Deciphering fluorine-fluorine interaction in an AIE-active trifluoromethyl-COF for trifluralin detection in the food chain.

The environmental persistence and inherent biodegradation resistance of pesticide residues pose a serious threat to ecosystems and human health, necessitating the development of efficient monitoring strategies. Herein, we decipher the fluorine-fluorine (F···F) interaction within an AIE-active, trifluoromethyl-functionalized covalent organic framework (PEFA-COF) and exploit this molecular recognition motif for the selective detection of trifluralin (TFR). Benefiting from abundant trifluoromethyl moieties and superior luminescence properties, the PEFA-COF enables specific TFR recognition through a synergistic interplay of electrostatic forces, hydrogen bonding, and F···F interactions. This recognition event triggers a pronounced fluorescence quenching response via the internal filtration effect (IFE), facilitating highly sensitive and selective TFR quantification. The constructed PEFA-COF-based fluorescent sensing platform was successfully validated in complex water and milk matrices, achieving an excellent fluorescence quenching coefficient and a detection limit as low as 0.06 μmol/L. Collectively, this work not only deciphers the critical role of F···F interaction in pesticide recognition but also advances the function-led design of AIE-active COFs toward practical and robust pesticide residue monitoring in food supply chains.