Green Hydrogen Separation from Nitrogen by Mixed-Matrix Membranes Consisting of Nanosized Sodalite Crystals

Nanosized sodalite (Nano-SOD) crystals were used as active filler to prepare mixed-matrix membranes (MMMs) for promoting the H₂ /N₂ gas-separation performance. The Nano-SOD crystals with extremely small crystallites (40-50 nm) were synthesized from a colloidal suspension free of organic structural directing agent and uniformly dispersed in the polyetherimide (PEI) matrix. The Nano-SOD filler with a suitable aperture size (2.8 Å) allowed only H₂ molecules to pass through and rejected the N₂ , thus improving the selectivity of the membranes. The high dispersion of Nano-SOD crystals in the polymer matrix and the interactions between the inorganic and organic phases greatly improved the membrane separation performance and minimized interfacial holes. The MMMs showed a high H₂ permeability (≈7155.1 Barrer at 25 °C under atmospheric pressure) and an ideal H₂ /N₂ selectivity factor of approximately 16.9 in a single gas test. Moreover, in a gas mixture (H₂ /N₂ , 25-100 °C), the selectivity factor increased significantly to approximately 30.9. The high stability of the MMMs, which consist of highly dispersed Nano-SOD crystals in a PEI matrix for H₂ /N₂ separation (6 weeks continuous test), makes them an important material for ammonia synthesis applications that require and also release a large amount of H₂ .