Oxidation coupling of terminal alkynes over CuPd bimetallic alloy enhanced by optimized charge transfer and alloy structure

Abstract

Homocoupling of terminal alkynes is an effective approach for the synthesis of 1,3-diyne, which is an important building block for numerous fine chemicals and pharmaceuticals. However, this reaction frequently encounters difficulties in catalyst recovery, and requires the addition of base or organic ligands, limiting their practical applications. Herein, we developed an efficient and recyclable CuPd bimetallic nanoalloy catalyst, which exhibited superior activity and selectivity in the homocoupling of terminal alkynes under mild conditions without any additives. In contrast to the low activity of monometallic Cu or Pd catalysts, a full conversion with a 100% selectivity for 1,3-diyne was achieved on bimetallic Cu2Pd1-400 nanoalloy with an extremely high activity. The comprehensive characterizations clearly evidenced that the alloying Cu with Pd was found to perturb the Cu electronic structure, and the positively charged Cu on the step and edge sites of CuPd nanoalloy catalyzed the homocoupling reaction via Cu-acetylide intermediates, and the density functional theory calculations revealed that the desorption of 1,3-diyne on CuPd nanoalloy was the rate-determining step for the whole reaction. This work provides a viable strategy for the rational design and fabrication of other nanoalloy catalysts for the green synthesis related to terminal alkyne oxidation.