Introduction

During the past several decades, research on developing sustainable processes with the aim of waste minimization and adherence to the principles of green chemistry has increased dramatically1,2,3,4,5. In organic synthesis, the use of toxic, inflammable, and harmful solvents can harm the environment and humans6,7,8,9. Therefore, it is essential to use green and sustainable protocols such as catalyst and solvent (H2O, EtOH, …) to reduce hazardous substances and control pollution10,11. The organic transformation should generate less waste material or by-products, use less energy, and decrease the use of poisonous and toxic solvents such as toluene or catalysts12,13,14,15,16. The objective of green chemistry is to create products and processes that are biocompatible and minimize the use and generation of harmful substances for both humans and the natural environment17.

Scientists are driven to create synthetic methods to reduce the creation of toxic material using green chemistry concepts18. Organic production and ecological synthesis both require green catalysts19. It is the most efficient technique for chemical synthesis since it avoids the need for hazardous volatile solvents, reagents, catalysts, dangerous processes, and the required minimal reaction time without producing hazardous sludge11,20,21. One of the core tenets of green chemistry focuses on the development of eco-friendly, range of recyclable and readily available catalysts22.

Homogeneous catalysts generally provide higher selectivity and catalytic activity compared to heterogeneous catalysts. However, they also present several drawbacks, including material corrosion, waste production, separation and recycling issues, high costs, and low efficiency23. Consequently, a major research goal in organic and green chemistry is to develop highly active and selective heterogeneous catalysts. These challenges can be addressed by immobilizing homogeneous catalysts on various supports, such as polymers, mesoporous materials, metal-organic frameworks (MOFs), metal oxides, and nanoparticles24,25,26.

Nanocatalysts serve as a bridge between homogeneous and heterogeneous catalysis. Recently, various nanoparticles (NPs) have been widely used as effective adsorbents or supports for the immobilization of different homogeneous catalysts across various research fields, owing to their unique particle size and high surface area27. Among these nanoparticles, nano metal oxides such as Fe2O3, Fe3O4, TiO2, Al2O3, ZnO, etc., offer numerous advantages due to their exceptional physical and chemical properties17. These NPs have found diverse applications in catalysis, optics, electrochemistry, medicine (including pharmaceuticals and magnetic resonance imaging, MRI), as well as in adsorption and separation technologies28,29.

Magnetic nanoparticles (MNPs) have recently garnered attention as solid support materials for various homogeneous catalysts and as nanocatalysts in organic synthesis due to several advantages30,31,32. These include high stability, low cost, low toxicity, biocompatibility, environmental benignity, easy functionalization and preparation and the high surface area that creates highly active sites on the particle surface and high loading capacity33,34,35.

In recent years, Fe3O4 magnetic nanoparticles have gained considerable interest as outstanding supports for immobilizing various catalysts due to their unique properties, containing being insoluble in most reaction solvents, highly compatible, nontoxic, easy to prepare, cost-effective, stable, and having a high surface area36,37,38,39,40. These nanoparticles can be readily retrieved using an external magnet41,42,43,44. Additionally, Fe3O4 nanoparticles can be coated with a range of organic and inorganic materials, including silica, surfactants, polymers, cellulose, carbon, and chitosan, and can be engineered with a core–shell structure45,46,47. Moreover, it is feasible to functionalize the surface of Fe3O4 nanoparticles with various organic and inorganic ligands that are rich in electron donors, such as cyclodextrins, metal-organic frameworks (MOFs), silanes, and melamine48,49.

Melamine (2,4,6-triamino-1,3,5-triazine) is a stable six-membered heterocyclic aromatic organic compound with three amino groups50. It is readily synthesized and commercially available. Originally used to produce amino resins and plastics, melamine has numerous industrial applications51,52. Due to the electron-withdrawing nature of the triazine ring and the abundance of lone pairs of electrons on nitrogen atoms, melamine can serve as a beneficent support for nano-sized catalysts53. It is conventionally recognized and widely used as an effective cross-linker because of its chelating ability with metal ions, attributed to the presence of numerous aminal groups that provide ample sites for metal chelation, making chemical post-modification straightforward54.

Multicomponent reactions (MCRs) being efficient and effective methods for the synthesis of heterocyclic scaffolds from several diversity elements in a one pot operation with high degree of selectivity, diversity, synthetic convergence and atom-economy55. In recent decades, design of new MCRs with employing catalyst and the green solvents has attracted much attention.

Benzimidazole and its derivatives are significant heterocyclic compounds with high biological and pharmaceutical activities56. Alternatively, the most prominent benzimidazole compound in nature is N-ribosyl-dimethylbenzimidazole, which has a distinct cobalt linkage to vitamin B12. These compounds have garnered the attention of scientists and have become a focal point for synthetic research due to their important applications40,58. Substituted benzimidazoles are extensively used as key components in antiviral and antitumor agents, as well as in antidepressant, anti-inflammatory, analgesic, antibiotic, antifungal, antimycotic, anti-allergic, antibacterial and antiulcerative drugs59. Some well-known medications such as thiabendazole, cimetidine, azomycine, metronidazole, misonidazole, clotrimazole, astemizole, and omeprazole contain a benzimidazole core in their structures60,61.

Due to our previous works in the synthesis of heterocyclic compounds using nanocatalysts62,63, we aim to report the preparation, characterization, and catalytic study of two melamine-functionalized magnetic nanocomposites and their applications in the synthesis of biologically active benzimidazole derivatives.

Experimental

Materials and methods

All reagents were purchased from Fluka and Merck companies and were used without any purification. Melting points were determined using an Electrothermal 9200 apparatus, and elemental analysis was conducted with a Vario EL III elemental analyzer. Thin layer chromatography (TLC) was performed on Merck 0.2 mm silica gel 60 F-254 Al-plates. FT-IR spectra were recorded on a Galaxy series FT-IR 5000 spectrometer, using KBr pellets in the range of 400–4000 cm− 1. 1H and 13C NMR spectra were obtained on a Bruker Avance spectrometer operating at 400 MHz for 1H and 13C, respectively. Thermogravimetric analysis (TGA) was carried out using a Mettler TA4000 System. X-ray diffraction (XRD) was performed on a Philips X-Pert diffractometer (Cu-Ka radiation, λ = 0.15405 nm) in the range of 2θ = 20°–80° with a step length of 0.04°. A Hitachi S-4700 field emission-scanning electron microscope (FE-SEM) was used to study particle size, external shape, and to detect the elements present in the nanocomposites via EDS analysis.

Synthesis of Fe3O4 magnetic nanoparticles (Fe3O4 MNPs)

Fe3O4 magnetic nanoparticles were synthesized by Fe2+ (FeSO4·7H2O) and Fe3+ (FeCl3·6H2O) reagent in an alkaline solution under hydrothermal conditions36. First, a 100 ml solution of NaOH (4 M) was stirred in a three-neck flask. Then the alkaline solution was bubbled with nitrogen atmosphere for 40 min at 63 °C. A mixture of iron ions, consisting of 20 ml of FeSO4·7H2O (0.5 M) and 23 ml of FeCl3·6H2O (0.5 M), was quickly added to the alkaline solution. The appearance of a black precipitate indicated the formation of iron oxide particles. Afterward, the reaction mixture was stirred for 90 min and the reaction mixture was cooled to 25 °C. The magnetic nanoparticles were collected by a super magnet, washed with distilled water to neutralize the pH, and subsequently with dry acetone and ethanol. Then, the nanoparticles were dried under vacuum conditions at 25 °C for 3 days to ensure complete dryness64.

Synthesis of Fe3O4@CPTMS (Fe3O4/Pr-Cl)

The Chloro-functionalized Fe3O4 MNPs (Fe3O4/Pr-Cl) were synthesized by reacting 1 gram of Fe3O4 nanoparticles with 5 ml of 3-Chloropropyltrimethoxysilane (CPTMS) in 50 ml of n-hexane. The resulting mixture was sonicated for 30 min. The reaction mixture was then refluxed for 24 h at 80 °C under nitrogen atmosphere to obtain the Fe3O4/Pr-Cl nanoparticles. The resulting Fe3O4/Pr-Cl MNPs were separated by an external magnet, washed repeatedly with ethanol, and dried at room temperature17.

Synthesis of Fe3O4@Melamine (Fe3O4@Mel)

Fe3O4@Mel was synthesized using a simple method. First, 0.2 g of Fe3O4@CPTMS and 0.33 g of K2CO3 were added to 50 mL of ethanol. Then, 0.3 g of melamine was added to the mixture. Finally, resulting mixture was sonicated for 15 min and then refluxed for 24 h at 78 °C. The formed product was collected using an external magnetic field, washed with ethanol, and dried overnight in an oven at 60 °C38.

Synthesis of Fe3O4@Mel@CuO

The prepared Fe3O4@Mel (0.4 g) was well dispersed in deionized water via sonication for 10 min. Then, 0.134 g copper oxide and 0.27 g sodium hydroxide were added in several sections. Finally, the mixture was extremely stirred under reflux conditions for 14 h. The synthesized Fe3O4@Mel@CuO nanocomposite 1 was separated using a super magnet, washed repeatedly with ethanol and deionized water, and dried overnight in an oven at 60 °C.

Synthesis of Fe3O4@ Mel-CC@TEPA@CuO

Synthesis of Fe3O4@ Mel-CC

Fe3O4@Mel-CC was synthesized using a simple method. First, 0.52 g of Fe3O4@Mel and 0.25 g of cyanuric chloride (CC) were added to 50 mL ethanol. The resulting mixture was sonicated for 15 min and refluxed under nitrogen atmosphere for 16 h at 78 °C. The formed product was separated using a super magnet, washed with ethanol, and dried overnight in an oven at 60 °C75.

Synthesis of Fe3O4@Mel-CC@TEPA

The Fe3O4@Mel-CC@TEPA was synthesized by reacting 0.5 g of Fe3O4@Mel-CC with 0.27 ml of tetraethylenepentamine (TEPA) in 50 ml of ethanol, and sonicated for 15 min. Then, the reaction mixture was stirred under reflux conditions for 24 h to obtain the nanocomposite.

Synthesis of Fe3O4@Mel-CC@TEPA@CuO

The prepared Fe3O4@Mel-CC@TEPA (0.5 g) was well dispersed in deionized water via sonication for 10 min. Then, 0.33 g copper oxide and 0.33 g sodium hydroxide were added in several sections. Finally, the mixture was extremely stirred under reflux conditions for 14 h. The produced Fe3O4@Mel-CC@TEPA@CuO nanocomposite 2 was collected using a super magnet, washed repeatedly with deionized water and ethanol, and dried overnight in an oven at 60 °C.

General procedure for the Preparation of benzimidazole derivatives in the presence of nanocomposite 2

The synthesis of benzimidazole derivatives was done by a mixture containing 1,2-phenylenediamine (1 mmol), aromatic aldehydes (1 mmol), and Fe3O4@Mel-CC@TEPA@CuO (20 mg, 16.2 mol%) in 2 mL of ethanol, which was stirred at room temperature. The progress of the reactions was monitored by thin layer chromatography (TLC) (ethyl acetate: n-hexane, 2:3). After the reaction was complete, the catalyst was separated using an external magnetic field, the solvent was evaporated, and the residue was recrystallized in ethanol. The products were analyzed by 1H NMR and 13C NMR (See Supplementary Information).

Results and discussion

The magnetic nanoparticles (MNPs) were easily synthesized by the chemical co-precipitation of Fe2+ and Fe3+ ions in a basic solution, which were used as precursors for the synthesis of 3-chloropropyl-functionalized magnetic nanoparticles (Fe3O4@Pr-Cl). Afterward, melamine was grafted onto the surface of Fe3O4@Pr-Cl. Finally, the melamine-functionalized magnetic nanoparticles were functionalized with CuO nanoparticles to form Fe3O4@Mel@CuO nanocomposite (Fig. 1). Figure 2 illustrates the procedure for the preparation of Fe3O4@Mel-CC@TEPA@CuO nanocomposite. First, the Fe3O4@Mel was modified by grafting cyanuric chloride onto the amino groups of the melamine moieties to prepare Fe3O4@Mel-CC. Then, the amino groups of tetraethylenepentamine were replaced with the chlorine atoms of cyanuric chloride, resulting to the formation of Fe3O4@Mel-CC@TEPA. Subsequently, Fe3O4@Mel-CC@TEPA was dispersed in a solution of CuO to form Fe3O4@Mel-CC@TEPA@CuO nanocomposite. Therefore, we prepared two novels magnetically nanocomposites via immobilization of melamine on Fe3O4. Then, the aliphatic amine (TEPA) was attached to the aromatic amine (Melamine) by cyanuric chloride as linker. Thusly, the number of active sites increased in nanocomposite 2 and higher percentage of CuO was supported on it.

Fig. 1
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Illustration of the synthesis of Fe3O4@Mel@CuO nanocomposite.

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Fig. 2
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Illustration of the synthesis of Fe3O4@Mel-CC@TEPA@CuO nanocomposite.

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The synthesized nanocomposites were then fully characterized using various techniques as discussed below.

FT-IR

In the FT-IR spectrum of Fe3O4@Si-Cl (Fig. 3a), a very strong and broad band, spanning from 2800 to 3600 cm− 1, is indicative of the O–H stretching vibration. This band broadened due to the increase in nitrogen groups and CuO, from Fig. 3a to f. The peaks visible at 1023 and 697 cm− 1 are attributed to Si-O-Si and Fe-O-Si stretching vibrations, respectively. The characteristic bands for the asymmetric and symmetric stretching vibrations of N–H groups are not visible in the FT-IR spectra of Fe3O4@Mel (Fig. 3b) and Fe3O4@Mel-CC@TEPA (Fig. 3d), likely due to their overlap with the broad band associated with OH groups27,38. An additional weak band (at 2854 cm− 1) is related to C–H stretching vibrations (Fig. 3a) and broadened from Fig. 3a and f. In the spectra of the two compounds, two new bands were observed at 1437 cm− 1 and 1548 cm− 1 (Fig. 3b)40 and it became sharpener in Fig. 3d. These bands are attributed to the semicircle stretching and quadrant stretching of the triazine groups in 3b and TEPA in 3d, respectively. The signal at 769 cm− 1 in Fig. 3c can be attributed to the C–Cl bond. Additionally, the characteristic band for Cu–O stretching vibrations was observed at 550 cm− 1 in Fig. 3e and 537 cm− 1 in Fig. 3f.

Fig. 3
figure 3

FTIR spectroscopy of (a) Fe3O4@Si-Cl, (b) Fe3O4@Mel, (c) Fe3O4@Mel-CC (d) Fe3O4@Mel-CC@TEPA, (e) Fe3O4@Mel@CuO, (f) Fe3O4@Mel-CC@TEPA@CuO.

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FE‑SEM

The size and shape of Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites were examined using FE-SEM, as shown in Figs. 4 and 5. The diameter of the nanoparticles was found to be between 40 and 90 nm. Additionally, some aggregation observed in the FE-SEM images confirmed the successful grafting of copper oxide onto the surface of the magnetic nanoparticles.

Fig. 4
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FE-SEM image of Fe3O4@Mel@CuO nanocomposite.

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Fig. 5
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FE-SEM image of Fe3O4@Mel-CC@TEPA@CuO nanocomposite.

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EDS

The components of Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites were examined using energy dispersive X-ray spectrometry (EDS) (Figs. 6 and 7). As can be seen, Cu existed in both the Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites. Moreover, the signals assigned to other elements like C, Si, O, Fe, and N were shown in the EDS analysis. The presence of all the expected atoms in the EDS analysis confirmed the successful synthesis of the Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites.

Fig. 6
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The EDS analysis of (a) Fe3O4@Mel and (b) Fe3O4@Mel @CuO nanocomposites.

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Fig. 7
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The EDS analysis of (a) Fe3O4@Mel-CC@TEPA and (b) Fe3O4@Mel-CC@TEPA @CuO nanocomposites.

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ICP

ICP analyses was performed on two nanocomposites and evaluation of Cu content on their surface was found 2.57 mmol/g for nanocomposite1 and 8.08 mmol/g for nanocomposite 2.

XRD

The XRD patterns of Fe3O4@Mel (Fig. 8a), Fe3O4@Mel@CuO (Fig. 8b), Fe3O4@Mel-CC@TEPA (Fig. 9a) and Fe3O4@Mel-CC@TEPA@CuO (Fig. 9b) nanocomposites exhibited diffraction peaks at 2θ values of 30.4, 35.7, 43.3, 53.9, 57.3, 62.7, and 74.5. These peaks correspond to the cubic structure of Fe3O4 nanoparticles. This XRD pattern aligns closely with the standard Fe3O4 sample (JCPDS card No. 85–1436) confirming the presence of pure Fe3O4 with a cubic spinel structure.

Fig. 8
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XRD of (a) Fe3O4@Mel and (b) Fe3O4@Mel@CuO nanocomposites.

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Fig. 9
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XRD of (a) Fe3O4@Mel-CC@TEPA and (b) Fe3O4@Mel-CC@TEPA@CuO nanocomposites.

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TGA

The thermal stability of Fe3O4@Mel, Fe3O4@Mel@CuO, Fe3O4@Mel-CC@TEPA, and Fe3O4@Mel-CC@TEPA@CuO nanocomposites were examined, and the results are illustrated in Figs. 10 and 11. Two weight loss steps were observed for these compounds. The weight loss below 110 °C was assigned to the removal of physically water and trapped solvents, while the weight loss over the range of 200–450 °C (2.55%) in Fig. 10a, (1.1%) in Fig. 10b and (67.5%) in Fig. 11a, (39.5%) in Fig. 11b was related to the decomposition of the coating organic layer in nanocomposites.

Fig. 10
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TGA of the (a) Fe3O4@Mel, (b) Fe3O4@Mel@CuO nanocomposites.

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Fig. 11
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TGA of analysis (a) Fe3O4@Mel-CC@TEPA and, (b) Fe3O4@Mel-CC@TEPA@CuO nanocomposites.

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VSM

The room temperature magnetization behaviors of Fe3O4 and Fe3O4@Mel@CuO nanocomposite (Fig. 12), Fe3O4 and Fe3O4@Mel-CC@TEPA@CuO nanocomposite (Fig. 13) was investigated by VSM analytical method. The VSM curves shown in Figs. 12a and 13a indicated that the bare Fe3O4 nanoparticles have a saturation magnetization of approximately 67.96 emu/g (Figs. 12a and 13a). It is apparent that the magnetic properties of Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites decreased (26.40 emu/g, Fig. 12b) and (59.23 emu/g, Fig. 13b) after surface modification of Fe3O4 nanoparticles. These decreation in magnetization saturation value of Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO nanocomposites could be attributed to the successful coating of melamine and tetraethylenepentamine and successful immobilization of CuO on the surface of Fe3O4 nanoparticles.

Fig. 12
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VSM analysis of (a) Fe3O4, (b) Fe3O4@Mel@CuO nanocomposite.

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Fig. 13
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VSM analysis of (a) Fe3O4, (b) Fe3O4@Mel-CC@TEPA@CuO nanocomposite.

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Catalytic studies

Following the characterization of the Fe3O4@Mel@CuO nanocomposite (1) and the Fe3O4@Mel-CC@TEPA@CuO nanocomposite (2), the synthesis of benzimidazole derivatives was selected to evaluate their catalytic performance. The model reaction chosen for this purpose was the synthesis of compound 4, involving 1,2-phenylenediamine 2 (1 mmol) and benzaldehyde 3 (1 mmol). The reaction conditions were optimized by varying parameters such as the solvent, the type and amount of catalyst, and temperature and the results of this study was illustrated in Table 1. In the absence of catalyst, no reaction occurred after 300 min under reflux in ethanol or water (Table 1, entry 1, 2). The model reaction carried out using Fe3O4, Fe3O4@Mel, Fe3O4@Mel-CC@TEPA, Fe3O4@Mel-CC@TEPA@CuO as catalyst and their catalytic effects were moderate (Table 1, entry 3–6). The reaction proceeded more efficiently in the presence of Fe3O4@Mel-CC@TEPA@CuO nanocomposite in various solvents such as THF, CHCl3, EtOAc, CH3CN, H2O, EtOH/H2O and EtOH (Table 1, entry 7–13). Also, the temperature effect was examined at room temperature and 50 °C in EtOH (Table 1, entry 13–14). Under similar conditions, increasing the catalyst amount from 10 to 20 mg raised the yield from 75 to 95%, but 25 mg of catalyst did not affect improving the reaction yield (Table 1, entry 14–16). The Fe3O4@Mel-CC@TEPA@CuO nanocomposite indicated a much higher catalytic activity than Fe3O4@Mel@CuO nanocomposite under the same conditions (Table 1, entry 14, 17). According to the findings presented in Table 1, the optimal conditions involved using Fe3O4@Mel-CC@TEPA@CuO as the catalyst at room temperature in ethanol, with 20 mg of the catalyst being sufficient to achieve the desired outcome. Therefore, with growing of the first nanocomposite by addition of cyanuric chloride and tetraethylenepentamine, the number of active sites has increased in nanocomposite 2 and as the ICP results show, a higher percentage of Cu was supported on nanocomposite 2 (8.08 mmol/g) and its efficiency was increased when used as a catalyst.

Table 1 The optimization of the reaction conditions for the reaction of 1,2-phenylenediamine and aldehydesa.
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To explore the versatility and broad applicability of Fe3O4@Mel-CC@TEPA@CuO as a heterogeneous catalyst for synthesizing benzimidazoles, various aromatic aldehydes with either electron-donating or electron-withdrawing groups were reacted with 1,2-phenylenediamine. The outcomes of these reactions are detailed in Table 2.

Table 2 Synthesis of benzimidazole derivatives in the presence of Fe3O4@Mel-CC@TEPA@CuO as the catalysta.
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The structures of all benzimidazole derivatives were assigned using melting point, 1H NMR and 13C NMR spectroscopy which agreed well with the data obtained in the mentioned literatures.

To assess the catalytic efficiency of Fe3O4@Mel-CC@TEPA@CuO, a comprehensive list of various organic and inorganic catalysts employed for the synthesis of benzimidazole derivatives under optimal conditions was compiled in Table 3. Among these catalysts, Fe3O4@Mel-CC@TEPA@CuO stands out due to its unique magnetic properties. Additionally, other benefits such as short reaction times, simple reaction conditions, environmental friendliness, high recovery rate, easy work-up, and low cost make Fe3O4@Mel-CC@TEPA@CuO one of the most effective catalysts for synthesizing benzimidazoles.

Table 3 The comparison of Fe3O4@Mel-CC@TEPA@CuO with the other reported catalysts for the synthesis of benzimidazole derivativesa.
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The synthesis of benzimidazole derivatives (4) can be proposed to occur via the following mechanism, starting with reaction of 1,2-phenylenediamine (2) and aldehydes (3), catalyzed by nanocomposite 2. The nanocomposite functions as a Lewis acid, activating the aldehyde carbonyl group and facilitating the formation of the imine (5). The resulting imine undergoes ring closure through an intramolecular attack of the amino group on the C = N double bond, yielding intermediate (7). This intermediate then undergoes aromatization through aerial oxidation, leading to the formation of the desired products (4) as shown in Fig. 14.

Fig. 14
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Proposed mechanism for synthesis of benzimidazole derivatives.

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Catalyst recovery and reusability

The ability to recover and reuse catalysts is crucial in chemistry and is a significant factor for commercial and industrial applications. Therefore, the recovery and reusability of Fe3O4@Mel-CC@TEPA@CuO were evaluated in the synthesis of benzimidazole derivatives under optimized conditions. The findings demonstrated that the catalyst could be recycled at least five times without a notable decrease in the reaction yield (Fig. 15). The FT-IR of the fresh and recycled catalyst, Fe3O4@Mel-CC@TEPA@CuO, is given in Fig. 16.

Fig. 15
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Recycling of Fe3O4@Mel-CC@TEPA@CuO for the synthesis of benzimidazole reaction.

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Fig. 16
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(a) FT-IR analysis of (a) Fe3O4@Mel-CC@TEPA@CuO, (b) Recycle of Fe3O4@Mel-CC@TEPA@CuO.

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Conclusion

A straightforward, efficient, and cost-effective method was developed for the synthesis of two new, magnetically separable, stable and reusable nanocomposites Fe3O4@Mel@CuO and Fe3O4@Mel-CC@TEPA@CuO, as heterogeneous catalysts. These new nanocomposites were characterized using diverse analytical techniques, including FT-IR, XRD, VSM, TGA, FE-SEM, EDS, and ICP. Their performance was evaluated and compared in the synthesis of benzimidazole derivatives. As a result, Fe3O4@Mel-CC@TEPA@CuO showed better catalytic activity compared to Fe3O4@Mel@CuO. High catalytic activity, versatility, simple experimental procedure, excellent recovery capability, and easy work-up are among advantages of this catalytic method.

As the Outlook for future work, the produced benzimidazoles can be examine for their biological and medicinal activities. Also, we believe that Fe3O4@Mel-CC@TEPA@CuO nanocomposite may be use as a powerful catalyst for the diversity of organic synthesis such as coupling reactions. On the other hand, this nanocomposite can also be used in metal adsorption.