CN114614272A

CN114614272A - MXene/Co/C composite wave-absorbing material derived from MOF and preparation method thereof

Info

Publication number: CN114614272A
Application number: CN202210219574.2A
Authority: CN
Inventors: 叶晓云; 吕怡桦; 陈开榜; 王乾廷; 马立安; 李巍; 张磊; 陈文哲
Original assignee: Fujian University of Technology
Current assignee: Fujian University of Technology
Priority date: 2022-03-08
Filing date: 2022-03-08
Publication date: 2022-06-10

Abstract

The invention relates to a preparation method of an MOF-derived MXene/Co/C composite wave-absorbing material, which is suitable for the field of microwave absorption. The invention takes MXene as a substrate to be compounded with Co-MOF, and the MXene/Co-MOF compound is annealed to obtain the novel MOF-derived MXene/Co/C nano composite wave-absorbing material. MXene in the composite still maintains a multilayer sheet structure after calcination; Co-MOF is converted to a Co/C composite consisting of graphitic carbon and Co metal particles, which grows on the surface a plurality of uniformly distributed Carbon Nanotubes (CNTs) with Co particles at their tips.

Description

MXene/Co/C composite wave-absorbing material derived from MOF and preparation method thereof

Technical Field

The invention relates to the field of microwave absorption, in particular to an MXene/Co/C composite wave-absorbing material derived from MOF and a preparation method thereof.

Background

With the advent of the 5G era, the wide application of various electronic products brings convenience to the life of people, but generates non-negligible electromagnetic pollution. Meanwhile, in the military field, the wave-absorbing material with excellent performance has important scientific research significance for the research of radar stealth technology, detector technology and precise weaponry. Therefore, the development of high-performance microwave absorbing materials has received much attention. Although the carbon material has certain wave-absorbing performance, the carbon material has no magnetism, higher conductivity and single loss mechanism, mainly adopts resistance type loss, and has the defects of poor impedance matching, low attenuation capability, narrow frequency band and the like when being used alone. Magnetic metals (such as Fe, Co and Ni) and oxides thereof have high density, poor corrosion resistance and poor impedance matching, and are not generally used as wave-absorbing materials independently. In order to meet the requirements of high-quality wave-absorbing materials such as strong absorption, wide frequency band, light weight, thin thickness and the like, the novel carbon-based composite wave-absorbing material obtained by compounding the light carbon-based material and the magnetic metal material becomes a research hotspot.

MXene is a typical representative of two-dimensional materials and has the advantages of large specific surface area, more active sites, adjustable chemical composition, good electronic conduction and storage capacity and the like. But single MXene has poor wave absorbing performance due to high conductivity. MXene obtained by HF etching has a microwave absorption of-11 dB. On the basis, MXene is modified, for example, MXene obtained by HF etching is annealed, and the wave absorbing performance of the MXene after surface modification is obviously improved.

Meanwhile, the research on the wave-absorbing material derived from Metal Organic Frameworks (MOFs) can realize the introduction of magnetic metal into the carbon material. MOFs have the characteristics of adjustable chemical structure, large specific surface area, multiple metal coordination sites, various shapes and the like. The annealed MOFs not only can keep the advantages of the original shape structure, porous structure and the like, but also can generate metal particles, graphite carbon, defects and the like, so that the impedance matching of the material can be effectively improved, and the multiple electromagnetic wave loss is realized. Derivatization using Ni-MOFOne-dimensional CNTs and two-dimensional Ti₃C₂T_xMeanwhile, a three-dimensional conductive network is constructed, and a superstructure composite material can be formed. The optimal reflection loss of the composite material reaches-57.78 dB only under the condition that the impedance matching thickness is 1.49 mm. Therefore, the composite material of the magnetic material derived from the metal organic framework and the carbon material is an ideal light wave-absorbing material. At present, the research on the MOFs-derived wave-absorbing material is relatively few, and the impedance matching of the material needs to be further improved.

In order to overcome the defects of a single carbon material and a magnetic material serving as microwave absorption materials, MXene/Co-MOF is prepared by a room-temperature chemical solution method, and then the MXene/Co/C composite wave-absorbing material derived from Co-MOF is obtained by annealing treatment and is applied to the field of microwave absorption.

Disclosure of Invention

The invention aims to provide an MXene/Co/C composite wave-absorbing material derived from MOF and a preparation method thereof. The composite wave-absorbing material is simple in preparation method, good in magnetic component dispersibility and excellent in microwave absorption performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of an MOF-derived MXene/Co/C composite wave-absorbing material comprises the following steps:

(1) preparing MXene: mixing Ti₃AlC₂Adding the powder into an HF solution, heating in a water bath, washing and drying a product to obtain MXene;

(2) preparation of Co-MOF: respectively dissolving cobalt salt and an organic ligand in a solvent to obtain a solution A and a solution B. And adding the solution B into the solution A to obtain a mixed solution, magnetically stirring and reacting for a period of time at room temperature, and washing and drying a product to obtain the Co-MOF.

(3) Preparing MXene/Co-MOF complex: and (2) placing MXene prepared in the step (1) into a solution containing cobalt salt to obtain a solution C. Dissolving an organic ligand in a solvent to obtain a solution D, uniformly mixing and reacting the solution C and the solution D under magnetic stirring, and finally washing and drying a product to obtain the MXene/Co-MOF compound.

(4) Preparation of MXene/Co/C Complex: and (4) annealing the MXene/Co-MOF composite prepared in the step (3) to obtain the MXene/Co/C composite wave-absorbing material.

Further, the weight percentage of HF in the step (1) is 40 wt%.

Further, the washing in the step (1) is carried out by using deionized water for centrifugation for a plurality of times, and the pH value of the supernatant is 6-7.

Further, the cobalt salt in the step (2) is Co (NO)₃)·6H₂O。

Further, the solvent in the step (2) is deionized water, methanol, a deionized water/methanol mixed solution (volume ratio is 1:1), ethanol, and N, N-dimethylformamide.

Further, the reaction time in the step (2) is 12-24 h.

Further, the organic ligand in the step (2) is 2-methylimidazole.

Furthermore, the mass change range of MXene in the MXene/Co-MOF compound in the step (2) is 0-0.2 g.

Further, the annealing atmosphere in the step (4) is N₂Gas and Ar gas.

Further, the annealing temperature in the step (4) is 500-1000 ℃.

Further, the temperature rise rate in the step (4) is 0.5-5 ℃/min.

Further, the annealing time in the step (4) is 1-8 h.

The method adopts a room temperature chemical solution method to prepare MXene/Co-MOF, and prepares MXene/Co/C composite wave-absorbing materials derived from MXene and Co-MOF with modified surfaces through calcination; the Co-MOF is used as a precursor of the wave-absorbing composite material, and can provide high specific surface area, adjustable components and structures; the carbonized wave-absorbing material has the advantages of increased pore canals and low density, and further reduces the filling proportion in application, thereby realizing light weight.

The invention has the following advantages:

(1) MXene in the compound of the invention still maintains a multilayer sheet structure; Co-MOF is converted to a Co/C composite consisting of graphitic carbon and Co metal particles, which grows on the surface a plurality of uniformly distributed Carbon Nanotubes (CNTs) with Co particles at their tips. By adjusting the size of Co-MOF in the MXene/Co-MOF compound and the content of MXene, the prepared MXene/Co/C composite wave-absorbing material has a multilayer ordered pore channel structure, adjustable components, a structure and electromagnetic parameters.

(2) The carbon material and the magnetic material are combined, compared with a single wave-absorbing material, the multiple interfaces have multiple loss mechanisms, and the impedance matching of the material can be effectively improved.

(3) The MXene/Co/C composite wave-absorbing material prepared by the invention has simple preparation process and excellent microwave absorption performance, and can be used for guiding the preparation of other C composite wave-absorbing materials derived from magnetic MOF.

(4) In the composite structure, the polyhedral structure formed by the MXene sheet layer and the Co-MOF derivative is favorable for multiple reflection and refraction of electromagnetic waves, the carbon nano tubes on the surface of graphite carbon can form a conductive network, the magnetism of Co metal particles is favorable for improving the impedance matching of the composite, and the characteristics can effectively improve the microwave absorption performance of the composite material. The MXene/Co/C composite material derived from the MOF prepared by the invention has the advantages of light weight, strong wave-absorbing capability, wide absorption frequency band, thin matching thickness and the like, and has potential application prospects in the fields of microwave absorption, electromagnetic shielding and the like.

Drawings

FIG. 1 is an SEM image of the Co-MOF material prepared in examples 1-3 (a: Co-MOF-1; b: Co-MOF-2; c: Co-MOF-3) and a particle size distribution diagram (d: Co-MOF-1; e: Co-MOF-2; f: Co-MOF-3);

FIG. 2 is SEM images of MXene/Co-MOF materials obtained in examples 4-8 and MXene/Co/C-1 obtained in example 4 (a: MXene; b: MXene/Co-MOF-1; C: MXene/Co-MOF-2; d: MXene/Co-MOF-3; e: MXene/Co-MOF-4; f: MXene/Co-MOF-5; g-i: MXene/Co/C-1);

FIG. 3 is a TEM image of MXene/Co/C-1 prepared in example 4;

FIG. 4 is an XRD pattern of an XRD pattern sample of materials prepared in examples 1-8 (a: before annealing; b: after annealing);

FIG. 5 is a reflection loss diagram of the MXene/Co/C composite wave-absorbing material prepared in examples 1-8 (a: Co/C-1; b: MXene/Co/C-1; C: MXene/Co/C-2; d: MXene/Co/C-3; e: MXene/Co/C-4; f: MXene/Co/C-5);

FIG. 6 is an impedance matching graph of the MXene/Co/C composite wave-absorbing material prepared in examples 1-8 (a: Co/C-1; b: MXene/Co/C-1; C: MXene/Co/C-2; d: MXene/Co/C-3; e: MXene/Co/C-4; f: MXene/Co/C-5);

FIG. 7 is a magnetic hysteresis loop diagram of the MXene/Co/C-1 composite wave-absorbing material prepared in example 4.

Detailed Description

The present invention is further illustrated by the following examples, which are provided by way of illustration only and are not intended to limit the scope of the invention.

Example 1: preparation of MXene

First, 5g of Ti₃AlC₂Adding the powder into 50mL of HF acid solution for multiple times in a small amount, and magnetically stirring for 24 hours at the water bath heating temperature of 60 ℃; secondly, washing the solution after the reaction for several times by using deionized water until the solution is neutral, wherein the centrifugal speed of a centrifugal machine is 6000rpm, and the time is 3 min; finally, the washed sample is dried in a vacuum oven at 60 ℃ for 24h, and MXene is obtained as dark gray powder after drying.

Example 2: preparation of Co-MOF

0.9g of Co (NO)₃)₂.6H₂Adding O into 24mL of deionized water, and carrying out ultrasonic treatment for 10min to obtain solution A; adding 11g of 2-methylimidazole into 16mL of deionized water, and carrying out ultrasonic treatment for 10min to obtain solution B; slowly dripping the solution B into the solution A under magnetic stirring, and reacting at room temperature for 24h to obtain a purple solution; and then washing the purple solution with methanol for 4-5 times, and then drying the sample in a vacuum oven at 60 ℃ for 24h, wherein the dried product is named as Co-MOF-1.

Examples 3 and 4

The preparation process was the same as in example 2, and only by changing the solvent and adjusting the reaction time (see Table 1), samples were prepared and named Co-MOF-2 and Co-MOF-3, respectively.

Example 5: preparation of MXene/Co-MOF-1 and MXene/Co/C-1 composite materials

0.1g MXene and 0.9g Co (NO)₃)₂.6H₂And adding O into 24mL of deionized water, and performing ultrasonic treatment for 10min to fully and uniformly dissolve the O to obtain solution A. Then adding 11g of 2-methylimidazole into 160mL of deionized water, and carrying out ultrasonic treatment for 10min to obtain solution B; then, slowly dripping the solution B into the solution A under magnetic stirring, and reacting for 24 hours at room temperature to obtain a bluish purple solution; washing the bluish purple solution with methanol for 4-5 times, drying the sample in a vacuum oven at 60 ℃ for 24h to obtain bluish purple powder, which is named as MXene/Co-MOF-1.

Annealing the sample at N₂Raising the temperature from room temperature to 800 ℃ at the speed of 5 ℃/min under the atmosphere, and preserving the temperature for 2h, wherein the black powder after final annealing is the MXene/Co/C-1 composite material.

Examples 6 to 9

Similar to example 5, samples before and after annealing, namely MXene/Co-MOF-2, MXene/Co-MOF-3, MXene/Co-MOF-4, MXene/Co-MOF-5, MXene/Co/C-2, MXene/Co/C-3, MXene/Co/C-4 and MXene/Co/C-5, respectively, were obtained by changing the kind of solvent, the reaction time and the component distribution ratio (see Table 1).

Table 1 experimental materials formula table

The samples obtained in the above examples 1 to 9 were characterized by a scanning electron microscope, a transmission electron microscope, X-ray powder diffraction, a comprehensive physical property measurement system, a network vector analyzer, and the like. The specific test results are shown in FIGS. 1 to 7.

FIG. 1 is an SEM image of Co-MOF. As can be seen, the Co-MOF is polyhedral and is uniformly distributed in width; the particle sizes of Co-MOF-1, Co-MOF-2 and Co-MOF-3 are significantly different. As can be seen from the particle size distribution diagram, the average particle size of Co-MOF-1 is about 2 μm, and the average particle sizes of Co-MOF-2 and Co-MOF-3 are significantly reduced, respectively to about 400nm and 260 nm.

Fig. 2 is an SEM image of each sample. As shown in fig. 2a, MXene is in a sheet form; in FIGS. 2 b-d, as the Co-MOF particle size decreases, the MXene is more and more tightly encapsulated by Co-MOF. As the amount of MXene increased, the Co-MOF distribution became sparser (FIGS. 2e and 2 f). After carbonization, MXene in MXene/Co-MOF still keeps lamellar, and Co/C derived from Co-MOF is in a collapsed polyhedral structure (FIGS. 2 g-i).

FIG. 3 is a TEM image of MXene/Co/C-1. As is clear from the figure, many carbon nanotubes with Co metal particles at the tips are generated on the surface of the composite.

Fig. 4 is an XRD pattern before and after annealing of the sample. The successful preparation of MXene, Co-MOF, MXene/Co-MOF and MXene/Co/C can be further proved by characteristic peaks of each component appearing in the figure.

Fig. 5 is a graph of the loss of the sample. As can be seen from FIG. 5a, the Co-MOF derivative Co/C has poor wave-absorbing performance, and the minimum reflection loss is only-9.04 dB; after compounding with MXene, the wave absorbing performance of MXene/Co/C compound is improved along with the increase of Co-MOF particle size (fig. 5 b-d). The wave-absorbing performance of MXene/Co/C-1 is optimal and can reach-45.48 dB, and the ratio of MXene in the MXene/Co/C composite is increased or decreased, so that the wave-absorbing performance of the composite material is obviously poor as shown in figures 5e and 5 f.

Fig. 6 is a graph of impedance matching for the samples. As can be seen from the figure, MXene/Co/C-1 has the best impedance matching, the area with the impedance matching value closest to 1 is the largest, while the impedance matching values of other samples are hardly close to 1. FIG. 7 is a hysteresis loop diagram of MXene/Co/C-1. As can be seen, the MXene/Co/C-1 composite material has an Ms of 0.38 emu/g and shows weak magnetism.

Claims

1. A preparation method of an MXene/Co/C composite wave-absorbing material derived from MOF is characterized by comprising the following steps:

step 1) preparation of MXene: mixing Ti₃AlC₂Adding the powder into an HF solution, heating in a water bath, washing and drying a product to obtain MXene;

step 2) preparing Co-MOF: respectively dissolving cobalt salt and an organic ligand in a solvent to obtain a solution A and a solution B; adding the solution B into the solution A to obtain a mixed solution, carrying out magnetic stirring reaction, washing and drying a product to obtain Co-MOF;

step 3) preparing MXene/Co-MOF compound: placing MXene prepared in the step 1) in a solution containing cobalt salt to obtain a solution C; dissolving the Co-MOF prepared in the step 2) in a solvent to obtain a solution D; under the condition of continuous stirring, uniformly mixing and reacting the solution C and the solution D, and washing and drying a product to obtain an MXene/Co-MOF compound;

step 4) preparing MXene/Co/C compound: and (3) annealing the MXene/Co-MOF compound prepared in the step 3) to obtain the MXene/Co/C composite wave-absorbing material.

2. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: the weight percentage of the HF solution in the step (1) is 35-45 wt%.

3. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: and the washing in the step 1) is carried out by using deionized water for multiple times of centrifugal treatment, and the pH value of the supernatant is 6-7.

4. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: the cobalt salt in the step 2) is Co (NO)₃)·6H₂O。

5. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: the solvent in the step (2) is at least one of deionized water, methanol, ethanol and N, N-dimethylformamide.

6. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: and 2) the reaction time is 12-24 h.

7. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: the organic ligand in the step 2) is 2-methylimidazole.

8. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: the mass change range of MXene in the MXene/Co-MOF compound in the step (3) is 0-0.2 g.

9. The preparation method of the MOF-derived MXene/Co/C composite wave-absorbing material according to claim 1, characterized in that: step 4), the heating rate is 0.5-5 ℃/min; the annealing temperature is 500-1000 ℃; the annealing time is 1-8 h; annealing atmosphere is N₂Gas or Ar gas.

10. An MOF-derived MXene/Co/C composite wave-absorbing material prepared by the preparation method of any one of claims 1-9.