Triazine-based covalent organic polycalix[4]arenes for highly efficient and reversible iodine capture in water

Novel triazine-based covalent organic polycalix[4]arenes, CalCOPs, were synthesized via the copolymerization of calix[4]arene derivatives and 2,4,6-trichloro-1,3,5-triazine (TCT) or 2,4-dichloro-1,3,5-triazine (DCT). The resulting CalCOPs have permanent pores that can be regulated by the variation of the alkyl chain lengths of the calixarene backbones and the reaction sites. With the alkyl chain length at the low rim in calixarene units increasing from ethyl to butyl during the reaction, the Brunauer–Emmett–Teller surface areas decrease with surface areas of 280, 31.5, 18.4 and 1.6 m2 g−1 obtained for CalCOP1, CalCOP2, CalCOP3 and CalCOP4, respectively. Among these CalCOPs, CalCOP1 shows ultrahigh absorption for iodine capture in a water solution with an uptake of up to 232 wt%. Furthermore, the adsorption and release efficiency of iodine were obtained by using the UV–Vis spectroscopy. In addition, these polymers can be recycled at least five times while maintaining high removal capacity, suggesting that CalCOPs are ideal absorbent materials for reversible iodine capture in the mitigation of environmental issues. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.