Magnetically-recoverable Catalyst Research Articles

N-rich MOFs derived N-doped carbon nanotubes encapsulating cobalt nanoparticles as efficient and magnetic recoverable catalysts for nitro aromatics reduction

A rational and convenient strategy was designed to synthesize high level N-doped Co@NCNTs composites derived from adenine-based AD-MOF-1 and Bio-MOF-11 via one-step pyrolysis method. Adenine can be used as an endogenous nitrogen source to apparently increase the N content of the materials. N-rich CNTs form a protecting layer for Co nanoparticles to avoid the aggregation of metal nanoparticles. The abundant nitrogen content can enhance electronic conductivity and bring additional active sites. The prepared Co@NCNTs display high catalytic efficiency for various nitro aromatics reduction in aqueous solution. The Co@NCNT-1-800 implies outstanding catalytic efficiency of 96% for the reduction of 4-NP. A mechanistic analysis revealed the abundant Co catalytic sites on the surface of catalysts to promote electron transfer efficiency and improve catalytic performance significantly. Moreover, the magnetic Co-based catalysts remained excellent catalytic activity and reusability even after five cycles.

Silver and copper–magnetite nanocomposites as green and magnetic recoverable catalysts for the preparation of cyclopentadiene derivatives from a tri-component condensation

Utilizing Citrus sinensis peels extract, acting as the stabilizing and reducing agents, an eco-friendly and green method is described for the preparation of copper/magnetite and silver/magnetite nanocomposites (NCs) via biological reduction of Ag+ and Cu2+ ions. The total phenolic compounds of the C. sinensis peels extract and extract’s ability to inhibition the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical were determined. The obtained results verified which the C. sinensis peels extract has the capability to reduce the silver(I) and copper(II) ions to its metallic nanoparticles (NPs). The deposition of silver and copper NPs on magnetite (Fe3O4) ones was confirmed by absorption bands at λmax values of 422 and 732 nm in their UV–Vis spectra, being related to the plasmon bands of silver and copper NPs. The catalytic performance of silver/Fe3O4 and copper/Fe3O4 NCs was investigated in the three-component condensation reaction of synthesis of 1,3-cyclopentadiene derivatives. The present synthetic method is the simple, economic, green route and effective with high efficiency.

Bioinspired Palladium Nanoparticles Supported on Soil-Derived Humic Acid Coated Iron-Oxide Nanoparticles as Catalyst for C–C Cross-Coupling and Reduction Reactions

Pd nanoparticles supported on humic acid-coated nanoferrites as magnetically-recoverable catalyst was expediently prepared from inexpensive precursors and characterized by techniques such as SEM, TEM, XPS, FT-IR, XRD, ICP-AES, EDX. The as made catalyst displayed an admirable catalytic activity towards the Suzuki–Miyaura cross-coupling reaction of aryl halides (or) aryl diazonium salts with aryl boronic acid in non-toxic solvent EtOH/water under mild conditions. The same catalyst showed high efficiency for the Heck reaction of aryl halides with styrene was carried out with high efficiency offering good yields under ligand-free conditions. Additionally, the reduction of olefins using molecular hydrogen was also achieved using the same catalyst under ambient and base-free conditions affording the products in good to excellent yields. The magnetic activity of nano-Fe3O4 allowed the effortless recovery of the catalyst and demonstrated subsequent recyclability up to 5 cycles without a significant loss in the activity.

Nano-Polyoxotungstate as a Recyclable and Highly Efficient Catalyst for Cycloaddition of CO2 to Cyclic Carbonates under Solvent-free Conditions

Aim and Objective: In this study, for the first time keplerate cluster [Cu20Cl(OH)24(H2O)12 (P8W48O184)]25- (hereafter [W48P8Cu20]) was supported on SMNP (Fe3O4-@SiO2) via amine functionality (ASMNP) as a magnetically-recoverable catalyst (hereafter [WPCu@ASMNP]). This nanocatalyst showed high activity for the synthesis of cyclic carbonates under solvent-free conditions. Materials and Methods: After preparation, the nanocatalyst was characterized by FT-IR, XRD, ICP-AES, TGA, TEM and SEM. Surface acidity was determined by a potentiometric titration with n-butyl amine. The effect of different parameters like catalyst amount, reaction time, temperature and pressure in the presence of [WPCu@ASMNP] were studied. Results: Optimal reaction conditions were obtained for 0.5mol% of catalyst, reaction temperature of 100°C and CO2 pressure of 1.5 MPa. The [WPCu@ASMNP] could be separated from the reaction and reused for five times with an external magnet without notable decrease in the activity. Finally, stability of the catalyst and its reusability were evaluated using a hot filtration method. The FT-IR and the control experiments (hot filtration) after five cycles confirmed the strongly catalyst immobilization to the ASMNP. Conclusion: The nanocatalyst is shown to be effective heterogeneous and recyclable catalyst for the synthesis of cyclic carbonates from CO2 and epoxides under mild conditions without any additional co-solvent and cocatalyst. This catalyst has a good substrate tolerance as demonstrated by its activity towards different epoxides. Importantly, the reaction could be carried out under solvent free conditions. The heterogeneous nature of the catalyst is proved by recovering and reusing this catalyst without any appreciable loss in catalytic activity and by the FT-IR spectroscopic characterization of the fresh and spent catalyst. The product separation and catalyst recycling are short using an external magnet.

The influence of sintering temperature on the structure, optical and magnetic properties of Yttrium iron oxide YFeO3 prepared via Lα-alanine assisted combustion method

Single-crystalline YFeO3 nanoparticles with orthorhombic perovskite structure were synthesized via Lα-alanine assisted combustion approach. The effect of sintering temperature on the lattice and distortion parameters of the YFeO3 was discussed. The increase of the sintering temperature increased the lattice parameters and crystallite size, while decreased spontaneous strain, cell distortion, orthorhombic distortion and global instability factors. The sintering temperature did not show any significant effect of the atomic percentage of the elemental compositions of the YFeO3, where the powders showed excellent stoichiometry preserving the Y:Fe ratio (1:1). SEM micrographs showed that the YFeO3 powders exhibited quasi-rectangular shape. The magnetic properties showed an improvement of the remnant magnetization and coercivity with increasing the sintering temperature, owing to the decrease of distortion of orthorhombic perovskite structure. The diffuse reflectance UV–vis spectrophotometer was employed to investigate the optical behavior and band gap of the sintered YFeO3 powders at different temperatures. It was noticed that the reflectance bands are blue shifted and the optical band gap is decreased from 2.02 to 1.44eV. This will gave rise to the possibility to use the developed YFeO3 orthoferrites as magnetic recoverable catalyst.

Environmentally friendly and highly efficient synthesis of benzoxazepine and malonamide derivatives using HPA/TPI‐Fe3O4 nanoparticles as recoverable catalyst in aqueous media

A magnetic inorganic–organic nanohybrid material (HPA/TPI‐Fe3O4 NPs) was produced as an efficient, highly recyclable and eco‐friendly catalyst for the one‐pot multi‐component synthesis of malonamide and 2,3,4,5‐tetrahydrobenzo[b][1,4]oxazepine derivatives with high yields in short reaction times (25–35 min) in aqueous media at room temperature. The nanohybrid catalyst was prepared by the chemical anchoring of H6P2W18O62 onto the surface of modified Fe3O4 nanoparticles (NPs) with N‐[3‐(triethoxysilyl)propyl]isonicotinamide (TPI) linker. The magnetic recoverable catalyst was easily recycled at least ten times without any loss of catalytic activity.

Facile synthesis of porous NiCo2O4 nanoflakes as magnetic recoverable catalysts towards the efficient degradation of RhB

Flake-like NiCo2O4 was prepared via a facile chemical reaction process. The NiCo2O4/PMS heterogeneous catalysts can completely degrade RhB within 30 min and display excellent cycling durability.

Cu–EDTA-modified APTMS-Fe3O4@SiO2 core–shell nanocatalyst: a novel magnetic recoverable catalyst for the Biginelli reaction

A novel copper–ethylenediamine tetracarboxylate modified core–shell magnetic catalyst is introduced.

Heterogeneous Fe3O4@chitosan-Schiff base Pd nanocatalyst: Fabrication, characterization and application as highly efficient and magnetically-recoverable catalyst for Suzuki–Miyaura and Heck–Mizoroki C–C coupling reactions

An environmentally friendly palladium-based catalyst supported on magnetite nanoparticles was successfully prepared. FT-IR, XRD, VSM, SEM, EDS and TGA studies have been used to characterize the nanocatalyst. The catalytic activity of the as-prepared catalyst was evaluated as a heterogeneous catalyst for the Suzuki–Miyaura carbon–carbon cross-coupling reaction of aryl halides and phenylboronic acid. Furthermore, it was found that the catalyst showed a high activity for the Mizoroki–Heck reaction of aryl halides and n-butyl acrylate. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture and recycled consecutive five runs without any significant loss in activity.

Phosphotungstic acid supported on silica-coated CoFe2O4 nanoparticles: An efficient and magnetically-recoverable catalyst for N-formylation of amines under solvent-free conditions

Phosphotungstic acid (PTA) was rapidly and efficiently anchored on the surface of silica coated cobalt ferrite core to obtain a new three-component CoFe2O4@SiO2–PTA nanocomposite. The resultant composite was characterized by various techniques, including FT-IR, XRD, SEM, EDX, ICP-AES, and VSM. The as-synthesized nanocomposite was examined as catalyst for N-formylation of various amines under solvent-free conditions at room temperature. Due to the presence of magnetic core in this catalyst, it can be easily separated from the reaction media by applying an external magnetic field. The isolated catalyst can be reused for at least five successive times without significant leaching or loss of its high catalytic activity.

Magnetically recoverable Fe3O4@SBA-15: An improved catalyst for three component coupling reaction of aldehyde, amine and alkyne

We have synthesized Fe3O4 nanoparticles on mesoporous SBA-15 by an “in situ” approach. The synthesized nanocomposite material was well characterized using wide and low angle XRD, N2 adsorption–desorption isotherm, TEM, FTIR, XPS, and VSM analysis. The Fe3O4@SBA-15 nanocomposite material was used as a magnetically recoverable catalyst (MRC) for three component coupling reaction of aldehyde, amine and alkyne. The reported catalyst was recycled up to five times without significant loss in its catalytic activity.

Tributyltin grafted onto the surface of 3-aminopropyl functionalized γ-Fe2O3nanoparticles: a magnetically-recoverable catalyst for trimethylsilylation of alcohols and phenols

Bonding of a homogenous tributyltin chloride catalyst on the surface of functionalized magnetic nanoparticles provides a new stable, efficient and magnetically recyclable catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazan under mild reaction conditions. The catalyst showed good stability and could be reused at least 10 times. The catalyst was characterized using spectroscopic, magnetic, and thermal techniques (FT-IR, SEM, TEM, XRD, ICP, VSM, and TGA).

Preparation of uniform magnetic recoverable catalyst microspheres with hierarchically mesoporous structure by using porous polymer microsphere template

Merging nanoparticles with different functions into a single microsphere can exhibit profound impact on various applications. However, retaining the unique properties of each component after integration has proven to be a significant challenge. Our previous research demonstrated a facile method to incorporate magnetic nanoparticles into porous silica microspheres. Here, we report the fabrication of porous silica microspheres embedded with magnetic and gold nanoparticles as magnetic recoverable catalysts. The as-prepared multifunctional composite microspheres exhibit excellent magnetic and catalytic properties and a well-defined structure such as uniform size, high surface area, and large pore volume. As a result, the very little composite microspheres show high performance in catalytic reduction of 4-nitrophenol, special convenient magnetic separability, long life, and good reusability. The unique nanostructure makes the microspheres a novel stable and highly efficient catalyst system for various catalytic industry processes.

Ni/reduced graphene oxide nanocomposite as a magnetically recoverable catalyst with near infrared photothermally enhanced activity

A nanocomposite of nickel nanoparticles/reduced graphene oxide (Ni/rGO) has been developed as a magnetic recoverable catalyst with near-infrared (NIR) photothermally enhanced activity owing to the magnetic and catalytic properties of Ni nanoparticles as well as the large specific surface area and excellent NIR photothermal conversion property of rGO. By the hydrazine reduction in ethylene glycol, Ni ions, and graphene oxide were reduced simultaneously to form the Ni/rGO nanocomposite. The resulting Ni/rGO nanocomposite with about 62wt.% of Ni nanoparticles was nearly superparamagnetic and possessed good catalytic activity toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with sodium borohydride. The corresponding pseudo-first-order rate constants increased with increasing the temperature and 4-NP concentration, revealing activation energy of 43.7kJ/mol and the synergistic effect of rGO. Furthermore, under NIR irradiation, it was demonstrated that the Ni/rGO could efficiently enhance the reduction rate via the photothermal conversion which might induce the heating of local environment around the Ni nanoparticles and reaction medium. Such a nanocomposite was expected to be helpful in the development of NIR or solar photothermally enhanced catalytic systems.

Polyphosphoric acid supported on silica-coated NiFe2O4 nanoparticles: An efficient and magnetically-recoverable catalyst for N-formylation of amines

Abstract A rapid, green and simple method for the N-formylation of various aromatic amines with formic acid using polyphosphoric acid supported on silica-coated NiFe2O4 magnetic nanoparticles (NiFe2O4@SiO2–PPA) under solvent-free conditions at room temperature has been developed. The magnetic catalyst can be easily removed by a simple magnet and reused at least three times without any loss of its high catalytic activity. In addition to its facility, this protocol enhances product purity and promises economic and also environmental profits.

ChemInform Abstract: H3PW12O40 Supported on Silica‐Encapsulated γ‐Fe2O3 Nanoparticles: A Novel Magnetically‐Recoverable Catalyst for Three‐Component Mannich‐Type Reactions in Water.

AbstractThe separation of the catalyst is achieved by magnetism.

H3PW12O40 supported on silica-encapsulated γ-Fe2O3 nanoparticles: a novel magnetically-recoverable catalyst for three-component Mannich-type reactions in water

A new type of magnetically-recoverable catalyst was synthesized by the immobilization of H3PW12O40 on the surface of silica-encapsulated γ-Fe2O3 nanoparticles. This catalyst was characterized by transmission electron microscopy (TEM), a laser particle size analyzer, infrared spectroscopy (IR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results show that the particles are mostly spherical in shape and have an average size of approximately 94 nm. The characterization data derived from IR spectroscopy reveal that H3PW12O40 on the support exists in the Keggin structure. The acidity of the catalyst was measured by a potentiometric titration with n-butylamine. To our surprise, this very strong solid acid catalyst showed an excellent distribution of acid sites, suggesting that the catalyst possesses a higher number of surface active sites compared to its homogeneous analogues. The activity of the catalyst was probed through one-pot three-component Mannich-type reactions of aldehydes, amines and ketones in water at room temperature. The excellent conversions show that the catalyst has strong and sufficient acidic sites, which are responsible for its catalytic performance. After the reaction, the catalyst/product separation could be easily achieved with an external magnetic field, and more than 95% of the catalyst could usually be recovered. The catalyst was reused at least five times without any loss of its high catalytic activity.

Magnetic recoverable catalysts; assessment on CTAB-stabilized goldnanostructures

Highly active and magnetically recoverable colloidal catalysts were synthesized assembling iron oxide and platinum nanoparticles by means of mesoporous silica that upholds them as a core–shell structured system. Conveniently, these composites present multiple magnetic cores gaining special relevance in the catalyst’s recovery as responding to low magnetic fields. As a proof of concept, they were used to assess the retarded gold reduction in cetyltrimethylammonium bromide (CTAB) micelles, permitting to tune the gold reduction rate and therefore the production of spherical or anisotropic gold nanostructures.

97/00193 Design of magnetic recoverable catalysts for primary coal liquefaction

97/00193 Design of magnetic recoverable catalysts for primary coal liquefaction