Apparatus and method for steam-assisted continuous green preparation of MOF

Abstract

This invention relates to the field of adsorbent materials, specifically to an apparatus and method for the continuous and green preparation of MOFs using steam assistance. The method involves grinding the reactants and treating them with ammonia, followed by a steam-phase reaction using water as a solvent to prepare UTSA-280. Continuous production fully utilizes the advantage of the fast reaction speed of the steam-phase solid-phase reaction, saving time and solving the problem of fluctuations in product structure and performance caused by repeated feeding in intermittent production. Products produced through continuous steam-phase production are more uniform, have consistent structure, and maintain good performance. The yield can reach 91%, enabling the rapid preparation of kilogram-scale UTSA-280 materials. Simultaneously, the ammonia-assisted treatment of the reactants not only increases the reaction yield but also accelerates the reaction, which is beneficial for the formation of the coordination structure of the MOF, thereby improving its performance. Ammonia-assisted treatment in the steam-phase reaction accelerates the reaction and ensures a more complete and thorough reaction, resulting in higher yields and shorter reaction times.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials, and more specifically to an apparatus and method for the continuous and green preparation of MOFs assisted by steam. Background Technology

[0002] Metal-organic frameworks (MOFs) are a novel class of porous crystalline materials that have attracted widespread attention due to their advantages such as high porosity, large specific surface area, and tunable pore size. Given their structural diversity and designability, these materials show great potential for applications in adsorption separation, sensing, and catalysis. Although MOFs exhibit unparalleled performance advantages in multiple application areas, their large-scale industrial application remains slow, primarily due to the high cost of MOF preparation and the lack of large-scale continuous preparation methods. Many reported MOF synthesis methods suffer from drawbacks such as long reaction times, low yields, and high solvent consumption. In particular, the use of organic polluting solvents, such as N,N-dimethylformamide and acetonitrile, poses serious environmental damage and increases the cost of MOF preparation.

[0003] Among the green preparation methods for MOF materials, the vapor phase method is a highly distinctive approach. This method features rapid solid-phase nucleation, short reaction time, and low solvent usage. It can even use only water as a solvent, significantly reducing solvent consumption and thus lowering costs while maintaining high yields. This method holds promise for achieving efficient, green, and continuous production of MOF materials.

[0004] The UTSA-280 material, with its rigid one-dimensional channel ultramicroporous structure, can act as a molecular sieve, allowing C2H4 to pass through while completely blocking C2H6, achieving excellent C2H4 / C2H6 separation. Furthermore, the size of this MOF is larger than the kinetic diameter of CO2. Dynamic diameter smaller than N2 Size sieving effect also exists in the separation of CO2 / N2. UTSA-280 can maintain the stability of its structure and adsorption performance over a wide pH range (pH=1-12), and can also be processed into particles or powders of different sizes and shapes through different methods to adapt to different application scenarios and needs.

[0005] Traditional methods for synthesizing UTSA-280 use Ca(NO3)2 as the metal source. In continuous reactions, this leads to nitrate accumulation, affecting the separation performance of the synthesized UTSA-280. Furthermore, nitrates are easily explosive chemicals, difficult to purchase, costly, and environmentally harmful, hindering practical production applications. In the prior art, US20210284661A discloses the mechanochemical synthesis of metal-organic frameworks (MOFs) for molecular sieves, their compositions, and methods of use. UTSA-280 can be synthesized from calcium oxide (CaO) or calcium hydroxide (Ca(OH)2) and squaric acid (SA) via mechanochemical synthesis. After adding water, UTSA-280 is obtained. However, this method suffers from unstable MOF structures, long reaction times, and the need for further activation in large-scale production. Furthermore, continuous production of this method suffers from decreased yield and structural instability of the product.

[0006] Therefore, it is necessary to seek a continuous and green method for preparing MOFs, and to safely and greenly prepare UTSA-280 materials. Summary of the Invention

[0007] This invention overcomes the shortcomings of the prior art and provides a steam-assisted continuous green preparation device and method for MOFs. It uses a low-cost metal source Ca(OH) or CaO and a green solvent water to prepare UTSA-280. With the assistance of ammonia, the reaction time is shortened and the crystallinity is improved, thereby realizing the continuous production of kilogram-level MOFs in the laboratory. The method is also extended to the synthesis of materials such as MOF-303 and MIL-53(Al).

[0008] The technical solution adopted in this invention is as follows:

[0009] An apparatus for the continuous and green preparation of MOFs with steam assistance includes a steam generator and a conveying device. The two ends of the conveying device are respectively equipped with a feeder and a receiving device. The conveying device is equipped with a MOF placement device above and a heating platform below. The ligands of the MOF are acidic.

[0010] A steam-assisted, continuous, and green method for preparing MOFs, using the aforementioned apparatus, includes the following steps:

[0011] A. Mix and grind the reaction raw materials (metal and ligand molar ratio 1:1);

[0012] B. Treat the mixture from step A with ammonia assistance;

[0013] C. Add the mixture from step B to the feeder, turn on the conveyor to transfer the MOF to the steam generator, and simultaneously turn on the heating platform to carry out the reaction. After the reaction is completed, turn on the conveyor again to transfer the MOF to the tail end and collect it with the receiving device.

[0014] Furthermore, the ligand of the MOF is acidic, and the reaction raw materials are MOF metal raw materials and MOF corresponding ligands. The MOF metal raw materials are the metal salt, metal oxide or metal hydroxide corresponding to the MOF.

[0015] Furthermore, the MOF material is one of UTSA-280, MOF-303, and MIL-53(Al).

[0016] Furthermore, when the prepared MOF material is UTSA-280, the molar ratio of the raw materials in step A is 1:1.

[0017] Furthermore, when the prepared MOF material is UTSA-280, the volume fraction of ammonia water used in the ammonia-assisted treatment in step B is 10%.

[0018] Furthermore, when the prepared MOF material is UTSA-280, the temperature of the heating stage in step C is 120°C.

[0019] Furthermore, when the prepared MOF material is UTSA-280, the solvent in the steam generator in step C is water.

[0020] Technical effect

[0021] This invention utilizes a vapor phase approach for the rapid synthesis of UTSA-280, resulting in a short reaction time, low cost, convenient preparation method, simple operation, and suitability for industrial production. This is because continuous production fully leverages the rapid reaction speed of the vapor phase solid phase. The process from feeding, reaction, to discharging is relatively short, and continuous production consumes less time, achieving higher yields within the same time frame compared to batch production. Furthermore, the continuous addition of pre-treated materials saves time and solves the problem of fluctuations in product structure and performance caused by repeated feeding in batch production. Products produced through continuous vapor phase production are more uniform, have consistent structure, and maintain good performance.

[0022] This application also employs ammonia-assisted treatment of the reaction raw materials, which not only increases the reaction yield but also accelerates the reaction, facilitating the formation of the coordination structure of the MOF and thus improving its performance. This is because the reaction raw materials in this application are pre-mixed with acidic ligands and metal salts or metal oxides. Ammonia-assisted treatment of the raw materials allows the acidic ligands to dissolve rapidly in a low-humidity environment. Furthermore, ammonia ionizes to release hydroxide ions, which can deprotonate the ligands and accelerate the coordination between the metal salts or metal oxides and the ligands. UTSA-280, MOF-303, and MIL-53(Al) can all be prepared using this method. This is because the ligands of UTSA-280, MOF-303, and MIL-53(Al) are squaric acid, pyrazole-3,5-dicarboxylic acid, and terephthalic acid, respectively. All three ligands are acidic. In particular, the acid dissolves slowly in the synthesis of UTSA-280, resulting in a slow reaction rate. The vapor phase reaction keeps the reactants in a slightly moist environment throughout the reaction process. With the aid of ammonia, the reaction can be accelerated and made more complete, thus obtaining a higher yield and a shorter reaction time. As a result, the UTSA-280 obtained has a higher CO2 adsorption capacity.

[0023] The method of this invention achieves optimal performance and meets the requirements of industrial applications through controlled ammonia-assisted synthesis. UTSA-280 is synthesized via a vapor phase, which is simple to operate, has a short reaction time, and a high yield (approximately 150g per batch) of up to 91%. Continuous production using this equipment allows for the preparation of 1 kg of UTSA-280 material in 7 hours. At 298 K, the CO2 adsorption capacity reaches 56 cm³ / g, demonstrating stable adsorption performance, which is beneficial for promoting the large-scale production of MOF materials. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the apparatus for the steam-assisted continuous green preparation of MOF materials according to the present invention;

[0025] Steam generator (1), conveyor (2), heating table (3). Feeder (4). Receiving device (5), MOF placer (6);

[0026] Figure 2 XRD patterns of raw materials and ground materials for the steam-assisted continuous green preparation of UTSA-280 material in this embodiment of the invention;

[0027] Figure 3 The XRD patterns of UTSA-280 materials synthesized by ammonia-assisted steam continuous green preparation and pure water steam synthesis are shown in the embodiments of the present invention.

[0028] Figure 4The XRD pattern of the continuous green preparation of MOF-303 material using ammonia-assisted steam in an embodiment of the present invention is shown.

[0029] Figure 5 The CO2 adsorption isotherm (298K) of UTSA-280 material synthesized by ammonia-assisted steam continuous green preparation and pure water steam is shown in this embodiment of the invention.

[0030] Figure 6 The N2 adsorption isotherm (77K) for the steam-assisted continuous green preparation of MOF-303 material in this embodiment of the invention;

[0031] Figure 7 This is a water absorption curve (298K) of MOF-303 material prepared by steam-assisted continuous green process in an embodiment of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] like Figure 1 As shown, a steam-assisted continuous green preparation device for MOF includes a steam generator (1), a conveying device (2), a feeder (4) and a receiver (5) at both ends of the conveying device (2), and a MOF placer (6) above the conveying device (2) and a heating table (3) below it.

[0034] The steam-assisted continuous green preparation method for UTSA-280 used in this embodiment includes the following steps:

[0035] A. Add calcium hydroxide and squaric acid to a mortar and mix and grind them in a molar ratio of 1:1;

[0036] B. Treat the mixture from step A with ammonia assistance;

[0037] C. Add the mixture from step B to the feeder, turn on the conveyor to transfer the MOF to the steam generator, and simultaneously turn on the heating platform to heat to 120°C for reaction. After the reaction is complete, turn on the conveyor again to transfer the MOF to the tail end and collect it with the receiving device.

[0038] Example 1

[0039] 1 mol each of Ca(OH)₂ and squaric acid were mixed in a mortar at a molar ratio of 1:1 and manually ground for 5 min. The ground reactants were then sprayed with 5 mL of ammonia solution (10% by volume). The reactants were then loaded into a feeder, and the heating plate was turned on to heat the water to 100°C. The conveyor was then activated to transfer the reactants to a steam generator for a steam phase reaction for 1 h. After the reaction was complete, the conveyor was restarted to transfer the MOF to the tail end, where it was collected using a receiver. The synthesized sample was designated as sample C, and the product yield was 91%.

[0040] Example 2

[0041] AlCl3·6H2O and 3,5-pyrazole dicarboxylic acid, 1 mol each, were mixed in a mortar at a molar ratio of 1:1 and manually ground for 5 min. The ground reactants were then sprayed with 5 mL of ammonia solution (10% by volume). The reactants were then loaded into a feeder, and the heating plate was turned on to heat the water to 100°C. The conveyor was then activated to transfer the reactants to a steam generator for a steam phase reaction for 8 h. After the reaction was complete, the conveyor was restarted to transfer the MOF to the tail end, where it was collected using a receiver. The synthesized sample was designated as sample D, and the product yield was 91%.

[0042] Comparative Example 1

[0043] Mix 1 mol each of Ca(OH)2 and squaric acid in a 1:1 molar ratio in a mortar and grind manually for 5 minutes. The resulting sample is denoted as sample A.

[0044] Comparative Example 2

[0045] 1 mol each of Ca(OH)₂ and squaric acid were mixed in a mortar at a molar ratio of 1:1 and manually ground for 5 minutes. The ground reactants were then loaded into a feeder. The heating platform was turned on, and water was heated to 100°C and boiled. The conveyor was started to transfer the reactants to a steam generator for a steam phase reaction for 1 hour. After the reaction was completed, the conveyor was turned on again to transfer the MOF to the tail end, where it was collected using a receiver. The synthesized sample was designated as Sample B, and the product yield was 62%.

[0046] Performance testing experiment example

[0047] 1. The crystal structures of the samples prepared in comparative cases 1-2 and the samples prepared in implementation cases 1-2 of this invention were characterized using a Bruker D8 Advance X-ray diffractometer.

[0048] 2. Adopt The TriStar IIPlus fully automated surface area and porosity analyzer was used to determine the CO2 adsorption capacity and specific surface area of ​​the samples prepared in Examples 1 and 2 of this invention.

[0049] 3. The water adsorption of the sample prepared in Example 2 of this invention was measured using a BELSORP-MAXⅡ physical vapor adsorption instrument from Bayer, Germany.

[0050] Results Analysis

[0051] like Figure 2-3 As shown, the starting materials did not form UTSA-280 material after grinding. Sample A did not react, indicating that UTSA-280 cannot be formed without ammonia treatment. Combined with the results of samples B and C, this demonstrates that Example 1 can obtain UTSA-280 material with higher crystallinity under ammonia-assisted vapor phase conditions. Figure 4 The spectrum of sample D shown is consistent with that of MOF-303, indicating that MOF-303 was successfully prepared in Example 2, and verifying that the device can successfully prepare UTSA-280 and MOF-303 materials.

[0052] like Figure 5 As shown, the CO2 adsorption isotherms for samples B and C are presented. At 298 K, the CO2 adsorption capacity of sample B, synthesized in a pure water system, is only 44.2 cm³. 3 The CO2 adsorption capacity of sample C synthesized with ammonia assistance can reach 55.8 cm³ / g. 3 / g, which indicates that ammonia-assisted treatment can accelerate the reaction and effectively improve the MOF structure, resulting in a product with strong adsorption capacity.

[0053] like Figure 6-7 As shown, the N2 adsorption isotherm (77 K) of sample D is given, and the specific surface area of ​​the sample is 914 m² / kJ. 2 MOF-303 synthesized by vapor phase has a water absorption capacity of 0.36 g / g at 298 K and 30% RH. -1 .

[0054] Table 1 Performance results of samples B to D

[0055]

[0056] The above description is merely a specific embodiment of the present invention, but 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 technical scope 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 steam-assisted, continuous, and green method for preparing MOFs, characterized in that, The method uses a steam-assisted continuous green MOF preparation device, which specifically includes a steam generator and a conveying device. The two ends of the conveying device are respectively equipped with a feeder and a receiving device, and there is a MOF placement device above the conveying device and a heating platform below the conveying device. The method includes the following steps: A. Mix and grind the reaction materials; B. The ground MOF is subjected to ammonia-assisted treatment; C. Add the mixture from step B to the feeder, turn on the conveyor to transfer the MOF to the steam generator, and turn on the heating platform to react. After the reaction is complete, turn on the conveyor again to transfer the MOF to the tail end and collect it with the receiving device. The ligand of the MOF is acidic, and the reaction raw materials are MOF metal raw materials and MOF corresponding ligands. The MOF metal raw materials are the metal salt, metal oxide or metal hydroxide corresponding to the MOF. The MOFs are UTSA-280, MOF-303, and MIL-53(Al); The apparatus is suitable for vapor-phase solid-phase reactions.

2. A method for steam-assisted continuous green preparation of MOF as described in claim 1, characterized in that, When the MOF material in step A is UTSA-280, the molar ratio of the raw materials is 1:

1.

3. A method for steam-assisted continuous green preparation of MOF as described in claim 1, characterized in that, The volume fraction of ammonia water used in the ammonia-assisted treatment in step B is 10%.

4. A method for steam-assisted continuous green preparation of MOF as described in claim 1, characterized in that, In step C, the temperature of the heating platform is 120°C.

5. A method for steam-assisted continuous green preparation of MOF as described in claim 1, characterized in that, In step C, the solvent in the steam generator is water.

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