Size-Controlled Synthesis of Palladium Nanoparticles on a Silica–Cyclodextrin Substrate: A Novel Palladium Catalyst System for the Heck Reaction in Water

Abstract

This study offers an example of using a silica–cyclodextrin (SCD) substrate for the capture of metal nanoparticles to prepare a novel nanocatalyst for catalytic organic reactions in water as a green solvent. Also, a simple and efficient method for the size control of palladium nanoparticles (PdNPs) using their immobilization on a SCD substrate was introduced. These new catalyst systems were fully characterized using some different techniques such as XRD, TEM, SEM, TGA, ICP, XPS, and FT-IR. The average size of immobilized PdNPs on silica α-, β-, and γ-CD substrates were obtained (10, 3, and 5 nm, respectively). The immobilized PdNPs on the silica β-CD substrate (PdNP-SβCD) was recognized as the best one for the Heck reaction in aqueous media. It seems that the anchored CD moieties on the silica surface can prevent removal of PdNPs and also their aggregations. Moreover, this substrate can provide appropriate catalytic sites for reactions in aqueous media; therefore, the PdNP-SβCD catalyst showed high activity in the Heck reaction in aqueous media.

Green synthesis of manganese oxide nanoparticles for the electrochemical sensing of p-nitrophenol

“…The peak was collectively broad due to amorphous nature of biosurfactant moieties covering MnO NPs and small size of MnO NPs. The size of NPs obtained from FESEM and TEM analysis is more accurate than the size calculated using XRD [34]. Overall, MnO NPs were of approximately 4 nm average size.…”

Immobilized Palladium Nanoparticles on Zirconium Carboxy-Aminophosphonates Nanosheets as an Efficient Recoverable Heterogeneous Catalyst for Suzuki–Miyaura and Heck Coupling

“…Pd@ZPGly-1, which mainly contains Pd(II) species, provided a lower conversion (63%) as compared to Pd@ZPGly-7 and -15 (78% and 85%, respectively) that also contained Pd(0) species. During the reaction, the reduction of Pd(II) occurs at the expense of EtOH [15,44,45], and after 9 h, the conversion was comparable (93-96%). At the end of the reactions, all of the recovered catalysts were black, supporting the more complete presence of Pd(0) species.…”

Synthesis of new surfactant-like triazine-functionalized ligands for Pd-catalyzed Heck and Sonogashira reactions in water

“…8 Since, the main problem is the use of toxic solvents such as DMF for these reactions several strategies have been reported to use water as solvent. For example, use of water dispersible Pd catalysts, 9 employ of solid-supported Pd catalysts with hydrophobic surfaces 10 and apply of hydrophobic substrates in reaction media such as saccharide. 11 Microemulsion and micellar catalysis are another approaches to do these reactions in water media based on the solubilisation phenomena.…”