A system and method for continuous flow synthesis of metal-organic framework materials

Abstract

The application relates to a system and method for continuously synthesizing metal organic framework (MOF) materials, belonging to the technical field of material preparation. The system comprises a feeding unit, a reaction unit, a discharging unit and a separation unit. The method is as follows: metal salt solution and organic ligand solution are used as reaction raw materials, and are continuously pumped into the reactor through the feeding unit; the reactor is used for reaction under the conditions of heating and stirring, and the mixture generated in the reaction is continuously pumped out through the discharging unit; the pumped product is subjected to solid-liquid separation, and the obtained solid product is a metal organic framework material. In the application, a continuously stirred tank reactor or a kettle reactor is used as a reactor for MOF crystal growth, metal salt and organic ligand solution are continuously pumped into the reactor, the product in the reactor is continuously pumped out and collected, and metal salt and ligand are added into a solvent as raw material solution to realize continuous circulation flow synthesis.

Description

Technical Field

[0001] This application belongs to the field of materials preparation technology, and in particular relates to a system and method for continuous flow synthesis of metal-organic framework materials. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with a periodic network structure, formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and bridging organic ligands. MOFs are a type of organic-inorganic hybrid material, also known as coordination polymers. Due to the diverse selection of metal centers and organic ligands, tens of thousands of MOFs have been synthesized. MOF materials have been extensively studied in recent years due to their excellent physical and chemical properties, such as high specific surface area, low density, high pore volume, tunable functional group structure, and high porosity, making them potential materials for adsorption, separation, gas storage, and catalysis.

[0003] The synthesis methods of metal-organic framework materials are diverse, mainly achieved through the self-assembly of metal ions and organic ligands. The core lies in controlling the crystallization process to obtain the target structure with high crystallinity and high porosity. Thermodynamic studies have shown that high-temperature long-time reaction conditions can reduce the nucleation energy barrier of MOFs, which is conducive to crystal crystallization and promotes the orderly arrangement of crystal structures; low-temperature short-time synthesis tends to produce MOFs with large pore sizes. MOFs prepared by different synthesis methods differ in terms of crystal growth direction, pore structure, topology, production efficiency and defects. To meet the needs of large-scale MOF production, the ideal preparation strategy needs to meet the following requirements: (1) It has a highly reproducible process, good product uniformity, and is environmentally friendly; (2) The single crystal size must meet the requirements. Existing synthesis technologies mainly include diffusion method, solvothermal synthesis method, microwave synthesis method, mechanical synthesis method, and ultrasonic synthesis method.

[0004] The mainstream synthesis method is currently solvothermal synthesis. Solvothermal synthesis has a wide range of applications and is the standard method for MOF synthesis. It is easy to generate high-quality crystals. However, this method also has obvious disadvantages. Solvothermal synthesis is a batch process, and the reaction cycle can last for several days. Due to the limitations of the production method and tools, the production capacity of MOF is greatly restricted. In response to the low production capacity of batch production, a new synthesis method called continuous flow synthesis has been applied in MOF synthesis. For example, Wang Ying et al. used microdroplet flow synthesis to synthesize a series of Zr-based MOF materials, including MOF-801, MOF-804, DUT-67 and MOF-808 (Chin. Chem. Lett. 2018, 29(6), 849–853). This synthesis method separates the precursor solution into small droplets through a continuous phase. Each droplet acts as a MOF microreactor, and the metal-organic framework material is synthesized after passing through a heating zone. Although this method changes the batch production mode compared to the solvothermal synthesis method, improves the space-time yield of the product, and can obtain products with uniform particle size, it has inherent defects: (1) low production throughput, difficulty in scale-up, and difficulty in meeting the needs of large-scale industrial production; (2) the channel is easily blocked by the generated MOF crystals, resulting in poor long-term stability of the system; (3) it requires the introduction of an immiscible third phase (such as an oil phase), which increases the cost and complexity of subsequent separation and purification. To date, there is no effective method for synthesizing MOF materials that meets the requirements of large-scale continuous industrial production.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this application is to provide a system and method for continuous flow synthesis of metal-organic framework materials, which uses a continuous stirred tank or batch reactor as the reactor for MOF crystal growth, continuously pumps metal salt and organic ligand solutions into the reactor and pumps out and collects the products in the reactor, and adds metal salt and ligands to the solvent as a raw material solution to achieve continuous circulating flow synthesis.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a system for the continuous flow synthesis of metal-organic framework materials, comprising: The feeding unit is used for continuous conveying of reaction raw materials; The reaction unit includes a reactor whose inlet is connected to the feeding unit, a stirring device disposed inside the reactor, and a condensation reflux device disposed above the reactor; The discharge unit is connected to the outlet of the reactor and is used to continuously pump the reaction products out of the reactor. A separation unit, connected downstream of the discharge unit, is used to separate the product from the solvent.

[0008] Secondly, this application provides a method for the continuous flow synthesis of metal-organic framework materials based on the aforementioned system, comprising the following steps: S1: The metal salt solution and the organic ligand solution are used as reaction raw materials and are continuously pumped into the reactor through the feeding unit; S2: The reactor reacts under heating and stirring conditions, and the mixture produced by the reaction is continuously pumped out by the discharge unit; S3: Perform solid-liquid separation on the pumped product to obtain a solid product, which is a metal-organic framework material.

[0009] Compared with existing technologies, this application employs a continuous flow synthesis method, enabling the continuous synthesis of metal-organic framework materials. The synthesis process eliminates the need for template agents and post-processing. Metal-organic framework materials prepared using this method can achieve high spatial and temporal yields, the solvent can be recycled and reused, and the product yield can be increased by using a series of reactors. Furthermore, the process can be scaled up directly by simply increasing the number of reactors, making it simple, easy to implement, and suitable for large-scale continuous production. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the process equipment using the separate feeding method in this application; Figure 2 This is a schematic diagram of the process equipment using the mixed feeding method in this application; Figure 3 It is the one prepared in Embodiment 1 of this application. α -Mg3(HCOO)6 powder X-ray diffraction pattern; Figure 4 In Figure 4 a, Figure 4 b and Figure 4 c represents the products obtained in Examples 2-4 of this application. α -Mn3(HCOO)6、 α -Co3(HCOO)6 and α -Powder X-ray diffraction pattern of Ni3(HCOO)6; Figure 5 It is the one prepared in Embodiment 5 of this application.α Powder X-ray diffraction pattern of Mg3(HCOO)6.

[0012] Explanation of reference numerals in the attached figures: 1-First feed pump; 2-Second feed pump; 3-Y-type connector; 4-Reactor; 5-Discharge pump; 6-Single feed pump. Detailed Implementation

[0013] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0014] This application provides a system for the continuous flow synthesis of metal-organic framework materials, such as... Figure 1 and Figure 2 As shown, it includes: The feeding unit is used for continuous conveying of reaction raw materials; The reaction unit includes a reactor 4 whose inlet is connected to the feeding unit, a stirring device disposed inside the reactor 4, and a condensation reflux device disposed above the reactor 4. The discharge unit mainly includes a discharge pump 5, which is connected to the outlet of the reactor 4 and is used to continuously pump the reaction products out of the reactor 4. The separation unit, connected downstream of the discharge unit (i.e., discharge pump 5), is used to separate the product from the solvent.

[0015] Reactor 4 includes a CSTR reactor, i.e., a continuous stirred tank or batch reactor, which has a continuous reaction chamber without a stable phase interface inside. Those skilled in the art will understand that reactor 4 is equipped with a corresponding heating device, which can be one of an oil bath or a heating jacket, and the reaction temperature is set at 100-140 °C.

[0016] In some embodiments, such as Figure 1 As shown, the feeding unit includes a first feed pump 1, a second feed pump 2, and a Y-type connector 3; the outlets of the first feed pump 1 and the second feed pump 2 are respectively connected to the two inlets of the Y-type connector 3 through pipelines, and the outlet of the Y-type connector 3 is connected to the inlet of the reactor 4 through a pipeline.

[0017] In other embodiments, such as Figure 2 As shown, the feeding unit includes a single feed pump 6, which is directly connected to the inlet of the reactor 4 via a pipeline.

[0018] In some preferred embodiments, the system may include a combination of multiple units arranged in series, the combination including the feed unit, reaction unit, discharge unit, and separation unit arranged in series. This can increase the product yield and can be easily scaled up by simply increasing the number of units in the combination, making it simple and easy to implement.

[0019] In some alternative embodiments, the conduit may be made of a material with a polytetrafluoroethylene lining and a rubber outer material.

[0020] This application also provides a method for synthesizing metal-organic framework materials using the aforementioned system in a continuous flow process, comprising the following steps: S1: The metal salt solution and the organic ligand solution are used as reaction raw materials and are continuously pumped into the reactor through the feeding unit; S2: The reactor reacts under heating and stirring conditions, and the mixture produced by the reaction is continuously pumped out by the discharge unit; S3: Perform solid-liquid separation on the pumped product to obtain a solid product, which is a metal-organic framework material.

[0021] In some embodiments, the metal salt includes at least one of magnesium chloride hexahydrate, manganese acetate tetrahydrate, cobalt nitrate hexahydrate, or nickel nitrate hexahydrate, with a concentration of 0.5-2 mol / L.

[0022] In some embodiments, the organic ligand comprises formic acid at a concentration of 3-35 mol / L.

[0023] In some embodiments, the solvent is N,N-dimethylformamide (DMF).

[0024] In some embodiments, such as Figure 1 As shown, in step S1, separate feeding can be used, that is, the metal salt solution and the organic ligand solution are used as reaction raw materials, which are respectively fed through the first feed pump 1 and the second feed pump 2 and then merged into the Y-type connector 3, and finally enter the reactor 4 for reaction.

[0025] Furthermore, under the same pipe diameter, when using separate feeding methods, the flow rate ratio of the metal salt solution flow path to the organic ligand solution flow path is 2-5:1, and the sum of the two flow rates is equal to the pumping flow rate of the discharge unit.

[0026] In other embodiments, such as Figure 2 As shown, in step S1, a mixed feed can also be used, that is, the metal salt and organic ligand are pre-mixed and dissolved in a solvent as reaction raw materials, and then fed into reactor 4 via a single feed pump 6 for reaction.

[0027] Furthermore, under the same pipe diameter, when a mixed feeding method is used, the feed flow rate and the discharge flow rate are the same.

[0028] Furthermore, the heating temperature is 100-140 ℃, preferably 130 ℃.

[0029] Furthermore, during the reaction process, the condensation reflux device above the reactor is in the open state.

[0030] Furthermore, the stirring rate is 500-1200 rpm.

[0031] Reactor 4 is heated and stirred to react metal salts and organic ligands to form metal-organic framework materials. A reflux condenser is used above reactor 4 to reflux the solvent, and the product is pumped out by discharge pump 5 to an automatic sampler.

[0032] In some preferred embodiments, the method further includes step S4: collecting the solvent obtained after solid-liquid separation in S3, adding metal salts and / or organic ligands, and then circulating it into the reactor as a reaction raw material for reaction.

[0033] In this embodiment of the invention, the phase composition and crystallinity of the prepared metal-organic framework material were characterized by powder X-ray diffraction using a Rigaku Smart Lab 3kW instrument. Specific surface area was visualized using nitrogen adsorption-desorption curves using a BSD-660M A3MB3M instrument. All raw materials used in this embodiment of the invention were commercially available products.

[0034] The following description is based on specific embodiments.

[0035] Example 1 (1) Adopting such Figure 1 The separately fed system shown uses polytetrafluoroethylene-lined rubber hoses with an inner diameter of 1.6 mm and an outer diameter of 4.8 mm for all piping. Magnesium chloride hexahydrate is dispersed in N,N-dimethylformamide solution to prepare a 1.6 mol / L solution, which is then added to the feed solution of the first feed pump 1. Formic acid is dispersed in N,N-dimethylformamide solution to prepare a 9.6 mol / L solution, which is then added to the feed solution of the second feed pump 2.

[0036] (2) Reactor 4 is a continuous stirred tank reactor. The reactor 4 is heated by oil bath to 130 ℃; the stirring rate is set to 800 rpm / min. The flow rate of the first feed pump 1 is 0.63 mL / min, the flow rate of the second feed pump 2 is 0.21 mL / min, and the flow rate of the discharge pump 5 is 0.84 mL / min. All three pumps are turned on at the same time.

[0037] (3) Collect the product at the outlet of discharge pump 5, filter and separate the product and solvent to obtain the final product. α -Mg3(HCOO)6 metal-organic framework material. 0.16 mol magnesium chloride hexahydrate and 0.96 mol formic acid were added to 100 mL of the separated solvent, respectively, and then fed into the first feed pump 1 and the second feed pump 2 as the reaction solution.

[0038] The produced α The powder X-ray diffraction pattern of Mg3(HCOO)6 is shown below. Figure 3 As shown, by Figure 3 It can be seen that the synthesized product is α -Mg3(HCOO)6, the product has good crystallinity. The obtained... α The nitrogen adsorption-desorption curve of Mg3(HCOO)6 showed that its specific surface area was 411.9 m². 2 ·g -1 .

[0039] Example 2 (1) Adopting such Figure 1 The separately fed system shown uses polytetrafluoroethylene-lined rubber hoses with an inner diameter of 1.6 mm and an outer diameter of 4.8 mm for all piping. Manganese acetate tetrahydrate is dispersed in N,N-dimethylformamide solution to prepare a 1.6 mol / L solution, which is then added to the feed solution of the first feed pump 1. Formic acid is dispersed in N,N-dimethylformamide solution to prepare a 19.2 mol / L solution, which is then added to the feed solution of the second feed pump 2.

[0040] (2) Reactor 4 is a continuous stirred tank reactor. The reactor 4 is heated by oil bath to 130 ℃; the stirring rate is set to 1200 rpm / min. The flow rate of the first feed pump 1 is 0.63 mL / min, the flow rate of the second feed pump 2 is 0.21 mL / min, and the flow rate of the discharge pump 5 is 0.84 mL / min. All three pumps are turned on at the same time.

[0041] (3) Collect the product at the outlet of discharge pump 5, filter and separate the product and solvent to obtain the final product. α -Mn3(HCOO)6 metal-organic framework material. 0.16 mol manganese acetate tetrahydrate and 1.92 mol formic acid were added to 100 mL of the separated solvent, respectively, and then fed into the first feed pump 1 and the second feed pump 2 as the reaction solution.

[0042] The produced α The powder X-ray diffraction pattern of -Mn3(HCOO)6 is as follows: Figure 4 As shown in a, by Figure 4As can be seen from a, the synthesized product is α -Mn3(HCOO)6, the product has good crystallinity. The obtained... α The nitrogen adsorption-desorption curves of Mn3(HCOO)6 showed that its specific surface area was 279.4 m². 2 ·g -1 .

[0043] Example 3 (1) Adopting such Figure 1 The separately fed system shown uses polytetrafluoroethylene-lined rubber hoses with an inner diameter of 1.6 mm and an outer diameter of 4.8 mm for all piping. Cobalt nitrate hexahydrate is dispersed in N,N-dimethylformamide solution to prepare a 1.6 mol / L solution, which is then added to the feed solution of the first feed pump 1. Formic acid is dispersed in N,N-dimethylformamide solution to prepare a 33.6 mol / L solution, which is then added to the feed solution of the second feed pump 2.

[0044] (2) Reactor 4 is a continuous stirred tank reactor. The reactor 4 is heated by oil bath to 130 ℃; the stirring rate is set to 1200 rpm / min. The flow rate of the first feed pump 1 is 0.63 mL / min, the flow rate of the second feed pump 2 is 0.21 mL / min, and the flow rate of the discharge pump 5 is 0.84 mL / min. All three pumps are turned on at the same time.

[0045] (3) Collect the product at the outlet of discharge pump 5, filter and separate the product and solvent to obtain the final product. α -Co3(HCOO)6 metal-organic framework material. 0.16 mol of cobalt nitrate hexahydrate and 3.36 mol of formic acid were added to 100 mL of the separated solvent, respectively, and then fed into the first feed pump 1 and the second feed pump 2 as the reaction solution.

[0046] The produced α The powder X-ray diffraction pattern of -Co3(HCOO)6 is shown below. Figure 4 As shown in b, by Figure 4 b. It can be seen that the synthesized product is α -Co3(HCOO)6, the product has good crystallinity. The obtained... α The nitrogen adsorption-desorption curves of -Co3(HCOO)6 showed that its specific surface area was 360.9 m². 2 ·g -1 .

[0047] Example 4 (1) Adopting such Figure 1The separately fed system shown uses polytetrafluoroethylene-lined rubber hoses with an inner diameter of 1.6 mm and an outer diameter of 4.8 mm for all piping. Nickel nitrate hexahydrate is dispersed in N,N-dimethylformamide solution to prepare a 1.6 mol / L solution, which is then added to the feed solution of the first feed pump 1. Formic acid is dispersed in N,N-dimethylformamide solution to prepare a 24.0 mol / L solution, which is then added to the feed solution of the second feed pump 2.

[0048] (2) Reactor 4 is a continuous stirred tank reactor. The reactor 4 is heated by oil bath to 130 ℃; the stirring rate is set to 1200 rpm / min. The flow rate of the first feed pump 1 is 0.63 mL / min, the flow rate of the second feed pump 2 is 0.21 mL / min, and the flow rate of the discharge pump 5 is 0.84 mL / min. All three pumps are turned on at the same time.

[0049] (3) Collect the product at the outlet of discharge pump 5, filter and separate the product and solvent to obtain the final product. α -Ni3(HCOO)6 metal-organic framework material. 0.16 mol of nickel nitrate hexahydrate and 2.4 mol of formic acid were added to 100 mL of the separated solvent, respectively, and then fed into the first feed pump 1 and the second feed pump 2 as the reaction solution.

[0050] The produced α The powder X-ray diffraction pattern of Ni3(HCOO)6 is shown below. Figure 4 As shown in c, by Figure 4 c shows that the synthesized product is α -Ni3(HCOO)6, the product has good crystallinity. The obtained... α The nitrogen adsorption-desorption curves of Ni3(HCOO)6 showed that its specific surface area was 254.2 m². 2 ·g -1 .

[0051] Example 5 (1) Adopting such Figure 2 The mixed-feed system shown uses PTFE-lined rubber hoses with an inner diameter of 1.6 mm and an outer diameter of 4.8 mm for all piping. Magnesium chloride hexahydrate is dispersed in an N,N-dimethylformamide solution to prepare a 1.6 mol / L solution; formic acid is dispersed in an N,N-dimethylformamide solution to prepare a 3.2 mol / L solution; both solutions are mixed and added to the feed solution via a single feed pump 6.

[0052] (2) Reactor 4 is a continuous stirred tank reactor. The reactor 4 is heated by oil bath to 130 ℃; the stirring rate is set to 600 rpm / min. The flow rate of the single feed pump 6 is 0.84 mL / min, the flow rate of the discharge pump 5 is 0.84 mL / min, and both pumps are turned on at the same time.

[0053] (3) Collect the product at the outlet of discharge pump 5, filter and separate the product and solvent to obtain the final product. α -Mg3(HCOO)6 metal-organic framework material. 0.16 mol magnesium chloride hexahydrate and 0.32 mol formic acid were added to 100 mL of the separated solvent, and the mixture was fed into a single feed pump 6 as the reaction solution.

[0054] The produced α The powder X-ray diffraction pattern of Mg3(HCOO)6 is shown below. Figure 5 As shown, by Figure 5 It can be seen that the synthesized product is α -Mg3(HCOO)6, the product has good crystallinity. The obtained... α The nitrogen adsorption-desorption curve of Mg3(HCOO)6 showed that its specific surface area was 411.2 m². 2 ·g -1 .

[0055] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A system for continuous flow synthesis of metal-organic framework materials, characterized in that, include: The feeding unit is used for continuous conveying of reaction raw materials; The reaction unit includes a reactor whose inlet is connected to the feeding unit, a stirring device disposed inside the reactor, and a condensation reflux device disposed above the reactor; The discharge unit is connected to the outlet of the reactor and is used to continuously pump the reaction products out of the reactor. A separation unit, connected downstream of the discharge unit, is used to separate the product from the solvent.

2. The system as described in claim 1, characterized in that, The feeding unit includes a first feed pump, a second feed pump, and a Y-shaped connector; the outlets of the first feed pump and the second feed pump are respectively connected to the two inlets of the Y-shaped connector through pipelines, and the outlet of the Y-shaped connector is connected to the inlet of the reactor through a pipeline.

3. The system as described in claim 1, characterized in that, The feeding unit includes a single feed pump, which is directly connected to the inlet of the reactor via a pipeline.

4. The system as described in claim 1, characterized in that, The system includes a combination of multiple units arranged in series, which includes the feeding unit, reaction unit, discharge unit and separation unit arranged in series.

5. A method for continuous flow synthesis of metal-organic framework materials based on the system according to any one of claims 1-4, characterized in that, Includes the following steps: S1: The metal salt solution and the organic ligand solution are used as reaction raw materials and are continuously pumped into the reactor through the feeding unit; S2: The reactor reacts under heating and stirring conditions, and the mixture produced by the reaction is continuously pumped out by the discharge unit; S3: Perform solid-liquid separation on the pumped product to obtain a solid product, which is a metal-organic framework material.

6. The method as described in claim 5, characterized in that, In step S1, the metal salt includes at least one of magnesium chloride hexahydrate, manganese acetate tetrahydrate, cobalt nitrate hexahydrate, or nickel nitrate hexahydrate; And / or, the organic ligand includes formic acid; And / or, the solvent is N,N-dimethylformamide.

7. The method as described in claim 5, characterized in that, In step S1, the metal salt solution and the organic ligand solution are fed separately as reaction raw materials, which are fed through the first feed pump and the second feed pump respectively and then into the Y-type connector, and finally enter the reactor for reaction. And / or, a mixed feed is used: the metal salt and organic ligand are premixed and dissolved in a solvent as reactants, and then fed into the reactor via the single feed pump for reaction.

8. The method as described in claim 5, characterized in that, For the same pipe diameter, When a separate feeding method is adopted, the flow rate ratio of the metal salt solution flow path to the organic ligand solution flow path is 2-5:1, and the sum of the two flow rates is equal to the pumping flow rate of the discharge unit. When a mixed feeding method is used, the feed flow rate is the same as the discharge flow rate.

9. The method as described in claim 5, characterized in that, In step S2, the heating temperature is 100-140 ℃; And / or, during the reaction, the condensation reflux device above the reactor is in the open state; And / or, the stirring rate is 500-1200 rpm.

10. The method as described in claim 5, characterized in that, It also includes S4: collecting the solvent obtained after solid-liquid separation in S3, adding metal salts and / or organic ligands, and then using it as a reaction raw material to be circulated into the reactor for reaction.

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