Magnetic nanocomposite based on functionalized salep as a green support for immobilization of palladium nanoparticles: Reusable heterogeneous catalyst for Suzuki coupling reactions

Green Synthesis of Pd Nanoparticles for Sustainable and Environmentally Benign Processes

Among transition metal nanoparticles, palladium nanoparticles (PdNPs) are recognized for their high catalytic activity in a wide range of organic transformations that are of academic and industrial importance. The increased interest in environmental issues has led to the development of various green approaches for the preparation of efficient, low-cost and environmentally sustainable Pd-nanocatalysts. Environmentally friendly solvents, non-toxic reducing reagents, biodegradable capping and stabilizing agents and energy-efficient synthetic methods are the main aspects that have been taken into account for the production of Pd nanoparticles in a green approach. This review provides an overview of the fundamental approaches used for the green synthesis of PdNPs and their catalytic application in sustainable processes as cross-coupling reactions and reductions with particular attention afforded to the recovery and reuse of the palladium nanocatalyst, from 2015 to the present.

NiFe2O4@SiO2@ZrO2/SO42−/Cu/Co nanoparticles: a novel, efficient, magnetically recyclable and bimetallic catalyst for Pd-free Suzuki, Heck and C–N cross-coupling reactions in aqueous media

The novel heterogeneous bimetallic nanoparticles of Cu–Co were synthesized and successfully applied as a recyclable magnetically catalyst in Heck, Suzuki, and C–N cross-coupling via a quick, easy, efficacious and environmentally protocol.

Deposition of Palladium Nanoparticles by the Coating of the Carbonaceous Layer from Wastepaper-Derived Bio-Oil

A highly active and recyclable Pd-deposited catalyst has been successfully prepared for the Heck reaction. Bio-oil liquid, a byproduct from the microwave pyrolysis of wastepaper, is employed to immobilize palladium nanoparticles on a solid support. FTIR, GC, and NMR results indicate the self-polymerization feature of bio-oil, thus giving rise to a uniform carbonaceous layer coated around the surface of the catalyst. Characteristic analysis of the catalyst indicates that palladium nanoparticles are well-dispersed on the parent SBA-15 solid substrate, which is attributed to the carbonaceous layer that is derived from bio-oil carbonization, allowing a high catalytic performance as a heterogeneous catalyst for the Heck reaction. The as-synthesized catalyst demonstrates remarkable recyclability with firm deposition of palladium nanoparticles on the solid support and could be reused without a dramatic decrease in catalytic activity.

Core–shell structured magnetic mesoporous silica supported Schiff-base/Pd: an efficacious and reusable nanocatalyst

Preparation, characterization and catalytic application of a novel magnetic ordered mesoporous silica supported Schiff-base/Pd (Fe₃O₄@MCM-41-SB/Pd) are developed.

Study of Pd-based catalysts within red algae-derived polysaccharide supports in a Suzuki cross-coupling reaction

Simple palladium complexes were heterogenized into red algae derived polysaccharide supports, and the effects of polysaccharide, catalyst and solvent types on the performances in a Suzuki cross-coupling reaction were tested. It was found that using palladium salts with sodium triphenylphosphine trisulfonate (TPPTS) as a ligand supported on ι-carrageenans and ethanol as the solvent yielded the best systems. Moreover, the conversion rates of these heterogeneous systems were higher than their homogeneous analogues, and they were easily recycled five times. SEM-EDS analysis of Pd(OAc)2(TPPTS)2 that was immobilized on ι-carrageenan support was also performed, demonstrating that the system has a porous structure composed of Pd complex that was embedded within the ι-carrageenan. In addition, both ι-Pd(OAc)2(TPPTS)2 and ι-Pd(OAc)2 systems, were composed of nanoparticles, as proven by TEM analysis.

Modification Effects of B₂O₃ on The Structure and Catalytic Activity of WO₃-UiO-66 Catalyst

Tungsten oxide (WO₃) and boron oxide (B₂O₃) were irreversibly encapsulated into the nanocages of the Zr-based metal organic framework UiO-66, affording a hybrid material B₂O₃-WO₃/UiO-66 by a simple microwave-assisted deposition method. The novel B₂O₃-WO₃/UiO-66 material was systematically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray phosphorescence, and Fourier transform infrared (FTIR)-CO adsorption methods. It was found that WO₃ and B₂O₃ were highly dispersed in the nanocages of UiO-66, and the morphology and crystal structure of UiO-66 were well preserved. The B₂O₃ species are wrapped by WO₃ species, thus increasing the polymeric degree of the WO₃ species, which are mainly located in low-condensed oligomeric environments. Moreover, when compared with WO₃/UiO-66, the B₂O₃-WO₃/UiO-66 material has a little weaker acidity, which decreased by 10% upon the B₂O₃ introduction. The as-obtained novel material exhibits higher catalytic performance in the cyclopentene selective oxidation to glutaraldehyde than WO₃/UiO-66. The high catalytic performance was attributed to a proper amount of B₂O₃ and WO₃ with an appropriate acidity, their high dispersion, and the synergistic effects between them. In addition, these oxide species hardly leached in the reaction solution, endowing the catalyst with a good stability. The catalyst could be used for six reaction cycles without an obvious loss of catalytic activity.

Preparation, Characterization and Application of Polysaccharide-Based Metallic Nanoparticles: A Review

Polysaccharides are natural biopolymers that have been recognized to be the most promising hosts for the synthesis of metallic nanoparticles (MNPs) because of their outstanding biocompatible and biodegradable properties. Polysaccharides are diverse in size and molecular chains, making them suitable for the reduction and stabilization of MNPs. Considerable research has been directed toward investigating polysaccharide-based metallic nanoparticles (PMNPs) through host⁻guest strategy. In this review, approaches of preparation, including top-down and bottom-up approaches, are presented and compared. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, dynamic light scattering, UV-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and small-angle X-ray scattering are discussed in detail. Besides, the applications of PMNPs in the field of wound healing, targeted delivery, biosensing, catalysis and agents with antimicrobial, antiviral and anticancer capabilities are specifically highlighted. The controversial toxicological effects of PMNPs are also discussed. This review can provide significant insights into the utilization of polysaccharides as the hosts to synthesize MPNs and facilitate their further development in synthesis approaches, characterization techniques as well as potential applications.