Abstract
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•Colorful defective TiO2-x microspheres cooperating with titanium Schiff base complex were synthesized.•The formation mechanism of TiO2-x-Ti(acacen)y complexes was proposed based on the Schiff base reaction.•Ti3+ and oxygen vacancies are self-doped into TiO2 lattice to form defective TiO2-x.•Red TiO2-x-Ti(acacen)y complexes have a narrow bandgap of 2.16 eV and high specific surface area over 255.4 m2 g−1.•Red TiO2-x-Ti(acacen)y complexes show high performance of photocatalysis superior to yellowish TiO2 microspheres.
As a promising photocatalyst, the large band gap of TiO2 imposes restriction on its light absorption in the visible region, making it less application in industrial fields. Herein, we design a facile solvothermal method to fabricate colorful defective TiO2-x microspheres with controllable morphological and porous structure, large specific surface area and tunable band gap on the basis of the Schiff base reaction between acetylacetone and ethylenediamine which produce bis(acetylacetone)ethylenediamine (acacen). The acacen, as a tetradentate Schiff-base ligand, has four binding sites which can stabilize titanium centers to produce titanium Schiff base complexes. The color of TiO2-x-Ti(acacen)y complexes changes from yellowish to brown and red with the variation of the acacen ligand, and the corresponding bandgap narrows from 3.25 eV to 2.16 eV as a result of the newly formed Ti3+ and oxygen vacancies (Vo) in the TiO2 lattice. In addition, red TiO2-x microspheres cooperating with titanium Schiff base complex demonstrate high photocatalytic efficiency in methylene blue under visible light as well as hydroxyl radical generation in contrast to yellowish TiO2 microspheres, revealing the significance of this strategy for morphological and bandgap manipulation in defective TiO2-x nanomaterials for high-performance photocatalysis.