State-of-the-art desalination membranes exhibit high water-salt selectivity, but their ability to discriminate between ions is limited. Elucidating the fundamental mechanisms underlying ion transport and selectivity in subnanometer pores is therefore imperative for the development of ion-selective membranes. Here, we compare the overall energy barrier for salt transport and energy barriers for individual ion transport, showing that cations and anions traverse the membrane pore in an independent manner. Supported by density functional theory simulations, we demonstrate that electrostatic interactions between permeating counterion and fixed charges on the membrane substantially hinder intrapore diffusion. Furthermore, using quartz crystal microbalance, we break down the contributions of partitioning at the pore mouth and intrapore diffusion to the overall energy barrier for salt transport. Overall, our results indicate that intrapore diffusion governs salt transport through subnanometer pores due to ion-pore wall interactions, providing the scientific base for the design of membranes with high ion-ion selectivity.

最先进的脱盐膜具有很高的水盐选择性，但是它们区分离子的能力有限。因此，阐明在亚纳米孔中离子迁移和选择性的基本机理对于开发离子选择性膜至关重要。在这里，我们比较了盐传输的整体能垒和单个离子传输的能垒，表明阳离子和阴离子以独立的方式横穿膜孔。在密度泛函理论模拟的支持下，我们证明了渗透抗衡离子与膜上固定电荷之间的静电相互作用实质上阻碍了孔内扩散。此外，使用石英晶体微量天平，我们打破了在孔口分配和孔内扩散对盐转运总能垒的贡献。总体而言，我们的结果表明，由于离子-孔壁的相互作用，孔内扩散控制盐通过亚纳米孔的迁移，为设计具有高离子-离子选择性的膜提供了科学依据。