Copper-metalated COFs with oxidase-like activity for colorimetric glyphosate monitoring using a handheld device

Glyphosate (GLY), as a pesticide, is extensively utilized in farming, and excessive glyphosate residues in food pose serious toxicity to humans. Monitoring of GLY is essential for upholding food safety, public health, and ecosystem well-being. Herein, copper-based covalent organic frameworks (Cu@COFs) as nanozymes were designed to develop a colorimetric strategy for GLY monitoring. Cu@COFs were fabricated using a straightforward one-pot approach to serve as oxidase mimics for 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. In the detection system, upon the introduction of GLY, the Cu@COF-based platform presented a low-intensity color response due to the coordination between GLY and the Cu ions of Cu@COFs. The colorimetric platform demonstrated a low detection limit (LOD) of 0.5 mg L^-1 (3 S/N), with dual linear ranges of 0.5-7 mg L^-1 and 10-100 mg L^-1, along with excellent sensitivity and selectivity. The proposed sensing platform was utilized to monitor foods containing GLY, including soybean, corn, and sunflower seeds. Meanwhile, a smartphone-compatible handheld device was fabricated for portable, real-time, and user-friendly GLY detection in field settings. Our detection platform provides a promising prospect for application.