Layer-by-layer assembled PI@ZIF-67/PDMS/PEI@ZIF-67 composite membranes with multilayer synergies for efficient H2/CO2 separation

Polyimide (PI) has emerged as a promising material for constructing efficient gas separation membranes due to its excellent stability and gas separation properties. Herein, we report a novel composite membrane structure that utilizes the synergistic effect to achieve efficient H 2 /CO 2 separation by skillfully integrating the advantages of three different functional layers. The support layer consists of a PI fiber membrane loaded with zeolitic imidazolate framework-67 (ZIF-67) using an in-situ growth method, which not only enhances the overall mechanical strength of the membrane, but also provides complex gas transport pathways to improve selectivity. The intermediate layer is made of polydimethylsiloxane (PDMS), which prevents excessive penetration of the selective layer solution into the support layer. The selective layer is a mixed matrix membrane composed of polyetherimide (PEI) as the polymer matrix and zeolitic imidazolate framework-67 (ZIF-67) as the porous filler, which provides critical molecular sieving functionality. Compared to pure polyetherimide (PEI) film, the composite membranes have significantly improved mechanical and gas transport properties, with H 2 permeability of 83.4 Barrer and H 2 /CO 2 selectivity of 5.4. Additionally, the composite membranes exhibit excellent hydrophobicity and thermal stability. Given their outstanding overall performance, the composite membranes developed in this study demonstrate significant potential for CO 2 capture and H 2 recovery applications.