Fabrication of three-component hydrogen-bonded covalent-organic polymers for ciprofloxacin decontamination from water: adsorption mechanism and modeling

A three-component hydrogen-bonded covalent organic polymer, namely JLUE-H_COP-66, was fabricated via a facile multiple-linking-site solvothermal approach to overcome the weakness of poor function complexity and limited structure diversity of the pure covalent skeletons. The as-prepared JLUE-H_COP-66 polymers were employed to decontaminate ciprofloxacin (CIP), a popular F-quinolones (FQNs) antibiotic, from water and exhibited satisfactory adsorption performance. Specifically, JLUE-H_COP-66 polymers have high adsorption capacity with the maximum contribution of 111.1 mg/g according to the Langmuir model, good antiinterference to NaCl salts, and excellent regeneration property. The pH-dependent experiment results signified the probably dominated mechanism of electrostatic interaction. In addition, adsorption studies and structural characterization in combination illustrated that the pore-filling effect, hydrogen bonding formation might also govern the whole process, accompanied by electrostatic interaction, dipole-dipole complexation, π-π EDA interaction, and hydrophobic-hydrophobic interaction besides. Moreover, electrostatic potentials, as well as the frontier molecular orbital distributions (HOMO and LUMO) of CIP and JLUE-H_COP-66 fragment, were calculated using density functional theory to theoretically support the research. Furthermore, the response surface methodology (RSM) according to the CCD matrix was used to not only study the interactive and cooperative effects of initial CIP concentration, initial pH, ionic strength along with JLUE-H_COP-66 dosage on CIP removal using JLUE-H_COP-66 but also optimize the operation conditions. Given the peculiar structure and functional feature, this work could hopefully bring H_COPs into the practical applications of such challenging and persistent ciprofloxacin potent removal with further large-scale efficiency.