Preparation of ZnIn2S4/MOF S-scheme heterojunction photocatalysts for the efficient degradation of tetracycline

Abstract

Photocatalysis is a promising strategy for eliminating antibiotic contaminants. ZnIn₂S₄, with its layered structure and narrow bandgap, shows great potential but suffers from severe carrier recombination. Here, we report the in situ construction of an S-scheme ZnIn₂S₄/MOF-808 heterojunction. MOF-808 is indispensable due to its exceptional structural stability, abundant Zr-based active sites, and highly oxidative valence band, which complement ZnIn₂S₄ and enable efficient charge separation beyond the capability of other MOFs. Comprehensive characterization confirmed intimate interfacial coupling and a reinforced built-in electric field. Importantly, mechanistic analysis clarified the origin of the theory–experiment discrepancy: the theoretical carrier density underestimated actual electron consumption owing to recombination, interfacial transport inefficiencies, and side reactions, while KPFM measurements revealed a stronger interfacial electric field than classical models predicted. These results confirmed that the S-scheme pathway governs charge transfer and radical generation. Among the composites, ZM₁₀–15 % achieved 88.2 % tetracycline degradation with excellent stability and anti-interference ability, highlighting the critical role of MOF-808 in constructing high-performance photocatalysts.