Application of MOF with Co2Ti metal cluster in catalytic degradation of ozone

Abstract

The invention belongs to the technical field of ozone degradation, and particularly relates to application of MOF with Co2Ti metal clusters in catalytic degradation of ozone. The molecular formula of the Co2Ti metal cluster is Co2Ti (mu3-O) (COO) 6 (H2O) 3, two H2O molecules on Co atom coordination can be removed after activation, Co2Ti (mu3-O) (COO) 6 (H2O) is formed, and two open metal sites of Co are generated. The MOF with the Co2Ti metal cluster can be used for catalytic degradation of ozone.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ozone degradation, and particularly relates to application of MOF with Co2Ti metal cluster in catalytic degradation of ozone. BACKGROUND

[0002] Ozone pollution near the ground is one of the current severe environmental problems, which poses a serious threat to human health, crop growth and ecological environment. Traditional ozone removal technologies mainly rely on metal oxides (such as manganese oxides, iron oxides, etc.) and activated carbon materials. Although these materials perform well in stability, their degradation efficiency significantly decreases under high-concentration ozone conditions, especially in high-humidity environments, which limits their practical application range. In addition, the existing catalytic materials still lack the ability to continuously and efficiently degrade low-concentration ozone (such as 1 ppm) under high-humidity conditions, which is difficult to meet the indoor air quality standards (such as the ozone concentration limit value specified in GB / T 18883-2022).

[0003] Metal-organic framework materials (MOF) have broad prospects in the field of catalysis due to their adjustable pore structure, high specific surface area and clear active sites. However, the MOF materials currently used for ozone degradation are mostly limited to single metal clusters (such as Mn and Fe-based MOF), and their adaptability and stability to complex environmental conditions (such as full humidity range or high-concentration ozone) still need to be improved. In particular, the application of bimetallic cluster MOF with high activity, high stability and environmental adaptability in ozone catalytic degradation has not been fully explored. SUMMARY

[0004] In view of the problems in the prior art, the application provides application of MOF with Co2Ti metal cluster in catalytic degradation of ozone.

[0005] Further, the molecular formula of the Co2Ti metal cluster is Co2Ti(μ3-O)(COO)6(H2O)3. When the MOF material is activated, Co2Ti(μ3-O)(COO)6(H2O)3 will lose 2 H2O molecules coordinated to Co atoms to form Co2Ti(μ3-O)(COO)6(H2O), thereby generating two open metal sites of Co.

[0006] Further, the MOF with Co2Ti metal cluster is one of PCN-250(Co2Ti) and MIL-100(Co2Ti).

[0007] Further, the molecular formula of the PCN-250(Co2Ti) is C 24 H 15 Co2N3O 16Ti, is an orange crystal material synthesized by 3,3', 5,5'-tetracarboxy azobenzene, tetrapropyl titanate and cobalt acetate tetrahydrate under solvothermal conditions.

[0008] Further, the molecular formula of the MIL-100(Co2Ti) is C 42 H 30 Co2O 16 Ti, is a light pink crystal material synthesized by 1,3,5-benzenetricarboxylic acid, tetrapropyl titanate and cobalt nitrate hexahydrate under solvothermal conditions.

[0009] Further, the synthesis method of the PCN-250(Co2Ti) comprises the following steps: The cobalt acetate tetrahydrate is dissolved in N,N dimethylformamide (DMF), the solid is completely dissolved by ultrasonic, tetrapropyl titanate and acetic acid are added, and the high-pressure reaction kettle is put into 130 ℃ for 2h, 3,3', 5,5'-tetracarboxy azobenzene is added in the high-pressure reaction kettle and reacted at 130 ℃ for 60h, after the reaction is completed, centrifugal separation is carried out, and the material is activated to obtain the material PCN-250(Co2Ti).

[0010] Further, the mass ratio of the 3,3', 5,5'-tetracarboxy azobenzene and the cobalt acetate tetrahydrate is 1:1, the volume ratio of the tetrapropyl titanate, acetic acid and DMF is 0.3:36:60, and the volume (mL) of DMF corresponding to each milligram of the organic ligand 3,3', 5,5'-tetracarboxy azobenzene is 12:1.

[0011] Further, the synthesis method of the MIL-100(Co2Ti) comprises the following steps: The cobalt nitrate hexahydrate and 1,3,5-benzenetricarboxylic acid are dissolved in a mixed solvent of N,N dimethylacetamide (DMA) and ethylene glycol, tetrapropyl titanate is added, and the high-pressure reaction kettle is put into 150 ℃ for 210 min, after the reaction is completed, centrifugal separation is carried out, and the material is activated to obtain the material MIL-100(Co2Ti).

[0012] Further, the molar ratio of the 1,3,5-benzenetricarboxylic acid and the Co(NO3)2·6H2O is 1:1, the volume ratio of the ethylene glycol and the DMA is 6:1, and the volume ratio of the tetrapropyl titanate and the mixed solvent is 5 μL:7 mL.

[0013] Further, the activation method of the PCN-250(Co2Ti) and the MIL-100(Co2Ti) material is that the sample is washed with a DMF solvent, then immersed in a methanol solvent for solvent exchange for 3-4 times, then the sample immersed in the methanol is dried at room temperature, and the desolvated dry sample is obtained by degassing at 120 ℃ for 12 hours.

[0014] Further, PCN-250(Co2Ti) can realize catalytic degradation of low-concentration ozone under full humidity, and the ozone degradation rate is above 98% when the ozone concentration is 1 ppm.

[0015] Further, MIL-100(Co2Ti) can realize catalytic degradation of high-concentration ozone under the condition of RH = 0-20%, and the ozone degradation rate is above 99.9% when the ozone concentration is 50 ppm.

[0016] Compared with the prior art, the application has the following beneficial effects: (1) PCN-250(Co2Ti) can maintain a degradation rate of above 98% under the condition of low-concentration ozone (1 ppm) even in a high-humidity (RH = 90%) environment, and the continuous stability is above 1400 minutes.

[0017] (2) MIL-100(Co2Ti) can realize a degradation efficiency of above 99.9% under the condition of 50 ppm high-concentration ozone and low humidity (RH = 0-20%).

[0018] (3) Through directional design of open metal sites, the material still maintains crystal structure integrity after long-term ozone blowing (PCN-250(Co2Ti) for 100 hours, and MIL-100(Co2Ti) for 24 hours), and no obvious activity attenuation is found.

[0019] (4) The metal cluster Co2Ti(μ3-O)(COO)6(H2O)3 forms Co open sites after activation, directly participates in catalysis and decomposition of ozone, and the number of active sites can be accurately controlled through synthesis conditions.

[0020] In summary, the Co2Ti-MOF material provided by the application not only overcomes the limitations of traditional catalysts in high-humidity or high-concentration ozone environments, but also realizes efficient, stable and environment-adaptive ozone degradation through a double-metal synergistic effect, and has significant industrial application potential. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a PCN-250(Co2Ti) powder X-ray diffraction (PXRD) pattern.

[0022] Figure 2 is a MIL-100(Co2Ti) powder X-ray diffraction pattern.

[0023] Figure 3 is a PCN-250(Co2Ti) degradation efficiency curve under the condition of an inlet flow of 1000 mL / min and a relative humidity RH < 1% for ozone with a concentration of 1 ppm.

[0024] Figure 4 Degradation efficiency curve of PCN-250 (Co2Ti) for 1 ppm ozone at an inlet flow of 1000 mL / min and relative humidity RH = 50%.

[0025] Figure 5 Degradation efficiency curve of PCN-250 (Co2Ti) for 1 ppm ozone at an inlet flow of 1000 mL / min and relative humidity RH = 90%.

[0026] Figure 6 Degradation efficiency curve of MIL-100 (Co2Ti) for 50 ppm ozone at an inlet flow of 1000 mL / min and relative humidity RH < 1%.

[0027] Figure 7 Degradation efficiency curve of MIL-100 (Co2Ti) for 50 ppm ozone at an inlet flow of 1000 mL / min and relative humidity RH = 20%.

[0028] Figure 8 Powder X-ray diffraction (PXRD) of PCN-250 (Co2Ti) at an inlet flow of 1000 mL / min and relative humidity RH = 50% for 50 ppm ozone after 24 h and 100 h of ozone exposure.

[0029] Figure 9 Powder X-ray diffraction (PXRD) of MIL-100 (Co2Ti) at an inlet flow of 1000 mL / min and relative humidity RH = 50% for 50 ppm ozone after 24 h of ozone exposure.

[0030] Figure 10 Catalytic mechanism diagram of the present application.

[0031] Figure 11 Schematic diagram of water molecule removal of metal cluster of the present application. DETAILED DESCRIPTION

[0032] Example 1 Synthesis of PCN-250 (Co2Ti) PCN-250(Co2Ti) was synthesized by dissolving 720 mg of cobalt acetate tetrahydrate in 60 mL of N,N-dimethylformamide (DMF) with ultrasonic treatment to dissolve the solid completely, adding titanium tetrapropoxide 300 μL and acetic acid 36 mL, and placing the mixture in an autoclave for reaction at 130 °C for 2 h. Then, 720 mg of 3,3',5,5'-tetracarboxyazobenzene was added to the autoclave and the mixture was reacted at 130 °C for 60 h. After the reaction was completed, the mixture was centrifuged, washed with DMF and methanol alternately, and vacuum-dried at 100-120 °C for 8-12 h to obtain the material PCN-250(Co2Ti).

[0033] Example 2 Synthesis of MIL-100(Co2Ti) PCN-250(Co2Ti) was synthesized by dissolving 720 mg of cobalt acetate tetrahydrate in 60 mL of N,N-dimethylformamide (DMF) with ultrasonic treatment to dissolve the solid completely, adding titanium tetrapropoxide 300 μL and acetic acid 36 mL, and placing the mixture in an autoclave for reaction at 130 °C for 2 h. Then, 720 mg of 3,3',5,5'-tetracarboxyazobenzene was added to the autoclave and the mixture was reacted at 130 °C for 60 h. After the reaction was completed, the mixture was centrifuged, washed with DMF and methanol alternately, and vacuum-dried at 100-120 °C for 8-12 h to obtain the material PCN-250(Co2Ti).

[0034] Example 1 PXRD of PCN-250(Co2Ti) and MIL-100(Co2Ti) obtained as shown in Figure 1 and Figure 2 , indicating that the two MOF materials described above have been successfully synthesized.

[0035] Example 3 Test of the ozone catalytic performance of PCN-250(Co2Ti) 30 mg of the synthesized PCN-250(Co2Ti) and 200 mg of quartz sand (40-60 mesh) were mixed uniformly and placed in a quartz tube with a length of 15 cm and an inner diameter of 4 mm. Vacuum degassing was performed at a temperature of 120 °C. After the vacuum degassing was completed, the ozone concentration at the gas outlet was detected by an ozone detector. When the ozone concentration was 1 ppm, the permeation tube was connected to the outlet of the ozone generator for testing.

[0036] The results are shown in Figure 3 , Figure 4 , Figure 5 , indicating that the ozone degradation rate of PCN-250(Co2Ti) was more than 98% within 1400 min in an environment with a gas inlet humidity of RH <1%, RH = 50%, and RH = 90%, and the detected ozone concentration was less than 20 ppb.

[0037] Example 4 Test of the ozone catalytic performance of MIL-100(Co2Ti) Take 30 mg of synthesized MIL-100(Co2Ti) and 200 mg of quartz sand (40-60 mesh) and mix them evenly, place them in a quartz tube with a length of 15 cm and an inner diameter of 4 mm, vacuum degas at a temperature of 120°C, and after the ozone detector detects that the ozone concentration at the gas outlet is 50 ppm, the degassing is completed, and then the penetration tube is connected to the ozone generator outlet for testing.

[0038] The results, as shown in Figure 6 , Figure 7 , show that the ozone degradation rate of MIL-100(Co2Ti) is more than 99.99% within 1400 min under the conditions of RH < 1% and RH = 20% at the gas inlet, and the detected ozone concentration is less than 20 ppb.

[0039] Example 5: Ozone stability test of PCN-250(Co2Ti) Take 15 mg of synthesized PCN-250(Co2Ti) and place it in a 4 mL glass vial, and blow RH = 50% and ozone concentration of 50 ppm gas flow at a flow rate of 500 mL / L for a period of time, and then perform powder X-ray diffraction (PXRD) on the material, and the results are shown in Figure 8 , which show that the crystallinity of PCN-250(Co2Ti) is good after 100 h of blowing, indicating its excellent stability.

[0040] Example 6: Ozone stability test of MIL-100(Co2Ti) Take 15 mg of synthesized MIL-100(Co2Ti) and place it in a 4 mL glass vial, and blow RH = 50% and ozone concentration of 50 ppm gas flow at a flow rate of 500 mL / L for a period of time, and then perform powder X-ray diffraction (PXRD) on the material, and the results are shown in Figure 9 , which show that the crystallinity of MIL-100(Co2Ti) is good after 24 h of blowing, indicating its excellent stability.

[0041] Degradation mechanism of the present application Figure 10 : PCN-250(Co2Ti) and MIL-100(Co2Ti) share the same cobalt-based metal cluster structural unit, Co2Ti(μ3-O)(COO)6(H2O)3. In this unit, two Co(II) atoms and one Ti(IV) atom carry eight positive charges, while six carboxylate groups and one oxygen atom carry eight negative charges, achieving charge balance within the metal cluster and thus stabilizing the MOF material's framework structure. During MOF material activation, two H2O molecules are removed from the coordination of the Co atoms, resulting in the molecular formula Co2Ti(μ3-O)(COO)6(H2O) (see...). Figure 11 This leads to the creation of two open metal sites for Co. Under dry conditions, O3 can directly coordinate with the open Co sites to initiate the catalytic cycle. In the presence of H2O molecules in the catalytic environment, the open Co sites will first coordinate with H2O molecules and then react with O3 to initiate the catalytic cycle.

Claims

1. The application of a MOF with a Co2Ti metal cluster in the catalytic degradation of ozone, characterized in that: The molecular formula of the Co2Ti metal cluster is Co2Ti(μ3-O)(COO)6(H2O)3. When the MOF material is activated, Co2Ti(μ3-O)(COO)6(H2O)3 will lose two H2O molecules coordinated to the Co atom to form Co2Ti(μ3-O)(COO)6(H2O), thereby generating two open metal sites for Co.

2. The application of the MOF with Co2Ti metal clusters according to claim 1 in the catalytic degradation of ozone, characterized in that: The MOF containing the Co2Ti metal cluster is PCN-250(Co2Ti), and the molecular formula of PCN-250(Co2Ti) is C. 24 H 15 Co2N3O 16 Ti is an orange crystalline material synthesized under solvothermal conditions using 3,3',5,5'-tetracarboxylated azobenzene, tetrapropyl titanate, and cobalt acetate tetrahydrate.

3. The application of the MOF with Co2Ti metal clusters according to claim 1 in the catalytic degradation of ozone, characterized in that: The MOF containing the Co2Ti metal cluster is MIL-100(Co2Ti), and the molecular formula of MIL-100(Co2Ti) is C. 42 H 30 Co2O 16 Ti is a light pink crystalline material synthesized by solvothermal conditions using pyromellitic acid, tetrapropyl titanate, and cobalt nitrate hexahydrate.

4. The application of the MOF with Co2Ti metal clusters according to claim 2 in the catalytic degradation of ozone, characterized in that: The synthesis method of PCN-250 (Co2Ti) includes the following steps: Cobalt acetate tetrahydrate was dissolved in N,N-dimethylformamide (DMF), and the solid was sonicated until completely dissolved. Tetrapropyl titanate and acetic acid were added, and the mixture was placed in a high-pressure reactor and reacted at 130 °C for 2 h. Then, 3,3',5,5'-tetracarboxylated azobenzene was added to the high-pressure reactor and reacted at 130 °C for 60 h. After the reaction was completed, the mixture was centrifuged and the material was activated to obtain material PCN-250 (Co2Ti).

5. The application of the MOF with Co2Ti metal clusters according to claim 4 in the catalytic degradation of ozone, characterized in that: The mass ratio of 3,3',5,5'-tetracarboxylated azobenzene to cobalt acetate tetrahydrate is 1:1, the volume ratio of tetrapropyl titanate, acetic acid and DMF is 0.3:36:60, and the volume ratio of DMF (mL) per milligram of organic ligand 3,3',5,5'-tetracarboxylated azobenzene is 12:

1.

6. The application of the MOF with Co2Ti metal clusters according to claim 3 in the catalytic degradation of ozone, characterized in that: The synthesis method of MIL-100(Co2Ti) includes the following steps: Cobalt nitrate hexahydrate and pyromellitic acid were dissolved in a mixed solvent of N,N-dimethylacetamide (DMA) and ethylene glycol. Tetrapropyl titanate was then added, and the mixture was placed in a high-pressure reactor and reacted at 150 °C for 210 min. After the reaction was completed, the mixture was centrifuged and the material was activated to obtain material MIL-100 (Co2Ti).

7. The application of the MOF with Co2Ti metal clusters according to claim 6 in the catalytic degradation of ozone, characterized in that: The molar ratio of pyromellitic acid and Co(NO3)2·6H2O is 1:1, the volume ratio of ethylene glycol and DMA is 6:1, and the volume ratio of tetrapropyl titanate and mixed solvent is 5 μL:7 mL.

8. The application of the MOF with Co2Ti metal clusters according to claim 2 or 3 in the catalytic degradation of ozone, characterized in that: The activation method for the PCN-250 (Co2Ti) and MIL-100 (Co2Ti) materials is as follows: the sample is washed with DMF solvent, then immersed in methanol solvent, and solvent exchange is performed for 3-4 times. The sample immersed in methanol is then dried at room temperature and degassed at 120 °C for 12 hours to obtain the desolventized dry sample of the material.

9. The application of the MOF with Co2Ti metal clusters according to claim 2 in the catalytic degradation of ozone, characterized in that: PCN-250(Co2Ti) can achieve catalytic degradation of low concentrations of ozone under full humidity conditions, with an ozone concentration of 1 ppm and an ozone degradation rate of over 98%.

10. The application of the MOF with Co2Ti metal clusters according to claim 2 in the catalytic degradation of ozone, characterized in that: MIL-100(Co2Ti) can achieve catalytic degradation of high concentrations of ozone under RH = 0-20% conditions, with an ozone concentration of 50 ppm and an ozone degradation rate of over 99.9%.

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