Systematic Regulation of Ternary Covalent Organic Frameworks for Boosted Photocatalytic Hydrogen Evolution

Donor–acceptor covalent organic frameworks (D–A-COFs) have emerged as promising materials for photocatalytic water splitting owing to their intrinsic electron transfer mechanism. However, their practical applications are still constrained by inefficient charge separation. Herein, we developed a series of ternary COFs by systematically regulating distinct acceptor components to optimize charge separation and transfer in photocatalysis. By employing a sulfone-based ligand as the donor and modulating the molar ratio of the two acceptor ligands, we successfully synthesized five ternary COFs (DS–OHOMe-COF-1 to DS–OHOMe-COF-5). Remarkably, DS–OHOMe-COF-3 exhibited a photocatalytic hydrogen evolution rate of 141.8 mmol g–1 h–1 under visible light irradiation (≥420 nm) with 1 wt % platinum loading, up to 13.1 times higher than that of binary systems DS-OMe-COF (10.8 mmol g–1 h–1). In addition, the apparent quantum yield (AQY) of DS–OHOMe-COF-3 increased up to 1.33% at 420 nm. Comprehensive characterizations including electrochemical tests, transient absorption spectroscopy, fluorescence decay curves, etc. revealed that the asymmetric ternary COF system significantly optimized the electronic configuration by introducing multiple monomers, thus promoting spatial charge separation and suppressing electron–hole recombination. Density functional theory calculations further demonstrate that the ternary DS–OHOMe-COF-3 exhibits a distinct D-π-A electronic structure and the lowest energy barrier for efficient charge separation and hydrogen evolution reaction. This work provides insights into enhancing the photocatalytic hydrogen production activity of COFs through the systematic structural engineering of donor and acceptor components.