MXene/ZIF-L co-stacking membranes with high water permeation for solute-tailored selectivity

Abstract

Herein, we design a composite MXene membrane with high permeability and stability by introducing highly porous two-dimensional ZIF (zeolitic imidazolate framework)-L sheets. On the one hand, the ZIF-L sheets provide additional nanochannels in the vertical direction, which shorten and enrich the mass transport pathways of the MXene membrane. On the other hand, a moderate increase in interlayer spacing of Ti3C2TX nanosheets is detected after introducing ZIF-L. Additionally, the Ti-O-Zn/Ti-F-Zn chemical bonds between Ti3C2Tx and ZIF-L nanosheets provide structural stability to the composite membrane. When applied in nanofiltration, the optimal co-stacking membrane with a ZIF-L mass fraction of 9.10 % exhibits an ultrahigh pure water flux of 287.29 L m-2h−1 bar−1, which is ∼ 2.41 times higher than the pristine MXene membrane (124.98 L m-2h−1 bar−1). Meanwhile, the composite MXene/ZIF-L membrane shows an excellent dye/salt separation efficiency, as indicated by the high Congo Red rejection (99.2 %) and the low MgCl2 rejection (1.58 %) in a mixing dye/salt system. This work provides a promising strategy for constructing a two-dimensional membrane with high permeation for dye/salt separation.