Hydrothermally stable Zr-doped organosilica membranes for H₂/CO₂ separation

Homogeneous zirconium-doped hybrid organosilica membranes are successfully prepared through the sol-gel route via co-hydrolysis and co-condensation of 1,2-bis(triethoxysilyl)ethane (BTESE) and zirconium n-propoxide (ZrP). Gas permeation measurements and hydrothermal stability tests are carried out for the prepared membranes. Smaller sols are more prone to form a dense structure and thus lead to low gas permeability. Hybrid organosilica membranes with low zirconium content have high hydrogen permeability and H₂/CO₂ selectivity. As zirconium content in the sol increases, membrane structure becomes denser and gas permeability decreases. Excellent hydrothermal stability can be achieved by incorporating Zr into the hybrid silica membranes. This is caused by the improved hydrophobicity due to the presence of hybrid organic-inorganic groups (-Si-CH₂-CH₂-Si-) and the dense, robust membrane structure that formed after zirconium-doping. A ball-and-stick model is proposed based on the characterization data. Our results offer significant insights into understanding the correlations between particles (e.g. size and distribution), structure (e.g. porosity and pore size) and performance (e.g. gas permeability and hydrothermal stability) of organosilica membranes.