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Layered RUB-36 and PREFER (lamellar precursor of ferrierite) are the precursors of CDO and FER-type zeolites, respectively. Both are composed of the same ferrierite (FER) layer building blocks. Topotactic conversion from RUB-36 to pure silica zeolite ZSM-35 has been demonstrated in the presence of a surfactant cetyltrimethylammonium hydroxide (CTAOH). The transformation mechanism of this process was revealed, for the first time, by the detailed investigations of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis, and one- and two-dimensional (2-D) solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) as well as theoretical simulations. During swelling at room temperature, cetyltrimethylammonium cations (CTA+) replacing the original template were intercalated into FER layers to expand the interlayer distance remarkably and consequently to destroy the strong hydrogen-bonding interactions between the layers. 2-D 1H–29Si heteronuclear correlation (HETCOR) NMR ...

The hydrous layer silicate RUB-36, (C6H16N)4 [H4Si36O76], has been used for an interlayer expansion reaction with dichlorodimethylsilane to interconnect neighboring ferrierite-type layers to a three-dimensional framework silicate. The linker group (−O–Si(CH3)2–O−) still has the two methyl groups in the as-synthesized form (material name COE-3 [Si20O38(CH3)4] for the silicate framework) rendering hydrophobic properties. The interlayer expanded zeolite, IEZ, is thermally stable and can be calcined at 550 °C to yield a hydrophilic material COE-4 [Si20O38(OH)4]. 29Si solid state MAS NMR experiments confirm the insertion of the linker group and the methyl and hydroxyl substitution in the as-made and calcined form, respectively. The BET surface area is 238 m2/g for COE-3 and 350 m2/g for COE-4. COE-3 and COE-4 crystallize in space group Pm with a = 12.2503(3) A, b = 13.9752(2) A, c = 7.3850(1) A, and β = 107.33(1)° and a = 12.16985(4) A, b = 13.95066(3) A, c = 7.37058(2) A, and β = 107.30(1)°, respectively. Rie...

Interlayer expansion reaction leads to a new family of microporous framework silicates using hydrous layer silicates as precursors. Using silylating agents such as dichlor-dimethylsilane (DCDMS), neighboring layers connect. In addition to the topotactic condensation of hydrous silicates, this leads to expanded silicate frameworks, with the number of pore openings increased by two Si-units. The hydrous layer silicate RUB-39 has been subjected to interlayer expansion reaction, using DCDMS at 180 °C, yielding new, crystalline microporous frameworks (COE-1 and COE-2), varying in their methyl function carrying as-made and oxidized calcined forms, respectively. An intersecting two-dimensional (2D) channel system with 10- and 12-membered rings is accessible for probe molecules, leading to a surface area of 540 m2/g and a pore volume of 0.169 cm3/g. The powder diagram was indexed in space group P2 with a = 15.609(3) A, b = 11.163(1) A, c = 7.301(1) A, and β = 91.2(1)° for COE-1 and a = 15.594(4) A, b = 11.039(2) ...

Discrete mesoporous silica nanospheres (MSNSs) with a narrow size distribution were prepared by a newly developed method, which is based on the emulsion system containing Si(OEt)4 (TEOS), water, cationic surfactant, and basic amino acid under weakly basic conditions (pH 9−10). The average 20 nm sized discrete MSNSs have uniform craterlike mesopores about 3 nm in diameter. The size of the discrete spheres can be regulated in the range of 15−200 nm by, for example, changing the stirring rate in the synthesis stage. Furthermore, introduction of tetrahedrally coordinated Ti species onto the pore of MSNSs and their catalytic performance in epoxidation of different-sized alkenes, cyclohexene, cis-stilbene and caryophyllene were also demonstrated.

Several mesoporous TaxW10−x mixed oxides prepared from TaCl5 and WCl6 in the presence of poly block copolymer surfactant Pluronic P-123 were examined as potential solid acid catalysts. Amorphous wormhole-type mesopores were observed in samples with x values from 3 to 10, whereas W-rich samples (x = 0−2) formed nonmesoporous structures with crystallized tungsten oxide (WO3). The acid strength increased with addition of W for mesoporous TaxW10−x oxides, and mesoporous Ta3W7 oxide exhibited the highest acid catalytic activity for the Friedel−Crafts alkylation of anisole and the hydrolysis of disaccharides. The results are compared with those of nonporous Ta2O5−WO3, HTaWO6 nanosheets, which were a solid acid obtained by exfoliation and aggregation of layered HTaWO6 with strong Bronsted acid sites in the interlayer, and a range of conventional solid acid catalysts. Mesoporous Ta−W oxides exhibited a turnover rate higher than that of nonporous Ta2O5−WO3 and HTaWO6 nanosheets, indicating that the mesoporous stru...

A liquid-phase method for preparing uniform-sized silica nanospheres (SNSs) 12 nm in size and their three-dimensionally ordered arrangement upon solvent evaporation have recently been pioneered by us. The SNSs are formed in the emulsion system containing Si(OEt)4 (TEOS), water, and basic amino acids under weakly basic conditions (pH 9−10). Here, we report the formation mechanism of the SNSs; the reasons for the uniform size and the ordered arrangement are described in detail. The formation process is monitored by FE-SEM, SAXS, and liquid-state NMR. The FE-SEM observations reveal that silica nanoparticles ca. 4 nm in size are formed in the water phase at the early stage (∼0.5 h) of the reaction. The SAXS measurements suggest that the number density of the particles remains unchanged when they are gradually grown. Liquid-state 1H NMR analyses suggest that TEOS are slowly hydrolyzed at the oil−water interface to continuously supply silicate species into the water phase. The silicate species are immediately c...

Sulfonic acid group (SO3H)-bearing amorphous carbon/mesoporous silica composites were studied for use as solid acid catalysts. Sugar-derived amorphous carbon with SO3H cannot catalyze hydrophobic acid-catalyzed reactions, such as the dimerization of R-methylstyrene, because of the small surface area. However, SO3H-bearing sugar-derived amorphous carbon supported on mesoporous silica exhibits remarkable catalytic performance for the dimerization of R-methylstyrene. Under optimal conditions, the selectivity of the composite catalysts for unsaturated dimers exceeds 98%. Structural and reaction analyses revealed that SO3H-bearing carbon particles with large surface areas are formed in the mesopores and prevent intramolecular Friedel-Crafts alkylation, resulting in high catalytic activity.

A novel type of organic–inorganic hybrid zeolite material ZOL (zeolite with organic group as lattice) is reviewed. ZOL materials are synthesized from an organosilane in which a methylene group bridges two silicon atoms to supersede an oxygen atom in the zeolite framework. ZOLs of various structures with the LTA, MFI, and *BEA topologies can be synthesized under synthesis conditions similar to those for conventional zeolites. The presence of framework methylene is demonstrated through the 13C MAS NMR analyses, although the presence of Si−CH3 formed through the hydrolysis of Si−CH2−Si linkage is also observed. Although ZOL has physical properties similar to those of its inorganic counterpart, it shows higher hydrophobicity because of the presence of the framework organic group. The organic moieties in ZOL materials are thermally stable enough to be retained after the combustion of occluded organic structure directing agents.

New multifunctional luminescent hybrid mesoporous silicas (LHMS) containing a tunable chemosensor diimine moiety inside the pore wall have been synthesized. XRD and TEM image analyses indicate the formation of highly ordered 2D hexagonal mesophase from a 1:3 mixture of diimine organosilica and tetraethyl orthosilicate (TEOS) assisted by the supramolecular assembly of cetyltrimethylammonium bromide (CTAB); the use of diimine organosilica precursor alone leads to disordered mesophase. 13C CP MAS, 29Si MAS NMR, and UV−visible spectroscopic data show the incorporation of bridging organic diimine in the solid mesoporous materials. N2 sorption data suggest high BET surface areas together with type IV isotherms for the LHMS samples. These hybrid mesoporous materials show very strong affinity for metal cations (Fe3+, Zn2+, etc.), which could be utilized for possible application to metal ion chemosensors. All the LHMS samples exhibit very strong photoluminescence at room temperature and strong dependence of emissi...

Carbonization of d-glucose at 573−723 K followed by sulfonation produces a functionalized amorphous carbon material with acid catalytic activity as a solid-acid replacement for sulfuric acid. The carbon material contains phenolic hydroxyl, carboxylic acid, and sulfonic acid groups and exhibits high catalytic performance for liquid-phase acid-catalyzed reactions. Carbonization at higher temperature followed by sulfonation also results in amorphous carbon, but the resultant does not exhibit catalytic activity although the amorphous carbon has sufficient amount of sulfonic acid groups. Structural and active site analyses suggest that the marked difference in catalytic activity is due to the accessibility of reactants to sulfonic acid groups in the carbon structure.

The presence of various counteranions in the interfacial region of the silicate−surfactant mesophase introduces opportunities for manipulation of the phase structure. Well-ordered three-dimensional hexagonal P63/mmc, cubic Pm3n, two-dimensional hexagonal p6mm, and cubic Ia3d mesoporous materials have been synthesized with the same surfactant (cetyltriethylammonium bromide), depending on the kind of acids. The counteranions of acidic media have resulted in increasing surfactant packing parameter g in the order SO42- < Cl- < Br- < NO3-, which leads to different formation routes to the mesostructures. It has been found that the mesophases are always transformed from the lower curvature one into the higher curvature one in the acidic synthesis gel. The combination of X-ray diffraction patterns, scanning electron microscope images, and high-resolution transmission electron microscope images presented visible evidence for the mesostructural constructions. In particular, the synthesis of a cubic Pm3n mesoporo...

A novel type of organic−inorganic hybrid zeolite has been successfully synthesized, in which lattice oxygen atoms are partially superseded by methylene groups. Various types of hybrid materials with the LTA, MFI, and *BEA structures are obtained from an organosilane in which a methylene group bridges two silicon atoms under synthesis conditions similar to those for conventional zeolites. The presence of a methylene group in the framework is demonstrated by 29Si and 13C MAS NMR and IR, although the Si−C bonds are partially cleaved during the hydrothermal synthesis to give rise to terminal methyl groups. The organic framework is thermally stable enough to remain after the combustion of the occluded organic structure directing agents (SDAs). The thermal stability of the organic framework is much higher than that in amorphous materials synthesized from the same silicon source and is dependent on the zeolite structures. The SDA-free materials not only show microporosity like ordinary zeolites but also exhibit ...

A mesostructured hollow sphere form of carbon can be synthesized by using mesocellular foam (MCF) silica as template. A carbon structure composed of spherical hollows with closed walls and with mesopores of around 4 nm in diameter was prepared by the two-step impregnation of sucrose and successive carbonization under flowing argon at 900 °C. A temperature-programmed oxidation experiment revealed that the mesoporous carbon released argon atoms when heated above 600 °C, when oxidation of the carbon walls occurred. This result provides evidence for the presence of a large void volume inside the carbon spheres and implies that the pore size of 4 nm is due to the interspheric space. A single-step impregnation of sucrose resulted in the formation of open-walled mesospheres with pores of 4, 18, and 24 nm. The two larger pore sizes are attributed to the diameters of the window and of the cell as in MCF−silica. Platinum was loaded on these mesoporous carbons. The metal was highly dispersed (∼0.4 nm by EXAFS) on th...

We show that Fe3+, Co2+, Ni2+, and Cu2+ fixed by diamino-functionalized MCM-41 and MCM-48 work as adsorption centers for arsenate ions. The stoichiometry of the N/metal cation was determined as well as the As/metal cation for the adsorption of arsenate. The effectiveness of the removal of arsenate from a dilute solution is ordered according to Fe3+ > H+ ∼ Co2+ > Ni2+ ∼ Cu2+, which is slightly different from the adsorption capacity: Fe3+ > Co2+ ∼ H+ > Ni2+ > Cu2+. The distribution coefficients, Kd, exceed 200 000 at [arsenate] < 100 ppm in Fe/NN-MCM-41. The Fe center binds nearly three arsenate ions, which allows the adsorption capacity of Fe/NN-MCM-48 to be one of the largest at 2.5 mmol (g of adsorbent)-1 among the adsorbents of arsenate. The difference between the meso-framework structures appears in their adsorption capacity; cation/NN-MCM-48 adsorbs a larger amount of arsenate than cation/NN-MCM-41. This is mainly caused by the difference of cation content in these functionalized mesoporous silicas. ...

To reveal the potential properties of mesoporous titania with a BET surface area of more than 1000 m2·g-1, we incorporated vanadium into mesoporous titania by co-condensation (direct incorporation, V-meso TiO2) and by postsynthesis impregnation (impregnation, V/meso TiO2). The mesostructure remained until the loading reached 5 wt % as V metal for V-meso TiO2. The catalysts were characterized by transmission XANES and room-temperature ESR spectroscopies. The pre-edge absorption in V K edge spectra of V-meso TiO2 demonstrated that the valence of V is 4+ under atmospheric conditions (i.e., exposed to air and at room temperature). Ti K edge XANES showed that 5-fold coordinated Ti, which originally comprised 37% of the total titanium in the mesoporous titania, was substituted by V. In contrast, V in V/meso TiO2 was assigned to a valence of 5+. In ESR spectra, both of these catalysts showed strong hfs multiples characteristic of isolated vanadyl species in either square pyramidal or distorted octahedral coordin...

We report the characteristics of aminosilane-grafted mesoporous silicas as adsorbents of oxyanions in acidic conditions. Mono-, di-, and triamino-functionalized silicas were prepared to examine the influence of amino group density. The triaminosilane-grafted mesoporous silica adsorbed more chromate and arsenate than expected from the increased number of sites, suggesting stable complex formations. Functionalized SBA-1 showed larger adsorption capacities than MCM-41 derivatives. The adsorption capacity was independent of the average surface density of monoamino groups, demonstrating domain formation of fixed silanes. These structural characteristics on molecular and meso scales may offer insights into understanding the mechanism of heterogeneous oxyanion capture by amino-functionalized solids, which are promising inexpensive reagents for reducing toxic anion pollution.

Mesoporous Ti-SBA-15 has been postsynthesized by the titanation of pure silica SBA-15 in glycerol with the assistance of quaternary organic ammonium hydroxides, and has been extensively characterized by various techniques to investigate the mesostructural and catalytic properties, and the chemical nature of the incorporated Ti species, in comparison with those of Ti-MCM-41. To incorporate tetrahedral Ti species into the silica walls of SAB-15, the titanation needs to be carried out at elevated temperature and using an optimum amount of organic ammonium hydroxide. Ti-SBA-15 samples with a Si/Ti ratio ranging from 376 to 16 are successfully prepared with the retention of hexagonal mesostructure by elaborately conducting the titanation. The nature of the Ti species depends greatly on the Ti loading. At Si/Ti ratios higher than 50, the Ti species are mainly tetrahedrally coordinated in isolated states, while poorly dispersed Ti species of octahedral coordination are formed at higher Ti incorporation levels; h...

Mesoporous titania with BET surface area over 1200 m2/g-1 was synthesized by primary amine templating. Dodecyl-, tetradecyl-, and hexadecylamines gave intense XRD patterns with narrow pore-size distributions in which the most probable diameter changed according to the carbon chain length. Thermal treatment was necessary for the formation of a stable structure, which strongly depends on the vapor pressure during the process. No diffraction patterns were observed above 2θ = 10°, suggesting the amorphous nature of the mesoporous titania. UV−vis and XANES spectroscopies demonstrated that the local structure of titanium was mainly 5-coordinated and Oh (6-coordinated) Ti. Chemical vapor deposition (CVD) of titanium isopropoxide followed by its decomposition with water vapor was carried out to improve the thermal stability of template-extracted titania. Although this CVD treatment resulted in a decrease in the BET surface area by 20%, the treated TiO2 showed high thermal stability; surface areas higher than 500 ...

Chiral mesoporous organosilicas with helicity perfectly controlled were synthesized by using N-myristoyl-l-alanine and bis(triethoxysilyl)ethylene in the presence of l-arginine; the left-/right-handed ratios for the helical particles have proved to be 0/100.

Mesoporous silica containing a large amount of aminopropyl groups has been successfully synthesized via the anionic templating route. The electrostatic interaction between the positively charged amino groups in 3-aminopropyltriethoxysilane and the negatively charged sulfate head groups in sodium dodecyl sulfate is a driving force for the self-assembly of silica−micelle composite.

By elaborate adjustment of synthesis conditions, cubic (Pm3n) SBA-1 samples with well-defined crystal morphologies of a large number of facets have been synthesized, which are supposed to be obtained as a result of highly isotropic crystal growth under the conditions near thermodynamic equilibrium. The high-resolution transmission electron microscope image revealed regular periodicity over very large areas and this clearly indicates the crystal is a single crystal with a well-ordered mesostructure.