Abstract: Covalent organic framework (COF)-based heterojunction has emerged as a promising photocatalyst toward solar-to-fuel conversion. However, achieving high charge carrier separation efficiency and superior photocatalytic performance still remain a significant challenge. Herein, CYANO-COF was integrated with ZnIn₂S₄ via a facile in-situ growth method, thus forming CYANO-COF/ZnIn₂S₄ heterojunction. According to the in-situ light irradiation X-ray photoelectron spectroscopy (XPS) characterization and theoretical calculation, CYANO-COF/ZnIn₂S₄ heterojunction was verified to adopt an S-scheme charge transfer mechanism capable of fast charge carrier transfer rate and strong redox ability. As a result, the optimized CYANO-COF/ZnIn₂S₄-7.5 % exhibited a superior photocatalytic hydrogen production rate of 129.1 mmol g^-1 h^-1, which was 3.9 and 56 times higher than that of pristine CYANO-COF (33.2 mmol g^-1 h^-1) and ZnIn₂S₄ (2.3 mmol g^-1 h^-1), respectively, and the apparent quantum efficiency (AQE) at 420 nm was 20.5 %. The study shed light on the great promising of COF-based organic/inorganic S-scheme heterojunction toward solar fuel generation.

Key words: Photocatalytic hydrogen generation, Covalent organic frameworks, ZnIn₂S₄, S-scheme heterojunction