Infiltrating Molecular Gatekeepers with Coexisting Molecular-Solubility and 3D-Intrinsic-Porosity into Microporous Polymer Scaffold for Gas Separation
The inherently broad pore-size distribution in polymer membranes imparts them with less size-selective microporous regions that could impair their performance and would require challenging size control at the angstrom level for enabling energy-efficient gas separations. Here, we successfully remodeled the non-selective microporous regions in polymer membranes with sub-angstrom size-sensitivity via a unconventional post-(membrane)-fabrication infiltration (PFI) method based on a water-soluble member of the highly tunable and expandable organic macrocyclic family; namely, the 4-sulfocalixarene (SCA4). The small molecular size and attached multiple sulfonic groups of SCA4 molecules have enabled their complete solvation in common membrane-treating protic solvents, like methanol, such that they could molecularly infiltrate the entire microporous structure of already fabricated polymer membranes which plays the role of an interactive scaffold with extensive hydrogen- or ionic bonding sites. Meanwhile, bearing an intrinsic size-sieving 3D open cavity, SCA4 molecules could act as molecular gatekeepers that effectively retard size-indiscriminative gas transports for realizing exceptional molecular-sieving properties towards efficient separations of multiple important gas pairs. This ultra-facile yet unconventional PFI design frees itself from longstanding issues of interfacial nano-defects and pore blockage and is empowered and potentially diversifiable by a pool of other water-soluble and functionalizable macrocyclic counterparts for uncovering new composite-membrane design possibilities.
- This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers