Self-Standing Macro-Mesocellular Inorganic Aerogels Obtained While Coupling a Direct Concentrated Emulsion, Sol-Gel...

A scCO₂ drying/lixiviation process allows self-standing inorganic macrocelullar aerogels to be produced within 1 h. The applied depressurization rate permits the macrocellular internal throats to be tuned with native hydrodynamic instability. scCO₂ treatment advantageously addresses lixiviation of the tensioactive molecules employed as the templating agent. Final calcined aero-Si(HIPE) materials, at the optimum temperature of 450 °C, afford a specific surface area of up to 1400 m² g^-1. The lower treatment temperature and lower tension-active contents dramatically reduce the carbon footprint penalty, compared with that of traditional xero-Si(HIPE). Further annealing of these aero-Si(HIPE) foams at 1200 °C drastically decreases the specific surface area while maintaining both the open macroposity and the self-standing character. Concomitantly, severe shrinkage and densification of the monoliths occur upon cristobalite crystallization. For the sake of making this generic endeavor, the scCO₂ drying/lixiviation approach has also been extended to MUB-110, MUB-200, and MUB-300 co-oxide(HIPE) catalysts describing the same scenario of fostering the specific surface area, maintaining the monolith-type character and associated macroporous open tortuosity, and minimizing the carbon footprint penalty.