Palladium Nanoparticles Decorated over Polydopamine-coated Zn–Al-layered Double Hydroxide (Zn-Al LDH@PDA/Pd NPs) as Recyclable Heterogeneous Nanocatalyst for Suzuki–Miyaura Coupling Reactions

Polydopamine (PDA)-coated Zn–Al-layered double hydroxide (Zn-Al LDH@PDA) have been synthesized through a simple and green procedure. In the present study, for the first time, Pd nanoparticles were successfully deposited using Zn-Al LDH@PDA as an efficient reducing biotemplate and stabilizing support. In this protocol, Pd ions were adsorbed on surfaces of Zn-Al LDH@PDA through immersion of the Zn-Al LDH@PDA nanocomposite into a palladium plating bath. Next, they were reduced in situ to palladium nanoparticles using PDA’s N-containing groups and reducing ability. The structure, morphology and physicochemical properties of the synthesized nanoparticles were characterized by different analytical techniques such as energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT),inductively coupled plasma (ICP), nitrogen physical adsorption (BET), elemental mapping and X-ray Diffraction (XRD).The catalytic potential of Zn-Al LDH@PDA/Pd NPs nanocatalyst was then evaluated in the Suzuki–Miyaura coupling reactions. These tests indicated that Zn-Al LDH@PDA/Pd NPs nanocatalyst is tolerant against various functional groups, and the desired biphenyl products were acquired with good to high yields within short times. The Zn-Al LDH@PDA/Pd NPs nanocatalyst was isolated by centrifuge and it was stable enough to be reused for 7 consecutive times without considerable loss in activity.