Eu3+-Functionalized Nanoporous Covalent Organic Frameworks for Fluorescence Detection and Removal of Tetracycline

Tetracycline (TC) abuse has caused a serious threat to human health and the ecological environment, so it is very important to develop the materials that can simultaneously detect and remove TC in animal feed and environmental water. In this present work, at first, an original oxygen-rich 2D nanoporous covalent organic framework (BrPz-COF) was synthesized by an irreversible condensation reaction of tetrabromo-1,4-benzoquinone and piperazine and then a rare-earth covalent organic framework (Ln@COF) was successfully obtained for the detection and removal of tetracycline by post-synthesis modification. The carbonyl group contained in BrPz-COF provides a large number of active sites for the binding of Eu3+ ions by post-synthetic modifications so that the resulting Eu3+@BrPz-COF hybrid shows a good chemical stability under harsh chemical conditions such as strong acid, strong base, and various organic solvents. The resulting Eu3+@BrPz-COF exhibited a turn-on response toward tetracycline, which allowed this interesting material to be applied as a fluorescence sensor. It is worth mentioning that the reusable sensor had a high sensitivity and excellent selectivity to TC, and the detection limit was 7 nM, which can be applied to detect TC in animal feed. In addition, Eu3+@BrPz-COF also showed a good performance in the removal of TC with the maximum adsorption amount of 205.34 mg·g–1. Metal-COF-based hybrid materials with the performances of simultaneous detection and removal of TC are rare, so this work is very significant for developing a material to solve this matter.