Tailoring CO₂-Activated Ion Nanochannels Using Macrocyclic Pillararenes

Gas-responsive nanochannels have great relevance for applications in many fields. Inspired by CO2-sensitive ion channels, herein we present an approach for designing solid-state nanochannels that allow controlled regulation of ion transport in response to alternate CO2/N2 stimuli. The pillar[5]arene (P5N) bearing diethylamine groups can convert into the water-soluble host P5C, containing cationic tertiary ammonium salt groups after absorbing CO2. Subsequently, the nanochannel walls are tailored using P5N-based host–guest chemistry. The ion transport rate of K+ in the P5N nanochannels under CO2 was 1.66 × 10–4 mol h–1 m–2, whereas that under N2 was 7.98 × 10–4 mol h–1 m–2. Notably, there was no significant change to the ion current after eight cycles, which may indicate the stability and repeatability of CO2-activated ion nanochannels. It is speculated that the difference in ion conductance resulted from the change in wettability and surface charge within the nanochannels in response to the gas stimuli. Achieving CO2-activated ion transport in solid-state nanochannels opens new avenues for biomimetic nanopore systems and advanced separation processes.