(27b) Enhancing CO2 Permeability of Cross-Linked Poly(ethylene oxide) By Doping with Crown Ethers and Metal-Organic Frameworks for CO2 Capture

Poly(ethylene oxide) (PEO) based materials are leading membrane materials for CO₂/N₂ separation with a balanced high CO₂ permeability and CO₂/N₂ selectivity. For example, amorphous copolymers prepared from macromonomers of poly(ethylene glycol) diacrylate (PEGDA, 20 wt.%) and poly(ethylene glycol) methyl ether acrylate (PEGMEA, 80 wt%) exhibit high CO₂ permeability (~590 Barrers) and good CO₂/N₂ selectivity (~47) at 35 ^oC. However, for the CO₂ capture from flue gas with enormous volume and low CO₂ partial pressure, membrane materials should have CO₂ permeability as high as possible. We demonstrate that the CO₂ permeability of PEGDA-co-PEGMEA can be further increased by doping with 18-Crown-6 and metal-organic frameworks (MOFs) without sacrificing CO₂/N₂ selectivity. The crown ether can be fully “dissolved” in the PEO matrix and increase the polymer chain flexibility. For example, adding 50 wt% of 18-Crown-6 in the copolymers decreases the glass transition temperature (T_g) from -61 ^oC to -72 ^oC. Consistently, CO₂ permeability increases from 590 Barrers to 1100 Barrers while retaining CO₂/N₂ selectivity at 45 at 35 ^oC. An addition of ~1.0 wt% UiO-66 (functionalized with NH₂) can further increase the CO₂ permeability to 1800 Barrers and retain CO₂/N₂ selectivity of 41 at 35 ^oC. Using a simulated flue gas containing 50% CO₂ and 50% N₂ at 60 ^oC, the doped copolymer shows an impressive mixed-gas CO₂ permeability of ~2200 Barrers and mixed-gas CO₂/N₂ selectivity of 25. These materials show the CO₂/N₂ separation properties above the 2008 Robeson’s upper bound, indicating their promise for the practical applications. This presentation will also discuss the structure/property relationship in these interesting materials.