Rational Design of MXene Hollow Fiber Membranes for Gas Separations.

One scalable and facile dip-coating approach was utilized to construct a thin CO-selection layer of Pebax/PEGDA-MXene on a hollow fiber PVDF substrate. An interlayer spacing of 3.59 Å was rationally designed and precisely controlled for the MXene stacks in the coated layer, allowing efficient separation of the CO (3.3 Å) from N (3.6 Å) and CH (3.8 Å). In addition, CO-philic nanodomains in the separation layer were constructed by grafting PEGDA into MXene interlayers, which enhanced the CO affinity through the MXene interlayers, while non-CO-philic nanodomains could promote CO transport due to the low resistance. The membrane could exhibit optimal separation performance with a CO permeance of 765.5 GPU, a CO/N selectivity of 54.5, and a CO/CH selectivity of 66.2, overcoming the 2008 Robeson upper bounds limitation. Overall, this facile approach endows a precise controlled molecular sieving MXene membrane for superior CO separation, which could be applied for interlayer spacing control of other 2D materials during membrane construction.