Layer-by-layer repaired lamellar membrane for low stacking defect of MXene nanosheets and efficient separation performance in water purification

Two-dimensional (2D) materials have been widely considered to be used in advanced membranes for their excellent separation efficiencies. The filtration performance of lamellar membrane will be further improved after overcoming the stacking defects of 2D materials in membrane fabrication. Herein, a novel layer-by-layer repair method was proposed to fabricate MXene lamellar membranes with few defects via serial layer-by-layer compaction, crosslinking, glass rod rolling treatment and self-crosslinking. The method reduced the irregular arrangement of MXene nanosheets, repaired the wrinkled surface of every few-layer MXene nanosheets and enhanced the link between adjacent MXene nanosheets. The thickness of the layer-by-layer repaired MXene membranes was 50 nm. The layer-by-layer repaired MXene membranes possessed the rejection rates of NaCl, MgCl2 and methylene blue of 72.6%, 93.8% and 99.8% respectively associating with water flux of 5.9 L·m−2·h−1, 7.4 L·m−2·h−1 and 9.8 L·m−2·h−1 due to their regular nanochannels. They represented high stability in nanofiltration for 120 h. The swelling of MXene nanosheets was weakened in the filtration. The repair strategy is potentially applied in fabrication of other 2D lamellar membranes and their enhancement of filtration performance.