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. 2026 Jul 30;20(1):166. doi: 10.1186/s13065-026-01850-w

Thermal transformation of MIL-53(Fe)/GO into EMI shielding materials

Mohamed E Elmowafy 1, Ramy Sadek 2, Mahmoud Zorainy 1, Osama Abuzalat 1, Ahmad Baraka 1, Mohamed F Hagag 3, Hesham Tantawy 1,✉
PMCID: PMC13428442  PMID: 42538559

Abstract

The pyrolysis process parameters were systematically investigated to develop a highly effective EMI shielding composite. By evaluating the key synthesis conditions of pyrolysis temperatures (350 °C, 450 °C, and 550 °C) and durations (0.5 h, 1 h and 2 h), a significant structural transformations and degradation were observed. Optimal conditions were identified at 450℃ for 1 h under an inert argon atmosphere. Under these conditions, enhanced graphitization occurred via the in-situ reduction of GO, alongside the partial degradation of MIL-53(Fe) structure into γ-Fe2O3, yielding a ternary composite structure. This optimized composite achieved a total shielding effectiveness (SET) of 43 dB, with absorption shielding efficiency (SEA) of 40 dB and minimal wave reflection (SER) of 2.9 dB. The synergistic properties of this ternary composite make it a promising candidate for a wide range of EMI shielding applications. Its combined dielectric and magnetic characteristics offer a lightweight, efficient, and robust material for effective electromagnetic wave attenuation.

Keywords: Graphene, Metal–organic framework, Thermal treatment, Electromagnetic wave, Pyrolysis, Shielding, Synergism

Introduction

Electromagnetic interference (EMI) is critical concern that causes electromagnetic pollution due to the advancement in communication technology and intensive use of electronics from both the military and the civilian sectors [1, 2]. As a result, EMI exhibits a serious risks from health issues to information security [3].

Many composites have been developed to safeguard against EMI, either depending on reflection or based on its capability to absorb the EM waves. Recently, researchers are attracted to develop EMI shielding materials with higher absorption capability to avoid secondary reflection which are considered as a source of EM pollution [4, 5]. In addition, these composites should offer low weight, thin thickness, broadband absorption, high thermal conductivity, corrosion resistance, and low cost to comply with the recent market demands [6].

Carbon based materials are preferred for EMI shielding due to their high electrical conductivity, tunable properties, inexpensive cost, extensive availability, and relatively low density [7]. Over the past ten years, a variety of carbon materials, including graphene, carbon nanotubes (CNT), and carbon nanofibers (CNF), have emerged as the most promising materials for EMI shielding [8, 9]. Consequently, the presence of carbonaceous material is crucial because it will increase the dielectric losses of the composite and increase its EMI shielding potential. Still the incorporation of a magnetic loss material, usually ferrites, is required to integrate a dual effect to face the electric and magnetic energies that forms the EM waves [10, 11]. The combination of both will lead to a higher shielding performance [12].

Ferrites such as Fe3O4, CoFe2O4, and γ-Fe2O3, have attracted significant attention due to their high saturation magnetization, strong chemical stability, distinctive magnetic behavior, ease of manipulation, and low cost [13–15]. They are used frequently in conjunction with carbonaceous materials to form nanocomposites for EMI shielding applications, taking the advantage of the synergistic effect due to the presence of both materials [16–18]. Similarly, metal-organic frameworks (MOFs) offer a suitable alternative and a versatile platform for designing specific structures, as they consist of metal ions and organic ligands arranged in a spatially repeating pattern [19, 20]. With features like high porosity, an ordered distribution of pore sizes, a large specific surface area, and active sites [21]. MOFs find their way to a numerous application such as drug delivery, gas separation, catalysis, energy storage and EMI shielding [22, 23]. Many magnetic MOFs were prepared and have promising magnetic properties that make it a promising candidate for EMI shielding composites [24, 25].

Currently, crystalline metal-organic framework (MOF) materials with regular morphology are being studied using the MOF derived method as sources of both metal and carbon in the development of carbon-based composites [26]. This approach facilitates simultaneous pyrolysis and reduction reactions within the same microarchitecture which enables MOFs to function as a microwave absorption materials [27].

In this study, graphene oxide (GO) and MIL-53(Fe) were synthesized by loading MIL-53(Fe) onto the GO surface, maintaining a 20% GO ratio during the hydrothermal synthesis process. The resulting sample was subjected to heat treatments at 350 °C, 450 °C, and 550 °C for 0.5 h, 1 h, and 2 h, respectively, in a tube furnace under an argon atmosphere to produce P-MIL-53(Fe)/RGO composites under varying conditions. Furthermore, the shielding performance of the samples was evaluated to optimize preparation conditions for achieving high shielding efficiency.

It should be noted that a related study by our group recently reported EMI shielding performance of MIL-53(Fe)/RGO composites pyrolyzed under fixed conditions (450 °C, 1 h), focusing on the preservation of MOF structural features at this specific condition [28]. In contrast, the present work provides the foundational thermal screening study that identified this condition as optimal through systematic variation of both pyrolysis temperature (350–550 °C) and duration (0.5–2 h), thereby establishing the process, structure and property relationships that underpin the composite’s shielding behavior.

Experimental work

All chemicals were purchased from Alfa Aesar with high purity, including graphite powder (99.8%), H2SO4 (98%), H3PO4 (85%), KMnO4 (99%),1,4-benzene dicarboxylic acid (H2BDC, 98%), H2O2 (10% solution), FeCl3⋅ 6H2O (98%), and N, N-dimethylformamide (DMF, 99.8%).

Synthesis of GO

The improved Hummer was utilized to synthesize GO. Graphite powder (5 g), H2SO4 (593 ml), and H3PO4 (74 ml) were mixed in a 1000 ml beaker. KMnO4 (30 g) was added gradually while stirring to prevent heat buildup and particle aggregation. After cooling, the mixture was further agitated for three days to produce the thick honey like product. Then, the product was added gradually to icy distilled water (DW) stored at 5 °C while being stirred at 400 rpm using a mechanical mixer for one hour. H₂O₂ (10%) solution was added dropwise until the solution turned the characteristic yellow color of graphene oxide. The GO particles were then washed and decanted three times with 15% HCl to remove residual precursors. After centrifugation, the particles were dried at 45 °C for 48 h [29, 30].

Synthesis of MIL‑53(Fe)

MIL-53(Fe) was synthesized using the solvothermal method approach. A magnetic stirrer was employed to mix FeCl3⋅6H2O (13.5 g), H2BDC (8.2 g) and 250 ml of DMF in one-liter Pyrex bottles for 30 min before being placed in an oil bath. After 15 h of continuous stirring at 120 °C, the process produced MIL-53(Fe) in a finely powdered reactant medium.

The resulting MIL-53(Fe) precipitate was collected and filtered using a Buchner funnel. The precipitate was then washed with acetone and methanol. Finally, the MIL-53(Fe) was dried in an oven at 45 °C for four hours [31, 32].

Synthesis of MIL‑53(Fe)/GO and P‑MIL‑53(Fe)/RGO

Following the synthesis steps of MIL‑53(Fe), FeCl3⋅6H2O (13.5 g) and H2BDC (8.2 g) were dissolved in 250 ml of DMF and agitated at room temperature for one hour. Then, GO was introduced in the desired mixing amount, maintaining the mass proportion of GO to MIL-53(Fe) at 20%, defined as MIL-53(Fe)/GO. The resulting mixture was homogenized using an ultrasonic mixing technique for 20 min. The mixture was transferred to a one-liter Pyrex container and stirred for 30 min. To ensure the required homogeneity of the composite, solvothermal technique was applied by putting the experimental system in an oil bath and heated continuously at a steady temperature of 120 °C while being stirred for 15 h and left to cool at room temperature. The resultant powdered sample was washed and collected using Buchner filtration with acetone and methanol. After purification, the MIL-53(Fe)/GO was dried in an oven at 45 °C [33].

The MIL-53(Fe)/GO composite was heated in a tubular furnace under a continuous flow of Ar gas (conventional slow pyrolysis) to produce P-MIL-53(Fe)/RGO at pyrolysis temperatures of 350 °C, 450 °C, and 550 °C. At each temperature, heating durations of 0.5 h, 1 h, and 2 h were applied. A schematic illustration of the preparation process is shown in Fig. 1.

Fig. 1.

Fig. 1

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Schematic illustration of the MIL-53(Fe)/GO and P-MIL-53(Fe)/RGO preparation

Characterization

The diffraction patterns of the synthesized materials were analyzed using powder X-ray diffraction (PXRD) with a Panalytical X’PERT PRO MPD diffractometer (England) with a CuKα₁ radiation source at 40 kV and 40 mA, with a wavelength of 1.5406 Å. A resolution of 0.02° per step was achieved, with a step time of 0.4 s for each scan. The measurements were conducted over a temperature range of 4 °C to 80 °C to ensure precise material characterization.

A dispersive Raman microscope (Sentera II model, Bruker Optics, Germany) was employed to analyze the s Raman spectrum of the samples. The setup employed a 10 mW Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser operating at 532 nm, with a Nikon 20X objective lens was utilized to focus the laser beam. Fourier transform infrared (FTIR) analysis was performed using a JASKO 4100 spectrometer at a resolution of 4 cm− 1 across the wavelength range of 400–4000 cm-1. high signal-to-noise ratio (SNR) were obtained for each sample by integrating data from 100 scans.

Transmission electron microscopy (TEM) was conducted using a Talos F200i TEM operating in transmission mode. Thermogravimetric analysis (TGA) was conducted using a Shimadzu TGA-60 instrument (Japan). Thermal stability was assessed at a heating rate of 10 °C per minute, with the temperature ramped up to 600 °C under an inert atmosphere. The magnetic characteristics of the composites were analyzed at room temperature using a vibrating sample magnetometer (Lakeshore, VSM-7410).

The electrical conductivity of each sample was measured in compliance with the ASTM D257 standard. A four-probe setup, connected to a Keithley 220 instrument, applied a small voltage range of − 0.1 to 0.1 V. A Zahner IM6ex potentiostat stabilized the voltage supply, ensuring measurement accuracy. For consistency, five repeated measurements were taken per sample. The final conductivity value for each sample was derived from the average of these replicates.

The S-parameters were measured with an HP 8510 C vector network analyzer configured with two ports, at frequencies ranging from 8 to 12 GHz. A standard rectangular waveguide flange (WR-90) with dimensions of 22.86 mm and 10.16 mm was employed along with a sample holder, where the samples, having a 5 mm thickness, were compressed under a pressure of ten tons.

Results and discussion

The XRD pattern shown in Fig. 2-A for the synthesized MIL-53(Fe) and MIL-53(Fe)/GO exhibits two major peaks at 2θ = 9.2° and 12.4°, which aligns well with previous reported results, confirming a successful synthesis process [34]. Generally, these peaks are affected by the pyrolysis conditions, including temperature and time.

Fig. 2.

Fig. 2

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XRD patterns of MIL-53(Fe), MIL-53(Fe)/GO, and γ-Fe₂O₃ [JCPDS 25-1402], along with P-MIL-53(Fe)/RGO subjected to different heating durations and temperatures: A at 350℃ B at 450℃ C at 550℃

As shown in Fig. 2-A, MIL-53(Fe)/GO undergoes transformation into P-MIL-53(Fe)/RGO upon pyrolysis at 350 °C. The XRD peaks shift from 2θ = 9.2° and 12.4° to 2θ = 8.7° and 10.4°, respectively, indicating lattice expansion due to internal stress generated during high-temperature synthesis. This observation aligns with the Raman spectroscopy results Fig. 2-A, where the increased ID/IG ratio after pyrolysis at 350 °C suggests a higher degree of structural disorder, likely caused by the removal of oxygen functional groups from GO. The resulting disorder may contribute to greater interlayer spacing in P-MIL-53(Fe)/RGO, which broadens the XRD peaks and shifts them toward lower 2θ angles. Notably, the treatment duration (i.e., 0.5 h, 1 h, and 2 h) does not significantly influence the observed XRD patterns.

At 450 ℃ for 0.5 h, the P-MIL-53(Fe)/RGO pattern shows one peak at 2θ = 8.2° referred to the MIL-53 structure while the increased effect in the inner stress led to the volume growing in the lattice structure and the disappearance of the peak at 2θ = 10.4°. As the treatment duration increased, the intensity of the 2θ = 8.2° decreased and several distinctive peaks appeared at 2θ = 30.2, 35.4, 44, 53.6, 57.3, and 63.7, as illustrated in Fig. 2-B.

These peaks correspond to the crystallographic planes of γ-Fe₂O₃, identified using Xpert HighScore Plus software and matching the card number (JCPDS 25-1402): 30.2 (220), 35.4 (311), 44 (400), 53.6 (422), 57.3 (511), and 63.7 (440) [35]. This observation confirms that γ-Fe2O3 was integrated in the composite after pyrolysis, while the framework structure of MIL-53(Fe) was still maintained under these treatment conditions.

Figure 2C demonstrates the XRD diffraction peaks of P-MIL-53(Fe)/RGO at 550℃. The patterns reveal the complete decomposition of MIL-53(Fe) into into γ-Fe2O3 for 1 h and 2 h duration, except at 0.5 h, where a peak at 2θ = 8.8° indicates the presence of residual MIL-53(Fe) non decomposed structure.

These findings highlight the crucial role of both pyrolysis temperature and duration on the final product’s structure. However, the presence of RGO remains uncertain and requires further confirmation through RAMAN spectroscopy.

The Raman spectrum confirms the presence of RGO in the composite under varying pyrolysis temperatures and durations (Fig. 3), as evidenced by the characteristic D and G bands at approximately 1350 cm⁻¹ and 1590 cm⁻¹, respectively [36]. Figure 3-A illustrates the influence of pyrolysis temperature (350 °C) on the composite structure at different exposure times. All samples display D and G bands at 1345 cm⁻¹ and 1583 cm⁻¹, respectively. Notably, the treatment duration significantly affected the reduction of GO, as reflected in the decreasing ID/IG ratios with increasing time. This trend indicates a progressive restoration of the graphitic structure (sp²-hybridized carbon networks) over defect sites. The ID/IG ratio decreased from 0.98 (30 min) to 0.91 (1 h), reaching its lowest value of 0.87 after 2 h of pyrolysis [37].

Fig. 3.

Fig. 3

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The Raman spectra of P-MIL-53(Fe)/RGO under different treatment duration at: A 350℃ B 450℃ C 550℃

At 450 °C and 550 °C, the Raman spectra (Fig. 3B, C) demonstrate the effect of thermal treatment duration on the RGO structure. After 30 min of pyrolysis, the decreased ID/IG ratios suggest partial GO reduction and an improved graphitic structure. However, prolonged treatment (2 h) leads to increased structural defects, as evidenced by higher ID/IG ratios of 0.96 and 1.01 at 450 °C and 550 °C, respectively. Notably, a 1 h treatment yields the lowest ID/IG ratios (0.79 at 450 °C and 0.73 at 550 °C), indicating higher RGO quality [38].These results reveal that 1 h is the optimal pyrolysis duration for achieving efficient GO reduction and high-quality RGO with minimal defects.

The FTIR results, shown in Fig. 4, support the findings from the XRD and RAMAN analysis. Figures 3-B and 4-A display a peak at 522 cm⁻¹, corresponding to the vibration of (Fe–O) bonds [39]. Additionally, (C-H) bending vibrations are observed at 735 cm⁻¹ [40], while the vibrational stretching of (C-O) in alkoxy and epoxy groups appears around 1000 and 1200 cm− 1, respectively. Furthermore, The symmetric and asymmetric (C-O) stretching of dicarboxylate linkers is verified by peaks at 1373 cm− 1 and 1535 cm− 1, respectively [41]. These finding confirm that the MOF structure is preserved during thermal treatments at 350℃ and 450℃ across all durations.

Fig. 4.

Fig. 4

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P-MIL-53(Fe)/RGO FTIR spectrum under different durations at: A 350℃ B 450℃ C 550℃

In contrast, at 550℃, the characteristic peaks of symmetric and asymmetric (C-O) stretching in dicarboxylate linkers disappear, indicating that the MOF structure is deteriorated. However, an exception is observed with the 30-minute treatment, as shown in Fig. 4-C.

According to the XRD, RAMAN, and FTIR analysis, pyrolysis at 450℃ for 1 h produces a P-MIL-53(Fe)/RGO ternary composite with optimal RGO quality, along with γ-Fe₂O₃ and MIL-53(Fe), while pyrolysis at 550℃ results in a binary composite consisting of RGO and γ-Fe₂O₃ only, as the structure shows no distinct MOF peaks, indicating that the framework structure of MIL-53(Fe) is completely decomposed.

The magnetic properties of P-MIL-53(Fe)/RGO composites treated at 350℃, 450℃, and 550℃ for 0.5 h, 1 h and 2 h. were assessed using a VSM at room temperature, as illustrated in Fig. 5.

Fig. 5.

Fig. 5

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The hysteresis Loops of P-MIL-53(Fe)/RGO (A) at: A 350℃, B 450℃, C 550℃

At 350℃, all P-MIL-53(Fe)/RGO samples exhibited nonmagnetic behavior due to the absence of the formation of magnetic γ-Fe2O3, which matches the XRD results despite the treatment duration, as presented in Fig. 5-A. However, at higher temperatures (i.e., 450 and 550℃), the emergence of γ-Fe2O3 results in the formation of a hysteresis loop, indicating ferromagnetic behavior in the composite.

On the other hand, at 450℃, we assumed that the lowest Ms value of 4 emu/g which observed for the 30 min duration is due to the incomplete oxidation of iron ions the MOF structure as shown in Fig. 5-B. However, for 1 h and 2 h treatments, we suggest that the Ms which increased to 22 and 25 emu/g, respectively, with Hc reaching 160 Oe is due to pyrolysis longer time lead to more complete oxidation of iron ions and more formation of magnetic γ-Fe₂O₃.

For 550℃, the 2 h treatment demonstrated the highest saturation magnetization (Ms) of 45 emu/g and a coercive force (Hc) of 105 Oe, correlating with the complete decomposition of the MOF structure into γ-Fe2O3, while the 0.5 h and 1 h treatments were 30 and 32 emu/g, respectively (Fig. 5-C).

The morphology of the prepared composites was examined using TEM at a magnification of 28 K with a 500 nm scale, as illustrated in Fig. 6.

Fig. 6.

Fig. 6

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TEM images of P-MIL-53(Fe)/RGO

RGO sheets are visible in all samples, with increasing layer transparency indicating a higher degree of exfoliation and suggesting reduced thickness. Figure 6A-C depict the MOF structure deposited on the graphene layers across all duration.

At 450℃, Fig. 6E-F shows certain particles not associated with the MOF structure, likely corresponding to the γ-Fe2O3. Finally, Fig. 6G-I  demonstrate the critical effect of pyrolysis at 550℃, which results in the complete degradation of the MOF structure into γ-Fe2O3 which align with the XRD and FTIR results.

Figure 7-A illustrates the thermal degradation of P-MIL-53(Fe)/RGO at 350℃. The 0.5 h treatment exhibits a weight loss of approximately 15% at 250℃, while the 1 h and 2 h treatments demonstrate greater thermal stability. This suggests that the 0.5 h was insufficient to eliminate entrapped H2O molecules and CO2 emissions within the composite structure during pyrolysis. Beyond 450℃, all composites show a total weight loss 60%, attributed to the complete decomposition and sublimation of the carbon backbone of RGO.

Fig. 7.

Fig. 7

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TGA of P-MIL-53(Fe)/RGO at: (A) 350℃ (B) 450℃ (C) 550℃

At 450℃ (Fig. 7-B), the 0.5 h remains inadequate for the pyrolysis process, showing a weight loss of approximately 15% around 250℃. However, the 1 h. treatment exhibits the highest thermal stability, with weight loss detected only after 450 °C, corresponding to the complete degradation of the RGO layers, resulting in a total weight loss of almost 25%. Similarly, the 2 h treatment shows a significant impact on the rapid deterioration of RGO, with degradation starting around 400 °C and leading to a 25% weight loss.

Figure 7-C shows that at 550℃, the thermal degradation trends across all treatment durations are similar to those observed at 450 °C, with no significant variations.

From the TGA analysis, it can be concluded that a 0.5 h treatment duration is inadequate period for the pyrolysis process, despite of the temperature applied. Furthermore, a pyrolysis exceeding 550℃ negatively impacts the RGO structure, which is vital for EMI applications. Starting from a 1 h treatment at 450 °C, the pyrolysis process produces samples with both dielectric and magnetic properties, making them promising candidates for EMI shielding materials.

Figure 8 compares the electrical conductivity (σ) of P-MIL-53(Fe)/RGO composites synthesized at different pyrolysis temperatures (350℃, 450℃, and 550℃) and durations (0.5, 1, and 2 h). Among these, the composite pyrolyzed at 450℃ for 1 h exhibited the highest conductivity (25 S/m), outperforming samples treated at other temperatures (e.g., 350 and 550℃) or shorter/longer durations (e.g., 0.5–2 h at 450 °C). This peak performance can be attributed to the optimal reduction of graphene oxide (GO) under these conditions, which balances defect removal and structural integrity, yielding high-quality RGO with minimal lattice disruptions. The resulting composite’s superior conductivity highlights its potential as an efficient electromagnetic interference (EMI) shielding material, where electrical conductivity is a critical performance metric.

Fig. 8.

Fig. 8

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Electrical conductivity of P-MIL-53(Fe)/RGO

EMI shielding effectiveness evaluation

The EMI shielding mechanism, shown in Fig. 9, is based on the total shielding efficiency (SET), along with at either the reflection shielding efficiency (SER) and the absorption shielding efficiency (SEA), as they are interrelated according to Eq. 1 [42, 43].

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Fig. 9.

Fig. 9

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Electromagnetic shielding mechanisms schematic diagram

The multiple internal reflections (SEM) are neglected for materials capable to achieve (SET) higher than 10 dB [44].

The shielding effectiveness evaluation of the nanocomposite can be achieved, by measuring the scattering parameters (S) derived from VNA (Vector Network Analyzer) data through a 2-port measurement waveguide transmission line method to give (S11, S12, S21, and S22), and followed by applying the following formulas [45]:

graphic file with name d33e807.gif 2
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Where : (T) is the transmittance coefficient, which signifies the portion of electromagnetic waves that pass through the shielding material without any attenuation effects by absorption or reflection inside the shielding material. (R) is the reflectance coefficient, which represents the part of the electromagnetic wave that is reflected from the interface between the shielding material surface and air due to the impedance mismatch. (A) is the absorbance coefficient, which stands for the portion of electromagnetic waves that are attenuated inside the shielding material due to the effect of multiple internal reflections, reflection loss, and magnetic loss.

Consequently, the absorbance, reflectance, and transmittance coefficients are calculated based on measured S parameters. ET is the transmitted wave of an electric field; ER is the reflected wave of an electric field and Ei is the incident wave of an electric field.

Additionally, the three primary mechanisms of EMI shielding material effectiveness are illustrated in Eqs. 5,6 and 7 [33].

graphic file with name d33e843.gif 5
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Where the reflection shielding efficiency is presented as (SER), the absorption shielding efficiency is (SEA), and the total shielding efficiency is (SET).

These equations indicate that evaluating a material’s microwave absorption properties cannot rely solely on the shielding efficiency due to reflection (SER); the total shielding efficiency (SET) must also be considered. It is important to note that the shielding effectiveness due to absorption (SEA) is fundamentally determined by the material’s intrinsic physical properties that facilitate microwave absorption [46]. When a material absorbs microwaves, it generates internal ohmic losses, which produce heat and contribute to the wave absorption phenomenon [47]. Typically, the shielding materials are characterized by dielectric and magnetic losses parameters which have an impact on the electromagnetic wave attenuation in addition to their matching of impedance [48–51].

All synthesized P-MIL-53(Fe)/RGO composites, pyrolyzed at 350 °C, 450 °C, and 550 °C, were evaluated for their EMI shielding performance. Samples with a fixed mass of 2 g were loaded into the waveguide, and their S-parameters were measured across the X-band frequency range (8–12 GHz) to assess shielding effectiveness. The shielding effectiveness (SE) was calculated, and the results are presented in Fig. 10. A consistent trend was observed for all samples, where the absorption mechanism dominated over the reflection mechanism.

Fig. 10.

Fig. 10

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Shielding effectiveness (SE) of P-MIL-53(Fe)/RGO at: A 350℃ B 450℃ C 550℃

At 350℃, the average total shielding efficiency (SET) of P-MIL-53(Fe)/RGO was 28 dB, 30 dB, and 35 dB for treatments of 0.5, 1, and 2 h, respectively (Fig. 8-A). This highlights the vital role of RGO as shielding material. The increased reduction of GO and subsequent graphitization within the structure at higher temperatures enhance the composite’s dielectric properties, positively influencing the (SET).

Figure 10-B illustrates the average total shielding efficiency (SET) of P-MIL-53(Fe)/RGO pyrolyzed at 450℃. This condition yields a higher RGO, resulting in improved SET values. The SET was 35 dB for the 0.5 h treatment, increased to 43 dB for the 1 h treatment, and slightly decreased to 40 dB for 2 h treatment. The observed decrease in SET with extended treatment duration is attributed to dual effects, first the degradation of the RGO structure, which impacts its conductivity; and second, the decomposition of the MOF structure and formation of γ-Fe2O3. The combination of both magnetic and conductive properties in these composites lead to a notable improvement over the performance at 350℃. This highlights the synergistic effect of RGO, MIL-53(Fe), and γ-Fe2O3 making these composites promising candidates for EMI shielding applications.

The negative impact of pyrolysis temperature and the extended treatment duration on the RGO and MOF structure is evident at 550℃, as shown in Fig. 10-C. A dramatic decrease in SET values was observed, with the 0.5 h treatment achieving an SET of 18 dB, increasing to 23 dB and 28 dB for the 1 and 2 h treatment, respectively. This decline is attributed to the highly defected RGO structure, which reduces the overall dielectric properties of the P-MIL-53(Fe)/RGO composite. Additionally, the complete decomposition of the MOF into γ-Fe2O3 makes γ-Fe₂O₃ the primary contributor to EMI shielding. As a result, the synergistic effects between RGO, MIL-53(Fe), and γ-Fe₂O₃ are diminished, adversely affecting the overall EMI shielding performance. Table 1 provides a summary of all shielding efficiency results.

Table 1.

EMI shielding effectiveness summary of P-MIL-53(Fe)/RGO

350℃ 450℃ 550℃
0.5 h 1 h 2 h 0.5 h 1 h 2 h 0.5 h 1 h 2 h
SET 28 30 35 35 43 40 18 23 28
SEA 25 28 31 31 40 37 14 20 24
SER 2.9 3.2 3.3 2.3 2.9 3.1 3.2 4.1 5.1
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As demonstrated in Table 1, the P-MIL-53(Fe)/RGO composite pyrolyzed at 450 °C for 1 h exhibits superior EMI shielding performance, with a high specific electromagnetic absorption SEA of 40 dB (∼99.99% attenuation of incident waves). The low surface reflection (SER = 2.9 dB) further confirms that absorption is the dominant shielding mechanism. This characteristic is particularly advantageous for applications where reflected waves could cause secondary interference, such as in aerospace electronics, 5G communication systems, and military radar-absorbing materials.

The EMI shielding results highlight the crucial role of RGO as a dielectric material in P-MIL-53(Fe)/RGO composites and the significant impact of pyrolysis temperature and durations on both the reduction of GO and the transformation of MOF into γ-Fe₂O₃. The optimal pyrolysis conditions were determined to be 450 °C for 1 h, resulting in a ternary composite comprising RGO, MIL-53(Fe), and γ-Fe2O3. The synergistic interaction between these three components in the composite leads to enhanced shielding performance, offering a promising pathway for developing advanced EMI shielding materials for civilian and military applications.

Conclusion

The impact of pyrolysis temperature and exposure time on the MIL-53(Fe)/GO composite is both critical and condition-sensitive. The in-situ reduction of GO results in varying RGO quality, dependent on temperature and exposure duration, while the MOF structure degrades at elevated temperature, forming γ-Fe2O3.

An optimization was achieved to produce P-MIL-53(Fe)/RGO at 450℃ for one hour with a 20% GO loading percentage. Under these conditions the MIL-53(Fe)/GO binary composite produces a ternary composite comprising RGO, MIL-53(Fe), and γ-Fe2O3. This ternary structure exhibits a synergistic effect, achieving high EMI shielding performance with SET of 43 dB, including 40 dB for SEA and 2.9 dB for SER.

This approach delivers a lightweight composite with a dominant absorption mechanism, paving the way for advanced EMI shielding materials suitable for a wide range of civilian and military applications.

Acknowledgements

Not applicable.

Third party material

All the material is owned by the authors and no permissions are required.

Author contributions

Mohamed E. Elmowafy: Planned and performed the experiments, sample preparation, data collection, analysis, and interpretation of the results, and writing the manuscript. Ramy Sadek: Contributed to the interpretation of the results, Critical revision of the article, and Final approval of the version to be published. Mahmoud Zorainy: Contributed to the interpretation of the results, Critical revision of the article, and Final approval of the version to be published. Osama Abuzalat: Supervises experiments and sample preparation. Ahmad Baraka: Contributed to the interpretation of the results and critical revision of the article. Mohamed F. Hagag: Contributed to the EMI shielding measurements and evaluation. Hesham Tantawy: Design of the work, contributed to the interpretation of the results, Critical revision of the article, and Final approval of the version to be published.All authors provided critical feedback and helped shape the research, analysis, and manuscript.

Funding

This research was conducted without any financial support.

Data availability

All data generated or analyzed during this study are included in this published article.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

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