Graphene Nanoribbon Hybridization of Zeolitic Imidazolate Framework Membranes for Intrinsic Molecular Separation

Zeolitic imidazolate frameworks (ZIFs) are promising for gas separation membrane, but their molecular cut-off differs from that expected from its intrinsic aperture structure because of their flexibility. Herein, we introduced graphene nanoribbons (GNRs) to rigidify the ZIF framework. Because the sp² edge of the GNRs induces strong anchoring effects, the modified layer can be rigidified. Particularly, when the GNRs were embedded and distributed in the ZIF-8 layer, an intrinsic aperture size of 3.4 Å was observed, resulting in high H₂ /CO₂ separation (H₂ permeance: 5.2×10^-6  mol/m²  Pa s, ideal selectivity: 142). The performance surpasses the upper bound of polycrystalline MOF membrane performance. In addition, the membrane can be applied to blue H₂ production, as demonstrated with a simulated steam reformed gas containing H₂ /CO₂ /CH₄ . The separation performance was retained in the presence of water. The fundamentals of the molecular transport through the rigid ZIF-8 framework were revealed using molecular dynamics simulations.