Sonochemical in situ immobilization of Pd nanoparticles on green tea extract coated Fe3O4 nanoparticles: An efficient and magnetically recyclable nanocatalyst for synthesis of biphenyl compounds under ultrasound irradiations

This work describes (i) an eco-friendly approach for in situ immobilization of Pd nanoparticles on the surface of Fe3O4 nanoparticles, with help of green tea extract and ultrasound irradiations, without using any toxic reducing agents and (ii) development of ultrasound assisted simple protocol for synthesis of biphenyl compounds. The structural, morphological and physicochemical characteristics of the catalyst were determined by different analytical methods including inductively coupled plasma (ICP) analysis, Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). Catalytic performance of Pd/Fe3O4 NPs as magnetic and heterogeneous catalyst was evaluated in synthesis of various biphenyl compounds throughout Suzuki coupling reactions by using the ultrasound-assisted method that was developed in this study. The Pd/Fe3O4 NPs demonstrated a noticeable catalytic activity by giving high product yields. Furthermore, the heterogeneous nanocatalyst was successfully recovered up to six times without significant activity loss. Additionally, with respect to conventional coupling reactions, the ultrasound-assisted synthesis reactions presented the advantages of green conditions, short reaction times, high yields and easier work-up.