A metal organic framework and a preparation method and application thereof

Abstract

This invention relates to the field of organic materials technology, specifically to a metal-organic framework (MOF), its preparation method, and its applications. The MOF is a CuBaTi MOF; wherein the MOF has a layered and porous structure; the CuBaTi MOF is modified with a surfactant; and the CuBaTi MOF is composited with mineral components. This MOF can effectively inhibit bacteria and adsorb ethylene. When made into an antibacterial film, it can not only preserve and inhibit bacteria in fruits and vegetables, delaying ripening and spoilage, but also possesses good mechanical properties. Furthermore, the preparation method of this MOF is simple, convenient, low-cost, and environmentally friendly, showing broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of organic materials technology, specifically to a metal-organic framework, its preparation method, and its application. Background Technology

[0002] Traditional food preservation films are typically made of polymer materials such as polyethylene (PE), polyvinyl chloride (PVC), or polyvinylidene chloride (PVDC), primarily delaying food spoilage through physical barriers (such as blocking oxygen and water vapor). However, these materials can only passively prevent external microbial contamination and cannot inhibit the growth of bacteria, mold, and other microorganisms already present on the food surface, resulting in limited preservation effects, especially for high-moisture, high-nutrient foods (such as meat, fruits and vegetables, and dairy products).

[0003] With increasing demands for food safety and extended shelf life, simple physical barriers are no longer sufficient. Food is susceptible to microbial contamination during processing, transportation, and storage, leading to spoilage and even foodborne illnesses. Therefore, developing food preservation films with active antibacterial functions has become a research hotspot, aiming to inhibit or kill pathogenic bacteria (such as Escherichia coli, Staphylococcus aureus, Salmonella, etc.) and spoilage microorganisms on the surface of food, thereby extending its shelf life.

[0004] The core of antibacterial films lies in introducing antibacterial components into traditional polymer substrates, enabling them to possess continuous or sustained-release antibacterial properties. Currently, the main technical routes include: a) Natural antibacterial agents: such as chitosan (with broad-spectrum antibacterial properties), plant essential oils (such as cinnamaldehyde and thymol), lysozyme, etc., which have attracted attention due to their safety and biodegradability; b) Inorganic antibacterial agents: such as nano-silver (Ag), nano-zinc oxide (ZnO), and nano-titanium dioxide (TiO2), which disrupt microbial structures through metal ion release or photocatalysis; c) Organically synthesized antibacterial agents: such as quaternary ammonium salts and potassium sorbate, which interfere with microbial cell membrane function through charge interactions; d) Composite antibacterial systems: combining multiple antibacterial agents or carriers (such as cyclodextrin and nanocellulose) to improve synergistic effects and sustained-release performance.

[0005] Despite the promising future of antibacterial films, several challenges remain to be addressed in their technological implementation: Antibacterial performance relies on metal coatings such as silver and zinc, which presents issues including high cost, risk of heavy metal migration, and a narrow antibacterial spectrum. Furthermore, traditional films cannot effectively adsorb ethylene gas released by fruits and vegetables, leading to accelerated ripening and shortened shelf life.

[0006] Therefore, it is necessary to develop a new antibacterial film. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of insufficient antibacterial performance and weak ethylene control ability of traditional fruit and vegetable packaging, thereby providing a metal-organic framework, its preparation method and application. This metal-organic framework can effectively inhibit bacteria and adsorb ethylene. When made into an antibacterial film, it can not only achieve the preservation and antibacterial properties of fruits and vegetables and delay their ripening and spoilage, but also has good mechanical properties. At the same time, the preparation method of this metal-organic framework is simple, convenient, low-cost, green and environmentally friendly, and has broad application prospects.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a metal-organic framework, wherein the metal-organic framework is CuBaTi MOFs; wherein...

[0009] The metal-organic framework has a layered structure and a porous structure;

[0010] The CuBaTi MOFs were modified with surfactants;

[0011] The CuBaTi MOFs are composites of mineral components.

[0012] Preferably, the surfactant is hexadecyltrimethylammonium bromide.

[0013] Preferably, the mineral component is carboxylated nano-mica and / or diatomaceous earth.

[0014] In a second aspect, the present invention provides a method for preparing a metal-organic framework as described in the first aspect, the method comprising:

[0015] 1) Dissolve copper and barium sources in a solvent for the first mixing, add titanium source for the second mixing, add ligands for the third mixing, and carry out microwave solvothermal reaction to obtain a copper-barium-titanium three-dimensional framework.

[0016] 2) The copper-barium-titanium three-dimensional framework is modified with a surfactant and then mineral components are added for ultrasonic composite.

[0017] Preferably, in step 1), the copper source is selected from one or more of copper sulfate, copper nitrate, copper chloride, and copper acetate.

[0018] Preferably, in step 1), the barium source is selected from barium chloride and / or barium nitrate.

[0019] More preferably, in step 1), the titanium source is selected from one or more of tetrabutyl titanate, titanium tetrachloride, and isopropyl titanate.

[0020] More preferably, in step 1), the solvent is an aqueous solution of N,N-dimethylformamide;

[0021] More preferably, the ligand is selected from one or more of pyromellitic acid, terephthalic acid and 2-methylimidazole.

[0022] Preferably, in step 1), the molar ratio of the copper source, barium source, titanium source and ligand is 1:0.5-2:0.5-2:1-3, wherein the copper source is calculated as copper ions, the barium source as barium ions, and the titanium source as titanium ions.

[0023] Preferably, in step 1), the conditions for the first mixing include a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0024] Preferably, in step 1), the conditions for the second mixing include: a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0025] More preferably, in step 1), the conditions for the third mixing include: a temperature of 15-30°C, a stirring rate of 300-600 rpm, and a time of 10-30 min.

[0026] More preferably, in step 1), the conditions for the microwave solvothermal reaction include: microwave power of 200-500w, temperature of 110-150℃, and time of 20-60min.

[0027] Preferably, in step 2), the surfactant is hexadecyltrimethylammonium bromide.

[0028] Preferably, in step 2), the mineral component is carboxylated nano-mica and / or diatomaceous earth.

[0029] Preferably, in step 2), the concentration of the surfactant is 0.01–0.05 mol / L.

[0030] Preferably, in step 2), the mass ratio of the copper-barium-titanium three-dimensional framework to the mineral components is 1:1-5.

[0031] Preferably, in step 2), the modification conditions include: a temperature of 40-80℃, an ultrasonic power of 200-400W, and a time of 10-30min.

[0032] Preferably, in step 2), the conditions for the composite include: a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0033] Thirdly, the present invention provides an antibacterial film, characterized in that the antibacterial film comprises a metal-organic framework and a PE resin as described in the first aspect.

[0034] In the above technical solution, the metal-organic framework CuBaTi MOFs of the present invention contain Cu 2+ and Ti 4+ Cu 2+ and Ti 4+ By disrupting bacterial cell membranes and inducing the generation of reactive oxygen species (ROS), the antibacterial rate against pathogenic bacteria and molds on the surface of fruits and vegetables is ≥99.99%. Furthermore, the metal-organic framework is modified with CTAB. The hydrophobic alkyl chains of CTAB are inserted into the phospholipid bilayer of the bacterial membrane, disrupting the membrane integrity. The positively charged quaternary ammonium groups combine with the negatively charged groups (such as phospholipid head groups) on the membrane surface, inducing membrane perforation. Moreover, the physical confinement effect of the MOF channels on CTAB slows down its release rate, thereby achieving long-lasting antibacterial effect.

[0035] Furthermore, the Ba in the metal-organic framework CuBaTi MOFs of the present invention 2+ π-complexation, Ba 2+ The d-orbital electrons of Cu delocalize with the π-bond electron cloud of ethylene, forming a stable ethylene adsorbent complex; simultaneously, Cu / Ti open sites synergistically adsorb ethylene. 2+ The Lewis acidic sites enhance the adsorption strength of ethylene through charge transfer, while Ti 4+ The coordination unsaturated sites enhance the ethylene capture rate through dynamic adsorption-desorption equilibrium; MOF pore breathing effect: CO2 adsorption causes slight shrinkage of the MOF skeleton (pore size reduction), which further enhances the ethylene retention capacity through size sieving effect.

[0036] The antibacterial film prepared by the metal-organic framework CuBaTi MOFs of the present invention has a spontaneous modified atmosphere effect, which can spontaneously form a low-oxygen (reduced O2 concentration) and high-CO2 gaseous microenvironment. This environment inhibits the aerobic metabolic pathway in the respiration of fruits and vegetables, delays ripening and spoilage, and has high mechanical properties due to the addition of mineral components and the metal-organic framework.

[0037] Meanwhile, the metal-organic framework CuBaTi MOFs of the present invention are prepared by a solvothermal method, which is simple, easy to operate, and convenient for industrial mass production, and has broad application prospects.

[0038] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0040] Figure 1The image shows the X-ray diffraction (XRD) analysis of CuBaTi MOFs prepared in Example 1 of this invention.

[0041] Figure 2 This is a TEM image of CuBaTiMOFs obtained in Example 1 of the present invention;

[0042] Figure 3 The image shows the FTIR analysis of the MOF thin film prepared in Application Example 1 of this invention.

[0043] Figure 4 Here is a SEM image of the MOFs thin film prepared in Application Example 1 of this invention;

[0044] Figure 5 The TGA analysis image is shown for the MOF thin film prepared in Application Example 1 of this invention.

[0045] Figure 6 This is a record of the changes in the appearance of the perfume lemon during the experiment of Example 6 of the present invention;

[0046] Figure 7 This is a graph showing the changing trends of various indicators of the perfume lemon during the experiment of Example 6 of the present invention;

[0047] Figure 8 This is a record of the changes in the appearance of broccoli during the experiment of Example 7 of the present invention;

[0048] Figure 9 This is a graph showing the changing trends of various indicators of broccoli during the experiment of Example 7 of the present invention. Detailed Implementation

[0049] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0050] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0051] In a first aspect, the present invention provides a metal-organic framework, wherein the metal-organic framework is CuBaTi MOFs; wherein...

[0052] The metal-organic framework has a layered structure and a porous structure;

[0053] The CuBaTi MOFs were modified with surfactants;

[0054] The CuBaTi MOFs are composites of mineral components.

[0055] The metal-organic framework CuBaTi MOFs of the present invention contain Cu 2+ and Ti 4+ Cu 2+ and Ti 4+ By disrupting bacterial cell membranes and inducing the generation of reactive oxygen species (ROS), the antibacterial rate against pathogenic bacteria and molds on the surface of fruits and vegetables is ≥99.99%. Furthermore, the metal-organic framework is modified with CTAB. The hydrophobic alkyl chains of CTAB are inserted into the phospholipid bilayer of the bacterial membrane, disrupting the membrane integrity. The positively charged quaternary ammonium groups combine with the negatively charged groups (such as phospholipid head groups) on the membrane surface, inducing membrane perforation. Moreover, the physical confinement effect of the MOF channels on CTAB slows down its release rate, thereby achieving long-lasting antibacterial effect.

[0056] Furthermore, the Ba in the metal-organic framework CuBaTi MOFs of the present invention 2+ π-complexation, Ba 2+ The d-orbital electrons of Cu delocalize with the π-bond electron cloud of ethylene, forming a stable ethylene adsorbent complex; simultaneously, Cu / Ti open sites synergistically adsorb ethylene. 2+ The Lewis acidic sites enhance the adsorption strength of ethylene through charge transfer, while Ti 4+ The coordination unsaturated sites enhance the ethylene capture rate through dynamic adsorption-desorption equilibrium; MOF pore breathing effect: CO2 adsorption causes slight shrinkage of the MOF skeleton (pore size reduction), which further enhances the ethylene retention capacity through size sieving effect.

[0057] In a preferred embodiment of the present invention, the surfactant is hexadecyltrimethylammonium bromide.

[0058] In a preferred embodiment of the present invention, the mineral component is carboxylated nano-mica and / or diatomaceous earth.

[0059] In a second aspect, the present invention provides a method for preparing a metal-organic framework as described in the first aspect, the method comprising:

[0060] 1) Dissolve copper and barium sources in a solvent for the first mixing, add titanium source for the second mixing, add ligands for the third mixing, and carry out microwave solvothermal reaction to obtain a copper-barium-titanium three-dimensional framework.

[0061] 2) The copper-barium-titanium three-dimensional framework is modified with a surfactant and then mineral components are added for ultrasonic composite.

[0062] The metal-organic framework CuBaTi MOFs of the present invention are prepared by a solvothermal method, which is simple, easy to operate, and convenient for industrial mass production, and has broad application prospects.

[0063] In a preferred embodiment of the present invention, in step 1), the copper source is selected from one or more of copper sulfate, copper nitrate, copper chloride, and copper acetate.

[0064] In a preferred embodiment of the present invention, in step 1), the barium source is selected from barium chloride and / or barium nitrate.

[0065] In a preferred embodiment of the present invention, in step 1), the titanium source is selected from one or more of tetrabutyl titanate, titanium tetrachloride and isopropyl titanate.

[0066] In a preferred embodiment of the present invention, in step 1), the solvent is an aqueous solution of N,N-dimethylformamide.

[0067] In a preferred embodiment of the present invention, in step 1), the ligand is selected from one or more of pyromellitic acid, terephthalic acid and 2-methylimidazole.

[0068] In a preferred embodiment of the present invention, in step 1), the molar ratio of the copper source, barium source, titanium source and ligand is 1:0.5-2:0.5-2:1-3, wherein the copper source is calculated as copper ions, the barium source as barium ions, and the titanium source as titanium ions.

[0069] In a preferred embodiment of the present invention, in step 1), the conditions for the first mixing include a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0070] In a preferred embodiment of the present invention, in step 1), the conditions for the second mixing include: a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0071] In a preferred embodiment of the present invention, in step 1), the conditions for the third mixing include: a temperature of 15-30°C, a stirring rate of 300-600 rpm, and a time of 10-30 min.

[0072] In a preferred embodiment of the present invention, in step 1), the conditions for the microwave solvothermal reaction include: a temperature of 110-150°C and a time of 20-60 min.

[0073] In a preferred embodiment of the present invention, in step 2), in order to regulate the microenvironment of the pores, suppress excessive grain growth, and optimize the adsorption sites of MOFs for ethylene, the surfactant is hexadecyltrimethylammonium bromide.

[0074] In a preferred embodiment of the present invention, in step 2), in order to improve the mechanical properties and gas barrier properties of the film, the mineral component is carboxylated nano-mica and / or diatomaceous earth.

[0075] In a preferred embodiment of the present invention, in step 2), the concentration of the surfactant is 0.01-0.05 mol / L.

[0076] In a preferred embodiment of the present invention, in step 2), the mass ratio of the copper-barium-titanium three-dimensional framework to the mineral components is 1:1-5.

[0077] In a preferred embodiment of the present invention, in step 2), in order to regulate the microenvironment of the pores, suppress excessive grain growth, and optimize the adsorption sites of MOFs for ethylene, the modification conditions include: a temperature of 40-80℃, an ultrasonic power of 200-400W, and a time of 10-30min.

[0078] In a preferred embodiment of the present invention, in step 2), the conditions for the composite process include: a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes.

[0079] Thirdly, the present invention provides an antibacterial film, characterized in that the antibacterial film comprises a metal-organic framework and a PE resin as described in the first aspect.

[0080] The antibacterial film prepared by the metal-organic framework CuBaTi MOFs of the present invention has a spontaneous modified atmosphere effect, which can spontaneously form a low-oxygen (reduced O2 concentration) and high-CO2 gaseous microenvironment. This environment inhibits the aerobic metabolic pathway in the respiration of fruits and vegetables, delays ripening and spoilage, and has high mechanical properties due to the addition of mineral components to the metal-organic framework.

[0081] The present invention will be described in detail below through examples. In the following examples, the pharmaceuticals and agents are all conventional commercially available products.

[0082] Example 1

[0083] (1) Dissolve 1 mmol of copper sulfate and 1 mmol of barium chloride in a mixed solvent of deionized water and N,N-dimethylformamide (v / v = 1:1), add 1 mmol of tetrabutyl titanate and stir at 300 rpm until homogeneous. Then add 1.5 mmol of trimesic acid as a ligand and mix thoroughly. Transfer the mixture to a reaction vessel and heat to 130°C with a microwave power of 300 W for 20 min to form a Cu-BTC main framework and in-situ dope Ti. 4+ and Ba 2+After cooling, the product is separated by centrifugation and washed with ethanol and deionized water 3-5 times in sequence, which is the primary CuBaTi ternary MOFs.

[0084] (2) The primary CuBaTi ternary MOFs obtained in step (1) were modified with a 0.05 mol / L cetyltrimethylammonium bromide (CTAB) solution to inhibit excessive grain growth;

[0085] (3) The mixture of carboxylated nanomica (5nm) and diatomaceous earth (20nm pore size) (mass ratio of 1:1) is mixed with the CuBaTi ternary MOFs modified by CTAB in step (2) at a mass ratio of 1:2, and then the mixture is ultrasonically co-precipitated into the pores of the MOFs to obtain CuBaTi MOFs, denoted as A1.

[0086] Example 2

[0087] The method of Example 1 was carried out, except that copper sulfate in step (1) was replaced with copper nitrate and barium chloride was replaced with barium nitrate, while other conditions remained unchanged, and CuBaTiMOFs were obtained, denoted as A2.

[0088] Example 3

[0089] The method of Example 1 was carried out, except that the pyromellitic acid in step (1) was replaced with terephthalic acid, while other conditions remained unchanged, and CuBaTi MOFs were obtained, denoted as A3.

[0090] Example 4

[0091] The method of Example 1 was carried out, except that the mixture of carboxylated nanomica (5nm) and diatomaceous earth (20nm pore size) in step (3) was replaced with an equal mass of carboxylated nanomica (5nm), while other conditions remained unchanged, and CuBaTi MOFs were obtained, denoted as A3.

[0092] Depend on Figure 1 The X-ray diffraction pattern of CuBaTi MOFs shows that the CuBaTi MOFs of Example 1 of this invention exhibit a series of diffraction peaks at 22.8°, 29.1°, 31.2°, 37.8°, 39.1°, 42.9°, 46.8°, 56.3°, 60.6°, and 64.5°. These characteristic diffraction peaks can be attributed to the phases of CuBaTi MOFs, indicating that Example 1 of this invention successfully synthesized CuBaTi MOFs.

[0093] Depend on Figure 2The TEM images of CuBaTi MOFs shown indicate that mineral components are incorporated into the microporous channels and surface of CuBaTi MOFs, demonstrating the successful synthesis of CuBaTi MOFs.

[0094] Application Example 1

[0095] (1) The ingredients were prepared according to the following ratio: 85% polyethylene resin, 3% antistatic agent, 5% ultraviolet absorber, 5% maleic anhydride graft copolymer, and 2% CuBaTi MOFs prepared in Example 1.

[0096] (2) Put the above ingredients into a high-speed mixer and premix for 5-10 minutes to ensure that the components are evenly dispersed. Add the mixture to a twin-screw extruder and set the temperature gradient as 160℃ (feed section) → 180℃ (compression section) → 200-220℃ (melting section) → 210℃ (die section). The melt is extruded through a T-die to form a sheet fluid.

[0097] (3) The melt flows from the T-die to the chrome-plated cooling roller (roller temperature 15-25℃), and is rapidly cooled and shaped by the high-speed rotation of the roller to form a primary film with uniform thickness.

[0098] (4) After cooling, the film is pulled by the tension control system, trimmed and then wound up. The winding speed is adjusted synchronously with the traction speed to avoid wrinkles or uneven stretching, thus producing a plastic film containing CuBaTi MOFs, referred to as MOF film.

[0099] Depend on Figure 3 The FTIR analysis of the MOF film shown indicates that the MOF film at 1645.28 cm⁻¹... -1 and 2160.71cm -1 The appearance of a characteristic infrared absorption peak at this location indicates that the stretching peak is generated by the CH stretching vibration of CTAB, representing the successful modification of the original CuBaTi MOFs by CTAB.

[0100] like Figure 4 The SEM image of the MOF film shown shows that the plastic film prepared using the CuBaTi MOFs of the present invention has a porous structure. The film appears rough and dense, indicating that the CuBaTi MOFs are effectively dispersed in the film.

[0101] Depend on Figure 5The TGA analysis of the MOF films shows that the first weight loss stage occurs between 268-400℃, with a weight loss rate of 1.8%. The second stage occurs between 400-500℃. This is because the PE film begins to soften and melt at 120-130℃ (melting point). When the temperature exceeds 300℃, the long-chain molecules of PE begin to break, resulting in thermal decomposition. As the temperature gradually rises to 500℃, the PE film completely decomposes. The TGA analysis indicates that the addition of CuBaTi MOFs increases the melting point of the PE film, and the CuBaTi MOFs exhibit excellent thermal stability before the PE film decomposes.

[0102] Detection Example 1

[0103] In Application Example 1, the strength of the plastic film prepared using CuBaTi MOFs (hereinafter referred to as MOF film) and the commercially available ordinary PE plastic film (hereinafter referred to as ordinary PE) were compared. The test method was in accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106] As can be seen from the data in Table 1, the CuBaTi MOFs of the present invention have better tensile properties than ordinary plastic films on the market when used to prepare plastic films.

[0107] Detection Example 2

[0108] In Application Example 1, the anti-adhesion properties of the plastic film prepared by CuBaTi MOFs (hereinafter referred to as MOF film) and the commercially available ordinary PE plastic film (hereinafter referred to as ordinary PE) were tested. The test method was in accordance with GB / T 10006-2021 "Determination of the coefficient of friction of plastic films and sheets". The test results are shown in Table 2.

[0109] Table 2

[0110] static friction coefficient coefficient of kinetic friction MOF thin films 0.183 0.159 Ordinary PE 0.367 0.352

[0111] Detection Example 3

[0112] In test application example 1, the anti-adhesion properties of the plastic film prepared using CuBaTi MOFs (hereinafter referred to as MOF film) and the commercially available ordinary PE plastic film (hereinafter referred to as ordinary PE) were compared. The test method was based on the parallel plate method of ASTM D3354 to measure the adhesion load of the plastic film. The test results are shown in Table 3.

[0113] Table 3

[0114] Peel force (N / cm) MOF thin films 0.3 Ordinary PE 0.8

[0115] As can be seen from the data in Tables 2 and 3, the CuBaTi MOFs of the present invention have better anti-adhesion properties than ordinary plastic films on the market when used to prepare plastic films.

[0116] Detection Example 4

[0117] In Application Example 1, the antibacterial properties of the plastic film prepared using CuBaTi MOFs (hereinafter referred to as MOF film) and the commercially available ordinary PE plastic film (hereinafter referred to as ordinary PE) were compared. The test method was in accordance with GB / T31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials". The test results are shown in Table 4.

[0118] Table 4

[0119] Escherichia coli inhibition rate (%) Staphylococcus aureus inhibition rate (%) MOF thin films 99.99 99.99 Ordinary PE 0.52 0.27

[0120] As can be seen from the data in Table 4, the antibacterial properties of the CuBaTi MOFs of the present invention used to prepare plastic films are far superior to those of ordinary plastic films on the market, indicating that the plastic films of the present invention have better antibacterial properties.

[0121] Case 5

[0122] In test application example 1, the ethylene adsorption rate of plastic film prepared using CuBaTi MOFs (hereinafter referred to as MOF film) and ordinary PE plastic film on the market (hereinafter referred to as ordinary PE) was compared. The test method was in accordance with GB21551.4-2024 "Antibacterial, sterilization and purification functions of household and similar electrical appliances" and the ethylene adsorption test was carried out in a 3.9L glass box. The results are shown in Table 5.

[0123] Table 5

[0124] Ethylene adsorption rate (%) CuBaTi MOFs-containing plastic films 62.86 Ordinary plastic film 4.73

[0125] As shown in Table 5, the ethylene adsorption rate of the CuBaTi MOFs of the present invention used to prepare plastic films is much higher than that of ordinary plastic films on the market, indicating that the plastic films of the present invention have better preservation capabilities.

[0126] Case 6

[0127] The specific method for determining the freshness-locking performance of perfume lemons is as follows:

[0128] (1) Prepare a 30×45cm packaging bag by using the plastic film (MOF film) prepared by CuBaTi MOFs in Application Example 1 and the commercially available ordinary PE plastic film (ordinary PE);

[0129] (2) Select fragrant lemons with consistent maturity, no mechanical damage, no rot, and similar size, and package them using MOFs film and ordinary PE respectively. Set up 5 parallel groups for MOFs film and ordinary PE, with 5 catties of fragrant lemons in each group, and ensure that each group of fruit has the same air volume after packaging.

[0130] (3) The above-mentioned fragrant lemons were stored at room temperature (25℃) away from light. Every 3 days, their appearance was photographed and their weight loss rate, yellowing rate, vitamin C content, soluble solids content, O2 / CO2 volume fraction in the bag, peroxidase (POD) content, and polyphenol oxidase (PPO) content were measured. The results are shown in Table 6. Figures 6-7 As shown.

[0131] Among them, the weight loss rate was determined by using a balance to measure the weight of the perfume lemon and calculating the weight loss rate by the difference between the initial weight and the measured weight. The weight loss rate is calculated as follows: weight loss rate = (initial weight - measured weight) / initial weight × 100%.

[0132] Yellowing rate determination: Yellowing rate = Number of yellowed fruits / Total number of fruits in the group × 100%;

[0133] Vitamin C content determination: The vitamin C content was determined by the third method, 2,6-dichlorophenolindophenol titration, according to GB 5009.86-2016 "National Food Safety Standard - Determination of Ascorbic Acid in Food". The test was repeated 3 times.

[0134] Soluble solids content determination: determined using a portable digital refractometer.

[0135] O2 / CO2 volume fraction determination: The volume fraction of gas inside the packaging was determined using a portable O2 / CO2 analyzer;

[0136] Peroxidase (POD) content determination: The peroxidase content was determined using spectrophotometry.

[0137] Polyphenol oxidase (PPO) content determination: The polyphenol oxidase content was determined using spectrophotometry.

[0138] Table 6

[0139]

[0140]

[0141] From the data in Table 6 and Figures 6-7 As can be seen from the content, the various indicators obtained by using the MOFs film of the present invention to preserve perfume lemons are superior to those of ordinary PE films on the market, indicating that the MOFs film of the present invention can better retain the moisture and nutrients of perfume lemons and delay the ripening of perfume lemons.

[0142] Case 7

[0143] The specific method for determining the freshness retention performance of broccoli is as follows:

[0144] (1) Prepare a 25×30cm packaging bag by using CuBaTi-MOFs fresh food dormancy-locking film (MOFs film) and ordinary blank PE film (ordinary PE);

[0145] Select broccoli that are of uniform maturity, free from mechanical damage and rot, and of similar size. Pack them with MOFs film and ordinary PE respectively. Set up 10 parallel groups for MOFs film and ordinary PE, with 10 broccoli in each group, and ensure that each group of broccoli has the same air volume after packaging.

[0146] (3) Broccoli was sealed and stored in a cold storage at a temperature of 0–5℃ and a relative humidity of 90%–95%. Every 3 days, its appearance was photographed and recorded to determine the weight loss rate, yellowing rate, vitamin C content, soluble solids content, chlorophyll content, O2 / CO2 volume fraction in the bag, peroxidase (POD) content, and polyphenol oxidase (PPO) content. The results are shown in Table 7. Figures 8-9 As shown.

[0147] Among them, the weight loss rate was determined by using a balance to measure the weight of the broccoli and calculating the weight loss rate by the difference between the initial and measured weights. The weight loss rate is calculated as follows: weight loss rate = (initial weight - measured weight) / initial weight × 100%.

[0148] Yellowing rate determination: Yellowing rate = Number of yellowed cells / Total number of cells in the group × 100%;

[0149] Vitamin C content determination: The vitamin C content was determined by the third method, 2,6-dichlorophenolindophenol titration, according to GB 5009.86-2016 "National Food Safety Standard - Determination of Ascorbic Acid in Food". The test was repeated 3 times.

[0150] Soluble solids content determination: determined using a portable digital refractometer;

[0151] Chlorophyll content determination: The chlorophyll content was determined using a portable chlorophyll meter;

[0152] O2 / CO2 volume fraction determination: The volume fraction of gas inside the packaging was determined using a portable O2 / CO2 analyzer;

[0153] Peroxidase (POD) content determination: The peroxidase content was determined using spectrophotometry.

[0154] Polyphenol oxidase (PPO) content determination: The polyphenol oxidase content was determined using spectrophotometry.

[0155] Table 7

[0156]

[0157]

[0158] From the data in Table 7 and Figures 8-9 As can be seen from the content, the various indicators obtained by using the MOFs film of the present invention to preserve broccoli are superior to those of ordinary PE film on the market, indicating that the MOFs film of the present invention can better retain the moisture and nutrients of broccoli and delay its spoilage.

[0159] In summary, the metal-organic framework CuBaTiMOFs of this invention, when applied to the preparation of plastic films, can effectively inhibit bacteria and adsorb ethylene. The antibacterial films can not only preserve and inhibit the growth of fruits and vegetables, delaying their ripening and spoilage, but also possess good mechanical properties. Furthermore, the preparation method of this metal-organic framework is simple, convenient, low-cost, and environmentally friendly, and has broad application prospects.

[0160] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0161] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0162] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A metal-organic framework, characterized in that, The metal-organic framework is CuBaTi MOFs; wherein... The metal-organic framework has a layered structure and a porous structure, and the metal-organic framework is a copper-barium-titanium three-dimensional framework. The CuBaTi MOFs were modified with hexadecyltrimethylammonium bromide, wherein the concentration of hexadecyltrimethylammonium bromide was 0.01-0.05 mol / L; The CuBaTi MOFs are composited with mineral components, the mineral components being carboxylated nano-mica and / or diatomaceous earth, and the mass ratio of the copper-barium-titanium three-dimensional framework to the mineral components is 1:1-5. The ligand of the CuBaTi MOFs is pyromellitic acid; The metal-organic framework is prepared by the following method, including: 1) Dissolve copper and barium sources in solvent for the first mixing, add titanium source for the second mixing, add ligand for the third mixing, and carry out microwave solvothermal reaction to obtain a copper-barium-titanium three-dimensional framework. 2) The copper-barium-titanium three-dimensional framework is modified with a surfactant and then mineral components are added for ultrasonic composite.

2. A method for preparing a metal-organic framework as described in claim 1, characterized in that, The preparation method includes: 1) Dissolve copper and barium sources in solvent for the first mixing, add titanium source for the second mixing, add ligand for the third mixing, and carry out microwave solvothermal reaction to obtain a copper-barium-titanium three-dimensional framework. 2) The copper-barium-titanium three-dimensional framework is modified with a surfactant and then mineral components are added for ultrasonic composite.

3. The preparation method according to claim 2, characterized in that, In step 1), the copper source is selected from one or more of copper sulfate, copper nitrate, copper chloride, and copper acetate; The barium source is selected from barium chloride and / or barium nitrate; The titanium source is selected from one or more of tetrabutyl titanate, titanium tetrachloride and isopropyl titanate. The solvent is an aqueous solution of N,N-dimethylformamide.

4. The preparation method according to claim 3, characterized in that, In step 1), the molar ratio of the copper source, barium source, titanium source and ligand is 1:0.5-2:0.5-2:1-3, wherein the copper source is calculated as copper ions, the barium source as barium ions, and the titanium source as titanium ions.

5. The preparation method according to any one of claims 2-4, characterized in that, In step 1), the conditions for the first mixing include: a temperature of 15-30°C, an ultrasonic power of 200-400W, and a time of 10-30 minutes; The conditions for the second mixing include: a temperature of 15-30℃, an ultrasonic power of 200-400W, and a time of 10-30 minutes; The conditions for the third mixing include: a temperature of 15-30℃, a stirring rate of 300-600 rpm, and a time of 10-30 min; The conditions for the microwave solvothermal reaction include: microwave power of 200-500w, temperature of 110-150℃, and time of 20-60min.

6. The preparation method according to claim 5, characterized in that, In step 2), the mineral components are carboxylated nano-mica and / or diatomaceous earth.

7. The preparation method according to claim 6, characterized in that, In step 2), the modification conditions include: temperature of 40-80℃, ultrasonic power of 200-400W, and time of 10-30min; The conditions for the composite process include: a temperature of 15-30℃, an ultrasonic power of 200-400W, and a time of 10-30min.

8. An antibacterial film, characterized in that, The antibacterial film comprises the metal-organic framework and PE resin as described in claim 1.

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