An mMOFs / GO-CS composite film, a preparation method thereof and application thereof

Abstract

This application proposes an mMOFs / GO-CS composite film, its preparation method, and its application, which can be used for fruit and vegetable preservation. The method includes the following steps: Step S1: Prepare modified mMOFs; Step S2: Weigh water, film-forming agent, glycerol, and graphene oxide dispersion. First, stir the water, film-forming agent, and glycerol until dissolved to obtain a transparent solution A; Under stirring conditions, add the graphene oxide dispersion dropwise to the transparent solution A to obtain solution B; Step S3: Weigh the mMOFs prepared in Step S1, disperse them in distilled water, and then add them dropwise to solution B under stirring conditions. Cast the film, and after drying, obtain the mMOFs / GO-CS film. This application describes the preparation of mMOFs with high surface area, large porosity and adjustable pore size, with graphene oxide as a linker, and chitosan to construct a bifunctional preservation film with both antibacterial and ethylene adsorption properties. The preparation method is simple and the composite film is biodegradable. It can be used to preserve freshly picked fruits and vegetables, extend the storage time of fruits and vegetables, and reduce the damage and waste of fruits and vegetables with respiratory climacteric effects.

Description

Technical Field

[0001] This application belongs to the field of fruit and vegetable preservation technology, specifically relating to an mMOFs / GO-CS composite film, its preparation method and its application, which has both antibacterial and ethylene adsorption functions. Background Technology

[0002] The main mechanisms of fruit and vegetable preservation include: controlling the relative temperature and humidity of the storage environment; inhibiting the life activities of harvested fruits and vegetables, such as respiration, self-oxidation, and ethylene release; and preventing microbial contamination. Therefore, research on antibacterial properties in fruit and vegetable packaging and ethylene adsorption are crucial for advancing fruit and vegetable preservation and storage technologies. CN103965539B discloses an intelligent breathing functional film for fruit and vegetable preservation and its preparation method. This film utilizes ethylene adsorption materials and a porous structure to eliminate ethylene, while simultaneously using N-acetamido-4-vinylpyridine to inhibit bacterial growth, thereby extending the preservation time of fruits and vegetables. CN113442540A discloses a biodegradable membrane material, its preparation method, and its application. Through the construction of a three-layer microstructure and the formation of a transcrystalline structure due to a nucleating agent, along with the addition of oxidants and antibacterial agents, the film synergistically regulates the permeability of oxygen, carbon dioxide, and water vapor through the membrane, eliminates decomposed ethylene gas, and inhibits bacterial growth.

[0003] Existing technologies suffer from drawbacks such as complex and ineffective ethylene elimination and antibacterial processes. They are generally general-purpose preservation films, lacking specific protection for climacteric fruits and vegetables, resulting in significant losses and waste. Furthermore, current technologies primarily use polyethylene and other similar raw materials, which are difficult to degrade and have low recycling rates, causing serious environmental pollution.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0005] This application provides an mMOFs / GO-CS composite film, its preparation method and its application, which has both antibacterial and ethylene adsorption functions.

[0006] A method for preparing an mMOFs / GO-CS composite film, which can be used for fruit and vegetable preservation, includes the following steps: Step S1: Using dodecyltrimethylammonium bromide as a soft template agent, weigh Cu(NO3)2·3H2O and H3BTC according to the proportion, add them to the mixture of ethanol and aqueous solution, and stir to mix; then transfer the reaction mixture to a reaction vessel, control the temperature in the reaction vessel within the range of 120℃-150℃, and process for 12-16 hours; after the reaction is completed, wash the product several times, and finally vacuum dry to obtain the modified product mMOFs; Step S2: Weigh 100 parts water, 2-5 parts film-forming agent, 1-1.5 parts glycerol, and 0.2-1 parts graphene oxide by weight. First, stir the water, film-forming agent, and glycerol at 40-50℃ until dissolved to obtain a transparent solution A, and then cool it to room temperature. Add the graphene oxide dispersion dropwise to the transparent solution A while stirring. After the addition is complete, continue stirring for 2-4 hours until the mixture is uniform to obtain solution B. Step S3: Weigh a predetermined amount of mMOFs prepared in step S1 by weight, disperse them in distilled water, and then add them dropwise to solution B under stirring. After the addition is complete, continue stirring for 2-4 hours. After drying, the mMOFs / GO-CS membrane is obtained.

[0007] In some embodiments of this application, the film-forming agent is chitosan or carboxymethyl chitosan.

[0008] In some embodiments of this application, the molar ratio of Cu(NO3)2·3H2O and H3BTC is 1:0.56.

[0009] In some embodiments of this application, the volume ratio of the ethanol and aqueous solution mixture is 1:1.

[0010] In some embodiments of this application, the ethanol and aqueous solution mixture is 30 mL.

[0011] In some embodiments of this application, in step S1, the product is washed multiple times with distilled water and ethanol, respectively.

[0012] In some embodiments of this application, in step S1, the vacuum drying temperature is 60°C and the drying time is 12 hours.

[0013] In some embodiments of this application, in step S2, the mass concentration of the graphene oxide dispersion is 2 mg / ml.

[0014] In some embodiments of this application, in step S3, 0.1 to 0.8 parts by weight of mMOFs are weighed, and after continuous stirring for 2 to 4 hours, the mixture is allowed to stand to defoam, then cast into a film, and dried to obtain an mMOFs / GO-CS composite film with both antibacterial and ethylene adsorption functions.

[0015] In some embodiments of this application, in step S3, 1 to 5 parts by weight of mMOFs are weighed, stirred continuously for 2 to 4 hours, crosslinked, and dried to obtain an mMOFs / GO-CS composite hydrogel membrane.

[0016] In some embodiments of this application, the inhibition zone test method is used to determine the antibacterial performance.

[0017] In some embodiments of this application, the ethylene adsorption performance is determined using a multi-station extended fully automated specific surface area and pore size analyzer.

[0018] In another embodiment of this application, a MOFs / GO-CS composite film is also proposed, which is prepared by the above preparation method.

[0019] In another embodiment of this application, an MOFs / GO-CS composite film is used for fruit and vegetable preservation.

[0020] In another embodiment of this application, an MOFs / GO-CS composite film is used for the preservation of respiratory climacteric fruits and vegetables.

[0021] Compared with the prior art, this application has at least the following advantages: This application presents an mMOFs / GO-CS composite film, its preparation method, and its application. This film possesses both antibacterial and ethylene adsorption functions. Modified mMOFs with adjustable porosity and pore size are prepared, and graphene oxide serves as a linker. Together with chitosan, they construct a bifunctional preservation film with both antibacterial and ethylene adsorption properties. The preparation method is simple, and the composite film is biodegradable. It can be used for preserving freshly harvested fruits and vegetables, extending their storage time and reducing damage and waste in fruits and vegetables with climacteric respiration. This system tightly combines the adjustable porosity and antibacterial properties of MOFs, the mechanical strength of graphene oxide, and the film-forming and antibacterial properties of chitosan, thus obtaining a bifunctional preservation film with both antibacterial and ethylene adsorption properties. Testing showed that the ethylene adsorption capacity of the modified mMOFs reached 111.88 cm⁻¹. 3 / g (STP); when tested as a preservation film, its tensile strength reached 15 MPa and its light transmittance exceeded 70%, effectively extending the storage period of climacteric fruits and vegetables. Furthermore, the preparation process is simple, using biodegradable materials as the packaging substrate, and comprehensively utilizing the advantages of each component material, it holds promise as a new generation of preservation material for the storage and preservation of climacteric fruits and vegetables. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The images shown are SEM and EDS energy dispersive spectra of the modified mMOFs prepared in the embodiments of this application. Figure 2The infrared spectrum of the mMOFs / GO-CS composite film obtained in the embodiments of this application is shown below. Figure 3 This is a graph showing the ethylene adsorption performance of the mMOFs nanomaterials obtained in the embodiments of this application; Figure 4 This is a diagram showing the antibacterial zone effect of the mMOFs / GO-CS composite membrane obtained in the embodiments of this application; Figure 5 This demonstrates the preservation effect of the mMOFs / GO-CS composite film obtained in the embodiments of this application on cherry tomatoes. Detailed Implementation

[0024] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of this application, but not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application.

[0025] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0026] The following examples further illustrate the above-mentioned content of this application, but it should not be construed as limiting the scope of the above-mentioned subject matter of this application to the following examples. All technologies implemented based on the above-mentioned content of this application fall within the scope of this application. Example

[0027] A method for preparing an mMOFs / GO-CS composite thin film includes the following steps: Step S1: Using dodecyltrimethylammonium bromide as a soft template agent, weigh 1.087 g Cu(NO3)2•3H2O and 0.525 g H3BTC and add them to 30 mL of a mixture of ethanol and aqueous solution (volume ratio 1:1), and stir thoroughly; then transfer the reaction mixture to a reaction vessel and process it at 120℃ for 12 hours; after the reaction is completed, wash the product several times with distilled water and ethanol, and finally dry it under vacuum at 60℃ for 12 h to obtain the modified product mMOFs; Step S2: Weigh 100 parts water, 2 parts film-forming agent, 1 part glycerol and 0.9 parts graphene oxide by weight. First, stir the water, film-forming agent and glycerol at 40~50℃ until completely dissolved to obtain a transparent solution A. After complete dissolution, cool to room temperature. Add the graphene oxide dispersion dropwise to solution A under vigorous stirring. After the addition is complete, continue stirring at room temperature for 2 hours until the mixture is uniform to obtain solution B.

[0028] Step S3: Weigh 0.7 parts by weight of MOFs and disperse them in an appropriate amount of distilled water. Then, add the MOFs dropwise to solution B under vigorous stirring. After the addition is complete, continue stirring at room temperature for 2 hours. After mixing and allowing to stand to defoam, cast the mixture to obtain an mMOFs / GO-CS composite film with both antibacterial and ethylene adsorption functions.

[0029] The antibacterial performance was determined by the inhibition zone test, and the ethylene adsorption performance was determined by a multi-station extended fully automated specific surface area and pore size analyzer. Example

[0030] A method for preparing an mMOFs / GO-CS composite thin film includes the following steps: Step S1: Using dodecyltrimethylammonium bromide as a soft template agent, weigh 1.087 g Cu(NO3)2•3H2O and 0.525 g H3BTC and add them to 30 mL of a mixture of ethanol and aqueous solution (volume ratio 1:1), and stir thoroughly; then transfer the reaction mixture to a reaction vessel and process it at 120℃ for 12 hours; after the reaction is completed, wash the product several times with distilled water and ethanol, and finally dry it under vacuum at 60℃ for 12 h to obtain the modified product mMOFs.

[0031] Step S2: Weigh 100 parts water, 5 parts film-forming agent, 1 part glycerol and 0.7 parts graphene oxide by weight. First, stir the water, film-forming agent and glycerol at 40~50℃ until completely dissolved to obtain a transparent solution A. Add the graphene oxide dispersion dropwise to solution A under vigorous stirring. After the addition is complete, keep the temperature constant and continue stirring for 2 hours until the mixture is uniform to obtain solution B.

[0032] Step S3: Weigh 3 parts by weight of MOFs and disperse them in an appropriate amount of distilled water. Then, add them dropwise to solution B under vigorous stirring. After the addition is complete, stir continuously at 40-50℃ for 4 hours. After mixing and crosslinking, an mMOFs / GO-CS composite hydrogel with both antibacterial and ethylene adsorption functions is obtained. After drying, a composite hydrogel membrane is obtained.

[0033] The antibacterial performance was determined by the inhibition zone test; the ethylene adsorption performance was determined by a multi-station extended fully automated specific surface area and pore size analyzer.

[0034] In some embodiments of this application, by controlling the content of mMOFs, composite hydrogel membranes can be prepared. As the content of MOFs increases, more functional groups crosslink with chitosan (CS) and graphene oxide (GO), tending to form a gel morphology with a three-dimensional network structure.

[0035] Depend on Figure 1 (a)- Figure 1 (d) It can be seen that, at different magnifications, the modified mMOFs prepared in the embodiments of this application exhibit a regular octahedral structure. Figure 1 (e)- Figure 1 (f) shows that the C, N, O and Cu elements are displayed through the EDS mapping image.

[0036] Depend on Figure 2 The infrared spectrum of the mMOFs / GO-CS composite film obtained in the embodiments of this application is shown. The composite film contains characteristic peaks of CS, GO and mMOFs. The mMOFs are successfully composited with graphene oxide and chitosan to form a uniform film structure with excellent adsorption and antibacterial effects.

[0037] Depend on Figure 3 It can be seen that, under standard conditions, the maximum ethylene adsorption value of mMOFs is 111.88 cm⁻¹. 3 / g. Because the mMOFs / GO-CS prepared in this application possesses a copper-based metal-organic framework porous structure and excellent surface chemistry, ethylene molecules can fully enter its porous structure and interact with its surface under high relative pressure, leading to an increase in adsorption capacity. Furthermore, as the relative pressure continues to increase, the porous structure of the copper-based metal-organic framework gradually becomes saturated, and the rate of increase in adsorption rate and adsorption capacity gradually slows down until an equilibrium adsorption capacity is reached.

[0038] Figure 4 This is an image showing the antibacterial zone effect of the mMOFs / GO-CS composite film obtained in the embodiments of this application. Since both chitosan and the metal ions in mMOFs have antibacterial properties, the mMOFs / GO-CS composite film exhibits good antibacterial effects, effectively inhibiting bacterial growth and reproduction. GO-CS represents a composite film of graphene oxide and chitosan without added mMOFs.

[0039] Figure 5This application describes the preservation effect of the mMOFs / GO-CS composite film on cherry tomatoes. After 15 days of storage, the rot rate of cherry tomatoes packaged with the mMOFs / GO-CS composite film was significantly lower than that of cherry tomatoes packaged with ordinary supermarket plastic wrap (CK), CS, and GO-CS films. Furthermore, tests on indicators such as hardness, titratable acid, soluble solids, and vitamin C all showed that the nutritional components and quality of cherry tomatoes packaged with the mMOFs / GO-CS composite film were effectively protected, effectively slowing down fruit ripening and senescence, and effectively extending the shelf life of cherry tomatoes by approximately 5 days. The above embodiments describe the basic principles, main features and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of this application. Various changes and improvements can be made to this application without departing from the scope of the principles of this application, and all such changes and improvements fall within the protection scope of this application.

[0040] Based on the above-described preferred embodiments according to this application, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing an mMOFs / GO-CS composite film, wherein the mMOFs / GO-CS composite film is used for fruit and vegetable preservation, characterized in that, Includes the following steps: Step S1: Using dodecyltrimethylammonium bromide as a soft template agent, weigh Cu(NO3)2·3H2O and H3BTC according to the proportion, add them to the mixture of ethanol and aqueous solution, and stir to mix; then transfer the reaction mixture to a reaction vessel, control the temperature in the reaction vessel within the range of 120℃-150℃, and process for 12-16 hours; after the reaction is completed, wash the product several times, and finally vacuum dry to obtain the modified product mMOFs; Step S2: Weigh 100 parts water, 2-5 parts film-forming agent, 1-1.5 parts glycerol, and 0.2-1 parts graphene oxide by weight. First, stir the water, film-forming agent, and glycerol at 40-50℃ until dissolved to obtain a transparent solution A, and then cool it to room temperature. Add the graphene oxide dispersion dropwise to the transparent solution A while stirring. After the addition is complete, continue stirring for 2-4 hours until the mixture is uniform to obtain solution B. Step S3: Weigh a predetermined amount of mMOFs prepared in step S1 by weight, disperse them in distilled water, and then add them dropwise to solution B under stirring. After the addition is complete, continue stirring for 2-4 hours. After drying, the mMOFs / GO-CS composite film is obtained. The film-forming agent is carboxymethyl chitosan.

2. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, The molar ratio of Cu(NO3)2·3H2O and H3BTC is 1:0.

56.

3. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, The volume ratio of the ethanol and aqueous solution mixture is 1:

1.

4. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, The amount of the ethanol and aqueous solution mixture used is 30 mL.

5. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, In step S1, the product is washed multiple times with distilled water and ethanol, respectively; in step S1, the vacuum drying temperature is 60℃ and the drying time is 12 hours.

6. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, In step S2, the mass concentration of the graphene oxide dispersion is 2 mg / ml.

7. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, In step S3, 0.1 to 0.8 parts by weight of mMOFs are weighed, and after continuous stirring for 2 to 4 hours, the mixture is allowed to stand to defoam, then cast into a film and dried to obtain an mMOFs / GO-CS composite film with both antibacterial and ethylene adsorption functions.

8. The method for preparing an mMOFs / GO-CS composite thin film according to claim 1, characterized in that, In step S3, 1 to 5 parts by weight of mMOFs are weighed, stirred continuously for 2 to 4 hours, crosslinked, and dried to obtain mMOFs / GO-CS composite film.

9. An mMOFs / GO-CS composite thin film, characterized in that, It is prepared by the method of any one of claims 1-8 for preparing an mMOFs / GO-CS composite film, and has dual functions of antibacterial and ethylene adsorption.

10. The application of the mMOFs / GO-CS composite thin film as described in claim 9, characterized in that, The composite film is used as a preservation film for the preservation of fruits and vegetables with climacteric respiration.

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