Selective C-C coupling of terminal alkynes under an air atmosphere without base over Cu-NX-C catalysts

The fabrication of a silk fibroin-drived porous, in situ nitrogenated carbon skeleton with highly dispersed Cu-N-X-C active sites via a sol-gel and pyrolysis treatment was demonstrated. Cu-N-X-C was used to catalyze the oxidative homo-coupling of terminal alkynes with excellent functional group tolerance and high yields under an air atmosphere without base and additives. The small amount of catalyst (2 mol%) and suitable recyclability further demonstrated its good activity and stability. The excellent activity of the Cu-N-X-C catalyst can be ascribed to its high surface area, porous structure, small size of the highly dispersed Cu-N-X-C active sites and graphitic N. A possible mechanism was deduced according to the structural and surface valence analyses of the sample before and after the reaction. The report aims to demonstrate that such a nature-based sustainable catalyst can provide new insights into the design of coupling reaction catalysts with outstanding catalytic C-C coupling performance.