Nanosized Carbonate-Doped TiO_2–x Mesocrystals for Visible-Light-Driven Photocatalytic Removal of Water Pollutants

Nonaqueous sol–gel routes are considered to be effective alternatives to aqueous approaches for producing nanostructured metal oxides with desired morphologies and intriguing photo-electronic properties for harvesting and converting solar energy to alleviate serious problems of water pollution. Despite significant progress, the exploration of green and recyclable organic solvents for producing functional nanostructures of metal oxides remains a great challenge. Herein, we demonstrate that by utilizing ethyl formate, which is generally recognized as safe by the U.S. Food and Drug Administration and widely employed in the food industry, as the sole solvent, nanosized carbonate-doped TiO2–x mesocrystals could be controllably fabricated via nonaqueous solvothermal reactions and subsequent calcination in air at moderate temperatures. Such a green solvent of ethyl formate could be recycled and further used at least three more times, with the mesocrystalline architecture of the precipitated anatase crystals well retained, illustrating its high effectiveness in mesocrystal production with a minimized impact on the environment. Owing to their carbonate-doped, oxygen-deficient, and mesocrystalline nature, the as-synthesized nanosized carbonated-doped TiO2–x mesocrystals exhibited strengthened light harvesting and bolstered photogenerated electron–hole separation and thus displayed a noticeable enhancement on photocatalytic activity toward the removal of the water pollutants sulfathiazole and CrVI under visible-light irradiation.