A rare earth heterojunction photocatalyst material and a preparation method thereof

Abstract

A method for preparing a rare-earth-containing heterojunction catalyst material CeO2 / Sm-MOF involves dissolving samarium nitrate hexahydrate and H4TBAPy in a composite solvent to form a mixed solution, followed by hydrothermal reaction to obtain Sm-MOF. Cerium ammonium nitrate and Sm-MOF are then dissolved in an aqueous solution of γ-valerolactone, followed by the addition of H2O2 and triethanolamine to form a mixed solution. The mixture is magnetically stirred at 45-55°C for 2-3 hours, followed by hydrothermal reaction and calcination. This invention improves the thermal stability of Sm-MOF by using cerium ammonium nitrate as the Ce source and combining a two-step heat treatment process. This effectively enhances the bonding force and distribution uniformity of CeO2 on the Sm-MOF surface, improving the catalytic activity and cycle stability of CeO2 / Sm-MOF. It exhibits excellent degradation efficiency for MB, RhB, ATZ, CIP, etc., and demonstrates excellent cycle stability during cycling.

Description

Technical Field

[0001] This invention relates to the field of rare earth catalyst technology, specifically to a rare earth heterojunction photocatalyst and its preparation method. Background Technology

[0002] With rapid economic and social development and accelerated urbanization, environmental pollution and energy shortages have become increasingly serious problems. Photocatalysis is a technology that uses semiconductor materials as its core, absorbing light energy of specific wavelengths (such as ultraviolet or visible light) to excite the material to generate photo-generated electrons (electrons) with strong redox activity. - and hole h + This is a green catalytic technology that drives target chemical reactions (such as pollutant degradation, energy conversion, and substance synthesis). Its core feature is the use of clean energy (light energy) to achieve a low-energy-consumption, pollution-free reaction process. Moreover, the catalyst only provides active sites in the reaction and is not consumed, which conforms to the concepts of "atom economy" and "sustainable development".

[0003] Despite its wide range of applications, photocatalysis technology still faces three major challenges: firstly, the photocatalysts lack a broad spectral response, only responding to ultraviolet light (accounting for 4% of solar energy); secondly, the photocatalysts have low carrier separation efficiency, resulting in low photogenerated energy. - -h + The recombination rate is fast; some catalysts, such as MOF, have poor stability and are easily decomposed under light, resulting in poor cycle performance. Cerium oxide (CeO2) has the advantages of abundant reserves, low price, strong oxygen storage and release capacity, and stable chemical properties. It has received increasing attention in the field of photocatalysis and is expected to replace traditional photocatalysts in applications such as wastewater and waste gas treatment, water splitting to produce hydrogen and oxygen, and carbon dioxide reduction. CeO2 has shown significant advantages in photocatalytic degradation of industrial chemical pollutants, such as high efficiency, non-toxicity, and low cost. However, the application of CeO2 photocatalyst as a low-cost semiconductor photocatalyst still has shortcomings: (1) Due to the large gap width, it does not make sufficient use of solar visible light and only responds significantly to ultraviolet light; (2) Due to the limited photogenerated electron transport channels in the CeO2 monomer structure and the short lifetime of photogenerated carriers, the photogenerated carriers are very easy to recombine, resulting in unsatisfactory photocatalytic performance.

[0004] Therefore, photocatalytic materials with advantages such as high chemical stability, wide light absorption range, strong light absorption capacity, and high carrier separation efficiency have become a research hotspot. When CeO2 is combined with other semiconductors, MOF materials possess specific catalyst grafting sites, which can effectively promote the construction of heterogeneous photocatalysts. When metal oxides are dispersed inside the MOF, their interaction with ligands inevitably leads to partial charging of the MOF region, and this structural unit can serve as a potential active reaction center. Furthermore, rare earth metal-organic frameworks (RE-MOFs) provide more photocatalytic reaction centers due to the higher coordination number of rare earth metal ions and the abundant open metal sites. Summary of the Invention

[0005] The purpose of this invention is to provide a heterojunction photocatalyst material containing rare earth oxide CeO2. This effectively solves the problems of insufficient utilization of visible solar light due to its large gap width, resulting in only a significant response to ultraviolet light, and the high likelihood of recombination of photogenerated carriers due to the limited photogenerated electron transport channels and short lifetime of photogenerated carriers in the CeO2 monomer structure.

[0006] This invention provides a method for preparing rare-earth heterojunction photocatalyst materials. CeO2 nanoparticles are immobilized on Sm-MOF via a hydrothermal method to construct a photogenerated charge regulation system. This method addresses the problems of severe CeO2 aggregation on the MOF surface and weak binding force with the MOF, as well as the poor thermal stability of the MOF, which leads to structural collapse during the hydrothermal reaction, affecting the binding and distribution uniformity of CeO2. This method enhances the photogenerated carrier separation and migration capabilities of the CeO2 material, further improving the surface reaction rate and thus enhancing its photocatalytic performance, enabling applications in the photocatalytic degradation of organic matter.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a CeO2 / Sm-MOF heterojunction catalyst material, characterized by comprising the following steps: Synthesis of S1.Sm-MOF Samarium nitrate hexahydrate Sm(NO3)3-6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) were mixed and dissolved in a composite solvent to form a mixture, which was then subjected to a hydrothermal reaction to obtain Sm-TBAPy. Synthesis of S2.CeO2 / Sm-MOF (1) Low temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixture. The mixture was magnetically stirred at 45~55℃ for 2~3h. (2) Hydrothermal treatment: The mixed solution is transferred to a high-pressure reactor for hydrothermal reaction; (3) Roast the hydrothermal products.

[0008] Furthermore, in step S1, the hydrothermal reaction involves heating the mixture at a constant temperature of 115~125℃ for 48~55 hours.

[0009] Furthermore, in step S1, the composite solvent is composed of N,N-dimethylformamide (DMF), water, and γ-valerol (GVL) in a volume ratio of 3:1.5~2.5:0.5~0.8.

[0010] Furthermore, in step S1, the molar volume ratio of Sm(NO3)3-6H2O, H4TBAPy and the composite solvent is 0.4 mmol: 0.25~0.35 mmol: 40 mL.

[0011] Furthermore, the hydrothermal treatment temperature in S2 is 95~105℃, and the reaction time is 40~48h.

[0012] Furthermore, the molar volume ratio of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerol in the aqueous solution of S2 is 0.2~0.4mmol:0.1mmol:40mL, and the concentration of γ-valerol in the aqueous solution of γ-valerol is 1.5~2mol / L.

[0013] Furthermore, the molar ratio of H2O2, triethanolamine, and Sm-TBAPy in S2 is 0.3~0.6:0.1~0.12:0.1.

[0014] Furthermore, the calcination treatment involves heating the product to 330-360°C at a rate of 4-6°C / min and holding it at that temperature for 1.5-2.5 hours, followed by natural cooling to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

[0015] Using cerium nitrate as the Ce source resulted in severe agglomeration of CeO2 particles, and during the hydrothermal process, Ce... 3+ It is difficult to completely oxidize to form Ce 4+ It easily generates impurity phases, and the catalytic activity of CeO2 depends on Ce. 4+ / Ce 3+ Valence cycling and the presence of a large number of impurities significantly reduce carrier separation efficiency. Meanwhile, the Sm-MOF ligand (TBAPy) contains a large π-conjugated system (pyrene ring) and a carboxyl group (-COO). - These groups have weak reducing properties in aqueous solution and will inhibit Ce to some extent. 4+ The generation of Ce increases 3+ The content significantly reduces the crystal phase purity of CeO2. 3+The formation of impurity phases disrupts the heterojunction interface and reduces photocatalytic efficiency. In this invention, cerium ammonium nitrate (Ce(NH4)2(NO3)6) is selected as the Ce source to directly provide Ce. 4+ NH4 + It can also act as a pH buffer to prevent Ce from forming. 4+ Hydrolysis and aggregation, and the addition of H2O2 during heat treatment, reduce Ce... 3+ Re-oxidized to Ce 4+ It can improve the crystal phase purity of CeO2, and it can also regulate the Ce phase. 4+ The hydrolysis rate is reduced, the growth rate of CeO2 is decreased, thereby inhibiting the abnormal growth of CeO2 size.

[0016] Because Sm-MOF has poor thermal stability, it is prone to collapse during the subsequent hydrothermal composite of CeO2 on its surface. In this invention, DMF and water are used as the main solvents, with the addition of a small amount of γ-valerol (GVL). GVL is a green, strongly polar solvent containing ester groups. The ester group oxygen reacts with Sm... 3+ The formation of weak coordination modulates the crystallization kinetics of Sm-MOF, thereby guiding the localization of Sm. 3+ The -COO- directional coordination with H4TBATy optimizes the coordination process, shortens the hydrothermal reaction time, and improves the thermal stability of Sm-MOF.

[0017] A method for preparing a CeO2 / Sm-MOF heterojunction catalyst material, characterized by comprising the following steps: Synthesis of S1.Sm-MOF First, samarium nitrate hexahydrate Sm(NO3)3-6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) were mixed and dissolved in a composite solvent and magnetically stirred to obtain a homogeneous mixture. The mixture was heated at 115-125℃ for 48-55 h until the hydrothermal reaction was completed and cooled to room temperature. The obtained product was washed at least 3 times and finally dried in a forced-air drying oven to obtain the final Sm-TBAPy. The molar volume ratio of Sm(NO3)3-6H2O, H4TBAPy and composite solvent was 0.4 mmol:0.25-0.35 mmol:40 mL. The composite solvent was composed of N,N-dimethylformamide (DMF), water and γ-valerol (GVL) in a volume ratio of 3:1.5-2.5:0.5-0.8. Synthesis of S2.CeO2 / Sm-MOF (1) Low-temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 45~55℃ for 2~3h. The molar volume ratio of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerolactone aqueous solution was 0.2~0.4mmol:0.1mmol:40mL. The concentration of γ-valerolactone in the aqueous solution was 1.5~2mol / L. The molar ratio of H2O2, triethanolamine and Sm-TBAPy was 0.3~0.6:0.1~0.12:0.1. (2) Hydrothermal treatment: The mixed solution is transferred to a high-pressure reactor for hydrothermal reaction at a temperature of 95-105°C for 40-48 hours. After the hydrothermal reaction is completed and cooled to room temperature, the product is washed at least 3 times. (3) Calcination treatment: The product is heated to 330~360℃ at a rate of 4~6℃ / min and kept at the temperature for 1.5~2.5h, and then naturally cooled to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

[0018] In this invention, cerium ammonium nitrate is used as the Ce source, and a two-step heat treatment process combining low-temperature pretreatment and low-temperature hydrothermal treatment is employed. First, low-temperature pretreatment is used to allow the incompletely coordinated carboxyl groups on the Sm-TBAPy surface to react with Ce. 4+ This combination forms a pre-coordinated structure, which weakens the hydrolysis kinetics during the second-step low-temperature hydrothermal process, allowing Ce to... 4+ Slow crystallization increases crystallinity and reduces CeO2 particle size. The hydroxyl groups in TEA act as bridges, connecting with the carboxyl groups and CeO2 on the Sm-MOF surface. 4+ Combine, to Ce 4+ The uniform anchoring of CeO2 on the Sm-MOF surface enhances the high binding force and uniform distribution of CeO2 on the Sm-MOF surface, thereby improving the catalytic activity and cycle stability of the material.

[0019] A CeO2 / Sm-MOF heterojunction material is characterized by: mixing and dissolving samarium nitrate hexahydrate Sm(NO3)3-6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) in a composite solvent to form a mixed solution, and then reacting it with hydrothermal solution to obtain Sm-TBAPy; mixing and dissolving cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy in an aqueous solution of γ-valerolactone, and then adding H2O2 and triethanolamine to form a mixed solution; and then magnetically stirring the solution at 45~55℃ for 2~3h. The mixed solution is then subjected to hydrothermal treatment and calcination treatment in sequence.

[0020] Furthermore, the hydrothermal reaction involves heating the mixture at a constant temperature of 115~125℃ for 48~55 hours.

[0021] Furthermore, the composite solvent is composed of N,N-dimethylformamide (DMF), water, and γ-valerol (GVL) in a volume ratio of 3:1.5~2.5:0.5~0.8.

[0022] Furthermore, the molar volume ratio of Sm(NO3)3-6H2O, H4TBAPy and the composite solvent is 0.4 mmol: 0.25~0.35 mmol: 40 mL.

[0023] Furthermore, the hydrothermal treatment temperature is 95~105℃, and the reaction time is 40~48h.

[0024] Furthermore, the molar volume ratio of the aqueous solutions of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerol is 0.2~0.4mmol:0.1mmol:40mL, and the concentration of γ-valerol in the aqueous solution is 1.5~2mol / L.

[0025] Furthermore, the molar ratio of H2O2, triethanolamine, and Sm-TBAPy is 0.3~0.6:0.1~0.12:0.1.

[0026] Furthermore, the calcination treatment involves heating the product to 330-360°C at a rate of 4-6°C / min and holding it at that temperature for 1.5-2.5 hours, followed by natural cooling to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

[0027] The present invention has the following technical effects: In this invention, a specific composite solvent is used to prepare Sm-MOF, which improves the thermal stability of Sm-MOF, making its structure stable and not collapse during subsequent heat treatment. Cerium ammonium nitrate is then used as the Ce source, combined with a two-step heat treatment process, which effectively improves the binding force and distribution uniformity of CeO2 on the Sm-MOF surface, and enhances the catalytic activity and cycling stability of CeO2 / Sm-MOF. It exhibits excellent degradation efficiency for organic dyes such as methylene blue (MB) and rhodamine B (RhB), pesticide pollutants such as atrazine (ATZ), and antibiotics such as ciprofloxacin (CIP), and also has excellent cycling stability during cycling. Attached Figure Description

[0028] Figure 1 Scanning electron microscope image of CeO2 / Sm-MOF prepared in Example 1 of this invention.

[0029] Figure 2Thermogravimetric analysis curves of Sm-MOFs prepared in Example 1 and Comparative Example 1 of this invention.

[0030] Figure 3 The degradation efficiency curves of organic dyes in Example 1 and the comparative examples of the present invention are shown in the figure; (a) is methylene blue, and (b) is rhodamine B.

[0031] Figure 4 The degradation efficiency curves of antibiotics, pesticides and other organic substances in Example 1 and the comparative examples of the present invention are shown in the figure; (a) Example 1, (b) Comparative Example 1, (c) Comparative Example 2, and (d) Comparative Example 3.

[0032] Figure 5 Photocatalytic degradation cycle diagrams of Example 1 and various comparative examples of the present invention. Detailed Implementation

[0033] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0034] Example 1 A method for preparing a CeO2 / Sm-MOF heterojunction material includes the following steps: Synthesis of S1.Sm-MOF First, 0.4 mmol of samarium nitrate hexahydrate Sm(NO3)3-6H2O and 0.3 mmol of 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) were mixed and dissolved in 40 mL of a composite solvent and magnetically stirred to obtain a homogeneous mixture. The mixture was heated at 120 °C for 50 h. After the hydrothermal reaction was completed, it was cooled to room temperature. The product was washed three times and finally dried to obtain Sm-TBAPy. The composite solvent was composed of DMF, water and GVL in a volume ratio of 3:2:0.6. Synthesis of S2.CeO2 / Sm-MOF (1) Low-temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 50°C for 2.5 h. The molar volume ratio of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerolactone aqueous solution was 0.3 mmol:0.1 mmol:40 mL. The concentration of γ-valerolactone in the aqueous solution was 1.6 mol / L. The molar ratio of H2O2, triethanolamine and Sm-TBAPy was 0.4:0.11:0.1. (2) Hydrothermal treatment: The mixed solution was transferred to a high-pressure reactor for hydrothermal reaction at a temperature of 100°C for 45 hours. After the hydrothermal reaction was completed and cooled to room temperature, the product was washed three times. (3) Calcination treatment: The product was heated to 350℃ at a rate of 5℃ / min and kept at that temperature for 2h, and then naturally cooled to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

[0035] The CeO2 / Sm-TBAPy prepared in this embodiment is as follows: Figure 1 As shown, the material has a regular morphology, and CeO2 particles are uniformly attached to the surface of Sm-TBAPy.

[0036] Comparative Example 1 The difference from Example 1 is that the composite solvent used in step S1 is 1,4-dioxane (C4H8O2) instead of GVL (C5H8O2) in Example 1, while the other steps are the same.

[0037] Comparative Example 2 Compared with Example 1, cerium nitrate hexahydrate was used instead of ammonium cerium nitrate, and the remaining steps were the same as in Example 1.

[0038] Comparative Example 3 Compared with Example 1, the difference is that a one-step heat treatment process is used in step S2. Specifically, the mixture obtained in S2 (1) is magnetically stirred at room temperature for 2.5 hours, and then the mixture is transferred to a high-pressure reactor for hydrothermal reaction. The remaining steps are the same as in Example 1.

[0039] Thermogravimetric analysis (TGA) tests of Sm-TBAPy prepared in Example 1 and Comparative Example 1 are as follows: Figure 2 As shown, the Sm-TBAPy prepared in Example 1 exhibits minimal mass loss below 200℃, but significant mass loss occurs between 200 and 500℃, although the loss is gradual and the decomposition temperature is relatively high. This indicates that the Sm-MOF framework contains oxidative decomposition of organic ligands such as pyrene rings and carboxyl groups at this temperature. The Sm-TBAPy prepared in Comparative Example 1 shows a sharp decrease in mass at 200℃, and a rapid decrease in mass within a short temperature range of 300–400℃. This suggests that the Sm-MOF prepared in Comparative Example 1 has numerous defects in its MOF framework, making it prone to collapse during subsequent bonding with CeO2, and that the bonding between CeO2 and the MOF interface is weak.

[0040] The degradation of organic matter by the CeO2 / Sm-TBAPy photocatalyst materials prepared in each group: (1) Degradation of organic dyes: Take 50 mL of a 10 mg / L contaminant solution (methylene blue, rhodamine B), add 50 mg of CeO2 / Sm-MOF catalyst, and stir for 30 min in the dark. After dark adsorption equilibrium is reached, measure the initial absorbance A0 (corresponding to concentration C0). Then turn on the light source (300W full-spectrum xenon lamp) and take 5 mL samples at 30 min, 60 min, 90 min, and 120 min respectively. After filtration, measure the absorbance A. t (Corresponding concentration is C) t The degradation rate is calculated using the following formula: η(%) = [(A0- A t ) / A0] × 100% The results are as follows Figure 3 As shown, CeO2 / Sm-TBAPy prepared in Example 1 has excellent degradation ability for organic dyes methylene blue and rhodamine B. The degradation rate of methylene blue reached 99.2% after 60 min, and the degradation efficiency of rhodamine B reached 95.3% after 60 min. However, the degradation time of each comparative example needs to be further extended to more than 120 min in order to achieve a degradation efficiency of more than 90%.

[0041] (2) Degradation of antibiotic and pesticide organic matter: As in step (1), ciprofloxacin solution, atrazine solution, and pentachlorophenol solution of the same concentration (C0) were taken for catalytic degradation, but after sampling, they were separated and quantified by high performance liquid chromatography (HPLC): Chromatographic column: C18 reversed-phase column (250mm×4.6mm, 5μm, such as Agilent ZORBAX SB-C18); Mobile phase: Ciprofloxacin is treated with "methanol-0.1% phosphoric acid aqueous solution" (volume ratio 30:70), and atrazine is treated with "acetonitrile-water" (volume ratio 40:60). Flow rate: 1.0 mL / min; column temperature: 30℃; detection wavelengths: ciprofloxacin 278 nm, atrazine 222 nm, pentachlorophenol 210 nm; injection volume: 20 μL.

[0042] Prepare standard solutions of pollutants at concentrations of 0.1, 1, 5, 10, and 20 mg / L, inject the samples, and measure the peak area. Plot a standard curve using the "concentration-peak area" formula, record the peak areas, and calculate the corresponding concentration Ct using the Lambert-Beer law. Then, calculate A0 / A... t ≈C0 / C t The degradation rate is calculated using the same formula as above.

[0043] The results are as follows Figure 4As shown, the CeO2 / Sm-MOF catalyst prepared in Example 1 achieved a 95.4% degradation rate of ciprofloxacin at 90 min, and 96.1% and 90.2% degradation rates of atrazine and pentachlorophenol at 90 min, respectively. While the degradation efficiency for pentachlorophenol was slightly lower, it further increased to 93.6% when the degradation time was extended to 120 min. In contrast, the CeO2 / Sm-TBAPy catalysts prepared in each comparative example showed significantly lower degradation efficiencies for the aforementioned organic compounds at the same time compared to Example 1.

[0044] Catalyst catalytic cycle stability test: After 90 min of ciprofloxacin degradation, the catalyst was centrifuged at 8000 rpm for 10 min to recover it. It was then washed three times with deionized water, vacuum dried, and added back into a fresh contaminant solution for repeated degradation. The cycle curve is shown below. Figure 5 As shown. The CeO2 / Sm-MOF prepared in Example 1 still achieved a degradation and removal rate of over 95% of the initial degradation efficiency for ciprofloxacin after 5 cycles, demonstrating excellent cycling stability. In contrast, the degradation efficiency of each comparative example decreased significantly after 5 cycles, with Comparative Example 3 showing the most severe decrease.

[0045] Example 2 A method for preparing a CeO2 / Sm-MOF heterojunction material includes the following steps: Synthesis of S1Sm-MOF First, samarium nitrate hexahydrate Sm(NO3)3–6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) were mixed and dissolved in 40 mL of composite solvent at a molar ratio of 4:3 (0.4 mmol Sm(NO3)3–6H2O + 0.3 mmol H4TBAPy) and magnetically stirred to obtain a homogeneous mixture. The mixture was heated at 115 °C for 48 h. After the hydrothermal reaction was completed, it was cooled to room temperature. The obtained product was washed three times and dried to obtain the final Sm-TBAPy. The composite solvent was composed of DMF, water and GVL in a volume ratio of 3:1.5:0.5. Synthesis of S2.CeO2 / Sm-MOF (1) Low-temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 45°C for 3 h. The molar volume ratio of the aqueous solution of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerolactone was 0.2 mmol:0.1 mmol:40 mL. The concentration of γ-valerolactone in the aqueous solution was 1.5 mol / L. The molar ratio of H2O2, triethanolamine and Sm-TBAPy was 0.3:0.1:0.1. (2) Hydrothermal treatment: The mixed solution is then transferred to a high-pressure reactor for hydrothermal reaction at a temperature of 105°C for 40 hours. After the hydrothermal reaction is completed and cooled to room temperature, the product is washed three times. (3) Calcination treatment: The product was heated to 330℃ at a rate of 4℃ / min and kept at that temperature for 2.5h, and then naturally cooled to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

[0046] Example 3 A method for preparing a CeO2 / Sm-MOF heterojunction material includes the following steps: Synthesis of S1.Sm-MOF First, samarium nitrate hexahydrate Sm(NO3)3-6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) were simultaneously dissolved in 40 mL of a composite solvent at a molar ratio of 4:2.5 (0.4 mmol Sm(NO3)3-6H2O + 0.25 mmol H4TBAPy). The mixture was then magnetically stirred to obtain a homogeneous solution. The solution was heated at 125 °C for 55 h. After the hydrothermal reaction was completed, the solution was cooled to room temperature. The resulting product was washed three times and dried to obtain the final Sm-TBAPy. The composite solvent was composed of DMF, water, and GVL in a volume ratio of 3:2.5:0.8. Synthesis of S2.CeO2 / Sm-MOF (1) Low-temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 55°C for 2 hours. The molar volume ratio of the aqueous solution of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerolactone was 0.4 mmol:0.1 mmol:40 mL. The concentration of γ-valerolactone in the aqueous solution was 2 mol / L, and the molar ratio of H2O2, triethanolamine and Sm-TBAPy was 0.6:0.12:0.1. (2) Hydrothermal treatment: The mixed solution was transferred to a high-pressure reactor for hydrothermal reaction at a temperature of 95°C for 48 hours. After the hydrothermal reaction was completed and cooled to room temperature, the product was washed three times. (3) Calcination treatment: The product was heated to 360℃ at a rate of 6℃ / min and kept at that temperature for 1.5h, and then naturally cooled to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst.

Claims

1. A method for preparing a CeO2 / Sm-MOF heterojunction catalyst material, characterized in that, Includes the following steps: Synthesis of S1.Sm-MOF Samarium nitrate hexahydrate Sm(NO3)3·6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy were mixed and dissolved in a composite solvent to form a mixture. After hydrothermal reaction, Sm-TBAPy was obtained. The composite solvent was composed of N,N-dimethylformamide DMF, water and γ-valerol GVL in a volume ratio of 3:1.5~2.5:0.5~0.

8. The molar volume ratio of Sm(NO3)3·6H2O, H4TBAPy and composite solvent was 0.4mmol:0.25~0.35mmol:40mL. Synthesis of S2.CeO2 / Sm-MOF (1) Low temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 45~55℃ for 2~3h. (2) Hydrothermal treatment: The mixed solution is transferred to a high-pressure reactor for hydrothermal reaction; (3) Roast the hydrothermal products.

2. The preparation method of a CeO2 / Sm-MOF heterojunction catalyst material as described in claim 1, characterized in that: In step S1, the hydrothermal reaction involves heating the mixture at a constant temperature of 115-125°C for 48-55 hours.

3. The preparation method of a CeO2 / Sm-MOF heterojunction catalyst material as described in claim 2, characterized in that: The hydrothermal treatment in S2 is carried out at a temperature of 95~105℃ for a reaction time of 40~48h.

4. The method for preparing a CeO2 / Sm-MOF heterojunction catalyst material as described in claim 3, characterized in that: The molar volume ratio of the aqueous solutions of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerol in S2 is 0.2~0.4mmol:0.1mmol:40mL, and the concentration of γ-valerol in the aqueous solution is 1.5~2mol / L.

5. The method for preparing a CeO2 / Sm-MOF heterojunction catalyst material as described in claim 3 or 4, characterized in that: The molar ratio of H2O2, triethanolamine and Sm-TBAPy in S2 is 0.3~0.6:0.1~0.12:0.

1.

6. A method for preparing a CeO2 / Sm-MOF heterojunction catalyst material, characterized in that, It includes the following steps: Synthesis of S1.Sm-MOF First, samarium nitrate hexahydrate Sm(NO3)3·6H2O and 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy were mixed and dissolved in a composite solvent and magnetically stirred to obtain a homogeneous mixture. The mixture was heated at 115~125℃ for 48~55h until the hydrothermal reaction was completed and cooled to room temperature. The obtained product was washed at least 3 times and finally dried in a forced-air drying oven to obtain the final Sm-TBAPy. The molar volume ratio of Sm(NO3)3·6H2O, H4TBAPy and composite solvent was 0.4mmol:0.25~0.35mmol:40mL. The composite solvent was composed of N,N-dimethylformamide (DMF), water and γ-valerol (GVL) in a volume ratio of 3:1.5~2.5:0.5~0.

8. Synthesis of S2.CeO2 / Sm-MOF (1) Low-temperature pretreatment: Cerium ammonium nitrate Ce(NH4)2(NO3)6 and Sm-TBAPy were mixed and dissolved in an aqueous solution of γ-valerolactone, and then H2O2 and triethanolamine were added to form a mixed solution. The solution was magnetically stirred at 45~55℃ for 2~3h. The molar volume ratio of the aqueous solution of Ce(NH4)2(NO3)6, Sm-TBAPy and γ-valerolactone was 0.2~0.4mmol:0.1mmol:40mL. The concentration of γ-valerolactone in the aqueous solution was 1.5~2mol / L. The molar ratio of H2O2, triethanolamine and Sm-TBAPy was 0.3~0.6:0.1~0.12:0.

1. (2) Hydrothermal treatment: The mixed solution is transferred to a high-pressure reactor for hydrothermal reaction at a temperature of 95-105°C for 40-48 hours. After the hydrothermal reaction is completed and cooled to room temperature, the product is washed at least 3 times. (3) Calcination treatment: The product is heated to 330~360℃ at a rate of 4~6℃ / min and kept at the temperature for 1.5~2.5h, and then naturally cooled to room temperature to obtain CeO2 / Sm-TBAPy photocatalyst material.

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