Challenge and promise of mixed matrix hollow fiber composite membranes for CO₂ separations

Mixed matrix materials synergistically combining excellent processability from polymers and unique separation properties from nanofillers have been pursued to achieve superior CO₂/gas separation properties. They can be fabricated into hollow fiber composite membranes with little materials required while attaining high packing density and excellent separation performance. This review aims to provide a comprehensive and timely overview of the advancement of these mixed matrix hollow fiber composite membranes (MM-HFCMs) for practical CO₂ separations. First, we describe membrane configurations and various methods to fabricate defect-free HFCMs. Second, the state-of-the-art membranes containing various polymers and nanofillers with superior CO₂/gas separation properties are discussed, and strategies to mitigate interfacial incompatibility are highlighted. Third, parameters defining the enhancement of the separation properties by nanofillers are reviewed and used to identify the best nanofillers for CO₂ separations. Finally, we outline future directions for membrane development to unlock the potential of the MM-HFCMs.