Ion selective membranes are fundamental components of biological, energy, and computing systems. The fabrication of solid-state ultrathin membranes that can separate ions of similar size and the same charge with both high selectivity and permeance remains a challenge, however. Here, we present a method, utilizing the application of a remote electric field, to fabricate a high-density of (sub)nm pores in situ. This method takes advantage of the grain boundaries in few-layer polycrystalline MoS₂ to enable the synthesis of nanoporous membranes with average pore size tunable from <1 to ~4 nm in diameter (with in situ pore expansion resolution of ~0.2 nm² s⁻¹). These membranes demonstrate selective transport of monovalent ions (K⁺, Na⁺ and Li⁺) as well as divalent ions (Mg²⁺ and Ca²⁺), outperforming existing two-dimensional material nanoporous membranes that display similar total permeance. We investigate the mechanism of selectivity using molecular dynamics simulations and unveil that the interactions between cations and the sluggish water confined to the pore, as well as cation-anion interactions, result in the different transport behaviors observed between ions.

离子选择性膜是生物、能源和计算系统的基本组成部分。然而，制造能够以高选择性和渗透性分离相似尺寸和相同电荷的离子的固态超薄膜仍然是一个挑战。在这里，我们提出了一种利用远程电场的应用来原位制造高密度（亚）纳米孔的方法。该方法利用少层多晶 MoS ₂中的晶界来合成平均孔径可从 <1 调节至直径约 4 nm 的纳米多孔膜（原位孔径扩展分辨率为约 0.2 nm ² s ^{- 1} ）。这些膜表现出单价离子（K ⁺ 、Na ⁺和 Li ⁺ ）以及二价离子（Mg ²⁺和 Ca ²⁺ ）的选择性传输，优于具有相似总渗透性的现有二维材料纳米多孔膜。我们使用分子动力学模拟研究了选择性机制，并揭示了阳离子与限制在孔隙内的滞流水之间的相互作用以及阳离子-阴离子相互作用，导致了离子之间观察到的不同传输行为。