Interfacial Design of Mixed Matrix Membranes via Grafting PVA on UiO-66-NH to Enhance the Gas Separation Performance.

In this study, defect-free facilitated transport mixed matrix membrane (MMM) with high loading amount of UiO-66-NH nanoparticles as metal-organic frameworks (MOFs) was fabricated. The MOFs were covalently bonded with poly (vinyl alcohol) (PVA) to incorporate into a poly (vinyl amine) (PVAm) matrix solution. A uniform UiO-66-NH dispersion up to 55 wt.% was observed without precipitation and agglomeration after one month. This can be attributed to the high covalent interaction at interfaces of UiO-66-NH and PVAm, which was provided by PVA as a functionalized organic linker. The CO permeability and CO/N and selectivity were significantly enhanced for the fabricated MMM by using optimal fabrication parameters. This improvement in gas performance is due to the strong impact of solubility and decreasing diffusion in obtained dense membrane to promote CO transport with a bicarbonate reversible reaction. Therefore, the highest amount of amine functional groups of PVAm among all polymers, plus the abundant amount of amines from UiO-66-NH, facilitated the preferential CO permeation through the bicarbonate reversible reaction between CO and -NH in humidified conditions. XRD and FTIR were employed to study the MMM chemical structure and polymers-MOF particle interactions. Cross-sectional and surface morphology of the MMM was observed by SEM-EDX and 3D optical profilometer to detect the dispersion of MOFs into the polymer matrix and explore their interfacial morphology. This approach can be extended for a variety of polymer-filler interfacial designs for gas separation applications.