Poly(ionic liquid)-Functionalized UiO-66-(OH)2: Improved Interfacial Compatibility and Separation Ability in Mixed Matrix Membranes for CO2 Separation

Incorporating porous materials into a polymeric matrix to produce mixed matrix membranes (MMMs) usually offers the combined properties of each component. However, it requires efficient dispersity of porous materials in a polymeric matrix and good compatibility between them. To enhance the compatibility, we report an approach by covalent grafting of poly(ionic liquid) (PIL) brushes on the surface of metal–organic framework (MOF) UiO-66-(OH)2. Benefiting from the surface grafted PIL brushes, the as-synthesized UiO-66-(OH)2@PIL shows an improved dispersity in the solvent media and Pebax matrix due to the hydrophilicity of PIL and the formed hydrogen bonds between the MOF fillers and Pebax matrix. The obtained UiO-66-(OH)2@PIL-based MMMs manifest simultaneously increased selectivity and permeability for CO2/N2 separation, with the best performance at 20 wt % of loading (CO2 permeability of 132 Barrer and CO2/N2 separation factor of 71). This work highlights the efficiency of MOF functionality to achieve enhanced interfacial compatibility and membrane separation performance.