Hierarchical Fibrous Metal–Organic Framework/Ionic Liquid Membranes for Efficient CO₂/N₂ Separation

The structural diversity and chemical functionality of metal-organic frameworks (MOFs) render them promising candidates for CO₂ adsorption and separation. However, their applications are often restricted by their intrinsic fragility and decreased processability. Herein, a hierarchical fibrous MOF/ionic liquid (IL) membrane was constructed by assembling well-ordered ZIF-8 nanounits with an encapsulated IL along the polyimide (PI) fibers. This design promotes the formation of an efficient three-dimensional gas transfer network and generates an abundance of nanopores decorated with CO₂-philic units, thereby enhancing the separation of CO₂ from N₂. The hierarchical fibrous PI/ZIF-8/IL membranes exhibit remarkable structural features, including a large specific surface area of 79.89 m² g^-1, a high porosity of 93.28%, and excellent mechanical stability. Moreover, the PI/ZIF-8/IL membranes demonstrate an enhanced CO₂ adsorption capacity of 3.32 mmol/g at 298 K and 1 bar, an excellent CO₂/N₂ selectivity of 28, and a stable recyclable regeneration capability. The integrated hierarchical pore structure proposed in this study provides a practical direction for the rational design of MOF/IL membranes for targeted gas separation applications.