Covalent Organic Frameworks Anchoring Single‐Atom Pt for Three‐Phase Interface‐Assisted Photocatalytic Overall Water Splitting

Covalent organic frameworks (COFs) are promising photocatalysts for overall water splitting (OWS) due to their high crystallinity, porosity and tunable structures. However, current COF-based systems rely on cocatalysts, which suffer from low atomic utilization and poor distribution due to aggregation. In addition, the oxygen reduction reaction (ORR) backward reaction severely undermines catalytic efficiency and stability in long time reaction. Herein, we present a strategy that combines atomically dispersed Pt sites anchored via N/O coordination within triazine-based COFs and a gas-liquid-solid three-phase interface-assisted photocatalytic system to enhance both performance and durability. As a result, the Pt-TBPyT-COF achieves superior OWS performance with H₂ and O₂ evolution rates of 469.8 and 234.9 µmol·g^-1·h^-1, respectively, and an apparent quantum yield of 8.91% at 450 nm. Notably, the OWS via gas-liquid-solid three-phase interface-assisted method effectively suppresses ORR backward reaction and reaches average rates as high as 568.7 and 284.3 µmol·g^-1·h^-1 for H₂ and O₂ in 5 h, respectively, and maintained stable photocatalytic activity over a 30 h continuous reaction. Further, density functional theory calculations and in situ experiments reveal that the single-atoms Pt coordination accelerates *H desorption, while the triazine units in COFs benefits charge separation and reduced energy barriers of OER rate-determining step.