Bromine-Functionalized Covalent Organic Frameworks Enhancing the Desorption Efficiency and Enabling Preconcentration of Brominated Pollutants for Mass Spectrometry Detection.

Covalent organic frameworks (COFs) exhibit exceptional adsorption capacity but suffer from challenging desorption. In this study, a bromine-functionalized magnetic COF composite (Fe3O4@COF-Br) was synthesized via bromodimethylsulfonium bromide-mediated bromination of imine-linked COF on Fe3O4 nanospheres (Fe3O4@COF), where the COF framework was constructed by 1,3,5-tris(4-formylphenyl)benzene and 2,6-diamino-3,5-diethynylpyridine. Compared with pristine Fe3O4@COF, Fe3O4@COF-Br enhanced desorption efficiencies for brominated contaminants by about 30% while maintaining adsorption capacity. Systematic characterization and DFT simulations revealed reduced host-guest binding strengths in the brominated composite with interaction energies lowered by about 30 kcal mol-1. Employing Fe3O4@COF-Br as the magnetic solid-phase extraction (MSPE) adsorbent coupled with ESI-MS detection, the method achieved detection limits of 1.4-9.5 ng L-1 for tetrabromobisphenol A (TBBPA) and its derivatives (TBBPA-BHEE, TBBPA-BGE, TBBPA-BME, TBBPA-BAE, TBBPA-BDBPE), with coefficients of determination (R2) > 0.99 and precision (relative standard deviations) ≤ 8.4%. Validated in landfill leachate, soil, lake water, tap water, juice, soy sauce, and urine matrices, the method delivered 75-125% recoveries, demonstrating practicability and accuracy for complex environmental analysis.