High-flux CO₂ separation using thin-film composite polyether block amide membranes fabricated by transient-filler treatment

An energy-efficient and eco-friendly membrane-based CO₂ separation process is required to address global concerns pertaining to energy and environment. In this context, polymer materials such as polyimides, polyvinyl alcohol, and polyether block amide (PEBA) have been intensively explored, and a high CO₂ selectivity has been attained; however, these membranes exhibit a low permeance, thereby hindering process efficiency. Gas permeance depends mainly on the thickness and morphology of the selective layer; but it is difficult to overcome the limitation of the intrinsic permeability of the polymer material by controlling the thickness of the selective layer. Herein, we report a method for manufacturing thin-film composite (TFC) membranes with a defect-free, ultrathin, and highly permeable selective layer through transient-filler (TF) treatment consisting of blending a TF/polymer matrix and then removing the TF. Polyethylene glycol (PEG), used as the TF, was homogeneously blended through hydrogen bonding with the polymer matrix, PEBA. The blended membrane, PEG/PEBA, possessed a less crystalline structure than that of PEBA and a large free volume, thereby exhibiting a high gas permeance. After the removal of the TF from PEG/PEBA, the resultant PEBA (r-PEBA) retained the less crystalline structure, and the thickness of the selective layer decreased substantially. The permeance of the r-PEBA TFC membrane, 2371 GPU, was substantially higher than that of neat PEBA, 1350 GPU, owing to the aforementioned synergistic effects.