A ZIF-derived cobalt-based wave-absorbing and heat-conducting composite material and a preparation method thereof

Abstract

This invention discloses a ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material and its preparation method, belonging to the field of microwave absorbing and thermally conductive composite material preparation. The invention first synthesizes a B / P in-situ doped ZIF-7 precursor at room temperature, then encapsulates it with tannic acid, and then reacts it in a methanol solution of cobalt acetate tetrahydrate to obtain a ZIF precursor. The obtained ZIF precursor is then calcined at high temperature to obtain a ZIF derivative with a cobalt single atom, cobalt nanoparticles, and a B / P-N co-doped porous carbon structure. This derivative is uniformly dispersed in an aqueous polyurethane matrix and polymerized to obtain a flexible microwave absorbing and thermally conductive composite material. The material obtained by this invention possesses both efficient electromagnetic wave absorption and thermal conductivity, and can be used to prepare integrated electromagnetic compatibility and thermal management structures for integrated circuit chips, thus showing good application prospects and significant economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing and thermally conductive composite material preparation, specifically relating to a ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material and its preparation method. Background Technology

[0002] With the rapid development of electronic devices towards higher power, higher frequency, and higher integration, electromagnetic interference and thermal management issues are becoming increasingly prominent. Microwave-absorbing materials generally have low thermal conductivity, and their insertion significantly increases interfacial thermal resistance. This causes electromagnetic energy to be absorbed and converted into heat energy. If this heat cannot be dissipated in time, it leads to localized overheating, which in turn weakens the material's dielectric or magnetic loss properties, creating a vicious cycle of mutual constraint between absorption and heat dissipation. Therefore, developing integrated dual-functional materials that combine efficient microwave absorption with high thermal conductivity has become a key requirement for advanced electronic packaging.

[0003] Porous carbon composites derived from metal-organic frameworks (MOFs) have shown great potential in broadband microwave absorption due to their tunable electromagnetic parameters and abundant polarization interfaces, especially systems containing transition metals, which can enhance absorption intensity through the synergistic effect of magnetic and dielectric losses. However, these materials are mostly rigid powders or porous bulk materials, making it difficult to achieve tight adhesion to device surfaces during actual assembly, easily leading to air gaps at the interfaces. Since air has extremely low thermal conductivity, it severely hinders lateral and longitudinal heat transfer, causing hotspot accumulation and limiting its application in high-power scenarios. To improve thermal transport performance, flexible polymer matrices are often used as the continuous phase in composite materials, possessing good processability, elasticity, and interfacial adaptability, effectively filling microscopic voids and reducing contact thermal resistance. Therefore, by combining multifunctional fillers with flexible matrices, it is hoped that highly efficient synergy between electromagnetic absorption and thermal conduction can be achieved within a single material system. Summary of the Invention

[0004] The purpose of this invention is to provide a cobalt-based microwave absorbing and thermally conductive composite material derived from ZIF and its preparation method, which can solve the problems of electromagnetic interference and heat accumulation in the operation of electronic devices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A cobalt-based microwave absorbing and thermally conductive composite material derived from ZIF is prepared by first synthesizing a B / P in-situ doped ZIF precursor at room temperature, then encapsulating it with tannic acid, and then reacting it with a cobalt source solution to obtain a ZIF precursor. The obtained ZIF precursor is calcined to obtain a ZIF derivative, which is then added to an aqueous polyurethane for polymerization and curing to finally obtain the composite material.

[0006] The preparation method of the ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material includes the following steps: (1) Under continuous stirring, a DMF solution containing zinc acetate and triarylphosphine or boric acid was added to a methanol solution of benzimidazole. After mixing evenly, the solution was reacted, and then centrifuged, washed, and vacuum activated to obtain B / P in-situ doped ZIF-7. (2) The obtained B / P in-situ doped ZIF-7 was ultrasonically dispersed in deionized water, and then tannic acid solution was added under continuous stirring. After stirring and mixing, the mixture was centrifuged and washed. The obtained powder was then added to a methanol solution of cobalt acetate tetrahydrate and stirred at room temperature for 2-4 h. After centrifugation, washing and vacuum activation were performed to obtain the ZIF precursor. (3) The obtained ZIF precursor was calcined and ground under an Ar atmosphere to obtain ZIF derivatives; (4) The obtained ZIF derivative is added to waterborne polyurethane, mixed evenly, and then polymerized to obtain a cobalt-based composite material derived from ZIF.

[0007] Furthermore, the molar ratio of zinc acetate to benzimidazole used in step (1) is 25-40:100.

[0008] Furthermore, the molar ratio of zinc acetate to triarylphosphine or boric acid used in step (1) is 100-120:100.

[0009] Furthermore, the volume ratio of methanol to DMF used in step (1) is 1:1~2.

[0010] Furthermore, the reaction in step (1) is carried out at a temperature of 15-30°C for 12-24 hours.

[0011] Furthermore, the concentration of the tannic acid solution in step (2) is 24 mM, the pH is 8, and its dosage is calculated based on the mass ratio of the tannic acid contained therein to the B / P in-situ doped ZIF-7 as 1.36:1.

[0012] Further, in step (2), after adding the tannic acid solution, stir for 5-10 min.

[0013] Furthermore, the ratio of the amount of cobalt acetate tetrahydrate used in step (2) to the mass ratio of B / P in-situ doped ZIF-7 is 1:2.

[0014] Furthermore, the vacuum activation temperature in steps (1) and (2) is 60°C, and the time is 3-5 h.

[0015] Furthermore, the calcination in step (3) involves heating to 1000-1200℃ at a rate of 5℃ / min and holding at that temperature for 1-2 hours.

[0016] Furthermore, in step (4), the mass ratio of waterborne polyurethane to ZIF derivative is 100:10-20.

[0017] Furthermore, the polymerization temperature in step (4) is 15-30°C and the time is 24 h.

[0018] The ZIF derivative prepared in this invention simultaneously possesses a porous carbon structure with cobalt single atoms, cobalt nanoparticles, and B / PN co-doped components. The B / P atoms, doped into the carbon framework, exhibit a significant difference in electronegativity compared to carbon atoms, enabling the construction of a highly asymmetric local electronic environment within the confined pores of the ZIF. This asymmetric coordination environment not only induces strong dipole polarization and interfacial polarization, significantly enhancing the material's dielectric loss capability, but also modulates phonon propagation paths, reduces lattice thermal resistance, and effectively suppresses cobalt atom migration during pyrolysis, leading to the in-situ formation of highly dispersed cobalt single atoms and magnetic nanoparticles. Furthermore, the presence of cobalt species synergistically enhances both magnetic and conduction losses, thereby endowing the material with excellent electromagnetic wave absorption capabilities. Simultaneously, the continuous nitrogen-doped carbon framework and cobalt components construct an efficient thermal conduction pathway, significantly improving the material's thermal conductivity, thus achieving a synergistic integration of electromagnetic wave absorption and thermal conduction functions. By introducing this ZIF derivative as a multifunctional filler into a flexible polymer matrix, a continuous magneto-electric coupling network and a vertical heat conduction channel can be constructed simultaneously. As a result, the composite material can have both broadband microwave absorption and high-efficiency out-of-plane thermal conductivity, effectively alleviating the problem of local overheating caused by electromagnetic energy dissipation. It can be used to prepare Cu / Kovar / Cu metal shells with shielding and heat dissipation functions, copper heat sinks embedded in substrates, and heat dissipation through-hole arrays, etc., for integrated electromagnetic compatibility and thermal management structures for integrated circuit chips.

[0019] The beneficial effects of this invention are as follows: (1) In this invention, heteroatoms B / P are introduced into ZIF-7. After pyrolysis, the carbon framework co-doped with B / PN can effectively anchor cobalt species through strong coordination, significantly inhibiting their migration and aggregation, thereby obtaining metal nanoparticles with smaller size and more uniform distribution.

[0020] (2) B / P doping can construct highly asymmetric local electronic structures within the confined channels of MOF, significantly enhancing dipole polarization and defect polarization responses, synergistically improving dielectric loss capability, and achieving strong absorption microwave attenuation performance.

[0021] (3) The B / PN co-doped carbon network and the high thermal conductivity cobalt component can form a continuous thermal conduction path in the waterborne polyurethane matrix, which can effectively improve the out-of-plane thermal conductivity while achieving broadband strong absorption, thereby solving the problem of local overheating caused by electromagnetic energy dissipation and providing a new idea for the development of electromagnetic-thermal integrated functional materials. Attached Figure Description

[0022] Figure 1XRD spectra of ZIF-7, B-ZIF-7, P-ZIF-7 (a) and Co-N / C, CoB-N / C and CoP-N / C (b) prepared for the examples.

[0023] Figure 2 R-space EXAFS spectra (a) of Co-N / C, CoB-N / C and CoP-N / C prepared for the example, and HAADF-STEM images (bd) of the three.

[0024] Figure 3 TEM images of Co-N / C (a), CoB-N / C (b), and CoP-N / C (c) prepared for the examples.

[0025] Figure 4 The dielectric loss tangent tanδ of the Co-N / C-WPU, CoB-N / C-WPU, and CoP-N / C-WPU prepared for the examples ε (a) Conduction loss ε c "and polarization loss ε" p (b) and magnetic loss tangent tanδ μ (c).

[0026] Figure 5 The minimum reflection loss RL of Co-N / C-WPU, CoB-N / C-WPU and CoP-N / C-WPU prepared for the examples min Curve (a), attenuation constant α under minimum reflection loss (b), and impedance matching coefficient |Z in / Z0|(c).

[0027] Figure 6 Thermal conductivity of Co-N / C-WPU, CoB-N / C-WPU, CoP-N / C-WPU and pure WPU prepared for the examples. Detailed Implementation

[0028] A ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material, the preparation method of which includes the following steps: (1) Under continuous stirring, add DMF solution containing zinc acetate and triarylphosphine or boric acid to the methanol solution of benzimidazole, mix evenly and react at 15-30℃ for 12-24 h, then centrifuge, wash with methanol, and activate under vacuum at 60℃ for 3-5 h to obtain B / P in-situ doped ZIF-7. (2) The obtained B / P in-situ doped ZIF-7 was ultrasonically dispersed in deionized water, and then 24 mM tannic acid solution (pH=8) was added under continuous stirring. After stirring for 5-10 min, the mixture was centrifuged and washed with methanol. The resulting powder was then added to a methanol solution of cobalt acetate tetrahydrate and stirred at room temperature for 2-4 h. After centrifugation and washing with methanol, the mixture was activated at 60℃ for 3-5 h to obtain the ZIF precursor. (3) The obtained ZIF precursor was heated to 1000-1200℃ at a rate of 5℃ / min under Ar atmosphere, and calcined for 1-2 h. Then it was ground to obtain ZIF derivative. (4) The obtained ZIF derivative was added to waterborne polyurethane at a mass ratio of 10-20:100. After mixing evenly, it was polymerized at 15-30℃ for 24 h to obtain ZIF-derived cobalt-based composite material.

[0029] In step (1), the molar ratio of zinc acetate to benzimidazole is 25-40:100. The molar ratio of zinc acetate to triarylphosphine or boric acid is 100-120:100. The volume ratio of methanol to DMF is 1:1~2.

[0030] In step (2), the amount of tannic acid solution used is calculated based on a mass ratio of tannic acid to B / P in-situ doped ZIF-7 of 1.36:1. The mass ratio of cobalt acetate tetrahydrate to B / P in-situ doped ZIF-7 is 1:2.

[0031] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods. Example 1

[0033] (1) First, add 8.86 g benzimidazole to 150 mL methanol and disperse it evenly. Then add it to 150 mL DMF solution containing 3.6 g zinc acetate and mix evenly. Stir continuously at room temperature (25℃) for 12 h. Then centrifuge at 9000 rpm for 5 min to collect the precipitate. Wash the precipitate with methanol 3 times and activate it at 60℃ for 5 h. The dried powder is then ground to obtain ZIF-7 powder.

[0034] (2) Disperse 300 mg of ZIF-7 powder obtained in step (1) in deionized water by ultrasonication for 10 min. Then, add 10 mL of 24 mM tannic acid solution (adjust pH=8 by adding 6 M KOH aqueous solution) under constant stirring. After stirring for 5 min, collect the solid product by centrifugation. Wash it three times with methanol and add it to 30 mL of 0.02 M cobalt acetate tetrahydrate / methanol solution. Stir the reaction at room temperature for 3 h. Then, collect the solid product by centrifugation and wash it several times with methanol. Place the product in an oven at 60℃ for 5 h. Then place the obtained product in a porcelain boat and heat it to 1000℃ at a rate of 5 ℃ / min under Ar atmosphere. Maintain the temperature for 2 h and then cool it to room temperature. Grind the product to obtain the sample named Co-N / C.

[0035] (3) Take 0.015 g of Co-N / C and 0.085 g of WPU, mix them evenly, fill them into a polytetrafluoroethylene mold, let them stand at room temperature for 24 h, collect the demolded sample, and label it as Co-N / C-WPU. Example 2

[0036] (1) First, add 8.86 g benzimidazole to 150 mL methanol and disperse it evenly. Then add it to 300 mL DMF solution containing 3.6 g zinc acetate and 3.74 g triarylphosphine. Stir continuously at room temperature (25℃) for 12 h. Then centrifuge at 9000 rpm for 5 min to collect the precipitate. Wash the precipitate with methanol 3 times and activate it at 60℃ for 5 h. The dried powder is then ground to obtain P-ZIF-7 powder.

[0037] (2) 300 mg of P-ZIF-7 powder obtained in step (1) was ultrasonically dispersed in deionized water for 10 min. Then, 10 mL of 24 mM tannic acid solution was added under continuous stirring (pH=8 was adjusted by adding 6 M KOH aqueous solution). After stirring for 5 min, the solid product was collected by centrifugation and washed 3 times with methanol. Then, it was added to 30 mL of 0.02 M cobalt acetate tetrahydrate / methanol solution and stirred at room temperature for 3 h. After centrifugation, the solid product was collected and washed several times with methanol. The product was then placed in an oven at 60 °C for 5 h to activate. The obtained product was then placed in a porcelain boat and heated to 1000 °C at a rate of 5 °C / min under Ar atmosphere for 2 h. After cooling to room temperature and grinding, the sample was named CoP-N / C.

[0038] (3) Take 0.015 g CoP-N / C and 0.085 g WPU, mix them evenly, fill them into a polytetrafluoroethylene mold, let them stand at room temperature for 24 h, collect the demolded sample, and label it as CoP-N / C-WPU. Example 3

[0039] (1) First, add 8.86 g benzimidazole to 150 mL methanol and disperse it evenly. Then add it to 300 mL DMF solution containing 3.6 g zinc acetate and 6.8 g boric acid. Stir continuously at room temperature (25℃) for 12 h. Then centrifuge at 9000 rpm for 5 min to collect the precipitate. Wash the precipitate with methanol 3 times and activate it at 60℃ for 5 h. The dried powder is then ground to obtain B-ZIF-7 powder.

[0040] (2) 300 mg of B-ZIF-7 powder obtained in step (1) was ultrasonically dispersed in deionized water for 10 min. Then, 10 mL of 24 mM tannic acid solution was added under continuous stirring (pH=8 was adjusted by adding 6 M KOH aqueous solution). After stirring for 5 min, the solid product was collected by centrifugation and washed 3 times with methanol. Then, it was added to 30 mL of 0.02 M cobalt acetate tetrahydrate / methanol solution and stirred at room temperature for 3 h. After centrifugation, the solid product was collected and washed several times with methanol. The product was then placed in an oven at 60 °C for 5 h to activate. The obtained product was then placed in a porcelain boat and heated to 1000 °C at a rate of 5 °C / min under Ar atmosphere for 2 h. After cooling to room temperature and grinding, the sample was named CoB-N / C.

[0041] (3) Take 0.015 g CoP-N / C and 0.085 g WPU, mix them evenly, fill them into a polytetrafluoroethylene mold, let them stand at room temperature for 24 h, collect the demolded sample, and label it as CoB-N / C-WPU.

[0042] Figure 1 The crystal structures of ZIF and ZIF derivatives prepared in the examples are shown. The figures show that ZIF-7, B-ZIF-7 and P-ZIF-7 were successfully synthesized and have good crystallinity, while the ZIF derivatives Co-N / C, CoB-N / C and CoP-N / C are mainly composed of metallic cobalt and graphitic carbon.

[0043] Figure 2 The examples demonstrate that the Co species in the ZIF derivatives Co-N / C, CoB-N / C, and CoP-N / C prepared in the examples exist in the form of Co single atoms and Co metal particles.

[0044] Figure 3 The morphologies of the ZIF derivatives Co-N / C, CoB-N / C, and CoP-N / C prepared in the examples are shown, where it can be seen that doping with B or P can make the metal particles smaller and more dispersed.

[0045] Figure 4The dielectric loss tangent tanδ of the Co-N / C-WPU, CoB-N / C-WPU, and CoP-N / C-WPU prepared in the examples is shown. ε ε conduction loss c "and polarization loss ε" p "and magnetic loss tangent tanδ" μ It can be seen that tanδ ε Much greater than tanδ μ This indicates that the main loss is dielectric loss, with CoP-N / C exhibiting the strongest polarization loss.

[0046] Figure 5 The study demonstrates that the CoP-N / C-WPU exhibits a minimum reflection loss of -61.1 dB at a matching thickness of 2 mm and a frequency of 9.12 GHz, indicating that the CoP-N / C-WPU possesses excellent microwave absorption performance. The CoP-N / C-WPU also exhibits good impedance matching and microwave attenuation capabilities at appropriate frequencies, which are crucial factors contributing to its superior microwave absorption performance.

[0047] Table 1. Microwave absorption performance data of Co-N / C-WPU, CoB-N / C-WPU and CoP-N / C-WPU

[0048] As can be seen from Table 1, the obtained CoP-N / C-WPU has excellent microwave absorption performance.

[0049] Figure 6 The thermal conductivity of Co-N / C-WPU, CoB-N / C-WPU, CoP-N / C-WPU and pure WPU were shown, demonstrating that CoP-N / C-WPU has excellent thermal management performance.

[0050] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material, characterized in that: Includes the following steps: (1) Under continuous stirring, a DMF solution containing zinc acetate and triarylphosphine or boric acid was added to a methanol solution of benzimidazole. After mixing evenly, the solution was reacted, and then centrifuged, washed, and vacuum activated to obtain in-situ doped ZIF-7. (2) The obtained in-situ doped ZIF-7 was ultrasonically dispersed in deionized water, and then tannic acid solution was added under continuous stirring. After stirring and mixing, the mixture was centrifuged and washed. The obtained powder was then added to a methanol solution of cobalt acetate tetrahydrate and stirred at room temperature for 2-4 h. After centrifugation, washing and vacuum activation were performed to obtain the ZIF precursor. (3) The obtained ZIF precursor was calcined and ground under an Ar atmosphere to obtain ZIF derivatives; (4) The obtained ZIF derivative is added to waterborne polyurethane, mixed evenly, and then polymerized to obtain a cobalt-based composite material derived from ZIF.

2. The preparation method according to claim 1, characterized in that: The molar ratio of zinc acetate to benzimidazole used in step (1) is 25-40:100; the molar ratio of zinc acetate to triarylphosphine or boric acid is 100-120:100; and the volume ratio of methanol to DMF is 1:1~2.

3. The preparation method according to claim 1, characterized in that: The reaction in step (1) is carried out at a temperature of 15-30℃ for 12-24 h.

4. The preparation method according to claim 1, characterized in that: The concentration of the tannic acid solution in step (2) is 24 mM and the pH is 8. The amount of tannic acid is calculated based on the mass ratio of the tannic acid to the in-situ doped ZIF-7 as 1.36:

1. The mass ratio of the amount of cobalt acetate tetrahydrate to the in-situ doped ZIF-7 is 1:

2.

5. The preparation method according to claim 1, characterized in that: The vacuum activation temperature in steps (1) and (2) is 60°C, and the time is 3-5 h.

6. The preparation method according to claim 1, characterized in that: The calcination in step (3) involves heating to 1000-1200℃ at a rate of 5℃ / min and holding at that temperature for 1-2 hours.

7. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of waterborne polyurethane to ZIF derivative is 100:10-20.

8. The preparation method according to claim 1, characterized in that: The polymerization temperature in step (4) is 15-30℃ and the time is 24 h.

9. A ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material prepared by the method described in claim 1.

10. The application of a ZIF-derived cobalt-based microwave absorbing and thermally conductive composite material as described in claim 9 in the fabrication of an integrated electromagnetic compatibility and thermal management structure for integrated circuit chips.

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