Post-synthetic modification of conjugated microporous polymer with imidazolium for highly efficient anionic dyes removal from water

Abstract

• A cationic CMP-Im was synthesized by post-synthetic modification. • CMP-Im showed superior adsorption and separation capacity for anionic dyes. • The conjugation, porosity and cation benefit the adsorption results of CMP-Im . • CMP-Im can be used to prepare packed column and beads to remove anionic dyes. Water pollution caused by organic dyes is a severe environmental problem in developing society. Adsorption has been considered as a versatile and simple water-purification method. Therefore, it is desirable to develop adsorbents with high capacity and efficiency to remove dyes. In this work, through two-step post-synthetic modification to introduce imidazolium in a conjugated microporous polymer (CMP), an effective adsorbent ( CMP-Im ) was obtained to study the rational conjugated and cationic skeleton for anionic dyes removal. All these polymers exhibited inherent porous structures and high stability. CMP-Im showed Brunauer–Emmett–Teller (BET) surface area of 533 m 2 g −1 and possessed cationic framework of imidazolium unit favoring interaction with anionic guests. Due to the conjugated, cationic and porous framework, CMP-Im exhibited fast and efficient adsorption of anionic dyes such as methyl orange (MO) and Congo red (CR), and the adsorption capacity for MO and CR were 588 and 2500 mg g −1 , respectively. CMP-Im also exhibited excellent removal ability when it was used as stuffing to prepare packed column and adsorption beads. Hence, CMP-Im can be a promising candidate for dyes removal from water. This work opens up the exploration of post-synthetic CMPs and expands the application of cationic CMPs in dye adsorption.