MOF forming material and preparation method thereof

Abstract

The invention discloses an MOF (Metal Organic Framework) forming material and a preparation method thereof, and the preparation method comprises the following steps: (1) adding MOF powder into a phenolic resin aqueous solution, and uniformly mixing to obtain a plastomer; (2) molding, granulating and drying the plastomer obtained in the step (1) to obtain a particle precursor with uniform particle size; and (3) carbonizing in an inert gas atmosphere to obtain the MOF molding material. The MOF forming material is high in strength and large in specific surface area, and the preparation method is simple in process, low in cost, high in operation repeatability and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of nanoporous materials, and specifically relates to a method for preparing a MOF molding material with high strength and high specific surface area. Background Art

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

[0003] The MOF products obtained by conventional preparation methods are usually crystalline powders, which are difficult to be directly applied in industry. For example, in the field of adsorption separation, the pressure will drop significantly when the gas flows through the powdered adsorption bed, and the mechanical strength of the powdered MOF is not ideal, it is easy to wear and produce heat loss, the internal pores are easy to clog, and regeneration is difficult. MOF molded bodies can effectively solve the problems of low mechanical strength, easy agglomeration, difficult recycling and dust pollution faced by traditional MOF powders in the adsorption process, making MOF materials better applied in the field of gas adsorption separation.

[0004] Industrial adsorbents are generally required to have a mechanical strength greater than 20N / particle. MOF molded bodies are usually prepared by mixing a binder with MOF powder, molding and drying. The method is simple, but the mechanical strength of the obtained MOF molded body is average and cannot meet special industrial requirements. In addition, the use of binders in conventional methods will block the pores and active sites of MOF materials, reduce their specific surface area, and thus affect industrial applications. A new MOF molding method that can be used to prepare high-strength and high-specific surface area MOFs on a large scale is urgently needed.

[0005] CN112705168A discloses a method for preparing an ultra-microporous MOF adsorbent material: the first step is to add polyvinyl alcohol (PVA) to water at room temperature, heat and stir to form a colloidal aqueous solution of PVA; the second step is to evenly stir the ultra-microporous MOF adsorbent powder with an appropriate amount of methyl cellulose (MC); the third step is to add the above-mentioned PVA aqueous solution, mix and stir, form and granulate, and obtain spherical particles after drying. The mechanical strength of the spherical particles prepared by the method described in the invention is >20N / particle, which can only meet the conventional industrial demand for adsorbents.

[0006] CN114042436A discloses a method for preparing a molded MOF material: in the first step, MOF powder, sodium alginate and deionized water are mixed and stirred into a uniform solution, and the uniform solution is added dropwise to a calcium chloride solution with a concentration of 0.03-0.05 mol / L, and the MOF powder is molded into a sphere in the solution; in the second step, the spherical MOF product of step S1 is soaked in the calcium chloride solution for 20-30 minutes, filtered, soaked in deionized water for 2-4 hours, and vacuum dried at 70-100°C to obtain a molded MOF material with a specific surface area of ​​350 m 2 ·g -1 The method described in the invention is simple to form, green, 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 is greatly reduced after forming, which affects its use as an adsorbent. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a MOF molding material and a preparation method thereof. The MOF molding material of the present invention has high strength and large specific surface area, and the preparation method is simple, low in cost, and has strong operation repeatability, and is suitable for industrial production.

[0008] The preparation method of the MOF molding material of the present invention comprises the following contents: (1) Adding MOF powder to phenolic resin aqueous solution and mixing evenly to obtain a plastic body; (2) forming and granulating the plastic obtained in step (1), and drying the plastic to obtain a granular precursor having a uniform particle size; (3) Carbonization under an inert gas atmosphere to obtain MOF molding material.

[0009] In the method of the present invention, the MOF described in step (1) is one or more MOF materials such as ZIF-8, ZIF-7, ZIF-90, MIL-53, MIL-101 and UiO-66.

[0010] In the method of the present invention, the phenolic resin in step (1) is generally a water-soluble phenolic resin.

[0011] In the method of the present invention, the mass ratio of the MOF powder, phenolic resin and water in step (1) is 20-30 g: 1-2 g: 20-30 mL, preferably 20-25 g: 1.5-2 g: 20-25 mL.

[0012] In the method of the present invention, the molding and granulation described in step (2) is well known to those skilled in the art, and particle precursors in spherical, strip-shaped, irregular-shaped, etc. shapes can be prepared as needed, such as by syringe extrusion molding and granulation or compression molding and granulation, preferably syringe extrusion molding and granulation.

[0013] In the method of the present invention, the drying method in step (2) is air atmosphere drying or vacuum drying, preferably air atmosphere drying at a temperature of 90-110° C. for 3-5 hours.

[0014] In the method of the present invention, the carbonization temperature in step (3) is 400-500° C., preferably 450-480° C., and the carbonization time is 6-8 hours; the carbonization process is generally carried out in a tubular furnace.

[0015] The MOF molding material of the present invention is a spherical particle with a strength of more than 60N / particle, preferably more than 66N / particle, and a specific surface area of ​​800-1000m 2 / g, thermal stability is not less than 500°C, wherein the carbon content is 2wt%-6.5wt%, and the spherical particles can be prepared into different particle sizes as needed, preferably 3-6mm.

[0016] Compared with the prior art, the present invention has the following advantages: In the present invention, the MOF material is mixed with the phenolic resin aqueous solution during the preparation process, and the interaction between the MOF material and the phenolic resin is strong, so that the surface of the MOF molded body is uniform and not easy to agglomerate; further, the phenolic resin is pyrolyzed at high temperature by high-temperature calcination, and the internal aromatic carbon layer is disorderly stacked to form a graphitized carbon microcrystalline structure, and the gaps between the carbon layers and the disordered stacking of the carbon microcrystalline structure form a microporous structure, thereby improving the mechanical strength and specific surface area of ​​the MOF molded body, which can be achieved by Figure 3 The nitrogen adsorption and desorption curves of the MOF molded body before and after carbonization are compared. The MOF molded body in the present invention can effectively resist the impact generated during transportation, loading and use, as well as the wear caused by fluid flow, which is beneficial to prolonging the service life of the MOF material. The increase in specific surface area also improves the use effect of the MOF molded body as an adsorption material, promoting the commercial and industrial application of MOF materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the XRD spectrum of the MOF molded body prepared in Example 1 of the present invention.

[0018] Figure 2 It is the TGA curve of the MOF molded body prepared in Example 1 of the present invention.

[0019] Figure 3 3 and 1 are isothermal nitrogen adsorption-desorption curves of the MOF molded bodies prepared in Example 3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and through specific implementation methods, but the content of the present invention is not limited to the following examples. Unless otherwise specified, the reagents used in this embodiment are all commonly used or commercially available products in this industry. The BET specific surface area was tested by low-temperature liquid nitrogen adsorption method, the mechanical strength was tested by catalyst particle strength tester, the thermal stability was tested by thermogravimetric analyzer, and the nitrogen isothermal adsorption and desorption curve was measured by nitrogen adsorption instrument. Example 1

[0021] At room temperature, add 1g of water-soluble phenolic resin to 15mL of water, heat and stir to form a uniform solution; add 15g of ZIF-8 powder to the phenolic resin solution, stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 110°C for 5h in an air atmosphere to obtain a spherical precursor. In a nitrogen gas atmosphere, calcine at 450°C in a tubular furnace for 8h and high-temperature carbonize to obtain a MOF molded body. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 75 N / particle, a thermal stability of 550°C, and a specific surface area of ​​950m 2 / g. Example 2

[0022] At room temperature, add 1g of water-soluble phenolic resin to 20mL of water, heat and stir to form a uniform solution; add 20g of MIL-53 powder to the phenolic resin solution and stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 100°C for 5h in an air atmosphere to obtain a spherical precursor. Then, it is calcined at 420°C in a tubular furnace for 6h under an argon gas atmosphere, and high-temperature carbonization is performed to obtain a MOF molded body. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 70N / particle, a thermal stability of 550°C, and a specific surface area of ​​810 m 2 / g. Example 3

[0023] At room temperature, add 1g of water-soluble phenolic resin to 15mL of water, heat and stir to form a uniform solution; add 15g of UiO-66 powder to the phenolic resin solution and stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 90°C for 4h in an air atmosphere to obtain a spherical precursor. Then, it is calcined at 450°C in a tubular furnace for 6h under an argon gas atmosphere, and high-temperature carbonization is performed to obtain a MOF molded body. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 66N / particle, a thermal stability of 500°C, and a specific surface area of ​​850 m 2 / g. Example 4

[0024] At room temperature, add 1 g of water-soluble phenolic resin to 10 mL of water, heat and stir to form a uniform solution; add 10 g of ZIF-90 powder to the phenolic resin solution, stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 90 ° C for 3 hours under vacuum conditions to obtain a spherical precursor. Then, it is calcined at 450 ° C in a tubular furnace for 6 hours under a nitrogen gas atmosphere, and high-temperature carbonization is performed to obtain a MOF molded body. The obtained spherical particles have 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 m 2 / g.

[0025] Comparative Example 1 At room temperature, 1g of water-soluble phenolic resin was added to 15mL of water, heated and stirred to form a uniform solution; 15g of UiO-66 powder was added to the phenolic resin solution and stirred to obtain a plastic body; the plastic body was squeezed into a sphere through a syringe, and then dried at 90°C for 4h in an air atmosphere to obtain spherical particles. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 38N / particle, a thermal stability of 500°C, and a specific surface area of ​​650 m 2 / g.

[0026] Comparative Example 2 At room temperature, 1 g of water-soluble phenolic resin was added to 10 mL of water, heated and stirred to form a uniform solution; 10 g of ZIF-90 powder was added to the phenolic resin solution and stirred to obtain a plastic body; the plastic body was squeezed into a sphere through a syringe, and then dried at 90 ° C for 3 h in an air atmosphere to obtain spherical particles. The obtained spherical particles have 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 m 2 / g.

[0027] Comparative Example 3 At room temperature, add 3g of water-soluble phenolic resin to 10mL of water, heat and stir to form a uniform solution; add 10g of ZIF-8 powder to the phenolic resin solution, stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 110°C for 5h in an air atmosphere to obtain a spherical precursor. In a nitrogen gas atmosphere, calcine at 450°C in a tubular furnace for 8h and carbonize it at high temperature to obtain a MOF molded body. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 65 N / particle, a thermal stability of 550°C, and a specific surface area of ​​700m 2 / g.

[0028] Comparative Example 4 At room temperature, add 1g of water-soluble phenolic resin to 30mL of water, heat and stir to form a uniform solution; add 30g of ZIF-8 powder to the phenolic resin solution, stir evenly to obtain a plastic body; extrude the plastic body into a sphere through a syringe, and then dry it at 110°C for 5h in an air atmosphere to obtain a spherical precursor. In a nitrogen gas atmosphere, calcine at 450°C in a tubular furnace for 8h and high-temperature carbonize to obtain a MOF molded body. The obtained spherical particles have a particle size of 3mm, a mechanical strength of 60 N / particle, a thermal stability of 550°C, and a specific surface area of ​​600m 2 / g.

[0029] Comparative Examples 1 and 2 were not subjected to high-temperature carbonization, and the mechanical strength of the prepared particles decreased by 43%, and the specific surface area decreased by 24%, confirming that high-temperature carbonization greatly increased the mechanical strength and specific surface area of ​​the MOF molded body. For Comparative Examples 3 and 4, in which the amount of water-soluble phenolic resin added was higher or lower than the scope of the present invention, the mechanical strength and specific surface area of ​​the MOF molded body decreased by 8% and 14%, respectively. The MOF molded body produced according to this method has high mechanical strength and large specific surface area, can meet industrial application standards, and can be used for large-scale production.

Claims

1. A method for preparing a MOF molding material, characterized in that The method comprises the following contents: (1) adding MOF powder to a phenolic resin aqueous solution and mixing them uniformly to obtain a plastic body; (2) molding and granulating the plastic body in step (1) and drying it to obtain a particle precursor with uniform particle size; and (3) carbonizing the plastic body in an inert gas atmosphere to obtain a MOF molding material.

2. The method according to claim 1, characterized in that: The MOF described in step (1) is one or more of ZIF-8, ZIF-7, ZIF-90, MIL-53, MIL-101 and UiO-66 MOF materials.

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

4. The method according to claim 1, characterized in that: The mass ratio of the MOF powder, phenolic resin and water in step (1) is 20-30 g: 1-2 g: 20-30 mL, preferably 20-25 g: 1.5-2 g: 20-25 mL.

5. The method according to claim 1, characterized in that: The molding granulation in step (2) can prepare spherical, strip-shaped or irregular-shaped particles as required.

6. The method according to claim 1, characterized in that: The drying conditions in step (2) are as follows: a temperature of 90-110° C. and a drying time of 3-5 hours.

7. The method according to claim 1, characterized in that: The carbonization temperature in step (3) is 400-500°C, preferably 450-480°C, and the carbonization time is 6-8 hours.

8. The MOF molding material prepared according to any one of claims 1 to 7, characterized in that: The MOF molding material is spherical particles with a strength greater than 60N / particle, preferably greater than 66N / particle, and a specific surface area of ​​800-1000m 2 / g, thermal stability not less than 500℃.

9. The MOF molding material prepared by the method according to any one of claims 1 to 7, characterized in that: The carbon content is 2wt%-6.5wt%; the spherical particles are prepared into different particle sizes according to needs, preferably 3-6mm.

10. Application of the MOF molding material prepared by the method according to any one of claims 1 to 7 in the field of adsorption.

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