Regulating the coordination microenvironment of zinc single-atom catalysts to enhance intramolecular hydroamination performance

Abstract

Precise tuning of the coordination microenvironment is essential to enhance the intrinsic catalytic performance and reaction kinetics of metal single-atom catalysts (SACs). This study proposes a novel strategy to optimize the electronic properties of zinc (Zn) SACs by manipulating the s-band center of the Zn atom within the zinc–nitrogen moieties (Zn–N_x, x = 2, 3, and 4) through adjusting the number of coordination atoms (N) and introducing heteroatoms (P, B, and S) with varying electronegativity. The results demonstrate that the Zn–N₂P site, characterized by optimal electron density, exhibits superior performance (conversion ≥ 99.9%, chemoselectivity = 100%), and accelerated reaction kinetics (E_a as low as 94.7 kJ mol⁻¹) in the intramolecular hydroamination of 2-(2-phenylethynyl)aniline, surpassing state-of-the-art transition metal catalysts. In contrast, both experimental and theoretical results indicate that Zn–N₂B and Zn–N₂S catalysts exhibit significantly lower activities than Zn–N₂P and Zn–N₃. The superior performance of Zn–N₂P originates from an electronic effect, where the electron-donating P heteroatom redistributes the electron cloud, adjusts the polarization of the Zn–N₂P moiety, and thereby markedly enhances the adsorption and activation capabilities of 2-(2-phenylethynyl)aniline. This study provides a promising approach for the efficient regulation of the coordination microenvironment of SACs in heterogeneous catalysis.