surfactant,the majority products were disordered mesostructures with wide pore size distribu-tions,or the mesophases collapsed after aging at low tempera-tures.This could be attributed to the uncontrollable polymerization of organic precursors,the di?culty in removal of cationic micellar templates without destruction or obstruc-tion of pore structures,and the weakened interaction between organic polymer frameworks and quaternary ammonium surfactants.57,60,61

Then inspired by the successful preparation of ordered mesoporous silicates from amphiphilic block copolymers,

9,10

Fig.2A comparison between the direct synthesis and nanocasting strategies to prepare ordered mesoporous carbons.

these templates were used in the synthesis of mesoporous carbons.However,mesoporous carbons could not be fabricated by the direct pyrolysis of self-assembled block copolymers,62because of their very poor carbon yields in carbonization reactions.The melting of the linearly structured copolymers before carboniza-tion reactions occur and the massive loss of carbon in the form of volatile carbon-containing species during pyrolysis,both result in the inability to preserve the pre-organized ordered nanostructures.Therefore,adding suitable carbon precursors to the supra-molecular aggregates of block copolymers is necessary.By blending an amphiphilic diblock copolymer,poly(ethylene oxide)–poly(ethylene-alt -propylene)(PEO–PEP),with a poly-merizable epoxy resin,Bates et al.obtained ordered meso-structured thermosetting materials.63The epoxy resin selec-tively mixed with the PEO block and the separation of the block copolymer and epoxy was avoided due to the strong dipole polarization between them.Di?erent morphologies containing lamellar,cubic bicontinuous,hexagonally packed cylinders and body-centered cubic packed spheres were obtained depending on epoxy concentration.However,the template was not removed,possibly because of the small di?erence in the chemical and thermal stability between the block copolymers and epoxy resins.

The direct synthesis of ordered mesoporous carbons is now resorting to the hydrogen-bonding interaction between templates and precursors,which has been proved to be an e?cient route to prepare mesoporous materials.9,64The hydrogen-bonding interactions between the pyridine-group-containing or PEO-containing block-copolymers and the hydroxyl-group-containing organic precursors are demonstrated in Fig.3.Ikkala and colleagues prepared ordered mesostructured or mesoporous polymeric composites by utilizing the strong hydrogen-bonding interaction between phenolic hydroxyl groups and poly(2-vinyl-pyridine)–poly(isoprene)(P2VP–PI)65or poly(4-vinylpyridine)–polystyrene (P4VP–PS).66–68The self-assembled mesostructure could be tuned from lamellar to cylindrical and spherical phases,by tailoring the block lengths of PI or PS.Unfortunately,the pore network of the synthesized materials were often thermally unstable,perhaps because of the lack of the 3D interconnecting sites of the linear novolac phenolic resin.54Thus,only porous

polymers and polymeric composites were obtained instead of the pure carbon framework.

The real breakthrough of the preparation of ordered mesoporous carbons was achieved by Dai and co-workers,who developed a stepwise assembly approach to fabricate highly ordered nano-porous carbon ?lms using polystyrene–blockpoly(4-vinylpyridine)(PS–P4VP)as the soft template.48Using N ,N 0-dimethylformamide (DMF)as the solvent,the resorcinol monomers were ?rst pre-organized into a well-ordered PS–P4VP nanostructured ?lm through spin-coating followed by solvent annealing in DMF/benzene vapor.The self-assembly of the PS–P4VP/resorcinol mixture was driven by the hydrogen-bonding inter-action between resorcinol and the P4VP block.The su?cient repulsion between the PS domains and the P4VP/resorcinol domains favors the reserve of the highly ordered alignment together with the enrichment of resorcinol in the matrix upon solvent evaporation.The microphase-separated ?lm was then exposed to formaldehyde vapor to form a highly cross-linked phenolic resin located in the P4VP domain,followed by the decomposition of the block copolymer template to generate ordered nanopores,and the carbonization of the nanostruc-tured phenolic resin to form the carbon pore walls at 8001C in nitrogen.Highly ordered and crack-free mesoporous carbon thin ?lms were obtained by this method.The mesopores were oriented perpendicular to the ?lm surface with a pore diameter of 33.7?2.5nm and a wall thickness of 9.0?1.1nm.The amphiphilic copolymers direct the formation of the phenolic resin nanostructure and serve as templates for the nanopores.Nishiyama and co-workers 50reported the synthesis of mesoporous carbons with an ordered channel structure (COU-1),which were fabricated via the direct carbonization of an organic–organic nanocomposite.The choice of an appropriate set of thermosetting polymers and thermally decomposable surfactants is the most important factor in controlling the structure of these ordered mesoporous carbons.Resorcinol/formaldehyde and triethyl orthoacetate were used as the carbon co-precursors;commercially available and inexpensive pluronic PEO–PPO–PEO [poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)]block copolymer F127(EO 106PO 70EO 106)was used as the surfactant.The reaction mixture containing the surfactant and carbon precursors was spin-casted on a silicon substrate,followed by polymerization and carbonization at di?erent temperatures.The resultant COU-1materials showed a periodic mesostructure consisting of hexagonally arranged pores,which were parallel to the ?lm surface.The whole preparation procedure of their method could be accomplished in the liquid phase instead of the formaldehyde gas that was used in the work of Dai et al.48A carbon co-precursor triethyl orthoacetate has to be used,but its role is uncertain.The addition of triethyl orthoacetate apparently has a favorable e?ect on the stabilization of the periodic mesostructure,since a poor periodic structure was obtained in the absence of triethyl orthoacetate.

Zhao’s group has made major contributions to the direct synthesis of ordered mesoporous carbon materials through an organic–organic self-assembly approach.Highly ordered mesoporous carbons,denoted as FDU-15and FDU-16,were synthesized through a solvent evaporation induced self-assembly method (EISA)by using amphiphilic triblock

copolymers

Fig.3Hydrogen-bonding interaction between (a)pyridine-group-containing and (b)PEO-containing block-copolymers and the hydroxyl-group-containing organic precursors.Reprinted with permission from ref.54.

(PEO–PPO–PEO)as templates and a soluble low-molecular weight resol of phenol and formaldehyde as the precursor.51Fig.4illustrates the preparation procedure of the ordered mesoporous carbons.Low-molecular-weight resol was ?rst mixed with F127in an ethanolic solvent,followed by the evaporation of the solvent.The choice of resol as a precursor is essential for the successful organization of organic–organic mesostructures because resol has a large number of hydroxy groups,which can interact strongly with F127surfactant through the formation of hydrogen bonds.Driven by the hydrogen-bonding interaction between the PEO block and resol,an ordered mesostructure of the resol/F127composite formed.Curing the resol at 1001C solidi?ed the polymeric framework,yielding a rigid zeolite-like hydrocarbon network with three-connected benzene rings through the formation of covalent bonds.Because of the di?erence in chemical and thermal stability between the resin and the triblock copolymer,the template could be removed by calcination at 3501C in nitrogen.The carbonization was carried at 700–14001C under an inert atmosphere to transform the polymeric framework into the carbon mesostructures.The resultant solids had well-structured mesoporosity with uniform pore size distribution.After carbonization at 9001C,FDU-15had a large BET surface area of 968m 2g à1and a pore volume of 0.56cm 3g à1;FDU-16had a surface area of 778m 2g à1and a pore volume of 0.44cm 3g à1.

Although many self-assembly mechanisms have been utilized for the synthesis of mesoporous oxide materials under di?erent pH conditions,9,10,14,15such as I àS +,I +X àS +,and I 0S 0(I:inorganic precursor,S:surfactant,X à:Cl à,Br à,I à,NO 3à,H y SO 4à2+y ,H y PO 4à3+y ,etc.),only self-assembly induced by hydrogen-bonding (I 0S 0)has been mostly utilized for making ordered mesoporous carbon materials.Noticeably,by using strongly acidic conditions,Dai and co-workers expanded the self-assembly process to coulombic interaction (I +X àS +)for the successful preparation of ordered meso-porous carbons,denoted as C-ORNL-1.69C-ORNL-1could be synthesized in a wide range of acid concentrations (e.g.,0.5–2.0mol L à1)in the mixed solution of ethanol and water,

with resorcinol/formaldehyde and pluronic surfactant F127as precursors and template,respectively.Under highly acidic conditions,phenols and cross-linked phenols are protonated,and the EO blocks of F127are also protonated.The presence of Cl àwas con?rmed as a mediator.Thus the I +X àS +mechanism driven by coulombic interactions was suggested.10The self-assembly of surfactant–polymer nanocomposites could be attributed to the combination of coulombic inter-actions and hydrogen-bonding interaction.This method was suitable for large-scale synthesis of ordered mesoporous carbons with high thermal stability,but mant halogenide ions were introduced to the reaction system,which would be unfavorable for some applications and green production.As we can see through the evolution of the direct synthesis strategy of ordered mesoporous carbons,the addition of carbon precursors besides the surfactant template is necessary.The development trend,considering economical and clean production,is to utilize fewer types of carbon sources without extra carbon co-precursors and to use precursors in liquid or even solid phases,avoiding toxic gas emission.Although the PEO–PPO–PEO type copolymers are the most utilized templates,and the driving force in the organic–organic assembly is mainly based on the hydrogen-bonding interaction,other interactions like coulombic and van der Waals interactions are also very promising to be involved in the assembly.If so,more kinds of templates,like cationic quaternary ammonium and nonionic alkyl PEO oligomeric surfactants,can be used independently or together with block copolymers in the preparation,which can break the threshold of the pore size in the present carbons by the direct strategy to obtain smaller or even multi-scaled mesoporosity.2.2Synthesis pathway

2.2.1EISA method.Ordered mesoporous carbon materials can be successfully synthesized through di?erent pathways,and some typical examples are summarized in Table 1,which contains the main experimental parameters.The EISA of block copolymer and resols (phenol,resorcinol,or phloroglucinol/formaldehyde)has been demonstrated as one of the e?cient paths.48,50,51The EISA method avoids the cooperative assembling process between the precursor and the surfactant template,which can separate the cross-linking and thermopolymerization processes of the resols from the assembly.70It is a facile method under wide synthetic conditions,such as acidity of the reaction solution,surfactant and phenol/template ratio.Evaporation of the solvent can be simply performed in an open-mouthed dish,51and a spin-coating or dip-coating technique is sometimes applied.48,50Since the mesostructures are formed on the surface by the EISA method,it meets the demands of preparing mesostructured ?lms.

By utilizing the EISA method,a series of ordered meso-porous carbons with various structures including 2D hexago-nal (p 6mm ),3D bicontinuous (Ia %3

d ),body-centered cubic (Im %3

m )and lamellar mesostructures could be prepared from an organic–organic assembly of PEO–PPO–PEO triblock copolymers with low-molecular-weight phenolic resin precursors.71The step-wise synthesis procedure is shown in Fig.4.The precursor derived from phenol and formaldehyde was formed in a basic

solution

Fig.4Scheme for the preparation of ordered mesoporous carbon frameworks by the EISA method.Reprinted with permission from ref.51.

catalyzed by NaOH,while the EISA process was carried out in a nearly neutral system.Ethanol and other organic solvents,such as methanol,acetone,and tetrahydrofuran (THF),can be used as a solvent,but water is not adopted because the evaporation is too slow.The evaporation of ethanol progres-sively enriches the concentration of the copolymer;and the organic–organic assembly between the block copolymer and the resol precursor is mainly driven by the hydrogen-bonding interaction.71The obtained carbons exhibited well-structured porosity with high surface area,large pore volume and uniform pore size.The high thermal stability of mesoporous carbons is attributed to the covalently bonded constructions and the very thick pore walls.They also have a higher mechanical stability in comparison with CMK-3that was prepared by the nanocasting strategy,39which may be attributed to the continuous frame-work of the former.

Complicated self-assembly behaviors may occur during the solvent evaporation and thermopolymerization stages of the EISA synthesis method,and thus many e?orts have been made to study the surfactant–resol system using di?erent techniques.72,73Very recently,Goldfarb and co-workers studied the transformation of F127-phenolic resol composites

in the preparation of FDU-16(Im %3

m )by the EISA method,74utilizing the spin probe electron paramagnetic resonance (EPR)method,which is widely used in mechanistic studies of ordered mesoporous silica materials.75,76In the EPR measurement,two pluronic-derived spin probes with di?erent lengths of PPO and PEO blocks were used to sense the PEO

region (by the probe with long PEO chains)and the PPO–PEO interface (by the probe with relatively shorter PEO chains),respectively.77,78A better understanding of the EISA pathway was accessed,and it was found that the F127-resol composite was formed through hydrogen-bond interactions during the solvent evaporation process.The resol was distributed throughout the PEO blocks,all the way to the PPO–PEO interface.Weaker hydrogen bonds between the PPO block and resol may also be formed.At the end of the evaporation there is no polarity gradient along the PEO blocks,and the meso-phase is not well-structured without a de?nite PPO–PEO interface.During the following thermopolymerization stage,the hydrogen bonds of resol with the PPO block and close to the PEO–PPO interface are disrupted,and the PPO and the PEO regions are better segregated.The polymerizing resol is driven out to the outer region of the PEO corona,where it continues to polymerize,trapping part of the PEO chains to form the pore wall.A corona of resin–pluronic composite and a resol-free PPO core are formed,and the ?nal periodic meso-structure is ?xed during this thermopolymerization step.742.2.2Dilute aqueous route.Despite the success of the EISA method,it can barely meet the demands of large-scaled industrial production of powder materials due to the engineering di?culties,including sample collection,reactor design (large surface vessel),etc.Moreover,uniaxial structural distortion is always observed for the mesoporous materials prepared by the EISA method,and pore size tailoring is still a great challenge.79

Table 1Synthetic conditions for ordered mesoporous carbon materials by the direct strategy Reaction pH Precursor Pathway Solvent Catalyst Template Mesophase Annotation a Ref.Neutral Resorcinol EISA DMF Not

available PS–P4VP p 6mm Formaldehyde gas 48Neutral Phenol EISA THF Not

available PEO–PS Fm %3

m Resol precursor 105Neutral Phenol EISA THF NaOH PEO–PMMA Fm %3

m Resol precursor

106

Neutral Phenol EISA Ethanol NaOH P123,F127

p 6mm,Ia %3d,Im %3m Resol precursor 51,71,74,149

Neutral Phenol EISA Ethanol NaOH PPO–PEO–PPO Fd %3

m Resol precursor 107,108Basic Phenol Dilute aqueous

Water

NaOH P123,F127p 6mm,Ia %3d,Im %3m

Hexadecane or decane

52,80,115,116Basic Phenol Hydrothermal Water NaOH P123,F127p 6mm,Im %3

m Autoclaving 87,124Basic Resorcinol EISA

Ethanol NaOH F108Im %3m

—

90Basic Resorcinol Hydrothermal

Water/ethanol

Lysine F127p 6mm Autoclaving 101Acidic Resorcinol Hydrothermal Water/

ethanol

HCl F127p 6mm Autoclaving 86,134Acidic Resorcinol Hydrothermal Water/

ethanol

Citric acid F127p 6mm Autoclaving 102,103,104Acidic Resorcinol EISA Ethanol HCl F127p 6mm,Im %3

m Furfural 95Acidic Resorcinol EISA Water/

ethanol

HCl F127p 6mm Triethyl orthoacetate 50Acidic Resorcinol Phase separation Water/ethanol HCl F127p 6mm Strong acid condition 69,84,85,146Acidic Resorcinol Phase separation Water Glutamic acid F127p 6mm —

100

Acidic Resorcinol/phloroglucinol EISA Water/

ethanol

HCl F127Fmmm,p 6mm Spin or dip coating 91,92,93Acidic Phloroglucinol Phase separation Water/ethanol HCl F127p 6mm Low HCl concentration 49,146Acidic

Phloroglucinol

Phase separation Water/ethanol

HCl

F127

p 6mm

Glyoxal

Special experimental conditions or reagents needed.

The surfactant induced self-assembly method in aqueous solution,which has been widely used in the synthesis of many ordered mesoporous siliceous materials,is considered as an alternative path to prepare mesoporous carbons.The ordered mesostructures derived from this method have the advantages of few defects,easily tailored pore sizes,and well-controlled https://www.wendangku.net/doc/546538459.html,pared with the EISA method,the aqueous route exhibits better reproducibility and an unlimited fabrica-tion batch size,which is suitable for industrial production.A dilute aqueous pathway was used to fabricate the ordered mesoporous carbon (FDU-14)for the ?rst time by Zhao’s group.52The synthesis was performed through the organic–organic self-assembly of pluronic surfactant P123(EO 20PO 70EO 20)with resols (phenol/formaldehyde)in a dilute aqueous solution.FDU-14possessed a typical 3D bicontinuous cubic

space group (Ia %3

d ).Th

e synthesized materials,after carboni-zation at 7001C,had a high surface area o

f 1150m 2

g à1and uniform pore size distribution at 3.8nm.Many micropores were derived on the pore wall during the carbonization process.Subsequently,the aqueous pathway was used to the synthesize a series of ordered mesoporous carbon materials wit

h hexagonal and cubic structures through the self-assembly of phenol/formaldehyde resols and triblock copolymer templates.With the assistance of hydrocarbon (hexadecane or decane)as a swelling agent,highly ordered mesoporous carbons FDU-15with 2D hexagonal (p 6mm )structure and enlarged pore sizes could be synthesized by using P123as the template.80The hydrocarbon molecules can interact with the hydrophobic PPO segment of the triblock copolymers leading to the lattice enlargement or the phase transition,which have been used as pore size swelling agents for the synthesis of mesoporous silicate materials in aqueous conditions with triblock copolymers as the template.81–83Ordered mesoporous carbon FDU-16

with body-centered cubic structure (Im %3

m )was also synthesized under basic aqueous conditions by using template F127with a relatively wide range of concentrations.80

The synthesis in the aqueous system was supposed to follow a cooperative self-assembly route.The resol interacts with block copolymers through one-layer hydrogen bonds between the phenolic groups of the resol and the ether groups of the PEO.The resulting complexes further assemble into a mesostructure,and the resol polymerizes around the block copolymer aggregates to form large phenolic resin–pluronic composite particles.After removal of the triblock copolymers and carbonization,the ?nal mesoporous carbon materials are obtained.Basic conditions,with a pH value of around 9.0,of the reaction solution is necessary to obtain a rigid and stable mesoporous framework,while the hydrogen bonds are weakened in the relatively strong basic solution and the polymerization is too slow in neutral or weak acidic media.52,80Thus,the narrow acidity range is a limitation of the aqueous pathway.

2.2.3Macroscopic phase separation.When resorcinol or phloroglucinol is used as the precursor to polymerize with formaldehyde in a acidic system,it undergoes a macroscopic phase separation process during the generation of ordered mesoporous carbons.49,69,84,85For example,Zhang and co-workers synthesized ordered mesoporous carbons through the self-assembly

of resorcinol/formaldehyde and surfactant F127in the mixed solution of ethanol and water.84,85The synthesis was performed in a strong acidic system with hydrochloric acid as the catalyst.After adding the precursors,F127and hydro-chloric acid,into the ethanol/water solution,the mixture turned cloudy and began to separate into two phases.The upper phase (consisting mainly of water/ethanol)was discarded,whereas the composite of resorcinol/formaldehyde oligomers and F127was formed in the lower polymer-rich phase.After aging,curing and carbonization,mesoporous carbons could be obtained.The phase separation of the polymer-rich phase from the ethanol/water solvent is the key step in their synthesis.Resorcinol and formaldehyde ?rst polymerized slowly to ethanol-soluble resol oligomers with a low polymerization degree,which would interact with the PEO segments of the self-assembled triblock copolymers through hydrogen bonds.When the linear resols further polymerized with each other to achieve a relatively large molecular weight,a glue-like polymer product began to separate from the solvent,resulting in macroscopic phase separation.The larger amount of resorcinol would lead to stronger hydrogen-bonding interactions and the longer aging time would lead to less defects,thus it was found that both the excess amount of resorcinol (resorcinol/formaldehyde Z 1/2)and the long aging time (96h)were favorable for the formation of highly ordered mesoporosity.84,85The resultant mesoporous carbons possessed high surface areas of 674–781m 2g à1and large pore volumes of 0.52–0.72cm 3g à1.84The same macroscopic phase separation phenomenon was also observed when Dai and co-workers performed the synthesis of ordered mesoporous carbons in the acidic solution by using phloroglucinol 49or resorcinol 69as the monomer.

2.2.4Hydrothermal autoclaving process.Hydrothermal preparation through an autoclaving treatment is a more e?cient approach under controlled temperature and pressure that has been extensively used in the preparation of many nanoporous materials.This powerful method is faster and more energy e?cient than conventional aqueous chemical processing pathways.Yuan and co-workers demonstrated a low-temperature autoclaving method to prepare ordered meso-porous carbon monoliths with F127template and resorcinol/formaldehyde precursor in a mixed ethanol/water acidic solution.86The precursors,surfactant F127and catalyst HCl were mixed at room temperature into the ethanol/water solution,followed by autoclaving treatment at 501C.Ordered mesoporous carbons could be collected after ?ltration,washing,drying and carbonization.A 2D hexagonal pore system with uniform pore size of B 5nm and high surface area of B 675m 2g à1was obtained.The optimal conditions to access ordered mesoporosity were ?xed at the formaldehyde/resorcinol molar ratio r 2and the autoclaving treatment time Z 48hours.In comparison,they also prepared mesoporous carbons under the identical conditions using a mixed ethanol/water solvent,but through the EISA method.It was interesting to ?nd that only wormhole-like mesopores were obtained when they tried to mold the meso-porous carbons from the EISA method into di?erent morphologies.It could be attributed to the problem that the shapes of the molds made the reaction mixture possess only a small area to come into

contact with the atmosphere during the EISA process,and the existence of water caused the solvent evaporation rate to not be easily controlled.However,highly ordered structures can be obtained if a directional force is applied to the polymer.In the low-temperature autoclaving method,a certain temperature (501C)and autogenous pressure enhanced the interaction between the molecules and induced the faster polymerization rate,which led to the periodic assembly between precursor and template molecules.86Zhao and co-workers synthesized meso-porous carbons by using phenolic resols (phenol/formaldehyde)as precursors and mixed triblock copolymers of P123and F127as templates via a hydrothermal autoclaving approach in a basic system.The autoclaving treatment was carried out at 1001C for 10hours,leading to ordered 2D hexagonal mesoporous carbon materials with a uniform pore size around 3nm.87

Each synthetic pathway has its own advantages and short-comings.The dilute aqueous route is limited by the narrow reaction acidity,while the EISA method can operate under wide preparation conditions,like acidity and precursor ratios.On the other hand,the aqueous route is much more facile for large-scaled production compared with the EISA method,which is restricted by the reactor size.Although the hydro-thermal autoclaving process is a quick and e?cient route,energy consumption is required for the high temperature and pressure.The macroscopic phase separation method is easily operated and has high yields,but strong acidic conditions are often needed,which may result in the corrosion of equipment and halogenide ion pollution.Thus,one should select the most suitable pathway depending on the practical situation.The development of a low-cost,environmentally friendly and reproducible method is still urgent.2.3

Precursor

Phenol,resorcinol,and phloroglucinol are the three most common phenolic resin monomers used for the preparation of mesostructured resin polymers and the corresponding mesoporous carbons.These three monomers can form single,double,and triple hydrogen bonds to the polyethylene oxide (PEO)chains of the PEO–PPO–PEO block copolymers,which is the driving force of the organic–organic self-assembly.The reactivity of di?erent monomers with formaldehyde follows a trend of phloroglucinol c resorcinol c phenol.Under acidic conditions,the reaction and polymerization of phloroglucinol,resorcinol or phenol with formaldehyde involves the proto-nation of hydrated formaldehyde and electrophilic aromatic substitution reactions of phenols.88Therefore,the concen-tration of acid and the reactivity of di?erent phenols are two key factors in determining the polymerization rate of phenolic resins.

The utilization of di?erent monomers to prepare porous carbons was compared at low acid concentration (10à2mol L à1)and room temperature in a mixed solution of ethanol and water.49The polymerization of phenol was very slow in the presence of F127,and the resulting polymer yielded porous carbons possessing very low surface areas (o 5m 2g à1).Resorcinol polymerized slightly faster than phenol at room temperature,but the speci?c surface area was mainly contributed to micropore surfaces.Phloroglucinol,which was found to be an excellent

precursor for the synthesis at low acid concentration,poly-merized much faster than either resorcinol or phenol.The macroscopic phase separation of the reaction mixture occurred within 30min,and the phloroglucinol/formaldehyde oligomers existed in the lower layer of a polymer-rich phase.The super-iority of using phloroglucinol was attributed to the high hydroxy density in the oligomers formed from phloroglucinol,providing the greater driving force for the self-assembly inter-action with the PEO blocks than those provided by the oligomers from phenol and resorcinol.49The ordered meso-porous carbons could be obtained under mild reaction condi-tions and in a wide composition range (weight ratios of phloroglucinol:F127:formaldehyde :ethanol :water :HCl E 1:1:0.26–0.48:150–1:90–10:0.03–0.003).However,the fast polymerization rate of phloroglucinol with formaldehyde is some-times not favorable for the formation of ordered mesostructures.For example,only irregular mesoporous carbons were obtained when the synthesis was performed under higher acid concentra-tions (HCl/phloroglucinol weight ratio of 0.036–0.144).89

On the other hand,resorcinol monomers were used in the original reports for ordered mesoporous carbon preparation through the spin-coating technique,which had to be polymerized with formaldehyde vapor 48or by the assistance of co-precursor triethyl orthoacetate.50Although it seems not to be a suitable monomer at low acid concentrations and room temperature (mainly microporosity)compared with phloroglucinol,49resorcinol/formaldehyde precursors have been used to success-fully prepare ordered mesoporous carbons under strong acidic conditions as we mentioned above (Table 1).69,84–86In addi-tion,Song and co-workers prepared mesoporous carbons with Im %3

m symmetry by direct carbonization of self-assembled F108(EO 132PO 50EO 132)and resorcinol/formaldehyde compo-sites.90Their synthesis was accomplished in a basic ethanol solution catalyzed by NaOH through the EISA method.Moreover,by using mixed phenolic resin monomers of resor-cinol and phloroglucinol,Tanaka and co-workers synthesized ordered mesoporous carbon membranes with F127as the template catalyzed by HCl.91–93The obtained materials possessed a face-centered orthorhombic Fmmm symmetry,and high speci?c surface area of B 670m 2g à1after carboniza-tion at 6001C.93It was demonstrated that using a combination of phloroglucinol and resorcinol reduced the weight loss of the resin compared with using only resorcinol/formaldehyde and thus improved the thermal stability.

Phenol,as a cheaper monomer than resorcinol and phloro-glucinol,has been widely used to prepare ordered mesoporous carbons through the EISA,51,71dilute aqueous,52,80and hydrothermal pathways (Table 1).87Low-molecular-weight and soluble resols derived from the polymerization of phenol and formaldehyde in a basic system were chosen as the organic precursors.There are many advantages for this speci?c precursor.First,phenol has fewer reactive sites than those in resorcinol and phloroglucinol,and thus the polymerization rate of resols is easily controlled,which favors the ordered assembly between phenolic resins and copolymer templates.Many benzyl hydroxyl groups,besides phenolic hydroxyl groups,formed during the polymerization of phenol and formaldehyde in basic system,which enhanced the hydrogen-bonding interactions with PEO blocks of the copolymer

PEO–PPO–PEO templates.Furthermore,a rigid zeolite-like hydrocarbon network with three-connected benzene rings through the formation of covalent bonds was obtained for phenolic resin after the thermopolymerization process,94and this stable mesostructure could be preserved upon template removal by calcination.For the EISA method,resol precursors are di?cult to evaporate,which results in not only the constant composition with high yield but also the avoidance of formal-dehyde emission.71

In fact,phenol,resorcinol,and phloroglucinol/formaldehyde pairs are not the only reported precursors to prepare meso-porous polymers and corresponding mesoporous carbons.There are also some illustrations of replacing formaldehyde that is a severe air pollutant.For example,highly ordered mesoporous carbon spheres with hexagonal and body-centered cubic phases were designed inside an ethanol-in-oil emulsion system by utilizing the EISA method combined with the suspension polymerization method.95The organic–organic assembly was accomplished between the surfactant F127and the carbon precursor of resorcinol–furfural oligomers catalyzed by HCl in the presence of hexamethylenetetramine.The typical hexagonally arranged structures with large domains are shown in the TEM images (Fig.5a and b).With decreasing the added amount of F127,the cubic mesophase Imm was then obtained,shown in Fig.5c–e.Another example is the use of glyoxal instead of formaldehyde.As mentioned above,phloroglucinol reacts faster than resorcinol or phenol with formaldehyde.96To obtain an ordered porous carbon,the fast reactivity of phloroglucinol must be countered by a low acid concentration 49or a slower reacting aldehyde than formaldehyde.Glyoxal is a slow reacting aldehyde,potentially due to the possible enol-tautomerization that can stabilize a reaction intermediate structure and hinder further cross-linking.Dai and co-workers synthesized highly ordered mesoporous carbons with a surface area of 410m 2g à1and a uniform pore size at 7.5nm from the phloroglucinol/glyoxal precursor in the presence of F127.97Moreover,Yuan and co-workers developed a novel method to synthesize porous polymer and carbon by using hexamethyl-enetetramine as one of the carbon precursors under the

hydrothermal conditions.98First,the partial hydrolysis of hexamethylenetetramine produced formaldehyde and ammo-nia.Ammonia could catalyze the polymerization of resorcinol and formaldehyde and initiate their condensation process.As the reaction proceeded,more hexamethylenetetramine slowly decomposed to provide a gradual and controlled supply of formaldehyde and ammonia,which quickly reacted with resorcinol to form numerous hydroxymethyl-substituted and/or amino-methyl-substituted species.These hydroxymethyl-substituted and/or aminomethyl-substituted species were positioned at the surface of the polymer owing to the electrostatic interaction with the ammonia molecules,and further cross-linking of these species occurred during the hydrothermal treatment.This strategy is user-friendly,avoiding the use of toxic formaldehyde,which is promising to construct many mesostructured carbon materials.Although most of the organic–organic self-assemblies have been applied for phenolic resins up to now,there are still some attempts of other polymer compositions with a comparable mesostructure.Melamine resins belong to the class of amino resins or amino plastics,which are closely related to their phenolic analogs both in synthesis and application.Hong and co-workers successfully synthesized mesoporous melamine resins using hexamethoxymethyl melamine as the monomer and F127as the template.99The template could be removed by solvent extraction,yielding 2D hexagonal mesoporous polymers with a surface area of up to 258m 2g à1and pore diameter of 7.8nm.Though mesoporous carbons were not yet obtained,which is probably due to the ?exible pore walls of melamine resins,this method extends the composition of mesoporous polymeric frameworks.2.4Catalyst

The polymerization of phenolic resins can be performed in either acidic or basic systems.For the preparation of ordered mesoporous carbons,the polymerization between phloro-glucinol or resorcinol precursors with formaldehyde is often catalyzed by hydrochloric acid,49,50,69,84–86or sodium hydro-xide,90while low-molecular-weight resols derived from the polymerization of phenol and formaldehyde in basic systems are also chosen as the precursors (Table 1).51,52,71,80However,it is still necessary to ?nd alternative catalysts for the commonly used NaOH and HCl,which are not convenient and environ-mentally friendly due to the corrosion of the equipment and the pollution of halogenide ions.

An amino acid was used as the catalyst in the direct synthesis of ordered mesoporous carbons.Lu et al.synthesized mesoporous carbons through the self-assembly of resorcinol/formaldehyde polymer and surfactant F127in aqueous phase with glutamic acid as the catalyst.100The highly ordered hexagonal mesophase was obtained with a p 6mm space group.The obtained materials possessed high surface areas of around 720m 2g à1,which could be easily tuned by varying the pyrolysis temperature.The glutamic acid acted as a catalyst to polymerize resorcinol and formaldehyde,and simultaneously it initiated the interaction between resorcinol/formaldehyde polymer and F127through hydrogen-bonding,resulting in self-assembly into a mesostructure.Thus,the amount of glutamic acid was important in determining the mesopore ordering of

carbons.

Fig.5TEM images of ordered hexagonal mesoporous carbon spheres recorded from the (a)[110]and (b)[001]directions,and cubic mesoporous carbon spheres recorded from the (c)[110],(d)[111]and (e)[100]directions.The insets are the corresponding fast Fourier transform di?ractographs.Reprinted with permission from ref.95.

The particular feature of their synthesis is that no inorganic compounds were involved,and therefore carbon materials with high purity can be achieved.Lu and co-workers further investigated the function of amino acids in the direct synthesis of mesoporous carbons by using organic base lysine as both the polymerization catalyst and mesostructure assembly promoter.101As shown in Fig.6,lysine molecules could form intra-molecule salts,so the deprotonated carboxyl group and the protonated NH 3+group could form hydrogen bonds with the –OH group of resorcinol and the hydrophilic EO (N–H áááO)segment of F127.Thus the lysine molecule would enhance the assembly of the mesostructure between F127and phenolic resins.Moreover,the basic lysine could provide a basic environment for the polymerization of resorcinol and formaldehyde.101

Independently,Yuan and co-workers demonstrated the synthesis of ordered mesoporous carbon materials with the use of citric acid to catalyze the polymerization of resorcinol/formaldehyde resin.102–104The obtained carbon materials,with high thermal stability,have a 2D hexagonal mesopore system with a uniform pore size of B 5.2nm and a high surface area of 612–851m 2g à1.102A reaction temperature of 50–801C and a molar ratio of formaldehyde to citric acid of Z 3favored the formation of the highly ordered p 6mm mesostruc-tures.Citric acid played an important role in the formation of a periodic mesostructure,being attributed to the abundant –COOH groups in citric acid,which may enhance the inter-action between the resorcinol/formaldehyde precursor and F127.The enhancement e?ect further caused the polyethylene oxide (PEO)segments of triblock copolymer to embed into the resins during the polymerization process.Thus,more micro-porosity was introduced than when catalyzed by HCl,because the removal of the PEO block would cause some dis?gurement in the pore wall of the ?nal products.10The synthesized mesoporous carbons also had a high thermal stability,due to the highly cross-linked resorcinol/formaldehyde polymers and the resulting rigid carbon framework.A good mesoscopic order was still re?ected after carbonization at 600–10001C,and the pore size was almost unchanged,which is superior to

the previously reported ordered mesoporous carbons su?ering from serious structure shrinkage and collapse.51,52,71,80,902.5Template

A proper template should interact strongly with both precursors and be easily removed.The PEO–PPO–PEO type amphiphilic triblock copolymers,such as F127,F108and P123,are most widely utilized (Table 1).The organic–organic self-assembly is driven by the hydrogen-bonding interaction,and the PEO–PPO–PEO templates can be easily removed at low temperature without destroying the resin framework,because they contain many oxygen atoms and have a low glass transition temperature (lower than room temperature).71Although cationic quaternary ammonium and nonionic alkyl PEO oligomeric surfactants were also used to prepare mesostructured resin-surfactant composites,these templates were di?cult to remove.

Following this concept,other PEO-containing block copolymers can be chosen as templates for the mesoporous carbon preparation.By using a laboratory-made poly(ethylene oxide)–polystyrene diblock copolymer PEO 125–PS 230as the template,ordered mesoporous carbons with ultralarge pore sizes and face-centered cubic closed-packing mesostructures (Fm %3

m )were obtained through the EISA method.105

The long PS segment was the key to obtaining the large mesopores with a cubic closed-packing structure.During the solvent evaporation process,resol precursors could interact with the PEO segment of the diblock copolymer by hydrogen-bonding,and discrete cubic-packed spheres of PS blocks were formed in a matrix of the PEO block and resin.Upon thermosetting,the framework polymerized,causing the mesostructure of discrete micelles to

form the Fm %3

m mesophase.The pore size depended on the length of the hydrophobic PS blocks,while the micropores were generated to connect the primary mesopores due to the pyrolysis of the PEO blocks.Therefore,mesoporous carbon frameworks possessing a uniform large pore size of B 23nm were obtained with a large amount of microporosity.105

A similar poly(ethylene oxide)–poly(methyl methacrylate)diblock copolymer PEO 125–PMMA 144was also used as the template to synthesize mesoporous carbon materials.106The preparation was carried out through the EISA method by using soluble resol and THF as the carbon source and the solvent,respectively.The obtained carbons had a high surface area up to 1050m 2g à1and a uniform large mesopore

B 10.5nm after carbonized at 8001C,and a face-centered cubic close-packed mesostructure (Fm %3

m ),which was the same as that prepared from PEO 125–PS 230.105Despite the similar experi-mental procedures and the identical hydrophilic PEO chain length,the mesoporous carbons prepared by PEO 125–PMMA 144had an ultra thick pore wall of 11.5–12.4nm,com-pared with that prepared by PEO 125–PS 230(B 9.9nm)and the previously reported mesoporous carbons.This could be explained by the weaker hydrophobic PMMA block containing ester groups,which could partially associate with the resol molecules,while the PS segment formed an extremely hydrophobic core and could not interact with the hydrophilic resol molecules.Thus,more resol molecules were present around the hydro-phobic phase in the PEO–PMMA/resol composites,leading to the ultra thick pore wall.106Enhanced

mechanical/chemical

Fig.6Schematic of the rapid synthesis of mesoporous carbons with lysine as the catalyst.Reprinted with permission from ref.101.

stability and related applications were expected for these thick wall carbon materials.

Although reverse-type PPO–PEO–PPO copolymers are thermodynamically di?cult to form mesostructures under general hydrophilic synthesis conditions,which makes them seldom used to synthesize mesoporous carbon materials,the PPO–PEO–PPO copolymer possessing a long PEO chain is capable of lowering the curving energy and forming the mesophase with high curvature.Huang et al.chose phenolic resol and PO 53EO 136PO 53as the precursor and the template respectively,to prepare ordered mesoporous carbons with a

3D face-centered cubic (Fd %3

m )structure through the EISA method.107,108

The ordered mesoporous materials had high thermal stability,and the BET surface area was around 870m 2g à1with a pore volume of 0.54cm 3g à1after carbonization

at 10001C.107The formation of the cubic Fd %3

m mesophase was attributed to the characteristic phase behaviors of the reverse PPO–PEO–PPO copolymers.The two outer PPO blocks in a chain participate in two di?erent micelles or aggregates,109,110forming interconnected micelles.111,112The assembly of the reversed PPO–PEO–PPO with a large PEO weight fraction of 45%and the resol precursor rendered the face-centered cubic packed spheres of PPO blocks in the PEO/

phenolic resin matrix,and the resultant Fd %3

m mesophase with the high interface curvature was not observed in the PEO–PPO–PEO system.

Various mesostructured carbon materials with lamellar,

bicontinuous cubic (Ia %3

d ),hexagonal (p 6mm )and body-centered cubic (Im %3

m )mesophases were obtained by using di?erent triblock copolymer templates.It is found that the mesophase of the ?nal mesoporous carbons are determined by the hydrophilic/hydrophobic volume ratio in the entire system,which is referred to the hydrophilic to hydrophobic PEO/PPO ratio in copolymer templates and the phenol/surfactant ratio.On the one hand,with the increase of PEO/PPO ratio in the triblock copolymer template,the mesophase with a higher interface curvature is obtained,and the mesophase transforms from lamellar to the bicontinuous cubic,hexagonal,and body-centered cubic structure.On the other hand,hydrophilic resols can interact with PEO segments,leading to the hydro-philic volume swelling,while the hydrophobic volume per block remains essentially constant.Thus,with the increase of the phenol/surfactant ratio,the hydrophilic/hydrophobic volume ratio in this system may also increase,resulting in the mesophase with a higher interface curvature.51,52,71,80For example,when using the aqueous synthesis pathway,F127(EO 106PO 70EO 106)with a larger PEO/PPO ratio induced the

formation of the body-centered cubic (Im %3

m )mesostructure with high curvature,while P123(EO 20PO 70EO 20)with a smaller PEO/PPO ratio induced a bicontinuous cubic meso-phase (Ia %3

d )with low interfac

e curvature.In addition,a phase transition from Ia %3

d to p 6mm was observed with increasing of th

e phenol/P123molar ratio.80When using the EISA method,

the mesostructure transformed from lamellae to Ia %3

d and then to p 6mm with an increasing phenol/P123ratio,but th

e Im %3

m structure was not obtained,even with a high phenol/P123ratio,due to the small PEO/PPO ratio in P123.In the case of

the F127template,the mesophase shifted from p 6mm to Im %3

m with an increasing phenol/F127ratio.71For the F108template

(EO 132PO 50EO 132)with a much higher PEO/PPO ratio than

F127and P123,only the Im %3

m mesostructure with high inter-face curvature was obtained in the literature.71,90

As mentioned above,carbon sources,templates and cata-lysts are the three main constituents added into the solvent to prepare ordered mesoporous carbons.For carbon sources,phenol,resorcinol,and phloroglucinol/formaldehyde pairs are most commonly used so far;and with the reactivity increasing from phenol to phloroglucinol,lower acid concentrations or slower reacting aldehydes have to be adopted to control the reaction rate.The replacing of conventional precursors and catalysts always aims at decreasing formaldehyde and halogenide pollution,protecting reaction equipment from corrosion,as well as obtaining enhanced organic–organic assembly and various compositions in the mesopore walls.Thus,amino acids and citric acid were used as alternative catalysts;hexamethylenetetramine,furfural and glyoxal were chosen instead of https://www.wendangku.net/doc/546538459.html,anic acids/bases and even solid acids/bases should be used as catalysts in the future.New mesoporous polymeric frameworks,besides phenolic resins,are still needed,in which the melamine resin is a promising candidate.Among many of the diblock copolymer and tri-block copolymer templates,the PEO–PPO–PEO type copolymer remains dominant because of its commercial availability and easy-handling,though the utilization of special surfactants may some-times generate novel pore structures.The rational adjustment of the mesophase is now mainly based on changing the hydrophilic/hydrophobic volume ratio of the system.2.6Pore and morphology control

2.6.1Pore size control.The pore sizes of mesoporous carbon materials mainly depend on the hydrophobic groups in surfactants.As for the conventional PEO–PPO–PEO tri-block copolymers,the pore sizes can be enlarged with the increase of the molecular weight of the hydrophobic blocks rather than those of the copolymers.In the organic–organic self-assembly to mesoporous carbon materials,triblock copolymers,i.e.,F127and P123,are used as the template to produce mesopores.However,the pore size of the obtained carbons is usually smaller than 4nm when phenol/formaldehyde is used as the carbon precursor as a result of the low molecular weights of the hydrophobic blocks of F127or P12

3.52

Adding organic swelling agents is a signi?cant way to expand the pore sizes.The hydrophobic organic species can be solubilized inside the hydrophobic regions of surfactant micelles,which leads to the micelle swelling.The pore sizes are expanded by the additives of large organic hydrocarbons,such as decane and hexadecane.For example,Zhao and co-workers reported that with the aid of hexadecane molecules,the pore size could be enlarged from 3.1to 3.8nm for the 8001C-carbonized sample;when utilizing decane as the swelling agent,the pore size could be further enlarged to 4.1nm.80These results suggest that hydrocarbon molecules with relatively shorter chains have a stronger interaction with the copolymer templates and conse-quently lead to larger pores and a larger lattice parameter.83However,when hydrocarbon molecules smaller than decane,such as 1,3,5-trimethylbenzene,heptane,hexane,etc.,were used as swelling agents in this system,the resulting mesoporous

carbon materials were rather disordered,though the reason for this phenomenon is not yet clear.Considering that the pore size of carbons usually decreased signi?cantly with the increase of the carbonization temperature due to the serious structure shrinkage of the polymeric framework,silicate was combined through a triconstituent co-assembly process into the material network.113The presence of rigid silicates in the nanocompo-sites can greatly reduce structural shrinkage during the carbo-nization.After etching of the silica,carbon with enlarged mesopores of 5.8nm could be obtained.

Since the concentration of the acid and the reactivity of phenols are two key factors that determine the polymerization rate of the phenolic resins,49when phloroglucinol,which is of high reactivity,was employed as the carbon precursor,the pore size of the obtained carbon was enlarged to 19.2nm (Fig.7a and b)using F127or P123as template under high acid concentration (phloroglucinol/HCl molar ratio of 2).89The high acid concentration facilitated the formation of high-molecular-weight phloroglucinol/formaldehyde polymer particles,which randomly distribute around the F127or P123template micelles through hydrogen-bonding (Fig.7),instead of assembling with the PEO segments.In addition,the spherical particle packing preferably reduces the structure shrinkage during the carbonization process,causing pore size enlargement of the ?nal carbons.This indicates that the high acid concentration could e?ciently bene?t the improvement of the porosity and textural properties of the resultant carbon materials,but decrease the pore regularity.In addition,carbons with ultra-large pores of 420nm could be accessible with the use of unusual copolymers with large molecular weight as template,e.g.,PS–P4VP could fabricate large pores with a dimension of 33nm,48PEO–PS revealed large mesopores of B 23nm,105and PEO–PMMA fabricated uniform large meso-pores of B 10.5nm.106

Hierarchical pore structures are bene?cial for special applica-tions.Multimicellar systems can give bimodal pore architec-tures.Carbons with bimodal mesoporous structures consisting of small (3.2–4.0nm)and large (5.4–6.9nm)mesopores could

be produced with the use of the reverse amphiphilic triblock copolymer PO 53EO 136PO 53.107,108Bridging con?guration was energetically favorable for the reverse PPO–PEO–PPO copolymer with a long PEO chain,in which the two outer PPO blocks participated in two sets of intercrossing micelles of di?erent sizes.This resulted in the formation of a unique bimodal pore mesostructure.When monodispersed silica colloidal crystals were introduced to the amphiphilic triblock copolymer/resols system,hierarchically ordered macro-/meso-porous carbons with tunable pore sizes of 230–430nm and interconnected windows with a size of 30–65nm were obtained from a dual-templating approach.114The rigid silica spheres could prevent the shrinkage of the mesostructure during the thermosetting and carbonization procedure,resulting in large cell parameters (B 18nm)and pore sizes (B 11nm).Mean-while,the bimodal porous carbons had large BET surface areas up to 760m 2g à1and large pore volumes of B 1.25cm 3g à1,with partially graphitized frameworks.

2.6.2Morphology control.The morphology of mesoporous carbons is important for industrial applications,for example,released mesoporous carbon microwires and nanowires as lightweight functional ?ller materials,?lms in catalysis and separation,monoliths in optics,and uniformly sized spheres in chromatography.Controllable synthesis on both the meso-scale (mesostructure)and macroscale (morphology)is there-fore necessary.

Since ordered mesoporous carbon is always based on the self-assembly of block copolymers and surfactants.The mesopore arrays thus formed may show a well-developed local order.Morphologies of the mesoporous carbon materials synthesized from the EISA method are usually ?lms and monolithic,whereas the aqueous route usually yields powder carbon materials with particle sizes in the micrometer or millimeter scale.Otherwise,the control over shape and arrangement of the mesoporous entities on a macroscopic scale has also made great progress.The aqueous cooperative assembly route from phenol/formaldehyde and triblock copolymer (F127and P123)under weakly basic conditions produced pellet-like mesoporous carbons in the size range of 1–5mm,rod-like particles ranging from 5to 200m m,and 3D cubic mesoporous carbon FDU-16rhombdodecahedron-like single-crystals with a uniform size of 5m m.115,116The match of the rate between the polymerization of resols and the growth of mesostructured crystals might be responsible for these phenomena.Both the stirring rate and synthesis temperature are key factors for the formation of high-quality single-crystals.The medium temperature (661C)could balance the assembly and condensation;the medium stirring rate (B 300rpm)favored the mass transport for the precipitation of large single crystals.Thus,large single crystals (B 5m m)of body-centered cubic

(Im %3

m )mesoporous carbon with a perfect rhombdodecahe-dral morphology could be obtained (Fig.8).A higher stirring rate (B 500rpm)could result in irregular morphology,while small crystals (1–2m m)were obtained at a lower rate (B 150rpm).No precipitation was observed at a temperature of B 701C,and only irregular crystals were obtained at B 601C.It is highlighted that the body-centered cubic single crystals were formed by a layer-by-layer growth mode from the centers of twelve

{110}

Fig.7(a)Nitrogen sorption analysis,(b)the corresponding pore size distribution,and (c)the formation mechanism of carbon materials with ultra-large mesopores.Reprinted with permission from ref.89.

planes.2D hexagonal mesoporous carbon FDU-15crystals with discus-like morphology have also been fabricated by mixing F127with P123as templates.

Mesostructured carbon ?bers can be obtained by growing within a con?ned space,like in an anodic aluminum oxide (AAO)membrane.117,118To obtain ?bers with well-aligned mesopores,a shear-aligned block copolymer/polymeric matrix is usually needed,i.e.,a phenolic resin/F127composite formed by phloroglucinol/F127complex reacting with formaldehyde.Macroscopic alignment by shearing force,such as spin-coating and ?ber-extrusion produced mesostructured ?lms and ?bers (Fig.9a and b).48,49Martin et al.119reported mesoporous carbon microwires and nanowires by in?ltration of a solvent-free carbon precursor into porous alumina.The removal of the solvents prior to the in?ltration step circumvented the occurrence of macro-scopic phase separation and hydrodynamic instabilities during solvent evaporation from the pores.The mesoporous carbon nanowires released by etching alumina had a pore diameter of B 60nm with lengths of a few tens of micrometers (Fig.9c).The wormy mesostructures could be assembled to more ordered hexagonal mesostructures through controlled solvent evapora-tion or shear force.Both spin-coating and ?ber-extrusion were employed to provide the shear force for synthesizing the meso-porous carbon ?lms and ?bers with more ordered mesostruc-tures.By varying the P123and/or the amount of phenol/formaldehyde resol introduced into the phenolic resin/surfactants system,1D carbon ?bers with a core–shell structure and carbon ribbons with circular mesopores running parallel to the long-itudinal axis of the ribbon were obtained within the AAO membranes (Fig.9d).120Otherwise,biological templates are generally abundant,renewable,inexpensive and environmentally benign compared with arti?cial templates.Considering its unique morphology and structure,natural crab shell was also used to fabricate carbon nano?ber arrays with ordered mesopores (11nm)and macroporous voids (interspacing void of 70nm between nano?bers).121

Aerosol-assisted co-assembly has been regarded as an e?cient and productive route for simultaneously controlling

the morphology and mesostructures.122Mesoporous carbo-naceous polydisperse spheres with diameters from 100nm to 5mm were prepared via an aerosol-assisted organic–organic assembly (Fig.9e).123The pore size and mesostructures can be varied by changing the amphiphilic surfactant and polymeric oligomer assembly process.In order to get the spherical diameters limited to the nanoscale with uniform size,Fang et al.124proposed a low-concentration hydrothermal autoclaving

route and fabricated highly ordered body-centered cubic (Im %3

m )mesoporous carbon nanoparticles with spherical morphology (Fig.9f).The ordered mesostructures were retained while the spherical diameters were tuned from 20to 140nm by simply varying the reagent concentration.A spherical monomicelle assembly process promoted by high-temperature hydrothermal treatment at 1301C was proposed to explain the formation of the ordered mesoporous carbon nanospheres.The low-concentration (ca.10à7mol L à1surfactant)controlled hydrothermal treat-ment was crucial to obtain the nanostructure and con?ne the particle size.

Phenol/formaldehyde oligomers are always elastic but non-sticky.Thus,it is easily molded.When the oligomers and templates are assembled under hydrothermal autoclaving condi-tions,carbonaceous monoliths with certain shapes were usually formed.Huang et al.87hydrothermally synthesized carbonaceous monoliths with a hierarchical macro-mesomicroporous

structure

Fig.8(A,B)SEM images and (C)structural model of mesoporous carbon FDU-16.Reprinted with permission from ref.

115.

Fig.9Mesoporous carbons with di?erent morphologies:(a)the electron microscopy image from the Z -axle of the carbon ?lm in a 4m m ?3m m area (scale bar 1m m),(b)the photo of the carbon sheet fabric,(c)the SEM image of released microwires (scale bar 20m m),(d)the TEM image of the mesoporous carbon nano?ber and nano-ribbon (scale bar 100nm),(e)the SEM image of mesoporous carbon spheres (inset:a TEM image),and (f)the high-resolution SEM image of ordered mesoporous carbon nanospheres.Reprinted with permis-sion from ref.48,49,119,120,123and 124.

by employing F127-P123mixed triblock copolymers as templates and phenolic resols as carbon precursors.Their monoliths showed an ordered 2D hexagonal mesostructure with a uniform pore size of B 3nm,but the synthesis temperature was relatively high (1001C)and the volume shrinkage was as high as 75%during the carbonization process.A low-temperature (501C)autoclaving method was applied to produce crack-free monolithic carbon materials with an ordered mesostructure.86The polymer monolith obtained from this process had a columned shape with a diameter of approx.16mm and length of approx.30mm (Fig.10a and b).Carbonization caused the color of the polymer monolith to change to black,but the columned shape was well retained,and the monolith was crack-free,even when an obvious shrinkage (31%)in size occurred (Fig.10c,12mm in diameter and 21mm in length).A mooncake-like polymer monolith (diameter of approx.21mm and height of approx.7mm)and its corresponding carbon monolith (diameter of approx.17mm and height of approx.5mm)could also be obtained (Fig.10d and e)by changing the size of the Te?on-lined autoclave.The formation mechanism of the monolithic mesoporous carbons is shown in Fig.10f.In comparison,monolithic mesoporous carbon materials prepared through an EISA method were partly cracked with a disordered wormhole-like mesostructure.

The controlled synthesis of mesoporous carbons includes the adjustment of mesopore size,mesophase symmetry,micro-architecture as well as macroscopic morphology of the obtained materials.Despite much progress on changing meso-porous size by adding organic swelling agents,incorporating

rigid silicates and tuning reaction acidity,one can still not obtain very small mesopores (o 3nm)by the direct strategy due to the copolymer templates used.Thus,mesoporous carbons with a much wider pore-size range still needs to be prepared.The micro-architectures,like nanowires,nano-spheres and nanocrystals,can be obtained by a spontaneous process or with external assistance,in which dual templates and an aerosol-assisted method are typical examples.Notice-ably,crack-free monoliths with various macroscopic shapes and high mechanical strength are easy to obtain for meso-porous carbons,which is expected to ?nd broad applications as devices in industrial ?elds.

3.Modi?cation and applications

The applications of nanocasting-synthesized ordered meso-porous carbons have been widely reported in the past few decades.125–130In this section,we discuss only the potentials of direct-synthesized mesoporous carbons after functionalization or not,summarized in Fig.11.Some recent progress is presented as follows.

3.1Pure mesoporous carbons

Dehydrogenation of propane is the main approach to meet the growing demand for propylene.The industrial catalytic processes generally use chromia-or platinum-based catalysts supported on alumina and are promoted with alkali metals.131Although nanocarbons have been found to be e?cient in the oxidative dehydrogenation of ethylbenzene and butane,132,133little e?ort to date has been focused on the direct dehydro-genation reaction over mesoporous carbon materials.Yuan and co-workers reported ordered mesoporous carbons (OMC-1and OMC-2with a similar mesoporous structure)being applied as a new catalyst for the direct dehydrogenation of propane to propylene under steam-free conditions,exhibiting high activity and selectivity,as well as good stability.134The catalytic activity of OMC-1and OMC-2was compared with that of CMK-3,carbon nanotubes and graphite carbon.

Fig.10(a–e)Photographs of the polymeric monoliths (orange)and the corresponding carbon monoliths (black)obtained through the low temperature autoclaving approach after carbonization at 6001C.(f)Formation mechanism of the monolithic mesoporous carbons through di?erent approaches.Reprinted with permission from ref.

86.

Fig.11A summary of various morphologies,modi?cations and potential applications of ordered mesoporous carbons prepared from the direct strategy.

shown in Fig.12,the initial activities (15min at 873K)measured by the conversion for OMC-1and OMC-2were 69.3%and 65.7%with propylene yields of 43.1%and 46.4%,respectively,much greater than that of the CMK-3carbon catalyst (propane conversion of 54.3%with propylene yield of 15%).Poor dehydrogenation activity (only 6.5–9%of propane conversion)was observed for carbon nanotubes and graphite carbon due to the lack of reactant O 2.132,133The propylene selectivity of OMC materials remained stable over a 100h reaction,which is related to the large void volume of the composite available for the gas stream,avoiding local trans-port limitations and hot spots.135The ?nal conversions after 100h were 44.5%,39.3%and 49.8%,with ?nal yields of 37.9%,34.8%and 32.9%and ?nal selectivities of 85.1%,88.6%and 68.0%for OMC-1,OMC-2and CMK-3,respec-tively.The stable propylene yield of higher than 38%over OMC-1was comparable with that of the previously reported Pt/Sn–Ce based catalysts,136and much higher than that of the Pt/Sn based catalysts.137,138

For ordered mesoporous carbon catalysts,the presence of carbonyl/quinone groups is essential for the high catalytic activity and reaction rate.Unsaturated ketonic C Q O groups and quinone groups have substantial electron density at the oxygen atom,which can serve as a Lewis base to activate saturated hydrocarbon propane.132,133,139Propylene is pro-duced and hydroxyl groups (C–OH)remain as intermediates.The reaction cycle is closed by the thermal decomposition of C–OH to C Q O and molecular hydrogen.Meanwhile,deacti-vation of the C Q O active site can be further induced by hydrogen passivation during the prolonged reaction period.140On the other hand,the high catalytic activity of mesoporous carbons can also be related to their unique structure of large porosity that is advantageous for mass transport and good thermal stability,141but the abundance of micropores in CMK-3would hinder the produced propylene coming out of the pores and bring about the subsequent deep cracking,decreasing the propylene selectivity.Monolithic OMC materials were also used for direct dehydrogenation and oxidative dehydro-genation applications,exhibiting high catalytic activity and stability.103,104The basic oxygen groups on the catalyst surface were the active sites for selective dehydrogenation.The regen-eration of the active sites was achieved by oxidation of C–OH

in the oxidative dehydrogenation process and thermal decom-position of C–OH in the direct dehydrogenation process.Due to the highly ordered mesopores of the directly synthe-sized carbons,they exhibit much superiority over conventional carbon materials,such as carbon aerogels,activated carbons and carbon blacks,the most surface area of which is from micropores.Capacitive deionization is being developed as a potential method for removing salts from aqueous solution.142,143Capacitive deionization has many advantages compared with conventional desalination methods,including reversibility,operation at low voltages,the potential for low energy require-ments,and reduction of secondary wastes.144,145Electrodes of low electrical resistivity and high surface area are favorable for a higher ion removal capacity.Tsouris and co-workers synthe-sized mesoporous carbons using both resorcinol/formaldehyde and phloroglucinol/formaldehyde as the precursors,and then assembled the single-cell capacitive deionization reactor for water deionization (Fig.13).146The performance of these mesoporous carbons was compared with that of a carbon aerogel in salt concentrations between 1000and 35000ppm.It was shown that the mesoporous carbons removed up to 15.2–21mg salt per gram of carbon,which was much higher than the 5.8mg salt per gram of carbon removed by the carbon aerogel.The mesoporous carbon-coated electrode exhibited not only a larger ion removal capacity than the carbon aerogel,but also more e?cient removal at a higher temperature.It can be explained that a large majority of the carbon aerogel surface area comes from micropores that cannot be accessed by ions.A higher surface area associated with microporosity does not contribute to a higher ion capa-city because of the electrical double-layer overlapping,144and the microporosity limits mass transport rates and is more susceptible to collapse at higher temperatures.147Therefore,although the carbon aerogel has a relatively high surface area and was previously used in capacitive deionization,142,148its removal capacity is not as high as that of mesoporous materials.Moreover,by incorporation of the macroporosity into the mesoporous carbons,the in?uence of a pore hierarchy on the capacitive deionization process was also investigated.97,146The hierarchical porosity could enable higher active surface areas and increased transport rates of ions through the mesoporous

structure.

Fig.12(a)Conversion and (b)selectivity of the dehydrogenation of propane to propylene over di?erent mesoporous carbons.Reprinted with permission from ref.

134.

Fig.13Single-cell capacitive deionization reactor with two half cells,each of which containing (1)a Plexiglas cover,(2)a current collector,(3)a carbon electrode,and (4)a middle hollow plate.Right:STEM images of the mesoporous carbon-coated graphite electrode materials.Reprinted with permission from ref.146.

Capacitive deionization tests indicated that the material with a meso-/macroporous hierarchical structure was a better electrode than that of mesoporous carbons for the removal of salts from brackish solution due to the faster ion uptake kinetics.97

The ordered mesoporous carbons also exhibited excellent performances in adsorption.Wan and co-workers systemically investigated ordered mesoporous carbons with large pore sizes in the e?cient removal of bulky dye molecules from wastewater,including methylthionine chloride,fuchsin basic,rhodamine B,brilliant yellow,victoria blue B,methyl orange and Sudan G.149The mesoporous carbons were directly added into wastewater without any treatment and adjustment of the pH value.The ordered mesoporous carbons exhibited large adsorption capacities,almost one time higher than those of the activated carbons for basic,acidic and azo dyes,except for large victoria blue B molecules,the adsorption capacity of which was similar on these two types of adsorbents.The adsorption of dyes with a low concentration was also investigated,because this value is a decisive factor for the residue concentration of dyes in water.The adsorption rates of all mesoporous carbons for low-concentration dyes were higher than 99.9%,suggesting complete removal.The adsorption properties for dyes were sensitively dependent on the pore properties and dye molecular sizes,which were proved by using adsorbents with various pore sizes.The desorption of partial adsorbed dyes could be realized by acetic acid elution,and mesoporous adsorbents were stable with well preserved ordered mesostructures,indicative of reusability.149It is found that in the case of adsorption of dyes with large molecular sizes,the mesoporous carbon from the direct strategy with a large pore size,large pore volume,and high surface area is a good candidate.

The adsorption property of mesoporous carbons can also be extended to biological ?elds,such as drug delivery and cell imaging.For example,ordered mesoporous carbon spheres were used for the drug delivery of ibuprofen.124The adsorp-tion amount of ibuprofen in organic solvent was found to increase as the concentration of the mesoporous carbon nano-spheres increased,and the largest quantity reached 30mg g à1in a short time,demonstrating a good adsorption capacity.The cell permeability and the cell viability were investigated to ensure the practicability of the mesoporous carbon spheres as a drug carrier.124The carbon materials were functionalized by ?uorescein isothiocyanate as a tracer before penetrating into living cells.The remarkable luminescence from the cytoplasm of the cells was observed,indicating that the mesoporous carbon nanospheres could enter into the cells.Measurements of the cell viability by the methyl thiazolyl tetrazolium assay revealed that the nanospheres seemed to not be highly cyto-toxic.The cell viability remained above 90%and above 65%after culturing in high concentrations of mesoporous carbon spheres of 50and 100m g mL à1,respectively.Therefore,the large delivery capacity with good cell permeability and high cell viability made the mesoporous carbon spheres promising materials for biological and clinical applications.

The applications of pure mesoporous carbons are relatively limited because of the lack of functional groups or active sites on the pore wall surface.Although some attempts were presented,such as catalytic propane dehydrogenation,capacitive desalination,

dye adsorption and drug delivery,they mainly utilized the uniform pore structure with the high surface area of meso-porous carbons.For more speci?c and e?cient applications,post-treatment of carbons are needed.3.2Functionalized mesoporous carbons

Unlike mesoporous silicates that have plenty of reactive hydroxyls on the surface,the functionalization of carbon is encounters the problems of poor controllability due to the inert surface,and the high-temperature carbonization can eliminate the functional groups and weak C–X bonds.Although functionalization of ordered mesoporous carbons from the direct strategy is still lacking so far compared with that synthesized from the nanocasting strategy,there are some successful illustrations of metallic and non-metallic modi?cation through in situ polymerization or a post-treatment method.

3.2.1Nonmetallic modi?cation.N-doped ordered mesoporous carbons could be utilized as an e?cient oxygen reduction reaction catalyst,potentially useful in polymer electrolyte membrane fuel cells.150N-doped mesoporous carbons were prepared by heat treatment of pre-made mesoporous carbons 69under ?owing NH 3at high temperatures.The reactions between carbon and NH 3involves the replacement of oxygen-bearing species by N-containing groups and the etching of carbon fragments by the radicals generated by the decomposition of NH 3at elevated temperatures.151Con?rmed by the polarization curves of oxygen reduction on N-doped ordered mesoporous carbons,the oxygen reduction reaction activity increased with the NH 3treatment temperature,reaching an onset positional at about 720mV (vs.NHE),which was higher than other reported N-doped irregular mesoporous or microporous carbon catalysts.152,153Pyridinic and graphitic types of nitrogen were believed to be responsible for the oxygen reduction reaction activity.Moreover,N-doped ordered mesoporous carbons were much more stable than the platinum-based electrocatalysts and exhibited a much higher resistance to CO poisoning.Platinum nanoparticles supported on high surface area carbons often su?er from instability due to the corrosion of the carbon support under the operation conditions and the agglomeration and detachment of platinum particles,leading to a decrease in catalytic surface areas.154The higher stability of the N-doped mesoporous carbons was attributed to the nature of its active sites,which were induced by N doping and were less amenable to change by carbon corrosion and other degradation mechanisms that Pt supported catalysts su?er.

N-doped mesoporous carbons can also be used for CO 2capture.CO 2capture has been at the center of interests in the scienti?c community in recent years,this is because of the implications for global warming.155–158The development of e?cient methods for capturing CO 2from industrial ?ue gas has become an important issue.159–163Ordered mesoporous carbons were treated in a NH 3?ow at the temperatures of 650–10001C,102which was demonstrated to be e?ective in introducing basic functionalities that enhanced the speci?c interaction of CO 2and adsorbent.The nitrogen content increased with the temperature from 650to 8001C,reaching a maximum of 4.52wt%,and then decreased with the further

increase of the nitridation temperature.The N-doped carbons contained a large amount of a pyrrolic type of nitrogen,which is useful for CO 2capture.164,165Compared with pristine carbons,the N-doped carbons exhibited enhanced CO 2uptake with the highest CO 2capture capacity of 3.46mmol g à1at 251C and 760mmHg for the 10001C-nitrided sample.Both the textural and surface chemistry in?uenced the CO 2capture performance of the resultant mesoporous carbon adsorbents.102The CO 2capture capacities of the mesoporous carbons nitrided below 8001C were strongly in?uenced by the surface chemistry properties,and the covalently tethered nitrogen functional groups served as Lewis-base active sites for bonding the acidic CO 2;while the capacities of samples nitrided at 900and 10001C were mainly controlled by the adsorption on the narrow micropores,because the useful pyrrole N for CO 2adsorption slowly converted to pyridinic or quaternary N when treated at higher than 8001C.166Therefore,the CO 2capture capacity is considerably enhanced if an adequate and well developed porosity is joined to a favorable chemistry.Besides by ?owing NH 3treatment at high temperatures,Lu and co-workers accomplished the N-doping by employing organic amines during the organic–organic assembly of the resorcinol/formal-dehyde precursor and the F127template.167They prepared ordered mesoporous carbon monoliths with a hierarchical structure in the presence of 1,6-diaminohexane,which led to a N-containing framework.The obtained materials exhibited out-standing CO 2capture and separation capacities,high selectivity,and facile regeneration at room temperature.

Fluorinated mesoporous carbons were synthesized by organic–organic assembly of F127and organic precursors of phenol,formaldehyde,and a functional monomer of p -?uorophenol through the EISA process.168The co-condensation of p -?uoro-phenol,phenol,and formaldehyde ?rst formed F-resols,which assembled with F127during the evaporation of ethanol.Then the thermopolymerization of the phenolic resins was proceeded to solidify the F-phenolic resin/F127nanocomposites,followed by removal of the template and carbonization to give F-containing ordered mesoporous carbons.The obtained ?uorinated carbons possessed highly ordered mesostructures,high surface areas of 693–998m 2g à1and large pore sizes of 3.0–4.4nm.Di?erent mesophases of 2D hexagonal and 3D body-centered cubic struc-tures could be synthesized by tuning the ratios of p -?uorophenol/phenol or phenol/F127.The molar ratio p -?uorophenol/total phenol in the organic precursors could be adjusted from 0to 83%,but the content of p -?uorophenol showed a minor e?ect on the structural regularity.The ?uorinated mesoporous carbons have carbon frameworks with C–F covalent bonds,which could be retained even after high temperature carbonization owing to the high energy.169The ?uorinated carbon-modi?ed glassy carbon electrode exhibited a higher electron transfer rate than both the pure mesoporous carbon modi?ed and bare glassy carbon electrodes.168The high redox ability may be attributed to the integrity of the carbon framework,170large pore sizes and F incorporation,making the F-modi?ed ordered mesoporous carbon materials potentially useful in electrocatalytic reactions.Dai and co-workers developed the method for the post-synthesis phosphorylation of mesoporous carbon materials without a?ecting the adsorption and structural properties of the starting mesoporous carbon support.171The mesoporous

carbons were synthesized through the direct strategy 48and the phosphorylation was accomplished by stirring the obtained carbon supports in phosphoric acid at room temperature.1wt%phosphorus was doped on the mesoporous carbon pore wall.This method did not induce the activation of the original carbons as the ?nal surface areas and micropore volumes were similar to the starting material.The phosphorylation was proposed to be a simple dehydration involving surface hydroxyl species and phosphoric acid.172NH 3-TPD (temperature-programmed desorption)results con?rmed that a total amount of 132m mol NH 3g à1desorbed from the acid sites,arising from the acidic phosphate groups on the mesoporous carbons.Isopropanol dehydration was used as the probe reaction to characterize the catalytic site.The point of 50%conversion of isopropanol was observed at 2451C.Despite the relatively low phosphate contents,the sites were highly active,resulting in similar activity to carbons with higher phosphate contents (3–4wt%)as observed in other work.173Such high activities and selectivities were attributed to the large and uniform mesopores of the carbon materials.

B-incorporated,P-incorporated,and B,P-coincorporated ordered mesoporous carbons were prepared by the direct strategy.85The incorporation was achieved by simply adding boric acid or phosphoric acid or mixed boric acid and phosphoric acid into the reaction solution.Heteroatom-incorporated carbons possessed highly ordered hexagonal mesoporous structures,uniform pore size distributions,and large surface areas ranging from 500to 700m 2g à1.The incorporation of these nonmetal elements could e?ectively limit the framework shrinkage during the carbonization process,which brought about the same e?ect to the incorporation of metal or metal oxide into the carbon framework.84The simultaneous incorporation of B and P not only increased the actual concentration of B and P in the materials compared with that in the solo-incorporated counter-parts because of the interaction between B and P species,174but also facilitated the formation of the mesoporous structure.The formation mechanism of the heteroatom-incorporated meso-porous carbons is shown in Fig.14.Since the reaction was performed in a strong acidic system,the self-assembly of surfactant–polymer nanocomposites could be attributed to the combination of coulombic interactions and hydrogen-bonding interaction.69The nonmetal element-incorporated mesoporous carbons were evaluated as the electrodes of supercapacitors.The results showed that the B-incorporated,P-incorporated,and B,P-coincorporated carbons exhibited superior electro-chemical performances compared to the nonincorporated coun-terpart.It could be explained that the incorporation of P or/and B into the carbon framework not only produced the heteroatom functional groups on the carbon surface,but also yielded additional surface oxygen groups.The high speci?c surface area with ordered mesoporosity and abundant functional groups can contribute to the enhanced capacitance.175–177

SO 3H-functionalized porous carbons are usually used as ?ne powders in catalysis.Xiao and co-workers reported SO 3H-functionalized ordered mesoporous resin and carbon materials.178Sulfonation of the samples was performed by chlorosulfonic acid treatment in CH 2Cl 2.The acid concentrations of the SO 3H-functionalized resin and carbon were con?rmed to be 1.56and 0.91mmol g à1,respectively.The solid acid catalysts

showed high activity in the esteri?cation of acetic acid with butanol,esteri?cation of acetic acid with cyclohexanol,and condensation of benzaldehyde with ethylene glycol.They also exhibited excellent recyclability compared with conventional acid catalysts.Wu and co-workers reported the SO 3H-func-tionalized ordered mesoporous polymers from direct synthesis strategy.179Careful sulfonation of the samples was carried out through a gas–solid reaction,in which the sample powders were contacted with the vapor from 50%SO 3/H 2SO 4.This process was very important for inducing an e?ective but structurally nondestructive sulfonation modi?cation.The concentration of acid sites quanti?ed by an acid–base titration was 2.1–2.5mmol g à1,while the element analyses indicated 1.8–2.2mmol g à1of sulfonic acid groups were attached.The catalytic properties of the solid acids were tested for the liquid-phase Beckmann rearrangement of cyclohexanone oxime as well as the condensation of bulky aldehydes with alcohol.Owing to their large mesopore dimensions (42nm)and considerable amounts of Bro nsted acid sites,they showed superior activity to the conventional acid Dowex resin and many microporous zeolite catalysts.

Surface oxidation is one of the most convenient and simplest methods for modifying the carbon surface,with not only the attachment of oxygen-containing groups,but also alteration of the surface hydrophobic/hydrophilic balance.180–182As a result,the inert and hydrophobic nature with poor wettability and dispersibility in polar solvents of pristine mesoporous carbon materials,which is unfavorable for many applications,can be changed.Zhao and co-workers systematically investigated the pore evolution,mesostructural oxidation resistance,and simultaneous surface functionalization of ordered mesoporous carbon FDU-15under various oxidation conditions.183When wet oxidation was performed by an acidic (NH 4)2S 2O 8solution

as a gentle oxidant,the mesostructural regularity of the products was retained.However,the micropores/small meso-pores were blocked by the attached surface functional groups.Abundant surface oxygen-containing groups,especially carboxylic groups could be generated during oxidation,and the sample became much more hydrophilic and showed a higher adsorption a?nity toward water.The high and strong adsorbed NH 3capacity was also observed,attributed to the surface acidic carboxylic and phenolic groups.When the HNO 3solution was used as a strong oxidant,the blocked micropores could be reopened.(NH 4)2S 2O 8treatment could introduce more carboxylic groups than the HNO 3solution under mild conditions.The mesostructural analogue CMK-3showed much poorer oxidation stability compared with the FDU-15,due to the relatively unstable structure of CMK-3.The surface functionalized mesoporous carbon materials could be used as e?cient adsorbents for heavy metal ions such as Fe 3+,Cu 2+,Cd 2+,Pb 2+ions and organic dyes,and could also be used for drug delivery.

In nonmetallic modi?cation,both the post-treatment and one-pot synthesis method were used.For N-doping,NH 3treatment on pre-made mesoporous carbons and the addition of organic amines during the organic–organic assembly were both e?cient.P-doping could be realized by either dehydra-tion condensation between phosphoric acid and mesoporous carbons or the addition of phosphoric acid during the meso-porous carbon preparation.B-or B,P-coincorporated carbons could be obtained by the one-pot synthesis.Functional groups like SO 3H–and COOH–were usually grafted by post-sulfona-tion and post-oxidation,https://www.wendangku.net/doc/546538459.html,pared with the unfunctionalized pure carbons,these materials are expected to have more speci?c functions.The carbons with a basic surface (N-doping)may favor acidic gas (CO 2)adsorption;while carbons with an acidic surface (phosphorylated carbons)may have a large capacity for basic gas (NH 3)adsorption.The sulfonated carbons can act as a strong solid acid catalyst,and the oxygen-containing groups are useful claws for adsorbates like metal ions and dyes.

3.2.2Metallic modi?cation.A series of highly ordered iridium-containing ordered mesoporous carbons (Ir-OMC)through a one-pot direct strategy were synthesized by adding H 2IrCl 6into the reaction system of resorcinol/formaldehyde polymer and surfactant F127.84H 2IrCl 6was then reduced to metallic Ir by the emitted reducing gases,such as CO and H 2,or were even reduced by carbon itself under a N 2atmosphere.Ir particles,with loading amounts of 2.6–7.7wt%and uniform sizes of B 2nm,were observed on the carbon supports,while the ordered mesostructure of the carbons remained.The high dispersity and the high thermal stability of the Ir particles should result from its imbedding into the carbon matrix during the one-pot synthesis process.Ir-doped mesoporous carbons obtained by post-impregnating the carbon supports with H 2IrCl 6were also prepared for comparison.However,the post-impregnation method led to an uncontrollable and thus polydispersed particle size distribution.Hydrazine (N 2H 4)decomposition was chosen as a probe reaction,which has been widely used in the altitude control of spacecrafts.184–187The N 2H 4conversions on Ir-OMC catalysts attained

100%

Fig.14Proposed mechanism for the multicomponent self-assembly of resorcinol,formaldehyde,F127,and B or/and P precursors.Reprinted with permission from ref.85.

even at 301C,and no decay was observed over a 300min run,demonstrating their high activities and stabilities;while the N 2H 4conversion on the Ir-doped mesoporous carbon catalysts prepared by the post-impregnation method under the same reaction conditions dropped rapidly with the reaction time.The enhanced mass transfer caused by the ordered mesoporosity and the highly dispersed uniform iridium particles both contrib-uted to their outstanding catalytic performance.

Ordered mesoporous carbon-supported calcium oxide materials were synthesized by the three-constitute co-assembly of F127,resol precursor and Ca(NO 3)2through the EISA method.188The obtained materials possessed a 2D hexagonal mesophase with high surface areas of 615–1058m 2g à1and CaO weight percentages of 3.0–20.4%.The CaO particles were anchored within and/or between the mesopore walls of the carbon support with good dispersion when their contents were lower than 13.5wt%;while further increasing the CaO content would lead to larger nanoparticles with obvious aggregation and a less ordered mesostructure.The CaO-loaded carbon materials were used for low-temperature physisorption of CO 2,showing a high adsorption capacity of up to B 5.0mmol g à1at 251C and B 7.0mmol g à1at 01C,which is comparable with the previously reported adsorbents for CO 2capture at low temperatures.189–191Moreover,the CaO-loaded carbon materials delivered good adsorption selectivity for CO 2over N 2.Due to their small particle sizes,the nanocrystalline calcium oxides in the mesoporous carbons were also active for high-temperature CO 2chemisorption,with a high adsorption capacity at 200–5001C (up to B 3.25mmol g à1),high initial conversions (nearly 100%)and fast reaction-based kinetics at 4501C.The cyclic stability was improved due to the con?nement of nanoparticles within the mesopores.188

The loading of magnesium oxides into ordered mesoporous carbons can also lead to the excellent solid base property as well as the enhanced adsorption capacity for CO 2.These materials were prepared by the simple one-pot assembly of triblock copolymer F127,resol,and magnesium nitrate,followed by thermal curing and carbonization.192The periclase MgO nanocrystals with a uniform size of 4.5–13nm were well-dispersed in the carbon framework.The highest incorporation amount of MgO was around 37wt%,and a phase transforma-tion from the hexagonal (p 6mm )to body-centred cubic (Im %3

m )mesostructure occurred as the Mg content increased,which could be explained by a higher MgO content leading to a larger volume ratio of hydrophilic to hydrophobic PEO/PPO.71,80When the MgO particles had sizes larger than the wall thick-ness,they could extend from the carbon walls into the mesopore channels,resulting in a rougher pore surface and a lower degree of mesostructure regularity.Moreover,con?rmed by the CO 2-TPD analysis,the basicity was greatly enhanced due to the incorporation of the Mg species,and the number and strength of the basic sites were quite related to the content of MgO in the resultant solids.The well-structured mesoporosity and the outstanding basic property make these materials promising candidates for selective adsorption and catalysis.

The doping of Fe and Ni species can make the resultant carbon materials magnetically separable.For example,maghemite-loaded ordered mesoporous carbons with superparamagnetism were synthesized via the one-pot co-assembly of F127,resol,

and ferric citrate,followed by thermal curing and carboniza-tion.193The mesoporous materials with a low g -Fe 2O 3content of 9.0wt%,possessed an ordered 2D hexagonal structure with a uniform mesopore of 4.0nm and a high surface area of 590m 2g à1.Maghemite nanocrystals with a small particle size of 9.3nm were con?ned in the matrix of the amorphous carbon frameworks,and their high dispersion was due to the interaction between the iron citrate complex and the phenolic resin matrix during the cooperative assembly process,which was important to avoid the aggregation of iron ions.194The g -Fe 2O 3loaded carbons exhibited excellent superparamagnetic behaviors,and high stability during the H 2O 2oxidation process.They showed a high adsorption capacity of up to 220mg g à1for fuchsin base dye molecules.The large mesopores,with a high pore volume,hydrophilic property after H 2O 2treatment,and magnetic framework for easy separation,make these g -Fe 2O 3-loaded ordered mesoporous carbons promising adsorbents to treat wastewater for industrial use.

Ni-doped ordered mesoporous carbons were synthesized via the co-assembly of resol,tetraethyl orthosilicate,Ni(NO 3)2á6H 2O and F127,followed by carbonization and silicate removal with NaOH etching.195The Ni 2+was reduced to Ni by carbon and/or by the emitted reducing gas CO during the pyrolysis.The magnetic Ni nanocrystals with particle sizes of 16.0nm were con?ned in the matrix of the carbon frame-works.As the Ni,Co and Fe species could act as catalysts for the formation of the graphitic structure during the carboniza-tion step,196–200in some regions of the high resolution TEM image of the Ni-doped mesoporous carbons,the Ni nano-particles were fully crystallized and the carbons nearby were partially graphitized.The incorporation of rigid silicates in the pore walls could reduce the framework shrinkage signi?cantly,creating large mesopores.The obtained material possessed an ordered 2D hexagonal structure with a large mesopore of 6.8nm and a high surface area of 1580m 2g à1.Due to the enlarged mesopores with high surface area for free mass transportation,149these materials showed higher adsorption capacity for fuchsin base (up to 420mg g à1)than pure mesoporous carbon FDU-15(118mg g à1).Moreover,the adsorbents could be easily separated from solution by a magnetic ?eld because of the existence of the magnetic Ni nanoparticles in the framework.Doong and co-workers reported magnetically-separable hierarchically ordered porous carbons with graphitic structures,which were directly synthesized by one-pot dual-templating EISA method.201Polystyrene latex spheres and F127were used as macroporous and mesoporous structure-directing agents,while phenol/formaldehyde resins and Ni species were chosen as the carbon source and graphitization catalyst,respectively.Addition of a nickel species catalyzed the graphitization at relatively low carbonization temperatures under di?erent atmospheres (N 2or H 2/N 2).The graphitic structures in these hierarchically ordered porous carbon materials could be obtained at 800–10001C,which was much lower than the high graphitization temperature of B 20001C without catalysts.202,203The obtained materials contained amorphous carbons in the pore walls and graphitized carbons around the surface of Ni nanoparticles.These carbon materials exhibited improved electrocatalytic activity towards I 3àand I 2reductions in dye-sensitized solar cells with a conversion e?ciency up to 5.2%,

which could be due to the high conductivity and low charge transfer resistance caused by the high graphitization degree.The magnetically-separable materials also showed acid resistance and a high adsorption capacity for methylene blue.201Thus,the doping of a Ni species into mesoporous carbons can not only introduce a magnet property to the composites but also increases the graphi-tization degree at lower temperatures,which is important for electrochemical applications due to the enhanced conductivity.However,the in?uence of the graphitization degree on the adsorp-tion behaviors is not obvious.

Inspired by using ferric citrates as precursors to prepare maghemite-loaded carbons,193other metal citrates were also tested.For example,ordered mesoporous TiC/carbon materials were prepared by the EISA method from resol,titanium citrate,and F127,combined with in situ carbothermal reduction.204The cubic crystalline TiC were con?ned in the matrix of the amorphous carbon pore walls with controllable titanium contents of 12–32wt%,and small particle sizes of 4–6nm.The utilization of titanium citrate as a precursor was crucial to obtain highly dispersed TiC.The polycarboxylate chelated titanium ions,related to titanium citrate and resol involved in the Pechini-like process,61could restrict the aggregation and condensation of the TiO species and the esteri?cation between titanium and the phenol hydroxyl group,205,206while other titanium precursors,such as titanium isopropoxide,would result in serious precipitation and macrophase separation.This method facilitated the absence of the crystalline titanium oxide phase before the formation of TiC nanocrystals by carbo-thermal reduction,and thus the structural ordering was well preserved.The loading of TiC nanocrystals could not only enhance the oxidation resistance ability of the amorphous carbons but also improve their electrical properties,making the resultant solids potentially useful as electrode materials and alternative options for noble metal-supported catalysts.

Unlike nonmetallic doping,the incorporation of a metal species into direct-synthesized mesoporous carbons is often achieved by the one-pot co-assembly of copolymer templates,carbon sources and metal precursors.Metal oxides,like CaO and MgO,can introduce an excellent solid base property and an enhanced adsorption capacity for CO 2;magnetic Fe 2O 3and Ni can make the mesoporous carbon adsorbents or catalysts easily separable.It is still promising for mesoporous carbons to load more kinds of metal species with distinctive functions,including Ir-doped carbons for hydrazine decom-position,CuO/carbons for CO oxidation,noble metal-doped carbons as highly-e?cient catalysts for many reactions and TiC/carbons for electrode materials,etc.Importantly,the incorporation of both nonmetallic and metallic species should avoid damage to the integrity of the chemical and porous structures of the mesoporous carbons.207–210

3.2.3Interpenetrating carbon-based composites.The major component of the above-mentioned mesoporous carbonac-eous materials,functionalized by either metallic or nonmetallic elements,is still carbon,and the heterogeneous species are modi?ed on the carbon surface or/and enchased inside the mesopore wall.However,in some cases,especially carbon–silica nanocomposites,interpenetrating networks of carbon and silica can be accessed with homogenous and continuous

composition with the ratios ranging from zero to in?nity for the two constituents.For example,mesoporous polymer–silica and carbon–silica nanocomposites could be prepared by the triconstituent co-assembly of soluble resols,prehydrolyzed silica oligomers from tetraethyl orthosilicate,and F127.113,211–213Silicate species in the nanocomposite with a complex chemical environ-ment had a relatively high crosslinking degree and some interac-tions with the carbon species,but no Si–C bonding modes were formed.214The ratios of polymer/silica or carbon/silica could be tuned from zero to in?nity by varying the mass ratios of resols to tetraethyl orthosilicate.The synthesized ordered mesoporous materials were con?rmed to have ‘‘reinforced concrete’’-structured frameworks (Fig.15).During the EISA process,resols exhibited low condensation rates under acidic conditions at room temperature,forming nanosized ‘‘concrete’’structures in the nanocomposites.Silicate oligomers not only assembled with the surfactants,but also condensed and cross-linked together around the nanosized resols to generate 3D ‘‘reinforcing-steel-bar’’frameworks.Then the interpenetrating large domain sized polymer resins and silicates shaped during the succedent thermopolymerization with the homogenous composition.The ordered mesoporous carbon–silica nanocomposites can be used as catalyst supports for noble metals,such as palladium,by isochoric impregnation using PdCl 2as the precursor.215The palladium content was about 5wt%.Accessible Pd nano-particles were well dispersed inside the pores with a particle size of about 3nm,which could be explained by the hybrid nature of the carrier.The silica and carbon components uniformly dispersed inside the pore walls to construct a continuous framework.Metallic ions were selectively adsorbed on the surface of silica,while the inert and hydrophobic component carbon possibly played a role in separating https://www.wendangku.net/doc/546538459.html,pared with the pure polymer,silica or carbon supports,the mesoporous carbon–silica nanocomposites were superior.They exhibited a high yield of B 60%for trans -stilbene at 1001C in the Heck coupling reaction of chlorobenzene and styrene,as well as a high yield of 46%for biphenyl at 301C in the Ullmann coupling of chlorobenzene with water as the solvent.The high catalytic activity was also observed when using substituted aryl chlorides in the system.The Pd catalysts supported on mesoporous carbon–silica nanocomposites were stable,which showed negligible metal leaching and could be reused more than 20

times.

Fig.15Formation mechanism of ordered mesoporous polymer–silica and carbon–silica nanocomposites,and the corresponding ordered mesoporous silica and carbon frameworks.Reprinted with permission from ref.113.

有序介孔材料的发展和面临的挑战

有序介孔材料的发展和面临的挑战霍启升吉林大学无机合成与制备化学国家重点实验室，中国吉林长春，邮编：130012 E-mail: huoqisheng@https://www.wendangku.net/doc/546538459.html, 摘要简要介绍有序介孔材料的发现和发展历史，讨论合成、结构、应用等方面所面临的挑战。有序介孔材料有序介孔材料是指孔道规则且有序排列的介孔材料，早在1971年介孔材料的合成工作就已开始，日本的科学家们在1990年之前也已通过层状硅酸盐在表面活性剂存在下转化开始介孔材料合成，1992年Mobil的报导才引起人们的广泛注意，并被认为是介孔材料合成的真正开始。Mobil 使用表面活性剂作为模板剂，合成了M41S 系列介孔材料，包括MCM-41（六方相）、MCM-48（立方相）和MCM-50（层状结构）。经过近二十年的全球性科学家的团结努力和辛苦工作，介孔材料的研究工作发展极快，并且成效显著，涉及到合成、结构、性质、应用等各个方面，参与研究的科学家专业分布极其广泛，介孔材料研究是近年来少有的受人瞩目且快速发展的研究领域。有序介孔材料的优势有序介孔材料的优势在于材料的独特的介孔结构（均一孔道尺寸及形状、高比表面、大孔体积）和合成过程简单，合成可重复，原料价格低廉，容易直接合成各类等级的可控结构，如薄膜、粉末、块体、微球、纤维、纳米级材料、各种微观形貌。介孔材料的组成容易多样化，易掺杂。尤其是二氧化硅基材料，表面羟基反应活性高，容易用各种有机基团修饰。合成化学与结构及性质的研究起初介孔材料的合成化学的研究以介孔二氧化硅材料为主，后来被开展到其它组成。合成机理的研究也是以二氧化硅体系为主要对象，根据不同的合成条件及体系，主要生成机理包括：从层状结构的转化、无机－有机静电作用、表面活性剂分子堆积参数的主导作用的协同自组装、真正液晶模板。在上述机理的指导下，介孔材料合成工作迅速展开。材料组成从硅酸盐系列扩展到非硅酸盐无机系列，后来又到有机－无机杂化材料、有机材料、碳材料。典型的硅酸盐系列材料的骨架为无定形的，具有沸石结构单元的预合成的微粒或晶体可以被用来组成介孔材料的骨架，而有些易结晶的氧化物的介孔材料在合成过程或后处理过程中直接晶化导致介孔材料的骨架含有纳米级晶体。模板剂也从最初简单的阳离子表面活性剂扩展到复杂的阳离子表面活性剂、非离子表面活性剂、高分子聚合物、阴离子表面活性剂，甚至各类非表面活性剂。新模板方法的开发，新合成原料（前驱物）和表面活性剂的选择和组合等仍有许多研究工作需要完成。合成方法也多样化，如evaporation induced self-assembly (EISA)（常被作为合成薄膜材料的首选方法），多种合成策略的运用（如硬模板的应用）。今后介孔材料合成在很大程度上应该从有机合成、高分子聚合、大分子及生物分子的自组装，以及固体材料合成借鉴更多的方法与策略。典型材料从M41S材料发展出包括SBA系列、FDU系列、KIT系列等等。介孔材料的结构也从最初的二维六方相（MCM－41）和立方相（Ia3d，MCM-48）扩展到几乎所有可能的介观结构：p6mm,

介孔碳材料的合成及应用分析研究

介孔碳材料的合成及应用研究李璐 (哈尔滨师范大学> =摘要> 综述了介孔碳材料的合成及应用.关键词: 介孔碳。合成。应用 0 引言介孔碳是近年来发现的一类新型非硅介孔材料, 它是由有序介孔材料为模板制备的结构复制品. 由于其具有大的比表面( 可高达2500m2# g- 1 >和孔容(可达到2. 25 cm3 # g- 1 >,良好的导电性、对绝大多数化学反应的惰性等优越的性能, 且易通过煅烧除去, 与氧化物材料在很多方面具有互补性, 使其在催化、吸附、分离、储氢、电化学等方面得到应用而受到高度重视. 1 介孔碳材料的合成介孔碳的制备通常采用硬模板法, 选择适当的碳源前驱物如葡萄糖、蔗糖乙炔、中间相沥青、呋喃甲醇[ 1]、苯酚/甲醛树脂[ 2]等, 通过浸渍或气相沉积等方法, 将其引入介孔氧化硅的孔道中, 在酸催化下使前驱物热分解碳化, 并沉积在模板介孔材料的孔道内, 用NaOH或HF溶掉SiO2 模板,即可得到介孔碳. 以下介绍几种介孔碳材料的合成方法及性质.

1. 1 CMK- 1 Ryoo首次用MCM- 48为模板合成了介孔碳材料(CMK- 1>. 由于MCM- 48具有两套不相连通的孔道组成, 这些孔道将变成碳材料的固体部分, 而MCM- 48中氧化硅部分则会变成碳材料的孔道. 因此CMK- 1 并不是MCM- 48 真正的复制品, 而是其反转品. 在脱除MCM- 48 的氧化硅过程中, 其结晶学对称性下降[ 3] , 后续的研究表明与所用的碳前驱物有关, 其中一个具有I41 /a对称性[ 4] .1. 2 CMK- 3 使用SBA- 15 合成六方的介孔碳( CMK 3>, 由于二维孔道的SBA- 15孔壁上有微孔, 因图1 孔道不相连的的模板(MCM- 41或1234K 下焙烧的SBA - 15> 制备的无序碳材料( A>。孔道相连的模板( 1173K温度以下焙烧的SBA - 15> 制备的有序介孔碳材料CMK- 3( B>

介孔材料简介

介孔材料简介摘要：介孔材料作为一种新兴的材料在光化学、催化及分离等领域具有十分重要的应用,是当今研究的热点之。本文阐述了介孔材料的研究进展,概述了介孔材料的分类及合成机理,并展望了介孔材料的应用前景，并简要介绍了孔径调节以及改性方法。关键词：介孔材料，模板法，溶胶-凝胶法，合成机理，孔径调节Research development of mesoporous materials Abstract:Mesoporousmaterial is of much use in the fields of photochemistry, catalyst and separationetc, and it is one of hot spots of research. The research p rogress of the mesoporous materials is reviewed in this paper. And the classification and synthesis mechanism of the mesoporousmaterials are also outlined. The potential application foreground of the mesoporousmaterial is discussed as well.And briefly describes the aperture adjustment and modification methods. Key words：mesoporousmaterials; template method; sol - gel methods synthesis mechanism ;aperture adjustment 1 前言人类社会的进步与材料科学的发展密切相关[ 1, 2 ],尤其是近几十年中,出现了许多具有特殊功能的新材料,其中介孔材料就是一种。介孔材料是指孔径为2. 0～50nm的多孔材料,如气凝胶、柱状黏土、M41S 材料。上世纪九十年代以来,有序介孔材料由于其特殊的性能已经成为目前国际上跨学科的研究热点之一[ 3 ]。从最初的硅基介孔材料到其他非硅基介孔材料,各种形貌与结构的介孔材料已制备出来[ 4 ]。目前有关介孔材料的研究还处于起步阶段,制备工艺、物理化学性质=质尚需进一步开展和改进。但是,由于它具有较大的比表面积,孔径极为均一、可调,并且具有维度有序等特点,因而在光化学、生物模拟、催

介孔材料

有序介孔材料有序介孔材料是上世纪90年代迅速兴起的新型纳米结构材料，它一诞生就得到国际物理学、化学与材料学界的高度重视，并迅速发展成为跨学科的研究热点之一。有序介孔材料虽然目前尚未获得大规模的工业化应用，但它所具有的孔道大小均匀、排列有序、孔径可在2－50nm范围内连续调节等特性，使其在分离提纯、生物材料、催化、新型组装材料等方面有着巨大的应用潜力。化工领域有序介孔材料具有较大的比表面积，相对大的孔径以及规整的孔道结构，可以处理较大的分子或基团，是很好的择形催化剂。特别是在催化有大体积分子参加的反应中，有序介孔材料显示出优于沸石分子筛的催化活性。因此，有序介孔材料的使用为重油、渣油等催化裂化开辟了新天地。有序介孔材料直接作为酸碱催化剂使用时，能够改善固体酸催化剂上的结炭，提高产物的扩散速度，转化率可达90％，产物的选择性达100％。除了直接酸催化作用外，还可在有序介孔材料骨架中掺杂具有氧化还原能力的过渡元素、稀土元素或者负载氧化还原催化剂制造接枝材料。这种接枝材料具有更高的催化活性和择形性，这也是目前开发介孔分子筛催化剂最活跃的领域。有序介孔材料由于孔径尺寸大，还可应用于高分子合成领域，特别是聚合反应的纳米反应器。由于孔内聚合在一定程度上减少了双基终止的机会，延长了自由基的寿命，而且有序介孔材料孔道内聚合得到的聚合物的分子量分布也比相应条件下一般的自由基聚合窄，通过改变单体和引发剂的量可以控制聚合物的分子量。并且可以在聚合反应器的骨架中键入或者引入活性中心，加快反应进程，提高产率。生物医药领域一般生物大分子如蛋白质、酶、核酸等，当它们的分子质量大约在1～100万之间时尺寸小于10nm，相对分子质量在1000万左右的病毒其尺寸在30nm左右。有序介孔材料的孔径可在2－50nm范围内连续调节和无生理毒性的特点使其非常适用于酶、蛋白质等的固定和分离。实验发现，葡萄糖、麦芽糖等合成的有序介孔材料既可成功的将酶固化，又可抑制酶的泄漏，并且这种酶固定化的方法可以很好地保留酶的活性。生物芯片的出现是近年来高新技术领域中极具时代特征的重大进展，是物理学、微电子学与分子生物学综合交叉形成的高新技术。有序介孔材料的出现使这一技术实现了突破性进展，在不同的有序介孔材料基片上能形成连续的结合牢固的膜材料，这些膜可直接进行细胞/DNA的分离，以用于构建微芯片实验室。药物的直接包埋和控释也是有序介孔材料很好的应用领域。有序介孔材料具有很大的比表面积和比孔容，可以在材料的孔道里载上卟啉、吡啶，或者固定包埋蛋白等生物药物，通过对官能团修饰控释药物，提高药效的持久性。利用生物导向作用，可以有效、准确地击中靶子如癌细胞和病变部位，充分发挥药物的疗效。环境和能源领域有序介孔材料作为光催化剂用于环境污染物的处理是近年研究的热点之一。例如介孔TiO2比纳米TiO2（P25）具有更高的光催化活性，因为介孔结构的高比表面积提高了与有机分子接触，增加了表面吸附的水和羟基，水和羟基可与催化剂表面光激发的空穴反应产生羟基自由基，而羟基自由基是降解有机物的强

有序介孔材料

有序介孔材料姓名：班级：学号：专业：

摘要：有序介孔材料是上世纪90年代迅速兴起的新型纳米结构材料，它一诞生就得到国际物理学、化学与材料学界的高度重视，并迅速发展成为跨学科的研究热点之一。由于其具有大的表面积和相对大的孔径以及规整的孔道结构，介孔材料在催化、储能和分离吸附领域有独特的应用地位。以下我将主要从有序介孔材料的背景特点、有序介孔材料的应用以及未来展望来介绍一下有序介孔材料。关键词：有序介孔材料、催化领域、储能、分离吸附一、有序介孔材料的背景及特点的简介定义：有序介孔材料是以表面活性分子聚集体为模板，通过有机物与无机物之间的界面作用组装生成的孔道结构规则、孔径介于2-50nm的多孔材料。 1、发展历史 1992年Mobil公司的科学家首次报道合成了MCM（Mobil Com- position of Matter）-41介孔分子筛，揭开了分子筛科学的新纪元。1994年，Huo等在酸性条件下合成出APMs 介孔材料，结束MCM系列只能在碱性条件下进行的历史，拓展了人们对模板法合成介孔材料的认识。介孔材料合成的突破性进展是酸性合成体系中使用嵌段共聚物（非离子表面活性剂)为模板，得到孔径大、有序程度高的介孔分子筛SBA-15 。1996年Bagshaw等采用聚氧乙烯表面活性剂，N0I0非离子型合成路线，首次合成出介孔分子筛Al2O3。其表面积可达600 m2/g，去除模板剂后的热稳定性可达700℃。1998年Wei等首次以非表面活性剂有机化合物（如D-葡萄糖等）为模板剂制备出具有较大比表面积和孔体积的介孔二氧化硅。 2、有序介孔材料的合成目前介孔材料的合成方法主要有硬模板法和软模板法。如下图1是软模板法，图2是硬模板法。

介孔碳材料

介孔碳材料：合成及修饰关键词：嵌段共聚物，介孔碳材料，自组装，模板合成许多应用领域对多孔材料的兴趣是由于他们的高比表面积和理化性质。传统的合成只能随机产生多孔材料，对超过孔径分布几乎是无法控制的，更不用说细观结构了。最新的突破是其它多孔材料的制备工艺，这将导致具有极高比表面积和有序介孔结构的介孔材料制备方法的发展。随着催化剂的发展，分离介质和先进的电子材料被用在许多科学学科。目前合成方法可归类为硬模板法和软模板法。这两种方法都是用来审查碳材料表面功能化取得的进展。 1.简介多孔碳材料是无处不在和不可或缺的，应用于许多的现在科学领域。多孔碳材料被广泛用作制备电池电极、燃料电池、超级电容。作为分离过程和储气的吸附剂，应用于许多重要的催化过程。介孔碳材料的用途在不同的应用中有着直接的联系，不仅仅关系到其优良的物理和化学性能，如导电、热导率、化学稳定性和低密度，而且关系到其广泛的可用性。近年来碳技术已经取得了很大进展，同时也通过开发和引进新的合成技术改变现有的制备方法。多孔碳材料根据其孔径可分为微孔（孔径<2nm）；中孔（2nm<孔径<50nm）；大孔（孔径>50nm）。传统的多孔碳材料，例如活性炭和碳分子筛，被热解和物理或是被有机体化学活化合成的。有机体包括在高温下的煤、风、果壳、聚合物[1-3]。这些碳材料通常在中孔和微孔范围内有广泛的孔径分布。活性碳和碳分子筛已大批量生产并被广泛用于吸附、分离和催化方面。微孔碳材料综述的主要进展包括（a）合成碳材料（表面积高达3000m2g-1）[4,5]使用的氢氧化钾,(b)带有卤素气体的碳选择性反应可控制碳材料产生的微孔大小[6]。后一种方法使用碳化物为碳源，并且卤素气体选择性的除去金属离子。这种化学蚀刻法产生一个具有很窄的粒度分布的微孔。这些碳材料产生的微孔能提供高比表面积、大孔容、吸附气体和液体。尽管微孔材料被广泛应用在吸附分离和催化上，生产使用的方法遭到限制。活性炭微孔材料的缺点（a）由于空间限制规定小孔径使分子运输速度缓慢，（b)低电导率的产生是由于表面官能团的缺陷产生的，（c）多孔结构被高温或石墨化破坏。为了克服上述这些限制努力寻求其他的合成方法，方法如下：（a）通过物理或组合物理/化学方法的高度活化,[1,7-9]（b）碳前躯体碳化是热固性组成成分之一，也是热不稳定性成分，[10,11]（c）催化剂辅助活化碳前驱体与金属（氧化物）或有机金属化合物，[9,12-14]（d）碳化气凝胶或冷冻，[15,16]（e）通过浸渍硬模板复制合成介孔碳，碳化和模板拆除。[17,18]（f）自组装通过缩合和碳化使用软模板[19-21]。方法a之d只会导致介孔碳材料有广泛孔径分布（PSD）和可观微孔[9,22]。因此，这些方法都缺乏吸引力。值得重新审查的是方法e和方法f，这两种方法与有良好控制孔径的介孔碳材料的合成有关联。方法e涉及预合成的有机或无机模板的使用，也被称为硬模板合成方法。这些模板主要是作为介孔碳的模具材料，并且没有明显的化学作用采取前体之间发生模板和碳化[23]。相应的多孔结构是由有明确定义的纳米结构模板预定的。反过来，方法f涉及软模板，通过生成有机分子自组装纳米结构。相应的孔径结构确定合成条件，如混合比、溶剂和温度。虽然该术语"软模板"尚未正式确定，软模板法在本次审查是指自组装模板。软模板法不同于有机自组装硬模板法，分子或基团被操纵在分子能级和被组织成纳米空间氢键或疏水/亲

有序介孔材料应用

T. J. Pinnavaia：采用非离子取代先前的CTAB或CTAC离子型表面活性剂合成了无序的介孔分子筛HMS与MSU G. D. Stucky：SBA-n系列分子筛篇篇都上Nature和Science，霍启升，赵东元，Yang Peidong。介孔材料的合成机理上（和霍一起干的），以及三篏段共聚物为模板合成水热稳定的介孔材料（和赵一起的，特别是SBA－15）。 Ryoo：韩国这边Kaist，介孔碳分子筛介孔薄膜的合成：无疑sol－gel 的大师人物该出来说话了。其中Brinker C. J.和Sanchez C.无疑是最杰出的。Brinker搞有机硅的溶胶凝胶出来的，工作当然主要集中在介孔SiO2薄膜上有序介孔材料直接作为酸碱催化剂使用时，能够改善固体酸催化剂上的结炭，提高产物的扩散速度，转化率可达90％，产物的选择性达100％。除了直接酸催化作用外，还可在有序介孔材料骨架中掺杂具有氧化还原能力的过渡元素、稀土元素或者负载氧化还原催化剂制造接枝材料。这种接枝材料具有更高的催化活性和择形性，这也是目前开发介孔分子筛催化剂最活跃的领域。有序介孔材料由于孔径尺寸大，还可应用于高分子合成领域，特别是聚合反应的纳米反应器。由于孔内聚合在一定程度上减少了双基终止的机会，延长了自由基的寿命，而且有序介孔材料孔道内聚合得到的聚合物的分子量分布也比相应条件下一般的自由基聚合窄，通过改变单体和引发剂的量可以控制聚合物的分子量。并且可以在聚合反应器的骨架中键入或者引入活性中心，加快反应进程，提高产率。

在环境治理和保护方面用于降解有机废料，用于水质净化和汽车尾气的转化处理等。在高技术先进材料领域，用于贮能材料用于功能纳米客体在介孔材料中的组装。国际上纳米领域：王中林，夏幼南，杨培东 1. 介孔材料的诞生－－1992年MS41系列分子筛(典型的是MCM-41,MCM-48,MCM-50)的合成（严格来讲，应该是1991年日本人合成出来）：Nature. 1992, 359, 710-712（J. S. Beck） J Am Chem Soc. 1992, 114: 10834-10843（J. S. Beck） Science. 1993, 261: 1299-1303(霍启升） 2.介孔材料制备的另一里程碑－－1998年赵东元合成了SBA-15 Science. 1998, 279: 548-552（赵东元） J. Am. Chem. Soc. 1998, 120, 6024-6036 （赵东元） 3.通过硬模板法合成炭基介孔材料，也是一大重要成绩－－1999年由韩国人刘龙完成： J Am Chem Soc. 2002, 124: 1156-1157( Ryoo R.) 介孔相关的几个牛人的课题组： https://www.wendangku.net/doc/546538459.html,/mrl/info/publications/（G. D. Stucky) https://www.wendangku.net/doc/546538459.html,/~pinnweb/（Thomas J. Pinnavaia） https://www.wendangku.net/doc/546538459.html,/staff/GAO/flashed/menu.htm（Ozin's group）https://www.wendangku.net/doc/546538459.html,/~dyzhao/（赵东元） http://rryoo.kaist.ac.kr/pub.html (韩国刘龙（R. Ryoo）) https://www.wendangku.net/doc/546538459.html,.sg/~chezxs/Zhao/publication.htm（新加坡赵修松Xiusong Zhao) http://www.ucm.es/info/inorg/inv... iones/2001/2001.htm (西班牙M. Vallet-Regi 首先把介孔材料应用到药物缓释）因为以前不小心把自己的收藏夹弄没了，所以有还有几个课题组现在没有了链接，但是其课题负责人还是记得：台湾的牟中原和他的弟子林弘平；上海硅所的施剑林；吉林大学的肖丰收和裘式伦；大化所的包信和（涉及得不多）推荐几篇介孔材料重要的综述： Chem. Mater. 1996, 8, 1147-1160 Surfactant Control of Phases in the Synthesis of Mesoporous Silica-Based Materials(Stucky和霍启升表面活性剂的堆积参数和结构的关系） Chem. Rev. 1997, 97, 2373-2419 From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis（主要介绍介孔作催化载体的应用） Chem. Rev. 2006, 106, 3790-3812 Advances in the Synthesis and Catalytic Applications of Organosulfonic-Functionalized Mesostructured Materials

有机高分子有序介孔材料的研究现状

有序有机高分子介孔材料的研究进展及应用前景冯恩科091623 （同济大学材料科学与工程学院，上海201804）摘要：有序有机高分子介孔材料是当前具有广泛应用前景的一类新材料，在分离提纯、生物材料、化学合成及转化的催化剂、超轻结构材料等许多领域有着潜在的用途，成为了当今国际上的一个研究热点。本文阐述了有序有机高分子介孔材料目前的研究进展，概述了介孔材料的分类、有序有机高分子介孔材料的合成方法、表征手段，应用，展望了有序有机高分子介孔材料的应用前景。关键词：有序有机高分子介孔材料合成方法表征方法应用 The research development and application prospects of polymericordered mesoporousmaterials FENG Enke 091623 （School of Materials Science and Engineering, Tongji University ,Shanghai 201804）Abstract:As a class of new materials ,polymeric ordered mesoporous materials , which possess current wide prospects for potential uses , such as separation and purification , biological material , chemical synthesis and conversion catalysts , the materials of ultra - light structure and many other areas , have become an international hot spot . In this article , the research development of polymeric ordered mesoporous materials is introduced. Many aspects of polymeric ordered mesoporous materials are outlined , such as classification , synthesis methods, characterizing methods , and applications. It is showed that the polymeric orderedmesoporous materials have wide applicationprospects. Key words:polymeric ordered mesoporous materials;synthesis methods; characterizing methods ; applications 1、前言多孔材料的最初定义源自于其吸附性能，分子筛(molecular sieve) 即得名于此，McBain 于1932年提出，用于描述一类具有选择性吸附性能的材料。因此，通常以孔的特征来区分不同的多孔材料，国际纯粹和应用化学协会( IUPAC) 根据多孔材料孔径（d）的大小，把多孔材料分为三类，微孔材料(microporous materials ，d < 2 nm) 、介孔材料(mesoporous materials ，2 < d < 50 nm) 和大孔材料(macroporous materials ，d > 50 nm) ，而根据结构特征，多孔材料可以分为两类:无序孔结构材料(无定形) 和有序孔结构材料(一定程度有序) 。

酶在有序介孔材料上的固定化

84 CPCI 中国石油和化工化工设计酶在有序介孔材料上的固定化焦志勇（南京工业大学　江苏南京　211800）摘要：目前，对酶在有序介孔材料上的固定化研究取得了巨大进步，研究人员通过对酶在有序介孔材料上固定化的研究，发现了各种方法的优缺点及其在实践中的应用。这对石油的开采和利用具有重要的意义。具体分析石油受有序介孔材料固定化酶的活性及因素的影响，并分别讨论了这些因素，以促进酶在有序介孔材料上固定化的发展，进一步挖掘固定化酶潜在的应用价值，使之最大限度地为现代化石油工业服务。关键词：有序介孔材料石油酶固定化 1 酶固定化的意义酶广泛应用于各种领域，它是一种生物催化剂，具有很高的专一性。需在温和的条件下反应，具有很高的催化效率。但因游离酶自身的特点，其应用容易受到限制。它具有难以回收、稳定性差、不易循环利用和易混入产品等特点。经过实践表明，酶固定化后，酶的热稳定性和PH 稳定性会大大提高，在各种领域被广泛应用。因此，对酶在有序介孔材料上的固定化研究具有重要的现实意义，且发展前景广阔。 2 酶在有序介孔材料上的固定化概括近几年，酶在有序介孔材料上的固定化有很多载体，常见的有：天然产物、凝胶、分子筛及树脂等。在物理和化学性质上面，无机载体比有机载体具有较大的优势。有序介孔材料是一种无机材料，具有很多优势，例如：它具有可以调变的孔径，化学稳定性高，成本低等特点。被广泛应用于各行各业。有序介孔材料的发现，使它作为一种新的载体，在酶的固定化方面具有很大的发展前景。 3 酶在有序介孔材料上的固定化方法目前，酶在有序介孔材料上的固定化方法主要有3种，分别为：化学键合法、包埋法和直接物理吸附法。 3.1 化学键合法有机集团能够在温和条件下，在载体表面上与酶反应，这是化合键合法固定化酶的前提。其中有机集团可以是：乙烯、羧基、氨丙基和环氧基等。通过后嫁接法和共聚合法这两种方法可以在有序介孔材料表面引入有机集团。后嫁接法的特点是：对有序介孔材料表面的修饰不均匀，外表面上有大量的修饰基，因此，将大量的酶固定到载体外表面上及孔道口处，会使更多的酶受到阻碍，不能进入有序介孔材料的孔道。化学键合法固定化酶的优点是：固定化酶的操作稳定性大大提高了。有序介孔材料化学键合法固定化酶经过修饰后，对尺寸有一定的选择性。 3.2 包埋法包埋法是指在有序介孔材料的孔道内部吸附酶分子，使孔口尺寸改变，且小于酶分子直径，从而达到在有序介孔材料孔道内将酶包埋在的目的。这种方法的使用，可以有效避免物理吸附方法中酶的脱落。生物学家在缓冲剂溶液中放入MCM-41及胰蛋白酶，使酶吸附在载体上，在分离载体及溶液后，继而进行硅烷化修饰，修饰用的酶为3-氨丙基三乙氧基硅烷。这种方法的目的是减少孔口直径，使酶很难从载体孔道内流出。经过研究发现，包埋法能够避免酶分子从孔道内流出，但对酶而言，由于硅烷化反应条件剧烈，酶会失去活性。此外由于有序介孔材料的孔道口直径减小，反应产物及底物出入孔道受到限制，从而降低了固定化酶的活性。 3.3 直接物理吸附法直接物理吸附法是指：将有序介孔材料和酶溶液充分接触，在载体上吸附到酶。这由于它主要依靠载体与酶之间的范德华力和静电吸引力，酶的结构不易受到影响，且不易破坏酶的活动中心和高级结构。因此，这种方法使酶的活性不易损失。但是，因为有较弱的酶固定化作用力，所以当温度、溶液离子强度和PH 值、及剧烈搅拌等条件改变时，酶分子很容易从有序介孔材料的载体上脱落。通过对直接吸附在纯硅和SBA-15上胰蛋白酶的研究发现，酶极易从载体上脱落，在缓冲液中搅拌2小时后，有32%-35%的酶会脱落。对酶在有序介孔材料上的直接物理吸附法的研究表明，酶的直接物理吸附对尺寸有一定的选择性。在有序介孔材料SBA-15上固定化粗脂肪酶，粗脂肪酶中含有脂肪酶和蛋白酶，最终发现在SBA-15上有90%的脂肪酶被吸附，但在载体上吸附的蛋白酶量仅为20%。此外，酶吸附在有序介孔材料孔道内，可以使酶的稳定性提高。酶只有进入介孔材料的孔道内部，介孔分子筛的大孔容积和大比表面积才能被酶有效地利用。因为酶的吸附形式和吸附速度对酶的固定化效率有很大的影响，所以应加大对酶的吸附形式和速度的研究。 3.4 酶的其他固定化法这种方法主要是将其他一些新型的固定化法与以上3种固定化方法结合起来。例如冷冻真空吸附法及先吸附再交联的方法等。冷冻真空吸附法与普通的方法相比，使固定化酶在载体上具有较高的吸附量、稳定性及活性。先吸附再交联的方法能有效地阻止酶从分子筛孔道内流出来，固定化酶不会因为溶液的剧烈搅动，而改变其活性。 4 总结对有序介孔材料上的固定化酶的研究，大大提高了对石油的开采和利用效率。在石油、医药等方面具有广阔的发展前景，对我国的经济发展将产生重要影响。我们应加大对这种技术的研究，使它广泛应用于各种领域。有序介孔材料上的固定化酶在石油领域具有重要的研究价值。另一方面，因为载体与酶之间有多种相互作用力，这些作用力的有效利用，能提高载体上生物酶的附着力，从而使固定化酶的稳定性大大提高，在石油的开采和利用方面能起到举足轻重的作用。参考文献：[1] 许云强，有序介孔材料对脂肪酶的固定及对药物控释的研[J]山东轻工业学院学报.2009 [2] 田修营，何文，赵洪石等.介孔材料的研究进展及应用前景[J].山东轻工业学院学报.2008.

介孔碳材料及负载金属催化剂表征

介孔碳材料及负载金属催化剂表征摘要：介孔材料作为纳米材料的一个重要发展,已成为国际科技界普遍关注的新的研究热点.本文综述了以氧化铝、活性炭为载体负载镍基催化剂的研究方法。 1．前言近几年来，介孔材料作为一种新兴的材料在光化学、催化及分离等领域具有十分重要的应用，是当今研究的热点之一。按照国际纯粹与应用化学协会(IUPAC)的定义，孔径在2-50nm范围的多孔材料称为介孔(中孔)材料。按照化学组成，介孔材料可分为硅基和非硅基组成两大类，后者主要包括碳、过渡金属氧化物、磷酸盐和硫化物等，由于它们一般存在着可变价态，有可能为介孔材料开辟新的应用领域，展示出硅基介孔材料所不能及的应用前景[1]。按照介孔是否有序，介孔材料可分为无定形(无序)介孔材料和有序介孔材料[2]。前者如普通的SiO2气凝胶、微晶玻璃等，孔径范围较大，孔道形状不规则；后者是以表面活性剂形成的超分结构为模板，利用溶胶-凝胶工艺，通过有机物和无机物之间的界面定向导引作用组装成一类孔径约在1.5-30nm，孔径分布窄且有规则孔道结构的无机多孔材料，如M41S等。介孔材料的特点在于其结构和性能介于无定形无机多孔材料(如无定形硅铝酸盐)和具有晶体结构的无机多孔材料(如沸石分子筛)之间,其主要特征[3]为：具有规则的孔道结构；孔径分布窄，且在1.5-10 nm之间可以调节；经过优化合成条件或后处理，可具有很好的热稳定性和一定的水热稳定性；颗粒具有规则外形，且可在微米尺度内保持高度的孔道有序性。现阶段有多种方法可对介孔材料进行表征。差热/热重(DTA/TG)分析可用于表征物质表面吸附、脱附机理及晶型转变温度，并可鉴别中间体。X射线衍射分析(XRD)法是利用衍射的位置决定晶胞的形状和大小，以及晶格常数。透射电镜(TEM)是在极高、极大倍数下直接观察样品的形貌、结构、粒径大小，并能进行纳米级的晶体表面及化学组成分析。而气体吸附测试(Adsorption measurement)法则是通过向介孔材料中通人氮气等气体来测试其孔径[4]。对介孔材料中装载纳米微粒的表征，同样可以借助许多经典及现代测试手段获得。如利用X射线衍射及广延X射线精细结构能得到孔穴中纳米微粒的元素组成、离子间距及尺寸形

介孔材料常用的表征方法[1]

介孔吸附材料常用的表征方法摘要：介孔材料具有优越的性能和广泛的应用价值，成为各个领域研究的热点。本文简单介绍了介孔材料在吸附方面的应用以及常用的表征方法，如XRD、电镜分析、热重分析、BET法等。关键词：介孔材料、吸附、XRD、BET、电镜分析介孔材料是一种具有多种优良性质，应用广泛的新型材料。新型介孔吸附材料具有吸附容量大，选择性高，热稳定性好等[1]优点，成为研究的热点。对于气体的分离，如CO2的吸附（缓解温室效应）具有重要意义。 1.介孔吸附材料的简介 1.1介孔材料介孔材料是一种多孔材料，IUPAC分类标准规定孔径2.0～50nm的为中孔，也就是介孔[2]。随着不断深入的研究，从最初的硅基介孔材料到现在各种各样的非硅基介孔材料被制备出来，并广泛应用于催化剂制备，新型吸附材料等行业。最初的介孔材料源于沸石，沸石是指多孔的天然铝硅酸盐矿物。这类矿物的骨架中含有结晶水，骨架结构稳定，在结晶水脱附或吸附时都不会被破坏掉[2]。后来人们根据沸石的性质结合实际需要相继合成了人造沸石（分子筛）。目前以SiO2为基础合成的介孔材料成为国际众多领域研究的热点。主要的研究方法是通过浸渍的方法在分子筛上负载相应的有机物分子，优化分子筛的表面特性，如较高的吸附容量，好的选择性及较多的活性位等，在生物材料，吸附分离，催化，新型复合材料等领域具有重要的应用价值和前景。介孔材料具有独特的有点[3,4]：①孔道高度有序，均一性好，孔道分布单一，孔径可调范围宽。②具有较高的热稳定性和水热稳定性。③比表面积大，孔隙率高。④通过优化可形成具有不同结构、骨架、性质的孔道，孔道形貌具有多样性。 ⑤可负载有机分子，制备功能材料。 1.2新型吸附材料上世纪90年代，Mobil Oil公司以二氧化硅作为主要氧化物，用长链烷基伯胺作模板剂，水热法制备出含有均匀孔道，孔径可调，呈蜂窝状的MCM-41介孔材料。它具有孔道呈六方有序排列、大小均匀、孔径可在2～10nm内连续调节，比表面积大等特点[2]，对于开发新型的吸附剂具有重要意义。目前，研究的热点是由负载改性的介孔材料制备出选择性高、吸附容量大、热稳定性好、再生容易的复合吸附材料。研究较多的是用有机胺改性的MCM-41和SBA-15介孔材料制备高效的CO2吸附剂[5]。研究发现二异丙醇胺通过浸渍的方法负载到MCM-41和SBA-15上可显著提高其吸附容量，XRD图像说明负载前后的吸附剂孔径结构并未发生改变，负载不同的胺可得到不同的吸附效果[6]。 2.常用的表征方法

介孔材料合成方法

三维介孔材料SBA-16的制备分别称取12 g F108和31.44 g硫酸钾放入500 mL烧杯中，加入360 g浓度为2 M的盐酸。在室温下（25 °C）搅拌4 h，使表面活性剂全部溶解并且分散均匀后，将温度升至38 °C。待恒温后，在剧烈搅拌下，逐滴加入25.2 g正硅酸乙酯（TEOS），连续搅拌20 min后停止。静置保持反应物24 h，整个过程维持38 °C 不变。所得白色粉末，通过离心进行收集（转速5000 rpm）,用去离子水洗涤6次，并在烘箱中40 °C干燥。表面活性剂在500 °C空气中焙烧5 h去除，升温速度控制在2 °C /min。二维介孔二氧化硅材料SBA-15的制备室温下，将1 g P123和2.24 g KCl溶于30 g 2 M的盐酸中，当搅拌至均一溶液后，逐滴加入2.08 g正硅酸乙酯（TEOS）,并强烈搅拌30 min。静置24 h 后，把所得混合物转移至带聚四氟乙烯衬套的不锈钢反应釜中，100 °C晶化24 h。自然冷却后，经抽滤，反复洗涤，在烘箱中过夜烘干。三维介孔二氧化硅材料SBA-16的制备在45 °C下，将4.0 g F127和8.0 g浓盐酸（37 wt%）溶于192 g蒸馏水中。在搅拌均一后，加入12.0 g 正丁醇，并强烈搅拌1 h。逐滴加入18 g正硅酸乙酯（TEOS）后，在相同温度下搅拌24 h。将所得混合物转移至带聚四氟乙烯衬套的不锈钢反应釜中，100°C晶化24 h。自然冷却，经抽滤，反复洗涤，所得粉末样品在烘箱中过夜烘干。 MCM-41的合成将4.38 g CTAB加入到含1.10 g NaOH的200 g蒸馏水中。室温搅拌使其完全溶解，逐滴加入5.21 g TEOS，并继续搅拌24 h。将混合物转移至带有聚四氟乙烯内衬的反应釜中，在110 °C条件下晶化24 h。所得产物抽滤后，用蒸馏水反复冲洗直至滤液呈中性，将产物干燥。介孔二氧化硅分子筛KIT-6的制备

介孔材料概述

关于介孔材料的综述人类社会的进步与材料科学的发展密切相关[ 1, 2 ],尤其是近几十年中,出现了许多具有特殊功能的新材料,其中介孔材料就是一种。介孔材料是指孔径为2. 0～50nm的多孔材料,如气凝胶、柱状黏土、M41S 材料。上世纪九十年代以来,有序介孔材料由于其特殊的性能已经成为目前国际上跨学科的研究热点之一[ 3 ]。从最初的硅基介孔材料到其他非硅基介孔材料,各种形貌与结构的介孔材料已制备出来[ 4 ]。目前有关介孔材料的研究还处于起步阶段,制备工艺、物理化学性质=质尚需进一步开展和改进。但是,由于它具有较大的比表面积,孔径极为均一、可调,并且具有维度有序等特点,因而在光化学、生物模拟、催化、分离以及功能材料等领域已经体现出重要的应用价值。有序介孔材料具有较大的比表面积,相对大的孔径以及规整的孔道结构,在催化反应中适用于活化较大的分子或基团,显示出了优于沸石分子筛的催化性能。有序介孔材料直接作为酸碱催化剂使用时,能够减少固体酸催化剂上的结炭,提高产物的扩散速度。另外,还可在有序介孔材料骨架中引入金属离子及氧化物等改变材料的性能,以适用于不同类型的催化反应。一、介孔材料的概述介孔材料是指孔径介于2-50nm，具有显著表面效应的多孔碳。由其定义可知，介孔材料不仅指孔径大小和纳米尺度，孔隙率和表面效应也是一个重要参数。介孔材料的平均孔径和孔隙率可在较大范围内变化，这取决于所研究的与表面有关的性能。对于具有介观尺度孔径

2-50nm的介孔固体，对应的临界表面原子分数大于20％，其最小孔隙率必须大于40％。一般，平均孔径越大，最小的孔隙率也越大。纳米颗粒复合的介孔碳的复合体系，是近年来纳米科学应用性越来越引人注目的前沿领域。例如，在水的净化处理中采用复合介孔碳可使净化效率大大提高，光电碳中使用复合介孔碳有利于新功能的发挥等等。二、介孔材料的分类按照化学组成分类，介孔碳一般可分为硅系和非硅系两大类。 1. 硅基介孔材料孔径分布狭窄，孔道结构规则，并且技术成熟，研究颇多。硅系材料可用催化，分离提纯，药物包埋缓释，气体传感等领域。硅基材料又可根据纯硅和掺杂其他元素而分为两类。进而可根据掺杂元素种类及不同的元素个数不同进行细化分类。杂原子的掺杂可以看作是杂原子取代了原来硅原子的位置，不同杂原子的引入会给材料带来很多新的性质，例如稳定性的变化、亲疏水性质的变化、以及催化活性的变化等等。 2. 非硅系介孔材料主要包括过渡金属氧化物、磷酸盐和硫化物等。如TiO2、Al2O3 、ZnS[5]、磷酸铝铬锆(ZrCrAlPO)和磷酸铝铬(CrAlPO)[6],它们一般存在着可变价态，有可能开辟介孔材料新的应用领域。由于它们一般存在着可变价态，有可能为介孔材料开辟新的应用领域，展示硅基介孔材料所不能及的应用前景。例如：铝磷酸基分子筛材料中部分P被Si取代后形成的硅铝磷酸盐

有序介孔材料的合成

?封面故事? 有序介孔材料的合成赵东元教授介孔材料具有高度有序的纳米孔道、超高的表面积和丰富迷人的介观结构,在多相催化、吸附分离、传感器、光电磁微器件、纳米器件等高新技术领域具有广阔的应用前景,受到了人们的广泛重视。介孔材料科学已经成为国际上跨化学、物理、材料等多学科的热点前沿领域之一。复旦大学赵东元教授课题组在有序介孔材料的合成和结构研究领域取得了丰硕的成果。他们合成了一系列以复旦大学命名(F DU 系列)的新型介孔分子筛材料,被很多国际同行使用和研究。他们提出了普适的“酸碱对”路线,按无机物的酸碱性(p K a )大小进行反应配对,控制金属离子的水解,成功地合成了一系列高质量、热稳定的、大孔径的、高度有序的、各种组成的、多种结构的非硅介孔氧化物、混合氧化物、金属磷酸盐(硼酸盐)、混合金属磷(硼)酸盐等介孔分子筛。最近,他们又选用一种低分子量可溶性的酚醛树脂为高分子前驱体,商品化的三嵌段聚合物PEO 2PPO 2PEO 为模板,通过溶剂挥发诱导有机—有机自组装,制备了一类高有序度的高分子和碳介孔材料,分别命名为FDU 214(Ia 3d )、FDU 215(p 6m )和FDU 216(I m 3m )。采用PPO 2PEO 2PP O 型和PEO 2b 2PS 型嵌段共聚物为模板分别得到了介孔碳F DU 217(Fd 3m )和FDU 218(Fm 3m )。同时,利用水相下嵌段共聚物与酚醛树脂的有机—有机自组装,也成功地合成出了介孔碳材料(F DU 214,15和16),使得介孔碳的大批量制备成为可能。另外,通过控制条件还制备了介孔碳F DU 216单晶。在上述研究的基础上,他们还将有机—有机自组装方法,扩展到三元共组装体系,成功地合成出了有序介孔高分子—氧化硅和碳—氧化硅纳米复合材料,得到了具有开放孔道的有序介孔高分子和碳材料(见封面),打破了传统的硬模板合成的限制,推动了有序的碳介孔材料在吸附、分离、催化剂载体、电极材料和储氢等领域的应用。该系列成果发表在《自然?材料》(N a tu re M a teria ls )、《德国应用化学》 (A nge w.Che m.In t .Ed )、《美国化学会志》(J.Am.Che m.S oc .)、《化学材料》 (Che m.M a ter .)等国际权威刊物上,得到了国际相关领域的关注。 (复旦大学先进材料实验室) 1 51? 1994-2009 China Academic Journal Electronic Publishing House. All rights reserved. https://www.wendangku.net/doc/546538459.html,

介孔材料

介孔材料化学系 0801 顾天宇 09 介孔材料是指孔径为2.0～50nm的多孔材料,如气凝胶、柱状黏土、M41S材料。按照化学组成分类，可分为硅基和非硅基两大类。按照介孔是否有序分类，可分为有序和无序介孔材料。介孔材料的制备主要有模板法、水热法、溶胶- 凝胶法等几种方法。模板法： 1)阳离子表面活性剂阳离子表面活性剂作模板剂,在介孔材料制备中的应用较为普遍,常采用三甲基季铵盐(ATMA)为结构导向剂,在水热体系中用合成时,通过改变合成条件可得到不同结构的介孔材料。如Ch. Danumah等利用十六烷基三甲基氯化铵/十六烷基三甲基氢氧化铵和乳胶粒子作为模板剂,制备出具有中孔和大孔分层孔结构的硅基分子筛。使用长链烷基季铵盐阳离子表面活性剂合成出的介孔材料比较单一,通常仅限于M41S型类似结构的介孔分子筛,孔径只有2～5 nm,孔壁较薄,提高材料的水热稳定性是其应用开发研究的首要问题。闫欣等报道,以低聚季铵盐表面活性剂作为模板剂,在中性条件下,合成了结构高度有序的介孔硅铝酸盐材料MCM - 41。由于低聚表面活性剂的端基电荷密度高、CMC值小、在水中的自组装能力强,因而可以在低温、低表面活性剂浓度下合成有序性较高的介孔材料。 2)阴离子表面活性剂阴离子表面活性剂主要是长链烷基硫酸盐、长链烷基磷酸盐和羧酸盐等,常用于合成具有阳离子聚合过程的无机材料,如金属氧化物介孔分子筛的制备。V. Luca等采用新的合成法,以价廉的十二烷基硫酸盐为模板剂,合成了具有蠕虫洞孔道的介孔二氧化钛。该法分两步进行,第一步是十二烷基硫酸钠与TiCl3在水溶液中反应生成十二烷基硫酸钛,第二步是将合成的十二烷基硫酸钛溶于无水乙醇中,加入钛酸异丙酯调节硫酸盐比,最后在一定的湿度和空气流速下可获得介孔二氧化钛。其热稳定性较差,但经改性后,可在300～400 ℃保持稳定。3)非离子表面活性剂由于非离子表面活性剂在溶液中呈中性,氢键被认为是介孔相形成的驱动力。长碳链伯胺是一类主要的非离子表面活性剂。H. Yoshitake 等用长链烷基(C 分别为10,12, 16和18)伯胺模板剂,合成出螺旋形孔道的介孔TiO2光催化剂,其孔径随模板剂碳链的增加呈非线性增大,比表面积可达 1 200 m2 /g。螺旋形孔道结构有利于反应物到达活性中心,从而改善了TiO2的光催化活性。4)混合表面活性剂这类模板剂通常是将离子型表面活性剂与非离子型表面活性剂进行混合,以发挥出其各自的优势,由此对胶束大小和形状进行控制, 以更好地控制介孔材料的形貌。M. M.Yusuf等以钛酸丁酯为钛源,盐酸为酸催化剂,以CTAC + PEG作为模板剂,制备