One-pot synthesis of bio-supported Pd nanoparticles by using clove leaf and their catalytic performance for Suzuki coupling reaction

Abstract

Bio-supported palladium nanoparticles (PdNPs/RCL-b) were synthesized by one-pot method without adding any chemical reducing and stabilizing agents. In the preparation process, Clove leaf (CL) was used as carrier, reducing and stabilizing agents. The extraction of reducing compounds from CL, the reduction and stabilization of Pd2+, and palladium nanoparticles (PdNPs) loading on the extraction residue of CL (RCL) were accomplished simultaneously, avoiding the agglomeration of PdNPs and ensuring PdNPs loading evenly on RCL. The prepared PdNPs/RCL-b catalysts were characterized by XRD, UV–Vis, Micro-infrared spectroscopy, FT-IR and TEM. The hydroxyl groups and other reductive groups which exist in polyphenols and flavonoids reduced Pd2+ to PdNPs, while the CO, C–O and other groups containing O served as good protective agents and stabilizers for the formation of PdNPs. The PdNPs had a face-centered cubic structure with a particle size distribution of 1.26–8.78 nm and an average particle size of 4.49 nm, and uniformly dispersed on the surface of RCL. The results of catalytic Suzuki coupling reaction between 4-bromonitrobenzene and phenylboronic acid over PdNPs/RCL-b at 60 °C showed that the yield was 96.22% for 20 min and the value of TOF was 5773.2 h−1. After the reaction between 4-bromotoluene and phenylboronic acid repeated for 8 times, the yield remains above 91%. This method provides a more facile, efficient and green approach to the preparation of supported nano-palladium catalysts.