Separable Heterogeneous Catalyst Research Articles

Environmentally Benign and Expeditious Access to 4‐Aryl Methylene‐isoxazole‐5(4H)‐Ones Using Magnetically Separable Nanoparticles

AbstractAn environmentally benign and expeditious protocol was developed for the one‐pot multicomponent synthesis of 4‐aryl‐3‐methylisoxazol‐5(4H)‐ones by the condensation of aldehyde, hydroxyl amine hydrochloride, and ethyl acetoacetate in 50% aq. ethanol at 50 °C. The reaction was catalyzed by magnetically separable carbon microspheres co‐decorated with nanosized iron sulfide and magnetite nanoparticles in 10 wt% amount. The FeS1‐x‐Fe3O4/C nanocatalyst was prepared from iron(III) sulfate loaded iminodiacetate group functionalized styrene‐divinylbenzene based ion exchanger by pyrolysis reaction performed at 600 °C for 4 h. The use of magnetically separable heterogeneous catalyst, aqueous ethanol, short reaction time (30 min), and nonchromatographic purification methods are the striking features of the developed protocol. The isolated yield of the condensation products varied between 81% and 96%. Furthermore, the protocol exhibits high functional group tolerance and includes the use of noncorrosive, nonhazardous reaction conditions affording the product in excellent yields and short reaction time.

Core–shell magnetic mesoporous 3-aminophenol–formaldehyde resin microspheres with rich functional groups via interface co-assembly and polymerization

Core–shell magnetic mesoporous 3-aminophenol–formaldehyde resin microspheres were designed to immobilize Au nanoparticles for use as magnetically separable heterogeneous catalysts for the efficient hydrogenation of 4-nitrophenol at room temperature.

Facile synthesis of anthracene-based derivatives via a magnetically retrievable Fe3O4@SiO2 immobilized selenoether functionalised NHC-Pd(II) heterogenous catalyst: Photophysical, electrochemical and DFT studies of novel 9,10-anthracene based derivatives

A series of anthracene-based derivatives, which are promising candidates for Organic light-emitting diode (OLEDs) applications, have been synthesized through the Suzuki Miyuara cross-coupling reaction of dibromo anthracene and phenylboronic acids derivatives. A magnetically separable heterogeneous catalyst Fe3O4@SiO2@NHC^SePh-Pd(II) was used, and the coupling reaction was investigated under aerobic conditions using water as a green solvent. A very mild approach for the arylation of the 9,10-dibromo anthracene molecules was adopted to harvest a series of highly conjugated anthracene derivatives. The catalyst was reused for up to seven catalytic cycles without much loss in catalytic efficiency. The 55% transformation in the seventh catalytic cycle indicates the catalyst's robustness and high catalytic potential. Necessary photophysical studies were conducted for selected synthesized anthracene-based derivatives, which includes the absorption, emission and cyclic voltammetric studies. Moreover, the thermogravimetric analysis (TGA) was also conducted to check the thermal stability of the compounds. Finally, a Density Functional Theory (DFT) study was conducted, and it revealed that comparing two anthracene derivatives, the Highest occupied molecular orbital (HOMO) and Least unoccupied molecular orbital (LUMO) energy levels, as well as the HOMO-LUMO gap (HLG), differ, with 9-([1,1′-biphenyl]-4-yl)-10-(4-fluorophenyl) anthracene exhibiting a relatively large HLG. The HOMO is localised along the molecule's main axis, while the LUMO is more delocalised on atoms.

An efficient protocol for the synthesis of pyridines and hydroquinolones using IRMOF-3/GO/CuFe2O4 composite as a magnetically separable heterogeneous catalyst

This study reports a facile and cost-effective technique for preparing magnetic copper ferrite nanoparticles supported on IRMOF-3/GO [IRMOF-3/GO/CuFe2O4]. The synthesized IRMOF-3/GO/CuFe2O4 was characterized with IR, SEM, TGA, XRD, BET, EDX, VSM, and elemental mapping. The prepared catalyst revealed higher catalytic behavior in synthesizing heterocyclic compounds through a one-pot reaction between various aromatic aldehydes, diverse primary amines, malononitrile, and dimedone under ultrasound irradiations. Among the notable features of this technique are higher efficiency, easy recovery from the reaction mixture, removal of a heterogeneous catalyst, and uncomplicated route. In this catalytic system, the activity level was almost constant after various stages of reuse and recovery.

Activation of peroxymonosulfate by a magnetic Co doped NiFe2O4 catalyst for efficient Bisphenol A degradation in water

BackgroundSulfate radicals-based advanced oxidation process (AOPs) were considered to be an effective process for treating organic wastewater. However, the difficult separation of catalysts and the toxicity of metal ions may cause secondary pollution. A new efficient and separable heterogeneous catalyst is desirable to be explored. MethodsMagnetic porous Co-doped NiFe2O4 (CoxNi1-xFe2O4, x = 0, 0.05, 0.2 and 0.5), prepared by a simple sol-gel method, were used as heterogeneous catalysts for the removal of Bisphenol A (BPA) in aqueous solution by the generation of strong oxidizing radicals and reactive oxygen species from activating peroxymonosulfate (PMS). Significant findingsCo addition increased the saturation magnetism of the catalyst and decreased the redox preparation temperature. Increasing the amount of Co-doping resulted in a pronounced enhancement of BPA removal, which the removal rate increased by 33.6% with Co-doping amount from 0 to 0.2. The hydroxyl groups on the catalyst surface plays a vital role in activating PMS, and the main reactive species for BPA degradation was determined as sulfate radical (SO4•-) and singlet oxygen (1O2) in Co0.2Ni0.8Fe2O4/PMS system. The conversion of Ni2+/Ni3+, Co2+/Co3+, and O2-/O2 for maintaining Co0.2Ni0.8Fe2O4 charge balance, PMS was activated simultaneously.

Green synthesis and characterization of mixed-phase Fe2O3 nanorods as a novel magnetically recoverable heterogeneous catalyst for Biginelli synthesis

For the first time, mixed-phase (Hematite and Maghemite) magnetic Fe2O3 nanorods were successfully biosynthesis by sol-gel auto-combustion method using the 1:1 mixture of Eucalyptus citriodora and Murraya koenigii leaf extract as a capping agent, and its catalytic effect on synthesis of 6-(chloromethyl)-1,2,3,4-tetrahydro-2-pyrimidinone (THPMs) derivatives were investigated. Further, the phase formation, surface topography, and crystallinity of biosynthesized Fe2O3 nanorods (NRs) were explored using powder XRD (X-Ray Diffraction), UVDRS (UV–Visible Reflectance Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), FESEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive X-Ray), and VSM (Vibrating Sample Magnetometry). Furthermore, the catalytic activity of biosynthesized Fe2O3 NRs (C1, C2, and C3) was examined for one-pot synthesis of ethyl 6-(chloromethyl)-1,2,3,4-tetrahydro-2-oxo-4-arylpyrimidine-5-carboxylate via Biginelli reaction. To achieve high yields (93–99 %) of 6-(chloromethyl)-1,2,3,4-tetrahydro-2-pyrimidinone derivatives, this heterogeneous catalytic method is used with a wide range of aromatic aldehydes within a minimum reaction time, simple reaction work-up, and easily recoverable catalyst by an external magnet. The recovered catalyst is then employed for five successive cycles without non-noticeable loss of catalytic activity. We believe that this protocol presents a broad scope for Biginelli reaction through greenly produced and magnetically separable heterogeneous catalysts.

Synthesis and characterization of titanium-substituted nanocrystalline Co2-Y hexaferrite: magnetically retrievable photocatalyst for treatment of methyl orange contaminated wastewater.

Rapid industrial growth causes considerable environmental havoc, adversely affecting human and aqueous life. It becomes a significant concern to deal with adequate wastewater treatment strategies by converging on water scarcity. This research work explored the synthesis of titanium-substituted Y-type barium hexaferrite (Co2-Y), having a general formula of Ba2Co2Fe12-xTixO22 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5), using a facile nitrate-based sol-gel auto-combustion route and its suitability was investigated as a heterogeneous catalyst within the photo-Fenton-based degradation of methyl orange (MO), one of the significant pollutants generated from textile industries. Developing a thermochemically stable and magnetically separable heterogeneous catalyst for photocatalytic decomposition of nonbiodegradable organic dye from wastewater was also emphasized. The as-prepared nanocrystalline Co2-Y powders were analyzed using XRD, FTIR, DLS, UV-visible spectroscopy, SEM, VSM, and XPS. Furthermore, the photocatalytic degradation performance of pristine and titanium substituted Ba2Co2Fe11.6Ti0.4O22 ferrite, having the lowest bandgap value among all samples, was quantified and compared in terms of apparent rate constant (karc) value and turnover frequency values. The enriched photocatalytic performance was correlated with the existence of multi-valance states of transition metal cations and the availability of oxygen vacancy, confirmed by the surface chemistry using the XPS analysis. The modified (enhanced thermal and chemical stability) hexaferrite catalyst was magnetically separable and reusable without significant losses to its catalytic performance. This promising catalyst may be considered as a replacement for soft ferrite materials to catalyze the degradation of several other nonbiodegradable organic pollutants from wastewater in large-scale industries.

A post-sulfonated one-pot synthesized magnetic cellulose nanocomposite for Knoevenagel and Thorpe-Ziegler reactions.

The development of biodegradable and active cellulosic-based heterogeneous catalysts for the synthesis of different organic compounds would be attractive in pharmaceutical and petrochemical-related industries. Herein, a post-sulfonated composite of one-pot synthesized magnetite (Fe3O4) and cellulose nanocrystals (CNCs) was used as an effective and easily separable heterogeneous catalyst for activating the Knoevenagel and Thorpe-Ziegler reactions. The composite was developed hydrothermally from microcrystalline cellulose (MCC), iron chlorides, urea, and hydrochloric acid at 180 °C for 20 h in a one-pot reaction. After collecting the magnetic CNCs (MCNCs), post-sulfonation was performed using chlorosulfonic acid (ClSO3H) in DMF at room temperature producing sulfonated MCNCs (SMCNCs). The results confirmed the presence of sulfonated Fe3O4 and CNCs with a hydrodynamic size of 391 nm (±25). The presence of cellulose was beneficial for preventing Fe3O4 oxidation or the formation of agglomerations without requiring the presence of capping agents, organic solvents, or an inert environment. The SMCNC catalyst was applied to activate the Knoevenagel condensation and the Thorpe-Ziegler reaction with determining the optimal reaction conditions. The presence of the SMCNC catalyst facilitated these transformations under green procedures, which enabled us to synthesize a new series of olefins and thienopyridines, and the yields of some isolated olefins and thienopyridines were up to 99% and 95%, respectively. Besides, the catalyst was stable for five cycles without a significant decrease in its reactivity, and the mechanistic routes of both reactions on the SMCNCs were postulated.

Microstructural investigation of sonochemically synthesized Zn substituted CuFe2O4 nanoparticles for heterogeneous green catalytic click chemistry and dye degradation

Heterogeneous green catalysis by means of magnetically separable nanometal–oxide catalysts is an attractive field of present day research. The microstructural characterization, optical and magnetic properties of sonochemically synthesized Zn substituted CuFe2O4 (CZF) nanoparticles (NPs) are investigated and compared with the unsubstituted CuFe2O4. PXRD (powder X-ray diffraction) pattern and HRTEM (high-resolution transmisson electron microscopy) observation with FTIR (Fourier transform infrared) spectroscopy are applied to analyze the microstructural and optical properties of nanosized (∼14.7 nm) zinc substituted copper ferrite. Rietveld refinement of the PXRD pattern reveals the mixed spinel structure of zinc substituted copper ferrite NPs. Magnetic data confirms the presence of ferromagnetic/ferrimagnetic phase with some admixture of finer superparamagnetic (SPM) nanophases within the sample. The lack of saturation in the M-H loops is due to the presence of spin-canting as well as SPM NPs in the system. These coupled Zn substituted CuFe2O4 magnetic NPs are used as a heterogeneous catalyst for three-component Huisgen 1,3-dipolar CuAAC green catalytic click reactions in aqueous media and dye degradation. Its catalytic reactivity has been compared with CuFe2O4 NPs. By this synthesized magnetic catalytic CZF NPs, we have successfully coupled alkyl halides and boronic acids with terminal alkynes to obtain 1,4-disubstituted 1,2,3-triazoles in good to excellent yields within a short time. The Heterogeneity, reproducibility and reusability of the catalyst has been also tested successfully up to several cycles without significant decrease in the product yield. We have explored CZF NPs as magnetically separable heterogeneous green catalyst for multi-component click reaction. Our synthesized CZF NPs has been used as photocatalyst for the photo degradation of organic dyes under visible light irradiation. The results demonstrate that the unique features of the CZF NPs make it an excellent material for a click chemistry catalyst as well as a highly active photocatalyst under visible light irradiation.

Synthesis of a Pyrrolo[1,2-a]quinazoline-1,5-dione Derivative by Mechanochemical Double Cyclocondensation Cascade.

N-heterocyclic compounds, such as quinazolinone derivatives, have significant biological activities. Nowadays, as the demand for environmentally benign, sustainable processes increases, the application of compounds from renewable sources, easily separable heterogeneous catalysts and efficient, alternative activation methods is of great importance. In this study, we have developed a convenient, green procedure for the preparation of 3a-methyl-2,3,3a,4-tetrahydropyrrolo[1,2-a]quinazoline-1,5-dione through a double cyclocondensation cascade using anthranilamide and ethyl levulinate. Screening of various heterogeneous Brønsted acid catalysts showed that Amberlyst® 15 is a convenient choice. By applying mechanochemical activation in the preparation of this N-heterotricyclic compound for the first time, it was possible to shorten the necessary time to three hours compared to the 24 h needed under conventional conditions to obtain a high yield of the target product.

PANI-Fe3O4@ZnO nanocomposite as magnetically recoverable organometallic nanocatalyst promoted synthesis of new Azo chromene dyes and evaluation of their antioxidant and antimicrobial activities.

A new series of azo chromene dyes were synthesized via a facile cyclocondensation reaction of (E)-1,2-diphenyl-1-diazene and 4-aminocoumarin with 1:2 molar ratio catalyzed by the polyaniline-Fe3O4@ZnO nanocomposite (PANI-Fe3O4@ZnO). The salient features of this protocol lie in simple experimental procedure, moderate reaction conditions, and uses PANI-Fe3O4@ZnO nanocomposite as a magnetically separable heterogeneous catalyst. Two well-known methods were employed for assessing the antioxidant abilities of the target compounds, including free radical trapping of 2,2-diphenyl-1-picrylhydrazyl (DPPH), as well as ferric reducing antioxidant power assay. Also, several synthesized compounds were screened for their in vitro antimicrobial activities by employing the disk diffusion test on Gram-negative as well as Gram-positive bacteria.

Fe3+-doped ordered mesoporous γ-Fe2O3/SiO2 microspheres as a highly efficient magnetically separable heterogeneous Fenton catalyst

Here, several γ-Fe2O3/SiO2 nanocomposite microspheres were synthesized, characterized and tested as magnetically separable heterogeneous catalysts in an advanced oxidation process. A strong relation between the structure and the activity of these materials was evidenced. Two parameters, including the porosity of the silica support and the doping of the material with Fe3+ ions in addition to the γ-Fe2O3 nanoparticles, were investigated. The structure of the catalytic materials was determined by the use of different methods, in particular SEM, TEM, XRD, N2 physisorption, magnetometry, UV–Vis spectroscopy and XPS. The results demonstrated that the irregular microporosity of the silica framework can be replaced by an ordered mesoporosity, adding a second surfactant during the synthesis. For the mesoporous material, it was observed that the additional Fe3+ are dispersed in the mesoporous silica framework as individual cations and small clusters of Fe(III) species. The materials were tested as heterogeneous Fenton catalysts on two model aqueous pollutants, methyl orange (MO) and reactive black 5 (RB5). It was observed that the oxidation and mineralization rates of the two dyes is significantly enhanced when a doped catalytic material is used. This effect is particularly strong with the mesoporous silica support. In addition, the doped mesoporous catalyst retained its activity for a large range of conditions. These improvements were attributed to the strong activity of the additional Fe(III) species, although the presence of the mesoporosity also plays a significant role.

Magnetically separable ZnFe2O4 nanoparticles: A low cost and sustainable catalyst for propargyl amine and NH-triazole synthesis

The multicomponent reaction (MCR) strategy for the construction of important molecular scaffolds is in trending nowadays and among them, A3-coupling stands in a significant position. Aldehyde, amine and alkynes are coupled in this particular reaction via C-H activation process. Herein, we have reported zinc ferrite nanoparticles as magnetically separable heterogeneous catalyst for A3-coupling reaction with attractive attributes like excellent productivity, selectivity and better reusability. Moreover, the catalyst can also be effectively applied for the synthesis of various NH-triazoles with quantitative yields of the products. A plausible mechanism has been proposed for the synthesis of NH-triazoles followed by validation with computational study.

Efficient magnetically separable heterogeneous platinum catalyst bearing imidazolyl schiff base ligands for hydrosilylation

Reported herein is a magnetically separable heterogeneous nano catalyst Fe3O4@SiO2-biIMI- PtCl2, which is prepared by firstly applying a SiO2 coating onto readily synthesized magnetite nanoparticles via the hydrolysis condensation of tetraethyl orthosilicate (TEOS) under basic conditions, then modifying it using aminopropyl triethoxysilane and bis(imidazole) aldehyde, and finally incorporating a PtCl2 complex via coordination chemistry. The chemical structure and morphology of the nanocatalyst as well as the valence state and content of platinum within this catalyst were carefully characterized. This catalyst can mediate the hydrosilylation between 1-octene and hydrosilane, with the conversion of 1-octene reaching up to 99%, and it shows good regioselectivity as only β-adducts are identified. In addition, this catalyst can be reused for at least 5 cycles. The hydrosilylation reaction between different olefins and hydrosilanes can also be efficiently mediated by Fe3O4@SiO2-biIMI-PtCl2.

Magnetic Fe3O4 nanoparticles as easily separable catalysts for efficient catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol

Magnetic Fe3O4-12 nanoparticles, an easily separable heterogeneous catalyst, exhibits high catalytic performance in the catalytic transfer hydrogenation (CTH) reaction of biomass-derived furfural (FAL) to furfuryl alcohol (FOL) with 2-propanol (2-PrOH) as the hydrogen source (90.1 % FOL yield at 160 °C for 5 h). Comparing Fe3O4 nanoparticles with different particle sizes found that the smaller the nanoparticles, the larger the BET surface area, pore volume and pore diameter, resulting in more acid-base active sites through BET, SEM, TEM, NH3-/CO2-TPD and other characterizations. Moreover, a scaled-up CTH experiment of FAL and a stepwise reaction from xylose to FOL verified that the catalytic system has great industrial application prospects. A feasible flowchart of the chemical process from xylose to FOL was designed, which can realize the regeneration of biomass resources (xylose derived from corncob), the reuse and recycling of catalysts and solvents, and minimize the amount of solvents and pollutant emissions.

Reduced graphene oxide/iron oxide hybrid composite material as an efficient magnetically separable heterogeneous catalyst for transfer hydrogenation of ketones

Reduced graphene oxide was synthesized and functionalized with FeSO4⋅7H2O to form a reduced graphene oxide/iron oxide hybrid composite. The hybrid composite was extensively characterized using various techniques. Its application for transfer hydrogenation of various ketones was studied. The investigation showed that it serves as a good catalyst for transfer hydrogenation of aromatic and some aliphatic ketones resulting in excellent isolated yields (97–99%) of products. It is magnetically separable showing good reusability. The products were characterized and compared with authentic ones.

Carbon-based solid acids: a review

Green chemistry has fostered research on recyclable, insoluble and easily separable heterogeneous catalysts. Carbon materials are widely used for renewable energy and environmental studies. Here, we review the synthesis, properties and applications of carbon solid acids in the form of biomass, polymers, and carbon/silica-based catalysts. We show in particular that mesoporosity has a major role in catalysis, notably when bulk materials are transformed into valuable products.

Green Fabrication of 2D Fe3O4/Mg(OH)2 and 2D Fe3O4/MgO Nanocomposites Using [OMIM]Br Ionic Liquid and Comparing Catalytic Activity with Green Metrics

In this article, Fe3O4 nanoparticles, 2D Fe3O4/Mg(OH)2, and 2D Fe3O4/MgO nanocomposites were synthesized using ionic liquid [OMIM]Br as green designer and stabilizer at ambient pressure. Here, we report a special method for a sandwich like magnetic nanocomposites synthesis. The characterization of these nanocomposites was performed by IR, XRD, SEM, TEM, BET, and VSM techniques. Synthesized nanostructures were employed in the synthesis of 4H-chromene, 4H-pyran, and oxepine derivatives in three-component tandem reactions. Although, Fe3O4/Mg(OH)2 nanocomposite, as magnetically separable heterogeneous catalyst, has showed lower surface area in comparison to Fe3O4/MgO, exhibited a significant enhancement in the yield of the desired products. The described protocol has various advantages including simple work-up, mild reaction condition, green solvent, and the high atomic economy that make attractive procedure. The nanocatalysts exhibited remarkable reusable activity. Also, investigation of green chemistry metrics approved that Fe3O4/Mg(OH)2 nanocomposites play an essential role in the improvement of the reaction yield of 4H-chromene, among other products.

Heterogeneous Cr-zeolites (USY and Beta) for the conversion of glucose and cellulose to 5-hydroxymethylfurfural (HMF)

For the first time, the heterogeneous calcined forms of chromium loaded USY, ZSM-5 and Beta zeolites were studied for the synthesis of HMF from glucose and cellulose in different solvents such as 1-butyl-3-methylimidazolium chloride (BMIMCl) and dimethyl sulfoxide (DMSO). Catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, inductive coupling plasma-mass spectrometry and temperature programmed desorption (NH3-TPD). It was found that calcined forms of chromium-zeolites provide better HMF yield in (BMIMCl) ionic liquid than chromium-free zeolites. The 58.8% and 54.5% HMF yields from glucose and 34.1% and 34.3% HMF yields from cellulose were obtained at 130 °C after 60 min in BMIMCl ionic liquid with Cr-Beta (SiO2/Al2O3 = 28) and Cr-USY (SiO2/Al2O3 = 6) zeolites, respectively. 35% HMF yield was achieved with heterogeneous Cr-USY (SiO2/Al2O3 = 6) zeolite at 160 °C after 90 min in DMSO. However, HMF yield from cellulose was not observed in DMSO. Although chromium leaching from catalyst occurred in BMIMCI solvent, no loss of catalytic activity and no chromium leaching from catalyst was observed in DMSO for five times recycling reactions. It can be said that DMSO is highly suitable solvent for easily separable heterogeneous Cr-USY catalyst for glucose to HMF conversion.

Ag3[PMo12O40]: An efficient and green catalyst for the synthesis of highly functionalized pyran‐annulated heterocycles via multicomponent reaction

A facile, efficient and eco‐friendly catalytic protocol was developed for the synthesis of medicinally important pyran‐annulated heterocycles via multicomponent reaction (MCR). Cyclocondensation of differently substituted aromatic aldehydes, malononitrile/ethyl cyanoacetate and various β‐dicarbonyl compounds in the presence of Ag3[PMo12O40]⋅nH2O as heterogeneous catalyst, in EtOH–H2O, afforded diverse pyran‐fused chromene analogues. The merits observed for this approach were it being conducted via MCR, using commercially available or easily accessible starting materials in the presence of a green and easily separable heterogeneous and reusable catalyst, and affording high yields of desired products in very short reaction times with high purity in one‐pot fashion, thus providing a superior alternative approach for the synthesis of pyran‐annulated heterocycles.