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

Abstract

The present application relates to the field of adsorption materials, in particular to a device and method for ultrasonic-assisted continuous green preparation of MOF, in particular to a method for preparing MOF-801 by ultrasonic-assisted form and using water and formic acid as solvents. The method can obtain the product in 6 minutes, the reaction time is significantly shortened, by adding a flocculating agent polyacrylamide, the MOF-801 can be quickly settled in 5 minutes, and the MOF-801 can be directly filtered without centrifugation. The sample is soaked in ethanol and water respectively, and the obtained MOF-801 material has water absorption performance equivalent to that of the sample synthesized by an organic solvent DMF. Ultrasonic assistance is a method for rapidly preparing MOF-801 material, and water is used as a reaction solvent, which is more green and friendly to the environment, and the method has important industrial application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adsorption materials, in particular to a device and method for ultrasonic-assisted continuous green preparation of MOF. BACKGROUND

[0002] Metal-organic frameworks (MOFs) as a new type of porous material, have the advantages of rich structure, super large specific surface area, designability of morphology and size, and diversity of chemical functions. At the same time, it has good water vapor adsorption characteristics, and can be used in various application fields (such as heat pump, cooler, humidity control, hydrolysis catalysis, atmospheric water collection, etc.). Although MOF has attracted great academic interest in the past two decades, with thousands of new structures and very promising applications, only a few have been mass-produced and used in practical applications. So far, the solvothermal method is the most common method to obtain gram-scale MOFs in laboratories around the world. This method involves mixing a solution of inorganic salt with an organic linker in a sealed reactor vessel, which is then heated to promote the formation of metal-organic framework materials, which can take several days or a week to complete, and sometimes involves the use of toxic organic solvents such as dimethylformamide (DMF). Therefore, its application in large-scale MOF production is not feasible. At the same time, many aspects should also be considered when producing MOF, including the type of solvent, the corrosive or strong oxidizing effect of the metal salt, and the related high potential risks, which will bring additional safety considerations (also resulting in additional costs).

[0003] In the green synthesis technology of MOF, the sonochemical method uses very high frequency (20 kHz-10 MHz) ultrasound. It is a cost-effective, selective and environmentally friendly method that helps to obtain high-yield final products with uniform structure and morphology. The sonochemical method has been proven to have better effects in simplicity, ease of synthesis of porous materials, reduction of crystallization time and improvement of energy efficiency, and is expected to realize efficient green continuous production of MOF materials. The continuous preparation device designed for laboratory use and the method for green and rapid preparation of MOF are the key to realizing the batch production of MOF.

[0004] At the same time, the separation of MOF after synthesis is difficult, and centrifugation is needed to separate the product, which has the problems of high energy consumption and complex operation. The flocculant is added to the product, so that it can achieve the effect of natural sedimentation, and facilitate subsequent processing.

[0005] There are many other factors, including those related to the solvent, starting ingredients and heating temperature of the mixture, that can affect the final composition of MOF during synthesis. In order to minimize the impact on the environment, the reaction solvent and activation solvent should be low in volume and low in toxicity, avoiding the use of toxic solvent DMF. "Green" solvents include water, ethanol, ethyl acetate, etc.

[0006] MOF-801 is a kind of metal organic framework material that can be used for atmospheric water collection, which is synthesized by zirconium oxychloride and fumaric acid, MOF-801 has three different cavities, which can capture and concentrate water molecules in it, even in low humidity areas, MOF-801 also shows excellent water absorption performance. Omar Yaghi et al. proved that the water absorption capacity of MOF-801 (synthetic solvent is DMF) is 0.28g g -1 at 298K, 30% RH. In 2023, Sadegh et al. synthesized MOF-801 with water as solvent at room temperature for 48 hours, and its water absorption capacity was 0.37g g -1 at 298K, 30% RH, the reaction time is longer.

[0007] The traditional method for synthesizing MOF-801 is a solvothermal method using DMF as the solvent, which has high energy consumption and is harmful to the environment, which is not conducive to actual production and application.

[0008] Therefore, it is necessary to seek a fast and green method for preparing MOF, and to prepare MOF-801. SUMMARY

[0009] The present application overcomes the shortcomings of the prior art, and provides a device and method for ultrasonic-assisted continuous green preparation of MOF, which can greenly prepare MOF-801, shorten the reaction time, and make it quickly settle by adding a flocculating agent, thereby realizing its industrial application.

[0010] The ultrasonic-assisted method for synthesizing MOF-801 is simple to operate and costs less, and uses water as a green solvent for reaction, which is conducive to promoting large-scale production of MOF materials and ultimately pushing them to the market. If 1L of reaction solution needs to be treated, a small centrifuge in the laboratory can treat 250ml at a time, which takes 5 minutes, and it takes 20 minutes to complete the treatment. Similarly, the solution can be stirred for 5 minutes after adding the flocculating agent to obtain the precipitate, which is much faster.

[0011] To solve the above technical problems, the technical scheme adopted by the present application is:

[0012] An ultrasonic-assisted continuous green preparation device for MOF, comprising a device shell, a feed inlet is arranged at the top of the device shell, and a discharge outlet is arranged at the bottom of the device shell; a raw material tank, a spiral pipe and a product tank are sequentially and throughly connected inside the device shell from top to bottom between the feed inlet and the discharge outlet; an ultrasonic heating device 5 is installed outside the spiral pipe.

[0013] A method for ultrasonic-assisted continuous green preparation of MOF, which is carried out by using the above device, comprising the following steps:

[0014] A, the reaction raw materials (metal ligand molar ratio 1:1) are dissolved in a green solvent;

[0015] B, the mixture of step A is added to the raw material tank through the feeding port, and the ultrasonic heating device is started to continuously generate MOF materials in the spiral pipeline in an ultrasonic assisted manner;

[0016] C, a flocculating agent is added to the raw material tank to make the MOF material settle, and the MOF material is obtained in the product tank after filtration, washing and drying, and is collected from the discharge port.

[0017] Further, the prepared MOF material is MOF-808 or MOF-801.

[0018] Further, when the prepared MOF material is MOF-801, the green solvent in step A is a solution of water and formic acid, and the volume ratio of water to formic acid is 5:1.

[0019] Further, when the prepared MOF material is MOF-801, the molar volume ratio of the reaction raw materials to the green solvent in step A is 0.09 mol / L.

[0020] Further, the ultrasonic assistance in step B is carried out at a frequency of 40 kHz.

[0021] Further, when the prepared MOF material is MOF-801, the flocculating agent in step C is polyacrylamide.

[0022] Further, the molar ratio of the reaction raw materials ligand and metal in step C is 1:1, and the addition amount of the flocculating agent polyacrylamide is 3g / L.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The present application rapidly synthesizes MOF-801 by ultrasonic assistance, directly adds a flocculating agent to the solution after reaction to achieve rapid settling, has fast reaction time, and has the advantages of convenient preparation method, simple operation and facilitation of industrialized production.

[0025] The present application can obtain MOF-801 material in 6 minutes, and the water adsorption amount is 0.32g g -1 . BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a structure schematic view of the ultrasonic-assisted continuous green preparation MOF device of the present application.

[0027] Figure 2The XRD patterns of MOF-801 and MOF-808 materials prepared by ultrasound-assisted continuous green method in an embodiment of the present invention are shown.

[0028] Figure 3 This is a diagram of the N2 adsorption-desorption isotherm (77K) for the ultrasonic-assisted continuous green preparation of MOF-801 material according to an embodiment of the present invention. The curves with solid dots represent adsorption curves, and the curves with hollow dots represent desorption curves.

[0029] Figure 4 This is a water absorption curve (298K) of MOF-801 material prepared by ultrasonic-assisted continuous green process in an embodiment of the present invention.

[0030] The markings in the image are as follows:

[0031] 1-Equipment casing, 2-Inlet, 3-Raw material tank, 4-Spiral pipeline, 5-Ultrasonic heating device, 6-Product tank, 7-Outlet. Detailed Implementation

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

[0033] like Figure 1 As shown, an ultrasonic-assisted continuous green preparation device for MOF includes a device shell 1, with a feed inlet 2 at the top and a discharge outlet 7 at the bottom; inside the device shell 1 between the feed inlet 2 and the discharge outlet 7, a raw material tank 3, a spiral pipeline 4 and a product tank 6 are sequentially connected from top to bottom; an ultrasonic heating device 5 is sleeved on the outside of the spiral pipeline 4.

[0034] The ultrasound-assisted green preparation method for MOF-801 used in this embodiment includes the following steps:

[0035] A. Dissolve zirconium oxychloride octahydrate and fumaric acid in water and formic acid, with a water to formic acid volume ratio of (5:1);

[0036] B. Add the mixture from step A into the raw material tank 3 through the feed inlet 2, and turn on the ultrasonic heating device 5 to continuously generate MOF material in the spiral pipeline 4 with ultrasonic assistance; the ultrasonic frequency is 40kHz.

[0037] C. Add flocculant polyacrylamide to the reaction solution in step B, stir to obtain a white flocculent product, filter, wash and dry to obtain MOF-801 material.

[0038] Comparative Example 1

[0039] ZrOCl2*8H2O and fumaric acid were dissolved in a mixed solution of water and formic acid with a molar ratio of 1:1 (wherein ZrOCl2*8H2O and fumaric acid were both 0.008 mol, and the volume of the solution of water and formic acid was 0.012 L), the volume ratio of water to formic acid was (5:1), and the obtained solution was placed in an ultrasonic machine with a frequency of 40 kHz for ultrasonic treatment for 2 h. After the reaction was completed, the product was collected by centrifugation, washed, and dried to obtain the MOF-801 material. The synthesized sample is denoted as sample A.

[0040] Comparative Example 2

[0041] ZrOCl2*8H2O and fumaric acid were dissolved in a mixed solution of water and formic acid with a molar ratio of 1:1 (wherein ZrOCl2*8H2O and fumaric acid were both 0.024 mol, and the volume of the solution of water and formic acid was 0.36 L), the volume ratio of water to formic acid was (5:1), and the reaction was carried out under hydrothermal conditions for 6 h. After the reaction was completed, the product was collected by centrifugation, washed, and dried to obtain the MOF-801 material. The synthesized sample is denoted as sample B.

[0042] Comparative Example 3

[0043] ZrOCl2*8H2O and fumaric acid were dissolved in a mixed solution of water and formic acid with a molar ratio of 1:1 (wherein ZrOCl2*8H2O and fumaric acid were both 0.048 mol, and the volume of the solution of water and formic acid was 0.72 L), the volume ratio of water to formic acid was (5:1), and the obtained solution was placed in an ultrasonic machine with a frequency of 40 kHz for direct heating reaction for 40 minutes. A white flocculent precipitate appeared after the addition of a flocculating agent, and the synthesized sample was denoted as sample C after filtration, washing, and drying.

[0044] Example 1

[0045] ZrOCl2*8H2O and fumaric acid were dissolved in a mixed solution of water and formic acid with a molar ratio of 1:1 (wherein ZrOCl2*8H2O and fumaric acid were both 0.0011 mol, and the volume of the solution of water and formic acid was 0.012 L), the volume ratio of water to formic acid was (5:1), and the reaction solution was passed into the spiral pipe of the device as shown in FIG. 1. An MOF-801 solution was obtained in 6 minutes under ultrasonic treatment with a frequency of 40 kHz. A white flocculent precipitate appeared after the addition of a flocculating agent, and the synthesized sample was denoted as sample D after filtration, washing, and drying. Figure 1

[0046] Example 2

[0047] ​Extended preparation of MOF-808: ZrOCl2·8H2O and trimesin were dissolved in a mixed solution of water and formic acid in a molar ratio of 3:1 (where ZrOCl2·8H2O was 0.0019 mol, trimesin was 0.00067 mol, and the total volume of water and formic acid was 0.01 L). The volume ratio of water to formic acid was 1:1. The reaction solution was then passed through a... Figure 1 In the spiral tube of the apparatus shown, the ultrasonic frequency is 40kHz, and MOF-808 solution can be obtained in 10 minutes. After the reaction is completed, hydroxymethyl cellulose is added, and flocculent precipitate appears. After filtration, washing and drying, the product is obtained.

[0048] Performance testing experiment example

[0049] 1. The crystal structures of the samples prepared in Examples 1 to 4 of this invention were characterized using a Bruker D8 Advance X-ray diffractometer.

[0050] 2. Adopt The TriStar IIPlus fully automated surface area and porosity analyzer was used to measure the specific surface area of ​​the samples prepared in Examples 1 to 4 of this invention.

[0051] 3. The water adsorption of the samples prepared in Examples 1 to 4 of this invention was measured using a BELSORP-MAXⅡ physical vapor adsorption instrument from Bayer, Germany.

[0052] Results Analysis

[0053] like Figure 2 As shown, Figure 2 (a) Samples A, B, C and D in the examples show that MOF-801 was successfully prepared in Examples 1 to 4; Figure 2 (b) shows the preparation of extended MOF-808, which was also successfully prepared.

[0054] like Figure 3 As shown, the N2 adsorption-desorption isotherms of the samples are all within the range of 700 m² / m². 2 Approximately / g.

[0055] like Figure 4 As shown, the water adsorption properties of MOF-801 prepared by different methods vary. Among them, sample B has the worst water absorption, with a water absorption capacity of 0.27 g / L at 298 K and 30% RH. -1 .

[0056] Based on the above analysis, sample D prepared in Example 4 yielded a product within 6 minutes, and the water absorption capacity of MOF-801 at 298K and 30% RH was 0.32 g / L. -1 .

[0057] The performance results of Comparative Examples 1 to 3 and Example 1 Sample A to Sample D are shown in Table 1

[0058] Table 1 Performance results of Sample A to Sample D

[0059]

[0060] The above descriptions are merely specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for ultrasonic-assisted continuous green preparation of MOF-801, characterized in that, The device for continuously preparing MOF with ultrasonic assistance is prepared by a green method, and the device comprises a device shell (1), a feeding port (2) is arranged at the top of the device shell (1), and a discharging port (7) is arranged at the bottom of the device shell (1); a raw material tank (3), a spiral pipeline (4) and a product tank (6) are sequentially and throughly connected from top to bottom in the device shell (1) between the feeding port (2) and the discharging port (7); an ultrasonic heating device (5) is arranged on the outer side of the spiral pipeline (4); The method for preparing MOF-801 with ultrasonic assistance in a green way comprises the following steps: A. Dissolve zirconium oxychloride octahydrate and fumaric acid in water and formic acid, and the volume ratio of water to formic acid is 5:1; B. The mixture in step A is added into the raw material tank (3) through the feeding port (2), and the ultrasonic heating device (5) is started to continuously generate MOF material in the spiral pipeline (4) in an ultrasonic assisted way; the ultrasonic frequency is 40 kHz; C. Add flocculant polyacrylamide to the reaction solution in step B, stir to obtain a white flocculent product, filter, wash and dry, and obtain MOF-801 material in the product tank (6), and collect the product from the discharging port (7).

2. The method of claim 1, wherein the method is characterized by, In step A, the molar volume ratio of the reaction raw material to water and formic acid is 0.09 mol / L.

3. The method of claim 1, wherein the method is characterized by, In step C, the molar ratio of the reaction raw material ligand to metal is 1:1, and the addition amount of the flocculant polyacrylamide is 3 g / L.

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