High-Efficiency Desalination with MXene Membranes via Tailored Surface Terminations and Nanochannel Architectures

Abstract

Freshwater scarcity has driven growing interest in MXene membranes for seawater desalination. However, improving the trade-off between water permeability and ion selectivity remains a key challenge. In this study, we investigated the performance of MXene membranes for seawater desalination via reverse osmosis through molecular dynamics simulations. Specifically, the impacts of layer number, slit geometry, and surface terminations on separation efficiency were systematically evaluated. Our results revealed that a trilayer misaligned slit geometry markedly increased ion rejection, compared with their bilayer and monolayer counterparts. Furthermore, we also identified a key synergy in the desalination process between geometric confinement and surface chemistry. A mixed-termination strategy could overcome conventional performance limits, which combined hydrophilic hydroxyl (−OH) termination with electronegative fluorine (−F) and oxygen (−O) terminations. The −OH terminations enhanced water permeability by lowering the free-energy barrier. In contrast, the other two terminations (−F, −O) achieved complete ion rejection through strong electrostatic repulsion. Consequently, a trilayer misaligned MXene membrane with mixed terminations achieved a favorable balance between flux and selectivity. These molecular-level insights provide qualitative guidance for regulating terminal groups and slit geometry in MXene nanochannels, thereby offering the design of more efficient and practical desalination membranes.