Metal-organic framework composites based on bacterial cellulose, their preparation and application

Abstract

This invention discloses a metal-organic framework composite material based on bacterial cellulose, its preparation method, and its antibacterial application. The metal-organic framework composite material comprises bacterial cellulose and a metal-organic framework material grown on the bacterial cellulose; the metal-organic framework material is formed by the substitution coordination linking of an organic ligand with a Zr6 metal cluster; the organic ligand has the following chemical structure: the Zr6 metal cluster has the following chemical structure:

Description

Technical Field

[0001] This invention relates to the field of metal-organic framework composites, and more specifically to a bacterial cellulose-based metal-organic framework composite material, its preparation method, and its application. Background Technology

[0002] Infectious pathogens pose a serious public safety problem globally and can severely disrupt global commerce and human health, making the development of safeguards against these biological threats urgent. However, the sporadic nature of outbreaks and the threat of new diseases caused by emerging pathogens complicate and challenge the development of protective technologies. A significant mode of transmission for these pathogens is through express delivery packaging and fabrics; studies have demonstrated that pathogens can survive on packaging bags and fabrics for several days, increasing the spread of infectious diseases. Given this challenge, sterilization of packaging and fabric materials is an effective strategy to reduce microbial contamination and further pathogen transmission. In particular, the development of photosensitive self-antimicrobial materials is one promising approach.

[0003] Metal-organic frameworks (MOFs) are three-dimensional or two-dimensional crystalline porous materials composed of secondary structural units and organic ligands. They possess high tunability, skeletal rigidity, and high water stability, and through the rational selection of metal clusters and organic ligands, they can become promising photosensitizers. Patent specification CN115772272A discloses a silver-modified two-dimensional metal-organic framework nanomaterial, its preparation method, and its application in the preparation of antibacterial products. This patented technology complexes iron-containing organic ligands with Zr ions to form Zr-Fc-MOF nanosheets with photothermal properties. Ag is loaded onto the Zr-Fc-MOF nanosheets using an in-situ reduction method under xenon lamp irradiation to synthesize Zr-Fc-MOF@Ag materials. The photothermal properties of this antibacterial material can accelerate the release of silver ions to achieve a highly efficient antibacterial effect. The patent specification with publication number CN113875771A discloses the application of Zr-MOF nanomaterials in the preparation of photocatalytic antibacterial materials. Zr-MOF nanomaterials are formed by the complexation of Zr ions with organic ligands containing benzothiazole. The presence of benzothiazole endows MOFs with the ability to generate photoactive oxygen. Mechanism studies have shown that the generation of singlet oxygen is the main reason for the bactericidal effect of this Zr-MOF.

[0004] Bacterial cellulose is a natural cellulose synthesized by certain bacteria, particularly *Acetobacter xylitol*. Unlike cellulose derived from plants or wood, bacterial cellulose possesses a unique three-dimensional structure with an ultrafine nanofiber network. Furthermore, it exhibits excellent physical and mechanical properties, including high purity and degree of polymerization, superior fabric strength, high porosity, and good biocompatibility. It serves as a photosensitizer carrier suitable for bio-antibacterial applications, and the resulting composite materials can be used as packaging and textile raw materials. Summary of the Invention

[0005] In the first aspect, the present invention provides a metal-organic framework composite material based on bacterial cellulose, which is novel in design, easy to synthesize, and has excellent properties, with high stability and excellent antibacterial effect, and is a promising photosensitive self-antibacterial material.

[0006] A metal-organic framework composite material based on bacterial cellulose (represented as Zr-TSS@BC) comprises bacterial cellulose (BC) and a metal-organic framework material (represented as Zr-TSS) grown on the bacterial cellulose.

[0007] The metal-organic framework material is formed by the substitution coordination linking of organic ligands (which can be represented as TSS) and Zr6 metal clusters (Zr6 cluster);

[0008] The organic ligand has the following chemical structure:

[0009]

[0010] The Zr6 metal clusters have the following chemical structures:

[0011]

[0012] In the process of substitution coordination, the organic ligand forms a coordination link with the Zr6 metal cluster by substituting the OCO in the Zr6 metal cluster with the same structure using its carboxyl group.

[0013] The aforementioned metal-organic framework composite material based on bacterial cellulose can be formed by in-situ growth on bacterial cellulose through the substitution of coordination between organic ligands and Zr6 metal clusters.

[0014] In a second aspect, the present invention provides a method for preparing the metal-organic framework composite material based on bacterial cellulose as described in the first aspect, wherein a mixed solution of DMF (N,N-dimethylformamide) and FA (formic acid) containing the organic ligand, ZrOCl2 and bacterial cellulose membrane is subjected to a solvothermal reaction to obtain the metal-organic framework composite material.

[0015] The process of in-situ loading of metal-organic frameworks onto bacterial cellulose membranes to form composite materials can be found in [reference needed]. Figure 1 .

[0016] This invention first selects a suitable photosensitizer carrier—a bacterial cellulose membrane—and then loads a stable metal-organic framework (MOF) onto it under specific and suitable conditions to prepare a novel and stable MOF composite material. This MOF composite material exhibits good stability and excellent photosensitivity, and demonstrates superior antibacterial properties under simulated fluorescent lighting conditions. The aforementioned MOF composite material is stable, has a wide range of applications, high practical value, and can be used repeatedly and for extended periods.

[0017] The preparation method of the organic ligand may include: adding 1,1,2,2-tetra(thiophen-2-yl)ethylene to tetrahydrofuran under anhydrous and oxygen-free conditions, adding butyllithium at -75 to -80°C, mixing and reacting thoroughly at -80°C to room temperature, then introducing carbon dioxide gas at -75 to -80°C and stirring continuously for a period of time, then quenching the reaction with hydrochloric acid, and extracting with dichloromethane. The resulting organic phase is washed with saturated brine, dried with anhydrous sodium sulfate, and the organic solvent is evaporated to obtain the organic ligand.

[0018] 1,1,2,2-tetratetra(thiophen-2-yl)ethylene can be prepared by referring to existing technical literature Chem. Sci., 2017, 8, 2629-2639.

[0019] In the preparation method of the organic ligand, the ratio of 1,1,2,2-tetra(thiophene-2-yl)ethylene to tetrahydrofuran can be 0.5-1.5 g: 100 mL.

[0020] In the preparation method of the organic ligand, the molar ratio of 1,1,2,2-tetra(thiophene-2-yl)ethylene to butyllithium can be 0.5 to 1.5:10.

[0021] In the preparation method of the organic ligand, the butyllithium can be added in the form of a butyllithium n-hexane solution.

[0022] In the method for preparing the organic ligand, the concentration of butyllithium in the hexane solution of butyllithium can be 2-3 M.

[0023] In the preparation method of the organic ligand, an excess of carbon dioxide gas may be introduced.

[0024] In the method for preparing the organic ligand, the temperature of the continuously stirred reaction can be -80℃ to room temperature.

[0025] In the preparation method of the bacterial cellulose-based metal-organic framework composite material, the mass ratio of ZrOCl2 to the organic ligand can be no less than 2:1.

[0026] In the preparation method of the bacterial cellulose-based metal-organic framework composite material, the mass ratio of the bacterial cellulose membrane to the organic ligand is 2g:25-35mg.

[0027] In the preparation method of the bacterial cellulose-based metal-organic framework composite material, the volume ratio of DMF to FA can be 1:0.5 to 0.7.

[0028] In the preparation method of the bacterial cellulose-based metal-organic framework composite material, the ratio of the organic ligand to DMF can be 30 mg: 1-3 mL.

[0029] In the preparation method of the bacterial cellulose-based metal-organic framework composite material, the temperature of the solvothermal reaction can be 125-135℃ and the time can be 15-25h.

[0030] In the preparation method of the metal-organic framework composite material based on bacterial cellulose, the mixed solution can be obtained by first ultrasonically mixing the organic ligand, ZrOCl2, bacterial cellulose and DMF, and then adding FA and ultrasonically mixing again.

[0031] In the preparation method of the metal-organic framework composite material based on bacterial cellulose, after the solvothermal reaction is completed, the following post-processing operation can be performed: take the solid product, wash and soak it with DMF, then wash and soak it with acetone, and dry it to obtain the metal-organic framework composite material.

[0032] Thirdly, the present invention provides the use of the bacterial cellulose-based metal-organic framework composite material described in the first aspect for antibacterial activity under visible light.

[0033] The bacterial cellulose-based metal-organic framework composite material can be used to resist Staphylococcus aureus under visible light.

[0034] The bacterial cellulose-based metal-organic framework composite material was first sterilized in 75 vol% ethanol for 24 hours, followed by solvent exchange with acetone for 24 hours, then air-dried and stored in a sealed container. All culture media (nutrient agar and nutrient broth) and other materials were autoclaved at 121°C for 30 minutes to avoid contamination by other bacteria.

[0035] In actual experiments, Gram-positive bacterial strains were selected to representatively determine the antibacterial effect of Zr-TSS@BC, and the effectiveness of the antibacterial treatment was determined according to the AATCC TM100-2019 evaluation method for antimicrobial textiles. After two hours of simulated fluorescent lamp irradiation, BC and Zr-TSS@BC showed significant differences in antibacterial activity. According to calculations, BC had almost no antibacterial effect, while Zr-TSS@BC achieved an antibacterial rate of approximately 98%. This is attributed to the high porosity and specific surface area of ​​the composite material; on the other hand, the high stability and strong photosensitivity of MOF contribute to the excellent antibacterial performance of the composite material, making it stable and suitable for long-term and repeated use.

[0036] As a general inventive concept, in a fourth aspect, the present invention provides the use of the metal-organic framework material described in the first aspect for antibacterial activity under visible light.

[0037] Compared with the prior art, the beneficial effects of this invention are as follows:

[0038] 1. This invention creatively designs and synthesizes a novel and stable metal-organic framework composite material.

[0039] 2. The preparation method of the composite material provided by the present invention is simple, easy to operate, has high yield and low cost, and is suitable for large-scale synthesis.

[0040] 3. The composite material designed in this invention has excellent antibacterial properties under visible light.

[0041] 4. The metal-organic framework composite material provided by this invention has high stability and practical value, and has a wide range of applications. Attached Figure Description

[0042] Figure 1 A schematic diagram of a composite material formed by loading a metal-organic framework onto a bacterial cellulose membrane.

[0043] Figure 2 The following are powder X-ray diffraction (PXRD) images of Zr-TSS, Zr-TSS@BC, and bacterial cellulose membrane (labeled BC) in Example 1.

[0044] Figure 3 The images are scanning electron microscope (SEM) images of Zr-TSS@BC and bacterial cellulose membrane (labeled BC) from Example 1.

[0045] Figure 4 This is a comparison chart of the amount of bacteria remaining after the antibacterial experiment between Zr-TSS@BC and bacterial cellulose membrane (labeled BC) in Example 2. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] Example 1

[0048] 1 g of 1,1,2,2-tetra(thiophene-2-yl)ethylene was weighed into a 250 mL flask with a side arm. The system was purged under a nitrogen atmosphere and 100 mL of anhydrous tetrahydrofuran was introduced under anhydrous and oxygen-free conditions. The flask was then placed in a cryogenic bath at -78 °C. 11.2 mL of a 2.5 M butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the mixture was stirred at -78 °C for 30 min. The system was then transferred to room temperature and stirred for 3 h to promote complete lithiation. The system gradually became a turbid liquid. The system was then transferred back to -78 °C, and carbon dioxide (CO2) gas was continuously introduced. The cryogenic refrigeration was turned off, and the mixture was stirred overnight. The reaction was quenched with 2 M hydrochloric acid, and the mixture was extracted twice with dichloromethane. The combined organic phases were washed with saturated brine, and then dried over anhydrous sodium sulfate. The organic solvent was evaporated to obtain product TSS (1.46 g, 98% yield). 1 H NMR (600MHz, DMSO-d6): δ13.31(s,4H),7.61(d,4H),7.01(d,4H).

[0049] The prepared TSS (30 mg) and ZrOCl2 (60 mg) were placed in a 15 mL Pyrex vial, and then 2 mL of DMF and 0.6 mL of FA were added. The solution was sonicated until clear, and then placed in a 130 °C oven for a solvothermal reaction for two days. After cooling to room temperature, the mother liquor was removed by centrifugation, and the solution was washed twice with fresh DMF. It was then soaked in DMF for two days, replacing the DMF three times, and then soaked in acetone for two days, replacing the acetone three times. The metal-organic framework material, named Zr-TSS, was obtained by vacuum drying at 60 °C, with a yield of 90%.

[0050] Take the prepared TSS (30 mg) and ZrOCl2 (60 mg) into a 15 mL Pyrex vial, add 4 pieces of bacterial cellulose membrane (size: 1 cm × 1 cm, about 2 g in total) and 2 mL DMF, and sonicate for 5 h until homogeneous. Then add 1.2 mL FA and sonicate for 5 h until homogeneous. Place in a 130℃ oven for solvothermal reaction for 15 h. After cooling to room temperature, remove the mother liquor and wash twice with fresh DMF. Then soak in DMF for two days, replacing the DMF three times during this period, and then soak in acetone for two days, replacing the acetone three times during this period. Dry in air at room temperature to obtain the metal-organic framework composite material, named Zr-TSS@BC.

[0051] The synthesized Zr-TSS@BC was subjected to X-ray powder diffraction (PXRD) and scanning electron microscopy (SEM) analyses. PXRD image ( Figure 2The curve of Zr-TSS@BC is basically consistent with that of Zr-TSS, indicating that Zr-TSS has successfully grown on BC. SEM further shows that Zr-TSS grows uniformly on BC, which is completely different from the blank BC.

[0052] Example 2

[0053] Antibacterial test methods:

[0054] Step (1): Zr-TSS@BC from Example 1 was sterilized in 75 vol% ethanol for 24 hours, followed by solvent exchange with acetone for 24 hours, then air-dried and stored in a sealed container. All culture media (nutrient agar and nutrient broth) and other materials were autoclaved at 121°C for 30 minutes.

[0055] Step (2): Dilute the activated test Staphylococcus aureus strain to approximately 2 × 10⁻⁶. 7 CFU / mL, 10 μL of inoculum was added to the bacterial cellulose membrane and Zr-TSS@BC (1 cm × 1 cm) from Example 1. Then, it was incubated under a fluorescent lamp (PHILIPSTLD 18W / 865YZ18RR25COOLDAYLIGHT 6500K) at approximately 15.38 W / m². 2 The samples were irradiated with light for 2 hours. Immediately after irradiation, 990 μL of phosphate-buffered saline (PBS) was added to each sample, and the solution was vigorously shaken for 1 minute to wash away any adhering bacteria. The solution containing the recovered bacteria was then serially diluted with PBS and placed on agar plates. The agar plates were then incubated at 37°C for 18 hours, and bacterial counts were obtained for each sample. According to the calculations, the bacterial cellulose membrane had almost no antibacterial effect, while Zr-TSS@BC achieved an antibacterial rate of approximately 98%.

[0056] In addition, we also recycled Zr-TSS@BC and conducted a second antibacterial experiment under light after ethanol sterilization. The antibacterial rate still reached about 97%, which further proved the stability and reusability of the composite material.

[0057] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A metal-organic framework composite material based on bacterial cellulose, characterized in that, Includes bacterial cellulose and metal-organic framework materials grown on the bacterial cellulose; The metal-organic framework material is formed by the substitution coordination linking of organic ligands with Zr6 metal clusters; The organic ligand has the following chemical structure: The Zr6 metal clusters have the following chemical structures:

2. The method for preparing the bacterial cellulose-based metal-organic framework composite material according to claim 1, characterized in that, A mixed solution of DMF and FA containing the organic ligand, ZrOCl2, and bacterial cellulose membrane was subjected to a solvothermal reaction to obtain the metal-organic framework composite material.

3. The preparation method according to claim 2, characterized in that, The method for preparing the organic ligand includes: adding 1,1,2,2-tetra(thiophen-2-yl)ethylene to tetrahydrofuran under anhydrous and oxygen-free conditions, adding butyllithium at -75 to -80°C, mixing and reacting thoroughly at -80°C to room temperature, then introducing carbon dioxide gas at -75 to -80°C and continuously stirring the reaction for a period of time, then quenching the reaction with hydrochloric acid, and extracting with dichloromethane. The resulting organic phase is washed with saturated brine, dried with anhydrous sodium sulfate, and the organic solvent is evaporated to obtain the organic ligand.

4. The preparation method according to claim 3, characterized in that, In the preparation method of the organic ligand: The ratio of 1,1,2,2-tetra(thiophene-2-yl)ethylene to tetrahydrofuran is 0.5–1.5 g: 100 mL; The molar ratio of 1,1,2,2-tetra(thiophen-2-yl)ethylene to butyllithium is 0.5–1.5:10; The butyllithium was added in the form of a butyllithium n-hexane solution; The concentration of butyllithium in the hexane solution is 2-3 M; Excessive carbon dioxide gas was introduced; The temperature of the continuously stirred reaction is -80℃ to room temperature.

5. The preparation method according to claim 2, characterized in that, The mass ratio of ZrOCl2 to the organic ligand is not less than 2:1; The mass ratio of the bacterial cellulose membrane to the organic ligand is 2g:25-35mg; The volume ratio of DMF to FA is 1:0.5 to 0.7; The ratio of the organic ligand to DMF is 30 mg: 1-3 mL; The solvothermal reaction is carried out at a temperature of 125–135°C for a duration of 15–25 h.

6. The preparation method according to claim 2, characterized in that, The mixed solution was obtained by first ultrasonically mixing the organic ligand, ZrOCl2, bacterial cellulose and DMF, and then adding FA and ultrasonically mixing again.

7. The preparation method according to claim 2, characterized in that, After the solvothermal reaction is completed, the following post-processing operations are performed: the solid product is washed and soaked with DMF, then washed and soaked with acetone, and dried to obtain the metal-organic framework composite material.

8. The use of the bacterial cellulose-based metal-organic framework composite material according to claim 1 for antibacterial activity under visible light.

9. The use according to claim 8, characterized in that, The bacterial cellulose-based metal-organic framework composite material is used to resist Staphylococcus aureus under visible light.

10. The use of a metal-organic framework material for antibacterial activity under visible light, characterized in that, The metal-organic framework material is formed by the substitution coordination linking of organic ligands with Zr6 metal clusters; The organic ligand has the following chemical structure: The Zr6 metal clusters have the following chemical structures:

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