MOF / cellulose hydrogel, and preparation method therefor and use thereof

Abstract

The present invention provides an MOF / cellulose hydrogel, and a preparation method therefor and the use thereof. By defining the composition and sequence of added components, MOF is combined into the matrix of a hydrogel, and self-assembly is performed to generate a reticular nanofiber structure, thereby greatly improving the mechanical strength, the fatigue resistance, the self-repairing property and the biocompatibility of the hydrogel; the cellulose is defined, and in the case that any chemical cross-linking agent is not added, the hydrogel is reinforced and toughened by means of the combined action of modified carboxymethyl cellulose nanofibers with a polyanionic cellulose, a hydrogen bond, and the complexation of a metal and ligand carboxyl group, so as to achieve antibacterial durability; and a coordination compound of metal ions in the metal salt solution is defined, and rigid 1,2,4,5-pyromellitic acid is used as a main ligand and flexible 1,3-bis(1H-imidazol-1-ylmethyl)benzene is used as an auxiliary ligand to perform self-assembly, so as to generate a reticular hyperbranched nanofiber structure, thereby greatly improving the mechanical property and the antibacterial performance of the hydrogel.

Description

A MOF / cellulose hydrogel and its preparation method and application Technical Field

[0001] The present invention relates to the field of hydrogels, in particular to a MOF / cellulose hydrogel and a preparation method and application thereof. Background Art

[0002] As a soft material, hydrogels are cross-linked polymer networks with water as the dispersion medium. They swell rapidly in water and retain a large volume of water in the swollen state without dissolving. Structurally, hydrogels are very similar to the extracellular matrix and are functional. Hydrogels can be modified by introducing biofriendly monomers and macromolecules, or further modified by loading bioactive molecules. Therefore, they have broad application prospects in biomedical materials such as corneas, wound dressings, drug carriers, artificial cartilage, and adhesives. Traditional hydrogels are brittle and have low strength, making them difficult to meet the needs of some existing high-performance applications.

[0003] Metal-organic frameworks (MOFs) are a new type of porous material that has developed rapidly over the past two decades. They are widely used in catalysis, gas adsorption, optoelectronics, and other fields, and are considered to have the greatest potential as an adsorption material. However, MOFs used in existing technologies are mostly in granular or powder form, making them difficult to recycle and reuse. Furthermore, their high material cost makes large-scale production difficult, significantly hindering their practical application.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a MOF / cellulose hydrogel and a preparation method and application thereof to solve the problems in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0008] S1: Mix cellulose and anhydrous ethanol, add sodium hydroxide, and heat to 60-80°C. After the reaction, filter while hot, and wash with 75% ethanol and isopropanol to obtain a cellulose treatment solution.

[0009] S2: adding anhydrous ethanol, sodium hydroxide solution, and N,N-methylenebisacrylamide to the cellulose treatment solution, heating to 60-80°C with stirring, filtering while hot, washing and filtering with 75% ethanol, and freeze-drying to obtain a precursor;

[0010] S3: The metal salt solution is dispersed and impregnated in the precursor using the incipient wetness impregnation method. After grinding, it is dried for 12 hours and then immersed in an N,N-dimethylformamide solution containing 2-methylimidazole. The precursor is transferred to a hydrothermal reactor and reacted at 120°C for 4-6 hours. After that, the precursor is fully cooled to 18-25°C and washed by centrifugation to obtain a MOF / cellulose hydrogel.

[0011] This invention incorporates MOFs into a hydrogel matrix, imparting enhanced mechanical strength, excellent self-recovery, fatigue resistance, and self-healing properties through an energy dissipation mechanism. This leverages the advantages of a single material while overcoming the shortcomings of existing materials. The combination of the microporosity and mesoporosity of MOFs with the mesoporosity and macroporosity of the hydrogels creates a hierarchically porous hydrogel composite, significantly enhancing its superior performance.

[0012] Furthermore, the cellulose is one of carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.

[0013] Furthermore, the metal salt solution is Ag + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ One or more solutions.

[0014] Furthermore, the mass volume ratio of the precursor to the metal salt solution is 2g:300uL.

[0015] Furthermore, the preparation method comprises the following steps:

[0016] S1: polyanionic cellulose, modified carboxymethyl cellulose nanofibers, and anhydrous ethanol are mixed and stirred, sodium hydroxide is added, and the temperature is raised to 60-80°C. After the reaction, the mixture is filtered while hot, and the mixture is stirred and washed with 75% ethanol and isopropanol to obtain a cellulose treatment solution;

[0017] S2: Add acrylamide, tetramethylethylenediamine solution, and ammonium persulfate solution to the cellulose treatment solution under nitrogen flow, react at 15-20°C for 24 hours, filter while hot, and freeze-dry to obtain a precursor;

[0018] S3: Zinc nitrate hexahydrate and cobalt nitrate hexahydrate are mixed with deionized water in a molar ratio of 1:4 to obtain a metal salt solution. The metal salt solution is dispersed and infiltrated into the precursor by the incipient wetness impregnation method. After grinding, it is dried for 12 hours. A mixed solution of 1,2,4,5-pyromellitic acid, 1,3-bis(1H-imidazol-1-ylmethyl)benzene, N,N-dimethylformamide and deionized water is added, and the mixture is transferred to a hydrothermal autoclave. After reacting at 120°C for 4-6 hours, it is fully cooled to 18-25°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0019] Furthermore, the mass ratio of polyanionic cellulose to modified carboxymethyl cellulose nanofibers is 1:(1-2); the mass ratio of the polyanionic cellulose to acrylamide is 2-4%; and the molar ratio of the tetramethylethylenediamine solution to the ammonium persulfate solution is 125:8.

[0020] Furthermore, the molar ratio of zinc nitrate hexahydrate to cobalt nitrate hexahydrate is 1:5.

[0021] The present invention prepares a metal complex type carboxylated cellulose derivative composite hydrogel through a multi-step process. Acrylamide is subjected to in-situ free radical polymerization in a polyanionic cellulose and modified carboxymethyl cellulose nanofiber solution without introducing any chemical crosslinking agent. A stable primary hydrogel is formed by hydrogen bonding and physical entanglement between the cellulose derivative and the polyacrylamide polymer chain. The hydrogel is then treated with a metal salt solution to introduce a stronger complexation between the metal and the ligand carboxyl group, further enhancing the mechanical properties of the hydrogel. The hydrogel contains more carboxyl groups and will react with Ag. + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ The formation of more coordination bonds leads to a tighter cross-linked network, but reduces the swelling ratio and water content of the hydrogel;

[0022] The gel's reinforcing and toughening effects stem from the combined effects of nanofibers, hydrogen bonds, and complexation between metal and ligand carboxyl groups. Modified carboxymethyl cellulose nanofibers, formed by hydrogen bonds within the cellulose chain and internal macromolecular crosslinking, are far more stable than nanofibers formed by polyanionic cellulose self-assembly through complexation. When the gel deforms due to external forces, hydrogen bonds and complexation break, absorbing energy and delaying the formation of macrocracks. In this case, the self-assembled polyanionic cellulose nanofibers formed by complexation are more likely to decompose and absorb energy. Therefore, to achieve hydrogels exhibiting higher rigidity and strength in both compression and tension, the mass ratio of polyanionic cellulose to modified carboxymethyl cellulose nanofibers is limited to 1:(1-2).

[0023] Furthermore, the molar ratio of 1,2,4,5-pyromellitic acid and 1,3-bis(1H-imidazol-1-ylmethyl)benzene is 1:1, and Ag + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ The molar ratio of the sum of the moles of 1,2,4,5-pyromellitic acid is 1:1.

[0024] The present invention selects 1,2,4,5-pyromellitic acid, a rigid aromatic tetracarboxylic acid ligand containing multiple carboxyl groups, rich coordination sites, and flexible coordination modes, as the main ligand. The four carboxyl groups of the ligand can provide potential eight coordination sites. The ligand and 1,3-bis(1H-imidazol-1-ylmethyl)benzene serve as ligands together. The two imidazole rings in 1,3-bis(1H-imidazol-1-ylmethyl)benzene rotate freely through the C-C bond. By using a hydrothermal method, 1,2,4,5-pyromellitic acid is used as the main ligand and 1,3-bis(1H-imidazol-1-ylmethyl)benzene is used as the auxiliary ligand. A limited Ag is introduced. + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ Form a stable coordination compound, limiting Ag + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ The addition amount is adjusted to construct a three-dimensional network structure with rich pore structure, stable chemical properties and easy modification, which synergistically improves the water absorption and salt resistance of the hydrogel and improves the mechanical and chemical properties of the hydrogel.

[0025] Furthermore, the preparation method of modified carboxymethyl cellulose nanofibers includes the following steps: mixing a carboxymethyl starch solution with a sodium periodate solution and stirring the mixture in the dark at 18-25°C for 16 hours, dialyzing and freeze-drying to obtain oxidized carboxymethyl starch; ultrasonically stirring carboxymethyl cellulose, polyvinyl alcohol, and deionized water, and then adding oxidized carboxymethyl starch, polyethylene oxide, polyethylene glycol octylphenyl ether, and dimethyl sulfoxide and mixing to obtain an electrospinning solution, which is transferred to a syringe for electrospinning at a flow rate of 300 μL / h and a voltage of 18 kV to obtain nanofibers; mixing adipic acid dihydrazide, ethanol, and deionized water to obtain an impregnation solution; immersing the nanofibers in the impregnation solution and shaking for 5 hours, rinsing with deionized water and ethanol in turn, and drying with chloroform to obtain modified carboxymethyl cellulose nanofibers.

[0026] Furthermore, a 2% carboxymethyl starch solution was prepared, the molar ratio of carboxymethyl starch unit to sodium periodate was 5:4; the mass ratio of carboxymethyl cellulose, polyvinyl alcohol, and oxidized carboxymethyl starch was 1:2:0.7; the volume ratio of ethanol and deionized water was 4:1; and the mass volume ratio of nanofibers to the impregnation solution was 1g:1L.

[0027] Due to the water solubility of carboxymethyl starch, it will dissolve in water, thus losing its mechanical strength. The present invention modifies it and introduces it into the hydrogel to make it water-resistant; the carboxymethylation modification will reduce the molecular weight and crystallinity of the polysaccharide, resulting in low mechanical strength of the nanofiber membrane, but the hydrogel prepared by the present invention has high mechanical strength, indicating that it contains more amylose after modification, has good molecular movement freedom, and can be oriented into parallel arrangements, thereby forming hydrogen bonds. The tensile strength of the hydrogel prepared by the present invention increases with the increase of oxidation degree, because the sample with a high oxidation degree has a large cross-linking density, more intermolecular amide bonds, and tighter molecular links, and the amide bonds are not easily destroyed by water to form new hydrogen bonds;

[0028] Oxidized carboxymethyl starch and carboxymethyl cellulose are electrospun into nanofibers and cross-linked with adipic acid dihydrazide. The cross-linked nanofibers have a smooth surface and porous structure, and their average diameter increases, which will improve the internal cross-linking degree and biocompatibility of the hydrogel.

[0029] The introduction of polyanionic cellulose also enhances the hydrogen bonding effect in the gel, increases more cross-linking points within the network, and leads to a decrease in pore size. When the composite gel is treated with a metal salt solution, the water content increases, but its network structure is denser than that of the primary gel. This is because Ag + 、Co 2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ The introduction of gives the composite gel a new cross-linking metal and ligand carboxyl complexation, thereby significantly increasing the cross-linking density within the network. The metal and carboxyl complexation work synergistically with hydrogen bonds to assemble the polyanionic cellulose polymer chains into a nanofiber structure, which will present nanoscale branched fibers. The complexation is further enhanced, making the network structure denser and the nanofibers intertwined with each other.

[0030] Furthermore, a MOF / cellulose hydrogel is used to prevent external wound infection; the hydrogel is carbonized under high-temperature nitrogen to obtain a porous lightweight conductive material with high conductivity and high specific surface area; the hydrogel is carbonized under high-temperature nitrogen and used for application research on the electroreduction of carbon dioxide.

[0031] Beneficial effects of the present invention:

[0032] The present invention provides a MOF / cellulose hydrogel and its preparation method and application. By limiting the components and order of addition, MOF is incorporated into the hydrogel matrix, and self-assembled to produce a mesh nanofiber structure, which greatly improves the mechanical strength, fatigue resistance, self-repairability, and biocompatibility of the hydrogel. The MOF / cellulose hydrogel prepared by the present invention is not only used to prevent external wound infection, but also used to prepare porous lightweight conductive materials and for research on the electroreduction of carbon dioxide.

[0033] By limiting the content of the components, the combined effects of modified carboxymethyl cellulose nanofibers, polyanionic cellulose, hydrogen bonds, and metal and ligand carboxyl complexation are utilized to achieve the strengthening and toughening of the hydrogel, resulting in the prepared hydrogel having higher tensile strength and better antibacterial properties. The modified carboxymethyl cellulose nanofibers are formed by cross-linking oxidized carboxymethyl starch, carboxymethyl cellulose, and adipic acid dihydrazide. The prepared hydrogel has an increasing tensile strength as the degree of oxidation increases, which will increase the intermolecular amide bonds in the hydrogel, make the molecules more tightly linked, form new hydrogen bonds, and improve the internal cross-linking degree and biocompatibility of the hydrogel.

[0034] Ag in metal salt solution + 、Co2+ 、Zn 2+ Mg 2+ 、Fe 2+ 、Cu 2+ 、Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ The coordination compound is limited, with rigid 1,2,4,5-benzenetracarboxylic acid as the main ligand and flexible 1,3-bis(1H-imidazol-1-ylmethyl)benzene as the auxiliary ligand, and limited divalent zinc ions and divalent cobalt ions are introduced to form a stable coordination compound, which greatly improves the density of the hydrogel network structure and gives the hydrogel a new cross-linking metal and ligand carboxyl complexation effect, thereby significantly increasing the cross-linking density inside the network, improving the antibacterial firmness, and self-assembly to produce a network hyperbranched nanofiber structure, which greatly improves the water absorption and salt resistance of the hydrogel, and improves the mechanical and chemical properties of the hydrogel. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., such directional indications are only used to explain a specific posture, such as the relative position relationship between components, the movement status, etc. If the specific posture changes, the directional indication will also change accordingly. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. If the combination of technical solutions is mutually inconsistent or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] The technical solutions of the present invention are further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely used to explain the present invention and are not intended to limit the present invention.

[0038] Example 1

[0039] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0040] S1: 4 g of carboxymethyl cellulose and 100 mL of anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 60°C. After the reaction, the mixture was filtered while hot, and then washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0041] S2: Add 100 mL of anhydrous ethanol, 4% sodium hydroxide solution, and 0.5 g of N,N-methylenebisacrylamide to the cellulose treatment solution, then heat to 60°C with stirring, filter while hot, wash with 75% ethanol, filter, and freeze-dry to obtain a precursor;

[0042] S3: 0.3 mL of zinc nitrate hexahydrate solution was dispersed and infiltrated into 2 g of the precursor using the incipient wetness impregnation method. After grinding, the precursor was dried for 12 h and then immersed in an N,N-dimethylformamide solution containing 1.3 g of 2-methylimidazole. The precursor was transferred to a hydrothermal reactor and hydroheated at 120 ° C for 4 h. After that, the precursor was fully cooled to 18 ° C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0043] Example 2

[0044] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0045] S1: 4 g of carboxyethyl cellulose and 100 mL of anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 70°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0046] S2: Add 100 mL of anhydrous ethanol, 4% sodium hydroxide solution, and 0.5 g of N,N-methylenebisacrylamide to the cellulose treatment solution, heat to 70°C and stir, filter while hot, wash and filter with 75% ethanol, and freeze-dry to obtain the precursor;

[0047] S3: 0.3 mL of zinc nitrate hexahydrate solution was dispersed and infiltrated into 2 g of the precursor using the incipient wetness impregnation method. After grinding, the precursor was dried for 12 h and then immersed in an N,N-dimethylformamide solution containing 1.3 g of 2-methylimidazole. The precursor was transferred to a hydrothermal reactor and hydroheated at 120 ° C for 5 h. The precursor was then fully cooled to 22 ° C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0048] Example 3

[0049] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0050] S1: 4 g of hydroxypropyl cellulose and 100 mL of anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 80°C. After the reaction, the mixture was filtered while hot, and the mixture was stirred and washed with 75% ethanol and isopropanol to obtain a cellulose treatment solution;

[0051] S2: Add 100 mL of anhydrous ethanol, 4% sodium hydroxide solution, and 0.5 g of N,N-methylenebisacrylamide to the cellulose treatment solution, heat to 80°C and stir, filter while hot, wash and filter with 75% ethanol, and freeze-dry to obtain the precursor;

[0052] S3: 0.3 mL of zinc nitrate hexahydrate solution and cobalt nitrate hexahydrate solution were dispersed and infiltrated into 2 g of the precursor in a volume ratio of 1:1 using the incipient wetness impregnation method. After grinding, the mixture was dried for 12 hours and then immersed in an N,N-dimethylformamide solution containing 2-methylimidazole (1.3 g). The mixture was transferred to a hydrothermal autoclave and hydroheated at 120°C for 6 hours. The mixture was then fully cooled to 25°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0053] Example 4

[0054] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0055] S1: 2 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and 100 mL of anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 60°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0056] The preparation method of modified carboxymethyl cellulose nanofibers includes the following steps: mixing a 2% carboxymethyl starch solution with a 4mmol sodium periodate solution and stirring the mixture in the dark at 18°C ​​for 16 hours, wherein the carboxymethyl starch unit is 5mmol, dialyzing, and freeze-drying to obtain oxidized carboxymethyl starch; ultrasonically stirring 0.7g carboxymethyl cellulose, 0.5g polyvinyl alcohol, and deionized water, and then adding 1g oxidized carboxymethyl starch, 2g polyethylene oxide, 1% polyethylene glycol octylphenyl ether, and 5% dimethyl sulfoxide and mixing to obtain an electrospinning solution, which is transferred to a syringe for electrospinning at a flow rate of 300μL / h and a voltage of 18kV to obtain nanofibers; mixing adipic acid dihydrazide, 4L ethanol, and 1L deionized water to obtain a 25mmol / L adipic acid dihydrazide impregnation solution; immersing 5g of nanofibers in 5L of the impregnation solution and shaking for 5 hours, rinsing with deionized water and ethanol in sequence, and drying with chloroform to obtain modified carboxymethyl cellulose nanofibers;

[0057] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 15°C for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0058] S3: 0.4mmol zinc nitrate hexahydrate, 1.6mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300uL of the metal salt solution was dispersed and infiltrated into 2g of the precursor by the incipient wetness impregnation method. After grinding and drying for 12h, a mixed solution of 2mmol of 1,2,4,5-pyromellitic acid, 2mmol of 1,3-bis(1H-imidazol-1-ylmethyl)benzene, 8mL of N,N-dimethylformamide and 30mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100°C for 60h, it was fully cooled to 18°C ​​and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0059] Example 5

[0060] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0061] S1: 3 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and 100 mL of anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 70°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0062] The preparation method of modified carboxymethyl cellulose nanofibers includes the following steps: mixing a 2% carboxymethyl starch solution with a 4mmol sodium periodate solution, stirring the mixture in the dark at 20°C for 16 hours, wherein the carboxymethyl starch unit is 5mmol, dialyzing, and freeze-drying to obtain oxidized carboxymethyl starch; ultrasonically stirring 0.7g carboxymethyl cellulose, 0.5g polyvinyl alcohol, and deionized water, then adding 1g oxidized carboxymethyl starch, 2g polyethylene oxide, 1% polyethylene glycol octylphenyl ether, and 5% dimethyl sulfoxide and stirring to obtain an electrospinning solution, transferring the solution to a syringe for electrospinning at a flow rate of 300μL / h and a voltage of 18kV to obtain nanofibers; mixing adipic acid dihydrazide, 4L ethanol, and 1L deionized water to obtain a 25mmol / L adipic acid dihydrazide impregnation solution; immersing 5g of nanofibers in 5L of the impregnation solution and shaking for 5 hours, followed by rinsing with deionized water and ethanol, and drying with chloroform to obtain modified carboxymethyl cellulose nanofibers;

[0063] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 18°C ​​for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0064] S3: 0.4mmol zinc nitrate hexahydrate, 1.6mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300uL of the metal salt solution was dispersed and infiltrated into 2g of the precursor by the incipient wetness impregnation method. After grinding and drying for 12h, a mixed solution of 2mmol of 1,2,4,5-pyromellitic acid, 2mmol of 1,3-bis(1H-imidazol-1-ylmethyl)benzene, 8mL of N,N-dimethylformamide and 30mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100℃ for 65h, it was fully cooled to 20℃ and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0065] Example 6

[0066] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0067] S1: 4 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 80°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0068] The preparation method of modified carboxymethyl cellulose nanofibers includes the following steps: mixing a 2% carboxymethyl starch solution with a 4mmol sodium periodate solution, stirring the mixture in the dark at 25°C for 16 hours, wherein the carboxymethyl starch unit is 5mmol, dialyzing, and freeze-drying to obtain oxidized carboxymethyl starch; ultrasonically stirring 0.7g carboxymethyl cellulose, 0.5g polyvinyl alcohol, and deionized water, and then adding 1g oxidized carboxymethyl starch, 2g polyethylene oxide, 1% polyethylene glycol octylphenyl ether, and 5% dimethyl sulfoxide and mixing to obtain an electrospinning solution, which is transferred to a syringe for electrospinning at a flow rate of 300μL / h and a voltage of 18kV to obtain nanofibers; mixing adipic acid dihydrazide, 4L ethanol, and 1L deionized water to obtain a 25mmol / L adipic acid dihydrazide impregnation solution; immersing 5g of nanofibers in 5L of the impregnation solution and shaking for 5 hours, rinsing with deionized water and ethanol in sequence, and drying with chloroform to obtain modified carboxymethyl cellulose nanofibers;

[0069] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 20°C for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0070] S3: 0.4mmol zinc nitrate hexahydrate, 1.6mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300uL of the metal salt solution was dispersed and infiltrated into 2g of the precursor by the incipient wetness impregnation method. After grinding and drying for 12h, a mixed solution of 2mmol of 1,2,4,5-pyromellitic acid, 2mmol of 1,3-bis(1H-imidazol-1-ylmethyl)benzene, 8mL of N,N-dimethylformamide and 30mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100°C for 68h, it was fully cooled to 25°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0071] Comparative Example 1

[0072] Example 5 was used as a control group, in which only 2 mmol of 1,2,4,5-pyromellitic acid was added, and 1,3-bis(1H-imidazol-1-ylmethyl)benzene was not added. Other processes were carried out normally.

[0073] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0074] S1: 3 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 70°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0075] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 18°C ​​for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0076] S3: 0.4 mmol zinc nitrate hexahydrate, 1.6 mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300 uL of the metal salt solution was dispersed and infiltrated into 2 g of the precursor using the incipient wetness impregnation method. After grinding and drying for 12 hours, a mixed solution of 2 mmol 1,2,4,5-pyromellitic acid, 8 mL N,N-dimethylformamide and 30 mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100°C for 65 hours, it was fully cooled to 20°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0077] Comparative Example 2

[0078] Taking Example 5 as a control group, the molar ratio of 1,2,4,5-pyromellitic acid to 1,3-bis(1H-imidazol-1-ylmethyl)benzene was 2:1, and the other processes were normal.

[0079] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0080] S1: 3 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 70°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0081] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 18°C ​​for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0082] S3: 0.4 mmol zinc nitrate hexahydrate, 1.6 mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300 uL of the metal salt solution was dispersed and infiltrated into 2 g of the precursor by the incipient wetness impregnation method. After grinding and drying for 12 hours, a mixed solution of 4 mmol of 1,2,4,5-pyromellitic acid, 2 mmol of 1,3-bis(1H-imidazol-1-ylmethyl)benzene, 8 mL of N,N-dimethylformamide and 30 mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100°C for 65 hours, it was fully cooled to 20°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0083] Comparative Example 3

[0084] Taking Example 5 as a control group, the molar ratio of the 1,2,4,5-pyromellitic acid to 1,3-bis(1H-imidazol-1-ylmethyl)benzene is 2:1, and the molar ratio of the sum of the moles of zinc nitrate hexahydrate and cobalt nitrate hexahydrate to 1,2,4,5-pyromellitic acid is 2:1, which is not within the range defined by the present invention.

[0085] A method for preparing a MOF / cellulose hydrogel comprises the following steps:

[0086] S1: 3 g of polyanionic cellulose, 2 g of modified carboxymethyl cellulose nanofibers, and anhydrous ethanol were mixed and stirred, sodium hydroxide was added, and the temperature was raised to 70°C. After the reaction, the mixture was filtered while hot and washed with 75% ethanol and isopropanol with stirring to obtain a cellulose treatment solution;

[0087] S2: Under nitrogen, add 100 g acrylamide, 5 mL 1.25 mol / L tetramethylethylenediamine solution, and 5 mL 0.08 mol / L ammonium persulfate solution to the cellulose treatment solution, react at 18°C ​​for 24 h, filter while hot, and freeze-dry to obtain the precursor;

[0088] S3: 0.4 mmol zinc nitrate hexahydrate, 1.6 mmol cobalt nitrate hexahydrate and deionized water were mixed to obtain a metal salt solution. 300 uL of the metal salt solution was dispersed and infiltrated into 2 g of the precursor by the incipient wetness impregnation method. After grinding and drying for 12 hours, a mixed solution of 1 mmol of 1,2,4,5-pyromellitic acid, 0.5 mmol of 1,3-bis(1H-imidazol-1-ylmethyl)benzene, 8 mL of N,N-dimethylformamide and 30 mL of deionized water was added, and the mixture was transferred to a hydrothermal autoclave. After hydroheating at 100°C for 65 hours, it was fully cooled to 20°C and centrifuged and washed to obtain a MOF / cellulose hydrogel.

[0089] Comparative Example 4

[0090] Example 6 was used as a control group, in which only 4 g of polyanionic cellulose was added without adding modified carboxymethyl cellulose nanofibers, and the other steps were normal.

[0091] Comparative Example 5

[0092] Example 6 was used as a control group, in which only 2 g of modified carboxymethyl cellulose nanofibers were added without polyanionic cellulose, and other processes were carried out normally.

[0093] Comparative Example 6

[0094] Example 6 was used as a control group, 6 g of polyanionic cellulose and 2 g of modified carboxymethyl cellulose nanofibers were added, and other processes were normal.

[0095] Comparative Example 7

[0096] Taking Example 6 as the control group, hydroxyethyl cellulose was selected as the cellulose, and the other processes were normal.

[0097] Comparative Example 8

[0098] Example 5 was used as a control group. 1,2,4,5-pyromellitic acid and 1,3-bis(1H-imidazol-1-ylmethyl)benzene were not added, 1 mmol of isophthalic acid was added, and other processes were carried out normally.

[0099] Performance testing: The hydrogels prepared in Examples 1-6 and Comparative Examples 1-8 were subjected to performance testing. The mechanical properties (compressive stress at 90% compressive strain), swelling properties, and adsorption properties of the hydrogels prepared above were measured.

[0100] Compression test: Measured by a universal testing machine at 20-25°C; the compression rate is 2 mm / min; the test sample is a cylinder with a diameter of 13 mm and a height of 8 mm. The compressive strain and compressive strength of the hydrogel are also obtained from the rupture point.

[0101] The strength calculation formula is: P = W / (πr 2), W is the maximum load, N; r is the radius of the cylinder, mm; the compression strain is calculated as follows: σ = L1 / L × 100%, L1 is the distance compressed by the compressor, mm; L is the original height of the sample column, mm;

[0102] Swelling performance test: The pre-weighed hydrogel was soaked in distilled water at 20-25°C for one week to allow it to swell fully. After removal, it was dried on the surface of filter paper and weighed. The swelling performance was expressed as the swelling degree R, which was calculated as follows: R = (m1-m) / m×100%, where m1 is the mass of the hydrogel after swelling; m is the weight of the dry hydrogel.

[0103] Antibacterial performance test: The antibacterial properties of the hydrogels of Examples 1-6 and Comparative Examples 1-8 were tested by absorbance. The inhibition rate was calculated according to the formula: ɑ = (A1-A) / A×100%, where A1 is the absorbance of the bacterial culture medium with cellulose hydrogel added, and A is the absorbance of the bacterial culture medium without hydrogel. Staphylococcus aureus and Escherichia coli were selected as the bacterial species. The test results are shown in Table 1.

[0104] Table 1

[0105] Examples 1-6 are hydrogels prepared according to the present invention. By comparing Example 2 and Example 5 with Comparative Examples 1-3 and Comparative Example 8, it can be seen that the coordination compounds of divalent zinc ions and divalent cobalt ions are limited, rigid 1,2,4,5-pyromellitic acid is used as the main ligand, and flexible 1,3-bis(1H-imidazol-1-ylmethyl)benzene is used as the auxiliary ligand. The addition amount of divalent zinc ions and divalent cobalt ions is limited, and the addition amount of the main ligand and the auxiliary ligand is limited. The density of the hydrogel network structure is greatly improved, and the hydrogel is given a new cross-linked Co-COO- and Zn-COO- complexation effect, thereby significantly increasing the cross-linking density within the network, and self-assembly produces a network hyperbranched nanofiber structure, which greatly improves the water absorption of the hydrogel and improves the mechanical properties and chemical properties of the hydrogel.

[0106] By comparing Example 3 and Example 6 with Comparative Example 4, it can be seen that when the cellulose is modified carboxymethyl cellulose nanofibers and polyanionic cellulose, the oxidized carboxymethyl starch and carboxymethyl cellulose are electrospun into nanofibers and cross-linked with adipic acid dihydrazide, the amide bonds are not easily destroyed by water to form new hydrogen bonds; the various properties of the hydrogel can be greatly improved; by comparing Example 3 with Comparative Examples 5, 6 and 7, it can be seen that without adding any chemical cross-linking agent, by limiting the content in the components, the combined effect of modified carboxymethyl cellulose nanofibers and polyanionic cellulose, hydrogen bonds and Co-COO-, Zn-COO- complexation is utilized to achieve the enhancement and toughening of the hydrogel and enhance the antibacterial durability of the hydrogel.

[0107] In summary, the hydrogel prepared by the present invention not only has excellent mechanical and chemical properties, but also has long-lasting antibacterial properties, and has good application prospects in the field of hydrogels.

[0108] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention specification under the inventive concept of the present invention, or any direct / indirect application in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a MOF / cellulose hydrogel, characterized in that: The preparation method comprises the following steps: S1: Mix cellulose and anhydrous ethanol and stir, add sodium hydroxide and heat to 60-80°C, filter while hot after reaction, and stir and wash with 75% ethanol and isopropanol to obtain a cellulose treatment solution; S2: adding anhydrous ethanol, sodium hydroxide solution, and N,N-methylenebisacrylamide to the cellulose treatment solution, heating to 60-80°C with stirring, filtering while hot, washing and filtering with 75% ethanol, and freeze-drying to obtain a precursor; S3: The metal salt solution is dispersed and infiltrated into the precursor by the incipient wetness impregnation method, dried for 12 hours after grinding, and then immersed in an N,N-dimethylformamide solution containing 2-methylimidazole, transferred to a hydrothermal autoclave, reacted at 120°C for 4-6 hours, fully cooled to 18-25°C, centrifuged and washed, to obtain a MOF / cellulose hydrogel.

2. The method for preparing a MOF / cellulose hydrogel according to claim 1, characterized in that: The cellulose is one of carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; the metal salt solution is Ag + 、Co 2+ 、Zn 2+ Mg 2+ , Fe 2+ , Cu 2+ , Sr 2+ 、Ni 2+ Cr 3+ 、Al 3+ One or a combination of solutions.

3. The method for preparing a MOF / cellulose hydrogel according to claim 1, characterized in that: The mass volume ratio of the precursor to the metal salt solution is 2g:300uL.

4. The method for preparing a MOF / cellulose hydrogel according to claim 1, characterized in that: The preparation method comprises the following steps: S1: Mix polyanionic cellulose, modified carboxymethyl cellulose nanofibers and anhydrous ethanol, add sodium hydroxide and heat to 60-80° C., filter while hot after reaction, and stir and wash with 75% ethanol and isopropanol to obtain a cellulose treatment solution; S2: Add acrylamide, tetramethylethylenediamine solution and ammonium persulfate solution to the cellulose treatment solution under nitrogen flow, react at 15-20°C for 24 hours, filter while hot, and freeze-dry to obtain a precursor; S3: Zinc nitrate hexahydrate and cobalt nitrate hexahydrate are mixed with deionized water to obtain a metal salt solution, which is dispersed and infiltrated into the precursor by the incipient wetness impregnation method. The precursor is ground and dried for 12 hours, and a mixed solution of 1,2,4,5-pyromellitic acid, 1,3-bis(1H-imidazole-1-ylmethyl)benzene, N,N-dimethylformamide and deionized water is added. The precursor is transferred to a hydrothermal autoclave, reacted at 120°C for 4-6 hours, and then fully cooled to 18-25°C. The precursor is centrifuged and washed to obtain a MOF / cellulose hydrogel.

5. The method for preparing a MOF / cellulose hydrogel according to claim 4, characterized in that: The mass ratio of the polyanionic cellulose and the modified carboxymethyl cellulose nanofibers is 1:(1-2); the mass ratio of the polyanionic cellulose to acrylamide is 2-4%; the molar ratio of the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate is 1:4; the molar ratio of the 1,2,4,5-pyromellitic acid and 1,3-bis(1H-imidazole-1-ylmethyl)benzene is 1:1; the molar ratio of the sum of the moles of the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate to the 1,2,4,5-pyromellitic acid is 1:

1.

6. The method for preparing a MOF / cellulose hydrogel according to claim 4, characterized in that: The preparation method of the modified carboxymethyl cellulose nanofiber comprises the following steps: mixing a carboxymethyl starch solution with a sodium periodate solution, stirring the mixture in the dark at 18-25° C. for 16 hours, dialyzing and freeze-drying to obtain oxidized carboxymethyl starch; ultrasonically stirring carboxymethyl cellulose, polyvinyl alcohol and deionized water, then adding oxidized carboxymethyl starch, polyethylene oxide, polyethylene glycol octylphenyl ether and dimethyl sulfoxide and mixing the mixture to obtain an electrospinning solution, transferring the mixture to a syringe for electrospinning at a flow rate of 300 μL / h and a voltage of 18 kV to obtain nanofibers; mixing adipic acid dihydrazide, ethanol and deionized water to obtain an impregnation solution; immersing the nanofibers in the impregnation solution and shaking the mixture for 5 hours, washing the mixture with deionized water and ethanol in turn, and drying the mixture with chloroform to obtain the modified carboxymethyl cellulose nanofibers.

7. The method for preparing a MOF / cellulose hydrogel according to claim 6, characterized in that: The mass ratio of the carboxymethyl cellulose, polyvinyl alcohol and oxidized carboxymethyl starch is 1:2:0.7; the mass volume ratio of the nanofibers to the impregnation liquid is 1g:1L.

8. A MOF / cellulose hydrogel, characterized in that The compound is prepared by any one of the preparation methods of claims 1 to 7.

9. The use of a MOF / cellulose hydrogel according to claim 8, characterized in that: Used to prevent external wound infections.

10. The use of a MOF / cellulose hydrogel according to claim 8, characterized in that: The MOF / cellulose hydrogel is carbonized under nitrogen to obtain a porous lightweight conductive material with high conductivity and high specific surface area.

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