Tuning ligand substituents of metal-organic frameworks enhances laccase-like activity for pesticide detection.

Nanozymes exhibit huge potential in developing sensors, there are still significant challenges in designing nanozymes and exploring catalytic mechanisms. Inspired by the ligand-environment effect, ligands with differently charged substituents were introduced into a copper metal-organic framework (Cu-BDC-X, X = OH, NH, COOH, NO) to study the relationship between ligand structure and laccase-like activity. Attractively, tuning the ligand substituents directly regulates the laccase-like activity of Cu-BDC. In-depth experiments showed that the introduction of electron-withdrawing substituent ligands not only increased the ratio of Cu in Cu-BDC but also enlarged the pore diameter of the Cu-BDC. As a concept of the application, a Cu-BDC-NO nanozyme-based colorimetric sensor was developed for the detection of glyphosate pesticide. Importantly, Cu-BDC-NO nanozyme was embedded in hydrogels to fabricate a portable platform for in situ detection of glyphosate pesticide. This work is expected to provide new ideas for building advanced nanozymes and holds great promise for food safety.