Photocatalytic oxidation mediated by reactive oxygen species (ROS) provides an effective platform for a wide range of important chemical transformations. However, conventional oxygen-vacancy engineering strategy, while enhancing O2 activation, often hampers subsequent ROS evolution due to overly strong adsorption, thereby limiting oxidation kinetics. Here, we demonstrate that asymmetric vacancies in ZnGa2O4, characterized by a ZnTd-Ov-GaOh configuration, can overcome this intrinsic limitation by synergistically coupling O2 activation with efficient ROS evolution. Specifically, the dynamic GaOh site preferentially promotes O2 adsorption and activation, whereas the ZnTd site interacts weakly with oxygen-derived species, facilitating ROS release and vacancy replenishment, thereby achieving an optimal balance between these critical steps. Consequently, Ag/ZnGa2O4 delivers the highest turnover number (TON) reported to date among Ag-based catalysts for the photocatalytic oxidative coupling of methane via a ROS-mediated pathway. The general effectiveness of this asymmetric-vacancy strategy is further validated in other representative photocatalytic reactions, including hydrogen peroxide production and the oxidative coupling of benzyl alcohol.
Zhang et al. (Mon,) studied this question.