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 (R > 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.