Composite porous nanostructures as multi-action adsorbents and membrane fillers for carbon dioxide separation: Comparative performance of metal organic framework - graphene oxide hybrids

Adsorption- and membrane-based processes and materials for capture and separation of CO₂ are gaining increased attention as alternatives to overcome current limitations of the traditional amine based absorption. In this study, hybrid nanostructures of metal organic frameworks (MOFs) and graphene oxide (GO) were synthesized, functionalized and used as adsorbents as well as fillers in mixed matrix membranes (MMMs). GO was fabricated by oxidation/exfoliation of graphite flakes and was subsequently functionalized with various amine-bearing agents. Two MOFs, ZIF-8 and UiO-66, and their composites with GO were also developed and further functionalized with amine groups as to enhance CO₂ capacity and selectivity. In addition, MMMs synthesized using ZIF-8 and ZIF-8/GO composite fillers with polysulfone (PSF) as the polymeric phase were realized. The combined action of the MOF and GO counterparts towards enhancing CO₂ separation performance was exemplified in both adsorbent and membrane modes.