Visible-light-driven organic transformations integrated with H2 production on semiconductors

Due to its clean and sustainable nature, solar energy has been widely recognized as a green energy source in driving a variety of reactions, ranging from small molecule activation and organic transformation to biomass valorization. Within this context, organic reactions coupled with H-2 evolution via semiconductor-based photocatalytic systems under visible light irradiation have gained increasing attention in recent years, which utilize both excited electrons and holes generated on semiconductors and produce two types of value-added products, organics and H-2, simultaneously. Based on the nature of the organic reactions, in this review article we classify semiconductor-based photocatalytic organic transformations and H-2 evolution into three categories: (i) photocatalytic organic oxidation reactions coupled with H-2 production, including oxidative upgrading of alcohols and biomass-derived intermediate compounds; (ii) photocatalytic oxidative coupling reactions integrated with H-2 generation, such as C-C, C-N, and S-S coupling reactions; and (iii) photo-reforming reactions together with H-2 formation using organic plastics, pollutants, and biomass as the substrates. Representative heterogeneous photocatalytic systems will be highlighted. Specific emphasis will be placed on their synthesis, characterization, and photocatalytic mechanism, as well as the organic reaction scope and practical application.