Selective hydroxylation of benzene via enhanced generation and utilization of hydroxyl radicals with CuZnSbO photocatalyst

Abstract

Photocatalytic selective benzene hydroxylation via activation of C(sp2)–H under visible light remains a challenging reaction. Copper-incorporated mixed metal oxide photocatalysts have shown promise in addressing this difficulty by enabling visible light harvesting, controlled reactive oxygen species (ROS) generation, effective ROS utilization, and reactant adsorption. However, copper incorporated metal oxide catalysts were suffered from poor catalytic activity and selectivity due to leaching of Cu species. To solve this problem, herein, a novel stable mixed metal oxide (CuZnSbO) was prepared for the first time by applying a facile method. Copper introduction brought about the suitable band gap energy for a wide range of visible light harvesting of the CuZnSbO catalyst. The copper species play a key role in activating H₂O₂ to produce hydroxyl radicals (^•OH) for benzene oxidation by controlling charge recombination. The mixed metal oxide of zinc and antimony supports the included copper strongly enabling copper stability. The CuZnSbO not only generates available hydroxyl radicals but also facilitates efficient hydroxyl radical consumption to initiate C(sp2)–H activation, forming benzene radical intermediates en route to phenol. That is ever reported. CuZnSbO delivered 31.51 % benzene conversion and 100 % phenol selectivity. This work demonstrates the promise of engineered mixed metal oxide that boosts Cu species utilization for H₂O₂ and benzene activation. The photocatalyst showed good activity in selective oxidative hydroxylation reactions through harnessing visible light and controlled ROS generation. Importantly, Cu cations govern the photocatalytic ^•OH generation mechanisms as shown by XPS and active site deactivation analysis.