A MOF molding material and a method for preparing the same

Abstract

The application discloses a MOF shaped material and a preparation method thereof, and comprises the following steps: (1) adding MOF powder into a phenolic resin aqueous solution and uniformly mixing to obtain a plastic body; (2) performing shaping granulation and drying on the plastic body in step (1) to obtain a granule precursor with uniform particle size; and (3) carbonizing under an inert gas atmosphere to obtain the MOF shaped material. The MOF shaped material has high strength and large specific surface area, the preparation method is simple in process, low in cost and strong in operation repeatability, and is suitable for industrialized production.

Description

Technical Field

[0001] This invention belongs to the field of nanoporous materials, specifically relating to a method for preparing a high-strength, high-specific-surface-area MOF molding material. Background Technology

[0002] Metal-organic frameworks (MOFs) are organic-inorganic hybrid porous crystalline materials composed of metal ion centers and organic ligands. They have advantages such as porosity, high porosity, large specific surface area, tunable pore size, and easy functionalization of pore surfaces, and are widely used in energy storage, catalysis, sensing, adsorption and separation.

[0003] MOF products obtained through conventional preparation methods are typically crystalline powders, making them difficult to apply directly in industry. For example, in adsorption separation, the pressure drops significantly when gas flows through a powdered adsorption bed, and powdered MOFs have poor mechanical strength, are prone to wear and heat loss, easily clog internal channels, and are difficult to regenerate. Molded MOFs effectively solve the problems faced by traditional MOF powders during adsorption, such as low mechanical strength, easy agglomeration, difficult recovery, and dust pollution, enabling MOF materials to be better applied in gas adsorption separation.

[0004] Industrial adsorbents generally require a mechanical strength greater than 20 N / particle. MOF molded bodies are typically prepared by mixing binders with MOF powder, followed by molding and drying. While this method is simple, the resulting MOF molded bodies generally have low mechanical strength, failing to meet specific industrial requirements. Furthermore, the use of binders in conventional methods can clog the pores and active sites of the MOF material, reducing its specific surface area and thus affecting industrial applications. Therefore, there is an urgent need for novel molding methods that can mass-produce high-strength, high-specific-surface-area MOFs.

[0005] CN112705168A discloses a method for preparing an ultraporous MOF adsorbent material: First, polyvinyl alcohol (PVA) is added to water at room temperature and heated and stirred to form a colloidal aqueous solution of PVA; second, ultraporous MOF adsorbent powder is mixed with an appropriate amount of methylcellulose (MC) and stirred until homogeneous; third, the above PVA aqueous solution is added, mixed and stirred, granulated, and dried to obtain spherical particles. The mechanical strength of the spherical particles prepared by the method described in this invention is >20 N / particle, which only meets the conventional industrial requirements for adsorbents.

[0006] CN114042436A discloses a method for preparing molded MOF materials: First, MOF powder, sodium alginate, and deionized water are mixed and stirred into a homogeneous solution. This homogeneous solution is then added dropwise to a calcium chloride solution with a concentration of 0.03-0.05 mol / L, causing the MOF powder to form spherical shapes in the solution. Second, the spherical MOF product from step S1 is soaked in the calcium chloride solution for 20-30 minutes, filtered, soaked in deionized water for 2-4 hours, and then vacuum dried at 70-100℃ to obtain the molded MOF material with a specific surface area of ​​350 m². 2 ·g -1 The method described in this invention is simple to form, environmentally friendly and economical, but the mechanical properties of the formed body are difficult to meet industrial requirements, and the specific surface area of ​​the MOF material decreases significantly after forming, affecting its effectiveness as an adsorbent. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a MOF molding material and its preparation method. The MOF molding material of this invention exhibits high strength and a large specific surface area. The preparation method is simple, low-cost, and highly repeatable, making it suitable for industrial production.

[0008] The method for preparing the MOF molding material of the present invention includes the following:

[0009] (1) Add MOF powder to phenolic resin aqueous solution and mix evenly to obtain a plastic body;

[0010] (2) The plastic body described in step (1) is shaped, granulated, and dried to obtain a particle precursor with uniform particle size;

[0011] (3) The MOF molding material is obtained by carbonization in an inert gas atmosphere.

[0012] In the method of the present invention, the MOF mentioned in step (1) is one or more of MOF materials such as ZIF-8, ZIF-7, ZIF-90, MIL-53, MIL-101 and UiO-66.

[0013] In the method of the present invention, the phenolic resin in step (1) is generally a water-soluble phenolic resin.

[0014] In the method of the present invention, the mass ratio of MOF powder, phenolic resin and water in step (1) is 20-30g:1-2g:20-30mL, preferably 20-25g:1.5-2g:20-25mL.

[0015] In the method of the present invention, the molding and granulation described in step (2) is well known to those skilled in the art. Particle precursors of spherical, strip, and irregular shapes can be prepared as needed, such as by syringe extrusion molding or compression molding, preferably syringe extrusion molding.

[0016] In the method of the present invention, the drying method in step (2) is air drying or vacuum drying, preferably air drying, at a temperature of 90-110℃ and for 3-5 hours.

[0017] In the method of the present invention, the carbonization temperature in step (3) is 400-500℃, preferably 450-480℃, and the carbonization time is 6-8 hours; the carbonization process is generally carried out in a tube furnace.

[0018] The MOF molding material of this invention has spherical particles with a strength greater than 60 N / particle, preferably greater than 66 N / particle, and a specific surface area of ​​800-1000 m². 2 / g, with a thermal stability of not less than 500℃, wherein the carbon content is 2wt%-6.5wt%, and the spherical particles can be prepared into different particle sizes as needed, preferably 3~6mm.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] This invention mixes MOF materials with an aqueous solution of phenolic resin during the preparation process. The strong interaction between the MOF materials and the phenolic resin results in a uniform surface and reduced agglomeration of the MOF molded body. Further, high-temperature calcination and carbonization lead to the high-temperature pyrolysis of the phenolic resin, causing the disordered accumulation of internal aromatic carbon layers to form a graphitized carbon microcrystalline structure. The voids between the carbon layers and the disordered stacking of the carbon microcrystalline structure create a microporous structure, improving the mechanical strength and specific surface area of ​​the MOF molded body. This can be achieved through… Figure 3 The adsorption-desorption curves of nitrogen before and after carbonization of the MOF molded body were obtained by comparison. The MOF molded body in this invention can effectively resist the impact generated during transportation, filling and use, as well as the wear caused by fluid flow, which is beneficial to extending the service life of MOF materials. The increase in specific surface area also improves the performance of MOF molded body as an adsorbent material, promoting the commercial and industrial application of MOF materials. Attached Figure Description

[0021] Figure 1 This is the XRD pattern of the MOF molded body prepared in Example 1 of the present invention.

[0022] Figure 2 This is the TGA curve of the MOF molded body prepared in Example 1 of the present invention.

[0023] Figure 3These are the isothermal nitrogen adsorption-desorption curves of the MOF molded bodies prepared in Example 3 and Comparative Example 1 of this invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the content of the present invention is not limited to the following embodiments. Unless otherwise specified, the reagents used in this embodiment are commonly used or commercially available products in the industry. The BET specific surface area was tested using a low-temperature liquid nitrogen adsorption method, the mechanical strength was tested using a catalyst particle strength tester, the thermal stability was tested using a thermogravimetric analyzer, and the nitrogen adsorption-desorption curves were measured using a nitrogen adsorption meter. Example 1

[0025] At room temperature, 1g of water-soluble phenolic resin was added to 15mL of water, heated and stirred to form a homogeneous solution. 15g of ZIF-8 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe, and then dried at 110℃ for 5 hours in air to obtain a spherical precursor. This precursor was then calcined at 450℃ for 8 hours in a tube furnace under a nitrogen atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 75 N / particle, a thermal stability of 550℃, and a specific surface area of ​​950m². 2 / g. Example 2

[0026] At room temperature, 1g of water-soluble phenolic resin was added to 20mL of water, heated and stirred to form a homogeneous solution. 20g of MIL-53 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe, and then dried at 100℃ for 5 hours in air to obtain a spherical precursor. This precursor was then calcined in a tube furnace at 420℃ for 6 hours under an argon atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 70N / particle, a thermal stability of 550℃, and a specific surface area of ​​810 m². 2 / g. Example 3

[0027] At room temperature, 1g of water-soluble phenolic resin was added to 15mL of water, heated and stirred to form a homogeneous solution. 15g of UiO-66 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe, and then dried at 90℃ for 4 hours in air to obtain a spherical precursor. This precursor was then calcined at 450℃ for 6 hours in a tube furnace under an argon atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 66N / particle, a thermal stability of 500℃, and a specific surface area of ​​850 m². 2 / g. Example 4

[0028] At room temperature, 1 g of water-soluble phenolic resin was added to 10 mL of water and heated and stirred to form a homogeneous solution. 10 g of ZIF-90 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe and then dried at 90°C under vacuum for 3 hours to obtain a spherical precursor. This precursor was then calcined in a tube furnace at 450°C for 6 hours under a nitrogen atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3 mm, a mechanical strength of 72 N / particle, a thermal stability of 500°C, and a specific surface area of ​​800 m². 2 / g.

[0029] Comparative Example 1

[0030] At room temperature, 1g of water-soluble phenolic resin was added to 15mL of water, heated and stirred to form a homogeneous solution; 15g of UiO-66 powder was added to the phenolic resin solution and stirred evenly to obtain a plastic body; the plastic body was extruded into spherical shapes using a syringe, and then dried at 90℃ in air for 4 hours to obtain spherical particles. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 38N / particle, a thermal stability of 500℃, and a specific surface area of ​​650 m². 2 / g.

[0031] Comparative Example 2

[0032] At room temperature, 1 g of water-soluble phenolic resin was added to 10 mL of water, heated and stirred to form a homogeneous solution; 10 g of ZIF-90 powder was added to the phenolic resin solution and stirred until homogeneous to obtain a plastic body; the plastic body was extruded into spherical shapes using a syringe, and then dried at 90°C in air for 3 hours to obtain spherical particles. The obtained spherical particles had a particle size of 3 mm, a mechanical strength of 40 N / particle, a thermal stability of 500°C, and a specific surface area of ​​600 m². 2 / g.

[0033] Comparative Example 3

[0034] At room temperature, 3g of water-soluble phenolic resin was added to 10mL of water, heated and stirred to form a homogeneous solution. 10g of ZIF-8 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe, and then dried at 110℃ for 5 hours in air to obtain a spherical precursor. This precursor was then calcined at 450℃ for 8 hours in a tube furnace under a nitrogen atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 65 N / particle, a thermal stability of 550℃, and a specific surface area of ​​700m². 2 / g.

[0035] Comparative Example 4

[0036] At room temperature, 1g of water-soluble phenolic resin was added to 30mL of water, heated and stirred to form a homogeneous solution. 30g of ZIF-8 powder was added to the phenolic resin solution and stirred until homogeneous, yielding a plastic body. The plastic body was extruded into spherical shapes using a syringe, and then dried at 110℃ for 5 hours in air to obtain a spherical precursor. This precursor was then calcined at 450℃ for 8 hours in a tube furnace under a nitrogen atmosphere to obtain a MOF molded body. The obtained spherical particles had a particle size of 3mm, a mechanical strength of 60 N / particle, a thermal stability of 550℃, and a specific surface area of ​​600m². 2 / g.

[0037] Comparative Examples 1 and 2, without high-temperature carbonization, showed a 43% decrease in mechanical strength and a 24% decrease in specific surface area, confirming that high-temperature carbonization significantly increases the mechanical strength and specific surface area of ​​the MOF molded articles. For Comparative Examples 3 and 4, where the amount of water-soluble phenolic resin added was higher or lower than the range of this invention, the mechanical strength and specific surface area of ​​the MOF molded articles decreased by 8% and 14%, respectively. The MOF molded articles produced according to this method have high mechanical strength and large specific surface area, meeting industrial application standards and suitable for large-scale production.

Claims

1. A method for preparing a MOF molding material, characterized in that... The process includes the following steps: (1) adding MOF powder to a phenolic resin aqueous solution and mixing them evenly to obtain a plastic body; (2) molding, granulating, and drying the plastic body obtained in step (1) to obtain a particle precursor with uniform particle size; (3) carbonizing the MOF molding material under an inert gas atmosphere. The MOF mentioned in step (1) is one or more of ZIF-8, ZIF-7, ZIF-90, MIL-53, MIL-101 and UiO-66; The mass ratio of MOF powder, phenolic resin and water in step (1) is 20-30g:1-2g:20-30mL; The carbonization temperature in step (3) is 400-500℃.

2. The method according to claim 1, characterized in that: The phenolic resin mentioned in step (1) is a water-soluble phenolic resin.

3. The method according to claim 1, characterized in that: The mass ratio of MOF powder, phenolic resin and water in step (1) is 20-25g:1.5-2g:20-25mL.

4. The method according to claim 1, characterized in that: Step (2) involves granulation to prepare spherical, strip-shaped, or irregularly shaped particles as needed.

5. The method according to claim 1, characterized in that: The drying conditions described in step (2) are: temperature of 90-110℃ and time of 3-5 hours.

6. The method according to claim 1, characterized in that: The carbonization temperature in step (3) is 450-480℃ and the carbonization time is 6-8 hours.

7. The MOF molding material prepared according to any one of claims 1 to 6, characterized in that: MOF molding material consists of spherical particles with a strength greater than 60 N / particle and a specific surface area of ​​800-1000 m². 2 / g, thermal stability not less than 500℃.

8. The MOF molding material according to claim 7, characterized in that: The strength of the MOF molding material is greater than 66 N / piece.

9. The MOF molding material according to claim 7, characterized in that: The carbon content of the MOF molding material is 2wt%-6.5wt%; the particle size of the spherical particles is 3-6mm.

10. The application of the MOF molded material prepared by the method according to any one of claims 1 to 6 in the field of adsorption.

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