Fe / Fe3O4 multifunctional composite aerogel material based on MOF derivation as well as preparation method and application of Fe / Fe3O4 multifunctional composite aerogel material

Abstract

The invention relates to a Fe / Fe3O4 multifunctional composite aerogel material based on MOF derivation and a preparation method and application thereof.The preparation method includes the steps that S1, an iron source, 2-aminoterephthalic acid and polyvinylpyrrolidone are weighed and added into DMF, stirring and dissolving are conducted, and a mixed solution is obtained; s2, transferring the mixed solution into a reaction kettle for hydrothermal reaction, and washing and drying an obtained reaction product to obtain MOF precursor powder; s3, adding the MOF precursor powder, chitosan and glacial acetic acid into deionized water, mechanically stirring uniformly, carrying out ultrasonic dispersion, pouring into a mold, carrying out pre-freezing treatment, and then carrying out vacuum freeze drying; and S4, calcining the dried sample in an inert atmosphere to obtain a target product. Compared with the prior art, the effective absorption bandwidth of the composite material is as high as 6.88 GHz under the thickness of 2.15 mm, and the whole Ku (12-18 GHz) wave band is covered. The composite material has the characteristics of hydrophobicity, heat insulation and the like while high-performance electromagnetic wave absorption is realized, so that the composite material adapts to constantly changing application scenes.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, and relates to a multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, its preparation method and application. Background Technology

[0002] In recent years, the rapid development of wireless communication technology and the trend towards miniaturization and portability of electronic devices have brought great convenience to human life. However, the wider range of operating scenarios and different operating frequencies of electronic devices have exacerbated electromagnetic pollution. Therefore, electromagnetic wave absorbing materials play a crucial role in protecting human health and sensitive instruments from harmful electromagnetic radiation and interference. Carbon aerogels have attracted great interest due to their wide availability, good conductivity, and low density. Their unique 3D porous structure enables them to effectively reflect and dissipate electromagnetic waves through various scattering and dielectric loss mechanisms. However, the inherent electromagnetic and chemical properties of carbon materials, as well as the single loss mechanism, mean that carbon aerogel materials still face the problem of a narrow electromagnetic wave frequency coverage range. Currently, introducing magnetic components such as ferromagnetic oxides, alloys, and metal particles into carbon materials can introduce magnetic losses, thereby optimizing impedance matching and broadening the absorption bandwidth. However, the uneven distribution of magnetic particles on the carbon matrix reduces magnetic coupling efficiency, further limiting the electromagnetic wave frequency absorption range.

[0003] For example, the chitosan aerogel / MOF-derived Fe / Fe2O3 / C composite material provided in Chinese patent application CN202410058663.2 is prepared as follows: H2BDC and trivalent Fe salt undergo a solvothermal reaction to generate a precursor FeMOF, denoted as substance A; chitosan powder is added to an aqueous acetic acid solution and stirred to obtain a pale yellow chitosan hydrogel precursor, denoted as substance B; substance A is added to substance B and stirred, followed by freeze treatment and vacuum freeze-drying, and then calcination under an inert atmosphere to obtain the target product. Because the reducing power of the carbon matrix obtained by the pyrolysis of H2BDC ligands is relatively weak, the carbonization process leads to a decrease in the reducibility of Fe... 3+ The reduction is insufficient, and the final product is Fe2O3, which has semiconductor properties. Therefore, the composite material prepared by this method has limited magnetic loss capability and weak magnetoelectric synergy, resulting in a narrow effective absorption bandwidth and poor overall electromagnetic wave absorption effect. Summary of the Invention

[0004] The purpose of this invention is to provide a multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, its preparation method, and its application, which achieves broadband electromagnetic wave absorption and high electromagnetic wave absorption efficiency.

[0005] The objective of this invention can be achieved through the following technical solutions: In one aspect, the present invention provides a method for preparing a multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, comprising the following steps: S1. Weigh out the iron source, 2-aminoterephthalic acid, and polyvinylpyrrolidone, add them to N,N-dimethylformamide, stir to dissolve, and obtain a mixed solution; S2: The mixed solution obtained in S1 is transferred to a reaction vessel for hydrothermal reaction. The resulting reaction product is washed and dried to obtain MOF precursor powder. S3: Take MOF precursor powder, chitosan, and glacial acetic acid, add them to deionized water, stir mechanically until uniform, disperse ultrasonically, pour into a mold, pre-freeze, and then freeze-dry in a vacuum freeze dryer. S4: The dried sample obtained in S3 is calcined under an inert atmosphere to obtain the MOF-derived Fe / Fe3O4 multifunctional composite aerogel material, which is the target product.

[0006] Furthermore, in S1, the ratio of the amount of iron source, 2-aminoterephthalic acid, and polyvinylpyrrolidone added is (0.004~0.006) mol: (0.004~0.006) mol: 1g.

[0007] Furthermore, in S1, the iron source is ferric nitrate or its hydrate.

[0008] Furthermore, in S2, the hydrothermal reaction temperature is 150~160℃ and the time is 7~9h.

[0009] Furthermore, in S3, the ratio of the amount of MOF precursor powder, chitosan, and glacial acetic acid added is (0.1~0.4) g: 1 g: (0.6~0.8) mL.

[0010] Furthermore, in S3, the pre-freezing treatment temperature is -5~15℃, and the time is 10~12h; The freeze-drying temperature is -45~-55℃, and the time is 30~36h.

[0011] Furthermore, in S3, the calcination treatment temperature is 600~800℃, and the time is 2~4h.

[0012] Furthermore, in S3, the inert atmosphere is provided by N2 or Ar.

[0013] In a second aspect, the present invention provides a multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, which is prepared by the preparation method described above.

[0014] In a third aspect, the present invention provides an application of MOF-derived Fe / Fe3O4 multifunctional composite aerogel material in the field of electromagnetic wave absorption.

[0015] Compared with the prior art, the present invention has the following advantages: (1) This invention synthesizes MOF-derived Fe / Fe3O4 multifunctional composite aerogel materials through a simple and controllable cryogenic casting and high-temperature carbonization process. The uniform distribution of magnetic particles is achieved under the confinement effect of the aerogel and MOF framework, avoiding agglomeration. Furthermore, the preparation method is simple, the raw materials are widely available, and it is suitable for large-scale production.

[0016] (2) By introducing 2-aminoterephthalic acid as an organic ligand, the characteristic of its amino functional group being converted into nitrogen-doped carbon during pyrolysis is cleverly utilized, which significantly enhances the reducibility of the carbon matrix. At the same time, the carbonization temperature is optimized, and the Fe / Fe3O4 / C composite material is finally obtained, which optimizes the impedance matching and further broadens the electromagnetic wave frequency absorption range.

[0017] (3) The porous structure of aerogels provides a site for multiple reflections of electromagnetic waves, thus extending the electromagnetic wave dissipation path. MOF-derived high-density magnetic carbon nanoparticles have abundant heterogeneous interfaces, which enhances interfacial polarization loss. At the same time, the uniformly distributed magnetic particles also construct an enhanced magnetic coupling network, thereby enhancing magnetic response capability.

[0018] (4) The Fe / Fe3O4 multifunctional composite aerogel material of the present invention exhibits excellent electromagnetic wave absorption performance. Its effective absorption bandwidth (<-10 dB) can reach 6.88 GHz with a thickness of 2.15 mm, completely covering the Ku band (12~18 GHz); its reflection loss value can reach 48.44 dB. It also has good hydrophobicity, thermal management performance and infrared stealth characteristics. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the precursor MIL-88B prepared in Example 1.

[0020] Figure 2 The images show the XRD patterns of the composite materials prepared in Examples 1-4 and Comparative Example 1.

[0021] Figure 3 The images shown are scanning electron microscope (SEM) images of the composite materials prepared in Examples 1-4.

[0022] Figure 4 The images shown are transmission electron microscope (TEM) images of the composite materials prepared in Examples 1-4.

[0023] Figure 5 The electromagnetic parameters of the composite materials prepared in Examples 1-4 and Comparative Example 1 are shown.

[0024] Figure 6The microwave absorption performance curves of the composite materials prepared in Examples 1-4 are shown.

[0025] Figure 7 The microwave absorption performance curve of the composite material prepared in Comparative Example 1 is shown.

[0026] Figure 8 The image shows the XRD pattern of the composite material prepared in Comparative Example 2.

[0027] Figure 9 The image shows a SEM image of the MOF precursor prepared in Comparative Example 3.

[0028] Figure 10 The electromagnetic parameters of the composite materials prepared in Comparative Examples 2-3 are shown in the figure.

[0029] Figure 11 The microwave absorption performance curves of the composite materials prepared in Comparative Examples 2-3 are shown.

[0030] Figure 12 The images show the multifunctionality of the composite materials prepared in Examples 1-4. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0034] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0035] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0036] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0037] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0038] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0039] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0040] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0041] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0043] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0046] In the following examples, 2-aminoterephthalic acid, polyvinylpyrrolidone, ferric nitrate nonahydrate, and N,N-dimethylformamide were all purchased from Sinopharm Reagent Co., Ltd. Chitosan and glacial acetic acid were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Unless otherwise specified, all other raw materials or processing techniques are commercially available and conventional in the art.

[0047] Example 1 A method for preparing MOF-derived Fe / Fe3O4 multifunctional composite aerogel material, comprising the following steps: S1: 0.005 mol ferric nitrate nonahydrate, 0.005 mol 2-aminoterephthalic acid, and 1 g polyvinylpyrrolidone were dissolved in 30 mL of N,N-dimethylformamide and magnetically stirred for 12 h. The mixture was then transferred to a 50 mL polytetrafluoroethylene autoclave and heated at 155 °C for 8 h. After cooling to room temperature, the mixture was washed three times with ethanol and deionized water and vacuum dried at 70 °C for 12 h. The final MOF precursor powder was obtained and designated MIL-88B.

[0048] S2: Dissolve 0.2 g of MIL-88B and 1.0 g of chitosan powder in 40 mL of deionized water and stir magnetically for 30 min. Then, add 0.6 mL of glacial acetic acid to the solution, stir mechanically for 2 h, and sonicate for 30 min. Pour the resulting MOF / chitosan hydrogel solution into a mold and pre-freeze at -10 ℃ for 12 h. Then, freeze-dry the frozen sample at -60 ℃ for 48 h in a vacuum freeze dryer.

[0049] S3: The sample after freeze-drying was calcined at 700℃ for 3 h in a N2 atmosphere. This ultimately yielded a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material.

[0050] Example 2 Compared with Example 1, most of the steps are the same, except for step S2: 0.1 g of MIL-88B and 1.0 g of chitosan powder were dissolved in 40 mL of deionized water and magnetically stirred for 30 min. Then, 0.6 mL of glacial acetic acid was added to the solution, and the mixture was mechanically stirred for 2 h and ultrasonically dispersed for 30 min. The MOF / chitosan hydrogel solution was poured into a specially designed mold and pre-frozen at -10 °C for 12 h. The frozen sample was then freeze-dried at -60 °C for 48 h in a vacuum freeze dryer.

[0051] Example 3 Compared with Example 1, most of the steps are the same, except for step S2: 0.3 g of MIL-88B and 1.0 g of chitosan powder were dissolved in 40 mL of deionized water and magnetically stirred for 30 min. Then, 0.6 mL of glacial acetic acid was added to the solution, and the mixture was mechanically stirred for 2 h and ultrasonically dispersed for 30 min. The MOF / chitosan hydrogel solution was poured into a specially designed mold and pre-frozen at -10 °C for 12 h. The frozen sample was then freeze-dried at -60 °C for 48 h in a vacuum freeze dryer.

[0052] Example 4 Compared with Example 1, most of the steps are the same, except for step S2: 0.4 g of MIL-88B and 1.0 g of chitosan powder were dissolved in 40 mL of deionized water and magnetically stirred for 30 min. Then, 0.6 mL of glacial acetic acid was added to the solution, and the mixture was mechanically stirred for 2 h and ultrasonically dispersed for 30 min. The MOF / chitosan hydrogel solution was poured into a specially designed mold and pre-frozen at -10 °C for 12 h. The frozen sample was then freeze-dried at -60 °C for 48 h in a vacuum freeze dryer.

[0053] Comparative Example 1 Compared to Example 1, no MOF precursor powder was introduced, and the steps are as follows: S1: Dissolve 1.0 g of chitosan powder in 40 mL of deionized water and stir magnetically for 30 min. Then, add 0.6 mL of glacial acetic acid to the solution, stir mechanically for 2 h, and sonicate for 30 min. Pour the chitosan hydrogel solution into a specially made mold and pre-freeze at -10 ℃ for 12 h. Then, place the frozen sample in a vacuum freeze dryer and freeze-dry at -60 ℃ for 48 hours.

[0054] S2: The sample after freeze-drying was calcined at 700℃ for 3 h in a N2 atmosphere. The final product was a carbon aerogel material.

[0055] Comparative Example 2: It is largely the same as Example 1, except that 2-aminoterephthalic acid is replaced with an equimolar amount of terephthalic acid.

[0056] Comparative Example 3: It is largely the same as Example 1, except that the addition of polyvinylpyrrolidone is omitted.

[0057] X-ray electron diffraction (XRD) was performed on the precursor MIL-88B prepared in Example 1. The test results are as follows: Figure 1 As shown, the XRD pattern of the MIL-88B prepared in this invention matches well with the results of crystallographic data simulation.

[0058] XRD tests were performed on the materials prepared in Examples 1-4 and Comparative Example 1. The test results are as follows: Figure 2 As shown, Examples 1-4 and Comparative Example 1 exhibit distinct diffraction peaks near 2θ = 44.7°, 65.0°, and 82.3°, corresponding to the (110), (200), and (211) crystal planes of Fe, respectively. Diffraction peaks at 2θ = 35.4°, 56.9°, and 62.5° also correspond to the (311), (511), and (440) crystal planes of Fe3O4. Furthermore, the broad peak at 20°-30° closely matches the broad peak of carbon. The intensity of the corresponding diffraction peaks gradually increases with increasing content of the precursor MIL-88B.

[0059] The materials prepared in Examples 1-4 were tested using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The test results are as follows: Figure 3 and Figure 4 As shown, cavities of different sizes are interspersed, forming a sponge-like porous structure. This structural configuration provides a site for the absorption-reflection-reabsorption of electromagnetic waves, effectively extending the absorption path. Highly dispersed MIL-88B particles are uniformly distributed on the aerogel framework. Furthermore, the octahedral structure of MIL-88B is well inherited after carbonization, while uniformly distributed nanoscale magnetic carbon units are generated within its structure.

[0060] The electromagnetic properties of the materials prepared in Examples 1-4 and Comparative Example 1 were analyzed using a vector network analyzer (VNA, Agilent N5224B, 2-18 GHz). The test results are as follows: Figure 5 As shown, the dielectric constant of the material increases with increasing MIL-88B content. Specifically, the real part of the dielectric constant ( ε' The average value of the dielectric constant gradually increases from 4.6 to 7.1 in the range of 2-18 GHz, and the imaginary part of the dielectric constant ( ε" The average value of the dielectric constant increased from 2.0 to 17.0. This increase in dielectric constant also indicates that the uniformly distributed nano-magnetic carbon units construct a rich heterogeneous interface, enhancing interfacial polarization. The MIL-88B-derived Fe / Fe3O4@C particles enable the aerogel to store and dissipate magnetic energy, which significantly affects magnetic loss. The real part of the complex permeability of the composite material (… μ' ) and imaginary part ( μ" The concentration of MIL-88B also gradually increases with the increase of MIL-88B content.

[0061] Figure 6 The absorption performance curves for Examples 1-4 are shown. Example 1, with a matching thickness of 2.6 mm, achieved a minimum reflection loss of -48.44 dB; the maximum effective absorption bandwidth reached 6.88 GHz when the absorbing coating thickness was only 2.15 mm. Example 2, with a thickness of 3.3 mm, achieved a minimum reflection loss of -43.03 dB; the maximum effective absorption bandwidth reached 4.48 GHz when the absorbing coating thickness was 2.35 mm. Due to the continuously increasing MIL-88B content, the high conductivity of the composite material led to impedance mismatch, reducing the electromagnetic wave absorption efficiency. Therefore, Example 3 achieved a minimum reflection loss of only -10.21 dB, and Example 4 did not exceed -10 dB in the 2-18 GHz range. Comparative Example 1, serving as a control group, also demonstrates that the MOF-derived Fe / Fe3O4 multifunctional composite aerogel material exhibits excellent electromagnetic wave absorption performance.

[0062] Figure 7 The image shows the absorption performance curve for Comparative Example 1. Comparative Example 1 exhibits a minimum reflection loss of only -24.55 dB when the matched thickness is 2.1 mm. This further demonstrates the excellent electromagnetic wave absorption performance of the MOF-derived Fe / Fe3O4 multifunctional composite aerogel material.

[0063] Figure 8 The XRD results are for Comparative Example 2. Comparative Example 2 shows distinct diffraction peaks near 2θ = 44.7°, 65.0°, and 82.3°, corresponding to the (110), (200), and (211) crystal planes of Fe, respectively. Furthermore, the diffraction peaks at 2θ = 35.6° and 62.3° also correspond to the (110) and (214) planes of Fe₂O₃. Because the carbon matrix obtained from the pyrolysis of H₂BDC ligands has relatively weak reducibility, it leads to a decrease in the reducibility of Fe during carbonization. 3+ Insufficient reduction ultimately results in the presence of a small amount of Fe2O3 in the carbonization products.

[0064] Figure 9The image shows the SEM image of the precursor in Comparative Example 3. The MOF particles aggregate in the image, and the morphology does not exhibit a regular spindle-shaped octahedral structure. This is mainly because the omission of polyvinylpyrrolidone (PVP) prevents the control of the growth rate of different crystal faces, thus hindering crystal growth.

[0065] Figure 10 The electromagnetic parameter curves for Comparative Example 2-3 are shown. The real part of the dielectric constant in Comparative Example 2 is... ε' ) and the imaginary part of the dielectric constant ( ε" The magnetic permeability of Example 1 was higher than that of Comparative Example 2. However, the real and imaginary parts of the magnetic permeability of Example 1 were higher than those of Comparative Example 2, which reflects the influence of 2-aminoterephthalic acid as an organic ligand on the composition of the composite material. The electromagnetic parameters of Comparative Example 3 were generally lower than those of Example 1. This is mainly because the agglomeration of MOF particles in Comparative Example 3 is not conducive to the construction of the conductive network, thus affecting the dielectric and magnetic properties.

[0066] Figure 11 The absorption performance curves for Comparative Examples 2 and 3 are shown. Comparative Example 2, with a matching thickness of 2.5 mm, achieved a minimum reflection loss of -27.85 dB and a maximum effective absorption bandwidth of 5.28 GHz. Comparative Example 3, with a thickness of 1.75 mm, achieved a minimum reflection loss of -19.01 dB; however, the maximum effective absorption bandwidth was only 4.72 GHz when the absorbing coating thickness was 1.95 mm. Because Comparative Example 2 contains Fe₂O₃, its magnetic loss capability is weak, which is detrimental to impedance matching optimization. Therefore, both the reflection loss and effective absorption bandwidth of Comparative Example 2 are reduced to some extent. Furthermore, the lack of polyvinylpyrrolidone in Comparative Example 3 caused the MOF precursor particles to agglomerate, affecting their dispersion in the aerogel, reducing magnetic coupling efficiency, and limiting electromagnetic wave absorption.

[0067] Figure 12 These figures illustrate the multifunctional characteristics of Examples 1-4. The presence of wrinkles and folds on the material surface prevents direct contact between water droplets and the aerogel surface, thus inducing a Cassie impregnation wetting state. Therefore, Example 1 exhibits a water contact angle of 122.5°, demonstrating certain hydrophobic properties. The material was placed on a heating stage at 110 °C, and the surface temperature change of the aerogel was recorded using an infrared camera. After continuous heating for 30 minutes, the aerogel surface temperature only reached approximately 50 °C. This excellent thermal insulation performance is attributed to the aerogel's unique porous structure, which significantly restricts the free flow of air and reduces thermal convection effects.

[0068] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, characterized in that, Includes the following steps: S1. Weigh out the iron source, 2-aminoterephthalic acid, and polyvinylpyrrolidone, add them to N,N-dimethylformamide, stir to dissolve, and obtain a mixed solution; S2: The mixed solution obtained in S1 is transferred to a reaction vessel for hydrothermal reaction. The resulting reaction product is washed and dried to obtain MOF precursor powder. S3: Take MOF precursor powder, chitosan, and glacial acetic acid, add them to deionized water, stir mechanically until uniform, disperse ultrasonically, pour into a mold, pre-freeze, and then freeze-dry in a vacuum freeze dryer. S4: The dried sample obtained in S3 is calcined under an inert atmosphere to obtain the MOF-derived Fe / Fe3O4 multifunctional composite aerogel material, which is the target product.

2. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S1, the ratio of the amount of iron source, 2-aminoterephthalic acid, and polyvinylpyrrolidone added is (0.004~0.006) mol: (0.004~0.006) mol: 1g.

3. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S1, the iron source is ferric nitrate or its hydrate.

4. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S2, the hydrothermal reaction temperature is 150~160℃ and the time is 7~9h.

5. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S3, the ratio of MOF precursor powder, chitosan, and glacial acetic acid is (0.1~0.4) g: 1 g: (0.6~0.8) mL.

6. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S3, the pre-freezing treatment temperature is -5~15℃ and the time is 10~12h; The freeze-drying temperature is -45~-55℃, and the time is 30~36h.

7. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S3, the calcination temperature is 600~800℃ and the time is 2~4h.

8. The method for preparing a MOF-derived Fe / Fe3O4 multifunctional composite aerogel material according to claim 1, characterized in that, In S3, the inert atmosphere is provided by N2 or Ar.

9. A multifunctional composite aerogel material based on MOF-derived Fe / Fe3O4, which is prepared by the preparation method according to any one of claims 1-8.

10. The application of the MOF-derived Fe / Fe3O4 multifunctional composite aerogel material as described in claim 9 in the field of electromagnetic wave absorption.

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