Trimetal MOFs / MXene derived aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of aerogel wave-absorbing materials, and particularly relates to trimetal MOFs / MXene derived aerogel as well as a preparation method and application thereof. According to the preparation method, Ni (NO3) 2.6 H2O, Co (NO3) 2.6 H2O and Cu (NO3) 2.3 H2O are used as metal sources, water-induced self-assembly, freeze drying and heat treatment are performed to prepare the aerogel, and the aerogel is of a 0D / 1D / 2D composite structure and contains nano twin crystals. The MXene content and the filler content are regulated and controlled to optimize the performance, the minimum reflection loss of the optimal sample NiCoCu / MX5-A reaches-83.73 dB, and the effective absorption bandwidth is 6.46 GHz. The aerogel has the advantages of light weight (9.2 mg.cm <-3 >), heat insulation, 82.93% photothermal conversion efficiency, 102.4 kPa compressive strength and hydrophobic property, is suitable for the fields of electromagnetic protection and the like, and provides support for design of multi-element aerogel-based wave-absorbing materials.

Description

A trimetallic MOFs / MXene-derived aerogel, its preparation method and application Technical Field

[0001] This invention belongs to the field of aerogel absorbing materials technology, specifically relating to a trimetallic MOFs / MXene derived aerogel, its preparation method, and its application. Background Technology

[0002] With the rapid development of modern science and technology and industry, electromagnetic radiation pollution has become an increasingly prominent problem, posing a serious threat to the normal operation of electronic equipment, human health, and information security. Therefore, the development of high-performance electromagnetic absorbing materials (EMWA materials) has become a research hotspot. Ideal EWA materials need to possess characteristics such as lightweight, wide absorption bandwidth, high absorption intensity, good environmental adaptability, and multifunctional integration to meet the needs of different application scenarios.

[0003] Metal-organic frameworks (MOFs) possess advantages such as high specific surface area, controllable pore structure, and abundant constituent elements, and their derivatives show great potential in the field of electromagnetic wave absorption. MXene, as a novel two-dimensional layered material, has excellent conductivity, a unique layered structure, and good chemical stability. Combining it with MOFs can synergistically optimize wave absorption performance.

[0004] In the existing technology, relevant research has been carried out on bimetallic MOFs / MXene-derived aerogels, and two core laws have been identified: First, the synergistic effect of bimetals can optimize the microwave absorption performance of materials by regulating the dielectric / magnetic loss balance; second, the three-dimensional porous structure of aerogels can effectively overcome the limitations of high density and low porosity of composite powders, greatly enhance the lightweight properties and multi-interface loss effect of materials, and provide a structural basis for multifunctional integration.

[0005] However, the limited range of electronic structure and phase evolution in bimetallic MOFs / MXene aerogel systems makes it difficult to achieve finer electromagnetic parameter control and wider absorption coverage, thus restricting their application in high-performance microwave absorption scenarios. In contrast, trimetallic MOFs / MXene systems can incorporate more variable-valence metals. Through the synergistic control of the trimetallic electronic structure and the interaction between multiple elements, they can provide a broader scope for further fine optimization of electromagnetic parameters and the achievement of broadband microwave absorption.

[0006] Based on the existing research foundation and shortcomings of the above-mentioned technologies, developing a trimetallic MOFs / MXene-derived aerogel with superior performance and more comprehensive functions, as well as its preparation method, is of great significance for promoting the development of electromagnetic absorbing materials. Summary of the Invention

[0007] The purpose of this invention is to provide a trimetallic MOFs / MXene-derived aerogel, its preparation method, and its application. It is not only suitable for the field of electromagnetic protection, but also meets the diversified needs of lightweight heat insulation and photothermal utilization. It provides a new path for the multifunctional and practical development of aerogel-based microwave absorbing materials and has important theoretical and practical application value.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] This invention provides a trimetallic MOFs / MXene-derived aerogel, which is prepared by water-induced self-assembly of a trimetallic NiCoCu-BTC precursor and MXene, freeze-drying, and heat treatment. The aerogel has an 0D / 1D / 2D composite structure, namely a metal nanoparticle / fiber / MXene nanosheet composite structure. The metal nanoparticles contain trimetallic elements Ni, Co, and Cu, as well as nanoclusters, and the nanoclusters have twin grain boundaries.

[0010] Furthermore, the BET specific surface area of ​​the aerogel is ≥100 cm². 2 ·g -1 Pore ​​volume ≥ 0.12 cm 3 ·g -1 Porosity ≥ 99%.

[0011] Furthermore, the aerogel has a minimum reflection loss of ≤-10dB in the 2~18GHz frequency band and an effective absorption bandwidth of ≥0.46GHz.

[0012] This invention also provides a method for preparing the aforementioned trimetallic MOFs / MXene-derived aerogel, comprising the following steps:

[0013] (1) The trimetallic NiCoCu-BTC precursor was prepared by oil bath method;

[0014] (2) The NiCoCu-BTC precursor and MXene suspension were water-induced to self-assemble to form a hydrogel;

[0015] (3) The hydrogel was freeze-dried to obtain an unpyrolyzed aerogel, and then heat-treated under an inert atmosphere to obtain the trimetallic MOFs / MXene-derived aerogel.

[0016] Furthermore, in step (1), the raw materials for preparing the trimetallic NiCoCu-BTC precursor include Ni(NO3)2·6H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O and H3BTC, and the molar ratio of the three metal salts is 1:1:1, and the molar ratio of the metal salts to H3BTC is 1:1.

[0017] Furthermore, in step (2), the amount of MXene suspension added is 0~10 mL, and the concentration is 10 mg·mL. -1 In step (3), the heat treatment temperature is 873 K and the heating rate is 5 K·min. -1 The heat preservation time is 2 hours.

[0018] Furthermore, it also includes the step of adjusting the filler content, wherein the filler content is 10~30wt%.

[0019] The present invention also provides an application of the aforementioned trimetallic MOFs / MXene-derived aerogel in microwave absorbing materials.

[0020] Furthermore, the aerogel also possesses heat insulation, photothermal conversion, mechanical elasticity, and hydrophobic properties, making it suitable for use in the field of multifunctional electromagnetic protection materials.

[0021] Furthermore, the thermal conductivity of the aerogel is ≤0.03 W·m. -1 ·K -1 Photothermal conversion efficiency ≥80%, compressive strength ≥10kPa, hydrophobic contact angle ≥136°.

[0022] The beneficial effects of this invention are as follows:

[0023] The trimetallic MOFs / MXene-derived aerogel and its preparation method provided by this invention achieve significant breakthroughs and optimizations in microwave absorption performance. Compared with traditional bimetallic aerogel systems, this invention, by introducing the synergistic effect of Ni, Co, and Cu trimetallic particles and combining it with the modulation effect of MXene, provides a broader scope for fine optimization of electromagnetic parameters and broadband microwave absorption. After water-induced self-assembly and heat treatment, the aerogel forms a unique 0D / 1D / 2D metal nanoparticle / fiber / MXene nanosheet composite structure, in which NiCoCu three atoms and nanoclusters with twin grain boundaries are uniformly loaded on the surface of MXene nanosheets, constructing highly discrete polarization centers. The appropriate introduction of MXene not only promotes the reduction and crystallization of the metal phase, but also synergistically constructs an open and loose three-dimensional network structure with MOFs-derived carbon, giving the aerogel suitable specific surface area, pore volume, and reasonable pore structure distribution, effectively extending the electromagnetic wave transmission path and promoting interfacial polarization and multiple scattering. The electromagnetic loss of this aerogel is dominated by dielectric loss. MXene-induced mid-range polarization relaxation is significantly enhanced, with τ2 and τ3 increasing to 0.901 ns and 1.122 ns, respectively. The polarization loss ε in the 8.5–18 GHz frequency band is relatively stable. p '' represents the conductivity loss ε cMore than ten times that of traditional absorbing materials, covering the X and Ku bands. Among them, the NiCoCu / MX5-A sample exhibits the best absorption performance, with an effective absorption bandwidth (EAB) of 6.46 GHz at a thickness of only 2.63 mm and a minimum reflection loss (RLmin) of -83.73 dB at a thickness of 2.41 mm, corresponding to an effective absorption of 99.999999%. At the same time, the absorption effect can be further optimized by adjusting the filler content, which solves the technical pain points of traditional absorbing materials such as narrow absorption bandwidth, high reflection loss, and large thickness.

[0024] The trimetallic MOFs / MXene-derived aerogel of this invention achieves multifunctional integration of lightweight, thermal insulation, photothermal conversion, mechanoelasticity, and hydrophobic properties, expanding its application scenarios and practical value. This aerogel exhibits ultra-low density; the loose packing density of NiCoCu / MX5-A is only 9.2 mg·cm³. -3 With a porosity as high as 99.60%, it combines lightweight properties with structural integrity; its thermal conductivity is as low as 0.029 W·m. -1 ·K -1 It can reduce the ambient temperature by 116.7K, demonstrating excellent thermal insulation performance. Thanks to the localized surface plasmon resonance characteristics of MXene, the aerogel achieves this at 200mW·cm⁻¹. -2 The photothermal conversion efficiency reaches 82.93% at power density and maintains good stability during nine on / off cycles, demonstrating highly efficient and reversible photothermal conversion capabilities. In terms of mechanical properties, MXene-assisted crosslinking increases the compressive strength of NiCoCu / MX5-A to 102.4 kPa, allowing it to fully recover to its initial state after compression without mechanical fracture, exhibiting excellent compressive and fatigue resistance. Simultaneously, the aerogel possesses excellent hydrophobic properties, with NiCoCu / MX5-A achieving a hydrophobic contact angle of 139.2°, adapting to complex operating environments. This multifunctional integrated characteristic makes the aerogel suitable not only for electromagnetic protection but also for lightweight thermal insulation, photothermal utilization, and other diverse applications, providing a new path for the multifunctional and practical development of aerogel-based microwave absorbing materials, and possessing significant theoretical and practical application value. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 is a schematic diagram of the preparation process of NiCoCu / MXene-A aerogel;

[0027] Figure 2 shows the transformation process of water-induced trimetallic NiCoCu-BTC aerogel, where (a) is an electron microscope image; (b) is a SEM image; and (c) is an XRD pattern.

[0028] Figure 3 shows the thermogravimetric curves and XRD patterns of NiCoCu / MX-A with different MXene contents, where (a) is the TG curve of NiCoCu-BTC-H and NiCoCu-BTC / MX5-H; and (b) is the XRD pattern of NiCoCu / MX-A with different MXene contents.

[0029] Figure 4 shows the SEM and EDS elemental distribution of NiCoCu / MX-A with different MXene contents, where (a) is NiCoCu-A; (b) is NiCoCu / MX5-A; and (c) is NiCoCu / MX10-A.

[0030] Figure 5 shows the AC-STEM and EDS images of NiCoCu-A and NiCoCu / MX5-A, where (a) is the HAADF-STEM and EDS image of NiCoCu-A; (bd) is the AC-STEM image of NiCoCu / MX5-A; (e) is the atomic lattice image of nano-Cu in NiCoCu / MX5-A; and (f) is the HAADF-EDS image of NiCoCu / MX5-A.

[0031] Figure 6 shows the FT-IR and Raman spectra of NiCoCu / MX-A with different MXene contents, where (a) is the FT-IR spectrum and (b) is the Raman spectrum.

[0032] Figure 7 shows the nitrogen adsorption / desorption curves and pore size distribution of NiCoCu / MX-A aerogels with different MXene contents, where (a) is the nitrogen adsorption / desorption curve and (b) is the pore size distribution.

[0033] Figure 8 shows the electromagnetic parameters of NiCoCu / MX-A aerogels with different MXene contents, where (a) is ε' (real part of dielectric constant), (b) is ε'' (imaginary part of dielectric constant); and (c) is the dielectric loss tangent (tanδ). e (d) shows the comparison of loss tangent values;

[0034] Figure 9 shows the polarization loss (εp'') and conductivity loss (εc'') of NiCoCu / MX-A aerogels with different MXene contents, where (a) is the εp'' spectrum, (b) is the εc'' spectrum, (c) is the relationship between εp'' and εc'', and (d) is the two-dimensional εp'' / εc'' plot fitted to the dielectric loss from 2 to 18 GHz.

[0035] Figure 10 shows the relationship between ε'' / f and ε' for NiCoCu / MX-A with different MXene contents, where (a) is NiCoCu-A, (b) is NiCoCu / MX2.5-A, (c) is NiCoCu / MX5-A, (d) is NiCoCu / MX7.5-A, and (e) is NiCoCu / MX10-A;

[0036] Figure 11 shows the two-dimensional RL plots and EMWA performance comparison charts of NiCoCu / MX-A aerogels with different MXene contents, where (a) represents NiCoCu-A; (b) represents NiCoCu / MX2.5-A; (c) represents NiCoCu / MX5-A; (d) represents NiCoCu / MX7.5-A; (e) represents NiCoCu / MX10-A; and (f) is the EMWA performance comparison chart.

[0037] Figure 12 shows the impedance matching Smith chart and attenuation constant for NiCoCu / MX-A with different MXene contents, where (a) is the Smith chart and (b) is the attenuation constant (α) spectrum.

[0038] Figure 13 shows the two-dimensional and three-dimensional RL plots of NiCoCu / MX5-A with different filler contents, where (a) represents a filler content of 10 wt%; (b) represents a filler content of 15 wt%; (c) represents a filler content of 25 wt%; and (d) represents a filler content of 30 wt%.

[0039] Figure 14 shows the physical properties of trimetallic MOFs / MXene-derived aerogels, where (a) is an electron microscope image; (b) is density-related data; and (c) is effective thermal conductivity data.

[0040] Figure 15 shows the thermal insulation performance test results of NiCoCu-A and NiCoCu / MX5-A, where (a) is an electronic photograph of the heating process; (b) is the average temperature data; and (c) is the heating curve.

[0041] Figure 16 shows the photothermal conversion performance test and cycle stability test results of NiCoCu / MX5-A, where (a) is the photothermal conversion curve under different light power densities; (bc) is the photothermal efficiency fitting curve; and (d) is the cycle stability test result.

[0042] Figure 17 shows the mechanical property test diagrams of NiCoCu-A and NiCoCu / MX5-A, where (a) is an electron photograph before and after applying pressure; (b) is the compressive stress-strain curve; and (c) is a comparison of compression parameters.

[0043] Figure 18 shows the hydrophobicity test results of NiCoCu-A and NiCoCu / MX-A;

[0044] Figure 19 shows the EMWA mechanism of NiCoCu / MX-A aerogel. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0050] The present invention will be further illustrated below through examples.

[0051] Example 1: Preparation of trimetallic MOFs / MXene-derived composite aerogels

[0052] The experimental reagents used in this embodiment are as follows:

[0053] Nickel nitrate hexahydrate (Ni(NO3)2·6H2O), cobalt nitrate hexahydrate (Co(NO3)2·6H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), trimesic acid (H3BTC), N,N-dimethylformamide (DMF), ethanol, LiF, hydrochloric acid (HCl), and Ti3AlC2 powder were all analytical grade and used directly without further purification.

[0054] The experimental instruments used in this embodiment are as follows:

[0055] Oil bath, ultrasonic cleaner, centrifuge, vacuum oven, freeze dryer (for ice crystal template method), tube furnace (with argon protection device), X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM, including high-angle annular dark-field scanning transmission mode AC-STEM), energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectrometer (FT-IR), Raman spectrometer, nitrogen adsorption-desorption analyzer (BET), coaxial cable vector network analyzer, Hall effect tester, differential scanning calorimeter (DSC), thermogravimetric analyzer (TG), contact angle meter, laser source.

[0056] This embodiment prepares trimetallic MOFs / MXene-derived aerogels using a water-induced self-assembly method combined with a freeze-drying-heat treatment process. The specific steps are as follows, with the concentration of MXene suspension being 10 mg·mL in each step. -1 The heating rate during the pyrolysis process was 5 K·min. -1 .

[0057] 1. Preparation of trimetallic NiCoCu-BTC precursor

[0058] The trimetallic NiCoCu-BTC precursor was synthesized using an oil bath method. 0.97 g (3.33 mmol) Ni(NO3)2·6H2O, 0.97 g (3.33 mmol) Co(NO3)2·6H2O, 0.81 g (3.33 mmol) Cu(NO3)2·3H2O, and 2.10 g (10 mmol) H3BTC were dissolved in 50 mL DMF and stirred continuously in an oil bath at 423 K for 150 min. Subsequent processing was the same as for bimetallic BTC to obtain the trimetallic NiCoCu-BTC precursor.

[0059] 2. Preparation of water-induced trimetallic NiCoCu-BTC hydrogel

[0060] Take 1.0 g of the NiCoCu-BTC precursor prepared in step 1 and place it in 5 beakers. Add 25 mL of mixed solution (water: ethanol = 9:1) to each beaker in turn, and add 0 mL, 2.5 mL, 5 mL, 7.5 mL, and 10 mL of MXene black suspension (in place of an equal volume of water), respectively. After sonicating each beaker for 5 min, let it stand for 5 min to form trimetallic NiCoCu-BTC / MXene hydrogels with different MXene contents, and label them as NiCoCu-BTC-H (0 mL MXene), NiCoCu-BTC / MX2.5-H (2.5 mL MXene), NiCoCu-BTC / MX5-H (5 mL MXene), NiCoCu-BTC / MX7.5-H (7.5 mL MXene), and NiCoCu-BTC / MX10-H (10 mL MXene).

[0061] 3. Preparation of trimetallic NiCoCu-BTC / MXene-derived aerogels

[0062] The five hydrogels prepared in step 2 were frozen overnight in a freeze dryer at 213K to obtain the corresponding unpyrolyzed aerogels, named NiCoCu-BTC-A, NiCoCu-BTC / MX2.5-A, NiCoCu-BTC / MX5-A, NiCoCu-BTC / MX7.5-A, and NiCoCu-BTC / MX10-A, respectively. Subsequently, the above unpyrolyzed aerogels were pyrolyzed in an Ar atmosphere at 873K for 2 hours to obtain trimetallic NiCoCu / MXene-derived aerogels. The final products were labeled as NiCoCu-A, NiCoCu / MX2.5-A, NiCoCu / MX5-A, NiCoCu / MX7.5-A, and NiCoCu / MX10-A (where "A" stands for "aerogels"), as shown in Table 1.

[0063] Table 1. Sample nomenclature of NiCoCu-BTC / MXene-derived aerogels with different MXene contents

[0064]

[0065] 4. Preparation of trimetallic MOFs / MXene-derived aerogels

[0066] Based on the NiCoCu / MX5-A with the best performance in step 3, samples with filler contents of 10 wt%, 15 wt%, 25 wt%, and 30 wt% were prepared respectively. During the preparation process, only the filler addition ratio was adjusted, and the other process parameters (pyrolysis temperature, atmosphere, heating rate, etc.) were the same as in step 3. The preparation process of trimetallic NiCoCu-BTC / MXene derived aerogel is shown in Figure 1.

[0067] Experimental Example 1: Effect of MXene content on the microstructure of trimetallic MOFs / MXene aerogels

[0068] Phase analysis of the product was performed using X-ray diffraction, and the results are shown in Figure 2. It can be observed that, similar to Ni-BTC and NiCu-BTC, the original NiCoCu-BTC powder exhibits an irregular layered stacked structure with a regular morphology but few pores and a thickness of approximately 10 μm. After water induction, the layered structure peels away from each other, transforming into a porous network structure of nanofibers with a diameter of approximately 40 nm, demonstrating an evolution from dense NiCoCu-BTC crystals to a porous aerogel precursor. Electron micrographs macroscopically show that the NiCoCu-BTC powder is deep blue, combining the pale green of Ni-BTC, the magenta of Co-BTC, and the sky blue of Cu-BTC. XRD patterns revealed that the original Ni-BTC powder structure conforms to Ni(BTC)DMF2·(guest) (CCDC No. 636901), while the water-induced transformation NiCoCu-BTC-H hydrogel phase conforms to Ni3(BTC)2·12H2O (CCDC No. 921721), combining the structures of NiCu-BTC and NiCo-BTC, thus demonstrating the successful preparation of NiCoCu-BTC. Furthermore, the disappearance of the characteristic peaks at 12.8° and 18.5° confirms the phase transition during the water-induced process, with the solvent molecules replacing DMF with H2O.

[0069] Figure 3(a) shows the TG curves of NiCoCu-BTC-H and NiCoCu-BTC / MX5-H hydrogels. It can be observed that the weight loss can be divided into three thermal decomposition stages. The first stage is the low-temperature range of 273 K to 428 K, with a mass loss of 19.5 wt%, attributed to the evaporation of physically adsorbed water / surface-bound water and the decomposition of MXene surface functional groups. The second stage is the mid-temperature range of 428 K to 637 K, with mass loss attributed to the removal of the solvent DMF. The final stage is the high-temperature range of 637 K to 1073 K, primarily involving the decomposition of the organic ligand BTC and the crystallization of the inorganic phase. It can be observed that NiCoCu-BTC / MX5-H exhibits a faster mass loss rate in the initial and middle stages, while the loss is more gradual in the later stages, resulting in a higher residual mass. This indicates that the interfacial interaction between MXene and MOF enhances the high-temperature residual rate and thermal stability.

[0070] Figure 3(b) shows the XRD patterns of NiCoCu / MX-A with different MXene contents. It can be observed that for NiCoCu-A aerogel, the main diffraction peaks are those of elemental Ni (No. 00-004-0850), Co (No. 00-015-0806), and Cu (No. 01-070-3039), with some weaker CuO (No. 00-015-7390) diffraction peaks, indicating that the trimetallic NiCoCu-BTC pyrolysis products are predominantly metallic. When MXene is introduced, a characteristic peak of TiO2 (No. 01-078-1508) appears, originating from the oxidation of Ti during MXene pyrolysis. The characteristic peaks of metallic Cu and TiO2 significantly increase with increasing MXene content, with the most significant enhancement observed in NiCoCu / MX10-A. This indicates that MXene, as a carbon source and conductive matrix, promotes the reduction and crystallization of the metallic phase, and can control the grain size and crystallinity of the pyrolysis products.

[0071] Figure 4 shows the SEM and corresponding EDS elemental distribution maps of NiCoCu / MX-A with different MXene contents. It can be observed that after pyrolysis, NiCoCu-A still exhibits a fine fibrous network morphology, with some small particles attached to the surface, which, based on the XRD pattern, are likely CuO particles. The EDS elemental distribution map confirms that Ni, Co, Cu, and O elements are uniformly distributed in the fibers. Simultaneously, elemental line scanning also verifies the uniformity of each element along the fibers, with Ni, Co, Cu, and O contents of 13.9 at%, 8.4 at%, 21.8 at%, and 55.9 at%, respectively. After the introduction of MXene, fiber networks are observed interspersed on the surface and between layers of the MXene sheet structure in both NiCoCu / MX5-A and NiCoCu / MX10-A. The distribution of Ti in the EDS image corresponds to the MXene region, confirming the successful composite and uniform dispersion of MXene in the NiCoCu fibers, forming a composite structure of 0D / 1D / 2D metal nanoparticles / fibers / MXene nanosheets. Furthermore, NiCoCu / MX10-A exhibits a richer and higher proportion of MXene lamellar structures, and the signal of Ti element is significantly enhanced and widely distributed in the EDS diagram. The EDS results show that the contents of Ni, Co, Cu, O and Ti elements are 10.1 at%, 9.7 at%, 15.6 at%, 53.8 at%, and 10.9 at%, respectively.

[0072] Figure 5 shows the AC-STEM and EDS images of NiCoCu-A and NiCoCu / MX5-A. As shown in Figure 5(a), NiCoCu-A has a classic 1D fibrous structure with a diameter of approximately 60 nm, and CuO nanoparticles are attached to the 1D fibers. The EDS results show that Ni, Co, Cu, C, and O elements are uniformly dispersed on the fibers, with contents of 9.82 at%, 3.28 at%, 3.64 at%, 77.54 at%, and 5.72 at%, respectively. Figure 5(b) shows a large number of single atoms and clusters (yellow dashed circles) in the high-resolution STEM image of NiCoCu / MX5-A. The signal intensity distribution in Region A indicates that the three NiCoCu atoms are anchored on the surface of the MXene nanosheet matrix, and line A shows a 3.5 nm spacing between Cu and Co atoms. This indicates that the trimetallic NiCoCu / MXene-A possesses highly discrete metal single-atom polarization centers and metal nanoclusters, and the complementarity between the two in terms of time scale and frequency response can significantly broaden the absorption bandwidth. Figure 5(c) shows an ADF-STEM image illustrating the Mott-Schottky heterostructure between the metal fiber and MXene. Figure 5(d) reveals a fully crystalline Cu@C structure with a core-shell structure, with a graphitic carbon shell thickness of approximately 2 nm. Furthermore, Figure 5(e) shows a distinct twin boundary (marked with white parallelograms) in the atomic-resolution HAADF-STEM image of Cu@C. Twin boundaries, acting as interfaces between regions with different lattice orientations, hinder the migration of free electrons, leading to charge accumulation at the interface and the formation of Maxwell-Wagner type interfacial polarization. Moreover, the twinning process easily introduces defects such as lattice distortion and stacking faults, inducing defect dipoles and enhancing dipole polarization. The lattice spacing corresponding to Line B is 0.206 nm, further indicating that this twin is the (111) crystal plane of Cu. Figure 5(f) is the HAADF-EDS diagram of NiCoCu / MX5-A, showing the uniform distribution of C, O, Ni, Co, Cu and Ti elements.

[0073] Figure 6(a) shows the FT-IR spectra of NiCoCu / MX-A with different MXene contents. It can be observed that at 3450 cm⁻¹... -1 The peak intensity and width increase significantly with increasing MXene content, attributed to the symmetric stretching vibration of the hydroxyl group (-OH), indicating that this peak mainly originates from the hydrophilic groups on the MXene surface. Furthermore, a peak located at 1625 cm⁻¹... -1 The peak at 1375 cm⁻¹ represents the bending vibration of HOH, indicating that the C=O derived from MOFs forms hydrogen bonds with the -OH group of MXene, and the intensity of this peak is enhanced due to the stabilization of the MXene hydrogen bonds.-1 The -COOH group at the ligand gradually disappears with increasing MXene content, indicating that MXene interacts with the carboxylic acid group in the ligand, and that pyrolysis destroys its carboxylate structure. Located at 500–700 cm⁻¹ -1 The peaks in this region correspond to the Ni-O, Co-O, and Cu-O bonds and the Ti-O bonds formed after NiCoCu-BTC derivatization. With the increase of MXene content, the peaks in this region are significantly enhanced, reflecting the enhanced interaction between MXene and the metal.

[0074] Figure 6(b) shows the Raman spectra of NiCoCu / MX-A with different MXene contents. It can be observed that the NiCoCu-A sample contains MXene at 520 cm⁻¹. -1 The sharp peak at 699 cm⁻¹ is attributed to the stretching vibration peak of Ni-O, and this peak gradually transforms into a peak at 699 cm⁻¹ with the introduction of MXene. -1 The Ti-O peak at [location missing]. This peak originates from the B1g vibrational mode of TiO2 and blue-shifts by 15 cm⁻¹ with increasing MXene content. -1 This is because the high MXene content forms a rigid three-dimensional network. During the cooling process from the pyrolysis temperature to room temperature, the different thermal expansion coefficients of the components generate strong compressive stress on the in-situ generated TiO2 nanoparticles, leading to an increase in the vibrational frequency of the Ti-O bonds. It can be observed that the sample at 1350 cm⁻¹ exhibits increased vibrational frequency. -1 and 1580 cm -1 Two distinct peaks appear nearby, corresponding to the D peak and the G peak, I D / I G The value can be used as an indicator to quantify the degree of structural disorder or defects in carbon materials. With increasing MXene content, I... D / I G The values ​​were 0.843, 0.844, 0.849, 0.851, and 0.857, respectively, indicating that a large number of heterogeneous interfaces were formed between the high specific surface area MXene and MOF-derived carbon / metal nanoparticles. Lattice mismatch and stress at the interfaces induced additional structural defects, and MXene inhibited the complete graphitization of carbon materials during pyrolysis. Furthermore, the value at 2900 cm⁻¹... -1 The wider peaks nearby correspond to the D+G combined peak (D+D' peak), which originates from the combination of the D peak and the vibrational mode of another phonon, further confirming the presence of numerous structural defects in the material.

[0075] Figure 7 shows the nitrogen adsorption / desorption curves and pore size distribution of NiCoCu / MX-A with different MXene contents. It can be observed that all samples exhibit capillary condensation (H3-type hysteresis loop) at P / P0 = 0.46, indicating a type IV adsorption isotherm and the simultaneous presence of micropores and numerous mesopores in the samples. Table 2 shows the BET specific surface area, pore volume, and pore size of the NiCoCu / MX-A aerogel. It can be seen that with increasing MXene content, the BET specific surface area of ​​the NiCoCu / MX-A aerogel first increases and then decreases, with NiCoCu / MX2.5-A exhibiting a larger BET specific surface area (185.64 cm²). 2 ·g -1 ) and pore volume (0.193 cm) 3 ·g -1 This indicates that an appropriate amount of MXene can serve as a two-dimensional template, effectively preventing the disordered stacking of MOF-derived carbon during pyrolysis, and synergistically constructing a more open and loose three-dimensional network structure with the carbon matrix, thereby synergistically increasing the specific surface area and pore volume. When the MXene content is further increased, the specific surface area and pore volume show a systematic decreasing trend, with the BET specific surface area being lower than the 151.66 cm² of the NiCoCu-A reference sample without MXene. 2 ·g -1 However, its pore volume and pore size are both higher than those of NiCoCu-A (0.126 cm⁻¹). 3 ·g -1 The specific surface area and pore size of 12.11 nm indicate that the introduction of MXene can broaden the pore structure. As shown in Figure 7(b), all NiCoCu / MX-A aerogels exhibit a distribution of micropores (3.86 nm) and a large number of small mesopores (10.24 nm). Furthermore, Table 2 shows the proportions of micropores, mesopores, and macropores in the NiCoCu / MX-A aerogels. It can be seen that the proportion of micropores gradually decreases from 34.02% in NiCoCu-A to 12.92% in NiCoCu / MX10-A, while the proportion of macropores gradually increases from 22.39% in NiCoCu-A to 37.14% in NiCoCu / MX10-A, indicating that MXene can transform the pore structure of the aerogel from "mainly micropores and small mesopores" to "mainly mesopores and macropores." Suitable specific surface area and pore structure help improve electron transport performance, extend the electromagnetic wave propagation path, thereby promoting interfacial polarization and multiple scattering.

[0076] Table 2. BET specific surface area, pore volume, and pore size of NiCoCu / MX-A aerogels with different MXene contents.

[0077]

[0078] Experimental Example 2: Effect of MXene content on the microwave absorption properties of trimetallic MOFs / MXene aerogel

[0079] Figure 8 shows the electromagnetic parameters of NiCoCu / MX-A with different MXene contents. The results show that with increasing MXene content, the ε' and ε'' values ​​of the composite aerogel exhibit a significant upward trend, with NiCoCu / MX10-A showing the highest dielectric constant, and its initial ε' and ε'' values ​​being 7.43 and 3.50, respectively. This indicates that the introduction of MXene alters the charge storage and polarization characteristics of the NiCoCu / MX-A aerogel, which may be related to changes in pore structure and interfacial interactions. Furthermore, as shown in Figure 8(d), the red curve (tanδ)... e The values ​​in the 2–18 GHz frequency band are all higher than the blue curve (tanδ). μ ), tanδ μ The value even drops to 0.1 at mid-to-high frequencies, indicating that the electromagnetic loss of NiCoCu / MX-A is mainly due to dielectric loss, with magnetic loss contributing little.

[0080] Figure 9 shows the polarization loss (ε) of NiCoCu / MX-A aerogels with different MXene contents. p '') and conductivity loss (ε c Figure 9(ab) shows that as the amount of MXene added increases, the ε of NiCoCu / MX-A aerogel increases. p '' and ε c The values ​​of ε and ε' gradually increase. The enhanced conductivity loss is due to the excellent conductivity of MXene, while the polarization loss is due to the construction of numerous heterostructure interfaces (Maxwell-Wagner effect) and the enhanced dipole polarization induced by defects on the MXene / carbon surface. As shown in Figure 9(c), after the introduction of MXene, the polarization loss ε' gradually increases. p The proportion of '' increased from 0.814 to 0.885 and gradually stabilized. Figure 9(d) shows the two-dimensional planar results of dielectric loss fitting from 2 to 18 GHz. It can be seen that NiCoCu-A aerogel has a slightly lower polarization loss effect in the mid-to-low frequency region (2~8 GHz) (ε p '' / ε c ε'≤5), while NiCoCu / MX-A aerogel has a range of 2~4 GHz in this region. Furthermore, NiCoCu / MX-A aerogel has an ε'≤5 in the range of 8.5 GHz~18 GHz. p ''Compared to ε c "More than ten times higher, covering the X and Ku bands."

[0081] Figure 10 shows the relationship between ε'' / f and ε' for NiCoCu / MX-A aerogels with different MXene contents. The polarization times of NiCoCu / MX-A aerogels with different MXene contents were calculated and are shown in Table 3. It can be observed that the relaxation time of NiCoCu / MX-A can be roughly divided into short-range polarization (τ≤0.01 ns), mid-range polarization (τ≈0.01~1 ns), and long-range polarization (τ≥1 ns). Both NiCoCu-A and NiCoCu / MX5-A exhibit ultrafast short-range polarization (0.0002 ns), which mainly occurs at the atomic / electronic scale and typically contributes little to losses. Mid-range polarization originates from heterojunction charge accumulation (Maxwell-Wagner effect) and defect-induced space charge migration, mainly contributed by interfacial polarization and dipole polarization. Furthermore, the formation of nanotwinned copper also introduces a new relaxation process, creating a large built-in electric field, altering the charge distribution and barrier height in the surrounding region, and further extending the effective polarization relaxation time. Long-range polarization is related to the migration of charge carriers along the conductive path and is a relatively slow process. With the increase of MXene content, the dielectric polarization relaxation behavior of the composite aerogel is significantly enhanced, especially the mid-range polarization, which is significantly enhanced and optimized, with τ2 and τ3 increasing to 0.901 ns and 1.122 ns, respectively. Further increasing MXene content, however, leads to a decrease in polarization time, indicating that excessive MXene inhibits effective interfacial polarization and dipole polarization. This may be due to the stacking of MXene sheets, which reduces the area of ​​the effective heterointerface.

[0082] Table 3 Polarization time of NiCoCu / MX-A aerogels with different MXene contents

[0083]

[0084] Figure 11 shows the two-dimensional RL plots of NiCoCu / MX-A aerogels with different MXene contents. It can be observed that the NiCoCu-A aerogel without MXene has a lower RL at a thickness of 4.90 mm. min With an absorption of only -10.16 dB, barely reaching effective absorption, its EAB is 0.46 GHz (4.94 mm thickness). As the MXene content increases, RL... min Both RL and EAB have been significantly improved. For NiCoCu / MX2.5-A at a thickness of 4.83 mm, RL... min The EAB is -18.69 dB; at a thickness of 3.04 mm, its EAB is 5.39 GHz. Among them, NiCoCu / MX5-A exhibits better EMWA performance, achieving an EAB of 6.46 GHz at a thickness of 2.63 mm; it is worth emphasizing that its RL... minIt can reach -83.73 dB (corresponding to 99.999999% effective absorption), far exceeding other samples. However, with further increasing the MXene content, the EMWA performance decreased; for NiCoCu / MX7.5-A at a thickness of 1.90 mm, the RL... min The EAB is -51.36 dB; at a thickness of 2.30 mm, its EAB is 5.84 GHz. For NiCoCu / MX10-A at a thickness of 1.74 mm, the RL... min The EAB is -20.38 dB; at a thickness of 2.06 mm, its EAB is 5.32 GHz. As shown in Figure 11(f) of the EMWA performance comparison chart, the overall RL... min EAB max With its coating thickness, NiCoCu / MX5-A exhibits excellent EMWA performance.

[0085] Figure 12 shows the impedance matching Smith chart and attenuation constant of NiCoCu / MX-A aerogels with different MXene contents. As shown in Figure 12(a), NiCoCu / MX5-A has more absorption points within the perfect absorption range (within the green circle) and is closer to 1+0j, indicating its excellent impedance matching characteristics. As shown in Figure 12(b), the attenuation constant α increases with frequency, and with increasing MXene content, the value of α shows a clear increasing trend: NiCoCu / MX10-A > NiCoCu / MX7.5-A > NiCoCu / MX5-A > NiCoCu / MX2.5-A > NiCoCu-A. This indicates that MXene enhances the dielectric properties to improve the attenuation of electromagnetic waves.

[0086] By combining the impedance matching Smith circle, attenuation constant, and EMWA performance, it was demonstrated that adjusting the MXene content can effectively regulate the impedance matching characteristics and attenuation capability of NiCoCu / MX-A aerogel. For the trimetallic NiCoCu / MXene-derived aerogel in this experiment, the optimal MXene content is 5 mL.

[0087] Experimental Example 3: Effect of Filler Content on the Microwave Absorption Properties of Trimetallic MOFs / MXene Aerogel

[0088] Figure 13 shows the two-dimensional and three-dimensional absorption ratio (RL) plots of NiCoCu / MX5-A with different filler contents. The results indicate that NiCoCu / MX5-A does not achieve effective absorption at a filler content of 10 wt%; while at a filler content of 15 wt% and a thickness of 4.89 mm, the absorption efficiency (EAB) is only 3.09 GHz, and its RL... minOnly -13.26 dB. With a filler content of 25 wt% and a thickness of 2.18 mm, EAB can reach 5.42 GHz; with a thickness of 1.76 mm, RL... min The EAB is -47.61 dB. With a filler content of 30 wt% and a thickness of 1.91 mm, the EAB is 5.19 GHz. Therefore, it can be concluded that NiCoCu / MX5-A exhibits better EMWA performance with a filler content of 20 wt%.

[0089] Experimental Example 4: Investigation into the multifunctionality of trimetallic MOFs / MXene-derived aerogels

[0090] Figure 14 shows the physical properties of trimetallic MOFs / MXene-derived aerogels. As shown in Figure 14(a), uncarbonized NiCoCu-BTC-A and NiCoCu-BTC / MX5-A, as well as carbonized NiCoCu / MX5-A, can all be placed on yellow flowers, indicating that NiCoCu / MX-A aerogels also achieve lightweighting, and the gel network retains sufficient skeletal integrity after carbonization. Measurements and calculations show that the bulk densities of carbonized NiCoCu-A and NiCoCu / MX5-A are 16.7 mg·cm³. -3 and 9.2 mg·cm -3 The true densities are 2.74 g·cm³. -3 and 2.31 g·cm -3 This indicates that the addition of MXene acts as a robust two-dimensional framework supporting a larger three-dimensional structure, significantly reducing the density of the aerogel. NiCoCu / MX5-A exhibits ultra-high porosity (99.60%). The ultra-low density allows for impedance matching adjustment over a wide range, while the ultra-high porosity creates millimeter-scale multiple scattering channels and wavepath extension effects, significantly improving effective propagation loss and reducing volume reflection. Figure 14(c) shows the effective thermal conductivity of different samples, indicating that NiCoCu / MX5-A possesses ultra-low thermal conductivity (0.029 W·m). -1 ·K -1 The concentration was significantly lower than that of NiCoCu-BTC-A and NiCoCu-A, but slightly higher than that of NiCo / MXene-A (0.025 W·m). -1 ·K -1 This indicates a slight reduction in the phonon scattering effect in the NiCoCu ternary alloy, thereby enhancing the overall heat transfer capability of the solid network.

[0091] Figure 15 shows the thermal insulation performance tests of NiCoCu-A and NiCoCu / MX5-A. The tests involved placing the samples on a heating stage at 473 K for 600 s. Figure 15 (ac) shows the electron micrograph, average temperature, and heating curve during the heating process, respectively. It can be observed that NiCoCu-A and NiCoCu / MX5-A exhibit excellent thermal insulation performance. The average surface temperature of NiCoCu-A is 369.8 K, while that of NiCoCu / MX5-A is 359.5 K. Compared to the average ambient temperature (476.2 K), the NiCoCu / MX5-A aerogel can reduce the temperature by 116.7 K, which is attributed to the synergistic effect of the aerogel's high porosity and MXene's ultra-low thermal conductivity. The extremely high porosity means that air is separated into countless nanoscale pores, suppressing air convection heat transfer, thus giving the aerogel excellent thermal insulation performance.

[0092] Figure 16 shows the photothermal conversion performance and cycle stability tests of NiCoCu / MX5-A. Laser irradiation was used to simulate the photothermal conversion performance of NiCoCu / MX5-A under sunlight. Due to the local surface plasmon resonance (LSPR) characteristics of MXene nanosheets, the surface temperature of NiCoCu / MX5-A can rapidly rise to the equilibrium temperature under laser irradiation, as shown in Figure 16(a). With the increase of irradiation light power density, the equilibrium temperature of the aerogel increases linearly. When the light power density increases from 25 mW·cm⁻¹, the equilibrium temperature of the aerogel increases linearly. -2 Increased to 200 mW·cm -2 When the power of the laser source is turned off (equivalent to twice the power of direct sunlight at noon), its equilibrium temperature rises from 318.9 K to 363.1 K. After the laser source is turned off, the surface temperature rapidly drops to near room temperature, demonstrating efficient and reversible photothermal conversion performance. As shown in Figure 16 (bc), the photothermal efficiency (η) of the aerogel was calculated using the linear relationship between cooling time t and -lnθ. PT The mass of NiCoCu / MX5-A was 44.6 mg. The specific heat capacity (C5) of NiCo / MXene-A was determined by differential scanning calorimetry. p The value is 0.616 J·g -1 ·K -1 The calculated hA value is 0.00259. Substituting the hA value into equation (5.1), the photothermal conversion efficiency (η) of NiCoCu / MX5-A can be calculated. PT The percentage was 82.93% (power density of 200 mW·cm). -2 Figure 16(d) shows that NiCoCu / MX5-A exhibits excellent responsiveness at different laser power densities, with its infrared thermal images showing performance at 100, 150, and 200 mW·cm⁻¹. -2The surface temperatures of the aerogel at the power densities were 337.5 K, 352.0 K, and 359.6 K, respectively. Furthermore, NiCoCu / MX5-A exhibited photothermal cycling stability during nine on / off cycles of the laser source.

[0093] Figure 17 shows the mechanical property test results of NiCoCu / MX5-A. When NiCoCu / MX5-A was placed under a 500 g weight, a comparison before and after the pressure was applied reveals that the aerogel underwent significant deformation. After the external pressure was removed, NiCoCu / MX5-A completely returned to its initial state without any mechanical fracture. No deformation was observed after the compression performance test, demonstrating its good compressive strength and fatigue resistance. Figure 17 (bc) shows the compressive stress-strain curves and data comparison. NiCoCu-A exhibited a relatively low compressive strength of 10.5 kPa and a compressive modulus of 0.4 kPa at 87% strain. After the introduction of MXene, the compressive strength of NiCoCu / MX5-A significantly increased to 102.4 kPa, indicating that MXene-assisted crosslinking significantly improved the mechanical elasticity of the aerogel.

[0094] Figure 18 shows the contact angle test results for NiCoCu-A and NiCoCu / MX-A. It can be observed that all samples exhibit excellent hydrophobic properties. Among them, NiCoCu-A has the largest contact angle of 142.3°. The contact angle gradually decreases with increasing MXene content, which is attributed to the hydrophilic functional groups on the MXene surface.

[0095] Experimental Example 5: Wave Absorption Mechanism of Trimetallic MOFs / MXene-Derived Aerogels

[0096] Figure 19 shows the EMWA mechanism of the trimetallic NiCoCu / MX-A aerogel. It can be seen that the EMWA mechanism of the trimetallic NiCoCu-MOFs / MXene-derived aerogel is mainly driven by dielectric loss, with magnetic loss as a secondary factor, and achieves synergistic enhancement of impedance matching and multiple scattering through structural optimization. The main EMWA mechanism analysis is as follows:

[0097] (1) Composite aerogels form a large number of heterogeneous interfaces, such as MXene / C, MXene / NiCoCu and NiCoCu / CuO, which generate Maxwell-Wagner type interface polarization under electromagnetic fields. (2) The conductive network formed by MXene and graphitized carbon allows charge carriers to migrate freely and generate current. Due to resistance, Joule heating is generated, and electromagnetic waves are dissipated in the form of heat. (3) The formation of nanotwins gives the material highly discrete polarization centers, and the loading of NiCoCu triatoms provides additional defect polarization centers, which generate dipole polarization under alternating electromagnetic fields. (4) High porosity aerogels provide a rich porous structure on a macroscopic level, which allows incident electromagnetic waves to be reflected and scattered multiple times, extending the transmission path of electromagnetic waves.

[0098] In summary, this invention prepares trimetallic NiCoCu-BTC / MXene aerogels via self-assembly and an ice crystal template method, and obtains NiCoCu / MX-A composite aerogels containing nanotwins after heat treatment. Under water-induced effects, the NiCoCu-BTC powder transforms from a disordered, layered stacked structure to a 1D fibrous structure, ultimately forming an 0D / 1D / 2D (metal nanoparticles / fibers / MXene nanosheets) composite structure, with NiCoCu atoms and nanoclusters (including twin grain boundaries) loaded on the surface of the MXene nanosheets; among them, the BET specific surface area of ​​NiCoCu / MX2.5-A reaches 185.64 cm². 2 ·g -1 The pore volume is 0.193cm 3 ·g -3 As the MXene content increased, the proportion of micropores decreased from 34.02% to 12.92%, while the proportion of macropores increased from 22.39% to 37.14%.

[0099] Adjusting the MXene and filler content can optimize the performance of aerogel EMWA, with NiCoCu / MX5-A showing the best performance: an effective absorption bandwidth (EAB) of 6.46 GHz at a thickness of 2.63 mm and a minimum reflection loss (RLmin) of -83.73 dB (corresponding to 99.999999% absorption) at a thickness of 2.41 mm. Its superior performance stems from MXene-induced enhanced mid-range polarization relaxation (τ2=0.901 ns, τ3=1.122 ns), and a low polarization loss ε in the 8.5–18 GHz frequency band. p '' represents the conductivity loss ε c It is more than ten times that of other bands, covering the X and Ku bands; the aerogel has the best microwave absorption performance when the filler content is 20wt%.

[0100] Trimetallic NiCoCu / MX-A aerogel achieves multifunctional integration: NiCoCu / MX5-A has a bulk density of 9.2 mg·cm³. -3Porosity of 99.60% and thermal conductivity as low as 0.029 W·m -1 ·K -1 It can insulate against ambient temperatures of 116.7K and 200mW·cm. -2 It has a photothermal conversion efficiency of 82.93% at power density and excellent cycle stability; its compressive strength reaches 102.4 kPa and it can fully recover after being compressed; its hydrophobic contact angle reaches 139.2°; and it combines lightweight, heat insulation, photothermal conversion, mechanical elasticity and hydrophobic properties.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A trimetallic MOFs / MXene-derived aerogel, characterized in that, The aerogel was prepared by water-induced self-assembly of a trimetallic NiCoCu-BTC precursor and MXene, followed by freeze-drying and heat treatment. The aerogel has an 0D / 1D / 2D composite structure, namely a metal nanoparticle / fiber / MXene nanosheet composite structure. The metal nanoparticles contain trimetallic elements Ni, Co, and Cu, as well as nanoclusters, and the nanoclusters have twin grain boundaries.

2. The trimetallic MOFs / MXene-derived aerogel according to claim 1, characterized in that, The aerogel has a BET specific surface area ≥ 100 cm². 2 ·g -1 Pore ​​volume ≥ 0.12 cm 3 ·g -1 Porosity ≥ 99%.

3. The trimetallic MOFs / MXene-derived aerogel according to claim 1, characterized in that, The aerogel has a minimum reflection loss of ≤-10dB in the 2~18GHz frequency band and an effective absorption bandwidth of ≥0.46GHz.

4. A method for preparing trimetallic MOFs / MXene-derived aerogels as described in any one of claims 1-3, characterized in that, The process includes the following steps: (1) preparing a trimetallic NiCoCu-BTC precursor using an oil bath method; (2) forming a hydrogel by water-induced self-assembly of the NiCoCu-BTC precursor and MXene suspension; (3) obtaining an unpyrolyzed aerogel by freeze-drying the hydrogel and then obtaining the trimetallic MOFs / MXene-derived aerogel by heat treatment under an inert atmosphere.

5. The preparation method according to claim 4, characterized in that, In step (1), the raw materials for preparing the trimetallic NiCoCu-BTC precursor include Ni(NO3)2·6H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O and H3BTC. The molar ratio of the three metal salts is 1:1:1, and the molar ratio of the metal salts to H3BTC is 1:

1.

6. The preparation method according to claim 4, characterized in that, In step (2), the amount of MXene suspension added is 0~10 mL, and the concentration is 10 mg·mL. -1 In step (3), the heat treatment temperature is 873 K and the heating rate is 5 K·min. -1 The heat preservation time is 2 hours.

7. The preparation method according to claim 4, characterized in that, It also includes the step of adjusting the filler content, wherein the filler content is 10~30wt%.

8. The application of the trimetallic MOFs / MXene-derived aerogel as described in any one of claims 1-3 in microwave absorbing materials.

9. The application according to claim 8, characterized in that, The aerogel also has heat insulation, photothermal conversion, mechanical elasticity and hydrophobicity functions, and can be used in the field of multifunctional electromagnetic protection materials.

10. The application according to claim 8, characterized in that, The thermal conductivity of the aerogel is ≤0.03 W·m. -1 ·K -1 Photothermal conversion efficiency ≥80%, compressive strength ≥10kPa, hydrophobic contact angle ≥136°.

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