Graphene Quantum Dot Modified Fe3O4 Nanoparticles Stabilize PdCu Nanoparticles for Enhanced Catalytic Activity in the Sonogashira Reaction

In this report, Fe3O4 nanoparticles are modified for the first time with graphene quantum dots (GQD) and used for the stabilization of PdCu bimetallic nanoparticles. The new magnetic compound, PdCu@GQD@Fe3O4, is characterized by different methods such as SEM, high-resolution (HR)-TEM, energy-dispersive X-ray spectroscopy (EDS) mapping, XRD, and X-ray photoelectron spectroscopy (XPS). This material is applied as an efficient catalyst for the Sonogashira reaction of aryl iodides, bromides, and chlorides in toluene or N,N-dimethylacetamide at 60-110 degrees C in very high yields with 0.3 mol% of Pd loading. According to different tests, such as polyvinylpyridine poisoning, hot filtration, and kinetic studies, this catalyst works under heterogeneous conditions. By magnetic separation of the catalyst, it can be recycled for six consecutive runs with only a small decrease in activity without appreciable structural modification of the reused catalyst, which is characterized by TEM and XPS.