Tailored covalent organic frameworks with tunable fluorine groups for efficient adsorption of bisphenol analogues

Bisphenol analogues (BPs) are widespread endocrine-disrupting contaminants that threaten ecosystems and human health. Herein, covalent organic frameworks (COFs) with tunable fluorine groups were designed to achieve efficient adsorption of BPs. By systematically regulating the number of fluorine groups in the monomers, it was demonstrated that the adsorption of BPs did not increase monotonically with fluorination; instead, an optimal structure-function balance was achieved at moderate fluorine substitution. The optimized fluorinated COF exhibited high adsorption capacities of 779.60, 416.69, and 559.74 mg/g for bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS), respectively, representing increases of 79.43%, 55.03%, and 148.46% compared with the non-fluorinated COF. To improve recyclability and practical applicability, the optimized COF was integrated with chitosan (CS) to construct monolithic COF/CS aerogels. The aerogels showed further capacity enhancements of 24.27-30.66% and significantly accelerated adsorption kinetics, with pseudo-second-order rate constants increasing by ≥ 168.18%. Mechanistic studies revealed that the adsorption of BPs was governed by pore filling, π-π stacking, hydrogen bonds, and hydrophobic interactions. The aerogels were successfully applied in food pretreatment and environmental water treatment, demonstrating efficient enrichment, strong anti-interference capability, and good reusability.