A MOF-derived iron monatomic-anchored nitrogen and phosphorus co-doped carbon-based wave-absorbing material, a preparation method and application thereof

Abstract

This invention provides a MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, its preparation method, and its applications. The preparation method involves dissolving an iron salt and a zinc salt in deionized water at a molar ratio of 0.01–0.04:1; dissolving a nitrogen-containing heterocyclic ligand in deionized water; mixing the two solutions and reacting them; separating and drying the products after the reaction to obtain an Fe / Zn-ZIF-L precursor; and then pyrolyzing the precursor at high temperature under a protective atmosphere to introduce a phosphorus-containing compound, thereby obtaining the microwave absorbing material. This invention utilizes the natural confinement effect of the MOF precursor and the abundant atomic-level vacancies generated by the thermal volatilization of Zn sites to achieve stable anchoring of Fe atoms in the carbon framework with a Fe-Nx coordination structure, while simultaneously forming a microporous-mesoporous hierarchical structure and an interwoven one-dimensional carbon nanotube network. The resulting material is beneficial for optimizing impedance matching, enhancing conductivity loss, dipole polarization loss, and interfacial polarization loss, and promoting electromagnetic wave multiple scattering.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials, and in particular relates to a MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, its preparation method, and its application. Background Technology

[0002] With the rapid development of electronic information, wireless communication, radar detection, and high-frequency device technologies, electromagnetic waves are increasingly widely used in military, industrial, and civilian fields. At the same time, electromagnetic interference and pollution caused by electromagnetic radiation are becoming increasingly prominent. Excessive electromagnetic waves can not only affect the normal operation of electronic equipment but may also have adverse effects on human health and national defense security. Therefore, the development of lightweight, efficient, and broadband microwave absorbing materials is of great significance.

[0003] Carbon-based materials have attracted widespread attention in the field of microwave absorption due to their advantages such as low density, good chemical stability, strong corrosion resistance, and tunable conductivity. However, traditional carbon materials often suffer from poor impedance matching performance and relatively simple loss mechanisms, causing incident electromagnetic waves to be easily reflected at the material surface and difficult to penetrate into the material and be effectively dissipated. Therefore, how to simultaneously improve impedance matching and dielectric loss capabilities through structural design and compositional control has become a key issue in the research of carbon-based microwave absorbing materials.

[0004] To improve the microwave absorption performance of carbon-based materials, researchers typically employ strategies such as constructing porous structures, hollow structures, and one-dimensional conductive networks, or introducing heteroatoms for doping. On the one hand, hierarchical porous structures can reduce the equivalent dielectric constant of the material, optimize impedance matching, and extend the propagation path of electromagnetic waves within the material through multiple scattering. On the other hand, doping with heteroatoms such as N and P can disrupt the charge distribution symmetry of the carbon framework, induce defects and dipole centers, thereby enhancing dipole polarization and interfacial polarization losses.

[0005] To address the shortcomings of traditional metal / carbon composite systems, such as low atom utilization, percolation effect, and skin effect, anchoring metal single atoms in carbon-based materials to achieve atomic-level control is a breakthrough approach for designing high-performance electromagnetic wave absorbing materials. Its core advantages lie primarily in the construction of atomic-level polarization centers and the asymmetric control of electronic structure. The charge distribution within metal nanoparticles is relatively uniform, and their electromagnetic loss mainly depends on interfacial polarization at the heteroatom interface. In contrast, single-atom sites, by anchoring isolated metal atoms with stable chemical bonds in a heteroatom-doped carbon lattice, break the original electronic symmetry within the material. Due to significant charge transfer between the metal atom and surrounding coordinating atoms, an extremely strong local electric dipole moment is formed around the single-atom center. This atomic-scale dipole exhibits high-frequency directional polarization under alternating electromagnetic fields, with polarization intensity and density far exceeding that of the heteroatom interface, thus significantly enhancing the material's dielectric loss capability. However, during high-temperature heat treatment, metal atoms are prone to migration and aggregation, making it difficult to maintain a stable single-atom dispersion state, which limits its application in microwave absorbing materials.

[0006] Metal-organic frameworks (MOFs) possess advantages such as tunable composition and structure, abundant pores, and uniform distribution of metal nodes, making them ideal precursors for constructing single-atom carbon-based microwave absorbing materials. During pyrolysis, MOFs retain some of the porous structure of the precursor and provide a natural confinement environment for metal sites at the molecular scale, effectively suppressing metal atom aggregation. Furthermore, nitrogen-containing organic ligands can form stable M-Nx coordination structures after carbonization. If a phosphorus source is further introduced during pyrolysis to achieve N and P co-doping, it is expected to further regulate the electronic structure, defect structure, and impedance matching performance of the material.

[0007] Some MOF-derived carbon-based microwave absorbing materials utilize metals such as iron, cobalt, and nickel, or metal carbides, to catalyze the growth of carbon nanotubes, thereby constructing low-dimensional carbon networks. However, these materials typically rely on metal nanoparticles or metal carbide particles for their function. Iron tends to aggregate, making atomic-scale dispersion difficult. Furthermore, they primarily depend on the conductive losses of the carbon network and the magnetic losses of the metal particles, lacking a synergistic electronic regulation mechanism between metal single-atom sites and N / P heteroatom co-doping.

[0008] Therefore, it is necessary to provide a high-performance microwave absorbing material based on MOF precursors, capable of stably anchoring iron single atoms and possessing nitrogen-phosphorus co-doping, hierarchical porous structure and one-dimensional carbon nanotube network. Summary of the Invention

[0009] In view of this, to solve the above-mentioned technical problems, this invention proposes a MOF-derived iron single-atom anchored nitrogen and phosphorus co-doped carbon-based microwave absorbing material, its preparation method, and its application. By constructing a low-iron, zinc-rich Fe / Zn-ZIF-L precursor and simultaneously introducing a phosphorus source through high-temperature pyrolysis under a protective atmosphere, stable anchoring of Fe single atoms and synergistic doping of N and P atoms are achieved, with iron forming Fe-N... x The single-atom form of the coordination structure is anchored in the nitrogen-phosphorus co-doped carbon framework, constructing a fine structure of Fe single atom-N coordination-N / P co-doped carbon framework, obtaining a microwave absorbing material with a multi-level porous structure and a one-dimensional carbon nanotube network, which significantly improves the impedance matching capability and dielectric loss capability of the material.

[0010] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0011] This invention provides a method for preparing MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials, comprising the following steps:

[0012] S1. Dissolve zinc salt and iron salt in deionized water to obtain a metal salt solution; wherein the molar ratio of iron salt to zinc salt is 0.01 to 0.04:1;

[0013] S2. Dissolve the nitrogen-containing heterocyclic ligand in deionized water to obtain a ligand solution;

[0014] S3. Add the metal salt solution to the ligand solution to carry out the reaction. After the reaction is completed, separate and dry the product to obtain the Fe / Zn-ZIF-L precursor.

[0015] S4. The Fe / Zn-ZIF-L precursor is subjected to high-temperature pyrolysis under a protective atmosphere, and phosphorus-containing compounds are introduced during the pyrolysis process to obtain the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material. Iron is anchored in the nitrogen-phosphorus co-doped carbon framework in the form of single atoms with Fe-Nx coordination structure, thus constructing a fine structure of Fe single atom-N coordination-N / P co-doped carbon framework.

[0016] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in S1, the zinc salt is any one or more of zinc nitrate hexahydrate, zinc acetate dihydrate, zinc chloride, and zinc sulfate heptahydrate; the iron salt is any one or more of ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric nitrate nonahydrate, ferrous nitrate, ferrous sulfate heptahydrate, ferrous sulfate, ferric acetate, and ferrous acetate.

[0017] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in step S1, the molar ratio of iron salt to zinc salt is 0.02:1; the concentration of zinc salt in the metal salt solution is 0.1 mol / L to 0.15 mol / L.

[0018] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in S2, the nitrogen-containing heterocyclic ligand is 2-methylimidazole; or a mixture of 2-methylimidazole and at least one imidazole ligand selected from imidazole, 4-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, and 2-aminoimidazole.

[0019] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, the concentration of the ligand solution in S2 is 0.5 mol / L.

[0020] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in step S3, the volume ratio of metal salt solution to ligand solution is 1:1; after the metal salt solution is added to the ligand solution, the mixture is stirred and reacted at room temperature for 8 to 14 hours; the drying method is vacuum drying at a temperature of 50 to 80°C for 8 to 12 hours.

[0021] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in step S4, the protective atmosphere is nitrogen or argon; the phosphorus-containing compound is sodium dihydrogen phosphate, disodium hydrogen phosphate, or sodium phosphate; and the mass ratio of the phosphorus-containing compound to the Fe / Zn-ZIF-L precursor is 1:40.

[0022] In some preferred embodiments of the preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials of the present invention, in step S4, the high-temperature pyrolysis conditions are to heat to 800-950°C at a heating rate of 1-5°C / min, hold at that temperature for 2-4 hours, and then allow to cool naturally.

[0023] Another aspect of the present invention provides a MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, wherein the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material has a microporous-mesoporous hierarchical porous structure and a one-dimensional hollow carbon nanotube network structure, wherein the Fe atoms are arranged in Fe-N x The single-atom form of the coordination structure is anchored in the nitrogen-phosphorus co-doped carbon framework.

[0024] Fe exists in a highly dispersed single-atom dispersion form, rather than aggregated as metal nanoparticles or clusters. P, as a secondary shell atom, effectively modulates the Fe-N mixture. x The local symmetry and electron density distribution at the sites induce a high density of dipole centers. Under the influence of a high-frequency alternating electric field, these polar sites undergo strong dipole-directed polarization relaxation, which can significantly enhance the electromagnetic wave attenuation capability of the material.

[0025] The third aspect of this invention provides the use of a MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, wherein the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material is used in the field of microwave absorption.

[0026] The MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material is combined with paraffin, resin, rubber or polymer matrix to prepare coatings, films, sheets or structural components for electromagnetic shielding, radar stealth, electromagnetic interference protection of electronic devices, protection of communication equipment and electromagnetic protection in aerospace, etc., and is especially suitable for electromagnetic wave absorption in the 2 to 18 GHz frequency band.

[0027] Compared with existing technologies, the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, its preparation method, and its application described in this invention have the following advantages:

[0028] (1) This invention uses Fe / Zn-ZIF-L as a self-template precursor, and through low-iron-rich zinc composition design, high-temperature confined pyrolysis and in-situ phosphorus source introduction, realizes Fe single atoms in Fe-N x The coordination structure is stably anchored within the N and P co-doped carbon framework, simultaneously constructing a microporous-mesoporous hierarchical structure and a one-dimensional hollow carbon nanotube conductive network. The prepared material exhibits excellent microwave absorption performance due to the synergistic effect of Fe single-atom polarization centers, N / P heteroatom defects, hierarchical pore scattering, and CNT conductive pathways, which significantly optimize impedance matching and enhance electromagnetic wave attenuation.

[0029] (2) This invention uses MOF as a self-template precursor, which eliminates the need for an additional template removal process and simplifies the process. It mainly achieves the synergistic effect mechanism of "precursor confinement - atomic-level anchoring - heteroatom regulation - structure-guided growth". It is not a simple addition of components, but rather achieves the simultaneous construction of single-atom sites, heteroatom doping, multi-level porous structure and one-dimensional conductive network through precursor design. It constructs a fine structure of Fe single atom-N coordination-N / P co-doped carbon skeleton, which provides an effective way for the preparation of high-performance carbon-based microwave absorbing materials and shows broad application prospects in the field of microwave absorption.

[0030] (3) In this invention, the content of Zn in the MOF precursor is much higher than that of Fe. The high concentration of Zn atoms acts as an atomic spacer in carbonization, effectively suppressing the migration and collision of Fe atoms at high temperature through spatial confinement effect. By utilizing the natural confinement effect of metal nodes in the MOF precursor and the volatilization effect of Zn in the pyrolysis process, abundant atomic-level vacancies are formed in the carbon skeleton, so that Fe atoms are stably anchored in Fe-Nx structure, thereby avoiding the formation of iron nanoclusters or nanoparticles under high temperature conditions.

[0031] (4) The present invention constructs a microporous-mesoporous multi-level pore structure through MOF pyrolysis and Zn volatilization process, which is beneficial to optimize impedance matching, reduce electromagnetic wave surface reflection, and enhance the multiple reflection and scattering of electromagnetic waves inside the material.

[0032] (5) In this invention, Fe sites induce the formation of an interwoven one-dimensional carbon nanotube network during high-temperature pyrolysis, which is beneficial for constructing a continuous electron transport pathway and enhancing the material's conductivity loss capability.

[0033] (6) In this invention, the electronic structure of the carbon skeleton is synergistically regulated by N and P atom co-doping and Fe single atom sites, inducing abundant defect sites and dipole polarization centers, thereby enhancing dipole polarization loss and interface polarization loss.

[0034] (7) The MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material prepared by the present invention has both good impedance matching and strong electromagnetic wave attenuation capability, and can achieve excellent microwave absorption performance under conditions of low filling amount and thin thickness. Attached Figure Description

[0035] Figure 1 middle: Figure 1 (a) Fe prepared in Example 1 0.02 SEM images of / Zn-ZIF-L; Figure 1 (b) is Fe 0.02 -NPC's SEM; Figure 1 (c) is Fe 0.02 - TEM images of NPC; Figure 1 (d) represents Fe 0.02 -NPC's STEM images; Figure 1 (e) represents Fe 0.02 -NPC's EDS map; Figure 1 (f) represents Fe 0.02 HAADF-STEM image of NPC;

[0036] Figure 2 middle: Figure 2 (a) is a SEM image of the NPC prepared in Comparative Example 1; Figure 2 (b) Fe prepared in Example 20.01 -SEM image of NPC; Figure 2 (c) Fe prepared in Example 3 0.04 -SEM image of NPC;

[0037] Figure 3 middle: Figure 3 (a) NPC and Fe prepared in the examples and comparative examples 0.01 -NPC, Fe 0.02 -NPC, Fe 0.04 -NPC's XRD pattern; Figure 3 (b) NPC and Fe prepared in the examples and comparative examples 0.01 -NPC, Fe 0.02 -NPC, Fe 0.04 - Raman spectrum of NPC;

[0038] Figure 4 NPC and Fe prepared in the examples and comparative examples 0.01 -NPC, Fe 0.02 -NPC, Fe 0.04 -NPC polarization loss;

[0039] Figure 5 middle: Figure 5 (a) A three-dimensional plot of reflection loss of the NPC prepared as a comparative example; Figure 5 (b) A two-dimensional projection of the NPC prepared as a comparative example; Figure 5 (c) A graph of the NPC prepared as a comparative example; Figure 5 (d) Fe prepared in Example 2 0.01 - 3D diagram of reflection loss of NPC; Figure 5 (e) Fe prepared in Example 2 0.01 -A two-dimensional projection of the NPC; Figure 5 (f) Fe prepared in Example 2 0.01 -NPC's graph; Figure 5 (g) is Fe prepared in Example 1 0.02 - 3D diagram of reflection loss of NPC; Figure 5 (h) is Fe prepared in Example 1 0.02 -A two-dimensional projection of the NPC; Figure 5 (i) Fe prepared in Example 1 0.02 -NPC's graph; Figure 5 (j) is Fe prepared in Example 3 0.04 - 3D diagram of reflection loss of NPC; Figure 5 (k) is Fe prepared in Example 3 0.04 -A two-dimensional projection of the NPC; Figure 5 (l) Fe prepared in Example 30.04 -NPC's graph. Detailed Implementation

[0040] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0041] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0042] Example 1

[0043] The steps for preparing MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon nano-based microwave absorbing materials are as follows:

[0044] (1) Preparation of precursor Fe / Zn-ZIF-L

[0045] 1.487 g Zn(NO3)2·6H2O and 20 mg FeCl3·6H2O were dissolved in 40 mL of deionized water to form a homogeneous metal salt solution.

[0046] 1.64 g of 2-methylimidazole was dissolved in 40 mL of deionized water to form a clear solution, thus obtaining the ligand solution;

[0047] The metal salt solution was added to the ligand solution, and the mixture was stirred vigorously at room temperature for 12 h to ensure complete reaction. After the reaction was complete, the product was collected by centrifugation and dried in a vacuum drying oven to obtain the precursor Fe. 0.02 / Zn-ZIF-L sample;

[0048] (2) Preparation of microwave absorbing materials

[0049] 400 mg Fe 0.02 / Zn-ZIF-L powder is evenly spread in the crucible and placed in the downstream area of ​​the tube furnace;

[0050] 10 mg of sodium dihydrogen phosphate was placed in another crucible and positioned upstream of the tube furnace;

[0051] Under a nitrogen atmosphere, the tube furnace was heated to 900 °C at a rate of 2 °C / min. The precursor Fe... 0.02 / Zn-ZIF-L underwent pyrolysis at this temperature for 3 hours; after the reaction was complete, the furnace was allowed to cool naturally to room temperature, and the resulting black powder sample was labeled as Fe. 0.02 -NPC.

[0052] Example 2

[0053] The amount of ferric chloride hexahydrate added in Example 1 was adjusted to 10 mg, and the remaining steps were the same as in Example 1. The resulting sample was denoted as Fe. 0.01 -NPC.

[0054] Example 3

[0055] The amount of ferric chloride hexahydrate added in Example 1 was adjusted to 40 mg, and the remaining steps were the same as in Example 1. The resulting sample was denoted as Fe. 0.04 -NPC.

[0056] Comparative Example 1

[0057] Ferric chloride hexahydrate was not added, and the remaining steps were the same as in Example 1. The resulting sample was denoted as NPC.

[0058] Fe prepared in Examples 1-3 0.01 -NPC, Fe 0.02 -NPC and Fe 0.04 -The structure and properties of the NPC and the NPC prepared in Comparative Example 1 were characterized.

[0059] (1) The morphology of the sample was characterized by scanning electron microscopy and transmission electron microscopy.

[0060] Figure 1 This indicates that Fe 0.02 The Zn-ZIF-L precursor exhibits a two-dimensional leaf-like structure; after high-temperature pyrolysis, the sample transforms into a hollow carbon nanotube structure. STEM and EDS mapping results show that N, P, and Fe elements are uniformly distributed within the carbon framework. Isolated bright spots are observed in the HAADF-STEM image, indicating that Fe is highly dispersed in the sample in single-atom form.

[0061] Figure 2 This indicates that no carbon nanotube structures were detected in NPC without an iron source. Figure 2 a) This indicates that the carbon substrate itself does not possess the driving force to form a one-dimensional structure. However, in Fe... 0.01 In the -NPC sample, due to the introduction of a small amount of Fe, fine carbon nanotube structures were observed in the sample edge region. Figure 2 (b) This demonstrates that even a small number of Fe centers possess catalytic activity, capable of inducing localized bending and growth of the carbon layer. With Fe... 3+ / Zn 2+ When the ratio increases to 0.04:1, in Fe 0.04 Larger diameter carbon nanotube structures can be observed in the SEM images of -NPC. Figure 3 c). Fe single atoms can act as structure directing agents during pyrolysis. By adjusting the Fe doping concentration, the distribution density of carbon nanotubes can be controlled.

[0062] (2) Figure 3 XRD results showed that NPC and Fe 0.01 -NPC, Fe 0.02 -NPC and Fe 0.04 The NPC sample exhibited diffraction peaks at approximately 25.3° and 43.9° of 2θ, corresponding to the (002) and (101) crystal planes of graphitic carbon, respectively. No obvious characteristic diffraction peaks of metallic iron or iron oxides were detected, indicating that Fe did not form detectable crystalline particles. Raman spectroscopy results showed that Fe... 0.02 -NPC has a high ID / IG value, indicating that it has abundant defect sites, which is beneficial to enhance dipole polarization loss.

[0063] (3) Put NPC, Fe 0.01 -NPC, Fe 0.02 -NPC and Fe 0.04 - After uniformly mixing NPC samples and paraffin wax at a mass ratio of 20:80, the paraffin wax was placed in an oven and heated for a period of time until melted, and then further stirred until homogeneous. After cooling, the samples were molded into coaxial rings with an outer diameter of 7 mm, an inner diameter of 3.04 mm, and a thickness of 2 mm. The electromagnetic parameters of each sample in the frequency range of 2-18 GHz were tested using an Agilent E5071C vector network analyzer.

[0064] Figure 4 The results showed that Fe 0.02 -NPC exhibits a higher polarization loss value, indicating that the appropriate introduction of Fe single atoms and the doping of N and P atoms in the carbon matrix construct a higher density of defect sites, combined with Fe-N x The single-atom sites in the coordination structure further modulate the electronic structure of the carbon framework and induce a high density of dipole centers, thereby triggering strong polarization losses. Under the action of a high-frequency alternating electric field, these polar sites undergo strong dipole-direction polarization relaxation, significantly enhancing the material's electromagnetic wave attenuation capability.

[0065] (4) In order to study the reflection loss (RL) distribution of composite materials under different thicknesses and frequencies, the RL value of composite materials was calculated based on transmission line theory. Figure 5 For NPC, Fe 0.01 -NPC, Fe 0.02 -NPC, Fe 0.04 - 3D plot, 2D projection plot, and curve plot of NPC's reflection loss. Fe 0.02 -NPC exhibits the best absorption performance, achieving a minimum reflection loss of -63.7 dB and an effective absorption bandwidth of 4.7 GHz with a matching thickness of 2.7 mm. In contrast, Fe... 0.04-NPC has a high Fe content, which leads to increased graphitization, poor impedance matching, and a reduction in defect sites, thus reducing its microwave absorption performance.

[0066] Impedance matching analysis shows that Fe 0.02 -NPC exhibits a normalized input impedance closer to the ideal value over a wider frequency range, indicating that it is more conducive to electromagnetic waves penetrating the material's interior. Attenuation constant analysis further shows that Fe... 0.02 -NPC exhibits strong electromagnetic wave attenuation capabilities. Therefore, the excellent absorption performance of this sample stems from the synergistic effect of good impedance matching and strong attenuation capabilities.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material, characterized in that, Includes the following steps: S1. Dissolve zinc salt and iron salt in deionized water to obtain a metal salt solution; wherein the molar ratio of iron salt to zinc salt is 0.01 to 0.04:1; S2. Dissolve the nitrogen-containing heterocyclic ligand in deionized water to obtain a ligand solution; S3. Add the metal salt solution to the ligand solution to carry out the reaction. After the reaction is completed, separate and dry the product to obtain the Fe / Zn-ZIF-L precursor. S4. The Fe / Zn-ZIF-L precursor is subjected to high-temperature pyrolysis under a protective atmosphere, and phosphorus-containing compounds are introduced during the pyrolysis process to obtain the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material.

2. The preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In S1, the zinc salt is any one or more of zinc nitrate hexahydrate, zinc acetate dihydrate, zinc chloride, and zinc sulfate heptahydrate; the iron salt is any one or more of ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric nitrate nonahydrate, ferrous nitrate, ferrous sulfate heptahydrate, ferrous sulfate, ferric acetate, and ferrous acetate.

3. The preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In S1, the molar ratio of iron salt to zinc salt is 0.02:1; the concentration of zinc salt in the metal salt solution is 0.1 mol / L to 0.15 mol / L.

4. The method for preparing MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In S2, the nitrogen-containing heterocyclic ligand is 2-methylimidazole; Or a mixture of 2-methylimidazole and at least one imidazole ligand selected from imidazole, 4-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, and 2-aminoimidazole.

5. The preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In S2, the concentration of the ligand solution is 0.5 mol / L.

6. The preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In step S3, the volume ratio of the metal salt solution to the ligand solution is 1:1; after the metal salt solution is added to the ligand solution, the mixture is stirred at room temperature for 8–14 h; the drying method is vacuum drying at a temperature of 50–80 °C for 8–12 h.

7. The preparation method of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In step S4, the protective atmosphere is nitrogen or argon; the phosphorus-containing compound is sodium dihydrogen phosphate, disodium hydrogen phosphate, or sodium phosphate; and the mass ratio of the phosphorus-containing compound to the Fe / Zn-ZIF-L precursor is 1:

40.

8. The method for preparing MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 1, characterized in that: In S4, the high-temperature pyrolysis conditions are to heat to 800-950°C at a heating rate of 1-5°C / min, hold at that temperature for 2-4 hours, and then allow to cool naturally.

9. The MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material has a microporous-mesoporous hierarchical porous structure and a one-dimensional hollow carbon nanotube network structure, wherein iron is in the form of Fe-N x The single-atom form of the coordination structure is anchored in the nitrogen-phosphorus co-doped carbon framework.

10. The use of the MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing material according to claim 9, characterized in that: Application of MOF-derived iron single-atom anchored nitrogen-phosphorus co-doped carbon-based microwave absorbing materials in the field of microwave absorption.

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