(609e) Peculiar Effect of Low Loading of Metal-Organic Polyhedra on CO2/N2 Separation Properties of Cross-Linked Polyethers

Mixed matrix materials (MMMs) containing porous fillers merge the excellent processability of polymers with the well-controlled pores and strong size-sieving ability of the fillers. Gas permeability of MMMs is often described using the Maxwell model, and high loadings are often required to maximize the benefits of the porous fillers. Herein, we demonstrate that MMMs comprising low loading of metal-organic polyhedra (MOP) and cross-linked polyethers exhibit unexpectedly high gas permeability compared with the Maxwell model. MOPs are discrete nanocages with high porosity and excellent compatibility with polymers. To prepare MMMs, the MOPs were first dispersed in prepolymer solutions containing macromonomers of polyether before photopolymerization. Several MOPs are studied, including Cu-MOP, Fe-MOP, and Zr-MOP, and ether macromonomers studied include poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) methyl ether acrylate (PEGMEA), and poly(1,3 dioxolane). As the Cu-MOP content increases from 0 to 3 wt.% in PEGDA-co-PEGMEA, CO₂ permeability increases from 510 Barrer to 1000 Barrer while retaining the high CO₂/N₂ selectivity at 35 °C; a further increase of loading to 5 wt.% decreases CO₂ permeability to 730 Barrer without influencing CO₂/N₂ selectivity. By contrast, at the Cu-MOP loading of 10 wt.% or above, the gas permeability can be satisfactorily described by the Maxwell model. Similar behavior have been observed for MMMs containing low content of Fe-MOP, and Zr-MOP. These MMMs were thoroughly characterized using FTIR, WAXD, DSC, and SEM. Gas sorption was measured, and gas diffusivity was calculated. The free volume was determined by positron annihilation lifetime spectroscopy (PALS). We will present the structure/property relationship in these MMMs. The MMMs with low loadings and much-improved permeability can be easily integrated into current manufacturing processes of thin film composite membranes.