CN113861432B - Application of conductive MOF as wave-absorbing material - Google Patents
Application of conductive MOF as wave-absorbing material Download PDFInfo
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- CN113861432B CN113861432B CN202111018698.6A CN202111018698A CN113861432B CN 113861432 B CN113861432 B CN 113861432B CN 202111018698 A CN202111018698 A CN 202111018698A CN 113861432 B CN113861432 B CN 113861432B
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Abstract
The invention provides an application of conductive MOF as a wave-absorbing material, which comprises the following steps: HHTP and Cu (OAc) 2 ·H 2 The O powder was added to deionized water and dissolved by magnetic stirring.Then NMP was added dropwise to the above solution, briefly sonicated, and the mixture was reacted under heating for 12 hours. After the reaction was cooled to room temperature, the black precipitate was filtered, washed with water and acetone, and dried under vacuum overnight. The conductive MOF wave-absorbing material prepared by the invention has excellent performance which can be attributed to the electric conduction loss caused by the proper electric conductivity, the dipole polarization relaxation loss caused by the local defect of the material and the good impedance matching formed by the unique two-dimensional layered porous structure.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to application of conductive MOF as a wave-absorbing material.
Background
On one hand, with the rapid development of wireless communication and electronic technology, the electromagnetic pollution problems such as electromagnetic radiation and electromagnetic interference caused by high-power signal base stations and household WIFI transmitters become one of the primary problems in daily life. Military aircraft, on the other hand, are strongly hampered by full-time omnidirectional radar detection. Therefore, there is a strong demand for high-performance electromagnetic wave absorbers for both civil and military use. In recent years, different dielectric materials are in particular carbon (e.g. CNT, graphene, etc.), carbides (e.g. SiC, MXene, etc.) and most non-magnetic oxides (e.g. ZnO, tiO, etc.) 2 Etc.) are of interest because of their high conductivity, special microstructure and small density and freedom from curie effects when used at high temperatures. However, such materials suffer from complicated processes or lengthy synthetic procedures, which largely limit their applications. Therefore, it is still challenging to develop new wave-absorbing materials with excellent properties. The conductive polymer is a macromolecule with resistivity between a conductor and a semiconductor, and the structure of the conductive polymer contains a single-double bond repetitive structural unit, so that conjugated bonds can be formed easily, and the conductive polymer has conductivity. Conductive polymers have been widely studied as wave-absorbing materials due to their advantages of low density, low cost, corrosion resistance, ease of preparation, and the like. Therefore, it has been a agenda for people to develop a novel carbonaceous material with a simple process, and conductive MOF has attracted a wide scientific interest as a special conductive polymer due to its simple preparation method and ultra-high conductivity.
Disclosure of Invention
The invention aims to solve the problems of complex process, long synthesis period, high cost, difficult storage, narrow effective absorption bandwidth and the like of dielectric loss type wave-absorbing materials in the prior art, and provides application of conductive MOF as a wave-absorbing material. The preparation method is simple in preparation process and low in cost, large-scale mass production can be realized, and the prepared wave-absorbing material has good conductivity, excellent dielectric loss and strong electromagnetic wave absorption.
In order to solve the technical problems, the invention adopts the following technical scheme:
the application of the conductive MOF as a wave-absorbing material is characterized in that the conductive MOF is prepared by the following method:
2,3,6,7,10,11-hexahydroxy-triphenyl (HHTP) and Cu (OAc) 2 ·H 2 Adding O (added in a powder form) into deionized water, dissolving by magnetic stirring, dropwise adding N-methylpyrrolidone (NMP) for 1-60 min by ultrasound, and reacting the obtained mixture at 60-100 ℃ for 1-20 h (preferably 80-95 ℃ for 12 h, particularly preferably 85 ℃); carrying out post-treatment on the obtained reaction liquid to obtain the conductive MOF; the 2,3,6,7,10, 11-hexahydroxytriphenyl (HHTP) and Cu (OAc) 2 ·H 2 The mass ratio of O is 1-10: 1 (preferably 1.23; the volume of the N-methylpyrrolidone is 10 to 100mL/g (preferably 70 mL/g) based on the mass of the 2,3,6,7,10, 11-hexahydroxytriphenyl.
The invention particularly recommends the application of the conductive MOF as a wave-absorbing material in absorbing electromagnetic waves in the frequency range of 2-18 GHz.
Preferably, the volume of the deionized water is 100 to 600mL/g (preferably 462 mL/g) based on the mass of 2,3,6,7,10, 11-hexahydroxy triphenyl.
Preferably, the time of the magnetic stirring is 1 to 60min.
Further, the post-treatment is: and after the reaction is cooled to room temperature, filtering to obtain a black precipitate, washing with water and acetone, and drying in vacuum overnight to obtain the conductive MOF.
Preferably, the number of washing is 1 to 10.
Preferably, the drying temperature is 60 to 80 ℃.
Compared with the prior art, the invention has the following beneficial effects:
1. compared with the existing preparation technology of most MOF-derived wave-absorbing materials, the preparation method provided by the invention has the advantages that the calcination process under inert gas is omitted through one-step reaction synthesis, the synthesis process is simple, the environment is protected, and the synthesis period is short.
2. The conductive MOF wave-absorbing material prepared by the invention has a unique microstructure, and the 2D sheet-shaped porous structure is favorable for realizing the impedance equivalent to air and the electromagnetic wave entering the porous structure to realize multiple reflection and scattering, thereby prolonging the propagation path of the electromagnetic wave and effectively attenuating the energy of the electromagnetic wave.
3. The conductive MOF wave-absorbing material prepared by the invention can form a continuous conductive network, and can generate electron hopping and induced eddy current as a bridge for gathering induced charge transmission, so that incident electromagnetic waves are dissipated in the form of heat energy.
4. The conductive MOF wave-absorbing material prepared by the invention has excellent electromagnetic absorption performance. Minimum value of Reflection Loss (RL) of the conductive MOF absorbing material through dielectric loss derived from conductance loss and polarization loss min ) Reaching-45 dB.
Drawings
FIG. 1 is an XRD pattern of the conductive MOF wave-absorbing material prepared in example 1.
FIG. 2 is a TEM image of the conductive MOF wave-absorbing material prepared in example 1.
FIG. 3 is a BET diagram of the conductive MOF wave-absorbing material prepared in example 1.
FIG. 4 is a Reflection Loss (RL) curve of the conductive MOF absorbing material prepared in example 1.
FIG. 5 is a Reflection Loss (RL) curve of the conductive MOF absorbing material prepared in example 2.
FIG. 6 is a Reflection Loss (RL) curve of the conductive MOF absorbing material prepared in example 3.
Detailed Description
To facilitate an understanding of the invention for those skilled in the art, a specific embodiment thereof will be described below with reference to the accompanying drawings. It is to be understood that the following text is merely illustrative of one or more specific embodiments of the invention and does not strictly limit the scope of the invention as specifically claimed.
XRD (PANalytical X' Pert PRO) analysis was used to determine the phase and crystal structure of the wave-absorbing material. And analyzing the appearance and the microstructure of the wave-absorbing material by a TEM (JEOL JEM-2100). And measuring the graphitization degree of the wave-absorbing material by using a Raman spectrometer (Raman WITec Alpha 300R) system with an excitation wavelength of 532 nm. The dielectric constant and permeability of the material in the frequency range of 2-18GHz were measured using a vector network analyzer (Agilent PNA N5234A) with a test step size of 0.08GHz. The test sample preparation procedure was as follows: firstly, 0.03g of material to be tested and 0.07g of paraffin are weighed and added into a beaker with preset 2mL of normal hexane, the paraffin is completely dissolved in the normal hexane by ultrasonic treatment for 5min, and meanwhile, the test powder is uniformly dispersed. Then the beaker was placed in a water bath at 70 ℃ and n-hexane was volatilized while stirring to obtain a uniform paraffin-coated powder. And finally, putting the powder into a die, applying certain pressure to press the powder into a circular test sample. The test specimen had an outer diameter of 7mm and an inner diameter of 3.04mm. The reflection loss caused by the electromagnetic wave entering the wave-absorbing coating can be calculated by the following equation:
in the formula, z 0 Is the free space wave impedance, mu r Is magnetic permeability, epsilon r Is the dielectric constant, f is the frequency of the electromagnetic wave, d is the coating thickness, and c is the speed of light in vacuum.
Example 1
A preparation method and application of a conductive MOF wave-absorbing material comprise the following steps:
24mg of Cu (OAc) 2 ·H 2 O and 19.5mg of HHTP (1.23 in terms of mass ratio) were added to 9mL of deionized water, and the mixture was dissolved by magnetic stirring for 15 min. Then, 1.35mL of NMP was added dropwise to the above solution, briefly sonicated for 15min, and the mixture was heated to 85 ℃ for 12 hours of reaction. After the reaction was cooled to room temperature, a black precipitate was obtained by filtration, washed three times with water and acetone, respectively, and dried under vacuum at 70 ℃ overnight.
XRD test is carried out on the conductive MOF wave-absorbing material prepared in the example 1. The test result is shown in figure 1, all diffraction peaks are similar to the result of the crystallography data simulation, and the conductive MOF wave-absorbing material is proved to be successfully synthesized by the method.
The conductive MOF absorbing material prepared in example 1 was subjected to TEM testing. The test results are shown in fig. 2, and the material exhibits a 2D sheet structure and sufficiently high crystallinity. Furthermore, the porous structure of the conductive MOFs can also be observed, which provides the possibility of multiple scattering and reflection of electromagnetic waves within the absorber.
The conductive MOF wave absorbing material prepared in example 1 was subjected to BET test. Test results as shown in fig. 3, the conductive MOFs showed typical type IV isotherms and long, narrow adsorption curves were observed at relative pressures from 0 to 1.0. The specific surface area of the material is calculated to be 56.5m 2 g -1 . In addition, the pore distribution characteristics of the conductive MOF wave absorbing material are given by the inset in fig. 3, confirming the presence of nanopores in the sample, in concert with the TEM results.
Electromagnetic wave-absorbing performance calculation is carried out on the conductive MOF wave-absorbing material prepared in the example 1, and a Reflection Loss (RL) curve of the material under the thickness of 1.0-5.5 mm and the frequency of 2-18GHz is shown in figure 4. Typically using RL min (minimum value of reflection loss) and f e The performance of the electromagnetic wave absorbing material was evaluated by the optimum value of (effective absorption bandwidth). From FIG. 4 we can see the RL of the conductive MOF absorbing material min Is-45 dB and the thickness is only 1.5mm. By adjusting the thickness from 1.0mm to 5.5mm e Is 13.4GHz (3.7-14.2 GHz, 15.1-18 GHz). This superior performance can be attributed to the loss of conductance due to its appropriate conductivity, the loss of dipole polarization relaxation due to local defects in the material and the formation of good impedance matching by the unique two-dimensional layered porous structure due to the multifunctional surface groups. Therefore, the work provides a simple method for preparing the high-performance electromagnetic wave absorbing material by using the conductive polymer, and also provides a new thought for designing and synthesizing the high-performance electromagnetic wave absorbing material.
Example 2
A preparation method and application of a conductive MOF wave-absorbing material comprise the following steps:
24mg of Cu (OAc) 2 ·H 2 O and 19.5mg of HHTP (1.23 in terms of mass ratio) were added to 9mL of deionized water, and the mixture was dissolved by magnetic stirring for 15 min. Then, 1.35mL of NMP was added dropwise to the above solution, briefly sonicated for 15min, and the mixture was heated to 95 ℃ for 12 hours of reaction. After the reaction was cooled to room temperature, a black precipitate was obtained by filtration, washed three times with water and acetone, respectively, and dried under vacuum at 70 ℃ overnight.
Electromagnetic wave absorption performance calculation is carried out on the conductive MOF wave-absorbing material prepared in the embodiment 2, and a Reflection Loss (RL) curve of the material under the thickness of 1.0-5.5 mm and the frequency of 2-18GHz is shown in figure 5. It can be seen that RL of the conductive MOF absorbing material min Is-37 dB and the thickness is 2mm. Compared with example 1, the performance of the conductive MOF synthesized in example 2 is reduced, which is probably because the original crystalline structure of MOF is destroyed by increasing the reaction temperature, and the collapse of the pore structure is caused, thereby affecting the absorption of electromagnetic waves.
Example 3
A preparation method and application of a conductive MOF wave-absorbing material comprise the following steps:
24mg of Cu (OAc) 2 ·H 2 O and 19.5mg of HHTP (1.23 in terms of mass ratio) were added to 9mL of deionized water and dissolved by magnetic stirring for 15 min. Then, 1.35mL of NMP was added dropwise to the above solution, briefly sonicated for 15min, and the mixture was heated to 80 ℃ for 12 hours of reaction. After the reaction was cooled to room temperature, a black precipitate was obtained by filtration, washed three times with water and acetone, respectively, and dried under vacuum at 70 ℃ overnight.
Electromagnetic wave absorption performance calculation is carried out on the conductive MOF wave-absorbing material prepared in the embodiment 3, and a Reflection Loss (RL) curve of the material under the thickness of 1.0-5.5 mm and the frequency of 2-18GHz is shown in figure 6. It can be seen that RL of the conductive MOF absorbing material min Is-29 dB and the thickness is 2mm. The absorption performance of the synthesized conductive MOF to electromagnetic waves is changed along with different synthesis temperatures and different coordination abilities of organic ligands.
The embodiments of the present invention are described in detail with reference to the examples, but the present invention is not limited thereto in any way. It will be apparent to those skilled in the art that various modifications and substitutions can be made thereto without departing from the spirit of the invention, and all such equivalent modifications and substitutions are intended to be included within the scope of the appended claims.
Claims (10)
1. The application of the conductive MOF as a wave-absorbing material is characterized in that the conductive MOF is prepared by the following method:
2,3,6,7,10, 11-hexahydroxytriphenyl and Cu (OAc) 2 ·H 2 Adding O into deionized water, stirring and dissolving by magnetic force, dropwise adding N-methyl pyrrolidone, performing ultrasonic treatment for 1-60 min, and reacting the obtained mixture for 1-20 hours at the temperature of 60-100 ℃; carrying out post-treatment on the obtained reaction liquid to obtain the conductive MOF; the 2,3,6,7,10, 11-hexahydroxy-tri-benzene and Cu (OAc) 2 ·H 2 The mass ratio of O is 1-10: 1; the volume of the N-methylpyrrolidone is 10-100mL/g based on the mass of the 2,3,6,7,10, 11-hexahydroxy triphenyl.
2. The use of the conductive MOF of claim 1 as a wave absorbing material for absorbing electromagnetic waves in the frequency range of 2-18 GHz.
3. Use according to claim 1 or 2, characterized in that: the volume of the deionized water is 100-600 mL/g based on the mass of 2,3,6,7,10, 11-hexahydroxy triphenyl.
4. Use according to claim 1 or 2, characterized in that: the magnetic stirring time is 1-60 min.
5. Use according to claim 1 or 2, characterized in that: the reaction temperature is 80-95 ℃.
6. The use of claim 5, wherein: the temperature of the reaction was 85 ℃.
7. Use according to claim 1 or 2, characterized in that: the 2,3,6,7,10, 11-hexahydroxy-tri-benzene and Cu (OAc) 2 ·H 2 The mass ratio of O is 1.23.
8. Use according to claim 1 or 2, characterized in that the post-processing is: and after the reaction is cooled to room temperature, filtering to obtain a black precipitate, washing with water and acetone, and drying in vacuum overnight to obtain the conductive MOF.
9. The use of claim 8, wherein: the number of washing times is 1 to 10.
10. The use of claim 8, wherein: the drying temperature is 60-80 ℃.
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