N-Modulated Graphdiyne Iron Single-Atom Nanozyme through Long-Range Interactions for Photothermal Amplified Multifunctional Catalytic Antibacterial Therapy.

The rational design of single-atom nanozymes (SAzymes) can be achieved by regulation of the first and second coordination shells near the metal coordination center. However, the impact of structural changes at distances further away from the metal coordination center on the catalytic activity has been rarely reported. Herein, graphdiyne (GDY)-derived Fe SAzymes (GFeN SAzymes) with tunable N dopants (amino-N, pyridinic-N, graphitic-N) were synthesized via controlled NH3 pyrolysis. Fe-centered single-atom sites were stabilized within the GDY-derived framework, while N dopants modulated their catalytic behavior through long-range electronic effects. GFeN SAzymes possess multi-enzyme activities, including oxidase, peroxidase, catalase, and superoxide dismutase. Catalytic performance was modulated by N type: pyridinic-N provides more favorable regulation of Fe-centered catalysis, whereas amino-N is associated with less favorable catalytic behavior. Remarkably, SAzymes are pH-responsive, scavenging reactive oxygen species (ROS) under neutral conditions and generating ROS in acidic environments, enabling adaptive antibacterial action and wound repair. GFeN SAzyme pyrolyzed at 700 °C exhibited a photothermal conversion efficiency of 28.3% under 808 nm laser irradiation, synergistically enhancing catalytic sterilization. In vitro and in vivo experiments confirmed excellent wound disinfection and healing via photothermal amplified catalytic therapy. This work highlights the crucial role of long-range interactions in regulating catalytic activity and offers a strategy for designing highly efficient SAzymes.