The outstanding ionic sieving capabilities of the nanoporous membranes have been evident; however, the selectivity in mixed solutions is often lower than that in single salt solutions. Given that the inherent properties of nanochannels remain the same, the ionic coordination structure in mixed solution becomes a remarkable factor for the inferior selectivity, and may change due to the interaction between anions and multivalent cations, a phenomenon rarely explored. Herein, molecular simulations demonstrated some free hydrated ions transfer to ionic clusters consisting of multi-ions in representative LiCl/MgCl₂ mixed solutions, and the ionic permeability discrepancy is exponentially associated with ionic cluster change. Ionic clusters are engaged by the enhanced coordination of chloride ions under the interference of divalent cations. Hence, by introducing anions with weak coordination ability, this detrimental effect is mitigated and ion selectivity is improved. This work provides essential theoretical foundations for further ion sieving applications in complex system.

中文翻译：

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调节离子配位环境以提高混合溶液中 Li+/Mg2+ 的选择性


纳米多孔膜出色的离子筛分能力是显而易见的；然而，混合溶液中的选择性通常低于单一盐溶液中的选择性。鉴于纳米通道的固有性质保持不变，混合溶液中的离子配位结构成为选择性较差的显着因素，并且可能由于阴离子和多价阳离子之间的相互作用而发生变化，这种现象很少被研究。在此，分子模拟表明，在代表性LiCl/MgCl ₂混合溶液中，一些游离水合离子转移至由多离子组成的离子簇，并且离子渗透率差异与离子簇变化呈指数关系。在二价阳离子的干扰下，离子簇通过氯离子的增强配位而参与。因此，通过引入配位能力较弱的阴离子，可以减轻这种不利影响并提高离子选择性。这项工作为复杂系统中离子筛分的进一步应用提供了重要的理论基础。