Growth of quinoline-linked covalent organic frameworks on electrospun nanofibers with enhanced adsorption on chlorinated phenols

Covalent organic frameworks (COFs) have attracted increasing interest as adsorbents in water treatment,   but the lack of high-performance adsorbents materials and effective morphological structures limits their practical application. In this work, a novel quinoline-linked COFs (COF-QL-Ph) with high crystallinity was synthesized by post-synthetic-modification (PSM). Firstly, the precursor organic ligands of imine-linked COFs were directly electrospinning with polyacrylonitrile (PAN) solution as the seeded nanofibers. Subsequently, the imine-linked COFs formed from 1,3,5-benzenetricarboxaldehyde (TFB) and 2,6-diaminonaphthalene (2,6-DAN) were grown on the seeded PAN nanofibers. Finally, self-supporting imine-linked COFs hollow nanofibers were obtained by etching the polymeric substrates. These were then transformed into quinoline-linked COF-QL-Ph nanofiber through the Povarov reaction between phenylacetylene and the matrix imine-linked COFs. The resulting COF-QL-Ph nanofibers exhibit a developed hollow structure and high porosity for effective adsorption of chlorinated phenols in water. The adsorption behavior of 2,4-dichlorophenol (2,4-DCP) on COF-QL-Ph nanofibers followed the Langmuir model, and the maximum adsorption capacity was 616.9 mg g −1 . The abundant benzene rings and quinoline structures in COF-QL-Ph nanofibers provided a great number of sites for the interaction with 2,4-DCP, which were confirmed by simulation and adsorption characterization. As expected, the self-supporting hollow structure of COF-QL-Ph nanofibers greatly improved the mass transfer rate of adsorbed analytes and accelerated the kinetic process. Furthermore, COF-QL-Ph nanofibers exhibited good structural stability and high recovery performance after six adsorption–desorption cycles. Thus, COF-QL-Ph nanofiber represents a highly promising adsorbent suitable for purifying chlorinated phenols in environmental waters.