Improved photocatalytic hydrogen production with the π-d conjugation between amino groups in COFs and CoS2, along with the S-scheme heterojunction

Covalent organic frameworks are promising polymer semiconductors for solar-driven hydrogen production. However, rapid charge recombination and low surface reaction kinetics currently limit their photocatalytic performance. A two-dimensional Schiff base TaTp-covalent organic framework loaded with CoS₂ was synthesized via a one-pot solid-state thermal method in this study, and an inorganic-organic S-scheme heterojunction CoS₂/TaTp-COF composite material was thereby constructed. When the CoS₂ loading reached 11 wt%, an optimal photocatalytic H₂ evolution rate was demonstrated by the composite, achieving an apparent quantum efficiency of 5.91 % at 500 nm. This notable improvement can be ascribed to the π-d conjugation effect occurring at the heterojunction interface. This phenomenon facilitates effective charge separation and transfer, consequently boosting the redox capabilities. Both experimental results and theoretical calculations confirmed the successful formation of the S-scheme heterojunction and elucidated the underlying charge transfer mechanism. This research not only provides new insights into COF-based photocatalytic hydrogen evolution but also offers valuable strategies for designing heterojunction catalysts.