Amphiphilic Zeolitic Imidazolate Framework for Improved CO ₂ Separation in PIM‐1 Mixed Matrix Membranes

Abstract

This study aims to enhance the compatibility between filler and polymer in mixed matrix membranes (MMMs), addressing an important challenge in membrane development. ZIF-94, known for its affinity to CO₂, was partially modified with 2-undecylimidazolate (umIm) through the solvent-assisted ligand exchange (SALE) method to improve its compatibility with the prototypical polymer of intrinsic microporosity PIM-1. The modified ZIF-94 (ZIF-94-umIm) can be considered as an amphiphilic MOF with both hydrophilic and hydrophobic moieties, while maintaining a considerably high CO₂ adsorption capacity (2.34 mmol g^-1 at 90 kPa and 0 °C). Gas separation experiments were performed using mixed gas compositions of 15/85 CO₂/N₂ at 3 bar and 35 °C. The resulting MMM with a 5 wt.% loading exhibited an enhanced CO₂ separation performance, with ca. 70% and 10% increases in CO₂ permeability (8900 Barrer) and CO₂/N₂ selectivity (20.2), respectively, compared to pristine PIM-1 membranes. In addition, thin film nanocomposite membranes were prepared showing a 23.5 CO₂/N₂ selectivity at 2350 GPU of CO₂. This modification strategy shows a great potential for improving the CO₂ capture technologies, highlighting the potential of tailoring MOF fillers for advanced membrane materials in gas separation applications.