Pebax/ionic liquid modified graphene oxide mixed matrix membranes for enhanced CO₂ capture

The development of mixed matrix membranes (MMMs) is mostly challenged by the filler dispersion and the fabrication of defect-free membranes with an ultra-thin selective layer. Graphene oxide based MMMs are promising materials for gas separation application. The low filler content and preference of extended GO lamella to align perpendicular to a membrane surface, and hence the gas flow direction permits the development of thin film composite membrane (TFC). Here, facilitated transport MMMs were fabricated by incorporating ionic liquid functionalized graphene oxide (GO-IL) into poly(ether-block-amide) (Pebax 1657). The 1-(3-aminopropyl)-3-methylimidazolium bromide ionic liquid was reacted to graphene oxide sheets, enhancing the CO₂ solubility and CO₂/gas selectivity of the MMMs. Moreover, hydrogen bonding interactions between the ionic liquid and amide moieties in Pebax provide a homogeneous dispersion of GO-IL. The pure (H₂, CO₂, O₂, N₂, CH₄) and mixed (CO₂/H₂, CO₂/N₂) gas permeability of the membranes were performed at 25 °C and 4 bar. The gas permeability measurements indicate an improvement of over 90% in CO₂/N₂ selectivity and 50% in CO₂ permeability for the GO-IL MMMs compared to the pure Pebax membrane. The resulting TFC membranes showed high CO₂ permeance up to 900 GPU (10⁻⁶ cm³ (STP) cm⁻² s⁻¹ cm Hg⁻¹) and the CO₂/N₂ and CO₂/H₂ selectivities of about 45 and 5.8, respectively. Our finding underlines the importance of GO-IL nanosheet to design high selective thin film membranes, providing a direction to fulfil the concept of mixed matrix membranes for practical applications.