Preparation of highly ordered mesoporous ethane-silicas under weakly acidic conditions and their hydrothermal stability

Periodic mesoporous organosilicas were prepared using 1,2-bis(triethoxysilyl)ethane (BTEE) in the presence of a poly(ethylene oxide)-b-poly(d,l-lactic acid-co-glycolic acid)-b-poly(ethylene oxide) triblock copolymer (LGE538) template under strongly and weakly acidic conditions. White solid powders were obtained even under weakly acidic conditions using iron chloride hexahydrate. Small angle X-ray scattering (SAXS) and nitrogen adsorption isotherms showed a highly ordered hexagonal (p6mm) mesostructure and a high specific surface area of around 1000 m² g^-1. The hydrothermal stability of these materials was also investigated because it is a crucial factor in their usage in the chemical industry. The powders were placed in sealed vials inside a convection oven at 373 K for 4 weeks. The hydrothermally treated samples were analyzed every week over the 4 weeks using SAXS and nitrogen adsorption. Solid-state ²⁹Si CP-MAS NMR analysis was also performed to observe the stability of siloxane bonds over the 4 weeks of hydrothermal treatment. The results indicate that the ethane-silica samples show quite good stability, which makes them attractive as catalysts or supporting materials for up to one month.