Solvent-free mechanochemical synthesis of a sodium disulfonate covalent organic framework for simultaneous highly efficient selective capture and sensitive fluorescence detection of fluoroquinolones

Abstract

Covalent organic frameworks (COFs) have great adsorption potential due to their tunable pore size and pore architecture as well as tailorable functionalities. However, the green and rapid synthesis of COFs with excellent adsorption properties remains a great challenge. Here, we presented a solvent-free and facile mechanochemical approach for the synthesis of COFs. The as-prepared COF TpBD-(SO₃Na)₂ containing sulfonate ions exhibited good thermal and chemical stability and can serve as an effective adsorbent for selective capture of fluoroquinolone antibiotics (FQs) benefiting from the ionic interface and abundant negatively charged sites. The maximum adsorption capacities of norfloxacin, enoxacin, and ciprofloxacin were 1709.6, 1661.5, and 1362.8 mg g⁻¹, respectively, which outperformed those of other reported adsorbents. The adsorption mechanism was deeply explored through characterizations combined with density functional theory calculations, proving the synergistic adsorption effects of TpBD-(SO₃Na)₂ and FQs, including π-π* interactions, electrostatic interactions, and hydrogen bonding. Moreover, a fluorescence detection platform for FQs was developed based on the fluorescence signal of sodium disulfonate TpBD-(SO₃Na)₂. The limit of detection of norfloxacin was 8 nmol/L with a linear range from 0.03 to 6 μmol/L. This research provides a new strategy for the green synthesis of COFs and expands their application in the synchronous detection and removal of FQs in aquatic environments.