Hydrotalcite-supported gold catalysts for a selective aerobic oxidation of benzyl alcohol driven by visible light

Abstract

Hydrotalcite-supported gold nanoparticles are studied as photocatalysts for the aerobic oxidation of benzyl alcohol and its derivatives without additional base under irradiation by visible light. The effects of the solvent, the hydrotalcite constitution and the gold content on the catalytic reaction are studied. The reactions utilizing benzotrifluoride as the solvent yield the best results. When varying the gold content and support, 2 wt% Au/HT-3 exhibits good catalytic activity. Furthermore, the rate of conversion under visible light is far superior to that in the dark. The catalytic activity can be tuned by manipulating the intensity or wavelength of the light. A reaction mechanism is proposed to rationalize these results: the primary reason for the lower activity observed on recycled catalysts is that the basic sites of hydrotalcite are decreased during the reaction in light.