Review: organic–inorganic hybrid S-scheme photocatalysts—structural design principles, interfacial charge dynamics and mechanistic insights into solar-driven H2 evolution

Organic–inorganic S-scheme heterojunctions (OI-SHJ) have been developed as an emerging photocatalytic platform for the solar-driven H2 production. In this review, comprehensive discussion is presented on the design and mechanistic understanding of OI-SHJ photocatalysts with a focus on the engineering of the heterointerface, modulation of the band alignment and the role of the internal electric field to direct charge transfer pathways. Strategies involving S-scheme structures with polymers, covalent organic frameworks, carbonaceous materials and metal–organic frameworks are explored, with a particular attention placed on the impact of molecular tuning, defect engineering and interfacial coupling on photocatalytic H₂ production. In addition, the systematic correlation of the synthesis approaches, electronic structure control and the charge transfer pathway along with the influence of structural design on photocatalytic performance, durability and carrier migration is critically discussed. Lastly, the current issues of scalable synthesis, interfacial stability and electronic modulation of solar-to-hydrogen conversion are highlighted for future perspectives of sustainable solar-to-H2 conversion.