Green synthesis of silver nanoparticles using Eucalyptus comadulensis leaves extract and its immobilization on magnetic nanocomposite (GO-Fe3O4/PAA/Ag) as a recoverable catalyst for degradation of organic dyes in water

The magnetically recyclable graphene oxide-Fe₃O₄/polyallylamine (PAA)/Ag nanocatalyst was prepared via a green route using Eucalyptus comadulensis leaves extract as both reducing and stabilizing agent. The catalytic activity of this nanocatalyst was investigated for the reduction reaction of methylene blue and methyl orange in the presence of NaBH₄ in aqueous medium at room temperature. The prepared nanocatalyst was characterized by different methods such as Fourier transformed infrared spectroscopy, X-ray diffraction, scanning electron microscopy–energy dispersive X–ray spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, transmission electron microscopy, and UV–visible spectroscopy. The results show that graphene oxide/PAA/Ag nanocatalyst has good activity and recyclability, and can be reused several times without major loss of activity in the reduction process. The apparent rate constants of the methyl orange (MO) and methylene blue (MB) were calculated to be 0.077 s⁻¹ (3 mg of catalyst) and 0.15 s⁻¹ (2 mg of catalyst), respectively.     

Small Pd nanoparticles supported in large pores of mesocellular foam: an excellent catalyst for racemization of amines

Highly dispersed palladium nanoparticles (1–2 nm) supported in large‐pore mesocellular foam (MCF; 29 nm) were synthesized. The Pd‐nanocatalyst/MCF system was characterized by transmission electron microscopy (TEM), powder X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The performance of the Pd nanocatalyst obtained was examined for amine racemization. The Pd nanocatalyst showed higher activity and selectivity toward racemization of (S)‐1‐phenylethyl amine than any other amine racemization catalyst reported so far and it could be reused several times. Our data from TEM and XRD suggest a restructuring of the Pd nanocatalyst from amorphous to crystalline and an increase in Pd nanocatalyst size during the racemization reaction. This led to an unexpected increase of activity after the first use. The Pd nanocatalyst obtained can be integrated with other resolving processes of racemic organic compounds to increase the yield of chiral organic products.     

A green synthesis of palladium nanoparticles by Sapindus mukorossi seed extract and use in efficient room temperature Suzuki–Miyaura cross‐coupling reaction

A simple and green method for the synthesis of palladium nanoparticles using an aqueous extract of Sapindus mukorossi seed has been demonstrated. The synthesized nanoparticles were characterized using UV–visible spectroscopy, powxder X‐ray diffraction, energy‐dispersive X‐ray analysis and transmission electron microscopy. The nanocatalyst was successfully utilized in an efficient Suzuki–Miyaura cross‐coupling reaction at room temperature.     

Preparation and characterization of a silica‐based magnetic nanocomposite and its application as a recoverable catalyst for the one‐pot multicomponent synthesis of quinazolinone derivatives

An environmentally benign magnetic silica‐based nanocomposite (Fe₃O₄/SBA‐15) as a heterogeneous nanocatalyst was prepared and characterized using Fourier transform infrared and ultraviolet–visible diffuse reflectance spectroscopies, scanning electron microscopy, X‐ray diffraction, vibrating sample magnetometry and Brunauer–Emmett–Teller multilayer nitrogen adsorption. Its catalytic activity was investigated for the one‐pot multicomponent synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones starting from isatoic anhydride, ammonium acetate and various aldehydes under mild reaction conditions and easy work‐up procedure in refluxing ethanol with good yields. The nanocatalyst can be recovered easily and reused several times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Fabrication of nitrogen-enriched graphene oxide/Cu NPs as a highly efficient and recyclable heterogeneous nanocatalyst for the Chan–Lam cross-coupling reaction

Herein, we demonstrate the direct polymerization of melamine and cyanuric chloride in the surface of graphene oxide (GO) (N-enriched GO) in order to develop a new nanocatalyst. The supramolecular polymerized GO acts not only as a spacer to prevent the restacking of graphene sheets but also as a nitrogen source to generate active centers for Cu NP attachments. Subsequently, the nitrogen on the surface of the GO sheets coordinates with copper ions to generate copper nanoparticles. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. This catalyst showed high efficiency and good activity in the Chan–Lam cross-coupling reaction of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, the nanocatalyst was easily recovered and reused for five consecutive runs without any noticeable loss of performance.     

Palladium nanoparticles supported on cucurbit[6]uril: an efficient heterogeneous catalyst for the Suzuki reaction under mild conditions

A new NC palladacycle was synthesized and supported on cucurbit[6]uril (CB[6]). The CB[6]‐supported palladium was used as an efficient nanocatalyst for the Suzuki reaction. In these reactions various aryl halides were reacted with arylboronic acids in H₂O–EtOH at both room temperature and 40 °C. The obtained Pd nanocatalyst exhibited excellent reactivity and stability in C ? C bond formation, which confirms that the catalyst is a completely active heterogeneous species. The Pd nanocatalyst was characterized using X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Anchoring Ni (II) on Fe3O4@tryptophan: A recyclable,green and extremely efficient magnetic nanocatalyst for one‐pot synthesis of 5‐substituted 1H‐tetrazoles and chemoselective oxidation of sulfides and thiols

A green, novel and extremely efficient nanocatalyst was successfully synthesized by the immobilization of Ni as a transition metal on Fe₃O₄ nanoparticles coated with tryptophan. This nanostructured material was characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, inductively coupled plasma optical emission spectroscopy, vibrating sample magnetometry and X‐ray diffraction. The prepared nanocatalyst was applied for the oxidation of sulfides, oxidative coupling of thiols and synthesis of 5‐substituted 1H‐tetrazoles. The use of non‐toxic, green and inexpensive materials, easy separation of magnetic nanoparticles from a reaction mixture using a magnetic field, efficient and one‐pot synthesis, and high yields of products are the most important advantages of this nanocatalyst.     

Nano 5% Fe–ZnO: A highly efficient and recyclable heterogeneous solid nano catalyst for the Biginelli reaction

In this paper, we report the synthesis and catalytic application of 5% Fe–ZnO nanocatalyst for the synthesis of 3,4-dihydropyrimidin-2-one derivatives as a highly efficient heterogeneous nanocatalyst. The structural and morphological features of the synthesized nanocatalysts were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Using Debye-Scherer's formula, the average particle size for undoped ZnO was calculated to be 24.55 nm, while the average particle size for 5% Fe–ZnO was calculated to be 22.37 nm. The high resolution transmission electron microscopy (HR-TEM) revealed a hexagonal crystal lattice type. The Brunauer–Emmett–Teller (BET) surface area of ZnO and 5% Fe–ZnO was found to be 56.50 m²/g and 72.65 m²/g, respectively. Energy Dispersive X-Ray Analysis (EDX) confirmed the elemental composition of undoped ZnO and doped 5% Fe–ZnO nanocatalysts. Biginelli products were produced using a one-pot three-component reaction of urea, β-dicarbonyl compound, and various aromatic aldehydes using 5% Fe–ZnO under clean conditions. It was found that a 5% Fe–ZnO nanocatalyst is a highly efficient heterogeneous nanocatalyst for the synthesis of 3,4-dihydropirimidinones. ¹H NMR and ¹³C NMR analysis was used to confirm the structure of the synthesized Biginelli adducts. This synthetic protocol offers several advantages, including a short reaction time and purity of the synthesized, reusability and ease of catalyst separation, and a clean and quick workup.     

CuI/Fe3O4 NPs@Biimidazole IL‐KCC‐1 as a leach proof nanocatalyst for the synthesis of imidazo[1,2‐a]pyridines in aqueous medium

In the present work, an innovative leach proof nanocatalyst based on dendritic fibrous nanosilica (DFNS) modified with ionic liquid loaded Fe₃O₄ NPs and CuI salts was designed and applied for the rapid synthesis of imidazo[1,2‐a]pyridines from the reaction of phenyl acetylene, 2‐aminopyridine, and aldehydes in aqueous medium. The structure of the synthesized nanocatalyst was studied by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FT‐IR), flame atomic absorption spectroscopy (FAAS), energy‐dispersive X‐ray (EDX), and X‐ray diffraction (XRD), vapor–liquid–solid (VLS), and adsorption/desorption analysis (Brunauer–Emmett–Teller [BET] equation) instrumental techniques. CuI/Fe₃O₄NPs@IL‐KCC‐1 with high surface area (225 m² g^?1) and porous structure not only exhibited excellent catalytic activity in aqueous media but also, with its good stability, simply recovered by an external magnet and recycled for eight cycles without significant loss in its intrinsic activity. Higher catalytic activity of CuI/Fe₃O₄NPs@IL‐KCC‐1 is due to exceptional dendritic fibrous structure of KCC‐1 and the ionic liquid groups that perform as strong anchors to the loaded magnetic nanoparticles (MNPs) and avoid leaching them from the pore of the nanocatalyst. Green reaction media, shorter reaction times, higher yields (71–97%), easy workup, and no need to use the chromatographic column are the advantages of the reported synthetic method.     

CuI heterogenized on thiosemicarbazide modified‐multi walled carbon nanotubes (thiosemicarbazide‐MWCNTs‐CuI): Novel heterogeneous and reusable nanocatalyst in the C‐N Ullmann coupling reactions

Herein we described the synthesis of novel thiosemicarbazide‐MWCNTs‐CuI nanocatalyst by covalent grafting of thiosemicarbazide on carbon nanotubes surface and subsequent coordination with CuI catalyst. The formation of nanocatalyst was analyzed by Raman spectroscopy, energy dispersive spectroscopy (EDS), wavelength‐dispersive X‐ray spectroscopy (WDX) and ICP analysis. The morphology of the nanocatalyst was characterized using scanning and transmission electron microscopes (SEM and TEM). Additionally, the (thiosemicarbazide‐MWCNTs‐CuI) nanocatalyst was successfully employed in the N ‐arylation of indole, amines and imidazoles through intermolecular C(aryl)‐N bond formation from the corresponding aryl halides (Ar–I, Ar–Br, Ar–Cl) with amines through Ullmann‐type coupling reactions. Interestingly, the novel catalyst could be recovered and recycled five times.     

Trisaminomethane–cobalt complex supported on Fe3O4 magnetic nanoparticles as an efficient recoverable nanocatalyst for oxidation of sulfides and C–S coupling reactions

In this work, trisaminomethane–cobalt complex immobilized onto the surface of Fe₃O₄ magnetic nanoparticles was successfully prepared via a simple and inexpensive procedure. The prepared nanocatalyst was considered a robust and clean nanoreactor catalyst for the oxidation and synthesis of sulfides under green conditions. This ecofriendly heterogeneous catalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, inductively coupled plasma-atomic emission spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, X-ray mapping, scanning electron microscopy, and transmission electron microscopy techniques. Use of green medium, easy separation and workup, excellent reusability of the nanocatalyst, and short reaction time are some outstanding advantages of this method.     

Solvent‐free synthesis of propargylamines catalyzed by an efficient recyclable ZnO‐supported CuO/Al2O3 nanocatalyst

An efficient nanocatalyst of ZnO‐supported CuO/Al₂O₃ (CuO/ZnO/Al₂O₃ nanocatalyst) was prepared by the co‐precipitation method and characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray powder diffraction and Brunauer–Emmett–Teller surface area analysis. CuO/ZnO/Al₂O₃ nanocatalyst proved to be a very efficient catalyst on the synthesis of propargylamines under solvent‐free conditions in high yields. Moreover, the catalyst can be recyclable without reducing catalytic activity up to five times.     

Cu(I)-anchored polyvinyl alcohol coated-magnetic nanoparticles as heterogeneous nanocatalyst in Ullmann-type C–N coupling reactions

In this paper, the preparation of a novel magnetic nanocatalyst (Fe₃O₄@PVA/CuCl) is described, which involves coating of polyvinyl alcohol (PVA) onto the surface of Fe₃O₄ nanoparticles and its subsequent coordination with CuCl catalyst. The nanocatalyst was characterized by various analytical methods, including Fourier-transform infrared, X-ray diffraction, inductively coupled plasma spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy, vibrating-sample magnetometry, and EDX elemental mapping. Moreover, the nanocatalyst was efficiently used in the N-arylation of amines via the formation of a carbon–nitrogen bond between the aryl halides and amines by Ullmann-type coupling reactions. The catalyst was sufficiently stable and can be reused for at least seven times in a model Ullmann reaction without remarkable alteration in its catalytic behavior. Heterogeneity of the catalyst was investigated by a hot filtration test.     

Synthesis of 5-substituted 1H-tetrazoles and oxidation of sulfides by using boehmite nanoparticles/nickel-curcumin as a robust and extremely efficient green nanocatalyst

Nickel-anchored curcumin-functionalized boehmite nanoparticles (BNPs@Cur-Ni) as a robust and versatile nanocatalyst was synthesized and well-characterized by using Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray mapping, thermogravimetric analysis (TGA), differential thermal analysis (DTA), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The synthesis of 5-substituted 1H-tetrazoles and the oxidation of sulfides were conducted by BNPs@Cur-Ni with excellent turnover number (TON) and turnover frequency (TOF) outcomes. Also, the catalyst was reused for several sequential runs without Ni leaching or decreasing in reaction yield. Utilizing the curcumin and boehmite with a natural source as well as poly(ethylene glycol) (PEG) as a solvent in this simple protocol can be based on green chemistry rules.     

Cu@KCC-1-NH-CS2 as a new and highly efficient nanocatalyst for the synthesis of 2-amino-4H-chromene derivatives

In the present work, Cu@KCC-1-NH-CS₂ as a green, efficient, and reusable nano-reactor was designed and used for the one-pot, three-component synthesis of 2-amino-4H-chromene derivatives using the reaction of cyclic 1,3-diketones, arylglyoxals, and malononitrile, under reflux conditions in EtOH. Engineered nanocatalyst characterized using different methods including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), adsorption/desorption analysis (BET), and energy dispersive X-ray spectroscopy (EDS). According to the obtained results, presented protocol for the synthesis of 2-amino-4H-chromenes using Cu@KCC-1-NH-CS₂ gave the desired products in higher yields (89–98%) with short reaction times. Also, under mild reaction conditions this green nanocatalyst indicated recyclable behavior five times with minor reduce in its catalytic activity.     

One‐pot multicomponent synthesis of novel 2‐(piperazin‐1‐yl) quinoxaline and benzimidazole derivatives,using a novel sulfamic acid functionalized Fe3O4 MNPs as highly effective nanocatalyst

The immobilization of sulfonic acid on the surface of Fe₃O₄ magnetic nanoparticles (MNPs) as a novel acid nanocatalyst has been successfully reported. The morphological features, thermal stability, magnetic properties, and other physicochemical properties of the prepared superparamagnetic core–shell (Fe₃O₄@PFBA–Metformin@SO₃H) were thoroughly characterized using Fourier transform infrared (FTIR), X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDS), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric analysis–differential thermal analysis (TGA‐DTA), atomic force microscopy (AFM), dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM) techniques. It was applied as an efficient and reusable catalyst for the synthesis of 2‐(piperazin‐1‐yl) quinoxaline and benzimidazole derivatives via a one‐pot multiple‐component cascade reaction under green conditions. The results displayed the excellent catalytic activity of Fe₃O₄@PFBA–metformin@SO₃H as an organic–inorganic hybrid nanocatalyst in condensation and multicomponent Mannich‐type reactions. The easy separation, simple workup, excellent stability, and reusability of the nanocatalyst and quantitative yields of products and short reaction time are some outstanding advantages of this protocol.     

Application of novel and reusable Fe3O4@CoII(macrocyclic Schiff base ligand) for multicomponent reactions of highly substituted thiopyridine and 4H-chromene derivatives

In this research study we designed and synthesized Co^II(macrocyclic Schiff base ligand containing 1,4-diazepane) immobilized on Fe₃O₄ nanoparticles as a novel, recyclable, and heterogeneous catalyst. The nanomaterial was fully characterized using various techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersiveX-ray spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, differential reflectance spectroscopy, Brunauere–Emmette–Teller method, inductively coupled plasma, and elemental analysis (CHNS). Then, the catalytic performance was successfully investigated in the multicomponent synthesis of 2-amino-4-aryl-6-(phenylsulfanyl)pyridine-3,5-dicarbonitrile and 2-amino-5,10-dioxo-4-aryl-5,10-dihydro-4H-benzo[g]chromene-3-carbonitrile derivatives. Furthermore, the catalyst was isolated using a simple filtration, and recovery of the nanocatalyst was demonstrated five times without any loss of activity.     

Synthesis and application of novel 1,2,3‐triazolylferrocene‐containing ionic liquid supported on Fe3O4 nanocatalyst in the synthesis of new pyran‐substituted Betti bases

A novel magnetic ferrocene‐labelled ionic liquid based on triazolium, [Fe₃O₄@SiO₂@Triazol‐Fc][HCO₃], has been synthesized and has been successfully introduced as a recyclable heterogeneous nanocatalyst. The catalytic activity of the novel magnetic nanoparticles was evaluated in the one‐pot three‐component synthesis of a wide variety of Betti bases. A simple, facile and highly efficient green method has been developed for the synthesis of kojic acid‐containing Betti base derivatives at room temperature. Additionally, this new protocol has notable advantages such as short reaction times, green reaction conditions, high yields and simple workup and purification steps. Also, the novel nanocatalyst could be easily recovered using an external magnetic field and reused for six consecutive reaction cycles without significant loss of activity. The newly synthesized nanocatalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller measurements.     

Ultrasound assisted eco-friendly synthesis of 3-cinnamoyl coumarins using N,N'-(1,2-phenylene)bis(2-aminobenzamide) dichloro cobalt immobilized on mesoporous Al-SBA-15 as a new and recyclable catalyst

ABSTRACT

A novel mesoporous Al-SBA-15 modified by N,N'-(1,2-phenylene)bis(2-aminobenzamide) dichloro cobalt has been prepared and applied as a reusable catalyst in the 3-cinnamoyl coumarins synthesis via three-component reaction between benzaldehydes, salicylaldehydes and ethyl acetoacetate by the assist of ultrasonic irradiation. By using of the nanocatalyst and also ultrasound irradiation, the easiness and velocity of the abovementioned reaction were enhanced and an environment friendly condition was provided to synthesis of various 3-cinnamoyl coumarin compounds. The properties and structure of nanocatalyst have been specified by methods including powder X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis and scanning electronic microscopy (SEM). Superiority of this novel and viable method is due to mild reaction condition, short reaction times, high yields of 3-cinnamoyl coumarins, environmentally benign, recoverability of the CoCl₂N,N'-(1,2-phenylene)bis(2-aminobenzamide)/Al-SBA-15 catalyst and reusability with important preservation in its catalytic activity.     

A palladium complex immobilized onto mesoporous silica: a highly efficient and reusable catalytic system for carbon–carbon bond formation and anilines synthesis

A palladium complex supported on functionalized mesoporous silica MCM-41 proved to be a highly efficient, recoverable catalyst for C–C coupling reactions and amination of aryl halides to afford anilines. The nanocatalyst was characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption isotherms and inductively coupled plasma analysis. The catalyst could be reused for several consecutive runs without significant loss of activity. The excellent yields of products, simple reaction procedures and short reaction times are the main advantages of this methodology.