Copper-based metal-organic framework derived carbon composite nanofiber and preparation method and application thereof

Abstract

The application discloses a copper-based metal organic framework derived carbon composite nanofiber and a preparation method and application thereof, and comprises a three-dimensional network structure matrix formed by stacking one-dimensional carbon fibers and octahedral Cu9S5 / C nanoparticles monodispersed in the one-dimensional carbon fibers and on the surfaces of the one-dimensional carbon fibers. The MOF derived Cu9S5 / C nanoparticles are dispersed and arranged in the carbon fibers, and a conductive network is constructed among the MOF derived particles by using the carbon fibers. The prepared hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material has the characteristics of high absorption intensity, wide absorption frequency band, thin matching thickness, low filling amount and the like. Meanwhile, the preparation method is simple and easy to implement, low in cost, and has an excellent industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials, specifically relating to a copper-based metal-organic framework-derived carbon composite nanofiber, its preparation method, and its application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] The rapid development of fifth-generation mobile communication technology heralds the arrival of the global smart era, but the resulting electromagnetic pollution has attracted widespread public attention. The ubiquitous electromagnetic radiation places higher demands on electromagnetic wave absorbing materials: these materials need to simultaneously achieve high absorption intensity, lightweight, thinness, and wide absorption bandwidth. Metal-organic framework (MOF)-derived carbon-based composites are considered a strong candidate for achieving high absorption intensity, thinness, and wide absorption bandwidth due to their diverse defects, selectable components, and abundant interfaces. Meanwhile, transition metal sulfides, as the second component of MOF-derived carbon-based composites, have also attracted considerable attention because they possess higher chemical stability than metals and richer loss pathways than metal oxides.

[0004] However, MOF-derived carbon-based composites suffer from a significant problem: their filler content typically exceeds 40 wt%, which contradicts the goal of lightweight electromagnetic wave absorbing materials. This phenomenon can be attributed to the discontinuity of the conductive path caused by the separability of MOF-derived particles, leading to an increased penetration threshold of the absorber. Currently, various strategies have been employed to optimize conductivity, such as increasing the carbonization temperature, optimizing component selection, or combining with highly conductive materials (e.g., graphene, carbon nanotubes). However, the first two methods suffer from structural collapse and insufficient conductivity improvement, respectively. For MOF-derived carbon-based particles combined with graphene or carbon nanotubes, currently widely used methods (direct loading and in-situ growth) cannot simultaneously achieve precise loading and stable dispersion of MOF particles, limiting breakthroughs in electromagnetic wave absorption performance and the design of future high-efficiency electromagnetic wave absorbers. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a copper-based metal-organic framework (MOF)-derived carbon composite nanofiber, its preparation method, and its applications. This invention disperses MOF-derived Cu9S5 / C nanoparticles within carbon fibers, utilizing the carbon fibers to construct a conductive network between the MOF-derived particles. The prepared hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material exhibits high absorption intensity, wide absorption bandwidth, thin matching thickness, and low filling amount. Furthermore, the preparation method of this invention is simple, easy to implement, and low-cost, making it highly promising for industrial applications.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a copper-based metal-organic framework-derived carbon composite nanofiber, comprising a three-dimensional network structure matrix formed by stacking one-dimensional carbon fibers and octahedral Cu9S5 / C nanoparticles monodispersed inside and on the surface of the one-dimensional carbon fibers.

[0008] Copper-based MOF-derived octahedral Cu9S5 / C nanoparticles are monodispersed within one-dimensional carbon fibers. The carbon fibers construct a conductive network between the MOF-derived particles, achieving improved conductivity, optimized impedance matching, and the synergistic effect of multiple loss mechanisms. First, the unique hierarchical structure and the appropriate selection of MOF loading lead to optimized electromagnetic parameters, resulting in optimal impedance matching characteristics. Second, the N, O, and S dopants in carbon and the inherent defects in Cu9S5 act as polarization centers, trapping unpaired electrons and inducing dipole polarization. Third, the special layered carbon structure and abundant Cu9S5-C interfaces result in high interfacial polarization losses. Finally, the three-dimensional conductive network provides channels for carrier migration and switching within the MOF-derived composite particles, forming a micro-current amplifier and promoting conductivity loss.

[0009] In some embodiments, the diameter of the one-dimensional carbon fiber is 100-500 nm.

[0010] In some embodiments, the average particle size of the octahedral Cu9S5 / C nanoparticles is 500-600 nm.

[0011] Preferably, the average diameter of Cu9S5 particles is 80-120 nm.

[0012] In some embodiments, the mass percentage of octahedral Cu9S5 / C nanoparticles in the composite nanofibers is 0wt%-50wt%, and is not 0;

[0013] Preferably, the octahedral Cu9S5 / C nanoparticles account for 5wt%-40wt% of the mass of the composite nanofibers.

[0014] More preferably, the octahedral Cu9S5 / C nanoparticles account for 10wt%-40wt% of the mass of the composite nanofibers.

[0015] Secondly, the present invention provides a method for preparing the copper-based metal-organic framework-derived carbon composite nanofibers, comprising the following steps:

[0016] A viscous electrospinning solution was prepared by using copper-based MOF powder and a carbon source, and then electrospinning was performed to obtain nanofibers. The nanofibers were dried and pre-oxidized. The copper-based MOF was HKUST-1 or Cu-BDC.

[0017] The pre-oxidized nanofibers are calcined once in an inert atmosphere to reduce copper ions to copper, transform organic ligands into octahedral carbon frameworks, and transform carbon source fiber matrix into nano carbon fibers.

[0018] The calcined nanofibers are then co-calcined with thiourea in an inert atmosphere to obtain the final product.

[0019] This invention utilizes high-voltage electrospinning to prepare hierarchical carbon nanofibers with a one-dimensional microstructure. The stacked fibers form a three-dimensional network structure, which improves the conductivity of the composite material. At the same time, the hierarchical structure optimizes impedance matching. During calcination, the H2S generated by the decomposition of thiourea converts elemental copper into Cu9S5, which also causes sulfur doping in the carbon fibers. The organic ligands of PVP and MOF, as organic carbon sources, contain a large amount of N and O elements. During calcination, the N and O elements remain in the carbon fibers, forming nitrogen and oxygen doping.

[0020] In some embodiments, the carbon source in the viscous electrospinning solution is polyvinylpyrrolidone, and the solvent is N,N-dimethylformamide (DMF).

[0021] Preferably, in the viscous electrospinning solution, the addition ratio of copper-based MOF, carbon source and DMF is 3.5-1.4:1-2:5-20, g:g:mL;

[0022] More preferably, in the viscous electrospinning solution, the addition ratio of copper-based MOF, carbon source and DMF is 6-12:1.4:6-10, g:g:mL;

[0023] More preferably, the ratio of copper-based MOF, carbon source and DMF added to the viscous electrospinning solution is 0.933:1.4:7.05, g:g:mL.

[0024] In some embodiments, the drying temperature is 45-60°C and the drying time is 12-24 hours.

[0025] In some embodiments, the pre-oxidation method involves holding the dried nanofibers at 150-200°C for 2-3 hours. Pre-oxidation allows the organic carbon chains to initially form a ring structure, preventing them from breaking down during subsequent carbonization and thus avoiding structural collapse.

[0026] In some embodiments, the temperature of the first calcination is 600-900℃, and the calcination time is 0.5-5h.

[0027] Preferably, the calcination temperature is 650-800℃ and the calcination time is 1-2 hours.

[0028] In some embodiments, the temperature for co-calcination with thiourea is 400-500°C, and the calcination time is 0.2-0.5 h.

[0029] Thirdly, the present invention provides the application of the copper-based metal-organic framework-derived carbon composite nanofibers in the fabrication of electromagnetic wave absorbing devices.

[0030] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0031] (1) The copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared by the present invention achieves improved conductivity and adjustment of electromagnetic parameters of composite material by constructing a conductive network of MOF through carbon fibers.

[0032] (2) The copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared by the present invention achieves impedance matching optimization through hierarchical structure, and can achieve a wide impedance matching frequency band with a thickness of less than 2 mm.

[0033] (3) The copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared in this invention achieves a synergistic effect of multiple loss pathways. The doped atoms in carbon and the inherent defects in Cu9S5 can act as polarization centers, capturing unpaired electrons and inducing dipole polarization effects. The special hierarchical carbon structure and abundant Cu9S5-carbon interfaces lead to richer interfacial polarization losses. The three-dimensional conductive network provides channels for carrier migration and switching in carbon and Cu9S5, forming a micro-current amplifier and promoting conductive losses. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0035] Figure 1 This is a SEM image of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared in Example 1.

[0036] Figure 2 This is a TEM image of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared in Example 1.

[0037] Figure 3This is the XRD pattern of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared in Example 1.

[0038] Figure 4 XPS spectra of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material prepared in Example 1; 4a is the full spectrum containing C, N, O, Cu, and S elements; 4b is a magnified energy spectrum of C element; 4c is a magnified energy spectrum of N element; 4d is a magnified energy spectrum of Cu element; and 4e is a magnified energy spectrum of S element.

[0039] Figure 5 These are electromagnetic parameter diagrams of the absorbers prepared in Examples 2, 3, 4, 5, and 6. Detailed Implementation

[0040] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] The present invention will be further described below with reference to the embodiments.

[0042] Example 1

[0043] A method for preparing a copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material includes the following steps:

[0044] (1) Dissolve 0.933g HKUST-1 powder in 7.05ml DMF, disperse by ultrasonication, then add 1.4g PVP and stir vigorously to obtain a homogeneous viscous solution;

[0045] (2) Under 12kV high voltage electrostatic conditions, the viscous solution in step (1) is spun by high voltage electrospinning process to obtain organic fibers. The organic fibers are dried at 50°C for 12h and then kept at 180°C for 3h for pre-oxidation treatment.

[0046] (3) Place the product after pre-oxidation treatment in step (2) in a closed tube furnace and calcine it at 700°C for 2 hours in a nitrogen atmosphere.

[0047] (4) Place the product after calcination in step (3) in a closed tube furnace, place excess thiourea upstream and the product downstream in a nitrogen atmosphere, and calcine at 450°C for 0.5h to obtain copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material.

[0048] Figure 1 The image shows a SEM image of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material prepared in Example 1. The image shows that the prepared material has a "beaded" profile, with irregular nanoparticles embedded within the fibers. The high aspect ratio carbon-based fibers stack together to form a three-dimensional network structure.

[0049] Figure 2 This is a TEM image of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material prepared in Example 1. Numerous cavities with a diameter of approximately 150 nm exist within the fiber matrix, and these cavities are consistently accompanied by nanoparticles. Simultaneously, a distinct hierarchical interface structure exists within the fiber.

[0050] Figure 3 The image shows the XRD pattern of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material prepared in Example 1. It indicates that the synthesized composite material contains Cu9S5 and C, and the XRD pattern shows good agreement with the standard diffraction pattern of Cu9S5 (JCPDS No. 47-1748). The amorphous carbon peaks in the XRD pattern are low in intensity and not sharp, which is due to its poor crystallinity.

[0051] Figure 4 The image shows the XPS diagram of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material prepared in Example 1. It can be seen from the image that the ions in Cu9S5 are composed of multiple valence states, and the carbon fibers are doped with a large number of N, S and O.

[0052] Example 2

[0053] The microwave absorption performance of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material prepared in Example 1 was tested. The obtained copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material was mixed with paraffin at 50°C to obtain an electromagnetic wave absorber. The mass ratio of the copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber material to paraffin was 1:4.

[0054] Table 1 shows the minimum reflection loss of the absorber prepared in Example 2 at typical thicknesses. The strongest absorption performance is -69.6 dB at 3.18 mm.

[0055] Table 1

[0056]

[0057] Example 3

[0058] A method for preparing a copper-based MOF-derived Cu9S5-carbon composite nanoparticle electromagnetic wave absorbing material is the same as the first embodiment, except that steps (1) and (2) are not required, and HKUST-1 powder is used directly for subsequent steps.

[0059] The obtained copper-based MOF-derived Cu9S5-carbon composite nanoparticles were mixed with paraffin at 50°C to obtain an electromagnetic wave absorber. The mass ratio of the copper-based MOF-derived Cu9S5-carbon composite nanoparticles to paraffin was 1:4.

[0060] Table 2 shows the minimum reflection loss of the absorber prepared in Example 3 at typical thicknesses. The strongest absorption performance is -1.2 dB when the absorber thickness is 2.59 mm.

[0061] Table 2

[0062]

[0063] Example 4

[0064] A method for preparing a carbon fiber electromagnetic wave absorbing material is the same as the first embodiment, except that the amount of HKUST-1 powder added in step (1) is 0g.

[0065] The obtained carbon fiber electromagnetic wave absorbing material was mixed with paraffin at 50°C to obtain an electromagnetic wave absorber. The mass ratio of carbon fiber electromagnetic wave absorbing material to paraffin was 1:4.

[0066] Table 3 shows the minimum reflection loss of the absorber prepared in Example 4 at typical thicknesses. The strongest absorption performance is -20.3 dB when the absorber thickness is 1.55 mm.

[0067] Table 3

[0068]

[0069] Example 5

[0070] A method for preparing a copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material is the same as the first embodiment, except that the amount of HKUST-1 powder added in step (1) is 0.35g.

[0071] The obtained copper-based MOF-derived Cu9S5-carbon composite nanoparticles were mixed with paraffin at 50°C to obtain an electromagnetic wave absorber. The mass ratio of the copper-based MOF-derived Cu9S5-carbon composite nanoparticles to paraffin was 1:4.

[0072] Table 4 shows the minimum reflection loss of the absorber prepared in Example 5 at typical thicknesses. The strongest absorption performance is -13.6 dB when the absorber thickness is 5.00 mm.

[0073] Table 4

[0074]

[0075] Example 6

[0076] A method for preparing a copper-based MOF-derived hierarchical Cu9S5-carbon composite nanofiber electromagnetic wave absorbing material is the same as the first embodiment, except that the amount of HKUST-1 powder added in step (1) is 1.4g.

[0077] The obtained copper-based MOF-derived Cu9S5-carbon composite nanoparticles were mixed with paraffin at 50°C to obtain an electromagnetic wave absorber. The mass ratio of the copper-based MOF-derived Cu9S5-carbon composite nanoparticles to paraffin was 1:4.

[0078] Table 5 shows the minimum reflection loss of the absorber prepared in Example 6 at typical thicknesses. The strongest absorption performance is -9.1 dB when the absorber thickness is 1.25 mm.

[0079] Table 5

[0080]

[0081] A comparison of the reflection loss values ​​of Examples 3, 4, 5, and 6 with that of Example 2 shows that the construction of the conductive network and the adjustment of the MOF loading can affect the absorption effect. Example 2 exhibits better absorption than Examples 3, 4, 5, and 6. Table 6 shows the conductivity of the absorbers prepared in Examples 2, 3, 4, 5, and 6. As can be seen from Table 6, constructing a conductive network of MOF-derived particles using carbon fibers can amplify the conductivity, and adjusting the MOF loading can control the conductivity.

[0082] Table 6

[0083]

[0084] Figure 5 These are electromagnetic parameter diagrams of the absorbers prepared in Examples 2, 3, 4, 5, and 6. From... Figure 5 As can be seen, the electromagnetic parameters of the composite material were adjusted by regulating the MOF loading, which is also the reason for the improved absorption performance in Example 2.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A copper-based metal-organic framework-derived carbon composite nanofiber, characterized in that: It includes a three-dimensional network structure matrix formed by stacking one-dimensional carbon fibers and octahedral Cu9S5 / C nanoparticles that are monodispersed inside and on the surface of one-dimensional carbon fibers. The preparation method of the copper-based metal-organic framework-derived carbon composite nanofibers includes the following steps: A viscous electrospinning solution was prepared by using copper-based MOF powder and a carbon source, and then electrospinning was performed to obtain nanofibers. The nanofibers were dried and pre-oxidized. In the viscous electrospinning solution, the carbon source was polyvinylpyrrolidone, the solvent was DMF, and the copper-based MOF was HKUST-1. The pre-oxidized nanofibers are calcined once in an inert atmosphere to reduce copper ions to copper, transform organic ligands into octahedral carbon frameworks, and transform carbon source fiber matrix into nano carbon fibers. The calcined nanofibers are reacted with thiourea in an inert atmosphere to obtain the final product. The addition ratio of copper-based MOF, carbon source and DMF was 0.933g:1.4g:7.05mL; Alternatively, the ratio of copper-based MOF, carbon source, and DMF added is 0.35g:1.4g:7.05mL; Alternatively, the ratio of copper-based MOF, carbon source, and DMF added is 1.4g:1.4g:7.05mL.

2. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 1, characterized in that: One-dimensional carbon fibers have a diameter of 100-500 nm.

3. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 1, characterized in that: The average particle size of the octahedral Cu9S5 / C nanoparticles is 500-600 nm.

4. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 3, characterized in that: The average diameter of Cu9S5 particles is 80-120 nm.

5. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 1, characterized in that: Octahedral Cu9S5 / C nanoparticles account for 5wt%-50wt% of the composite nanofibers.

6. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 5, characterized in that: Octahedral Cu9S5 / C nanoparticles account for 5wt%-40wt% of the composite nanofibers.

7. The copper-based metal-organic framework-derived carbon composite nanofibers according to claim 6, characterized in that: Octahedral Cu9S5 / C nanoparticles account for 10wt%-40wt% of the mass of the composite nanofibers.

8. The method for preparing copper-based metal-organic framework-derived carbon composite nanofibers according to any one of claims 1-7, characterized in that: Includes the following steps: A viscous electrospinning solution was prepared by using copper-based MOF powder and a carbon source, and then electrospinning was performed to obtain nanofibers. The nanofibers were dried and pre-oxidized. In the viscous electrospinning solution, the carbon source was polyvinylpyrrolidone, the solvent was DMF, and the copper-based MOF was HKUST-1. The pre-oxidized nanofibers are calcined once in an inert atmosphere to reduce copper ions to copper, transform organic ligands into octahedral carbon frameworks, and transform carbon source fiber matrix into nano carbon fibers. The calcined nanofibers are reacted with thiourea in an inert atmosphere to obtain the final product. In the viscous electrospinning solution, the addition ratio of copper-based MOF, carbon source and DMF is 0.933g:1.4g:7.05mL; Alternatively, the ratio of copper-based MOF, carbon source, and DMF added is 0.35g:1.4g:7.05mL; Alternatively, the ratio of copper-based MOF, carbon source, and DMF added is 1.4g:1.4g:7.05mL.

9. The method for preparing copper-based metal-organic framework-derived carbon composite nanofibers according to claim 8, characterized in that: The pre-oxidation method is as follows: the dried nanofibers are kept at 150-200℃ for 2-3 hours.

10. The method for preparing copper-based metal-organic framework-derived carbon composite nanofibers according to claim 8, characterized in that: The temperature of the first calcination is 600-900℃, and the calcination time is 0.5-5h.

11. The method for preparing copper-based metal-organic framework-derived carbon composite nanofibers according to claim 10, characterized in that: The calcination temperature is 650-800℃ and the calcination time is 1-2 hours.

12. The method for preparing copper-based metal-organic framework-derived carbon composite nanofibers according to claim 8, characterized in that: The temperature for co-calcination with thiourea is 400-500℃, and the calcination time is 0.2-0.5h.

13. The application of the copper-based metal-organic framework-derived carbon composite nanofibers according to any one of claims 1-7 in the preparation of electromagnetic wave absorbing devices.

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