Ingenious strategy of a strong intermolecular force-linked donor–acceptor–donor system in COFs for efficient and improved photocatalytic hydrogen production

Abstract

To overcome the problem of low electron–hole recombination in semiconductors, the covalent organic framework (COF) based photocatalyst TAT-COF/TAF-COF (TATT-COF) was designed and synthesized. The dual-COF design strategy not only incorporates hydrophilic groups to enhance catalyst dispersion in aqueous media but also enables adaptive conformational adjustments via ether linkages between s-triazine and benzene rings in TATT-COF. This structural flexibility facilitates rapid engagement in reduction processes. Comprehensive phase characterization and photoelectrochemical studies confirm the crystalline framework and semiconductor properties. Density functional theory (DFT) calculations of work functions, band structures, and charge density differences provide mechanistic evidence for interfacial charge transfer in photocatalytic hydrogen evolution. The heterojunction architecture of TATT-COF exhibits a 7 times enhancement in interfacial charge transfer magnitude compared to the homojunction TAF-COF. This improvement arises from synergistic effects: hydrophilic group introduction provides charge-transfer pathways, while the S-scheme heterojunction design establishes directional charge migration channels.