Electric-Symmetric-Breaking in Cu Single-Atom Catalysts for Enhanced Acetylene Hydrochlorination.

Abstract

Acetylene hydrochlorination for vinyl chloride monomer (VCM) synthesis represents a vital industrial reaction, where the development of nonmercury catalysts has emerged as a critical research frontier. While metal-nitrogen-carbon (metal-N-C) materials, particularly Cu-N-C catalysts, have shown promise as mercury alternatives, their practical application has been hindered by the inherent limitations of the symmetric <i>D</i>_4<i>h</i> electric field in planar Cu-N₄ structures, which induces excessive adsorption of *C₂H₃Cl intermediates and compromises long-term stability. Herein, we present a design strategy through the development of electric-symmetry-broken Cu single-atom catalysts, designated as CuN₄-P/C, achieved by the strategic incorporation of phosphorus atoms into the second coordination shell. Comprehensive experimental investigations coupled with density functional theory calculations demonstrate that the engineered asymmetric electric field effectively modulates the electron cloud distribution around the Cu-N bond and downshifts the d-band center, endowing the exceptional coke resistance. This structural innovation dramatically reduces carbon accumulation from 12.1% to a mere 0.28%. Consequently, the prepared catalysts demonstrate a VCM yield (>98.5%) and stability (>400 h, 180 h^-1) in pilot-scale trials, surpassing those of previously reported Cu counterparts. Overall, these findings offer a strategy to suppress the deactivation by overadsorption of intermediates on Cu sites during acetylene hydrochlorination.