Thin Film Composite Mixed-Matrix Membranes Based on Matrimid and Zeolitic Imidazolate Frameworks for CO₂/N₂ Separation Performance

Membrane-based gas separation processes are a technology in continuous evolution. Various types of polymer membranes have been developed, many exhibiting high CO₂ permeability and selective properties over competing gases such as N₂ and CH₄. In order to be competitive, membranes must be less-expensive, more stable, and more efficient, and their production must be scalable. One solution is to develop thin-film composites with mixed-matrix membranes (TFC_MMM) that have the potential to boost productivity while maintaining low costs. In this work, TFC_MMMs containing Matrimid mixed with 12 wt % ZIF-94 were prepared by kiss coating on a porous support. The SEM analysis showed that defect-free membranes with a 3 μm selective layer have been obtained. At 1 bar, the addition of ZIF resulted in improved the separation performance for the CO₂/N₂ pair, with CO₂ permeance of 4 GPU and CO₂/N₂ selectivity of 40, surpassing neat TFC-Matrimid (CO₂ permeance ≈ 3 GPU, CO₂/N₂ selectivity ≈ 29). The use of ZIF-94 also had a stabilizing effect on the membranes against CO₂ plasticization at high pressure.