Novel Magnetic Bimetallic AuCu Catalyst for Reduction of Nitroarenes and Degradation of Organic Dyes

doi:10.21203/rs.3.rs-3629262/v1

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Novel Magnetic Bimetallic AuCu Catalyst for Reduction of Nitroarenes and Degradation of Organic Dyes

https://doi.org/10.21203/rs.3.rs-3629262/v1

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published 11 Mar, 2024

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Herein, core-shell magnetic nanoparticles are modified with imidazolium-tagged phosphine and propylene glycol moieties and used for stabilization of bimetallic AuCu nanoparticles. The structure and morphology of prepared material is identified with SEM, TEM, XRD, XPS, atomic absorption spectroscopy, Fourier translation infrared spectroscopy, and vibrating sample magnetometer. This hydrophilic magnetic bimetallic catalyst applied in the reduction of toxic nitroarenes and degradation of hazardous organic dyes of methyl orange (MO), methyl red (MR), and rhodamine B (RhB), as well as in the degradation of tetracycline (TC). This magnetic AuCu catalyst indicated superior activity in all three mentioned reactions in comparison with its single metal analogs Au and Cu. This catalyst was recycled for 17 consecutive runs in the reduction of 4-nitrophenol to 4-aminophenol without a significant decreasing in catalytic activity and recycled catalyst was characterized.

Earth and environmental sciences/Environmental sciences

Physical sciences/Chemistry

Physical sciences/Nanoscience and technology

Bimetallic

Magnetic

AuCu

Water dispersible

Reduction

Magnetic catalysts with high surface-area-to-volume ratio, super magnetism, easy separation, high mechanical and thermal stability, simple synthesis method, nontoxicity, and biocompatibility are considered as promising materials for designing heterogeneous catalysts.¹ Along this line, for achieving magnetic catalysts with the desired activity and properties such as high water dispersibility; various ligands, polymers, and ionic liquids have been used. Ionic liquids are molten salts that receive special attention due to their unique chemical and physical features in various fields as well as the design of catalysts.^2,3 However, high price and difficulty of their synthesis encourage chemists to support them on the surface of solid supports. This approach lead to reduce the amount of used IL allowing the reaction on the thin IL layer on the support surface.^1,4

Gold-based catalysts have been received much attention over the past two decades. Gold is a productive element and very attractive in metal coordination area and organometallic chemistry and extensively effective as a homogeneous or heterogeneous catalyst.^5–7 Despite of efficiency and exploitable properties of gold catalysts, there are disadvantages concerning the high cost and the scarce catalytic application in industrial scale. One effective way to solve this problem is to combine gold with cheap and available metals such as copper, nickel, and cobalt to create gold based bimetallic catalysts.^8,9 Bimetallic catalysts use to promote the synergy of the activity of the two metals if compared with their individual activities.^10,11

Recently, the rapid growth of industrialization has led to the environmental pollution caused by toxic compounds.¹² Organic dyes are classified as serious contaminant that many industries, such as rubber processing, food processing, textile, cosmetics, leather, printing, and pharmaceuticals, use their manufactures.¹³ In addition, some portions of these dyes are released in sewage producing harmful effects to humans, animals, and all living organisms.¹⁴ Adsorption, coagulation, oxidation, and membrane separation are some of the practical methods for removing dyes from industrial effluents.¹⁵ Tetracycline (TC) is other damaging contaminant, which is broadly utilized as antibiotic in the bacterial infections treatment, agriculture, and fish farming.¹⁶ Released TC can be stay in the environment for a long time due to its high chemical stability leading to increase the resistance of microorganisms, disruption of photosynthesis in aquatic organisms, and acute toxicity to humans.^17,18 Advanced oxidation and adsorption are the two main and accepted methods for eliminating tetracycline from wastewater.¹⁹

In addition, nitroaromatic compounds, especially nitrophenols, are the largest industrial wastes and pose a high risk to human and animal health due to their mutagenic and carcinogenic potential.²⁰ Numerous methods have been used to decompose or convert nitroarenes, being the catalytic reduction of them the most suitable approach. Interestingly, the produced amines are useful building blocks for the synthesis of antioxidants, drugs, pharmaceuticals, agrochemicals, dyes, pesticides and polymers.²¹ Among different efficient, economical, and environmentally friendly processes for removing pollutants from the environment, much attention has been paid to the employment of heterogeneous catalysts with superior activity and good recyclability using conventional methods such as centrifugation and filtration, which are time-consuming, wasteful, and industrially inefficient.²²

Herein, we report a novel phosphine, ionic liquid and diol modified magnetic nanoparticles supported AuCu species, Fe₃O₄@Phos-IL-AuCu, as an extremely water dispersible and magnetically recyclable catalyst with high efficiency in the reduction of nitroarenes, organic dyes, and degradation of tetracycline.

The complete procedure for the preparation of the titled bimetallic catalyst is detailed in Scheme 1. The freshly prepared Fe₃O₄ nanoparticles, obtained from the reaction of FeCl₂⋅4H₂O and FeCl₃⋅6H₂O, were treated with Si(OEt)₄ to afford Fe₃O₄@SiO₂ core-shell. Next (3-glycidyloxypropyl)trimethoxysilane was used to introduce the epoxy group (I). Then, the synthesized 1- (2-propynyl)-1H-imidazole (II) and chlorodiphenylphosphine were allowed to react with epoxy functionalized magnetic nanoparticles(I) to achieve phosphorous and IL modified MNPs. Then, alkyne group was subjected to CuAAC reaction to introduce diol group. Finally, modified MNPs were treated with Au and Cu salts followed with reaction with NaBH₄ to give AuCu supported on modified MNPs. This material refers to as Fe₃O₄@Phos-IL-AuCu NPs throughout of this article.

The contents of Cu and Au in the Fe₃O₄@Phos-IL-AuCu were quantified by ICP to be 0.03 and 0.07 mmol/g, respectively. Every stage of the preparation of Fe₃O₄@Phos-IL-AuCu is analyzed by FT-IR spectroscopy at (Fig. 1). Peaks located at 461 cm^-1, 570 cm^-1, and 638 cm^-1 corresponded to the Fe-O vibrations. Signals positioned at 800 cm^-1, 954 cm^-1, and 1119 cm^-1 derived from the Si-O, Si-OH, and Si-O-Si vibrations, respectively.^23,24 Broad bands centered at 2867 cm^-1 and 2927 cm^-1 were caused by C-H stretching vibrations.²⁵ The spectra of Fe₃O₄@SiO₂-OPPh₂-propargylimidazole and Fe₃O₄@Phos-IL compounds reveal that the peak at 1650 cm^-1 is related to the C = N and C = C bonds of imidazole.^26–28 However, this peak overlaps with the bending vibration of absorbed water molecules. Additionally, the present peak at 1071 cm^-1 in the spectrum of these compounds is due to the vibrations of the P-O bond, which is overlapping with the peak corresponding to the stretching vibration of the Si-O-Si bond.²⁹ In addition, the peak at 2120 cm^-1 in the spectrum of Fe₃O₄@SiO₂-OPPh₂-propargylimidazole is ascribed to the existence of the terminal alkyne group.³⁰ The disappearance of this peak in the final stage of the compound (Fe₃O₄@Phos-IL) signifies that the successful completion of the CuAAC 1,3-dipolar reaction occurred. In the Fe₃O₄@Phos-IL spectrum, the peak at 3138 cm^-1 is caused by the stretching vibration of the C-H bond of the triazole moiety, while the peak at 1636 cm^-1 is the result of overlapping bending vibrations of water, as well as C = C and C = N vibrations of imidazolium.^{31, 32} In all cases the wide band centered at 3400 cm^-1 is associated to O-H stretching vibration.³³ (Fig. 1).

The ionic liquid on increased the hydrophilic nature of the catalyst. This effect was studied by the calculation of the contact angle of the Fe₃O₄@C₂H₄OPPh₂@1-(2-propynyl)-1H-imidazole and Fe₃O₄@Phos-IL aggregates. Results showed that contact angle of Fe₃O₄@Phos-IL is lower than the contact angle observed for Fe₃O₄@C₂H₄OPPh₂@1-(2-propynyl)-1H-imidazole confirming the impressive effect of ionic liquid in increasing hydrophilicity (Fig. 2).

The results of transmission electron microscopy (TEM) analysis of Fe₃O₄@Phos-IL-AuCu NPs samples revealed a distinct core-shell structure, with evidence of the presence of AuCu nanoparticles on the surface of the substrate with the determined average size of 1.1 nm for AuCu NPs (see Fig. S1 and Fig. 3).

The scanning electron microscopy (SEM) images revealed the formation of Fe₃O₄@Phos-IL-AuCu NPs nanoparticles with a uniform distribution, good dispersion, and near spherical morphology (Fig. 4).

X-ray photoelectron spectroscopy (XPS) of Fe₃O₄@Phos-IL-AuCu in Fe, Si, C, N, Cl, P, Au, and Cu areas were analyzed (Fig. 5). The XPS plot of the Fe 2p region showed peaks at 709, 710, 712.5, and 716 eV, which correspond to Fe 2p3/2. Also, in this spectrum, the peaks in the regions of 723.9, 725.5 and 728.5 eV corresponded to Fe 2p1/2 (Fig. 5a).^34–36 In the Si 2p spectroscopy, the peaks at 101.6, 102.8, and 103.5 eV corresponded to Si-C, Si-O-C, and O-Si-O, respectively (Fig. 5b).^{37, 38} XPS analysis of C 1s plot showed peaks located at 284.8, 286, and 288.5 eV which were ascribed to C-C, C-OH, and N-C = N, individually (Fig. 5c).^39,40 In the N 1s spectroscopy, the peak at 399.5 eV was associated to the C-N bond, the 400 eV peak was attributed to the C = N bond, and the peak at 401.6 eV in this region was associated to the NR₃⁺ species in imidazolium (Fig. 5d).^41–43 In the Cl 2p spectral analysis, the peaks at 197.5, 199.4, and 201.7 eV were attributed to the Cl 2p3/2, while the peak at 200.4 eV was associated with the Cl 2p5/2 (Fig. 5e).^44–47 XPS of phosphorus revealed two peaks in the 2p region, located at 131.2 and 133.4 eV, corresponding to the bonding states of P-C and P-O, respectively (Fig. 5f).^{48, 49} Additionally, the XPS plot of the gold 4f area revealed two peaks located at 83.5 and 87.5 eV, both of them conforming to the Au(0) (Fig. 5g).⁵⁰ Finally, the XPS analysis was performed on the Cu 2p area, revealing two signals at 931.5 and 932 eV, corresponding to Cu₂O. The peak observed at 933.5 eV was attributed to Cu 2p3/2, while the peaks at 953.4 and 955 eV were assigned to Cu 2p1/2 in CuO. Additionally, smaller peaks in the regions of 935, 940, and 943 eV were attributed to metallic copper(II), copper(II) oxide and copper(II) hydroxide (Fig. 5h).^51–53

The X-ray diffraction analysis of the Fe₃O₄@Phos-IL-AuCu NPs catalyst demonstrated the existence of magnetic Fe₃O₄ nanoparticles, evidenced by the Bragg reflections at 2θ = 30.1°, 35.5°, 43.1°, 57.2°, and 62.8°.^54,55 The reflections at 2θ = 43.85° and 37.58° corresponded to the gold nanoparticles in the bimetallic gold-copper structure, while the reflections at 2θ = 50.0° and 73.8° corresponded to the copper nanoparticles.^56–59 Additionally, a wide band around 2θ = 22.0 was related to SiO₂ (Fig. 6).

The superparamagnetic behavior of Fe₃O₄@Phos-IL-AuCu NPs was studied by vibrating-sample magnetometer (VSM) in which result indicated zero-coercivity together with remanence on the magnetization-loop proving superparamagnetic nature of the material and possibility of easy separation by external magnetic field (Fig. 7).

After characterization of Fe₃O₄@Phos-IL-AuCu NPs, its catalytic activity was initially assessed in the reduction of nitro aromatic compounds. The reduction of the starting compound 4-chloronitrobenzene was selected as the reference reaction and various factors like type of reductant, solvent, catalyst loading (mol%), and reaction time were analyzed (Table 1). Initial results indicated that a good yield was obtained by using catalyst with 0.04 mol% Au and 0.09 mol% Cu by using NaBH₄ (2 mmol) in H₂O during 2 h at room temperature (Table 1, entry 1). Results showed that enhancement of catalyst amount to Au (0.06 mol%) and Cu (0.13 mol%), a 65% yield of the desired amine was obtained, whilst with higher amounts of Au (0.09 mol%) and Cu (0.19mol%), quantitative yield was achieved (Table 1, entries 2 and 3). Also, the yield of the reaction involving 4-chloroaniline decreased using lower amounts of NaBH₄ (1 mmol) (Table 1, entry 4) and shorter reaction times (Table 1, entries 5, and 6). Other reluctant agents such as hydrazine, formic acid and glycerol were investigated giving lower yields of the expected amine (Table 1, entries 7–9). By using of other solvents such as CH₃CN, DMF and toluene obtained lower yields (Table 1, entries 10–12). Therefore, conditions including catalyst with 0.09 mol% of Au, 0.19 mol% of Cu, NaBH₄ as reducing agent, in neat H₂O, at room temperature, was selected as the optimal reaction conditions. This reference reaction, in the absence of catalyst, did not do any progress (Table 1, entry 13). To highlight the advantage of using bimetallic Fe₃O₄@Phos-IL-AuCu, we have examined the activity of single-metal catalysts, Fe₃O₄@Phos-IL-Au and Fe₃O₄@Phos-IL-Cu, in this reaction and using the optimized conditions. The experimental results indicated that both single-metal catalysts offered poorer yields than the reaction performed with bimetallic catalyst (Table 1, entries 14, and 15).

After determination of optimum reaction conditions, the reduction of different nitroarenes compounds were assessed (Table 2). The results showed that high to excellent yields were obtained in the reduction of nitro aromatic compounds with both groups of electron-donating groups such as -Me, - CH₂OH, NH₂, and –OH and electron‐withdrawing groups such as -F, -Cl, -Br, –CN, and ―COMe. In general, the results show that the reduction of electron-rich nitroarenes was slower than the substrates-containing electron deficient arrangements (Table 2, entries 2–15). Also, in the example run with 4-nitrobenzaldehyde, the aldehyde group was also reduced along with nitro group, (Table 2, entry 13). However, during the reduction of acetylnitroarenes only the nitro group was reduced (Table 2, entries 14, 15). In addition, nitro aromatic compounds with two nitro groups were completely reduced, using more amount of NaBH₄ in longer times (Table 2, entries 16–19). Also, compound with both electron‐donating and electron‐withdrawing substitutions had good yields (Table 2, entry 20). Reduction of 4- nitrobenzylchloride was performed very good and corresponded amine obtained in excellent yield (Table 2, entry 21). Finally, the reduction of heterocyclic nitro compounds were carried out efficiently and the expected amines were isolated in 83–89% yields (Table 2, entries 22–24). Besides, the carbonyl group of the amide remained intact (Table 2, entries 22 and 23).

The catalytic performance of Fe₃O₄@Phos-IL-AuCu in the reduction of organic dyes, including methyl red (MR), methyl orange (MO), and rhodamine B (RhB) was evaluated. Progress of reduction was recorded by using UV-Vis spectrophotometer. The absorption of all MR (λmax = 435), MO (λmax = 467 nm), and RhB (λmax = 556 nm) dyes decreased in time when using Fe₃O₄@Phos-IL-AuCu as catalyst together with NaBH₄ as reducing agent. Generally, MO (λmax = 467 nm), MR (λmax = 435), and RhB (λmax = 556 nm) dyes completely declined in 3 min, 2 min and 1 min, respectively and during desired times all dyes became colorless (Fig. 8a-c).^60,61 Diagrams of ln (At/A0) vs reaction time for the dyes reduction were drawn and the rate constant (k) of MO, MR, and RhB were 1.5, 2.1, and 2.6 min^− 1, respectively, which indicates the good performance of the titled synthesized catalyst (Fig. 8d).

In order to compare the activity of the prepared bimetallic catalyst with the activity of the single metal catalysts such as Fe₃O₄@Phos-IL-Au and Fe₃O₄@Phos-IL-Cu, the reduction of dyes MO, MR, and RhB was investigated (Fig. S2). The results showed that 31.5%, 27%, 11.5% yield were obtained in the reduction of MO, MR, and RB dyes when using Fe₃O₄@Phos-IL-Au catalyst. Also, 5%, 3%, and 9% yields were obtained in the reduction of MO, MR, and RB dyes with Fe₃O₄@Phos-IL-Cu catalyst. These results confirmed the higher catalytic activity of Fe₃O₄@Phos-IL-AuCu due to synergetic effect between Cu and Au species.

Finally, the catalytic activity of the as-prepared Fe₃O₄@Phos-IL-AuCu catalyst has been assessed in the tetracycline (TC) degradation by using the ammonium peroxodisulfate at diverse pH (3, 5, 7, 9, and 11) (Fig. 9a-e). The reaction process was recorded by UV-Vis spectrophotometer. Results showed that the absorbance of tetracycline gradually decreased when increasing the reaction time, and, similarly to the experience in previous reports, the best result was obtained under alkaline media.

Degradation of tetracycline with Fe₃O₄@Phos-IL-Au (Fig. S3), and Fe₃O₄@Phos-IL-Cu (Fig. S4) were also investigated. Here, the higher efficiency of bimetallic catalyst Fe₃O₄@Phos-IL-AuCu is demonstrated once more versus the reactions run in the presence of monometallic catalytic species (Table S1).

Since the reduction of 4-nitrophenol was proceeded very efficiently (Table 2, entry 8), we studied synthesis of acetaminophen via one-pot reduction/amidation of 4-nitrophenol. Results show that reaction proceed very effectively and desire product was obtained in 84% isolated yield (scheme 2).

Efficiently recovering and reusing magnetic heterogeneous catalysts is crucial for both environmental and economic perspectives. In this regard, the recovery and the recycling facilities of Fe₃O₄@Phos-IL-AuCu were studied in the reduction of 4-nitrophenol under optimized reaction conditions (Fig. 10). To achieve this objective, the catalyst was recovered after 30 min using an external magnet, washed with ethyl acetate and after drying, it was utilized in another new batch of the reaction. According to these findings, the catalyst demonstrated the ability to be reused for 16 consecutive runs with only a slight decrease in activity. However, during the 17th run, the yield dropped to 81%.

To determine whether the Fe₃O₄@Phos-IL-AuCu is heterogeneous or homogeneous in nature, the filtration test was used for the reduction of 4-chloronitrobenzene under optimal conditions. During the course of the experiment, the reaction proceeded to a level of 39% completion after an initial reaction time of one hour. At this stage, the reaction mixture was subjected to filtration, following which the filtrate was allowed to continue the reaction for an additional hour. Subsequent analysis using gas chromatography (GC) revealed that the progress of the reaction was slowed down and the product was formed at a yield of only 49% (Fig. 11). This result indicated negligible leaching of active catalysts to reaction mixture and possible heterogeneous nature of the catalyst.

In order to investigate the stability of the catalyst, the structure of the reused catalyst was analyzed by VSM (Fig. 7), XPS (Fig. 12), XRD (Fig. 13), and TEM (Fig. 14). VSM analysis of reused catalyst showed preservation of magnetic property of the catalyst during recycling. The information revealed by XPS spectrum in Fe, Si, C, N, Cl, P, Au, and Cu regions indicated that similar patterns of elements to the fresh catalyst existed, confirming the high stability of the catalyst during the reaction.

Furthermore, the XRD spectra obtained from the reused catalyst showed peaks corresponding to Fe₃O₄, Si, Au and Cu, which are closely to the analogous ones detected in the newly prepared catalyst, providing evidence of the catalyst's durability (Fig. 13).

TEM images of reused catalysts was also showed very similar pattern to fresh catalyst with small increase in average size of nanoparticles confirming stability of the catalyst (Fig. 14 and Fig. S5).

Materials

Copper(II) sulfate pentahydrate (CuSO₄·5H₂O), sodium tetrachloroaurate(III) dihydrate (NaAuCl₄·2H₂O), iron(III) chloride hexahydrate (FeCl₃·6H₂O), iron(II) chloride tetrahydrate (FeCl₂·4H₂O), silicon dioxide (SiO₂), (3-glycidyloxypropyl)trimethoxysilane, polyvinylpyrrolidone (PVP, MW ~ 10000), imidazole, propargyl bromide, chlorodiphenylphosphine, sodium borohydride (NaBH₄), methyl orange (MO), sodium azide, 3-chloro-1,2-propanediol, ascorbic acid, rhodamine B (RhB), nitro compounds, methyl red (MR), and tetracycline (TC) were purchased from Sigma-Aldrich, Acros and Merck MilliporeSigma.

Synthesis of Fe₃O₄ NPs

Firstly, FeCl₃⋅6H₂O (16 mmol, 4.3 g), FeCl₂⋅4H₂O (8 mmol, 1.6 g), and distilled water (70 mL) were mixed and stirred under an argon atmosphere at room temperature for 10 min. After that, aqueous ammonia (25%, 10 mL) was poured gradually, and the suspension stirred at 80°C for 4 h. Finally, an external magnet allowed the separation of the magnetic particles which were washed with distilled H₂O (3 × 20 mL) and EtOH (3 × 20 mL), and dried using an oven at 60°C.

Synthesis of Fe₃O₄@SiO₂

Fe₃O₄ nanoparticles (2 g) were sonicated in ethanol (200 mL) during 30 min and tetraethyl orthosilicate (3 mL) and aqueous ammonia (25%, 12 mL) were added under argon atmosphere, respectively. The resultant mixture was stirred at room temperature for 24 h. Afterward, Fe₃O₄@SiO₂ nanoparticles were separated using an external magnet, washed with distilled water (3 × 20 mL) and ethanol (3 × 20 mL), and dried overnight in the oven at 60°C.

Synthesis of Fe₃O₄@SiO₂@epoxide

Freshly obtained Fe₃O₄@SiO₂ (1 g) was suspended in dry toluene (30 mL) and the sonicated for 30 min. Next, (3-glycidyloxypropyl)trimethoxysilane (5 mmol, 1.1 mL) was added to the above mixture under argon atmosphere. The suspension was stirred at 105°C for 1 d. Fe₃O₄@SiO₂@epoxide product was separated magnetically, washed repeatedly with distilled water and dichloromethane and lastly dried at 60°C for 4 h.

Synthesis of Fe₃O₄@C₂H₄OPPh₂@1-(2-propynyl)-1H-imidazole

Fe₃O₄@SiO₂@epoxide (1 g) and 1-(2-propynyl)-1H-imidazole (5 mmol, 0.53 g) were sonicated in dry dichloromethane for 15 min, and next, chlorodiphenylphosphine (5 mmol, 0.9 ml) was added to the mixture and stirred for 24 h at 50°C. Lastly, an external magnet was used to separate the solid, which was washed by distilled water (2 × 20 mL) and dichloromethane (2 × 20 ml), and dried in the oven at 60°C overnight.

Synthesis of Fe₃O₄@Phos-IL

Sodium azide (8 mmol, 0.52 g) and 3-Chloro-1,2-propanediol (5 mmol, 0.4 mL) were dissolved in N,N-dimethylformamide (10 mL), and then, the reaction mixture was stirred at 100°C for 24 h. In the next step, the mixture was cooled at room temperature and the phosphine functionalized magnetic NPs (1 g) added to mixture. Then, a solution containing copper(II) sulfate (0.09 mmol, 14.3 mg) and ascorbic acid (0.17 mmol, 30 mg) were mixed in DMF (1 mL) and the final solution was stirred at 70°C during 24 h. The precipitate was separated employing an external magnet and washed repeatedly with distilled water (20 ml) and ethyl acetate (20 ml) and dried at 70°C for 24 h.

Synthesis of Fe₃O₄@Phos-IL-AuCu

A suspension of Fe₃O₄@Phos-IL (300 mg) in distilled water (6 mL) was sonicated for 15 min, and then, a solution of CuSO₄∙5H₂O (7.5 mg) and NaAuCl₄·2H₂O, (7.5 mg) in H₂O (2 mL) was added to the mixture and then stirred for 20 min in an ice bath under argon atmosphere. Next, NaBH₄ (0.6 mmol, 22.6 mg) in H₂O (1 mL) was added slowly and the reaction stirred for 1 d at 25 ºC. Finally, the resulting solid was separated and treated such it was described above.

Catalytic reduction of nitro compounds

Nitroarene (0.5 mmol), catalyst (25 mg containing 0.09 mol% Au and 0.19 mol% Cu), NaBH₄ (2 mmol, 75 mg), were mixed in H₂O (1.4 mL), and then, the mixture stirred at room temperature. Reaction was monitored by GC analysis and stopped when it was judged complete. The crude substance was treated with ethyl acetate (3 × 5 mL) and the organic residue purified by chromatography (column or plate).

General procedure for the catalytic reduction of MO, MR, and RhB dyes

A 2.5 mL of the desired dye’s solution (MO or MR or RhB, 0.06 mM), the catalyst (1 mg) and 0.5 mL of an aqueous solution of NaBH₄ (0.5 M) were poured into a quartz cuvette and the mixture stirred at room temperature. UV–Visible spectroscopy was selected to control the progress of the reaction.

Typical procedures for the degradation of TC

TC (0.005 mmol, 2.5 mg), catalyst (15 mg), and H₂O (50 mL) were poured into an Erlenmeyer flask and stirred for 3 min, and then ammonium peroxydisulfate (1 mmol, 240 mg) was poured to the mixture. Again, the reaction course was controlled every 10 min through UV–Visible spectroscopy.

Onepot synthesis of acetaminophen

In a 5 mL flask, 4-nitrophenol (0.4 mmol, 55.6 mg), NaBH₄ (1.6 mmol, 60.5 mg), catalyst (10 mg), and H₂O (1.5 mL) were added and the reaction was stirred at 25 ºC. After 2 h, acetic anhydride (1 mmol, 0.1 mL) was poured into the flask, and the reaction mixture was stirred for 2 additional hours at 100°C. The crude material was extracted with ethyl acetate (3×5 mL), purified by column/plate chromatography, obtaining acetaminophen in 84% isolated yield. It was only characterized by ¹H NMR.

In conclusion, a new magnetic and recyclable bimetallic Fe₃O₄@Phos-IL-AuCu catalyst was synthesized. This catalyst showed high activity in reducing nitro compounds, reduction of organic dyes, and degrading tetracycline. It also promoted all three of these reactions at room temperature in water solvent as a green solvent. Fe₃O₄@Phos-IL-AuCu catalyst showed the highest activity in comparison with its single metal species such as Fe₃O₄@Phos-IL-Au, and Fe₃O₄@Phos-IL-Cu in all the three reactions mentioned, which confirms the synergistic effects between gold and copper particles. In addition, the synthesized catalyst can be easily recycled due to its magnetic properties and reused for consecutive 17th times without noticeable decreasing in its activity.

Authors Contributions

Material preparation and data collection were performed by SMB. Analysis and edit of manuscript were performed by JMS and MG. The first draft of the manuscript was written by MG and SMB. All authors read and approved the final manuscript.

Competing Interests

Authors declare they have no financial interests.

Availability of data and materials

Data available on request from the authors

Acknowledgements

The authors are grateful to Institute for Advanced Studies in Basic Sciences (IASBS) Research Council and University of Alicante. We also thankful for financial support to the Ministerio de Ciencia, Innovación y Universidades (RED2018-102387-T, PID2019-107268GB-100), and FEDER, the Generalitat Valenciana (IDIFEDER/2021/013).

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Table 1 and 2 are available in the Supplementary Files section.

Schemes 1 and 2 are available in the Supplementary Files section

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Novel Magnetic Bimetallic AuCu Catalyst for Reduction of Nitroarenes and Degradation of Organic Dyes

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Result and Discussion

Experimental

Materials

Synthesis of Fe₃O₄ NPs

Synthesis of Fe₃O₄@SiO₂

Synthesis of Fe₃O₄@SiO₂@epoxide

Synthesis of Fe₃O₄@C₂H₄OPPh₂@1-(2-propynyl)-1H-imidazole

Synthesis of Fe₃O₄@Phos-IL

Synthesis of Fe₃O₄@Phos-IL-AuCu

Catalytic reduction of nitro compounds

General procedure for the catalytic reduction of MO, MR, and RhB dyes

Typical procedures for the degradation of TC

Onepot synthesis of acetaminophen

Conclusion

Declarations

References

Tables

Schemes

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1

Novel Magnetic Bimetallic AuCu Catalyst for Reduction of Nitroarenes and Degradation of Organic Dyes

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Result and Discussion

Experimental

Materials

Synthesis of Fe3O4 NPs

Synthesis of Fe3O4@SiO2

Synthesis of Fe3O4@SiO2@epoxide

Synthesis of Fe3O4@C2H4OPPh2@1-(2-propynyl)-1H-imidazole

Synthesis of Fe3O4@Phos-IL

Synthesis of Fe3O4@Phos-IL-AuCu

Catalytic reduction of nitro compounds

General procedure for the catalytic reduction of MO, MR, and RhB dyes

Typical procedures for the degradation of TC

Onepot synthesis of acetaminophen

Conclusion

Declarations

References

Tables

Schemes

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1

Synthesis of Fe₃O₄ NPs

Synthesis of Fe₃O₄@SiO₂

Synthesis of Fe₃O₄@SiO₂@epoxide

Synthesis of Fe₃O₄@C₂H₄OPPh₂@1-(2-propynyl)-1H-imidazole

Synthesis of Fe₃O₄@Phos-IL

Synthesis of Fe₃O₄@Phos-IL-AuCu