Green synthesis method of MOF (Metal Organic Framework) material for efficient carbon capture

Abstract

The invention belongs to the technical field of MOF (Metal Organic Framework) materials, and discloses a green synthesis method of an MOF material for efficient carbon capture, which comprises the following steps: S1, dissolving raw materials: sequentially adding a substance containing citrate radicals, alkali and metal salt into water in proportion, and stirring to obtain a precursor solution; s2, ultrasonic-assisted reaction: heating the precursor solution to a certain temperature under the condition of synchronous ultrasonic and stirring treatment; s3, aging treatment: turning off ultrasound, continuously keeping stirring, and aging; and S4, post-treatment: filtering the mixed solution, washing, and drying to obtain the MOF material. The influence of organic solvents or auxiliaries in the raw materials is effectively reduced, and the cost of the raw materials is reduced; meanwhile, the pollution possibility and the treatment cost are reduced. The problems that in the prior art, on the premise that the carbon capture efficiency is guaranteed, the preparation cost is difficult to reduce, and use of high-pollution substances in raw materials is difficult to reduce are solved.

Description

Technical Field

[0001] This invention belongs to the field of MOF material technology, specifically relating to a green synthesis method for MOF materials used for efficient carbon capture. Background Technology

[0002] In the field of MOF material technology, some existing technologies employ hydrothermal synthesis, placing a mixture of cobalt acetate, citric acid, and potassium hydroxide in an ethanol-water reactor and reacting it at 120°C for 48 hours. While this method can produce UTSA-16, it requires specialized high-pressure equipment, has a long reaction cycle, high energy consumption, and the mixed solvent increases separation costs. Other technologies require the addition of solvent auxiliaries and alkaline solutions (ammonia or triethylamine) to adjust the pH. These alkaline substances are volatile and highly corrosive; increasing the water ratio during preparation prevents the formation of the target product, and subsequent washing with ether and soaking in methanol reduces environmental benefits and significantly increases production costs. Similarly, some existing technologies still require a mixture of water and alkyl alcohols as a solvent during synthesis, leading to increased solvent costs and thus posing environmental pollution risks and high production costs. Therefore, they cannot meet the requirements for cost, scalability, and carbon capture performance of UTSA-16 materials for industrial carbon capture applications. Summary of the Invention

[0003] The purpose of this invention is to provide a green synthesis method for MOF materials with high carbon capture efficiency, so as to solve the technical problems in the prior art that it is difficult to reduce the preparation cost and the use of highly polluting substances in the raw materials while ensuring carbon capture efficiency.

[0004] The green synthesis method for MOF materials with high-efficiency carbon capture includes the following steps: S1. Raw material dissolution: Add the citrate-containing substance, alkali and metal salt to water in proportion and stir to obtain the precursor solution; S2, Ultrasonic-assisted reaction: The precursor solution is heated to a certain temperature under conditions of simultaneous ultrasonic and stirring treatment; S3. Aging treatment: Turn off the ultrasonic cleaner, continue stirring, and carry out the aging process; S4. Post-processing: The mixed solution is filtered, washed, and dried to obtain MOF material.

[0005] Preferably, in step S2, the ultrasonic treatment time is 2~60 min, the stirring speed is 50~1500 r / min, and the reaction system temperature is controlled at 20~150℃.

[0006] Preferably, substances containing citrate ions include citric acid and / or citrate salts.

[0007] Preferably, the citrate includes any one, two or more of potassium citrate, sodium citrate, lithium citrate, and cesium citrate.

[0008] Preferably, the metal salt includes any one, two, or more of the following: chloride, nitrate, and acetate salts of a metal cation, wherein the metal cation is Zn. 2+ Co 2+ Cu 2+ Fe 2+ Mn 2+ Ca 2+ Mg 2+ Sn 2+ Zr 2+ Ni 2+ Zn 2+ Co 2+ Cu 2+ Fe 2 + Mn 2+ Ca 2+ Mg 2+ Sn 2+ Zr 2+ Ni 2+ Any one, two, or more of them.

[0009] Preferably, the alkali is any one, two or more of potassium hydroxide, sodium hydroxide, cesium hydroxide, and lithium hydroxide.

[0010] Preferably, the molar ratio of the sum of metal ions in the alkali and the citrate-containing substance to the citrate-containing substance is 3:1, and the molar ratio of the citrate-containing substance to the metal salt is 0.5~2.0:1.

[0011] Preferably, in step S3, the aging time is 0-10 hours.

[0012] Preferably, in step S4, the washing solvent is one, two, or more of deionized water, methanol, and ethanol; the drying temperature is 60~150℃.

[0013] Preferably, the MOF material is UTSA-16 material, and the purity of UTSA-16 material is ≥98%, with a specific surface area of ​​700 m². 2 / g or more.

[0014] The technical advantages of this invention are as follows: Only water is used as the solvent in this invention, with no other organic solvents added. An ultrasonic-assisted pure water stirring method was designed to prepare UTSA-16 metal-organic framework materials with efficient carbon capture in a short time. The microbubbles generated by ultrasonic cavitation have high surface energy and active sites, which can adsorb metal ions and organic ligands, reducing the interfacial energy barrier during nucleation and becoming MOF nuclei. Therefore, the specific surface area of ​​the prepared UTSA-16 is 700 m². 2 / g, exhibiting excellent adsorption capacity and selectivity for carbon dioxide. Furthermore, by reducing the use of organic solvents and solvent additives such as triethylamine, the influence of organic solvents or additives in the raw materials is effectively reduced, lowering raw material costs; simultaneously, the potential for pollution and treatment costs are reduced. This solves the problem in existing technologies where it is difficult to reduce preparation costs and the use of highly polluting substances in raw materials while ensuring carbon capture efficiency. Attached Figure Description

[0015] Figure 1 The image shows the XRD pattern of the MOF material prepared in Example 1 of this invention.

[0016] Figure 2 The image shows the XRD pattern of the MOF material prepared in Example 2 of this invention.

[0017] Figure 3 The image shows the XRD pattern of the MOF material prepared in Example 3 of this invention.

[0018] Figure 4 The image shows the XRD pattern of the MOF material prepared in Example 4 of this invention.

[0019] Figure 5 The image shows the XRD pattern of the MOF material prepared in Example 5 of this invention.

[0020] Figure 6 The image shows the XRD pattern of the MOF material prepared in Example 6 of this invention.

[0021] Figure 7 The image shows the XRD pattern of the MOF material prepared in Comparative Example 1.

[0022] Figure 8 The image shows the XRD pattern of the MOF material prepared in Comparative Example 2.

[0023] Figure 9 The transmission curve of the MOF material prepared in Example 1 of this invention is obtained by applying it in an environment of 25°C with CO2 / N2=20 / 80.

[0024] Figure 10 The breakthrough curve of CO2 / N2=20 / 80 was measured for the application of the MOF material prepared in Comparative Example 1 in an environment of 25℃.

[0025] Figure 11 The image shows the N2 adsorption isotherm of the MOF material prepared in Example 1 of this invention at -196℃.

[0026] Figure 12 The image shows the N2 adsorption isotherm of the MOF material prepared in Comparative Example 2 at -196℃. Detailed Implementation

[0027] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0028] Traditional synthesis methods have consistently struggled to balance synthesis efficiency, production cost, and high carbon capture performance, becoming a key bottleneck restricting their large-scale application. Existing UTSA-16 synthesis methods generally suffer from core flaws that severely hinder industrial implementation: ① Some methods require demanding reaction conditions, with most requiring high temperature and pressure or complex mechanical control, resulting in high operational risks and large equipment investments, hindering continuous production; ② Most methods are unbalanced between environmental friendliness and cost, relying on ethanol-water mixed solvents and requiring the addition of additives, increasing solvent recovery costs and posing environmental pollution risks, with the cost per ton of product per solvent being 40,000 yuan higher than that of a pure aqueous solvent system; ③ Some methods use dry ball milling to improve reaction efficiency, but the product has a low specific surface area and poor carbon capture performance; ④ Some methods suffer from poor crystallinity. Therefore, they cannot meet the requirements of cost, scalability, and carbon capture performance for UTSA-16 materials used in the carbon capture industry.

[0029] Therefore, there is an urgent need to develop a green, low-cost method for preparing UTSA-16 that produces products with excellent carbon capture performance.

[0030] This invention provides a green synthesis method for MOF materials with high-efficiency carbon capture, comprising the following steps: S1. Raw material dissolution: Add the citrate-containing substance, alkali and metal salt to water in proportion and stir to obtain the precursor solution.

[0031] In this step, only water is used as the solvent, and no other organic solvents are added.

[0032] Substances containing citrate ions include citric acid and / or citrate salts.

[0033] The citrate includes any one or more of potassium citrate, sodium citrate, lithium citrate, and cesium citrate.

[0034] Metal salts include any one, two, or more of the following: chloride, nitrate, and acetate salts of metal cations, wherein the metal cation is Zn. 2+ Co2+ Cu 2+ Fe 2+ Mn 2+ Ca 2+ Mg 2+ Sn 2+ Zr 2+ Ni 2+ Zn 2+ Co 2+ Cu 2+ Fe 2+ Mn 2+ Ca 2+ Mg 2+ Sn 2+ Zr 2+ Ni 2+ Any one, two, or more of them.

[0035] The alkali is any one, two or more of potassium hydroxide, sodium hydroxide, cesium hydroxide, and lithium hydroxide.

[0036] The molar ratio of the sum of metal ions in the base and the citrate-containing substance to the citrate-containing substance is 3:1, and the molar ratio of the citrate-containing substance to the metal salt is 0.5~2.0:1.

[0037] S2. Ultrasonic-assisted reaction: The precursor solution is heated to a certain temperature under the condition of simultaneous ultrasonic and stirring treatment, and the microbubbles generated by ultrasonic treatment serve as heterogeneous nucleation sites.

[0038] The ultrasonic treatment time is 2~60 min, the stirring speed is 50~1500 r / min, and the reaction system temperature is controlled at 20~150℃ (at normal pressure).

[0039] S3. Aging treatment: Turn off the ultrasonic cleaner, continue stirring, and carry out aging.

[0040] The aging time is 0-10 hours.

[0041] S4. Post-processing: The mixed solution is filtered, washed, and dried to obtain MOF material.

[0042] The washing solvent is one, two, or more of deionized water, methanol, and ethanol; the drying temperature is 60~150℃.

[0043] The MOF material is UTSA-16. UTSA-16 material has a purity ≥98% and a specific surface area of ​​700 m². 2 / g or more. The CO2 adsorption capacity of the MOF material at 25℃ and 0.2 bar is ≥33mL / g.

[0044] The specific implementation of this solution is as follows.

[0045] Example 1.

[0046] S1. Raw material dissolution: In a 5L beaker, dissolve citric acid (0.5mol), potassium hydroxide (1.5mol), magnesium nitrate (0.2mol), and calcium chloride (0.2mol) in 2L of water and stir until well mixed.

[0047] S2. Ultrasonic-assisted reaction: Transfer the beaker to an ultrasonic and stirring device, maintain 120°C, and treat with ultrasonication and stirring simultaneously for 10 minutes.

[0048] S3. Aging treatment: Turn off the ultrasonic treatment and continue stirring for 5 hours to complete the aging process.

[0049] S4. Post-treatment: Filter the reaction solution and wash it several times with water; dry the collected solid in an oven at 100℃ for 24 hours to obtain UTSA-16 material.

[0050] Example 2.

[0051] The preparation method is basically the same as that in Example 1. The difference is that the alkali in the raw materials is replaced with potassium hydroxide (0.9 mol) and sodium hydroxide (0.6 mol); the metal salt is replaced with manganese acetate (0.2 mol) and zinc acetate (0.1 mol); the ultrasonic and stirring treatment time is 5 minutes and the treatment temperature is 110℃; the aging time is 2 hours and the drying temperature is 60℃.

[0052] Example 3.

[0053] The preparation method is basically the same as that in Example 1. The difference is that the metal salt in the raw materials is replaced with cobalt acetate (0.05 mol) and copper nitrate (0.35 mol), the ultrasonic and stirring treatment time is 0.5 minutes, and the aging time is 3 hours.

[0054] Example 4.

[0055] The preparation method is basically the same as that in Example 1. The difference is that the citrate-containing substances in the raw materials are replaced with citric acid (0.25 mol) and potassium citrate (0.25 mol); the alkali is replaced with potassium hydroxide (0.55 mol) and sodium hydroxide (0.2 mol); the metal salt is replaced with copper nitrate (0.25 mol) and nickel zinc nitrate (0.15 mol); the ultrasonic and stirring treatment time is 2 minutes; the aging time is 1 hour; and the drying temperature is 120℃.

[0056] Example 5.

[0057] The preparation method is basically the same as that in Example 1. The difference is that the citrate-containing substances in the raw materials are replaced with citric acid (0.25 mol) and potassium citrate (0.25 mol); the alkali is replaced with potassium hydroxide (0.25 mol), sodium hydroxide (0.25 mol) and lithium hydroxide (0.25 mol); the metal salt is replaced with magnesium nitrate (0.3 mol); the ultrasonic and stirring treatment time is 30 minutes; and the aging time is 0.5 h.

[0058] Example 6.

[0059] The preparation method is basically the same as that in Example 1. The difference is that the citrate-containing substances in the raw materials are replaced with citric acid (0.25 mol) and sodium citrate (0.25 mol); the alkali is replaced with potassium hydroxide (0.3 mol) and lithium hydroxide (0.45 mol); the metal salt is replaced with magnesium nitrate (0.2 mol), zirconium chloride (0.1 mol) and manganese acetate (0.05 mol); the ultrasonic and stirring treatment time is 30 minutes; and the aging time is 0.5 h.

[0060] As a comparative example, the applicant also conducted the following experiments.

[0061] Comparative Example 1.

[0062] The preparation method is basically the same as that in Example 1. The difference is that the metal salt in the raw materials is replaced with cobalt acetate (0.2 mol) and calcium chloride (0.2 mol), and the simultaneous ultrasonic and stirring treatment is replaced with simple stirring treatment. The stirring time is 30 minutes and the stirring temperature is 110°C.

[0063] Table 1 shows a comparison of the relevant parameters of the preparation methods of the above embodiments and comparative examples.

[0064] Table 1: Comparison of relevant parameters of the preparation methods of the embodiments of the present invention and Comparative Example 1

[0065] The applicant also set up a comparative example 2 with different preparation methods.

[0066] Comparative Example 2.

[0067] The preparation method of Comparative Example 2 included: weighing 6 mmol of citric acid monohydrate and 18 mmol of KOH, stirring and mixing them evenly, then adding them to a ball mill and ball milling for 10 min at a speed of 200 r / min. After the reaction was completed, 6 mmol of Zn(CH3COO)2·2H2O (0.0042 M) was added to the ball mill jar, and ball milling was performed again for 10 min at a speed of 200 r / min. After the reaction was completed, the product was washed with water and dried at a higher temperature to obtain UTSA-16 material.

[0068] Performance verification: The products obtained in Examples 1-6 of the present invention and the products of Comparative Examples 1 and 2 were subjected to performance tests, and the relevant descriptions are as follows.

[0069] (1) CO2 adsorption capacity test: The CO2 adsorption capacity of the molded particles was tested by static volumetric method under the conditions of 25℃ and 1 bar using a physical adsorption instrument, and the decrease in adsorption capacity relative to the raw material MOF powder was calculated.

[0070] (2) CO2 / N2 selectivity test: A multi-component competitive gas breakthrough curve analyzer was used to simulate the industrial flue gas composition (20 vol% CO2 + 80 vol% N2) under the conditions of 25℃, 1 bar and gas flow rate of 50 mL / min. The CO2 / N2 separation coefficient was calculated by breakthrough curve.

[0071] Table 2: Performance Comparison Table of Products from Examples 1-6 of the Present Invention and Comparative Examples 1 and 2

[0072] By combining the above table with the appendix Figure 1-12 It can be seen that the difference between Comparative Example 1 and the Example is that the pure water stirring method lacks ultrasonic assistance, resulting in products with poor crystallinity and poor carbon dioxide adsorption performance. The main reason is that, compared with the water-ethanol solvothermal synthesis method, the pure water stirring method has a weaker ability to control the solubility and coordination environment of the UTSA-16 precursor, which is inherently unfavorable for crystal nucleation and growth. Ultrasound can compensate for the deficiencies of pure water. The microbubbles generated by ultrasonic cavitation have high surface energy and active sites, which can adsorb metal ions and organic ligands, reduce the interfacial energy barrier during nucleation, and become MOF crystal nuclei. Without ultrasound, the inherent defects of pure water cannot be improved, further inhibiting the crystal formation of UTSA-16.

[0073] Comparative Example 2 prepared UTSA-16 MOF material using a dry ball milling method, but the specific surface area decreased by 72.1% compared to the MOF material prepared in Example 1 of this invention, resulting in a decrease of 77.6% and 58% or more in CO2 adsorption capacity and CO2 / N2 separation coefficient, respectively. The main reasons are: dry ball milling relies on high mechanical force to drive the reaction, and mechanical force can easily cause crystal lattice defects, pore collapse or blockage, resulting in a reduction in the number of effective pores and uneven pore size distribution, thus significantly reducing the specific surface area; in addition, dry ball milling has no solvent dispersion effect, and the UTSA-16 nanoparticles generated in the reaction are prone to irreversible agglomeration due to their high surface energy, forming large-sized agglomerates, which leads to a significant reduction in specific surface area.

[0074] Therefore, this invention innovatively designs an ultrasonic-assisted pure water stirring method to prepare UTSA-16 metal-organic framework material with high carbon capture efficiency in a short time. This invention combines the characteristics of green and low cost, high-efficiency synthesis, and excellent carbon capture performance, providing key technical support for the industrial and green production of UTSA-16 material and laying the foundation for the iterative upgrading of carbon capture adsorbents.

[0075] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A green synthesis method for MOF materials used for efficient carbon capture, characterized in that, Includes the following steps: S1. Raw material dissolution: Add the citrate-containing substance, alkali and metal salt to water in proportion and stir to obtain the precursor solution; S2, Ultrasonic-assisted reaction: The precursor solution is heated to a certain temperature under conditions of simultaneous ultrasonic and stirring treatment; S3. Aging treatment: Turn off the ultrasonic cleaner, continue stirring, and carry out the aging process; S4. Post-processing: The mixed solution is filtered, washed, and dried to obtain MOF material.

2. The green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, In step S2, the ultrasonic treatment time is 2~60 min, the stirring speed is 50~1500 r / min, and the reaction system temperature is controlled at 20~150℃.

3. The green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, Substances containing citrate ions include citric acid and / or citrate salts.

4. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 3, characterized in that, Citrates include any one, two or more of potassium citrate, sodium citrate, lithium citrate, and cesium citrate.

5. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, Metal salts include any one, two, or more of the following: chloride, nitrate, and acetate salts of metal cations, wherein the metal cation is Zn. 2+ Co 2+ Cu 2+ Fe 2+ Mn 2+ Ca 2+ Mg 2+ Sn 2+ Zr 2+ Ni 2+ Zn 2+ Co 2+ Cu 2+ Fe 2+ Mn 2+ Ca 2+ Mg 2 + Sn 2+ Zr 2+ Ni 2+ Any one, two, or more of them.

6. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, The alkali is any one, two or more of potassium hydroxide, sodium hydroxide, cesium hydroxide, and lithium hydroxide.

7. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, The molar ratio of the sum of metal ions in the base and the citrate-containing substance to the citrate-containing substance is 3:1, and the molar ratio of the citrate-containing substance to the metal salt is 0.5~2.0:

1.

8. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, In step S3, the aging time is 0-10 hours.

9. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, In step S4, the washing solvent is one, two, or more of deionized water, methanol, and ethanol; the drying temperature is 60~150℃.

10. A green synthesis method for MOF materials with high-efficiency carbon capture according to claim 1, characterized in that, The MOF material is UTSA-16, with a purity ≥98% and a specific surface area of ​​700 m². 2 / g or more.

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