Mixed Matrix Membranes With Modified MOFs for Post-Combustion CO2 Capture

Mixed matrix membrane (MMM) materials comprising organic polymers with dispersed inorganic fillers have the potential to overcome limitations of traditional polymers for gas separation resulting in a substantial increase in permselectivity. Metal Organic Frameworks (MOF) are crystalline compounds consisting of metal ions and rigid organic ligands that have displayed high permselectivity, as a result, these are good candidates for MMM filler particles. The most difficult challenge associated with MMM fabrication is ensuring good interface between the polymer and the filler particle. To overcome this challenge, MOFs were modified to improve their interaction with the polymer matrix. The modification of the MOFs was characterized by Nuclear Magnetic Resonance spectrometry, X-Ray diffraction analysis, and Mass Spectroscopy to confirm that the modification does not alter the MOF structure. Flat sheet MMM consisting of a polymer as the continuous phase with different loadings (up to 40%) of unmodified and modified MOFs were fabricated by solution casting. The mechanical properties of the mixed matrix membranes containing the modified MOF were improved, confirming improved interaction between the continuous and dispersed phases. Pure gas transport properties of CO₂ and N₂ were measured for the MMMs with different MOF loadings. A significant increase in both the CO₂ permeability and the CO₂/N₂ selectivity is observed for these MMMs. These results will be presented in detail and the effect of the MOF modification on the MMM properties will be discussed.