Microporous silica membranes: Effect of doping on structure and stability

Hydrothermal stability is a crucial factor for the application of microporous silica-based membranes in industrial processes. Indeed, it is well established that steam exposure may cause densification and defect formation in microporous silica membranes, which are the detrimental to both membrane permeability and selectivity. There is a vast literature that shows that microporous transition metal doped-silica membranes are hydrothermally more stable than pure silica membranes, but less permeable. Here we present a quantitative study on the impact of type and concentration of transition metal ions on the microporous structure, stability and permeability of amorphous silica-based membranes. We provide information on how to design chemical compositions and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile microporous structure.