CN115835612A - A composite material derived from rare earth MOF and its application - Google Patents

Abstract

The invention discloses a composite material derived from rare earth MOF and its application. It is prepared by the following preparation method: adding cerium salt and 1,3,5-benzenetricarboxylic acid to ethanol aqueous solution, cerium salt, 1,3, The addition ratio of 5-benzenetricarboxylic acid and ethanol aqueous solution is 0.2-1:0.05-0.5:40, g:g:mL, mix well, and let stand to obtain Ce-MOF precursor; in ethanol aqueous solution, the volume fraction of ethanol is 25-50%; the Ce-MOF precursor is calcined at 700-800°C for 0.5-4h to obtain the target product. This kind of composite material also has the characteristics of strong reflection loss, thin thickness, wide frequency band and light weight, as well as good impedance matching performance and strong electromagnetic wave loss capability, so that it can be applied in the field of electromagnetic wave absorption.

Description

A composite material derived from rare earth MOF and its application

technical field

The invention belongs to the technical field of electromagnetic wave absorbing materials, and in particular relates to a composite material derived from rare earth MOF and its application.

Background technique

The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

With the development of electromagnetic technology, electronic and wireless equipment are widely used in military and civilian fields. The resulting electromagnetic waves not only affect the normal operation of electronic equipment, but also pollute the environment and cause certain harm to human health. Therefore, it is an effective way to solve electromagnetic pollution by researching electromagnetic wave absorbing materials and converting unwanted electromagnetic waves into heat energy or other types of energy to achieve the absorption of electromagnetic waves. In recent years, metal-organic framework (MOF)-derived carbon composites have attracted increasing attention in electromagnetic wave absorption applications due to their wide variety of organic ligands, tunable chemical composition and degree of graphitization, and porous structure. As a typical rare earth oxide, cerium oxide (CeO ₂ ) has the advantages of good chemical stability, convenient preparation, low cost, significant dielectric loss and charge polarization relaxation caused by oxygen vacancy effect, and is a potential microwave dissipative materials. However, the low microwave attenuation and high density greatly limit the practical application of _CeO2 .

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention provides a composite material derived from rare earth MOF and its application. This kind of composite material has the characteristics of strong reflection loss, thin thickness, wide frequency band and light weight, as well as good impedance matching performance and strong electromagnetic wave loss capability, so that it can be applied in the field of electromagnetic wave absorption.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

In the first aspect, the present invention provides a composite material derived from rare earth MOF, which is prepared by the following preparation method: adding cerium salt and 1,3,5-benzenetricarboxylic acid to ethanol aqueous solution, cerium salt, 1,3, The addition ratio of 5-benzenetricarboxylic acid and ethanol aqueous solution is 0.2-1:0.05-0.5:40, g:g:mL, mix evenly, and stand still to obtain the Ce-MOF precursor;

In the aqueous ethanol solution, the volume fraction of ethanol is 25-50%;

The Ce-MOF precursor is calcined at a high temperature of 600-800°C for 0.5-4h to obtain the target product.

In a second aspect, the present invention provides the application of the rare earth MOF-derived composite material as a wave absorbing material.

The beneficial effects obtained by one or more embodiments of the present invention are as follows:

(1) The CeO ₂ @C composite material prepared by the present invention, on the one hand, the unique structure of the CeO ₂ @C composite material and the porous structure derived from the original MOF skeleton can optimize the impedance matching of the material, so that electromagnetic waves can enter the material smoothly Internal reflection does not occur, and it can cause multiple scattering, so that the material’s loss of electromagnetic waves is enhanced; on the other hand, as a dielectric material, the charge polarization relaxation caused by the oxygen vacancy effect of CeO ₂ can be used for The electromagnetic waves entering the absorber are effectively lost, and graphite carbon has excellent conductance loss for electromagnetic waves. The coordination of various loss mechanisms makes the absorber have better loss capabilities.

(2) Compared with the prior art, the Ce-MOF prepared by the present invention has a high yield, and the preparation process is simple and fast, which overcomes the disadvantages of the traditional hydrothermal or solvothermal method in the preparation of MOF, such as the long cycle and the inability to realize large-scale production. The unique "wheat bundle" structure and porous characteristics of the original MOF are retained in the CeO ₂ @C composite obtained by high-temperature calcination.

(3) After compounding CeO ₂ @C composite material and binder, the absorbing material is obtained. The reflection loss of electromagnetic wave at the frequency of 13.3GHz reaches -50.1dB, the matching thickness is 2.3mm, and the best effective absorption bandwidth reaches 6.0GHz . CeO ₂ @C composites have certain microwave-absorbing properties and have a wide range of applications.

(4) The material prepared by the present invention has a good wave-absorbing effect, so it is expected to be widely used in the preparation of electromagnetic wave-absorbing materials.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is the XRD figure of Ce-MOF and CeO ₂ @C composite material prepared in embodiment 1;

Fig. 2 is the SEM picture of the Ce-MOF precursor prepared in embodiment 1;

FIG. 3 is an SEM image of the CeO ₂ @C composite material obtained after calcination in Example 1. FIG.

Figure a in Figure 4 is the permittivity diagram of the CeO ₂ @C composite aerogel prepared in Example 1, diagram b is the magnetic permeability diagram, and diagram c is the dielectric loss tangent.

Fig. 5 is the reflection loss diagram of the CeO ₂ @C composite material absorber prepared in the experimental example.

FIG. 6 is a reflection loss diagram of the material prepared in Comparative Example 1. FIG.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, 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 invention belongs.

In the first aspect, the present invention provides a composite material derived from rare earth MOF, which is prepared by the following preparation method: adding cerium salt and 1,3,5-benzenetricarboxylic acid to ethanol aqueous solution, cerium salt, 1,3, The addition ratio of 5-benzenetricarboxylic acid and ethanol aqueous solution is 0.2-1:0.05-0.5:40, g:g:mL, mix evenly, and stand still to obtain the Ce-MOF precursor;

In the aqueous ethanol solution, the volume fraction of ethanol is 25-50%;

The Ce-MOF precursor is calcined at a high temperature of 600-800°C for 0.5-4h to obtain the target product.

The Ce-MOF-derived CeO ₂ @C composite material was obtained by high-temperature calcination. The composite material contains Ce, C, and O elements. Among them, the Ce element and the O element exist in the form of CeO ₂ , and the C element is mainly graphite. Existing in the form of carbon, the CeO ₂ @C composite retains the "wheat bundle" structure of the original MOF before calcination, and has good porous characteristics.

On the one hand, the unique structure of the CeO ₂ @C composite material and the porous structure derived from the original MOF framework can optimize the impedance matching of the material, so that electromagnetic waves can enter the material without reflection, and can cause multiple scattering, so that The loss of the material to the electromagnetic wave is enhanced; on the other hand, as a dielectric material, the charge polarization relaxation caused by the oxygen vacancy effect of CeO ₂ can effectively lose the electromagnetic wave entering the wave absorbing agent. Excellent conductance loss, the coordination of various loss mechanisms makes the absorber have better loss capability.

Compared with the prior art, the Ce-MOF prepared by the present invention has a high yield, and the preparation process is simple and fast, which overcomes the disadvantages of traditional hydrothermal or solvothermal methods such as long cycle time and inability to realize large-scale production of MOF.

The standing still means standing at room temperature, and room temperature generally refers to a temperature of about 20-30°C.

The central Ce atom forms nine coordinations with six oxygen atoms from water molecules and three oxygen atoms from the carboxyl group of the 1,3,5-benzenetricarboxylic acid ligand. The unique coordination mode enables the two to quickly coordinate to form MOF. Other types of ligands cannot react to form MOFs under this condition.

Changes in solution polarity lead to different dipole-dipole interactions, which alter the initial morphology, interfere with crystal growth, kinetically control the splitting process, and induce the assembly and packing of MOF molecules in different modes. The unique "wheat bundle" structure can be induced to form under ethanol aqueous solution. The nanorods that make up the wheat bundle structure are beneficial to have a large aspect ratio, which is beneficial to the transmission of carriers and the polarization of dipoles, and to improve the dielectric loss capability; at the same time, the gaps between the nanorods are conducive to the multiple reflection of electromagnetic waves, which promotes Attenuation of electromagnetic waves.

The calcination temperature has an important influence on the degree of graphitization of carbon in the material. Calcination in this temperature range can keep the degree of graphitization of the material at an appropriate level so that the dielectric constant of the material is moderate, so that the material has better absorption. wave performance.

In some embodiments, the cerium salt is cerium chloride.

In some embodiments, in the aqueous ethanol solution, the volume fraction of ethanol is 25%-50%.

In some embodiments, the addition ratio of cerium salt, 1,3,5-benzenetricarboxylic acid and ethanol aqueous solution is 0.2-1:0.05-0.5:40, g:g:mL.

In some embodiments, the calcination temperature is 600-800° C., and the calcination time is 1-3 h.

Preferably, the calcination temperature is 700-800°C, and the calcination time is 1-3h.

Preferably, the heating rate is 1-5°C/min. During this process, the organic ligands in the Ce-MOF are carbonized, and the metal ions form CeO ₂ .

Further preferably, the heating rate is 1-3°C/min.

In a second aspect, the present invention provides the application of the rare earth MOF-derived composite material as a wave absorbing material.

The present invention will be described in further detail below in conjunction with specific examples. It should be pointed out that the specific examples are to explain rather than limit the present invention.

Example 1

(1) Dissolve 0.37g of cerium chloride heptahydrate and 0.21g of 1,3,5-benzenetricarboxylic acid in 40mL of aqueous ethanol (20ml of ethanol + 20ml of water), let stand at room temperature for 20 minutes, and centrifuge at a low speed The white precipitate was collected, washed four times with water and ethanol, and dried overnight at 60 °C to obtain the Ce-MOF precursor.

(2) The Ce-MOF precursor obtained in step (1) was calcined at 700° C. for 2 h at a heating rate of 2° C./min under a nitrogen atmosphere to obtain a CeO ₂ @C composite material.

Fig. 1 is the XRD pattern of the CeO ₂ @C composite material composite airgel prepared in Example 1, and it is confirmed that the prepared one is CeO ₂ @C.

Figure 2 is an SEM image of the Ce-MOF precursor prepared in Example 1, which has a "wheat bundle" structure and a smooth surface;

Fig. 3 is an SEM image of the CeO ₂ @C composite material obtained by final calcination in Example 1, the composite material maintains the structure of the original MOF precursor, but the surface becomes rougher.

Experimental example

The CeO ₂ @C and paraffin wax of the embodiment were mixed respectively to obtain the CeO ₂ @C composite material composite wave-absorbing material, and the electromagnetic parameter test was carried out using the Agilent Technologies E8363A electromagnetic wave vector network analyzer, and the wave-absorbing performance of the material was calculated according to the electromagnetic parameters, and the following was obtained: The results are shown in Figure 5.

It can be seen from Figure 4 that the CeO ₂ @C composite composite airgel composite absorbing material has strong dielectric loss. CeO ₂ @C composite material composite absorbing material has no magnetic loss, which conforms to its non-magnetic material characteristics.

It can be seen from Figure 5 that the CeO ₂ @C composite absorbing material has excellent electromagnetic wave absorbing properties. The reflection loss of the electromagnetic wave at the frequency of 13.3GHz reaches -50.1dB, and the matching thickness is 2.3mm.

Example 2

The difference from Example 1 is that the calcination temperature of Ce-MOF is increased to 800°C. The Agilent Technologies E8363A electromagnetic wave vector network analyzer is used to test the electromagnetic parameters, and the absorbing performance of the material is calculated according to the electromagnetic parameters.

Figure 6 is the performance diagram of the sample prepared in Example 2. It can be seen that in the range of 2-18GHz, the lowest reflection loss is -58.7dB, and the absorbing performance is slightly better than that of Example 1, but the bandwidth becomes lower, which is 4.8GHz .

Example 3

(1) Dissolve 0.37g of cerium chloride heptahydrate and 0.21g of 1,3,5-benzenetricarboxylic acid in 40mL of aqueous ethanol (10ml of ethanol + 30ml of water), let it stand at room temperature for 20 minutes, and centrifuge at a low speed The white precipitate was collected, washed four times with water and ethanol, and dried overnight at 60 °C to obtain the Ce-MOF precursor.

(2) The Ce-MOF precursor obtained in step (1) was calcined at 700° C. for 2 h at a heating rate of 2° C./min under a nitrogen atmosphere to obtain a CeO ₂ @C composite material.

Example 4

(1) Dissolve 0.74g cerium chloride heptahydrate and 0.46g 1,3,5-benzenetricarboxylic acid in 30mL ethanol aqueous solution (20ml ethanol + 20ml water), let stand at room temperature for 20 minutes, and centrifuge at low speed The white precipitate was collected, washed four times with water and ethanol, and dried overnight at 60 °C to obtain the Ce-MOF precursor.

(2) The Ce-MOF precursor obtained in step (1) was calcined at 700° C. for 2 h at a heating rate of 2° C./min under a nitrogen atmosphere to obtain a CeO ₂ @C composite material.

Example 5

(1) Dissolve 0.37g of cerium chloride heptahydrate and 0.21g of 1,3,5-benzenetricarboxylic acid in 50mL of aqueous ethanol (20ml of ethanol + 20ml of water), stir at room temperature for 20 minutes, and collect by low-speed centrifugation The white precipitate was washed four times with water and ethanol, respectively, and dried overnight at 60 °C to obtain the Ce-MOF precursor.

(2) The Ce-MOF precursor obtained in step (1) was calcined at 700° C. for 2 h at a heating rate of 2° C./min under a nitrogen atmosphere to obtain a CeO ₂ @C composite material.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A rare earth MOF derived composite characterized by: the preparation method comprises the following steps: adding a cerium salt and 1,3, 5-benzene tricarboxylic acid into an ethanol water solution, wherein the addition ratio of the cerium salt to the 1,3, 5-benzene tricarboxylic acid to the ethanol water solution is 0.2-1: g: mL, uniformly mixing, and standing to obtain a Ce-MOF precursor;

in the ethanol water solution, the volume fraction of ethanol is 25-50%;

and calcining the Ce-MOF precursor at 600-800 ℃ for 0.5-4h to obtain the target product.

2. The rare earth MOF-derived composite material according to claim 1, wherein: the cerium salt is cerium chloride.

3. The rare earth MOF-derived composite material according to claim 1, wherein: in the ethanol water solution, the volume fraction of ethanol is 25-50%.

4. The rare earth MOF derived composite of claim 1, wherein: the addition ratio of the cerium salt, the 1,3, 5-benzene tricarboxylic acid and the ethanol water solution is 0.2-0.5: g: and (mL).

5. The rare earth MOF derived composite of claim 1, wherein: the standing time is 20min.

6. The rare earth MOF-derived composite material according to claim 1, wherein: the calcining temperature is 600-800 ℃, and the calcining time is 1-3h.

7. The rare earth MOF derived composite material of claim 6, wherein: the calcining temperature is 700-800 ℃, and the calcining time is 1-3h.

8. The rare earth MOF derived composite material according to claim 7, wherein: the heating rate is 1-5 ℃/min.

9. The rare earth MOF derived composite material of claim 8, wherein: the heating rate is 1-3 deg.C/min.

10. Use of a rare earth MOF derived composite material according to any one of claims 1 to 9 as a wave absorbing material.

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