摘要

A two‐dimensional (2D) laminar membrane with Li+ selective transport channels is obtained by stacking MXene nanosheets with the introduction of poly(sodium 4‐styrene sulfonate) (PSS) with active sulfonate sites, which exhibits excellent Li+ selectivity from ionic mixture solutions of Na+, K+, and Mg2+. The Li+ permeation rate through the MXene@PSS composite membrane is as high as 0.08?mol?m?2?h?1, while the Li+/Mg2+, Li+/Na+, and Li+/K+ selectivities are 28, 15.5, and 12.7, respectively. Combining the simulation and experimental results, we further confirm that the highly selective rapid transport of partially dehydrated Li+ within subnanochannels can be attributed to the precisely controlled interlayer spacing and the relatively weaker ion‐terminal (?SO3?) interaction. This study deepens the understanding of ion‐selective permeation in confined channels and provides a general membrane design concept.(#br)Lamellar MXene (Ti3C2Tx)@PSS membranes with specific size exclusion and Li+ identification property show excellent mono/multi‐valent ions separation performance. Compared with the traditional 2D membranes, the selectivity of Li+/Na+, Li+/K+, and Li+/Mg2+ through such membranes is five to ten times improved.