Synthesis method of al2o3 / c e o2 hexagonal bipyramidal particles and the resulting product

Abstract

The application discloses a synthesis method of Al2O3 / CeO2 hexagonal bipyramid particles and the obtained product, and steps of the method comprise the following: dissolving soluble cerium salt and 2-methyl imidazole in methanol, washing and drying the precipitate after standing, and obtaining Ce-MOF; then, adding aluminum nitrate nonahydrate (Al(NO3)3.9H2O), Ce-MOF, tetra-n-octylammonium bromide and L-lysine into a mixed solution of N,N-dimethylformamide, methanol, ethylene glycol and neopentyl glycol, carrying out water bath heating and irradiating with an ultraviolet lamp; carrying out hydrothermal reaction on the obtained uniform solution, centrifuging, drying and calcining the product, and obtaining Al2O3 / CeO2 hexagonal bipyramid structure. The raw materials used in the application are all rich in sources, convenient to transport and store, and low in processing cost; the reaction is easy to control; the product is special in micro-morphology, adjustable in size, and uniform in distribution, and has potential application value in the fields of mechanical polishing, industrial catalysis, automobile exhaust purification, fuel cells, precision ceramics, coating additives, gas sensitive sensing, flame retardants, magnetic media, abrasives, catalytic reactions and the like.

Description

Technical Field

[0001] This invention relates to a method for synthesizing Al2O3 / CeO2 hexagonal bipyramidal particles, specifically a solvothermal synthesis method for Al2O3 / CeO2 hexagonal bipyramidal structures with adjustable growth size and controllable morphology. Background Technology

[0002] In recent years, oxide semiconductor materials have shown great application value in energy, optoelectronics, sensing and other fields, attracting widespread attention. By controlling the microstructure of these oxides (such as size, crystal exposure surface, lattice defects, crystal phase composition, etc.), unique physicochemical properties can be obtained, and they have been widely used in chemical, magnetic, mechanical, optical and electrical devices.

[0003] Al2O3 is widely used in catalyst supports, automotive, chemical, cutting tools, and aerospace industries due to its high elastic modulus, good thermal stability, high hardness, abrasion resistance, corrosion resistance, good insulation, abundant raw material sources, and low price. With the rapid development of industries such as bioceramics, pharmaceuticals, electronics, and machinery, the market demand for alumina is increasing, further driving up the production and demand of Al2O3. Common Al2O3 materials are mainly synthesized through chemical and physical methods. CeO2, an abundant and inexpensive rare-earth metal oxide semiconductor material with a band gap of 2.7 eV, has attracted much attention. CeO2 exhibits adjustable oxygen vacancy concentration (through reversible CeO2 conversion). 3+ and Ce 4+ CeO2 nanoparticles possess physicochemical properties such as high oxygen storage capacity and high oxygen ion conductivity, showing significant application prospects in sensors, electronics, glass polishing materials, and magnetic materials. For example, CeO2 nanoparticles can be used in mechanical polishing fluids and also serve as excellent photocatalyst degradation materials. Currently, the main methods for synthesizing CeO2 include calcination, hydrothermal (solvothermal), sol-gel, and electrochemical methods.

[0004] Precipitation and heat treatment methods are commonly used to prepare oxide-based composite materials, offering advantages such as low energy consumption and simple equipment. However, the resulting Al2O3 and its composites primarily exhibit spherical microstructures, and synthetic routes for polyhedral micro / nano structures are relatively rare. To date, no reports have been found domestically or internationally regarding Al2O3 / CeO2 hexagonal bipyramidal particles with tunable size and controllable morphology. In fact, by adjusting the parameters of the water bath reaction and ultraviolet irradiation, and designing novel reaction systems, it is possible to achieve size control of Al2O3 / CeO2 hexagonal bipyramidal particles, enabling large-scale production of Al2O3 / CeO2 composite materials and promoting their applications in mechanical polishing, industrial catalysis, automotive exhaust purification, fuel cells, precision ceramics, coating additives, gas sensors, flame retardants, magnetic media, abrasives, and catalytic reactions. Summary of the Invention

[0005] To address the current lack of a combined precipitation and heat treatment method for preparing Al2O3 / CeO2 polyhedral structures, this invention provides a method for preparing Al2O3 / CeO2 hexagonal bipyramidal particles. First, Ce-MOF is prepared via precipitation, followed by hydrothermal and calcination techniques to synthesize the final Al2O3 / CeO2 composite material. This method precisely controls the complex chemical reaction process and crystal formation habits by effectively adjusting the water bath reaction temperature, UV irradiation parameters, and the selection and amount of surfactant, thereby controlling the size of the Al2O3 / CeO2 hexagonal bipyramidal particles. This method is simple, highly controllable, uses widely available raw materials, is highly practical, and the microstructure of the obtained product is adjustable, making it suitable for industrial production.

[0006] This invention provides a method for preparing Al2O3 / CeO2 hexagonal bipyramidal particles, comprising the following steps:

[0007] (1) At room temperature, a methanol solution containing Ce(NO3)3·6H2O was added dropwise to an equal volume of a methanol solution of 2-methylimidazole. After stirring continuously for 2 h, a flocculent complex was formed. Then, the mixture was allowed to stand at room temperature for 24 h to form a precipitate.

[0008] (2) The product from step (1) was centrifuged, washed, and dried to obtain Ce-MOF;

[0009] (3) Add Al(NO3)3·9H2O, Ce-MOF from step (2), tetra-n-octylammonium bromide, and L-lysine to a mixed solution of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol;

[0010] (4) Place the mixed solution from step (3) under an ultraviolet lamp with a wavelength of 365 nm and heat and stir it in a water bath for a certain period of time to obtain a homogeneous mixed solution.

[0011] (5) Transfer the mixed solution from step (4) to the reaction vessel and carry out a solvothermal reaction under closed conditions;

[0012] (6) After the reaction, the product was centrifuged and dried to obtain precursor particles;

[0013] (7) The precursor from step (6) is calcined at high temperature in a muffle furnace to obtain an Al2O3 / CeO2 micro / nano structure with adjustable morphology. The Al2O3 / CeO2 micro / nano structure has a particle size of 0.5-5.0 μm, hexagonal bipyramidal structure at both ends, and short pillars in the middle region with a size of 0.2-2.5 μm.

[0014] This invention first prepares Ce-MOF using methanol, 2-methylimidazole, and cerium nitrate as raw materials. Then, it involves water bath heating in a system containing aluminum nitrate, Ce-MOF, and various surfactants, using N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol as solvents. Simultaneously, ultraviolet light irradiation is applied. The reaction rate and microstructure growth are controlled through solvothermal reaction and high-temperature calcination, ultimately synthesizing size-tunable Al₂O₃ / CeO₂ hexagonal bipyramidal structures. This invention directly influences the crystal growth process and nucleation rate by selecting different surfactants, ultraviolet irradiation conditions, and heat treatment processes, obtaining tunable exposed crystal faces, altering the crystal growth habit, and yielding Al₂O₃ / CeO₂ hexagonal bipyramidal particles.

[0015] In step (1) above, the concentration of Ce(NO3)3·6H2O / methanol solution is 0.1-0.5 mol / L, and the concentration of 2-methylimidazole / methanol solution is 0.6-1.2 mol / L.

[0016] In step (2) above, the drying temperature of the precipitate is 60 ℃ and the drying time is 5 h.

[0017] In step (3) above, the concentration of Al(NO3)3·9H2O in the mixed solution is 0.03-0.05 mol / L, the volume ratio of N,N-dimethylformamide, methanol, ethylene glycol and neopentyl glycol is 1:0.25-0.3:0.02-0.10:0.04-0.06, and the mass ratio of Al(NO3)3·9H2O, Ce-MOF, tetra-n-octylammonium bromide and L-lysine is 1:0.2-0.3:0.01-0.02:0.005-0.010.

[0018] In step (4) above, the reaction regime in the water bath is as follows: heating temperature 50-60 ℃; ultraviolet light wavelength 365nm, illuminance 120-150 mW / cm². 2The process takes 30-60 minutes.

[0019] In step (5) above, the temperature of the solvothermal reaction is 150-200 °C and the reaction time is 12-24 h.

[0020] In step (6) above, the drying temperature is 60 ℃ and the drying time is 5 h.

[0021] In step (7) above, the calcination process is as follows: the temperature is raised to 600-700 ℃ at a rate of 1-5 ℃ / min in an air atmosphere, and then held for 2-4 h.

[0022] According to the above method, Al2O3 / CeO2 micro / nano structures with tunable morphology are obtained. The characteristics are: the particle size of Al2O3 / CeO2 micro / nano structures is 0.5-5.0 μm, the two ends are hexagonal bipyramidal structures, and the short pillar size in the middle region is 0.2-2.5 μm.

[0023] This invention employs a composite reaction of aluminum salt and Ce-MOF. By designing the composition and ratio of the mixed solvent, the amount and concentration of raw materials, the stirring temperature, and the parameters of ultraviolet irradiation and solvothermal reaction, the synthesis process of Al2O3 / CeO2 hexagonal bipyramidal particles can be easily controlled. The Ce-MOF added in this invention exhibits a near-spherical structure. A certain proportion of 2-methylimidazole can improve the viscosity of the solution and regulate the size of the Ce-MOF during precipitation. Through water bath heating and stirring under ultraviolet irradiation and subsequent heat treatment, the nucleation process of the composite grains is precisely controlled by the combined action of various surfactants, realizing the morphological evolution and crystal growth process of the hexagonal bipyramidal composite product. In the solution system, the mixed solvent composed of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol promotes better deprotonation of the surfactant, facilitating the reaction. Ultraviolet irradiation under water bath heating conditions facilitates the generation of active free radicals in unreacted portions of the material, initiating photopolymerization. This allows for the rapid preparation of thermally cross-linked composite precursors that are cured by ultraviolet light within a shorter timeframe. It also provides suitable energy for the reaction in solution, controlling the micro-reaction rate of the two-phase composite and promoting uniform growth of the Al2O3 / CeO2 composite precursor after nucleation. Furthermore, during the hydrothermal reaction, a specific ratio of solvent and surfactant adjusts the pH value required for the reaction, providing the necessary microenvironment for its smooth progress. In solution, tetra-n-octylammonium bromide (TOAB), a quaternary ammonium salt belonging to the cationic surfactant family, strongly adsorbs at the solid-liquid interface of the reaction system. After dissolving in the solvent, it produces TOA containing four long alkyl chains, which is beneficial for reacting with Al in the solution. 3+In combination, steric hindrance and electrostatic interactions promote the adsorption of Al precursors onto Ce-MOF, accelerating electron exchange and facilitating uniform nucleation of Al₂O₃ / CeO₂. Simultaneously, the slow hydrolysis of L-lysine to generate amino groups increases the concentration of amine organic compounds present in the reaction system. Under suitable solution pH conditions, this synergistic effect with TOAB as both a phase transfer agent and surfactant further aids the adsorption process, influencing grain growth and resulting in Al₂O₃ / CeO₂ particles with small average particle size, high dispersibility, and good uniformity. Furthermore, the amine organic compounds generated from L-lysine hydrolysis exhibit a three-dimensional structure, making them relatively bulky in the chemical reaction system. The resulting products are not entirely regular, showing differences in direction and tendency. TOAB can selectively and preferentially adsorb organic compounds onto the high-energy crystal faces of the products during the synthesis of Al₂O₃ / CeO₂. During the solvothermal reaction, this biased adsorption causes significant differences in the growth rate of particles on different crystal planes in the reaction system, thereby enabling the control of the composite of spherical Ce-MOF and aluminum salt, resulting in the formation of conical surfaces and edges of the composite material, as well as the elongation of the middle part in one dimension. Combined with the heat treatment process, the nucleation and crystallization process of Al2O3 / CeO2 two-phase composite is controlled, and finally a unique Al2O3 / CeO2 hexagonal bipyramidal structure is obtained.

[0024] This invention designs a novel solution system and modulates the effect of surfactants on the composite process of aluminum salt and Ce-MOF during preparation. Utilizing surface modulation by ultraviolet irradiation, solvothermal reaction, and subsequent heat treatment, size-tunable Al2O3 / CeO2 hexagonal bipyramidal particles are obtained. Compared with Al2O3-based composite materials reported domestically and internationally, this invention differs fundamentally in its material synthesis mechanism and process. The synthesis method provided by this invention is simple and controllable; moreover, the reagents used in the synthesis are all commercially available and widely sourced; the product has a narrow particle size distribution range, stable morphology, and is easy to scale up for production. The product has potential applications in mechanical polishing, industrial catalysis, automotive exhaust purification, fuel cells, precision ceramics, coating additives, gas sensors, flame retardants, magnetic media, abrasives, and catalytic reactions. Attached Figure Description

[0025] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the Ce-MOF-like spherical particles synthesized in Example 1 of this invention.

[0026] Figure 2 This is a scanning electron microscope (SEM) image of Ce-MOF-like spherical particles synthesized in Example 1 of the present invention.

[0027] Figure 3The image shows the XRD pattern of the Al2O3 / CeO2 hexagonal bipyramidal particles synthesized in Example 1 of this invention.

[0028] Figure 4 and Figure 5 This is a SEM image of the Al2O3 / CeO2 hexagonal bipyramidal particles synthesized in Example 1 of this invention.

[0029] Figure 6 The results of gas-sensitive testing are for the Al2O3 / CeO2 hexagonal bipyramidal particles synthesized in Example 1 of this invention.

[0030] Figure 7 This is a SEM image of the product synthesized in Counterexample 1 of the present invention. Implementation

[0031] The present invention will be further illustrated by the following embodiments. The following description is only for explaining the present invention and does not limit its content.

[0032] Example 1

[0033] 1.1 Under magnetic stirring at room temperature, 0.575 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 0.868 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. The mixed solution was stirred for 2 h and then allowed to stand at room temperature for 24 h. The precipitate was washed several times and dried in a 60 ℃ oven for 5 h to obtain spherical Ce-MOFs with a size of 0.9-1.1 μm (XRD results are shown in figure). Figure 1 As shown, the SEM results are as follows: Figure 2 (as shown)

[0034] 1.2 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. Then, 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to 35 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0035] 1.3 The solution was subjected to a hydrothermal reaction at 180 °C for 12 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0036] 1.4 The product was placed in a muffle furnace for heat treatment at a temperature of 600 ℃, a heating rate of 1 ℃ / min, and a holding time of 3 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0037] The XRD results of the product are as follows Figure 3 As shown in the figure, all the stronger diffraction peaks are consistent with the Al2O3 standard XRD card (10-0425), while the weaker diffraction peaks correspond to the CeO2 standard XRD card (34-0394), proving that the obtained product is a composite crystalline phase of cubic Al2O3 and cubic CeO2; the SEM of the product is shown in the figure. Figure 4 , Figure 5 As shown, this invention yields an Al2O3 / CeO2 micro / nano structure, characterized by a particle size of 2.8-3.1 μm, hexagonal bipyramidal ends, and short pillars in the middle region with a size of 0.9-1.1 μm. Testing revealed that this material exhibits good gas-sensitive response to 100 ppm acetone at 360 ℃. Figure 6 ).

[0038] Example 2

[0039] 2.1 Under magnetic stirring at room temperature, 0.534 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 0.6 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. After stirring the mixed solution for 2 h, it was allowed to stand at room temperature for 24 h. The precipitate was washed several times, and the obtained precipitate was dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 0.6-0.7 μm.

[0040] 2.2 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.4 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.18 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.002 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. Simultaneously, the solution was irradiated with a 365 nm ultraviolet lamp for 40 min at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0041] 2.3 The solution was subjected to a hydrothermal reaction at 160 °C for 16 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0042] 2.4 The product was placed in a muffle furnace for heat treatment at a temperature of 600 ℃, a heating rate of 2 ℃ / min, and a holding time of 2 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0043] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 0.7-0.9 μm, hexagonal bipyramidal structure at both ends, and short pillars in the middle region with a size of 0.25-0.30 μm.

[0044] Example 3

[0045] 3.1 Under magnetic stirring at room temperature, 0.657 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 1.303 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. The mixed solution was stirred for 2 h and then allowed to stand at room temperature for 24 h. The precipitate was washed several times and dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.4-1.6 μm.

[0046] 3.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.7 mL of ethylene glycol, and 0.5 mL of neopentyl glycol were mixed to obtain a homogeneous solution. Then, 0.22 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0017 g of L-lysine were added to the resulting solution. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 35 min at an illuminance of 150 mW / cm². 2 A mixed solution is obtained;

[0047] 3.3 The solution was subjected to a hydrothermal reaction at 180 °C for 20 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0048] 3.4 The product was placed in a muffle furnace for heat treatment at a temperature of 650 ℃, a heating rate of 3 ℃ / min, and a holding time of 3 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0049] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 4.6-4.8 μm, a hexagonal bipyramidal structure at both ends, and a short column size of 2.0-2.2 μm in the middle region.

[0050] Example 4

[0051] 4.1 Under magnetic stirring at room temperature, 0.903 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 1.737 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. After stirring the mixed solution for 2 h, it was allowed to stand at room temperature for 24 h. The precipitate was washed several times, and the obtained precipitate was dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.9-2.1 μm.

[0052] 4.2 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.6 mL of methanol, 0.2 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.19 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0016 g of L-lysine were added to the resulting solution. This process was then subjected to 50 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0053] 4.3 The solution was subjected to a hydrothermal reaction at 160 °C for 18 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0054] 4.4 The product was placed in a muffle furnace for heat treatment at a temperature of 650 ℃, a heating rate of 1 ℃ / min, and a holding time of 4 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0055] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 2.3-2.5 μm, a hexagonal bipyramidal structure at both ends, and a short column size of 0.8-0.9 μm in the middle region.

[0056] Example 5

[0057] 5.1 Under magnetic stirring at room temperature, 0.903 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 1.737 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. After stirring the mixed solution for 2 h, it was allowed to stand at room temperature for 24 h. The precipitate was washed several times, and the obtained precipitate was dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.9-2.1 μm.

[0058] 5.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.4 mL of methanol, 0.5 mL of ethylene glycol, and 0.5 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.21 g of Al(NO3)3·9H2O, 0.06 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0018 g of L-lysine were added to the resulting solution. This process was then subjected to 50 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0059] 5.3 The solution was subjected to a hydrothermal reaction at 180 °C for 18 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0060] 5.4 The product was placed in a muffle furnace for heat treatment at a temperature of 650 ℃, a heating rate of 2 ℃ / min, and a holding time of 2 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0061] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 4.1-4.4 μm, a hexagonal bipyramidal structure at both ends, and a short column size of 1.2-1.4 μm in the middle region.

[0062] Example 6

[0063] 6.1 Under magnetic stirring at room temperature, 0.8 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 10 mL of methanol solution containing 1 g of Ce(NO3)3·6H2O was added dropwise to obtain a mixed solution. The mixed solution was stirred for 2 h and then allowed to stand at room temperature for 24 h. The precipitate was washed several times and dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.7-1.9 μm.

[0064] 6.2 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.5 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0018 g of L-lysine were added to the resulting solution. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 40 min at an illuminance of 140 mW / cm².2 A mixed solution is obtained;

[0065] 6.3 The solution was subjected to a hydrothermal reaction at 160 °C for 18 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0066] 6.4 The product was placed in a muffle furnace for heat treatment at a temperature of 650 ℃, a heating rate of 2 ℃ / min, and a holding time of 3 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0067] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 2.2-2.4 μm, hexagonal bipyramidal structure at both ends, and short pillars in the middle region with a size of 0.7-0.8 μm.

[0068] Example 7

[0069] 7.1 Under magnetic stirring at room temperature, 0.8 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 1 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. The mixed solution was stirred for 2 h and then allowed to stand at room temperature for 24 h. The precipitate was washed several times and dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.7-1.9 μm.

[0070] 7.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.4 mL of methanol, 0.6 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.0035 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 35 min at an illuminance of 140 mW / cm². 2 A mixed solution is obtained;

[0071] 7.3 The solution was subjected to a hydrothermal reaction at 180 °C for 16 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0072] 7.4 The product was placed in a muffle furnace for heat treatment at 700 ℃, with a heating rate of 1 ℃ / min and a holding time of 4 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0073] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 3.9-4.1 μm, hexagonal bipyramidal structure at both ends, and short pillars in the middle region with a size of 1.0-1.2 μm.

[0074] Example 8

[0075] 8.1 Under magnetic stirring at room temperature, 0.8 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 10 mL of methanol solution containing 1.4 g of Ce(NO3)3·6H2O was added dropwise to obtain a mixed solution. The mixed solution was stirred for 2 h and then allowed to stand at room temperature for 24 h. The precipitate was washed several times and dried in an oven at 60 ℃ for 5 h to obtain spherical Ce-MOF with a size of 1.8-2.0 μm.

[0076] 8.2 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.6 mL of methanol, 0.8 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.22 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.0035 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to 50 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 140 mW / cm². 2 A mixed solution is obtained;

[0077] 8.3 The solution was subjected to a hydrothermal reaction at 170 °C for 18 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0078] 8.4 The product was placed in a muffle furnace for heat treatment at 700 ℃, with a heating rate of 1 ℃ / min and a holding time of 2 h. After furnace cooling, Al2O3 / CeO2 hexagonal bipyramidal particles were obtained.

[0079] After the sample was cooled in the furnace, an Al2O3 / CeO2 micro / nano structure was obtained. The structure is characterized by a particle size of 2.6-2.8 μm, a hexagonal bipyramidal structure at both ends, and a short column size of 0.8-1.0 μm in the middle region.

[0080] Comparative Example 1

[0081] 1.1 Under magnetic stirring at room temperature, 1.5 g of 2-methylimidazole was dissolved in 10.0 mL of methanol, and then 0.2 g of Ce(NO3)3·6H2O was dissolved in 10.0 mL of methanol to obtain a mixed solution. After stirring the mixed solution for 2 h, it was allowed to stand at room temperature for 24 h. The precipitate was washed several times, and the resulting precipitate was dried in a 60 ℃ oven for 5 h.

[0082] 1.2 Same as Example 1;

[0083] 1.3 Same as Example 1;

[0084] 1.4 Same as Example 1.

[0085] After the samples were cooled in the furnace, irregularly shaped, fragmented Al2O3 / CeO2 spherical micro / nanostructures with a particle size of 0.2-3.0 μm were obtained. Figure 7 This shows that Ce-MOFs with suitable microstructure and size have a significant impact on the microstructure of the product.

[0086] Comparative Example 2

[0087] 2.1 In a 50 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. Then, 0.115 g of Ce(NO3)3·6H2O, 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to 35 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0088] 2.2 Same as Example 1;

[0089] 2.3 Same as Example 1.

[0090] After furnace cooling, the samples yielded irregular Al2O3 / CeO2 particles with a particle size of 1.5–2.9 μm. This demonstrates that the introduction of Ce-MOF has a significant impact on the microstructure of the product.

[0091] Comparative Example 3

[0092] 3.1 Same as Example 1;

[0093] 3.2 In a 50 ℃ constant temperature water bath, 0.2 g Al(NO3)3·9H2O, 0.05 g Ce-MOF, 0.003 g tetra-n-octylammonium bromide, and 0.0015 g L-lysine were added to 15.0 mL of N,N-dimethylformamide. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 35 min at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0094] 3.3 Same as Example 1;

[0095] 3.4 Same as Example 1.

[0096] After furnace cooling, the samples yielded Al₂O₃ / CeO₂ spherical micro / nano structures with particle sizes ranging from 1.0 to 3.0 μm. This demonstrates that the addition of a mixed solution of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol significantly influences the final microstructure of the product.

[0097] Comparative Example 4

[0098] 4.1 Same as Example 1;

[0099] 4.2 In a 60 ℃ constant temperature water bath, 15.0 mL of N,N-dimethylformamide, 5.0 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous mixed solution. Then, 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 35 min at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0100] 4.3 Same as Example 1;

[0101] 4.4 Same as Example 1.

[0102] After furnace cooling, Al₂O₃ / CeO₂ spherical micro / nano structures with particle sizes of 1.5–3.5 μm were obtained. This demonstrates that the proportions of the mixed solution of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol significantly influence the microstructure of the product.

[0103] Comparative Example 5

[0104] 5.1 Same as Example 1;

[0105] 5.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 1.0 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to 35 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0106] 5.3 Same as Example 1;

[0107] 5.4 Same as Example 1.

[0108] After furnace cooling, the product obtained was irregular Al2O3 / CeO2 spherical particles with a size of 2.2-4.0 μm. This shows that the concentration of Al(NO3)3·9H2O has a significant impact on the microstructure of the product.

[0109] Comparative Example 6

[0110] 6.1 Same as Example 1;

[0111] 6.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous mixed solution. 0.2 g of Al(NO3)3·9H2O and 0.05 g of Ce-MOF were added to the resulting solution. This process was then subjected to 35 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0112] 6.3 Same as Example 1;

[0113] 6.4 Same as Example 1.

[0114] Uneven, irregular, and non-dispersed agglomerated particles with sizes ranging from 1.2 to 4.5 μm were obtained. This demonstrates that the addition of tetra-n-octylammonium bromide and L-lysine has a significant impact on the microstructure of the product.

[0115] Comparative Example 7

[0116] 7.1 Same as Example 1;

[0117] 7.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.001 g of tetra-n-octylammonium bromide, and 0.05 g of L-lysine were added to the resulting solution. This process was then subjected to irradiation with a 365 nm ultraviolet lamp for 35 min at an illuminance of 120 mW / cm². 2 A mixed solution is obtained;

[0118] 7.3 Same as Example 1;

[0119] 7.4 Same as Example 1.

[0120] Irregular particles with a size of 2.0-3.5 μm were obtained. This shows that the amount of tetra-n-octylammonium bromide and L-lysine added has a significant impact on the microstructure of the product.

[0121] Comparative Example 8

[0122] 8.1 Same as Example 1;

[0123] 8.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous mixed solution; 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the obtained solution under dark conditions to obtain a mixed solution;

[0124] 8.3 Same as Example 1;

[0125] 8.4 Same as Example 1.

[0126] No product was obtained. This shows that the introduction of ultraviolet irradiation can promote the formation of precursors.

[0127] Comparative Example 9

[0128] 9.1 Same as Example 1;

[0129] 9.2 In a 60 ℃ constant temperature water bath, 9.0 mL of N,N-dimethylformamide, 2.5 mL of methanol, 0.5 mL of ethylene glycol, and 0.4 mL of neopentyl glycol were mixed to obtain a homogeneous solution. 0.2 g of Al(NO3)3·9H2O, 0.05 g of Ce-MOF, 0.003 g of tetra-n-octylammonium bromide, and 0.0015 g of L-lysine were added to the resulting solution. This process was then subjected to 180 min of irradiation with a 365 nm ultraviolet lamp at an illuminance of 200 mW / cm². 2 A mixed solution is obtained;

[0130] 9.3 Same as Example 1;

[0131] 9.4 Same as Example 1.

[0132] Non-uniform, fragmented, spherical particles with sizes ranging from 1.5 to 3.5 μm were obtained. This demonstrates that the parameters of ultraviolet irradiation have a significant impact on the microstructure of the product.

[0133] Comparative Example 10

[0134] 10.1 Same as Example 1;

[0135] 10.2 Same as Example 1;

[0136] 10.3 The solution was subjected to a hydrothermal reaction at 120 °C for 6 h. Then, it was centrifuged at 8000 r / min, washed with DMF and ethanol, and dried at 60 °C to obtain the product.

[0137] 10.4 Same as Example 1.

[0138] No product was obtained. This shows that the relevant parameters of the solvothermal reaction are important conditions for promoting precursor formation.

[0139] Comparative Example 11

[0140] 11.1 Same as Example 1;

[0141] 11.2 Same as Example 1;

[0142] 11.3 Same as Example 1;

[0143] 11.4 The product was placed in a muffle furnace for heat treatment at a temperature of 850 °C, a heating rate of 10 °C / min, and a holding time of 24 h.

[0144] After furnace cooling, the samples yielded irregularly agglomerated particles with a diameter of 3.0–7.0 μm. This demonstrates that the calcination regime has a significant impact on the microstructure of the product.

Claims

1. A method for synthesizing Al2O3 / CeO2 hexagonal bipyramidal particles, characterized in that... Includes the following steps: (1) At room temperature, a methanol solution containing cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was added dropwise to an equal volume of a methanol solution of 2-methylimidazole. The mixture was stirred continuously for 2 h to form a flocculent complex. The precipitate was then allowed to stand at room temperature for 24 h to form. The concentration of the Ce(NO3)3·6H2O / methanol solution was 0.1-0.5 mol / L, and the concentration of the 2-methylimidazole / methanol solution was 0.6-1.2 mol / L. The product was then centrifuged, washed, and dried at 60°C for 5 h to obtain Ce-MOF. Aluminum nitrate nonahydrate (Al(NO3)3·9H2O), Ce-MOF, tetra-n-octylammonium bromide, and L-lysine were added to a mixed solution of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol. The concentration of Al(NO3)3·9H2O in the mixed solution was 0.03-0.05 mol / L. The volume ratio of N,N-dimethylformamide, methanol, ethylene glycol, and neopentyl glycol was 1:0.25-0.30:0.02-0.10:0.04-0.06 (mol / L); the mass ratio of Al(NO3)3·9H2O, Ce-MOF, tetra-n-octylammonium bromide, and L-lysine was 1:0.2-0.3:0.01-0.02:0.005-0.

010. The mixed solution was heated and stirred in a water bath under UV light irradiation with an auxiliary UV lamp. The UV light wavelength was 365 nm, and the illuminance was 120-150 mW / cm². 2 The heating temperature in the water bath is 50-60°C, and the process takes 30-60 min. The mixed solution is then transferred to a reaction vessel for a solvothermal reaction under closed conditions at 150-200°C for 12-24 h. After the reaction, the product is centrifuged and dried at 60°C for 5 h to obtain precursor particles. (2) The above precursor was calcined at high temperature in a muffle furnace to obtain Al2O3 / CeO2 composite material. The calcination regime was as follows: the temperature was raised to 600-700°C at a heating rate of 1-5 °C / min in an air atmosphere and held for 2-4 h to obtain Al2O3 / CeO2 as hexagonal bipyramidal particles.

2. The synthesis method according to claim 1, characterized in that: The obtained Al2O3 / CeO2 hexagonal bipyramidal particles have a size of 0.5-5.0 μm, with hexagonal bipyramidal structures at both ends and short pillars in the middle region having a size of 0.2-2.5 μm.

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