A High-Performance N 2 -Selective MXene Membrane with Double Selectivity Mechanism for N 2 /CH 4 Separation.

Membrane-based separation process for unconventional natural gas purification (mainly N 2 /CH 4 separation) has attracted more attention due to its considerable economic benefits. However, the majority of separation membranes at this stage, particularly N 2 -selective membranes, achieve the desired separation target by mainly relying on the diffusivity-selectivity mechanism. To overcome the limitation of a single mechanism, 2D lamellar MXene membranes with a double selectivity mechanism are prepared to enhance N 2 permeance and N 2 /CH 4 selectivity via introducing unsaturated metal sites into MXene, which can form specific interactions with N 2 molecules and enhance N 2 permeation. The resulting membranes exhibit an inspiring N 2 /CH 4 separation performance with an N 2 permeance of 344 GPU and N 2 /CH 4 selectivity of 13.76. The collaboration of the double selectivity mechanism provides a new idea for the development of a novel N 2 -selective membrane for N 2 removal and CH 4 purification, which further broadens the application prospects of membrane separation technology in the field of unconventional natural gas purification.