Plant Extract Mediated Eco-friendly Synthesis of Pd@Graphene Nanocatalyst: An Efficient and Reusable Catalyst for the Suzuki-Miyaura Coupling.

Journal Article

Publication Abstract

Suzuki-Miyaura coupling reaction catalyzed by the palladium (Pd)-based nanomaterials
is one of the most versatile methods for the preparation of biaryls. However, use of organic
solvents as reaction medium causes a big threat to environment due to the generation of toxic
byproducts as waste during the work up of these reactions. Therefore, the use of water as
reaction media has attracted tremendous attention due to its environmental, economic, and safety
benefits. In this study, we report on the synthesis of green Pd@graphene nanocatalyst based
on an in situ functionalization approach which exhibited excellent catalytic activity towards the
Suzuki–Miyaura cross-coupling reactions of phenyl halides with phenyl boronic acids under facile
conditions in water. The green and environmentally friendly synthesis of Pd@graphene nanocatalyst
(PG-HRG-Pd) is carried out by simultaneous reduction of graphene oxide (GRO) and PdCl2 using
Pulicaria glutinosa extract (PGE) as reducing and stabilizing agent. The phytomolecules present in
the plant extract (PE) not only facilitated the reduction of PdCl2, but also helped to stabilize the
surface of PG-HRG-Pd nanocatalyst, which significantly enhanced the dispersibility of nanocatalyst
in water. The identification of PG-HRG-Pd was established by various spectroscopic and microscopic
techniques, including, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction
(XRD), ultraviolet–visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR),
and Raman spectroscopy. The as-prepared PG-HRG-Pd nanocatalyst demonstrated excellent catalytic
activity towards the Suzuki-Miyaura cross coupling reactions under aqueous, ligand free, and aerobic
conditions. Apart from this the reusability of the catalyst was also evaluated and the catalyst
yielded excellent results upon reuse for several times with marginal loss of its catalytic performance.
Therefore, the method developed for the green synthesis of PG-HRG-Pd nanocatalyst and the
eco-friendly protocol used for the Suzuki coupling offers a mild and effective substitute to the existing
protocols and may significantly contribute to the endeavors of green chemistry.