Oxolinic Acid Generated Green Fluorescence Based on a Terbium-Functionalized Covalent Organic Framework

Oxolinic acid (OXO), a classic environmental contaminant, has a terrible detrimental effect on human health. The exploration of efficient strategies to detect and detecting OXO has remarkable significance. Herein, we reported a novel terbium(III)-functionalized covalent organic framework (Bpy-DhBt-COF@Tb³⁺) by fixing Tb³⁺ on the bipyridine-connecting COF (Bpy-DhBt-COF) as a turn-on fluorescent switch toward OXO for the first time. In this platform, Tb³⁺ acts as the specific recognition units for OXO and the response signal, while Bpy-DhBt-COF acts as the safehaven for Tb³⁺. Once introducing OXO to Bpy-DhBt-COF@Tb³⁺, OXO can instead water molecules coordinate with Tb³⁺ and sensitize Tb³⁺ instantly, thereby producing a significant fluorescence signal. Profiting from the excellent porosity of Bpy-DhBt-COF@Tb³⁺, it can obtain optimal response toward OXO only within 10 s with an ultrasensitive detection limit of 12.5 nM. Furthermore, Bpy-DhBt-COF@Tb³⁺ displayed outstanding selectivity toward OXO than other general quinolones. Based on these, a Tb³⁺-based COF was explored for the first time for the turn-on fluorescence detection of an OXO with rapid response, high sensitivity, and outstanding selectivity. In this work, we not only exhibit the attractive performance of Tb³⁺-functionalized COF to detect OXO but also propose a prospect strategy for creating other fluorescent sensors for multiple targets.