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Issue 14, 2012
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Ordered mesoporous Cr2O3 frameworks incorporating Keggin-type 12-phosphotungstic acids as efficient catalysts for oxidation of benzyl alcohols

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Abstract

Ordered mesoporous chromium(III) oxide–phosphotungstic acid (PWA) nanocomposite structures with controllable composition (∼17 to 49 wt% in PWA) have been successfully prepared via an ultrasound-assisted nanocasting route, using mesoporous SBA-15 silica as a rigid mold. These materials possess 3D hexagonal mesostructure, large internal BET surface areas of ∼67 to 80 m2 g−1, and uniform pores of ∼3 to 4 nm size according to small-angle X-ray scattering, high resolution transmission electron microscopy and N2 physisorption. The Keggin-type structure of [PW12O40]3− anions is preserved intact into the Cr2O3 framework, as confirmed by total X-ray diffuse scattering and pair distribution function analysis and infrared and diffuse reflectance ultraviolet-visible (UV-vis) spectroscopy. The integration of regular porosity, large internal surface area, and Cr2O3–PWA composition makes these materials highly promising for applications in oxidation catalysis. Although pure mesoporous Cr2O3 and PWA compounds exhibit low catalytic activity, the mesoporous Cr2O3–PWA composites showed superior activity and selectivity for the oxidation of selected secondary benzyl alcohols, giving good-to-high yields within a short reaction time. Furthermore, the Cr2O3–PWA composite frameworks demonstrated remarkable durability and reusability upon multiple usages without leaching or decomposition of the incorporated PWA clusters. This enhancement is attributed to the synergistic interactions between the PWA and Cr2O3 components as well as the well-ordered open-pore structure and large catalytically active surface area.

Graphical abstract: Ordered mesoporous Cr2O3 frameworks incorporating Keggin-type 12-phosphotungstic acids as efficient catalysts for oxidation of benzyl alcohols

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Supplementary files

Article information


Submitted
06 Dec 2011
Accepted
06 Jan 2012
First published
28 Feb 2012

J. Mater. Chem., 2012,22, 6919-6927
Article type
Paper

Ordered mesoporous Cr2O3 frameworks incorporating Keggin-type 12-phosphotungstic acids as efficient catalysts for oxidation of benzyl alcohols

I. Tamiolakis, I. N. Lykakis, A. P. Katsoulidis, C. D. Malliakas and G. S. Armatas, J. Mater. Chem., 2012, 22, 6919
DOI: 10.1039/C2JM16390J

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