合成介孔材料-综述.pdf

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Terms 1 H Volume 46 Number 32 2010 ChemComm Pages 5813 5976 COMMUNICATION J Fraser Stoddart et al Directed self assembly of a ring in ring complex FEATURE ARTICLE Wenbin Lin et al Hybrid nanomaterials for biomedical applications Chemical Science Downloaded by University of Science and Technology of China on 30 November 2012 Published on 29 November 2012 on http pubs rsc org doi 10 1039 C2CC36964H View Article Online Journal Homepage Journal Name Cite this DOI 10 1039 c0 xx00000 x www rsc org xxxxxx Dynamic Article Links A ARTICLE TYPERTICLE TYPE This journal is The Royal Society of Chemistry year journal year vol 00 00 1 An Overview of the Synthesis of Ordered Mesoporous Materials Wei Li and Dongyuan Zhao Received in XXX XXX Xth XXXXXXXXX 20XX Accepted Xth XXXXXXXXX 20XX DOI 10 1039 b000000 x In this viewpoint we focus on two highly cited papers published in Chem Commun by Inagaki et al in 5 1993 and Kleitz et al in 2003 respectively which are undoubted landmarks in the development of ordered mesoporous materials Here we present an overview of their historical contributions in the synthesis and evolution of this field since its discovery and the progress based on the achievements Porous materials are of great interest because of their ability to interact with atoms ions molecules and nanoparticles not only at 10 their surfaces but throughout the bulk of the materials 1 3 Therefore the presence of pores in nanostructured materials greatly promotes their physical and chemical properties 4 Recently the well understanding design and manipulation of pores have significantly advanced science and technology and 15 are playing increasingly important roles in modern society According to the definition of the International Union of Pure and Applied Chemistry IUPAC porous materials can be classified into microporous with pore diameter 50 nm 20 respectively 5 Among them microporous materials zeolite molecular sieves have been widely used in chemical and petrochemical industry processes 1 3 In the case of mesoporous materials the structural capabilities at the scale of a few nanometers and high surface area can meet the demands of the 25 growing applications such as adsorption separation catalysis drug delivery sensors photonics energy storage and conversion and nanodevices especially for dealing with large molecules such as biomolecules and heavy oils Zeolites or microporous materials are far away from these demands 1 2 These motivations 30 spark the proliferation of mesoporous materials Science 1980s pillared clays containing mesopores have been well studied 2 6 However their disordered rectangular pores could not be fully opened Molecules could not easily pass through these pores leading to coking in catalytic processes Moreover the pore sizes 35 are widely distributed and difficult to control and the arrangement of pores is disordered 2 Technical advances in the fields of chemistry materials science biology and engineering require the development of mesoporous materials with controllable structures and tuneable pore architecture 40 In 1992 Mobil scientists reported the synthesis of ordered mesoporous molecular sieves M41S from liquid crystal templates 7 This is the first time that the term mesoporous molecular sieves appears in a publication paper although mesopore is not a new term according to IUPAC definition and 45 a US patent was firstly applied in Jan 1990 5 8 In fact in the early time 1969 Vincent et al had prepared MCM 41 analogues but unfortunately they only claimed low bulk density silica due to the lack of detailed characterizations 9 Another worth mention is that in Apr 1990 Japanese scientists reported 50 the synthesis of alkytrimethylammonium kanemite complexes with a mixed phase 10 Although N2 sorption isotherms showed narrow pore size distribution at 2 4 nm for the products the authors did not realize mesopores and mesoporous molecular sieves In 1993 Inagaki Fukushima and Kuroda optimized the 55 synthesis condition and obtained a pure ordered mesoporous silicate 11 The results were published in Chem Commun with the title of Synthesis of Highly Ordered Mesoporous Materials from a Layered Polysilicate The main contribution described in this paper is the realization of the significance of a template that has 60 been widely used in zeolite synthesis for preparing ordered mesoporous materials 1 2 They first reported the synthesis of ordered mesoporous silica with a pure hexagonal phase which showed similar XRD patterns Fig 1a with MCM 41 and was different with the former results 7 10 In addition it is the first time 65 to simply prepare highly ordered mesoporous materials from the natural minerals Later the large domain regularity of the products denoted as FSM 16 was verified by TEM images Fig 1b and 1c which was further elaborated by the authors 12 Significantly at the low concentration of surfactants the 70 proposed pillared mechanism greatly enriches and expands the mechanism of liquid crystal templating LCT Since then the soft templating method has become a general pathway for the synthesis of ordered mesoporous materials and the refinement of Fig 1 a XRD patterns of the as made silicate organic complex and calcined products at 700 and 1000 C respectively b TEM images of the as made silicate organic complex and calcined products at 550 C from the original Inagaki et al papers Panel a and b c are reproduced with permission from ref 11 and 12 respectively Page 1 of 3ChemComm Chemical Communications Accepted Manuscript Downloaded by University of Science and Technology of China on 30 November 2012 Published on 29 November 2012 on http pubs rsc org doi 10 1039 C2CC36964H View Article Online 2 Journal Name year vol 00 00 This journal is The Royal Society of Chemistry year this method via two synthetic strategies cooperative self assembly and true liquid crystal templating process was soon reported Fig 2 2 13 In the cooperative self assembly process inorganic species interact with surfactants driven by Coulomb force or hydrogen bonding The inorganic species at the interface 5 polymerize and cross link and thus cooperatively assemble with surfactants With the reaction the cooperative arrangements of surfactants and the charge density between inorganic and organic species influence each other Hence the compositions of inorganic organic hybrids differ to some degree The matching of 10 charge density at the surfactant inorganic interfaces governs the assembly process thus resulting in phase separation and reorganization finally leading to the formation of ordered 3 D arrangement with the lowest energy The true liquid crystal templating process is based on true or semi liquid crystal 15 mesophase micelles produced by high concentration surfactants as templates The condensation of inorganic precursors is improved by reaction of the confined growth around surfactants forming ceramic like frameworks After condensation the organic templates can be removed The inorganic materials 20 nanocast the mesostructures pore sizes and symmetries from the liquid crystal scaffolds Using this soft templating method numerous novel ordered mesoporous materials composed of inorganic organic and inorganic organic composite frameworks have been prepared via various synthetic methods such as 25 aqueous processes nonaqueous approach which is also well known as evaporation induced self assembly EISA process hydrothermal method etc 2 14 15 Plenty of soft templates including cationic anionic and non ionic surfactants and mixed surfactant systems have been utilized to synthesize ordered 30 mesoporous materials with controllable structures and tuneable pore architecture 2 Of particular mention was the remarkable findings by Zhao et al regarding the preparation of large pore ordered mesoporous silica with a 2D hexagonal structure by using triblock copolymers as templates which is very famous 35 known as SBA 15 16 In 1998 Yang et al first used block copolymers as structure directing agents to prepare various ordered mesoporous metal oxides through a EISA process 17 Another well worth mention was the great achievement illustrated by the Ryoo group Korea which was also published in 40 Chem Common in 2003 appeared under the title of Cubic Ia3d large mesoporous silica synthesis and replication to platinum nanowires carbon nanorods and carbon nanotubes 18 In this article they reported the synthesis of large pore ordered cubic Ia3d 45 mesoporous silica known as KIT 6 Fig 3a and 3c 19 20 Although Liu et al first reported the synthesis of large pore 3D bicontinuous mesoporous silica by using a commercial triblock copolymer as a template the quick self 50 assembled approach in the EISA process produce a plenty of defects in the resultant ordered mesostructures leading to low quality XRD patterns 21 Here butanol was first employed to tailor the mesophase of block 55 copolymers micelles in aqueous phase because it can swell the hydrophobic chains and thus decrease the curvature leading to the mesophase change from hexagonal to cubic phase The high quality XRD patterns clearly illustrated the 60 perfect mesostructures which is the appealing bicontinuous helix channel structure and very rare in nature Despite the great success of the soft templating method it was soon realised that it was not sufficient enough to prepare many non siliceous mesostructured materials because the non siliceous 65 precursors are more susceptible to hydrolysis lack of condensation redox reactions weak connection with surfactants or phase transitions accompanied by thermal breakdown of the structural integrity which make it much more difficult to construct ordered mesostructures and remove the templates 22 23 70 Significantly in this context Ryoo and coworkers employed the resultant KIT 6 as a hard template for the synthesis of ordered mesoporous materials via three steps i precursor infiltration inside mesochannels of the silica template ii conversion of the precursor in the nanochannels iii removal of mesoporous silica 75 template which is well known as nanocasting because the entire manufacturing procedure is similar with the traditional casting Fig 3 XRD patterns a b and TEM images c d of the ordered cubic Ia3d mesoporous silica KIT 6 and ordered mesoporous carbons from KIT 6 respectively The insets in a and b are the corresponding structure modes Panels a b and c d are reproduced with permission from ref 18 20 and 19 25 respectively Fig 2 Schematic representation of the soft templating method via two synthetic strategies A cooperative self assembly and B true liquid crystal templating process for the synthesis of ordered mesoporous materials Reproduced with permission from ref 3 Page 2 of 3ChemComm Chemical Communications Accepted Manuscript Downloaded by University of Science and Technology of China on 30 November 2012 Published on 29 November 2012 on http pubs rsc org doi 10 1039 C2CC36964H View Article Online This journal is The Royal Society of Chemistry year Journal Name year vol 00 00 3 method but in the nanoscale Fig 4 13 22 24 The high quality XRD pattern and TEM image Fig 3b and 3d 18 19 of the resulted mesoporous carbons clearly announced the feasiblity of this nanocasting strategy and the novel hard template concept for preparing mesoporous materials which since became a hot topic 5 in the research field of ordered mesostructured materials especially for those unavailable via the soft templating method In this nanocasting approach Fig 4 the regular arrangement comes from the preformed ordered mesoporous template It should be mentioned that the small mesotunnels inside the 10 template s pore walls are necessary for nanocasting They can be replicated to small nanorods which thus support the nanowire nanopipes replicated from the primary mesopores to form stable mesostructured replica arrays Otherwise the obtained replicas cannot maintain their mesostructures once the 15 templates are removed resulting in isolated nanowires nanopipes or low symmetry mesostructured products Moreover the resultant mesostructured replica arrays can also be used as a new hard template for ordered mesoporous materials It should be noted that the earliest example could be traced back to 1999 also 20 reported by the Ryoo group using MCM 48 templates 26 however the symmetry of the resulted negative replica was reduced In contrast using the KIT 6 as a hard template ordered mesoporous carbons with the same Ia3d symmetry were synthesized That is because the KIT 6 possesses plentiful micropores connecting the 25 two enantiomeric pore systems which would be replicated to small nanorods and thus support the ordered mesostructures of replicas Therefore KIT 6 is a best choice for a hard template candidate just like SBA 15 but to synthesize cubic mesoporous materials Since then various highly ordered mesoporous oxides 30 or non oxides especially with high crystalline or even single crystal frameworks are well developed by using KIT 6 silicas as the templates via the nanocasting process 13 22 24 Conclusions The work by Inagaki et al in 1993 was nevertheless not the 35 first paper claiming the synthesis of ordered mesoporous materials but it undoubtedly constituted a breakthrough because of the first realization of the significance of a template concept from zeolites to ordered mesoporous materials synthesis and the pure ordered mesophase from the natural minerals which was 40 rarely reported before At the low concentration of surfactants the proposed pillared mechanism greatly enriches and expands the mechanism of LCD This paper stimulated an enormous amount of work to develop and refine the soft templating method for the synthesis of ordered mesoporous materials The article by 45 Kleitz et al in 2003 not only reported the synthesis of high quality large pore ordered cubic Ia3d mesoporous silica KIT 6 but also first showed the perfect replication of the cubic mother silica mesostructures It helped establish the hard templating method or nanocasting as one of the most versatile and accessible 50 pathways for various ordered mesoporous materials The high citations since their publications demonstrated their tremendous impact as pioneers of the research field of ordered mesoporous materials especially on the synthetic pathways Although great achievements have been made in this field over the past 20 years 55 we believe more efforts should be invested in future to develop new synthetic method expand properties and applications We expect more exciting discoveries will appear soon We thank Dr Z X Wu Monash Univ for the help This work was supported by the State Key Basic Research Program of 60 the PRC 2012CB224805 and 2009CB930400 Notes and references Department of Chemistry and Laboratory of Advanced Materials Fudan University Shanghai 200433 P R China Tel 86 21 5163 0205 Fax 86 21 5163 0307 E mail dyzhao 65 1 M E Davis Nature 2002 417 813 2 A Corma Chem Rev 1997 97 2373 3 Y Wan and D Y Zhao Chem Rev 2007 107 2821 4 W Li F Zhang Y Q Dou Z X Wu H J Liu X F Qian D Gu Y Y Xia B Tu and D Y Zhao Adv Energy Mater 2011 1 382 70 5 IUPAC Manual of symbols and terminology Pure Appl Chem 1972 31 578 6 T J Pinnavaia Science 1983 220 365 7 C T Kresge M E Leonowicz W J Roth J C Vartuli and J S Beck Nature 1992 359 710 75 8 J S Beck C T W Chu I D Johnson C T Kresge M E Leonowicz W J