A facile and efficient synthesis of highly functionalized pyrroles via a four-component one-pot reaction in the presence of Ni(II) Schiff base/SBA-15 heterogeneous catalyst

In this study, the Ni(II) Schiff base/SBA-15 catalyst was successfully synthesized and characterized by employing FT-IR, XRD, TGA, EDX, ICP-OES, TEM, and SEM analysis. In addition, BJH and BET techniques were used to determine the specific surface area, pore size, and pore volume of the catalyst, which were 538 m2 g−1, 6 nm, and 1.01 cm3 g−1, correspondingly. Under favorable conditions, we have designed a one-pot multicomponent reaction combining aromatic amines, aldehydes, nitroalkanes, and 1,3-dicarbonyl compounds in conjunction with the presence of the Ni(II) Schiff base/SBA-15 as a heterogeneous catalyst to synthesize a range of functionalized pyrroles in reasonable to excellent yields an admirable yield percentage (94%), a short reaction time of approximately 8 h, mild reaction conditions of 70 °C, a wide range of substrates, the possibility of large-scale synthesis, low cost, and the avoidance of hazardous reagents and solvents. In addition, this method can synthesize more desirable pyrroles by adding or altering numerous functional groups to the reactants in a one-pot process. Specifically, a Hammett plot variant was employed to evaluate the reaction effectively.


Introduction
Green chemistry, or environmentally friendly chemical synthesis, has piqued scientists' interest in the hopes of lowering the usage of toxic and hazardous reagents [1][2][3][4]. Multicomponent reactions (MCRs) are among the most promising means of reaching green chemistry standards. MCRs are utilized as an efficient method for forming or dissociating multiple new bonds in a single-pot reaction due to their convergence, ease of automation, and operability. The number of extractions and purification processes and the amount of waste produced are reduced using this strategy [5][6][7]. Furthermore, water utilization in these reactions has become an increasingly popular and promising research topic in recent years. Water is nature's most affordable, abundant, and non-toxic substance; as a result, the majority of organic reactions, including the synthesis of heterocycles, have been effectively conducted in water as the reaction media [8,9].
Heterocycles are chemical structures containing heteroatoms, including oxygen, sulfur, and nitrogen; their biologically important functions are unique among heterocyclic compounds [10]. Important heterocycles, such as pyrroles, are represented in a variety of natural products, including vitamin B12, bile pigments, and chlorophyll heme [11]. Its derivatives are, moreover, present in the majority of synthetic and natural drug chemical structures. As well as playing a pivotal role in organic synthesis, pyrrole derivatives have biological significance activities, including antimalarial [12], antitumor [13], antiallergic [14], fungicidal [15], antiviral [16], antidiabetic [17], antibacterial [18], antioxidant [19], antitubercular [20], anti-inflammatory agents [21], and tyrosine kinase inhibiting agents [22]. Various strategies are employed to prepare these precious compounds, namely Hantzsch [23], Paal-Knorr [24], transition metal-catalyzed [25], and multicomponent couplings [26]. Mesoporous silicate-aluminosilicate structures, Santa Barbara Amorphous (SBA) materials have drawn much attention due to their uniform pore size (4.6-30 nm), large surface area, excellent pore structure-size distribution, high thermal stability, and support a wide range of active species (Lewis acids and metal ions). Owing to its uniform, hexagonally-arrayed channels and small pore size distribution, SBA-15 has been widely acknowledged as a potential support template for synthesizing catalysts [27]. Its high surface area and hydrothermal stability make it the prime support candidate for incorporating active molecules onto its surface; transition metal ions with Lewis acid characteristics, such as Ni, Fe, Pd, Cu, etcetera, can also be used be supported on SBA-15 to obtain an active heterogeneous catalyst. As a result, SBA-15 has led to substantial breakthroughs in heterogeneous catalysis during the past few decades, possessing a large surface area, a tunable pore size distribution, and high hydrothermal and mechanical stability [28].
The tremendous potential for applying transition metal-ligand complexes in various fields [29,30] has brought them to attention in recent decades. Their nanoscale size makes them an excellent candidate for immobilization on a wide range of support materials, aiming to increase activity more efficiently. Many studies and projects were recently conducted on Schiff-base transition metal complexes due to their catalytic activities in various reactions. Furthermore, chemists worldwide have paid great attention to these complexes due to their crucial role in homogeneous or heterogeneous catalysis [31]. Overall, Schiff base complexes are immobilized on a variety of support materials, including clay [32,33], alumina [34,35], polymers [36,37], zeolites [38], and silica [39][40][41], to improve catalyst stability, permit catalyst recycling, and facilitate product separation. Taking advantage of their high surface areas and large pores, mesoporous silica materials have been extensively employed as adjustable supports to produce various hybrid materials for drug delivery, biomedical applications, biosensing, enzyme immobilization, and catalysis. Due to its larger pore diameters (3-30 nm), the rod-like, hexagonally ordered mesoporous SBA-15 material has been used as support more frequently than mesoporous silica materials [42]. Moreover, the surface modification of SBA-15 using various organic functional groups for attaching metal ions and metal complexes through a Schiff base can also enhance the applications of SBA-15 materials [43].
Although various transition metal catalyzed reactions, catalyst-free, solvent-free, and multicomponent coupling strategies have been developed during the last decade, due to the importance of pyrroles, numerous projects are conducting to investigate new approaches for synthesizing pyrroles. As a progression of our efforts to develop novel green chemistry techniques and our desire to use heterogeneous metal complexes of Schiff bases in organic reactions catalyzed by SBA-15, we investigated the one-pot multicomponent reaction to synthesize functionalized pyrroles using Ni(II) Schiff base/SBA-15 as a heterogeneous catalyst (Scheme 1) [43]. The resulting catalyst and synthesized compounds were characterized using different techniques. In addition, the yield percentages of several compounds synthesized with various catalysts in this research and comparable prior work were compared.

Characterization
The infrared spectra of samples (500-4000 cm −1 ) were acquired using the KBr disk method on a Jasco 4200 FT-IR spectrophotometer. The capillary tube method and a Buchi B540 melting point instrument are used to determine uncorrected melting points. Schertz (Hz) was used to measure the coupling constant (J), and parts per million (ppm) were used to measure the chemical shift. The dimensions of the materials were determined using transmission electron microscopy (TEM) on a Hitachi H-700 CTEM. In addition, scanning electron microscopy (SEM) and the energy dispersive X-ray (EDX) were recorded on a TESCAN VEGA scanning electron microscope equipped with a 15-kV acceleration voltage. As an internal standard, CDCl 3 or DMSO-d 6 solution was used to obtain nuclear magnetic resonance spectra of protons at 300 MHz and carbon at 75 MHz on a Bruker NMR Spectrometer. ICP-OES was used to determine the Ni concentration (Model: VISTA-PRO, Varian, Australia). It was achieved by digesting 0.100 g of the catalyst in HNO3 and stirring at room temperature for a week. The filtered mixture was rinsed several times with double-distilled water (DDW) to produce a colorless filtrate solution for ICP measurement. Thermogravimetric analysis (TGA) curves were generated using Shimadzu-50 TGA/DTA equipment heated at a maximum rate of 10 °C min −1 . Quantachrome Autosorb-1 equipment was used to measure nitrogen adsorption and desorption isotherms at liquid nitrogen temperatures. To define the properties of the Scheme 1 a general reactions of Ni(II) Schiff base/SBA-15 catalyst preparation and 1HNMR (inset image), b preparation of the catalyst schematically materials, they are outgassed overnight at 120 °C prior to measurements. The XRD pattern was acquired using a Bruker D8 ADVANCE with Ni-filtered CuKα1 radiation at a wavelength of 1.5406 angstroms, a scan speed of 2° min −1 , and a step of 0.05°. Additionally, the Brunauer-Emmett-Teller (BET) approach was used to calculate surface areas, and the Barrett-Joyner-Halenda (BJH) model was used to establish pore-size distributions using desorption branches of nitrogen isotherms.

SBA-15 mesoporous synthesis and activation
The first step involved dissolving 2.00 g of poly(ethylene glycol)-blockpoly(propylene glycol)-block-poly(ethylene glycol)-block-poly(ethylene glycol) surfactant called P123 in 15 mL of double-distilled water (DDW) and 60 mL of 2 M hydrochloric acid at room temperature, followed by adding 4.25 g of TEOS. The mixture was stirred at 40 °C for 24 h before the temperature was elevated to 100 °C and stirred for another 24 h. After filtering and rinsing with DDW, the mixture was dried at room temperature. The resulting solid was heated in a vacuum oven at 600 °C for 8 h. In order to activate SBA, the residue was located in HCl 6 M for 6 h at room temperature. After filtration and rinsing with DDW, the residue was placed in a vacuum oven at 120 °C for 12 h.

Schiff base synthesis
According to the method discussed by Rezanejad et al. [44], briefly, 1 mmol of salicylaldehyde was dissolved in EtOH and added to 1 mmol of APTMS. The solution was stirred and constantly stirred at room temperature for three hours to form the Schiff base product. The yellow tint was immediately apparent, indicating the presence of imine. Following the stirring period, 0.5 mmol of nickel (II) acetate was added to the prior solution and stirred for another 3 h. This process enabled the complexation of Ni 2+ cations and the Schiff base ligand, which was immobilized on the surface of SBA-15.

Catalyst synthesis
The Ni 2+ -Schiff base complex solution was shaken for 24 h at room temperature with 1.50 g of previously activated SBA-15. Following the stirring period, the solvent was evaporated using the rotary method. After processing was completed, the residue was placed in an 80 °C vacuum oven for 24 h. The solid was washed with EtOH and DDW and dried in a vacuum oven at 80 °C to remove unreacted reactants, particularly metal ions, and purify the catalyst. Moreover, the chief aim of attaching Schiff base-Ni 2+ complex to SBA-15 is to obtain a heterogeneous catalyst that can easily separate from other components in the reaction. APTMS was utilized as a linker to react with salicylaldehyde, a ligand that can further bind to Ni 2+ . APTMS, on the other hand, has -Si (OMe) 3 groups that permit attachment to the surface of SBA-15. This allowed us to leverage the advantages of Ni 2+ in organic transformation reactions.

Synthesizing pyrrole derivatives using a heterogeneous catalyst
Pyrrole derivatives were synthesized by adding 1.5 mmol of different amines, 1 mmol of various aldehydes, 1 mmol of 1-3 dicarbonyl, nitromethane, and 0.01 g of prepared Ni catalyst in a round-bottomed flask. The mixture was stirred and refluxed at 70 °C until the reaction was completed. In order to survey the reaction progress, we utilized the TLC technique (using ethyl acetate and n-hexane in a ratio of 1:4). After completing the reaction, the mixture was allowed to reduce its temperature and was filtered; consequently, the product was collected and purified using column chromatography, followed by crystallization.

Spectral data
All compounds provided sufficient 1 H and 13 C NMR spectral data; the spectral images for all heterocycles are included in the supporting information section.

Synthesis of nickel nanoporous catalyst
Ni (II)-Schiff base/SBA-15 was synthesized in this study utilizing a technique illustrated in Schemes 1a and b. The application of the catalyst was carried out in the process of synthesizing pyrrole derivatives. The structure of the nanocatalyst was characterized by employing Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and N 2 adsorption and desorption (BET) techniques. It is worth mentioning that 1 HNMR confirmed synthesizing of the Schiff base to TEOS (Scheme 1a-inset image) [45].

X-ray diffraction analysis
The X-ray diffractograms of SBA-15 and Ni(II) Schiff base/SBA-15, which are shown in Fig. 1b, were used to detect the hexagonal structure characteristic of mesoporous materials of type SBA-15. As shown in the figure, three diffraction peaks are observed in the 0.9-2.0 region (archived as 100, 110, and 200 reflections), which is related to the order hexagonal unit cell of typical SBA-15 materials. In addition, Ni(II) Schiff base/SBA-15 diffraction peaks have three values between 0.9 and 2.0. While the mesoporous structure of Ni(II) Schiff base/SBA-15 has remained constant, the long-range order has significantly decreased compared to SBA-15. The contrast between the silicate framework and bulky organometallic groups results in the peak positions of Ni(II) Schiff base/SBA-15 materials shifting to a greater angle, indicating reduced pore size (in SBA-15 channels).

Thermogravimetry analysis and Inductively coupled plasma optical emission spectrometry
Thermogravimetric analysis was performed to examine the thermal characteristics of the nanocatalyst (Fig. 1c). Parent SBA-15 and Ni(II) Schiff base/SBA-15 TGA graphs indicate two distinct regions of the sample losing weight. The first region was detected between 25 and 100° C (roughly 8% weight loss for the catalyst and 5% for SBA-15), which could be due to the presence of water molecules in the samples. There was an exothermic weight loss region (about 26.5% weight loss) in the catalyst plot at temperatures between 180 and 410 °C, which may be explained by the decomposition of organic groups and ligands on the surface of the catalyst, which produces carbon dioxide, carbon monoxide, and nitrous oxide gases. However, in this region, there was negligible thermal decomposition in SBA-15 (approximately 12%). In comparison with the parent material, the catalyst exhibited decreased thermal stability, implying the presence of organic molecules and ligands on the surface. The specific amount of Ni loaded on SBA-15 was also determined by ICP-OES analysis, which served to widen the scope of the catalyst characterization even further. The concentration was found to be 0.22 mmol g −1 after extensive testing.

Nitrogen adsorption-desorption and pore-size distributions
The nitrogen gas adsorption and desorption isotherms are plotted in Fig. 1d to characterize the mesoporous nature of the nanocatalyst and parent structure. The SBA-15 isotherm plots demonstrated that the isotherm is a type-IV adsorption/desorption attributable to the SBA-15's mesoporous structure. Additionally, according to the International Union of Pure and Applied Chemistry, the hysteresis loop is a regular type of H1. In the case of the Ni(II) Schiff base/SBA-15 catalyst, the adsorption/desorption isotherm is also type IV. Barrett-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) techniques were utilized to obtain the specific area and pore size of the materials (Table 1). According to the pore size (6 ± 0.3 nm), the high BET surface area (538 m 2 g −1 ), and the large pore volume (1.01 cm 3 g −1 ) of SBA-15, it has the potential to be exploited as a host material. In comparison to parent SBA-15, SBA-15 functionalized with Ni (II)-Schiff base via covalent bond results in reduced pore size, specific area, and a dramatic decrease in pore volume (from 538 to 471 m 2 g −1 , 79 to 44, and 1.01 to 0.88 cm 3 g −1 , respectively). The chief reason for this issue may be the presence of organic ligands on the inner surfaces of the pores.

a. TEM, SEM, and EDX analysis
The morphological information regarding the precursor SBA-15 Fig. 2a and the catalyst Ni(II) Schiff base/SBA-15 Fig. 2b are illustrated. As can be observed from the comparison of the two images, the physical structure of the catalyst has remained unchanged during the reaction and anchoring of Ni ions. The elemental Map-SEM of Si and Ni (Fig. 2c and d) is affiliated with the catalyst and reveals that the elements' distribution is homogeneous all across the structure. Energy Dispersive X-Ray Analysis (EDX) study of the catalyst was conducted to determine the presence of nickel metal ions on the SBA-15 surface (Fig. 2e). The results suggest the presence of Si, C, N, O, and Ni in the complex, and the relative mass percentages are 35.61 percent, 16.53 percent, 3.70 percent, 29.33 percent, and 14.81 percent, respectively. TEM images of SBA-15 and Ni(II) Schiff base/SBA-15 nanocatalyst ( Fig. 3a and b) indicate a well-ordered two-dimensional hexagonal structure of mesoporous channels parallel to the pore axis; additionally, the pore size of the channels is approximated to be around 6 nm. These results suggest that the metal complex did not affect the typical pore diameters and channel structures of the support material and that the TEM results agree with XRD patterns.

Application of the catalyst
One-pot synthesis of several highly substituted pyrrole derivatives was carried out using the well-characterized Ni(II) Schiff base/SBA-15 as a catalyst to investigate its effects. The experimental approach for this condensation reaction was somewhat basic and straightforward, involving mixing amines, aldehydes, 1-3 dicarbonyls, and nitromethane ( Table 2). Several reaction variables, including the amount of catalyst and temperature, were investigated in order to assess the model reaction's efficiency. Notably, the model reaction was investigated at different temperatures, ranging from 25 °C to 100 °C, and under solvent-free conditions, without employing heat or a catalyst. As shown in Table 2, entry 1, the yield was negligible even at 70 and 100 °C. To summarize, the optimal catalyst concentration for this tandem reaction at 70 °C   Table 2, entry 4).

The synthesis of pyrroles
The Michael addition reaction can be used to synthesize pyrroles by reacting β-enamino ketones to nitroalkenes, followed by cyclization. This approach makes it crucial that two intermediates, A: nitroalkenes (from aldehyde and nitroalkanes) and B: β-enamino ketone (from amine and β-dicarbonyl), be produced. Consequently, the  reaction's nature provides an ideal opportunity to dramatically improve the reaction by manipulating the functional groups bonded to intermediates. Taking advantage of the opportunity, the simultaneous synthesis of intermediates, such as beta-ketoenamines and nitrostyrene, was proposed in one pot using commercially available materials and a nanoporous catalyst (Scheme 2). This represents a tandem synthesis of functionalized pyrroles. As well as altering the functional groups bonded to products, the various aromatic amines were used in this study to expand the scope of the investigation (Table 3). It was observed that the reaction proceeded efficiently to synthesize substituted pyrrole derivatives in desirable yields of 60 to 94%. For electron-rich aromatic amines, such as p-methoxy aniline and p-toluidine, however, good to exceptional yields (in the range of 85 to 94 percent) were obtained  (Table 3, entries 5, 11, 13, and 14). In order to scrutinize the effects of functional groups on aromatic amines and aldehydes, a variation of the Hammett plot was employed, with the y-axis representing yield percentage and the x-axis signifying para-substitution constants σ p (Fig. 4). The yield percentages of amines with  different functional groups that reacted with (I) benzaldehyde and (II) 4-Methylbenzaldehyde are presented in Fig. 4a. Yields increase as the electron-donating characteristic of the substituted groups of amines increases; higher yields have emerged from electron-donating groups (EDG), such as methoxy and methyl on the phenyl ring of amines, which match the hypothesized process entirely. On the phenyl ring of amines, electron-withdrawing groups (EWG), including chlorine and fluorine, led to lower yields. However, Fig. 4b shows the corresponding plot for aldehydes with various substituents on the phenyl ring that reacted with (I) aniline and (II) 4-fluoroaniline. The most rational conclusion is that benzaldehyde containing EWG, such as chlorine, was also subjected to the reaction with the highest yield of 89% (Fig. 4I) ( Table 3, entry 12). On the contrary, as the electron-donating properties of aldehydes increased, lower yields were obtained. Interestingly, aldehydes with different substituents on the phenyl ring reacted with 4-fluoraniline on the same trend as they reacted with aniline. The only difference between these two groups (I and II) is the slope of their plots. It is noteworthy that the slope of the plot played the identical role as ρ played in the original Hammett equation. In other words, a higher negative magnitude of the amine plot (Fig. 4a) implies that they are more sensitive to altering substituents and that their yield increases as the electron-donating character of substituents rise.
Conversely, aldehydes had a positive and lower quantity of slope (Fig. 4b), revealing that they are not only less sensitive to alterations in substituents but also that their yield showed that the more electron-withdrawing characteristics substituents on a phenyl ring have, the higher the yield percentage they produce. Generally, the reactions were conducted with a minimal 0.01 g of catalyst, and the optimal temperature was set at 70 °C. This condition was suitable enough for the reaction to progress smoothly for a broad range of substituents on the phenyl ring of both amines and aldehydes, ranging from methoxy to fluorine. A significant yield of nearly 93 percent was obtained in the instance of product 5a when both reactants possess hydrogen as a functional group. The effective interaction of the catalyst with the intermediate may account for this high percent yield.

Catalyst reusability
Lastly, the recyclability and reusability of the catalyst were investigated by utilizing the optimum condition. Only after the reaction was completed was the catalyst thoroughly and quickly extracted from the reaction mixture using centrifugation and washed multiple times with acetone and water. The catalyst was then dried and reused directly for six runs without significant loss of Ni(II) Schiff base/SBA-15 catalytic activity. The partial activity loss of the catalyst could result from minimal nickel loss (Fig. 5c). SEM, map-SEM, and TEM techniques were used to study the nature of the recovered catalyst after 6 runs (Fig. 5a, b). It is evident from the map-SEM and SEM images of the catalyst after six runs and recovery that Ni 2+ ions have remained essentially intact at the surface of the nanoporous structure.
Moreover, we conducted a hot filtration experiment on the condensation reaction of 1-(2-methyl-1,4-diphenyl-1H-pyrrol-3-yl) ethenone (5a) at optimum reaction conditions to determine whether Ni ions leached from the reaction mixture. Half the reaction time was halted, and the catalyst was filtered. At this stage, the desired product yielded 55%. Under the same reaction conditions, the reaction was resumed, but the yield was not significantly changed. This result demonstrates the heterogeneity of the Ni(II) Schiff base/SBA-15 catalyst and reveals that negligible Ni 2+ ions were leached from the catalyst into the reaction mixture during the catalytic reaction (Fig. 5c).
After catalyzing six reactions consecutively, the EDX analysis of the catalyst demonstrates that the complex contained Si, C, N, O, and Ni, and the percentage of nickel ions remains relatively unchanged, about 11.24% in the catalyst (Fig. 5 d).
Overall, the catalyst can be used in 6 reactions after recycling without appreciably affecting the yield percentage of the reaction or its mesoporosity and structure.

Comparative analysis
Our study continued with the synthesis of pyrrole derivatives using a variety of different catalysts in order to increase our understanding. We compared seven of our products (distinct pyrroles 5a, 5d, 5e, 5i, 5 k, 5 m, and 5n) with the results of previous studies, including those by Maita et al. [43] and Rezanejad et al. [44] and other researchers, in terms of catalyst quantity, reaction time, and yield (Tables 4 and 5). According to Table 4, the comparison demonstrated that two metal-Schiff base/SBA-15 catalysts functioned exceptionally well in all products, with the highest yield percentage of 93 percent in product 5a. Additionally, not only were they highly productive, but they also dramatically decreased reaction time. Although the efficiency of the two metal-Schiff base/SBA-15 catalysts was nearly identical, the Ni(II) Schiff base/SBA-15 catalyst enhanced the yield percentage slightly and decreased the reaction time dramatically. The most significant increase in percent yield was observed with product 5a, which was 39 percent greater than FeCl3 and 15% higher than Fe(III)-Schiff base/SBA-15; moreover, the reaction time of the product was the most optimal (about 8 h) among all pyrroles. Another competitive advantage is the appropriate amount of Ni(II) Schiff base/SBA-15 catalyst in the process, which was 0.0022 mmol; also, it can be recycled and used exceeding five times without significant loss of its catalytic characteristics. This property implies that the catalyst was used minimally and can be reapplied several times. In addition to the catalysts mentioned earlier, various catalysts that researchers had previously studied were investigated in order to compare them to our mesoporous catalyst in synthesizing an identical product, 5a (1-(2-Methyl-1,4-diphenyl-1H-pyrrol-3-yl)ethenone). The identities of the catalysts and the parameters considered are presented in Table 5. By intensifying the electrophilic nature of 1,3-dicarbonyl compounds, Lewis acids such as FeCl3 accelerated the synthesis of beta-enamino carbonyl compounds  [46]. However, FeCl 3 was activated more strongly than the other Lewis or Brønsted-Lowry acids, resulting in more favorable results. Despite the fact that imine production is a much faster process than the other reactions, the intended outcome was achieved by the formation of beta-enamino carbonyl compounds and nitrostyrene as a result of imine formation [46,47]. As indicated, acid catalysts had a wide range of yield percentages, ranging from a trace quantity of product to 48%. The most remarkable feature is that anhydrous FeCl 3 achieved the best performance of the common catalysts in the case of acids. Schiff base catalysts, on the other hand, performed extraordinarily well, with a maximum yield percentage of 93 percent for Ni(II) Schiff base/SBA-15 and 78 percent for Fe (III) Schiff base/SBA-15. This suggests that Schiff base complexes are more efficient at catalyzing the tandem reaction than other catalysts. Enhanced catalytic activities might result from the diverse nickel compositions incorporated into mesoporous siliceous materials. In addition, the fully ordered structure of mesoporous silica produces a framework with regular porosity, allowing ligands to be effectively immobilized on its surface.

Conclusions
The nickel catalyst was successfully synthesized according to a report by Rezanejad et al. and characterized by employing FT-IR, XRD, TGA, TEM, SEM, and EDX analysis. We increased the percentage yield of pyrrole derivatives by using a Ni(II) Schiff base/SBA-15 nanocatalyst and a one-pot four-component coupling reaction approach, which is simple to operate, inexpensive, and environmentally friendly. The primary competitive advantage of utilizing Ni(II) Schiff base/SBA-15 as a heterogeneous catalyst in the synthesis of pyrroles is the improved percentage yield of the tandem, which ranged from roughly 8% to 40% in comparison to earlier work. Another promising feature was the substantial decrease in reaction time, which was approximately 2 to 5 h in different products compared to previous reports. An investigation of a version of the Hammett plot revealed that electron-donating substituents on aromatic amines and electron-withdrawing substituents on aromatic aldehydes might result in greater yields. In addition, the reusability of the catalyst indicated that the catalyst could be used several times after recycling. Moreover, by comparing catalysts, including Lewis and Bronsted acids, with Schiff base ligands, it was observed that the metal-Schiff base could catalyze the tandem more efficiently.