Ru/UiO-66 Catalyst for the Reduction of Nitroarenes and Tandem Reaction of Alcohol Oxidation/Knoevenagel Condensation

Abstract

A 3.1% Ru/UiO-66 material was prepared by adsorption of RuCl ₃ from ethyl acetate on to MOF UiO-66, followed by reduction with NaBH ₄. The presence of acid–base and ox-red sites allows this 3.1% Ru/UiO-66 material acting as a bifunctional catalyst for the reduction of nitroarenes and tandem reaction of alcohol oxidation/Knoevenagel condensation. The high efficiency of 3.1% Ru/UiO-66 was demonstrated in the reduction of nitroarenes to amines. This system can be applied as a catalyst for at least six successive cycles without loss of activity. The 3.1% Ru/UiO-66 catalyst also was active in the tandem aerobic oxidation of alcohols/Knoevenagel condensation with malononitrile. However, the activity of this catalyst strongly decreased in the second cycle. A combination of physicochemical and catalytic experimental data indicated that Ru nanoparticles are the active sites both for the catalytic reduction of nitro compounds and the aerobic oxidation of alcohols. The activity for the Knoevenagel condensation reaction was from the existence of the “Zr ⁿ⁺ –O ^2– Lewis acid–base” pair in the framework of UiO-66.