Calix[4]arene-based Supramolecular Gels for Mercury Ion Removal in Water

A calix[4]arene-based gelator 1, with lower-rim mono triazolylpyridine group, capable of spontaneous self-assembly into microspheres in different ethanol/H2O mixtures, is synthesized. The concentration-dependent H-1 NMR spectra and X-ray single-crystal structure of 1 provided evidence for self-assembly of gelator 1 via cooperative interactions of intermolecular noncovalent forces. Furthermore, metallogels by self-assembly of 1 was found to exhibit remarkable selectivity toward Hg2+ ions. H-1 NMR spectra support that Hg2+ ion was bound to the nitrogen atoms of two coordination sites of 1, which composed of triazole and pyridine. Moreover, the results of field emission scanning electron microscopy and rheology experiments indicated that Hg2+ ions not only enhanced the gelling ability of gelator 1 in ethanol but also led to morphological change of its self-assembly through metal-ligand interactions. Finally, the in situ gelation, triggered by mixing a gelator solution of 1 in ethanol with water samples such as deionized (DI), tap, and lake water, leads to the effective removal of Hg(II) from a water sample which reduced from 400 to 1.6 ppm.

Automated summary

In this study, a calix[4]arene-based gelator 1 capable of self-assembling into microspheres in ethanol/H2O mixtures was synthesized. The self-assembly of gelator 1 was found to be driven by cooperative interactions of intermolecular noncovalent forces. Additionally, gelator 1 demonstrated remarkable selectivity towards Hg2+ ions, and the presence of Hg2+ ions enhanced the gelling ability and led to morphological changes of the self-assembled structures through metal-ligand interactions.