Oxygen vacancy enriched and Cu single-atom contained covalent organic frameworks: A competitive photocatalyst to promote hydrogen evolution under visible light

Single-atom loaded covalent organic frameworks (COFs) have been rapidly developed in the field of photocatalytic hydrogen production in recent years. Despite the insufficient active sites has been introduced, the high recombination rate of photogenerated carriers has hindered the progress of catalyst development. In this work, a novel approach is proposed to construct oxygen vacancies (OVs) on single atom Cu contained COF-TpPa, acting as an electron collector to facilitate the transfer and utilization of electrons. The Cu-OV-TpPa can provide a remarkable H2 production rate of 2.77 mmol g- 1 h- 1 under visible light, which is 2.6 times of Cu-P-TpPa (a H2 production rate of 1.02 mmol g- 1 h- 1). It achieves a high apparent quantum efficiency (AQE) of 20 % at 420 nm with no noble metal cocatalyst. A thorough analysis of carrier lifetime, recombination rate, electric conductivity and charge density reveals that the synergistic effect between OVs and single-atom Cu significantly enhances photogenerated carrier separation efficiency and reduces activation energy. This study presents a new strategy to design COF-based photocatalysts towards a competitive H2 production under visible light.