Dual active sites of single-atom copper and oxygen vacancies formed in situ on ultrathin TiO₂(B) nanosheets boost the photocatalytic dehalogenative C-C coupling synthesis of bibenzyl

The combination of photocatalytic dehalogenation of halogenated aromatics and C-C coupling synthesis of valuable organics is an interesting method for the elimination of pollutants and synthesis of valuable chemicals. Herein, we present a green method for the photocatalytic dehalogenation of benzyl bromide and selective coupling synthesis of bibenzyl achieved on the dual active sites of single-atom Cu and surface oxygen vacancies (V-OS) generated in situ on ultrathin 2D-TiO2(B) nanosheets. The experimental results show that single-atom Cu sites on ultrathin TiO2(B) nanosheets can improve charge transfer and separation efficiency and stabilize V-OS formed in situ; the presence of V-OS not only improves light absorption capacity but also favors the adsorption of reactant benzyl bromide molecules. More importantly, the dual sites of single-atom Cu and adjacent V-OS form a solid frustrated Lewis pair, favor the adsorption of benzyl bromide molecules, activate the C-Br bond, and boost the C-C coupling synthesis of bibenzyl. This work provides a novel insight into photocatalytic C-C coupling through the synergistic effect of single-atom Cu and V-OS on ultrathin nanosheet photocatalysts.