Double Z-Scheme Heterojunctions of CdS and ZnS Nanoparticles on Bimetallic Metal–Organic Frameworks for Photocatalytic H₂ Production

Construction of a heterojunction is one of the promising methods for obtaining the required photocatalysts with enhanced photocatalytic activity. In this study, the ternary heterostructures of ZnS/CdS/Zn-Cd-MOF were synthesized using a semiderivatization of bimetallic MOF strategy. The photocatalytic hydrogen evolution activity of ZnS/CdS/Zn-Cd-MOF under visible light irradiation was investigated. Its maximum hydrogen production rate is 27.65 mmol g–1 h–1, which is 32 times that of pure ZnS nanoparticles and 13 times that of pure CdS nanoparticles. Mechanism studies using UV–visible DRS, photoluminescence, surface photovoltage, Mott–Schottky diagrams, and electron EPR reveal that the double Z-scheme heterostructure is formed between ZnS, CdS nanoparticles, and Zn-Cd-MOF, which provides a directional carrier migration channel, further promotes electron transfer, and effectively separates photogenerated carriers, which significantly improves photocatalytic activity and stability. This study proposes a reasonable double Z-scheme heterojunction photocatalyst with high efficiency for hydrogen production.