A reversible ion transportation switch of ON–OFF–ON type by a ligand-gated calix[6]arene channel

Calix[6]arene (CX6) was found to be an efficient ion transmembrane channel, which could be blocked by methylene blue (MB) through host–guest interactions. The blocked CX6 channel could be reopened by 4-sulfonated calix[6]arene owing to its stronger affinity with MB, thereby achieving a reversible ON–OFF–ON type switch.