Surface modification of bilayer structure on metal-organic frameworks towards mixed matrix membranes for efficient propylene/propane separation

Rational matching of filler-matrix in mixed matrix membranes (MMMs) is crucial but challenging for highly efficient gas separation. Herein, we propose a bilayer structure modification strategy on metal-organic frameworks (MOFs) to design various MOF-based MMMs for efficient propylene/propane separation. The octadecylphosphonic acid-lecithin-cholesterol bilayer structure grafted onto the surface of MOFs strengthens their sieving capacity under the premise of maintaining good interfacial compatibility, and promotes the formation of holes in the cross-linked poly(ethylene oxide) (XLPEO) polymer matrix. This allows for the simultaneous enhancement of gas permeability (∼266 Barrer) and C3H6/C3H8 selectivity (40.5). We briefly investigated the effect of the modified bilayer structure on the gas separation performance. More importantly, this constructing strategy is also effective for other MOF fillers in MMMs; thus this design of bilayer modification at a molecular level opens new insights into optimizing MOF-based MMMs in the challenging olefin/paraffin separation.