ZIF-8/graphene nanoribbon hybrid nanoplates for mixed-matrix membranes with enhanced CO2 separation performance

초록

Pore-tuned metal-organic frameworks (MOFs) have been extensively utilized for the development of mixed matrix membranes (MMMs). In this study, we synthesized a ZIF-8/graphene oxide nanoribbon (GONR) hybrid nanoplate and incorporated it into 6FDA-DAM-type polyimide polymers. The process began with the shearinduced assembly of graphene oxide nanoribbons (GONRs) into high-aspect-ratio nanosheets by extruding GONR dispersions through a micro-gap channel. During the subsequent solvothermal synthesis of ZIF-8, ZIF-8 nanoparticles were grown and densely intergrown within the GONR nanosheets, resulting in hybrid nanoplates with a thickness of several hundred nanometers. The resulting MMMs, containing 5 wt% of the ZIF-8/GONR hybrid filler, exhibited significantly enhanced CO2 separation performance. They achieved a CO2 permeability of 639 Barrer, with ideal selectivities of 19.3 for CO2/N-2 and 31 for CO2/CH4. Unlike conventional ZIF-8-based MMMs showing limited improvement in CO2 separation due to the larger and flexible aperture size (similar to 4 angstrom) of ZIF-8, the enhanced CO2 selectivity is attributed to the GONR-induced pore tuning of ZIF-8. This tuning effectively narrows the aperture size, hindering the permeation of larger molecules and improving CO2 selective permeation.

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