Cobalt–imidazolate framework nanozyme with carboxylesterase-mimicking activity for dual-mode detection of carbaryl via substrate-specific mechanistic validation

Carbaryl, a widely used carbamate pesticide, poses significant environmental and health risks, necessitating the development of reliable and field-deployable detection strategies. Herein, we report an unprecedented carboxylesterase (CES)-mimicking nanozyme based on cobalt–imidazolate framework (ZIF-67), which exhibits exceptional hydrolytic activity toward ester bonds and enables direct detection of carbaryl. Unlike previously reported oxidoreductase-mimicking nanozymes, ZIF-67 demonstrates unique CES-like functionality, catalyzing the hydrolysis of carbaryl to produce 1-naphthol and methylamine acetic acid with remarkable efficiency. Kinetic studies revealed a very low K m (0.06 mM) and high catalytic turnover, surpassing both natural CES and other reported CES-mimicking nanozymes. Density functional theory (DFT) calculations further confirmed that Co–N coordination sites within the ZIF-67 framework reduce the hydrolysis barrier and stabilize the transition state, thereby rationalizing its superior performance compared to ZIF-8 (Zn) and non-catalyst controls. Leveraging this activity, we established a dual-mode carbaryl sensing platform based on the intrinsic emission of 1-naphthol and the color formation of 1-naphthol/2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) complex. Both methods showed excellent selectivity and sensitivity with LOD of 0.054 µM for fluorometric assay and 0.92 µM for colorimetric assay. In addition, the developed approach also exhibits the good precision and reproducibility via excellent recovery rate (97.6–102.6%) in real samples, including tap water and vegetable extracts. These findings highlight ZIF-67 as the first MOF-based CES-mimicking nanozyme and a powerful platform for developing reliable, sensitive, and field-deployable biosensing tools for food safety and environmental monitoring. ZIF-67 demonstrates unprecedented carboxylesterase-mimicking activity and represents the first MOF nanozyme capable of directly hydrolyzing carbamate pesticides. Substrate-specific DFT calculations reveal that Co–N coordination activates water and stabilizes the transition state. Building on this mechanism, a dual-mode fluorometric/colorimetric assay achieves selective and sensitive carbaryl detection in real water and food samples.