Cross-Linked Supramolecular Polymer Based on Calix[4]pyrrole-Decorated Pillar[5]arene and Its Application in Micropollutant Removal

A calix[4]pyrrole-decorated pillar[5]arene was synthesized via azide-alkyne “click” chemistry and used to prepare a cross-linked supramolecular polymer in chloroform based on the anion recognition ability of calix[4]pyrrole. Complexation experiments revealed that while one of the cross-linkers, terephthalate anion, was not able to form strong complexation, suberate anion was found to act as a suitable cross-linker. Supramolecular polymerization and performance of monomers were monitored with a combination of techniques including ¹H-, diffusion-ordered ¹H NMR spectroscopy experiments, viscosity, and SEM analyses. Thermo and competing anion responsiveness of the cross-linked supramolecular polymer were also shown by means of ¹H-NMR analyses and viscosity measurements. Micropollutant removal ability of the cross-linked supramolecular polymer in solid and gel forms was also investigated by using methylene blue, methyl violet 2B, and rhodamine B as surrogate pollutants, and UV/Vis experiments revealed that while the solid form of the supramolecular polymer performs better in the case of methylene blue and methyl violet, its gel form provides slightly better removal efficiency for rhodamine B.