Ershov Alexander, Xu Hengyu, Li Ying, Tong Tiezheng, Epsztein Razi
Faculty of Civil and Environmental Engineering, Technion─Israel Institute of Technology, Haifa 32000, Israel.
Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
Environ Sci Technol. 2025 Sep 2;59(34):17997-18009. doi: 10.1021/acs.est.5c04303. Epub 2025 Aug 19.
Fabricating polymeric membranes with ion-specific selectivity has been targeted in recent years to address the growing challenges of water and resource scarcity. Inspired by discoveries of the selectivity mechanisms in biological channels, ion dehydration has been increasingly recognized as a key phenomenon governing the transport and selectivity in dense polymeric membranes and other synthetic nanochannels. However, understanding the molecular details of this phenomenon and leveraging and controlling it to increase the selectivity between ions in state-of-the-art membranes remain elusive. In this Perspective, we discuss the foundations of ion dehydration and explore opportunities to study and leverage this phenomenon for improving ion-ion selectivity in membranes. We first introduce the fundamentals and measurements of ion's hydration properties in solution, distinguishing between static and dynamic hydration properties. Next, we discuss simulation and experimental techniques to study ion dehydration under confinement, highlighting critical knowledge gaps that impede our understanding of this phenomenon. We then discuss effects of ion dehydration on the energy landscape of ion transport and analyze attempts in the literature to improve ion selectivity by promoting dehydration of specific ions. We conclude by proposing research directions to enhance our understanding of ion dehydration and fabricate sustainable and robust membranes with ion-specific selectivity.
近年来，制造具有离子特异性选择性的聚合物膜已成为应对日益严峻的水资源和资源短缺挑战的目标。受生物通道中选择性机制发现的启发，离子脱水越来越被认为是控制致密聚合物膜和其他合成纳米通道中传输和选择性的关键现象。然而，了解这一现象的分子细节，并利用和控制它以提高现有膜中离子之间的选择性，仍然难以实现。在这篇综述中，我们讨论了离子脱水的基础，并探索研究和利用这一现象以改善膜中离子-离子选择性的机会。我们首先介绍溶液中离子水合性质的基本原理和测量方法，区分静态和动态水合性质。接下来，我们讨论研究受限条件下离子脱水的模拟和实验技术，强调阻碍我们理解这一现象的关键知识空白。然后，我们讨论离子脱水对离子传输能量景观的影响，并分析文献中通过促进特定离子脱水来提高离子选择性的尝试。我们最后提出研究方向，以增强我们对离子脱水的理解，并制造具有离子特异性选择性的可持续且坚固的膜。
