Highly active and robust copper-ceria catalyst engineered by reduction and reoxidation for oxidative alkyne homocoupling

A highly active copper-ceria catalyst for the base-free aerobic oxidative homocoupling of terminal alkynes was successfully developed via a calcination-reduction-calcination (CRC) strategy. Comprehensive characterization using H 2 -TPR, Raman, XPS, and CO-DRIFTS revealed that CRC treatment promotes the formation of highly dispersed copper oxide (CuO x ) clusters, increases the concentration of oxygen vacancies, and enhances the interaction between the Cu species and the CeO 2 support. The optimized catalyst exhibited exceptional performance, achieving a high apparent turnover frequency of 11.0h −1 and a 99 % yield in the model reaction. It also demonstrated remarkable stability, being reusable for up to 16 cycles, and broad substrate applicability. The migration of copper species and the associated electron transfer between copper and cerium were identified as crucial factors for the high catalytic activity. A synergistic mechanism is proposed wherein the surface CuO x clusters serve as the primary sites for alkyne activation and carbon–carbon coupling, while the oxygen vacancies in the Cu-O x -Ce interface facilitate electron transfer and oxygen activation, collectively improving the efficiency for oxidative homocoupling. This work provides a valuable insight for the rational design of copper-ceria catalysts via structural engineering for oxidative organic synthesis reactions.