The development of advanced membranes for post-combustion CO₂ capture is a critical step toward mitigating the current climate crisis. In this work, we prepared a series of composite mixed-matrix membranes (MMMs) composed of ultrathin selective layers (~100 nm), integrating UiO-66 nanocrystals bearing three different functional groups (-H, -Br, -NO₂) into a poly(glycidyl methacrylate-co-poly(oxyethylene methacrylate)) (PGO) matrix, supported by poly[1-(trimethylsilyl-1-propyne)] (PTMSP)-coated polysulfone substrates. The inclusion of functionalized UiO-66 fillers led to notable improvements in CO₂ permeance and CO₂/N₂ and CO₂/CH₄ selectivities, attributed to enhanced CO₂ sorption and diffusional transport. Among the MMMs tested, the PGO/UiO-66-NO₂ membrane demonstrated the most outstanding separation performance, surpassing those containing -H and -Br functionalized MOFs. This superior behavior is ascribed to the high CO₂ adsorption capacity of UiO-66-NO₂ and its excellent compatibility with the PGO polymer matrix. The best performance was observed at a 20 wt% loading of UiO-66-NO₂, delivering a CO₂ permeance of 1816 GPU, with CO₂/N₂ and CO₂/CH₄ selectivities of 37 and 14, respectively. These results underscore the effectiveness of UiO-66-based MMMs for post-combustion CO₂ separation. Furthermore, this study highlights the importance of simultaneously optimizing the CO₂ uptake ability of MOF fillers and their interfacial compatibility with the polymer matrix to achieve high membrane performance.
