Regenerated cellulose aerogel fibers with in-situ grown mofs and methods of making and using the same

Abstract

The application provides regenerated cellulose aerogel fibers with in-situ growth of MOF and a preparation method and application thereof. The method comprises the following steps: homogeneously esterifying and modifying cellulose in a cellulose solution to introduce active functional groups on the cellulose chain, and forming a pre-anchoring structure by coordination of metal ions and the active functional groups; spinning; sequentially passing a primary coagulation bath and a secondary coagulation bath by the primary liquid stream, realizing regeneration of the cellulose in the primary coagulation bath, and realizing in-situ growth of MOF by coordination and self-assembly of the organic ligand and the pre-anchored metal ions in the fiber; exchanging the solvent in the secondary coagulation bath; and obtaining the regenerated cellulose aerogel fibers with in-situ growth of MOF through drafting, drying, curling and winding. The technical problem to be solved is how to realize uniform in-situ growth of MOF in the regenerated cellulose fibers through an integrated process, simultaneously obtain the composite fibers with excellent heat preservation and insulation, flame retardation and moisture resistance, antibacterial performance and good flexibility and weavability, and simplify the preparation process to realize continuous production.

Description

Technical Field

[0001] This invention relates to the field of biomass new materials technology, and in particular to a regenerated cellulose aerogel fiber grown in situ by MOF, its preparation method and application. Background Technology

[0002] High-performance thermal insulation materials are in high demand in fields such as construction, aerospace, petrochemicals, and protective clothing. Aerogel materials, due to their unique nanoporous structure and extremely low thermal conductivity, are promising new thermal insulation materials. Among them, traditional silica (SiO2) aerogels have been extensively studied, but their inherent brittleness, easy powdering, and poor flexibility severely limit their application in flexible textiles.

[0003] Cellulose, as the most abundant natural polymer, produces third-generation aerogel materials that combine low thermal conductivity, high porosity, renewability, and biodegradability, while exhibiting superior mechanical toughness and processability compared to SiO2 aerogels. However, pure cellulose aerogels suffer from insufficient high-temperature thermal stability and are prone to moisture absorption and collapse in humid environments, affecting their long-term performance.

[0004] To improve the performance of pure cellulose aerogels, researchers have attempted to composite metal-organic frameworks (MOFs) with cellulose, hoping to enhance the adsorption, flame retardant, and antibacterial properties of the composite material by leveraging the high specific surface area, tunable pore size, and abundant functional groups of MOFs. However, the preparation of existing MOF / cellulose composites still faces many technical challenges: First, the composite method is mostly physical blending or secondary growth on a solid substrate, resulting in uneven MOF distribution, low loading, and weak interfacial bonding with the cellulose matrix, making it easy to detach and affecting performance uniformity and durability; second, the preparation process is cumbersome, requiring the preparation of a cellulose carrier before MOF composite, making continuous production difficult; third, the products are mostly in block or film form, with poor flexibility and high brittleness, making it impossible to process into continuous fibers through textile processing, which fails to meet the flexibility and weavability requirements of wearable protective equipment, greatly limiting downstream applications; fourth, during fiber formation, it is difficult to achieve uniform dispersion and stable bonding of MOF particles, making it impossible to balance the functionality and formability of the material. Summary of the Invention

[0005] The main objective of this invention is to provide a regenerated cellulose aerogel fiber with MOF in situ growth, its preparation method, and its application. The technical problem to be solved is how to achieve uniform in situ growth of MOF in regenerated cellulose fiber through an integrated process, while obtaining a composite fiber with excellent thermal insulation, flame retardancy, moisture resistance, antibacterial properties, good flexibility, and weavability. The preparation process is simplified to achieve continuous production, making it more suitable for practical use.

[0006] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A method for preparing MOF-grown in-situ regenerated cellulose aerogel fibers according to this invention includes the following steps:

[0007] S1 involves homogeneous esterification modification of cellulose in a cellulose solution to obtain a modified cellulose solution; the homogeneous esterification modification includes adding an esterifying agent and a metal salt to the cellulose solution, introducing active functional groups on the cellulose chain through the esterifying agent, and coordinating the metal ions dissociated from the metal salt with the active functional groups to form a pre-anchored structure.

[0008] S2 was used to vacuum degas the modified cellulose solution to obtain the spinning solution;

[0009] S3 uses wet spinning or dry-jet wet spinning to spin the spinning solution into fine streams; the fine streams pass sequentially through a first coagulation bath and a second coagulation bath to obtain nascent cellulose fibers; the first coagulation bath contains organic ligands; the fine streams achieve cellulose regeneration in the first coagulation bath, while the organic ligands coordinate with pre-anchored metal ions within the fiber for self-assembly, resulting in in-situ growth of MOFs; in the second coagulation bath, solvent exchange replaces residual solvent and unreacted substances in the fiber, ensuring fiber purity;

[0010] S4 nascent cellulose fibers are stretched, dried, crimped, and wound to obtain MOF in-situ grown regenerated cellulose aerogel fibers.

[0011] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0012] Preferably, in the preparation method, the cellulose solution is obtained by dissolving cellulose raw materials in a solvent; the cellulose raw materials are selected from at least one of cotton linters, bleached sulfate softwood pulp, bleached sulfate hardwood pulp, bleached bamboo pulp, softwood dissolving pulp, hardwood dissolving pulp, refined cotton, wheat straw dissolving pulp, reed dissolving pulp, straw dissolving pulp, bamboo dissolving pulp, microcrystalline cellulose, and nanocellulose; the solvent is selected from at least one of imidazole acetate ionic liquid, superalkali acetate ionic liquid, imidazole chloride ionic liquid, imidazole hydrogen sulfate ionic liquid, and eutectic solvent; the mass concentration of the cellulose solution is 4-12%.

[0013] Preferably, in the preparation method, the esterifying agent is selected from at least one of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, isopropylene acetate, vinyl propionate, vinyl butyrate, vinyl cinnamate, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, citric anhydride, ethylenediaminetetraacetic dianhydride, pyromellitic dianhydride, 3,4-dihydrocoumarin, α-angelicolone, acetyl chloride, propionyl chloride, butyryl chloride, lauroyl chloride, palmitoyl chloride, benzoyl chloride, and p-methylbenzoyl chloride; the metal salt is selected from copper nitrate trihydrate, copper chloride, and acetic acid. The mixture contains at least one of the following: copper, copper sulfate, zinc chloride, zinc sulfate, zinc acetate, zinc nitrate hexahydrate, zinc gluconate, zinc lactate, cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, nickel nitrate hexahydrate, nickel chloride, ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate nonahydrate, manganese chloride, manganese acetate, aluminum nitrate nonahydrate, aluminum chloride, chromium chloride, chromium nitrate nonahydrate, zirconium tetrachloride, zirconium oxychloride, hafnium tetrachloride, magnesium nitrate, calcium nitrate, cadmium nitrate, cerium nitrate, cadmium chloride, and strontium chloride; the molar ratio of the esterifying agent, metal salt, and cellulose dehydrated glucose unit is 1~20:0.1~10:1; the homogeneous esterification modification reaction temperature is 30~100 ℃, and the reaction time is 10~180 min.

[0014] Preferably, in the preparation method, the organic ligand is selected from terephthalic acid, trimesic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenylenedicarboxylic acid, 2-aminoterephthalic acid, 2-hydroxyterephthalic acid, 2-sulfonic acidterephthalic acid, 1,3,5-tris(4-carboxyphenyl)benzene, 4,4′,4″-tricarboxytriphenylamine, 2-methylimidazole, 2-ethylimidazole, benzimidazole, 3,5-dimethylpyrazole, and 4-pyrazolecarboxylic acid. At least one of the following: 4,4′-bipyridine, 2,2′-bipyridine, 1,2-bis(4-pyridine)ethylene, 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-methyltetrazazole, p-pyridinecarboxylic acid, nicotinic acid, isonicotinic acid, 3-(4-pyridyl)benzoic acid, 2-pyrazinic acid, 2,5-dimercapto-1,4-phenylenediic acid, 1,4-phenylenediphosphonic acid, and 4,4′-biphenyldisulfonic acid; wherein the molar ratio of the organic ligand to the metal salt is 1 to 20:1.

[0015] Preferably, in the preparation method, the coagulation solvent of the first coagulation bath is selected from at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-ethylpyrrolidone, diethylacetamide, dimethyl sulfoxide, acetone, diethyl ether, ethyl acetate, methyl formate, dioxane, n-hexane, and carbon tetrachloride; the length of the first coagulation bath is 2-8 m, and the residence time of the raw liquid stream in the first coagulation bath is 10-60 min.

[0016] Preferably, in the preparation method, the coagulating liquid in the second coagulation bath is selected from at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, acetone, ethylene glycol, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; the length of the second coagulation bath is 2-4 m, and the residence time of the original liquid stream in the second coagulation bath is 15-20 min.

[0017] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A MOF-grown in-situ regenerated cellulose aerogel fiber according to this invention comprises:

[0018] The fiber body has a three-dimensional network structure; the fiber body is modified by homogeneous esterification to introduce active functional groups, and the degree of substitution of the active functional groups is 0.5~2.0.

[0019] MOF crystals are uniformly grown on the surface and inside the three-dimensional network structure of the fiber body.

[0020] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0021] Preferably, the regenerated cellulose aerogel fiber has a specific surface area > 400 m². 2 / g, density ≤0.08 g / cm³ 2 Thermal conductivity ≤0.023 W / m•K, dry tensile strength ≥11.2MPa, dry elongation at break 45.2~77.5%.

[0022] Preferably, the regenerated cellulose aerogel fiber is prepared according to the aforementioned preparation method.

[0023] The objective of this invention and the technical problem it solves are achieved through the following technical solution: An application of regenerated cellulose aerogel fiber grown in situ using MOF (Metal-Oxide-Foil) according to this invention in the field of thermal insulation technology.

[0024] By employing the above technical solution, the MOF in-situ grown regenerated cellulose aerogel fiber, its preparation method, and its application proposed in this invention have at least the following beneficial effects:

[0025] The regenerated cellulose aerogel fiber, its preparation method, and its application proposed in this invention fundamentally solve the technical problems of the prior art through homogeneous esterification modification, metal ion coordination pre-anchoring, MOF in-situ growth, and continuous spinning integrated process.

[0026] In the preparation method, homogeneous esterification modification introduces different types of active functional groups, such as strongly interacting carboxyl / amine groups, weakly interacting hydroxyl groups, and hydrophobic ester groups, which form a pre-anchored structure with metal ions. Strongly interacting functional groups can lower the nucleation barrier of MOFs, increasing the loading capacity and interfacial strength; an appropriate amount of weakly interacting functional groups can uniformly disperse the crystals; and hydrophobic functional groups regulate the nucleation rate through steric hindrance, ultimately providing uniform and robust anchoring points for MOF growth. Combined with the coordination self-assembly of organic ligands and pre-anchored metal ions in the first coagulation bath, uniform in-situ growth of MOFs on and within the fiber surface is achieved. This effectively avoids the problems of MOF agglomeration, uneven distribution, and weak interfacial bonding caused by physical blending or secondary growth, ensuring the uniformity and durability of the composite material's properties.

[0027] This invention uses ionic liquids or eutectic solvents as core solvents, both of which possess the advantages of being green, environmentally friendly, and recyclable. Ionic liquids serve as excellent homogeneous reaction platforms, efficiently disrupting hydrogen bonds in cellulose to achieve dissolution, while simultaneously supporting homogeneous chemical modification of cellulose and uniform dispersion of MOF precursors. Eutectic solvents, through hydrogen bonding, disrupt the aggregated structure of cellulose, achieving similarly efficient dissolution and homogeneous modification of cellulose, and are simpler and less expensive to prepare, providing diverse key support for integrated processes. Integrating cellulose modification, spinning, and in-situ MOF growth into a continuous process eliminates the need for pre-prepared cellulose carriers, significantly simplifying the process and enabling continuous production of high-performance composite fibers, thus lowering the barrier to large-scale application. Continuous fiber morphology is directly prepared using wet spinning or dry-jet wet spinning methods, combined with post-treatments such as drawing and drying, imparting excellent flexibility and weavability to the material. It can be processed into fabrics, non-woven fabrics, etc., using traditional textile technologies, overcoming the limitations of bulk or film-like aerogels, which are brittle and unsuitable for wearable devices. The three-dimensional network structure (mesoporous / macroporous) of the fiber body and the micropores (typically less than 2 nanometers) of MOF form a hierarchical structure of macropores, mesopores, and micropores. The pore size of MOF micropores is close to or even smaller than the mean free path of air molecules, significantly reducing heat transfer through gas collisions. Combined with the low thermal conductivity of MOF itself, the material's thermal conductivity is ≤0.023 W / m•K, resulting in excellent thermal insulation performance. MOFs (such as ZIF-8) can decompose at high temperatures to produce components such as zinc oxide, catalyzing the formation of a dense carbon layer in cellulose, greatly improving the fiber's thermal stability and flame retardancy. Their hydrophobicity also mitigates the hygroscopic nature of cellulose, preventing a decrease in thermal insulation performance due to moisture absorption. Some MOFs can slowly release zinc ions and other metal ions, endowing the fiber with broad-spectrum antibacterial properties, making them particularly suitable for protective equipment worn for extended periods.

[0028] The fiber matrix of this invention undergoes homogeneous esterification modification, with the degree of substitution of active functional groups controlled within the optimal range of 0.5 to 2.0. This ensures sufficient MOF anchoring points while avoiding fiber degradation caused by excessive modification. Combined with the synergistic effect of MOF and cellulose, the fiber exhibits a dry tensile strength ≥11.2 MPa and a dry elongation at break of 45.2–77.5%, meeting the mechanical properties required for textile processing and practical applications. The preparation process utilizes renewable cellulose raw materials, and the solvent can be recycled through treatment, aligning with the concepts of green production and sustainable development.

[0029] In summary, the composite fiber of the present invention has multiple advantages such as being lightweight and porous, having thermal insulation properties, being flame-retardant and moisture-resistant, being antibacterial and durable, and being flexible and woven. It has broad application prospects in the field of thermal insulation technology, especially in scenarios such as fire-fighting clothing, high-temperature protective clothing, and building energy-saving materials.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0031] Figure 1 These are the infrared spectra of regenerated cellulose fibers prepared in Example 1 and Comparative Example 1 of this invention;

[0032] Figure 2 This is a low-magnification scanning electron microscope image of the surface of the regenerated cellulose fibers prepared in Example 1 of this invention;

[0033] Figure 3 This is a low-magnification scanning electron microscope image of the cross-section of the regenerated cellulose fiber prepared in Example 1 of this invention;

[0034] Figure 4 This is a high-magnification scanning electron microscope image of the surface of the regenerated cellulose fibers prepared in Example 1 of this invention;

[0035] Figure 5 This is a high-magnification scanning electron microscope image of the cross-section of the regenerated cellulose fiber prepared in Example 1 of the present invention;

[0036] Figure 6 This is a high-magnification scanning electron microscope image of the cross-section of the regenerated cellulose fiber prepared in Comparative Example 1 of this invention. Detailed Implementation

[0037] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the appended tables and preferred embodiments, details the specific implementation methods and effects of a MOF in-situ grown regenerated cellulose aerogel fiber, its preparation method, and its application, based on the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, the results of one or more embodiments can be combined in any suitable manner. These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​described in these embodiments should be interpreted as merely exemplary and not as limiting.

[0038] This invention proposes a method for preparing regenerated cellulose aerogel fibers grown in situ using MOF (Metal-Oxide-Foil) technology, comprising the following steps:

[0039] The first step is to prepare a cellulose solution; specifically, this involves dissolving the cellulose raw material in a suitable solvent. The cellulose raw material can be commercially available, and the solvent can be the solvent corresponding to the cellulose raw material.

[0040] To ensure the physical properties of the fiber, in some specific embodiments of the present invention, the cellulose raw material is selected from at least one of cotton linters, bleached sulfate softwood pulp, bleached sulfate hardwood pulp, bleached bamboo pulp, softwood dissolving pulp, hardwood dissolving pulp, refined cotton, wheat straw dissolving pulp, reed dissolving pulp, straw dissolving pulp, bamboo dissolving pulp, microcrystalline cellulose, and nanocellulose. Further, the cellulose raw material is preferably at least one of softwood dissolving pulp, hardwood dissolving pulp, and refined cotton.

[0041] To better dissolve cellulose and facilitate subsequent spinning processes, the solvent for dissolving cellulose is selected from at least one of imidazole acetate ionic liquid, superalkali acetate ionic liquid, imidazole chloride ionic liquid, imidazole hydrogen sulfate ionic liquid, and a eutectic solvent. Furthermore, to ensure the quality of cellulose dissolution and modification efficiency, the solvent for dissolving cellulose is preferably at least one of imidazole acetate ionic liquid, superalkali acetate ionic liquid, imidazole chloride ionic liquid, and imidazole hydrogen sulfate ionic liquid.

[0042] This invention preferably uses ionic liquids or eutectic solvents as the core solvents. On the one hand, both have the advantages of being green, environmentally friendly, and recyclable; on the other hand, ionic liquids can serve as excellent homogeneous reaction platforms, efficiently breaking hydrogen bonds in cellulose to achieve dissolution, while supporting homogeneous chemical modification of cellulose and uniform dispersion of MOF precursors; eutectic solvents, through hydrogen bonding, break the aggregated structure of cellulose, thus also achieving efficient dissolution and homogeneous modification of cellulose; these preferred solvents provide convenient conditions for the realization of integrated processes.

[0043] When dissolving cellulose raw materials, the mass concentration of the cellulose solution is generally controlled to ensure good subsequent spinning. If the mass concentration of the cellulose solution is too high, the viscosity will be too large, which is not conducive to the extrusion of the spinning solution from the spinneret; while if the mass concentration of the cellulose solution is too low, the fiber forming effect will be poor. To ensure smooth spinning in subsequent processes and obtain high-quality fibers, this invention preferably controls the mass concentration of cellulose in the cellulose solution to 4–12%; further, the preferred mass concentration of cellulose in the cellulose solution is 6–10%.

[0044] The second step is to homogeneously esterify the cellulose in a cellulose solution to prepare a modified cellulose solution. Homogeneous esterification modification of cellulose is one of the key aspects of this invention. Specifically, an esterifying agent and a metal salt are added to the cellulose solution, mixed, and reacted at a certain temperature for a period of time. The esterifying agent introduces active functional groups onto the cellulose chain, and the metal ions dissociated from the metal salt coordinate with these active functional groups to form a pre-anchored structure.

[0045] In some specific embodiments of the present invention, the esterifying agent is preferably at least one selected from acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, isopropylene acetate, vinyl propionate, vinyl butyrate, vinyl cinnamate, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, citric anhydride, ethylenediaminetetraacetic anhydride, pyromellitic dianhydride, 3,4-dihydrocoumarin, α-angelicolone, acetyl chloride, propionyl chloride, butyryl chloride, lauroyl chloride, palmitoyl chloride, benzoyl chloride, and p-methylbenzoyl chloride. More preferably, at least one selected from succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, citric anhydride, ethylenediaminetetraacetic anhydride, and pyromellitic dianhydride. All esterifying agents used in the present invention are commercially available.

[0046] The technical purpose of adding esterifying agents to cellulose solutions is to enable homogeneous esterification reactions, yielding cellulose derivatives with controllable and uniform substitution degrees. These newly introduced active functional groups exhibit different interactions with metal ions. Generally, strongly interacting groups (such as carboxyl and amino groups) are key to achieving stable and high-density MOF growth. They can form strong coordination bonds with metal ions, significantly increasing nucleation density and binding force, and improving overall material stability through cross-linking. Weakly interacting groups mainly refer to the abundant hydroxyl groups naturally present on the cellulose backbone. They primarily interact with the organic ligands of MOFs or the hydrated shells of metal ions through hydrogen bonds, providing basic physical anchoring and nucleation driving force. Although their interaction strength is weaker than coordination bonds, their sheer number is the fundamental reason why MOFs can grow on natural cellulose. However, relying solely on hydroxyl groups often results in insufficient MOF binding force and easy detachment; unfavorable interacting groups (such as ester and acetyl groups) typically do not directly participate in coordination, and their effects are more negative. They physically hinder the approach of precursors and weaken the formation environment for interactions such as hydrogen bonds by steric hindrance and reducing the polarity of the cellulose matrix. Therefore, their introduction usually inhibits MOF growth, leading to decreased loading and uneven distribution.

[0047] In some specific embodiments of the present invention, the degree of substitution is preferably controlled at an optimal level by controlling the reaction conditions. The degree of substitution directly determines the product performance and is a key parameter connecting the preparation process and product performance. If the substitution is too low, such as <0.5, there will be insufficient active functional groups, poor metal ion pre-anchoring effect, low and uneven MOF loading, and the flame retardancy and mechanical properties of the fiber will decrease significantly (similar to the defects of Comparative Example 1). If the substitution is too high, such as >2.0, the cellulose chain will be excessively degraded, and the mechanical properties of the fiber (tensile strength, elongation at break) will deteriorate significantly (for example, in Example 6, the degree of substitution is 1.85, and the dry tensile strength is only 5.8 MPa, which is lower than other examples). The preferred degree of substitution range of the present invention is 0.5~2.0. This degree of substitution can ensure that the cellulose has sufficient MOF anchoring points and avoid fiber degradation, thus achieving a better balance of performance.

[0048] The degree of substitution is directly related to the amount of esterifying agent added, the reaction temperature, and the reaction time. If the amount of esterifying agent added is too low, the reaction temperature is too low, or the reaction time is too short, the fiber esterification rate may be too slow, resulting in a low degree of substitution and affecting the subsequent coordination of metal ions. Conversely, if the amount added is too high, the reaction temperature is too high, or the reaction time is too long, over-esterification and fiber degradation may occur, resulting in a high degree of substitution but severe degradation and a decrease in mechanical properties. In order to obtain fibers with excellent overall performance, in some specific embodiments of the present invention, it is preferable to control the amount of esterifying agent added to be 20:1 to 1:1 (based on the molar ratio with cellulose dehydrated glucose units (AGU)); further, it is preferable to control the amount of esterifying agent added to be 12:1 to 1:1 (based on the molar ratio with AGU); and even further, it is preferable to control the amount of esterifying agent added to be 8:1 to 1:1 (based on the molar ratio with AGU). In some specific embodiments of the present invention, it is preferred to control the reaction temperature at 30~100 ℃ and the reaction time at 10~180 min; further, it is preferred to control the reaction temperature at 30~90 ℃ and the reaction time at 30~150 min; even further, it is preferred to control the reaction temperature at 40~80 ℃ and the reaction time at 30~120 min.

[0049] In some specific embodiments of the present invention, the metal salt is preferably at least one selected from the following: copper nitrate trihydrate, copper chloride, copper acetate, copper sulfate, zinc chloride, zinc sulfate, zinc acetate, zinc nitrate hexahydrate, zinc gluconate, zinc lactate, cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, nickel nitrate hexahydrate, nickel chloride, ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate nonahydrate, manganese chloride, manganese acetate, aluminum nitrate nonahydrate, aluminum chloride, chromium chloride, chromium nitrate nonahydrate, zirconium tetrachloride, zirconium oxychloride, hafnium tetrachloride, magnesium nitrate, calcium nitrate, cadmium nitrate, cerium nitrate, cadmium chloride, and strontium chloride. All metal salts used in the present invention are commercially available.

[0050] The purpose of adding metal salts to cellulose solutions is to enable metal ions (such as Zn2+, Co3+, Cu2+, etc.) to coordinate with functional groups such as carboxyl and amino groups on the modified cellulose chains, and to be pre-anchored uniformly on the cellulose framework, thereby laying the foundation for the subsequent in-situ growth of MOF crystals.

[0051] The amount of metal salt added is closely related to the quality of the spinning solution and the subsequent in-situ growth of MOFs. If the amount added is too low, the functional groups such as carboxyl groups introduced through esterification modification on the cellulose chain may not be completely chelated, reducing the effective nucleation sites of the MOF. Conversely, if the amount added is too high, it may affect the rheological properties of the cellulose solution and even cause local flocculation, thereby reducing the stability and spinnability of the spinning solution and easily causing filament breakage during spinning. To better balance the uniformity of the spinning solution and the smoothness of spinning, this invention preferably controls the amount of metal salt added to be 10:1 to 1:10 (based on the molar ratio with AGU); further preferably, it controls the amount of metal salt added to be 6:1 to 1:6 (based on the molar ratio with AGU); even further preferably, it controls the amount of metal salt added to be 4:1 to 1:4 (based on the molar ratio with AGU); and even more preferably, it controls the amount of metal salt added to be 2:1 to 1:2 (based on the molar ratio with AGU).

[0052] Following the homogeneous esterification modification reaction of cellulose, it is preferable to perform vacuum degassing on the reaction solution to remove air bubbles trapped in the spinning solution during stirring, preventing fiber breakage during subsequent spinning and ensuring the prepared fibers are continuous and defect-free. During vacuum degassing, appropriate degassing temperature and time can maximize the quality of the spinning solution and the performance of subsequent products. The vacuum degassing process can be controlled using conventional methods in the art, and this invention does not specifically limit it.

[0053] In some specific embodiments of the present invention, the degassing temperature is preferably controlled at 25–90 °C, and the degassing time is 0.5–15 h; more preferably, the degassing temperature is 30–80 °C, and the degassing time is 1–5 h; even more preferably, the vacuum degassing temperature is 40–60 °C, and the vacuum degassing time is 2–4 h. The reason for setting the degassing parameters in this way is that if the degassing temperature is too low or the degassing time is too short, the spinning solution will not be completely degassed, which will easily lead to fiber breakage during the spinning process; while if the degassing temperature is too high or the degassing time is too long, fiber degradation may occur, which will lead to a decrease in the quality of the regenerated cellulose fiber.

[0054] The third step is spinning and MOF in situ growth; first, the spinning solution is spun using wet spinning or dry-jet wet spinning to form a fine stream of solution; then the fine stream of solution passes through the first coagulation bath and the second coagulation bath in sequence to obtain nascent cellulose fibers.

[0055] In the above spinning steps, the process parameters for spinning the dopant can adopt conventional processes in the art, as long as they enable the spinning dopant to form a fine stream. In some specific embodiments of the present invention, the spinning dopant is extruded from the spinneret at a pressure of 0.5 MPa, a temperature of 25–100 °C, and a speed of 0.5–5 m / min, and then passes through a first coagulation bath and a second coagulation bath to obtain nascent cellulose fibers. The above-mentioned spinning process parameters allow the spinning dopant to be rapidly extruded through the spinneret to form a fine stream. Preferably, the orifice diameter of the spinneret is 0.1–0.3 mm, and the number of spinneret holes on the spinneret is 100–200.

[0056] In the aforementioned spinning process, the most crucial step is the setting of the coagulation bath. This invention employs a two-stage coagulation bath, where the raw solution stream sequentially passes through the first and second coagulation baths to obtain nascent cellulose fibers. In the two-stage coagulation bath, the coagulation solution in the first bath is a solution containing organic ligands. Two synergistic and rapid processes occur in the first coagulation bath: firstly, the coagulation solution rapidly penetrates the stream, causing cellulose to precipitate from the solvent, achieving cellulose regeneration and forming a gel fiber framework with a three-dimensional network structure; secondly, the organic ligand molecules in the coagulation solution diffuse into the fiber interior, coordinating and self-assembling with pre-anchored metal ions, resulting in in-situ growth of MOF crystals. This achieves fiber forming and functionalization in one step, ensuring that MOF nanoparticles are confined to the cellulose network, achieving uniform molecular-level dispersion and strong interfacial bonding, effectively preventing MOF aggregation and detachment. The micropores of MOF, combined with the mesopores and macropores of cellulose aerogel, can construct a perfect "macropore-mesopore-micropore" multi-level pore structure. This structure greatly increases the specific surface area of ​​the material, providing an ideal microenvironment for thermal insulation. Then, thorough solvent exchange and washing are carried out through the coagulation liquid in the second coagulation bath to further replace and remove residual ionic liquids / eutectic solvents and unreacted substances in the fibers, ensuring the purity of the final product and avoiding the influence of residual solvents on the structure and properties of the subsequent aerogel.

[0057] To better control the fiber structure of MOF in situ growth, the coagulation solution in the first coagulation bath of the secondary coagulation bath is preferably a solution containing organic ligands. In some specific embodiments of the present invention, the organic ligands are preferably terephthalic acid, trimesic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenylenediic acid, 2-aminoterephthalic acid, 2-hydroxyterephthalic acid, 2-sulfonic terephthalic acid, 1,3,5-tris(4-carboxyphenyl)benzene, 4,4′,4″-tricarboxytriphenylamine, 2-methylimidazolium, 2-ethylimidazolium, benzimidazole, 3,5-dimethylpyrazole, 4-pyrazolecarboxylic acid, 4,4′-bipyridine, 2,2′-bipyridine, 1,2-di(4-pyridine)ethylene, 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-methyltetrazolium, and p-pyridine. Formic acid, nicotinic acid, isonicotinic acid, 3-(4-pyridyl)benzoic acid, 2-pyrazinic acid, 2,5-dimercapto-1,4-phenylenediic acid, 1,4-phenylenediphosphonic acid, and 4,4′-biphenyl disulfonic acid are all present in the present invention. The solution containing the organic ligand is preferably at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-ethylpyrrolidone, diethylacetamide, dimethyl sulfoxide, acetone, diethyl ether, ethyl acetate, methyl formate, dioxane, n-hexane, and carbon tetrachloride. Both the organic ligand and the solution used in this invention are commercially available. In this invention, the length of the first coagulation bath is set to 2–8 m, and the residence time of the thin stream of raw liquid in the first coagulation bath is 10–60 min.

[0058] In the first coagulation bath, the concentration of organic ligands is crucial for the in-situ growth of MOFs. If the concentration of organic ligands is too low, the ligands cannot fully coordinate with all metal ions, leading to incomplete MOF crystallization. The resulting composite material will contain a large number of unreacted metal ions and ligands, which not only fails to fully realize the functionality of the MOF but may also affect the long-term stability of the material. Conversely, if the concentration of organic ligands is too high, the MOF will crystallize too quickly, forming a dense shell on the fiber surface, hindering the continued reaction between the internal ligands and metal ions, resulting in uneven MOF growth. Excessive ligands also increase costs. To better balance the overall performance of the fiber, this invention preferably uses an organic ligand addition ratio of 1:1 to 20:1 (molar ratio to metal ions) in the first coagulation bath; further preferably, it uses a ratio of 15:1 to 2:1 (molar ratio to metal ions); and even more preferably, it uses a ratio of 12:1 to 4:1 (molar ratio to metal ions).

[0059] The main function of the second coagulation bath is to replace the solution containing organic ligands introduced by the first coagulation bath through solvent exchange, further replacing and removing the ionic liquid / eutectic solvent and unreacted substances remaining in the fiber, ensuring the purity of the final product, and preventing residual solvent from affecting the structure and properties of the aerogel.

[0060] In some specific embodiments of the present invention, the second coagulation bath is selected from, but not limited to, one or a mixture of two of, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, acetone, ethylene glycol, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide, with a volume ratio of 1:1 to 20 when the two coagulation solutions are mixed. All organic reagents used in the present invention are commercially available. The present invention sets the length of the second coagulation bath to 2–4 m, and the residence time of the original liquid stream in the second coagulation bath is 15–20 min.

[0061] Finally, the nascent cellulose fibers are drawn, dried, crimped, and wound to permanently fix the nanoporous structure of the fibers and obtain the final composite aerogel fibers. The process control in this step can be achieved using conventional processes in the prior art, and this invention does not impose specific limitations on this. In some specific embodiments of this invention, the preferred drawing ratio of the traction wheel in the drawing step is 1 to 1.2; the preferred drying method in the drying step is atmospheric pressure drying, freeze-drying, or supercritical drying; and the preferred linear speed of the take-up spool in the crimping and winding step is the same as the drawing speed in the previous stage.

[0062] This invention also proposes a regenerated cellulose aerogel fiber grown in situ using MOF, as shown in the attached figure. Figures 1-5 As shown, it comprises a fiber body and MOF crystals; the fiber body has a three-dimensional network structure; the fiber body is modified by homogeneous esterification to introduce active functional groups, and the degree of substitution of the active functional groups is 0.5~2.0; the MOF crystals are uniformly grown on the surface and inside the three-dimensional network structure of the fiber body. Further preferably, the degree of substitution of the active functional groups is 0.5~1.5.

[0063] The MOF-grown regenerated cellulose aerogel fibers described above combine the mesoporous / macroporous structures (tens to hundreds of nanometers) of cellulose aerogel with the micropores (typically less than 2 nanometers) of MOF materials (such as ZIF-8). This "macropore-mesopore-micropore" hierarchical structure significantly increases the air diffusion path, effectively suppressing convective heat transfer and gas heat conduction. In particular, the micropores of MOFs, with pore sizes close to or even smaller than the mean free path of air molecules, significantly weaken collisional heat transfer, further enhancing the fiber's insulation performance. Some MOF materials (such as ZIF-8) inherently possess good hydrophobicity. When uniformly distributed on the cellulose skeleton, they effectively improve the overall moisture resistance of the composite material. This means that even in humid environments, the material can avoid the replacement of air in the pores by water molecules with higher thermal conductivity due to moisture absorption, thus maintaining a dry state and stable insulation performance over a long period. This is crucial for applications such as building insulation or fire-fighting clothing.

[0064] In some specific embodiments of the present invention, the specific surface area of ​​the regenerated cellulose fiber is >400 m². 2 / g, density ≤0.08 g / cm³ 2 Thermal conductivity ≤0.023 W / m•K, dry tensile strength ≥11.2MPa, dry elongation at break 45.2~77.5%.

[0065] In some specific embodiments of the present invention, the regenerated cellulose aerogel fiber is prepared according to the aforementioned preparation method.

[0066] This invention also proposes an application of regenerated cellulose aerogel fibers grown in situ according to the aforementioned MOF in the field of thermal insulation technology.

[0067] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0068] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0069] Example 1

[0070] Softened conifer pulp was dissolved in imidazole acetate ionic liquid to obtain a cellulose solution with a mass concentration of 10%. Succinic anhydride and zinc nitrate hexahydrate (in molar ratio to AGU) were added to the cellulose solution in a molar ratio of 2:1, and the mixture was reacted at 60 °C for 60 min. Then, the mixture was degassed under vacuum at 50 °C for 2 h to obtain a homogeneous spinning solution.

[0071] The above spinning solution was extruded from the spinneret at a pressure of 0.5 MPa, a temperature of 40 °C, and a speed of 0.5 m / min. Regenerated cellulose aerogel fibers were prepared using a wet spinning process with a 150-hole spinneret with an orifice diameter of 0.2 mm. The two coagulation baths were methanol and tert-butanol containing 2-methylimidazole, respectively, with a molar ratio of 2-methylimidazole to metal salt of 4:1. After 1.1 times draw, the fiber residence times in the two coagulation baths were 40 min and 20 min, respectively. After freeze-drying, the fibers were crimped to obtain regenerated cellulose aerogel fibers, such as... Figure 1 As shown.

[0072] The infrared spectrum of the regenerated cellulose obtained in this embodiment is as follows: Figure 1 As shown, the scanning electron microscope and polarizing microscope images are as follows: Figures 2-5 As shown, the surface of the regenerated cellulose fiber is loaded with MOF particles ( Figure 2 , Figure 4 The cross-section shows that the regenerated cellulose fibers have a three-dimensional network structure, and the MOF particles grow uniformly on the cellulose backbone. Figure 3 , Figure 5 ).

[0073] The specific properties of the regenerated cellulose aerogel fibers obtained in this embodiment are shown in Table 1. All properties were tested using conventional methods in the art.

[0074] Example 2

[0075] Hardwood dissolving pulp was dissolved in superalkali acetate ionic liquid to obtain a cellulose solution with a mass concentration of 10%. Succinic anhydride and zinc acetate (molar ratio of 4:1 to AGU) were added to the cellulose solution, and the mixture was reacted at 60 °C for 90 min. Then, the mixture was degassed under vacuum at 50 °C for 2 h to obtain a homogeneous spinning solution.

[0076] The above spinning solution was extruded from the spinneret at a pressure of 0.5 MPa, a temperature of 50 °C, and a speed of 0.5 m / min. Regenerated cellulose aerogel fibers were prepared using a wet spinning process with a 100-hole spinneret with an orifice diameter of 0.2 mm. The two coagulation baths were methanol and tert-butanol containing 2-methylimidazole, respectively, with a molar ratio of 2-methylimidazole to metal salt of 8:1. After 1.1 times draw, the fiber residence times in the two coagulation baths were 40 min and 20 min, respectively. After freeze-drying, the fibers were crimped to obtain regenerated cellulose aerogel fibers.

[0077] The specific properties of the regenerated cellulose fiber obtained in this embodiment are shown in Table 1.

[0078] Example 3

[0079] Refined cotton was dissolved in an imidazole chloride ionic liquid to obtain a cellulose solution with a mass concentration of 8%. Maleic anhydride in a molar ratio of 4:1 and cobalt nitrate hexahydrate in a molar ratio of 1:2 (based on the molar ratio with AGU) were added to the cellulose solution, and the mixture was reacted at 40 °C for 120 min. Then, the mixture was degassed under vacuum at 50 °C for 2 h to obtain a homogeneous spinning solution.

[0080] The above spinning solution was extruded from the spinneret at a pressure of 0.5 MPa and a temperature of 60 °C at a speed of 1 m / min. Regenerated cellulose aerogel fibers were prepared using a wet spinning process with a 200-hole spinneret with an orifice diameter of 0.1 mm. The two coagulation baths were ethanol and water containing 2-methylimidazole, respectively, with a molar ratio of 2-methylimidazole to metal salt of 8:1. After 1.1 times draw, the fiber residence times in the two coagulation baths were 60 min and 20 min, respectively. After supercritical drying, the fibers were curled to obtain regenerated cellulose aerogel fibers.

[0081] The specific properties of the regenerated cellulose fiber obtained in this embodiment are shown in Table 1.

[0082] Example 4

[0083] Refined cotton was dissolved in imidazole acetate ionic liquid to obtain a cellulose solution with a mass concentration of 6%. Phthalic anhydride (4:1 molar ratio) and zirconium tetroxide (1:2 molar ratio with AGU) were added to the cellulose solution, and the mixture was reacted at 50 °C for 90 min. Then, the mixture was degassed under vacuum at 50 °C for 2 h to obtain a homogeneous spinning solution.

[0084] The above spinning solution was extruded from the spinneret at a pressure of 0.5 MPa and a temperature of 30 °C at a speed of 1 m / min. Regenerated cellulose aerogel fibers were prepared using a dry-jet wet spinning process with a 150-hole spinneret with an orifice diameter of 0.3 mm. The two coagulation baths were an aqueous solution containing 2-aminoterephthalic acid and water, respectively, with a molar ratio of 2-aminoterephthalic acid to metal salt of 12:1. After 1.1 times draw, the fiber residence times in the two coagulation baths were 30 min and 15 min, respectively. After supercritical drying, the fibers were crimped to obtain regenerated cellulose aerogel fibers.

[0085] The specific properties of the regenerated cellulose fiber obtained in this embodiment are shown in Table 1.

[0086] Example 5

[0087] Hardwood dissolving pulp was dissolved in imidazole chloride ionic liquid to obtain a cellulose solution with a mass concentration of 8%. Maleic anhydride and cobalt nitrate hexahydrate (in molar ratio to AGU) were added to the cellulose solution in a molar ratio of 4:1 and 2:1, respectively. The mixture was reacted at 40 °C for 120 min, and then degassed under vacuum at 50 °C for 2 h to obtain a homogeneous spinning solution.

[0088] The above spinning solution was extruded from the spinneret at a pressure of 0.5 MPa and a temperature of 60 °C at a speed of 1 m / min. Regenerated cellulose aerogel fibers were prepared using a wet spinning process with a 200-hole spinneret with an orifice diameter of 0.1 mm. The two coagulation baths were methanol and tert-butanol containing 2-methylimidazole, respectively, with a molar ratio of 2-methylimidazole to metal salt of 4:1. After 1.1 times draw, the fiber residence times in the two coagulation baths were 10 min and 20 min, respectively. After supercritical drying, the fibers were curled to obtain regenerated cellulose aerogel fibers.

[0089] The specific properties of the regenerated cellulose fiber obtained in this embodiment are shown in Table 1.

[0090] Comparative Example 1

[0091] Same as Example 1, except that no esterifying agent was added. The specific properties of the regenerated cellulose fibers obtained in this comparative example are shown in Table 1.

[0092] Comparative Example 2

[0093] Same as Example 2, except that no metal salts and organic ligands were added. The specific properties of the regenerated cellulose fibers obtained in this comparative example are shown in Table 1.

[0094] Comparative Example 3

[0095] Same as Example 3, except that no esterifying agent, metal salt, and organic ligand were added. The specific properties of the regenerated cellulose fibers obtained in this comparative example are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] As can be seen from the test data of the above embodiments, the regenerated cellulose fiber prepared by the technical solution of the present invention has excellent comprehensive performance, and it has a high specific surface area (>400 m²). 2 / g), low density (≤0.08 g / cm³) 2 It has low thermal conductivity (≤0.023 W / (m•K)) and good mechanical properties (dry tensile strength ≥11.2MPa, dry elongation at break 45.2~77.5%), as in Examples 1 to 5.

[0100] As can be seen from the test data of the comparative examples above, the only difference between Comparative Example 1 and Example 1 is that no esterification reagent was added; the test results show that the regenerated cellulose obtained in Comparative Example 1 was not modified. Figure 1 The specific surface area of ​​the aerogel fiber decreased by 50% compared to Example 1, the thermal conductivity increased by 209%, the density decreased by 6%, the dry tensile strength decreased by 23%, and the dry elongation at break decreased by 11%. In other words, the thermal insulation and mechanical properties of Comparative Example 1 deteriorated significantly. This may be because no esterification reaction occurred in Comparative Example 1, and the hydroxyl groups on the resulting regenerated cellulose were not replaced by strong coordinating groups. The hydroxyl groups formed weak coordination with metal ions, resulting in a milder effect. Simultaneously, the large number of hydroxyl groups hindered ion diffusion, which was detrimental to MOF growth. Therefore, the MOF loading on the fiber was low during the molding process. Figure 6 This results in a lower specific surface area and poorer thermal insulation performance. Meanwhile, because a small number of carboxyl groups can form a strong "ionic crosslinking" network with metal ions through electrostatic interactions, increasing the mechanical properties of the material, the mechanical properties of Comparative Example 1 are weaker than those of Example 1.

[0101] As can be seen from the test data of the comparative examples above, Comparative Example 2 differs from Example 2 only in that it did not add metal salts and organic ligands, i.e., it did not grow MOF. The test results show that the degree of substitution of the regenerated cellulose aerogel fiber obtained in Comparative Example 4 was unchanged compared to Example 2, but the specific surface area decreased by 72%, the thermal conductivity increased by 400%, the density decreased by 8%, the dry tensile strength decreased by 48%, and the dry elongation at break decreased by 73%. In other words, the thermal insulation and mechanical properties of Comparative Example 2 deteriorated significantly. This may be because the regenerated cellulose fiber in Comparative Example 2 was not composited with MOF. The thermal conductivity of MOF crystals is much lower than that of the cellulose skeleton, and it can form "rigid nodes" between nanofibers to disperse stress. In Comparative Example 2, these nodes disappeared, and the fibers were only weakly connected by hydrogen bonds, making them more prone to slippage and breakage during stretching, thus resulting in poor mechanical and thermal insulation properties.

[0102] As can be seen from the test data of the comparative examples above, Comparative Example 3 differs from Example 3 only in that it did not contain esterifying agents, metal salts, and organic ligands, i.e., it was unmodified and did not grow MOF. The test results show that the specific surface area of ​​the regenerated cellulose aerogel fiber obtained in Comparative Example 3 decreased by 78% compared to Example 3, the thermal conductivity increased by 355%, the density decreased by 17%, the dry tensile strength decreased by 48%, and the dry elongation at break decreased by 70%. In other words, the thermal insulation and mechanical properties of Comparative Example 3 deteriorated significantly. This may be because the regenerated cellulose fiber in Comparative Example 3 was not modified or composite with MOF. The three-dimensional network structure of unmodified regenerated cellulose mainly relies on the inherent hydrogen bonds between cellulose molecular chains. This force is relatively weak, and during the drying process, the disruption of surface tension more easily leads to the collapse of the pore structure and the generation of cracks, forming a fragile and defective network, thus resulting in poor mechanical and thermal insulation properties.

[0103] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing regenerated cellulose aerogel fibers grown in situ using MOF, characterized in that, It includes the following steps: S1 involves homogeneous esterification modification of cellulose in a cellulose solution to obtain a modified cellulose solution. The homogeneous esterification modification includes adding an esterifying agent and a metal salt to the cellulose solution. The esterifying agent introduces active functional groups onto the cellulose chain, and the metal ions dissociated from the metal salt coordinate with these active functional groups to form a pre-anchored structure. The esterifying agent is selected from acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, isopropylene acetate, vinyl propionate, vinyl butyrate, vinyl cinnamate, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, citric anhydride, ethylenediaminetetraacetic dianhydride, pyromellitic dianhydride, 3,4-dihydrocoumarin, and α-angelicinolone. The metal salt is selected from at least one of acetyl chloride, propionyl chloride, butyryl chloride, lauroyl chloride, palmitoyl chloride, benzoyl chloride, and p-methylbenzoyl chloride; the metal salt is selected from at least one of copper nitrate trihydrate, copper chloride, copper acetate, copper sulfate, zinc chloride, zinc sulfate, zinc acetate, zinc nitrate hexahydrate, zinc gluconate, zinc lactate, cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, nickel nitrate hexahydrate, nickel chloride, ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate nonahydrate, manganese chloride, manganese acetate, aluminum nitrate nonahydrate, aluminum chloride, chromium chloride, chromium nitrate nonahydrate, zirconium tetrachloride, zirconium oxychloride, hafnium tetrachloride, magnesium nitrate, calcium nitrate, cadmium nitrate, cerium nitrate, cadmium chloride, and strontium chloride; S2 was used to vacuum degas the modified cellulose solution to obtain the spinning solution; S3 employs wet spinning or dry-jet wet spinning to spin the spinning solution into fine streams. These streams sequentially pass through a first coagulation bath and a second coagulation bath to obtain nascent cellulose fibers. The first coagulation bath contains organic ligands. In the first coagulation bath, the cellulose is regenerated, and simultaneously, the organic ligands coordinate with pre-anchored metal ions within the fiber for self-assembly, resulting in in-situ growth of MOFs. In the second coagulation bath, solvent exchange replaces residual solvent and unreacted substances in the fiber, ensuring fiber purity. The organic ligands are selected from terephthalic acid, trimesic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyl dicarboxylic acid, and 2-aminoterephthalic acid. At least one of the following: 2-hydroxyterephthalic acid, 2-sulfonic terephthalic acid, 1,3,5-tris(4-carboxyphenyl)benzene, 4,4′,4″-tricarboxytriphenylamine, 2-methylimidazolium, 2-ethylimidazolium, benzimidazole, 3,5-dimethylpyrazole, 4-pyrazolecarboxylic acid, 4,4′-bipyridine, 2,2′-bipyridine, 1,2-di(4-pyridine)ethylene, 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-methyltetrazolium, p-pyridinecarboxylic acid, nicotinic acid, isonicotinic acid, 3-(4-pyridyl)benzoic acid, 2-pyrazinic acid, 2,5-dimercapto-1,4-phthalic acid, 1,4-benzenediphosphonic acid, and 4,4′-biphenyldisulfonic acid; S4 nascent cellulose fibers are stretched, dried, crimped, and wound to obtain MOF in-situ grown regenerated cellulose aerogel fibers.

2. The preparation method according to claim 1, characterized in that, The cellulose solution is obtained by dissolving cellulose raw materials in a solvent; the cellulose raw materials are selected from at least one of cotton linters, bleached sulfate softwood pulp, bleached sulfate hardwood pulp, bleached bamboo pulp, softwood dissolving pulp, hardwood dissolving pulp, refined cotton, wheat straw dissolving pulp, reed dissolving pulp, straw dissolving pulp, bamboo dissolving pulp, microcrystalline cellulose, and nanocellulose; the solvent is selected from at least one of imidazole acetate ionic liquid, superalkali acetate ionic liquid, imidazole chloride ionic liquid, imidazole hydrogen sulfate ionic liquid, and eutectic solvent; the mass concentration of the cellulose solution is 4-12%.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the esterifying agent, metal salt, and cellulose dehydrated glucose unit is 1~20 : 0.1~10 : 1; the reaction temperature for the homogeneous esterification modification is 30~100 ℃, and the reaction time is 10~180 min.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the organic ligand to the metal salt is 1–20:

1.

5. The preparation method according to claim 1, characterized in that, The coagulation solvent in the first coagulation bath is selected from at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-ethylpyrrolidone, diethylacetamide, dimethyl sulfoxide, acetone, diethyl ether, ethyl acetate, methyl formate, dioxane, n-hexane, and carbon tetrachloride; the length of the first coagulation bath is 2 to 8 m, and the residence time of the original liquid stream in the first coagulation bath is 10 to 60 min.

6. The preparation method according to claim 1, characterized in that, The coagulation solution in the second coagulation bath is selected from at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, acetone, ethylene glycol, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; the length of the second coagulation bath is 2 to 4 m, and the residence time of the original liquid stream in the second coagulation bath is 15 to 20 min.

7. A MOF in-situ grown regenerated cellulose aerogel fiber prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It includes: The fiber body has a three-dimensional network structure; The fiber body is modified by homogeneous esterification to introduce active functional groups, and the degree of substitution of the active functional groups is 0.5~2.

0. MOF crystals are uniformly grown on the surface and inside the three-dimensional network structure of the fiber body.

8. The regenerated cellulose aerogel fiber according to claim 7, characterized in that, Its specific surface area is >400 m² 2 / g, density ≤0.08 g / cm³ 2 Thermal conductivity ≤0.023 W / m•K, dry tensile strength ≥11.2 MPa, dry elongation at break 45.2~77.5%.

9. The application of a regenerated cellulose aerogel fiber grown in situ using MOF as described in claim 7 or 8 in the field of thermal insulation technology.

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