A size-controllable zeolite imidazolate framework material and a preparation method thereof

Abstract

This invention discloses a size-controllable zeolite-like imidazole ester framework material and its preparation method. The preparation method includes the following steps: Step 1, dissolving an organic ligand in a solvent to obtain an organic ligand solution; Step 2, adding a metal salt to the organic ligand solution under stirring conditions, and reacting at room temperature to obtain a suspension; Step 3, sequentially centrifuging, washing, and drying the suspension to obtain the zeolite-like imidazole ester framework material. The metal salt is selected from any one or two of cobalt salts and zinc salts. The organic ligand is selected from any one or more of imidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, imidazole-2-carboxaldehyde, and benzimidazole. This invention, without adding other raw materials or changing the reaction conditions, can successfully synthesize zeolite-like imidazole ester framework materials of different sizes simply by precisely controlling the concentration of the reaction precursor (i.e., imidazole derivative and coordinating metal ions). The control mechanism is simple and clear.

Description

Technical Field

[0001] This invention belongs to the field of combustion and explosion testing technology, specifically relating to a size-controllable zeolite-like imidazole ester framework material and its preparation method. Background Technology

[0002] Zeolitic imidazolate frameworks (ZIFs) are a widely used class of metal-organic frameworks (ZIFs), based on zinc ions (Zn). 2+ ), cobalt ions (Co) 2+ ZIFs are three-dimensional porous materials formed by bridging transition metal ions (such as imidazoles and their derivatives) with these ions as coordination centers. Due to their ordered structural features, large pore size and specific surface area, and tunable structure and function, ZIFs have broad application prospects in adsorption and separation, catalysis, and biomedicine.

[0003] The specific surface area, pore structure, and surface functional components of ZIFs materials are significantly affected by their microstructure and size, thus influencing their functional applications. Currently, ZIFs of different sizes have been synthesized, and their structures have been regulated. For example, the size of ZIF-8 has been controlled using the surfactant CTAB, achieving size regulation between 100 nm and 4 μm. However, the use of surfactants leads to high preparation costs and may cause environmental pollution, which is inconsistent with the principles of green chemistry. Furthermore, by changing the reaction parameters for synthesizing ZIF-8, such as temperature, concentration, reaction time, and reactant ratio, a series of ZIF-8 particles with sizes in the 147-915 nm range have been prepared. However, this method exhibits high randomness in particle size control, and the complex coupling relationships between various reaction parameters significantly reduce the controllability of the final product's particle size.

[0004] In summary, there are currently no reports of the green synthesis of a series of ZIFs with varying sizes in an aqueous phase under the same reaction conditions (temperature, time, stirring speed). Achieving precise control over the size of ZIF materials, elucidating the mechanism by which reaction precursors influence ZIF size, and realizing their controllable preparation remain critical technical challenges in this field. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the purpose of this invention is to provide a size-controllable zeolite-like imidazole ester framework material and its preparation method, so as to solve the technical problems of strong randomness and poor controllability in particle size regulation of ZIFs materials in the existing technology.

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

[0007] A method for preparing a size-controllable zeolite-like imidazole ester framework material includes the following steps: Step 1: Dissolve the organic ligand in a solvent to obtain an organic ligand solution; Step 2: Under stirring conditions, add a metal salt to the organic ligand solution and react at room temperature to obtain a suspension; Step 3: The suspension is centrifuged, washed, and dried sequentially to obtain a zeolite-like imidazole ester framework material.

[0008] The present invention also has the following technical features: Specifically, the metal salt is selected from any one or both of cobalt salts and zinc salts.

[0009] Furthermore, the organic ligand is selected from any one or more of imidazole, 2-methylimidazolium, 2-ethylimidazolium, 2-nitroimidazolium, imidazole-2-carboxaldehyde, and benzimidazole.

[0010] Furthermore, the molar ratio of the organic ligand to the metal ion compound is 70:1, the concentration of the organic ligand is 0.35 M to 4.2 M, and the concentration of the metal salt is 5 mM to 60 mM.

[0011] Furthermore, in step 2, the room temperature reaction temperature is 20~25℃, and the reaction time is 12~24 h.

[0012] Furthermore, in step 3, the centrifugal force is 9000~9500 g, the centrifugation time is 10~20 min, and the drying temperature is 50℃~60℃.

[0013] This invention also protects a size-controllable zeolite-like imidazole ester framework material, which is prepared by the above-described method for preparing zeolite-like imidazole ester framework materials.

[0014] Furthermore, the zeolite-like imidazole ester framework material has a dodecahedral morphology, and the particle size of the zeolite-like imidazole ester framework material is 0.06~1.10 μm. Compared with the prior art, the beneficial effects of the present invention are: The method of this invention can successfully synthesize zeolite-like imidazole ester framework materials of different sizes by precisely controlling the concentration of the reaction precursors (i.e., imidazole derivatives and coordinating metal ions) without adding other raw materials or changing the reaction conditions. The control mechanism is simple and clear, abandoning the traditional control method of complex coupling of multiple parameters, simplifying the complex problem of size control to the precise control of a single concentration variable, and has strong reproducibility. The method of this invention is green and economical. The entire synthesis process uses only water and basic chemical reagents, without the need for organic solvents or expensive additives. The reaction conditions are mild, which is in line with the principles of green chemistry, and the cost is low, making it suitable for large-scale production. Attached Figure Description

[0015] Figure 1 A scanning electron microscope image of a ZIF-8 microstructure with a size of 1.10 μm obtained in Example 1; Figure 2 A scanning electron microscope image of a ZIF-8 with a size of 0.85 μm obtained in Example 2; Figure 3 A scanning electron microscope image of a ZIF-8 with a size of 0.52 μm obtained in Example 3; Figure 4 A scanning electron microscope image of a ZIF-8 with a size of 0.25 μm obtained in Example 4; Figure 5 A scanning electron microscope image of a ZIF-8 with a size of 0.14 μm obtained in Example 5; Figure 6 A scanning electron microscope image of a ZIF-8 with a size of 0.06 μm obtained in Example 6; Figure 7 The graph shows the linear relationship between the size of ZIF-8 and the concentration of the 2-mIM precursor. Figure 8 Powder X-ray diffraction patterns of ZIF-8 of different sizes obtained in this invention; Figure 9 A scanning electron microscope image of a ZIF-7 with a size of 1.10 μm obtained in Example 7; Figure 10 A scanning electron microscope image of a ZIF-67 with a size of 1.10 μm obtained in Example 8; Figure 11 A scanning electron microscope image of the ZIF-90 with a size of 1.10 μm obtained in Example 9; The specific content of the present invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0016] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0017] The technical concept of this invention lies in the following: based on the inventive discovery that there is a deterministic single exponential decay relationship between the particle size of the material and the concentration of the precursor, i.e., the higher the concentration, the smaller the particle size of the resulting material, the following method is employed: in an aqueous system, while keeping all other synthesis conditions strictly constant, products of the target size can be continuously and controllably synthesized within a wide range from 0.06 μm to 1.10 μm by simply changing the concentration parameters. All products exhibit a regular dodecahedral morphology and a pure-phase crystal structure. The fixed reaction conditions include: reaction temperature (room temperature, 20–25 °C), reaction time (12–24 h), stirring speed, solvent system (water), and no addition of any surfactants or morphology modifiers.

[0018] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0019] Example 1 This embodiment discloses a method for preparing a zeolite-like imidazolium ester framework material, specifically including: Prepare a 2-methylimidazole aqueous solution (4 mL, 0.35 M), and add Zn(NO3)2 to the solution. 3)2 An emulsion was obtained by adding 1 mL of 6H2O aqueous solution (5 mM) to an aqueous solution of 2-methylimidazole and reacting for 24 h. Centrifuge at 9500 g relative centrifugation force for 10 min; wash the precipitate three times with ultrapure water; dry overnight in a vacuum oven at 50℃ to obtain a white powder.

[0020] Product appearance as follows Figure 1 As shown, the size was statistically determined using the Nano Measure, and the white product obtained in this embodiment was identified as ZIF-8, a regular dodecahedron with an average particle size of 1.10 μm.

[0021] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0022] Example 2 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, the concentration of the 2-methylimidazolium aqueous solution is 0.7M and the concentration of Zn(NO3)2·6H2O is 10 mM.

[0023] In this embodiment, ZIF-8, a regular dodecahedron with an average particle size of 0.85 μm, was finally obtained.

[0024] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0025] Example 3 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, the concentration of the 2-methylimidazolium aqueous solution is 1.4 M and the concentration of Zn(NO3)2·6H2O is 20 mM.

[0026] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0027] In this embodiment, ZIF-8, a regular dodecahedron with an average particle size of 0.52 μm, was finally obtained.

[0028] Example 4 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, the concentration of the 2-methylimidazolium aqueous solution is 2.1 M and the concentration of Zn(NO3)2·6H2O is 30 mM.

[0029] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0030] In this embodiment, ZIF-8, a regular dodecahedron with an average particle size of 0.25 μm, was finally obtained.

[0031] Example 5 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, the concentration of the 2-methylimidazolium aqueous solution is 2.8 M and the concentration of Zn(NO3)2·6H2O is 40 mM.

[0032] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0033] In this embodiment, ZIF-8, a regular dodecahedron with an average particle size of 0.14 μm, was finally obtained.

[0034] Example 6 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, the concentration of the 2-methylimidazolium aqueous solution is 4.2 M and the concentration of Zn(NO3)2·6H2O is 60 mM.

[0035] The X-ray diffraction pattern of the product obtained in this embodiment is as follows: Figure 8 As shown.

[0036] In this embodiment, ZIF-8, a regular dodecahedron with an average particle size of 0.06 μm, was finally obtained.

[0037] Example 7 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that in this embodiment, 2-methylimidazole is replaced with benzimidazole.

[0038] In this embodiment, ZIF-7, a regular dodecahedron with an average particle size of 1.10 μm, was finally obtained.

[0039] Example 8 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that Zn(NO3)2·6H2O is replaced with Co(NO3)2·6H2O.

[0040] In this embodiment, ZIF-67, a regular dodecahedron with an average particle size of 1.10 μm, was finally obtained.

[0041] Example 9 This embodiment discloses a method for preparing a zeolite-like imidazole ester framework material. The preparation method and steps used in this embodiment are the same as those in Example 1, except that 2-methylimidazolium is replaced with imidazole-2-carboxaldehyde.

[0042] In this embodiment, ZIF-90, a regular dodecahedron with an average particle size of 1.10 μm, was finally obtained.

[0043] In this application, the effect of precursor concentration on the size of ZIF-8 in Examples 1-6 was analyzed, and a linear relationship between the size of ZIF-8 and the concentration of the 2-methylimidazole precursor was plotted. The results are as follows: Figure 7 As shown in the figure, it can be seen that the size of ZIF-8 gradually decreases with increasing 2-methylimidazole concentration, which conforms to a single exponential decay model. The relationship between the two satisfies the following formula:

[0044] In the formula: y: ZIF-8 dimensions (μm); x: Concentration of 2-methylimidazole (M).

[0045] This is because the higher the precursor concentration, the easier it is for ZIF-8 to nucleate and grow, and the smaller its size.

[0046] Therefore, theoretically, ZIF-8 of any size can be prepared within the range of 0.06-1.10 μm by changing the specific concentration of the precursor.

[0047] The crystal structures of the zeolite-like imidazole ester framework materials of different sizes prepared in Examples 1-6 were characterized by powder X-ray diffraction, and the results are as follows: Figure 8 As shown, the diffraction peak signals of the prepared ZIF-8 powder crystals all match the simulated XRD data, indicating the successful synthesis of ZIF-8 crystals of different sizes.

[0048] As can be seen from Examples 7-9, other types of ZIFs with stable structures can be prepared according to the method of the present invention.

[0049] In summary, this invention provides a size-controllable ZIFs and its preparation method, successfully solving the technical problems of strong randomness and poor controllability in the particle size regulation of ZIFs materials in the prior art. It achieves the controllable preparation of ZIFs materials with specific and uniform particle sizes in an aqueous system, while keeping all other synthesis conditions strictly constant, simply by precisely controlling the concentration of the reaction precursors (organic ligands and metal salts).

[0050] The specific technical features described in the above embodiments can be combined in any suitable manner without contradiction, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a size-controllable zeolite-like imidazolium ester framework material, characterized in that, Includes the following steps: Step 1: Dissolve the organic ligand in a solvent to obtain an organic ligand solution; Step 2: Under stirring conditions, add a metal salt to the organic ligand solution and react at room temperature to obtain a suspension; Step 3: The suspension is centrifuged, washed, and dried sequentially to obtain a zeolite-like imidazole ester framework material.

2. The method for preparing the size-controllable zeolite-like imidazole ester framework material as described in claim 1, characterized in that, The metal salt is selected from any one or both of cobalt salts and zinc salts.

3. The method for preparing the size-controllable zeolite-like imidazole ester framework material as described in claim 1, characterized in that, The organic ligand is selected from any one or more of imidazole, 2-methylimidazolium, 2-ethylimidazolium, 2-nitroimidazolium, imidazole-2-carboxaldehyde, and benzimidazole.

4. The method for preparing the size-controllable zeolite-like imidazole ester framework material as described in claim 1, characterized in that, The molar ratio of the organic ligand to the metal salt is 70:1, the concentration of the organic ligand is 0.35 M to 4.2 M, and the concentration of the metal salt is 5 mM to 60 mM.

5. The method for preparing the size-controllable zeolite-like imidazole ester framework material as described in claim 1, characterized in that, In step 2, the room temperature reaction temperature is 20~25℃, and the reaction time is 12~24 h.

6. The method for preparing the size-controllable zeolite-like imidazole ester framework material as described in claim 1, characterized in that, In step 3, the centrifugal force is 9000~9500 g, the centrifugation time is 10~20 min, and the drying temperature is 50℃~60℃.

7. A size-controllable zeolite-like imidazole ester framework material, characterized in that it is prepared by the method for preparing zeolite-like imidazole ester framework materials as described in any one of claims 1 to 6.

8. The zeolite-like imidazole ester framework material as described in claim 1, characterized in that, The zeolite-like imidazole ester framework material has a dodecahedral morphology, and the particle size of the zeolite-like imidazole ester framework material is 0.06~1.10 μm.

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