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

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-Nx, 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 (Ea 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. The Zn-N2P site, engineered with optimal electron density, demonstrates superior performance and enhanced reaction kinetics in the intramolecular hydroamination of o-alkynylaniline, outperforming current heterogeneous transition metal catalysts.