Phase-selective modulation of TiO2 for visible light-driven C-H arylation: Tuning of absorption and adsorptivity

To understand and modify TiO2 for organic photoreaction, two points are important: improving light absorption and retaining adsorption sites for organic reagents. Herein, we tuning the absorption and adsorption of TiO2 by introducing the defects on each phase of TiO2, called phase-mixed structures of ordered anatase (OA) and disordered rutile (DR) (OA/DR P25) and disordered anatase (DA) and ordered rutile (OR) (DA/OR P25). Disordered structure of TiO2 broadened the absorption wavelength range including visible light, but changed surface structure reduced the adsorptivity of organic reactant. Additionally, anatase and rutile phase of TiO2 has different surface properties and energy band structure, so keeping the crystalline anatase surface for adsorption was important while introducing the TiO2. Thus, it is assumed that the phase combination of OA and DR can be the best photocatalytic structure of TiO2 even without any supporting materials and/or co-catalysts. In fact, the arylation yield of OA/DR P25 is the highest (63.4%), compared to those of untreated P25 (40.0%) and DA/OR (20.1%), highlighting the potential of OA/DR P25 in various visible light-driven photocatalytic organic reactions.