A trifluoromethyl-grafted ultra-stable fluorescent covalent organic framework for adsorption and detection of pesticides

Abstract

A fluorine-rich covalent organic framework, COF-(CF₃)₂, was designed and prepared by post-functionalization via the Povarov reaction in a flask in order to take up fluorinated pesticides. Compared with those obtained by a synthetic method performed in a Pyrex tube, the as-prepared COFs in our process not only possess higher specific surface areas, but also can be obtained on a large scale. It's worth noting that COF-(CF₃)₂ exhibits strong chemical stability even in KMnO₄ or NaBH₄ solutions, which is highly beneficial for its practical applications. Considering the strong and selective fluorine–fluorine interactions, COF-(CF₃)₂ was used for the uptake of fluorinated pesticides and showed higher adsorption capacities for trifluralin (151 mg g⁻¹) and fipronil (171 mg g⁻¹). We also found unexpectedly that COF-(CF₃)₂ possesses strong fluorescence due to the enhanced conjugated system via cycloaddition functionalization. This unique property can be applied in detecting trifluralin through fluorescence quenching induced by their interaction.