A recyclable Cu@C2N nano-catalyst applied in the transformation of alkynes: pH switchable access to ketones and 1,3-diynes

Abstract

The development of efficient noble metal-free heterogeneous catalysts with simple synthesis processes is of great value in synthetic chemistry. So far, the performance of heterogeneous catalysts under different acidic and alkaline conditions has rarely been considered. Herein, we demonstrate a multifunctional Cu@C₂N catalyst for pH switchable hydration of alkynes and the Glaser–Hay reaction, with maximum yields reaching 92% and 95%, respectively. The efficient conversion arises from strong metal–support synergistic effects, as the C₂N support adsorbs the reaction substrate and the Cu metal activates the reaction substrate well, collaboratively facilitating the conversion of alkynes. Furthermore, the Cu@C₂N catalyst shows good substrate compatibility and recyclability, which can be simply recovered and reused five times without significant loss of its catalytic activity. In addition, the Cu@C₂N catalyst has abundant acidic and alkaline sites, and the valence state and dispersed form of Cu can be well stabilized by C₂N. This work proves the successful application of a C₂N-based catalyst in the field of organic synthesis and points out the directions for designing low-cost, widely adaptable and environmentally-friendly catalytic systems.