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

ABSTRACT 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 Mg 2+ transport. Consequently, the membrane exhibits exceptional ideal Li + /Mg 2+ 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.