Synthesis of bipyridine-based covalent organic frameworks for visible-light-driven photocatalytic water oxidation

Covalent organic frameworks (COFs) with band gap engineering characters are attractive organic semiconductors. Although several COFs are being utilized for photocatalytic H2 production and CO2 reduction, few of them can realize the challenging water oxidation under visible light. Herein, we present the visible-light-driven photocatalytic water oxidation on bipyridine-based COFs (Bp-COF), which was synthesized through the Schiff base condensation reaction. Bp-COF displays impressive visible-light-driven water oxidation activity with O2 evolution rate of 152 μmol g−1 h−1 after coordinating with Co2+. Furthermore, the Bp-COF could also enable photocatalytic H2 production under visible light. The unique photocatalytic performance of BpCo-COF for both water oxidation and proton reduction could be attributed to its excellent light harvesting property, appropriate energy band structure, high porosity and wettability as well as coordinated cobalt for photocatalytic water splitting. This work demonstrates the potential of COFs as semiconductors for photocatalytic solar fuels conversion.