Ionothermal Stability of Mesoporous Silica Films

Abstract

We have examined the ionothermal stability of mesoporous silica films (MSFs) in four different imidazolium ionic liquids (ILs) and compared it to their hydrothermal stability in liquid water. Ionothermal treatment of MSFs in anhydrous 1-butyl-3-methylimidazolium acetate, bromide, chloride, and thiocyanate reveals that MSFs are thermochemically stable in these ILs up to 175°C for 24 h. Solvothermal stability of MSFs in imidazolium IL−water compositional mixtures was also investigated, and mesoporous silica is found to be stable in compositions greater than 25 mol % IL. A kinetic acceleration in MSF dissolution occurs at suitably low IL compositions relative to water for all ILs used and depends on the IL anion. Our findings suggest that anhydrous imidazolium ILs are unable to solvolytically depolymerize mesoprous silica, possibly making these better solvents than water for use with mesoporous silica.