Sodium-Ion\nTraps in a Two-Dimensional Confined Channel\nfor Effective Water and Ion Selective Transport

Nanoconfined interlayer channels in two-dimensional (2D)\nlaminates\nare promising for the construction of novel permselective membranes.\nControlling the interlayer spacing and modifying the interlayer chemical\nmicroenvironment are effective for high-efficiency separation. However,\nmanipulating ion-diffusion energy barriers in confined channels is\nchallenging, and their role in selective water–ion transport\nis unclear. This study engineered sodium-ion traps (SITs) in confined\ngraphene oxide (GO) interlayer channels by incorporating <i>N</i>-phenylaza-15-crown-5 (NPCE) to regulate the ion-diffusion energy\nbarriers. Partial reduction of GO enhanced membrane stability and\nenabled precise adjustment of interlayer spacing, while the addition\nof NPCE further constricted the free space and entrapped sodium ions\nby increasing their transport energy barriers. The optimized membrane\nwith NPCE-dominated SITs achieved mono/monovalent-ion efficient sieving\n(K<sup>+</sup>/Na<sup>+</sup> ≈ 10.2, and Li<sup>+</sup>/Na<sup>+</sup> ≈ 6.7) and rejection of Na<sub>2</sub>SO<sub>4</sub> (∼99.0%) and NaCl (∼90.0%), while maintaining stable\nperformance for >1500 h. The findings provide new insights into\nmanipulating\ntransport energy barriers and modifying other 2D material laminates.