AbstractTransition metal single atom catalysts (SACs) with M₁-N_x coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co₁/NPC catalyst with unsymmetrical single Co₁-N₃P₁ sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co₁-N₄ coordination, the electron density of Co atom in Co₁-N₃P₁ is increased, which is more favorable for H₂ dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co₁-N₃P₁ SAC exhibits a turnover frequency of 6560 h⁻¹, which is 60-fold higher than that of Co₁-N₄ SAC and one order of magnitude higher than the state-of-the-art M₁-N_x-C SACs in literatures. Furthermore, Co₁-N₃P₁ SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.