Tuning pore environment of NH₂-UiO-66 via ionic liquid confinement for enhanced CO₂/CH₄ separation in pebax mixed matrix membranes

With the increasing demand for natural gas purification and biogas upgrading, membrane materials capable of simultaneously achieving improved high CO₂ permeability and excellent CO₂/CH₄ selectivity have attracted considerable attention. Mixed matrix membranes (MMMs) incorporating ionic liquid (IL)-confined metal organic framework (MOF) fillers exhibit considerable potential. In this study, [APMIm][Tf₂N] was successfully confined within the pores of NH₂-UiO-66, yielding an IL@NH₂-UiO-66 filler, which was subsequently incorporated into Pebax to prepare MMMs. Confining ILs within the MOF framework regulated the local pore environment to enhance CO₂ affinity and adsorption selectivity, while the surface amino groups of NH₂-UiO-66 promoted favorable interactions with Pebax. When the filler loading was 3 wt%, CO₂ permeability rose to 142.11 Barrer, and CO₂/CH₄ selectivity reached 30.82. These results demonstrate that IL@NH₂-UiO-66 is an effective functional filler for simultaneously optimizing pore environment regulation and filler-polymer interfacial compatibility, thereby enabling a more favorable permeability-selectivity trade-off and providing a promising strategy for the design of high performance CO₂ separation membranes.