Efficient CO2 Separation Using a PIM-PI-Functionalized UiO-66 MOF Incorporated Mixed Matrix Membrane in a PIM-PI-1 Polymer

Metal–organic framework (MOF) incorporated mixed–matrix membranes (MMMs) attract great interest for gas separation applications because they overcome limitations faced by typical polymer membranes, including permeability–selectivity trade-off, aging effect, and plasticization phenomenon. However, optimal MOF–polymer interface compatibility is the key challenge in fabricating defect-free high-performance gas-separation MMMs. Here, a surface modification strategy of the UiO-66-NH₂ MOF using a covalently bound PIM-PI-oligomer is developed to engineer interface compatibility with the polymer that has an identical chemical structure (PIM-PI-1) in the MMMs. A series of MMMs are prepared with different loadings of homogeneously distributed PIM-PI-functionalized MOFs (PPM). Significant improvements in CO₂/N₂ and CO₂/CH₄ selectivity and permeability are achieved with these MMMs, ranging from 5 to 10 wt% of the PPM loadings. The MMM with 10 wt% loading (PPM-10@MMM) shows a CO₂ permeability of 3827.3 Barrer and a CO₂/N₂ and CO₂/CH₄ selectivity of 24 and 13.4, respectively. This surpasses the 2008 Robeson upper bound for CO₂/N₂ and is very close to the 2008 upper bound for CO₂/CH₄. The experimental results are further compared using Maxwell's equation for MMMs. The resulting MMMs show a plasticization resistance against CO₂ up to 25 atm pressure and anti-aging performance for 180 h.