Multi-sulfonated functionalized hydrophilic covalent organic framework for highly efficient dye removal from real samples

Abstract

Rationally designing porous materials with excellent hydrophilic performance for the selective removal of contaminants from wastewaters before discharge into the environment is highly desirable but still faces challenges. Herein, to address the shuttle issue, a hydrophilic covalent organic framework (BTA-BDSA-COF) was synthesized by introducing multi-sulfonated groups into a covalent framework structure and its potential applications in cationic dye capture have been evaluated in detail. Topological modulation and structural characteristics reveal the following: (1) a regular single-pore (SP) framework of BTA-BDSA-COF is constructed which is distinguishable from most reported COFs, with a condensation of D_2h symmetry and ditopic linear diamine building blocks. (2) BTA-BDSA-COF undergoing excellent hydrophilicity outperforms other studied COFs functioned with sulfonated groups. Furthermore, dye sorption selectivity and kinetic studies clearly state the following: (1) the hydrophilic feature of anionic BTA-BDSA-COF is a significant driving force to ameliorate the adsorption ability of cationic dyes. (2) The degree of match between the size of the BTA-BDSA-COF pore aperture and the volume of dye molecule is intimately related to the dye adsorption properties. Therefore, BTA-BDSA-COF exhibits an impressive MLB adsorptive capacity of 1280 mg g⁻¹ and a quick adsorption equilibrium of 30 min, owing to the moderately hydrophilic pore environment of BTA-BDSA-COF. Successful application in real water samples suggests that BTA-BDSA-COF with moderate hydrophilicity would be a promising adsorbent candidate for practical cationic dye capture.