Reduction-responsive metal organic framework material as well as preparation method and application thereof

Abstract

The invention provides a reduction response metal organic framework material and a preparation method and application thereof, and belongs to the field of nano sensing, an organic ligand of the metal organic framework material is diacid containing disulfide bonds, and coordination metal is Fe < 3 + >; the metal organic framework material is of a three-dimensional net structure. The invention provides a method for preparing a disulfide bond-based reductive response metal organic framework material by a solvothermal method, and a brand new metal organic framework structure is synthesized. The MOF-SS prepared by the method has disulfide bonds in an organic ligand structure, can realize response to a reducing agent (such as mercaptan), and enriches application choices of MOFs in the field of intelligent response. The obtained product is high in yield and uniform and stable in particle size, and the process is simple and non-toxic.

Description

Technical Field

[0001] The present invention relates to the field of nanosensing technology, and in particular to a reduction-responsive metal organic framework material and a preparation method and application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are a class of porous materials composed of metal ions or metal clusters connected to organic ligands through coordination bonds. Due to their structural diversity, high specific surface area, adjustable pore size and functionalized internal surface, MOFs have shown great application potential in gas storage, separation, catalysis, sensing and drug delivery. In recent years, the study of smart responsive materials has become a hot area in materials science. These materials can respond specifically to external physical, chemical or biological stimuli, thereby changing their physical or chemical properties. Such responses include but are not limited to temperature, light, electric field, magnetic field, pH value, ionic strength and reducing agents.

[0003] In the research of intelligent response, MOFs also show unique advantages. By rationally designing the types of metal ions and organic ligands, the structure and function of MOFs can be regulated to respond to specific external stimuli, thus being applied to fields such as sensing. Although significant progress has been made in many stimulus response studies, the current MOF intelligent response mostly utilizes the pH response of metal-organic joints or utilizes the modification and functionalization of existing MOFs to achieve response; while there are few studies on the reductive response of the organic ligands of MOFs materials themselves. Therefore, the development of a new type of reduction-responsive MOF has certain practical significance. Summary of the invention

[0004] In view of the technical problems existing in the background technology, the present application provides a reduction-responsive metal organic framework material and a preparation method and application thereof, aiming to solve the defect that existing MOFs need to rely on additional functional modifications to achieve reduction response.

[0005] In the first aspect, the present invention provides a reduction-responsive metal organic framework material, wherein the organic ligand of the metal organic framework material is 4,4'-dithiodibenzoic acid, and the coordination metal is Fe 3+ ; Metal-organic framework materials have a three-dimensional network structure.

[0006] In a second aspect, the present invention provides a method for preparing a reduction-responsive metal organic framework material, Fe 3+ The metal organic framework material is synthesized by solvothermal reaction with 4,4'-dithiodibenzoic acid and deionized water in a solvent.

[0007] Preferably, Fe 3+The source is soluble iron salts, including ferric chloride or ferric nitrate.

[0008] Preferably, Fe 3+ , the molar ratio of 4,4'-dithiodibenzoic acid and deionized water is 1:1:(110~550).

[0009] Preferably, the solvent is a small molecule alcohol, which includes methanol or ethanol.

[0010] Preferably, the solvothermal reaction step comprises: 3+ and 4,4'-dithiodibenzoic acid were dissolved in solvents to obtain Fe 3+ solution and 4,4'-dithiodibenzoic acid solution, Fe 3+ The solution is slowly added dropwise to the 4,4'-dithiodibenzoic acid solution, mixed and stirred evenly, then heated to 50-70°C, deionized water is added to initiate the reaction, and after reacting for 20-40 minutes, the metal organic framework material is obtained by centrifugation, washing and drying.

[0011] Preferably, the concentration of the 4,4'-dithiodibenzoic acid solution is 2-10 mg / mL.

[0012] Preferably, the reaction temperature after adding deionized water is 50-70°C.

[0013] In a third aspect, an embodiment of the present application provides an application of a reduction-responsive metal-organic framework material in analysis and detection based on reduction response.

[0014] Preferably, the invention is used in the detection of thiols.

[0015] Different from the existing technical solutions, the beneficial effects of this application include: This application provides a method for preparing a metal organic framework material (MOF-SS) based on disulfide bond reductive response by a solvothermal method, and synthesizes a new metal organic framework structure. The MOF-SS prepared by this method has a disulfide bond in the organic ligand structure, which can respond to reducing agents (such as thiols), enriching the application options of MOFs in the field of intelligent response. The obtained product has a high yield, uniform and stable particle size, and a simple and non-toxic process.

[0016] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is the X-ray diffraction pattern of MOF-SS prepared in Example 1 of the present application; Figure 2 is the hydrated particle size distribution of MOF-SS prepared in Examples 1 and 2 of the present application; Figure 3 This is a transmission electron microscopy image of the MOF-SS prepared in Example 1 of the present application; Figure 4 This is a graph showing the particle size-time variation of MOF-SS prepared in Example 1 of the present application; Figure 5 This is a graph showing the change in ultraviolet absorption of the solution before and after the reduction response of the MOF-SS prepared in Example 1 of the present application.

[0019] Figure 6 This is a diagram showing the actual changes in the solution before and after the reduction response of the MOF-SS prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0020] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0022] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0024] Currently, most MOF intelligent responses utilize the pH response of metal-organic joints or utilize the modification and functionalization of existing MOFs to achieve response; however, there are few studies that rely on the reductive response of the organic ligands of MOFs materials themselves.

[0025] In order to solve the defect that existing MOFs need to rely on additional functional modifications to achieve reductive response, the present application provides a reductively responsive metal organic framework material and its preparation method and application, wherein the present application provides a solvothermal method for preparing a reductively responsive metal organic framework material (MOF-SS) based on disulfide bonds, and synthesizes a new metal organic framework structure. The MOF-SS prepared by this method has a disulfide bond in the organic ligand structure, which can achieve response to reducing agents (such as thiols), enriching the application options of MOFs in the field of intelligent response.

[0026] In the first aspect, the present invention provides a reduction-responsive metal organic framework material, wherein the organic ligand of the metal organic framework material is a dibasic acid containing a disulfide bond, and the coordination metal is Fe 3+ ; Metal-organic framework materials have a three-dimensional network structure.

[0027] Preferably, the disulfide bond-containing dibasic acid includes one or more of 4,4'-dithiodibenzoic acid, 6,6'-dithiodicotinoic acid, 4,4'-dithiodiphenylacrylic acid, and 2,2'-dithioacetic acid.

[0028] In a second aspect, the present invention provides a method for preparing a reduction-responsive metal organic framework material, Fe 3+ The metal organic framework material is synthesized by solvothermal reaction with a dibasic acid containing a disulfide bond and deionized water in a solvent.

[0029] In the technical solution of the embodiment of the present application, Fe 3+ The self-assembly with the disulfide-containing diacid formed a metal organic framework material (MOF-SS) with disulfide bond reduction responsiveness. After adding deionized water, the carboxyl group of the disulfide-containing diacid was deprotonated and reacted with Fe 3+ The coordination bonds are formed and then self-assembled into a three-dimensional network structure. When the dibasic acid containing the disulfide bond is 4,4'-dithiodibenzoic acid, its two-dimensional structure is as follows: .

[0030] The disulfide bonds contained in MOF-SS can achieve reduction response. In the presence of reducing agents (such as thiols), the disulfide bonds are reduced and broken into thiol groups, and the three-dimensional network structure collapses. The reaction mechanism is as follows: .

[0031] Preferably, Fe 3+ The source is soluble iron salts.

[0032] Preferably, Fe 3+ , the molar ratio of the dibasic acid containing disulfide bonds and deionized water is 1:1: (110~550).

[0033] Preferably, the solvent is a small molecule alcohol.

[0034] Preferably, the solvothermal reaction step comprises: 3+ and a disulfide-bonded dibasic acid are dissolved in a solvent to obtain Fe 3+ solution and a disulfide-bonded dibasic acid solution to 3+ The solution is slowly added dropwise to the dibasic acid solution containing disulfide bonds, mixed and stirred evenly, then heated to 50-70°C, deionized water is added to initiate the reaction, and after reacting for 20-40 minutes, the reaction is centrifuged, washed, and dried to obtain a metal organic framework material.

[0035] Preferably, the concentration of the disulfide bond-containing dibasic acid solution is 2-10 mg / mL.

[0036] Preferably, the reaction temperature after adding deionized water is 50-70°C.

[0037] In a third aspect, an embodiment of the present application provides an application of a reduction-responsive metal-organic framework material in analysis and detection based on reduction response.

[0038] Preferably, the invention is used in the detection of thiols.

[0039] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0040] 1. Preparation method Example 1 The specific steps for preparing MOF-SS in this embodiment are as follows: (1) Dissolve 135 mg of ferric chloride hexahydrate in 50 mL of anhydrous ethanol and 152.2 mg of 4,4'-dithiodibenzoic acid in 50 mL of anhydrous ethanol; slowly drop the above ferric chloride hexahydrate solution into the 4,4'-dithiodibenzoic acid solution, mix the two solutions, and stir at 1500 rpm for 5 min. Transfer the reaction to a 50 ℃ oil bath, add 1000 μL of deionized water while stirring at 600 rpm, and after reacting for 20 min, the solution turns orange-yellow. Collect the product by centrifugation at 8000 rpm, and then wash it several times with anhydrous ethanol to obtain MOF-SS solid.

[0041] (2) The above MOF-SS solid was added into 20 mL of anhydrous ethanol and ultrasonically dispersed at 300 W for 2 min to obtain a MOF-SS nanoparticle solution, which was recorded as sample 1.

[0042] The specific steps of the reduction response of MOF-SS in this embodiment are as follows: Take 1 mL of the above MOF-SS solution and add β-mercaptoethanol. The solution does not change significantly. After slight heating, the solution becomes colorless.

[0043] Example 2 The specific steps for preparing MOF-SS in this embodiment are as follows: (1) Take 135 mg of ferric chloride hexahydrate and dissolve it in 50 mL of anhydrous ethanol. Take another 152.2 mg of 4,4'-dithiodibenzoic acid and dissolve it in 50 mL of anhydrous ethanol. Slowly add the above ferric chloride hexahydrate solution to the 4,4'-dithiodibenzoic acid solution. After the two solutions are mixed, stir at 1500 rpm for 5 min. Transfer the reaction to a 50 ℃ oil bath, add 1000 μL of deionized water while stirring at 600 rpm. After reacting for 20 min, the solution turns orange-yellow. Collect the product by centrifugation at 8000 rpm, and then wash it several times with anhydrous ethanol to obtain MOF-SS solid.

[0044] (2) The above MOF-SS solid was added to 20 mL of deionized water and ultrasonically dispersed at 300 W for 2 min to obtain a MOF-SS nanoparticle solution, which was recorded as Sample 2.

[0045] The specific steps of the reduction response of MOF-SS in this embodiment are as follows: Take 1 mL of the above MOF-SS solution and add β-mercaptoethanol. The solution does not change significantly. After slight heating, the solution becomes colorless.

[0046] 2. Test Method 1. Powder X-ray diffraction (XRD) test The MOF-SS prepared in Example 1 was freeze-dried, and the obtained powder was recorded on an X-ray diffractometer (Empyrean).

[0047] 2. Hydration particle size and Zeta potential test method Sample 1 and Sample 2 prepared in the above Example 1 and Example 2 were diluted with anhydrous ethanol and purified water respectively, and then ultrasonically treated for 1 minute to fully disperse the samples. The hydrated particle size distribution and Zeta potential were recorded on a Malvern particle size analyzer (Nano-ZS).

[0048] 3. Statistical method of particle size distribution The MOF-SS solution prepared in Example 1 was dropped onto a copper mesh. After the solvent was evaporated, the morphology of the nanoparticles was observed on a transmission electron microscope (JEM-1400plus), and the average particle size of the nanoparticles was calculated using Image.

[0049] 4. MOF-SS disulfide bond responsiveness test method Take two portions of 1 mL MOF-SS solution, add β-mercaptoethanol to one portion and add an equal volume of purified water to the other portion, heat the two solutions in an oil bath to 40-60 °C at the same time, and record the UV absorption spectra in the wavelength range of 200 nm to 400 nm on a UV spectrophotometer (UV-2600).

[0050] III. Analysis of test results of various embodiments and comparative examples (1) The MOF-SS prepared in Example 1 was subjected to powder X-ray diffraction (XRD) test. Figure 1 As shown, the characteristic peaks are sharp, indicating that the material has good crystallinity, and compared with the Cambridge Structural Database System (CSDS), it is different from the XRD spectrum of known crystals, proving that the prepared MOF-SS has a new crystal form.

[0051] (2) The hydrated particle size and Zeta potential of the MOF-SS nanoparticle solutions in Examples 1 and 2 were tested using a Malvern particle size analyzer, where the average particle size of sample 1 was 117 nm and the average particle size of sample 2 was 137 nm. Since MOF-SS is a hydrophilic substance, a hydration layer can be formed on the surface of the material in an aqueous solution compared with ethanol as a dispersed phase. Therefore, the hydrated particle size of sample 2 using water as a solvent is larger than that of sample 1 using ethanol as a dispersant, and the Zeta potential of the material is 23.47 ± 1.14 mV.

[0052] Specifically, the MOF-SS solutions prepared in Example 1 and Example 2 were selected for particle size distribution statistics. The results are as follows: Figure 2 As shown in the figure, it can be seen that the actual particle size distribution range of the MOF-SS solution prepared in Examples 1 and 2 is 100-200 nm, which is basically consistent with the results of the Malvern particle size analyzer. The morphology of MOF-SS was characterized by scanning electron microscopy, and the results are shown in FIG. Figure 3 As shown, the MOF-SS solution prepared in Example 1 has a relatively uniform material particle size under a scanning electron microscope.

[0053] (3) The particle size of the MOF-SS prepared in Example 1 was observed for a long time using a Malvern particle size analyzer. The results are as follows: Figure 4 As shown, it can be seen that MOF-SS can maintain a relatively stable particle size range in ethanol solution, and will not produce large particle size fluctuations over time.

[0054] (4) Disperse MOF-SS evenly in an appropriate solvent, take one portion and add the sample to be tested and another portion and add an equal amount of purified water. Mix well and then slightly heat to 40-60 °C. Then, detect the UV-visible absorption spectrum of the solution on a UV spectrophotometer. If the absorbance of the solution with the sample to be tested decreases or disappears at around 280 nm, it means that the sample to be tested contains thiol.

[0055] The prepared stable MOF-SS was tested for disulfide bond responsiveness. Figure 6 It is obvious that the color of the solution fades rapidly with the addition of the reducing agent. The UV absorption spectrum of the solution before and after the response is measured. Figure 5 It can be seen that the ultraviolet absorption of MOF-SS near 280 nm wavelength disappears after the addition of the reducing agent, and the ultraviolet absorption moves to shorter wavelengths compared with before the response. This is because the unbonded lone pair of electrons of sulfur in 4,4'-dithiodibenzoic acid has a certain conjugated effect. After the response, the disulfide bond breaks, the conjugated system decreases, and the ultraviolet absorption moves to shorter wavelengths.

[0056] Different from the prior art, the present invention provides a new MOF-SS with reduction response characteristics and a preparation method thereof. The MOF-SS is successfully prepared by a solvothermal preparation method, and the characteristics of its reduction response are verified, enriching the types of intelligent responses relying on MOFs themselves. The MOF-SS designed by this method also has the characteristics of fast response speed, which is conducive to further application in the subsequent sensing field; and the particle size is uniform, and the process is simple and non-toxic.

[0057] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A reduction-responsive metal organic framework material, characterized in that: The organic ligand of the metal organic framework material is a dibasic acid containing a disulfide bond, and the coordination metal is Fe 3+ ; The metal organic framework material is a three-dimensional network structure.

2. A reduction-responsive metal organic framework material according to claim 1, characterized in that: The disulfide bond-containing dibasic acid includes one or more of 4,4'-dithiodibenzoic acid, 6,6'-dithiodicotinoic acid, 4,4'-dithiodiphenylacrylic acid, and 2,2'-dithioacetic acid.

3. The method for preparing a reduction-responsive metal organic framework material according to claim 1 or 2, characterized in that: Fe 3+ The metal organic framework material is synthesized by solvothermal reaction with a dibasic acid containing a disulfide bond and deionized water in a solvent.

4. The method for preparing a reduction-responsive metal organic framework material according to claim 3, characterized in that: The Fe 3+ The source is soluble iron salts.

5. The method for preparing a reduction-responsive metal organic framework material according to claim 3, characterized in that: The Fe 3+ , the molar ratio of the dibasic acid containing disulfide bonds and deionized water is 1:1: (110~550).

6. The method for preparing a reduction-responsive metal organic framework material according to claim 3, characterized in that: The solvent is small molecule alcohol.

7. The method for preparing a reduction-responsive metal organic framework material according to claim 3, characterized in that: The solvothermal reaction comprises the steps of: 3+ and a disulfide-bonded dibasic acid are dissolved in a solvent to obtain Fe 3+ solution and a disulfide-bonded dibasic acid solution to 3+ The solution is slowly added dropwise to the disulfide bond-containing dibasic acid solution, mixed and stirred evenly, heated to 50-70°C, and deionized water is added to initiate the reaction. After reacting for 20-40 minutes, the metal organic framework material is obtained by centrifugation, washing, and drying.

8. The method for preparing a reduction-responsive metal organic framework material according to claim 7, characterized in that: The concentration of the disulfide bond-containing dibasic acid solution is 2-10 mg / mL.

9. The method for preparing a reduction-responsive metal organic framework material according to claim 7, characterized in that: The reaction temperature after adding deionized water is 50~70℃.

10. The use of a reduction-responsive metal organic framework material according to claim 1 or 2, characterized in that: Application in thiol detection.

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