Microwave-assisted high temperature hydrolysis of titanium oxysulfate, in the presence of ammonium fluoride, allows synthesizing nanocrystalline titanium dioxide photocatalysts possessing photocatalytic activity as high as the commercial photocatalyst Evonik Aeroxide® TiO2 P 25. Dye-sensitized reactions play an important role in organic dye discoloration in the presence of fluorinated titania.