Catalytic Hydrodechlorination of 1,2,4,5‐Tetrachlorobenzene over Various Supports Loaded Palladium Catalysts

Water pollution by polychlorinated aromatic hydrocarbons has always been a global issue. In this work, we reported a synthesis of supported palladium catalysts Pd/C, Pd/CeO₂, Pd/SBA‐15, Pd/ZrO₂,Pd/SiO₂, and Pd/Al₂O₃ as well as their catalytic activities on hydrodechlorination (HDC) of 1,2,4,5‐tetrachlorobenzene (TeCB). These Pd catalysts were characterized by Brunauer‐Emmett‐Teller (BET) specific surface area, Transmission electron microscopy (TEM), X‐ray diffraction (XRD), energy Dispersive X‐ray Fluorescence (EDXRF), CO‐chemisorption, and H2‐temperature programmed reduction (H2‐TPR) analysis. Pd/C, Pd/CeO₂ and Pd/SBA‐15 catalysts showed relatively high catalytic activities. The catalytic activities were associated with dispersion of Pd, metal surface area, and reaction temperature, etc.     

Zn3(BTC)2 as a Highly Efficient Reusable Catalyst for the Synthesis of 2‐Aryl‐1H‐Benzimidazole

Zn₃(BTC)₂ metal‐organic frameworks as recyclable and heterogeneous catalysts were effectively used to catalyze the synthesis of benzimidazole derivatives from o‐phenylendiamine and aldehydes in ethanol. This method provides 2‐aryl‐1H‐benzimidazoles in good to excellent yields with little catalyst loading. The catalyst was characterized using different techniques such as X‐ray diffraction (XRD), energy dispersive X‐ray (EDX) analysis, scanning electron microscopy (SEM), and Fourier transform infrared (FT‐IR) spectroscopy.     

A Non‐Enzymatic Glucose Sensor Based on Ni/MnO2 Nanocomposite Modified Glassy Carbon Electrode

A novel flower like 3D nickel/manganese dioxide (Ni/MnO₂) nanocomposite was synthesized by a kind of simple electrochemical method and the formation mechanism of flower like structure was also researched. In addition, morphology and composition of the nanocomposite were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). Then the Ni/MnO₂ nanocomposites were applied to fabricate electrochemical non‐enzymatic glucose sensor. The electrochemical investigation for the sensor indicated that it possessed an excellent electrocatalytic property for glucose, and could applied to the quantification of glucose with a linear range from 2.5×10^?7 to 3.5×10^?3 M, a sensitivity of 1.04 mA mM^?1 cm^?2, and a detection limit of 1×10^?7 M (S/N=3). The proposed sensor also presented attractive features such as interference‐free, and long‐term stability. The present study provided a general platform for the one‐step synthesis of nanomaterials with novel structure and can be extended to other optical, electronic and magnetic nanocompounds.     

Fe3O4‐supported Schiff‐base copper (II) complex: A valuable heterogeneous nanocatalyst for one‐pot synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives

A novel Cu (II) Schiff‐base complex immobilized on core‐shell magnetic Fe₃O₄ nanoparticles (Fe₃O₄@SPNC) was successfully designed and synthesized. The structural features of these nanoparticles were studied and confirmed by using various techniques including FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD), wavelength dispersive X‐ray spectroscopy (WDX), and inductively coupled plasma (ICP). These newly synthesized nanoparticles have been used as efficient heterogeneous catalytic system for one‐pot multicomponent synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives. Notably, the catalyst could be easily separated from the reaction mixture by using an external magnet and reused for several successive reaction runs with no significant loss of activity or copper leaching. The present protocol benefits from a hitherto unreported MNPs‐immobilized Cu (II) Schiff‐base complex as an efficient nanocatalyst for the synthesis of newly reported derivatives of pyrano[2,3‐b]pyridine‐3‐carboxamide from one‐pot multicomponent reactions.     

Synthesis and characterization of a novel magnetic nano‐palladium Schiff base complex: application in cross‐coupling reactions

A novel and task‐specific nano‐magnetic Schiff base ligand with phosphate spacer using 2‐aminoethyl dihydrogen phosphate instead of usual coating agents, i.e. tetraethoxysilane and 3‐aminopropyltriethoxysilane, for coating of nano‐magnetic Fe₃O₄ is introduced. The nano‐magnetic Schiff base ligand with phosphate spacer as a novel catalyst was synthesized and fully characterized using infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies, thermogravimetry, derivative thermogravimetry, vibrating sample magnetometry, atomic force microscopy, X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectroscopy. The resulting task‐specific nano‐magnetic Schiff base ligand with phosphate spacer was successfully employed as a magnetite Pd nanoparticle‐supported catalyst for Sonogashira and Mizoroki–Heck C–C coupling reactions. To the best of our knowledge, this is the first report of the synthesis and applications of magnetic nanoparticles of Fe₃O₄@O₂PO₂(CH₂)₂NH₂ as a suitable spacer for the preparation of a designable Schiff base ligand and its corresponding Pd complex. So the present work can open up a new and promising insight in the course of rational design, synthesis and applications of various task‐specific magnetic nanoparticle complexes. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Core‐Shell Selenium/Carbon Colloids and Hollow Carbon Capsules

A novel Se/C nanocomposite with core‐shell structures has been prepared through a facile one‐pot microwave‐induced hydrothermal process. The new material consists of a trigonal‐Se (t‐Se) core and an amorphous‐C (a‐C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy‐dispersive X‐ray (EDX) spectroscopy, and X‐ray photoelectron spectroscopy (XPS).     

Magnetic nanoporous MCM‐41 supported ionic liquid/palladium complex: An efficient nanocatalyst with high recoverability

In this study, a novel magnetic mesoporous MCM‐41 silica supported ionic liquid/palladium complex (Fe₃O₄@MCM@IL/Pd) with core‐structure was prepared and characterized and its catalytic performance was developed under green conditions. The Fe₃O₄@MCM@IL/Pd was prepared via a post grafting method and was characterized using Fourier transform infrared spectroscopy, thermal gravimetric analysis, wide‐ and low‐angle powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, vibration sample magnetometer and energy‐dispersive X‐ray analyses. This was applied as an efficient and recoverable nanocatalyst for the one‐pot synthesis of pyrano[2,3‐d]pyrimidine derivatives under ultrasonic conditions. The catalyst was magnetically recovered and reused for 12 consecutive cycles without significant loss of its activity and selectivity.     

Pd‐ Dithizone grafted onto magnetic nanoparticles and study of its catalyticactivity in C‐C and C‐N coupling reactions

In this paper, we report a simple, facile and efficient method for the synthesis of Fe₃O₄/SiO₂‐DTZ‐Pd. The immobilized palladium was an efficient catalyst without addition of phosphine ligands for Stille, Heck and N‐arylation reactions. This method has some advantages such as high yields and easy work up of products. In addition, the catalyst can be recovered using a magnet and reused several times without significant loss of its catalytic activity. This catalyst was characterized by various physico‐chemical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and inductively coupled plasma (ICP).     

A three‐component process for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐one derivatives using nanosized nickel aluminate spinel crystals as highly efficient catalysts

NiAl₂O₄ spinel nanocrystals were synthesized as mesoporous catalysts and were fully characterized using Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction patterns (XRD), scanning electron microscopy (SEM), and Energy‐dispersive X‐ray spectroscopy (EDS). These nanocrystals catalyzed the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐one derivatives via a one‐pot, three‐component condensation reaction of aromatic aldehydes, isatoic anhydride, and ammonium acetate or primary aromatic amine under microwave irradiation. By far, the most obvious advantages of the offered process are efficiency and recyclability of the catalyst as well as a significantly shorter reaction time.     

Efficient four‐component synthesis of spiroindole derivatives catalysed by a versatile and reusable nano‐paramagnetic catalyst

A simple, efficient and environmentally benign route was developed for the preparation of spiro(indoline‐3,4‐pyrano[2,3‐c ]pyrazole) derivatives with good yields from condensation of isatins, malononitrile (or ethyl cyanoacetate), hydrazine hydrate and ethyl acetoacetate catalysed by PFu@Fe₃O₄ nanocomposite. The use of easily available catalyst, shorter reaction times, better yields, simplicity of reaction, heterogeneous system and easy work‐up are the advantages of the method presented. Characterization of the catalyst was performed using Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy.     

CoFe2O4@SiO2‐CPTES‐Guanidine‐Cu(II): A novel and reusable nanocatalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and polyhydroquinolines and oxidation of sulfides

CoFe₂O₄@SiO₂‐CPTES‐Guanidine‐Cu(II) magnetic nanoparticles were synthesized and used as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of polyhydroquinolines and 2,3‐dihydroquinazoline‐4(1H)‐ones and for the oxidation of sulfides. The structure of this nanocatalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and inductively coupled plasma optical emission spectrometry. Simple preparation, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst are some of the advantages of this protocol.     

Application of the Fe3O4@1,10‐phenanthroline‐5,6‐diol@Mn nano‐catalyst for the green synthesis of tetrazoles and its biological performance

The Fe₃O₄ magnetic particles were modified with 1,10‐phenanthroline‐5,6‐diol (Phen) and the related Mn complex (Fe₃O₄@Phen@Mn) synthesized as a heterogeneous catalyst to be used for the one‐pot three‐component synthesis of various tetrazoles. The catalysts were characterized by several methods, such as the elemental analysis, FT‐IR, X‐ray powder diffraction, dispersive X‐ray spectroscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric‐differential thermal analysis, vibrating sample magnetometer and X‐ray photoelectron spectroscopy. In addition, the antioxidant and antibacterial activities of the catalyst and its Phen ligand were in vitro screened with 2,2‐diphenyl‐1‐picrylhydrazyl by free radical scavenging methods. Results showed that the synthesized compounds possess strong antioxidant activity (IC50; 0.172  ±  0.005 mg ml^?1) as well as a good antibacterial potential in comparison to standards.     

Cobalt nanoparticles anchored to porous silicon as a novel modifier for the construction of enzyme‐free hydrogen peroxide screen‐printed sensor

In this work, a screen‐printed carbon electrode (SPCE) was modified with a cobalt/porous silicon (Co@PSi) nanocomposite powder to develop a nonenzymatic sensor for the detection of hydrogen peroxide. The Co@PSi nanocomposite was synthesized through the chemical reaction between silicon powder in a HF/HNO₃ solution and cobalt cations. In this process, cobalt nanoparticles were anchored on the porous silicon. The structure and morphology of the synthesized nanocomposite were investigated by X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray photoemission spectroscopy, energy dispersive X‐ray spectroscopy, and field‐emission scanning electron microscopy. The constructed nonenzymatic, screen‐printed sensors based on the Co@PSi nanocomposite showed perfect electrocatalytic oxidation response to hydrogen peroxide over the range 1–170 and 170–3,770 μmol/L with the limit of detection of 0.8 μmol/L. In addition, the Co@PSi‐SPCE sensor exhibited good selectivity for the determination of H₂O₂ in the presence of common interfering species including glucose, ascorbic acid, uric acid, dopamine, nitrate, and nitrite ions. The constructed electrochemical sensor was successfully used for the determination of H₂O₂ in real samples.     

Finely dispersed palladium on silk‐fibroin as an efficient and ligand‐free catalyst for Heck cross‐coupling reaction

A palladium–fibroin complex (Pd/Fib.) was prepared by the addition of sonicated fibroin fiber in water to palladium acetate solution. Pd (OAc)₂ was absorbed by fibroin and reduced with NaBH₄ at room temperature to the Pd(0) nanoparticles. Powder‐X‐ray diffraction, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, Fourier transform‐infrared, CHN elemental analysis and inductively coupled plasma‐atomic emission spectroscopy were carried out to characterize the Pd/Fib. catalyst. Catalytic activity of this finely dispersed palladium was examined in the Heck coupling reaction. The catalytic coupling of aryl halides (‐Cl, ‐Br, ‐I) and olefins led to the formation of the corresponding coupled products in moderate to high yields under air atmosphere. A variety of substrates, including electron‐rich and electron‐poor aryl halides, were converted smoothly to the targeted products in simple procedure. Heterogeneous supported Pd catalyst can be recycled and reused several times.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

One‐pot synthesis of magnetic palladium–NiFe2O4–graphene oxide composite: an efficient and recyclable catalyst for Heck reaction

A magnetically separable NiFe₂O₄@GO–Pd composite (GO = graphene oxide) was successfully prepared by a facile one‐pot hydrothermal strategy. This new kind of hybrid material was fully characterized using powder X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy and vibrating sample magnetometry. Structural characterizations confirmed the formation of NiFe₂O₄ and Pd nanocrystals, and the close anchoring between nanoparticles and GO sheets. Additionally, the as‐prepared NiFe₂O₄@GO–Pd nanocomposite was effectively employed in the palladium‐catalyzed Heck reaction in an ethanol–water system as a green solvent. The catalyst was completely recoverable with the simple application of an external magnetic field and with no obvious loss of catalytic activity even after six repeated cycles. Copyright © 2016 John Wiley & Sons, Ltd.     

Palladium nanoparticles supported on modified hollow Fe3O4@TiO2: Preparation,characterization, and catalytic activity in Suzuki cross‐coupling reactions

Hollow Fe₃O₄@TiO₂‐NH₂/Pd as a light‐weight, magnetically heterogeneous catalyst was successfully prepared, and characterized by using different techniques including X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), vibrating sample magnetometer (VSM) measurements, and thermogravimetric analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross‐coupling reaction, and the results confirmed the success of this method. The catalyst could be separated easily using an external magnet and reused at least in five runs successfully without any appreciable loss in its catalytic activity.     

Pd‐Cu alloy nanoparticle supported on amine‐terminated ionic liquid functional 3D graphene and its application on Suzuki cross‐coupling reaction

Well distributed Pd‐Cu bimetallic alloy nanoparticles supported on amine‐terminated ionic liquid functional three‐dimensional graphene (3D IL‐rGO/Pd‐Cu) as an efficient catalyst for Suzuki cross‐coupling reaction has been prepared via a facile synthetic method. The introduction of IL‐NH₂ cations on the surface of graphene sheets can effectively avoid the re‐deposition of graphene sheets, allowing the catalyst to be reused up to 10 cycles. The addition of Cu not only saves cost but also ensures high catalytic efficiency. It is worthy to note that the catalyst 3D IL‐rGO/Pd_2.5Cu_2.5 can efficiently catalyze the Suzuki cross‐coupling reaction with the yield up to 100% in 0.25 h, almost one‐fold higher than that by the pristine IL‐rGO/Pd_2.5 catalyst (52%). The Powder X‐Ray Diffraction (XRD), combining energy dispersive X‐ray spectroscopy (EDS) mapping results confirm the existence and distribution of Pd and Cu in the bimetallic nanoparticles. The transmission electron microscopy (TEM) reveals the nanoparticle size with an average diameter of 3.0 ± 0.5 nm. X‐ray photoelectron spectroscopy (XPS) analysis proved the presence of electron transfer from Cu to Pd upon alloying. Such alloying‐induced electronic modification of Pd‐Cu alloy and 3D ionic liquid functional graphene with large specific surface area both accounted for the catalytic enhancement.     

Design and preparation of ZnS‐ZnFe2O4: a green and efficient hybrid nanocatalyst for the multicomponent synthesis of 2,4,5‐triaryl‐1H‐imidazoles

In the present work, a new protocol was introduced for the preparation of an efficient hybrid nanocatalyst ZnS‐ZnFe₂O₄ via the co‐precipitation method as well as its application in the synthesis of 2,4,5‐triaryl‐1H‐imidazoles derivatives starting from various aromatic aldehydes, benzil and ammonium acetate under ultrasonic irradiation in ethanol. ZnS‐ZnFe₂O₄ was characterized by Fourier transform infrared (FT‐IR) spectroscopy, energy‐dispersive X‐ray spectroscopy (EDS) analysis, scanning electron microscopy (SEM) image, X‐ray diffraction (XRD) pattern and vibrating sample magnetometer (VSM) curve. This method has advantages such as high efficiency of the heterogeneous catalyst, the use of environmentally‐friendly solvent, high yields, short reaction times and easy isolation of the products and chromatography‐free purification. Our outcomes illustrated that the present nanocatalyst with nearly spherical and Cauliflower‐like morphology and average particle size of 36 nm could be applied as an effective and magnetically recyclable catalyst without any significant decreasing of activity. Furthermore, the synergic effect of bimetallic Lewis acids was studied for the synthesis of imidazole derivatives.     

Pt‐Pd‐Co Trimetallic Alloy Network Nanostructures with Superior Electrocatalytic Activity towards the Oxygen Reduction Reaction

Pt alloy nanostructures show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. Herein, three‐dimensional (3D) Pt‐Pd‐Co trimetallic network nanostructures (TNNs) with a high degree of alloying are synthesized through a room temperature wet chemical synthetic method by using K₂PtCl₄/K₃Co(CN)₆–K₂PdCl₄/K₃Co(CN)₆ mixed cyanogels as the reaction precursor in the absence of surfactants and templates. The size, morphology, and surface composition of the Pt‐Pd‐Co TNNs are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), energy dispersive spectroscopy (EDS), EDS mapping, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The 3D backbone structure, solid nature, and trimetallic properties of the mixed cyanogels are responsible for the 3D structure and high degree of alloying of the as‐prepared products. Compared with commercially available Pt black, the Pt‐Pd‐Co TNNs exhibit superior electrocatalytic activity and stability towards the ORR, which is ascribed to their unique 3D structure, low hydroxyl surface coverage and alloy properties.