Charge- and Size-Selective Ion Sieving through Ti3C2Tx MXene Membranes

Nanometer-thin sheets of 2D Ti3C2Tx (MXene) have been assembled into freestanding or supported membranes for the charge- and size-selective rejection of ions and molecules. MXene membranes with controllable thicknesses ranging from hundreds of nanometers to several micrometers exhibited flexibility, high mechanical strength, hydrophilic surfaces, and electrical conductivity that render them promising for separation applications. Ti3C2Tx membranes demonstrate attractive separation properties based on their permeation selectivity toward cations of various sizes and charges. The hydrophilic nature of Ti3C2Tx accompanied by the presence of H2O between the layers promotes ultrafast water flux. Ti3C2Tx membranes show high selectivity toward single-, double- and triple-charged metal cations and dye cations of different sizes. Ti3C2Tx membranes demonstrate a better performance than GO in the separation of higher charge cations.