Selective Ion Transport in Two-Dimensional TiCT Nanochannel Decorated by Crown Ether.

Ion sieving is a critical process employed in various applications, such as desalination and ion extraction. Nevertheless, achieving rapid and accurate ion sieving remains an exceptionally difficult task. Drawing inspiration from the effective ion sieving capabilities of biological ion channels, we present the development of two-dimensional TiCT ion nanochannels incorporating 4-aminobenzo-15-crown-5-ether molecules as specific ion binding sites. These binding sites had a significant influence on the ion transport process and improved ion recognition. Permeation of both Na and K was facilitated because their ion diameters are compatible with the cavity in the ether ring. Moreover, owing to the strong electrostatic interactions, the permeation rate for Mg increased by a factor of 55 compared to that for the pristine channels, which was higher than those of all monovalent cations. Furthermore, the transport rate for Li was relatively lower than those of Na and K, which was attributed to difficult binding of the Li to the oxygens in the ether ring. Consequently, the ion selectivities of the composite nanochannel were up to 7.6 for Na/Li and 9.2 for Mg/Li. Our work presents a straightforward approach to creating nanochannels exhibiting precise ion discrimination.