Asymmetric Vacancies Efficiently Couple O ₂ Activation With Reactive Oxygen Species Evolution for Enhanced Photocatalytic Methane Conversion

ABSTRACT 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 O 2 activation, often hampers subsequent ROS evolution due to overly strong adsorption, thereby limiting oxidation kinetics. Here, we demonstrate that asymmetric vacancies in ZnGa 2 O 4 , characterized by a Zn Td −O v −Ga Oh configuration, can overcome this intrinsic limitation by synergistically coupling O 2 activation with efficient ROS evolution. Specifically, the dynamic Ga Oh site preferentially promotes O 2 adsorption and activation, whereas the Zn Td site interacts weakly with oxygen‐derived species, facilitating ROS release and vacancy replenishment, thereby achieving an optimal balance between these critical steps. Consequently, Ag/ZnGa 2 O 4 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.