CN111647167A - Novel metal organic framework material Zn-MOF, and synthesis method and application thereof - Google Patents

Abstract

The invention discloses a novel metal organic framework material Zn-MOF, a synthesis method and application thereof, wherein the method comprises the steps of material proportioning and mixing, grinding, vacuumizing, heating and preserving heat, cooling, purifying and the like, wherein after the vacuum heating temperature is 120-200 ℃, the heat is preserved for a specific time, the heating time is 24-112 h, and the metal organic framework material Zn-MOF prepared by the method has the advantages that: the synthetic method has the advantages of simple operation, less consumed materials, lower cost and less waste generation; impurities in the solid-phase reaction product can be well removed, and the crystallization of Zn-MOF can be promoted; the novel Zn-MOF material obtained by the method can regulate and control the emission spectrum performance of the material through laser.

Description

A new metal organic framework material Zn-MOF and its synthesis method and application

technical field

The invention belongs to the field of synthesis of metal-organic framework materials (MOF), and particularly relates to a Zn-MOF material synthesized by metal oxide (ZnO) and organic compound 2-methylimidazole (C4H6N2), a synthesis method and application thereof.

Background technique

The traditional metal oxide material ZnO has a unique band gap structure and high electron mobility, so it has a wide range of applications in sensing electrochemistry and photocatalysis, but the detection efficiency of the detector needs to be further improved. Metal-organic frameworks are a new type of porous coordination composites, which are widely used in gas separation, storage, and catalysis due to their high specific surface area, tunable pore size, high density of active sites, and high catalytic activity. Recent studies have found that metal-organic frameworks have the characteristics of a large number of highly active sites. Using them as precursors, metal oxides with unique structural characteristics can be obtained through specific technical means such as calcination under certain conditions, in order to improve metal oxides. Device applications in the fields of catalysis, energy and sensing.

The metal-organic framework of zinc is a composite material with a spatial topology structure with zinc ion as the central ion and organic molecular chain as the ligand. Due to its special topology, the thermal stability of the material is often poor, and related technologies still need to be improved. . At present, there are many methods for the synthesis of metal organic frameworks: water (solution) thermal method, diffusion method, solid-phase reaction method and so on. Among them, the most common synthesis method is the solution thermal method, which is conducive to the full contact reaction of the soluble reactants, and the product is usually a solid precipitation, which is easy to separate. However, the synthesis process of most solution thermal methods is relatively complicated. In the process, various organic solvents are required as combined solvents for the synthesis process, and some of the drugs used in the process are dangerous. For example, the existing Zn-MOF hydrothermal synthesis technology mostly uses zinc-containing nitrate as the zinc source, which has unfavorable problems such as corrosiveness, explosiveness, harmfulness to the environment, and harsh reaction conditions. And in the solution thermal method, the poorly soluble reactant (ZnO) is not suitable as the reactant. The solid-phase reaction method is suitable for the reaction of poorly soluble reactants, but the product obtained by the solid-phase reaction method is not easy to separate, and usually contains many impurities. As in other solid-phase reaction synthesis processes, the reactants need to be placed in a quartz glass tube, calcined and sealed, and heated at a higher temperature under nitrogen protection. The traditional solid-phase reaction method has the disadvantages of high manufacturing cost, low yield, complex synthesis process, and low purity of the synthesis.

SUMMARY OF THE INVENTION

The advantages of the solid-phase reaction method used in MOF synthesis are the advantages of being conducive to the reaction of insoluble reactants, simple operation, environmental protection (less use or no solution), etc., but the product generally contains more impurities, and the problem to be solved by the present invention is The solid-phase reaction method is improved, and the high-purity target product can be obtained through the subsequent purification process, and the product Zn-MOF can control the emission spectrum properties under laser excitation.

Its technical solutions are as follows:

A method for synthesizing a novel metal-organic framework material Zn-MOF, comprising the following steps:

(1) Step 1: take by weighing zinc oxide and 2-methylimidazole according to a certain mass ratio, and mix the two powders;

(2) step 2: the mixed powder in step (1) is placed in an agate mortar, and ground is carried out to mix well;

(3) Step 3: place the uniformly mixed powder in the step (2) in a specific container, put it into a vacuum constant temperature drying box and vacuumize and keep it below 0.1 MPa;

(4) Step 4: when the vacuum degree is above 0.1MPa, start heating to 120℃-200℃, and keep it for a specific time;

(5) Step 5: After reaching the holding time, cool to room temperature above 0.1MPa vacuum degree, and take out the material;

(6) Step 6: configure a certain concentration of ammonium chloride solution, put the material obtained in step (5) into the solution, stir evenly, place it in an incubator, and keep the temperature at a certain temperature for a certain period of time, so that the ammonium chloride solution and the residual After the zinc oxide was fully reacted, it was filtered and dried to obtain a new type of Zn-MOF material.

In addition, the present invention also discloses a metal-organic framework material Zn-MOF, which is prepared by the above-mentioned synthesis method of the novel metal-organic framework material Zn-MOF.

The invention also discloses an application of a device for improving the metal oxide in the fields of catalysis, energy and sensing, and the application includes the above-mentioned novel metal-organic framework material Zn-MOF.

Beneficial effects:

1: The entire material synthesis method is simple to operate, uses few consumables, low cost, low waste generation and water-based, safe and pollution-free. (By using a solid-phase reaction-based synthesis method).

2: The purification process is simple and easy to operate.

Description of drawings

Fig. 1 (1) is the XRD diffractogram of heating at 160 DEG C for 84 hours and 112 hours in the second and third examples of the present invention, and before and after purification; Fig. 1 (2) is the heating at 120 DEG C in the fourth and fifth examples of the present invention. XRD diffractogram after purification by heating at 200°C for 112 hours;

Fig. 2 is the SEM spectrum of incubation time 24h, 84h, 112h before and after purification;

Figure 3(1) is the emission spectrum of MAF-4, ZnO and C ₄ H ₆ N ₂ materials prepared in Example 3 of the present invention under the excitation of 265 nm light; Figure 3 (2) is MAF-4 prepared in Example 3 of the present invention , the emission spectra of ZnO and C ₄ H ₆ N ₂ materials under the excitation of 356nm light.

Detailed ways

This embodiment is a preferred example of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the scope of the principle of this embodiment should be included within the protection scope of the present invention.

A method for synthesizing a novel metal-organic framework material Zn-MOF, comprising the following steps:

(1) Weigh zinc oxide and 2-methylimidazole according to a certain mass ratio, and mix. Here, according to the coordination mode of metal-organic materials, the ratio of zinc oxide to 2-methylimidazole is about 1:2 for coordination;

(2) grinding: the mixed powder in step (1) is placed in an agate mortar, in order to make the reaction fully proceed, two kinds of powders need to be ground for about 15 minutes, and the two kinds of materials are ground into finer powders and uniformly mixed;

(3) Evacuation: the mixed powder in step (2) is placed in a specific container, because 2-methylimidazole will react with oxygen, so it cannot be in an aerobic environment during the heat preservation process, put it into a vacuum constant temperature drying box and vacuumize And keep below 0.1MPa;

(4) Heating and heat preservation: when the vacuum degree is below 0.1MPa, start heating to 120℃-200℃, and keep warm for a specific time;

(5) Cooling: After reaching the holding time, cool down to room temperature below 0.1MPa vacuum degree, and take out the material;

(6) Purification: Since the product contains zinc oxide as an impurity, the purity of Zn-MOF will be affected. Purify in this step. Prepare an ammonium chloride solution with a concentration of 0.1M-0.9M, put the material obtained in step (5) into the solution, stir evenly, place it in an incubator, and keep the temperature at 60 °C for 24h, so that the ammonium chloride solution and the residual oxidation After the zinc is fully reacted, it is filtered and dried to obtain a new type of Zn-MOF material.

Example 1

(1) Preparation of ingredients:

3.0121 grams of zinc oxide and 6.0135 grams of 2-methylimidazole with a purity greater than 99% (the mass ratio of the two is about 1:2) were put into an agate mortar and ground for 15 minutes, so that the two reactants were fully contacted and homogenized. , into a glass container.

(2) Vacuum heating and heat preservation:

Put the container in step (1) into a vacuum constant temperature drying box, vacuumize and keep it below 0.1 MPa, start heating to 160° C., and keep the temperature for 24 hours. Then cool to room temperature, deflate and remove.

(3) Purification:

Prepare 150 mL of 0.5M ammonium chloride aqueous solution, put the product obtained in step (2), soak in the solution, heat to 60° C., and keep the temperature for 24 hours. Then suction filtration and drying to obtain a new type of Zn-MOF material.

Example 2

(1) Preparation of ingredients:

3.0000 grams of zinc oxide and 6.0009 grams of 2-methylimidazole with a purity greater than 99% (the mass ratio of the two is about 1:2), put into an agate mortar and grind for 15 minutes, so that the two reactants are fully contacted and homogenized , into a glass container.

(2) Vacuum heating and heat preservation:

Put the container in step (1) into a vacuum constant temperature drying box, vacuumize and keep below 0.1 MPa, start heating to 160° C., and keep the temperature for 84 hours. Then cool to room temperature, deflate and remove.

(3) Purification:

Prepare 150 mL of 0.5M ammonium chloride aqueous solution, put the product obtained in step (2), soak in the solution, heat to 60° C., and keep the temperature for 24 hours. Then suction filtration and drying to obtain a new type of Zn-MOF material.

Example 3

(1) Preparation of ingredients:

3.0098 grams of zinc oxide and 6.0110 grams of 2-methylimidazole with a purity greater than 99% (the mass ratio of the two is about 1:2) were put into an agate mortar and ground for 15 minutes, so that the two reactants were fully contacted and homogenized. , into a glass container.

(2) Vacuum heating and heat preservation:

Put the container in step (1) into a vacuum constant temperature drying box, vacuumize and keep below 0.1 MPa, start heating to 160° C., and keep the temperature for 112 hours. Then cool to room temperature, deflate and remove.

(3) Purification:

Prepare 150 mL of 0.5M ammonium chloride aqueous solution, put the product obtained in step (2), soak in the solution, heat to 60° C., and keep the temperature for 24 hours. Then suction filtration and drying to obtain a new type of Zn-MOF material.

Example 4

(1) Preparation of ingredients:

3.0102 grams of zinc oxide and 6.0036 grams of 2-methylimidazole with a purity greater than 99% (the mass ratio of the two is about 1:2) were put into an agate mortar and ground for 15 minutes, so that the two reactants were fully contacted and homogenized. , into a glass container.

(2) Vacuum heating and heat preservation:

Put the container in step (1) into a vacuum constant temperature drying box, vacuumize and keep it below 0.1 MPa, start heating to 120° C., and keep the temperature for 112 hours. Then cool to room temperature, deflate and remove.

(3) Purification:

Prepare 150 mL of 0.5M ammonium chloride aqueous solution, put the product obtained in step (2), soak in the solution, heat to 60° C., and keep the temperature for 24 hours. Then suction filtration and drying to obtain a new type of Zn-MOF material.

Example 5

(1) Preparation of ingredients:

3.0007 grams of zinc oxide and 6.0002 grams of 2-methylimidazole with a purity greater than 99% (the mass ratio of the two is about 1:2) were put into an agate mortar and ground for 15 minutes, so that the two reactants were fully contacted and homogenized. , into a glass container.

(2) Vacuum heating and heat preservation:

Put the container in step (1) into a vacuum constant temperature drying box, vacuumize and keep it below 0.1 MPa, start heating to 200° C., and keep the temperature for 112 hours. Then cool to room temperature, deflate and remove.

(3) Purification:

Prepare 150 mL of 0.5M ammonium chloride aqueous solution, put the product obtained in step (2), soak in the solution, heat to 60° C., and keep the temperature for 24 hours. Then suction filtration and drying to obtain a new type of Zn-MOF material.

Through the above examples, the XRD diffraction pattern of the obtained novel Zn-MOF material is shown in FIG. 1 . In the pattern (1) of Fig. 1, a and c are the XRD diffraction patterns before and after purification at 160 °C for 84 h, b and d are the XRD diffraction patterns before and after purification at 160 °C for 112 h, and the simulated XRD patterns including Zn-MOF and Standard PDF card for ZnO, 2-methylimidazole. The e and f curves in the (2) pattern in Figure 1 are the XRD diffraction patterns after purifying at 120°C and 200°C for 112h. According to the XRD patterns of the curves c and d in Fig. 1 before purification, the synthesized new Zn-MOF material contains more ZnO impurities, which leads to less specific gravity and lower purity of the generated Zn-MOF. According to the purified XRD patterns of curves a and b in Figure 1, after the purification process, it can be seen that the peak corresponding to ZnO decreases, while the peak corresponding to Zn-MOF material increases significantly, the specific gravity of Zn-MOF becomes stronger, and the purity changes. high. And according to the curves of a, e, and f, Zn-MOF can be generated at 120 °C and 200 °C, but it is obvious that the specific gravity of the generated Zn-MOF is lower and the yield is lower. Therefore, 160 °C is the optimal temperature for synthesizing Zn-MOF.

The SEM microstructure image of the obtained Zn-MOF is shown in Fig. 2. In Figure 2, a and b are the SEM microstructure images of purified and unpurified after incubation at 160 °C for 24 hours, c and d are the SEM microstructure images of purified and unpurified after incubation at 160 °C for 84 hours, e and f are the thermal insulation at 160 °C SEM microstructure images of purified and unpurified after 112 h. According to a, c, and e in Figure 2, there are Zn-MOF crystals in the figure when they are not purified under each holding time, but it can also be seen from the image that there are many other impurities, which will affect the performance of the material. According to b, d, and f in Figure 2, there are a large number of clearly visible Zn-MOF crystals in the figure after the purification step under each holding time, and the impurities are obviously reduced. In addition, the SEM images of b, d, and f with different holding times in Fig. 2 are compared, and it can be seen that the longer the holding time is, the more sufficient the reaction is, and the less impurities are. Through this synthesis method, the resulting Zn-MOF is a high-purity crystalline material, which is easy to use.

The measured emission spectra of Zn-MOF under 265nm excitation are shown in Figure 3(1). By comparing with the emission spectra of ZnO and 2-methylimidazole C ₄ H ₆ N ₂ , the synthesized new material Zn-MOF ( That is, the peak of MAF-4) under excitation at 265 nm is shifted to the left than the peak of ZnO material, and is narrower than the emission spectrum of 2-methylimidazole (C ₄ H ₆ N ₂ ), which is easy to match with the photomultiplier tube to improve the detector. detection efficiency. The measured emission spectrum of Zn-MOF under excitation at 356 nm is shown in Figure 3 (2). By comparing with the emission spectrum under excitation at 265 nm, as shown in Figure 3 (1), the synthesized new material Zn-MOF (i.e. The peak of MAF-4) under the excitation of 356nm obviously exhibits two peaks, which is obviously different from the emission spectrum under the excitation of 265nm, and the synthesized new material Zn-MOF (ie MAF-4) has two peaks under the excitation of 356nm. The peak is more concentrated than the two peaks of the ZnO material, which is beneficial to improve the photoelectric conversion efficiency of the back-end photomultiplier tube.

Compared with the prior art, the present invention has the following advantages:

1: Compared with a solid-phase reaction-based synthesis method in the prior art, the entire material synthesis method of the present invention is simple to operate, uses less consumables, has lower cost, generates less waste and is mainly water, and is safe and pollution-free.

2: The purification process is simple and easy to operate, and through this purification process, impurities in the solid-phase reaction product can be well removed, and the crystallization of Zn-MOF can also be promoted. (through the immersion, filtration, drying and other purification processes of the NH4Cl solution in this method)

3: The new Zn-MOF material obtained by this method can control its emission spectral properties by laser. (by measuring the emission spectra under excitation at 265nm and 356nm)

4: Zinc hydroxide material is used in other synthesis methods. This material will decompose at 125 ° C, and introduce impurities into the synthesis process. The zinc oxide material used in this method has better thermal stability than the zinc hydroxide material, which is convenient for the reaction.

5: The temperature selected in the synthesis method is 160°C as the optimum reaction temperature. If the temperature is lower than 160°C, the reaction will not proceed sufficiently, and there will be many impurities; if the temperature is higher than 160°C, the flash point of dimethylimidazole will be reached, which is unfavorable for the reaction to proceed.

In addition, the present invention also discloses a metal-organic framework material Zn-MOF, which is prepared by the above-mentioned synthesis method of the novel metal-organic framework material Zn-MOF.

The invention also discloses an application of a device for improving the metal oxide in the fields of catalysis, energy and sensing, and the application includes the above-mentioned novel metal-organic framework material Zn-MOF.

To sum up, each parameter selected in the process of the synthesis method of the novel metal organic framework material Zn-MOF in the present invention is not selected by those skilled in the art for granted, but through the creative work of scientific researchers and countless times. The results obtained through experiments and scientific theoretical analysis are not conventional technical means easily thought of by those skilled in the art.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions describe only the principles of the present invention. Without departing from the spirit and scope of the present invention, there are various Variations and improvements are intended to fall within the scope of the claimed invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. A synthesis method of a novel metal organic framework material Zn-MOF comprises the following steps:

step 1: weighing zinc oxide and 2-methylimidazole according to a certain mass ratio, and mixing the two powders;

step 2: putting the mixed powder in the step (1) into an agate mortar, and grinding to mix uniformly;

and step 3: putting the uniformly mixed powder in the step (2) into a specific container, putting the container into a vacuum constant-temperature drying oven, vacuumizing and keeping the pressure below 0.1 MPa;

and 4, step 4: heating to 120-200 ℃ at a vacuum degree of more than 0.1MPa, and then preserving heat for a certain time;

and 5: cooling to room temperature at a vacuum degree of more than 0.1MPa after reaching the heat preservation time, and taking out the material;

step 6: preparing an ammonium chloride solution with a certain concentration, putting the material obtained in the step (5) into the solution, uniformly stirring, placing in a heat preservation box, fully reacting the ammonium chloride solution with the residual zinc oxide, performing suction filtration, and drying to obtain the novel Zn-MOF material.

2. The synthesis method of a novel metal organic framework material Zn-MOF according to claim 1, characterized in that: the purity of the zinc oxide and the purity of the 2-methylimidazole are both more than 99%.

3. The synthesis method of a novel metal organic framework material Zn-MOF according to claim 1, characterized in that: the particular container is a glass container.

4. The synthesis method of a novel metal organic framework material Zn-MOF according to claim 1, characterized in that: the specific time of the heat preservation is 24 to 112 hours.

5. The synthesis method of a novel metal organic framework material Zn-MOF according to claim 1, characterized in that: the concentration of the ammonium chloride solution in the step 6 is 0.1M-0.9M.

6. A novel metal organic framework material Zn-MOF is characterized in that: the metal organic framework material Zn-MOF is prepared by the synthesis method of the novel metal organic framework material Zn-MOF as claimed in any one of claims 1 to 5.

7. An application of the metal oxide in the field of catalysis, energy and sensing is improved, which is characterized in that: comprising the novel metal organic framework material Zn-MOF of claim 6.

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