Silica-based gas separation membranes: Structure–performance relationships across the Si–O continuum from polysilsesquioxanes to amorphous SiO2

초록

Membrane technology offers an energy-efficient and compact alternative to conventional thermally driven separation processes. However, polymeric membranes are limited by the permeability–selectivity trade-off, plasticization under high-pressure conditions, and physical aging. To overcome these limitations, two promising classes of silica-based membranes have emerged: (1) amorphous silica membranes fabricated via sol-gel or chemical vapor deposition (CVD), and (2) hybrid and composite membranes incorporating polyhedral oligomeric silsesquioxanes (POSS) or ladder-like polysilsesquioxanes (LPSQ) into polymer matrices. This review provides a comprehensive comparison of these silica-based membrane platforms, with a focus on their structure–performance relationships and application-specific advantages. In polysilsesquioxane (PSQ)-based systems, blending, copolymerization, and crosslinking strategies are shown to improve permeability, interfacial compatibility, and plasticization resistance. In contrast, amorphous silica membranes benefit from rigid Si–O–Si networks that enable molecular sieving, with pore size and connectivity tailored through parameters such as precursor type, pH, dopant addition, and thermal treatment. By consolidating recent progress in both material classes, this review highlights the critical role of molecular-level structural control in achieving targeted gas separation performance and offers a design-oriented perspective on the development of scalable, robust hybrid membranes for industrial separations, including low-pressure CO<inf>2</inf> capture and high-temperature H<inf>2</inf> purification. © 2025 Elsevier B.V.

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