Ion-Selective MXene-Based Membranes: Current Status and Prospects

Water pollution is a major global challenge, as conventional polymeric membranes are not adequate for water treatment anymore. Among emerging materials for water treatment, composite membranes are promising, as they have simultaneously improved water permeation and ions rejection. Recently, a new family of 2D materials called MXenes has attracted considerable attention due to their appealing properties and wide applications. MXenes can be incorporated into many polymeric materials due to their high compatibility. MXenes/polymer composite membranes have been found to have appealing electrical, thermal, mechanical, and transport properties, because of strong interactions between polymer chains and surface functional groups of MXenes and the selective nanochannels that are created. This article reviews advances made in the area of ion-selective MXene-based membranes for water purification. It puts the advances into perspective and provides prospects. MXenes' properties and synthesis methods are briefly described. Strategies for the preparation of MXene-based membranes including mixed-matrix membranes, thin-film nanocomposite membranes, and laminated membranes are reviewed. Recent advances in ion-separation and water-desalination MXene-based membranes are elucidated. The dependence of ion-separation performance of the membranes on fabrication techniques, MXene's interlayer spacing, and MXene's various surface terminations are elucidated. Finally, opportunities and challenges in ion-selective MXene-based membranes are discussed.