Regulating\nthe Atomic Active Center by Covalent Organic\nFramework-Derived Photothermal Nanozyme to Arm Self-Gelling Powder\nfor Bacterial Wound Healing

Creating simple methods to produce\nantioxidant nanozymes with clear\nstructure–activity relationships, particularly aiming to improve\ndisinfection and create practical drug formulations for bacterial\nwound healing, remains a crucial challenge. Herein, we synthesized\niron-loaded covalent organic framework nanospheres, which were then\ncontrollably transformed into a carbon-based nanozyme with both iron\nsingle atoms and iron clusters through simple pyrolysis. We discovered\nthat the gradual growth of iron clusters significantly boosted the\nnanozyme’s adsorption onto the substrate and electron transfer,\ngreatly influencing its activity. The nanozyme, optimized by the coexistence\nof single iron atoms and Fe<sub>4</sub> clusters, exhibited the strongest\ncatalase and superoxide dismutase enzyme activities as well as high\nphotothermal efficiency. Under physiological conditions, its peroxidase\nand oxidase enzymatic activities, which stimulate oxidative stress,\nremained low. Furthermore, we created an antibacterial self-gelling\npowder capable of dispersing the nanozyme using polyacrylamide and\npoly(acrylic acid). The powder can rapidly gel and adhere to wet wound\nareas, synergistically sterilizing the wound through the combined\nactions of the gel’s amino groups and the nanozyme’s\nphotothermal effect, while leveraging the antioxidant enzymatic effects\nto mitigate wound inflammation. These properties contribute to the\nfast healing of infectious wounds, thus promising a clear formulation\nand treatment.