Synthesis of covalent organic framework with in situ coordination of metal ions for photocatalytic hydrogen production

Photocatalytic water splitting for hydrogen production is a promising strategy to address energy and environmental challenges. Covalent organic frameworks (COFs) are potential materials, but metal ion incorporation typically requires complex multi-step synthesis. This work develops a Co²⁺-coordinated COF (Syn-Co-COF) through in situ coordination during COF synthesis, simultaneously constructing the framework and coordinating metal ions. This streamlined approach significantly enhances H₂ production efficiency versus metal-free TpBpy-COF and post-synthetically modified Post-Co-COF. Experimental and computational analyses reveal that the superior activity of Syn-Co-COF stems from its higher proportion of N–Co–N coordination structures. These structures inhibit pyridine ring torsion, broadening light absorption, accelerating charge separation/transfer, and extending excited-state lifetimes. The study provides valuable insights for efficient synthesis of metal-coordinated COF photocatalysts.