In-situ interfacial crosslinking of NH2-MIL-53 and polyimide in MOF-incorporated mixed matrix membranes for efficient H2 purification

The key issue to avoiding the degradation of gas separation performance due to the formation of non-selective defects in mixed matrix membranes (MMMs) is to promote the interfacial compatibility of fillers with the continuous polymer matrix. In this work, we report an efficient and simple method to prepare MMMs by crosslinking metal organic frameworks (MOF) and polyamic acid (PAA) (the precursor of polyimide), in which NH2-MIL-53 particles are thermally crosslinked with the PAA during the imidization reaction, forming hydrogen bonds and amide bonds at the interface. The resulting enhanced interfacial force greatly improves the interfacial compatibility of the membrane, which is also more conducive to the separation of H2/CO2. Among the as-prepared samples, PI-NH2-MIL-53 MMMs loaded with 30 wt% MOF exhibit excellent H2 permeability (384.1 Barrer) and H2/CO2 permeation selectivity (16.7), which are significantly higher than the 2008 Robeson upper bound. The membranes also display enhanced mechanical characteristics and long-term stability. Here, building strong interactions on MOF/polymer MMMs using an in-situ cross-linking strategy to enhance membrane performance provides a new opportunity to develop advanced membranes for industrial gas separation applications.