Metal-organic framework material with hollow structure and preparation method and application thereof

Abstract

The application discloses a metal organic framework material with a hollow structure and a preparation method and application thereof. The preparation method comprises the following steps: dissolving sodium deoxycholate in a buffer solution to form solution A, dissolving zinc nitrate hexahydrate in water to form solution B, stirring solution A in a water bath, then adding solution B to continue stirring, obtaining solution C after separation and dispersion, adding an organic ligand to solution C to react, and centrifuging, washing and drying the product to obtain the metal organic framework material with the hollow structure. The method has the advantages of simple operation, easy process control, high economy, wide popularization, fast transmission quality of the prepared MOFs material, high porosity, rich active components, more exposed active sites, good compatibility to harsh conditions, and wide application prospects in the fields of separation, sensing, catalysis, drug release and energy.

Description

Technical Field

[0001] This invention belongs to the field of functional materials synthesis technology, specifically relating to a metal-organic framework material with a hollow structure, its preparation method, and its application. Background Technology

[0002] Metal-organic frameworks (MOFs) are porous inorganic-organic hybrid materials with periodic network structures formed by the self-assembly of metal ions and organic ligands. Generally, MOF materials can be classified into three main categories based on different synthesis methods and component units: First, network-type MOFs, with MOF-5 being a representative structure; second, zeolite-based imidazole frameworks (ZIFs); and third, Lavoisier frameworks (MILs). MOFs possess characteristics such as tunable pore size, large specific surface area, high porosity, regular channels, and the diversity and modifiability of organic ligands. Their unique properties make them important for applications in hydrogen storage, gas adsorption and separation, sensors, drug delivery, and catalytic reactions. In recent years, metal-organic frameworks (MOFs) have attracted increasing attention.

[0003] Hollow MOFs are a special type of micro / nanostructure. Compared to solid structures, hollow structures give MOFs significant advantages, such as faster mass transport, higher porosity, richer active components, more exposed active sites, and better compatibility with harsh conditions. Therefore, materials based on hollow MOFs have broad application prospects in separation, sensing, catalysis, drug delivery, adsorption, and energy. Chinese invention patent CN113336955A discloses a hollow rare earth-based MOF material based on a solvothermal method. Lanthanide metal salts, 1,3,5-benzenetricarboxylic acid (H3BTC), and thiophene-2,5-dicarboxylic acid (H2TDC) are placed separately in a reactor and dissolved in a solvent. The three solutions are then mixed and heated in a closed system. Finally, the reaction products are subjected to solid-liquid separation and washing to obtain the hollow rare earth-based MOF material. This method uses H2TDC as a reaction promoter, H3BTC as an organic ligand, and lanthanide metals as the core to synthesize novel hollow spherical lanthanide metal-organic frameworks via a solvothermal method. Furthermore, Chinese invention patent CN111056545A discloses a method for preparing hollow porous carbon microspheres derived from metal-organic frameworks (MOFs), including the preparation and surface carboxylation of metal oxide (MOx) microspheres, the layer-by-layer growth of MOFs on the surface of MOx microspheres to obtain a MOx@MOFs core-shell structure composite material, the impregnation of MOx@MOFs with an organic small molecule crosslinking agent, followed by crosslinking and carbonization, and finally acid or alkali washing to obtain hollow porous carbon microspheres.

[0004] However, compared with solid MOFs, the synthesis of hollow MOFs is more challenging due to the increased structural complexity. The preparation methods disclosed in the aforementioned invention patents are relatively cumbersome and the reaction process is not easy to control. Therefore, providing a simple, more controllable, easy-to-promote, and economical synthesis method is an urgent problem to be solved in the development of MOFs. Summary of the Invention

[0005] This invention provides a metal-organic framework material with a hollow structure, its preparation method, and its application. The purpose is to provide a preparation method that is simple to operate, has a controllable process, is easy to promote, and is economical, in order to prepare MOF materials with better performance.

[0006] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0007] When sodium deoxycholate and zinc nitrate hexahydrate are mixed and heated, the hydroxyl functional group in sodium deoxycholate reacts with Zn... 2+ The product undergoes coordination and cross-linking to form a gel-like three-dimensional network structure;

[0008] Organic ligands are added to the product to react and a binary complex is obtained; the binary complex undergoes self-assembly and post-processing to obtain a metal-organic framework material with a hollow structure.

[0009] Further, the above preparation method includes dissolving sodium deoxycholate in a buffer solution to form solution A, dissolving zinc nitrate hexahydrate in water to form solution B, heating and stirring solution A in a water bath, adding solution B and continuing stirring, whereby the hydroxyl functional groups in sodium deoxycholate react with Zn... 2+ The product undergoes coordination and crosslinking to form a gel-like three-dimensional network structure. After separation and dispersion, solution C is obtained. Organic ligands are added to solution C to react and obtain the binary complex. The binary complex undergoes self-assembly and post-processing to obtain a metal-organic framework material with a hollow structure.

[0010] Furthermore, the buffer solution is a PBS buffer solution with a pH of 5-10.

[0011] Furthermore, the molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:1-4.

[0012] Further, solution A is heated to 25℃-70℃ and stirred for 1h-5h before solution B is added.

[0013] Further, after adding solution B, stir for 0.5h-2h.

[0014] Further, the organic ligand is any one or a combination of two or more of 2-methylimidazole, 2-ethylimidazole, 1-ethylimidazole, 1-methylimidazole, 2-nitroimidazole, pyrazole, and benzimidazole.

[0015] Further, the organic ligand is added and the reaction proceeds for 1-6 hours.

[0016] Furthermore, the post-processing specifically includes centrifuging the product, washing it sequentially with the PBS and deionized water, and finally drying it at 80℃-100℃ for 10-24h.

[0017] Furthermore, the dispersion specifically includes adding 30 mL to 50 mL of deionized water to form solution C.

[0018] The invention provides a method for preparing metal-organic framework materials with hollow structures, and their applications in separation, sensing, catalysis, drug release, or energy fields.

[0019] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0020] 1. The preparation method used in this invention is simple to operate, low in cost, and has a short reaction time, which greatly reduces the cost of raw materials and equipment, and has high stability and repeatability.

[0021] 2. The MOFs materials prepared by this invention are different from solid structures, having a unique hollow structure. They have characteristics such as fast mass transfer, high porosity, uniform distribution of mass transfer pores, rich active components, more exposed active sites, and better compatibility with harsh conditions.

[0022] 3. The method employed in this invention enables the large-scale production of hollow MOFs with high yield. The mild reaction environment results in lower industrial costs, and the obtained products hold promise for further applications in separation, sensing, catalysis, drug delivery, and energy. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is an X-ray diffraction pattern of the MOF powder in Example 1 of this application.

[0025] Figure 2 This is a scanning electron microscope image of the MOF powder in Example 1 of this application.

[0026] Figure 3 This is a transmission electron microscope (TEM) image of the MOF powder in Example 1 of this application.

[0027] Figure 4 This is the Fourier transform infrared spectrum of the MOF powder in Example 1 of this application.

[0028] Figure 5 This is a thermogravimetric curve of the MOF powder in Example 1 of this application.

[0029] Figure 6 This is a pore size distribution diagram of the MOF powder in Example 1 of this application.

[0030] Figure 7 This is a scanning electron microscope image of the MOF powder in Comparative Example 3 of this application. Detailed Implementation

[0031] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0032] This invention provides a method for preparing a metal-organic framework material with a hollow structure, comprising dissolving sodium deoxycholate in a buffer solution to form solution A, dissolving zinc nitrate hexahydrate in water to form solution B, heating and stirring solution A in a water bath, adding solution B and continuing stirring, separating and dispersing to obtain solution C, adding an organic ligand to solution C to react, and post-processing the product to obtain a metal-organic framework material with a hollow structure.

[0033] Specifically, the organic ligand includes any one or a combination of two or more of 2-methylimidazole, 2-ethylimidazole, 1-ethylimidazole, 1-methylimidazole, 2-nitroimidazole, pyrazole, and benzimidazole. The post-processing specifically includes centrifuging the product, washing it sequentially with the PBS and deionized water, and finally drying it at 80℃-100℃ for 10-24 h.

[0034] In this application, under appropriate conditions, such as pH value and ionic strength, the hydroxyl functional groups in sodium deoxycholate molecules coordinate with metal ions to form a cross-linked structure. These cross-linked structures are connected together by different interaction forces (such as hydrogen bonds and van der Waals forces) to form a three-dimensional network structure, thereby forming a gel state. The nitrogen atoms in the organic ligand interact with the Zn atoms in the gel. 2+Ions coordinate to form a binary complex, which then undergoes self-assembly within a spatial range to form a crystal structure with relatively uniform pore size. Using a metal-NaDC hydrogel as a soft template, a hollow MOF-based composite material, H-ZIF-8, was constructed using a simple method. H-ZIF-8 consists of multiple stacked structural units, exhibiting a highly ordered pore structure and good chemical stability, making it suitable for applications in adsorption, catalysis, and sensing.

[0035] Example 1

[0036] This embodiment provides a metal-organic framework material with a hollow structure. Specifically, the preparation method is as follows:

[0037] Dissolve 50 mg of sodium deoxycholate in 10 mL of PBS buffer solution with pH = 7. Place the solution in a round-bottom flask and stir in a 25°C water bath for 3 hours until the solution turns milky white. Then add 10 mL of zinc nitrate hexahydrate solution and continue stirring for 30 min. The molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:1.

[0038] The obtained product was centrifuged, and 30 mL of deionized water was added for dispersion. Then, 2-methylimidazole was added and reacted for 1 h. The product was centrifuged again, washed three times with PBS and deionized water, and finally dried in an 80°C oven for 24 h to obtain the target MOF powder with a hollow structure.

[0039] Performance Characterization

[0040] See Figure 1 The image shows the X-ray diffraction pattern of the MOF powder in Example 1. It can be seen that the MOF powder prepared in Example 1 exhibits characteristic peaks of ZIF-8. The X-ray diffraction (XRD) pattern of H-ZIF-8 contains the main crystal planes of ZIF-8, with peaks at 7.5°, 10.5°, and 12.5°, demonstrating the successful formation of H-ZIF-8 crystals. (See also...) Figure 2 The image shown is a scanning electron microscope (SEM) image of the MOF powder in Example 1. It clearly shows that the MOF powder forms a hollow framework structure. Figure 3 The image shows a transmission electron microscope (TEM) image of the MOF powder in Example 1. The MOF powder in the image is hollow, forming a framework structure with a diameter of 60-70 nm. Figure 4 The Fourier transform infrared spectrum of the MOF powder in Example 1 is shown at 421 cm⁻¹. 1 A stretching peak of ZIF-8 appeared. Figure 5 This is a thermogravimetric curve of the MOF powder in Example 1. The thermogravimetric curve of the MOF powder prepared in Example 1 is approximately the same as the standard ZIF-8 thermogravimetric curve. Figure 1 To. Figure 6This is a pore size distribution diagram of the MOF powder in Example 1. It shows that the powder has an average pore size of 1.48 nm, relatively uniform pore size, and high porosity, which enables faster mass transfer.

[0041] Example 2

[0042] This embodiment provides a metal-organic framework material with a hollow structure. Specifically, the preparation method is as follows:

[0043] Dissolve 50 mg of sodium deoxycholate in 10 mL of PBS buffer solution (pH 7). Place the solution in a round-bottom flask and stir in a 25°C water bath for 5 hours until the solution turns milky white. Add 10 mL of zinc nitrate hexahydrate solution and continue stirring for 30 minutes. The molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:1.

[0044] The obtained product was centrifuged and dispersed in 30 mL of deionized water. Then, 2-methylimidazole was added and reacted for 1 h.

[0045] The product was centrifuged, washed three times with PBS and deionized water, and finally dried in a 100℃ oven for 10 hours to obtain the target MOF powder with a hollow structure.

[0046] Example 3

[0047] This embodiment provides a metal-organic framework material with a hollow structure. Specifically, the preparation method is as follows:

[0048] Dissolve 50 mg of sodium deoxycholate in 10 mL of PBS buffer solution (pH 7). Place the solution in a round-bottom flask and stir in a 25°C water bath for 5 hours until the solution turns milky white. Add 10 mL of zinc nitrate hexahydrate solution and continue stirring for 1 hour. The molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:4.

[0049] The obtained product was centrifuged and dispersed in 50 mL of deionized water. Then, 2-methylimidazole was added and reacted for 2 h.

[0050] The product was centrifuged, washed three times with PBS and deionized water, and finally dried in a 90℃ oven for 15 hours to obtain the target MOF powder with a hollow structure.

[0051] Example 4

[0052] This embodiment provides a metal-organic framework material with a hollow structure. Specifically, the preparation method is as follows:

[0053] Dissolve 50 mg of sodium deoxycholate in 10 mL of PBS buffer solution (pH 7). Place the solution in a round-bottom flask and stir in a 35°C water bath for 2 hours until the solution turns milky white. Add 10 mL of zinc nitrate hexahydrate solution and continue stirring for 2 hours. The molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:1.

[0054] The obtained product was centrifuged and dispersed in 30 mL of deionized water. Then, 2-methylimidazole was added and reacted for 2 h.

[0055] The product was centrifuged, washed three times with PBS and deionized water, and finally dried in a 90℃ oven for 18 hours to obtain the target MOF powder with a hollow structure.

[0056] Example 5

[0057] The only difference between Example 5 and Example 1 is that the pH of the PBS buffer solution in Example 5 is 5, while the other conditions are the same as in Example 1.

[0058] Example 6

[0059] The only difference between Example 6 and Example 1 is that the pH of the PBS buffer solution in Example 6 is 10, while the other conditions are the same as in Example 1.

[0060] Example 7

[0061] The only difference between Example 7 and Example 1 is that in Example 7, 50 mg of sodium deoxycholate was dissolved in 10 mL of PBS buffer solution with a pH of 7. The solution was then placed in a round-bottom flask and stirred in a 70°C water bath for 1 hour until the solution turned milky white. All other conditions remained the same as in Example 1.

[0062] Example 8

[0063] The only difference between Example 8 and Example 1 is that in Example 8, the added organic ligand is 2-ethylimidazole. All other conditions are the same as in Example 1.

[0064] Example 9

[0065] The only difference between Example 9 and Example 1 is that in Example 9, the added organic ligand is 1-ethylimidazole. All other conditions are the same as in Example 1.

[0066] Example 10

[0067] The only difference between Example 10 and Example 1 is that in Example 10, the added organic ligand is 2-nitroimidazole. All other conditions are the same as in Example 1.

[0068] Example 11

[0069] The only difference between Example 11 and Example 1 is that in Example 11, the added organic ligand is a mixture of pyrazole and benzimidazole in a molar ratio of 1:1. All other conditions are the same as in Example 1.

[0070] Example 12

[0071] The only difference between Example 11 and Example 1 is that in Example 11, the reaction time for adding the organic ligand is 6 hours. All other conditions are the same as in the Example.

[0072] Comparative Example 1

[0073] The only difference between Comparative Example 1 and Example 1 is that the pH of the PBS buffer is 3, while the other conditions are the same as in Example 1.

[0074] The results showed that excessive acidity was not conducive to the formation of spherical deoxygenated sodium vanadate gels, and therefore a hollow structure could not be formed.

[0075] Comparative Example 2

[0076] The only difference between Comparative Example 2 and Example 1 is that the pH of the PBS buffer is 12, while the other conditions are the same as in Example 1.

[0077] The results showed that excessive alkalinity was not conducive to the formation of spherical deoxygenated sodium vanadate gels, and a hollow structure could not be formed.

[0078] Comparative Example 3

[0079] The only difference between Comparative Example 3 and Example 1 is that the molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:6. All other conditions are the same as in Example 1.

[0080] See Figure 7 The image shown is a scanning electron microscope image of the MOF powder in Comparative Example 3. When the molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is outside the range, a hollow structure cannot be formed. This phenomenon can be attributed to the structure of the hydroxyl and carboxyl groups of sodium deoxycholate, which affects the interaction between sodium deoxycholate and metal ions.

[0081] Comparative Example 4

[0082] The only difference between Comparative Example 4 and Example 1 is the addition of an organic ligand and a reaction time of 30 min. All other conditions are the same as in Example 1.

[0083] The results showed that if the reaction time was too short after adding the organic ligand, the reaction would be incomplete and a good hollow structure could not be formed.

[0084] In summary, this invention provides a method for preparing a metal-organic framework material with a hollow structure, specifically comprising dissolving sodium deoxycholate in a buffer solution to form solution A, dissolving zinc nitrate hexahydrate in water to form solution B, heating and stirring solution A in a water bath, adding solution B and continuing stirring, wherein the hydroxyl functional groups in sodium deoxycholate react with Zn... 2+ The product undergoes coordination and cross-linking to form a gel-like three-dimensional network structure. After separation and dispersion, solution C is obtained. Organic ligands are added to solution C to react and obtain a binary complex. The binary complex undergoes self-assembly, and after centrifugation, washing, and drying, a metal-organic framework material with a hollow structure is obtained.

[0085] Comparing Examples 1-12 with Comparative Examples 1-5 shows that the appropriate pH of the PBS buffer, the molar ratio of sodium deoxycholate to zinc nitrate hexahydrate, and the reaction time for adding the organic ligand have a significant impact on the performance of the product, and are beneficial to the interaction between the hydroxyl functional group in the sodium deoxycholate molecule and Zn. 2+ Coordination occurs, thereby forming a cross-linked structure.

[0086] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

Claims

1. A method for preparing a metal-organic framework material with a hollow structure, characterized in that... include: Sodium deoxycholate is dissolved in a buffer solution to form solution A, wherein the buffer solution is a PBS buffer solution with a pH of 5-10; Zinc nitrate hexahydrate is dissolved in water to form solution B; After heating solution A to 25-70°C and stirring for 1-5 hours, solution B is added, allowing the hydroxyl functional groups in sodium deoxycholate to react with Zn. 2+ The product undergoes coordination and cross-linking to form a gel-like three-dimensional network structure; The product of the three-dimensional network structure is then separated and dispersed to obtain solution C. An organic ligand is added to solution C to react and obtain a binary complex. The reaction is carried out for 1-6 hours after adding the organic ligand. The binary complex undergoes self-assembly and is then post-treated to obtain a metal-organic framework material with a hollow structure. The concentration of sodium deoxycholate is 5 mg / mL. The molar ratio of sodium deoxycholate to zinc nitrate hexahydrate is 1:1~4; After adding solution B, stir for 0.5 to 2 hours; The dispersion specifically includes adding 30-50 mL of deionized water to form solution C; The post-processing specifically includes centrifuging the product, washing it sequentially with the PBS and deionized water, and finally drying it at 80~100℃ for 10~24h.

2. The method for preparing a metal-organic framework material with a hollow structure according to claim 1, characterized in that: The organic ligand is any one or a combination of two or more of 2-methylimidazole, 2-ethylimidazole, 1-ethylimidazole, 1-methylimidazole, 2-nitroimidazole, and benzimidazole.

3. The method for preparing a metal-organic framework material with a hollow structure according to any one of claims 1-2, characterized in that: The hollow structure of the metal-organic framework material has a hollow structure diameter of 60~700nm; And / or, the average pore size of the mass transfer pores of the metal-organic framework material with a hollow structure is 1.48 nm.

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