Metal-organic framework-derived Fe/C/Bi2O3 as peroxidase-like nanozymes for the detection of organophosphorus pesticides

With the in-depth study of nanozymes, the specificity and catalytic activity of nanozymes still need to be improved for their diverse applications. Here, we report the preparation of Fe/C/Bi2O3 by thermal activation of Fe-doped Bi MOFs (FeBi MOFs) under an air atmosphere. It is found that the Fe/C/Bi2O3 has excellent peroxidase mimic activity due to the synergistic effect between two metals, while Fe is the crucial catalytic active site. The presence of abundant carboxyl groups gives it a high affinity for H2O2 with a low Km of 0.076, which is about 49 times lower than that of HRP. The results of radical quenching and ESR experiments indicate that the main reactive oxygen species during TMB oxidation reaction are •OH and O2•–. By combining Fe/C/Bi2O3 nanozymes with two natural enzymes, i.e., acetylcholinesterase (AChE) and choline oxidase (ChOx), a three-enzyme (Fe/C/Bi2O3, AChE, ChOx) cascade system is proposed for the colorimetric sensing of dichlorvos with a wide linear range from 0.60 to 100 μg L−1 and a low limit of quantitation of 0.60 μg L−1. This work not only provides a new strategy for the design and preparation of high activity Fe/C/Bi2O3 nanozymes, but also demonstrats their potential use in environmental analysis.