Covalent Functionalization of Zif-90 for Improved Co2 Separation by Mixed Matrix Membrane

This research article discusses the development of new membranes that allows the separation of challenging gas mixtures of hydrogen, carbon dioxide, nitrogen, and methane. Mixtures of these components are usually found in the combustion exhaust or natural gas streams. The slight differences in molecular size, as well as the proximity of their kinetic diameters (<1 Å), complicated the discrimination of these gases by membranes. Selective access control at the molecular level has not been very successful in the literature and requires further exploration. This research demonstrated the power of post-syntactic covalent functionalization in enhancing the selective diffusion properties of different gases in the MOF particles by altering the window size. ZIF-90 was selected as a platform for the modulation of the pore aperture because it possesses the functionality of the aldehyde that can undergo an imine condensation reaction under mild reaction conditions. The use of modified ZIF-90 as a filler in the mixed matrix membrane made it possible to change the separation mechanism that is reflected in the performance of the resulting membrane. Permeability measurement showed a promising potential for gas separation with 4 folds improved H 2 and CO 2 permeability compared to the membrane made of polyetherimide with no significant compromising of selectivity.