Extension of the alkyl chain length to adjust the properties of laccase-mimicking MOFs for phenolic detection and discrimination

2-Methylimidazole (MIM) is a classic organic ligand that shows excellent thermal stability and chemical robustness and is widely used in ZIFs. Recently, transformations of MOFs have been realized by using metals or ligands. In this study, we propose a new strategy—adjusting MIM by extending the alkyl chain length —to change the properties of related MOFs. Furthermore, we used copper as the metal core to replace zinc to mimic the active sites of laccases (electron transfer between copper and imidazole ring). As a result, the nanostructures transformed from nanoleaves to nanovesicles, which changed the Cu(II)/Cu(I) ratio from 3.7 to 1.7, as well as the lattice constant (decreased the diffraction angle) and enzyme-like activity (inhibition). In addition, we revealed that superoxidase anions were the main factors responsible for its laccase-like activity. We applied it to detect and discriminate phenolics. Laccase-mimicking activity was best at pH 7.0. When compared to protein laccase, the Cu-MeIm nanozyme had a greater Vmax at the same mass concentration. It was used to identify and distinguish phenolics. In the presence of Cu-MeIm nanozymes, the linear range is 0.1–2 mM and the detection limit of 2,4-DCP is 0.034 mM.