Hybrid organosilica membranes and processes: Status and outlook

• Organically bridged hybrid materials applied in hydrothermally stable membranes.
• Fabrication possible through sol–gel technology and chemical vapor deposition.
• Functional membranes can be deposited on ceramic and polymeric supports.
• Bridging and terminating organic moieties allow tailoring of the separation properties.
• The use of the organically modified silica membranes leads to important process improvements.

In the past, the research in molecular separation membranes prepared through sol–gel technologies has been dominated by ceramic membranes. Especially, silica membranes have been studied in great depth. Steps towards hybrid organosilica membranes were taken by using pendant organic groups. However, only with the appearance of organically bridged silica, stable and reliable membranes that are suitable for large scale industrial utilization have become available. In this paper, we provide an overview of recent development of hybrid silica membranes that contain organic bridges. The freedom of choice in precursor allows for a flexible approach towards tailoring of the membrane properties. New support materials can be used by applying alternative deposition methods, such as expanding thermal plasma chemical vapor deposition. The robustness of the membrane concept allows for the design of novel separation process concepts in which the demonstrated stability is required.