Sandwich membranes through a two-dimensional confinement strategy for gas separation

Abstract

Metal–organic frameworks (MOFs) with designable pore environments can be involved in graphene oxide (GO) layers as the filters to tailor the channels in laminar membranes for precise molecular separation. The well-distributed fillers, high compatibility between fillers and GO, and thin selective layers are critical aspects for capitalizing on the positive effect induced by the addition of a microporous phase. Herein, a two-dimensional confinement strategy for constructing the composite membrane is deduced by the in situ conversion of the metal hydroxide/GO precursors into MOF/GO “sandwich” membranes. This method is confirmed to be feasible for the creation of an ultra-thin composite membrane with uniform MOF filler dispersion and good compatibility with GO layers. The sandwich membranes show enhanced H₂/CO₂ separation performance: H₂ permeance of 5922 ± 1000 GPU and H₂/CO₂ selectivity of 75 ± 4 at 25 °C, which is six-fold increased compared with the GO membrane. Due to the combination of GO and MOF, the membrane also exhibited a H₂ permeance of 3654 ± 252 GPU and H₂/CO₂ selectivity of 31 ± 3 at 150 °C with the feed gas containing water vapor. Such a nanoscale confinement approach can be extended to other composite membranes, providing valuable insights into the design and development of advanced materials for membrane-based efficient molecular separation.