Zr-MOF/MnO2 Nanozyme with Chelation-Regulated Acitivity: From Sensitive Colorimetric Detection to Smartphone-Readable Paper-Based Assay for Glyphosate

As one of the most extensively applied herbicides globally, glyphosate (GLY) is frequently detected in food and water matrices, raising substantial concerns regarding its potential harm to human health. Addressing this challenge calls for analytical platforms that offer both reliable performance and operational convenience. In this work, a GLY-responsive nanoenzyme was developed by hybridizing Zr-based metal–organic frameworks (Zr-MOF) with manganese dioxide (MnO 2 ). The system capitalizes on the strong chelation between GLY and metal centers, which destabilizes the nanozyme structure and consequently modulates its catalytic activity toward colorimetric readout. The resulting composite enables precise quantification of GLY in solution and can be readily incorporated into paper substrates to support visual, user-friendly sensing. In solution format, the assay achieves a linear response over 0.001–10 mg/mL with a limit of detection (LOD) of 0.9 μg/mL, whereas the paper-based counterpart operates within 0.05–20 mg/mL and affords an LOD of 0.03 mg/mL, making it well-suited for cost-effective field applications. Both detection formats were validated using GLY-spiked fruit and water samples. Recovery rates fell between 90.5% and 110% for the solution-based method, and between 95.3% and 105% for the paper-based strips, with relative standard deviations (RSDs) of less than 15% and 7%, respectively, indicating satisfactory accuracy and reproducibility. Overall, this work presents a versatile strategy that bridges high analytical precision with straightforward operation, meeting the demands of both routine monitoring and point-of-use testing by non-professionals.