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The nature of external surface barriers in the zeolite ZSM-5 was explored by comparing mass transfer of n-heptane in samples with different crystal sizes, surface structure, and composition. These different surface properties were achieved by HF acid etching and SiO2 deposition on an as-synthesized ZSM-5 crystal sample. HF etching does not reduce surface barriers. SiO2 deposition on the same sample reduces surface barriers significantly. These insights into the nature of surface barriers could be used to guide the rational design of zeolitic materials with better mass transport properties.

Synthesis of hierarchically porous zeolites has drawn intensive interest because of their improved catalytic performance. It is highly desirable to find ways to generate these materials in a low-cost and scalable way for their commercial applications. A solvent evaporation route has been established to synthesize hierarchically porous titanosilicalite-1 (TS-1). In the protocol, hexadecyltrimethoxysilane was added to an ethanolic solution of titanium isopropoxide, tetraethyl orthosilicate and tetrapropylammonium hydroxide, i.e. the embryo solution of TS-1. The solution was subjected to solvent evaporation-induced self-assembly to afford an ordered dry gel. Subsequent steam-assisted crystallization converted the dry gel into a hierarchically porous TS-1. X-ray powder diffraction (XRD), UV–visible diffusive reflectance spectroscopy, N2 physisorption and electron microscopic characterizations have been employed to elucidate the structure. Ti is incorporated into the tetrahedral sites of the MFI structure and mesopores around 20 nm penetrating the crystalline framework are formed. Hexadecyltrimethoxysilane plays a key role in creating mesopores as well as increasing the crystal size. The hierarchically porous TS-1 exhibits improved activity in styrene oxidation and phenol hydroxylation. Copyright © 2014 John Wiley & Sons, Ltd.

Metastable magnesium hydroxymethoxide [Mg(OH)(OCH3)] powder with nanosheet morphology was derived from a direct bottom-up synthesis using magnesium acetate tetrahydrate as precursor under solvothermal conditions, with benzyl alcohol as structure-directing agent. The synthesis is driven by esterification of magnesium acetate to the corresponding methyl acetate, namely, ligand exchange and esterification of CH3COO– with CH3O–. A MgO powder featuring a Tasker III type (111) surface as its main exposed surface was produced after decomposition of the as-prepared Mg(OH)(OCH3) intermediate. X-ray diffraction (XRD) shows that the as-formed intermediate is Mg(OH)(OCH3), and methyl acetate is identified in the mother liquor by GC–MS measurements. XRD, SEM, and TEM images also show that the surface of the MgO nanosheets is covered by a Tasker III (111) surface. The vanadia supported on this MgO (111) nanosheet surface is more active than the conventional MgO-supported system for the oxidative dehydrogenation of ethylbenzene with carbon dioxide, which is attributed to the oxygen-rich nature and intermediate basicity of the MgO (111) surface.

One-dimensional V2O5 nanowires have been synthesized inside the channels of mesoporous silica SBA-15 through chemical approach, which involves aminosilylation of silanol groups on the silica surface, anchoring of isopoly acid, H6V10O28. by neutralization of basic amine groups, and thermal decomposition. The formation and physicochemical properties of the nanowires were monitored and studied by TG-DTA, variable temperature in situ XRD, TEM, N2 sorption measurements and UV-Vis DRS. The results indicate that V2O5 nanowires formed within SBA-15 channels belong to orthorhombic polycrystal domains. The oxygen-to-metal charge transfer band of V2O5 nanowires shows a blue shift in comparison with bulk V2O5, which clearly exhibits the quantum size effect of nanowires.

A mesoporous carbon prepared from sucrose was successfully employed as a hard template to produce hierarchical silicalite-1, thus providing a very simple and inexpensive route to desirable zeolite catalysts from widely available raw materials. The porous carbon was prepared by hydrothermal treatment of a mixture of sucrose and ammonia followed by carbonization of the mixture in N2 at high temperatures. The porous carbon produced by this method was subsequently applied as a hard template in the synthesis of mesoporous silicalite-1 and removed by combustion after synthesis. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAD), thermal gravimetry (TG), differential scanning calorimetry (DSC), N2 physisorption measurements, Hg porosimetry and CHN elemental analysis techniques were applied to investigate the porous carbon template as well as the mesoporous zeolite single-crystal material. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

MgO kristallisiert im Kochsalzgitter und hat üblicherweise die Mg(100) Ebene an der Oberfläche. Die Mg(111) Ebene besteht aus alternierenden Monoschichten von Sauerstoffanionen und Magnesiumkationen und hat große katalytische Aktivität beispielsweise bei der Claisen-Schmidt-Kondensation. Die bis jetzt bekannten Herstellungsmethoden für MgO(111) Oberflächen waren aufwendig oder uneffektiv. Bei der neuen Herstellungsmethode für (111) Nanoflächen wird eine Mischung von Wasser und Methanol zu einer Lösung von Magnesiummethylat in Methanol mit einer stoichiometrische Menge von 4-Nitro- oder 4-Methoxybenzylalkohol zugegeben und unter überkritischen Bedingungen auf 265 Grad C erhitzt. Nach Ablassen des Lösungsmitteldampfes entsteht ein weißes Pulver, das bei 500 Grad C kalziniert wird. Mehrere transmissionselektronenmikroskopische Bilder zeigen die Strukturen der MgO Nanoplättchen.

A new approach was developed to fabricate nanowires of mixed oxides MoO3-V2O5 inside the channels of mesoporous silica SBA-15. The method involves functionalization of the channel surface of SBA-15 with aminosilane groups, immobilization of Keggin-type molybdovanadophosphoric acids through an acid-base interaction, and heat treatment. The immobilization of the heteropolyacid containing mixed addenda makes the molar ratio of the loaded components controllable. The formation of the MoO3-V2O5 nanowires inside the channels was monitored by variable temperature in situ XRD. The materials obtained by heat treatment at 400 °C for 5 h were characterized by TEM, N2-sorption measurements, laser Raman spectra and UV-Vis diffuse reflectance spectra. Further heat treatment of the MoO3-V2O5 nanowires inside the SBA-15 channels at higher temperature (700 °C) destroys the framework integrity of SBA-15 by complete sublimation of MoO3 through the SBA-15 channel walls.

Bis(1,5-cyclooctadiene) nickel [Ni(COD)2] was employed as a nickel precursor to prepare nickel oxide nanoparticles upon high-surface-area mesoporous silica. Under protection of argon, Ni(COD)2 was dissolved in tetrahydrofuran (THF) to react with surface silanols of mesoporous silica SBA-15, which formed a black powder after completion of the surface reaction. Calcination of the powder produced ultrafine NiO inside the mesoporous silica matrix, which was evidenced by X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy and thermogravimetric analysis. The thermogravimetric analysis suggests that NiO formation is a result of surface nickel species calcination, whereas structural characterization clearly show that NiO nanoparticles of

As one of the naturally abundant elements, carbon can present in different molecular structures (allotropes) and thus lead to various physical/chemical properties of carbon-based materials which have found wide applications in a variety of fields including electrochemistry, optical, adsorption and catalysis, etc. On the other hand, its different allotropes also endow carbon-based materials with various morphostructures, which have been recently explored to prepare oxides and zeolites/zeotypes with tailored structures. In this review, we mainly summarize the recent advances in using carbon materials as hard templates to synthesize structural materials. Specifically, we focus on the development in the synthetic strategies, such as endotemplating, exotemplating approaches and using carbon materials as chemical reagents for the synthesis of metal carbides or nitrides, with an emphasis laid on the control of morphostructure. Meanwhile, the applications of the obtained materials will be highlighted, especially, in the field of heterogeneous catalysis where enhanced performances have been achieved with the materials derived from carbon-templated methods.

The cover picture shows a novel method for producing mesoporous zeolite single crystals by using cheap and easily prepared porous carbon as the mesopore template. The porous carbon template was obtained by carbonization in Ar of a hydrothermally treated sucrose/ammonia mixture, and it was successfully applied as an inert carbon matrix during zeolite crystallization. After hydrothermal crystallization, combustion of the carbon embedded in the zeolite crystals yielded mesoporous zeolite single crystals. Details are discussed in the article by C. H. Christensen et al. on p. 3955 f.