Cooperative and inhibitory ion transport in functionalized angstrom-scale two-dimensional channels

Significant success has been achieved in fabricating angstrom-scale artificial solid ionic channels aiming to replicate the biological ion channels (BICs). Besides high selectivity, BICs also exhibit sophisticated ion gating and interplay. However, such behavior and functionality are seldomly recreated in the artificial counterparts due to the insufficient understanding of the molecular origin. Here we report cooperative and inhibitory ion transport in angstrom-scale acetate functionalized MoS2 two-dimensional channels. For cooperative ion transport, the permeability of K+ is doubled in the presence of only 1% Pb2+ (versus K+ by molarity), while the permeability of Pb2+ is independent of K+. Molecular dynamics simulations reveal complex interplay among K+, Pb2+, and the anions in governing the cooperativity, such that Pb2+ ions capture and slow down the anions via long-range interaction, which leads to the synchronization of anions with K+ to transport as ion pairs with reduced interaction with the channel surface. For inhibitory ion transport, divalent Co2+ (or Ba2+) and Pb2+ can replace each other in the confined channel and compete for the limited transport cross section. Our work reveals ion transport phenomena in extreme confinement and highlights the potential of manipulating ion interplay in confinement for achieving advanced functionalities.