Post-modified fluorine-functionalized covalent organic frameworks with excellent stability and hydrophobicity and their application in fipronil adsorption

We designed and synthesized two fluorine-functionalized covalent organic frameworks (F-COFs) TAPT-DHTA-COF-(CF 3 ) and TAPT-DHTA-COF-3F via post-synthetic Povarov reaction. The irreversible conversion of imine linkages into ultra-stable quinoline moieties preserved crystallinity and conferred exceptional chemical stability under harsh conditions. Fluorine functionalization conferred exceptional hydrophobicity to the F-COFs, as evidenced by water contact angles of 133°. Adsorption studies revealed that fluorine substituents significantly modulate fipronil uptake, with TAPT-DHTA-COF-3F achieving a capacity of 193.9 mg g −1 —2.5-fold higher than non-fluorinated analogs, which can be ascribed to synergistic hydrophobic and fluorine-fluorine interactions. In addition, the F-COF possessing 3,4,5-trifluorophenyl moiety outperforms its 4-trifluoromethylphenyl counterpart due to its higher specific surface area and greater hydrophobicity and fluorophilicity. These results establish fluorinated COFs as promising platforms for high-efficiency environmental remediation, particularly for persistent halogenated contaminants.