A nano cerium oxide@ZIF-67 material and a preparation method thereof

Abstract

The application discloses a kind of nano cerium oxide @ ZIF-67 material and preparation method thereof, the nano cerium oxide @ ZIF-67 with nano cerium oxide as core, with ZIF-67 as shell, jointly constitute the nano cerium oxide @ ZIF-67 composite material with core-shell structure, wherein, nano cerium oxide core particle size size is 50-300nm.The nano cerium oxide @ ZIF-67 compared with pure nano cerium oxide, Ce 3+ The proportion increases from 26.31% to 33.76%. The preparation process comprises the following steps in sequence: preparation of cerium source methanol aqueous solution, solvothermal reaction, centrifugal washing and purification, ultrasonic dispersion mixing of nano cerium oxide and the like, realizes preparation of nano cerium oxide and coating of ZIF-67 on the surface of CeO2, and different morphology and size of nano cerium oxide particles and cerium oxide@ZIF-67 composite particles can be customized by adjusting process parameters and adding amount of additives, and the prepared nano cerium oxide@ZIF-67 has the advantages of uniform powder particles and large cerium loading, and the preparation process is simple and has good reproducibility.

Description

Technical Field

[0001] This invention belongs to the field of nanopowder materials technology, specifically relating to a nano-cerium oxide@ZIF-67 material and its preparation method. Background Technology

[0002] Nano-cerium oxide, due to its unique crystal structure and the variable valence state of oxygen vacancies (Ce... 3+ / Ce 4+ The properties of cerium oxide nanoparticles allow them to store and release oxygen like a "nano sponge," exhibiting unique advantages in catalysis, environmental remediation, biomedicine, and CMP polishing, particularly in applications requiring high catalytic activity and selectivity. Coating them with metal or metal-organic frameworks (MOFs) allows the metal ions in the coating to induce lattice distortion on the cerium oxide nanoparticle surface, thereby enabling Ce... 3+ The proportion of [a specific component] increases, and at the same time, the synergistic effect between the core and shell improves its catalytic efficiency, stability and selectivity.

[0003] The preparation of traditional nano-cerium oxide typically involves multiple steps, including solution preparation, pH adjustment, calcination, and dispersion. The pH adjustment process is particularly problematic due to its susceptibility to temperature and instrument precision issues, long processing time, and poor reproducibility. Furthermore, coating cerium oxide usually requires complex surface modifications to allow various materials to form a shell, making direct coating difficult and resulting in a complex and inefficient process. Therefore, developing a simple method for preparing nano-cerium oxide that eliminates the need for pH adjustment and a synthesis method that allows shell growth on cerium oxide surfaces without surface modification is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide a nano-cerium oxide@ZIF-67 material and its preparation method. A one-step alcohol-water solvothermal synthesis method is employed, utilizing the redox reaction between methanol and cerium nitrate to directly generate nano-cerium oxide. By adjusting the dimethylimidazole concentration, ZIF-67 can be grown directly on the cerium oxide surface at room temperature, simplifying the preparation process, improving production efficiency, and solving problems such as complex preparation steps, long preparation time, and poor reproducibility. Simultaneously, it improves the polishing and catalytic properties of cerium oxide-based materials.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing nano-cerium oxide@ZIF-67 material includes the following steps:

[0007] S1. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (PVP) are dissolved in an aqueous methanol solution to form a mixed solution of cerium nitrate and polyvinylpyrrolidone.

[0008] S2. Pour the mixed solution of cerium nitrate and polyvinylpyrrolidone prepared in S1 into a hydrothermal reactor and react at a temperature of 130-200℃ for 6-24 hours to form a nano-cerium oxide suspension.

[0009] S3. The nano-cerium oxide suspension prepared in S2 is centrifuged, washed and purified, and dried at a certain temperature to obtain nano-cerium oxide;

[0010] S4. Mix the nano-cerium oxide from S3 with dimethylimidazole in a methanol solution at a molar ratio of 1:30-60, and then disperse the mixture using ultrasound.

[0011] S5. Dissolve cobalt nitrate hexahydrate in methanol solution to form cobalt nitrate hexahydrate methanol solution. Slowly add the well-dispersed cerium oxide nano-methanol solution from S4 to the cobalt nitrate hexahydrate methanol solution under ultrasonic conditions to form cerium oxide nano-@ZIF-67;

[0012] S6. The nano-cerium oxide@ZIF-67 obtained in S5 was washed by centrifugation with anhydrous ethanol and dried under vacuum at 40-50℃ for 6-8 hours to obtain nano-cerium oxide@ZIF-67 material.

[0013] Furthermore, in S1, the methanol aqueous solution is obtained by mixing water and methanol at a volume ratio of 0.5-4:1.

[0014] Further, in S1, the molecular weight of the polyvinylpyrrolidone (PVP) is 10,000-58,000, and the polyvinylpyrrolidone (PVP) is mixed with cerium nitrate at a mass ratio of 0.3-3:1.

[0015] Furthermore, in S2, the filling ratio of the mixed solution of cerium nitrate and polyvinylpyrrolidone in the hydrothermal reactor is 30-80%.

[0016] Further, in step S3, the centrifugal washing purification involves sequential washing with water, acetone, and anhydrous ethanol until no nitrate ions are detected in the supernatant; wherein the washing is performed once with deionized water, once with acetone, and twice with anhydrous ethanol. Drying is performed using vacuum freeze-drying at a temperature ≤30℃.

[0017] Furthermore, in S4, the ultrasonic dispersion time is 20-30 min; the molar ratio of nano-cerium oxide to methanol is 1:1-2.

[0018] Further, in S5, the molar ratio of cobalt nitrate to nano-cerium oxide is 0.3-3:1, and the addition rate of the nano-cerium oxide methanol dispersion is 10-50 mL / h. The ultrasonic power of the ultrasonic environment is 900-3500 W, and the ultrasonic time is 5-50 min.

[0019] The nano-cerium oxide@ZIF-67 material prepared by the method of the present invention consists of octahedral particles with a particle size of 50-300 nm; the nano-cerium oxide core is encapsulated by a ZIF-67 shell with a thickness of 36-130 nm.

[0020] The advantages of this invention are as follows:

[0021] (1) The nano-cerium oxide@ZIF-67 material of the present invention is a core-shell composite material, with nano-cerium oxide as the core and ZIF-67 as the shell. Unlike the zinc in ZIF-8, the cobalt in ZIF-67 endows it with intrinsic redox catalytic activity. The variable Ce content in cerium oxide... 3+ / Ce 4+ The valence state can also interact strongly with the active center of cobalt in ZIF-67. This interaction can optimize the d-band electronic structure of cobalt, lower the reaction energy barrier, and this core-shell structure also allows for a significant increase in the loading of cerium, thereby significantly improving intrinsic catalytic activity and reactivity.

[0022] (2) The preparation process of this invention is simple. Nano-cerium oxide is synthesized using a one-step alcohol-water solvothermal method. Methanol is used as both a reactant and a solvent for the redox reaction with cerium nitrate due to its low surface tension, low boiling point, and ability to react with cerium nitrate. No pH adjustment is required to directly generate nano-cerium oxide. The preparation process of the ZIF-67 shell structure is also simple, requiring no surface modification of the cerium oxide surface. By adjusting the concentration of dimethylimidazole, ZIF-67 can be grown on the cerium oxide surface at room temperature. This simplifies the preparation process and improves production efficiency.

[0023] (3) The present invention can customize nano-cerium oxide particles and nano-cerium oxide@ZIF-67 composite particles with different morphologies and sizes by adjusting process parameters and the types and amounts of additives, so as to meet different needs and has strong flexibility and practicality.

[0024] (4) The cerium oxide nanoparticles prepared by this invention have a particle size of 50-300 nm, a crystallinity ≥98%, good dispersibility, and an octahedral morphology, mainly exposing the {111} crystal face, which is the most stable low-index crystal face and has good stability, enabling it to form a good match with the band structure of other materials. Compared with other morphologies of cerium oxide prepared by traditional methods, octahedral cerium oxide nanoparticles are the most ideal substrate for loading other materials and an efficient charge transfer medium. Compared with simple cerium oxide nanoparticles, the cerium oxide nanoparticles @ZIF-67 prepared by this method have a higher Ce content. 3+ The proportion increased from 26.31% to 33.76%. This is due to Ce... 3+With the increased proportion and the synergistic effect between the core and shell, CeO2@ZIF-67 exhibits excellent CMP polishing and catalytic properties. Attached Figure Description

[0025] Figure 1 This is a SEM characterization image of the nano-cerium oxide prepared in this invention.

[0026] Figure 2 The image shows the SEM characterization of the cerium oxide nanoparticles@ZIF-67 prepared in Example 1.

[0027] Figure 3 The image shows the SEM characterization of the cerium oxide nanoparticles@ZIF-67 prepared in Example 2.

[0028] Figure 4 The image shows the SEM characterization of the cerium oxide nanoparticles@ZIF-67 prepared in Example 3.

[0029] Figure 5 The images show the XRD characterization of the nano-cerium oxide and nano-cerium oxide@ZIF-67 prepared in this invention.

[0030] Figure 6 This is a TEM characterization image of the nano-cerium oxide@ZIF-67 prepared in this invention.

[0031] Figure 7 TEM images of nano-cerium oxide@ZIF-67 prepared in Examples 1, 2, 4 and 5, where (a) is Example 1, (b) is Example 2, (c) is Example 4 and (d) is Example 5.

[0032] Figure 8 CMP polishing tests were performed on nano-cerium oxide prepared by conventional methods and nano-cerium oxide@ZIF-67 prepared by the present invention. The 3D-AFM characterization images of the silicon wafer surface after polishing are shown, where (a) is nano-cerium oxide prepared by conventional methods; and (b) is nano-cerium oxide@ZIF-67 prepared by the present invention. Detailed Implementation

[0033] To further understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0034] Example 1:

[0035] A method for preparing nano-cerium oxide@ZIF-67 material includes the following steps:

[0036] S1. Mix deionized water and methanol at a volume ratio of 3:1 to form a methanol-water solution;

[0037] S2. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (molecular weight 10000) are dissolved in the above methanol aqueous solution at a mass ratio of 1:0.5 to form a cerium nitrate solution with a concentration of 0.05 mol / L.

[0038] S3. The above cerium nitrate solution is hydrothermally reacted at 130°C for 24 hours, with the filling ratio in the hydrothermal reactor being 80%, to form a nano-cerium oxide suspension.

[0039] S4. The nano-cerium oxide suspension was washed by centrifugation with deionized water, acetone and anhydrous ethanol to remove impurity ions such as nitrate, and then freeze-dried under vacuum at 30°C to obtain nano-cerium oxide.

[0040] S5. Weigh 0.15g of the above-mentioned nano-cerium oxide and dimethylimidazole and disperse them in 20ml of methanol solution at a molar ratio of 1:50, and sonicate for 30min.

[0041] S6. Prepare 20 ml of cobalt nitrate hexahydrate methanol solution. Place the cobalt nitrate hexahydrate methanol solution in an ultrasonic dispersion environment. Slowly add the nano-cerium oxide methanol solution dispersed in S5 to the cobalt nitrate hexahydrate methanol solution at an addition rate of 10 mL / h. The molar ratio of cobalt nitrate to nano-cerium oxide is 1:1. The ultrasonic power of the ultrasonic environment is 3500 W and the ultrasonic time is 5 min to form nano-cerium oxide@ZIF-67.

[0042] S7. The prepared cerium oxide nano@ZIF-67 was washed three times by centrifugation with anhydrous ethanol and dried under vacuum at 40℃ for 8 hours to obtain cerium oxide nano@ZIF-67 material.

[0043] Example 2:

[0044] A method for preparing nano-cerium oxide@ZIF-67 material includes the following steps:

[0045] S1. Mix deionized water and methanol at a volume ratio of 2:1 to form a methanol-water solution;

[0046] S2. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (molecular weight 35000) are dissolved in the above methanol aqueous solution at a mass ratio of 1:0.8 to form a cerium nitrate solution with a concentration of 0.1 mol / L.

[0047] S3. The above cerium nitrate solution is hydrothermally reacted at 180°C for 12 hours, with the filling ratio in the hydrothermal reactor being 70%, to form a nano-cerium oxide suspension.

[0048] S4. The nano-cerium oxide suspension was washed by centrifugation with deionized water, acetone and anhydrous ethanol to remove impurity ions such as nitrate, and then freeze-dried under vacuum at 25°C to obtain nano-cerium oxide.

[0049] S5. Weigh 0.13g of the above-mentioned nano-cerium oxide and dimethylimidazole and disperse them in 25ml of methanol solution at a molar ratio of 1:40, and sonicate for 35min.

[0050] S6. Prepare 25 ml of cobalt nitrate hexahydrate methanol solution. Place the cobalt nitrate hexahydrate methanol solution in an ultrasonic dispersion environment. Slowly add the nano-cerium oxide methanol solution dispersed in S5 to the cobalt nitrate hexahydrate methanol solution at an addition rate of 10 mL / h. The molar ratio of cobalt nitrate to nano-cerium oxide is 1.5:1. The ultrasonic power of the ultrasonic environment is 1500 W, and the ultrasonic time is 30 min to form nano-cerium oxide@ZIF-67.

[0051] S7. The prepared cerium oxide nano@ZIF-67 was washed three times by centrifugation with anhydrous ethanol and dried under vacuum at 40℃ for 8 hours to obtain cerium oxide nano@ZIF-67 material.

[0052] Example 3:

[0053] A method for preparing nano-cerium oxide@ZIF-67 material includes the following steps:

[0054] S1. Mix deionized water and methanol at a volume ratio of 3:1 to form a methanol-water solution;

[0055] S2. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (molecular weight 58000) are dissolved in the above methanol aqueous solution at a mass ratio of 1:0.3 to form a cerium nitrate solution with a concentration of 0.15 mol / L.

[0056] S3. The above cerium nitrate solution was hydrothermally reacted at 200°C for 16 hours, with the filling ratio in the hydrothermal reactor being 55%, to form a nano-cerium oxide suspension.

[0057] S4. The nano-cerium oxide suspension was washed by centrifugation with deionized water, acetone and anhydrous ethanol to remove impurity ions such as nitrate, and then freeze-dried under vacuum at 25°C to obtain nano-cerium oxide.

[0058] S5. Weigh 0.1g of the above-mentioned nano-cerium oxide and dimethylimidazole and disperse them in 10ml of methanol solution at a molar ratio of 1:30, and sonicate for 30min;

[0059] S6. Prepare 10 ml of cobalt nitrate hexahydrate methanol solution. Place the cobalt nitrate hexahydrate methanol solution in an ultrasonic dispersion environment. Slowly add the nano-cerium oxide methanol solution dispersed in S5 to the cobalt nitrate hexahydrate methanol solution at an addition rate of 30 mL / h. The molar ratio of cobalt nitrate to nano-cerium oxide is 0.5:1. The ultrasonic power of the ultrasonic environment is 1000 W, and the ultrasonic time is 45 min to form nano-cerium oxide@ZIF-67.

[0060] S7. The prepared cerium oxide nano@ZIF-67 was washed three times by centrifugation with anhydrous ethanol and dried under vacuum at 40℃ for 8 hours to obtain cerium oxide nano@ZIF-67 material.

[0061] Example 4:

[0062] A method for preparing nano-cerium oxide@ZIF-67 material includes the following steps:

[0063] S1. Mix deionized water and methanol at a volume ratio of 4:1 to form a methanol-water solution;

[0064] S2. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (molecular weight 10000) are dissolved in the above methanol aqueous solution at a mass ratio of 1:1 to form a cerium nitrate solution with a concentration of 0.05 mol / L.

[0065] S3. The above cerium nitrate solution was hydrothermally reacted at 150°C for 16 hours, with the filling ratio in the hydrothermal reactor being 45%, to form a nano-cerium oxide suspension.

[0066] S4. The nano-cerium oxide suspension was washed by centrifugation with deionized water, acetone and anhydrous ethanol to remove impurity ions such as nitrate, and then freeze-dried under vacuum at 30°C to obtain nano-cerium oxide.

[0067] S5. Weigh 0.1g of the above-mentioned nano-cerium oxide and dimethylimidazole and disperse them in 40ml of methanol solution at a molar ratio of 1:50, and sonicate for 30min.

[0068] S6. Prepare 40 ml of cobalt nitrate hexahydrate methanol solution. Place the cobalt nitrate hexahydrate methanol solution in an ultrasonic dispersion environment. Slowly add the nano-cerium oxide methanol solution dispersed in S5 to the cobalt nitrate hexahydrate methanol solution at an addition rate of 25 mL / h. The molar ratio of cobalt nitrate to nano-cerium oxide is 2:1. The ultrasonic power of the ultrasonic environment is 2500 W and the ultrasonic time is 15 min to form nano-cerium oxide@ZIF-67.

[0069] S7. The prepared nano-cerium oxide@ZIF-67 was washed three times by centrifugation with anhydrous ethanol and dried under vacuum at 45°C for 7 hours to obtain nano-cerium oxide@ZIF-67 material.

[0070] Example 5:

[0071] S1. Mix deionized water and methanol at a volume ratio of 0.5:1 to form a methanol-water solution;

[0072] S2. Cerium nitrate (Ce(NO3)3·6H2O) and polyvinylpyrrolidone (molecular weight 58000) are dissolved in the above methanol aqueous solution at a mass ratio of 1:0.5 to form a cerium nitrate solution with a concentration of 0.05mol / L.

[0073] S3. The above cerium nitrate solution was hydrothermally reacted at 200°C for 6 hours, with the filling ratio in the hydrothermal reactor being 65%, to form a nano-cerium oxide suspension.

[0074] S4. The nano-cerium oxide suspension was washed by centrifugation with deionized water, acetone and anhydrous ethanol to remove impurity ions such as nitrate, and then freeze-dried under vacuum at 20°C to obtain nano-cerium oxide.

[0075] S5. Weigh 0.1g of the above-mentioned nano-cerium oxide and dimethylimidazole and disperse them in 30ml of methanol solution at a molar ratio of 1:60, and sonicate for 20min.

[0076] S6. Prepare 30 ml of cobalt nitrate hexahydrate methanol solution. Place the cobalt nitrate hexahydrate methanol solution in an ultrasonic dispersion environment. Slowly add the nano-cerium oxide methanol solution dispersed in S5 to the cobalt nitrate hexahydrate methanol solution at an addition rate of 15 mL / h. The molar ratio of cobalt nitrate to nano-cerium oxide is 2.5:1. The ultrasonic power of the ultrasonic environment is 3000 W, and the ultrasonic time is 10 min to form nano-cerium oxide@ZIF-67.

[0077] S7. The prepared nano-cerium oxide@ZIF-67 was washed three times by centrifugation with anhydrous ethanol and dried under vacuum at 50°C for 6 hours to obtain nano-cerium oxide@ZIF-67 material.

[0078] Material property testing

[0079] I. Material Characterization

[0080] The nano-cerium oxide and nano-cerium oxide@ZIF-67 materials prepared in Examples 1-3 of this invention were subjected to SEM, XRD, and TEM tests to obtain... Figure 1-6 .

[0081] Figure 1 This is a SEM image of nano-cerium oxide. (The image was created using...) Figure 1 This indicates that the nano-cerium oxide prepared by this method has a small size and good monodispersity and uniformity.

[0082] Figure 2-4 The images show SEM images of the nano-cerium oxide@ZIF-67 materials prepared in Examples 1, 2, and 3, respectively, demonstrating that this method can effectively coat ZIF-67 onto the surface of nano-cerium oxide.

[0083] Figure 5The XRD characterization images of the nano-cerium oxide and nano-cerium oxide@ZIF-67 prepared in Example 1 are shown. By calculating the area of ​​the XRD pattern of nano-cerium oxide and subtracting the total area of ​​the XRD pattern from the peak area of ​​the diffraction peaks, the crystallinity of cerium oxide was calculated to be 99.32%. By comparing the diffraction peaks with those of pure nano-cerium oxide, the diffraction peaks of nano-cerium oxide@ZIF-67 can be compared with the PDF card of cerium oxide (PDF#34-0394) and the PDF card of ZIF-67 (PDF#67-1073), which indicates that ZIF-67 has been well coated on nano-cerium oxide.

[0084] Figure 6 The TEM image of cerium oxide nanoparticles@ZIF-67 clearly shows a core-shell structure with cerium oxide as the core and ZIF-67 as the shell.

[0085] Figure 7 (ab) are TEM images of nano-cerium oxide@ZIF-67 prepared in Examples 1, 2, 4 and 5. It can be seen that the thickness of the ZIF-67 shell of nano-cerium oxide@ZIF-67 prepared by this method is 38.68nm-123.92nm at its thickest point.

[0086] II. XPS Testing of Materials

[0087] XPS tests were performed on the nano-cerium oxide and nano-cerium oxide@ZIF-67 prepared in Examples 1-5 above. The peak areas of Ce3d5 / 2 and 3d3 / 2 were calculated by deconvolution peak fitting, and were u3, u2, u1, u and u0, and v3, v2, v1, v and v0, respectively. 3+ The proportions are calculated based on the peak area ratios of v0, v1, u0, u1 to v, v2, v3, u, u2, u3, and the results are shown in the table below:

[0088] Table 1. Results of XPS tests for various embodiments of the present invention.

[0089]

[0090] Note: Ce in Table 1 3+ The percentage refers to Ce 3+ With Ce 4+ The ratio between them.

[0091] As can be seen from the test results in Table 1, (1) the nano-cerium oxide particles prepared by the present invention are generally between 50-300 nm in size and have an octahedral structure, while the cerium oxide prepared by the traditional method is spherical; in terms of particle size, there is no particularly obvious difference between the two.

[0092] (2) The Ce of nano-cerium oxide prepared by this invention 3+The proportion of Ce in cerium oxide prepared by traditional methods is between 25.35% and 27.21%. 3+ The proportion is 21.93%, indicating that the method of this invention can increase Ce. 3+ The proportion can increase by 3.42%-5.28% compared to traditional methods.

[0093] (3) The cerium nano-oxide@ZIF-67 Ce prepared in this invention 3+ The proportion is between 33.42% and 36.11%, which is higher than that of nano-cerium oxide Ce. 3+ The proportion increases by about 7-9%. This indicates that the method of the present invention can significantly enhance the reactivity and catalytic activity.

[0094] III. CMP Polishing Test of Materials

[0095] The nano-cerium oxide and nano-cerium oxide@ZIF-67 prepared in Examples 1-5 above were subjected to CMP polishing tests. The tests used a non-woven polishing pad; polishing pressure 80 N; polishing head / pad rotation speed 80 rpm / 87 rpm; polishing time 3 min; slurry flow rate 80 mL / min.

[0096] The removal rate (MRR) is calculated using the formula MRR = Δm × 10. 7 / (ρSt) (where Δm represents the weight loss of the silicon wafer before and after CMP treatment; ρ represents the silicon wafer density (density: 2.335 g·cm³) -3 S (cm) 2 The area () represents the contact area of ​​the silicon wafer; t represents the polishing time (min). The Ra value and root mean square roughness Rq of the silicon wafer surface were measured using AFM atomic force microscopy. The results are shown in Table 2 below.

[0097] Table 2 Results of CMP polishing tests in various embodiments of the present invention

[0098]

[0099] The test results in Table 2 show that: (1) the nano-cerium oxide @ZIF-67 prepared in this invention has a significant improvement in removal rate (MRR) compared to cerium oxide prepared by traditional methods, increasing by 57.028-49.601 nm / min. Specifically, the removal rate in Example 1 was 75.71% higher than that prepared by traditional methods, indicating that high Ce... 3+ The increased proportion significantly improved the reactivity, providing more active sites and forming more Si-O-Ce bonds with the Si surface, thus greatly improving the removal rate (MRR).

[0100] (2) The average roughness Ra of the silicon wafer polished in Example 1 was 0.334 ± 0.023 nm, which is superior to the Ra of 0.423 ± 0.031 nm prepared by the traditional method for cerium oxide. The other examples all showed varying degrees of improvement in removal rate compared to commercially available products. This is because the examples possess higher Ce content. 3+ The higher reactivity resulting from the higher proportion.

[0101] Figure 8 (a) Nano-cerium oxide prepared by conventional methods; (b) Nano-cerium oxide@ZIF-67 prepared in Example 1. Both were used for silicon wafer CMP polishing tests, and the resulting 3D-AFM images were obtained. The nano-cerium oxide@ZIF-67 composite powder material prepared in Example 1 exhibits higher surface smoothness on the polished surface compared to single nano-cerium oxide prepared by conventional methods.

[0102] The test results show that the nano-cerium oxide@ZIF-67 prepared in this invention can significantly improve the polishing rate compared with the single nano-cerium oxide product prepared by traditional methods. Nano-cerium oxide@ZIF-67 can significantly increase the Ce content in cerium oxide. 3+ The higher proportion of active sites can significantly enhance its reactivity and result in excellent polishing rate and surface quality.

[0103] It will be understood by those skilled in the art that the above embodiments are merely examples, and the features of different embodiments can be combined with each other to obtain embodiments that are readily conceived of according to the content disclosed in the present invention but are not explicitly shown in the accompanying drawings. The present invention is not limited in this respect.

[0104] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and any variations or modifications may be made to the implementation of the present invention without departing from the stated principles.

Claims

1. A method for preparing nano-cerium oxide@ZIF-67 material, characterized in that, Includes the following steps: S1. Dissolve cerium nitrate and polyvinylpyrrolidone in an aqueous methanol solution to form a mixed solution of cerium nitrate and polyvinylpyrrolidone; S2. Pour the mixed solution of cerium nitrate and polyvinylpyrrolidone prepared in S1 into a hydrothermal reactor and react at a temperature of 130-200℃ for 6-24 hours to form a nano-cerium oxide suspension. S3. The nano-cerium oxide suspension prepared in S2 is centrifuged, washed, purified, and dried to obtain nano-cerium oxide; S4. Mix the nano-cerium oxide from S3 with dimethylimidazole in a methanol solution at a molar ratio of 1:30-60, and then disperse the mixture using ultrasound. S5. Dissolve cobalt nitrate hexahydrate in methanol solution to form cobalt nitrate hexahydrate methanol solution; slowly add the well dispersed nano-cerium oxide methanol solution from S4 to the cobalt nitrate hexahydrate methanol solution under ultrasonic conditions to form nano-cerium oxide@ZIF-67. S6. The nano-cerium oxide@ZIF-67 obtained in S5 was washed by centrifugation with anhydrous ethanol and dried under vacuum at 40-50℃ for 6-8 hours to obtain nano-cerium oxide@ZIF-67 material.

2. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S1, the methanol-water solution is obtained by mixing water and methanol at a volume ratio of 0.5-4:

1.

3. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S1, the molecular weight of the polyvinylpyrrolidone is 10,000-58,000, and the polyvinylpyrrolidone is mixed with cerium nitrate at a mass ratio of 0.3-3:

1.

4. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S2, the filling ratio of the mixed solution of cerium nitrate and polyvinylpyrrolidone in the hydrothermal reactor is 30-80%.

5. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S3, the centrifugal washing purification is carried out by washing with water, acetone and anhydrous ethanol in sequence until no nitrate ions are detected in the supernatant; the drying is carried out by vacuum freeze drying at a temperature of ≤30℃.

6. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S4, the ultrasonic dispersion time is 5-50 min; the molar ratio of nano-cerium oxide to methanol is 1:1-2.

7. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S5, the ultrasonic power of the ultrasonic environment is 900-3500w, and the ultrasonic time is 5-50min.

8. The method for preparing nano-cerium oxide@ZIF-67 material according to claim 1, characterized in that, In S5, the molar ratio of cobalt nitrate to nano-cerium oxide is 0.3-3:1, and the addition rate of the nano-cerium oxide methanol dispersion is 10-50 mL / h.

9. A nano-cerium oxide@ZIF-67 material prepared by the method according to any one of claims 1-8, characterized in that, The cerium oxide nanoparticles in the ZIF-67 material are octahedral particles with a particle size of 50-300 nm; the cerium oxide nanoparticle core is encapsulated by a ZIF-67 shell, and the total thickness of the ZIF-67 shell is 36-130 nm.

Images