An Eu (III)-functionalized covalent organic framework fluorescent probe for specific detection of Flumequine based on pore restriction and antenna effect.

The overuse of quinolone antibiotics has led to a series of health and environmental issues. Herein, we combine the distinct luminescence properties of Eu with the unique structure of covalent organic frameworks (COFs) to develop a precise and sensitive fluorescent probe for detecting Flumequine (Flu) in water. Eu is thoroughly anchored into the channels of COFs as recognition sites, while the synthesized probe material still maintains its intact framework structure. The unique structure of COFs provides excellent support and protection for Eu. Therefore, COF-Eu can rapidly bind with Flu which can transfer the absorbed energy to Eu through an "antenna effect", resulting in red fluorescence. Moreover, there is a good linear relationship between Flu concentration in the range of 0-30 µM, with a detection limit of 41 nM. Simultaneously, the material maintains remarkable reproducibility, with its performance remaining almost unchanged after five cycles of use. Remarkably, the probe demonstrates excellent Flu recovery rates in real samples. This study provides a viable approach for the recognition of flumequine in the environment through a customized fluorescence detection method.