Metal-organic framework/graphene nanoribbon/polyimide mixed-matrix membranes for high-temperature H2/N2 separation

Abstract

We report the application of mixed-matrix membranes for high-temperature hydrogen separation. To enhance hydrogen selectivity, graphene nanoribbons (GNRs) were incorporated into ZIF-8 fillers, forming a physically confined structure conducive to hydrogen transport. The metal-organic framework (MOF)/GNR filler embedded into a polyimide (PI) matrix yielded a much higher H2 permeability (298 Barrer, +40%) and H2/N2 selectivity (15, +25%) than the neat PI membrane. In particular, the as-prepared asymmetric membrane achieved a H2 permeance of 212 ± 45 Gas Permeation Unit (GPU) and H2/N2 selectivity of 19 ± 2 at 35°C. Remarkably, at 300°C, the H2 permeance rose to 775 ± 139 GPU while maintaining a H2/N2 selectivity of 13 ± 1, outperforming polymer-based membranes. A techno-economic analysis of an NH3 cracking process demonstrated that this high permeance reduces membrane area requirements by 68.2% and lowers H2 separation costs by 35.1% compared with operation at 35°C, leading to a 9.8% reduction in the levelized cost of hydrogen.