Analyte-Induced Specific Regulation of Light-Responsive COF-Cu Nanozyme Activity for Ultrafast Thiram Colorimetric Sensing.

A light-responsive covalent-organic framework (COF) nanozyme, which integrates the advantages of the COF structure and light-stimulated nanozyme catalysis, is a class of sensing star materials with wide application prospects. However, the sensing methods based on light-responsive COF nanozymes are relatively single at present. Therefore, it is necessary to develop new sensing strategies to broaden its application in chemical sensing and achieve highly efficient detection. Here, a Cu²⁺-modified COF composite material (TpDA-Cu) was rationally designed. The addition of Cu significantly inhibits the excellent light-responsive nanozyme activity of TpDA itself. However, because of the restoration of the enzyme activity by thiram (Tr) and the oxidase mimic activity of the newly formed Cu/Tr complex, TpDA-Cu/Tr exhibits stronger light-responsive nanozyme activity. Enzyme kinetic data show that compared with TpDA, TpDA-Cu/Tr has a larger V_max value, which can achieve efficient catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). In addition, the strong coordination effect of Tr and TpDA-Cu also plays a key role in achieving ultrafast, sensitive, and selective colorimetric detection of Tr. This work develops a dual activity regulation strategy of light-responsive COF nanozymes based on analyte induction and provides a new perspective for the application of light-responsive COF nanozymes in the field of sensing.