Surface modification of ZnIn₂S₄ layers to realize energy-transfer-mediated photocatalysis

Photocatalytic selective aerobic oxidation reactions are crucial in designing advanced organic intermediates, but suffer from low conversion efficiency. Hence, activating O₂ to create suitable reactive oxygen species, such as singlet oxygen (¹O₂), can significantly increase the yield of desired products. Herein, using ZnIn₂S₄ nanosheets as a model system, we build a surface-modified theoretical structure, where a surface-covered non-conductive macromolecular chain, polyvinyl pyrrolidone (PVP), is bound to ZnIn₂S₄ and influences the O₂ adsorption process. PVP on the surface significantly changes the electronic structure and suppresses electron conduction of ZnIn₂S₄ nanosheets. Therefore, abundantly photogenerated and long-lived species transfer their energy to physically absorbed O₂ to efficiently generate ¹O₂, which can oxidize sulphides into their corresponding sulphoxides. For sulphoxidation of different sulphides, surface modification brings a 3-9-fold increase in conversion efficiency and high selectivities ≥98%. This study provides a feasible way of boosting ¹O₂-generation-related photocatalytic reactions.