Kilogram-Scale Water-Mediated Exfoliation Strategy for Defect-Free Single-Layer MXene Nanosheets

Single-layer MXene nanosheets have garnered immense attention for their remarkable functional versatility; however, their ultimate performance and application potential are fundamentally limited by their intrinsic quality. Traditional high-yield methods for MXenes typically involve high-energy mechanical input, often introducing a substantial density of defects, which inevitably creates the trade-off between quality and scalability. Herein, we present a water-mediated exfoliation strategy that tailors the coordination environment of intercalated Li⁺ ions to expand the interlayer spacing beyond the critical threshold for spontaneous delamination. This strategy produces kilogram-scale, single-layer nanosheets with exceptional structural integrity, large lateral dimensions (>10 µm), and high yields (>80%). Furthermore, the highly oriented membrane assembly by these nanosheets minimizes inter-flake voids and imposes prohibitive steric hindrance to Mg²⁺ transport. Consequently, the membrane exhibits exceptional ideal Li⁺/Mg²⁺ selectivity (> 170) and achieves rapid direct lithium extraction from natural seawater (36% yield). This achievement effectively bridges the lab-to-industry gap, paving the way for scalable osmotic energy and resource recovery applications.