In situ irradiated XPS investigation on S-Scheme ZnIn2S4@COF-5 photocatalyst for enhanced photocatalytic degradation of RhB

Recently, the step-scheme (S-scheme) heterojunction has gained significant attention due to its effective electron-hole separation and strong redox capabilities. However, reports on covalent organic framework (COF)-based S-scheme heterojunctions for photocatalytic RhB degradation remain limited. In this study, an S-scheme ZnIn₂S₄@COF-5 heterojunction photocatalyst was successfully synthesized by growing COF-5 on the surface of ZnIn₂S₄ nanosheets, achieving efficient RhB degradation. Using 30 mg of COF-5@ ZnIn₂S₄, we degraded 50 mL of an 80 ppm RhB solution, achieving a 97% removal rate within 90 minutes. The photocatalytic performance of the COF-5@ ZnIn₂S₄ S-scheme heterojunction was approximately 1.7 times higher than that of ZnIn₂S₄ and 1.6 times higher than COF-5 alone. Compared to the other reported COF-based S-scheme heterojunctions and commercial photocatalysts, this ZnIn₂S₄@COF-5 photocatalyst exhibited superior photocatalytic performance. The S-scheme charge transfer mechanism of the ZnIn₂S₄@COF-5 heterojunction was elucidated through in situ irradiated XPS. Experimental results demonstrate that this rational design not only facilitates the effective separation of photogenerated electrons and holes, but also provides a large surface area and abundant active sites for efficient RhB degradation.