Self-assembled metal-organic polyhedra (MOP) are discrete molecular species that are highly porous and exhibit well-defined uniform sizes. MOP stability and solubility in a range of solvents makes them more processable as additives to mixed-matrix materials (MMMs) compared to analogous metal-organic framework (MOF). We initially studied MOPs containing copper(II), palladium(II), and iron(II) nodes as fillers for MMMs with a polyvinylidine fluoride (PVDF) polymer phase and contrasted them against MMM containing MOF-5. Based on microscopy and SEM imaging, we demonstrated the formation of thin, flexible, and homogeneous MMMs when a given MOP was soluble in the precursor solutions. Analogous MMM formation using either insoluble MOPs or the inherent insoluble MOF-5 showed a higher degree of phase separation and inhomogeneity. In addition, a significant particle size decrease was observed in contrast to the MOF-5 materials wherein the crystallites remained largely intact. This is a consequence of solubilizing the MOP fillers into the polymer solvent. The crystallinity and thermal stabilities of the MMMs were compared to pure PVDF using powder X-ray diffraction and differential scanning calorimetry, indicating that the incorporation of MOPs both decreased overall crystallinity as well as increased thermal stability. We also showed that MMMs containing PdMOP and FeMOP had improved gas permeabilities relative to pure PVDF for H2, N2, CH4, and CO2, with the 10 wt. % FeMOP membrane more selective for CO2 over N2 and H2.

Integration of self-assembled metal-organic polyhedra in polymeric mixed-matrix materials for enhanced membrane gas separation

256th National Meeting (2018)

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