Membranes can serve an important role as energy-efficient alternatives in several natural gas processing applications, including nitrogen and acid gas removal, as well as related applications in flue gas separations.  Membranes are typically composed of purely polymeric materials, but significant improvements in permeation properties can be achieved by incorporating nanostructured materials such as metal-organic frameworks (MOFs) into polymers to form mixed-matrix membranes (MMMs).  Unfortunately, micron-sized MOF particles often produce heterogeneous membranes with defective polymer-MOF interfaces, poor mechanical properties and other challenges that have frustrated industrial implementation.  To overcome these challenges, we synthesized a branched MOF architecture with high aspect ratios and small particle sizes.  MOF size and morphology was evaluated using SEM and DLS, while XRD confirmed a crystalline structure similar to that of the bulk MOFs. These unique MOFs were easily dispersed into stable casting solutions to form homogenous MMMs, compared to the traditional bulk architecture that resulted in aggregations and heterogeneity.  The branched MMMs showed significantly improved gas transport properties via increased permeabilities and consistent separation efficiencies.  Furthermore, the branched MMMs showed improved stability towards aggressive gas feeds by resisting membrane swelling up to 50 bar of CO<sub>2</sub>, compared to the pure polymer that adversely swelled at 15 bar.  The paradigm of branched MMMs may help overcome the limitations of prior MMMs with bulk MOFs and expedite the path towards industrial viability for these nanocomposite membranes.<br/>

Homogeneous nanocomposite membranes with improved properties in natural gas processing

256th National Meeting (2018)

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