Self-Crosslinked MXene (Ti₃C₂T_x) Membranes with Good Antiswelling Property for Monovalent Metal Ion Exclusion

Abstract

A 2D membrane-based separation technique has been increasingly applied to solve the problem of fresh water shortage via ion rejection. However, these 2D membranes often suffer from a notorious swelling problem when immersed in solution, resulting in poor rejection for the monovalent metal ion. The design of the antiswelling 2D lamellar membranes has been proved to be a big challenge for highly efficient desalination. Here a kind of self-crosslinked MXene membrane is proposed for ion rejection with an obviously suppressed swelling property, which takes advantage of the hydroxyl terminal groups on the MXene nanosheets by forming Ti–O–Ti bonds between the neighboring nanosheets via the self-crosslinking reaction (−OH + −OH = −O– + H2O) through a facile thermal treatment. The permeation rates of the monovalent metal ions through the self-crosslinked MXene membrane are about two orders of magnitude lower than those through the pristine MXene membrane, which indicates the obviously improved performance of the ion exclusion by self-crosslinking between the MXene lamellae. Moreover, the excellent stability of the self-crosslinked MXene membrane during the 70 h long-term ion separation also demonstrates its promising antiswelling property. Such a facile and efficient self-crosslinking strategy gives the MXene membrane a good antiswelling property for metal ion rejection, which is also suitable for many other 2D materials with tunable surface functional groups during membrane assembly.

Ion sieving by a two-dimensional Ti3C2Tx alginate lamellar membrane with stable interlayer spacing

“…17) 51 . The highresolution XPS spectra of Ti 2p also demonstrate that the proportion of TiO 2 in the as-prepared Ca-SAT membrane was negligible, and the Ti form also remained constant, indicating that the membrane oxidation was slight 32 . The regeneration ability of the Ca-SAT membrane was also evaluated, as shown in Supplementary Fig.…”

“…In addition, the functionalized surface allows Ti 3 C 2 T x to bond effectively with various species 25,26 . Ti 3 C 2 T x laminates have been evaluated as a potential competitor in energy storage, electromagnetic interference shielding, biosensors and other fields [27][28][29][30] , and their activity in ion sieving has recently begun to be described 31,32 .…”

MXene Materials for Designing Advanced Separation Membranes

“…Lu et al very recently proposed a strategy to address this issue. [124] By temperature-induced self-crosslinking of hydroxylated Ti 3 C 2 T x (via H 2 O condensation), they managed to develop antiswelling membranes. As expected, the salt rejection performances of the membranes improved as the degree of crosslinking increase but at the expense of decrease in permeability.…”

“…As expected, the salt rejection performances of the membranes improved as the degree of crosslinking increase but at the expense of decrease in permeability. [124] Further reducing the thickness of such membranes might be promising for a wide range of applications.…”

2D Nanocomposite Membranes: Water Purification and Fouling Mitigation

“…MXene forms another group of nanosheets that suffers from swelling with water when a nanosheet layer is stakced on top of a substrate. However, Lu et al [ 103 ] reported successful self-crosslinking of nanosheets via dehydroxylation on the surface of the basal planes. Strengthening the membrane structure via self-crosslinking resulted in the long-term stability of ion rejection, even under harsh acid or basic environments.…”