Variable-valence element doping mediated photogenerated electron trapping for selective oxidation reactions†

Abstract

Photocatalytic selective oxidation provides a green and mild way of producing high-value added chemicals, whose conversion and selectivity are limited by complex oxidation pathways mediated by various reactive radical species. Thus, using photogenerated holes as an oxidant to directly drive these oxidation reactions could overcome the above problems, whereas the simultaneously formed electrons would cause the quenching of holes or the formation of other unfavorable reactive oxygen species that would affect the reaction efficiency. Herein, a variable-valence element doping method was proposed to realize hole-mediated photocatalytic selective oxidation. By taking Cu-doped Bi₂WO₆ as a typical prototype, we show that the doped Cu element with monovalent and divalent character can effectively trap photogenerated electrons, thereby boosting hole accumulation for selective oxidation reactions. As expected, Cu-doped Bi₂WO₆ exhibited excellent catalytic performances in oxidative coupling of benzylamines. This study provides a perspective on optimizing selective oxidation by hole regulation.