Construction of hydrophilic covalent organic frameworks and their fast and efficient adsorption towards cationic dyes from aqueous solution

Abstract

Research about the functionalized covalent organic framework (COF) materials with well hydrophilic characteristics is significant on account of their application in the removal of dyes in wastewater. In this work, two anionic COF materials (TFPB-Pa-SO3H COF and TFPB-BDSA COF) were successfully synthesized with sulfonated modification as dyestuffs sorbent to be used in the adsorption of cationic dyes. Two prepared COF materials exhibited predominant hydrophilicity with lower water contact angles (35° and 27°) compared with reported COF materials. The sulfonated groups on COFs can efficiently adsorb cationic dyes through electrostatic interaction, which can moderately ameliorate the adsorptive capacity towards hydro soluble dyes. TFPB-Pa-SO3H COF and TFPB-BDSA COF showed superfast adsorption equilibrium to MLB (1 and 2 min) and the higher adsorption uptakes of CV (1559 and 1288 mg g−1), which manifested that the adsorption rate may be closely related to the solubilities of host COFs materials as well as guest dye molecule in aqueous solution; while the adsorption stability between COFs materials and the dye molecule adsorbed on the COFs skeleton accounted for the highly effective adsorption of the aim dye in large quantity. In addition, two COFs as adsorbing materials were successfully applied to the removal of dyes molecules in real water samples.