Modulating the secondary coordination sphere of the Cu site for boosting acetylene hydrochlorination

Abstract

Ligand modification of Cu catalysts has emerged as a promising strategy to enhance activity and stability in acetylene hydrochlorination. However, the limited availability of primary coordinating heteroatoms hinders precise engineering of the Cu active site microenvironment. Herein, a secondary coordination sphere modulation strategy was developed using various substituted hydrocarbon groups in the ligands. The local microenvironment around the Cu active sites was precisely tuned, leading to the Cu⁺ ratio of freshly prepared catalysts and reactive activity revealing a linear correlation, and the C₂H₂ adsorption energy exhibiting a distinct volcano plot correlation with catalytic activity. Among these catalysts, Cu-MMTB/AC exhibited the highest activity, achieving an acetylene conversion of 88.5% under the reaction conditions (T = 180 °C, gas hourly space velocity (GHSV) (C₂H₂) = 180 h⁻¹, and V(HCl): V(C₂H₂) = 1.2). Moreover, ^1#Cu₃-MMTB₁ exhibits advantages in both intermediate formation and HCl activation processes along the reaction pathway. This strategy offers a new avenue for designing high-performance Cu catalysts and promoting the use of mercury-free industrial catalysts.