Single−atom Co anchored on covalent organic framework for remarkable photocatalytic hydrogen evolution efficiency

Single - atom catalysts (SACs) have attracted extensive attention because of their high atomic utilization and superior catalytic activity. Herein, single - atom Co has anchored on the β - ketoenamine - linked covalent organic framework (Tp-Tta COF) pores and used for remarkable photocatalytic hydrogen(H 2 ) production under Ultraviolet – Visible light (UV – Vis light) irradiation. The single - atom Co is visualized by the aberration - corrected high - angle annular dark - field scanning transmission electron microscopy (AC HAADF - STEM), and the C 3 – Co – N 1 coordination structure is demonstrated by X - ray absorption fine structure (XAFS) measurements. The modified Co 0.4 -SAC/Tp-Tta COF shows a high photocatalytic H 2 production of 1798.5 μmol g −1  h −1 and the Apparent quantum yield(AQY) is 3.02% at 420 nm. The improvement of the activity and stability of the photocatalyst is mainly attributed to the incorporation of Co single-atom that boosts the separation efficiency of photogenerated electron-hole pair and provides well - dispersed active sites. This study provides valuable insights into the development of UV–Vis light-responsive photocatalysts at the atomic level.