Nanostructured membranes containing UiO-66 (Zr) and MIL-101 (Cr) for O2/N2 and CO2/N2 separation

Metal-Organic Frameworks (MOF) containing zirconium and chromium metals have been reported as gas materials for gas storage and separation, especially for CO2. The high selectivity of MOF can be exploited through their dispersion in a polymer matrix, producing mixed matrix membranes for different applications in gas separation and adsorption. This study reports the use of nanostructured mixed matrix membranes (MMM), produced by dispersion of the MOFs UiO-66 (Zr) and MIL-101 (Cr) in polyurethane for O2/N2 and CO2/N2 gas separation. UiO-66 (Zr), MIL-101 (Cr) and composites comprising these particles were characterized by SEM, XRD, TGA and FTIR analyses, which indicated that the MOFS were successfully synthesized. Defect-free dense PU/UiO-66 (Zr) membranes were obtained, with increased selectivity due to the higher oxygen permeability. For the MIL-101 (Cr) membrane, no significant increases in oxygen selectivity and permeability were observed. On the other hand, best performance for CO2/N2 separation was observed for the MIL-101 (Cr) membrane. A significantly greater CO2 permeability (around 220%) in comparison with polyurethane membrane was obtained. N2 permeability was also improved, resulting in the same selectivity as the original membrane. PU/UiO-66 (Zr) membrane exhibited enhanced CO2 permeability but accompanied by a reduction in selectivity as N2 transport through the membrane was more favored. To evaluate the effect of MOFs in gas capture, carbon dioxide adsorption capacity was determined at different temperatures for UiO-66 (Zr) and MIL-101 (Cr). The greatest CO2 adsorption capacity was exhibited by MIL-101 (Cr), which explains the increased gas permeability for the membrane prepared with this MOF.