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 synthesizedviaazide-alkyne "click" chemistry and used to prepare across-linked supramolecular polymer in chloroform based on the anionrecognition ability of calix[4]pyrrole. Complexation experiments revealedthat while one of the cross-linkers, terephthalate anion, was notable to form strong complexation, suberate anion was found to actas a suitable cross-linker. Supramolecular polymerization and performanceof monomers were monitored with a combination of techniques including H-1-, diffusion-ordered H-1 NMR spectroscopy experiments,viscosity, and SEM analyses. Thermo and competing anion responsivenessof the cross-linked supramolecular polymer were also shown by meansof H-1-NMR analyses and viscosity measurements. Micropollutantremoval ability of the cross-linked supramolecular polymer in solidand gel forms was also investigated by using methylene blue, methylviolet 2B, and rhodamine B as surrogate pollutants, and UV/Vis experimentsrevealed that while the solid form of the supramolecular polymer performsbetter in the case of methylene blue and methyl violet, its gel formprovides slightly better removal efficiency for rhodamine B.