Rapid ratiometric colorimetric determination of forchlorfenuron residues in agricultural products using a MIL ‐101( Fe )‐derived Fe–N–C nanozyme

Abstract BACKGROUND Forchlorfenuron (CPPU) is a widely used plant growth regulator, and its residues in agricultural products and medicinal herbs have raised concerns regarding food safety and human health. Conventional chromatographic methods provide reliable quantitative analysis but generally require sophisticated instrumentation, laborious sample preparation, and skilled operators, limiting their suitability for rapid screening. In this study, a MIL‐101(Fe)‐derived Fe–N–C nanozyme (FCM‐NC) was prepared and used to construct a visual colorimetric assay for CPPU detection based on the catalytic oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) by hydrogen peroxide. RESULTS FCM‐NC exhibited peroxidase‐like catalytic activity and efficiently catalyzed the oxidation of TMB. Addition of CPPU induced a characteristic change in the chromogenic system, enabling ratiometric colorimetric detection. Under optimized conditions, the assay showed a linear response over 20.2–201.9 μmol L −1 , with a limit of detection of 2.02 μmol L −1 . The method showed good repeatability, with relative standard deviations below 3.6% in real‐sample analyses. The proposed assay was further evaluated using environmental water, soil, agricultural products, and selected medicinal herb samples. The analytical results were generally consistent with those obtained by high‐performance liquid chromatography, supporting the feasibility of the proposed method for CPPU screening. CONCLUSION The FCM‐NC‐based visual colorimetric assay provides a visually distinguishable and selective response toward CPPU and enables rapid preliminary screening after appropriate sample pretreatment. This strategy provides a practical complementary approach for CPPU residue screening in agricultural and herbal samples. © 2026 Society of Chemical Industry.