Benzotrithiophene-based covalent organic frameworks for sensitive fluorescence detection and efficient removal of Ag⁺ from drinking water

The simultaneous detection and removal of Ag⁺ from drinking water was crucial for preventing human health, while it was also extremely challenging due to bifunctional materials that combine both Ag⁺ adsorption and detection functions rarely being explored. In this study, a benzotrithiophene-based covalent organic framework (TAPA-BTT) was synthesized and applied to detect and remove Ag⁺. TAPA-BTT exhibited high crystallinity, a large specific surface area, and good thermal stability. As a fluorescent probe, TAPA-BTT had a low detection limit (0.14 μg/L), wide linear range (0.2-700 μg/L), and good linearity (R² > 0.9948). It was also successfully applied to identify Ag⁺ in drinking water including tap, pure, and mineral water with satisfactory detection performance. Moreover, TAPA-BTT had a high efficiency in removing Ag⁺ from water, offering a high capacity for adsorption (344.83 mg/g) and a removal rate of 99.45 %. The adsorption of TAPA-BTT towards Ag⁺ can be well explained by the quasi-second-order kinetic model and the Langmuir isotherm model. In addition, experimental and theoretical studies revealed the interaction mechanism between TAPA-BTT and Ag⁺. The specific Ag⁺ detection by TAPA-BTT was assumed to be caused by the electron transfer from thiophene-S to Ag⁺, which enhanced the fluorescence of TAPA-BTT. The effective removal of Ag⁺ was attributed to the co-chelation of imine-N and thiophene-S on TAPA-BTT. These novel findings revealed the great potential of benzotrithiophene-based COFs in the detection and removal of Ag⁺, providing a new strategy and alternative material for monitoring and controlling Ag⁺ in drinking water.