A Tale of Two Separation Properties: Bulk and Thin Films of Mixed Matrix Materials

• Published in: Advanced functional materials 2024-11, Vol.34 (45), p.n/a
• Main Authors: Zhang, Gengyi, Shah, Chintan Jayesh, Lee, Won‐Il, Kisslinger, Kim, Esmaeili, Narjes, Bui, Vinh T., Zhu, Lingxiang, Nam, Chang‐Yong, Lin, Haiqing
• Format: Article
• Language: English
• Subjects: Bonding strength; Carbon dioxide; CO2/N2 separation; Ethylene oxide; Flue gas; Gas separation; Hydrogen bonds; Incompatibility; Matrix materials; Membranes; mixed matrix materials; Nanocomposites; NANOSCIENCE AND NANOTECHNOLOGY; poly(ethylene oxide); Polyethylene oxide; Polymers; Reluctance; thin film nanocomposite (TFN) membranes; Thin films; UiO-66-NH2; Upper bounds; Water vapor
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202404785

Mixed matrix materials (MMMs) integrating excellent processability from polymers and distinct separation properties from nanofillers are of interest for membrane gas separations, and they are often made into freestanding films (>100 µm) to demonstrate superior gas separation properties. However, they are difficult to fabricate into thin‐film nanocomposite (TFN) membranes due to interfacial incompatibility between polymers and nanofillers. Here TFN membranes based on MMMs (as thin as 200 nm) are successfully developed comprising amorphous poly(ethylene oxide) (aPEO) and UiO‐66‐NH2 enabling strong hydrogen bonds between the two matrices. Increasing the UiO‐66‐NH2 loading unexpectedly decreases CO2 permeability in freestanding films, but it surprisingly leads to the best CO2/N2 separation properties in the membranes at a loading of 10 mass% (CO2 permeance of 2900 GPU and CO2/N2 selectivity of 48). Nanoconfinement significantly influences the morphological and gas separation properties of the MMM layer. The membrane with 10 mass% UiO‐66‐NH2 demonstrates mixed‐gas CO2 permeance of 1400 GPU and CO2/N2 selectivity of 76 in the presence of 1.2 mol% water vapor at ≈23 °C, surpassing Robeson's upper bound. The membrane also demonstrates stable CO2/N2 separation performance when challenged with real flue gas for 700 h continuously. Adding 10 mass% UiO‐66‐NH2 nanoparticles (45–85 nm) in amorphous poly(ethylene oxide) decreases CO2 permeability in freestanding films (200 µm) but more than doubles the permeability of thin films (200 nm) in multi‐layer membranes, partially ascribed to the hydrogen bonds between the nanoparticles and polymer. The membranes demonstrate superior CO2/N2 separation properties with simulated and real flue gas.