Colorimetric determination of copper ions based on regulation of the enzyme-mimicking activity of covalent triazine frameworks

Covalent triazine frameworks (CTFs) have garnered increasing interest recently because of their unique structures and properties. However, their application as enzyme mimics for sensing remains unexplored. In this study, an efficient strategy for selective colorimetric detection of Cu2+ ions was developed based on CTFs. This strategy relies on the peroxidase-like catalytic activity of CTFs being rationally modulated by Cu2+ ions. In the presence of Cu2+ ions, the peroxidase-like catalytic activity of the CTF is significantly stimulated and enhanced; this enables the CTF to catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine, which produces a color change from colorless to blue in the presence of H2O2. On the basis of the colorimetric method, a good linear relationship for Cu2+ ions can be obtained from 1.0 μg/L to 80.0 μg/L, with a limit of detection of 0.05 μg/L. When this strategy was assessed for the detection of Cu2+ ions in real food samples, recoveries of 96.0-105.0% were attained. The proposed CTF material and colorimetric method constitute a promising approach for the rapid detection of Cu2+ ions that is selective, sensitive, and low cost.