Constructing N, O-Coordinated Metal Sites on β-Ketoenamine Covalent Organic Frameworks to Promote Photosynthetic Hydrogen Peroxide Production

Covalent organic frameworks (COFs) represent crystalline organic semiconductors with exceptional potential for artificial photosynthesis. Their highly regular structures, inherent porosity, and abundant coordination sites make COFs ideal substrates for anchoring single metal atoms that facilitate photogenerated electron accumulation and interfacial charge transfer. Herein, we construct metal coordination sites on β-ketoenamine Tp-Tta COF via an ultralow temperature coordination method to form stable M-SAC@COFs photocatalysts, where M represents Co, Ni, and Zn. The H₂O₂ production rate of Zn-SAC@COF is 2269 μmol g^-1 h^-1 without sacrificial agents, which is approximately 1.95 times higher than that of the pristine Tp-Tta COF, while achieving an apparent quantum efficiency of 2.3% at 420 nm. Theoretical calculations demonstrate that the synergistic interaction of metal active sites and Tp-Tta COF promotes the stepwise single-electron oxygen reduction reaction while diversifying orbital transitions, thereby enhancing overall photocatalytic performance. This work demonstrates that precise design of catalytic active sites on COFs offers a promising strategy for developing efficient solar-driven H₂O₂ synthesis systems.