High-Efficiency Photocatalytic Oxidation of Benzyl Alcohol by NH-UiO-66-(Indole-2,3-Dione)-Fe.

The photocatalytic oxidation of biomass-derived benzyl alcohol provides a promising way for the synthesis of benzoic acid, which is an important intermediate with wide applications. To improve the efficiency of photocatalytic benzyl alcohol oxidation to benzoic acid is of great interest. In this work, we propose the utilization of NH-UiO-66-ID-Fe catalyst for photocatalytic oxidation of benzyl alcohol to benzoic acid, where NH-UiO-66 is a typically used metal-organic framework, ID is indole-2,3-dione (ID) that has biocompatibility, light absorption property and can be covalently combined with amino-functionalized substances. The NH-UiO-66-ID-Fe catalyst exhibits improved light absorption and photo-generated electron-hole separation ability compared with NH-UiO-66. The photocatalytic performance of NH-UiO-66-ID-Fe was examined for the oxidation of bio-based benzyl alcohol under mild conditions of air atmosphere, room temperature and no additive or additional oxidant involved. The results show that the conversion of benzyl alcohol and the selectivity to benzoic acid could both reach over 99 % in 6 h, and the generation rate of benzoic acid per gram of catalyst is 3.36 mmol g h. The reaction mechanism was detected by radical trapping method and in situ electron paramagnetic resonance. This study presents an efficient and environmentally benign avenue for the synthesis of carboxylic acid compounds.