Facile preparation of hierarchically porous TiO₂ monoliths

Monolithic titania (TiO₂) with multiscale porous structures have been successfully prepared via the sol-gel route accompanied by phase separation utilizing a chelating agent and mineral salt. The TiO₂ gels obtained possess well-defined macropores derived from spinodal decomposition and mesopores as interstices of anatase TiO₂ nanocrystallites.Most of the chelating agent were removed by hydrolysis and subsequent decarbonation through the gradual solvent exchange from ethanol to water. The TiO₂ particles comprising TiO₂ gel skeletons spontaneously converted from amorphous to anatase through the solvent exchange process in a mild condition at 60°C. The present method of the fabrication of porous TiO₂ monoliths is advantageous for widespread applications because the reaction occurs under an almost neutral condition and does not require a hydrothermal process, which was indispensable to strengthen the monolith in the method previously reported