All the essential chemicals for this project were sourced from reputable suppliers, Fisher and Merck. We employed solvents and reagents from Sigma-Aldrich, Fluka, or Merck, directly utilizing them without any further purification. To closely monitor our reactions, we employed the thin-layer chromatography (TLC) technique, while purifying our compounds was achieved through meticulous column chromatography using high-quality Merck silica gel, graded between 230 and 400 mesh. Furthermore, we captured detailed 1H NMR and 13C NMR spectra, utilizing the sophisticated Bruker DRX-400 spectrophotometer operating at frequencies of 400 MHz and 100 MHz, respectively, to gain deeper insights into our molecular structures.

A 1-g quantity of graphene oxide (GO) was dispersed in 50 mL of distilled, deionized water and sonicated for 30 min, converting its surface carboxylic acid groups into carboxylate anions. Separately, 1 mmol (1.99 g) of iron (II) chloride tetrahydrate and 2 mmol (5.40 g) of iron (III) chloride hexahydrate were dissolved in 25 mL of distilled water, with their crystalline forms dissolving completely. This iron-rich solution was then gradually added to the GO suspension at room temperature, with vigorous stirring while a gentle nitrogen flow created a dynamic reaction atmosphere. Ammonia solution was slowly introduced, raising the pH to a brisk 12 and promoting the formation of magnetite nanoparticles (Fe₃O₄). As the reaction proceeded and the mixture reached 80 °C, stirring continued steadily for 5 h, allowing complex interactions to unfold. After cooling to room temperature, the suspension was rinsed with deionized water and subjected to magnetic separation to collect the product, which was then gently dried at 60 °C for 12 h. The result was a batch of magnetite nanoparticles embedded in or associated with the graphene oxide matrix, poised for further exploration of their properties and potential applications.

In a meticulously controlled laboratory environment, 2 g of GO/MNPs were subjected to vigorous reflux with 60 mL of thionyl chloride (SOCl₂) at 100 °C for 8 h, under a protective nitrogen blanket to prevent unwanted reactions. This crucial step activates and functionalizes the surface carboxyl groups of the graphene oxide. During the process, the carbonyl (C=O) group of the carboxylic acid reacts with the chloride ions released by thionyl chloride, forming acyl chlorides. To ensure product purity, anhydrous THF was used to thoroughly remove residual thionyl chloride from the newly formed acyl-functionalized graphene oxide, now designated GO/MNPs-COCl.

Following activation, the GO/MNPs-COCl nanomaterial underwent extensive purification, including three successive washes with anhydrous toluene to ensure complete elimination of impurities. After this cleansing sequence, the resulting solid GO/MNPs-COCl was efficiently separated using an external magnet. The final step involved gentle vacuum-drying at room temperature, a careful method chosen to preserve the functionalized material’s integrity and properties.

To construct the GO/MNPs-TEA nanocomposite, we began by combining 1 g of GO/MNPs-COCl with 2.5 g of triethanolamine in 50 mL of dimethylformamide (DMF) as the solvent, which promoted smooth dispersion. The mixture was then sonicated for 30 min, allowing high-frequency sound waves to agitate the components and promote thorough uniform integration. Following sonication, the blend was heated to 100 °C and stirred for 8 h to facilitate adequate bonding and enhance the nanocomposite’s structure. After the reaction, the GO/MNPs-TEA nanocomposite was isolated using a magnet to ensure efficient extraction. To ensure purity, the solid was washed three times with methylene chloride, using an external magnet to aid collection after each wash. Finally, the material was dried under vacuum, yielding a dry and stable GO/MNPs-TEA nanocomposite ready for future applications and research.

To prepare the innovative GO/MNPs-TEA-CuI nanocomposite, we began by adding 3 mmol of CuI to a well-blended suspension containing 1 g of ultrasonically dispersed graphene oxide and magnetic nanoparticles modified with triethanolamine (GO/MNPs-TEA), all in 50 mL of DMF. The mixture was heated to 100 °C and maintained at this temperature for 5 h to promote interactions and transformations among the components, ultimately yielding the iron oxide-coated silica nanocatalyst designated GO/MNPs-TEA-CuI. After synthesis, magnetic separation was used to recover the nanocomposite from the solution, and the material was thoroughly washed with hot water and ethanol to remove residual impurities. Finally, to ensure stability and optimal form, the product was gently dried at 60 °C, yielding a nanocomposite ready for further applications.

In a 20 mL flask, a carefully measured combination was assembled: 0.3 mmol of aryl aldehydes, 0.6 mmol of ammonium acetate, and 0.3 mmol of benzyl derivatives. To this reactive mixture, the GO/MNPs-TEA-CuI catalyst (6% molar scale) was added, initiating the transformation. The mixture was then gently stirred in 3 mL of water and brought to reflux, allowing the reaction to proceed for the designated intervals described in Table 2. The reaction was monitored closely by TLC to capture each stage of the transformation.

Upon completion, the catalyst was readily separated with a magnet, and the reaction mixture was cooled to room temperature. The cooled solution was diluted with 20 mL of dichloromethane (CH₂Cl₂) and filtered to remove any particulates, ensuring a clean organic phase. Solvent evaporation yielded the target product, which was subsequently isolated by silica gel flash chromatography using a eluent composed of hexane and ethyl acetate. The resulting 2,4,5-triaryl imidazole products were obtained as well-characterized compounds, with spectroscopic data aligning with established literature values. Additionally, comprehensive NMR data for the benzimidazole derivatives are documented in the Supplementary Material, providing a thorough record of the synthetic outcomes.

In a 20 mL round-bottom flask, a reaction was initiated as an aryl nitrile (0.5 mmol) and an alkyne (0.2 mmol) joined forces in the presence of the GO/MNPs-TEA-CuI catalyst (6% mol), all dissolved in a 4 mL of water. The mixture was brought to a gentle reflux, bubbling softly as the transformation progressed, with TLC diligently monitoring the reaction’s course. Upon completion, the catalyst was readily removed with a stirring bar, and the mixture was allowed to cool to room temperature. Aqueous Na₂CO₃ was added, the organic layer was separated and the aqueous phase was subjected. The organic phase was carefully separated, and the aqueous phase was subjected to a second extraction with ethyl acetate (2 × 10 mL) to recover any remaining product. Purification was achieved by silica gel column chromatography using a carefully chosen solvent system of petroleum ether and ethyl acetate (50:1), yielding a clean separation. The process yielded the desired 2,4,5-triaryl oxazole products, which were obtained as well-characterized compounds with spectroscopic data aligning with established literature values. Additionally, detailed NMR data for the benzimidazole derivatives are documented in the Supplementary Material, offering a comprehensive record of the successful outcomes from this synthetic endeavor.

The FT-IR spectra shown in Figure 1 provide insight into the stepwise chemical modifications of graphene oxide (GO) through the formation of the GO/MNPs–TEA–CuI nanocomposite. Each spectrum reflects the vibrational modes of functional groups present at various stages of synthesis, confirming successful chemical transformations. The FT-IR spectrum of Graphene Oxide (GO) displays characteristic absorption bands indicative of oxygen-containing functional groups. A broad peak around 3400 cm^-1 corresponds to O–H stretching vibrations from hydroxyl and carboxylic acid groups. The band at 1720 cm^-1 is attributed to C=O stretching of carbonyl groups, while peaks near 1620 cm^-1 correspond to C=C stretching from the aromatic ring. Additional peaks at 1220–1050 cm^-1 are assigned to C–O stretching vibrations from epoxy and alkoxy groups. In the GO/MNPs spectrum, there is a noticeable change compared to GO. The broad O–H peak persists, but the intensity of the C=O band around 1720 cm^-1 slightly decreases, suggesting interactions between GO’s oxygen groups and the Fe₃O₄ nanoparticles. A new band appears around 580–600 cm^-1, which is characteristic of Fe–O stretching, confirming the successful deposition of magnetic nanoparticles onto the GO surface.

The spectrum of GO/MNPs–Cl (after treatment with thionyl chloride) reveals a significant reduction in the O–H band, and the emergence of new bands near 1800–1780 cm^-1, indicating the formation of acid chloride (COCl) functionalities. The suppression of hydroxyl and carboxylic peaks confirms successful chlorination, replacing these groups with more reactive acyl chlorides. Upon reaction with triethanolamine (TEA), the GO/MNPs–TEA spectrum shows a reappearance and broadening of the O–H stretching band (∼3400 cm^-1), along with new peaks around 1100–1250 cm^-1, corresponding to C–N and C–O stretching from the TEA structure. These features confirm the successful attachment of TEA to the GO framework via ester or amide linkages, as well as the presence of its hydroxyl arms. Finally, the spectrum of GO/MNPs–TEA–CuI shows further changes. There is a slight shift and broadening of the bands in the region of 1000–1250 cm^-1, suggesting coordination between Cu(I) ions and the nitrogen or oxygen atoms of the TEA ligand. Additionally, new weaker peaks may appear below 600 cm^-1, typically associated with metal–ligand (Cu–O and Cu–N) interactions, supporting the successful incorporation of Cu(I) into the nanocomposite. Overall, the FT-IR data clearly illustrate the sequential chemical transformations and functionalizations throughout the synthesis process.

Figure 2 showcases the EDX spectrum and the elemental mapping analysis of the GO/MNPs–TEA–CuI nanocomposite, confirming the successful integration of several key elements into the material. The EDX spectrum reveals significant peaks for carbon (C), oxygen (O), nitrogen (N), iron (Fe), copper (Cu), and iodine (I). The presence of carbon and oxygen aligns with the expected characteristics of the graphene oxide structure, while the detection of iron signals indicates the successful embedding of Fe3O4 magnetic nanoparticles. The nitrogen signal stems from triethanolamine (TEA), which contains these nitrogen atoms. Notably, the peaks for copper and iodine highlight the successful coordination of copper(I) iodide with the TEA-functionalized GO/MNPs, confirming that the nanocomposite formation process has been completed.

Moreover, the elemental mapping images further reinforce the uniform distribution of each element across the composite’s surface. The consistent presence of carbon, nitrogen, and oxygen reflects the distribution of the GO backbone and TEA functional groups, while iron mapping shows an even incorporation of Fe₃O₄ nanoparticles, enhancing the composite’s magnetic properties. The consistent distribution of copper and iodine reinforces their stable coordination to the TEA ligands. This uniformity is essential for maintaining the structural integrity of the GO/MNPs–TEA–CuI nanocomposite, which is critical for its functionality in catalytic and environmental applications. Additionally, the ICP-OES analysis indicates a noteworthy copper concentration of 1.39 × 10⁻³ mol/g, confirming a substantial incorporation of copper within the composite structure, which is vital for its catalytic efficiency.

The Brunauer–Emmett–Teller (BET) analysis illustrated in Figure 3 (top graph) showcases the nitrogen adsorption–desorption isotherm for the GO/MNPs-TEA-CuI nanocomposite. The observed isotherm distinctly follows a Type IV curve, characterized by a pronounced hysteresis loop, a clear indication that the material possesses mesoporous properties. Upon a detailed investigation of the pore size distribution, it was determined that the average pore diameter of the catalyst measures 27.48 nm. Furthermore, the pore volume analysis revealed a significant reduction in this parameter, decreasing from an initial value of 11.298 cm³/g to 6.743 cm³/g. This reduction in pore volume might be attributed to alterations in the catalyst’s structural integrity or the occurrence of pore blockage phenomena. The porosity of the material is of paramount importance for catalytic applications, as it not only enhances the overall surface area but also promotes better accessibility of reactants to the active sites embedded within the composite structure.

The XRD pattern of the GO/MNPs-TEA-CuI nanocomposite reveals distinct peaks corresponding to each of its components, confirming successful synthesis (Figure 3). Notably, the broad peak typically observed for graphene oxide (GO) around 2θ ≈ 10°, which indicates the (001) plane, is either absent or considerably reduced. This significant change suggests that exfoliation and chemical modification of the GO layers have taken place, transforming their structure. Furthermore, the XRD analysis reveals characteristic peaks associated with Fe₃O₄ magnetic nanoparticles, appearing at specific angles of 2θ ≈ 30.1°, 35.5°, 43.2°, 53.5°, 57.1°, and 62.7°. These peaks correspond to the (220), (311), (400), (422), (511), and (440) crystallographic planes, respectively, which confirm the presence of crystalline magnetite within the composite. In addition to the GO and Fe₃O₄ signatures, distinct peaks observed at approximately 25.5°, 29.6°, 42.3°, 50.1°, and 61.3° further indicate the successful formation of the cubic-phase CuI. This peak positioning substantiates that copper(I) iodide has been effectively integrated and anchored within the nanocomposite structure. These results collectively confirm the structural integrity and integration of GO, Fe₃O₄, and CuI in the nanocomposite.

The Vibrating Sample Magnetometry (VSM) spectrum presented in the left graph of Figure 4 reveals the magnetic properties of the GO/MNPs-TEA-CuI nanocomposite, showcasing a clear hysteresis loop that indicates superparamagnetic behavior with minimal coercivity and remanence. This behavior is complemented by a remarkable saturation magnetization value of 44.726 emu/g, signifying a strong magnetic response primarily due to the presence of Fe₃O₄ magnetic nanoparticles (MNPs) within the graphene oxide (GO) matrix. Such impressive magnetic characteristics make the nanocomposite particularly advantageous for applications like magnetic separation, where the nanocatalyst can be easily and efficiently retrieved from reaction mixtures using an external magnet, thereby enhancing the effectiveness and simplicity of the recovery process.

The Thermogravimetric Analysis (TGA) spectrum, depicted in the right graph of Figure 4, offers valuable insights into the thermal stability and composition of the nanocomposite. The TGA curve reveals three distinct stages of weight loss that correspond to different thermal events. Initially, between 100 °C and 150 °C, the curve indicates the loss of adsorbed water and moisture trapped within the material. As the temperature rises to between 200 °C and 400 °C, we see a significant decline likely due to the thermal degradation of organic compounds, particularly triethanolamine (TEA), and the breakdown of oxygenated functional groups on graphene oxide (GO). The most significant weight loss occurs beyond 400 °C, marking the decomposition of the GO framework and the degradation of any remaining organic components. Notably, the residual weight observed beyond 600 °C points to the presence of thermally stable inorganic materials, like Fe₃O₄ and CuI, highlighting the composite’s hybrid nature. Overall, these TGA results emphasize the excellent thermal stability of the nanocomposite, positioning it as a promising candidate for high-temperature applications.

In Figure 5, the SEM images taken at different magnifications (2 μm, 1 μm, 500 nm, and 200 nm) provide comprehensive surface morphology information about the GO/MNPs-TEA-CuI catalyst. At lower magnifications (2 μm and 1 µm), the catalyst exhibits a highly aggregated, clustered morphology composed of spherical and semi-spherical nanoparticles forming dense, coral-like structures. These particles appear to be evenly distributed with some degree of agglomeration, which is typical for magnetic nanoparticles (MNPs) and indicates strong interparticle interactions. As the magnification increases (500 nm and 200 nm), the surface texture becomes clearer, revealing individual nanoparticles with smooth surfaces and relatively uniform sizes. The higher-resolution images suggest that the catalyst has a porous, high-surface-area structure, which is advantageous for catalytic reactions due to the increased number of accessible active sites. The observed particle size distribution and surface roughness imply that the functionalization with TEA and loading of CuI were successful and well-integrated into the GO matrix.

In Figure 6, the TEM images (150 nm and 100 nm scales) provide detailed internal and interfacial structural information of the GO/MNPs-TEA-CuI catalyst. These images show a distinct contrast between the darker, electron-dense regions—representing the MNPs/CuI nanoparticles—and the lighter, semi-transparent areas, which correspond to the thin layers of graphene oxide (GO). The TEM at 150 nm reveals a loosely packed network of nanoparticles spread over a wrinkled GO sheet, confirming the successful anchoring of the nanoparticles on the GO support. At 100 nm, more detail emerges: individual nanoparticles are clearly visible with well-defined boundaries, suggesting a narrow particle size distribution and minimal agglomeration. The intimate contact between the nanoparticles and GO sheets implies good chemical bonding and stable integration, likely due to the coordination with the TEA linker. This structural configuration enhances the dispersion of the active CuI sites and supports efficient electron transfer, which are critical factors for catalytic performance. Overall, the TEM analysis corroborates the SEM findings and further validates the nanocomposite’s homogeneity and well-organized microstructure.

Table 1 presents a detailed investigation into the optimization of reaction conditions for the synthesis of product 4a via a one-pot multicomponent reaction involving 4-chlorobenzaldehyde, benzyl, and ammonium acetate, catalyzed by a functionalized copper catalyst, GO/MNPs–TEA–Cu(I). The key goal was to identify the ideal catalyst loading, solvent, reaction time, and temperature to achieve the highest yield of the desired product.

Figure 7 illustrates the reusability of the GO/MNPs-TEA-CuI nanocatalyst in the synthesis of 2,4,5-triphenyl-1H-imidazole (product 4b) and 2,4,5-triphenyloxazole (product 7a) across nine consecutive reaction cycles. In the first three cycles, the catalyst exhibits excellent performance, maintaining a consistent yield of 98% for both products, indicating high catalytic stability and efficiency. From the fourth to sixth cycle, only a slight reduction is observed, with yields gradually decreasing to 97%–94% for product 4b and 97%–93% for product 7a. This slight decline suggests minor loss in catalytic activity, likely due to minimal structural or surface deactivation. In later cycles (7–9), a more pronounced decrease in yield is evident. Product 4b shows yields of 92%, 90%, and 88%, while product 7a exhibits slightly lower values of 91%, 87%, and 87%, respectively. Despite this gradual reduction, the yields remain within a high and acceptable range, confirming the durability and effectiveness of the GO/MNPs-TEA-CuI catalyst over multiple uses. The ability to retain over 87% yield after nine cycles highlights the catalyst’s excellent reusability, making it a promising and sustainable option for repeated applications in heterocyclic compound synthesis.

Figures 8, 9 illustrate the FT-IR and XRD spectra of the GO/MNPs-TEA-CuI catalyst in both fresh and reused states, clearly demonstrating the catalyst’s structural integrity after seven reaction cycles. The FT-IR spectra (Figure 8) for the fresh and reused catalysts exhibit nearly identical characteristic peaks with only slight shifts, indicating that the functional groups associated with GO, TEA, and CuI remain largely unchanged after repeated use. Similarly, the XRD patterns (Figure 9) show consistent diffraction peaks between the fresh and reused samples, confirming that the crystalline structure and phase purity of the catalyst are well-preserved. These findings suggest that the catalyst maintains its original morphology, crystallinity, and chemical structure, proving its high thermal and chemical stability during catalytic processes.

Figure 10 presents the Vibrating Sample Magnetometry (VSM) curve of the reused GO/MNPs-TEA-CuI catalyst, displaying a strong magnetic response with a saturation magnetization value of 41.634 emu/g. Although slightly lower than the fresh state, this high value confirms that the magnetic characteristics are still well-retained, allowing for efficient magnetic recovery and reuse of the catalyst. Additionally, the inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis shows that the copper content in the reused catalyst (1.36 × 10⁻³ mol/g) is only marginally lower than in the fresh catalyst (1.39 × 10⁻³ mol/g), indicating negligible metal leaching during the reaction process. Together, these results validate that the GO/MNPs-TEA-CuI nanocomposite not only offers excellent structural and magnetic stability but also possesses strong durability and reusability for prolonged catalytic applications.

Tables 4, 5 provide a comparative evaluation of the catalytic efficiency of the GO/MNPs-TEA-CuI nanocomposite (Entry 6) against other previously reported catalytic systems in the synthesis of triphenyl imidazole (4b) and triphenyl oxazole (7a), respectively. The comparison includes key metrics such as reaction time, reaction conditions, reusability, and product yield, offering a comprehensive assessment of the method’s overall performance.

Green check mark indicating a positive or successful action. Green Chemistry Approach: Reactions are performed in water without using toxic organic solvents or additives.

Green check mark indicating a positive or successful action. Broad Substrate Scope: Works well with electron-donating, electron-withdrawing, and heteroaryl substrates.

Green check mark indicating a positive or successful action. High Efficiency: High yields (77%–99%), low catalyst loading (6 mol%), and fast reaction times.

Green check mark indicating a positive or successful action. Mild Reaction Conditions: Requires only reflux in water with no harsh reagents, making it safer and energy-efficient.

Green check mark indicating a positive or successful action. Recyclable Catalyst: The magnetic GO/MNPs–TEA–CuI catalyst can be easily separated and potentially reused.

Green check mark indicating a positive or successful action. High TON and TOF: The catalyst exhibits excellent productivity, as demonstrated by high Turnover Number (TON) and Turnover Frequency (TOF).

Green check mark indicating a positive or successful action. Versatile Synthetic Utility: Applicable to the synthesis of imidazoles and oxazoles, which are key scaffolds in medicinal and organic chemistry.

Green check mark indicating a positive or successful action. Environmentally Friendly and Scalable: Simple workup and purification, minimal waste generation, and potential for large-scale applications.