| Summary: | Covalent organic framework (COF) has been attracting considerable attention as a novel crystalline material owing to its extended π-electron conjugation and excellent spectral behavior. In this study, we present an imine-linked two-dimensional (2D) crystalline sulfone-based covalent organic framework (TAS-COF) synthesized by 2,4,6-triformylphloroglucinol (Tp) and 3,7-diaminodibenzo[b,d]thiophene (DAS) via a Schiff base condensation reaction. The benzothiophene sulfone endows the as-synthesized TAS-COF with excellent oxidase-like activity under visible light irradiation, ascribed to the generation of superoxide radicals (O<sub>2</sub><sup>•−</sup>) by photo-generated electron transfer. TAS-COF can efficiently oxidase the colorless substrate 3,3′,5,5′-tetramethylbenzydine (TMB) into blue oxidized TMB (oxTMB) when exposed to visible light, and the presence of uranium (UO<sub>2</sub><sup>2+</sup>) leads to clear color fading due to the coordination between the imine of oxTMB and UO<sub>2</sub><sup>2+</sup>. A colorimetric strategy is thus developed for UO<sub>2</sub><sup>2+</sup> determination with a detection limit of 0.07 μmol L<sup>−1</sup>. Moreover, a paper-based visual sensing platform is also constructed to offer simple and fast UO<sub>2</sub><sup>2+</sup> content evaluation in water samples. The present study not only provides a promising strategy to prepare visible light-triggered COF-based metal-free nanoenzymes but also extends the applications of COF material in radionuclide detection.
|
|---|