Cu‐Based Nanoparticles as Emerging Environmental Catalysts

This account provides an overview of current research activities on nanoparticles containing the earth‐abundant and inexpensive element copper (Cu) and Cu‐based nanoparticles, especially in the field of environmental catalysis. The different synthetic strategies with possible modification of the chemical/ physical properties of these nanoparticles using such strategies and/or conditions to improve catalytic activity are presented. The design and development of support and/or bimetallic systems (e. g., alloys, intermetallic, etc.) are also included. Herein, we report synthetic approaches of Cu and Cu‐based nanoparticles (monometallic copper, bimetallic copper and copper (II) oxide nanoparticles/nanostructures) and impregnation of such nanoparticles onto support material (e. g., Co₃O₄ nanostructure), along with their applications as environmental catalyst for various oxidation and reduction reactions. Finally, this account provides necessary advances and perspectives of Cu‐based nanoparticles in the environmental catalysis.     

Preparation of Fe3O4@5,10‐dihydropyrido[2,3‐b]quinoxaline‐7,8‐diol copper complex: A capable nanocatalyst for the green synthesis of 1‐substituted 1H‐tetrazoles

Fe₃O₄ magnetic nanoparticles functionalized with 5,10‐dihydropyrido[2,3‐b]quinoxaline‐7,8‐diol were synthesized as was their complex with copper as a novel nanomagnetic iron oxide catalyst via a simple and green method, and characterized using various techniques. The capability of the catalyst was evaluated in the one‐pot three‐component synthesis of different tetrazoles, which showed very good results. Mild reaction conditions, good reusability and simple magnetic work‐up make this methodology interesting for the efficient synthesis of tetrazoles.     

CuO nanoparticles-catalyzed a novel method to the synthesis of symmetrical diselenides from aryl halides: selenoamide as an organic Se-donor reagent

A new method is reported for the synthesis of symmetrical diaryldiselenides from aryl halides using selenoamide as an organic Se-donor reagent in the presence of copper (II) oxide nanoparticles. CuO nanoparticles were found to be an efficient and inexpensive catalyst for ligand-free C-Se bond formation with a series of symmetrical diaryldiselenides obtained in good to excellent yield.     

Copper‐supported β‐cyclodextrin‐functionalized magnetic nanoparticles: Efficient multifunctional catalyst for one‐pot ‘green’ synthesis of 1,2,3‐triazolylquinazolinone derivatives

The green synthesis of 2‐(4‐((1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)oxy)phenyl)quinazolin‐4(3H)‐one derivatives is reported. The catalyst for this synthesis is copper‐supported β‐cyclodextrin‐functionalized magnetic silica–iron oxide nanoparticles ([Cu@BCD@SiO₂@SPION]). [Cu@BCD@SiO₂@SPION] simultaneously catalyses ‘click’ reaction, oxidation of C? N bond and multicomponent reaction. The desired 1,2,3‐triazolylquinazolinone product is easily obtained in water at room temperature under mild reaction conditions. Another advantage of the catalyst is its reusability. It can simply be isolated using an external magnet and reused in reactions with no significant decrease in catalyst efficiency. Transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy are used for exact characterization of the [Cu@BCD@SiO₂@SPION] catalyst.     

Cu-石墨烯类Fenton催化剂的制备及催化活性

通过一步水热法制备了Cu-石墨烯（Cu-RGO）催化剂,实现了Cu纳米颗粒的可控生长和氧化石墨烯（GO）还原的同步进行,并将所制备的Cu-RGO用于亚甲基蓝（MB）的催化降解研究。在H₂O₂存在条件下,当GO与Cu的质量比为3：17时,经过4h催化反应,Cu-RGO催化剂对亚甲基蓝的降解率可达到99.5%,经过6次循环使用对亚甲基蓝的降解率仍保持在98.1%以上,Cu-RGO催化剂展现了较高的催化活性及良好的稳定性。     

Magnetically water‐dispersible and recoverable rhodium organometallic catalyst derived from Wilkinson's catalyst for promoting organic reactions

A novel magnetic rhodium catalyst was prepared through immobilizing Wilkinson's catalyst on the surface of silica‐coated iron oxide nanoparticles. After (thio)diphenylphosphine (─S&─PPh₂) was modified on the surface of the silica‐coated iron oxide nanoparticles, tris(triphenylphosphine)rhodium(I) chloride was employed to synthesize the Rh(Cl)(PPh₃)₂(Ph₂P&─S&─) complex, affording a rhodium loading of 0.16 mmol g⁻¹. The Rh(I) organometallic magnetic nanoparticles form a novel class of heterogeneous catalyst which is particularly suitable for the practice of organic synthesis. The prepared system exhibits high catalytic efficiency in Suzuki–Miyaura and Miyaura–Michael reactions in ethanol–water solution. High yield, low reaction times, use of green solvents and non‐toxicity of the catalyst are the main merits of this protocol. Also, magnetic separation is an environmentally friendly alternative for the recovery of the catalyst, since it minimizes energy and catalyst loss by preventing mass loss and oxidation. The produced catalyst was characterized using a variety of techniques.     

Immobilization of copper ions onto α‐amidotriazole‐functionalized magnetic nanoparticles and their application in the synthesis of triazole derivatives in water

A new heterogeneous copper catalyst was synthesized by immobilization of copper ions onto magnetic nanoparticles with a new ligand based on triazole. The catalyst was characterized using scanning and transmission electron microscopies, atomic absorption and Fourier transform infrared spectroscopies, and thermogravimetric, elemental and energy‐dispersive X‐ray analyses. The results confirmed that a good level of organic groups was immobilized on the magnetic nanoparticles. Huisgen cycloaddition reaction was chosen as a model reaction for the investigation of catalyst activity under green conditions. Phenylacetylene and benzyl bromide derivatives were used for the synthesis of triazoles. The reaction proceeded with good to excellent yields for various alkynes and alkyl halides. To investigate catalyst activity for inactive alkynes, aliphatic alkynes were used in the model reaction. The corresponding triazoles were obtained in good to excellent yields and a high regioselectivity for products was obtained. The catalyst was easily separated using an external magnetic field and subsequently reused in ten reaction cycles without any loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Cu-石墨烯类Fenton催化剂的制备及催化活性

通过一步水热法制备了Cu-石墨烯(Cu-RGO)催化剂,实现了Cu纳米颗粒的可控生长和氧化石墨烯(GO)还原的同步进行,并将所制备的Cu-RGO用于亚甲基蓝(MB)的催化降解研究。在H2O2存在条件下,当GO与Cu的质量比为3∶17时,经过4 h催化反应,Cu-RGO催化剂对亚甲基蓝的降解率可达到99.5%,经过6次循环使用对亚甲基蓝的降解率仍保持在98.1%以上,CuRGO催化剂展现了较高的催化活性及良好的稳定性。     

Copper immobilized onto polymer‐coated magnetic nanoparticles as recoverable catalyst for ‘click’ reaction

Copper supported on polymer‐coated magnetic nanoparticles was designed and synthesized as a separable heterogeneous catalyst. The catalyst was fully characterized using several techniques such as Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning and transmission electron microscopies, X‐ray diffraction, vibrating sample magnetometry, thermogravimetric analysis and inductively coupled plasma atomic emission spectrometry. All results showed that copper was successfully supported on the polymer‐coated magnetic nanoparticles. Also, results showed that the synthesized material can be used as an efficient catalyst for the preparation of a series of 1,4‐disubstituted 1,2,3‐triazoles from corresponding halides, alkynes and sodium azide. The catalyst can be easily isolated from the reaction solution by applying an external magnet and reused for nine runs without any significant loss of catalytic activity.     

CuO nanoparticle‐catalyzed diaminations for synthesis of benzimidazole derivatives

Copper oxide nanoparticles have been applied as an efficient catalyst for the formation of C–N bonds. They can catalyze diaminations for the regiospecific synthesis of 1,2‐disubstituted benzimidazoles from 1,2‐dihaloarenes and N‐arylamidines. The best performance has been achieved using CuO nanoparticles with average diameter of 6.5 nm. In addition, the catalyst can be recycled and reused without any significant decrease in catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Reduced graphene oxide supported copper oxide nanocomposites: An efficient heterogeneous and reusable catalyst for the synthesis of ynones, 1,3-diynes and 1,5-benzodiazepines in one-pot under sustainable reaction conditions

A greener and efficient method for the synthesis of ynones and 1,3-diynes using copper oxide nanoparticles (CuONPs) doped reduced graphene oxide (CuO@rGO) catalyst under palladium, ligand and solvent free conditions have been developed. The catalyst was subsequently utilized for the synthesis of biologically active 1,5-benzodiazepines in one pot via sequential addition of acyl chlorides, terminal alkynes and o-phenylenediamines. The methodology initially involves in situ formation of ynones which react with o-phenylenediamines in presence of ethanol to afford a wide variety of benzodiazepines. Mild reaction conditions, good to an excellent yield of the products, cheap and recyclable catalyst make this methodology environmentally benign and sustainable.     

Immobilized polytriazole complexes of copper(I) onto graphene oxide as a recyclable nanocatalyst for synthesis of triazoles

An efficient solid‐supported catalyst for the Huisgen [3 + 2] cycloaddition reaction between azides and alkynes was prepared from copper(I) iodide and 1,2,3‐triazole‐functionalized graphene oxide. This catalyst was then used for the efficient synthesis of β‐hydroxy‐1,2,3‐triazoles giving access to these products in excellent yields. In this protocol, the catalyst was shown to have high activity, air‐stability and recyclability. The formation of copper triazolide is very straightforward and energetically desirable. The catalyst can be isolated from copper‐catalysed azide–alkyne cycloaddition reactions.     

Immobilized copper(II) on nitrogen‐rich polymer‐entrapped Fe3O4 nanoparticles: a highly loaded and magnetically recoverable catalyst for aqueous click chemistry

A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi‐layered poly(2‐dimethylaminoethyl acrylamide)‐coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one‐pot three‐component reaction of alkyl halide, sodium azide and alkyne, known as copper‐catalyzed click synthesis of 1,2,3‐triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of alkyl/benzyl/allyl bromide/chloride and alkyl/aryl terminal alkynes without isolation of azide intermediate, and good to excellent yields of products make this procedure highly economical. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Poly (methyl methacrylate)/Zinc Oxide Nanocomposite with Core-Shell Morphology by Atom Transfer Radical Polymerization

A method to prepare zinc oxide (ZnO) nanoparticles with a covalently bonded poly(methyl methacrylate) (PMMA) shell by surface initiated atom transfer radical polymerization (ATRP) was reported. First, the initiator for ATRP was covalently bonded onto the surface of zinc oxide nanoparticles through our novel method. Firstly, the surface of ZnO nanoparticle was treated with 3-aminopropyl triethoxysilane, a silane coupling agent, and then this functionalization nanoparticle was reacted with α-chloro phenyl acetyl chloride to prepare atom transfer radical polymerization macroinitiator. The metal-catalyzed radical polymerization of MMA with ZnOmacroinitiator was performed using a copper catalyst system to give the ZnO-based nanoparticles hybrids linking PMMA segments (poly (methyl methacrylate)/zinc oxide nanocomposite). These hybrid nanoparticles had an exceptionally good dispersability in organic solvents and were subjected to detailed characterization using FTIR, TEM and TGA and DSC analyzed.     

CuFe2O4 nanomaterials: Current discoveries in synthesis,catalytic efficiency in coupling reactions,and their environmental applications

In the last few decades, there has been enormous growth in ferrite nanoparticles. Magnetic, optical, and electrical properties of ferrites gain consideration due to their use in various applications such as rechargeable lithium batteries, medical diagnostics, solar energy devices, and so forth. A vast increase in interest in ferrite nanoparticles has led them to be used as catalysts in various applications as they possess a large surface area-to-volume ratio. Furthermore, iron-based magnetic characteristics make it simple to retrieve catalysts by using an external magnet. Iron's catalytic potential, however, is far less than copper's. Therefore, the catalytic scope is substantially increased by substituting copper within the crystal lattice. Recently copper ferrite nanoparticles have caught the interest of numerous researchers due to low-cost magnetic material, stability under diverse conditions, and ease at which catalyst can be retrieved using an external magnetic field and utilized repeatedly. This review of data from year 2010 through 2022 emphasizes the synthesis method, structure, application in dyes degradation, catalytic potential in the number of coupling reactions, recyclability, and reusability of the magnetic catalyst.     

Stabilization of Copper Catalysts for Liquid‐Phase Reactions by Atomic Layer Deposition

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid‐phase catalytic reactions (e.g., hydrogenation of biomass‐derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid‐phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X‐ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ‐Al₂O₃. Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under‐coordinated copper atoms on the nanoparticle surface.     

Recyclable Cu nanoparticle catalyzed azide-alkyne click polymerization

The Cu(I)-catalyzed alkyne-azide cycloaddition(CuAAC) has been developed into a powerful polymerization reaction for the synthesis of new polytriazoles with versatile properties. However, research on recyclable and reusable copper catalyst for click polymerization to meet the requirement of green chemistry was rarely reported. Copper nanoparticles were reported to be capable catalysts for CuAAC. Replacing conventional copper catalyst with copper nanoparticles may realize the recycle and reuse of the copper catalyst in click polymerization. In this paper, copper nanoparticles were prepared and used as an effective catalyst for click polymerization, and soluble polytriazoles with high molecular weights were obtained in excellent yields under optimized reaction conditions. Importantly, the copper nanoparticles can be recycled and reused for up to 11 times for the click polymerization. Moreover, introducing aggregation-induced emission(AIE)-active moiety of tetraphenylethylene into the monomers makes the resultant polymers retain the AIE feature. This work not only provides an efficient recyclable catalytic system for the azide-alkyne click polymerization, but also might inspire polymer chemists to use recyclable copper species to catalyze other polymerizations.     

Step-by-step synthesis of copper(I) complex supported on platinum nanoparticle-decorated mesoporous silica hollow spheres and its remarkable catalytic performance in Sonogashira coupling reaction

In this study, a step-by-step method for the synthesis of platinum nanoparticles and copper(I) complex supported on mesoporous silica hollow spheres (Pt-MSHSs-Cu) is introduced. Scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption, energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, and elemental and thermogravimetric analyses were applied for characterization of the surface, structure, size, phase composition, and morphology of the synthesized materials. The characterized material, Pt-MSHSs-Cu, was used as an efficient and heterogeneous catalyst in the Sonogashira coupling reaction under different reaction conditions. In comparison with MSHSs, Cu(I)-functionalized MSHSs (MSHSs-Cu), and Pt-MSHSs samples, the Pt-MSHSs-Cu catalyst exhibited significantly increased catalytic performance with 91.50% yield. Therefore, the results obtained suggested a synergistic effect derived from platinum nanoparticles, MSHSs substrate, and copper(I) complex, which enhanced the rate of the Sonogashira coupling reaction.     

Identical-location Transmission Electron Microscopy of Pt Nanoparticle Electrocatalysts Using Iridium-coated Au Grids for Fuel Cell Durability Tests Simulating Start-up and Shutdown Conditions

In an identical-location TEM (IL-TEM) analysis of an electrocatalyst, an Au grid is usually selected owing to its chemical stability under potential cycling conditions. A potential cycle between 1.0 and 1.5 V is applied to the catalyst-cast Au grid for cathode durability testing that simulates the start-up and shutdown conditions of fuel cells. Because of the redox potential of Au (1.36 V vs. RHE), the grid dissolves and redeposits on the catalyst under the applied potential, making it complicated to evaluate the catalyst nanoparticle shape and size after degradation. We fabricated an Au grid coated with an iridium oxide layer (Ir-coated Au grid) to suppress the dissolution of Au. The Ir-coated Au grid with carbon support was compared to the Au grid to confirm the effect of the iridium oxide layer. No Au deposition was observed, even after 3000 cycles at 60 °C for the Ir-coated Au grid, but Au was deposited on carbon on the Au grid after 1000 cycles. Consequently, the alkylamine-modified Pt nanoparticle catalyst (unwashed catalyst) was observed along with the Ir-coated Au grid using IL-TEM under durability tests simulating start-up and shutdown conditions. A catalyst with less alkylamine content was prepared by butylamine washing (washed catalyst) and observed using IL-TEM for comparison. The Pt nanoparticles of the washed catalyst aggregated and changed their morphology after 1000 cycles, while the alkylamine-modified nanoparticles of the unwashed catalyst almost maintained their original size and shape up to 1000 cycles. The Ir-coated gold grids allow proper IL-TEM analysis of catalysts in durability tests without the interference of Au dissolution.     

铜钴尖晶石复合氧化物催化剂的组成对二甲苯完全氧化反应催化性能的影响

具有特定结构的复合氧化物,如ABO3,A2BO4及AB2O4等对某些反应比单一氧化物具有更好的催化性能[1,2]. 然而,有关尖晶石型复合氧化物AB2O4对有机物燃烧反应催化性能的研究相对较少,且常用的模型反应大都是一氧化碳或甲烷的催化氧化反应[3]. 超微粒子由于具有大的比表面积和高的表面能等特性,在催化领域已日益引起人们的重视[4]. 低温固相合成是近十几年发展起来的一种新的超细粒子制备方法[5]; 它具有不使用溶剂,无废液排放,工艺过程简单,能耗低等优点,属于对环境友好的“绿色化学”. 目前,此法在合成多组分复合氧化物及催化化学中的应用仍不多见. 本文以含有结晶水的醋酸铜和醋酸钴为原料,采用低温固相合成法制备了单组分氧化铜和氧化钴,以及三种不同铜钴比的铜钴尖晶石型复合氧化物,并以二甲苯氧化为模型反应,采用XRD,BET及程序升温还原(TPR)等手段进行了研究.