CN116622086A - Bimetal organic frame material and preparation method and application thereof - Google Patents

Bimetal organic frame material and preparation method and application thereof Download PDF

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CN116622086A
CN116622086A CN202310690958.7A CN202310690958A CN116622086A CN 116622086 A CN116622086 A CN 116622086A CN 202310690958 A CN202310690958 A CN 202310690958A CN 116622086 A CN116622086 A CN 116622086A
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framework material
water
organic framework
mof
drying
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曹崇江
满威
年琳玉
李儒鸿
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China Pharmaceutical University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G83/00—Macromolecular compounds not provided for in groups C08G2/00 - C08G81/00
    • C08G83/008—Supramolecular polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
    • B65D65/38—Packaging materials of special type or form
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2389/00—Characterised by the use of proteins; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2487/00—Characterised by the use of unspecified macromolecular compounds, obtained otherwise than by polymerisation reactions only involving unsaturated carbon-to-carbon bonds

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  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

The invention discloses a bimetal organic framework material and a preparation method and application thereof, wherein the crystal structure of the framework material is octahedron, the framework material is formed by coordination of organic ligand fumaric acid and metal ion ligands, the metal ion ligands are zirconium ions and copper ions, and the doping amount of the copper ions accounts for 20-40% of the content of the metal ligands by calculation of molar ratio; the bimetallic organic framework material of the invention has the water vapor adsorption rate under various humidity gradients compared with undoped Cu 2+ Is 10-20% higher than that of the traditional Chinese medicine, and has stronger thermal stability and recycling performance, and the material is subjected to four high-temperature activitiesThe cycle of the chemical and the absorption of the water vapor is still kept at 0.27 g.g ‑1 The high-efficiency water absorption efficiency is reduced by only 0.5 percent compared with the first time; the frame material is applied to the preparation of the water-absorbing fresh-keeping packaging film, and can regulate and control the humidity of the fruit and vegetable packaging microenvironment and inhibit the growth of microorganisms, so that the shelf life of the picked fruits and vegetables is prolonged.

Description

Bimetal organic frame material and preparation method and application thereof
Technical Field
The invention relates to an organic frame material, in particular to a bimetal organic frame material, and also relates to a preparation method and application of the frame material.
Background
Fresh fruits and vegetables become indispensable food in daily life because of the fact that the fresh fruits and vegetables are rich in nutrient elements such as vitamins, dietary fibers, minerals and the like. However, after picking, the fruits and vegetables still perform the dynamic physiological process of respiration and transpiration, and a large amount of liquid water is generated, so that the Relative Humidity (RH) of the packaging microenvironment is increased. Plastic films are commonly used in current fruit and vegetable packages, but water vapor condensation is easily caused, and humidity in the package is increased. The micro-environment with high humidity is more easy to breed microorganisms, so that fruit and vegetable spoilage is accelerated, and food waste and economic loss are caused. Aiming at the humidity problem of fruit and vegetable packages, a desiccant is mostly used for adsorbing water vapor in the package microenvironment. The drying agent is a material with high porosity and large aperture, and shows larger water vapor absorption capacity, but the porous material can usually perform adsorption only when the relative humidity is high, namely the humidity is close to saturation, and has poor heat stability, so that the drying agent is a disposable product, is easy to cause resource waste, and increases the fresh-keeping cost of fruits.
Metal-organic frameworks (Metal-organic frameworks, MOFs), also known as porous coordination polymers (Porous coordination polymers, PCPs), are a class of porous crystalline materials with two-dimensional or three-dimensional structures formed by self-assembly of inorganic nodes (Metal ions/clusters) and organic ligands. Compared with other MOFs, the MOF-801 prepared based on the interaction between zirconium clusters and fumaric acid ligand in the framework has the advantages that the-COOH on the surface can be combined with a large amount of water, and the porous structure in the surface is also beneficial to the adsorption of water molecules. However, MOF-801 has insufficient water vapor absorption rate in low humidity microenvironments, limiting its application as a fresh fruit packaging film.
Disclosure of Invention
The invention aims to: the present invention aims to provide a bimetal organic frame material with good water vapor absorption rate in a low humidity microenvironment, a second aim is to provide a manufacturing method of the frame material, and a third aim is to provide the frame material application.
The technical scheme is as follows: the crystal structure of the bimetal organic framework material is octahedron, and is formed by coordination of organic ligand fumaric acid and metal ion ligands, wherein the metal ion ligands are zirconium ions and copper ions; in the metal ion ligand, the addition mole amount of copper ions is 20-40% of the total mole amount of the metal ion ligand according to the mole ratio.
Preferably, in the bimetallic organic framework material, the molar ratio of organic ligand fumaric acid to metal ion ligand is 1:1.
the preparation method of the bimetal organic frame material comprises the following steps:
(1) Dissolving fumaric acid, zirconium oxychloride octahydrate and copper nitrate trihydrate in a formic acid solution of N, N-dimethylformamide, and carrying out ultrasonic dissolution to obtain a mixed solution;
(2) Heating and pressurizing the mixed solution for reaction, and cooling at room temperature after the reaction is completed to obtain a solid material;
(3) And (3) centrifugally washing and vacuum drying the solid material to obtain the bimetal organic framework material.
Preferably, in the step (1), the molar ratio of fumaric acid, zirconium oxychloride octahydrate and copper nitrate trihydrate is 1:0.5 to 1:0.1 to 0.5; in the formic acid solution of N, N-dimethylformamide, the volume ratio of the N, N-dimethylformamide to the formic acid is 15-20: 5 to 7.
Preferably, in the step (2), the reaction temperature is 125-135 ℃ and the reaction time is 6-7 h, and the pressure is-0.1 MPa.
Preferably, in the step (3), the rotation speed of the centrifugation is 9500rpm/min, the centrifugation time is 10min, and the centrifugation temperature is 10-20 ℃; the vacuum drying is carried out at the temperature of 45-60 ℃ for 8-10 h, and the drying pressure is-0.09 to-0.1 MPa.
The application of the bimetal organic frame material in preparing the water-absorbing fresh-keeping packaging film.
Preferably, the water-absorbing fresh-keeping packaging film is obtained by mixing a bimetal organic framework material, a plasticizer, a film forming agent and sodium carboxymethyl cellulose, pouring the mixture into a mould and drying the mixture.
Preferably, the weight ratio of the bimetallic organic framework material to the plasticizer glycerol to the film forming agent gelatin to the sodium carboxymethyl cellulose is 0.1-0.2: 0.5 to 1:2:2.
preferably, the plasticizer is glycerol and the film forming agent is gelatin.
Preferably, the preparation method of the water-absorbing fresh-keeping packaging film specifically comprises the following steps:
(1) Preparing gelatin standing liquid, dissolving a bimetal organic framework material in the gelatin standing liquid, performing ultrasonic treatment to obtain a mixed solution A, dissolving sodium carboxymethylcellulose in water, and performing water bath stirring to obtain a mixed solution B; mixing the mixed solution A and the mixed solution B, adding glycerol, heating and stirring to obtain a film forming solution;
(2) Pouring the film forming liquid into a mold, standing at room temperature, and drying in an oven to obtain the water-absorbing fresh-keeping packaging film.
The principle of the invention: according to the bimetal organic framework material Cu@MOF-801, the water vapor adsorption efficiency in a low-humidity microenvironment is improved by doping transition metal Cu aiming at the organometallic framework material MOF-801; transition metal (Cu) changes the crystal structure of MOF-801, so that the internal gaps are changed, the adsorption of water vapor is increased, and the bimetallic active site is more beneficial to the adsorption of water vapor; copper ions doped into the MOF-801 can transfer valence electrons favorable for water molecule adsorption to metal clusters, so that the water absorption rate of the MOF-801 under the low humidity condition is increased; the electronegativity of copper and zirconium are 1.9 and 1.33, respectively, the higher the electronegativity value, the greater the ability of the metal to attract bond-forming electrons. Thus, cu-OH bonds combine with Zr-OH bonds, and can exhibit more polarity, thus exhibiting a higher water absorption rate.
Therefore, the packaging film prepared by taking Cu@MOF-801 as the water absorbent is expected to reduce the relative humidity in the fruit and vegetable packaging microenvironment, inhibit the growth of food-borne microorganisms such as mould and the like, achieve the effect of delaying fruit and vegetable spoilage, and have development potential in water absorbent products such as drying agents, 3D foams and the like.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: (1) The invention is characterized in thatBimetallic organic framework material with water vapor adsorption rate under various humidity gradients compared with undoped Cu 2+ Is 10-20% higher, and has strong thermal stability and recycling performance, and the material still maintains about 0.27 g.g after four times of high-temperature activation and water vapor absorption cycles -1 The high-efficiency water absorption efficiency is reduced by only 0.5 percent compared with the first time; (2) The packaging material prepared from the bimetal organic frame material can regulate and control the humidity of the fruit and vegetable packaging microenvironment and inhibit the growth of microorganisms, thereby prolonging the shelf life of the picked fruits and vegetables.
Drawings
FIG. 1 is a graph of the morphology change of strawberries stored under different humidity conditions;
FIG. 2 is a graph of total surface colony count of strawberry under different humidity conditions;
FIG. 3 is a graph of the microscopic morphologies of Cu@MOF-801 and MOF-801 in different proportions;
FIG. 4 is a water vapor sorption diagram of Cu@MOF-801 and other metal doped MOF-801 in different proportions;
FIG. 5 is a graph of water vapor adsorption cycles for Cu@MOF-801 and MOF-801 in different proportions;
FIG. 6 is a transparency diagram of a CuMGCF package;
fig. 7 is a graph of the strawberry preservative effect of the CuMGCF package.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Example 1
Cu 1/4 Preparation of @ MOF-801 Material:
(1) 5mmol of fumaric acid, 3.75mmol of zirconium oxychloride octahydrate and 1.25mmol of copper nitrate trihydrate are weighed and dissolved in a mixed solution of 20mL of DMF and 7mL of methanol, wherein the doping amount of copper ions accounts for 25% of the metal ligand content by calculation of molar ratio.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the precipitate in vacuum oven (50deg.C, 8 h), and openingVacuum pumping and drying until the pressure is minus 0.1MPa, thus obtaining the bimetal organic framework material Cu 1/2 @MOF-801。
Example 2
Cu 1/5 Preparation of @ MOF-801 Material:
in comparison with example 1, the preparation method of the frame material of example 2 changed the addition molar amount of copper ions to 20% of the total molar amount of metal ion ligands:
(1) 5mmol of fumaric acid, 4mmol of zirconium oxychloride octahydrate and 1mmol of copper nitrate trihydrate are weighed out and dissolved in a mixture of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the washed precipitate in a vacuum drying oven (50 ℃ for 8 hours), opening a vacuum pump to vacuum and dry until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material Cu 1/5 @MOF-801。
Example 3
Cu 1/3 Preparation of @ MOF-801 Material:
in comparison with example 1, the preparation method of the frame material of example 3 changed the addition molar amount of copper ions to 33.3% of the total molar amount of metal ion ligands:
(1) 5mmol of fumaric acid, 3.3mmol of zirconium oxychloride octahydrate and 1.7mmol of copper nitrate trihydrate are weighed out and dissolved in a mixture of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the washed precipitate in a vacuum drying oven (50 ℃ for 8 hours), opening a vacuum pump to vacuum and dry until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material Cu 1/3 @MOF-801。
As shown in FIG. 3, the microscopic morphology patterns of Cu@MOF-801-1 and MOF-801 in different proportions are shown, and the MOF-801 shows irregularity as can be seen from the SEM imageMorphology. But with transition metal Cu 2+ The morphology of the bimetallic MOF gradually exhibits a regular octahedral crystal structure with a relatively uniform particle size distribution. The change in the crystal form of the material affects its pore distribution, which may be a factor in improving the water absorption efficiency.
Comparative example 1
In comparison with example 1, the frame material of comparative example 1 was prepared without metallic Cu 2+ Doping.
(1) 5mmol of fumaric acid and 5mmol of zirconium oxychloride octahydrate were weighed out and dissolved in a mixed solution of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) And (3) putting the washed precipitate into a vacuum drying oven for drying (50 ℃ for 8 hours), and opening a vacuum pump for vacuumizing and drying until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material MOF-801.
Comparative example 2
The preparation method of the frame material of comparative example 2 changed the addition molar amount of copper ions to 50% of the total molar amount of metal ion ligands as compared to example 1.
(1) 5mmol of fumaric acid, 2.5mmol of zirconium oxychloride octahydrate and 2.5mmol of copper nitrate trihydrate were weighed out and dissolved in a mixed solution of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the washed precipitate in a vacuum drying oven (50 ℃ for 8 hours), opening a vacuum pump to vacuum and dry until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material Cu 1/2 @MOF-801。
Comparative example 3
The preparation method of the frame material of comparative example 3 was changed to change the copper ion doping to the cobalt ion doping as compared with example 1.
(1) 5mmol of fumaric acid, 3.75mmol of zirconium oxychloride octahydrate and 1.25mmol of cobalt nitrate hexahydrate were weighed out and dissolved in a mixed solution of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the washed precipitate in a vacuum drying oven (50 ℃ for 8 hours), opening a vacuum pump to vacuum and dry until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material Co 1/4 @MOF-801。
Comparative example 4
The preparation method of the frame material of comparative example 4 was changed to change the copper ion doping to the nickel ion doping as compared with example 1.
(1) 5mmol of fumaric acid, 3.75mmol of zirconium oxychloride octahydrate and 1.25mmol of copper nitrate trihydrate are weighed out and dissolved in a mixture of 20mL of DMF and 7mL of methanol.
(2) The mixed solution was transferred to a high-pressure reactor, and the reactor was put into an oven (130 ℃ C., 6 h) and cooled at room temperature after the reaction was completed. And then washed four times with DMF and methanol by centrifugation.
(3) Drying the washed precipitate in a vacuum drying oven (50 ℃ for 8 hours), opening a vacuum pump to vacuum and dry until the pressure is-0.1 MPa, thus obtaining the bimetal organic framework material Ni 1/4 @MOF-801。
Preparation of GCF composite film:
(1) 2g of gelatin Gel was weighed and dissolved in 30mL of distilled water (2%, w/v), and left standing at room temperature for 30min to sufficiently absorb water. Then, the mixture was stirred in a water bath at 60℃for 30 minutes to obtain a uniform suspension. Meanwhile, 2g CMC-Na (2%, w/v) was dissolved in 70mL distilled water and further stirred in a water bath at 60℃for 1 hour. The two prepared solutions were mixed, and 0.5mL of glycerin was added as a plasticizer to the mixed solution, and heated and stirred at 60 ℃ for 1 hour.
(2) 100mL of the film-forming solution was poured into an acrylic mold (20X 20 cm) 2 ) Then left to stand at room temperature for 20min. Drying in an oven (temperature 37 ℃ C., time 12 h), and the prepared package was named GCF composite film.
Preparation of a CuMGCF water-absorbing fresh-keeping packaging film:
(1) 2g of gelatin Gel was weighed and dissolved in 30mL of distilled water (2%, w/v), allowed to stand at room temperature for 30 minutes to allow sufficient absorption of water, 0.1g of Cu@MOF-801 prepared in example 1 was dissolved in 30mL of Gel standing liquid and subjected to ultrasonic treatment for 5 minutes, and at the same time, 2g of CMC-Na (2%, w/v) was dissolved in 70mL of distilled water, and further stirred in a water bath at 60℃for 1 hour. The two prepared solutions were mixed, and 0.5mL of glycerin was added as a plasticizer to the mixed solution, and heated and stirred at 60 ℃ for 1 hour.
(2) 100mL of the film-forming solution was poured into an acrylic mold (20X 20 cm) 2 ) Then left to stand at room temperature for 20min. Drying in an oven (temperature is 37 ℃ C., time is 12 h) to obtain the CuMGCF water-absorbing fresh-keeping packaging film.
In order to study the fresh-keeping effect of the packaging film of Cu@MOF-801 on fruits and vegetables, a packaged gelatin/sodium carboxymethylcellulose package (Gel/CMC-Na film, abbreviated as GCF) without adding materials is also arranged as a positive control package, and a common commercial plastic package (PE film, abbreviated as PEF) is also arranged as a negative control package.
For the above examples and comparative examples, the water absorption performance of Cu@MOF-801 and other metal doped MOF-801 was studied in different proportions:
(1) Samples of examples 1, 2, 3 and comparative examples 1, 2, 3, 4 were vacuum activated at 120℃for 3 hours and then cooled to room temperature in a vacuum dryer.
(2) Weigh the weight of the aluminum box weighing dish, record as M 1 . Weighing 0.1g of activated sample, placing in a weighing aluminum box, and recording the total weight of the sample as M 2 And placed in a constant temperature and humidity cabinet (temperature 25 ℃, relative humidity 50%). Taking out the aluminum box for weighing after a period of time, and when the weight of the aluminum box is constant, indicating that the water vapor adsorption of the material reaches saturation and recording the weight as M 3 。
The formula of the water absorption per gram of material:
wherein Y is in g.g -1 。
As shown in FIG. 4, the water vapor adsorption diagram of Cu@MOF-801 and other metal doped MOF-801 with different proportions shows that the water absorption capacity per gram of Cu@MOF-801 with different doping amounts is higher than that of MOF-801 at a relative humidity of 50%, wherein Cu 1/4 Water absorption capacity of @ MOF-801 of 0.38 g.g -1 28.4% higher than the original MOF. Compared with the Ni and Co doped MOF-801, the water absorption per gram is greatly reduced, and the minimum water absorption is only 0.11 g.g -1 . The transition metal Cu doped MOF-801 has improved water absorption capacity and good water vapor adsorption, and is expected to be used for developing packaging films for regulating and controlling the storage humidity of fruits and vegetables.
Cu@MOF-801 vapor adsorption cycle study
(1) The samples of examples 1, 2 and comparative examples 1, 2 were subjected to vacuum activation at 120 ℃ to remove adsorbed water vapor from the material. The specific operation is as follows, the material is put into a baking oven at 120 ℃ for drying for 3 hours, and then is transferred into a vacuum drier for vacuum cooling.
(2) Weighing the weight of the aluminum box weighing dish, and marking the weight as M1; 0.1g of the activated sample was weighed and placed in a weighing aluminum box, the total weight of which was noted My. The weighed sample was placed in a constant temperature and humidity box (relative humidity 50%,18 ℃). After the aluminum box is constant in weight, the weighed weight is taken out and recorded as Mn. And then the sample is repeatedly subjected to the process of the step 1 to finish activation, and is put into a constant temperature and humidity box again, and four cycles are repeated. The formula of the water absorption per gram of material:
wherein Y is in g.g -1 。
As shown in FIG. 5, the Cu@MOF-801 with different doping amounts is a water vapor adsorption cycle chart, and the Cu@MOF-801 still has good water absorption performance after five cycles of high-temperature activation and water vapor absorption, wherein Cu is a metal oxide 1/4 MOF-801 maintained at 0.32 g.g -1 The high-efficiency water absorption efficiency is reduced by only 3.2 percent compared with the first time. Whereas the performance was reduced by 16.6% for the original MOF-801 after cycling. The Cu doped material has the advantages of enhanced thermal stability and recycling performanceDifferent economic recycling values.
Strawberry morphology change and surface colony count research under different humidity conditions: and simulating the influence of different humidity on the packaging microenvironment of the fruits and vegetables, and selecting strawberries as experimental objects according to the fresh-keeping effect of the prepared CuMGCF package on the picked fruits and vegetables.
(1) Strawberry pretreatment: fresh strawberries were purchased from the market and transported to the laboratory at low temperature within 1h. Rapidly selecting samples with consistent size, appearance and maturity, no damage and no plant diseases and insect pests. And 25 selected samples are respectively placed in a constant temperature and humidity box (the temperature is 25 ℃) with the relative humidity of 45% and 90%, three strawberries on the 0 th day, the 1 st day, the 3 rd day, the 5 th day and the 7 th day are randomly taken and photographed and recorded, and the shape change of the strawberries stored under different humidity conditions is shown in figure 1.
(2) 25g of 0.5cm pulp from strawberry stored under 45% and 90% relative humidity conditions was randomly taken and sampled for 0, 2, 4 days. To 25g pulp samples, 225mL of sterile water was added for homogenization dilution, and 1 was pipetted with a 1mL sterile pipette: 10 samples were homogenized in 1mL and poured into centrifuge tubes containing 9mL of sterile water. The above experimental procedure was repeated twice, resulting in a dilution factor of 1000.
(3) 100uL of the average liquid with different dilution gradients was added to PDA culture medium for dilution and coating. Placing the culture medium after coating to a biochemical incubator at 22+/-1 ℃ for inverted culture for three days, and observing the colony number; the total number of surface colonies of the strawberries under different humidity conditions is shown in fig. 2.
As shown in fig. 1 and 2, the high humidity stored strawberries began to spoil at the 3d surface and mold, while the low humidity stored strawberries did not have significant mold at the 7d surface. Therefore, the development of the packaging film capable of regulating and controlling humidity in the microenvironment has market application potential in the field of fruit and vegetable corrosion inhibition and fresh-keeping.
Sample selection was performed as in step (1) of example 1. And packaging by using a PEF, GCF, cuMGCF packaging bag after ultraviolet sterilization. 3 strawberries were packed in each bag, sealed, stored in a constant temperature and humidity box, sampled at regular time and measured for quality index. Specifically, the storage environment of strawberries is: the temperature is 15+/-1 ℃, the relative humidity is 50+/-5 percent, and the storage is carried out for 7 days. The photographing recording was performed every 2d sampling except 1 d.
As shown in fig. 7, the strawberries in the PEF pack control group had started to deteriorate by day 2 and the strawberry juice had overflowed by day 3; the GCF package control group had not been edible at day 3 and the peel began to spoil and the strawberry surface began to develop colonies by day 7 of storage. Whereas a small portion of the pericarp of the CuMGCF-packaged strawberries did not begin to spoil until day 7. From the above-mentioned packaging experiment results, it can be seen that CuMGCF can regulate and control humidity of the packaging microenvironment, inhibit microbial growth, and thereby increase shelf life of strawberry after harvest.
Transparency study of CuMGCF water-absorbing fresh-keeping packaging film:
in the fruit and vegetable selling process, the transparency of the packaging film directly influences the visual impression and acceptance of the product by consumers, so that the product is compared with the package of the PEF and GCF films. As can be seen from fig. 6 and 7, the three films are covered on the surface of the picture, and the clarity of the picture is observed, and the packaging film after the addition of the material has good transparency compared with the packaging films of GCF and PEF.

Claims (10)

1. The bimetallic organic framework material is characterized in that the crystal structure of the framework material is octahedron, the framework material is formed by coordination of organic ligand fumaric acid and metal ion ligands, the metal ion ligands are zirconium ions and copper ions, and the doping amount of the copper ions accounts for 20% -40% of the content of the metal ligands by calculation of molar ratio.
2. A method of making a bimetallic organic framework material as claimed in claim 1, comprising the steps of:
(1) Dissolving fumaric acid, zirconium oxychloride octahydrate and copper nitrate trihydrate in a formic acid solution of N, N-dimethylformamide, and carrying out ultrasonic dissolution to obtain a mixed solution;
(2) Heating and pressurizing the mixed liquid for reaction, and cooling at room temperature after the reaction is completed to obtain a solid material;
(3) And (3) centrifugally washing the solid material, and drying in vacuum to obtain the bimetal organic framework material.
3. The method according to claim 2, wherein in the step (1), the molar ratio of fumaric acid, zirconium oxychloride octahydrate and copper nitrate trihydrate is 1:0.5 to 1:0.1 to 0.5.
4. The process according to claim 2, wherein in the step (1), the volume ratio of N, N-dimethylformamide to formic acid in the formic acid solution of N, N-dimethylformamide is 15 to 20:5 to 7.
5. The process according to claim 2, wherein in the step (2), the heating reaction is carried out at a temperature of 125 to 135℃for a period of 6 to 7 hours.
6. The method according to claim 2, wherein in the step (3), the centrifugation is performed at a rotation speed of 9500rpm/min for 10 minutes at a centrifugation temperature of 10 ℃ to 20 ℃.
7. The method according to claim 2, wherein in the step (3), the vacuum drying is performed at a temperature of 45 to 60 ℃ for 8 to 10 hours at a drying pressure of-0.09 to-0.1 MPa.
8. The use of the bimetal organic framework material of claim 1 in the preparation of a water-absorbing fresh-keeping packaging film.
9. The use according to claim 8, wherein the water-absorbing preservative packaging film is obtained by mixing a bimetal organic frame material, a plasticizer, a film forming agent and sodium carboxymethyl cellulose, pouring into a mold and drying.
10. The use according to claim 9, characterized in that the mass ratio of bimetallic organic framework material, plasticizer, film former and sodium carboxymethylcellulose is 0.1-0.2: 0.5 to 1:2:2.
CN202310690958.7A 2023-06-12 2023-06-12 Bimetal organic frame material and preparation method and application thereof Pending CN116622086A (en)

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