Intrinsic conductive metal organic framework material for efficient electromagnetic wave absorption and preparation method of intrinsic conductive metal organic framework material

Abstract

The invention discloses an intrinsic conductive metal organic framework material for efficient electromagnetic wave absorption and a preparation method of the intrinsic conductive metal organic framework material. According to the method, octahydroxy tetraphenyl selenopheno [3, 2-b] thiophene containing polarization factors is taken as a secondary building unit, coordination self-assembly is carried out through hydroxyl and metal copper salt, and the intrinsic conductive metal organic framework material SeT-OH-MOF is generated in one pot through a solvothermal method. The SeT-OH-MOF has efficient electromagnetic wave absorption, the reflection loss is up to-51dB, the thickness of the absorbent is 2.5 mm, the filling amount is only 25%, and far exceeds that of the same type of materials, and the SeT-OH-MOF has wide application prospects in the field of electromagnetic wave absorption.

Description

Technical Field

[0001] The present invention belongs to the field of metal-organic framework compounds, and relates to an intrinsically conductive metal-organic framework material for efficient electromagnetic wave absorption and a preparation method thereof. Background Art

[0002] The advent of the 5G era and the widespread adoption of terahertz technology have greatly promoted the development and utilization of electronic products, radar stealth detection, and related applications. However, these advancements will inevitably lead to a large amount of electromagnetic wave radiation, which will seriously interfere with communication networks and pose a health risk. Therefore, green electromagnetic wave absorbers (EMWAs) have become an indispensable part of radio frequency communication systems. In recent decades, various high-performance EMWAs, including ferrites, aerogels, metal oxides, synthetic resins, especially metal-organic framework (MOF) derivatives, have made great progress. Due to their highly regular topological structures and customizable functional properties, MOFs have become outstanding candidates in various fields. Especially in the field of EMWAs, the excellent porosity of MOFs, characterized by light structures, large surface areas, rich electron transport channels, and multivariable polarization sites, shows their key role in advancing EM functional materials. Developing multifunctional new EMWAs based on MOFs has become a frontier challenge in this field.

[0003] Although MOF-based electromagnetic wave absorbers have attracted extensive attention, some key challenges remain unresolved. First, current research mainly focuses on MOF-derived materials (Jiang C, Wen B. Construction of 1D heterogeneous Co / C@Ag nws with tunable electromagnetic wave absorption and shielding performance. Small. 2023, 19, 2301760). However, the high-temperature pyrolysis and guest doping processes often damage the intrinsic porous structure of MOFs, resulting in the loss of precise atomic-resolution structures. This hinders mass production, reproducibility, and especially the elucidation of the absorption mechanism. Second, the inherently low dielectric constant, weak magnetic effect, and limited electromagnetic wave loss mechanisms of pristine MOFs make them unable to meet the requirements of complex applications. Although dielectric polarization has been proven to effectively enhance absorption performance (Ma Z, Yang K, Li D, et al. The electron migration polarization boosting electromagnetic wave absorption based on Ce atoms modulated yolk@shell FexN@NGC.. Adv. Mater. 2024, 36, 2314233), accurately integrating the polarization factor into the pristine MOF structure to achieve natural polarization effects while maintaining framework stability remains a great challenge. Third, previous studies have identified various factors affecting the absorption performance of MOFs, including carbonization temperature, oxygen vacancy concentration, multi-metal synergistic effects, and defect sites (Yao L H, Shu J C, Zhao J G, et al. Heterodimensional Structure Integrating Electromagnetic Functions and Hybrid Energy Storage to Drive Multifunctional Devices. Adv. Funct. Mater. 2024, 2410928). From a crystallographic perspective, modifying the connection mode of secondary building units (SBUs) to generate different structures can effectively customize the geometric configuration, microstructure, polarization sites, and electromagnetic parameters of MOFs, all of which affect their final absorption performance. Summary of the Invention

[0004] The object of the present invention is to provide an intrinsically conductive metal-organic framework material for efficient electromagnetic wave absorption and a preparation method thereof. The present invention uses a selenophenothiophene group as a secondary building unit to construct a MOF material with unique properties. The introduction of the selenophenothiophene group not only enhances the conductivity of the material, endowing it with excellent electromagnetic wave absorption performance, but also exhibits good stability and processability.

[0005] The technical solution for achieving the object of the present invention is as follows:

[0006] The intrinsically conductive metal-organic framework material is SeT-OH-MOF, which is a one-dimensional chain structure synthesized by the formation of O---Cu---O coordination bonds between four hydroxyl groups in octahydroxyphthalocyanine [9,10-b]phthalocyanine [9',10':4,5]selenopheno[2,3-d]thiophene and metal copper ions. Its structural formula is as follows:

[0007]

[0008] The preparation method of the above-mentioned intrinsically conductive metal-organic framework material involves the following partial reaction routes:

[0009]

[0010]

[0011] It includes the following steps:

[0012] (1) Mix selenopheno[3,2-b]thiophene (TS), chloroform and glacial acetic acid and stir to dissolve, then slowly add liquid bromine, react at 60±5 °C, cool to room temperature after the reaction, add the reaction solution to a saturated sodium bisulfite solution, filter under vacuum, and filter the filter cake with water and ethanol in sequence to obtain perbrominated selenopheno[3,2-b]thiophene (TS-4Br);

[0013] (2) Mix TS-4Br, (3,4-dimethoxyphenyl)boronic acid, tetrakis(triphenylphosphine)palladium (Pd(PPh3)4), and K2CO3, evacuate, add anaerobic tetrahydrofuran (THF) and anaerobic water under an argon atmosphere, stir and react at 100±5 °C, cool to room temperature, then remove the solvent under reduced pressure and purify to obtain 2,3,5,6-tetrakis(3,4-dimethoxyphenyl)selenopheno[3,2-b]thiophene (TBTS-8OCH3);

[0014] (3) Evacuate TBTS-8OCH3, add anaerobic CH2Cl2 under an argon atmosphere, cool to 0 °C, add BBr3 solution, stir and react at room temperature, quickly quench the excess BBr3 with water, and obtain octahydroxytetraphenylselenopheno[3,2-b]thiophene (TBTS-8OH) by pumping and filtering;

[0015] (4) TBTS-8OH and anhydrous copper nitrate were added to a 50% ethanol solution, and ultrasonic dissolution was carried out until completely mixed evenly. Then, hydrothermal reaction was carried out at 100-120 °C. After the reaction ended, solid powder was obtained by suction filtration, and then washed three times with deionized water and ethanol respectively. Finally, it was vacuum dried overnight to obtain the intrinsic conductive metal-organic framework material SeT-OH-MOF.

[0016] Preferably, in step (4), the mass ratio of TBTS-8OH to anhydrous copper nitrate is 3:4.

[0017] Preferably, in step (4), the reaction time is 3 days.

[0018] Application of the above-mentioned intrinsic conductive metal-organic framework material as an electromagnetic shielding material in electromagnetic wave absorption.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] In the present invention, the intrinsic conductive MOF is generated in one pot by the solvothermal method, and the preparation of the metal-organic framework material is simply realized, with an accurate atomic resolution structure and a clear absorption mechanism. Without any post-treatment, high-efficiency electromagnetic wave absorption is achieved by regulating the conductivity of the material. The reflection loss is as high as -51 dB, the absorber thickness is 2.5 mm, and the filling amount is only 25%, far exceeding the same type of materials, and having broad application prospects in the field of electromagnetic wave absorption. Description of the Drawings

[0021] Figure 1 It is the X-ray powder diffraction pattern of SeT-OH-MOF;

[0022] Figure 2 It is the specific surface area diagram of SeT-OH-MOF;

[0023] Figure 3 It is the electromagnetic wave absorption performance diagram of 25% SeT-OH-MOF filling amount and 75% paraffin. Among them, (a) is the 3D RL diagram of SeT-OH-MOF-25%, and (b) is the corresponding 2D diagram;

[0024] Figure 4 It is the electromagnetic wave absorption performance diagram of 40% SeT-OH-MOF filling amount and 60% paraffin. Among them, (a) is the 3D RL diagram of SeT-OH-MOF-40%, and (b) is the corresponding 2D diagram. Detailed Embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Unless otherwise stated in the context of this application, the professional terms and abbreviations used in this application are widely known to those skilled in the art; unless otherwise indicated as the manufacturer in the following text, they are all conventional products that can be obtained through commercial purchase.

[0026] Example 1

[0027] The synthesis of SeT-OH-MOF is as follows:

[0028] (1) TS-4Br: Add 5 g of selenophene[3,2-b]thiophene (TS), 100 mL of chloroform and 100 mL of glacial acetic acid to a 250 mL round-bottom flask, and stir to dissolve. Then slowly add 10 mL of liquid bromine to the reaction solution, heat to 60 °C and keep for 12 h. Cool to room temperature, pour the reaction solution into 500 mL of saturated sodium bisulfite solution, filter under vacuum, and filter the cake with water and ethanol in sequence to obtain a white solid TS-4Br.

[0029] (2) TBTS-8OCH3: Add TS-4Br (1.5 g, 3.3 mmol), (3,4-dimethoxyphenyl)boronic acid (3.0 g, 16.5 mmol), Pd(PPh3)4 (300 mg) and K2CO3 (4.5 g, 39.6 mmol) to a 250 mL Schlenk, then evacuate the Schlenk for 30 minutes, during which argon is pumped three times, and then add anaerobic THF (80 mL) and anaerobic water (20 mL) under an Ar atmosphere. Stir the reaction mixture at 100 °C for 36 hours. After cooling to room temperature, remove the solvent under reduced pressure. The crude product is purified by silica gel column chromatography with dichloromethane as the eluent to obtain 2.0 g of yellow powder TBTS-8OCH3, with a yield of 91%.

[0030] (3) TBTS-8OH: Add TBTS-8OCH3 (500 mg, 0.73 mmol) to a 100 mL Schlenk, then evacuate the Schlenk for 30 minutes, during which argon is pumped three times, and then add anaerobic CH2Cl2 (20 mL) under an Ar atmosphere. Cool to 0 °C, add 17.5 mL of BBr3 solution (1 M CH2Cl2 solution), then raise the temperature to room temperature and stir for 5 hours. At the end of the reaction, quench the excess BBr3 with water, and obtain 396 mg of white TBTS-8OH powder by pumping and filtration, with a yield of 93%.

[0031] (4) Synthesis of SeT-OH-MOF: Weigh 12 mg of TBTS-8OH and 20 mg of anhydrous copper nitrate, add them into a 10 ml scintillation vial, then add 1 ml of ethanol and 1 ml of deionized water, and ultrasonically dissolve until completely and uniformly mixed. Then, seal the scintillation vial and place it in a high-temperature oven at 100 °C for 3 days. Filter by suction to obtain the required solid powder, and then wash it three times with deionized water and ethanol respectively. Finally, dry it overnight under vacuum at 60 °C to obtain the target product SeT-OH-MOF.

[0032] The powder diffraction pattern and specific surface area / pore structure analysis diagram of the SeT-OH-MOF material are as Figure 1 , 2 shown, indicating that the material has an accurate atomically resolved structure and an excellent crystalline natural pore structure.

[0033] Example 2

[0034] Under the transmission and reflection mode of 2 - 18 GHz, measure the electromagnetic parameters of all samples on a vector network analyzer (Agilent PNA N5224A). Uniformly mix 25% of SeT-OH-MOF with 75% of paraffin at room temperature (SeT-OH-MOF-25%), and press it into a standard ring for measuring electromagnetic wave absorption.

[0035] The outer diameter, inner diameter, and thickness of the annular specimen are set to 7.00, 3.04, and 3.00 mm respectively. The relative dielectric constant of paraffin is relatively low, which means it is almost transparent to EMW. The microwave absorption characteristics of the sample mixed with paraffin can be used to characterize the properties of the material.

[0036] Measure the four specific electromagnetic parameters obtained, which are the real part of the dielectric constant, the imaginary part of the dielectric constant, the real part of the magnetic permeability constant, and the imaginary part of the magnetic permeability constant. By calculating and simulating these four parameters, the fitting values of the reflection loss (RL) and absorption thickness of electromagnetic waves are determined to evaluate the electromagnetic wave absorption performance of the material.

[0037] The electromagnetic wave absorption performance at a filling amount of 25% is as Figure 3 shown. In the case of a thickness of only 2.5 mm, the minimum reflection loss can reach up to -51 dB.

[0038] Example 3

[0039] Under the transmission and reflection mode of 2 - 18 GHz, measure the electromagnetic parameters of all samples on a vector network analyzer (Agilent PNA N5224A). Uniformly mix 40% of SeT-OH-MOF with 60% of paraffin at room temperature (SeT-OH-MOF-40%), and press it into a standard ring for measuring electromagnetic wave absorption.

[0040] The outer diameter, inner diameter, and thickness of the annular specimen were set to 7.00, 3.04, and 3.00 mm, respectively. Paraffin has a relatively low dielectric constant, which means it is almost transparent to EMW. The microwave absorption characteristics of the sample mixed with paraffin can be used to characterize the properties of the material.

[0041] Four specific electromagnetic parameters were measured, namely the real part of the dielectric constant, the imaginary part of the dielectric constant, the real part of the permeability constant, and the imaginary part of the permeability constant. By calculating and simulating these four parameters, the fitting values of the reflection loss (RL) and absorption thickness of electromagnetic waves were obtained to determine the electromagnetic wave absorption performance of the material.

[0042] The electromagnetic wave absorption performance at a 40% filling amount is as Figure 4 shown. It can be seen that the electromagnetic wave absorption performance of SeT-OH-MOF-25% is better than that of SeT-OH-MOF-40%. When the thickness is only 2.5 mm, the minimum reflection loss can reach up to -51 dB.

Claims

1. Intrinsically conductive metal-organic framework material, characterized in that, It is a one-dimensional chain structure synthesized by the four hydroxyl groups in octahydroxyphilo[9,10-b]philo[9',10':4,5]selenopheno[2,3-d]thiophene and metal copper ions through the formation of O---Cu---O coordination bonds. Its structural formula is as follows: .

2. The preparation method of the intrinsic conductive metal-organic framework material according to claim 1, characterized in that, It includes the following steps: (1) Mix selenophene[3,2-b]thiophene, chloroform and glacial acetic acid and stir to dissolve, then slowly add liquid bromine, react at 60±5 °C, cool to room temperature after the reaction, add the reaction solution to saturated sodium bisulfite solution, filter under vacuum, filter the cake with water and ethanol in sequence to obtain perbrominated selenophene[3,2-b]thiophene; (2) Vacuumize the mixture of perbrominated selenophene[3,2-b]thiophene, (3,4-dimethoxyphenyl)boronic acid, Pd(PPh3)4, and K2CO3, add anaerobic THF and anaerobic water under an argon atmosphere, stir and react at 100±5 °C, after cooling to room temperature, remove the solvent under reduced pressure, and purify to obtain 2,3,5,6-tetrakis(3,4-dimethoxyphenyl)selenophene[3,2-b]thiophene; (3) Vacuumize 2,3,5,6-tetrakis(3,4-dimethoxyphenyl)selenophene[3,2-b]thiophene, add anaerobic CH2Cl2 under an argon atmosphere, cool to 0 °C, add BBr3 solution, stir and react at room temperature, quickly quench the excess BBr3 with water, and obtain octahydroxytetraphenylselenophene[3,2-b]thiophene by pumping and filtering; (4) Add octahydroxytetraphenylselenophene[3,2-b]thiophene and anhydrous copper nitrate to a 50% ethanol solution, ultrasonically dissolve until completely and evenly mixed, then carry out hydrothermal reaction at 100-120 °C, after the reaction is completed, filter to obtain a solid powder, then wash it three times each with deionized water and ethanol, and finally dry it overnight under vacuum to obtain the intrinsic conductive metal-organic framework material SeT-OH-MOF.

3. The preparation method according to claim 2, characterized in that, In step (4), the mass ratio of octahydroxytetraphenylselenophene[3,2-b]thiophene to anhydrous copper nitrate is 3:

4.

4. The preparation method according to claim 2, wherein, In step (4), the reaction time is 3 days.

5. Application of the intrinsic conductive metal-organic framework material described in claim 1 as an electromagnetic shielding material in electromagnetic wave absorption.

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