Palladium Nanoparticles on Chitosan-Coated Superparamagnetic Manganese Ferrite: A Biocompatible Heterogeneous Catalyst for Nitroarene Reduction and Allyl Carbamate Deprotection

Although metallic nanocatalysts such as palladium nanoparticles (Pd NPs) are known to possess higher catalytic activity due to their large surface-to-volume ratio, however, in nanosize greatly reducing their activity due to aggregation. To overcome this challenge, superparamagnetic chitosan-coated manganese ferrite was successfully prepared and used as a support for the immobilization of palladium nanoparticles to overcome the above-mentioned challenge. The Pd-Chit@MnFe₂O₄ catalyst exhibited high catalytic activity in 4-nitrophenol and 4-nitroaniline reductions, with respective turnover frequencies of 357.1 min^-1 and 571.4 min^-1, respectively. The catalyst can also be recovered easily by magnetic separation after each reaction. Additionally, the Pd-Chit@MnFe₂O₄ catalyst performed well in the reductive deprotection of allyl carbamate. Coating the catalyst with chitosan reduced the Pd leaching and its cytotoxicity. Therefore, the catalytic activity of Pd-Chit@MnFe₂O₄ was proven to be unrestricted in biology conditions.

Immobilized biogenic copper nanoparticles from metallic wastewater as catalyst for triazole synthesis by click reaction using water as solvent

In this study, biogenic copper nanoparticles from metallic wastewater were examined for triazoles synthesis by click reaction. The size of the copper nanoparticles obtained by biogenic sulfate reduction of synthetic...

Hyper-Cross-Linked Polystyrene as a Stabilizing Medium for Small Metal Clusters

Among different polymers nanostructured cross-linked aromatics have the greatest potential as catalytic supports due to their exceptional thermal and chemical stability and preservation of the active phase morphology. This work studies the ability of hyper-cross-linked polystyrene (HPS) to stabilize small Pd_n and Pt_n (n = 4 or 9) clusters. Unrestricted DFT calculations were carried out for benzene (BZ) adsorption at the BP level of theory using triple-zeta basis sets. The adsorption of BZ rings (stepwise from one to four) was found to result in noticeable gain in energy and stabilization of resulting adsorption complexes. Moreover, the interaction of metal clusters with HPS micropores was also addressed. For the first time, the incorporation of small clusters in the HPS structure was shown to influences its geometry resulting in the stabilization of polymer due to its partial relaxation.

Environmentally Benign Metal-Free Reduction of GO Using Molecular Hydrogen: A Mechanistic Insight

A simple yet effective methodology to obtain high-quality reduced graphene oxide (RGO) using a tetrahydrofuran suspension of GO under hydrogen at moderate pressure has been demonstrated. The extent of reduction as a function of the pressure of hydrogen gas, temperature, and time was studied, where the abstraction of oxygen is achievable with least mutilation of C-sp² bonds, hence upholding the integrity of the graphene sheet. Herein, the formation of a short-lived species is proposed, which is possibly responsible for such reduction. A detailed theoretical calculation along with in situ UV-visible experiments reveals the existence of a transient solvated electron species in the reaction medium. The hydrogen RGO (HRGO) achieved a C/O atomic ratio of 11.3. The conductivity measurements show that HRGO reached as high as 934 S/m, which indicates a high quality of RGO. The process is hassle-free, environmentally benign, and can be scaled up effortlessly without compromising the quality of the material.

Selective conversion of styrene oxide to 2-phenylethanol in cascade reactions over non-noble metal catalysts

Three cascade reactions using green efficient processes based on heterogeneous catalysts are proposed to selectively obtain 2-phenyl ethanol from styrene.

Dy/chitosan: a highly efficient and recyclable heterogeneous nano catalyst for the synthesis of hexahydropyrimidines in aqueous media

Dy(iii)/chitosan as a recyclable and heterogeneous catalyst is used for the sustainable preparation of hexahydropyrimidine derivatives in aqueous media.

CO2 as a regulator for the controllable preparation of highly dispersed chitosan-supported Pd catalysts in ionic liquids

A controllable synthetic route has been developed for the preparation of chitosan supported Pd catalysts in 1-butyl-3-methylimidazolium acetate by using compressed CO₂ as the anti-solvent and regulator.

Influence of support acidity on the performance of size-confined Pt nanoparticles in the chemoselective hydrogenation of acetophenone

Chemoselectivity of hydrogenation depends on strength of the covered BAS, whereas the free BAS enhance the rate.

Dual catalysis with magnetic chitosan: direct synthesis of cyclic carbonates from olefins with carbon dioxide using isobutyraldehyde as the sacrificial reductant

Magnetic chitosan was further functionalized with (ii) acetylacetonate complex [Co(acac)₂] and quaternary triphenylphosphonium bromide by targeting the –NH₂ and –OH moieties located on the surface of chitosan.

Hydrogenation of Styrene Oxide to 2-Phenylethanol over Nanocrystalline Ni Prepared by Ethylene Glycol Reduction Method

Nanocrystalline nickel prepared by glycol reduction method and characterized by XRD and magnetic measurements has been used as a catalyst for hydrogenation of styrene oxide to 2-phenylethanol. Effect of process variables such as particle size of the catalyst, temperature, and pressure have been optimized to achieve a maximum conversion of 98% of styrene oxide with 99% selectivity towards 2-phenylethanol. The structure of the transition state has been computed employing density functional theory and using Gaussian 09 suite. The enthalpy of reaction (ΔH) and activation energy (Ea) are calculated to be 85.3 kcal·mol−1and 123.03 kcal·mol−1, respectively. A tentative mechanism for the reaction is proposed according to which atomized hydrogen and styrene oxide react together over the catalyst surface to produce 2-phenylethanol.