Metal–Covalent Organic Frameworks Linked by Fe-Iminopyridine for Single-Atom Peroxidase-Mimetic Nanoenzymes

Metal–covalent organic frameworks (MCOFs) feature regular structures, adjustable pore channels, designable structures, and abundant tunable metal-catalytic active sites and are promising candidates for advanced single-atom enzymes. Here, we constructed porous and crystalline Fe-COFTAPB-BPA linked with Fe-iminopyridine moieties from the corresponding building blocks under ambient conditions in the time scale of minutes. Fe-COFTAPB-BPA with single-atom Fe dispersion could react with H2O2 to catalyze the oxidation of tetramethylbenzidine (TMB), demonstrating that an MCOF with a well-defined metallo ligand structure can function as a single-atom enzyme. Steady-state kinetic analysis showed that crystalline Fe-COFTAPB-BPA revealed a higher affinity to TMB than amorphous Fe-PolyTAPB-BPA at a similar Fe content attributed to its regular pore structure, higher specific surface area, and uniform distribution of catalytically active sites. As a peroxidase mimetic, Fe-COFTAPB-BPA exhibits the advantages of easy preparation, good stability, and higher catalytic efficiency.