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

AbstractTitanium(IV) oxide (TiO2) 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 TiO2 (OM/TiO2) and used OM/TiO2 for chemoselective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL) under irradiation of visible light without the use of hydrogen gas. All OM/TiO2 prepared in this study produced FOL and a linear relation between the reaction rate and amount of FAL adsorbed on the OM/TiO2 was observed. Among them, OM/TiO2 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 TiO2 (TB‐NDO/TiO2), the reaction rate was not dependent on the amount of TB‐NDO and the photoabsorption of TB‐NDO/TiO2 but was dependent on the amount of FAL adsorbed on TB‐NDO/TiO2. 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/TiO2 also showed high performance in H2‐free chemoselective reduction of benzaldehydes having reducible groups to corresponding benzyl alcohols.