In-situ interfacial engineering in NH₂-Zn₂(Bim)₄/Polyimide mixed matrix membranes for enhanced H₂ purification

Mixed matrix membranes (MMMs) incorporating metal–organic frameworks (MOFs) hold significant promise for gas separation applications. However, the inherent disparity between the organic polymer matrix and the inorganic fillers frequently leads to interfacial incompatibility issues. In this study, we adopted an in-situ interfacial crosslinking strategy to fabricate MMMs incorporating NH₂-Zn₂(Bim)₄ nanosheets that simultaneously act as nanofillers and reactive crosslinkers. Specifically, during the thermal imidization reaction process, the amino groups of NH₂-Zn₂(Bim)₄ not only establish hydrogen bonding interactions with the carbonyl groups of polyamic acid (PAA) (the precursor of polyimide), but undergo dehydration reactions with carboxyl groups, leading to the formation of stable amide linkages. Meanwhile, the aromatic structure of the BI units, a key monomer of polyimide, closely resembles that of the ligands of NH₂-Zn₂(Bim)₄, which can establish π-π stacking interactions, further improving the interfacial compatibility between the polymer matrix and MOF fillers. Among the prepared samples, MMMs incorporating 33.3 wt% NH₂-Zn₂(Bim)₄ nanosheets exhibit the maximum H₂ permeability of 680.5 Barrer, and its H₂/N₂ and H₂/CO₂ selectivities were 18.7 and 13.3, respectively, which were close to or even exceeded the Robeson upper bound. The proposed in-situ interfacial engineering based on chemical crosslinking provides a novel and effective route for fabricating high-performance MMMs with enhanced interfacial compatibility, demonstrating great potential for hydrogen separation applications.