MOF-Derived FeCo-NC Nanozyme for Colorimetric Sensing of Ascorbic Acid

Abstract A bimetallic FeCo-NC nanozyme was synthesized via pyrolysis of a FeCo-ZIF precursor and evaluated for its enzyme-like catalytic activity and colorimetric sensing performance. Structural characterizations confirmed the formation of a nitrogen-doped porous carbon framework with uniformly dispersed Fe and Co active sites. The FeCo-NC nanozyme exhibited superior oxidase-like activity compared with monometallic counterparts, which is attributed to the synergistic interaction between Fe and Co sites that facilitates electron transfer. Kinetic analysis revealed that the catalytic reaction follows typical Michaelis-Menten behavior, with a low Michaelis constant toward TMB, indicating high substrate affinity. Based on the efficient oxidation of TMB and the subsequent reduction of oxidized TMB by ascorbic acid (AA), a label-free colorimetric sensing platform was constructed. The proposed system showed a concentration-dependent response toward AA with two linear detection ranges (0.1–5 and 5–50 μM) and exhibited high selectivity against common interfering species. This work demonstrates that MOF-derived bimetallic nanozymes are effective catalysts for colorimetric sensing and provides a feasible strategy for the development of nanozyme-based platforms for biomolecule detection.