Europium(III)-functionalized covalent organic frameworks as fluorescent switches toward ultrasensitive detection of oxytetracycline

Tetracycline residues have raised widespread concern, among which oxytetracycline (OTC) has attracted particular attention because of its potential risks to human health. A sensitive analytical method for detecting tetracycline residues in complex samples is thus needed. Herein, a novel fluorescent sensing platform based on an europium(III) (Eu 3+ )-functionalized covalent organic frameworks (TpBy-COF) for the selective detection of OTC is developed. The fluorescence of TpBy-COF@Eu is hardly observed due to the non-radiative decay from coordinated water molecules. However, the fluorescence signals of TpBy-COF@Eu-based sensing platform is significantly enhanced with the introduction of OTC, attributed to the specific displacement of coordinated water molecules by OTC, which acts as an effective antenna ligand by transferring energy to the excited states of Eu 3+ ,thereby sensitizing its characteristic red emission. Moreover, this TpBy-COF@Eu-based sensing platform exhibits the favorable sensitivity and selectivity for OTC monitoring with a low detection limit as low as 0.12 μmol/L. The TpBy-COF@Eu-based sensing platform is successfully validated in real samples, demonstrating the practical potential for OTC monitoring in complex matrices.