CN116037078A - A novel polymetallic MOF material and its preparation method and application - Google Patents

Abstract

The invention discloses a novel multi-metal MOF material, which comprises the components of M (I) x (nM) y-MOF-74, wherein M (I) is an alkali metal with a valence of I, M is an alkali metal with a valence of I, II or III, and n represents the type of the M metal. The invention has the advantages that: the metal I is added as a secondary metal site, so that the pore diameter structure of the MOF material can be regulated, and the specific surface area of the MOF material is increased; meanwhile, the components of the material have structural diversity due to the electrostatic effect of Lewis acid and metal ions; an aliovalent-state multi-metal MOF material formed by using an I-valent alkali metal as a secondary metal site is excellent in acid-base property and electrostatic effect on the material; therefore, the carbon dioxide adsorption performance is stronger, the optimal CO2 adsorption performance is as high as 8.5mmol/g under the dynamic adsorption condition, the performance is improved by nearly 15% on the basis of the MOF material Mg-MOF-74 with the optimal adsorption effect at present, and is nearly 10 times that of commercial activated carbon, and compared with a bimetallic MOF material taking II metal as a secondary metal site, the performance is more excellent.

Description

A novel polymetallic MOF material and its preparation method and application

technical field

The invention relates to a novel polymetallic MOF material, a preparation method and an application thereof, and belongs to the technical field of CO2 adsorption.

Background technique

With the continuous development of industrialization, global climate change has become a major concern of people. In global climate change, the greenhouse effect is a hot issue. The emergence of the greenhouse effect will not only lead to the rise of the global sea and land surfaces, but also cause the melting of glaciers, the temperature of the sea water will rise, and the sea level will rise. According to research, in the past ten years, the melting rate of glaciers has accelerated many times compared to before, and the main factor that has caused adverse effects on the environment and caused global temperature changes is the emergence of greenhouse gases (GHGs). Common greenhouse gases include ozone, methane, CO2, fluoride, etc. Among them, CO2 is the gas that has the greatest impact on global climate change. Compared with other gases, CO2 will account for more than 60% of the greenhouse effect caused by all greenhouse gases, and CO2 gas stays in the air for the longest time. The main reason for the increase of CO2 concentration in the atmosphere is the use of fossil fuels. Coupled with the continuous improvement of people's living standards, society uses more and more energy, so CO2 emissions are also showing a gradual upward trend. According to data measured by the National Oceanic and Atmospheric Administration (NOAA), the current concentration of CO2 in the atmosphere has risen sharply from 340ppm in 1980 to 420.99ppm in 2022.

To achieve sustainable economic development, it is necessary to find a suitable CO2 capture technology and CO2 adsorbent, that is to say, finding a new type of high-efficiency CO2 adsorbent with a large adsorption capacity is a hot issue.

At present, mainstream low-temperature adsorbent materials mainly include carbonaceous adsorbent materials, zeolite molecular sieves, metal-organic frameworks (MOFs), etc. The main feature of these materials is that they can adsorb carbon dioxide at relatively low temperatures (usually below 200 °C). Carbonaceous adsorption materials are porous carbonaceous substances with high specific surface area made of coal or organic matter. Including activated carbon and activated carbon fibers, carbon nanotubes and other pure carbon-structured adsorbents. Activated carbon is mainly a carbonaceous adsorption material prepared by carbonization and activation with high carbon content as raw material. It has developed pore structure, large specific surface area, stable chemical properties, acid and alkali resistance, strong selective adsorption capacity, and easy regeneration after failure. Features. Activated carbon is a good potential adsorption material due to its microporous, mesopore and macroporous structure. At present, the carbon dioxide adsorption capacity of modified activated carbon in the laboratory can reach 2-3mmol/g. The carbon dioxide adsorption capacity of unmodified commercial activated carbon is relatively low, only 0.89mmol/g. Zeolite molecular sieves are hydrates of crystalline aluminosilicates containing alkali metal and alkaline earth metal oxides. It has selective absorption for the mixture of nitrogen and carbon dioxide, has strong adsorption capacity for carbon dioxide, and has good regeneration cycle adsorption performance, and can be used as an efficient and economical CO2 capture adsorbent. Metal-organic frameworks (Metal-Organic Frameworks, MOFs) mainly refer to porous materials with specific network structures prepared by mixing inorganic metal ions and organic ligands. Among the materials used in MOFs materials, inorganic metal ions mainly function as porous materials to form nodes. Commonly used inorganic metal ions include transition metals with low valence states, and common alkali metals and other transition metals. Compared with zeolite molecular sieves, the high specific surface area improves the carbon dioxide capture ability of MOFs. Especially when the pressure is less than 10bar, the maximum storage capacity of zeolite is only one-third of that of MOFs.

MOFs materials have a variety of unsaturated metal sites, so that MOFs can generate a large force with the adsorbate during the adsorption process, so MOFs materials have good development prospects in gas adsorption and separation. However, at present, under the conditions of normal temperature and pressure, the carbon dioxide adsorption capacity of MOF materials is mainly 4-6mmol/g, and the material stability is poor, and the cycle performance is not good.

So researchers modified MOFs materials to make MOF-74 materials. However, the inorganic metal ions added in the preparation of MOF-74 materials are mainly II-valent metal ions, such as adding Mg2+, Ni2+, Co2+, Cu2+, Zn2+ wait. For example, in the publication number CN103992339A, Liu Fu et al. used magnesium nitrate hexahydrate to prepare Mg-MOF-74 material. In the publication number CN105037444A, Liu Ying et al. used cobalt nitrate hexahydrate to prepare a pure-phase rod-shaped Co-MOF-74 crystal material. In terms of MOF multi-metal synthesis, the compounding of II metal elements is mainly used to modify the parent MOF material. For example, in the patent with the publication number: CN111393664A, Zou Jijun and others doped other II-valent metals Cr, Mn, Co, Ni, Cu, etc. in the iron source, so that the metal active center can be 100% exposed, which can greatly improve the metal center. Excellent utilization rate and catalytic activity. In the patent with the publication number CN111848972A, Luo Xubiao et al. based on the synthesis conditions of MOF-808, added different proportions of iron ions to the Zr source to form an adsorption material through in-situ doping, which improved the adsorption performance and stability of the material. An Xiaoyin, Lu Jinming, Liu Yi, Yang Jianhua, Zhang Yan, Zhang Wen.Synthesis of bimetallic MOF-74 and its gas adsorption and separation properties[J].New Chemical Materials,2020,48(04):185-190 .DOI: 10.19817/j.cnki.issn1006-3536.2020.04.042, the bimetallic MOF material synthesized by the author using II metal Co and Ni is Ni25Co-MOF-74, and the CO2 adsorption performance is 4.77mmol/g at normal temperature and pressure.

It can be seen that the introduction of different secondary metal sites can improve the performance of the material. However, the current research in the field of multi-metallic MOFs mainly focuses on the doping of two valent metals, and the CO2 adsorption performance, stability, and cycleability still need to be improved.

Contents of the invention

The technical problem to be solved in the present invention is to provide a novel polymetallic MOF material and its application in CO2 adsorption. The polymetallic MOF material is prepared by adding I-valent alkali metals as secondary metal sites. It is convenient, and the I-valent alkali metal is cheap, and the prepared multi-metallic MOF material has excellent carbon dioxide adsorption performance, good cycle performance and strong stability.

The present invention is realized by the following scheme: a novel polymetallic MOF material, its composition is M(I)x(nM)y-MOF-74, wherein, M(I) is I-valent alkali metal, and M is I-valent or Alkali metal with valence II or valence III, n represents the type of metal M, x+y=1, x>0, y>0, n≥1.

A kind of preparation method of novel polymetallic MOF material, it carries out according to the following steps:

Step 1. Quantitatively weighing one I-valent alkali metal salt, one or more II-valent metal salts, and 2,5-dihydroxyterephthalic acid to prepare drug A;

Step 2, adding DMF, methanol and deionized water to the drug A obtained in step 1 to prepare a mixed solution A;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to the reactor, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 110-140° C. for 22-30 hours. After the reactor is cooled to room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven to dry, put the sample in a beaker and soak it in methanol at room temperature for 2 to 5 days, during which the methanol is constantly replaced to remove DMF and unreacted reactants, and dry the final product in a vacuum oven at 80-100° C. for 6-12 hours to obtain the final product M(I)x(nM)y-MOF-74 material.

The type of the I-valent metal salt in the step 1 is an alkali metal salt, and the II-valent and III-valent metal salt is one of nitrate, chloride or acetate.

In the first step, the molar ratio of the total amount of metal salt to 2,5-dihydroxyterephthalic acid is 2-3:0.78. .

The volume ratio of DMF, methanol and deionized water added in the second step is V:V:V=(10-15):1:1.

The volume ratio of the amount of metal element to DMF in the step 2 is 2.5mmol:61.5mL.

The reactor used in the step 3 is a stainless steel hydrothermal reactor lined with polytetrafluoroethylene.

The temperature of the solution in the magnetic stirring process in the step 3 does not exceed 40°C, the drying time in the vacuum drying oven in the step 5 is 4 to 6 hours, and in the process of soaking the sample in methanol in the step 5, use a plastic wrap to seal the beaker, and in the step 5 The number of methanol substitutions was 3 times.

Application of a novel polymetallic MOF material in CO2 adsorption.

The beneficial effects of the present invention are:

1. A novel polymetallic MOF material of the present invention introduces lithium nitrate, sodium nitrate, and potassium nitrate as I-valent metal sources, respectively, and II- and III-valent metal salts are magnesium nitrate, nickel nitrate, zinc nitrate, cobalt nitrate, and copper nitrate. M(I)x(nM)y-MOF-74 crystalline material has been successfully prepared by zinc acetate, nitrate etc., and it is carried out _CO2 adsorption performance experimental test and partial characterization, the experimental results can be obtained, the prepared by the present invention All multimetallic MOF materials have good CO ₂ adsorption properties. Under the experimental conditions of 298K, 1bar, the CO ₂ adsorption capacity of Mg _0.5 Na _0.5 -MOF-74 is the highest, 8.5mmol/g, which is the highest among commercial activated carbons (0.89mmol /g) nearly 10 times, and the cycle performance is stable.

2. A new multi-metal MOF material of the present invention adds I-valent metals as secondary metal sites, which can not only adjust the pore structure of the MOF material, but also increase its specific surface area; at the same time, the components of the material will be affected by the static electricity of Lewis acids and metal ions. Effect, has the diversity of structure; the heterovalent polymetallic MOF material formed by using I-valent alkali metal as the secondary metal site has better effect on the acidity, alkalinity and electrostatic effect on the material; therefore carbon dioxide adsorption The performance is also stronger. Under dynamic adsorption conditions, its best CO2 adsorption performance is as high as 8.5mmol/g. On the basis of the current MOF material Mg-MOF-74 with the best adsorption effect, it has increased by nearly 15%. It is a commercial Nearly 10 times that of activated carbon, compared with the bimetallic MOF material with II metal as the secondary metal site, the performance is also more excellent. In the background technology, the bimetallic MOF material synthesized by II metal Co and Ni by An Xiaoyin and others is Ni25Co -MOF-74, the CO2 adsorption performance at normal temperature and pressure is 4.77mmol/g, and the adsorption performance is only 56% of that of Mg0.5Na0.5-MOF-74 in this application.

Description of drawings

Figure 1 is the CO2 adsorption breakthrough curve of M(I)x(nM)y-MOF-74 material.

Figure 2 is the XRD pattern of M(I)x(nM)y-MOF-74 material.

Figure 3 is a graph of the cycle stability performance of the CO2 adsorption experiment of M(I)x(nM)y-MOF-74.

Detailed ways

The present invention will be further described below in conjunction with FIGS. 1-3 , but the protection scope of the present invention is not limited to the content described above.

For the sake of clarity, not all features of an actual embodiment are described. In the following description, well-known functions and constructions are not described in detail since they would obscure the invention with unnecessary detail and should be considered in the development of any actual embodiment. , a great deal of implementation detail must be worked out to achieve the developer's specific goals, such as changing from one embodiment to another in accordance with system-related or business-related constraints, and it should also be recognized that such development work may be complex and time-consuming Yes, but just routine work for those skilled in the art.

Example 1:

This example is a comparative example, a method for synthesizing metal organic framework material Mg-MOF-74, which is carried out through the following steps:

Step 1. Weighing quantitative magnesium nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to obtain drug A; wherein, 10 mmol of magnesium nitrate and 3.12 mmol of 2,5-dihydroxy terephthalic acid;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product and obtain the Mg-MOF-74 material.

Example 2:

A method for synthesizing metal organic framework material Mg _0.5 Na _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative magnesium nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, 5 mmol of magnesium nitrate, 5 mmol of sodium nitrate, and 2,5-dihydroxy terephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=10:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is a Mg _0.5 Na _0.5 -MOF-74 material.

Example 3:

A method for synthesizing metal organic framework material Mg _0.5 Na _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative magnesium nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, 5 mmol of magnesium nitrate, 5 mmol of sodium nitrate, and 2,5-dihydroxy terephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=13:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is a Mg _0.5 Na _0.5 -MOF-74 material.

Example 4:

A method for synthesizing metal organic framework material Mg _0.5 Na _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative magnesium nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, 5 mmol of magnesium nitrate, 5 mmol of sodium nitrate, and 2,5-dihydroxy terephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is a Mg _0.5 Na _0.5 -MOF-74 material.

Example 5:

A method for synthesizing metal organic framework material Mg _0.5 Li _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative magnesium nitrate, lithium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, magnesium nitrate 0.5mmol, lithium nitrate 0.5mmol, 2,5-dihydroxyterephthalic acid Diformic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100°C for 12 hours to obtain the final product, which is a Mg _0.5 Li _0.5 -MOF-74 material.

Embodiment 6:

A method for synthesizing metal organic framework material Mg _0.9 K _0.1 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative magnesium nitrate, potassium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, 9 mmol of magnesium nitrate, 1 mmol of potassium nitrate, 2,5-dihydroxy terephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100°C for 12 hours to obtain the final product, and obtain the Mg _0.9 K _0.1 -MOF-74 material.

Embodiment 7:

A method for synthesizing the metal organic framework material Ni _0.5 Na _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative nickel nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, nickel nitrate 0.5mmol, sodium nitrate 5mmol, 2,5-dihydroxyterephthalic acid Formic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is Ni _0.5 Na _0.5 -MOF-74 material.

Embodiment 8:

A method for synthesizing metal organic framework material Zn _0.5 Na _0.5 -MOF-74 according to this embodiment is carried out through the following steps:

Step 1. Weigh quantitative zinc acetate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare medicine A; wherein, 5 mmol of zinc acetate, 0.5 mmol of sodium nitrate, 2,5-dihydroxyterephthalic acid Formic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is a Zn _0.5 Na0.5-MOF-74 material.

Embodiment 9:

A method for synthesizing a metal organic framework material Ga _0.5 Na _0.5 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative gallium nitrate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, 5 mmol of nitric acid, 0.5 mmol of sodium nitrate, 2,5-dihydroxyterephthalic acid Formic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100° C. for 12 hours to obtain the final product, which is a Ga _0.5 Na0.5-MOF-74 material.

Example 10:

A method for synthesizing metal organic framework material Mg _0.5 Ni _0.4 Na _o.1 -MOF-74 according to this embodiment is carried out through the following steps:

Step 1. Take quantitative zinc acetate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, magnesium nitrate 5mmol, nickel nitrate 0.4mmol, sodium nitrate 0.1mmol, 2,5- Dihydroxyterephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and unreacted reactants, the final product was dried in a vacuum oven at 100°C for 12 hours to obtain the final product, and Mg _0.5 Ni _0.4 Na _o.1 -MOF-74 material was obtained.

Example 11:

A method for synthesizing metal organic framework material Mg _0.5 Na _0.4 K _o.1 -MOF-74 in this embodiment is carried out through the following steps:

Step 1. Take quantitative zinc acetate, sodium nitrate and 2,5-dihydroxyterephthalic acid respectively to prepare drug A; wherein, magnesium nitrate 5mmol, sodium nitrate 0.4mmol, potassium nitrate 0.1mmol, 2,5- Dihydroxyterephthalic acid 3.12mmol;

Step 2, adding DMF, methanol and deionized water with a volume ratio of V:V:V=15:1:1 to the drug A obtained in step 1, to prepare a mixed solution A; wherein, the added DMF, methanol and Deionized water is 246ml, 16.4ml, 16.4ml respectively;

Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B;

Step 4. Transfer the mixed solution B obtained in step 3 to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 125°C for 24 hours, and wait for the reaction kettle to cool. After reaching room temperature, take out the reactor;

Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven and dry it for several hours, then place the sample in a beaker and soak it in methanol for 3 days at room temperature, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 100°C for 12 hours to obtain the final product, and obtain the Mg _0.5 Na _0.4 K _o.1 -MOF-74 material.

The CO ₂ dynamic adsorption performance test was carried out on the Mg _0.5 Na _0.5 -MOF-74 material prepared in Example 2-4. It was found that the volume ratio added in step 2 was V:V:V=(10-15):1: 1 of DMF, methanol and deionized water can successfully synthesize MOF-74 material, and the CO2 adsorption performance is close. Among them, the volume ratio of DMF, methanol and deionized water is 15:1:1, and the _CO2 adsorption performance of the synthesized material is the best. Good, but relatively more solvent is consumed, and the cost performance is slightly lower. The specific ratio can be determined by the actual situation.

The polymetallic MOF materials prepared in Examples 4-11 were tested for dynamic adsorption performance of CO ₂ , the results are shown in Table 1, wherein Mg _0.5 Na _0.5 -MOF-74 has the highest adsorption performance of 8.5 mmol/g, which is higher than the current CO ₂ adsorption The single metal MOF material with the best performance (Mg-MOF-74, 7.34mmol/g) improved by nearly 15%, followed by Mg _0.9 K _0.1 -MOF-74>Mg _0.5 Li _0.5 -MOF-74>Ni _0.9 Na _0.1 -MOF-74. This is due to the addition of I-valent metals Li, Na, and K as secondary metal sites in Mg-MOF-74, which can form a rich three-dimensional honeycomb structure, adjust the pore structure of the MOF material, and increase the number of micropores, thereby making it The _CO2 adsorption performance is significantly enhanced. From the cycle stability experiments, it can be seen that the stability of the material is also significantly improved by adding I-valent metals as secondary metal sites.

Table 1 Summary of CO2 adsorption performance of Mg-MOF-74 and multimetallic MOF after synthesis

Although the technical solutions of the present invention have been elaborated and listed in detail, it should be understood that for those skilled in the art, it is necessary for those skilled in the art to make modifications to the above-mentioned embodiments or adopt equivalent alternatives. Obviously, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. A novel polymetallic MOF material is characterized in that: its composition is M (I) x (nM) y-MOF-74, wherein, M (I) is I valence alkali metal, and M is I valence or II valence Or a III-valent alkali metal, n represents the type of M metal. 2. A novel polymetallic MOF material according to claim 1, characterized in that: x+y=1, x>0, y>0, n≥1. 3. A preparation method for a novel polymetallic MOF material, characterized in that: it proceeds according to the following steps: Step 1. Quantitatively weighing one I-valent alkali metal salt, one or more I-valent, II-valent or III-valent metal salts and 2,5-dihydroxyterephthalic acid to prepare drug A; Step 2, adding DMF, methanol and deionized water to the drug A obtained in step 1 to prepare a mixed solution A; Step 3, the mixed solution A obtained in step 2 is placed on a magnetic stirrer and stirred for several hours until the medicine is completely dissolved to obtain the mixed solution B; Step 4. Transfer the mixed solution B obtained in step 3 to the reactor, then put it into a constant temperature drying oven, and conduct a hydrothermal reaction at 110-140° C. for 22-30 hours. After the reactor is cooled to room temperature, take out the reactor; Step 5. Remove the solution in the reaction kettle by suction filtration, put the obtained product in a vacuum drying oven to dry, put the sample in a beaker and soak it in methanol at room temperature for 2 to 5 days, during which the methanol is constantly replaced to remove DMF and the unreacted reactants, and dry the final product in a vacuum oven at 80-100° C. for 6-12 hours to obtain the final product M(I)x(nM)y-MOF-74 material. 4. the preparation method of a kind of novel polymetallic MOF material according to claim 1, is characterized in that: the kind of I-valence metal salt is alkali metal salt in described step 1, and II-valence, III-valence metal salt are nitrates , chloride or acetate. 5. the preparation method of a kind of novel polymetallic MOF material according to claim 1, is characterized in that: the total amount of metal salt and 2 in described step 1, the mol ratio of 5-dihydroxyterephthalic acid is 2 ~3:0.78. 6. the preparation method of a kind of novel polymetallic MOF material according to claim 1 is characterized in that: the DMF added in the described step 2, methyl alcohol and deionized water volume ratio are V:V:V=(10 ~15): 1:1. 7. The preparation method of a novel polymetallic MOF material according to claim 1, characterized in that: the volume ratio of the amount of metal elements to DMF in the step 2 is 2.5mmol:61.5mL. 8. The preparation method of a novel polymetallic MOF material according to claim 1, characterized in that: the reactor used in the third step is a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. 9. The preparation method of a novel polymetallic MOF material according to claim 1, characterized in that: the temperature of the solution in the magnetic stirring process in the step 3 does not exceed 40°C, and the step 5 is dried in a vacuum oven The time is 4-6 hours. During the process of immersing the sample in methanol in step 5, use a plastic wrap to seal the beaker, and the number of methanol replacements in step 5 is 3 times. 10. The application of a novel polymetallic MOF material in CO2 adsorption.

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