Subject-object interface assembled double-ligand MOF (at) PVA mixed matrix composite membrane and application thereof

Abstract

The invention provides a subject-object interface assembled double-ligand MOF and PVA mixed matrix membrane, which is prepared by the following steps: jointly dissolving metal salt and amino acid in deionized water, carrying out ultrasonic treatment, adding a solubilizer, carrying out ultrasonic treatment, adding an active substance, carrying out ultrasonic treatment, carrying out hydrothermal reaction on the obtained mixture at 60-100 DEG C for 1-3 hours, centrifuging to take a solid, and drying to obtain the subject-object interface assembled double-ligand MOF and PVA mixed matrix membrane. Washing with ethanol, and drying to obtain a subject-object interface assembled double-ligand MOF (Metal Organic Framework); dispersing the film-forming matrix in deionized water, and performing water bath at 60-100 DEG C for 1-3 hours to obtain a film-forming matrix solution; adding the host-guest interface assembled double-ligand MOF into the film-forming matrix solution, uniformly stirring to obtain a film-forming solution, carrying out tape casting on the film-forming solution, and drying to obtain a host-guest interface assembled double-ligand MOF (at) PVA mixed matrix film; the preservative is safe and non-toxic, has good hydrophobic property, barrier property and remarkable antibacterial property, and lays a solid and reliable foundation for deep research in the field of preservation.

Description

Technical Field

[0001] This invention belongs to the field of food preservation technology and relates to a host-guest interface assembled dual-ligand MOF@PVA mixed matrix composite film and its application. Specifically, it is a MOF-based food preservation film with curcumin as a natural ligand and its preparation method. Background Technology

[0002] Fish, as one of the world's most consumed sources of high-quality protein and unsaturated fatty acids, is widely used in raw, cooked, and processed foods and is highly favored by consumers. However, due to its high water content, soft texture, and abundance of non-enzymatic active substances, fish becomes a perishable food after being caught. Because fish has an extremely short shelf life, fluctuations in environmental temperature and humidity accelerate its spoilage process, leading to a rapid decline in sensory quality and nutritional bioactive components. Therefore, post-harvest storage and transportation of fish face severe challenges.

[0003] Currently used fish preservation technologies include ice-temperature storage, freezing, modified atmosphere packaging, edible coatings, and active packaging. Active packaging regulates the gaseous environment inside the packaging (such as CO2). / Balanced or slow-release antibacterial / antioxidant active substances (such as MOF-loaded natural extracts) effectively inhibit bacterial growth and delay lipid oxidation. Compared to simple low-temperature storage, it not only maintains the color and texture of fish, but also reduces TVB-N value and extends shelf life by 30%-50%. Plastic wrap is a commonly used method in active packaging. Commonly used plastic wrap materials include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and composite films. Polyethylene film has poor barrier properties and is easily permeable to air and moisture; polypropylene film has poor oil resistance; PVC film is prone to embrittlement at low temperatures, while composite films provide better protection, but are more expensive and less prone to degradation. Furthermore, many plastic wrap materials struggle to maintain film performance while also being environmentally friendly.

[0004] Metal-organic frameworks (MOFs), as novel functional materials, have become a research hotspot in recent years due to their high porosity, tunable structure, and good adsorption properties. MOF materials can provide oxygen adsorption, moisture regulation, and antibacterial functions in packaging films, and are therefore widely used in food preservation. However, traditional MOFs (such as ZIF-8 and MIL-53) have limitations in their safety in food contact materials due to the potential risk of metal ion leaching and insufficient biocompatibility of organic ligands. Commonly used film-forming matrices include polyvinyl alcohol (PVA), gelatin, chitosan, and polylactic acid (PLA). These materials have good film-forming properties, biodegradability, and low toxicity, making them suitable for food contact materials. However, these methods either have high requirements for the production environment and equipment, or are very costly to prepare, and the preservation effect of the resulting materials is not ideal. SUMMARY

[0005] The application provides a host-guest interface assembled double-ligand MOF@PVA mixed matrix composite membrane and an application.

[0006] The technical scheme of the application is as follows: The application provides a host-guest interface assembled double-ligand MOF@PVA mixed matrix membrane, which is prepared by the following method: (1) dissolve the metal salt and amino acid in deionized water A together, ultrasonic treatment, add a solubilizing agent, ultrasonic treatment (20 min), add an active substance, ultrasonic treatment (20 min), and obtain a mixture, which is hydrothermally reacted at 60-100℃ (preferably 80℃) for 1-3h (preferably 2h), centrifuged (8000rpm for 6min), and then washed with ethanol (60℃) and dried to obtain a host-guest interface assembled double-ligand MOF; the mass ratio of the amino acid, the metal salt, the solubilizing agent and the active substance is 1:1-3:0.1-0.3:0.1-0.3 (preferably 1:2:0.25:0.25); the metal salt is a zinc salt, a zirconium salt, an iron salt or a cobalt salt; the amino acid is lysine, glutamic acid or serine; and the active substance is curcumin, gingerol or berberine.

[0007] (2) disperse the film-forming matrix in deionized water B, and obtain a film-forming matrix solution by water bath at 60-100℃ (preferably 80℃) for 1-3h (preferably 2h); add the host-guest interface assembled double-ligand MOF in step (1) to the film-forming matrix solution, stir uniformly to obtain a film-forming solution, and then flow casting and drying to obtain the host-guest interface assembled double-ligand MOF@PVA mixed matrix membrane; the film-forming matrix is one or more of polyvinyl alcohol, chitosan and sodium alginate; the total mass of the film-forming matrix is 0.02-0.05g / ml (preferably 0.04g / ml) based on the volume of the deionized water B; and the mass ratio of the film-forming matrix to the host-guest interface assembled double-ligand MOF is 1:0.05-0.2 (preferably 1:0.1).

[0008] Further, the metal salt is a zirconium salt (the zirconium salt is selected from one of zirconium sulfate, zirconium chloride or zirconium nitrate, preferably zirconium sulfate).

[0009] Further, the amino acid is lysine.

[0010] Further, the solubilizing agent is one or more of Tween-20, sucrose fatty acid ester or polyvinylpyrrolidone (preferably Tween-20)

[0011] Further, the active substance is curcumin.

[0012] Further, the mass of the active substance in step (1) is 0.02-0.04 g / ml (preferably 0.029 g / ml) based on the volume of the deionized water A.

[0013] Further, the film-forming base in step (2) is polyvinyl alcohol

[0014] The application also provides a use of a host-guest interface assembled dual-ligand MOF@PVA hybrid matrix film in fish preservation.

[0015] Further, the use is as follows: the host-guest interface assembled dual-ligand MOF@PVA hybrid matrix film is used to coat fish fillets for preservation at ≤4℃.

[0016] Compared with the prior art, the application has the following advantages: (1) The specific designed functional groups (such as -N ) in the dual-ligand MOF form strong interactions (such as hydrogen bonds) with the hydroxyl groups (-OH) in the PVA matrix, realizing the "molecular level" anchoring of the MOF filler and the polymer matrix. This interface interaction plays the role of a "molecular dispersant", effectively preventing the agglomeration tendency of the nanoscale MOF particles.

[0017] (2) The ligand is safe and non-toxic, and the use of active substances such as curcumin as natural ligands not only has stability but also can exert its antioxidant and antibacterial effects; the reaction system is aqueous, which has high biocompatibility and is green and environmentally friendly; (3) The use of amino acid MOF to embed active substances improves the stability of the active substances, and the MOF-embedded curcumin cooperates with curcumin as a natural ligand to inhibit bacteria; (4) The addition of MOF improves the mechanical properties, hydrophobic properties, barrier properties and antibacterial properties of the film, laying a good foundation for preservation research. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 In the figure, (a, c) are the MOF prepared in step 2 of Comparative Example 2, (b, d) are Cur@MOF prepared in step 4 of Example 1, (e) is the PVA film prepared in Comparative Example 1, and (f) is the SEM electron microscope photograph of PVA / Cur@MOF-10 prepared in Example 1.

[0019] Figure 2Figure 1. (a) FT-IR spectra of MOF, Curcumin and Cur@MOF; (b) FT-IR spectra of PVA film, PVA / MOF-10 (comparative example 2), PVA / Cur@MOF-2.5, PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5.

[0020] Figure 3 Figure 2. (a) XRD patterns of MOF, Curcumin, Cur@MOF; (b) XRD patterns of PVA film, PVA / MOF-10 (comparative example 2), PVA / Cur@MOF-10.

[0021] Figure 4 Figure 3. TGA curves of PVA / MOF-10, PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5 composite films.

[0022] Figure 5 Figure 4. Mechanical properties of PVA, PVA / MOF-10 and PVA film composite films doped with different proportions of Cur@MOF, including elongation at break (EB, %; a) and tensile strength (TS, MPa; b).

[0023] Figure 6 Figure 5. Water vapor transmission rate (WVTR) curves of PVA and composite films, including PVA / MOF-10, PVA / Cur@MOF-2.5, PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5.

[0024] Figure 7 Figure 6. Antibacterial rate curves of PVA and composite films.

[0025] Figure 8 Figure 7. Digital photos of fish fillets treated with different films, including PE (commercial preservative film), PVA, PVA / MOF-10, PVA / Cur@MOF-2.5, PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5, during refrigeration.

[0026] Figure 9 Figure 8. TBARS curves of fish fillets treated with different films during refrigeration.

[0027] Figure 10 Figure 9. Weight loss rates of fish fillets treated with different films during refrigeration. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0029] Embodiment 1 (best embodiment): The present embodiment provides a preparation method of an interface combined PVA functional composite film of an amino acid-curcumin dual-ligand MOF, and the preparation method comprises the following steps: (I) Preparation of MOF particles (host-guest interface assembled dual-ligand MOF): (1) 2.33 g of zirconium sulfate and 1.165 g of lysine were dissolved in 10 ml of water, and ultrasonic treatment was performed, to obtain product A, (2) 0.29 g of Tween-20 was added to product A, and ultrasonic treatment was performed for 20 min, to obtain product B, (3) 0.29 g of curcumin was added to product B, and ultrasonic treatment was performed for 20 min, to obtain product C, (4) Product C was moved into a reaction kettle and placed in an 80℃ oven for hydrothermal reaction for 2 h, and the solid was obtained by centrifugation at a speed of 8000 rpm for 6 min, and then washed with ethanol for three times to obtain product D, and product E was obtained after drying at 60℃, that is, the host-guest interface assembled dual-ligand MOF, that is, Cur@MOF.

[0030] (II) Preparation of host-guest interface assembled dual-ligand MOF@PVA mixed matrix film: (1) 4 g of polyvinyl alcohol was dispersed in 100 ml of deionized water, and a film-forming matrix solution was obtained by water bath at 80℃ for 2 h, (2) 10 wt% (based on the mass of polyvinyl alcohol) of MOF particles (product E) was added to the film-forming matrix solution, and stirring was performed until a uniform solution was formed, and then the solution was poured into a 9 cm round culture dish, and after drying at an oven temperature of 60℃ for 1 day, the host-guest interface assembled dual-ligand MOF@PVA mixed matrix film was peeled off.

[0031] In the present embodiment, the obtained host-guest interface assembled dual-ligand MOF@PVA mixed matrix film is named as “PVA / Cur@MOF-10”, wherein “10” represents that the addition amount of MOF in step (II)-(2) is 10 wt% (based on the mass of PVA), and the naming rule is also applicable hereinafter.

[0032] Embodiment 2: The embodiment provides a preparation method of a host-guest interface assembled double-ligand MOF@PVA hybrid matrix film, which is different from that of the embodiment 1 in that 2.5 wt% (based on the mass of polyvinyl alcohol) of MOF particles are added into 100 ml of a film-forming solution in step (II)-(2).

[0033] The remaining operations are the same as those in the embodiment 1, and finally obtained host-guest interface assembled double-ligand MOF@PVA hybrid matrix film is named as “PVA / Cur@MOF-2.5”.

[0034] Embodiment 3: The embodiment provides a preparation method of a host-guest interface assembled double-ligand MOF@PVA hybrid matrix film, which is different from that of the embodiment 1 in that 12.5 wt% (based on the mass of PVA) of MOF particles are added into 100 ml of a film-forming solution in step (II)-(2).

[0035] The remaining operations are the same as those in the embodiment 1, and finally obtained host-guest interface assembled double-ligand MOF@PVA hybrid matrix film is named as “PVA / Cur@MOF-12.5”.

[0036] Embodiment 4: The embodiment is an application of the host-guest interface assembled double-ligand MOF@PVA hybrid matrix film in grass carp preservation. The grass carp back muscles are cut into pieces of equal size (all the cutting boards and containers are sterilized in advance with 75% ethanol and ultraviolet rays to minimize microbial contamination), and the pieces are respectively fully wrapped with PE film, PVA film (i.e. the PVA film prepared in the comparative example 1), PVA / MOF-10 film (prepared in the comparative example 2) and PVA / Cur@MOF-10 film (prepared in the embodiment 1), and then placed in a glass dish, and the control group is not wrapped with a film, and then moved to a 4°C refrigerator for cold storage for 9 days, and digital photos of the samples in each group are taken by a mobile phone at 0th day, 2nd day, 5th day, 7th day and 9th day; in addition, the following multiple freshness indicators are measured to evaluate the quality and safety of the fish pieces: first, the weight loss rate of the fish pieces is obtained by calculating the ratio of the weight difference of the fish pieces after storage for a period of time to the initial weight; second, according to GB / 5009.181-2016 “Determination of Malondialdehyde in Food”, the sample is tested for malondialdehyde by a spectrophotometric method, and a data graph is drawn, and the results are shown in Figure 9 .

[0037] Comparative Example 1:

[0038] The embodiment provides a preparation method of a PVA film, and the preparation method comprises the following steps: (1) 4 g of polyvinyl alcohol is dispersed in 100 ml of deionized water, and the mixture is subjected to water bath at 80°C for 2 h to obtain a film-forming matrix solution, (2) Pour the film-forming base solution into a 9 cm round culture dish, and after drying in an oven at 60℃ for 1 day, the polyvinyl alcohol film can be peeled off.

[0039] In this comparative example, the difference from Example 1 is that MOF is not added, and the obtained polyvinyl alcohol film is named "PVA".

[0040] Comparative Example 2:

[0041] This example provides a preparation method of an amino acid MOF / PVA composite film, and the preparation method comprises the following steps:

[0042] (I) Preparation of MOF particles: (1) Dissolve 2.33 g of zirconium sulfate and 1.165 g of lysine in 10 ml of water, and ultrasonically treat to obtain product A, (2) Move product A into a reaction kettle and place it in an 80℃ oven for hydrothermal reaction for 2 h, centrifuge at 8000 rpm for 6 min to take the solid and wash it with ethanol three times to obtain product B, and after drying at 60℃, obtain product C, which is MOF.

[0043] (II) Preparation of polyvinyl alcohol-MOF composite film: (1) Disperse 4 g of polyvinyl alcohol in 100 mL of deionized water, and heat in a water bath at 80℃ for 2 h to obtain a film-forming base solution, (2) Add 10 wt% (based on the mass of polyvinyl alcohol) of MOF particles to the film-forming base solution, stir to form a uniform solution, and then pour it into a 9 cm round culture dish, and after drying in an oven at 60℃ for 1 day, a 10 wt% polyvinyl alcohol-MOF can be peeled off.

[0044] In this comparative example, the difference from Example 1 is that curcumin is not added, and the obtained polyvinyl alcohol-MOF composite film is named "PVA / MOF-10".

[0045] Test Example: Structural characterization and performance analysis of polyvinyl alcohol-MOF composite film

[0046] (I) Scanning electron microscopy (SEM)

[0047] The apparent morphology and fracture cross-section of the PVA / MOF-10 composite film were observed using a scanning electron microscope at an acceleration voltage of 10 kV.

[0048] (II) Fourier transform infrared spectroscopy (FTIR)

[0049] The infrared spectrometer was used to test in the wavelength range of 4000 cm -1 to 400 cm -1 .

[0050] (III) X-ray diffraction (XRD)

[0051] XRD spectra of the composite films and MOFs were obtained by X-ray diffractometer, the scanning range was 2θ = 5-80°, and the scanning rate was 1° / min.

[0052] (iv) Thermogravimetric analysis

[0053] The thermal stability of the composite film was tested by a thermogravimetric analyzer in the temperature range of 30-600℃, under nitrogen protection, and the heating rate was 10℃ / min.

[0054] (v) Mechanical properties

[0055] The film strip was fixed on the tensile testing machine, and the initial length L0 (m) of the composite film was recorded. The difference ΔL (m) between the maximum length at the time of film rupture and the initial length, and the maximum tensile force F (N) at the time of film rupture were measured. Three parallel samples were prepared for each sample.

[0056] The tensile strength was calculated according to the following formula:

[0057] In the formula, TS is the tensile strength of the film, MPa; F is the maximum tensile force at the time of film rupture, N; D is the film thickness, mm; and B is the film width, mm.

[0058] The elongation at break was calculated according to the following formula:

[0059] In the formula, EAB is the elongation at break, %; ΔL is the difference between the length at the time of film rupture and the initial length, mm; and L0 is the initial length of the film, mm.

[0060] (vi) Hydrophobic properties

[0061] First, pour about 2 / 3 of the volume of water into the moisture permeable cup, cut the sample to completely cover the cup opening, and tighten the seal with a sealing ring and nut; then place the moisture permeable cup in the tray according to the number, close the test chamber and start the instrument; then connect the gas cylinder (or air compressor) to the chamber to introduce 0.4 MPa compressed air; finally, run the test software to start automatic detection, and replace the gas cylinder every 3.5 hours during the process, without manual intervention. This method drives water vapor penetration by constant pressure airflow, combined with real-time monitoring by sensors, to achieve efficient and accurate WVTR determination.

[0062] (vii) Antibacterial properties

[0063] Gram-negative bacteria Escherichia coli was selected as the test strain, and the concentration of the bacterial suspension was adjusted to 10 6After 24 h, the PVA / Cur@MOF-12.5, PVA / Cur@MOF-10, PVA / Cur@MOF-2.5, PVA / MOF-10 and PVA / MOF-10 were mixed with the bacteria, respectively. After vortex mixing, the mixture was incubated at 37 °C for 2 h in the dark. After incubation, 10 3 Gradient dilution was performed, and 100 μL of the diluted solution was spread on nutrient agar plates, which were incubated at 37 °C for 24 h for colony counting.

[0064] Results and Discussion

[0065] (1) SEM results

[0066] This group of scanning electron microscope (SEM) images shows the morphology of MOF materials, drug-loaded MOF (Cur@MOF) and their morphology in PVA composite films, which helps to understand the structure and composite effect of the materials. Figures (a) and (c) are the morphology of MOF without drug loading. MOF is regular spherical, and the surface layer structure is clear, showing good crystal morphology and certain porosity. In figure (c), a hollow core-shell structure can be seen, which is beneficial for drug loading and release. Figures (b) and (d) are Cur@MOF particles after Curcumin (Curcumin) loading. The morphology is still spherical, but the surface is more dense and rough, and the layer structure becomes blurred, indicating that the drug has successfully entered the MOF channel or adsorbed on the surface, changing the microscopic morphology. Figure (e) is a pure PVA film, which is smooth and dense on the surface, showing good film-forming property. Figure (f) is a PVA / Cur@MOF composite film, which is overall flat, but small particles can be seen protruding, which is speculated to be Cur@MOF particles uniformly dispersed in the PVA matrix without obvious agglomeration. In summary, the SEM images verify that Cur is successfully loaded into MOF, and Cur@MOF can be well dispersed in PVA film, providing a structural basis for subsequent performance research.

[0067] (2) FTIR results

[0068] Figure 2 The FTIR spectra of MOF, Curcumin, Cur@MOF and their PVA composite under different doping ratios are shown, which are used to analyze the interaction between components and structural changes. In the left figure, Curcumin shows multiple characteristic absorption peaks, such as the aromatic ring C=C stretching vibration near 1600 c ¹ and the O-H stretching vibration peak between 3500-3200 c ¹. MOF shows a strong absorption peak at 1700-1400 c ¹showed the typical C=0 and C-O vibration absorption peaks of carboxylic acid ligand. The spectra of Cur@MOF retained some characteristic peaks of both MOF and Cur, but the absorption peaks in O-H and C=0 region were obviously weakened and slightly shifted compared to MOF, indicating that Cur was successfully loaded into the MOF structure and some degree of hydrogen bonding or coordination occurred. The right panel showed the FTIR spectra of PVA / Cur@MOF composite films with different ratios, and all samples showed a broad and strong O-H stretching vibration peak at 3300 cm ¹nearby, representing the alcohol hydroxyl group of PVA. As the Cur@MOF doping amount increased from 2.5 to 12.5, its O-H peak gradually broadened and slightly shifted, indicating that there was hydrogen bonding between Cur@MOF and PVA, which enhanced the interaction force. At the same time, the characteristic peaks of MOF were also observed in the 1700-1400 cm ¹region, indicating that Cur@MOF was well embedded in the PVA matrix without structural damage. In summary, the FTIR results confirmed that Cur was successfully loaded into MOF, and there was obvious physical and chemical interaction between Cur@MOF and PVA, which helped to improve the interface compatibility and structural stability of the composite material.

[0069] (ii) XRD results

[0070] Figure 3X-ray diffraction (XRD) patterns of MOF, Cur@MOF and their composite films with PVA were shown to analyze the changes of crystal structure. In the left figure, MOF sample showed clear diffraction peaks, indicating that it had good crystallinity. After loading curcumin (Curcumin), the diffraction peaks of Cur@MOF were significantly weakened, indicating that the crystallinity decreased, but the basic framework structure of MOF was still retained, indicating that curcumin may have been effectively loaded into the channel of MOF or adsorbed on its surface, causing the ordered structure of MOF to be disturbed to a certain extent. At the same time, the spectrum of pure Curcumin showed multiple sharp diffraction peaks, representing its highly crystalline properties, and no obvious Cur characteristic peaks were observed in Cur@MOF, indicating that Cur existed in MOF in an amorphous or highly dispersed state. The right figure shows the XRD spectra of PVA, PVA / MOF-10 and PVA / Cur@MOF three kinds of film materials. Pure PVA appeared a relatively wide diffraction peak at 2θ ≈ 19.5°, representing its typical semi-crystalline structure. After compounding, PVA / MOF-10 and PVA / Cur@MOF-10 still retained this diffraction peak, but the peak shape was wider and the intensity was lower, indicating that the introduction of MOF interfered with the crystallinity of PVA, and the influence of Cur@MOF was particularly significant, showing that its doping effect was stronger. In summary, the XRD results showed that Cur was successfully loaded into MOF, and Cur@MOF could be stably embedded in the PVA matrix and change its crystalline structure. The characteristic peaks of curcumin and MOF in the composite Cur@MOF were significantly changed or even disappeared, which ruled out the possibility of physical adsorption and proved the occurrence of chemical coordination between curcumin and metal. It was conducive to enhancing the flexibility and mechanical adaptability of the composite film, which was consistent with the SEM results.

[0071] (iv) Thermogravimetric analysis

[0072] Figure 4The thermal gravimetric analysis (TGA) curves of PVA / MOF-10 composite films at different ratios were used to evaluate their thermal stability. The mass loss of PVA / MOF-10, PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5 samples in the range of 30-600°C is shown in the figure. The initial mass loss of the three samples occurs at around 100°C, mainly due to the evaporation of moisture or volatile components. The second stage is between 270-380°C, and a significant mass loss occurs, which is the main stage of PVA backbone pyrolysis. It can be observed that the pyrolysis onset temperature of the Cur@MOF doped samples (red and blue) is slightly higher than that of the pure PVA / MOF-10 sample, indicating that the introduction of Cur enhances the thermal stability of the composite film to a certain extent. In addition, the residual mass of PVA / Cur@MOF-12.5 sample is slightly higher, indicating that higher Cur@MOF content gives the material stronger pyrolysis resistance. This shows that the synergistic effect of Cur and MOF helps to improve the thermal stability of the composite film, further confirming its application potential in high temperature environment.

[0073] (V) Mechanical property analysis

[0074] Figure 5 The mechanical properties of PVA and its different MOF / Cur@MOF composite films were demonstrated, including elongation at break (EB, %) and tensile strength (TS, MPa). From the EB column chart, the elongation at break of pure PVA film is the lowest, only about 120%, while with the increase of Cur@MOF doping ratio, EB increases significantly, especially for PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5, EB value increases to about 300%, indicating that Cur@MOF enhances the flexibility of the material. This may be due to the formation of reinforcing phase by Cur@MOF particles in the PVA matrix, and the promotion of chain segment slip by hydrogen bonding and other actions. The TS results show that the tensile strength also increases with the increase of Cur@MOF content, and the TS of PVA / Cur@MOF-12.5 is the highest, reaching about 33 MPa, indicating that the addition of Cur@MOF not only improves the toughness, but also enhances the mechanical strength of the film material, showing excellent toughening and strengthening effect.

[0075] (VI) Water resistance performance analysis

[0076] Figure 6This section presents water vapor transmission rate (WVTR) data for PVA and composite membranes. The results show that pure PVA membrane exhibits the highest WVTR, exceeding 400 g / m²·24h, indicating poor water vapor barrier performance. With the introduction of MOF and Cur@MOF, the WVTR gradually decreases, especially in the PVA / Cur@MOF-10 sample, where the WVTR drops to the lowest level of approximately 90 g / m²·24h, demonstrating its excellent barrier properties. Doping with MOF materials can significantly suppress water vapor diffusion by increasing transport paths and filling microscopic voids. Cur@MOF, with its better dispersibility and denser interfacial bonding, further enhances water barrier performance. The WVTR of the PVA / Cur@MOF-12.5 sample shows a slight increase, possibly related to localized agglomeration or microstructural damage caused by excessive MOF loading. In summary, the introduction of an appropriate amount of Cur@MOF significantly improves the mechanical strength and water barrier performance of PVA membranes, giving them broader application prospects in packaging and functional membranes.

[0077] (VII) Antibacterial Performance Analysis

[0078] Figure 7 The study showcased different antibacterial rates of various films, revealing a significant gradient in the antibacterial rates of different PVA-based composites: pure PVA film exhibited the lowest antibacterial rate, indicating limited antibacterial ability of the unmodified material; after adding 10% MOF (PVA / MOF-10), the antibacterial rate slightly increased to around 35%, indicating that MOF possesses certain antibacterial activity. The antibacterial rate gradually increased upon adding Cur@MOF to the matrix, with the optimal antibacterial effect observed in PVA / Cur@MOF-10, where the antibacterial rate approached 100%, highlighting the synergistic effect of the MOF carrier on Cur—the carrier enhances the dispersibility and contact efficiency of the active ingredient. Notably, when the loading increased to 12.5% ​​(PVA / Cur@MOF-12.5), the antibacterial rate actually decreased, suggesting that excessive loading may induce nanoparticle aggregation, hindering the exposure of active sites.

[0079] (VIII) Analysis of Preservation Results

[0080] Depend on Figure 8 It is evident that, compared to the control group which was severely spoiled on day 9, the fish fillets in the PVA / Cur@MOF-10 and PVA / Cur@MOF-12.5 groups had the color closest to their initial state, indicating the best preservation effect. Figure 9 The changes in TBARS values ​​indicate that the two groups of samples had the lowest values ​​at the end of storage, significantly lower than the control group, effectively inhibiting lipid oxidation. Figure 3The weight loss rate data further confirmed that the weight loss rate of the PVA / Cur@MOF treatment group was significantly lower than that of the control group, which indicated that it could effectively reduce juice loss and maintain product water retention. In summary, the application significantly prolongs the preservation period of fish fillets by the synergistic effect of bacteriostasis, oxidation resistance and water retention, especially with a 10% Cur@MOF addition amount.

[0081] (Nine) Conclusion

[0082] The application prepared PVA / MOF-10 composite films with different MOF addition amounts, and the microstructure and macroscopic properties were studied in detail.

[0083] (1) The morphology, crystal structure and thermal stability of the PVA / Cur@MOF composite film were characterized and analyzed. From the SEM image, it was observed that the pure PVA film surface was smooth and dense, and after adding Cur@MOF, uniform distribution of small particle protrusions appeared on the film surface, and no obvious agglomeration was observed, indicating that Cur@MOF was successfully combined and uniformly dispersed in the PVA matrix; through FTIR and XRD characterization, it was found that there was hydrogen bond interaction between Cur@MOF and PVA, the O-H stretching vibration peak was broadened and shifted, and the MOF characteristic peak of Cur@MOF was retained in the composite film but the intensity was weakened, indicating that curcumin and MOF metal nodes were coordinated, successfully loaded in the MOF structure, and existed in a highly dispersed state; through thermal gravimetric analysis, it was known that the main pyrolysis stage of PVA composite film occurred at 270-380°C, and after adding Cur@MOF, the pyrolysis onset temperature increased and the residual mass increased, indicating that the introduction of Cur@MOF enhanced the thermal stability of the composite film.

[0084] (2) Further observe the macroscopic properties of the composite film, by analyzing the mechanical properties, water resistance, antibacterial properties and biological safety of the composite film, it was found that when the Cur@MOF addition amount was 10-12.5%, the tensile strength and elongation at break of the composite film reached the optimal value, which increased to about 33 MPa and 300%, respectively; the water vapor permeability was significantly reduced to 90 g / m²·24h, and the water resistance was the best; the antibacterial performance test showed that the inhibition rate of PVA / Cur@MOF-10 to bacteria was close to 100%, showing excellent antibacterial effect.

[0085] (3) Comprehensive performance indicators, PVA / Cur@MOF composite film shows excellent comprehensive performance, among which the composite film with 10% Cur@MOF addition amount is optimal in mechanical properties, barrier properties, antibacterial properties and preservation effect, indicating that it has broad application prospects in the field of food active packaging.

[0086] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane, characterized in that, Prepared by the following method: (1) The metal salt and amino acid are dissolved together in deionized water A, ultrasonically treated, a solubilizer is added, ultrasonically treated again, an active substance is added, ultrasonically treated again, and the resulting mixture is hydrothermally reacted at 60-100℃ for 1-3 h. The solid is centrifuged, washed with ethanol, and dried to obtain a host-guest interface assembled dual-ligand MOF. The mass ratio of the amino acid, metal salt, solubilizer and active substance is 1:1-3:0.1-0.3:0.1-0.

3. The metal salt is zinc salt, zirconium salt, iron salt or cobalt salt. The amino acid is lysine, glutamic acid or serine. The active substance is curcumin, gingerol or berberine. (2) The film-forming matrix is ​​dispersed in deionized water B and bathed in a water bath at 60-100℃ for 1-3 hours to obtain a film-forming matrix solution; The host-guest interface assembled dual-ligand MOF described in step (1) is added to the film-forming matrix solution and stirred evenly to obtain a film-forming solution. The film-forming solution is then cast and dried to obtain the host-guest interface assembled dual-ligand MOF@PVA mixed matrix membrane. The film-forming matrix is ​​one or more of polyvinyl alcohol, chitosan, and sodium alginate. The total mass of the film-forming matrix is ​​0.02-0.05 g / ml based on the volume of deionized water B. The mass ratio of the film-forming matrix to the host-guest interface assembled dual-ligand MOF is 1:0.05-0.

2.

2. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The metal salt mentioned is a zirconium salt.

3. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The amino acid in question is lysine.

4. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The solubilizer is one or more of Tween-20, sucrose fatty acid ester, or polyvinylpyrrolidone.

5. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The active substance mentioned is curcumin.

6. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The mass of the active substance mentioned in step (1) is 0.02-0.04 g / ml based on the volume of the deionized water A.

7. The host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1, characterized in that, The film-forming matrix in step (2) is polyvinyl alcohol.

8. The application of the host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane as described in claim 1 in fish preservation.

9. The application as described in claim 8, characterized in that, The application is as follows: fish fillets are coated with a host-guest interface assembled dual-ligand MOF@PVA hybrid matrix membrane and preserved at ≤4℃.

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