Single-site cobalt complexes embedded into thiophene-ring doped carbon nitride aiming to promote photocatalytic hydrogen evolution

The evolution of hydrogen (H 2 ) from water using solar energy is one of the most promising solutions to the energy dilemma. Implementing a cost-effective photocatalyst that does not contain any noble metals is critical. Based on thiophene ring-doped polymer semiconductor carbon nitride (CNA), CNA/Co-dcbpy modified by Co-dcbpy, an active molecular complex cocatalyst, has been successfully designed. Following a mild reprocessing reaction, the amide bond formed between ligand dcbpy and CNA firmly binds Co-dcbpy to the skeleton of CNA. This structure not only realizes the terminal modification of CNA, but also contributes to a highly monodisperse of Co atoms, greatly increasing the active sites of photocatalytic reaction. This catalyst shows significant H 2 production of 1016 μmol h −1  g −1 under visible light, which is basically equivalent to the catalyst with the same Pt load. The doping of the electron-rich thiophene ring extends the π-conjugated system of CNA, enhances the visible light absorption, and promotes charge separation. The synergistic interaction with complex modification facilitates charge delocalization and mitigates carrier recombination. At the same time, the Co active sites enhanced the H adsorption-desorption balance, which was conducive to promote H 2 evolution. Therefore, the transition metal complex strategy is a strategic way to design cost-effective photocatalysts.