Electromagnetic wave absorbing material based on rare earth-based metal organic framework carbonized derivative and preparation method of electromagnetic wave absorbing material

Abstract

The invention discloses an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative and a preparation method of the electromagnetic wave absorbing material, and belongs to the technical field of electromagnetic wave absorbing materials. The preparation method comprises the following steps: performing high-temperature calcination and conductive polymer coating on a rare earth-based metal organic framework RE-MOF obtained by hydrothermal synthesis to obtain a RE-MOF carbonized derivative-conductive polymer composite material; the material has excellent chemical stability, good electromagnetic wave absorption performance and wider effective absorption frequency band, can be applied to electromagnetic protection of various equipment or vehicles, ships, machinery and the like under severe conditions, such as wave absorption and corrosion prevention integration of large ships and offshore wind power towers, and has wide application market and economic prospects.

Description

Technical Field

[0001] The present invention specifically relates to an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative and a preparation method thereof, belonging to the technical field of electromagnetic wave absorbing materials. Background Art

[0002] In modern society, with the widespread use of wireless communication technology and electronic devices, electromagnetic radiation and interference pose an increasing threat to military applications and human health. In order to meet this challenge, it is necessary to explore new materials with high-performance electromagnetic wave absorption functions to improve human living conditions and ensure safe and smooth production. However, the existing electromagnetic wave absorption materials are mainly metal / metal oxides, graphene carbonaceous materials, carbon nanofibers and carbon aerogels, etc., and their preparation and mass production costs are relatively high, and large-scale applications are difficult. In addition, the preparation conditions of existing magnetic materials are difficult to quantify and cannot meet the requirements of lightweight. Therefore, the development of new electromagnetic wave absorption materials still has a broad market demand.

[0003] Metal-organic frameworks (MOFs) are a type of crystalline polymer with rich microporous structures synthesized by chemical coordination of certain organic ligands and metal ions in a specific solvent. Compared with MOFs of other metal types, rare earth-based metal-organic frameworks (RE-MOFs) have special properties due to the unique 4f electron layer on their central atoms. With their porosity and the inherent anisotropy of the central rare earth metal (RE) ions, the carbon-based composite materials derived from them have rich electromagnetic loss mechanisms and have attracted widespread attention from researchers. Chinese patent CN116944494A provides a method for preparing a MOF-derived multi-rare earth-based composite absorber, the composition formula of which is Re y M 1-y / carbon framework, wherein 0.5<y<0.8; wherein Re includes any two or at least three of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb; M includes any one of Co, Ni, Cr or Fe; the absorbing material utilizes the synergistic effect of multi-element rare earth metal elements and metal elements to achieve strong electromagnetic wave reflection loss in the high-frequency Ku band and low thickness; Chinese patent CN116589691A discloses a rare A preparation method and application of soil-based spherical MOF. The preparation method of the material comprises: mixing a rare earth salt, a second metal salt, an intermediate and a solvent, and then filtering, drying and carbonizing the mixture in sequence. The prepared rare earth-based spherical MOF has good electromagnetic wave absorption performance. Chinese patent CN112292016A discloses a Nd2O2S / C rare earth composite absorbing material. When the matching thickness is 2.56 mm, the RL value of the material at a frequency of 12.72 GHz can reach -52.3 dB.

[0004] It can be seen that the existing RE-MOF-derived carbon-based composite materials (RE-MOF carbonized derivatives) have good potential as electromagnetic wave absorbing materials and can absorb electromagnetic waves of specific frequencies well. However, the existing RE-MOF carbonized derivatives require the synergy of multiple metals to exert good electromagnetic wave absorption performance, and the multi-metal doping process undoubtedly also leads to complex preparation steps and high implementation costs of absorbing materials, which limits its application scope. The single metal RE-MOF carbonized derivatives also face the problem of generally narrow effective absorption band (effective absorption frequency range) and weak effective absorption of electromagnetic waves of different bands. These factors limit the application of RE-MOF carbonized derivatives. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides an electromagnetic wave absorption material based on a carbonized derivative of a rare earth metal organic framework and a preparation method thereof; the present invention coats a conductive polymer on the surface of a carbonized derivative of a rare earth metal organic framework (RE-MOF) to obtain a RE-MOF carbonized derivative@conductive polymer core-shell structure composite material; the coating modification of the conductive polymer enables the composite material to have excellent chemical stability, good electromagnetic wave absorption performance and a wider effective absorption band, and can be applied to electromagnetic protection of various equipment or vehicles, ships and machinery under harsh conditions, such as large ships, integrated wave absorption and anti-corrosion of offshore wind power towers, etc., and has a broad application market and economic prospects.

[0006] The technical solution of the present invention is as follows:

[0007] One of the purposes of the present invention is to provide an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface.

[0008] Furthermore, the conductive polymer is one or more of polyaniline, polythiophene and polypyrrole.

[0009] Furthermore, the rare earth-based metal organic framework carbonized derivative is prepared by calcining the rare earth-based metal organic framework at 400-1000°C.

[0010] Furthermore, the rare earth-based metal organic framework is one or more of a praseodymium-based metal organic framework, a neodymium-based metal organic framework, a gadolinium-based metal organic framework, a terbium-based metal organic framework, a dysprosium-based metal organic framework, and an erbium-based metal organic framework.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned electromagnetic wave absorbing material, comprising the following steps:

[0012] S1. Preparing a rare earth metal organic framework: dispersing and dissolving a nitric acid compound containing a rare earth element, thiophene-2,5-dicarboxylic acid and ammonium acetate in a solvent, and reacting the resulting solution at 60 to 200° C. for 48 to 108 hours; after the reaction, washing and drying the product to obtain the rare earth metal organic framework;

[0013] S2, preparing a rare earth-based metal organic framework carbonized derivative: calcining the rare earth-based metal organic framework at 400-1000° C. for 1-4 hours to obtain the rare earth-based metal organic framework carbonized derivative;

[0014] S3. Surface modification of rare earth metal organic framework carbonized derivatives: Uniformly disperse the rare earth metal organic framework carbonized derivatives, sodium dodecylbenzene sulfonate and conductive polymer monomers in water, add 0.1-1 mol / L ferric chloride solution thereto and stir evenly, collect, wash and dry the product to obtain the electromagnetic wave absorbing material.

[0015] Furthermore, in step S1, the nitric acid compound containing rare earth elements is one or more of Pr(NO3)3, Nd(NO3)3, Gd(NO3)3, Tb(NO3)3, Dy(NO3)3, and Er(NO3)3.

[0016] Furthermore, in step S1, the molar ratio of the added amounts of the nitric acid compound containing rare earth elements, thiophene-2,5-dicarboxylic acid and ammonium acetate is 0.1:0.2:1; and the solvent is any one or both of deionized water and alcohol.

[0017] Furthermore, in step S3, the monomers of the conductive polymer are one or more of pyrrole, 3,4-ethylenedioxythiophene, and aniline.

[0018] Furthermore, in step S3, the mass ratio of the rare earth metal organic framework carbonized derivative to the conductive polymer monomer is 1:0.2 to 1:10.

[0019] Different from the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention coats a conductive polymer on the surface of a carbonized derivative of a rare earth metal organic framework (RE-MOF) to obtain a composite material of a carbonized derivative of RE-MOF @ conductive polymer core-shell structure; the 3D porous framework constructed by the carbonized derivative of RE-MOF and the conductive polymer causes the incident electromagnetic wave to be reflected and scattered multiple times in the composite material, thereby extending the propagation path and effectively attenuating the intensity of the electromagnetic wave. At the same time, the carbonization of RE-MOF and the coating of the conductive polymer also add additional electron transmission and migration channels to the composite material, thereby promoting an increase in the conductive loss of the electromagnetic wave; the above characteristics enable the composite material of the present invention to have good electromagnetic wave attenuation capability.

[0021] 2. Different from the prior art, the composite material provided by the present invention also realizes the efficient integration of the electromagnetic wave attenuation capabilities of RE-MOF, porous carbon and conductive polymer; the introduction of S, C and N elements in the composite material brings different electronegativity to the composite material, resulting in the separation of positive and negative charge centers, and then producing dipole polarization. At the same time, there is an accumulation and uneven distribution of spatial charges on the heterogeneous interface of the composite material, which also causes multiple interface polarizations. These polarizations greatly improve the dielectric loss capacity of the material; the composite material of the present invention benefits from the effective synergy between RE-MOF, porous carbon and conductive polymer, and its impedance matching is significantly improved, the electromagnetic wave absorption bandwidth of the composite material is significantly broadened, and the attenuation of electromagnetic waves can be achieved by means of the above-mentioned conductivity loss, interface polarization, dipole polarization and multiple reflections and other mechanisms.

[0022] 3. The present invention obtains a RE-MOF carbonized derivative @ conductive polymer composite material by high-temperature calcination and conductive polymer coating of the rare earth metal organic framework RE-MOF obtained by hydrothermal synthesis. The preparation process is simple, green and safe, and the cost is low. The conductive polymer can be any one of polyaniline, polypyrrole, and polythiophene. By adjusting the mass ratio of the conductive polymer monomer to the RE-MOF carbonized derivative, the dielectric loss of the material and the interface polarization between the RE-MOF carbonized derivative and polypyrrole can be changed to achieve regulation of the electromagnetic absorption performance of the composite material. In addition, by changing the type of the rare earth metal organic framework RE-MOF, the preparation method can also prepare a variety of composite materials based on different rare earth-based metal organic framework carbonized derivatives, thereby achieving improvement in the electromagnetic wave absorption performance of a variety of rare earth-based metal organic framework carbonized derivatives, and has good applicability and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1SEM images of O2Pr2S / C@PPy of Examples 1 to 4, where (a) is O2Pr2S / C@PPy-1, (b) is O2Pr2S / C@PPy-2, (c) is O2Pr2S / C@PPy-3, (d) is O2Pr2S / C@PPy-4 and (e and f) are pure PPy.

[0024] Figure 2 This is the infrared spectrum of O2Pr2S / C@PPy of Examples 1 to 4.

[0025] Figure 3 X-ray diffraction spectra of O2Pr2S / C@PPy of Examples 1 to 4.

[0026] Figure 4 ε' values ​​of O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3, O2Pr2S / C@PPy-4 and pure PPy of Examples 1 to 4.

[0027] Figure 5 ε” value of O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3, O2Pr2S / C@PPy-4 and pure PPy in Examples 1 to 4.

[0028] Figure 6 It is the decay constant (α) of O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3, O2Pr2S / C@PPy-4 and pure PPy of Examples 1 to 4.

[0029] Figure 7 The maximum absorption bandwidth and maximum reflection loss of the electromagnetic wave absorption materials of O2Pr2S / C@PPy-2 of Example 2 and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments. The given embodiments are only for illustrating the present invention, rather than for limiting the scope of the present invention.

[0031] Unless otherwise specified, the materials, reagents, etc. used in the following examples can be obtained from commercial sources; the methods in the following examples are conventional methods unless otherwise specified.

[0032] The invention provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative. The electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer wrapped on the surface.

[0033] In some preferred embodiments, the conductive polymer may be one or more of polyaniline, polythiophene, and polypyrrole.

[0034] In some preferred embodiments, the method for preparing the rare earth-based metal organic framework carbonized derivative comprises the following steps: calcining the rare earth-based metal organic framework at 400-1000° C. to obtain the rare earth-based metal organic framework carbonized derivative.

[0035] In some preferred embodiments, the rare earth-based metal organic framework may be one or more of a praseodymium-based metal organic framework, a neodymium-based metal organic framework, a gadolinium-based metal organic framework, a terbium-based metal organic framework, a dysprosium-based metal organic framework, and an erbium-based metal organic framework.

[0036] The present invention also provides a method for preparing the above electromagnetic wave absorbing material, comprising the following steps:

[0037] S1. Preparing a rare earth metal organic framework: dispersing and dissolving a nitric acid compound of a rare earth element, thiophene-2,5-dicarboxylic acid and ammonium acetate in a solvent, and reacting the solution at 60 to 200° C. for 48 to 108 hours; after the reaction is completed, washing and drying the product to obtain the rare earth metal organic framework;

[0038] S2, preparing a rare earth-based metal organic framework carbonized derivative: calcining the rare earth-based metal organic framework at 400-1000° C. for 1-4 hours to obtain the rare earth-based metal organic framework carbonized derivative;

[0039] S3. Surface modification of rare earth metal organic framework carbonized derivatives: disperse the rare earth metal organic framework carbonized derivatives, sodium dodecylbenzene sulfonate and conductive polymer monomers uniformly in water, add 0.1-1 mol / L ferric chloride solution thereto and stir evenly, collect, wash and dry the product to obtain the electromagnetic wave absorbing material.

[0040] In some preferred embodiments, in step S1, the nitric acid compound of the rare earth element may be one or more of Pr(NO3)3, Nd(NO3)3, Gd(NO3)3, Tb(NO3)3, Dy(NO3)3 and Er(NO3)3.

[0041] In some preferred embodiments, in step S1, the molar ratio of the added amounts of the nitric acid compound of the rare earth element, thiophene-2,5-dicarboxylic acid and ammonium acetate is 0.1:0.2:1; and the solvent is any one or both of deionized water and alcohol.

[0042] In some preferred embodiments, in step S3, the conductive polymer monomer may be one or more of pyrrole, 3,4-ethylenedioxythiophene, and aniline.

[0043] In some preferred embodiments, in step S3, the mass ratio of the rare earth metal organic framework carbonized derivative to the conductive polymer monomer is 1:0.5 to 1:10.

[0044] The electromagnetic wave absorbing material based on the carbonized derivative of the rare earth metal organic framework of the present invention is further described below in conjunction with specific embodiments:

[0045] Example 1

[0046] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0047] In this embodiment, the conductive polymer is polypyrrole; the rare earth metal organic framework is praseodymium metal organic framework Pr-MOFs;

[0048] The rare earth-based metal organic framework carbonized derivative is prepared by calcining Pr-MOFs at 800° C. for 2 h;

[0049] The preparation method of the electromagnetic wave absorbing material comprises the following steps:

[0050] S1. Preparation of rare earth metal organic frameworks: Slowly add rare earth element nitrate compound Pr(NO3)3·6H2O (0.1mmol, 0.044g), thiophene-2,5-dicarboxylic acid (H2TDA) (0.2mmol, 0.034g), and ammonium acetate (CH3COONH4) (1mmol, 0.077g) to a mixed solution of 2mL deionized water and 2mL ethanol, and ultrasonically vibrate for 20min to completely dissolve the drugs; place the mixed solution in a 25mL polytetrafluoroethylene-lined high-pressure reactor, heat at 100°C, and react for 72h; then cool naturally to room temperature, take out the reaction product, and repeatedly (at least three times) centrifuge and wash with deionized water and ethanol, the centrifuge speed is set to 8000r / min, and the centrifugation time is set to 5min; place the washed product in a vacuum oven at 60°C for drying, and the drying time is 24h to obtain the rare earth metal organic framework Pr-MOFs;

[0051] S2. Preparation of rare earth metal organic framework carbonized derivatives: placing the Pr-MOFs material prepared in step 1 in a boat-shaped corundum crucible, then transferring the corundum crucible to a horizontal tube furnace, introducing Ar atmosphere into the tube furnace, heating the Pr-MOFs material to 800° C. at a heating rate of 2° C. / min, and calcining at 800° C. for 2 h to obtain a black solid powder, which is the rare earth metal organic framework carbonized derivative O2Pr2S / C;

[0052] S3. Surface modification of rare earth metal organic framework carbonized derivatives: 12 mg of sodium dodecylbenzene sulfonate (SDBS) and 25 mg of pyrrole (Py) monomer were dispersed in 40 mL of deionized water under ultrasonic oscillation, and then 50 mg of the black O2Pr2S / C solid powder obtained in step 2 was added to the above mixture, and mechanically stirred for 60 min until it was evenly dispersed. Next, 5 mL of ferric chloride hexahydrate (FeCl3·6H2O) aqueous solution (0.3 mol / L) was directly added, and then polymerized for another 60 min, and then repeatedly (at least three times) centrifuged and washed with deionized water and ethanol. The centrifuge speed was set to 8000 r / min, and the centrifugation time was set to 5 min. The washed product was placed in a freeze dryer for freeze drying at -50 ° C for 48 h to obtain a surface morphology as shown Figure 1 The electromagnetic wave absorbing material O2Pr2S / C@PPy is shown.

[0053] Example 2

[0054] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0055] The conductive polymer, rare earth metal organic framework and carbonized derivatives thereof in the electromagnetic wave absorbing material described in this embodiment are the same as those in Embodiment 1 and will not be described in detail here.

[0056] The difference between the preparation method of the magnetic wave absorbing material and that of Example 1 is that:

[0057] In step S3, the amount of the pyrrole monomer added is 100 mg, and the amount of the rare earth metal organic framework carbonized derivative O2Pr2S / C added is 50 mg;

[0058] The preparation steps of the rare earth metal organic framework and the carbonized derivative of the rare earth metal organic framework are the same as those in Example 1 and will not be repeated here.

[0059] Example 3

[0060] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0061] The conductive polymer, rare earth metal organic framework and carbonized derivatives thereof in the electromagnetic wave absorbing material described in this embodiment are the same as those in Embodiment 1 and will not be described in detail here.

[0062] The difference between the preparation method of the electromagnetic wave absorbing material and that of Example 1 is that:

[0063] In step S3, the amount of the pyrrole monomer added is 100 mg, and the amount of the rare earth metal organic framework carbonized derivative O2Pr2S / C added is 50 mg;

[0064] The preparation steps of the rare earth metal organic framework and the carbonized derivative of the rare earth metal organic framework are the same as those in Example 1 and will not be repeated here.

[0065] Example 4

[0066] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0067] The conductive polymer, rare earth metal organic framework and carbonized derivatives thereof in the electromagnetic wave absorbing material described in this embodiment are the same as those in Embodiment 1 and will not be described in detail here.

[0068] The difference between the preparation method of the electromagnetic wave absorbing material and that of Example 1 is that:

[0069] In step S3, the amount of the pyrrole monomer added is 200 mg, and the amount of the rare earth metal organic framework carbonized derivative O2Pr2S / C added is 50 mg;

[0070] The preparation steps of the rare earth metal organic framework and the carbonized derivative of the rare earth metal organic framework are the same as those in Example 1 and will not be repeated here.

[0071] Example 5

[0072] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0073] In this embodiment, the conductive polymer is polypyrrole; the rare earth metal organic framework is praseodymium metal organic framework Pr-MOFs;

[0074] The rare earth-based metal organic framework carbonized derivative is prepared by calcining Pr-MOFs at 400° C. for 4 hours;

[0075] The method for preparing the electromagnetic wave absorbing material based on the carbonized derivative of the rare earth-based metal organic framework comprises the following steps:

[0076] S1. Preparation of rare earth metal organic frameworks: Slowly add rare earth element nitrate compound Pr(NO3)3·6H2O (0.1mmol, 0.044g), thiophene-2,5-dicarboxylic acid H2TDA (0.2mmol, 0.034g), and ammonium acetate CH3COONH4 (1mmol, 0.077g) to a mixed solution of 2mL deionized water and 2mL ethanol, and ultrasonically vibrate for 20min to completely dissolve the drugs; place the mixed solution in a 25mL polytetrafluoroethylene-lined high-pressure reactor, heat at 60°C, and react for 108h; then cool naturally to room temperature, take out the reaction product, and repeatedly (at least three times) centrifuge and wash with deionized water and ethanol, the centrifuge speed is set to 8000r / min, and the centrifugation time is set to 5min; place the washed product in a vacuum oven at 60°C for drying, and the drying time is 24h to obtain the rare earth metal organic framework Pr-MOFs;

[0077] S2. Preparation of rare earth metal organic framework carbonized derivatives: placing the Pr-MOFs material prepared in step 1 in a boat-shaped corundum crucible, then transferring the corundum crucible to a horizontal tube furnace, introducing an Ar atmosphere into the tube furnace, heating the Pr-MOFs material to 400° C. at a heating rate of 2° C. / min, and calcining at 400° C. for 4 h to obtain a black solid powder, which is the rare earth metal organic framework carbonized derivative O2Pr2S / C;

[0078] S3. Surface modification of rare earth metal organic framework carbonized derivatives: 12 mg of sodium dodecylbenzene sulfonate (SDBS) and 25 mg of pyrrole (Py) monomer were dispersed in 40 mL of deionized water under ultrasonic oscillation, and then 50 mg of the black O2Pr2S / C solid powder obtained in step 2 was added to the above mixture, and mechanically stirred for 60 min until it was evenly dispersed. Next, 5 mL of ferric chloride hexahydrate (FeCl3·6H2O) aqueous solution (0.3 mol / L) was directly added, and then polymerized for another 60 min, and then repeatedly (at least three times) centrifuged and washed with deionized water and ethanol. The centrifuge speed was set to 8000 r / min, and the centrifugation time was set to 5 min. The washed product was placed in a freeze dryer for freeze drying at -50 ° C for 48 h to obtain a surface morphology as shown Figure 1 The electromagnetic wave absorbing material O2Pr2S / C@PPy is shown.

[0079] Example 6

[0080] This embodiment provides an electromagnetic wave absorbing material based on a rare earth-based metal organic framework carbonized derivative, wherein the electromagnetic wave absorbing material is composed of a rare earth-based metal organic framework carbonized derivative with a conductive polymer coated on the surface;

[0081] In this embodiment, the conductive polymer is polypyrrole; the rare earth metal organic framework is praseodymium metal organic framework Pr-MOFs;

[0082] The rare earth-based metal organic framework carbonized derivative is prepared by calcining Pr-MOFs at 1000° C. for 4 hours;

[0083] The method for preparing the electromagnetic wave absorbing material based on the carbonized derivative of the rare earth-based metal organic framework comprises the following steps:

[0084] S1. Preparation of rare earth metal organic frameworks: Slowly add rare earth element nitrate compound Pr(NO3)3·6H2O (0.1mmol, 0.044g), thiophene-2,5-dicarboxylic acid H2TDA (0.2mmol, 0.034g), and ammonium acetate CH3COONH4 (1mmol, 0.077g) to a mixed solution of 2mL deionized water and 2mL ethanol, and ultrasonically vibrate for 20min to completely dissolve the drugs; place the mixed solution in a 25mL polytetrafluoroethylene-lined high-pressure reactor, heat at 200°C, and react for 108h; then cool naturally to room temperature, take out the reaction product, and repeatedly (at least three times) centrifuge and wash with deionized water and ethanol, the centrifuge speed is set to 8000r / min, and the centrifugation time is set to 5min; place the washed product in a vacuum oven at 60°C for drying, and the drying time is 24h to obtain the rare earth metal organic framework Pr-MOFs;

[0085] S2. Preparation of rare earth metal organic framework carbonized derivatives: placing the Pr-MOFs material prepared in step 1 in a boat-shaped corundum crucible, then transferring the corundum crucible to a horizontal tube furnace, introducing Ar atmosphere into the tube furnace, heating the Pr-MOFs material to 1000° C. at a heating rate of 2° C. / min, and calcining at 1000° C. for 1 h to obtain a black solid powder, which is the rare earth metal organic framework carbonized derivative O2Pr2S / C;

[0086] S3. Surface modification of rare earth metal organic framework carbonized derivatives: 12 mg of sodium dodecylbenzene sulfonate (SDBS) and 200 mg of pyrrole (Py) monomer were dispersed in 40 mL of deionized water under ultrasonic oscillation, and then 40 mg of the black O2Pr2S / C solid powder obtained in step 2 was added to the above mixture, and mechanically stirred for 60 min until uniformly dispersed. Next, 5 mL of ferric chloride hexahydrate (FeCl3·6H2O) aqueous solution (0.3 mol / L) was directly added, and polymerized for another 60 min, and then centrifuged and washed repeatedly (at least three times) with deionized water and ethanol. The centrifuge speed was set to 8000 r / min, and the centrifugation time was set to 5 min. The washed product was placed in a freeze dryer for freeze drying at -50 ° C for 48 h to obtain a surface morphology as shown Figure 1 The electromagnetic wave absorbing material O2Pr2S / C@PPy is shown.

[0087] Comparative Example 1

[0088] This comparative example provides an electromagnetic wave absorbing material, which is different from Example 1 in that:

[0089] The electromagnetic wave absorbing material is a praseodymium-based metal organic framework Pr-MOFs, which has not been calcined, carbonized or coated with a conductive polymer.

[0090] The preparation method of the electromagnetic wave absorbing material comprises the following steps:

[0091] The nitrate compounds of rare earth elements, praseodymium nitrate hexahydrate (Pr(NO3)3·6H2O) (0.1mmol, 0.044g), thiophene-2,5-dicarboxylic acid (H2TDA) (0.2mmol, 0.034g), and ammonium acetate (CH3COONH4) (1mmol, 0.077g) were slowly added to a mixed solution of 2mL deionized water and 2mL ethanol, and ultrasonically vibrated for 20min to completely dissolve the drugs; the mixed solution was placed in a 25mL polytetrafluoroethylene-lined high-pressure reactor, heated at 100°C, and reacted for 72h; then naturally cooled to room temperature, the reaction product was taken out, and centrifuged and washed repeatedly (at least three times) with deionized water and ethanol, the centrifuge speed was set to 8000r / min, and the centrifugation time was set to 5min; the washed product was placed in a vacuum oven at 60°C for drying, and the drying time was 24h to obtain the rare earth-based metal organic framework Pr-MOFs.

[0092] Comparative Example 2

[0093] This comparative example provides an electromagnetic wave absorbing material, which is different from Example 1 in that:

[0094] The electromagnetic wave absorbing material is a praseodymium-based metal organic framework carbonized derivative O2Pr2S / C, which is not coated with a conductive polymer.

[0095] The preparation method of the electromagnetic wave absorbing material comprises the following steps:

[0096] S1. Preparation of rare earth metal organic frameworks: Slowly add rare earth element nitrate compound hexahydrate praseodymium nitrate (Pr(NO3)3·6H2O) (0.1mmol, 0.044g), thiophene-2,5-dicarboxylic acid (H2TDA) (0.2mmol, 0.034g), and ammonium acetate (CH3COONH4) (1mmol, 0.077g) to a mixed solution of 2mL deionized water and 2mL ethanol, and ultrasonically vibrate for 20min to completely dissolve the drugs; place the mixed solution in a 25mL polytetrafluoroethylene-lined high-pressure reactor, heat at 100°C, and react for 72h; then cool naturally to room temperature, take out the reaction product, and repeatedly (at least three times) centrifuge and wash with deionized water and ethanol, the centrifuge speed is set to 8000r / min, and the centrifugation time is set to 5min; place the washed product in a vacuum oven at 60°C for drying, and the drying time is 24h to obtain the rare earth metal organic framework Pr-MOFs;

[0097] S2. Preparation of rare earth-based metal organic framework carbonized derivatives: Place the Pr-MOFs material prepared in step 1 in a boat-shaped corundum crucible, then transfer the corundum crucible to a horizontal tube furnace, introduce Ar atmosphere into the tube furnace, heat the Pr-MOFs material to 800°C at a heating rate of 2°C / min, and calcine at 800°C for 2h to obtain a black solid powder, which is the rare earth-based metal organic framework carbonized derivative O2Pr2S / C.

[0098] Performance Testing

[0099] In order to illustrate the improvement effect of conductive polymers on carbonized derivatives of rare earth-based metal organic frameworks, the present invention selects the electromagnetic wave absorption materials based on carbonized derivatives of rare earth-based metal organic frameworks described in the above Examples 1 to 4 for the following structural characterization and electromagnetic wave absorption performance test, wherein the O2Pr2S / C@PPy samples of Examples 1 to 4 are named O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3, and O2Pr2S / C@PPy-4, respectively.

[0100] (1) Structural characterization

[0101] The infrared spectra of O2Pr2S / C@PPy and pure PPy in Examples 1 to 4 are as follows: Figure 2As shown, the wavelength at 1550 cm -1 、1295cm -1 and 1038cm -1 The absorption peaks at 1162 and 922 cm-1 correspond to the CC stretching vibration, CN stretching vibration and in-plane deformation vibration of the pyrrole ring in the composite material, while the absorption peaks at 1162 and 922 cm-1 correspond to the CC stretching vibration, CN stretching vibration and in-plane deformation vibration of CH in the composite material. -1 The absorption peak at indicates the doping state of PPy. The above results show that on the composite material prepared by the preparation method of the present invention, the conductive polymer PPy has been successfully coated on the rare earth metal organic framework derived composite material O2Pr2S / C, and Figure 1 The SEM results are consistent with those of

[0102] The X-ray diffraction patterns of O2Pr2S / C@PPy and pure PPy in Examples 1 to 4 are as follows: Figure 3 As shown, the XRD patterns of O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3 and O2Pr2S / C@PPy-4 composite materials are basically consistent, which further proves the successful preparation of the O2Pr2S / C@PPy composite material of the present invention.

[0103] (2) Electromagnetic wave absorption performance test

[0104] ε' and ε", attenuation constant (α) of O2Pr2S / C@PPy-1, O2Pr2S / C@PPy-2, O2Pr2S / C@PPy-3, O2Pr2S / C@PPy-4 and PPy in the frequency range of 2 to 18 GHz are shown in Figure 4 , Figure 5 and Figure 6As shown. The results show that compared with the original material, the electromagnetic wave attenuation ability of the new porous O2Pr2S / C composite material prepared based on the carbonized derivative of Pr-MOFs and modified by coating PPy on its surface through chemical polymerization has been greatly enhanced; on the one hand, the 3D porous framework constructed by the carbonized derivative of Pr-MOFs and the conductive polymer makes the absorbed electromagnetic waves reflect and scatter multiple times in the composite material, which prolongs the propagation path and effectively attenuates the intensity of the electromagnetic waves. At the same time, the carbonization of Pr-MOFs and the coating of the conductive polymer also add additional electron transmission and migration channels to the composite material, which promotes the increase of electromagnetic wave conductive loss. On the other hand, the O2Pr2S, graphite C, and PPy that constitute the composite material introduce multiple elements such as S, C, and N into the composite material, which bring different electronegativity to the composite material, resulting in the separation of positive and negative charge centers and dipole polarization. There is also accumulation and uneven distribution of spatial charges on the heterogeneous interface of the composite material, which causes multiple interface polarizations. These polarizations greatly improve the dielectric loss capacity of the material. Benefiting from the synergistic effect of the above-mentioned O2Pr2S semiconductor, porous carbon and PPy, the composite material of the present invention has significantly improved impedance matching, significantly broadened the electromagnetic wave absorption bandwidth, and can achieve electromagnetic wave attenuation by means of various mechanisms such as conductivity loss, interface polarization, dipole polarization and multiple reflections.

[0105] The present invention prepares O2Pr2S / C@PPy with a paraffin wax mixing ratio of 20wt% and presses it into a ring with an inner diameter of 3.04mm and an outer diameter of 7.00mm. The electromagnetic parameters are tested by a vector network analyzer, and the reflection loss (RL) performance and other parameters are obtained by calculation. The results are as follows Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown. In the electromagnetic wave frequency range of 2-18GHz, the ε' and ε" values ​​of the composite material increase with the increase of the mass ratio of pyrrole monomer to rare earth metal organic framework derivative material O2Pr2S / C. Considering its performance parameters comprehensively, the preferred O2Pr2S / C@PPy-2 has the best electromagnetic absorption performance. In the performance test, the O2Pr2S / C@PPy-2 composite material has an RL of -54.24dB at a thickness of 2.9mm and a frequency of 13.40GHz. min The RL of the Pr-MOFs in comparative example 1 and the O2Pr2S / C composite material in comparative example 2 stands out. min The values ​​are -11.26dB and -16.50dB, and its EAB value reaches 7.36GHz (10.64-18.00GHz) when the matching thickness is 2.8mm. The results show that O2Pr2S / C@PPy composite material may become an attractive electromagnetic wave absorber.

[0106] In summary, the synergistic effect of the composite of praseodymium-based metal organic framework carbonized derivative O2Pr2S / C and conductive polymer can give the composite material excellent electromagnetic wave attenuation ability and outstanding impedance matching, which can effectively improve the electromagnetic wave absorption performance of existing rare earth-based metal organic framework carbonized derivatives.

[0107] In addition, in the preparation method of the electromagnetic wave absorption material described in the above-mentioned embodiment 1, the nitric acid compound of the rare earth element described in step S1 is replaced by one or more of Nd(NO3)3, Gd(NO3)3, Tb(NO3)3, Dy(NO3)3 or Er(NO3)3, and a variety of carbonized derivatives based on neodymium-based metal organic frameworks, gadolinium-based metal organic frameworks, terbium-based metal organic frameworks, dysprosium-based metal organic frameworks or erbium-based metal organic frameworks can be obtained accordingly, and used for the preparation of electromagnetic wave absorption materials. At the same time, the conductive polymer monomer in step S3 can also be 3,4-ethylenedioxythiophene, aniline, etc. to synthesize polythiophene and polyaniline to coat the carbonized derivatives of the rare earth metal organic framework to obtain electromagnetic wave absorption materials coated with different conductive polymers. The preparation method of the electromagnetic wave absorption material provided by the present invention can realize the preparation of a variety of conductive polymer-coated rare earth metal organic framework carbonized derivatives, and has broad application prospects.

[0108] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here, and all those derived from the technical solutions of the present invention are obvious.

Claims

1. An electromagnetic wave absorbing material based on a carbonized derivative of a rare earth-based metal organic framework, characterized in that: The electromagnetic wave absorbing material is composed of a rare earth metal organic framework carbonized derivative coated with a conductive polymer on the surface; the rare earth metal organic framework carbonized derivative is obtained by calcining the rare earth metal organic framework at 400-1000° C.; the conductive polymer is one or more of polyaniline, polythiophene, and polypyrrole.

2. The electromagnetic wave absorbing material based on the carbonized derivative of rare earth metal organic framework according to claim 1, characterized in that: The rare earth-based metal organic framework is one or more of a praseodymium-based metal organic framework, a neodymium-based metal organic framework, a gadolinium-based metal organic framework, a terbium-based metal organic framework, a dysprosium-based metal organic framework, and an erbium-based metal organic framework.

3. A method for preparing an electromagnetic wave absorbing material based on a carbonized derivative of a rare earth metal organic framework as claimed in claim 1 or 2, characterized in that: The steps include: S1. Preparing a rare earth metal organic framework: dispersing and dissolving a nitric acid compound containing a rare earth element, thiophene-2,5-dicarboxylic acid and ammonium acetate in a solvent, and reacting the resulting solution at 60 to 200° C. for 48 to 108 hours; after the reaction, washing and drying the product to obtain the rare earth metal organic framework; S2, preparing a rare earth-based metal organic framework carbonized derivative: calcining the rare earth-based metal organic framework at 400-1000° C. for 1-4 hours to obtain the rare earth-based metal organic framework carbonized derivative; S3. Surface modification of rare earth metal organic framework carbonized derivatives: Uniformly disperse the rare earth metal organic framework carbonized derivatives, sodium dodecylbenzene sulfonate and conductive polymer monomers in water, add 0.1-1 mol / L ferric chloride solution thereto and stir evenly, collect, wash and dry the product to obtain the electromagnetic wave absorbing material.

4. The method for preparing an electromagnetic wave absorbing material based on a carbonized derivative of a rare earth metal organic framework according to claim 3, characterized in that: In step S1, the nitric acid compound containing rare earth elements is one or more of Pr(NO3)3, Nd(NO3)3, Gd(NO3)3, Tb(NO3)3, Dy(NO3)3 or Er(NO3)3.

5. The method for preparing an electromagnetic wave absorbing material based on a carbonized derivative of a rare earth-based metal organic framework according to claim 3, characterized in that: In step S1, the molar ratio of the added amounts of the nitric acid compound containing rare earth elements, thiophene-2,5-dicarboxylic acid and ammonium acetate is 0.1:0.2:1; and the solvent is any one or both of deionized water and ethanol.

6. The method for preparing an electromagnetic wave absorbing material based on a carbonized derivative of a rare earth-based metal organic framework according to claim 3, characterized in that: In step S3, the monomers of the conductive polymer are one or more of pyrrole, 3,4-ethylenedioxythiophene, and aniline.

7. The method for preparing an electromagnetic wave absorbing material based on a carbonized derivative of a rare earth-based metal organic framework according to claim 3, characterized in that: In step S3, the mass ratio of the carbonized derivative of the rare earth metal organic framework to the monomer of the conductive polymer is 1:0.2 to 1:10.

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