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 m 2 g -1, and uniform pores of ∼3 to 4 nm size according to small-angle X-ray scattering, high resolution transmission electron microscopy and N 2 physisorption. The Keggin-type structure of [PW 12O 40] 3- anions is preserved intact into the Cr 2O 3 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 Cr 2O 3-PWA composition makes these materials highly promising for applications in oxidation catalysis. Although pure mesoporous Cr 2O 3 and PWA compounds exhibit low catalytic activity, the mesoporous Cr 2O 3-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 Cr 2O 3-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 Cr 2O 3 components as well as the well-ordered open-pore structure and large catalytically active surface area.
ASJC Scopus subject areas
- Materials Chemistry