Fabrication of polyimide doped MOF/organosilica tubular membranes for H₂/CO₂ separation

Organosilica membranes demonstrating robust hydrothermal stability show great potential for pre-combustion CO₂ capture, and the incorporation of ZIF-7 nanocrystals can effectively mitigate the trade-off effect typically associated with organosilica membranes. However, the phase transition of the ZIF-7 framework occurs when the solvent is removed. Polyimide (PI), a rigid polymer, was introduced after doping nanocrystals into 1, 2-bis(triethoxysilyl)ethane (BTESE). This approach effectively preserves the crystalline framework of ZIF-7 while maintaining high gas permeability and significantly enhancing both H₂/CO₂ and H₂/N₂ selectivity. Furthermore, it improves the overall hydrothermal stability of the hybrid membrane. When measured 200 °C, the PZB-5 wt % membrane demonstrated a hydrogen permeance of 2.34 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹, with impressive selectivity ratios of 5.54 for H₂/CO₂ and 25.2 for H₂/N₂. The findings indicate that the stability of nanoparticle-doped BTESE-derived membranes is markedly improved by the inclusion of rigid polymers.