A gradient crosslinking MOF forming method based on nanosized slurry and high-performance formed body

Abstract

A gradient crosslinking MOF forming method based on nano slurry and high-performance formed body. The present application belongs to the technical field of MOF forming. The purpose of the present application is to solve the technical problem that the MOF formed body is difficult to maintain high performance. The method of the present application is to nanoize the MOF material to 10-100 nm first, and then realize high-performance forming under mild conditions by using a gradient crosslinking process, a forming method that maximizes the original structure and performance of the metal organic framework material powder, and solves the contradiction between forming and performance maintenance. The specific surface area of the formed MOF material is maintained at more than 93% compared with the powder material, and the adsorption performance is maintained at more than 95%.

Description

Technical Field

[0001] This invention belongs to the field of MOF molding technology, specifically relating to a gradient crosslinking MOF molding method based on nano-sized slurry and a high-performance molded body. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of porous crystalline materials formed by the coordination bonds between metal ions or metal clusters and organic ligands. They have advantages such as large specific surface area, tunable pore structure, and high degree of functionalization, and show broad application prospects in fields such as gas adsorption and separation, catalysis, drug delivery, and environmental remediation.

[0003] However, MOF materials face a key technical bottleneck in practical applications: powder materials are difficult to apply directly to industrial devices. Powdered MOF materials have problems such as poor flowability, easy to fly, difficult to fill, and large pressure drop, which limit their application in industrial equipment such as fixed bed reactors and adsorption towers. To solve the above problems, researchers have developed a variety of MOF molding technologies, mainly including: (1) Binder molding method, which presses MOF powder into shape by adding polymers, inorganic oxides and other binders. However, the problem with this method is that the binder will block some pores, resulting in a significant decrease in specific surface area and pore volume, and serious loss of adsorption performance. (2) In-situ growth method, which directly synthesizes MOF crystals on substrate materials. However, the problem with this method is that the process is complicated, the repeatability is poor, and the substrate material will occupy a certain space, reducing the effective adsorption capacity per unit volume. (3) Hot pressing molding method, which directly presses the powder into shape by high temperature and high pressure. However, the problem with this method is that high pressure can easily cause the crystal structure to collapse, and high temperature may cause ligand decomposition, resulting in serious loss of performance. Currently, maximizing the specific surface area, pore volume, and adsorption performance of powder materials while ensuring the mechanical strength of the molded body has become a core technical challenge for the industrial application of MOF materials. Existing technologies generally suffer from the following shortcomings: severe performance loss: specific surface area typically decreases by 15-30% after molding; pore blockage: binders occupy pore space, reducing effective pore volume; structural damage: high-pressure molding causes partial collapse of the crystal structure; complex processes: some methods require multiple steps, resulting in high costs.

[0004] Therefore, developing a new method that can effectively protect the crystal structure and pores of MOFs during the molding process, and enable the properties of the molded body to approach or even reach the level of powder, has important theoretical significance and practical value. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, this invention provides a gradient crosslinking MOF molding method based on nano-sized slurry and a high-performance molded body. By first nano-sizing the MOF material to 10-100 nm, and then using a gradient crosslinking process under mild conditions to achieve high-performance molding, this molding method maximizes the preservation of the original structure and properties of the metal-organic framework material powder, thus resolving the contradiction between molding and performance preservation.

[0006] The technical solution of the present invention is as follows: One objective of this invention is to provide a gradient crosslinking MOF molding method based on nano-sized slurry, the method comprising the following steps: (1) Disperse MOF in a green solvent and grind it with a sand mill until the particle size is ≤100nm to obtain a nano-sized MOF dispersion; (2) Add functional resin and granulation aid to the nano-sized MOF dispersion, stir evenly, and adjust the solid content to 40-90% to obtain a uniform slurry; (3) The slurry was molded using different methods to obtain MOF molded wet particles; (4) The wet MOF molded particles obtained in step (3) are subjected to gradient crosslinking and curing. First, they are kept at room temperature for 1~10h, and then kept at 60~80℃ for 12~24h to obtain the MOF molded body.

[0007] Further specifying, the green solvent mentioned in step (1) includes water.

[0008] Further specifying, the solid content of MOF in the green solvent in step (1) is 5~20%.

[0009] Further specifying, the MOF mentioned in step (1) is UiO-66, UiO-66-OH, UiO-67-NH2, ZIF-7, ZIF-8, ZIF-67 (Co), ZIF-69, MIL-101 (Cr, Fe), MIL-53, MIL-100 (Al, Fe), MOF-801 or MOF-303.

[0010] Further specifying, the viscosity of 1% of the functional resin in step (2) is 20000~100000 m·Pa·S.

[0011] Furthermore, the functional resin is hydroxymethyl cellulose.

[0012] Further specifying, the mass ratio of the functional resin to the MOF in the nano-sized MOF dispersion in step (2) is (0.1~1):100.

[0013] Further specifying, the granulation aid mentioned in step (2) is selected from one or more of glycerol, propylene glycol, and polyethylene glycol.

[0014] To further specify, polyethylene glycol is hydroxyl-terminated polyethylene glycol.

[0015] Further specified, the amount of granulation aid added in step (2) is 0.1~5% of the total mass of the slurry.

[0016] Further specifying, the different methods mentioned in step (3) are extrusion-spheronization, spray granulation or drop ball method.

[0017] The second objective of this invention is to provide a MOF molded article obtained by the above method.

[0018] Furthermore, the MOF molded body retains a specific surface area of ​​over 92% and an adsorption performance of over 95%.

[0019] The advantages of this invention compared to existing technologies are: This invention significantly reduces the amount of binder and molding pressure by nano-processing MOF materials, thereby maximizing the performance of the molded MOF. Experiments show that the specific surface area of ​​the molded MOF material is maintained at over 93% compared to the powder material, and the adsorption performance is maintained at over 95%.

[0020] The method of this invention combines nanotechnology with mature industrial granulation process, which solves the technical problem of MOF molded bodies being unable to maintain high performance. It maintains the high performance brought by nanotechnology and realizes standardized particle production. It can be adapted to existing granulation equipment without special modification and has high compatibility. Attached Figure Description

[0021] Figure 1 The image shows the SEM image of the original MOF powder in Example 1. Figure 2 The image shows the SEM image of the MOF powder after sand milling in step (1) of Example 1. Figure 3 Photographs of the nano-sized MOF columnar prototype obtained in Example 1; Figure 4 This is a photograph of the un-nanosized MOF that could not be formed in Comparative Example 1; Figure 5 This is a photograph of the unnanosized MOF obtained in Comparative Example 2. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0024] Example 1: The gradient crosslinking MOF molding method based on nano-sized slurry in this example is carried out according to the following steps: (1) Add 1 kg of UiO-66 (specific surface area of ​​700 ~ 4000 m²) 2 / g, with a particle size of 600nm ~ 1μm) dispersed in deionized water (solid content of 20%), and ground by a sand mill in an intermittent mode of working for 20min and stopping for 5min for 1h until the particle size is ≤100nm. Then, it was filtered through a 100nm filter membrane to obtain a nano-sized MOF dispersion. (2) Add 1g of hydroxymethyl cellulose (1% viscosity: 100000 m·Pa·S) and 20g of hydroxyl-terminated polyethylene glycol (molecular weight: 400) to the nano-sized MOF dispersion, stir evenly, and then evaporate the solvent at 35°C until the solid content is 90% to obtain a uniform slurry; (3) Using the extrusion-spheronization method, the slurry is loaded into the extruder barrel and extruded through a stainless steel screen with a aperture of 0.5 mm. The extrusion pressure is 0.2 MPa to obtain a columnar shaped body with a diameter of 0.5 mm. Then, it is transferred to a spheronization machine and spheronized at a speed of 150 rpm for 15 min to obtain spherical particles, i.e., MOF shaped body wet particles. (4) The wet MOF molded particles obtained in step (3) are subjected to gradient crosslinking and curing. First, they are kept at room temperature for 4 hours, and then at 80°C for 16 hours to obtain the MOF molded body.

[0025] Comparative Example 1 The difference between this comparative example and Example 1 is that: in step (1), nano-sizing is not performed, and the original 1 kg UiO-66 is directly dispersed in deionized water to form a MOF dispersion with a solid content of 20%. Other steps and parameters are the same as in Example 1.

[0026] Comparative Example 2 The difference between this comparative example and Example 1 is that: in step (1), nano-sizing is not performed, and the original 1 kg UiO-66 is directly dispersed in deionized water to form a MOF dispersion with a solid content of 20%; in step (2), the hydroxymethyl cellulose is adjusted to 36 g. Other steps and parameters are the same as in Example 1.

[0027] The original MOF powder and the milled MOF material were observed using SEM. The particle size ranged from the original 600 nm to 1 μm. Figure 1) reduced to 80 ~ 90nm ( Figure 2 ).

[0028] The original MOF powder and the nano-sized MOF were molded together, and the molding effect was as follows: Figure 3-5 As shown in the comparison, the molded body obtained in Example 1 of the present invention has a uniform size, while the MOF powder in Comparative Example 1, which has not been nano-sized, cannot be molded. Comparative Example 2 can be molded, but the amount of binder used is too large.

[0029] The molding performance of the original MOF powder and the nano-sized MOF was also compared and tested, and the results are shown in Table 1.

[0030] Table 1. Performance indicators of MOF powder before and after molding

[0031] As can be clearly seen from Table 1, the BET and pore volume retention rates of the MOF molded bodies obtained in Example 1 of this invention are both 93% or higher. The methane and CO2 adsorption performance of this material was tested, and the performance retention rates of the MOF molded bodies were generally above 95%. Furthermore, using non-nanosized MOF powder with the same proportion of binder (0.1%), it was found that the powder could not be molded and remained in a powder state. Further, increasing the binder dosage to 3.6% (the proportion of MOF) allowed for granulation, but the BET and pore volume of the molded particles decreased significantly. More significantly, the adsorption capacity of methane and carbon dioxide decreased by as much as 30%.

[0032] In summary, this invention maintains the ultra-high performance brought about by nano-sizing while achieving perfect compatibility with existing granulation equipment, providing an ideal granular product for the industrial application of metal-organic framework materials.

[0033] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A gradient crosslinking MOF molding method based on nano-sized slurry, characterized in that, The method described: (1) Disperse MOF in a green solvent and grind it with a sand mill until the particle size is ≤100nm to obtain a nano-sized MOF dispersion; (2) Add functional resin and granulation aid to the nano-sized MOF dispersion, stir evenly, and adjust the solid content to 40-90% to obtain a uniform slurry; (3) The slurry was molded using different methods to obtain MOF molded wet particles; (4) The wet MOF molded particles obtained in step (3) are subjected to gradient crosslinking and curing. First, they are kept at room temperature for 1~10h, and then kept at 60~80℃ for 12~24h to obtain the MOF molded body.

2. The method according to claim 1, characterized in that, The green solvent mentioned in step (1) includes water, and the solid content of MOF in the green solvent is 5~20%.

3. The method according to claim 1, characterized in that, The MOF mentioned in step (1) is UiO-66, UiO-66-OH, UiO-67-NH2, ZIF-7, ZIF-8, ZIF-67 (Co), ZIF-69, MIL-101 (Cr, Fe), MIL-53, MIL-100 (Al, Fe), MOF-801 or MOF-303.

4. The method according to claim 1, characterized in that, The functional resin described in step (2) has a viscosity of 20,000~100,000 m·Pa·S at 1% and the mass ratio of the functional resin to the MOF in the nano-sized MOF dispersion is (0.1~1):

100.

5. The method according to claim 4, characterized in that, The functional resin is hydroxymethyl cellulose.

6. The method according to claim 1, characterized in that, The granulation aid mentioned in step (2) is selected from one or more of glycerol, propylene glycol, and polyethylene glycol, and the amount of granulation aid added is 0.1~5% of the total mass of slurry.

7. The method according to claim 6, characterized in that, Polyethylene glycol is hydroxyl-terminated polyethylene glycol.

8. The method according to claim 1, characterized in that, The different methods mentioned in step (3) are extrusion-spheronization, spray granulation, or drop ball method.

9. The MOF molded article obtained by the method according to any one of claims 1-8.

10. The MOF molded article according to claim 9, characterized in that, The MOF molded body retains a specific surface area of ​​over 92% and an adsorption performance of over 95%.

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