Preparation method and application of amorphous cobalt-based metal organic framework material
Amorphous Co-MOF-74-A was directly synthesized using an anion-controlled strategy, solving the problems of stability and efficiency of MOF materials in ozone decomposition. This achieved efficient ozone decomposition under full humidity conditions, simplified the synthesis steps, and reduced energy consumption.
Patent Information
- Application Number
- CN202511013768.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-11-07
AI Technical Summary
Existing MOF materials suffer from low stability, inactivation under extreme humidity conditions, and expensive raw materials in the field of ozone decomposition. Furthermore, the synthesis of amorphous MOFs is complex and energy-intensive, making it difficult to meet the requirements for efficient ozone decomposition.
Amorphous Co-MOF-74-A was directly synthesized using an anion-controlled strategy. Using 2,5-dihydroxyterephthalic acid and cobalt acetylacetonate as raw materials, the amorphous cobalt-based metal-organic framework material Co-MOF-74-A was prepared through ultrasonic dissolution, heating and washing steps, and then mixed with quartz sand for catalytic decomposition of ozone.
The prepared amorphous Co-MOF-74-A achieved nearly 100% ozone decomposition efficiency across the entire humidity range, exhibiting high catalytic activity and good moisture resistance. This overcomes the shortcomings of traditional MOF materials in ozone decomposition and provides a simple synthesis method.
Smart Images
Figure CN120904473A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of new materials, and relates to a preparation method and application of amorphous cobalt-based metal organic framework material Co-MOF-74-A, in particular to a preparation method and application of a catalyst with good moisture resistance and high efficiency in decomposing ozone in a full-humidity range. BACKGROUND
[0002] Ozone is one of the typical air pollutants defined by the World Health Organization, and indoor and outdoor ozone pollution problems have attracted widespread attention. Household items such as printers and air purifiers will produce a certain amount of ozone during use. Long-term exposure to high-concentration ozone environments indoors can cause damage to the respiratory and nervous systems, thereby causing irreversible damage to the body. Therefore, how to efficiently remove ozone has become one of the main problems in current research.
[0003] Metal organic frameworks (MOFs) are a new type of porous material, and have attracted much attention from researchers in various catalytic reactions due to their adjustable structure and diversified functions, and have shown great potential in the field of ozone decomposition. However, MOFs materials such as MIL-100 (Fe), ZZU-281 and PCN-250 mostly rely on the decomposition of ozone by metal sites in the framework, and still have problems such as low stability, deactivation under extreme humidity conditions and expensive raw materials. Therefore, it is urgent to develop new strategies to adjust MOFs to improve their catalytic activity in ozone decomposition.
[0004] Amorphization has been considered as an effective means to improve the catalytic performance of MOFs. Unlike crystalline MOFs, amorphous MOFs lack long-range order, but retain the basic structural units of MOFs, and at the same time produce rich structural defects, have higher electrical conductivity and more active sites. Although amorphous MOFs have shown great potential in frontier application fields, the research field is still in its infancy. On the one hand, the synthesis steps are complex, which makes it difficult to precisely control the crystallization process and phase transition; on the other hand, the long-term structural stability of MOFs under various operating conditions also faces many severe challenges. At present, most amorphous MOFs are prepared by applying external forces to the parent crystalline framework, such as heating, applying pressure (including hydrostatic pressure and non-hydrostatic pressure) and ball milling. These amorphization methods can prepare materials with specific advantages, but they usually have high energy consumption, and need to synthesize crystalline materials first, and sometimes the prepared materials do not have porosity. Therefore, it is a great challenge to design a simple and direct method to accurately synthesize amorphous MOFs and meet the efficient decomposition of ozone under various conditions. SUMMARY
[0005] To solve the above problems, the application proposes an anion regulation strategy to directly synthesize amorphous MOFs, selects MOF-74 with good thermal stability and chemical stability as a template to synthesize amorphous Co-MOF-74-A, and uses the amorphous Co-MOF-74-A as a catalyst to catalytically decompose ozone.
[0006] The technical scheme adopted by the application is:
[0007] A preparation method of an amorphous cobalt-based metal organic framework material, comprising the following steps:
[0008] 1) Dissolve 2,5-dihydroxyterephthalic acid and cobalt acetylacetonate (Co(C5H7O2)2·xH2O) in N,N-dimethylformamide, place them in a glass vial, and seal the vial;
[0009] 2) After ultrasonic dissolution, seal the container and place it in an oven for heating;
[0010] 3) After cooling to room temperature, wash the container with N,N-dimethylformamide and ethanol, centrifuge, dry, and collect the obtained powder as Co-MOF-74-A.
[0011] Further, in the above preparation method, in step 2), the heating condition is: heating at 120°C for 24 hours.
[0012] Further, in the above preparation method, in step 3), the drying temperature is 60°C.
[0013] The application of the amorphous cobalt-based metal organic framework material prepared by any one of the above preparation methods in catalytic ozone decomposition.
[0014] Further, in the above application, the method is as follows: uniformly mix the amorphous cobalt-based metal organic framework material Co-MOF-74-A with quartz sand in an agate mortar, place them in a U-shaped glass tube, seal and fix them with absorbent cotton on both sides, and perform catalytic decomposition of ozone.
[0015] Further, in the above application, the mass ratio of the Co-MOF-74-A to the quartz sand is 1:9.
[0016] Preferably, the amount of the Co-MOF-74-A is 50 mg.
[0017] Further, in the above application, the condition for catalytic decomposition of ozone is: at room temperature, the ozone concentration is 20 ppm, 30 ppm, or 40 ppm, and the humidity is 10% ≤ RH ≤ 90%.
[0018] The application has the following beneficial effects:
[0019] 1. The catalyst synthesis method of the present application is simple to operate, highly repeatable and mild in conditions.
[0020] 2. The amorphous Co-MOF-74-A prepared by the present application has the following characteristics: a) a large number of oxygen vacancies; b) a layered porous structure; and c) a high density of metal active centers, which synergistically reduces the binding energy between the metal sites and O3 molecules, promotes the adsorption and activation of O3 molecules, and thus improves the catalytic performance for O3 decomposition.
[0021] 3. The amorphous Co-MOF-74-A prepared by the present application can effectively solve the problems of insufficient catalytic ability, deactivation under extreme humidity conditions and high cost of raw materials for synthesis of some MOFs materials in the process of catalytic ozone decomposition. At the same time, the Co-MOF-74-A of the present application can achieve nearly 100% ozone decomposition efficiency under full humidity conditions, revealing the potential advantages of amorphous MOFs in the field of ozone decomposition, and providing new strategies and ideas for direct regulation of MOFs crystal state. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 Figure 1 is a PXRD pattern of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1.
[0023] Figure 2 Figure 2 is an ultraviolet-visible diffuse reflectance spectrum of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1.
[0024] Figure 3 Figure 3 is a 77 K nitrogen adsorption curve of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1.
[0025] Figure 4 Figure 4 is a SEM image of Co-MOF-74-N (a) prepared in Comparative Example 1, Co-MOF-74-C (b) prepared in Comparative Example 2 and Co-MOF-74-A (c) prepared in Example 1.
[0026] Figure 5 Figure 5 is an EPR spectrum of Co-MOF-74-N (a) prepared in Comparative Example 1, Co-MOF-74-C (b) prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1.
[0027] Figure 6is a plot of the ozone decomposition performance of Co-MOF-74-N (a) prepared in Comparative Example 1, Co-MOF-74-C (b) prepared in Comparative Example 2, and Co-MOF-74-A prepared in Example 1 at 30% RH.
[0028] Figure 7 is a plot of the ozone decomposition performance of Co-MOF-74-A prepared in Example 1 at different catalyst mass.
[0029] Figure 8 is a plot of the ozone decomposition performance of Co-MOF-74-A prepared in Example 1 at different relative humidity.
[0030] Figure 9 is a plot of the ozone decomposition performance of Co-MOF-74-A prepared in Example 1 at different ozone concentration.
[0031] Figure 10 is a plot of the ozone decomposition performance of Co-MOF-74-A prepared in Example 1 under dry-wet cycle test between 30% and 90% relative humidity. DETAILED DESCRIPTION
[0032] The present application is further described in the following examples. The examples described are part of the present application, but not all-inclusive of the present application.
[0033] Comparative Example 1
[0034] The method for preparing Co-MOF-74-N includes the following steps:
[0035] 1) Dissolve 2,5-dihydroxyterephthalic acid and cobalt nitrate (Co(N03)2·6H20) in 15 mL of N,N-dimethylformamide (DMF), place in a 20 mL glass vial and seal;
[0036] 2) After ultrasonic dissolution, seal the container and place it in a 120°C oven for 24 hours;
[0037] 3) After cooling to room temperature, wash with N,N-dimethylformamide and ethanol, centrifuge, dry in a 60°C oven, and collect the resulting powder as Co-MOF-74-N.
[0038] Comparative Example 2
[0039] The method for preparing Co-MOF-74-C includes the following steps:
[0040] 1) Dissolve 2,5-dihydroxyterephthalic acid and cobalt chloride (Co(Cl)2·6H20) in 15 mL of N,N-dimethylformamide (DMF), place in a 20 mL glass vial and seal;
[0041] 2) After ultrasonic dissolution, the container was sealed and placed in an oven at 120°C for 24 hours;
[0042] 3) After cooling to room temperature, washed with N,N-dimethylformamide and ethanol, centrifuged, dried in an oven at 60°C, and the resulting powder was collected as Co-MOF-74-C.
[0043] Example 1
[0044] The method for preparing Co-MOF-74-A includes the following steps:
[0045] 1) 2,5-dihydroxyterephthalic acid and cobalt acetylacetonate (Co(C5H7O2)2·xH2O) were dissolved in 15 mL N,N-dimethylformamide (DMF), placed in a 20 mL glass vial and sealed;
[0046] 2) After ultrasonic dissolution, the container was sealed and placed in an oven at 120°C for 24 hours;
[0047] 3) After cooling to room temperature, washed with N,N-dimethylformamide and ethanol, centrifuged, dried in an oven at 60°C, and the resulting powder was collected as Co-MOF-74-A.
[0048] Figure 1 PXRD patterns of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1. The testing instrument was Advance D8 of Bruker Company in Germany, using Cu target, and the scanning 2 theta range was 5-40°.
[0049] Figure 2 UV-Vis diffuse reflectance spectra of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1. The testing instrument was Agilent Cary 5000 type UV-Vis spectrophotometer, and the testing range was 200-700 nm.
[0050] Figure 3 77 K nitrogen adsorption curve of Co-MOF-74-N prepared in Comparative Example 1, Co-MOF-74-C prepared in Comparative Example 2 and Co-MOF-74-A prepared in Example 1. The testing instrument was 3H-2000PS1 of Belsim Instrument in China, and the activation was 120°C for 6 hours before testing.
[0051] Figure 4SEM images of Co-MOF-74-N (a) prepared in Comparative Example 1, Co-MOF-74-C (b) prepared in Comparative Example 2, and Co-MOF-74-A (c) prepared in Example 1. The testing instrument was Nova NanoSEM450.
[0052] Figure 5 EPR spectra of Co-MOF-74-N (a) prepared in Comparative Example 1, Co-MOF-74-C (b) prepared in Comparative Example 2, and Co-MOF-74-A prepared in Example 1. The testing instrument was EMXplus from Bruker, Germany.
[0053] PXRD tests showed that Co-MOF-74-N matched the diffraction peaks of the simulated crystal Co-MOF-74 perfectly, indicating that highly crystalline Co-MOF-74-N was successfully synthesized. Co-MOF-74-C showed weakened peak intensity (40% reduction at 6.82°), but periodicity was preserved, indicating that most of the ordered framework structure was maintained. In contrast, Co-MOF-74-A showed relatively broad and weak peaks near 6.80° and 11.80°, indicating the coexistence of short-range disorder and long-range order, which proved its amorphous nature. Ultraviolet-visible diffuse reflectance spectroscopy (DRS) showed obvious changes in crystal structure. In contrast, Co-MOF-74-A showed enhanced absorption tails between 450-600 nm compared to Co-MOF-74-N, which is a characteristic of amorphous materials. The comparison of N2 adsorption-desorption curves showed that Co-MOF-74-A had increased mesopore content due to its amorphous nature, and the BET surface area was significantly reduced, confirming that some coordination bonds were broken, but the integrity of the framework was still maintained. The differences in crystallinity were further confirmed by scanning electron microscopy (SEM), which confirmed the amorphous nature of Co-MOF-74-A. To further confirm the amount of oxygen vacancy content in the above Co-MOF-74 samples, electron paramagnetic resonance (EPR) experiments were performed. As shown in FIG. 6, the intensity order at g = 2.003 was Co-MOF-74-A > Co-MOF-74-C > Co-MOF-74-N, indicating that amorphous Co-MOF-74-A had a large amount of oxygen vacancies. Figure 5
[0054] Example 2 Catalytic ozonation performance evaluation of Co-MOF-74 metal organic framework materials with different crystallinities
[0055] The Co-MOF-74-N prepared in Comparative Example 1, the Co-MOF-74-C prepared in Comparative Example 2 and the Co-MOF-74-A sample prepared in Example 1 were respectively mixed with 9 times the mass of quartz sand in a maroon mortar, added to a U-shaped glass tube with a diameter of 6 mm, packaged and fixed on both sides with absorbent cotton, and placed in a self-built integrated catalytic ozone decomposition performance evaluation platform to evaluate the ozone decomposition performance. The evaluation platform includes an ozone preparation device, a flow rate detection device, a humidity control device, an ozone detection device, and a tail gas treatment device. Among them, the ozone detection device is Model 202 (2B Technology), and the test conditions are: room temperature, 50 mg of catalyst, 20 ppm of ozone concentration, and 30% relative humidity.
[0056] It was found (as shown in Figure 6 ), that the amorphous Co-MOF-74-A showed better catalytic durability and activity than its crystalline counterparts (Co-MOF-74-N and Co-MOF-74-C), and could maintain 100% O3 conversion rate for more than 40 hours under the condition of 30% relative humidity. This is in sharp contrast to the Co-MOF-74-N with high crystallinity, which rapidly lost 95% of its activity within the first hour of the reaction, reducing the conversion rate from 100% to 5%. This excellent catalytic effect indicates that the amorphous Co-MOF-74-A with a large number of oxygen vacancies has application potential in ozone decomposition.
[0057] Example 3: Catalytic ozone decomposition performance evaluation of amorphous Co-MOF-74-A metal organic framework material
[0058] 1) Effect of different catalyst masses
[0059] 30, 50, and 70 mg of Co-MOF-74-A were respectively mixed with 9 times the mass of quartz sand, the relative humidity was 40%, the inlet ozone concentration was 20 ppm, and the O3 decomposition activity of Co-MOF-74-A under different catalyst masses was tested to determine the optimal catalyst dosage. The results are shown in Figure 7 .
[0060] Under the same catalytic conditions, as the mass of the catalyst (Co-MOF-74-A) increased from 30 mg to 50 mg, the conversion rate of O3 significantly increased and could maintain 100% conversion rate for more than 10 h, and when the mass increased to 70 mg, the O3 conversion rate remained at 100% within 10 h. Therefore, the optimal mass of Co-MOF-74-A for catalytic ozone decomposition is 50 mg.
[0061] 2) Effect of different relative humidities
[0062] Take 50 mg Co-MOF-74-A and mix with 450 mg quartz sand, and the inlet ozone concentration is 20 ppm. By adjusting the humidity, the O3 decomposition activity of Co-MOF-74-A under different relative humidity is tested to analyze the change of the reaction activity of the catalyst in the presence of water molecules.
[0063] The test shows that Figure 8 , under the humidity environment of 10% ≤ RH ≤ 90%, the O3 conversion rate of Co-MOF-74-A can be maintained at 100%, and even after 12 hours of continuous reaction, the ozone decomposition activity can still be maintained stable. Compared with traditional cobalt-based catalysts, the latter is usually quickly deactivated by the factor of competitive adsorption of water, so the Co-MOF-74-A of the present application has good humidity resistance.
[0064] 3) Influence of different ozone concentrations
[0065] Take 50 mg Co-MOF-74-A and mix with 450 mg quartz sand, and the relative humidity is 30%. By adjusting the size of the inlet ozone concentration, the O3 decomposition activity of Co-MOF-74-A under different ozone concentrations is tested to analyze the long-term stability of the catalyst under harsh conditions.
[0066] The test shows that Figure 9 , under the condition of ozone concentration of 20 ppm, the ozone conversion rate is maintained at 100% for 40 hours, and the ozone decomposition effect is optimal; under the condition of ozone concentration of 30 ppm, the ozone conversion rate is maintained at 100% for the first 25 hours, and the ozone decomposition efficiency decreases to 90% after 40 hours; under the condition of 40 ppm ozone concentration, the O3 conversion rate is maintained at about 80% for 40 hours, so the Co-MOF-74-A of the present application can also exhibit excellent ozone decomposition activity under high concentration of ozone environment.
[0067] 4) Dry-wet alternating cycle test
[0068] In order to test the dry-wet cycle stability of Co-MOF-74-A, take 50 mg Co-MOF-74-A and mix with 450 mg quartz sand, and the inlet ozone concentration is 20 ppm, and the ozone catalytic decomposition performance test is carried out under the conditions of relative humidity of 30% and 90% alternately.
[0069] It is found that Figure 10 , the Co-MOF-74-A of the present application can maintain 100% ozone catalytic decomposition efficiency within about 12 h even under the exchange test conditions of RH=30% and RH=90%, and has good dry-wet switching stability and certain humidity resistance.
Claims
1. A method for preparing an amorphous cobalt-based metal-organic framework material, characterized in that, Comprising the following steps: 1) 2,5-dihydroxyterephthalic acid and cobalt acetylacetonate Co(C5H7O2)2·xH2O are dissolved in N,N-dimethylformamide, placed in a glass vial and sealed; 2) After ultrasonic dissolution, the container is sealed and heated in an oven; 3) After cooling to room temperature, washed with N,N-dimethylformamide and ethanol, centrifuged, dried, and the resulting powder is collected as Co-MOF-74-A.
2. The production method according to claim 1, characterized by, In step 2), the heating condition is: heating at 120℃ for 24 hours.
3. The production method according to claim 1, characterized by, In step 3), the drying temperature is 60℃.
4. Use of the amorphous cobalt-based metal organic framework material prepared by the preparation method of any one of claims 1-3 in catalyzing ozone decomposition.
5. Use according to claim 4, characterized in that, The method is as follows: amorphous cobalt-based metal organic framework material Co-MOF-74-A is mixed with quartz sand in a marbled mortar, placed in a U-shaped glass tube, and sealed and fixed on both sides with absorbent cotton, and ozone is catalytically decomposed.
6. Use according to claim 5, characterized in that, The mass ratio of Co-MOF-74-A to quartz sand is 1:
9.
7. Use according to claim 6, characterized in that, The amount of Co-MOF-74-A used is 50 mg.
8. Use according to claim 5, characterized in that, The condition for catalytically decomposing ozone is: at room temperature, ozone concentration is 20 ppm, 30 ppm or 40 ppm, and humidity is 10% ≤ RH ≤ 90%.