Melamine sponge loaded multi-metal MOF (Metal Organic Framework) wave-absorbing material with self-supporting function and preparation method thereof

Abstract

The invention relates to a melamine sponge loaded multi-metal MOF (Metal Organic Framework) wave-absorbing material with a self-supporting function and a preparation method thereof. The method comprises the following steps: washing and pretreating melamine sponge with diluted hydrochloric acid, ethanol and deionized water in sequence, and then drying; weighing cupric acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate and cobalt acetate tetrahydrate, dissolving in methanol, absorbing the solution by using the sponge, and then drying the sponge; the preparation method comprises the following steps: dissolving pyrazole in deionized water, dissolving zinc chloride in deionized water, adding ammonia water, uniformly stirring, and carrying out sponge water absorption drying twice; the method comprises the following steps: heating and preserving heat in a tubular furnace at a heating rate of 5 DEG C / min in an N2 atmosphere, cooling to obtain a wave-absorbing material, collecting the heated wave-absorbing material, grinding, mixing the wave-absorbing material with paraffin, pressing into an annular sample, and testing the reflection loss performance of the sample. The prepared wave-absorbing material has the optimal reflection loss when the thickness is 1.52 mm, the minimum reflection loss value is-81.4345 dB, and the effective wave-absorbing bandwidth smaller than-10 dB reaches 4.82 GHz.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a melamine sponge-loaded multi-metal MOF wave absorbing material with self-supporting function and its preparation method. Background Technology

[0002] With the widespread use of electronic devices, while they have brought many conveniences to people's lives, the resulting electronic radiation poses a potential threat to the environment and human health. Therefore, the development of materials with high microwave absorption properties has become a research hotspot.

[0003] In the current research and development and production of microwave absorbing materials, the preparation technology still faces many challenges. First, the preparation process has strict requirements for environmental conditions; multiple parameters such as temperature, humidity, and air pressure directly affect the integrity and uniformity of the material's internal structure. Second, in the doping stage, current research is mostly limited to single doping with a few common metals, which cannot fully utilize the synergistic effect of multiple metals and limits the improvement of the material's overall performance.

[0004] MOF (metal-organic framework) materials, due to their periodic network structure which enhances the reflection and scattering of electromagnetic waves, are considered strong candidates for microwave absorbing materials. However, their structural characteristics remain relatively simple, limiting their ability to optimize absorption performance. Melamine foam, with its readily available, low-density, high specific surface area, and self-supporting properties, has become an ideal matrix for reinforcing microwave absorbing materials. By combining melamine foam with MOFs, the microwave absorbing material can not only significantly enrich the propagation path of electromagnetic waves by leveraging the porous structure of both, but also achieve a significant improvement in absorption capacity through multiple synergistic effects such as magnetic loss, dielectric loss, and impedance matching. For example, patent number "202411022349.5" and patent name "Porous Photothermal Material with In-situ Supported MOF in Biomass and Preparation Method Thereof" discloses the preparation of a porous photothermal material with in-situ supported MOF in biomass at room temperature, using natural cotton as a carrier, growing MOF in-situ on the cotton, then incorporating transition metals to improve photothermal performance, and finally obtaining a porous photothermal material with in-situ supported multi-metal MOF through drying, high-temperature annealing reaction and cooling to room temperature. By adding natural cotton and MOF material, a photothermal material with high porosity and high stability is obtained. The problem is that the obtained porous photothermal material has weak propagation ability inside the material, resulting in low adsorption capacity, and its support capacity is also relatively weak. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function. The preparation method of this microwave absorbing material is simple, introduces five metals, and has excellent electromagnetic wave absorption performance.

[0006] To solve the above problems, the technical solution adopted in this invention is: a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function, comprising the following steps: 1) Pre-treat the melamine sponge by ultrasonically washing it sequentially with dilute hydrochloric acid, ethanol, and deionized water for 20 min, and then dry the sponge. 2) Weigh out copper acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate, and cobalt acetate tetrahydrate, dissolve them in methanol, stir and dissolve at room temperature, absorb the solution with the melamine sponge prepared in step 1), and then dry the sponge. 3) Dissolve pyrazole in deionized water and stir at room temperature. Absorb the solution with the sponge dried in step 2), and then dry the sponge. 4) Dissolve zinc chloride in deionized water, add ammonia and stir until homogeneous. Absorb the solution with the sponge dried in step 3), and then dry the sponge. 5) The dried sponge from step 4) is heated to 700-900℃ in a tube furnace under N2 atmosphere at a heating rate of 5℃ / min, held for 3 hours, and cooled to room temperature to obtain the microwave absorbing material. The carbonized microwave absorbing material is collected and ground. 6) Mix the microwave absorbing material and paraffin wax in a mass ratio of 2:8, and then press them into a ring-shaped sample.

[0007] Furthermore, the concentration of dilute hydrochloric acid in step 1 is 1-2 mol / L.

[0008] Furthermore, in step 2, the mass ratio of copper acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate, and cobalt acetate tetrahydrate is 5-6:4-5:10-11:11-12; and the volume of methanol is 10-14 mL.

[0009] Furthermore, in step 2, the stirring time is between 20 minutes and the drying temperature is 70-80℃.

[0010] Furthermore, in step 3, the mass of pyrazole is 0.5-0.8 g, and the volume of deionized water is 10-14 mL.

[0011] Furthermore, in step 3, the stirring time is between 5 and 10 minutes, and the drying temperature is 70-80℃.

[0012] Furthermore, in step 4, the mass of zinc chloride is 0.6-0.8 g, the volume of ammonia water is 0.2 mL, and the volume of deionized water is 10-14 mL.

[0013] Furthermore, in step 4, the stirring time is 10-15 minutes, and the drying temperature is 70-80℃.

[0014] The MOF absorbing material prepared by the above method.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention uses four metal salts: copper acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate, and cobalt acetate tetrahydrate, which improves the performance of the microwave absorbing material.

[0016] 2) This invention utilizes melamine sponge, which not only enriches the propagation path of electromagnetic waves, but also... It also gives the absorbing material a self-supporting function.

[0017] 3) The present invention adopts a multi-metal doping strategy, which not only optimizes the absorption performance of the material, but also significantly enhances its application potential in multiple frequency bands and multiple scenarios.

[0018] 4) The present invention increases the adsorption capacity of metal salt by changing the order of addition of metal salt and pyrazole.

[0019] 5) This invention synthesizes MOF microwave absorbing materials loaded with pentagonal metals in situ. By utilizing the lightweight and porous structure of melamine sponge and MOF carbon-based materials, microwave absorbing materials with excellent performance are obtained.

[0020] 6) The absorbing material prepared by this invention has the best reflection loss when the thickness is 1.52 mm, with a minimum reflection loss value of -81.4345 dB and an effective absorption bandwidth of 4.82 GHz less than -10 dB, thus effectively improving the absorption performance of the absorbing material.

[0021] 7) The preparation method of this invention is mild, simple, green and environmentally friendly, and highly efficient. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention.

[0023] Figure 2 This is a reflection loss diagram of the absorbing material of the present invention in the 2-18GHz frequency band.

[0024] Figure 3 This is a diagram showing the real part of the dielectric constant of the absorbing material of the present invention in the 2-18 GHz frequency band.

[0025] Figure 4 This is a diagram showing the imaginary part of the dielectric constant of the absorbing material of this invention in the 2-18 GHz frequency band.

[0026] Figure 5 This is the dielectric loss tangent of the absorbing material of the present invention in the 2-18GHz frequency band. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying embodiments.

[0028] The synthesis principle of the key steps in this invention is as follows: MOF microwave absorbing materials loaded with pentagonal metals were synthesized in situ on melamine sponge at room temperature. The porous structure of MOF and melamine sponge provides abundant propagation paths, which is beneficial for the propagation of incident electromagnetic waves inside the material.

[0029] Example 1 The specific steps of a method for preparing a melamine sponge-loaded multimetal MOF microwave absorbing material with self-supporting function are as follows: Figure 1 As shown: Step 1: The melamine sponge was pretreated by ultrasonic washing with 1.2 mol / L dilute hydrochloric acid, ethanol and deionized water for 20 min in sequence, and then the sponge was dried. Step 2: Weigh 0.06 g of copper acetate monohydrate, 0.0448 g of nickel nitrate hexahydrate, 0.1046 g of ferric chloride hexahydrate, and 0.1 g of cobalt acetate tetrahydrate. Dissolve them in methanol by stirring at room temperature for 20 min. Absorb the solution with the melamine sponge prepared in Step 1, and then dry it in an oven at 70°C. Step 3: Dissolve 0.6 g of pyrazole in 10 mL of deionized water, stir at room temperature for 10 min to dissolve, absorb the solution with the sponge dried in Step 2, and then dry in an oven at 70°C. Step 4: Dissolve 0.6456 g of zinc chloride in 10 mL of deionized water, add 0.2 mL of ammonia water and stir for 15 min until homogeneous. Absorb the solution with the sponge dried in Step 3, and then dry it in an oven at 70°C.

[0030] Step 5: The dried sponge from Step 4 is heated to 700°C in a tube furnace under N2 atmosphere at a heating rate of 5°C / min, held at that temperature for 3 hours, and then cooled to room temperature to obtain the microwave absorbing material. The heated microwave absorbing material is collected and ground.

[0031] Step 6: Mix the absorbing material and paraffin wax in a mass ratio of 2:8, then press them into a ring-shaped sample and test the reflection loss performance of the sample.

[0032] Example 2 Specific steps of a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function: Step 1: The melamine sponge was pretreated by ultrasonic washing with 1.8 mol / L dilute hydrochloric acid, ethanol and deionized water for 20 min in sequence, and then the sponge was dried. Step 2: Weigh 0.05 g copper acetate monohydrate, 0.0568 g nickel nitrate hexahydrate, 0.1056 g ferric chloride hexahydrate, and 0.15 g cobalt acetate tetrahydrate, stir at room temperature for 20 min to dissolve in methanol, absorb the solution with the melamine sponge prepared in Step 1, and then dry in an oven at 75°C. Step 3: Dissolve 0.5 g of pyrazole in 10 mL of deionized water and stir at room temperature for 8 min to dissolve. Absorb the solution with the sponge dried in Step 1 and then dry it in an oven at 75°C. Step 4: Dissolve 0.732 g of zinc chloride in 10 mL of deionized water, add 0.2 mL of ammonia water and stir for 12 min until homogeneous. Absorb the solution with the sponge dried in Step 3, and then dry it in an oven at 75°C.

[0033] Step 5: Heat the dried sponge from Step 4 to 800°C in a tube furnace under N2 atmosphere at a heating rate of 5°C / min. Hold at this temperature for 3 hours, then cool to room temperature to obtain the microwave absorbing material. Collect the heated microwave absorbing material and grind it.

[0034] Step 6: Mix the absorbing material and paraffin wax in a mass ratio of 2:8, then press them into a ring-shaped sample and test the reflection loss performance of the sample.

[0035] Example 3 Specific steps of a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function: Step 1: The melamine sponge was pretreated by ultrasonic washing with 1.5 mol / L dilute hydrochloric acid, ethanol and deionized water for 20 min in sequence, and then the sponge was dried.

[0036] Step 2: Weigh 0.059 g of copper acetate monohydrate, 0.0498 g of nickel nitrate hexahydrate, 0.1053 g of ferric chloride hexahydrate, and 0.150 g of cobalt acetate tetrahydrate. Dissolve them in methanol by stirring at room temperature for 20 min. Absorb the solution with the melamine sponge prepared in Step 1, and then dry it in an oven at 80°C. Step 3: Dissolve 0.8 g of pyrazole in 10 mL of deionized water, stir at room temperature for 10 min to dissolve, absorb the solution with the sponge dried in Step 2, and then dry in an oven at 80℃. Step 4: Dissolve 0.5796g of zinc chloride in 10 mL of deionized water, add 0.2 mL of ammonia water and stir for 15 min until homogeneous. Absorb the solution with the sponge dried in Step 3, and then dry it in an oven at 80℃.

[0037] Step 5: The dried sponge from Step 4 is heated to 700°C in a tube furnace under N2 atmosphere at a heating rate of 5°C / min. It is held at this temperature for 3 hours, then cooled to room temperature to obtain the microwave absorbing material. The heated microwave absorbing material is collected and ground.

[0038] Step 6: Mix the absorbing material and paraffin wax in a mass ratio of 2:8, then press them into a ring-shaped sample and test the reflection loss performance of the sample.

[0039] Example 4 Specific steps of a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function: Step 1: The melamine sponge was pretreated by ultrasonic washing with 1.6 mol / L dilute hydrochloric acid, ethanol and deionized water for 20 min in sequence, and then the sponge was dried.

[0040] Step 2: Weigh 0.065 g of copper acetate monohydrate, 0.0478 g of nickel nitrate hexahydrate, 0.1023 g of ferric chloride hexahydrate, and 0.111 g of cobalt acetate tetrahydrate. Dissolve them in methanol by stirring at room temperature for 20 min. Absorb the solution with the melamine sponge prepared in Step 1, and then dry it in an oven at 73°C. Step 3: Dissolve 0.75g of pyrazole in 14mL of deionized water, stir at room temperature for 7 min to dissolve, absorb the solution with the sponge dried in step 2, and then dry in an oven at 73℃. Step 4: Dissolve 0.7463 g of zinc chloride in 14 mL of deionized water, add 0.2 mL of ammonia water and stir for 12 min until homogeneous. Absorb the solution with the sponge dried in Step 3, and then dry it in an oven at 73°C.

[0041] Step 5: The dried sponge from Step 4 is heated to 700°C in a tube furnace under N2 atmosphere at a heating rate of 5°C / min. It is held at this temperature for 3 hours, then cooled to room temperature to obtain the microwave absorbing material. The heated microwave absorbing material is collected and ground.

[0042] Step 6: Mix the absorbing material and paraffin wax in a mass ratio of 2:8, then press them into a ring-shaped sample and test the reflection loss performance of the sample.

[0043] Example 5 Specific steps of a method for preparing a melamine sponge-loaded multi-metal MOF microwave absorbing material with self-supporting function: Step 1: The melamine sponge was pretreated by ultrasonic washing with 1.3 mol / L dilute hydrochloric acid, ethanol and deionized water for 20 min in sequence, and then the sponge was dried.

[0044] Step 2: Weigh 0.053 g copper acetate monohydrate, 0.0496 g nickel nitrate hexahydrate, 0.1145 g ferric chloride hexahydrate, and 0.108 g cobalt acetate tetrahydrate, stir at room temperature for 20 min to dissolve in methanol, absorb the solution with the melamine sponge prepared in Step 1, and then dry in an oven at 78°C. Step 3: Dissolve 0.65g of pyrazole in 14mL of deionized water and stir at room temperature for 7 min to dissolve. Absorb the solution with the sponge dried in Step 2 and then dry it in an oven at 78℃. Step 4: Dissolve 0.4963 g of zinc chloride in 14 mL of deionized water, add 0.2 mL of ammonia water and stir for 14 min until homogeneous. Absorb the solution with the sponge dried in Step 3, and then dry it in an oven at 78°C.

[0045] Step 5: The dried sponge from Step 4 is heated to 750°C in a tube furnace under N2 atmosphere at a heating rate of 5°C / min. It is held at this temperature for 3 hours, then cooled to room temperature to obtain the microwave absorbing material. The heated microwave absorbing material is collected and ground.

[0046] Step 6: Mix the absorbing material and paraffin wax in a mass ratio of 2:8, then press them into a ring-shaped sample and test the reflection loss performance of the sample.

[0047] like Figure 2 As shown, the reflection loss diagram of the absorbing material prepared by the method of the present invention in the 2-18 GHz frequency band is shown. The absorber has the best reflection loss when the thickness is 1.52 mm, and the minimum reflection loss value is -81.4345 dB.

[0048] like Figure 3 As shown, the real part diagram of the dielectric constant of the absorbing material prepared by the method of the present invention in the 2-18 GHz frequency band shows that the absorption capacity of the material decreases with increasing frequency, while the real part value is relatively high, indicating that the material has good storage capacity.

[0049] like Figure 4 As shown in the diagram, the imaginary part of the dielectric constant of the absorbing material prepared by the method of the present invention in the 2-18 GHz frequency band shows that the loss capability decreases with increasing frequency.

[0050] like Figure 5 The figure shows the dielectric loss tangent of the absorbing material prepared by the method of the present invention in the 2-18 GHz frequency band.

[0051] The above description is a specific illustration of the present invention, and not a limitation thereof. Those skilled in the art can make various equivalent technical solutions without departing from the scope of the present invention; therefore, all equivalent technical solutions should be included within the protection scope of the present invention.

Claims

1. A method for preparing a melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function, characterized in that, The steps are as follows: 1) Pre-treat the melamine sponge by ultrasonically washing it sequentially with dilute hydrochloric acid, ethanol, and deionized water for 20 min, and then dry the sponge. 2) Weigh out copper acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate, and cobalt acetate tetrahydrate, dissolve them in methanol, stir and dissolve at room temperature, absorb the solution with the melamine sponge prepared in step 1), and then dry the sponge. 3) Dissolve pyrazole in deionized water and stir at room temperature. Absorb the solution with the sponge dried in step 2), and then dry the sponge. 4) Dissolve zinc chloride in deionized water, add ammonia and stir until homogeneous. Absorb the solution with the sponge dried in step 3), and then dry the sponge. 5) The dried sponge from step 4) is heated to 700-900℃ in a tube furnace under N2 atmosphere at a heating rate of 5℃ / min, held for 3 hours, and cooled to room temperature to obtain the microwave absorbing material. The carbonized microwave absorbing material is collected and ground. 6) Mix the microwave absorbing material and paraffin wax in a mass ratio of 2:8, and then press them into a ring-shaped sample.

2. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 1, characterized in that, The concentration of dilute hydrochloric acid in step 1 is 1-2 mol / L.

3. The method for preparing a melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 1 or 2, characterized in that, In step 2, the mass ratio of copper acetate monohydrate, nickel nitrate hexahydrate, ferric chloride hexahydrate, and cobalt acetate tetrahydrate is 5-6:4-5:10-11:11-12; the volume of methanol is 10-14 mL.

4. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 3, characterized in that, In step 2, the stirring time is between 20 minutes and the drying temperature is 70-80℃.

5. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 4, characterized in that, In step 3, the mass of pyrazole is 0.5-0.8 g, and the volume of deionized water is 10-14 mL.

6. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 5, characterized in that, In step 3, the stirring time is between 5 and 10 minutes, and the drying temperature is 70-80℃.

7. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 6, characterized in that, In step 4, the mass of zinc chloride is 0.6-0.8 g, the volume of ammonia water is 0.2 mL, and the volume of deionized water is 10-14 mL.

8. The method for preparing the melamine sponge-loaded multi-metal MOF absorbing material with self-supporting function according to claim 7, characterized in that, In step 4, the stirring time is 10-15 minutes and the drying temperature is 70-80℃.

9. The MOF absorbing material prepared by the method according to claim 1.

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