Controllable Synthesis of Vacancy-Defect Cu Site and Its Catalysis for the Manufacture of Vinyl Chloride Monomer

Designing favorable structures of active sites and clarifying the structure–activity relationship are important to narrow the large activity gap between Cu-based and the noble-metal-based catalytic systems for vinyl chloride production. Herein, we report a facile controllable thermal method for fabricating the platform of Cu single-atom catalysts ranging from the standard no-vacancy-defect CuCl 3 –N to vacancy-defect CuCl 2 V–N (“V” for the vacancy-defect site) and to no-vacancy-defect CuN 4 . The gradually released C–Cl derivatives promote the vacancy-defect generation under elevated temperatures, and the activity gap between Cu- and the noble-metal-based systems is found to be dramatically narrowed from classic ∼37-fold to ∼1.5-fold on the vacancy-defect sites. Kinetic analysis shows that the competitive adsorption between acetylene and hydrogen chloride on the CuCl 2 V–N site contributed more to the catalytic performance than the single hydrogen chloride adsorption on site CuCl 3 –N or CuN 4 . Furthermore, when the CuCl 2 V–N site is preoccupied and adsorbed by acetylene, the reaction energy barrier decreases from 35 to 24 kJ/mol, indicating that the single activation of acetylene is more favorable for catalytic activity than that of the dual-activation of acetylene and hydrogen chloride. DFT calculations revealed the specific reaction mechanism catalyzed on the vacancy-defect CuCl 2 V–N site, i.e., where the vacancy-defect not only affects the activation behavior of substrates but also regulates the reaction pathway. Excellent catalytic performance can be maintained under the interaction of high concentration of vinyl chloride and H 2 S impurity. This work opens a new window for controllable synthesis of vacancy-defect sites of single metallic atoms in catalysis design and enhancing catalytic activity.