Interfacial Design of Mixed Matrix Membranes via Grafting PVA on UiO-66-NH2 to Enhance the Gas Separation Performance

Abstract

In this study, defect-free facilitated transport mixed matrix membrane (MMM) with high loading amount of UiO-66-NH2 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-NH2 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-NH2 and PVAm, which was provided by PVA as a functionalized organic linker. The CO2 permeability and CO2/N2 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 CO2 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-NH2, facilitated the preferential CO2 permeation through the bicarbonate reversible reaction between CO2 and –NH2 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.