Room temperature synthesis of magnetic covalent organic framework adsorbents for efficient extraction of trace benzotriazole ultraviolet absorbers in environmental waters.

Ultraviolet (UV) protection products as a class of pharmaceuticals and personal care products (PPCPs) have become emerging pollutants in the environment. It is of utmost significance to develop an efficient adsorbent for the reliable determination and control of UV protection products residuals in the water environment. In this work, we prepared a "rosette-like" magnetic imine-bonded covalent organic framework (COF) nanocomposite (Fe3O4@PDA@COF) through room temperature growth of 1,3,5-tris(4-aminophenyl) benzene (TAPB) and 1,3,5-tris(4-formylphenyl) benzene on polydopamine (PDA)-coated magnetic spheres. Due to the hydrophobic surface of magnetic nanocomposite, Fe3O4@PDA@COF) exhibited excellent enrichment capacity for four benzotriazole ultraviolet absorbers (BUVs) in environmental water samples. When combined with high-performance liquid chromatography (HPLC), the Fe3O4@PDA@COF minimized interfering components and reduced matrix effects while maintaining high enrichment efficiency, even after six adsorption-desorption cycles. Under optimal conditions, the present method gave the detection limits of 0.063 to 0.250 ng mL-1 for four BUVs with the linear ranges of 0.5-250 ng mL-1, and the recoveries of 84.6 %-117.4 % in lake water. Thus, the research provides a promising approach to prepare magnetic imine-bonded COF nanocomposite as efficient adsorbent for enriching or monitoring the trace BUVs in environmental water samples.