Zirconium-based MOF adsorbent containing fluorine and azo as well as preparation method and application of zirconium-based MOF adsorbent

Abstract

The invention provides a zirconium-based MOF adsorbent containing fluorine and azo as well as a preparation method and application of the zirconium-based MOF adsorbent, and belongs to the technical field of new energy materials. Zirconium chloride and azobenzene-3, 3 '-difluoro-4, 4'-dicarboxylic acid are used as raw materials, in an N, N-dimethylformamide solvent and an acetic acid solvent, the zirconium-based MOF adsorbent containing fluorine and azo is obtained through one-pot self-assembly, and the prepared zirconium-based MOF adsorbent containing fluorine and azo has the advantages of being large in pore diameter and specific surface area, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability, good in adsorbability and good in adsorbability. Meanwhile, the material has extremely high thermal stability and chemical stability, shows relatively high benzene adsorption capacity in a steam adsorption instrument, is relatively good in separation capacity through nuclear magnetic detection, provides a new idea for subsequent research and development, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and in particular relates to a zirconium-based MOF adsorbent containing fluorine and azo, and a preparation method and application thereof. Background Art

[0002] Light hydrocarbons (LHs, i.e. C1-C9 hydrocarbons) are the basic raw materials for the production of industrial commodities, which mainly come from petrochemical products or natural gas processing. Traditional separation methods (such as distillation, extraction and absorption) consume a lot of energy. From the perspective of energy sustainability and circular economy, specialized equipment and high production costs have exacerbated the limitations of traditional separation methods. In order to meet the separation needs of the petrochemical industry and reduce energy consumption in the separation process, it is crucial to develop efficient and energy-saving gas separation and purification technologies. In recent years, MOFs (metal organic framework compounds) have been widely used in applications such as gas storage and separation due to their advantages such as large specific surface area and adjustable pores.

[0003] In the petrochemical industry, cyclohexane (Cy) is an important raw material for the production of resins, nylon fibers and pharmaceutical intermediates. It is mainly produced by catalytic hydrogenation of benzene (Bz). However, the limited conversion rate in liquid phase production leads to the conversion of benzene and cyclohexane (C6H6 / C6H 12 ) The products are miscible, so a subsequent separation procedure is required to obtain high-purity cyclohexane. 12 Separation: Because their boiling points and kinetic diameters are very close, conventional distillation is generally not enough to separate benzene and cyclohexane, while special distillation methods such as azeotropic distillation and extractive distillation have the problems of complex processes and high energy requirements. To this end, the present invention proposes a zirconium-based MOF adsorbent containing fluorine and azo, and its preparation method and application. Summary of the invention

[0004] In order to solve the problems of difficulty in separating benzene and cyclohexane and high energy consumption, the present invention proposes a zirconium-based MOF adsorbent containing fluorine and azo, and a preparation method and application thereof. The present invention adopts zirconium hexaclusters as metal nodes and nitrogen benzene-3,3'-difluoro-4,4'-dicarboxylic acid as a coordination linker. A typical UiO-like structured MOF adsorbent material is synthesized by a one-pot self-assembly process in N,N-dimethylformamide solvent (DMF) and acetic acid solvent. The obtained adsorbent material has excellent benzene adsorption capacity and the ability to separate benzene and cyclohexane.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A method for preparing a zirconium-based MOF adsorbent containing fluorine and azo, using zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as raw materials, and obtaining the zirconium-based MOF adsorbent containing fluorine and azo by one-pot self-assembly in N,N-dimethylformamide solvent (DMF) and acetic acid solvent.

[0008] Furthermore, the preparation method of the zirconium-based MOF adsorbent containing fluorine and azo comprises the following steps:

[0009] Zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid are added together into a mixed solvent of N,N-dimethylformamide solvent and acetic acid solvent, and ultrasonicated to obtain a precursor solution; the precursor solution is added into a high-pressure reactor with a polytetrafluoroethylene liner for hydrothermal reaction, and the temperature is lowered after the reaction is complete, and the obtained solution is centrifuged, washed and vacuum dried to obtain the zirconium-based MOF adsorbent containing fluorine and azo.

[0010] Furthermore, the molar ratio of the zirconium chloride to phenylenediamine-3,3'-difluoro-4,4'-dicarboxylic acid is 1:1.

[0011] Furthermore, the volume ratio of the N,N-dimethylformamide solvent to the acetic acid solvent is 25:3.

[0012] Furthermore, the total amount of zirconium chloride and phenylazine-3,3'-difluoro-4,4'-dicarboxylic acid added to the mixed solvent is 3.85 g / L.

[0013] Furthermore, the hydrothermal reaction temperature is 120°C, the time is 3 days, and the cooling rate is 2°C / min.

[0014] Furthermore, the vacuum drying temperature is 60°C.

[0015] The second technical solution of the present invention:

[0016] A zirconium-based MOF adsorbent containing fluorine and azo prepared by the preparation method has zirconium hexaclusters as metal nodes and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as a coordination linker.

[0017] The third technical solution of the present invention:

[0018] The application of the zirconium-based MOF adsorbent containing fluorine and azo in the adsorption separation of benzene and cyclohexane.

[0019] Furthermore, adsorption tests of benzene and cyclohexane were carried out in a vapor adsorption instrument, and the separation performance of benzene and cyclohexane was evaluated by nuclear magnetic resonance.

[0020] The significant difference between benzene and cyclohexane is that conjugated π bonds are formed on the benzene ring. The aromatic ring on the organic ligand in the MOF adsorbent can form a π-π interaction with the guest molecule benzene, which provides a favorable structural basis for the specific recognition of benzene. Compared with cyclohexane, due to the existence of π-π interaction, it is easier to form a strong interaction force between benzene and the MOF adsorbent framework, thereby selectively separating benzene from the mixed liquid. The MOF adsorbent of the present invention emphasizes the synergistic effect between the fluorine atom of the electron-withdrawing group and the nitrogen atom with a conjugated π-electron system, and while forming CHF and CHN interactions, the phenyl face of the benzene molecule is parallel to the phenyl face of the aromatic ring of the framework, forming a more favorable π-π interaction. Therefore, the interaction between fluorine and azo formed in the MOF adsorbent of the present invention is the key to improving the benzene adsorption capacity of the MOF framework.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] (1) The zirconium-based MOF adsorbent containing fluorine and azo prepared by the present invention has the characteristics of large pore size and specific surface area in structure, and has abundant micropores, so that it has a high material adsorption capacity. Through the fine design of the functional sites on the ligand, the adsorbent has excellent adsorption capacity and high separation selectivity.

[0023] (2) The zirconium-based MOF adsorbent containing fluorine and azo prepared by the present invention has extremely high thermal stability and chemical stability, and exhibits a high benzene adsorption capacity (8.03 mmol / g) in the vapor adsorption instrument, and a good separation ability (76.73) detected by nuclear magnetic resonance, which provides new ideas for subsequent research and development and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 This is a SEM image of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1;

[0026] Figure 2 This is a BET image of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1;

[0027] Figure 3 This is the pore size curve of the zirconium-based MOF adsorption material containing fluorine and azo prepared in Example 1;

[0028] Figure 4This is a thermogravimetric curve of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1;

[0029] Figure 5 The XRD graphs of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1; wherein a is the XRD graph after being immersed in different organic solvents for three days; B is the XRD graph after being immersed in aqueous solutions with different pH values ​​for three days;

[0030] Figure 6 The vapor adsorption curves of the fluorine and azo zirconium-based MOF adsorbent material prepared in Example 1 and the MOF adsorbent material prepared in Comparative Examples 1-2, wherein a is the vapor adsorption curve of benzene; b is the vapor adsorption curve of cyclohexane;

[0031] Figure 7 A comparison chart of the separation performance of benzene and cyclohexane detected in NMR of the fluorine and azo zirconium-based MOF adsorbent material prepared in Example 1 and the MOF adsorbent material prepared in Comparative Examples 1-2;

[0032] Figure 8 This is the structural model of the fluorine and azo zirconium-based MOF adsorption material prepared in the present invention. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0035] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0038] The embodiment of the present invention provides a method for preparing a zirconium-based MOF adsorbent containing fluorine and azo, using zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as raw materials, and obtaining the zirconium-based MOF adsorbent containing fluorine and azo by one-pot self-assembly in N,N-dimethylformamide solvent (DMF) and acetic acid solvent, specifically comprising the following steps:

[0039] Zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid are added together into a mixed solvent of N,N-dimethylformamide solvent and acetic acid solvent, and ultrasonicated to obtain a precursor solution; the precursor solution is added into a high-pressure reactor with a polytetrafluoroethylene liner for hydrothermal reaction, and the temperature is lowered after the reaction is complete, and the obtained solution is centrifuged, washed and vacuum dried to obtain the zirconium-based MOF adsorbent containing fluorine and azo.

[0040] In a preferred embodiment of the present invention, the molar ratio of the zirconium chloride to phenylenediamine-3,3'-difluoro-4,4'-dicarboxylic acid is 1:1.

[0041] In a preferred embodiment of the present invention, the volume ratio of the N,N-dimethylformamide solvent to the acetic acid solvent is 25:3.

[0042] In a preferred embodiment of the present invention, the total amount of zirconium chloride and phenylazine-3,3'-difluoro-4,4'-dicarboxylic acid added to the mixed solvent is 3.85 g / L.

[0043] In a preferred embodiment of the present invention, the hydrothermal reaction temperature is 120° C., the time is 3 days, and the cooling is performed at a rate of 2° C. / min.

[0044] In a preferred embodiment of the present invention, the vacuum drying temperature is 60°C.

[0045] The embodiment of the present invention also proposes a zirconium-based MOF adsorbent containing fluorine and azo prepared by the preparation method, which has a zirconium hexa-cluster as a metal node and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as a coordination linker, and has a UiO-like structure.

[0046] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0047] The technical solution of the present invention is further illustrated by the following embodiments.

[0048] Example 1

[0049] A zirconium-based MOF adsorption material containing fluorine and azo is prepared by the following steps:

[0050] (1) adding 93.2 mg (0.4 mol) of zirconium chloride and 122.4 mg (0.4 mol) of phenylthiazolyl-3,3'-difluoro-4,4'-dicarboxylic acid to a mixed solvent consisting of 50 mL of DMF solvent and 6 mL of acetic acid solvent, and ultrasonicating for 20 min to obtain a precursor solution;

[0051] (2) The precursor solution was added to a 100 mL stainless steel reactor with a polytetrafluoroethylene liner and placed in a 120 °C oven for heating for 3 days, and then cooled to room temperature at a cooling rate of 2 °C / min;

[0052] (3) The solution obtained in step (2) is centrifuged to obtain a precipitate, the precipitate is washed three times with DMF, and dried in a vacuum drying oven at 60° C. to obtain a zirconium-based MOF adsorption material containing fluorine and azo.

[0053] Comparative Example 1

[0054] A zirconium-based MOF adsorbent containing azo is prepared by the following steps:

[0055] (1) adding 60 mg of zirconium chloride and 68.9 mg of 4,4'-azobenzenedicarboxylic acid into a mixed solvent consisting of 20 mL of DMF solvent and 11 mL of acetic acid solvent, and ultrasonicating for 20 min to obtain a precursor solution;

[0056] (2) The precursor solution was added to a 100 mL stainless steel reactor with a polytetrafluoroethylene liner and placed in a 120 °C oven for heating for 3 days, and then cooled to room temperature at a cooling rate of 5 °C / min;

[0057] (3) The solution obtained in step (2) is centrifuged to obtain a precipitate, the precipitate is washed three times with DMF, and dried in a vacuum drying oven at 60° C. to obtain a zirconium-based MOF adsorption material containing azo.

[0058] Comparative Example 2

[0059] A fluorine-free and azo-free zirconium-based MOF adsorbent is prepared by the following steps:

[0060] (1) 60 mg of zirconium chloride, 68.4 mg of 4,4'-stilbene dicarboxylic acid and 527 mg of L-proline were added together into 20 mL of DMF solvent and ultrasonicated for 20 min to obtain a precursor solution;

[0061] (2) The precursor solution was added to a 50 mL stainless steel reactor with a polytetrafluoroethylene liner and placed in a 120 °C oven for 3 days, and then cooled to room temperature at a cooling rate of 5 °C / min;

[0062] (3) The solution obtained in step (2) is centrifuged to obtain a precipitate, the precipitate is washed three times with DMF, and dried in a vacuum drying oven at 60° C. to obtain a zirconium-based MOF adsorbent free of fluorine and azo.

[0063] Performance Testing

[0064] The SEM image of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1 is shown in Figure 1 It can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 has an octahedral structure.

[0065] The BET diagram of the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 is shown in Figure 2 It can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 has a higher nitrogen adsorption capacity.

[0066] The pore size curve of the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1 is shown in Figure 3 It can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 has a larger pore size, the pore size is (pore size less than 2nm, classified as micropores).

[0067] The thermogravimetric curve of the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 is shown in Figure 4 It can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 has extremely high thermal stability.

[0068] The XRD pattern of the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 is shown in Figure 5 , wherein A is the XRD pattern of the MOF adsorbent after being immersed in different organic solvents for three days; B is the XRD pattern of the MOF adsorbent after being immersed in aqueous solutions with different pH values ​​for three days; it can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in this Example 1 has extremely high chemical stability.

[0069] The test was conducted at 298K and 308K. Before the adsorption test, the MOF adsorption material samples were soaked in acetone for 72h, and the exchanged samples were vacuum activated at 120°C for 10h. The single-component gas adsorption isotherms were measured on ASAP 2460. The vapor adsorption curves of the fluorine and azo zirconium-based MOF adsorption materials prepared in Example 1 of the present invention and the MOF adsorption materials prepared in Comparative Examples 1-2 are shown in FIG. Figure 6 , where a is the vapor adsorption curve of benzene; b is the vapor adsorption curve of cyclohexane (298K-1 represents the test result of the MOF adsorbent material of Example 1 at 298K, 298K-2 represents the test result of the MOF adsorbent material of Comparative Example 1 at 298K, and 298K-3 represents the test result of the MOF adsorbent material of Comparative Example 2 at 298K). It can be seen that the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 has a higher benzene adsorption amount and a lower cyclohexane adsorption amount.

[0070] The zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1 and the MOF adsorbent material prepared in Comparative Examples 1-2 were subjected to adsorption tests of benzene and cyclohexane in a vapor adsorption instrument, and the separation performance of benzene and cyclohexane was evaluated by nuclear magnetic resonance. The comparison of the separation performance of benzene and cyclohexane detected by nuclear magnetic resonance between the zirconium-based MOF adsorbent material containing fluorine and azo prepared in Example 1 of the present invention and the MOF adsorbent material prepared in Comparative Examples 1-2 is shown in FIG. Figure 7 , where 1 represents Example 1, 2 represents Comparative Example 1, and 3 represents Comparative Example 2. It can be seen that the separation capacity of the zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 is 76.73 through nuclear magnetic resonance detection, and it has a better adsorption capacity for benzene and cyclohexane, which is much higher than that of Comparative Examples 1 and 2.

[0071] The zirconium-based MOF adsorbent containing fluorine and azo prepared in Example 1 of the present invention has a zirconium hexa-cluster as a metal node and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as a coordination linker, and has a UiO-like structure. The structural model is shown in Figure 8 , it can be seen that the structure of the zirconium-based MOF adsorbent containing fluorine and azo contains two different types of polyhedral cage cavities: octahedral cages that share faces with 8 tetrahedral cages and octahedral cages that share edges with 8 additional octahedral cages.

[0072] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a zirconium-based MOF adsorbent containing fluorine and azo, characterized in that: The zirconium-based MOF adsorbent containing fluorine and azo is obtained by self-assembly in N,N-dimethylformamide solvent and acetic acid solvent using zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid as raw materials through a one-pot method.

2. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 1, characterized in that: The following steps are involved: Zirconium chloride and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid are added together into a mixed solvent of N,N-dimethylformamide and acetic acid and ultrasonically treated to obtain a precursor solution; the precursor solution is added into a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction, and after the reaction is complete, the temperature is lowered, and the obtained solution is centrifuged, washed and vacuum dried to obtain the zirconium-based MOF adsorbent containing fluorine and azo.

3. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 2, characterized in that: The molar ratio of the zirconium chloride to phenylenediamine-3,3'-difluoro-4,4'-dicarboxylic acid is 1:

1.

4. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 2, characterized in that: The volume ratio of the N,N-dimethylformamide to acetic acid is 25:

3.

5. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 2, characterized in that: The total amount of zirconium chloride and phenylazine-3,3'-difluoro-4,4'-dicarboxylic acid added to the mixed solvent is 3.85 g / L.

6. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 2, characterized in that: The hydrothermal reaction temperature is 120° C., the time is 3 days, and the cooling rate is 2° C. / min.

7. The method for preparing a zirconium-based MOF adsorbent containing fluorine and azo according to claim 2, characterized in that: The vacuum drying temperature is 60°C.

8. A zirconium-based MOF adsorbent containing fluorine and azo prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The zirconium hexacluster is used as the metal node and azobenzene-3,3'-difluoro-4,4'-dicarboxylic acid is used as the coordination linker.

9. Use of the zirconium-based MOF adsorbent containing fluorine and azo as claimed in claim 8 in the adsorption separation of benzene and cyclohexane.

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