A Pre-Coordinated Strategy Precisely Tailors the Coordination Structure of Single-Atom Sites Toward Efficient Catalysis

Abstract

Coordination structure engineering represents a promising approach for optimizing the catalytic properties of single-atom catalysts (SACs). However, the precise tailoring of single-atom sites remains challenging. Herein, a pre-coordination strategy is proposed to design SACs with tunable local coordination environments on 2D honeycomb-like carbon nanofoams. By pre-coordinating the metal precursor with customized functional groups on a layered Mg(OH)₂ template through strong d-p orbital hybridization, SACs featuring Co─N₄ (Co₁/NC), Co─C₄ (Co₁/CC), and Co─C₂S₂ (Co₁/CSC) configurations are fabricated. The lamellar honeycomb-like architecture facilitates active site exposure, reactant enrichment, and mass transfer during the reaction process. Consequently, the Co₁/NC catalyst, despite its extremely low Co loading of 0.12 wt.%, demonstrates exceptional catalytic activity and stability for nitroaromatics reduction, achieving an impressive overall turnover frequency (TOF) of 73668 h⁻¹ for the conversion of 4-nitrophenol to 4-nitroaniline, surpassing most reported catalysts. Theoretical calculations indicate the Co─N₄ configuration possesses moderate Fermi electronic states compared to Co─C₄ and Co─C₂S₂, significantly promoting the formation and utilization of reactive H^* species and accelerating the reaction kinetics for aromatic nitroreduction. This work establishes a novel avenue for the meticulous manipulation of coordination structures in SACs, paving the way for the advancement of sophisticated catalytic materials for chemical transformations.