Preparation method of manganese-based zeolite imidazole skeleton nanoparticles based on coprecipitation strategy

Abstract

The invention provides a preparation method of manganese-based zeolite imidazole skeleton nanoparticles based on a coprecipitation strategy, which comprises the following steps: (a) dissolving manganese chloride tetrahydrate in ultrapure water to prepare a metal precursor solution with the concentration of 0.1-1 mol / L; (b) dissolving 2-methylimidazole in ultrapure water to prepare a ligand solution with the concentration of 0.1 to 1 mol / L; (c) sequentially adding the solution obtained in the step (a) and the solution obtained in the step (b) into an aqueous solution containing polyvinylpyrrolidone, with the PVP concentration being 10-50 g / L and the molar ratio of metal to ligand being 1: 1-1: 3; (d) stirring and reacting for 10-60 minutes at the speed of 200-1000 rpm to form a turbid dispersion liquid; and (e) centrifuging the dispersion liquid at 15,000-35,000 * g for 1-5 minutes, and washing to obtain the manganese-based zeolite imidazole skeleton nanoparticles. According to the invention, the aqueous phase reaction is combined with the surfactant regulation and control, so that the uniform size, high dispersity and low toxicity of the nanoparticles are realized, and the problems of complex process, dependence on organic solvents and difficulty in particle size control in the prior art are solved.

Description

Technical Field

[0001] The present invention belongs to the field of metal organic framework (MOFs) material synthesis, and specifically relates to a method for controllably synthesizing manganese-based zeolite imidazole framework (Mn-ZIF) nanoparticles by an aqueous phase co-precipitation method. Background Art

[0002] Zeolitic imidazolate frameworks (ZIFs) are a class of zeolite-like structural materials synthesized by the reaction of transition metal ions and imidazole ligands, belonging to the family of metal-organic frameworks. ZIFs materials have more pore cage structures and more novel topological structures. By changing the types of metal ions and organic ligands, as well as the synthesis process and crystallization conditions, ZIFs materials with different structural characteristics and properties can be synthesized. The rich pore cage structure of ZIFs materials gives them a large specific surface area, which can be used as a drug carrier to load a variety of drugs. They also have strong biocompatibility and low biotoxicity, so they have broad application potential in biomedicine, pharmacy and other fields. Summary of the Invention

[0003] The present invention provides a method for preparing manganese-based zeolite imidazole framework nanoparticles based on a co-precipitation strategy. Through aqueous phase reaction combined with surfactant regulation, the nanoparticles are uniform in size, highly dispersible and low in toxicity, solving the problems of complex process, dependence on organic solvents and difficulty in particle size control in the prior art.

[0004] The specific steps are as follows: A method for preparing manganese-based zeolite imidazole framework nanoparticles comprises the following steps: (a) Dissolving manganese chloride tetrahydrate in ultrapure water to prepare a metal precursor solution with a concentration of 0.1-1 mol / L; (b) dissolving 2-methylimidazole in ultrapure water to prepare a ligand solution with a concentration of 0.1-1 mol / L; (c) adding the solutions of steps (a) and (b) sequentially to an aqueous solution containing polyvinyl pyrrolidone, wherein the concentration of polyvinyl pyrrolidone is 10-50 g / L and the molar ratio of metal to ligand is 1:1 to 1:3; (d) stirring the reaction at 200-1000 rpm for 10-60 minutes to form a turbid dispersion; (e) The dispersion was centrifuged at 15,000-35,000 × g for 1-5 min and washed to obtain manganese-based zeolite imidazole framework nanoparticles.

[0005] Preferably, the molecular weight of the ultrapure aqueous solution of polyvinyl pyrrolidone is 10,000-58,000, and preferably, the molecular weight of the ultrapure aqueous solution of polyvinyl pyrrolidone is 24,000.

[0006] Preferably, the magnetic stirring speed in step (d) is 500 rpm.

[0007] Preferably, the centrifugation condition in step (e) is 25,000×g for 2 minutes, and the washing process using ultrapure water is repeated 3 times.

[0008] Preferably, the volume ratio of the metal precursor solution to the ligand solution in step (c) is 1:2, and the metal precursor solution is added in two steps: first, the metal precursor solution is added and stirred for 3 minutes, and then the ligand solution is added and stirred for 30 minutes.

[0009] The present invention also provides manganese-based zeolite imidazole framework nanoparticles prepared by this method. The nanoparticles have an average particle size of 10-200 nm and a rod-like, cubic, or spherical morphology. The elemental composition includes Mn, C, O, and N, with a Mn content of 25.3 wt%. The manganese-based zeolite imidazole framework nanoparticles exhibit characteristic X-ray diffraction peaks at 2θ = 7.3° ± 0.2°, 10.4° ± 0.2°, and 12.7° ± 0.2°.

[0010] Correspondingly, the present invention also provides a manganese-based zeolite imidazole framework nanoparticle dispersion, comprising nanoparticles and ultrapure water, ethanol or PBS buffer, with a dispersion concentration of 1 mg / mL and a Zeta potential absolute value of ≤-3.26 mV.

[0011] Preferably, the redispersion solvent for the precipitated product after centrifugation in step (e) is selected from one or more of ultrapure water, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, tetrahydrofuran, anhydrous ethanol, methanol, isopropanol, chloroform, and dichloromethane, but is not limited thereto. The organic solvent used must be able to dissolve manganese chloride tetrahydrate, 2-methylimidazole, and polyvinylpyrrolidone powder at room temperature and pressure, but must not dissolve the manganese-based zeolite imidazole framework nanoparticles.

[0012] Preferably, the purity of the manganese chloride tetrahydrate and 2-methylimidazole powders is not less than analytical grade. More preferably, the purity of the precursor powder is not less than 3N (99.9%).

[0013] The manganese-based zeolite imidazole skeleton nanoparticles provided by the present invention have relatively uniform size, good dispersibility, and low toxicity, and are easy to use in the preparation of optics, electronics, and biomedicine, such as the preparation of photothermal therapy drugs, optical labeling drugs and other fields.

[0014] The preparation method mentioned in the present invention has a simple process, the materials and equipment are easily purchased, the biological toxicity of the materials used is low, the preparation cost is low, the time consumption is short, and the efficiency is high.

[0015] The particle size distribution range of the finished manganese-based zeolite imidazole framework nanoparticles mentioned in the present invention is relatively uniform, which is convenient for large-scale preparation and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a HRTEM image of manganese-based zeolite imidazole framework nanoparticles prepared according to an embodiment of the present invention.

[0017] Figure 2 This is an AFM image of manganese-based zeolite imidazole framework nanoparticles prepared according to one embodiment of the present invention; Figure 3 This is a Raman curve diagram of manganese-based zeolite imidazole framework nanoparticles prepared according to an embodiment of the present invention.

[0018] Figure 4 The figure shows the ultraviolet-visible-infrared absorption spectrum of manganese-based zeolite imidazole framework nanoparticles prepared according to an embodiment of the present invention.

[0019] Figure 5 The XRD spectrum of manganese-based zeolite imidazole framework nanoparticles prepared according to one embodiment of the present invention.

[0020] Figure 6 This is the HRTEM image of the product obtained in Comparative Example 3. DETAILED DESCRIPTION

[0021] Below in conjunction with the accompanying drawings, the preferred embodiments of the present invention are further described in detail: The following examples are provided to facilitate a better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent companies.

[0022] Example 1 A method for preparing manganese-based zeolite imidazole framework nanoparticles comprises the following steps: 1. Dissolve 1979.1 mg of manganese chloride tetrahydrate powder in 10 mL of ultrapure water in a 10 mL centrifuge tube to obtain a 1 mol / L manganese chloride stock solution. 2. In a 10 mL centrifuge tube, dissolve 821.06 mg of 2-methylimidazole powder in 10 mL of ultrapure water to obtain a 1 mol / L 2-methylimidazole stock solution in pure water. 3. Take a 100 mL Shu Niu blue glass bottle, add 500 mg of polyvinyl pyrrolidone (PVP24000) with a molecular weight of 24,000, and then add 20 mL of ultrapure water. Then continue stirring at 500 revolutions per minute (rpm) until the powder is completely dissolved. 4. Take 500 μL of the 1 mol / L manganese chloride ultrapure water stock solution prepared in step 1 and add it to the glass bottle in step 3. Continue stirring for 3 minutes. 5. Add 1 mL of the 1 mol / L 2-methylimidazole ultrapure water stock solution prepared in step 2 to the glass bottle in step 3 and continue stirring for 30 minutes. During this time, the solution in the bottle will gradually change from colorless, clear, and transparent to a turbid, dark brown. 6. Centrifuge the turbid dark brown dispersion obtained in step 5 at 25,000 x g for 2 minutes to obtain the resulting precipitate, which is the manganese-based zeolite imidazole framework nanoparticles; 7. The manganese-based zeolite imidazole framework nanoparticles obtained in step 6 were washed with ultrapure water for three times, redispersed in ultrapure water, sealed and stored at room temperature in a dark place.

[0023] Material characterization revealed that the average particle size of the manganese-based zeolite imidazole framework nanoparticles in Example 1 of the present invention was 50 nm. A batch of the product was weighed and found to have a mass of 108.5 mg.

[0024] Figure 1 This is a HRTEM (high-resolution transmission electron microscopy) image of manganese-based zeolite imidazole framework nanoparticles prepared in one embodiment of the present invention. Figure 1 This image shows the morphology and crystal structure of manganese-based zeolite imidazolate framework (Mn-ZIF) nanoparticles. Clear lattice fringes (interplanar spacing of 0.267 nm) demonstrate the material's high degree of crystallinity. Limited literature exists on this material, and no crystallographic data is available for reference; the interplanar spacing can only be measured using TEM images. Clear lattice fringes indicate a high degree of crystallinity.

[0025] Figure 2 AFM (atomic force microscopy) of manganese-based zeolite imidazole framework nanoparticles prepared in one embodiment of the present invention Figure 2 The 3D surface morphology and height information are provided, showing the vertical size of the particles (average height <3.5 nm). Cross-sectional analysis confirms that the particles are dispersed in a single layer, avoiding the performance degradation caused by multilayer stacking. This directly confirms the "irregular morphology" of the nanoparticles.

[0026] Figure 3 This is a Raman curve of the manganese-based zeolite imidazole framework nanoparticles prepared in one embodiment of the present invention, which shows the characteristic vibration peaks of the imidazole ligand, such as: CN stretching vibration peak (1140 cm -1): Verify the integrity of the 2-methylimidazole ligand. Mn-N coordination bond peak (480 cm -1 ): Confirmed Mn 2+ The coordination with the imidazole nitrogen atom supports the formation of the zeolite imidazole framework. The absence of impurity peaks indicates high purity of the synthesized product (in Comparative Example 3, insufficient washing times resulted in the presence of impurity peaks).

[0027] Figure 4 The UV-Vis-NIR absorption spectrum of manganese-based zeolite imidazole framework nanoparticles prepared in one embodiment of the present invention shows broad absorption across the 300-1000 nm range, with a particularly strong absorption peak in the near-infrared region (e.g., 808 nm), indicating potential applications in photothermal therapy and biomedical photonic sensors. The flat edges of the absorption bands indicate a uniform size distribution of the nanoparticles (consistent with the 50 nm particle size in Example 1).

[0028] Figure 5 This is the XRD (X-ray diffraction) spectrum of manganese-based zeolite imidazole framework nanoparticles prepared in one embodiment of the present invention. Characteristic diffraction peaks appear at 2θ = 7.3°, 10.4°, and 12.7°, confirming that the product's crystal structure is a zeolite imidazole framework. The sharp peaks and the absence of impurity peaks indicate high crystallinity and excellent purity. Summary: Figure 1-2 It can be concluded that the uniformity and dispersion of the nanoparticles are demonstrated from the morphology and size levels.

[0029] Figure 3-5 It can be concluded that the composition, function and effectiveness of the synthesis method of the product are verified from the perspectives of chemical structure, optical properties and crystallography.

[0030] Comparative Example 1 The difference from Example 1 is that in step (5), 500 μL of the 1 mol / L ultrapure water stock solution of 2-methylimidazole prepared in step 2 is added to the glass bottle in step 3, that is, the ratio of the pure water stock solution of manganese chloride tetrahydrate to the pure water stock solution of 2-methylimidazole is 1:1; Comparative Example 2 The difference from Example 1 is that the magnetic stirring time in step (5) is reduced to 10 minutes.

[0031] Comparative Example 3 The difference from Example 1 is that in step (7), the manganese-based zeolite imidazole framework nanoparticles obtained in step (6) are washed only once with ultrapure water.

[0032] turn out: Compared with Example 1, the product prepared in Comparative Example 1 has a yield of 54.2 mg / 108.5 mg of manganese-based zeolite imidazole framework nanoparticles, which is 49.95%.

[0033] Compared with Example 1, the product prepared in Comparative Example 2 showed that the solution in the bottle gradually changed from colorless, clear and transparent to a slightly turbid light brown. The yield of the manganese-based zeolite imidazole framework nanoparticles was 21.4 mg / 108.5 mg, which was 19.72%.

[0034] The difference between Comparative Examples 1 and 2 and Example 1 is only the yield, and the properties of the particles are the same.

[0035] The product obtained in Comparative Example 3 ( Figure 6 ) Compared with Example 1, the electron microscope image of the manganese-based zeolite imidazole framework nanoparticles contains more light-colored areas, and the product agglomerates into large particles with an average particle size of 150 nm.

[0036] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing manganese-based zeolite imidazole framework nanoparticles, characterized in that: The following steps are involved: (a) Dissolving manganese chloride tetrahydrate in ultrapure water to prepare a metal precursor solution with a concentration of 0.1-1 mol / L; (b) dissolving 2-methylimidazole in ultrapure water to prepare a ligand solution with a concentration of 0.1-1 mol / L; (c) adding the solutions of steps (a) and (b) sequentially to an aqueous solution containing polyvinyl pyrrolidone, wherein the PVP concentration is 10-50 g / L and the molar ratio of metal to ligand is 1:1 to 1:3; (d) stirring the reaction at 200-1000 rpm for 10-60 minutes to form a turbid dispersion; (e) The dispersion was centrifuged at 15,000-35,000 × g for 1-5 min and washed to obtain manganese-based zeolite imidazole framework nanoparticles.

2. The method according to claim 1, wherein: The molecular weight of the polyvinyl pyrrolidone is 10,000-58,000.

3. The method according to claim 1, wherein: The centrifugation condition in step (e) was 25,000×g for 2 minutes, and the washing process was repeated 3 times using ultrapure water.

4. The method according to claim 1, wherein: In step (c), the volume ratio of the metal precursor solution to the ligand solution is 1:2, and the solution is added in two steps: first, the metal precursor solution is added and stirred for 3 minutes, and then the ligand solution is added and stirred for 30 minutes.

5. A manganese-based zeolite imidazole framework nanoparticle prepared by the method of any one of claims 1 to 4, characterized in that: The average particle size is 10-200 nm, the morphology is rod-shaped, square or round, and the elemental composition includes Mn, C, O, and N, of which the Mn content is 25.3wt%.

6. The manganese-based zeolite imidazole framework nanoparticles according to claim 5, characterized in that: The X-ray diffraction pattern has characteristic peaks at 2θ=7.3°±0.2°, 10.4°±0.2°, and 12.7°±0.2°.

7. A manganese-based zeolite imidazole framework nanoparticle dispersion, characterized by: The nanoparticles according to any one of claims 5 to 6 and ultrapure water, ethanol or PBS buffer are contained, the dispersion concentration is 1 mg / mL, and the absolute value of the zeta potential is ≤-3.26 mV.

8. The method according to claim 1, wherein: The redispersion solvent of the precipitate after centrifugation in step (e) is selected from one or more of ultrapure water, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, acetone, tetrahydrofuran, anhydrous ethanol, methanol, isopropanol, chloroform and dichloromethane.

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