Mimicking Natural Photosynthesis: Bromide-Mediated Photocatalysis for Spatially Decoupled Olefin Epoxidation and Hydrogen Evolution

Selective photocatalytic epoxidation of olefins provides a green approach to chemical transformation, but it remains challenging because of competing water oxidation and olefin overoxidation. Herein, inspired by natural photosynthesis, we demonstrate a Br^–/BrO^–-mediated solar-fuel generator, which allows for simultaneous H₂ evolution and olefin epoxidation at two separate reactor chambers. In this design, the ErBi₂O₄Cl (EBOC) semiconductor drives H₂ evolution in the presence of Br^– ions under visible light irradiation, while the generated BrO^– species diffuse to a dark reactor chamber to selectively oxidize olefins. The rapid Br^– oxidation kinetics on the (010)/(100) facets of EBOC effectively suppresses the water oxidation reaction. More importantly, the decoupled system design prevents direct contact of olefins with the EBOC semiconductor, mitigating the olefin overoxidation. As a result, continuous H₂ production is achieved, accompanied by an olefin-to-epoxide selectivity as high as 97%, significantly higher than that obtained in a conventional single-compartment reactor system. This work demonstrates an effective mediator-assisted strategy to suppress both competing side reactions and undesired reaction pathways in photocatalysis, providing a promising route for the rational design of efficient artificial photosynthetic platforms. © 2026 American Chemical Society