|Category||Oxide mineral |
|CuFe2O4 or (Cu,Mg)Fe2O4|
|Crystal class||Hexoctahedral (m3m) |
H-M symbol: (4/m 3 2/m)
|Space group||Cubic |
Space group: Fd3m
|Formula mass||239.23 g/mol|
|Color||Black, gray in reflected light|
|Crystal habit||Irregular grains, laminae intergrown with hematite|
|Mohs scale hardness||6.5|
|Specific gravity||5 - 5.2|
|Refractive index||n = 1.8|
Copper iron oxide , cuprospinel, Copper diiron tetraoxide, Copper ferrite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Cuprospinel is a mineral that occurs naturally in Baie Verte, Newfoundland, Canada. The mineral was found in an exposed ore dump, on the property of Consolidated Rambler Mines Limited near Baie Verte, Newfoundland. The mineral was first characterized by Ernest Henry Nickel, a mineralogist with the Department of Energy, Mines and Resources in Australia, in 1973.
Cuprospinel is an inverse spinel with the formula CuFe2O4, where copper substitutes some of the iron cations in the structure. Its structure is similar to that of magnetite, Fe3O4, yet with slightly different chemical and physical properties due to the presence of copper.
- 1 Structural properties
- 2 Magnetic properties
- 3 Solid phase synthesis
- 4 Hydrothermal Synthesis
- 5 Uses
- 6 Recyclable catalyst for organic reactions
- 7 References
Cuprospinel, like many other spinels has the general formula AB2O4. Yet, cuprospinel is an inverse spinel in that its A element, in this case copper (Cu2+), only occupies octahedral sites in the structure and the B element, iron (Fe2+ and Fe3+), is split between the octahedral and tetrahedral sites in the structure. The Fe2+ species will occupy some of the octahedral sites and there will only be Fe3+ at the tetrahedral sites. Cuprospinel adopts both cubic and tetragonal phases at room temperature, yet as temperature is elevated the cubic form is most stable.
CuFe2O4 nanoparticles were characterized as superparamagnetic materials with saturated magnetization of Ms=49 emu g−1, remnant magnetization (Mr = 11.66 emu g−1) and coercivity (Hc = 63.1 mT). The magnetic properties of CuFe2O4 have correlated the size of particles. Particularly, the decreasing in saturated magnetization and remanence correspond to the decreasing in the size of CuFe2O4, whereas the coercivity increases.
Solid phase synthesis
Spinel CuFe2O4 was synthesized by solid phase synthesis at high temperature. In a particular procedure for this type of synthesis, the stoichiometric mixture of Cu(CH3COO)2· and FeC2O2 was ground together and stirred in solvent. After evaporation of the solvent, the powder was heated in a furnace at constant temperature around 900 0C in air-atmosphere environment. Then the resulting mixture was slowly cooled to room temperature in order to obtain stable spinel structure.
Hydrothermal method is widely known as an effective way to synthesize spinel oxide, especially for cooper iron oxide. Typically, NaOH was added dropwise to a solution of Fe3+(Fe(NO3)3 or Fe(acac)3) and Cu2+ (Cu(NO3)2 or CuCl2) in triethylene glycol at room temperature with constant stirring until a reddish-black precipitate formed completely. The resulting mixture was placed in an ultrasonic bath to mixing it well, followed by heating in a furnace at high temperature. Final products were then washed in diethyl ether, ethyl acetate, ethanol and deionized water, and then dried under vacuum to obtain oxide particles.
- H2O(v) + CO(g) → CO2(g) + H2(g)
This reaction is particularly important for hydrogen production and enrichment.
The interest of cuprospinel arises in that magnetite is a widely used catalyst for many industrial chemical reactions, such as the Fischer–Tropsch process, the Haber–Bosch process and the water-gas shift reaction. It has been shown that doping magnetite with other elements gives it different chemical and physical properties; these different properties sometimes allow the catalyst to work more efficiently. As such, cuprospinel is essentially magnetite doped with copper and this enhances magnetite's water gas shift properties as a heterogeneous catalyst.
Recyclable catalyst for organic reactions
Recent years, various research towards the heterogeneous catalytic ability of CuFe2O4 in organic synthesis have been published ranging from traditional reactions to modern organometallic transformation. By taking advantages of magnetic nature, the catalyst can be separated simply by external magnetism, which can overcome the difficulty to separate nano-scaled metal catalyst from the reaction mixture. Particularly, only by applying magnetic bar at the outer vessel, the catalyst can easily be held at the edge of container while removing solution and washing particles. The obtained particles can be readily used for the next catalyst cycles. Moreover, the catalytic site can be exploited in either cooper or iron center because of the large-surface area of nanoparticles, leading to wide scope to apply this material in various types of reactions.
Catalyst for Multi-component reaction (MCR)
Nano CuFe2O4 was utilized as a catalyst in one-pot synthesis of fluorine containing spirohexahydropyrimidine derivatives. It was also observed that the catalyst can be reused five times without significant loss in catalytic activity after each runs. In the reaction, iron plays a vital role in coordination with carbonyl group in order to increase the electrophilic property, which can facilitate the reaction condition and increase reaction rate.
Another example for MCR utilizing CuFe2O4 was published in a research towards the A3 coupling of aldehydes, amine with phenylacetylene to give the corresponding propargylamines. The catalyst can be reused three times without remarkable reduce in reaction yield.
Catalyst for C-O cross coupling
Pallapothula and coworkers demonstrated CuFe2O4 is an efficient catalyst for C-O cross-coupling between phenols and aryl halides. The catalyst exhibited superior activity in comparison with other nanoparticles oxides such as Co3O4, SnO2, Sb2O3. Moreover, the catalyst can benefit in applying C-O cross-coupling on alkyl alcohols, leading to widening scope for the transformation.
Catalyst for C-H activation
Nano CuFe2O4 catalyst was demonstrated its activity for C-H activation in Mannich type reaction. In the mechanistic study, the copper play a significant role in both generate radical from TBHP and activate C-H from substituted alkyne. In this reaction, iron center was considered as a magnetic source and this hypothesis was proved by the experiment, in which magnetic Fe3O4 had been used but failed to catalyze reaction in the absence of copper center.
CuFe2O4 can also be applied for C-C cleavage α-arylation between acetylacetone with iodobenzene. The phenylacetone product was obtained with excellent yield at 99% and 95% selectivity observed for principal product compared to 3-phenyl-2,4-pentanedione as the byproduct. The XRD results were observed that crystal structure of catalyst remained unchanged after the sixth run while catalytic activity slightly decreases at 97% conversion in the final run. In this reaction, the mechanistic study showed the catalytic cycle started from CuII to CuI and then oxidized to CuII by aryl iodine.
The role of copper has been further emphasized in the coupling reaction of ortho-arylated phenols and dialkylformamides. It was observed that there was a single-electron oxidative addition of copperII to copperIII through a radical step, then transformed back to copperI by reductive elimination in the presence of either oxygen or peroxide. Catalyst can be reused 9 times without significant loss in catalytic activities.
Synergistic effect of catalytic activity
Notably, synergistic effect was demonstrated for the case of CuFe2O4 in Sonogashira reaction. Both Fe and Cu center contribute to catalytic activity of the transformation between aryl halide and substituted alkynes. The product was obtained with 70% yield in the presence of Nano CuFe2O4, while only 25% yield and <1% yield observed when using CuO and Fe3O4 respectively.
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- Webmineral data
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