A fiber dehumidification anti-fog film based on in-situ growth of cyclodextrin metal organic framework and a preparation method and application thereof

Abstract

The application belongs to the technical field of dehumidification and anti-fogging, and particularly relates to a fiber dehumidification and anti-fogging film based on in-situ growth of a cyclodextrin metal organic framework and a preparation method and application thereof. The dehumidification and anti-fogging film takes an alkali-treated cellulose substrate as a support, and is then placed in a precursor solution containing cyclodextrin (CD), a potassium source, an alcohol-water mixed solvent and a surfactant to grow in-situ on the surface and in the pores of the cellulose fiber to form a composite dehumidification and anti-fogging film. The obtained composite dehumidification and anti-fogging film can quickly capture water vapor in a high relative humidity airflow such as exhaled air while maintaining a low air resistance. The composite dehumidification and anti-fogging film is integrated into a mask to reduce the local humidity and dew point temperature before the humid and hot exhaled air reaches the glasses lens, thereby inhibiting the fogging of the glasses. The preparation process is mild, the material is green and renewable, and the application is suitable for anti-fogging masks, glasses anti-fogging protective products, personal protective equipment and other wearable dehumidification systems that need humidity control.

Description

Technical Field

[0001] This invention belongs to the field of dehumidifying and anti-fogging membrane technology. More specifically, it relates to a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of a cyclodextrin metal-organic framework, its preparation method, and its application. Background Technology

[0002] Fogging of glasses is a common problem in scenarios such as wearing masks, medical protection, traveling in low temperatures, driving, and precision operations. It occurs because when warm, humid air comes into contact with a cooler, transparent surface, water vapor condenses, forming tiny droplets that scatter light, blurring vision and potentially posing safety risks. For example, in the case of wearing a mask, the air exhaled by the human body is close to saturated humidity and easily leaks along the bridge of the nose and the upper edge of the mask towards the glasses. When this warm, humid air reaches the cooler lenses, the local dew point temperature is higher than the lens surface temperature, causing water vapor to condense and form fog on the lenses.

[0003] Current mainstream anti-fogging strategies for eyeglasses rely on surface treatments such as anti-fog sprays, wipes, and hydrophilic or hydrophobic coatings, attempting to reduce fogging by altering the spreading, coalescence, or shedding behavior of condensation on the lens surface. However, these methods share common limitations: they all regulate fogging after water vapor has reached the lens and condensed, failing to reduce the water vapor content reaching the lens at the source, and are also ineffective in lowering the dew point temperature of the local air near the lens. Furthermore, they generally suffer from short effective time, the need for frequent re-treatment, insufficient coating durability, potential impact on light transmittance, and limited compatibility with different substrates. Therefore, pre-capturing water vapor from humid, hot exhaled air before it reaches the lens, reducing its moisture content and dew point temperature, is a crucial technological direction for achieving durable, comfortable, and highly effective anti-fogging.

[0004] Traditional moisture-absorbing materials such as silica gel, molecular sieves, calcium chloride, and water-absorbing resins have certain moisture-capturing capabilities, but they have revealed many shortcomings in wearable dehumidification scenarios: poor moisture absorption selectivity, harsh regeneration conditions, easy clumping or liquefaction after moisture absorption, easy powder shedding, and difficulty in balancing low air resistance and wearing comfort, making it difficult to meet the comprehensive requirements of masks, goggles, and protective face shields for being lightweight, flexible, breathable, safe, and stable.

[0005] Metal-organic frameworks (MOFs), as a class of porous crystalline materials constructed from metal ions / clusters and organic ligands, possess advantages such as regular channels, high specific surface area, tunable pore size, and designable adsorption sites, showing great potential in the fields of water vapor adsorption and air dehumidification. Compared to traditional desiccants, MOFs can achieve higher adsorption capacity, rapid adsorption kinetics, and good reversibility within a specific relative humidity range by controlling metal nodes, ligands, channels, and hydrophilic groups, making them suitable for dynamic humidity control scenarios. However, existing MOF materials are mostly in the form of powder, granules, or tablets. If directly filled or coated into mask materials, problems such as uneven dispersion, powder shedding, crystal agglomeration, pore blockage, decreased adsorption efficiency, and increased air resistance are likely to occur. At the same time, the interfacial bonding between MOF powder and flexible fiber substrate is weak, and it is easy to migrate and detach during the process of breathing airflow, bending, and regeneration, affecting the safety of use, moisture absorption stability, and long-term anti-fogging effect. Therefore, how to stably, uniformly and with low resistance integrate MOF materials into flexible breathable substrates is the key technical bottleneck for their application in wearable dehumidification.

[0006] In recent years, in-situ nucleation and directional growth of MOFs on the surface of substrates such as fibers, fabrics, or nonwovens has become an important route for constructing MOF composite functional materials. Compared with physical mixing or surface coating, in-situ growth can utilize the functional groups, rough structure, and pore network of the substrate surface to induce MOF crystal nucleation and growth, thereby improving the bonding stability and dispersion uniformity, while retaining the original continuous channels and breathable structure of the substrate. Cellulose-based nonwovens, cotton fibers, and regenerated cellulose fibers are widely available, flexible, have high pore connectivity, and are rich in hydroxyl groups on the surface, providing a good foundation for applications. However, it should be noted that existing MOF / cellulose composite materials are mostly geared towards applications such as gas separation, catalysis, antibacterial, or pollutant adsorption, with little attention paid to structural designs for pre-dehumidification of exhaled air in masks and anti-fogging of glasses. At the same time, there is still a lack of mature and effective technical solutions for achieving stable and uniform in-situ growth of MOFs on the fiber surface and in the pores between fibers without significantly sacrificing the flexibility, pore connectivity, and low air resistance of the cellulose substrate, and forming a dehumidifying and anti-fogging film with high moisture adsorption capacity, airflow erosion stability, and renewability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing anti-fog technology for eyeglasses, such as poor dispersion, weak bonding and lack of targeted structural design when MOF powder is integrated with cellulose substrate, which makes it difficult to achieve a stable, efficient, low-resistance and renewable dehumidifying and anti-fog film for masks. The primary objective is to provide a method for preparing a cellulose dehumidifying and anti-fog film based on in-situ growth of γ-CD-MOF.

[0008] The second objective of this invention is to provide a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF prepared by the aforementioned preparation method.

[0009] A third objective of this invention is to provide the application of the aforementioned cellulose dehumidifying and anti-fogging membrane based on γ-CD-MOF in situ growth.

[0010] The fourth objective of this invention is to provide a dehumidifying and anti-fog mask.

[0011] The fifth objective of this invention is to provide the application of the cellulose dehumidifying and anti-fogging film based on γ-CD-MOF in situ growth or the dehumidifying and anti-fogging mask in scenarios such as anti-fogging of eyeglasses, anti-fogging of goggles, anti-fogging of protective face shields, anti-fogging of transparent observation windows, dehumidification of exhaled air, and wearable humidity control.

[0012] The above-mentioned objective of this invention is achieved through the following technical solution: This invention protects a method for preparing a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF, comprising the following steps: (1) Dissolve γ-cyclodextrin, potassium source and surfactant fully in a mixed solvent of methanol and water to obtain γ-CD-MOF precursor solution; (2) The alkali-treated cellulose substrate is placed in the γ-CD-MOF precursor solution obtained in step (1) and in situ growth reaction is carried out at 20~80 ℃ for 20~40 h. After post-treatment, the cellulose dehumidification and anti-fog film based on γ-CD-MOF in situ growth is obtained. The mixing ratio of the γ-cyclodextrin and the potassium element in the potassium source is 1 g: (6~10) mmol.

[0013] Preferably, the mixing ratio of the γ-cyclodextrin and the potassium element in the potassium source is 1 g: (7~9) mmol, more preferably 1 g: (7.5~8) mmol.

[0014] Furthermore, the potassium source is selected from at least one of potassium hydroxide, potassium carbonate, potassium acetate, and potassium chloride.

[0015] Preferably, the potassium source is selected from potassium hydroxide.

[0016] Furthermore, the surfactant is at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, polyvinylpyrrolidone, and sodium dodecyl sulfate.

[0017] Preferably, the surfactant is hexadecyltrimethylammonium bromide.

[0018] Furthermore, the cellulose substrate is at least one of natural cellulose fiber fabric, regenerated cellulose fiber fabric, cellulose nonwoven fabric, and cellulose paper-based material.

[0019] Furthermore, the cellulose substrate is a porous cellulose substrate.

[0020] Furthermore, the cellulose nonwoven fabric includes natural cellulose nonwoven fabric and regenerated cellulose nonwoven fabric.

[0021] Furthermore, the preparation conditions of the preparation method include at least one of the following: (1) The mass ratio of the γ-cyclodextrin to the surfactant is (80~110):1; (2) The mass-to-volume ratio of the γ-cyclodextrin to the mixed solvent is 1 g: (40~60) mL; (3) The volume ratio of methanol to water is 1:(3~5).

[0022] Preferably, the mass ratio of the γ-cyclodextrin to the surfactant is (90~100):1, more preferably (94~95):1.

[0023] Preferably, the mass-to-volume ratio of the γ-cyclodextrin to the mixed solvent is 1 g: (45~55) mL, more preferably 1: (47~50).

[0024] Preferably, the volume ratio of methanol to water is 1:(3.5~4.5), more preferably 1:(3.8~4.2).

[0025] Further, in step (2), the method of complete dissolution is to use ultrasonic treatment to completely dissolve the γ-CD-MOF precursor solution.

[0026] Furthermore, the alkaline treatment is performed using an alkaline potassium source.

[0027] Preferably, the alkaline potassium source is selected from at least one of potassium hydroxide, sodium hydroxide, potassium carbonate, or an aqueous solution of sodium carbonate.

[0028] Preferably, the concentration of the aqueous solution of the alkaline potassium source is 0.01 to 2.0 mol / L, more preferably 0.1 to 0.3 mol / L.

[0029] Furthermore, the process prior to alkali treatment also includes washing and drying.

[0030] Specifically, the alkali treatment includes the following steps: immersing the cellulose substrate in an aqueous solution of an alkaline potassium source, ultrasonically treating it to fully expose and activate the hydroxyl groups on the surface of the cellulose fibers, removing the cellulose substrate after treatment, and drying it to obtain the alkali-treated cellulose substrate.

[0031] Furthermore, the alkaline potassium source is the same as described above.

[0032] Further, in the alkali treatment, the drying conditions are drying at 70~90 °C for 5~7 h. Further, in the alkali treatment, the ultrasonic treatment time is 5~120 min, preferably 20~40 min.

[0033] Preferably, in step (2), the temperature of the in-situ growth reaction is 40~60 ℃, more preferably 45~55 ℃.

[0034] Preferably, in step (2), the in-situ growth reaction takes 24 to 36 hours.

[0035] Furthermore, in step (2), the post-processing includes washing and vacuum drying.

[0036] Furthermore, in the post-processing, the washing is performed by repeatedly washing with methanol and isopropanol to remove unreacted precursors and free crystals.

[0037] Furthermore, in the post-processing, the vacuum drying temperature is 70~90 ℃, preferably 75~85 ℃.

[0038] This invention protects the cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF prepared by the aforementioned preparation method.

[0039] Furthermore, the loading of γ-CD-MOF in the cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF is 40wt%~85wt%, preferably 60wt%~75wt%, and even more preferably 65wt%~70wt%.

[0040] Furthermore, the cellulose dehumidifying and anti-fogging membrane includes a porous support network composed of cellulose and γ-CD-MOF crystals grown in situ on the surface of the cellulose and / or in the pores between the cellulose fibers.

[0041] Furthermore, the cellulose dehumidifying and anti-fogging membrane exhibits a high water vapor adsorption capacity (water vapor adsorption capacity > 700 mg / g) under conditions of 25–35 °C and relative humidity ≥ 90%, and a low water vapor adsorption capacity (water vapor adsorption capacity < 400 mg / g) under conditions of relative humidity ≤ 80%.

[0042] This invention protects the application of the cellulose dehumidifying and anti-fogging membrane based on γ-CD-MOF in situ growth in the preparation of dehumidifying and anti-fogging masks.

[0043] The present invention also protects a dehumidifying and anti-fog mask, the dehumidifying and anti-fog mask comprising an inner layer, an outer layer and a functional layer located between the inner layer and the outer layer, the functional layer comprising the cellulose dehumidifying and anti-fog membrane based on γ-CD-MOF in situ growth.

[0044] Furthermore, the functional layer can serve as a filter layer covering the entire mask area (such as a conventional meltblown fabric layer) to play a primary filtering role, or it can be locally set in the nose bridge area, the upper edge area of ​​the mask, or other areas in the filter area where exhaled air is prone to leak towards the glasses, to play a dehumidifying and / or anti-fogging role.

[0045] Furthermore, as an alternative, the material of the inner or outer layer is a nonwoven fabric.

[0046] This invention protects the application of the cellulose dehumidifying and anti-fog film based on γ-CD-MOF in situ growth or the dehumidifying and anti-fog mask in anti-fog and / or dehumidification, the application including preventing fogging on transparent surfaces, dehumidifying exhaled air, and serving as a humidity control function unit in wearable humidity control products.

[0047] Furthermore, the transparent body includes at least one of the following: spectacle lens, goggles, protective mask, observation window, lens, instrument window, and vehicle glass.

[0048] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts an in-situ growth strategy to stably load γ-CD-MOF constructed by cyclodextrin and potassium metal of specific crystal form onto the surface and pores of cellulose fibers. Compared with powder direct filling, physical mixing or surface coating, it can effectively improve the dispersion uniformity and interfacial bonding stability of MOF functional phase and reduce the risk of it falling off under the scouring of breathing airflow. (2) The present invention utilizes cyclodextrin with a specific crystal form and potassium metal to construct γ-CD-MOF, which has a good selective adsorption capacity for water vapor under high relative humidity conditions, so that the obtained γ-CD-MOF / cellulose dehumidifying and anti-fogging membrane can quickly dehumidify near-saturated humid air such as exhaled air, while the adsorption capacity is low under normal ambient humidity, which is beneficial to improve the effective working capacity of the material in anti-fogging scenarios. (3) The present invention uses fibrous porous materials such as cellulose nonwoven fabric as a support, while introducing high moisture adsorption function and retaining the flexibility, porosity and breathability of the substrate, so that the obtained γ-CD-MOF / cellulose dehumidifying and anti-fog film has low air resistance and good wearing comfort, and is suitable for direct integration with existing mask structure. (4) This invention achieves “pre-condensation dehumidification and anti-fogging” by reducing local humidity and dew point temperature before hot and humid exhaled air reaches the lens. Unlike traditional anti-fogging sprays or lens coatings that regulate the surface of condensed droplets, this invention can suppress water vapor condensation and fogging from the source. (5) The composite dehumidifying and anti-fogging membrane obtained by the present invention can be regenerated by heating at low or medium temperature. After the moisture absorption-desorption cycle, it still maintains good dehumidification and anti-fogging performance and has the potential for repeated use and practical application. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the in-situ growth of γ-CD-MOF on the surface and pores of cellulose nonwoven fabric in Embodiment 1 of the present invention, and a schematic diagram of the application of the obtained γ-CD-MOF / cellulose dehumidifying and anti-fog film in eyeglasses and anti-fog masks.

[0050] Figure 2 Scanning electron microscope (SEM) images of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging films prepared under different in-situ growth times in Example 1 of the present invention.

[0051] Figure 3 A statistical chart showing the percentage of γ-CD-MOF loading in the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0052] Figure 4 Statistical chart of air resistance test data for γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0053] Figure 5 The graph shows the mass change of the CDMC-24 sample prepared in Example 1 before and after multiple purging tests under continuous airflow conditions.

[0054] Figure 6 The diagram shows the water vapor adsorption performance test of the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane in Example 3 of the present invention (a) and the water vapor adsorption isotherm and cyclic adsorption-desorption performance curve (b).

[0055] Figure 7 This is a statistical chart showing the change in relative humidity before and after the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane in Example 4 of the present invention under simulated exhaled air conditions.

[0056] Figure 8 The performance test chart of the mask containing γ-CD-MOF / cellulose composite dehumidifying and anti-fogging film in Example 5 of the present invention for anti-fogging of glasses includes statistical charts of temperature and relative humidity changes near the glasses and dew point temperature changes.

[0057] Figure 9 The figures show the water vapor adsorption performance of CD-MOF / cellulose composite dehumidifying and anti-fogging membranes with different crystal forms in Comparative Example 1 and CDMC-24 prepared in Example 1 of the present invention.

[0058] Figure 10The figures show the water vapor adsorption performance of CD-MOF / cellulose composite dehumidifying and anti-fogging membranes constructed with different alkali metals in Comparative Example 2 and CDMC-24 prepared in Example 1. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0060] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0061] Commercial mask: Disposable medical Medicon mask, approximately 175 mm × 95 mm, purchased from Xiantao Wilmed Protective Equipment Co., Ltd.

[0062] Cellulose nonwoven fabric: TX609, TEXWIPE.

[0063] Example 1: Preparation of a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF The preparation of the cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF includes the following steps: Step 1: Cut the cellulose nonwoven fabric into 17.5 cm × 9.5 cm pieces, wash them sequentially with ethanol and deionized water, and dry them for later use. Then, immerse the washed cellulose nonwoven fabric in a 0.2 mol / L potassium hydroxide aqueous solution and sonicate it for 30 min to fully expose and activate the hydroxyl groups on the surface of the cellulose fibers. After treatment, remove the cellulose nonwoven fabric and dry it at 80 ℃ for 6 h to obtain the alkali-treated / activated cellulose nonwoven fabric.

[0064] Step 2: Weigh 448 mg (8 mmol) potassium hydroxide and 11 mg cetyltrimethylammonium bromide, add 40 mL of deionized water and dissolve them completely, then add 10 mL of methanol, followed by 1.0377 g of γ-cyclodextrin (γ-CD), and sonicate to dissolve it completely to prepare the γ-CD-MOF precursor solution.

[0065] Step 3: The alkali-treated / activated cellulose nonwoven fabric obtained in Step 1 was placed in the γ-CD-MOF precursor solution obtained in Step 2, and an in-situ growth reaction was carried out under a methanol vapor atmosphere at 50 °C for 6 h, 12 h, 24 h, and 36 h, respectively. After the reaction, the sample was taken out and repeatedly washed with methanol and isopropanol to remove unreacted precursors and free crystals, and then vacuum dried at 80 °C for 12 h to obtain the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane. The samples obtained at different growth times were designated as CDMC-6, CDMC-12, CDMC-24, and CDMC-36, respectively.

[0066] Depend on Figure 1 The diagram is combined with Figure 2 Scanning electron microscopy (SEM) images revealed that the cellulose nonwoven fabric's fiber surface was activated after alkali treatment, which facilitated the in-situ nucleation and growth of γ-CD-MOF on the fiber surface and in the pores. As the in-situ growth time increased from 6 h to 36 h, the number of γ-CD-MOF crystals on the surface and in the pores of the cellulose nonwoven fabric gradually increased, and the crystal morphology gradually changed from the initial nucleation structure to obvious cubic crystals. When the growth time was 24 h, the γ-CD-MOF crystals were relatively uniformly distributed in the fiber network, and the crystal size was moderate; when the growth time was further extended to 36 h, some crystals increased in size and showed some accumulation.

[0067] Therefore, this method can achieve in-situ growth of γ-CD-MOF on the surface and pores of cellulose nonwoven fabric, and successfully prepare γ-CD-MOF / cellulose composite dehumidifying and anti-fogging film, which can be applied to anti-fogging masks.

[0068] Example 2: Loading test of γ-CD-MOF in γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane The γ-CD-MOF loading capacity of the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared in Example 1 was tested. Specifically, the cellulose nonwoven fabric, after alkali treatment / activation, was dried to constant weight, and its mass was recorded as m0 (g). Subsequently, γ-CD-MOF in-situ growth reaction was carried out for different times according to the method in Example 1. After washing and vacuum drying, the mass of the composite membrane was recorded as m1 (g). The γ-CD-MOF loading capacity was calculated according to the formula γ-CD-MOF loading capacity = (m1 - m0) / m1 × 100%, which was used to evaluate the loading of γ-CD-MOF in the cellulose nonwoven fabric under different in-situ growth times.

[0069] Test results are as follows Figure 3As shown, the loading of γ-CD-MOF in cellulose nonwoven fabric gradually increased with the extension of in-situ growth time from 6 h to 36 h. The loadings of γ-CD-MOF in CDMC-6, CDMC-12, CDMC-24, and CDMC-36 were approximately 47.90 wt%, 53.57 wt%, 67.43 wt%, and 69.60 wt%, respectively. Among them, CDMC-24 already had a relatively high loading of γ-CD-MOF; after further extending the growth time to 36 h, the loading only increased slightly, indicating that the nucleation / binding sites on the surface of cellulose fibers and the loading space in the fiber network gradually approached saturation.

[0070] Therefore, the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared by the present invention can achieve effective in-situ loading of γ-CD-MOF in cellulose nonwoven fabric. The γ-CD-MOF loading in the resulting composite membrane is in the range of 40 wt% to 85 wt%, and preferably in the range of 65 wt% to 70 wt%, providing a high content of moisture-absorbing functional phase for its use as a dehumidifying and anti-fogging functional layer of a mask.

[0071] Example 2: Tests on the air permeability and airflow stability of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane The air permeability and airflow stability of the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared in Example 1 were tested. Specifically, the original cellulose nonwoven fabric and the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membranes obtained at different in-situ growth times were placed in an air resistance testing device and tested at 85 L·min⁻¹. -1 The pressure difference across the diaphragm was measured at a test flow rate to evaluate its air permeability as a functional layer in a mask. Simultaneously, CDMC-24, as a representative sample, was subjected to a purge test under continuous airflow conditions to evaluate the binding stability of in-situ grown γ-CD-MOF crystals in cellulose nonwoven fabric.

[0072] Test results show that in-situ growth of γ-CD-MOF in cellulose nonwoven fabric slightly increases the air resistance of the membrane, but the composite membrane still maintains good air permeability. Specifically, the CDMC-24 sample showed the best air permeability at 85 L·min⁻¹. - ¹The air resistance at the test flow rate is approximately 13 Pa, which is within the range suitable for use as a functional layer in face masks. Figure 4 After continuous airflow purging, the quality change of the composite membrane is relatively small. Figure 5 This indicates that γ-CD-MOF crystals can be stably loaded onto the surface and pores of cellulose fibers and are not easily detached under the scouring of respiratory airflow.

[0073] Therefore, the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared by this invention can maintain good air permeability and structural stability while having moisture absorption function, providing a basis for its application in wearable protective products such as masks.

[0074] Example 3: Water vapor adsorption performance test of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane The water vapor adsorption performance of the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared in Example 1 was tested. Specifically, the original cellulose nonwoven fabric, pure γ-CD-MOF powder, and γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membranes (i.e., CDMC-24 and CDMC-36) obtained at different in-situ growth times (24 h and 36 h) were dried and activated. Subsequently, water vapor adsorption tests were conducted at 25–35 °C, with a relative humidity (RH) range of 0%–95%. Simultaneously, CDMC-24 was used as a representative sample for multiple adsorption-desorption cycle tests (adsorption: 35 °C, 95% RH, 8 h; desorption: 80 °C, 8 h) to evaluate the cycle stability and regenerability of the composite dehumidifying and anti-fogging membrane obtained in this invention.

[0075] The preparation of pure γ-CD-MOF powder includes the following steps: 448 mg of potassium hydroxide and 11 mg of cetyltrimethylammonium bromide were weighed and dissolved thoroughly in 40 mL of deionized water. Then, 10 mL of methanol was added, followed by 1.0377 g of γ-cyclodextrin. The mixture was sonicated until completely dissolved, yielding a γ-CD-MOF precursor solution. The precursor solution was placed in a sealed reaction vessel and reacted at 50 °C under a methanol vapor atmosphere for 24 h, allowing γ-cyclodextrin to coordinate with potassium ions and crystallize to form γ-CD-MOF. After the reaction, the resulting white solid product was collected and repeatedly washed with methanol and isopropanol to remove unreacted γ-cyclodextrin, potassium hydroxide, and free surfactant. The product was then vacuum dried at 80 °C for 12 h to obtain pure γ-CD-MOF powder. The pure γ-CD-MOF powder was used as a control sample for comparative testing of its water vapor adsorption performance against that of original cellulose nonwoven fabric and a γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0076] The results are as follows Figure 6 As shown in Figure a), the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane exhibits low water vapor adsorption under low relative humidity conditions, but significantly increases water vapor adsorption under high relative humidity conditions, especially within the 90%–95% RH range, demonstrating high-humidity adsorption characteristics suitable for exhaled air dehumidification. Among samples with different in-situ growth times, CDMC-24 and CDMC-36 show higher water vapor adsorption capacity. Cyclic adsorption-desorption curves (…) Figure 6 Figure b) shows that CDMC-24's adsorption performance did not significantly decrease after multiple water vapor adsorption and desorption processes.

[0077] Therefore, the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared by this invention can effectively adsorb water vapor in high humidity air and has good cycle stability and regeneration potential.

[0078] Example 4: Dynamic dehumidification performance test of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane under simulated exhaled air conditions. The dynamic dehumidification performance of the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared in Example 1 was tested under simulated exhaled air conditions. The specific steps are as follows: A humid air circulation testing device was constructed, allowing air to pass through heated deionized water to generate a warm, humid airflow at approximately 35°C and a relative humidity of approximately 90%–95%, simulating human exhalation. The membrane under test was fixed in the center of the airflow channel, and its edges were sealed to prevent airflow from bypassing the membrane. Temperature and humidity sensors were placed at the front and rear ends of the membrane to record the relative humidity changes in real time before and after the warm, humid air passed through the membrane. Test samples included virgin cellulose nonwoven fabric, CDMC-24, and CDMC-36.

[0079] The results are as follows Figure 7 As shown, the original cellulose nonwoven fabric has a weak dehumidifying effect on humid and hot air, with little change in relative humidity before and after the membrane. In contrast, the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane can significantly reduce the relative humidity after the membrane, and the dynamic dehumidification capacity of the membrane increases with the increase of the in-situ growth of γ-CD-MOF. Among them, CDMC-24 exhibits excellent humidity reduction effect, indicating that it can effectively capture water vapor in flowing humid and hot gas.

[0080] Therefore, the γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane prepared in this invention not only exhibits good moisture absorption capacity in static water vapor adsorption tests, but also has effective dehumidification performance under dynamic conditions simulating exhaled air, making it suitable for controlling the humidity of exhaled air during mask wearing.

[0081] Example 5: Preparation of an anti-fog mask containing a γ-CD-MOF / cellulose composite dehumidifying and anti-fog film and its anti-fog performance test on eyeglasses. The composite dehumidifying and anti-fogging film CDMC-24 prepared in Example 1 was used as a representative composite film for testing the anti-fogging performance of eyeglasses.

[0082] An anti-fog mask containing a γ-CD-MOF / cellulose composite dehumidifying and anti-fog film was prepared, and its anti-fog performance on glasses was tested. The specific operation included the following steps: Commercial medical masks were used, and the CDMC-24 prepared in Example 1 was incorporated as a functional layer within the mask. This functional layer was positioned between the inner and outer nonwoven fabric layers, serving as a filter layer (e.g., a conventional meltblown fabric layer) covering the entire mask area and playing a primary filtering role. As a control, a control mask was prepared using cellulose nonwoven fabric without γ-CD-MOF loading instead of this functional layer. Both the control mask and the dehumidifying and anti-fog mask containing the CDMC-24 functional layer were worn on a human head model wearing glasses. Simulated exhaled air at approximately 35°C and a relative humidity of approximately 90%–95% was generated by heating a gas washing bottle and introduced into the inside of the mask. The test environment temperature was approximately 20°C, and the relative humidity was approximately 60%. Temperature and humidity sensors were placed near the glasses to record real-time changes in temperature and relative humidity near the glasses, and the dew point temperature was calculated based on the temperature and humidity data.

[0083] The results are as follows Figure 8 As shown in the diagram, when wearing the control mask, hot and humid exhaled air easily enters the area near the glasses along the upper edge of the mask, increasing the relative humidity and dew point temperature near the glasses. Water vapor easily condenses on the lens surface, forming droplets and causing the lenses to fog up. When wearing a mask containing a γ-CD-MOF / cellulose composite dehumidifying and anti-fog film, hot and humid exhaled air passes through the functional layer before reaching the lenses. Water vapor in this layer is adsorbed by the γ-CD-MOF, reducing the relative humidity and dew point temperature near the glasses, allowing the lenses to remain clear.

[0084] Therefore, the dehumidifying and anti-fog mask prepared by the present invention can achieve anti-fog for glasses by pre-dehumidifying exhaled air, without relying on anti-fog spray or anti-fog coating on the lens surface, and has good practical application value.

[0085] Comparative Example 1: Preparation of cellulose dehumidifying and antifogging membranes based on in-situ growth of α-CD-MOF or β-CD-MOF and testing of their water vapor adsorption performance. Compared with Example 1, the difference is that γ-cyclodextrin was replaced with α-cyclodextrin and β-cyclodextrin respectively, the in-situ growth reaction time was 24 h, and the other steps and parameters were the same as in Example 1, respectively obtaining α-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane and β-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0086] The water vapor adsorption performance of the above-mentioned composite dehumidifying and anti-fogging membrane was tested according to the test method of Example 3, and the results are as follows: Figure 9 As shown, the water vapor adsorption capacity of α-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane and β-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane in high humidity environment is significantly lower than that of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0087] Comparative Example 2: Preparation of cellulose dehumidifying and antifogging membranes based on in-situ growth of Cs-γ-CD-MOF or Na-γ-CD-MOF and testing of their water vapor adsorption performance. Compared with Example 1, the difference is that potassium hydroxide in step 1 is replaced with sodium hydroxide and cesium hydroxide respectively, the in-situ growth reaction time is 24 h, and the other steps and parameters are the same as in Example 1, respectively obtaining Na-γ-CD-MOF / cellulose composite dehumidifying and anti-fogging film and Cs-γ-CD-MOF / cellulose composite dehumidifying and anti-fogging film.

[0088] The water vapor adsorption performance of the above-mentioned composite dehumidifying and anti-fogging membrane was tested according to the test method of Example 3, and the results are as follows: Figure 10 As shown, the water vapor adsorption capacity of Cs-γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane and Na-γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane in high humidity environments is significantly lower than that of γ-CD-MOF / cellulose composite dehumidifying and anti-fogging membrane.

[0089] In summary, this invention develops a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF. This method utilizes the coordination of potassium ions with hydroxyl groups on the surface of cellulose nonwoven fabric during the formation of γ-CD-MOF, enabling the stable in-situ growth of γ-CD-MOF on the surface and within the pores of cellulose fibers. This results in a composite dehumidifying membrane possessing high moisture vapor adsorption capacity, good air permeability, and structural stability. Integrating this composite membrane as a functional layer into a face mask allows it to adsorb water vapor before hot, humid exhaled air reaches the eyeglass lenses, reducing the local relative humidity and dew point temperature near the glasses, thereby inhibiting fogging at its source. This invention provides a novel material solution and application path for anti-fog masks, goggles, protective face shields, and other wearable humidity control products.

[0090] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF, characterized in that, Includes the following steps: (1) Dissolve γ-cyclodextrin, potassium source and surfactant fully in a mixed solvent of methanol and water to obtain γ-CD-MOF precursor solution; (2) The alkali-treated cellulose substrate is placed in the γ-CD-MOF precursor solution obtained in step (1) and in situ growth reaction is carried out at 20~80 ℃ for 20~40 h. After post-treatment, the cellulose dehumidification and anti-fog film based on γ-CD-MOF in situ growth is obtained. The mixing ratio of the γ-cyclodextrin and the potassium element in the potassium source is 1 g: (6~10) mmol.

2. The preparation method according to claim 1, characterized in that, The potassium source is selected from at least one of potassium hydroxide, potassium carbonate, potassium acetate, and potassium chloride.

3. The preparation method according to claim 1, characterized in that, The surfactant is at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, polyvinylpyrrolidone, and sodium dodecyl sulfate.

4. The preparation method according to claim 1, characterized in that, The cellulose substrate is at least one of natural cellulose fiber fabric, regenerated cellulose fiber fabric, cellulose nonwoven fabric, and cellulose paper-based material.

5. The preparation method according to claim 1, characterized in that, The preparation conditions of the preparation method include at least one of the following: (1) The mass ratio of the γ-cyclodextrin to the surfactant is (80~110):1; (2) The mass-to-volume ratio of the γ-cyclodextrin to the mixed solvent is 1 g: (40~60) mL; (3) The volume ratio of methanol to water is 1:(3~5).

6. The cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF prepared by the preparation method according to any one of claims 1 to 5.

7. The cellulose dehumidifying and anti-fogging membrane based on γ-CD-MOF in situ growth according to claim 6, characterized in that, The loading of γ-CD-MOF in the cellulose dehumidifying and anti-fogging membrane based on in-situ growth of γ-CD-MOF is 40wt%~85wt%.

8. The application of the cellulose dehumidifying and antifogging membrane based on γ-CD-MOF in situ growth as described in claim 6 or 7 in the preparation of dehumidifying and antifogging masks.

9. A dehumidifying and anti-fog mask, characterized in that, The dehumidifying and anti-fog mask includes an inner layer, an outer layer, and a functional layer located between the inner and outer layers, wherein the functional layer includes the cellulose dehumidifying and anti-fog membrane based on γ-CD-MOF in situ growth as described in claim 6 or 7.

10. The application of the cellulose desiccant and anti-fog membrane based on γ-CD-MOF in situ growth as described in claim 6 or 7, or the desiccant and anti-fog mask as described in claim 9, in anti-fog and / or desiccant applications, characterized in that, The applications include preventing fogging on transparent surfaces, dehumidifying exhaled air, and serving as a humidity control function unit for wearable humidity control products.

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