MOF-containing mixed-matrix membranes for CO2/CH4 and CO2/N2 binary gas mixture separations

Both dense and asymmetric metal organic frameworks (MOFs) containing membranes were respectively prepared by solvent evaporation and phase inversion with Matrimid® as base polymer and three different MOFs: [Cu3(BTC)2], ZIF-8 and MIL-53(Al) as filler. Incorporation of the fillers in the membranes resulted in an increase in thermal and mechanical stability of the membranes. However, the highest filler loadings (typically 40 wt%) deteriorated the properties of the membrane. An optimized priming protocol of the fillers before membrane preparation resulted in a homogeneous distribution of the MOFs, as confirmed with SEM. The possible presence of non-selective voids in the asymmetric membranes was overcome by coating a highly permeable silicone polymer layer on top of the MMMs. Dense membranes and asymmetric membranes for all the three studied MOFs showed improvement in CO2/CH4 and CO2/N2 selectivity and permeance as compared to the unfilled reference membrane.

► Mixed-matrix membranes (MMMs) fabricated with [Cu3(BTC)2], MIL-53(Al) and ZIF-8 and polyimide.
► Dense and asymmetric membranes showed higher permeance and selectivity than unfilled membrane.
► Dense and asymmetric membranes showed higher permeance and selectivity with increasing loadings.
► MMMs showed improved thermal and mechanical properties.