A fluorinated ligand-doped ZIF-8 / pbo composite nanometer paper and a preparation method and application thereof

Abstract

The application discloses a fluorinated ligand-doped ZIF-8 / PBO composite nanometer paper and a preparation method and application thereof, and belongs to the technical field of nanometer composite insulating materials and metal organic framework materials. The fluorinated ligand-doped ZIF-8 / PBO composite nanometer paper is obtained through suction filtration forming and hot pressing treatment after in-situ introduction of fluorinated ZIF-8 in a PBO nanofiber network. The fluorinated ZIF-8 is constructed by coordination self-assembly of a zinc source, an imidazole main ligand and a fluorine-containing imidazole co-ligand. The structure of ZIF-8 is controlled by introducing the fluorine-containing imidazole ligand, and the in-situ growth strategy is combined, so that the fluorinated ZIF-8 is uniformly anchored on the surface and in the network of the PBO nanofiber, the interface structure is optimized on a microscale, the polarization loss is reduced, and the material is endowed with excellent hydrophobic performance.

Description

Technical Field

[0001] This invention belongs to the technical field of nanocomposite insulating materials and metal-organic framework materials, and particularly relates to a fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, its preparation method and application. Background Technology

[0002] Poly(p-phenylenebenzodioxazole) cellulose (PBO) is hailed as the "super fiber of the 21st century," exhibiting significantly superior overall performance compared to traditional polymer fibers such as aramid, ultra-high molecular weight polyethylene, and polyimide. Its molecular chain is rich in conjugated aromatic structures, resulting in stable molecular configuration, low polarizability, an intrinsic dielectric constant of approximately 3.0, and a dielectric loss tangent as low as 0.001, demonstrating outstanding application potential in the field of low-dielectric materials. PBO nanofibers, derived from PBO fibers, can further retain and amplify its advantages of low dielectric constant, high mechanical strength, and heat resistance, making them ideal substrates for high-frequency communications, integrated circuit insulation, and radar wave transmission.

[0003] However, PBO fibers have a stable chemical structure and strong surface inertness, which limits the space for material design and functional modification. At the same time, zeolite imidazole ester skeleton material-8 (ZIF-8) is prone to agglomeration, uneven dispersion and weak interfacial bonding in PBO nanofiber networks, making it difficult to achieve uniform loading and synergistic effects, which seriously restricts the performance improvement and engineering application of PBO-based low dielectric composite materials. Summary of the Invention

[0004] This invention proposes a fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, its preparation method, and its application, in order to solve the problems of uneven distribution of ZIF-8 in PBO nanofiber networks, obvious interfacial polarization, and strong hygroscopicity of materials in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: One objective is to develop a fluorinated ligand-doped ZIF-8 / PBO composite nanopaper. This fluorinated ligand-doped ZIF-8 / PBO composite nanopaper is obtained by in-situ introduction of fluorinated ZIF-8 into a PBO nanofiber network, followed by vacuum filtration, molding, and hot pressing. The fluorinated ZIF-8 is constructed through coordination self-assembly of a zinc source, an imidazole host ligand, and a fluorinated imidazole co-ligand. During coordination, some imidazole ligands are replaced by fluorinated ligands, thereby introducing -CF3 functional groups into the ZIF-8 framework, resulting in a material with lower polarizability and higher hydrophobicity.

[0006] This invention modulates the structure of ZIF-8 by introducing fluorinated imidazole ligands and combining them with an in-situ growth strategy to uniformly anchor fluorinated ZIF-8 on the surface and inside the PBO nanofiber network. This optimizes the interface structure at the microscale, reduces polarization loss, and endows the material with excellent hydrophobic properties.

[0007] Furthermore, the zinc source is zinc nitrate hexahydrate, the imidazole main ligand is 2-methylimidazole, and the fluorinated imidazole co-ligand is 2-trifluoromethylbenzimidazole.

[0008] Furthermore, the molar amount of the fluorinated imidazole coligand in the fluorinated ZIF-8 is 5-30%. The doping ratio of the fluorinated imidazole coligand is adjustable to control the structural composition of the fluorinated ZIF-8 and the properties of the composite material.

[0009] Further, by mass parts, the raw materials of the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper include: 10-40 parts of PBO fiber, 100-250 parts of methanesulfonic acid, 100-250 parts of trifluoroacetic acid, 15-36 parts of zinc nitrate hexahydrate, 10-30 parts of 2-methylimidazole, 3-10 parts of 2-trifluoromethylbenzimidazole, 300-540 parts of methanol, 200-700 parts of distilled water, and 30-60 parts of N,N-dimethylformamide (DMF).

[0010] Furthermore, the PBO fiber has a length of 10–20 cm and a diameter of 10–15 μm.

[0011] Second objective: A method for preparing the above-mentioned fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, comprising the following steps: (1) PBO fibers were added to a mixture of methanesulfonic acid and trifluoroacetic acid and stirred for the first time to obtain a PBO nanofiber acid solution. (2) Add distilled water to the PBO nanofiber acid solution and stir for a second time to obtain PBO nanofiber aqueous dispersion; (3) Add methanol to the PBO nanofiber aqueous dispersion and stir for a third time to obtain PBO nanofiber methanol dispersion; (4) Dissolve zinc nitrate hexahydrate in N,N-dimethylformamide to obtain a zinc nitrate hexahydrate solution (zinc salt preferentially dissolves in N,N-dimethylformamide to form a homogeneous metal precursor solution); add the zinc nitrate hexahydrate solution to the PBO nanofiber methanol dispersion, stir for the fourth time, then add 2-methylimidazole and 2-trifluoromethylbenzimidazole, stir for the fifth time, to obtain a fluorinated ZIF-8 / PBO nanofiber dispersion. (5) The fluorinated ZIF-8 / PBO nanofiber dispersion is filtered (to form a continuous fiber membrane structure), hot-pressed (to improve the density and structural stability of the material), cooled to room temperature, and demolded to obtain fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

[0012] In this invention, PBO fibers undergo protonation dissolution in a mixed acid system composed of trifluoroacetic acid and methanesulfonic acid. Under the action of hydrogen ions, the molecular chains become positively charged, enhancing the electrostatic repulsion between chains and thus achieving a transformation from macroscopic fibers to molecular-level dispersion. Subsequently, by adding distilled water to initiate a deprotonation process, the PBO molecular chains gradually return to a neutral state, the π-π interactions between chains are re-established, and entanglement and recombination occur at the nanoscale, forming a stable PBO nanofiber dispersion system. During this process, the nitrogen-containing sites on the PBO molecular chains can interact with Zn. 2+ Coordination occurs, allowing zinc ions to preferentially adsorb and anchor on the nanofiber surface, thereby constructing a spatially uniform distribution of metal active sites. This process provides a uniform interface for the subsequent nucleation of ZIF-8, avoiding the particle aggregation problem caused by homogeneous nucleation in traditional solution systems. Based on this, zinc nitrate hexahydrate is dissolved in N,N-dimethylformamide to form a metal salt solution, while 2-methylimidazole and 2-trifluoromethylbenzimidazole are dissolved in methanol to form a ligand solution. At room temperature, the ligand solution is gradually added to a PBO nanofiber dispersion system containing zinc ions. Under stirring, a coordination reaction occurs, causing fluorinated ZIF-8 to undergo directional nucleation and growth along the fiber surface, gradually forming a continuously distributed ZIF structural layer.

[0013] This in-situ growth process has the following characteristics: (1) ZIF-8 preferentially grows on the fiber surface, achieving interface-dominated heterogeneous nucleation; (2) Fluorine-containing ligands participate in framework construction during growth, achieving in-structure doping rather than physical mixing; (3) A tight interface is formed between ZIF particles and fibers, which improves the interfacial bonding strength and reduces interfacial defects.

[0014] Subsequently, the composite system was deposited on the filter membrane surface to form a continuous fiber membrane structure by vacuum filtration, and the pores were further compacted and the interfiber contact was enhanced by hot pressing, thereby obtaining a fluorinated ligand-doped ZIF-8 / PBO composite nanopaper with a dense structure and excellent mechanical properties.

[0015] Furthermore, the first stirring is performed at a speed of 1500–1800 rpm for a duration of 50–60 hours; The second stirring speed is 1800-2200 rpm, and the time is 30 min; The third stirring was performed at a speed of 1200 rpm for 2 hours. The fourth stirring is performed at a speed of 800–1500 rpm for 30–60 min. The fifth stirring is performed at a speed of 800–1500 rpm for a duration of 8–72 hours.

[0016] Furthermore, the hot pressing treatment is performed at a temperature of 70–90°C for 24–72 hours and at a pressure of 0.1–0.3 MPa.

[0017] Through the above structural design and preparation methods, this invention realizes a multi-level synergistic system of "nanofiber framework-ZIF porous structure-fluorine-containing functional unit" at the microscale, and its mechanism of action is as follows: On the one hand, ZIF-8 itself has high porosity, and the air phase introduced into its channels significantly reduces the effective dielectric constant of the material. On the other hand, the introduction of fluorine-containing ligands reduces the skeletal polarization capability and decreases the contribution of dipole orientation polarization, thereby further reducing dielectric loss. Simultaneously, the hydrophobic structure effectively inhibits the adsorption and diffusion of water molecules in the material, reducing water-induced polarization and improving the electrical insulation stability of the material under high humidity environments. Furthermore, the dense interface structure formed by in-situ growth effectively reduces interface defects and charge accumulation, suppressing interface polarization effects. At the macroscopic level, the dense network structure constructed by filtration-hot pressing allows stress to be uniformly transferred between the fibers and ZIF, thereby reducing local stress concentration and improving the overall mechanical properties and structural stability of the material.

[0018] Third objective: Application of the above-mentioned fluorinated ligand-doped ZIF-8 / PBO composite nanopaper in the preparation of low dielectric constant insulating materials, high frequency communication substrates, radar transparent materials or integrated circuit packaging materials.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Low dielectric constant and low dielectric loss; (2) Excellent hydrophobic properties and environmental stability; (3) High mechanical strength and structural integrity; (4) Good interface bonding and anti-polarization ability.

[0020] Experimental results show that the dielectric constant of the composite nanopaper obtained by this invention can reach 1.43 to 1.52, the dielectric loss tangent is 0.008 to 0.02, and it also has high tensile strength and good toughness. It has important application potential in the fields of high-frequency communication, integrated circuits and advanced electrical insulation materials. Attached Figure Description

[0021] 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 undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram illustrating the preparation of fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to the present invention. Figure 2X-ray photoelectron spectroscopy (XPS) curves of the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Example 1; Figure 3 Scanning electron microscope (SEM) image of the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Example 1; Figure 4 Contact angle photographs of the fluorinated ligand-doped ZIF-8 / PBO composite nanopapers prepared in Examples 1-3; Figure 5 Contact angle photographs of the nanopapers prepared for comparative examples 1-4. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] This invention constructs fluorinated ligand-doped ZIF-8 in a PBO nanofiber network structure by sequentially adding zinc nitrate hexahydrate, 2-methylimidazole, and 2-trifluoromethylbenzimidazole ligands in different proportions to a PBO nanofiber dispersion using an in-situ growth strategy. Due to the low polarizability of the C–F bonds in the fluorinated ligands and the strong hydrophobicity of the benzo[a] group, the overall polarization of the material is effectively reduced, and the interfacial environment is improved. The porous structure of ZIF-8 itself further reduces the effective dielectric response of the composite system. Based on this, a dense composite paper material with uniformly distributed components is constructed through vacuum filtration molding combined with high-temperature hot pressing. The in-situ growth method avoids the agglomeration problem that easily occurs during traditional filler doping processes, allowing the fluorinated ZIF-8 to be uniformly anchored in the PBO nanofiber network, which is beneficial for interfacial bonding and stress transfer, thereby improving the mechanical properties and structural stability of the composite material. Simultaneously, the introduction of fluorinated groups effectively reduces the surface energy of the material and improves hydrophobicity, resulting in a composite paper with both low dielectric properties and good environmental adaptability.

[0028] This invention proposes a structural construction strategy based on a combination of fluorinated ligand regulation and in-situ growth, achieving synergistic integration of ZIF structures and high-performance fiber networks at the nanoscale. The fluorinated ZIF-8 is composed of Zn... 2+ A three-dimensional porous framework structure is constructed with imidazole ligands via coordination bonds, in which some 2-methylimidazolium is replaced by the fluorinated ligand 2-trifluoromethylbenzimidazole, thus forming a mixed-ligand type zeolite imidazole framework material. Fluorinated ZIF-8 maintains a ZIF-8-like topology (SOD type), while the introduction of a larger fluorinated aromatic ring ligand modulates the pore size distribution of the framework and introduces -CF3 low-polarity groups into the interior and surface of the framework. The molar ratio of 2-methylimidazolium to 2-trifluoromethylbenzimidazole is (1.5–15):1, preferably (3–7):1. The molar amount of the fluorinated imidazole co-ligand in fluorinated ZIF-8 is 5–30%, preferably 6–25%.

[0029] The preparation method of fluorinated ZIF-8 includes the following steps: (1) Dissolve zinc nitrate hexahydrate in N,N-dimethylformamide and stir to obtain a homogeneous and transparent metal salt solution; (2) Dissolve 2-methylimidazole and 2-trifluoromethylbenzimidazole in methanol to form a mixed ligand solution; (3) The metal salt solution is slowly added dropwise to the mixed ligand solution (or added dropwise in the reverse direction), and the reaction is carried out under stirring at room temperature to form a milky white or lightly turbid dispersion system; wherein, the preferred method of addition is uniform dropwise addition, the preferred addition time is 5 to 30 min; the temperature of the stirring reaction is 20 to 35℃, preferably 25℃; the stirring reaction time is 6 to 72 h, preferably 8 to 12 h; (4) After the reaction continues for a certain period of time, the solid product is separated by centrifugation and washed repeatedly with an alcohol solvent; the preferred washing solvent is methanol, ethanol or a mixture thereof; the preferred number of washing times is 3 to 6. (5) The obtained solid is dried under vacuum to obtain fluorinated ZIF-8 powder; the preferred drying conditions are: temperature 50-80℃ and time 10-24h.

[0030] The fluorinated ZIF-8 prepared by this method has a particle size of 50–500 nm, preferably 80–200 nm.

[0031] This invention provides a method for preparing fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, specifically as follows: I. Raw Material Preparation Prepare the following raw materials by weight: PBO fiber (length 10-20cm, diameter 10-15μm): 10-40 parts; such as 10 parts, 15 parts, 20 parts, 26 parts or 40 parts; Methanesulfonic acid: 100-250 parts; such as 100 parts, 120 parts, 200 parts or 250 parts; Trifluoroacetic acid (purity ≥98%): 100–250 parts; such as 100 parts, 120 parts, 150 parts, 200 parts or 250 parts; Zinc nitrate hexahydrate (zinc source, purity ≥98%): 15–36 parts; such as 15 parts, 20 parts, 28 parts, or 36 parts; 2-Methylimidazole (imidazolium main ligand, purity ≥99%): 10–30 parts; such as 15 parts, 18 parts, 20 parts, 24 parts or 30 parts; 2-Trifluoromethylbenzimidazole (purity ≥98%) (fluoroimidazole coligand, doping molar amount in fluorinated ZIF-8 is 5-30%): 3-10 parts; such as 3 parts, 4 parts, 5 parts, 6 parts or 10 parts; Methanol (purity ≥95%): 300-540 parts; such as 300 parts, 350 parts, 420 parts or 500 parts.

[0032] Distilled water: 200–700 parts; such as 200 parts, 300 parts, 350 parts, 500 parts, or 700 parts; N,N-Dimethylformamide (purity ≥99.5%): 30–60 parts, such as 30, 40, 50 or 60 parts.

[0033] II. Preparation Steps (1) Preparation of PBO nanofiber acid solution PBO fibers were added to a mixture of methanesulfonic acid and trifluoroacetic acid and stirred at 1500–1800 rpm for 50–60 h to obtain a PBO nanofiber acid solution. (2) Preparation of PBO nanofiber aqueous dispersion Distilled water was added to the PBO nanofiber acid solution obtained in step (1), and the mixture was stirred at 1800-2200 rpm for 30 min to obtain a PBO nanofiber aqueous dispersion. (3) Preparation of PBO nanofiber methanol dispersion Methanol was added to the PBO nanofiber aqueous dispersion obtained in step (2), and the mixture was stirred at 1200 rpm for 2 hours to obtain a PBO nanofiber methanol dispersion. (4) Preparation of fluorinated ZIF-8 / PBO nanofiber dispersion Zinc nitrate hexahydrate was dissolved in N,N-dimethylformamide to obtain a zinc nitrate hexahydrate solution; In the methanol dispersion of PBO nanofibers obtained in step (3), the above zinc nitrate hexahydrate solution was added and stirred at a speed of 800-1500 rpm for 30-60 min. Then, 2-methylimidazole and 2-trifluoromethylbenzimidazole were added and stirred at a speed of 800-1200 rpm for 8-72 h. This allowed the zinc source, main ligand and fluorinated co-ligand to coordinate and self-assemble to construct fluorinated ZIF-8 and introduce it in situ into the PBO nanofiber network, thus obtaining a fluorinated ZIF-8 / PBO nanofiber dispersion. (5) Filtering, molding and hot pressing The fluorinated ZIF-8 / PBO nanofiber dispersion obtained in step (4) is filtered to obtain wet nanopaper; then it is hot-pressed at a temperature of 70-90℃ (e.g., 70℃, 80℃ or 90℃) and a pressure of 0.1-0.3MPa (e.g., 0.1MPa, 0.25MPa or 0.3MPa) for 24-72h (e.g., 24h), cooled to room temperature, and demolded to obtain fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

[0034] In the process provided by this invention: (1) Zn 2+ (1) ZIF is preferentially adsorbed on the surface of PBO nanofibers, which restricts the nucleation sites of ZIF and thus avoids particle aggregation; (2) The -CF3 group in 2-trifluoromethylbenzimidazole has a strong electron-withdrawing effect, which can significantly reduce the electronic polarization ability of the material; (3) The porous structure of fluorinated ZIF-8 introduces a large number of "air pores" (k≈1) into the material, further reducing the overall dielectric constant; (4) Fluorine-containing groups migrate to the surface of the material, forming a low surface energy layer, increasing the contact angle (usually >110°), and giving it excellent hydrophobicity; (5) The ZIF-8 skeleton and PBO form an interfacial physical interlock and weak interaction, which improves the mechanical properties of the composite material.

[0035] This composite nanopaper can be used to prepare low dielectric constant insulating materials, high frequency communication substrates, radar transparent materials, or integrated circuit packaging materials.

[0036] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0037] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0038] All raw materials used in this invention were purchased from the market.

[0039] The following detailed description, in conjunction with embodiments, illustrates the fluorinated ZIF-8 and its preparation method, as well as the low dielectric constant and hydrophobic insulating paper and its preparation method provided by the present invention. However, this should not be construed as limiting the scope of protection of the present invention.

[0040] In the embodiments of the present invention, the amount of raw materials used is not limited to a specific mass value. As long as the required raw materials are added according to the mass fraction, molar ratio or proportion range described in the present invention, they can be used.

[0041] Example 1 A method for preparing fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, specifically as follows: (1) Preparation of PBO nanofiber acid solution: Take 40 parts of PBO fibers with a length of 10-20 cm and a diameter of 10-15 μm, add them to a mixture of 200 parts of methanesulfonic acid and 200 parts of trifluoroacetic acid, stir at 1800 rpm for 50 h until the PBO fibers are fully dispersed to obtain PBO nanofiber acid solution. (2) Preparation of PBO nanofiber aqueous dispersion: 300 parts of distilled water were slowly added to the prepared PBO nanofiber acid solution and stirred at 2200 rpm for 30 min to disperse the PBO nanofiber from the acid solution into the water to obtain a uniform PBO nanofiber aqueous dispersion. (3) Preparation of PBO nanofiber methanol dispersion: Add 300 parts of methanol to the above PBO nanofiber aqueous dispersion and stir at 1200 rpm for 2 hours to fully mix the system and obtain PBO nanofiber methanol dispersion. (4) Preparation of fluorinated ZIF-8 / PBO nanofiber dispersion: First, take 15 parts of zinc nitrate hexahydrate and dissolve it in 40 parts of N,N-dimethylformamide. Stir until completely dissolved to obtain zinc nitrate hexahydrate solution. Then, add the prepared zinc nitrate hexahydrate solution to the above PBO nanofiber methanol dispersion and stir at 1000 rpm for 30 min. Then, add 20 parts of 2-methylimidazole and 3 parts of 2-trifluoromethylbenzimidazole and stir at 1000 rpm for 12 h to allow the zinc source, main ligand and co-ligand to coordinate and self-assemble in situ in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtain fluorinated ZIF-8 / PBO nanofiber dispersion. (5) Molding and post-treatment: The above-mentioned fluorinated ZIF-8 / PBO nanofiber dispersion was filtered to allow the nanofibers and fluorinated ZIF-8 to be fully deposited to form a wet paper blank; then the wet paper blank was hot-pressed, with the hot-pressing temperature controlled at 90℃, the hot-pressing time at 24h, and the hot-pressing pressure at 0.1MPa; after hot pressing, the sample was cooled to room temperature and demolded to obtain the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

[0042] Example 2 (1) Preparation of PBO nanofiber acid solution: Take 40 parts of PBO fibers with a length of 10-20 cm and a diameter of 10-15 μm, add them to a mixture of 200 parts of methanesulfonic acid and 200 parts of trifluoroacetic acid, stir at 1800 rpm for 50 h until the PBO fibers are fully dispersed to obtain PBO nanofiber acid solution. (2) Preparation of PBO nanofiber aqueous dispersion: 300 parts of distilled water were slowly added to the prepared PBO nanofiber acid solution and stirred at 2200 rpm for 30 min to disperse the PBO nanofiber from the acid solution into the water to obtain a uniform PBO nanofiber aqueous dispersion. (3) Preparation of PBO nanofiber methanol dispersion: Add 300 parts of methanol to the above PBO nanofiber aqueous dispersion and stir at 1200 rpm for 2 hours to fully mix the system and obtain PBO nanofiber methanol dispersion. (4) Preparation of fluorinated ZIF-8 / PBO nanofiber dispersion: First, take 20 parts of zinc nitrate hexahydrate and dissolve it in 40 parts of N,N-dimethylformamide. Stir until completely dissolved to obtain zinc nitrate hexahydrate solution. Then, add the prepared zinc nitrate hexahydrate solution to the above PBO nanofiber methanol dispersion and stir at 1200 rpm for 40 min. Then, add 30 parts of 2-methylimidazole and 10 parts of 2-trifluoromethylbenzimidazole and stir at 1200 rpm for 8 h to allow the zinc source, main ligand and co-ligand to coordinate and self-assemble in situ in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtain fluorinated ZIF-8 / PBO nanofiber dispersion. (5) Molding and post-treatment: The above-mentioned fluorinated ZIF-8 / PBO nanofiber dispersion was filtered to allow the nanofibers and fluorinated ZIF-8 to be fully deposited to form a wet paper blank; then the wet paper blank was hot-pressed, with the hot-pressing temperature controlled at 70℃, the hot-pressing time at 24h, and the hot-pressing pressure at 0.3MPa; after hot pressing, the sample was cooled to room temperature and demolded to obtain the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

[0043] Example 3 (1) Preparation of PBO nanofiber acid solution: Take 10 parts of PBO fibers with a length of 10-20 cm and a diameter of 10-15 μm, add them to a mixture of 100 parts of methanesulfonic acid and 100 parts of trifluoroacetic acid, stir at 1500 rpm for 60 h until the PBO fibers are fully dispersed to obtain PBO nanofiber acid solution. (2) Preparation of PBO nanofiber aqueous dispersion: 200 parts of distilled water were slowly added to the prepared PBO nanofiber acid solution and stirred at 1800 rpm for 30 min to disperse the PBO nanofiber from the acid solution into the water to obtain a uniform PBO nanofiber aqueous dispersion. (3) Preparation of PBO nanofiber methanol dispersion: Add 500 parts of methanol to the above PBO nanofiber aqueous dispersion and stir at 1200 rpm for 2 hours to fully mix the system and obtain PBO nanofiber methanol dispersion. (4) Preparation of fluorinated ZIF-8 / PBO nanofiber dispersion: First, take 20 parts of zinc nitrate hexahydrate and dissolve it in 40 parts of N,N-dimethylformamide. Stir until completely dissolved to obtain zinc nitrate hexahydrate solution. Then, add the prepared zinc nitrate hexahydrate solution to the above PBO nanofiber methanol dispersion and stir at 1500 rpm for 60 min. Then, add 10 parts of 2-methylimidazole and 4 parts of 2-trifluoromethylbenzimidazole and stir at 1500 rpm for 10 h to allow the zinc source, main ligand and co-ligand to coordinate and self-assemble in situ in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtain fluorinated ZIF-8 / PBO nanofiber dispersion. (5) Molding and post-treatment: The above-mentioned fluorinated ZIF-8 / PBO nanofiber dispersion was filtered to allow the nanofibers and fluorinated ZIF-8 to be fully deposited to form a wet paper blank; then the wet paper blank was hot-pressed, with the hot-pressing temperature controlled at 80℃, the hot-pressing time at 24h, and the hot-pressing pressure at 0.25MPa; after hot pressing, the sample was cooled to room temperature and demolded to obtain the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

[0044] Examples 4-6 Same as Example 1, except that the raw material ratio is shown in Table 1.

[0045] Table 1. Mass parts (parts) of each raw material in Examples 4-6 Comparative Example 1 Same as Example 1, except that zinc nitrate hexahydrate and N,N-dimethylformamide are not added in step (4). Step (4) is as follows: 20 parts of 2-methylimidazole and 3 parts of 2-trifluoromethylbenzimidazole are dissolved in 40 parts of methanol and stirred until completely dissolved. The mixture is stirred at 1000 rpm until the ligand is completely dissolved. Then, it is added to the PBO nanofiber methanol dispersion and stirred at 1000 rpm for 12 hours to finally obtain the PBO nanofiber dispersion.

[0046] Comparative Example 2 Same as Example 1, except that 2-trifluoromethylbenzimidazole is not added in step (4). Step (4) is as follows: First, take 15 parts of zinc nitrate hexahydrate, dissolve it in 40 parts of N,N-dimethylformamide, and stir until completely dissolved to obtain zinc nitrate hexahydrate solution; then add the prepared zinc nitrate hexahydrate solution to the above PBO nanofiber methanol dispersion, stir at 1000 rpm for 30 min, continue to add 20 parts of 2-methylimidazole, stir at 1000 rpm for 12 h, so that the zinc source, main ligand and co-ligand are in situ coordinated and self-assembled in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtain ZIF-8 / PBO nanofiber dispersion.

[0047] Comparative Example 3 Same as Example 1, except that 2-methylimidazole is not added in step (4). Step (4) is as follows: First, take 15 parts of zinc nitrate hexahydrate, dissolve it in 40 parts of N,N-dimethylformamide, and stir until completely dissolved to obtain zinc nitrate hexahydrate solution; then add the prepared zinc nitrate hexahydrate solution to the above PBO nanofiber methanol dispersion, stir at 1000 rpm for 30 min, continue to add 3 parts of 2-trifluoromethylbenzimidazole, stir at 1000 rpm for 12 h, so that the zinc source, main ligand and co-ligand are in situ coordinated and self-assembled in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtain PBO nanofiber dispersion.

[0048] Comparative Example 4 Same as Example 1, except that step (3) is not performed. Step (4) is as follows: 15 parts of zinc nitrate hexahydrate are added to the above PBO nanofiber methanol dispersion and stirred at 1000 rpm for 30 min. Then, 20 parts of 2-methylimidazole and 3 parts of 2-trifluoromethylbenzimidazole are added and stirred at 1000 rpm for 12 h. This allows the zinc source, main ligand and co-ligand to coordinate and self-assemble in situ in the PBO nanofiber network to form fluorinated ZIF-8, and finally obtains fluorinated ZIF-8 / PBO nanofiber dispersion.

[0049] Comparative Example 5 Same as in Example 1, except that steps (3) and (4) are omitted, and step (5) is performed directly.

[0050] Experimental Example 1 The performance of the products obtained in the above embodiments and comparative examples was evaluated, and the results are summarized in Table 2. The specific test methods are as follows: (1) Tensile strength and toughness were tested using an electronic universal testing machine, and the test procedure was carried out in accordance with ASTM D5568-08 standard; (2) The dielectric constant and dielectric loss were tested using a WK6500B impedance analyzer, and the test method was performed in accordance with the ASTM D150 standard.

[0051] (3) Contact angle test: The contact angle between the aerogel and water was recorded using a contact angle meter (JY-82B Kruss DSA, Germany) according to ASTM D5725.

[0052] Table 2 Performance test results of products from Examples 1-6 and Comparative Examples 1-5 As can be seen from the performance data in Table 2, the present invention introduces fluorinated ZIF-8 into the PBO nanofiber network through an in-situ growth strategy, effectively reducing the dielectric constant and dielectric loss tangent of the PBO composite nanopaper, and enhancing its tensile strength, hydrophobicity, and toughness. The comparative examples show that the PBO composite nanopaper without the addition of zinc nitrate hexahydrate and / or the fluorinated ligand 2-trifluoromethylbenzimidazole exhibits lower mechanical strength and a higher dielectric constant, making it difficult to meet the requirements of practical engineering applications. Furthermore, Comparative Example 3 shows that when only the fluorinated ligand is added without the main ligand 2-methylimidazole, the mechanical and dielectric properties of the composite nanopaper are difficult to achieve ideal values ​​due to the inability to construct a complete ZIF framework structure. Comparative Example 4 shows that when the methanol and DMF solvent system is omitted, the ligand dissolution is insufficient, the fluorinated ZIF-8 is unevenly distributed, and the performance is significantly lower than in the examples. In summary, the low dielectric constant, hydrophobic, and insulating PBO nanopaper prepared by the present invention combines low dielectric, high strength, and high hydrophobicity, showing broad application prospects in the field of low dielectric materials such as integrated circuits.

[0053] Experimental Example 2 (1) Figure 1 This is a schematic diagram of the ZIF-8 / PBO composite nanopaper doped with fluorinated ligands prepared according to the present invention.

[0054] (2) X-ray photoelectron spectroscopy analysis was performed on the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Example 1. The results are shown in the figure. Figure 2 .Depend on Figure 2 It can be seen that the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Example 1 has four characteristic peaks at the C1s peak, located at 284.59 eV (corresponding to CC / C=C structure), 286 eV (corresponding to CO structure), 288.24 eV (corresponding to CN / C=N structure) and 290.70 eV (corresponding to CF structure). The appearance of the CF characteristic peak at 290.70 eV further proves that the fluorinated ligand 2-trifluoromethylbenzimidazole has been successfully introduced into the composite nanopaper structure.

[0055] (3) The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Example 1 was analyzed by SEM. The results are shown in the figure. Figure 3 . Figure 3 The prepared fluorinated ligand-doped ZIF-8 / PBO composite nanopaper exhibits a rhombic dodecahedral morphology with uniform grain size, clear outline, and obvious crystal surface texture, indicating that the incorporation of fluorinated ligands did not destroy the basic crystal structure of ZIF-8, and the resulting product has good crystallinity.

[0056] (4) The contact angle of the nanopapers prepared in Examples 1, 2, and 3, as well as Comparative Examples 1, 2, 3, and 4, was tested. The results are shown in the figure. Figure 4 and Figure 5 . Figure 4 This is the example set. Figure 5 This is the comparative example group. (From...) Figure 4 It can be seen that the contact angles of the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper prepared in Examples 1, 2 and 3 reached 127°, 124° and 130° respectively, all of which are much higher than 90°, showing excellent hydrophobic properties. Figure 5 The contact angles of the PBO nanopapers prepared in Comparative Examples 1 to 4 were 60°, 62°, 69° and 66°, respectively, all below 90°, showing obvious hydrophilic properties and poor hydrophobic properties. This further proves that the introduction of fluorine-containing ligands has a significant effect on improving the hydrophobicity of the material surface.

[0057] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, characterized in that, The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper is obtained by in-situ introduction of fluorinated ZIF-8 into a PBO nanofiber network, followed by vacuum filtration, molding, and hot pressing. The fluorinated ZIF-8 is constructed by coordination self-assembly of a zinc source, an imidazole main ligand, and a fluorinated imidazole co-ligand.

2. The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 1, characterized in that, The zinc source is zinc nitrate hexahydrate, the imidazole main ligand is 2-methylimidazole, and the fluorinated imidazole co-ligand is 2-trifluoromethylbenzimidazole.

3. The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 1, characterized in that, The molar amount of the fluorinated imidazole coligand in fluorinated ZIF-8 is 5-30%.

4. The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 1, characterized in that, The raw materials of the fluorinated ligand-doped ZIF-8 / PBO composite nanopaper, by mass fraction, include: 10-40 parts PBO fiber, 100-250 parts methanesulfonic acid, 100-250 parts trifluoroacetic acid, 15-36 parts zinc nitrate hexahydrate, 10-30 parts 2-methylimidazole, 3-10 parts 2-trifluoromethylbenzimidazole, 300-540 parts methanol, 200-700 parts distilled water, and 30-60 parts N,N-dimethylformamide.

5. The fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 4, characterized in that, The PBO fibers are 10–20 cm in length and 10–15 μm in diameter.

6. A method for preparing ZIF-8 / PBO composite nanopaper doped with fluorinated ligands as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) PBO fibers were added to a mixture of methanesulfonic acid and trifluoroacetic acid and stirred for the first time to obtain a PBO nanofiber acid solution. (2) Add distilled water to the PBO nanofiber acid solution and stir for a second time to obtain PBO nanofiber aqueous dispersion; (3) Add methanol to the PBO nanofiber aqueous dispersion and stir for a third time to obtain PBO nanofiber methanol dispersion; (4) Dissolve zinc nitrate hexahydrate in N,N-dimethylformamide to obtain zinc nitrate hexahydrate solution; add zinc nitrate hexahydrate solution to the PBO nanofiber methanol dispersion, stir for the fourth time, add 2-methylimidazole and 2-trifluoromethylbenzimidazole, stir for the fifth time to obtain fluorinated ZIF-8 / PBO nanofiber dispersion; (5) The fluorinated ZIF-8 / PBO nanofiber dispersion was filtered, hot-pressed, and cooled to room temperature to obtain fluorinated ligand-doped ZIF-8 / PBO composite nanopaper.

7. The method for preparing fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 6, characterized in that, The first stirring speed is 1500-1800 rpm, and the time is 50-60 h; The second stirring speed is 1800-2200 rpm, and the time is 30 min; The third stirring was performed at a speed of 1200 rpm for 2 hours. The fourth stirring is performed at a speed of 800–1500 rpm for 30–60 min. The fifth stirring is performed at a speed of 800–1500 rpm for a duration of 8–72 hours.

8. The method for preparing fluorinated ligand-doped ZIF-8 / PBO composite nanopaper according to claim 6, characterized in that, The hot pressing treatment is performed at a temperature of 70–90°C for 24–72 hours and at a pressure of 0.1–0.3 MPa.

9. The application of a fluorinated ligand-doped ZIF-8 / PBO composite nanopaper as described in any one of claims 1-5 in the preparation of low dielectric constant insulating materials, high frequency communication substrates, radar transparent materials, or integrated circuit packaging materials.

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