A unimolecular artificial cation channel based on cascaded hydrated acid groups.

A cation channel possessing cascaded hydrated acid groups has been successfully constructed using pillar[5]arene integrated with dual cyclodextrins. As a proof-of-concept, the secondary side of cyclodextrin substituted by 24 -CO2H groups presents high coordination sites, which helps hydrated cations to quickly dehydrate and accelerates efficient cation transport (Rb+ > Cs+ > K+ > Na+ > Li+). Notably, benefitted by the protonation and deprotonation of -CO2H groups, ion permeation activity of the channel molecules under acidic condition (pH = 6.0) is 2.8 times higher than that under alkaline conditions (pH = 8.0), exhibiting pH-modulated property and promising potential in building intelligent artificial ion channels with customized features.