Dong Xinyao, Ai Xinyu, He Weijun, Zhai Yeming, Guo Ruixiang, Li Yi-Wei, Ma Zhu-Qing, Yang Yang, Zhou Kai-Ge
Institute of Molecular Plus, Department of Chemistry, Tianjin University, Tianjin 300072, People's Republic of China.
Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, People's Republic of China.
ACS Nano. 2025 Feb 4;19(4):4233-4241. doi: 10.1021/acsnano.4c10606. Epub 2025 Jan 3.
Extracting lithium from salt lakes requires ion-selective membranes with customizable nanochannels. However, it remains a major challenge to separate alkali cations due to their same valences and similar ionic radius. Inspired by the K channel of KcsA K, significant progress has been made in adjusting nanochannel size to control the ion selectivity dominated by alkali cations dehydration. Besides, several works involved incorporating ligands, such as crown ether, into nanochannels based on coordination chemistry to try to promote alkali cation selectivity; nevertheless, only the separation between mono-/bivalent cations has been achieved. Herein, a series of heteropolyacid (HPA) ligands are designed to functionalize two-dimensional (2D) nanochannels, achieving superior lithium perm-selectivity over other alkali cations (16 for Li/K), with the Li permeation rate increased to four times that of the pristine 2D membrane. We discover that the switching of an ion between its hydration and ion-HPA coordination states elucidates ion-selective transport, and the relatively lower depth of energy well for the exchange from Li hydration to Li-HPA coordination results in the separation of Li from other alkali cations. This work demonstrates a principle for exploring novel ligands to develop alkali cation-selective membranes, expanding the potential applications of ion separation membranes in lithium extraction from aquatic sources.
从盐湖中提取锂需要具有可定制纳米通道的离子选择性膜。然而，由于碱金属阳离子具有相同的化合价和相似的离子半径，分离它们仍然是一个重大挑战。受KcsA K钾通道的启发，在调整纳米通道尺寸以控制由碱金属阳离子脱水主导的离子选择性方面取得了重大进展。此外，一些工作涉及基于配位化学将冠醚等配体纳入纳米通道，试图提高碱金属阳离子的选择性；然而，仅实现了单/二价阳离子之间的分离。在此，设计了一系列杂多酸（HPA）配体来功能化二维（2D）纳米通道，实现了优于其他碱金属阳离子的锂渗透选择性（Li/K为16），锂渗透速率提高到原始二维膜的四倍。我们发现离子在其水合和离子-HPA配位状态之间的转换阐明了离子选择性传输，并且从锂水合到锂-HPA配位交换的能量阱深度相对较低导致锂与其他碱金属阳离子的分离。这项工作展示了探索新型配体以开发碱金属阳离子选择性膜的原理，扩大了离子分离膜在从水源中提取锂方面的潜在应用。
