Comediation of voltage gating and ion charge in MXene membrane for controllable and selective monovalent cation separation
Xu Wang, Haiguang Zhang, Gaoliang Wei, Jiajian Xing, Shuo Chen, Xie Quan
Abstract
Artificial ion channels with controllable mono/monovalent cation separation fulfill important roles in biomedicine, ion separation, and energy conversion. However, it remains a daunting challenge to develop an artificial ion channel similar to biological ion channels due to ion-ion competitive transport and lack of ion-gating ability of channels. Here, we report a conductive MXene membrane with polydopamine-confined angstrom-scale channels and propose a voltage gating and ion charge comediation strategy to concurrently achieve gated and selective mono/monovalent cation separation. The membrane shows a highly switchable “on-off” ratio of ∼9.9 for K + transport and an excellent K + /Li + selectivity of 40.9, outperforming the ion selectivity of reported membranes with electrical gating (typically 1.5 to 6). Theoretical simulations reveal that the introduced high-charge cations such as Mg 2+ enable the preferential distribution of target K + over competing Li + at the channel entrance, and the surface potential reduces the ionic transport energy barrier for allowing K + to pass quickly through the channel.