Nanofluidic ion regulation membranes based on two-dimensional vacancy-containing CdPS₃ membrane

Nanofluidic ion regulation membranes have emerged as versatile platforms for applications in molecular/ion separation and energy conversion. The use of two-dimensional (2D) material-based membranes holds great potential for the regulation of nanofluidic ions owing to their unique properties of surface charges, nanochannels, and nanocapillary force. Herein, a class of 2D flexible ion-conductive membranes with surface charge-controllable and voltage-tunable ion transport properties, which are assembled with monolayered Cd vacancy-containing CdPS₃ (vc-CdPS₃)-based nanosheets, is reported. Importantly, the ion conductivity of the vc-CdPS₃ membrane is several orders of magnitude higher than that of bulk salt solutions up to 0.1 M and reaches a plateau of ∼10 mS cm⁻¹ in low concentrated solution (≤1 mM), demonstrating typical charge-controllable nanofluidic ion transport behavior. This membrane exhibits excellent stability and maintains an ion conductivity of 23 and 20 mS cm⁻¹ under harsh acidic and alkaline conditions, respectively. By applying positive/negative gating voltage, ion transportation within the vc-CdPS₃ membrane is tuned, resulting in low/high ion conductivity. The voltage-tunable behavior across a broad spectrum of cations with varying sizes and charges is observed, showcasing the ion-specific switch ratios of 12 and 10 for potassium and sodium ions, respectively, under an applied voltage of 2 V/−2 V. This work demonstrates the potential of vacancy-containing membranes for a variety of membrane separation applications and offer a strategy for preparing efficient ion transport devices. © 2024 The Royal Society of Chemistry.