MOF-Derived Porous Zn–Fe2O3 Nanozymes for Sensitive Colorimetric Assay of Acetylcholinesterase Activity

Porous Zn–Fe2O3 nanozymes were prepared through calcination of a Zn-MIL-53 precursor via a MOF-to-oxide conversion strategy. Benefiting from the self-sacrificial template effect and Zn incorporation, the obtained Zn–Fe2O3 retained the spindle-like morphology while developing a hierarchical micro/mesoporous structure with a larger specific surface area than Fe2O3. Meanwhile, Zn incorporation increased the Fe2+/Fe3+ ratio and enriched oxygen vacancy related defects, which collectively facilitated H2O2 activation and enhanced the peroxidase-like (POD-like) catalytic oxidation of TMB. As a result, Zn–Fe2O3 exhibited significantly higher POD-like activity than Fe2O3. Based on this enhanced catalytic performance, an inhibition-type colorimetric assay for acetylcholinesterase was established using acetylthiocholine as the substrate. Under the optimized conditions, the assay showed a linear range of 0–35 mU/mL and a detection limit of 0.144 mU/mL. This work demonstrates that combining MOF-derived porosity with dopant-induced electronic and defect modulation is an effective strategy for developing Fe-based nanozymes for nanozyme-based colorimetric AChE activity assays.