Introduction

Zeolites, as a class of crystalline minerals, have wide applications in various fields such as catalysis [1,2,3], separation [4] and adsorption [5, 6]. Recently, these materials have also been developed for promising applications such as separation technologies, gas storage, biomedicine, magnetic adsorption, and zeolite-polymer membranes [7]. In zeolites, the crystallization process has a great influence on the structural and physicochemical characteristics, which in many cases determine the catalytic properties. In heterogeneous catalysis, especially on nanomaterials, the dependence of catalytic efficiency on morphology is universally observed [8, 9]. Microporous zeolites of different shapes and sizes exhibit their peculiarities in reactions, mainly due to different diffusion limitations [8]. Zeolite morphology is one of the most important properties that determine its efficiency in various applications including adsorption and catalysis; however, the synthesis of zeolites with exceptional and defined morphology only by modifying the composition of the initial gel based on inorganic ions remains a challenging task [10]. A review [11] summarizes recent advances and the morphological control of zeolites. However, the rational design of zeolite materials and the production of zeolites with the required morphology have not been achieved so far because the crystallization mechanism of zeolites is not fully understood and, consequently, the processes of crystal nucleation and growth cannot be guided. The paper [9] reviews the progress that has been made in controlling the morphology of zeolites. The zeolite crystal shape has a significant influence on adsorption and separation as it modulates molecular diffusion, accessibility, interfacial energy, molecular partitioning, and inclusion properties [9]. The mechanisms of crystallization and assembly of zeolite crystals have been investigated, which provides a general idea of the regulation of zeolite crystal morphology. The chemical composition of the synthesis gel has a significant influence on crystal morphology. The influence of hydrothermal synthesis parameters, primarily such as the composition of the initial gel (silica and alumina content, alkalinity, water concentration) on morphological and other properties of zeolites has been reported [12].

Water content plays an important role in the hydrothermal synthesis of zeolites. It not only serves as a solvent in the crystallization process but also participates in the hydrolysis reactions of aluminosilicate gel and regulates the formation of possible precursors of zeolite frameworks [12]. Water plays a central role in the crystallization of various organic, inorganic, biological and hybrid materials; this is also true for zeolites and zeolite-like materials. Apart from the role of water as a solvent, the role of water as a structure-directing agent in the synthesis of zeolites has never been clearly elucidated [13]. However, several published results give some idea of the importance of taking this parameter into account. Thus, a series of Beta zeolites was prepared by the conventional hydrothermal method at different H2O/SiO2 ratios in the range from 10 to 60 [14]. It turned out that the water concentration has a great influence on the nucleation rate i.e., on the kinetics and thermodynamics of the process [15] and the growth of zeolites, which leads to different crystal morphologies, their size distribution, and textural properties of the obtained materials. By changing the amount of water in the gel, zeolite L can be synthesized in the form of crystals of different morphologies – disks, barrels, elongated tubes [16]. In [8], mordenite crystals were successfully synthesized in the form of nanosheets, bundles and flowers, respectively. In [10], by simply optimizing the alkali/water ratio, ZSM-5 zeolite crystals with different morphologies were obtained in a simple and controlled manner without affecting their physicochemical properties such as average particle size, microporosity, Si/Al ratio and acidity are well maintained at the same level.

Faujasite, whose acronym FAU is based on the three-letter codes proposed by the International Zeolite Association for topologically different zeolite structures [17] is one of the most commercially important and most widely used zeolites in the industry [6, 18, 19]. Its cubic crystal structure (space group \(Fd\overline{3}\), No. 203) has a three-dimensional network of large pores (input window diameter ~ 7.4 Å) [17]. There are two topologically identical but different in physicochemical properties varieties of FAU zeolite, which are classified by the value of Si/Al ratio; at Si/Al ratio < 1.5 in the aluminum-rich region of the structure, zeolite X (FAU-X) is formed, and at Si/Al ratio > 1.5 – zeolite Y (FAU-Y) [20]. The most common methods for the synthesis of FAU are sol–gel, hydrothermal, or a combination of both [21,22,23]. When these synthesis methods are used under standard conditions, FAU typically crystallizes as octahedrons with {111} faces as observed in the work of Mohd Nazir et al. [24] who obtained FAU-X by a combination of sol–gel and hydrothermal methods. They observed octahedral crystals with particle sizes ranging from 0.84 to 3.25 microns depending on the gel aging time. This well-formed isometric morphology owns at the same time unique size-calibrated micropores, which make zeolites possess molecular sieve action [25], but restrict the diffusive process of larger molecules, leading to a decrease in catalytic efficiency. For this reason, methods to reduce or eliminate diffusion limitations have been investigated, such as forming a hierarchical pore system that can reduce the diffusion path length within zeolitic micropore channels [23, 26], as well as searching for different crystal morphologies, such as the reticulated or layered aggregates of FAU particles described in [27]. Hierarchical FAU-X structures have been obtained by hydrothermal or sol–gel methods using additives, such as surfactants or salts, which give rise to the formation of layer-like FAU morphologies [27,28,29,30,31]. On the other hand, some authors have obtained similar morphologies as aggregated flakes/plates without the use of additives in the synthesis, but this requires the gel to be aged for some time, and in other cases, the crystallization time is significantly prolonged [28, 32,33,34]. Grass et al. [28] synthesized samples of layer-like NaX zeolite using three different synthesis routes: additive-free, or with the addition of either Li2CO3 or TPOAC addition. In three cases, the gel was incubated for 20 h at room temperature. The gel was then crystallized at 50 °C or 75 °C for 3 to 5 days, depending on the sample.

Our work aimed to study the physicochemical properties of single-phase FAU-X with layer-like morphology without gel incubation or additives, at a crystallization temperature of 90 °C for 24 h and calcination at 450 °C for 5 h. Furthermore, the changes in the structure and morphology of the FAU-X particles synthesized with different concentrations of water in the gel were analyzed. The results of this work demonstrate a fast and efficient synthesis method for obtaining layer-like morphology of FAU-X.

Materials and methods

The reagents chosen were sodium aluminate (NaAlO2; 50–56% Al2O3 and 40–45% Na2O; CAS 1138-49-1), sodium hydroxide (NaOH; 98.9%; CAS 1310-73-2) and fumed silica (99.8%; CAS 112945–52-5) which were supplied by Sigma-Aldrich. Sodium silicate was made in the laboratory (Na2SiO3; 26.5% SiO2; 10.6% Na2O) by hydrothermal method. For this, fumed silica was dissolved in NaOH solution under magnetic stirring at room temperature. This solution was then placed in an autoclave at 127 °C for 48 h.

The synthesis of FAU-X with reticulate morphology was carried out using the molar composition of NaAlO2: 2.01 SiO2: 7.9 NaOH: 163.7 H2O by mixing two solutions. Initially, 2.35 g of NaAlO2 was dissolved in 3.61 ml of H2O. Then, a 9.0% NaOH solution was added to form solution 1 (S1). Solution 2 (S2) was obtained by mixing 13.1 g of Na2SiO3 with a 9.0% NaOH solution. A gel was then obtained by adding 53.2 g S2 to 46.1 g S1 under vigorous stirring at room temperature. The gel was homogenized for 45 min under stirring and immediately transferred into polyethylene bottles. Crystallization was carried out in an oven at 90 °C for 24 h. The resulting product was filtered, washed with distilled water, and dried at 70 °C for 40 h. This sample was labeled as FAU. Finally, the FAU powder was calcined at 450 °C for 5 h; this sample was labeled as FAU-450.

As a comparison, a sample with conventional morphology was synthesized using the same procedure as above but increasing the amount of water. The composition of the gel is NaAlO2: 2.01 SiO2: 7.9 NaOH: 312.8 H2O. This sample was labeled FAU-312H.

The crystal structure was studied by X-ray diffraction (XRD) using an AERIS-Panalytical diffractometer with monochromatic Cu Kα radiation (λ = 1.54056 Å). The diffractograms were measurements with a step of 0.02 over a 2θ range from 5° to 90°. For the calculation of the lattice parameter, initially, the diffraction pattern was compared with the diffraction pattern from the IZA database for Faujasite. In this comparison, the Miller indexes were identified. The centers of the peaks from 5° to 41° were determined by peak fitting in Origin software. The interplanar distance was then calculated using the Bragg’s law equation: \(2d_{hkl} \sin \theta = n\lambda\), taking into account the Miller indexes identified above and λ = 1.54056 Å. Finally, the lattice parameter was calculated from the equation for the cubic cell:

$$\frac{1}{{d_{hkl}^{2} }} = \frac{{h^{2} + k^{2} + l^{2} }}{{a_{0}^{2} }}$$

The Si/Al ratio was calculated from Breck’s equation for Faujasite structure \({\text{Si}}/{\text{Al}} = \left( {25.858 - a_{0} } \right)/\left( {a_{0} - 24.191} \right)\), where \(a_{0}\) is the lattice parameter [35]. This equation was proposed by Breck, which was based on the linear relationship established between the \(a_{0}\) and the number of aluminum atoms in the Faujasite lattice through the least squares treatment of 37 experimental points [35]. The average crystallite size (\(D\)) was calculated from Scherrer’s equation considering the position and Full Width at Half Maximum (FWHM) of the most intense peak for FAU-X ((111) plane). Morphology was analyzed by Scanning Electron Microscopy (Hitachi Model SU3500) and Transmission Electron Microscopy (FEI TECNAI F30, 300 kV). The size distribution was carried out using ImageJ (version 1.54d). Energy Dispersive X-ray Spectroscopy (EDS) analysis was performed using a Focused Ion Beam Scanning Electron Microscope (JEOL JIB-4500). UV–Vis diffuse reflectance spectra were acquired using a UV–Vis-NIR spectrophotometer (Agilent, Cary 5000) equipped with an integrating sphere in the wavelength range of 200 nm-800 nm. The band gap energy was estimated from Tauc’s plot\({\left(F\left(R\right)*h\upsilon \right)}^{n}=A(h\upsilon -{E}_{{\text{g}}})\). Here \(F\left( R \right)\) is the Kubelka Munk function defined as \(F\left( R \right) = \left( {1 - R} \right)^{2} /\left( {2R} \right)\), \(R\) is the diffuse reflectance,\(h\upsilon\). is the photon energy, \(E_{{\text{g}}}\) is the band gap, and \(n\) represents the type of electronic transition (indirect \(n = 1/2\) and direct \(n = 2\)). Infrared spectra were measured in the range from 4000 cm−1 to 500 cm−1 using an FTIR-ATR spectrometer (ALPHAII Bruker). Textural properties were analyzed by nitrogen adsorption–desorption isotherms at 77 K on Micrometrics Tristar II equipment. The samples were previously degassed at 120 °C for 20 min and at 300 °C for 3 h under vacuum. The specific surface area was determined by the Brunauer–Emmett–Teller (BET, \(S_{{{\text{BET}}}}\)) and Dubinin-Astakhov (\(S_{{\text{D}}}\)) methods. The average pore diameter (\(D_{{\text{p}}}\)), mesopore surface area (\(S_{{{\text{meso}}}}\)) and mesopore volume (\(V_{{{\text{meso}}}}\)) was calculated by the Barrett–Joyner–Halenda method (BJH) using the desorption branch of the N2 isotherm. The micropore surface area (\(S_{{{\text{micro}}}}\)), external surface area (\(S_{{{\text{ext}}}}\)) and micropore volume (\(V_{{{\text{micro}}}}\)) were obtained by the t-plot method. To analyze the thermal stability of the samples, thermogravimetric and differential thermal analysis (TGA/DTA) were carried out on a thermal analyzer (SDT Q600) from 30 °C to 900 °C at a heating rate of 10 °C/min under nitrogen (N2) and oxygen (O2) atmosphere.

Results and discussion

Structural properties

Figure 1a shows the XRD patterns of the FAU, FAU-450 and FAU-312H. All synthesized samples present the peaks characteristic of the cubic phase of FAU-X (space group \(Fd\overline{3}\)) aording to the IZA database [17]. No trace of impurity phase was detected. In contrast to the works of Reiprich et al. [27] and Gaber et al. [34], we did not observe any shoulders in the (111) peak associated with the presence of EMT zeolite. On the other hand, for the FAU-312H sample, we can assure that the increase in the amount of water did not promote the growth of secondary phases, thus maintaining the pure phase of FAU-X. However, an increase in the intensity of the peaks is notable, which may be due to a larger crystallite size.

Figure 1
figure 1

a XRD patterns and b EDS spectra of FAU, FAU-450 and FAU-312H.

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The calculated lattice parameters (\({a}_{0}\)) are 24.98 Å and 24.96 Å for FAU and FAU-450, respectively (see Table 1), which is close to the values reported in the IZA Synthesis Commission for FAU-X [36]. For FAU-312H, the \({a}_{0}\) is the same value as the FAU-450 sample. These \({a}_{0}\) values are in agreement with the Si/Al ratio of the framework obtained by Breck’s equation, which is less than 1.5 confirming that it is a FAU-X [35]. This indicates that the framework has the appropriate amount of Si and Al atoms to form the FAU-X structure.

Table 1 Structural, compositional, and morphological parameters of FAU and FAU-450
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Figure 1b shows the normalized EDS spectra for FAU, FAU-450 and FAU-312H. Here, only the presence of Si, Al, Na and O is observed, which correspond to the characteristic elements present in FAU-X zeolite confirming that samples synthetized are free of impurities. From these spectra it was observed that the relative amount of Si and Al atoms are found in the materials in Si/Al ratios greater than those obtained from the XRD data, which may be due to the presence of extraframework atoms. However, these values are consistent with the Si/Al ratios corresponding to the FAU-X.

The \(D\) was calculated by Scherrer’s relation using the most intense peak (111), resulting in values around ~ 51 nm for FAU and FAU-450 while for FAU-312H it is ~ 56 nm (Table 1).

Morphology and textural properties

Figure 2a, b shows the crystal morphology for FAU and FAU-450 samples. It is evident that there is a tendency for the crystallization of individual homogeneous agglomerates, which may indicate the existence of homogeneous nucleation and growth during zeolite crystallization. The morphology of zeolite agglomerates is preserved after calcination. It is also observed that the agglomerates are composed of interlocking sheets. This morphology is not common for FAU, as this zeolite is generally crystallized in isometric octahedrons with {111} faces [24]. It should be noted that the authors who obtained similar layer morphologies used longer crystallization times and/or surfactants [27,28,29, 37], in contrast to the current work. In recent years, studies have begun to obtain similar morphologies without the addition of additives. Gaber et al. [34] obtained a morphology similar to the one presented in this work using a gel of composition Al2O3: 3.5 SiO2: 7.3 Na2O: XH2O (X: 214 → 300), performing crystallization after aging the gel for 24 h. In addition, crystallization was carried out at a reduced temperature of 60 °C for 2 and 3 days.

Figure 2
figure 2

SEM micrographs of a FAU, b FAU-450, c FAU-312H and d TEM micrographs of FAU-450.

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In other cases, according to Jain et al. [38], a similar morphology was obtained with a gel composition of 2.75 SiO2: 0.28 Al2O3: 11 NaOH: 173 H2O, which was crystallized at 60 °C for 5 h, while Liu et al. [39] used a molar composition of 1.43 Na2O: 1.0 Al2O3: 2.39 SiO2: 74.45 H2O and carried out crystallization at 70 °C for 48 h. These authors agree that the layer-like morphology of FAU is obtained by reducing the amount of water in the gel. At the same time, Ferdov et al. [32], by varying the amount of NaAlO2, obtained this morphology, and they obtained the most defined morphology when using a gel with a composition of 2.61 Na2O: 1.47 SiO2: 0.35 NaAlO2: 100 H2O, which was crystallized at 90 °C for 24 h. Grass et al. [28] employed a gel of the composition 1.0 Al2O3: 3.0 SiO2: 4 Na2O: 180 H2O, but the layer morphology was obtained by crystallization at 50 °C for 3 d. Summarizing their observations, these authors conclude that obtaining the layer-like morphology of FAU-X cannot be conditioned by any single parameter, since it can be obtained by varying different synthesis conditions. However, according to these authors, it can also be concluded that the most important variable in obtaining the layer morphology is the amount of water in the gel composition. In contrast, Mohd Nazir et al. [24] obtained FAU-X with conventional morphology (octahedrons) using a gel with molar composition of Al2O3: 4.8 SiO2: x Na2O: 975 H2O (x = 17, 18, 19), where it is evident that the amount of water is much greater than in the synthesis of layer-like morphology of FAU-X. This may indicate that when the amount of water in the gel composition is high, a regular morphology is more likely to be obtained, while when small amounts of water are used, a layer-like morphology of FAU-X can be obtained.

In our case, the layer morphology was obtained from a gel composition NaAlO2: 2.01 SiO2: 7.9 NaOH: 163.7 H2O. Agglomerate sizes and sheet thicknesses estimated from micrographs are presented in Table 1 and the histograms are presented in the Supplementary section Fig. S1 Here, it can be seen that the average agglomerate sizes are 1.3 µm and 1.6 µm for FAU and FAU-450, respectively. Average sheet thicknesses are 0.13 and 0.17 µm for FAU and FAU-450, respectively. On the other hand, it was evident that the conventional morphology of octahedra can be obtained by increasing the amount of water in the synthesis. In this case, we used a gel composition of NaAlO2: 2.01 SiO2: 7.9 NaOH: 312.8 H2O and obtained octahedrons of 5.1 µm as seen in Fig. 2c. Additionally, clusters of small particles were observed around the octahedra. Figure 2d shows a TEM micrograph in Z-contrast for FAU-450, where agglomerates of ~ 0.9 µm were observed on which ~ 0.1 µm wide bars or other sheets grow. Grass et al. [28] report values of particle size (1.60 μm) and layer thickness (126 nm) similar to those presented in this work, obtained from a similar synthesis for FAU-X (Si/Al = 1.38). However, more time was used for the synthesis: the gel was incubated for 20 h, crystallized for 3 days and calcined at 550 °C for 12 h. In another work, Liu et al. [39], agglomerates of hierarchical FAU-X (Si/Al = 1.31) zeolites with a “house-of-cards"-like morphology were obtained by hydrothermal method at a crystallization temperature of 70 °C for 48 h. The particles consist of nanosheet crystals with a typical thickness of ~ 100 nm. S. Ferdov [32] obtained the layer-like morphology of FAU-X by conventional method at a crystallization temperature of 90 °C for different times (4–24 h), varying the Si/Al ratios between 1.24–1.43. Layers with thicknesses of 60–150 nm and lengths ranging from less than 0.2 to more than 1 μm were observed.

The textural properties were studied by N2 adsorption–desorption isotherms for FAU, FAU-450 and FAU-312H as shown in Fig. 3. The sample with conventional octahedron morphology (FAU-312H) shows a type I isotherm without hysteresis which is characteristic of microporous solids [40]. On the other hand, the samples with layer morphology present type IV isotherms with hysteresis between P/P0 = 0.7 and 1, which indicates the presence of a three-dimensional mesoporosity [29, 40]. The textural properties of the synthesized samples are summarized in Table 2.

Figure 3
figure 3

Nitrogen physisorption isotherms and pore distribution (inset) for FAU, FAU-450 and FAU-312H.

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Table 2 Textural properties of FAU, FAU-450 and FAU-312H
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FAU shows a greater adsorbed volume which is reflected in the specific surface area (\(S_{{{\text{BET}}}} , \;S_{{\text{D}}}\)). However, upon calcination (FAU-450), a decrease in the absorbed volume is seen, which represents a decrease in its specific surface area, but at the same time, an increase in the area (\(S_{{{\text{meso}}}}\)) and volume of mesopores (\(V_{{{\text{meso}}}}\)) is observed. This may be because, during the calcination process, water molecules that are expelled from the micropores promote partial collapse of the pore or cracks and fractures may develop, generating the formation of mesopores. This can also lead to an increase in roughness on the external surface (\(S_{{{\text{ext}}}}\)) of the zeolite. In the case of sample FAU-312H, it is evident that the conventional morphology presents mostly an area of micropores and very few mesopores, which is evident in the low \(S_{{{\text{meso}}}}\) and \(V_{{{\text{meso}}}}\) compared to samples with layer morphology. The values of \(V_{{{\text{micro}}}}\) and \(V_{{{\text{meso}}}}\) for FAU and FAU-450 are close to those reported by Reiprich et al. [27] for layer morphology where they were 0.26 m3/g and 0.14 m3/g for \(V_{{{\text{micro}}}}\) and \(V_{{{\text{meso}}}}\), respectively.

The distribution of the pore width is presented in the inset of Fig. 3, where it is evident that the samples with layer morphology have pore widths between 2 and 18 nm which correspond to mesopores. Note that the presence of mesopores is not observed in the sample with conventional morphology.

Optical properties

Figure 4a shows the UV–Vis spectra of FAU and FAU-450 samples, where their fundamental similarity can be noted. Both spectra are similar, however, the absorption rise in the spectrum of FAU-450 is shifted to the right by approximately 5 nm, which may be due to the processes that took place in the structure during the water loss due to the sample calcination. Absorptions around 244 nm, 500 nm and 970 nm can be observed. The last two absorptions are possibly due to surface defects. Furthermore, a rightward shift of the main peak (250 nm) is observed, which may be due to the redistribution of some superficial chemical species, such as adsorbed molecules or ions, in the active sites of the zeolite. This can result in a different electronic occupancy of these sites affecting the absorption spectrum.

Figure 4
figure 4

a Absorbance spectra, b, c Tauc’s plot, and d FTIR-ATR spectrum of FAU and FAU-450.

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The direct and indirect band gaps of FAU and FAU-450 were determined from Tauc’s plot. The indirect band gaps of FAU and FAU-450 have similar values (Fig. 4b), which indicates that calcination at the selected temperature has no significant effect on the electronic properties. The same behavior is observed for the direct band gap (Fig. 4c). On the other hand, a difference of about 1.22 eV is observed between the direct and indirect band gaps. González et al. [41] using the Kubelka Munk transformation, calculated the value of an indirect band gap of 3.53 eV for their FAU-Y, which is close to that obtained in this work for FAU-X; this is in general agreement with the same topology of X and Y Faujasites. In another case, Popeneciu et al. [42] determined from DFT calculations the band gap for zeolites with FAU-type structure is 6.8 eV. Antúnez et al. [43] obtained from DFT calculations the band gap of Faujasite with one and two aluminum atoms in the lattice per unit cell, resulting in 6.01 eV and 5.87 eV, respectively. These values are far from the value determined in the present work because the real Si/Al ratio for our materials is about 1.16 and, therefore, FAU contains about 89 Al atoms per unit cell [44]; furthermore, DFT calculations were performed assuming that the zeolite contains no impurities or defects.

Figure 4d presents FTIR spectra obtained in the region of 500–4000 cm−1 for FAU and FAU-450. The bands at 563 y 568 cm−1 are assigned to the structural double ring (D6R) of the FAU framework [45,46,47]. The bands at 677 cm−1 and 744 cm−1 correspond to the external bond and O‒T‒O (T = Si, Al) vibrations internal within tetrahedral symmetrical stretching, respectively [46, 48]. The bands at 965 cm−1 and the shoulder at 1060 cm−1 represent the O‒T‒O asymmetric and symmetric stretching vibrations corresponding to the internal and external TO4 structure, respectively [45, 46, 48]. The band at 1642 cm−1 is attributed to the presence of absorbed water bonds, while the band at 3374 cm−1 corresponds to the hydroxyl groups Si‒OH, Si‒OH‒Al and OH [45, 47].

Thermal properties

Thermogravimetric and differential thermal analysis (TGA-DTA) curves revealed that the samples are thermally stable up to 700 °C under both N2 and air atmospheres. The total mass loss was about 21.01% and 15.96% under N2 atmosphere for FAU and FAU-450, respectively (see Fig. 5a). On the other hand, in O2 atmosphere the mass loss is 19.17% and 17.42% for FAU and FAU-450, respectively (see Fig. 5b). In both atmospheres, a smaller mass loss of the FAU-450 sample is observed compared to FAU, which may be due to the fact that the initial FAU loses a certain amount of hydroxyl groups upon calcination and does not recover them despite being exposed to the environment, and the surface properties in the calcined sample are altered. This is also confirmed by FTIR spectroscopy data, where a decrease in the intensity of signals associated with OH-groups is observed in the FAU-450 sample. The mass loss occurs in several steps and is related to the removal of physisorbed water at temperatures below 150 °C, manifested in the DTA plot as an endothermic peak at about 80 °C; water bound to the zeolite framework between 100–250 °C, shown as an endothermic peak on the DTA graph at about 150 °C, and, finally, slow desorption of more tightly bound water molecules from the zeolite, shown as an endothermic shoulder on the DTA graph at about 300 °C [49,50,51].

Figure 5
figure 5

TGA-DTA curves of FAU (solid line) and FAU-450 (dash line) under a N2 and b O2 atmosphere.

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Conclusions

In summary, layered FAU-X was successfully synthesized without the use of any additives (organic or salts) employing a molar composition of NaAlO2:2.01 SiO2:7.9 NaOH:163.7 H2O. The freshly prepared gel was crystallized at 90 °C for 24 h (FAU) and calcined at 450 °C for 5 h (FAU-450). By this method, homogeneous reticulated agglomerates of around ~ 1.3 µm and ~ 1.6 µm, respectively, consisting of sheets with a thickness of ~ 0.1 µm, which is not common in conventional methods of synthesis, were obtained. We were able to confirm that at reduced amounts of water in the gel composition (163.7 mol) layer morphology is obtained while at higher amounts of water (312.8 mol) the conventional octahedral morphology of FAU-X is obtained. It was shown that the conventional morphology mainly contains micropores while the layered morphology contains both micropores and mesopores, which considerably changes the textural properties of Faujasite; the presence of mesoporosity may make it more interesting for catalytic applications due to easier diffusion of bulk molecules in the transport pores. Additionally, we report experimental values of direct (3.24 eV) and indirect (4.45 eV) band gap, which to our knowledge are little reported or null specifically for layer FAU-X. Furthermore, these values are comparable with those obtained theoretically by other authors. On the other hand, the thermal stability of the obtained FAU and FAU-450 under N2 and O2 atmospheres from 30 °C to 700 °C was confirmed, which is attractive due to the potentially cost-effective and environmentally friendly method of producing potentially sought-after materials for various applications. Finally, it was possible to analyze the influence of the calcination temperature on the physicochemical properties, mainly the textural and optical properties of the layer FAU-X.