Bimetallic Au–Ru nanoparticles supported on zeolitic imidazolate framework-67 as highly efficient catalysts for the selective oxidation of benzyl alcohol

A highly dispersed bimetallic catalyst, AuRu/ZIF-67, and monometallic catalysts, Au/ZIF-67 and Ru/ZIF-67, were successfully prepared herein via co-impregnation/impregnation and hydrogen reduction methods. The catalytic performances of the bimetallic Au-Ru and monometallic Au and Ru catalysts for benzyl alcohol oxidation were compared under an O₂ atmosphere. Results revealed that the addition of Ru to the Au catalyst reduced the oxidation activity of benzyl alcohol while considerably improving the yield of benzaldehyde. The reaction solvent, temperature, pressure and time exerted crucial effects on the catalytic performance of AuRu/ZIF-67. The optimal reaction conditions when using AuRu/ZIF-67 for benzyl alcohol oxidation were 70℃, 5 bar O₂ and 4 h with tetrahydrofuran as the solvent. The benzyl alcohol conversion and benzaldehyde yield were 82.9% and 47.5%, respectively, under the optimal reaction conditions. AuRu/ZIF-67 exhibited excellent applicability towards alcohols; particularly for aromatic and aliphatic alcohols, where good conversions and acceptable yields of aldehydes were obtained. Moreover, the AuRu/ZIF-67 catalyst demonstrated good stability for benzyl alcohol oxidation, and it could be recycled four times without any changes in the benzaldehyde yield.