Preparation method of MOFs sequence microfiber composite moisture absorption material, product and application thereof

Abstract

This invention discloses a method for preparing MOF-based ordered microfiber composite moisture-absorbing materials, as well as their products and applications, belonging to the field of polymer materials technology. The method includes mixing MOF materials with a cellulose nanosheet suspension, stirring to obtain a mixed solution, maintaining a temperature difference of 20-80°C between the upper and lower parts of the mixed solution, and freeze-drying to obtain composite microfibers; dispersing the composite microfibers in the solution, and freeze-drying again to obtain the MOF-based ordered microfiber composite moisture-absorbing material; wherein the MOF material is FeCo-PBA. The MOF-based fibers constructed by this invention, when used as atmospheric water-collecting materials, can effectively change their morphology according to the application scenario and possess excellent sustainability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for preparing MOFs ordered microfiber composite moisture-absorbing materials, as well as their products and applications. Background Technology

[0002] In the field of atmospheric water collection, adsorbent-assisted atmospheric water collection technology has attracted widespread attention due to its ability to stably produce water over a wide relative humidity (RH) range. The core of this technology lies in the capture and release of water, and the key is the precise control of the interaction between water and the adsorbent. An ideal adsorbent should possess high water adsorption capacity, a rich porous structure, good thermal stability, and efficient thermal conversion performance. Currently, commonly used commercial adsorbents, such as silica gel, zeolite, and activated carbon, while possessing certain hygroscopic rates, specific surface areas, and pore structures, suffer from low water adsorption capacity, slow adsorption kinetics, and poor thermal stability, making it difficult to meet the demands of high-performance atmospheric water collection. While salt-based composite materials offer high water adsorption capacity, they face challenges such as salt leakage and slow adsorption kinetics; polymer adsorbents, although structurally tunable, still require improvement in adsorption and desorption performance; liquid adsorbents facilitate low-temperature water release, but suffer from slow adsorption kinetics and high application costs. Therefore, the development of a new generation of atmospheric water collection adsorbents with high water adsorption capacity, porosity, thermal stability, and good thermal conversion performance is urgently needed.

[0003] MOFs (Metal-Organic Facility Materials) are novel porous materials with high specific surface area, abundant pore structure, and hydrophilic properties. Numerous studies have shown that these materials, due to their unique structure and properties, can efficiently adsorb water molecules from the atmosphere, making them highly promising atmospheric water collection materials. For atmospheric water collection systems, under the premise of maintaining material structural stability, the faster the adsorption-desorption rate of water molecules and the more times the material is recycled, the higher the water collection efficiency. This means that regulating the pore structure and surface properties of MOFs plays a crucial role in improving atmospheric water collection performance. However, current MOF materials used in powder form for atmospheric water collection have several disadvantages. On the one hand, powdered MOF materials are prone to agglomeration in water collection devices, leading to a significant reduction in effective adsorption area and severely affecting water molecule adsorption efficiency. On the other hand, powdered materials have poor dispersibility, making efficient recovery difficult after the water collection process, resulting in material waste and increased subsequent treatment costs. Furthermore, powdered MOF materials have low mechanical strength and are easily broken during repeated use, further weakening their water collection performance and service life. Furthermore, due to their complex network crystal structure and the anisotropy of intermolecular forces, existing electrospinning and spinning technologies cannot directly transform MOF materials into continuous, oriented fibrous water-collecting materials. Therefore, fiberizing MOF materials to construct efficient, stable, and universally applicable atmospheric water-collecting structures remains a technological bottleneck. Summary of the Invention

[0004] The core of this invention lies in achieving a regular arrangement of MOFs through cellulose nanosheet powder material fibrosis technology, constructing a composite microfiber structure with an MOF array as the core and cellulose encapsulation. This unique structural design not only solves the problems of MOF powder agglomeration and poor dispersibility but also endows the material with superior adsorption performance. Specifically, this invention includes the following aspects:

[0005] Structural optimization enhances adsorption performance: Encapsulating MOFs within a cellulose structure provides a stable supporting framework for MOFs at the microstructural level, effectively preventing MOF aggregation and ensuring full utilization of their high specific surface area and abundant pore structure. Simultaneously, the hydroxyl groups and other functional groups on the cellulose molecular chains interact with the active sites on the MOF surface, forming hydrogen bonds or chemical bonds, thus enhancing the material's adsorption capacity for water molecules. This composite structure also alters the surface properties of the material, making it easier for water molecules to adhere and diffuse, thereby improving adsorption kinetics.

[0006] Screening for Superior MOFs to Improve Adsorption: MOFs with different structures exhibit significant differences in adsorption performance. This invention selected several representative MOFs (such as FeCo-PBA, CoCo-PBA, and MOF-303) for experimental comparison. The study found that MOFs with a three-dimensional interconnected pore structure and a high degree of matching between pore size and water molecule dynamics diameter are more conducive to water molecule transport and adsorption. Simultaneously, MOFs with abundant hydrophilic groups (such as hydroxyl and carboxyl groups) on their surface can form stronger interactions with water molecules, significantly increasing the adsorption capacity. Through this screening and comparison, MOFs more suitable for atmospheric water collection were identified, further optimizing the adsorption performance of the composite material.

[0007] Preparation method: The cellulose nanosheet-based powder material fibrosis technology used in this invention differs from traditional MOF-cellulose composite methods. Traditional methods often involve simple mixing, making it difficult to achieve uniform dispersion and orderly arrangement of MOFs in cellulose. This invention, however, achieves fibrosis of MOFs in a cellulose nanosheet suspension through precise control of reaction conditions, ensuring the uniformity and stability of the composite microfiber structure, thereby improving the overall performance of the material.

[0008] As one aspect of the present invention, the present invention provides a method for preparing a MOF-ordered microfiber composite moisture-absorbing material, comprising,

[0009] MOF materials were mixed with cellulose nanosheet suspension, and the mixture was stirred to obtain a mixed solution. The temperature difference between the upper and lower parts of the mixed solution was maintained at 20~80℃, and the solution was freeze-dried to obtain composite microfibers with MOF materials as the core and cellulose nanosheets encapsulating the core.

[0010] The composite microfibers were dispersed in a solution and freeze-dried to obtain a MOFs ordered microfiber composite moisture-absorbing material.

[0011] The MOF material is FeCo-PBA.

[0012] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite hygroscopic material of the present invention: the mass concentration of the cellulose nanosheet suspension is 1~2%; the mass ratio of MOFs material to cellulose nanosheet suspension is 1:0.5~2.

[0013] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite moisture-absorbing material of the present invention: the stirring reaction is carried out at a temperature of 25-35℃ for 1-4 hours.

[0014] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite moisture-absorbing material of the present invention: the stirring reaction is carried out at a stirring speed of 500~800r / min.

[0015] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite hygroscopic material of the present invention: in the cellulose nanosheet suspension, the diameter of the cellulose nanosheets is 0.1~20μm.

[0016] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite hygroscopic material of the present invention: the temperature difference between the upper and lower parts of the mixed solution is maintained at 20~80℃, and the temperature of the mixed solution is -40~5℃.

[0017] As a preferred embodiment of the preparation method of the MOFs sequenced microfiber composite moisture-absorbing material of the present invention, the preparation method of FeCo-PBA includes dissolving potassium cobalt cyanide in water, adding polyvinylpyrrolidone to obtain a premix; dissolving ferrous sulfate and cobalt acetate in water and mixing them with the premix, stirring and reacting, centrifuging, washing and drying to obtain FeCo-PBA.

[0018] As a preferred embodiment of the preparation method of the MOFs ordered microfiber composite moisture-absorbing material of the present invention: the composite microfibers are dispersed in a solution and freeze-dried, wherein the ultrasonic power is 50~1500W and the ultrasonic time is 0.5~5 min.

[0019] The beneficial effects of this invention are as follows: This invention regulates MOFs through cellulose nanosheet-based powder material fiberization technology, constructing microfibers with oriented MOF powder materials. The microfibers have a composite structure with an MOF array as the core and cellulose encapsulating the core; the MOF powder ordered microfibers are further used to prepare aerogels with universal structures. Through physical confinement and drying processes, cellulose and MOFs form a continuous structure with variable volume and morphology. When the constructed MOF-based fibers are used as atmospheric water collection materials, they can effectively change their morphology according to the application scenario and have excellent sustainability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, wherein:

[0021] Figure 1 The images show SEM images of the MOFs materials and composite microfibers used in Examples 1, 2, and 3, and the composite microfiber materials prepared in Comparative Examples 1, 2, and 3.

[0022] Figure 2 The image shows a low-magnification (500x) SEM image (left) of the composite microfibers obtained in step 1 of Example 1 and a high-magnification (5000x) SEM image (right) of the composite microfibers obtained in step 1 of Example 1.

[0023] Figure 3 The images show SEM images of the surface (left) and cross-section (right) of the MOFs ordered microfiber hydrophilic film obtained in Example 1.

[0024] Figure 4 This is a physical image of the MOFs ordered microfiber aerogel obtained in Example 1.

[0025] Figure 5 The performance of the aerogels prepared in each embodiment in terms of water adsorption capacity at 90% RH.

[0026] Figure 6 The images shown are TEM images of the composite microfibers obtained in step 1 of Examples 1-3.

[0027] Figure 7 The results of low-field NMR T2 tests are shown for the MOF material FeCo-PBA of Example 1 and the aerogel of Example 1. Detailed Implementation

[0028] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Example 1

[0029] (1) Accurately weigh 50 mg FeCo-PBA and slowly add it to 50 mg cellulose nanosheet suspension. Under the conditions of stirring speed of 600 r / min and reaction temperature of 30℃, ultrasonically disperse for 2 h. Place the resulting mixed solution in a container and use ultra-low temperature fluid fumigation to create a temperature difference between the upper (top) and lower (bottom) parts of the solution, with the upper part at 5℃ and the lower part at -40℃, and maintain this temperature difference for 24 h. Then, freeze dry it in a freeze dryer to obtain composite microfibers composed of MOFs and cellulose nanosheets.

[0030] The preparation method of the cellulose nanosheet suspension is as follows: 10 mg of cellulose nanosheets with a diameter of 0.1-20 μm are added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0031] The preparation method of FeCo-PBA includes: accurately weighing 0.664 g of potassium cobalt cyanide (K4[Fe(CN)6]·3H2O) and dissolving it in 400 mL of deionized water, and magnetically stirring at room temperature for 30 min until completely dissolved. Weighing 6 g of polyvinylpyrrolidone (PVP, average molecular weight 58000, K29-32), adding it to the above solution, and continuing to stir for 20 min until PVP is completely dissolved, obtaining solution A; separately, taking a beaker, weighing 0.42 g of FeSO4·7H2O and 0.394 g of Co(CH3COO) 2· Dissolve 4H₂O in 400 mL of deionized water to obtain solution B; add solution B dropwise to solution A at a uniform rate to form a homogeneous solution, and stir continuously at room temperature for 24 h. After stirring at room temperature for 24 h, a FeCo-PBA nanoparticle suspension is obtained. Collect the precipitate by centrifugation, wash three times with deionized water and anhydrous ethanol, and dry in a vacuum drying oven at 70 °C to obtain FeCo-PBA nanoparticles of uniform size.

[0032] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1) and disperse it in 100mL of water. The ultrasonic time is 2 minutes and the power is 200W to make the composite microfiber uniformly dispersed without structural damage. The dispersion is obtained by vacuum filtration of the dispersion to obtain a film with an area density of 5mg / cm².

[0033] (3) Preparation of MOFs ordered microfiber aerogel: Weigh 100mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, sonicate for 3 minutes at a power of 300W to make the composite microfiber uniformly dispersed, pour the dispersion into a polytetrafluoroethylene mold (3cm long × 3cm wide × 1cm high), and freeze dry at -80℃ for 24 hours to obtain aerogel. Example 2

[0034] (1) Accurately weigh 50 mg of CoCo-PBA and slowly add it to 50 mg of cellulose nanosheet suspension. Under the conditions of stirring speed of 600 r / min and reaction temperature of 30 °C, ultrasonically disperse for 2 h. Place the resulting mixed solution in a container and use ultra-low temperature fluid fumigation to achieve an upper temperature of 5 °C and a lower temperature of -40 °C for 24 h. Then, freeze dry it in a freeze dryer to obtain composite microfibers composed of MOFs and cellulose nanosheets.

[0035] The preparation method of the cellulose nanosheet suspension is as follows: 10 mg of cellulose nanosheets with a diameter of 0.1-20 μm are added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0036] The preparation method of CoCo-PBA includes: accurately weighing 0.664 g of potassium cobalt cyanide (K4[Co(CN)6]·3H2O) and dissolving it in 400 mL of deionized water, stirring magnetically for 30 min at room temperature until completely dissolved. Weighing 6 g of polyvinylpyrrolidone (PVP, average molecular weight 58000, K29-32), adding it to the above solution, and continuing to stir for 20 min until PVP is completely dissolved, obtaining solution A; separately, taking a beaker, weighing 0.786 g of Co(CH3COO) 2· Dissolve 4H₂O in 400 mL of deionized water to obtain solution B; add solution B dropwise to solution A at a uniform rate to form a homogeneous solution, and stir continuously at room temperature for 24 h. After stirring at room temperature for 24 h, a CoCo-PBA nanoparticle suspension is obtained. Collect the precipitate by centrifugation, wash three times with deionized water and anhydrous ethanol, and dry in a vacuum drying oven at 70 °C to obtain uniformly sized CoCo-PBA nanoparticles.

[0037] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1) and disperse it in 100mL of water. The ultrasonic time is 2 minutes and the power is 200W to make the composite microfiber uniformly dispersed without structural damage. The dispersion is obtained by vacuum filtration of the dispersion to obtain a film with an area density of 5mg / cm².

[0038] (3) Preparation of MOFs ordered microfiber aerogel: Weigh 100mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, sonicate for 3 minutes at a power of 300W to make the composite microfiber uniformly dispersed, pour the dispersion into a polytetrafluoroethylene mold (3cm long × 3cm wide × 1cm high), and freeze dry at -80℃ for 24 hours to obtain aerogel. Example 3

[0039] (1) Accurately weigh 50 mg of MOF-303 and slowly add it to 50 mg of cellulose nanosheet suspension. Under the conditions of stirring speed of 600 r / min and reaction temperature of 30 °C, ultrasonically disperse for 2 h. Place the resulting mixed solution in a container and use ultra-low temperature fluid fumigation to create a solution with an upper temperature of 5 °C and a lower temperature of -40 °C for 24 h. Then, freeze dry it in a freeze dryer to obtain composite microfibers composed of MOFs and cellulose nanosheets.

[0040] The preparation method of the cellulose nanosheet suspension is as follows: 10 mg of cellulose nanosheets with a diameter of 0.1-20 μm are added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0041] Preparation method of MOF-303: First, 0.3145 g (1.8 mmol) H2PZDC and 0.1440 g (3.6 mmol) NaOH were dissolved in 20 mL of deionized water and sonicated for 10 min; then, 0.4350 g (1.8 mmol) AlCl3·6H2O was added to the above mixture, and the flask containing the mixture was placed in an 800 W microwave reactor for 10 min; after rinsing five times with deionized water and methanol respectively, it was dried in a vacuum oven at 150 °C for 24 h; finally, 0.3248 g of MOF-303 nanocrystals were obtained.

[0042] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1) and disperse it in 100mL of water. The ultrasonic time is 2 minutes and the power is 200W to make the composite microfiber uniformly dispersed without structural damage. The dispersion is obtained by vacuum filtration of the dispersion to obtain a film with an area density of 5mg / cm².

[0043] (3) Preparation of MOFs ordered microfiber aerogel: Weigh 100mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, sonicate for 3 minutes at a power of 300W to make the composite microfiber uniformly dispersed, pour the dispersion into a polytetrafluoroethylene mold (3cm long × 3cm wide × 1cm high), and freeze dry at -80℃ for 24 hours to obtain aerogel. Comparative Example 1

[0044] (1) Accurately weigh 50 mg of FeCo-PBA and slowly add it to 50 mg of commercial filamentous cellulose nanofiber suspension. Under the conditions of stirring speed of 600 r / min and reaction temperature of 30 °C, ultrasonically disperse for 2 h. Place the resulting mixed solution in a container and use ultra-low temperature fluid fumigation to achieve a temperature of 5 °C at the top and -40 °C at the bottom of the solution, and maintain this for 24 h. Subsequently, freeze dry it in a freeze dryer to obtain composite microfibers.

[0045] The preparation method of commercial filamentous cellulose nanofiber suspension is as follows: 10 mg of cellulose nanofiber (Beijing Beifang Tianchen Technology Co., Ltd., product number TC-UCN-001) is added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0046] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1) and disperse it in 100mL of water. The ultrasonic time is 2 minutes and the power is 200W to make the composite microfiber uniformly dispersed without structural damage. The dispersion is obtained by vacuum filtration of the dispersion to obtain a film with an area density of 5mg / cm².

[0047] (3) Preparation of MOFs ordered microfiber aerogel: Weigh 100mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, sonicate for 3 minutes at a power of 300W to make the composite microfiber uniformly dispersed, pour the dispersion into a polytetrafluoroethylene mold (3cm long × 3cm wide × 1cm high), and freeze dry at -80℃ for 24 hours to obtain aerogel. Comparative Example 2

[0048] 50 mg of FeCo-PBA was accurately weighed and slowly added to 50 mg of a commercially available carboxylated cellulose nanofiber suspension. The mixture was ultrasonically dispersed for 2 hours at a stirring speed of 600 r / min and a reaction temperature of 30 °C. The resulting mixture was placed in a container and subjected to cryogenic fluid fumigation to maintain a temperature of 5 °C at the top and -40 °C at the bottom for 24 hours. Subsequently, it was freeze-dried in a freeze dryer to obtain the composite microfibers.

[0049] The preparation method of commercial carboxylated cellulose nanofiber suspension is as follows: 10 mg of commercial carboxylated cellulose nanofiber (Shanghai Mairui Biochemical Technology Co., Ltd., catalog number SD-H811414, diameter 50 nm, length 1~3 μm) is added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0050] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, control the ultrasonic time to 2 minutes and the power to 200W, so that the composite microfiber is uniformly dispersed without structural damage, and obtain a film with an area density of 5mg / cm² by vacuum filtration of the dispersion.

[0051] (3) Preparation of MOF-ordered microfiber aerogel: Weigh 100 mg of the composite microfiber obtained in step (1), disperse it in 100 mL of water, and control the ultrasonic time to 3 minutes and the power to 300 W to ensure uniform dispersion of the composite microfiber. Pour the dispersion into a polytetrafluoroethylene mold (3 cm long × 3 cm wide × 1 cm high), and freeze-dry it at -80℃ for 24 hours to obtain the aerogel. Comparative Example 3

[0052] Bacterial cellulose: 50 mg of FeCo-PBA was accurately weighed and slowly added to a 50 mg suspension of filamentous bacterial cellulose. The mixture was ultrasonically dispersed for 2 hours at a stirring speed of 600 r / min and a reaction temperature of 30 °C. The resulting mixture was placed in a container and subjected to cryogenic fluid fumigation to maintain a temperature of 5 °C at the top and -40 °C at the bottom for 24 hours. Subsequently, it was freeze-dried in a freeze dryer to obtain composite microfibers.

[0053] The preparation method of bacterial cellulose suspension is as follows: 10 mg of bacterial cellulose is added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0054] The aforementioned filamentous bacterial cellulose was purchased from Xidian Chemical Technology Co., Ltd., with CAS number 9004-34-6 and catalog number M81873-500G. It had a diameter of 75 nm and a length of ~20 μm.

[0055] (2) Preparation of hydrophilic film of MOFs ordered microfiber: Weigh 150mg of the composite microfiber obtained in step (1), disperse it in 100mL of water, control the ultrasonic time to 2 minutes and the power to 200W, so that the composite microfiber is uniformly dispersed without structural damage, and obtain a film with an area density of 5mg / cm² by vacuum filtration of the dispersion.

[0056] (3) Preparation of MOF-ordered microfiber aerogel: Weigh 100 mg of the composite microfiber obtained in step (1), disperse it in 100 mL of water, and control the ultrasonic time to 3 minutes and the power to 300 W to ensure uniform dispersion of the composite microfiber. Pour the dispersion into a polytetrafluoroethylene mold (3 cm long × 3 cm wide × 1 cm high), and freeze-dry it at -80℃ for 24 hours to obtain the aerogel. Comparative Example 4

[0057] (1) Accurately weigh 50mg FeCo-PBA and slowly add it to 50mg cellulose nanosheet suspension. Under the conditions of stirring speed of 600r / min and reaction temperature of 30℃, ultrasonically disperse for 2h and freeze dry.

[0058] The preparation method of the cellulose nanosheet suspension is as follows: 10 mg of cellulose nanosheets with a diameter of 0.1-20 μm are added to 100 mL of water, and a suspension with a mass concentration of 1% is obtained under the condition of stirring speed of 1000 r / min.

[0059] (2) Preparation of MOFs ordered microfiber aerogel: 100mg of the product obtained in step (1) was dispersed in 100mL of water, sonicated for 3 minutes at a power of 300W, and the dispersion was poured into a polytetrafluoroethylene mold (3cm long × 3cm wide × 1cm high). The aerogel was obtained by freeze drying at -80℃ for 24 hours.

[0060] Comparative Example 4 was unable to form the composite microfibers of cellulose-encapsulated MOFs material as in Example 1, and the aerogel obtained in Comparative Example 4 had poor moisture absorption properties.

[0061] Figure 1 The images show SEM images of the MOFs materials used in Examples 1, 2, and 3, the prepared composite microfibers, and the composite microfiber materials prepared in Comparative Examples 1, 2, and 3. It can be seen that the MOFs structures are disordered and easily aggregate. Figure 1 a represents FeCo-PBA nanoparticles, b represents CoCo-PBA nanoparticles, and c represents MOF-303 nanoparticles; d represents the composite microfiber containing FeCo-PBA nanoparticles constructed in Example 1, demonstrating that the present invention constructs a composite microfiber with a metal-organic framework array as the core and cellulose tightly encapsulating the core; e represents the composite microfiber containing CoCo-PBA nanoparticles constructed in Example 2, f represents the MOF-303 composite microfiber in Example 3; g represents the composite microfiber constructed from cellulose nanofibers, h represents the composite microfiber constructed using carboxylated cellulose nanofibers, and i represents the composite microfiber constructed using bacterial cellulose.

[0062] Figure 2 (Left) is a low-magnification (500x) SEM image of the composite microfibers obtained in step 1 of Example 1. It can be seen that the synthesized material is a fiber material. Figure 2 (Right) is a high-magnification (5000x) SEM image of the composite microfibers obtained in step 1 of Example 1. It can be seen that the MOF nanoparticles inside the coarse fibers exhibit an arrangement structure along the fiber direction.

[0063] Figure 3 The images show the surface (left) and cross-section (right) of the MOFs ordered microfiber hydrophilic film obtained in Example 1. It can be seen that the MOFs have been completely assembled into the microfibers, the microfiber structure is ordered, and there are a large number of micron-sized pore structures in the film.

[0064] Figure 4 This is a physical image of the MOFs ordered microfiber aerogel obtained in Example 1.

[0065] The composite water-collecting aerogel materials prepared in Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3, were subjected to water vapor adsorption tests in a constant temperature and humidity chamber simulating different relative humidity environments. The differences in moisture absorption performance were determined by comparing the water vapor absorption capacity of the aerogel materials provided in different examples. The indoor water vapor adsorption test used a self-made constant temperature and humidity chamber to simulate different relative humidity environments, with a relative humidity of 20-90%RH and a temperature of 20-45℃. Before the test, the composite water-collecting materials were dried at 100℃ for 1 hour to completely remove the moisture inside the aerogel material. After the environment inside the constant temperature and humidity chamber stabilized at 25℃ and 90%RH, the composite water-collecting materials were placed inside the chamber for water vapor adsorption testing. The mass change of each aerogel material was tracked over 12 hours using an electronic mass balance (AX224ZH / E, OHAUS). Figure 5 The water adsorption capacity of the aerogels prepared in each example was studied at 90% RH. The water adsorption capacity of the aerogel in Example 1 was 1.45 g·g. -1In Example 2, the aerogel had a water absorption capacity of 1.25 g·g. -1 Example 3: The aerogel has a water absorption capacity of 1.0 g·g. -1 . Figure 6 The images shown are TEM images of the composite microfibers obtained in step 1 of Examples 1-3. a is FeCo-PBA composite microfiber, b is CoCo-PBA composite microfiber, and c is composite microfiber composed of MOF-303. The results show that the samples in Example 1 are all based on MOF materials encapsulated in cellulose nanosheets. Figure 7 The results of low-field NMR T2 tests on the MOF material FeCo-PBA of Example 1 and the aerogel of Example 1 show that the microfiber aerogel of Example 1 with ordered MOFs has better hygroscopic properties, which is attributed to the small pore water bound by MOFs and the free water and macropore water in cellulose.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a MOFs ordered microfiber composite moisture-absorbing material, characterized in that: include, MOF materials were mixed with cellulose nanosheet suspension, and the mixture was stirred to obtain a mixed solution. The temperature difference between the upper and lower parts of the mixed solution was maintained at 20~80℃, and the solution was freeze-dried to obtain composite microfibers with MOF materials as the core and cellulose nanosheets encapsulating the core. The composite microfibers were dispersed in a solution, sonicated, and freeze-dried to obtain a MOFs ordered microfiber composite moisture-absorbing material. The MOF material is FeCo-PBA.

2. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1, characterized in that: The mass concentration of the cellulose nanosheet suspension is 1-2%; the mass ratio of MOFs material to cellulose nanosheet suspension is 1:0.5-2.

3. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1 or 2, characterized in that: The stirring reaction is carried out at a temperature of 25-35℃ for 1-4 hours.

4. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 3, characterized in that: The stirring reaction is carried out at a stirring speed of 500~800 r / min.

5. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1 or 2, characterized in that: In the cellulose nanosheet suspension, the diameter of the cellulose nanosheets is 0.1~20μm.

6. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1 or 2, characterized in that: The temperature difference between the upper and lower parts of the mixed solution is maintained at 20~80℃, and the temperature of the mixed solution is -40~5℃.

7. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1 or 2, characterized in that: The preparation method of FeCo-PBA includes dissolving potassium cobalt cyanide in water, adding polyvinylpyrrolidone to obtain a premix; dissolving ferrous sulfate and cobalt acetate in water and mixing them with the premix, stirring and reacting, centrifuging, washing and drying to obtain FeCo-PBA.

8. The method for preparing the MOFs ordered microfiber composite moisture-absorbing material according to claim 1 or 2, characterized in that: The ultrasonic power is 50~1500W, and the ultrasonic time is 0.5~5 min.

9. The MOFs ordered microfiber composite moisture-absorbing material prepared by the method described in claim 1.

10. The application of the MOFs ordered microfiber composite hygroscopic material prepared by the method described in claim 1 as an atmospheric water-collecting adsorbent.

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