Heterobilayer membranes from isostructural metal-organic frameworks for efficient CO2 separation

Metal-organic frameworks (MOFs) are promising candidates for membrane gas separation because of their high porosity and structural tunability. Although the appropriate size of the pore aperture of MOFs is required depending on the target molecules to separate, pore size control of MOFs occasionally influences crystal growth, preventing the fabrication of dense membranes. In this study, we present a heterobilayer membrane strategy using two isostructural MOFs. First, a MOF Kgm-OPr with fast nucleation rate was fabricated as a seed layer on an Al2O3 substrate, then the layer of Kgm-OMe or Kgm-H, which is isostructural to Kgm-OPr, was prepared on the Kgm-OPr seed layer through secondary growth. In this way, the high-quality membranes which selectively permeate CO2 over N2, CH4, and C2H4 were obtained, although all three MOFs did not form dense membranes when they were used alone. Our result would contribute to the expansion of the family of MOFs applicable to membranes for molecular separation. [Display omitted] Points Highlighting Novelty.•Heterobilayer MOF membranes were prepared from isostructural MOFs.•The heterobilayer membranes show better microstructure than a single MOF membrane.•Heterobilayer membranes exhibit higher selective CO2 permeation than single MOF membrane.