Facile synthesis of magnetic bromine-functionalized covalent organic framework for efficient solid-phase microextraction of polybrominated diphenyl ethers from water.

The widespread use of polybrominated diphenyl ethers (PBDEs) as flame retardants has led to their pervasive presence in aquatic environments, posing serious health risks. Herein, we report a facile synthesis of a novel magnetic bromine-functionalized covalent organic framework (Fe3O4@Br-COF) for the efficient magnetic solid-phase microextraction (MSPE) of trace PBDEs from water. A one-pot solvothermal strategy was employed to fabricate Fe3O4@Br-COF using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromoterephthalaldehyde as building blocks. The Br-COF coating significantly enhances the extraction selectivity and efficiency toward PBDEs through synergistic interactions, including potential halogen bonding, π-π stacking, and hydrophobic interactions. The MSPE conditions, including sorbent dosage, extraction time, pH, and desorption parameters, were systematically optimized. Under optimal conditions, the developed Fe3O4@Br-COF-MSPE coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) demonstrated excellent analytical sensitivity and linearity for four PBDEs (TPB, BBPE, TBBPA, and PBDE), with wide linear ranges (0.5-250 ng/mL, R2 > 0.997), low limits of detection (0.005-0.01 ng/mL), and good precision (relative standard deviations < 5.7%). The method was successfully applied to the analysis of PBDEs in environmental water samples, yielding satisfactory recoveries (81.6-109.3%). Moreover, the Fe3O4@Br-COF adsorbent demonstrated good reusability for up to five consecutive cycles. This work highlights the great potential of bromine-functionalized magnetic COFs as a powerful platform for the selective enrichment and determination of halogenated organic pollutants in complex environmental matrices.