Preparation method and application of MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite

Abstract

The application belongs to the technical field of new materials, and particularly relates to a preparation method and application of a MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite material. The application uses the metal-organic framework (MOF) material MIL-101(Fe) with two kinds of mesoporous cages and one kind of microporous cage as a carrier, encapsulates the MnO2 metal oxide nanoparticles in the three cage structures of the structure, and thus prepares a new composite material MnO2-in-MIL-101(Fe) in which the MnO2 nanoparticles completely enter the MOF cage instead of being aggregated on the surface to block the MOF channels. The MnO2-in-MIL-101(Fe) of the application is a catalytic material with high efficient catalytic capacity, and the highly dispersed nanoscale MnO2 can effectively exert the ozone degradation performance. Meanwhile, the preparation method of the application is simple in operation, good in repeatability, mild in conditions and friendly to the environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new materials, and particularly relates to a preparation method and application of a MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite material. BACKGROUND

[0002] With the rapid development of science and technology and economy in China, air pollution problems have gradually attracted close attention from all sectors of society. Ozone (O3) is one of the main air pollutants, and low-concentration O3 existing near the ground can threaten human health and the normal operation of the ecological system. Therefore, the governance of near-surface O3 is imminent. Due to reasons such as high efficiency and economy, the catalytic decomposition method is considered to be an effective way to solve O3 pollution. However, the humidity existing in the environment can greatly limit the efficiency of the catalyst. Therefore, it is of great significance to develop an O3 catalyst that is efficient, stable, safe and environmentally friendly in a wide humidity range.

[0003] Manganese atoms have 3d 5 4s 2 outer electron structure. Therefore, they can form a variety of oxides with different valence states. This unique feature determines that the oxides have good ability to participate in redox reactions. Among them, MnO2 has different crystal forms with special structures, and has been proven to have excellent catalytic ozone decomposition performance. Metal-organic frameworks (MOFs) are a class of functional materials with special structures. MOF materials have high specific surface area, porosity and active sites throughout the pores, making them have the potential to become high-quality ozone catalyst carriers with high catalytic activity and good humidity resistance.

[0004] At present, the main method used in the research of ozone pollution governance is the catalytic decomposition method. The catalysts used are mainly noble metals and manganese oxides. Noble metals have excellent ozone catalytic decomposition performance. However, their abundance in the earth's crust is low, making them expensive and difficult to be used on a large scale in the field of ozone catalytic decomposition. Then, the focus of research work gradually shifted to transition metal oxides, mainly manganese oxides. Studies have shown that MnO2 has good catalytic performance under dry conditions. However, as the relative humidity of the air increases, its effect will quickly decrease. In actual application scenarios, water vapor in the air inevitably comes into contact with MnO2, which hinders the practical application of MnO2. At the same time, the service life and catalytic ability of MnO2 are still difficult to meet the use requirements. Therefore, designing a high-humidity-resistant catalytic material based on high-efficiency MnO2 catalysts is the key to promoting the research of ozone pollution governance. SUMMARY

[0005] To solve the above problems, the application provides a preparation method and application of a MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite material.

[0006] The technical scheme adopted by the present application is:

[0007] A preparation method of a MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material, comprising the following steps:

[0008] 1) Dissolve a manganese source and an oxidizing agent in ultrapure water, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10°C;

[0009] 2) Suspend MIL-101(Fe) powder in a hydrophobic solvent, ultrasonic for 5-20 min, and vigorously stir to mix uniformly to obtain a MIL-101(Fe) suspension;

[0010] 3) Under the condition of 0-10°C and vigorous stirring, drop the manganese precursor solution into the MIL-101(Fe) suspension drop by drop, and continue to stir for 2-3 hours;

[0011] 4) After removing the hydrophobic solvent by filtration, heat for 1-2 hours, the manganese precursor gradually ages to form MnO2 nanoparticles, and further dry, and collect the obtained powder to obtain the MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material MnO2-in-MIL-101(Fe).

[0012] Further, in the step 1) of the above preparation method, the mass ratio of the manganese source and the oxidizing agent is 5:8-5:16.

[0013] Further, in the step 1) of the above preparation method, the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

[0014] Further, in the step 1) of the above preparation method, the oxidizing agent is a persulfate.

[0015] Further, in the step 1) of the above preparation method, the oxidizing agent is sodium persulfate or ammonium persulfate.

[0016] Further, in the step 2) of the above preparation method, the hydrophobic solvent is one or more of n-hexane, cyclohexane, ethyl acetoacetate and ethyl acetate.

[0017] Further, in the step 3) of the above preparation method, the dropwise volume of the manganese precursor solution is 0.05-0.15 mL.

[0018] Further, in the step 3) of the above preparation method, the dropwise speed of the manganese precursor solution is 0.001-0.01 mL·min -1 .

[0019] Further, in the above preparation method, the heating temperature in step 4) is 30-150 DEG C.

[0020] Application of the above-mentioned any one of MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite materials in catalytic ozone decomposition.

[0021] The present application has the following beneficial effects:

[0022] 1. The MnO2-in-MIL-101(Fe) composite catalytic material prepared by the present application has the following characteristics: a) the classic MOF MIL-101(Fe) is used as a carrier for encapsulating MnO2, and the crystal structure is well preserved during the whole preparation process; b) under the action of the hydrophobic solvent in the double-solvent method, the MnO2 nanoparticles are encapsulated into the three cage-shaped pores in MIL-101(Fe) instead of being aggregated on the surface; c) the MnO2 nanoparticles grown in the pores of MIL-101(Fe) do not block the pores, and the composite material still maintains good porosity.

[0023] 2. The preparation method of the present application is low in cost, simple in operation, high in repeatability and mild in conditions.

[0024] 3. The MnO2-in-MIL-101(Fe) composite catalytic material prepared by the present application can effectively solve the problems of insufficient catalytic ability, poor moisture resistance and short service life of manganese oxides in the process of catalytic ozone decomposition. At the same time, the MnO2-in-MIL-101(Fe) of the present application can achieve almost 100% ozone degradation efficiency under high humidity conditions, thereby realizing the treatment of ozone pollution problems under actual environmental conditions. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 4 is the PXRD pattern of the MnO2-in-MIL-101(Fe) and the original MIL-101(Fe) prepared in Example 1.

[0026] Figure 2 Figure 5 is the 77K nitrogen adsorption curve of the MnO2-in-MIL-101(Fe) and the original MIL-101(Fe) prepared in Example 1.

[0027] Figure 3 Figure 6 is the ozone degradation performance curve of the MnO2-in-MIL-101(Fe) and the original MIL-101(Fe), MnO2 under 90% RH prepared in Example 1. DETAILED DESCRIPTION

[0028] For the purpose, technical solutions and advantages of the present application, the technical solutions in the embodiments of the present application will be described in more detail below in combination with the preferred embodiments of the present application. The described embodiments are part of the embodiments of the present application, but not all.

[0029] Embodiment 1

[0030] A preparation method of a MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material, comprising the following steps:

[0031] 1) Dissolve manganese sulfate and ammonium persulfate in ultrapure water at a mass ratio of 5:8, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10℃;

[0032] 2) The MIL-101(Fe) powder is suspended in n-hexane, ultrasonic for 15-20min, and stirred vigorously to mix uniformly to obtain a MIL-101(Fe) suspension;

[0033] 3) Under the condition of 0-10℃ and vigorous stirring, 0.1mL of the manganese precursor solution is added dropwise into the MIL-101(Fe) suspension, the dropping speed is 0.005mL·min -1 , and the stirring is continued for 2-3 hours;

[0034] 4) After removing the hydrophobic solvent by filtration, heat at high temperature of 90℃ for 1-2 hours, the manganese precursor gradually ages to generate MnO2 nanoparticles, and further dry, and collect the obtained powder to obtain MnO2-in-MIL-101(Fe).

[0035] Embodiment 2

[0036] A preparation method of a MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material, comprising the following steps:

[0037] 1) Dissolve manganese sulfate and ammonium persulfate in ultrapure water at a mass ratio of 1:2, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10℃;

[0038] 2) The MIL-101(Fe) powder is suspended in n-hexane, ultrasonic for 15-20min, and stirred vigorously to mix uniformly to obtain a MIL-101(Fe) suspension;

[0039] 3) Under the condition of 0-10℃ and vigorous stirring, 0.1mL of the manganese precursor solution is added dropwise into the MIL-101(Fe) suspension, the dropping speed is 0.005mL·min -1 , and the stirring is continued for 2-3 hours;

[0040] 4) After removing the hydrophobic solvent by filtration, heat at high temperature 90℃ for 1-2 hours, the manganese precursor gradually ages to generate MnO2 nanoparticles, and further dry, collect the obtained powder as MnO2-in-MIL-101(Fe).

[0041] Example 3

[0042] A preparation method of a MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite material, comprising the following steps:

[0043] 1) Dissolve manganese sulfate and ammonium persulfate in ultrapure water at a mass ratio of 5:8, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10℃;

[0044] 2) Suspend the MIL-101(Fe) powder in n-hexane, ultrasonic for 15-20 min, and stir vigorously to mix uniformly to obtain a MIL-101(Fe) suspension;

[0045] 3) At 0-10℃ and under vigorous stirring, add 0.15mL of the manganese precursor solution dropwise to the MIL-101(Fe) suspension at a dropwise speed of 0.005mL·min -1 , and continue stirring for 2-3 hours;

[0046] 4) After removing the hydrophobic solvent by filtration, heat at high temperature 90℃ for 1-2 hours, the manganese precursor gradually ages to generate MnO2 nanoparticles, and further dry, collect the obtained powder as MnO2-in-MIL-101(Fe).

[0047] Example 4

[0048] A preparation method of a MIL-101(Fe) cage-encapsulated MnO2 nanoparticle composite material, comprising the following steps:

[0049] 1) Dissolve manganese sulfate and ammonium persulfate in ultrapure water at a mass ratio of 1:2, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10℃;

[0050] 2) Suspend the MIL-101(Fe) powder in n-hexane, ultrasonic for 15-20 min, and stir vigorously to mix uniformly to obtain a MIL-101(Fe) suspension;

[0051] 3) At 0-10℃ and under vigorous stirring, add 0.15mL of the manganese precursor solution dropwise to the MIL-101(Fe) suspension at a dropwise speed of 0.005mL·min -1 , and continue stirring for 2-3 hours;

[0052] 4) After the hydrophobic solvent was removed by filtration, the manganese precursor was gradually aged to form MnO2 nanoparticles at high temperature 90℃ for 1-2 hours, and further dried, and the collected powder was MnO2-in-MIL-101(Fe).

[0053] Figure 1 PXRD patterns of MnO2-in-MIL-101(Fe) and original MIL-101(Fe) prepared in Example 1. The testing instrument was Advance D8 of Bruker, Germany, with Cu target, scanning 2theta range of 5-40°.

[0054] Figure 2 77K nitrogen adsorption curves of MnO2-in-MIL-101(Fe) and original MIL-101(Fe) prepared in Example 1. The testing instrument was 3H-2000PS1 of Belsorp, China, activated at 70℃ for 6 hours before testing.

[0055] The PXRD peaks of MnO2-in-MIL-101(Fe) had no obvious difference from the original MIL-101(Fe). There were no MnO2 diffraction peaks in the PXRD pattern, indicating that MnO2 entered the pores of MIL-101(Fe) to form nanoparticles, so that no diffraction could be captured by PXRD. At the same time, the diffraction peaks of MIL-101(Fe) did not change due to the introduction of MnO2, indicating that its structure remained stable during the whole preparation process.

[0056] Example 5 Evaluation of the catalytic ozone decomposition performance of MnO2-in-MIL-101(Fe) composite material

[0057] 10-100 mg of MnO2-in-MIL-101(Fe) sample prepared in Example 1 was mixed with 9 times the mass of quartz sand, and then added to a double-pass quartz tube with a diameter of 6 mm, and placed in a self-built integrated catalytic ozone decomposition performance evaluation platform to evaluate the ozone decomposition performance. The evaluation platform includes an ozone preparation device, a flow rate detection device, a humidity control device, an ozone detection device, and a tail gas treatment device. Among them, the ozone detection device is Model 202 (2B Technology), and the specific test conditions are: 10-100 mg of catalyst, 0.1-1 L / min of inlet gas flow rate, 10-90% of relative humidity, and 20-30℃ of test temperature.

[0058] It was found (as shown in Figure 3 ), that the MnO2-in-MIL-101(Fe) composite catalytic material of the present application had nearly 100% ozone degradation efficiency at 10-90% RH, and the efficiency could be maintained for a long time.

[0059] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Use of MIL-101(Fe) cage encapsulated MnO2 nanoparticle composites in catalytic ozone decomposition, characterized in that, The preparation method of the MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material comprises the following steps: 1) Dissolve a manganese source and an oxidizing agent in ultrapure water, fully dissolve and mix uniformly to obtain a manganese precursor solution, and store the manganese precursor solution at 0-10°C; 2) suspend MIL-101(Fe) powder in a hydrophobic solvent, ultrasonic for 5-20 min, and mix uniformly under vigorous stirring to obtain a MIL-101(Fe) suspension; 3) under vigorous stirring, drop the manganese precursor solution into the MIL-101(Fe) suspension at 0-10°C, and continue stirring for 2-3 hours; 4) after removing the hydrophobic solvent by filtration, heat for 1-2 hours, the manganese precursor gradually ages to form MnO2 nanoparticles, and further dry, and collect the obtained powder, which is the MIL-101(Fe) cage encapsulated MnO2 nanoparticle composite material MnO2-in-MIL-101(Fe).

2. Use according to claim 1, characterized in that, In step 1), the mass ratio of the manganese source to the oxidizing agent is 5:8-5:

16.

3. Use according to claim 1, characterized in that, In step 1), the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

4. Use according to claim 1, characterized in that, In step 1), the oxidizing agent is a persulfate salt.

5. Use according to claim 4, characterized in that, In step 1), the oxidizing agent is sodium persulfate or ammonium persulfate.

6. Use according to claim 1, characterized in that, In step 2), the hydrophobic solvent is one or more of n-hexane, cyclohexane, ethyl acetoacetate and ethyl acetate.

7. Use according to claim 1, characterized in that, In step 3), the dropwise volume of the manganese precursor solution is 0.05-0.15 mL.

8. The use according to claim 1, characterized in that, In step 3), the dropping speed of the manganese precursor solution is 0.001-0.01 mL·min -1 .

9. The use according to claim 1, characterized in that, In step 4), the heating temperature is 30-150°C.

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