Bromine Substitution of Organic Modifiers Fixed on a Titanium(IV) Oxide Photocatalyst: A New Strategy Accelerating Visible Light‐Induced Hydrogen‐Free Hydrogenation of Furfural to Furfuryl Alcohol

Abstract Titanium(IV) oxide (TiO 2 ) modified with 2,3‐naphthalenediol (NDO) works as a photocatalyst for some reactions under irradiation of visible light. We prepared and characterized nine kinds of organically modified TiO 2 (OM/TiO 2 ) and used OM/TiO 2 for chemoselective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL) under irradiation of visible light without the use of hydrogen gas. All OM/TiO 2 prepared in this study produced FOL and a linear relation between the reaction rate and amount of FAL adsorbed on the OM/TiO 2 was observed. Among them, OM/TiO 2 having bromine (Br)‐substituted NDO exhibited larger reaction rates and the rate increased with an increase in the number of Br groups. In the case of the most active 1,4,6‐tribromo‐2,3‐naphthalenediol‐modified TiO 2 (TB‐NDO/TiO 2 ), the reaction rate was not dependent on the amount of TB‐NDO and the photoabsorption of TB‐NDO/TiO 2 but was dependent on the amount of FAL adsorbed on TB‐NDO/TiO 2 . These results revealed that substitution of hydrogen atoms of organic modifiers with Br is a simple but effective method for increasing the photocatalytic activity. The explored TB‐NDO/TiO 2 also showed high performance in H 2 ‐free chemoselective reduction of benzaldehydes having reducible groups to corresponding benzyl alcohols.