Facile synthesis of uniform, spherical, nitrogen- and sulfur-rich covalent organic frameworks for efficient extraction of herbicides containing chlorophenyl and acylamino groups

The escalating use of herbicides containing chlorophenyl and acylamino (HCAs) in agriculture has intensified concerns regarding their environmental impact, underscoring the need for efficient and eco-friendly methods for their extraction and detection. This study introduces the synthesis of a novel N/S rich covalent organic framework (COF), DFT-TPB-COF, using 2,5-diformylthiophene and 1,3,5-tri(4-aminophenyl) benzene as building blocks. The as -synthesized COF is uniform, spherical and monodisperse, making it an ideal candidate as packed materials in solid -phase extraction column for HCAs extraction from complex environmental samples. The DFTTPB-COFs show adsorption capabilities ranging from 2.52 to 30.34 mg g-1 for six HCAs, facilitated by pi-pi interactions, p-pi interactions, hydrogen bonding, electrostatic interactions, and hydrophobic interactions. The adsorption-desorption process is rapid (10 min). Additionally, the presence of other types of herbicides showed little interference in the adsorption efficiency of DFT-TPB-COF for HCAs. A sensitive and reliable method combining the DFT-TPB-COFs-filled SPE column with HPLC-UV was developed for detection of six HCAs in various environmental water and soil samples. The method exhibited excellent linearity (1-200.0 ng mL-1) and low limits of detection (0.3-0.9 ng mL-1) for HCAs. This study not only demonstrates the potential of DFT-TPBCOFs as a suitable packed material in solid -phase extraction column, but also opens avenues for the practical application of COFs in the adsorption of organic pollutants.