Bio‐Inspired 2D Asymmetric Nanochannels for High‐Resolution Li⁺/Mg²⁺ Separation

Extracting lithium from salt lake brines is crucial to achieve sustainable development of lithium resources. However, it remains a major challenge to design nanochannels with efficient selectivity and fast transport for target ions. Here, inspired by biological membranes, we reported a Janus graphene oxide membrane (JGOM) with an asymmetric structure that exhibits diode‐like ion transport behavior and achieves high‐efficiency Li + /Mg 2 ⁺ separation for lithium extraction applications. During the forward transport of ions, the nGO nanochannels modified by sulfonate groups (SO 3 − ) with precise size provide hopping recognition sites and additional electrostatic attraction for the fast transport of Li + , while imposed Mg 2+ dehydration and exposure to a stronger positive charge. The continuous pGO nanochannels modified by amino groups (NH 3 + ) further prevent the passage of dehydrated Mg 2+ by enhanced electrostatic repulsion while allowing Li + to transfer. Under the synergy of the two nanochannels, the JGOM demonstrates robust Li + /Mg 2+ separation performance, outperforming symmetrical structure GO membranes and other reported membranes, which was further confirmed by simulation results. This study provides a new insight into the rational design of ion sieving membranes.