Sol–gel synthesis of macroporous TiO₂ from ionic precursors via phase separation route

Monolithic macroporous titanium dioxide (TiO₂) derived from ionic precursors has been successfully prepared via the sol–gel route accompanied by phase separation in the presence of formamide (FA) and poly(vinylpyrrolidone) (PVP). The addition of FA promotes the gelation, whereas PVP enhances the polymerization-induced phase separation. Appropriate choice of the starting compositions allows the production of cocontinuous macroporous TiO₂ monoliths in large dimensions, and controls the size of macropores. The resultant dried gel is amorphous, whereas anatase and rutile phases are precipitated at 500 and 900 °C respectively, without spoiling the macroporous morphology. Nitrogen adsorption–desorption measurements revealed that the dried gels exhibits mesostructure with a median pore size of about 3 nm and BET surface area of 228 m²/g, whereas 15 nm and 73 m²/g for the gels calcined at 600 °C.