Highly efficient and selective one-pot tandem imine synthesis via amine-alcohol cross-coupling reaction catalysed by chromium-based MIL-101 supported Au nanoparticles


Gumus I., Rüzgar A. , Karataş Y. , Gülcan M.

MOLECULAR CATALYSIS, vol.501, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 501
  • Publication Date: 2021
  • Doi Number: 10.1016/j.mcat.2020.111363
  • Title of Journal : MOLECULAR CATALYSIS
  • Keywords: Au NPs, Catalyst, Cross-coupling reaction, Imine synthesis, MIL-101, METAL-ORGANIC FRAMEWORK, CORE-SHELL NANOPARTICLES, DIRECT N-ALKYLATION, HETEROGENEOUS CATALYST, GOLD NANOPARTICLES, BENZYL ALCOHOL, MULTIFUNCTIONAL CATALYSTS, BIFUNCTIONAL CATALYSTS, ROOM-TEMPERATURE, IN-SITU

Abstract

One-pot tandem synthesis of imines from alcohols and amines is regarded as an effective, economic and green approach under mild conditions. In this work, Au nanoparticles (NPs) dispersed on MIL-101 (Au/MIL-101) were demonstrated as highly active and selective bifunctional heterogeneous catalyst for production of various imine derivatives with excellent yields, via amine-alcohol cross-coupling reaction at 343 K in an open flask under an Ar atmosphere. Various physicochemical techniques, including inductively coupled plasma optical emission spectroscopy (ICP-OES), powder X-ray diffraction (P-XRD), X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) and N2 adsorption-desorption, were used to characterize of the Au/MIL-101 catalyst. The obtained bifunctional catalyst is highly active and selective towards one-pot imine formation and exhibited the highest TOF (30.15-51.47 h(-1)) among all the ever-reported MOF-supported Au catalysts. The reaction mechanism of the imine formation from alcohol and amine over Au/MIL-101 catalyst was proposed. Mechanism experiment results demonstrate that Au NPs highly effective in activating oxidation of benzyl alcohol to benzaldehyde while the Lewis acid sites on MIL-101 catalyzed the second condensation step without interfering with the oxidation step. As a result, the excellent catalytic performance of Au/MIL-101 can be ascribed to the synergistic effect between Au NPs with Lewis acid sites in MIL-101.