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

Authors: 
Huang, L., University at Buffalo, The State University of New York
Lin, H., University of Buffalo
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 (Tg) 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.