S‑Doped\nIron-Triazolate Metal–Organic\nFramework Nanozymes: Ligand-Engineered High-Efficiency Peroxidase\nMimics

Metal–organic framework (MOF)-based nanozymes\nhave aroused\nwide interest in biocatalysis. In this work, a kind of MOF-based nanozymes\nwere fabricated through a ligand regulation strategy. First, an iron-triazolate\n(MET(Fe)) nanozyme with the Fe–N structure was synthesized\nby the solvothermal method. Then, different proportions of the sulfur-containing\nligand were introduced by the the mixed-ligand growth method to obtain\na series of S-doped MET(Fe) (S-MET(Fe)) nanozymes. The S-containing\nligand would competitively coordinate with Fe instead of triazolate,\nforming a “–C–SO<sub><i>x</i></sub>” bond and thereby resulting in more oxygen defects. The investigation\nof the catalytic mechanism showed that the doping of S affected the\ncatalytic activity center of Fe, resulting in the generation of medium-spin\nspecies of Fe<sup>III</sup> and more coordination defects, thereby\nenhancing its catalytic activity. As a proof of concept, the 1/3-S-MET(Fe)\nnanozyme with outstanding peroxidase-like activity was used in biosensing\nand in the elimination of bacteria. This study provides new ideas\nfor the design and construction of highly active nanozymes.