Nanocluster-regulated porous ionic rotaxane assemblies with solvent-adaptability for selective adsorption and conductivity

Abstract

Porous supramolecular assemblies are increasingly recognized for the capabilities in mass transfer and selective loading and release. In this study, a dicationic cyclodextrin[3]rotaxane was synthesized to exhibit adaptivity in the flexible motion between the macrocycle and axle, allowing dynamic structural adjustment during their coassembly with polyanionic nanoclusters. Meanwhile, the anions regulate the assembly to form layered, fibrous, and porous structures. By simply mixing the charged components in solution, the porous ionic rotaxane-cluster assemblies have been prepared, showing selective adsorption and adaptive structural transformations. These assemblies exhibit a "breathing" effect in response to solvent adsorption/desorption, thereby enabling ABE mixture separation. DMSO disrupts hydrogen bonds and ionic interactions, allowing recrystallization to form a porous structure with larger pores. This transition is reversible by returning to the original structure in aqueous solution. The reorganization can change proton conductivity by about three orders between the two structures.