Dual‐Axial Chlorine Coordination Engineering of Fe─Fe Dual Single Atoms Boosts the Ascorbate Oxidase‐Like Activity

Abstract Dual single‐atom nanozymes (DAzymes) have garnered widespread attention in enzyme‐like catalysis. However, utilizing axial coordination engineering on dual single‐atom sites to enhance nanozyme activity remains a challenge. Herein, an ascorbate oxidase‐like (AAO‐like) Fe 2 N 6 Cl 2 /CNCl DAzyme with dual Fe‐N 4 Cl catalytic sites is developed via a dual‐axial Cl‐coordination strategy. Density functional theory (DFT) calculation reveals that compared to the planar Fe 2 N 6 /CN, the Fe 2 N 6 Cl 2 /CNCl exhibits higher AAO‐like activity due to dual‐axial chlorine coordination effect and synergistic catalytic effect between Fe‐N 4 Cl. Consistent with DFT result, the Fe 2 N 6 Cl 2 /CNCl shows a maximal reaction velocity that is 4.5 times higher than that of Fe 2 N 6 /CN. To implement this strategy, a Fe 2 N 6 Cl 2 /CNCl DAzyme fluorescent sensor array is developed for precise discrimination of aromatic amines based on Schiff base reactions. The highlight of the dual‐axial chlorine coordination in the Fe 2 N 6 Cl 2 /CNCl provides profound insights for guiding the design of DAzymes and advances the applications in sensor fields.