ARTICLE pubs.acs.org/Langmuir
Synthesis and Unique Catalytic Performance of Single-Site TiContaining Hierarchical Macroporous Silica with Mesoporous Frameworks Takashi Kamegawa,† Norihiko Suzuki,† Michel Che,‡ and Hiromi Yamashita*,† †
Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan ‡ Institut Universitaire de France and Laboratoire de Reactivite de Surface, Universite Pierre et Marie Curie, Paris 6, CNRS-UMR 7197, Paris, France
bS Supporting Information ABSTRACT: Single-site Ti-containing hierarchical macroporous silica with mesoporous frameworks (Ti-MMS) was successfully prepared by a solvent evaporation method using organic surfactant and poly(methyl methacrylate) (PMMA) colloidal crystals as the template. The formation of a well-defined macroporous structure composed of mesoporous silica walls was characterized by SEM and TEM observations. The successful incorporation of tetrahedrally coordinated Ti oxide moieties within their frameworks was also confirmed by spectroscopic techniques such as UV-vis and XAFS measurements. Comparative studies revealed that Ti-MMS exhibited higher catalytic activities for the epoxidation of linear R-olefin compared to Ti-containing mesoporous silica without macropores (TiMS). The reaction rate was significantly enhanced on Ti-MMS depending on increases in the alkyl chain length of linear R-olefins. It was also found that Ti-MMS showed good catalytic performance in the selective epoxidation of methyl oleate, which is a kind of unsaturated fatty acid methyl ester (FAME), under acid-free reaction conditions with tert-butylhydroperoxide (TBHP) because of the advantages of the combination of hierarchical macroporous and mesoporous structures.
1. INTRODUCTION For the past several decades, microporous and mesoporous materials have attracted considerable attention because of their fascinating characteristics such as unique pore structure, unusual surface topology, large surface area, and catalytic performance.1-6 In addition, recently, three-dimensionally ordered macroporous (3DOM) materials, which typically have submicrometer ranges of pores, were also intensively investigated and mainly prepared by using colloidal crystals of close-packed uniform microspheres such as polystyrene and poly(methyl methacrylate) (PMMA).7-26 These macroporous materials were of importance in the research fields of photonic crystals,9-11 sensor devices,12,13 and catalysts.14-17 The preparation methods based on colloidal crystals were widely employed because of the possibility of designing various fascinating macroporous materials by changing the size of the colloidal crystals and the nature of the precursor. The interstices of colloidal crystals used as a template were filled with material precursors, resulting in the formation of intermediate composite structured materials through the solidification of precursors. The structured materials were then recovered after the complete removal of colloidal crystals by calcination or extraction. Although the preparation of various macroporous materials such as oxides,14-20 bioceramics,21,22 and another unique materials23-26 has already been achieved, the preparation of tetrahedrally coordinated transitionmetal-containing hierarchical macroporous silica with mesoporous r 2011 American Chemical Society
frameworks and their catalytic performance have yet to be fully investigated. The incorporation of metal ions (e.g., titanium, vanadium, chromium, and molybdenum ions) within the framework structure of microporous and mesoporous materials and the anchoring of organometallic moieties on their surface have attracted a great deal of attention because of their prominent catalytic activity and selectivity for specific catalytic and photocatalytic reactions.27-37 Among them, Ti-containing porous materials are the most interesting candidates for practical applications, allowing the replacement of conventional stoichiometric reaction processes. Ti-containing porous materials show remarkable catalytic activity in the production of various organic chemicals through oxidation reactions in the presence of aqueous H2O2 or TBHP.3,27-31 However, in some cases, the catalytic performance is affected by the hydrophilic/hydrophobic properties of the catalyst surface as well as the accessibility of the active sites.5,6,38 The relatively small aperture diameter of micro/mesoporous materials and the large, dense powder shapes lead to diffusion limitations of molecular species.5,6,38 Received: September 3, 2010 Revised: January 12, 2011 Published: February 04, 2011 2873
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With this in mind, we deal in the present study with the design of Ti-containing hierarchical macroporous silica with mesoporous frameworks (Ti-MMS) by using an organic surfactant and colloidal crystals of PMMA as a template. The materials were characterized by various spectroscopic methods, and special attention was given to the relationship between the presence of hierarchical macroporous structure and catalytic performance. The epoxidation of linear R-olefins of different lengths and that of methyl oleate were investigated as model reactions.
2. EXPERIMENTAL SECTION 2.1. Materials. Tetramethoxysilane (abbreviated as TMOS), vinyltrimethoxysilane (VTMOS), octadecyltrimethylammonium chloride (C18TAC), and R-olefins (1-octene, 1-hexadecene, 1-hexadecene, and 1-eicosene) were purchased from Tokyo Kasei Kogyo Co., Ltd. Titanium isopropoxide (TIP), 2,20 -azobis(2-methylpropion amidine)dihydrochloride, and dichloromethane were obtained from Wako Pure Chemical Ind., Ltd. Methyl methacrylate monomer (MMA), HCl (37%), methanol, and ethyl acetate were purchased from Nacalai Tesque Inc. tert-Butyl hydroperoxide (TBHP, 5.0 M in decane) and methyl oleate were also obtained from Aldrich. All chemicals were used without further purification. 2.2. Preparation of the Catalyst. Monodisperse PMMA spheres were synthesized by a method reported earlier.39,40 MMA (80 mL) was added to 320 mL of H2O with stirring (350 rpm) at 343 K under an argon atmosphere. Then, 0.3 g of 2,20 -azobis(2-methylpropion amidine)dihydrochloride was added to the above mixture at the same temperature. After continuous stirring for 2 h, the mixture was first filtered with glass wool. The product was separated by centrifugation of the thus-obtained opalescent solution, washed with water, and then dried at 298 K for 24 h. The precursor solution of Ti-containing porous silica was prepared using TMOS, VTMOS, C18TAC, and TIP as discussed earlier by Ogawa et al.41 TMOS (27.4 g), VTMOS (8.9 g), and TIP (0.34 g) were dissolved in methanol (3.1 g) with stirring at 343 K. Then, C18TAC (10.4 g), an HCl aqueous solution (3 mL, 1 mol/L) and H2O (1.4 mL) were added to the above mixture. After stirring for 20 min, the solution was used for the preparation of Ti-MS and Ti-MMS. The molar ratios were as follows: (TMOS þ VTMOS)/TIP/C18TAC/ CH3OH/H2O = 1:1/200:1/8:1/2.5:1/3 and TMOS/VTMOS = 3:1. For the preparation of Ti-MMS, 20 mL of the precursor solution was slowly loaded with 5.0 g of colloidal crystals of PMMA as the template of macropores by a vacuum filtration methods using a Buchner funnel and a process similar to that reported by Holland et al.7 The schematic illustration of the synthesis procedure is shown in Figure 1. For the preparation of Ti-containing mesoporous silica without macropores (TiMS), the same precursor solution was spread on a poly(vinylidene chloride) sheet and dried at 298 K. All samples were calcined in air at 823 K for 5 h (heating rate 1 K 3 min-1), which was long enough for the complete removal of C18TAC and PMMA microspheres. C18TAC and PMMA microspheres within the silica matrix were decomposed at around 493 and 633 K, respectively. After calcination, Ti-MMS showed opalescence depending on the angle under fluorescent light, although the Ti-MS powder was simply white. 2.3. Characterization Techniques. Powder X-ray diffraction (XRD) patterns were recorded using a Rigaku RINT 2500 diffractometer with Cu KR radiation (λ = 1.5406 Å). Ultra-small-angle X-ray scattering (USAXS) measurements were carried out on a Rigaku SmartLab diffractometer with a Cu rotating anode X-ray source. The d spacing was calculated from the first diffraction peak observed in the USAXS profile by using Bragg’s equation: 2d sin θ = λ. Diffuse reflectance UV-vis spectra were recorded at 298 K with a Shimadzu UV-2450A double-beam digital spectrophotometer. Ti K-edge X-ray absorption fine structure (XAFS) spectra of Ti-containing porous silica
Figure 1. Schematic diagram of the procedures for the preparation of Ti-MMS. were recorded at 298 K in fluorescence mode at the BL-7C facility of the Photon Factory at the High-Energy Acceleration Research Organization (KEK) in Tsukuba, Japan. The synchrotron radiation from a 2.5 GeV electron storage ring was monochromatized by a Si(111) double crystal. The extended X-ray absorption fine structure (EXAFS) data were examined using the analysis program (Rigaku REX2000). The pre-edge peaks in the X-ray absorption near-edge structure (XANES) regions were normalized for atomic absorption on the basis of the average absorption coefficient of the spectral region. Fourier transformations were performed on k3-weighted EXAFS oscillations in the range of 310 Å-1 to obtain the radial structure function. Prior to UV-vis and XAFS measurements, samples were calcined in O2 (>2.66 kPa) at 723 K for 1 h and then degassed at 473 K for 1 h. Scanning electron microscope (SEM) investigations were carried out using a JSM-6500 field-emission microscope (JEOL). Prior to SEM analyses, sample surfaces were coated with gold/palladium using an ion-sputtering device (JEOL JFC-1100) to improve the electrical conductivity. The transmission electron microscopy (TEM) image was obtained with a Hitachi Hf-2000 FE-TEM equipped with a Kevex energy-dispersive X-ray detector operated at 200 kV. Nitrogen adsorption-desorption isotherms were recorded by using a BEL-SORP max (BEL Japan, Inc.) at 77 K after degassing samples under vacuum at 473 K for 2 h. The specific surface area was determined according to the Brunauer-Emmett-Teller (BET) method at a relative pressure of 0.05-0.3. Inductively coupled plasma (ICP) measurements for the analysis of Ti content were performed using a Nippon Jarrell-Ash ICAP-575 Mark II instrument. 2.4. Epoxidation of Linear r-Olefins. The epoxidation of linear R-olefins (1-octene, 1-dodecene, 1-hexadecene, and 1-eicosene) with TBHP was used as a test reaction. The reaction vessel, which was equipped with a reflux condenser, was charged with catalyst (Ti-MMS and Ti-MS, 50 mg), linear R-olefin (10 mmol), CH2Cl2 (10 mL), and TBHP (2 mL) and then heated to 323 K with magnetic stirring. The molar ratio of TBHP/Rolefin was adjusted to 1.0. The analysis of the product in both reactions was performed on a gas chromatograph (Shimadzu GC-14B with a flame ionization detector) equipped with a TC-1 capillary column. The turnover number (TON) of each reaction was determined by the ratio of the formed amount of epoxide and the contents of Ti oxide moieties in 50 mg of Ti-MS and Ti-MMS, respectively. 2.5. Epoxidation of Methyl Oleate. The epoxidation of methyl oleate was also performed using the same equipment. The reaction 2874
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Figure 2. SEM images of (a) PMMA particles, (b) Ti-MS, and (c, d) Ti-MMS. vessel was charged with catalyst (50 mg), methyl oleate (3 mmol), ethyl acetate (3 mL), and TBHP as the oxidant (0.9 mL, TBHP/methyl oleate molar ratio = 1.5). The resulting mixture was reacted at 363 K with magnetic stirring under an argon atmosphere. The analysis of the product was performed on a gas chromatograph (Shimadzu GC-2014 with a flame ionization detector)-equipped TC-1 capillary column. TON was defined as epoxide/Ti atoms in a catalyst. The selectivity of the epoxide was calculated by the ratio of the formed amount of methyl 9,10-epoxy stearate to the consumed amount of methyl oleate.
3. RESULTS AND DISCUSSION 3.1. Characterization of Ti-MS and Ti-MMS. The SEM image of PMMA particles used to prepare the colloidal crystals (Figure 2a) shows that they are approximately spherical with a narrow size distribution (diameter ca. 400 nm). Colloidal crystals of these PMMA particles were used as templates to form the macroporous structure. The precursor solutions used to synthesize mesoporous silica thin films and powders through the evaporation of solvents followed by calcination to remove the organic surfactant were taken as appropriate reaction liquids for the preparation of hierarchical macroporous silica with mesoporous frameworks because there is no need for vigorous stirring, a long aging time, or conventional hydrothermal processes. These types of precursor solutions were consequently selected for the preparation of Ti-MS and Ti-MMS. SEM images of the prepared samples are shown in Figure 2b-d. Ti-MS has a dense powder form with an ill-defined morphology compared to Ti-MMS. In line with the structure of aligned PMMA colloidal crystals, a uniform macroporous structure of Ti-MMS was successfully obtained by using the same precursor solution of Ti-MS, as shown in Figure 2c. The magnified SEM image (Figure 2d) of Ti-MMS clearly suggests the formation of interconnecting macroporous networks. The silica walls separating two neighboring macropores were formed by regularly aligned and interconnected small particles.
The thickness of these walls was estimated to be about 70-80 nm, which is much smaller than the particle size of Ti-MS (Figure 2b). Thus, Ti-MMS has many mesopore entrances with short mesoporous channels. The macropore diameter (ca. 300 nm) was also slightly smaller than the original PMMA particles size because of the shrinkage of the silica network during calcination. TEM images providing more detailed information about the overview of hierarchical macroporous and mesoporous structures of Ti-MMS are shown in Figure 3. These images show the uniformity and direct evidence of the existence of interconnected hierarchical macropores. Moreover, it was confirmed that the silica walls, which divide the neighboring macropores, consist mainly of mesoporous structure. The USAXS profiles of Ti-MS and Ti-MMS were measured to investigate the structural differences between Ti-MS and TiMMS. USAXS is quite effective at characterizing density fluctuations on the submicrometer scale. As shown in Figure 4, Ti-MMS showed periodic peaks in the region of 2θ < 0.07°, but no peak was observed in the case of Ti-MS. The d spacing calculated from the peak (2θ = 0.025°) was determined to be ca. 353 nm, which was quite similar to the interval of the hierarchical macroporous layer. These results clearly indicated the structural differences between Ti-MS and Ti-MMS due to the existence of hierarchical macroporous structure. XRD patterns of Ti-MS and Ti-MMS were also measured to confirm the formation of mesoporous structure (Figure 5). The diffraction peak assigned to the mesoporous structure was clearly observed in the region of 2θ < 5°. Although the position of the most intense peak was almost the same in both samples, Ti-MMS exhibits a broad, relatively weak diffraction peak because of the destruction of ordered mesoporous structure to some degree by the construction of macropores. In the nitrogen adsorption/desorption measurements, Ti-MS and Ti-MMS exhibit a typical type-IV isotherm (Figure 6). The inflections of the isotherms attributed to the capillary condensation 2875
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Figure 5. XRD patterns of (a) Ti-MS and (b) Ti-MMS.
Figure 3. (a) TEM image of Ti-MMS. (b) Enlargement of image a.
Figure 6. Nitrogen adsorption/desorption isotherms and pore size distribution curve (inset) of (a) Ti-MS and (b) Ti-MMS.
Figure 4. Ultra-small-angle X-ray scattering profiles of (a) Ti-MS and (b) Ti-MMS.
of nitrogen in mesopores are observed in the same P/P0 region. The increase in the amount of nitrogen adsorbed on Ti-MMS in the high P/P0 region can be taken as an estimate of small interstices between the connected mesoporous particles. The BET surface areas of Ti-MS and Ti-MMS were measured to be 972 and 1053 m2/g, respectively. It was also confirmed that the pore size distributions are scarcely changed by the presence of macroporous structure, showing the formation of relatively uniform mesopores. The concentrations of Ti oxide moieties within prepared Ti-MS and Ti-MMS were determined to be 0.37 and 0.31 wt % as Ti metal, respectively, by inductively coupled plasma (ICP) analysis. Ti K-edge XAFS and UV-vis absorption spectra were used to clarify the nature of Ti oxide moieties incorporated within the mesoporous silica frameworks. The local structure of Ti oxide moieties was investigated by Ti K-edge XAFS measurements. As can be seen in Figure 7, Ti oxide moieties show a well-defined pre-edge peak depending on the environment of titanium. TiO2 powder shows well-defined pre-edge peaks attributed to the
transition from the 1s core level of the Ti atom to three different kinds of molecular orbitals (1t1g, 2t2g, and 3eg) of anatase TiO2 with octahedral geometry.42-44 Meanwhile, in the case of TIP, a sharp, single pre-edge peak was observed at around 4970 eV, which was due to the 1s to 3d transition of isolated titanium atoms surrounded by four oxygen atoms. Ti-MMS and Ti-MS also exhibited a characteristic, intense single pre-edge peak. This peak was quite similar to that of TIP, showing the existence of Ti oxide moieties with tetrahedral coordination in Ti-MS and TiMMS.42-44 The Fourier transforms of EXAFS spectra of TiMMS and Ti-MS show an intense peak assigned to the existence of oxygen neighbors (Ti-O) at ca. 1.8 Å (without a phase-shift correction), but other peaks due to the Ti neighbors (Ti-OTi) were hardly observed between 2.0 and 3.0 Å.42-44 These results clearly indicate the successful incorporation of isolated tetrahedral Ti oxide moieties within the mesopores without the formation of aggregated Ti oxide species. UV-vis absorption depends not only on the structure but also on the dispersion of Ti oxide moieties. It has already been reported that the absorption below 250 nm is attributed to isolated tetrahedral Ti oxide monomers and the bands above 250 nm are assigned to tetrahedral Ti oxide dimers or small oligomers.42-44 The absorption edge of Ti-MS and Ti-MMS is located at around 250 nm (Figure 8). The distinct peak observed at around 210 nm is assigned to the ligand-to-metal chargetransfer (LMCT) transition of the isolated Ti oxide monomer 2876
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Figure 7. (A-D) XANES and (a-d) Fourier transforms of EXAFS spectra of (A, a) TiO2 (anatase), (B, b) tetrapropyl orthotitanate, (C, c) Ti-MS, and (D, d) Ti-MMS.
Figure 8. Diffuse reflectance UV-vis spectra of (a) Ti-MS and (b) TiMMS.
with tetrahedral coordination.42-44 These results clearly show the existence of isolated Ti oxide monomers as dominant Ti oxide moieties within Ti-MS and Ti-MMS, in good agreement with the XAFS results. The above characterizations clearly indicated the successful incorporation of tetrahedral Ti oxide moieties with a single-site nature into silica-based material possessing hierarchical macroporous and mesoporous structures. 3.2. Catalytic Reactions. The epoxidation of linear R-olefins (1-octene (C8), 1-dodecene (C12), 1-hexadecene (C16), and 1-eicosene (C20)) with TBHP was used as a test reaction to investigate the effect of the hierarchical macroporous structure on the catalytic performances of Ti-containing porous silica. Figure 9 shows the turnover number (TON) defined as the ratio of produced epoxide to the number of Ti moieties included in TiMS and Ti-MMS. The selectivity of corresponding epoxides was almost the same on both catalysts. For example, the selectivity of epoxide was as high as 98% in the case of the epoxidation of 1-octene. As shown in Figure 9A-D, decreases in catalytic activity were observed with increasing chain length of linear Rolefins from 1-octene (CH2dCH(CH2)5CH3) to 1-eicosene (CH2dCH(CH2)17CH3) on Ti-MS and Ti-MMS, respectively. The relatively small size of the pores and the long diffusion path adversely affecting the catalytic performance of microporous and
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Figure 9. Epoxidation of linear R-olefins ((A) 1-octene, (B) 1-dodecene, (C) 1-hexadecene, and (D) 1-eicosene) by TBHP on Ti-MS and Ti-MMS (reaction time 24 h).
mesoporous materials has also been reported.5,6,38 The observed order of catalytic activity could be explained by the increasing diffusion limitation of linear R-olefins in both catalysts. However, in each reaction system, Ti-MMS had a higher catalytic performance in the production of the corresponding epoxide than did Ti-MS, although both catalysts contain almost the same number of Ti oxide moieties. The ratio of TON ((TON on TiMMS)/(TON on Ti-MS)) in each reaction system increased as epoxidation of 1-octene (ca. 1.6) < 1-dodecene (ca. 1.7) < 1-hexadecene (ca. 2.4) < 1-eicosene (ca. 2.6), indicating the advantages of hierarchical macroporous and mesoporous structures. Compared with the molecular size of 1-octene, the mesopores are enough large and do not inhibit the diffusion of 1-octene to the inside of the pores. However, with increases in the alkyl chain length of R-olefin, the differences between the alkyl chain length and the size of the mesopores become small, leading to limitations of reactants diffusing to the inside of pores. As a consequence, Ti-MMS having many mesopores apertures and a short mesoporous channel is advantageous to each reaction system, especially the epoxidation of R-olefin with a long alkyl chain. The efficient catalytic performance is presumably accomplished by decreasing diffusion limitations and facilitating the efficient transport of reactants to the catalytically active sites in each reaction system. The uses of renewable raw materials have recently attracted much attention because of the natural resource savings as well as the design of a sustainable system. Among them, the derivatives of FAMEs were commercially used for plasticizers, additives in lubricants, and so on.45,46 These chemicals are mainly produced through acid-catalyzed reactions on the industrial level.45 The selective epoxidation of FAMEs obtained from renewable raw materials has also been investigated by using Ti-containing catalysts in an environmentally friendly way with high efficiency,30,47 whereas the development of more efficient systems is strongly desired. Considering the above experimental results for the epoxidation of linear R-olefins, Ti-MMS could be expected to show higher catalytic performance in the transformation of bulky compounds such as FAMEs to the corresponding epoxides. The 2877
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the higher catalytic performances of Ti-MMS are achieved by their advantageous structure for the diffusion of substances during each reaction. Moreover, Ti-MMS was effective at transforming methyl oleate to the corresponding epoxide, showing the possibilities of hierarchical macroporous and mesoporous structures in the design of more efficient catalysts.
’ ASSOCIATED CONTENT
bS
Supporting Information. XRD pattern of recovered TiMMS after the epoxidation reaction of methyl oleate and the reaction-time profiles of the epoxidation of methyl oleate with the selectivity of epoxide over Ti-MS and Ti-MMS. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author Figure 10. Epoxidation of methyl oleate to methyl 9,10-epoxy stearate by TBHP on Ti-MS and Ti-MMS (reaction time 4 h).
selective epoxidation of methyl oleate, which is a kind of FAME, was thus performed on Ti-MS and Ti-MMS using TBHP as a model reaction. As shown in Figure 10, Ti-MMS exhibited about a 2.8 times higher catalytic performance for the epoxidation of methyl oleate to methyl 9,10-epoxy stearate than did Ti-MS without the formation of undesired byproducts. Even though the structure of the catalysts was quite different, the selectivities of methyl 9,10-epoxy stearate and TBHP were as high as 97 and 98% on each catalyst. The conversion of methyl oleate increased in proportion to the reaction time and was reached at around 70% on Ti-MMS after 24 h (Figure S1). After the filtration of TiMMS at a reaction temperature in the middle term of the reaction, it was confirmed that further conversion of methyl oleate to methyl 9,10-epoxy stearate was stopped. This result is clear evidence of the absence of Ti leaching from Ti-MMS into the liquid phase, which shows good correspondence with the stability of a previously reported Ti-containing catalyst.47 Moreover, it was found that the structure of Ti-MMS was maintained even after the catalytic reaction (Figure S2). These results clearly shows the advantages of hierarchical macroporous and mesoporous structures in the transformation of bulky molecules obtained from renewable raw materials to corresponding high-value-added products.
4. CONCLUSIONS Isolated tetrahedral Ti oxide moieties containing hierarchical macroporous silica with mesoporous structure (Ti-MMS) were successfully prepared by applying a solvent evaporation method using two kinds of templates: an organic surfactant and PMMA colloidal crystals. The formation of hierarchical macroporous and mesoporous structures and nature of Ti oxide moieties were investigated in detail by SEM, TEM, and other spectroscopic measurements. It was found that Ti-MMS led to a significant enhancement of the reaction rate in the epoxidation of longchain R-olefins compared to Ti-MS because of the advantageous structure for the efficient diffusion of reactants to the catalytically active sites. The most important point in the construction of hierarchical macroporous structure is reducing the particle size of mesoporous silica accompanying the formation of many apertures and the shortening of the mesoporous channels. We estimate that
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’ ACKNOWLEDGMENT This work was supported by a grant-in-aid for scientific research (KAKENHI) from the Ministry of Education, Culture, Sports, Science and Technology (no. 21760630). The X-ray absorption measurements were performed at the BL-7C facility of the Photon Factory at the National Laboratory for HighEnergy Physics, Tsukuba, Japan (2009G169). We thank Dr. Eiji Taguchi and Prof. Hirotaro Mori at the Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, for assistance with TEM measurements. We thank Rigaku Corporation for measurements of ultra-small-angle X-ray scattering profiles. H.Y. acknowledges his invited professorship at UPMC. ’ REFERENCES (1) Cundy, C. S.; Cox, P. A. Chem. Rev. 2003, 103, 663. (2) Wight, A. P.; Davis, M. E. Chem. Rev. 2002, 102, 3589. (3) Notari, B. Adv. Catal. 1996, 41, 253. (4) Corma, A. Chem. Rev. 1997, 97, 2373. (5) Tao, Y.; Kanoh, H.; Abrams, L.; Kaneko, K. Chem. Rev. 2006, 106, 896. (6) Egeblad, K.; Christensen, C. H.; Kustova, M.; Christensen, C. H. Chem. Mater. 2008, 20, 946. (7) Velev, O. D.; Jede, T. A.; Lobo, R. F.; Lenhoff, A. M. Nature 1997, 389, 447. (8) Holland, B. T.; Blanford, C. F.; Stein, A. Science 1998, 281, 538. (9) Wijnhoven, J. E. G.J.; Vos, W. L. Science 1998, 281, 802. (10) Blanco, A.; Chomski, E.; Grabtchak, S.; Ibisate, M.; John, S.; Leonard, S. W.; Lopez, C.; Meseguer, F.; Miguez, H.; Mondia, J. P.; Ozin, G. A.; Toader, O.; van Driel, H. M. Nature 2000, 405, 437. (11) Vlasov, Y. A.; Bo, X. Z.; Sturm, J. C.; Norris, D. J. Nature 2001, 414, 289. (12) Lee, Y. J.; Heitzman, C. E.; Frei, W. R.; Johnson, H. T.; Braun, P. V. J. Phys. Chem. B 2006, 110, 19300. (13) Barry, R. A.; Wiltzius, P. Langmuir 2006, 22, 1369. (14) Sadakane, M.; Sasaki, K.; Kunioku, H.; Ohtani, B.; Ueda, W.; Abe, R. Chem. Commun. 2008, 6552. (15) Kamegawa, T.; Suzuki, N.; Yamashita, H. Chem. Lett. 2009, 38, 610. (16) Chen, X.; Li, Z.; Ye., J.; Zou, Z. Chem. Mater. 2010, 22, 3583. (17) Dhainaut, J.; Dacquin, J. P.; Lee, A. F.; Wilson, K. Green Chem. 2010, 12, 296. (18) Li, F.; Wang, Z.; Ergang, N. S.; Fyfe, C. A.; Stein, A. Langmuir 2007, 23, 3996. 2878
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(19) Loiola, A. R.; da Silva, L. R. D.; Cubillas, P.; Anderson, M. W. J. Mater. Chem. 2008, 18, 4985. (20) Xue, C.; Wang, J.; Tu, Bo.; Zhao, D. Chem. Mater. 2010, 22, 494. (21) Yan, H. W.; Zhang, K.; Blanford, C. F.; Francis, L. F.; Stein, A. Chem. Mater. 2001, 13, 1374. (22) Melde, B. J.; Stein, A. Chem. Mater. 2002, 14, 3326. (23) Wijnhoven, J. E. G. J.; Zevenhuizen, S. J. M.; Hendriks, M. A.; Vanmaekelbergh, D.; Kelly, J. J.; Vos, W. L. Adv. Mater. 2000, 12, 888. (24) Stein, A. Microporous Mesoporous Mater. 2001, 44-45, 227. (25) Stein, A.; Schroden, R. C. Curr. Opin. Solid State Mater. Sci. 2001, 5, 553. (26) Sadakane, M.; Takahashi, C.; Kato, N.; Ogihara, H.; Nodasaka, Y.; Doi, Y.; Hinatsu, Y.; Ueda, Y. Bull. Chem. Soc. Jpn. 2007, 80, 677. (27) Sheldon, R. A.; Wallau, M.; Arends, I. W. C. E.; Schuchardt, U. Acc. Chem. Res. 1998, 31, 485. (28) Thomas, J. M.; Raja, R.; Lewis, D. W. Angew. Chem., Int. Ed. 2005, 44, 6456. (29) Corma, A.; Garcia, H. Adv. Synth. Catal. 2006, 348, 1391. (30) Guidotti, M.; Ravasio, N.; Psaro, R.; Gianotti, E.; Marchese, L.; Coluccia, S. Green Chem. 2003, 5, 421. (31) Wu, P.; Tatsumi, T. Catal. Surv. Asia 2004, 8, 137. (32) Kamegawa, T.; Takeuchi, R.; Matsuoka, M.; Anpo, M. Catal. Today 2006, 111, 248. (33) Yamashita, H.; Yoshizawa, K.; Ariyuki, M.; Higashimoto, S.; Che, M.; Anpo, M. Chem. Commun. 2001, 435. (34) Kamegawa, T.; Morishima, J.; Matsuoka, M.; Thomas, J. M.; Anpo, M. J. Phys. Chem. C 2007, 111, 1076. (35) Mori, K.; Miura, Y.; Shironita, S.; Yamashita, H. Langmuir 2009, 25, 11180. (36) Lin, W. Y.; Frei, H. J. Am. Chem. Soc. 2005, 127, 1610. (37) Kamegawa, T.; Sakai, T.; Matsuoka, M.; Anpo, M. J. Am. Chem. Soc. 2005, 127, 16784. (38) Choi, M.; Na, K.; Kim, J.; Sakamoto, Y.; Terasaki, O.; Ryoo, R. Nature 2009, 461, 246. (39) Zou, D.; Ma, S.; Guan, R.; Park, M.; Sun, L.; Aklonis, J. J.; Salovey, R. J. Polym. Sci., Part A: Polym. Chem. 1992, 30, 137. (40) Schroden, R. C.; Al-Daous, M.; Blanford, C. F.; Stein, A. Chem. Mater. 2002, 14, 3305. (41) Ogawa, M.; Ikeue, K.; Anpo, M. Chem. Mater. 2001, 13, 2900. (42) Thomas, J. M.; Sankar, G. Acc. Chem. Res. 2001, 34, 571. (43) Yamashita, H.; Kawasaki, S.; Ichihashi, Y.; Harada, M.; Takeuchi, M.; Anpo, M.; Stewart, G.; Fox, M. A.; Louis, C.; Che, M. J. Phys. Chem. B 1998, 102, 5870. (44) Marchese, L.; Maschmeyer, T.; Gianotti, E.; Coluccia, S.; Thomas, J. M. J. Phys. Chem. B 1997, 101, 8836. (45) Biermann, U.; Friedt, W.; Lang, S.; L€uhs, W.; Machm€uller, G.; Metzger, J. O.; R€usch gen. Klaas, M.; Schfer, H. J.; Schneider, M. P. Angew. Chem., Int. Ed. 2000, 39, 2206. (46) Meier, M. A. R.; Metzger, J. O.; Schubert, U. S. Chem. Soc. Rev. 2007, 36, 1788. (47) Rios, L. A.; Weckes, P.; Schuster, H.; Hoelderich, W. F. J. Catal. 2005, 232, 19.
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dx.doi.org/10.1021/la1048634 |Langmuir 2011, 27, 2873–2879
