A mesoporous structure bimetallic MOFs material and its efficient synthesis and screening method

Abstract

The application discloses a kind of bimetallic MOFs material of mesoporous structure and its efficient synthesis and screening method, with vanadyl sulfate and iron nitrate hydrate as two metal center ion source, with uniform benzene tricarboxylic acid as ligand material preparation formation mesoporous structure bimetallic MOFs material, 1,3,5-uniform benzene tricarboxylic acid is dissolved in mixed solvent one and obtained solution A, the mixed solvent one is 1:1 mixed solvent of ethanol and DMF;Metal salt one and metal salt two are dissolved in water, and a certain amount of ammonium fluoride is added, and gel B is formed;The metal salt one is Fe (NO3) 3·9H2O, and the metal salt two is VOSO4;Solution A is mixed with gel B and forms gel C after stirring for a certain time;Gel C is centrifuged and separated, then washed with ethanol, and then soaked in dichloromethane for multiple times;The obtained product is dried first, then activated, and powder D is obtained.The application can be synthesized at room temperature with bimetallic MOFs material with more optimal mesoporous structure, improve the yield, stability and excellent performance of material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthesis of bimetallic MOFs materials, and particularly relates to a bimetallic MOFs material with mesoporous structure and a high-efficiency synthesis and screening method thereof. BACKGROUND

[0002] Bimetallic MOFs materials have a wide range of applications in various fields due to the combination of the properties of two different metal ions. They can be used as efficient catalysts to promote chemical reactions, utilize their high porosity and large specific surface area for gas storage and separation, and exhibit excellent performance in the field of electrochemistry, and can also be used in energy conversion and environmental remediation projects, thereby promoting the process of sustainable development and environmental protection. At the same time, mesoporous structure materials also have a large specific surface area and excellent properties that other porous materials do not have, so the bimetallic MOFs material with mesoporous structure has great development prospects. Traditional synthesis methods of bimetallic MOFs mainly include solvothermal method, coprecipitation method and post-synthesis modification method, etc. These methods usually require long reaction time, and therefore have problems of large energy consumption and low production efficiency. SUMMARY

[0003] The present application provides a bimetallic MOFs material with mesoporous structure and a high-efficiency synthesis and screening method thereof, which can synthesize the bimetallic MOFs material with more optimal mesoporous structure at room temperature, and improve the yield, stability and excellent performance of the material.

[0004] Technical scheme: To achieve the above-mentioned purpose, the bimetallic MOFs material with mesoporous structure and the high-efficiency synthesis and screening method thereof according to the present application are prepared by taking vanadyl sulfate and iron nitrate hydrate as two metal center ion sources and taking trimesic acid as a ligand material. 3+ Part of Fe 4+ is replaced by V to cause coordination loss and form mesopores inside. The preparation process is carried out at room temperature, which can not only reduce energy consumption and simplify the production process, but also improve the yield and purity of the material. The synthesis and screening method of the bimetallic MOFs material comprises the following steps:

[0005] Step I, dissolving 1,3,5-benzenetricarboxylic acid in a mixed solvent I to obtain solution A, wherein the mixed solvent I is a mixed solvent of ethanol and DMF;

[0006] Step II, dissolving metal salt one and metal salt two in water, and adding a certain amount of ammonium fluoride to form gel B; the metal salt one is Fe(NO3)3·9H2O, the metal salt two is one of VOSO4, Cr(NO3)3·9H2O, Al(NO3)3·9H2O, corresponding to form gel B1, gel B2, gel B3;

[0007] Step III, mixing solution A with gel B1, gel B2, gel B3 respectively, and forming gel C1, gel C2, gel C3 respectively after stirring for a certain time;

[0008] Step IV, centrifuging gel C1, gel C2, gel C3, then washing with ethanol, and then soaking in dichloromethane for multiple times;

[0009] Step V, drying the three products obtained in step IV, then activating to obtain powder D1, powder D2, powder D3 respectively;

[0010] Step VI, comparing the XRD comparison chart of powder D1, powder D2, powder D3 and MIL-100(Fe), to determine whether the bimetallic organic framework structure of powder D1, powder D2, powder D3 is prepared into shape;

[0011] Step VII, performing nitrogen adsorption test on powder D1, powder D2, powder D3, and screening the bimetallic MOFs material with mesoporous structure by comparing the nitrogen adsorption isotherms of the three.

[0012] Further, in step I, the concentration of 1,3,5-benzenetricarboxylic acid in solution A is 0.0156 g / ml; in step II, the concentration of Fe(NO3)3·9H2O in gel B is 0.072 g / ml, the molar ratio of Fe(NO3)3·9H2O to metal salt two is 1:1 or 0.5:1, and the content of added ammonium fluoride is 5%-15%; in step III, mixing is carried out at room temperature, and stirring for 24-72 hours to form gel C.

[0013] Further, in step IV, after centrifugation, washing with ethanol at room temperature for 1 hour, and then soaking in dichloromethane twice.

[0014] Further, in step V, drying at 70°C for 24 hours, and then activating at 150°C for 24 hours.

[0015] Further, in step II, when the metal salt two is VOSO4, 0.72g, 1.8mmol of Fe(NO3)3·9H2O and 0.29g, 1.8mmol of VOSO4 are dissolved in 10ml of water, and 0.0125g of ammonium fluoride is added to prepare the gel B1; in step III, the solution A and the gel B1 are mixed and stirred for 24 hours to form the gel C1, and finally the powder D1 is 10% F-MIL-100(Fe, V).

[0016] Further, in step II, when the metal salt two is Cr(NO3)3·9H2O, 0.72g, 1.8mmol of Fe(NO3)3·9H2O and 0.72g, 1.8mmol of Cr(NO3)3·9H2O are dissolved in 10ml of water, and 0.025g of ammonium fluoride is added to prepare the gel B2; in step III, the solution A and the gel B2 are mixed and stirred for 72 hours to form the gel C2, and finally the powder D2 is 10% F-MIL-100(Fe, Cr).

[0017] Further, in step II, when the metal salt two is Al(NO3)3·9H2O, 0.72g, 1.8mmol of Fe(NO3)3·9H2O and 0.68g, 1.8mmol of Al(NO3)3·9H2O are dissolved in 10ml of water, and 0.025g of ammonium fluoride is added to prepare the gel B3; in step III, the solution A and the gel B3 are mixed and stirred for 72 hours to form the gel C3, and finally the powder D3 is 10% F-MIL-100(Fe, Al).

[0018] Beneficial effects: The mesoporous structure of the bimetallic MOFs material and the efficient synthesis and screening method thereof, taking iron nitrate hydrate as the first metal center ion source, taking V, Cr and Al three kinds of metal salts as the second metal center ion source, and taking uniform trimellitic acid as the ligand material to prepare three different sample materials, through comparison and screening, the bimetallic MOFs material with larger specific surface area, mesoporous structure and larger pore size is 10% F-MIL-100(Fe, V), the preparation process is carried out at room temperature, the energy consumption is reduced, the yield and purity of the material are improved, and the obtained bimetallic MOFs material has higher stability and excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The XRD comparison chart of the bimetallic MIL-100 sample prepared by the method of the application and MIL-100(Fe);

[0020] Figure 2 The nitrogen adsorption isotherm of 10% F-MIL-100(Fe, V);

[0021] Figure 3 Nitrogen adsorption isotherm of 10% F-MIL-100(Fe, Cr);

[0022] Figure 4 Nitrogen adsorption isotherm of 10% F-MIL-100(Fe, Al). DETAILED DESCRIPTION

[0023] The application will be described in further detail below with reference to the drawings.

[0024] As shown in the accompanying drawings Figures 1-4 The mesoporous dual-metal MOFs material and the efficient synthesis and screening method thereof, wherein the mesoporous dual-metal MOFs material is prepared by taking vanadyl sulfate and iron nitrate hydrate as two kinds of metal center ion sources and taking uniform trimellitic acid as a ligand material; part of Fe 3+ in the dual-metal MOFs material is replaced by V 4+ , causing coordination loss, and forming mesopores inside; V 4+ replaces part of Fe 3+ , so that the coordination bond constructed by Fe 3+ cannot be generated, and thus a pore with a larger pore size is generated at the replacement position.

[0025] The scheme is based on the research on solvent effect, interaction between metal ions and organic ligands, and influence of additives on the synthesis process. A room temperature synthesis process of the dual-metal MOFs material is designed, and V, Cr and Al metal salts are respectively taken as the second metal center ion source other than Fe to synthesize and prepare three kinds of dual-metal MIL-100 samples of (Fe, V), (Fe, Cr) and (Fe, Al), and then a nitrogen adsorption test is performed to screen the dual-metal MOFs material with excellent mesoporous structure. Among them, MIL-100(Fe, Cr) and MIL-100(Fe, Al) are known dual-metal MOFs materials, and MIL-100(Fe, Cr) is a known dual-metal MOFs material with mesoporous structure, so the two kinds of dual-metal MIL-100 samples of (Fe, Cr) and (Fe, Al) are selected as the reference groups of the dual-metal MIL-100 sample of (Fe, V) combination, so as to obtain the test results more quickly.

[0026] The room temperature synthesis and screening method of the mesoporous dual-metal MOFs material, comprising the following steps:

[0027] Step I, dissolving 1,3,5-benzenetricarboxylic acid in mixed solvent I to obtain solution A, the concentration of 1,3,5-benzenetricarboxylic acid in solution A is 0.0156 g / ml, and the mixed solvent I is a 1:1 mixed solvent of ethanol and DMF. Ethanol is a polar solvent, and the polarity of DMF is between that of water and ethanol. The use of mixed solvents helps to adjust the polarity of the solution, thereby affecting the interaction between metal ions and organic ligands, thereby affecting the pore structure and chemical properties of the MOFs material, which is conducive to the formation of mesoporous structures. Ethanol and DMF have good mutual solubility, so they can provide a more uniform reaction environment, allowing metal ions and ligands to be uniformly dispersed in the solution to achieve effective assembly.

[0028] Step II, dissolving metal salt I and metal salt II in water and adding 5%-15% ammonium fluoride to form gel B; the metal salt I is Fe(NO3)3·9H2O, and the metal salt II is one of VOSO4, Cr(NO3)3·9H2O and Al(NO3)3·9H2O, corresponding to gel B1, gel B2 and gel B3; the concentration of Fe(NO3)3·9H2O in gel B is 0.072 g / ml, and the molar ratio of Fe(NO3)3·9H2O to metal salt II is 1:1 or 0.5:1.

[0029] Step III, mixing solution A with gel B1, gel B2 and gel B3 at room temperature of 25-35°C, and stirring for 24-72 hours to form gel C1, gel C2 and gel C3, respectively; gel C1, gel C2 and gel C3 are collectively referred to as gel C.

[0030] Step IV, centrifuging gel C1, gel C2 and gel C3, washing the obtained solid with ethanol, and then soaking in dichloromethane for multiple times, each time for 24-48 hours.

[0031] Step V, drying and activating the three products obtained in step IV to obtain powder D1, powder D2 and powder D3, respectively.

[0032] Based on the above process, specific preparation step examples of powder D1, powder D2 and powder D3 are provided.

[0033] The specific preparation steps of powder D1 are as follows:

[0034] The solution A was prepared by dissolving 0.25 g of 1,3,5-benzenetricarboxylic acid in 16 ml of mixed solvent 1. The gel B1 was prepared by dissolving 0.72 g, 1.8 mmol of Fe(N03)3.9H20 and 0.29 g, 1.8 mmol of VOS04 in 10 ml of water and adding 0.0125 g of ammonium fluoride. The solution A and the gel B1 were mixed at room temperature and the gel C1 was formed after stirring for 24 hours. The gel C1 was centrifuged, washed with ethanol at room temperature for 1 hour and then twice in dichloromethane. Finally, the product was dried at 70°C for 24 hours and then activated at 150°C for 24 hours. The powder D1 of 10% F-MIL-100(Fe,V) was obtained.

[0035] The specific preparation steps of the powder D2 are as follows:

[0036] The solution A was prepared by dissolving 0.25 g of 1,3,5-benzenetricarboxylic acid in 16 ml of mixed solvent 1. The gel B2 was prepared by dissolving 0.72 g, 1.8 mmol of Fe(N03)3.9H20 and 0.72 g, 1.8 mmol of Cr(N03)3.9H20 in 10 ml of water and adding 0.025 g of ammonium fluoride. The solution A and the gel B2 were mixed at room temperature and the gel C2 was formed after stirring for 72 hours. The gel C2 was centrifuged, washed with ethanol at room temperature for 1 hour and then twice in dichloromethane. Finally, the product was dried at 70°C for 24 hours and then activated at 150°C for 24 hours. The powder D2 of 10% F-MIL-100(Fe,Cr) was obtained.

[0037] The specific preparation steps of the powder D3 are as follows:

[0038] The solution A was prepared by dissolving 0.25 g of 1,3,5-benzenetricarboxylic acid in 16 ml of mixed solvent 1. The gel B3 was prepared by dissolving 0.72 g, 1.8 mmol of Fe(N03)3.9H20 and 0.68 g, 1.8 mmol of Al(N03)3.9H20 in 10 ml of water and adding 0.025 g of ammonium fluoride. The solution A and the gel B3 were mixed at room temperature and the gel C3 was formed after stirring for 72 hours. The gel C3 was centrifuged, washed with ethanol at room temperature for 1 hour and then twice in dichloromethane. Finally, the product was dried at 70°C for 24 hours and then activated at 150°C for 24 hours. The powder D3 of 10% F-MIL-100(Fe,Al) was obtained.

[0039] Step VI: Comparing the XRD patterns of powder D1, powder D2, powder D3 and MIL-100(Fe) to determine whether the bimetallic organic framework structures of powder D1, powder D2 and powder D3 are prepared.

[0040] As attached Figure 1 As shown in the figure, it is an XRD comparison diagram of the bimetallic MIL-100 sample prepared by the method of this scheme and MIL-100 (Fe). The bimetallic MIL-100 sample includes the above-mentioned 10% F-MIL-100 (Fe, V), 10% F-MIL-100 (Fe, Cr), and 10% F-MIL-100 (Fe, Al). It can be seen from the figure that the bimetallic MIL-100 sample materials all maintain high-resolution X-ray diffraction peaks, and the peak positions are the same as those of MIL-100 (Fe), indicating that the bimetallic MIL-100 structure is successfully prepared and has a high degree of crystallinity.

[0041] Step VII: Perform a nitrogen adsorption test on powder D1, powder D2, and powder D3, and screen out the bimetallic MOFs material with a mesoporous structure by comparing the nitrogen adsorption isotherms of the three.

[0042] As attached Figures 2-3 As shown in Figure 1, the nitrogen adsorption isotherms of the bimetallic MIL-100 samples are shown in Figure 2. As can be seen from the figure, the specific surface areas of the three bimetallic MIL-100 materials are 952m 2 / g、936m 2 / g、902m 2 / g, which is comparable to the MIL-100 material. Among them, MIL-100 (Fe, Cr) is a known bimetallic MOFs material with a mesoporous structure. By comparison, the adsorption isotherm of 10% F-MIL-100 (Fe, V) has a clear hysteresis loop, indicating that it also has a mesoporous structure. The pore distribution results show that its mesopore size is 3.5nm, and thus 10% F-MIL-100 (Fe, V) is screened as a bimetallic MOFs material with a mesoporous structure with a larger specific surface area and pore size, with better structural stability and excellent performance, suitable for a variety of applications.

[0043] Compared with the preparation processes of the above three samples of 10% F-MIL-100(Fe, V), 10% F-MIL-100(Fe, Cr) and 10% F-MIL-100(Fe, Al), the overall preparation time of 10% F-MIL-100(Fe, V) is shorter than that of the other two samples, so that 10% F-MIL-100(Fe, V) is a dual-metal MOFs material with higher preparation efficiency and more excellent mesoporous structure. Moreover, due to the addition of an appropriate amount of ammonium fluoride as a structure directing agent, by adjusting the pH value of the solution or providing additional coordination sites, the fluorine element forms a stronger coordination bond with the metal ions, enhances the structural stability of the material, is conducive to the formation and maintenance of large-size mesoporous structure, and the fluorine element can improve the chemical stability of the material to environmental factors such as water and oxygen, which is helpful to promote the nucleation and growth process of MOFs, thereby optimizing the crystallinity and morphology of the material.

[0044] The above description is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the above principles of the present application, a number of improvements and refinements can also be made, which are also considered to be within the scope of protection of the present application.

Claims

1. A method for screening bimetallic MOFs materials with a mesoporous structure, characterized by: The screening method of the bimetallic MOFs material comprises the following steps: Step I: dissolving 1,3,5-trimethylbenzene tricarboxylic acid in a mixed solvent to prepare a solution A, wherein the mixed solvent is a mixed solvent of ethanol and DMF; Step II, dissolving metal salt 1 and metal salt 2 in water, and adding a certain amount of ammonium fluoride to form gel B; the metal salt 1 is Fe(NO3)3·9H2O, and the metal salt 2 is one of VOSO4, Cr(NO3)3·9H2O, and Al(NO3)3·9H2O, and gels B1, B2, and B3 are formed accordingly; Step III, mixing solution A with gel B1, gel B2, and gel B3, respectively, and stirring for a certain period of time to form gel C1, gel C2, and gel C3, respectively; Step IV, gel C1, gel C2, and gel C3 are centrifuged, washed with ethanol, and then soaked in dichloromethane multiple times; Step V, drying and then activating the three products obtained in step IV to obtain powder D1, powder D2, and powder D3, respectively; Step VI, comparing the XRD patterns of powder D1, powder D2, powder D3 and MIL-100 (Fe) to determine whether the bimetallic organic framework structure of powder D1, powder D2 and powder D3 is prepared; Step VII: Perform a nitrogen adsorption test on powder D1, powder D2, and powder D3, and screen out the bimetallic MOFs material with a mesoporous structure by comparing the nitrogen adsorption isotherms of the three.

2. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 1, characterized in that: In step I, the concentration of 1,3,5-tricarboxylic acid in solution A is 0.0156 g / ml; in step II, the concentration of Fe(NO3)3·9H2O in gel B is 0.072 g / ml, the molar ratio of Fe(NO3)3·9H2O to metal salt II is 1:1 or 0.5:1, and the content of ammonium fluoride added is 5%-15%; in step III, mixing is carried out at room temperature and stirring for 24-72 hours to form gel C.

3. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 2, characterized in that: In step IV, after centrifugation, the sample was washed with ethanol at room temperature for 1 hour and then soaked in dichloromethane twice.

4. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 3, characterized in that: In step V, the mixture is dried at 70°C for 24 hours and then activated at 150°C for 24 hours.

5. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 4, characterized in that: In step II, when the second metal salt is VOSO4, 0.72 g, 1.8 mmol of Fe(NO3)3·9H2O and 0.29 g, 1.8 mmol of VOSO4 are dissolved in 10 ml of water, and 0.0125 g of ammonium fluoride is added to prepare the gel B1; in step III, solution A and gel B1 are mixed and stirred for 24 hours to form the gel C1, and the final powder D1 obtained is 10% F-MIL-100 (Fe, V).

6. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 5, characterized in that: In step II, when the metal salt II is Cr(NO3)3·9H2O, 0.72 g, 1.8 mmol of Fe(NO3)3·9H2O and 0.72 g, 1.8 mmol of Cr(NO3)3·9H2O are dissolved in 10 ml of water, and 0.025 g of ammonium fluoride is added to prepare the gel B2; in step III, solution A and gel B2 are mixed and stirred for 72 hours to form the gel C2, and finally the powder D2 is 10% F-MIL-100 (Fe, Cr).

7. The method for screening bimetallic MOFs materials with a mesoporous structure according to claim 6, characterized in that: In step II, when the second metal salt is Al(NO3)3·9H2O, 0.72g, 1.8mmol of Fe(NO3)3·9H2O and 0.68g, 1.8mmol of Al(NO3)3·9H2O are dissolved in 10ml of water, and 0.025g of ammonium fluoride is added to prepare the gel B3; in step III, solution A and gel B3 are mixed and stirred for 72 hours to form the gel C3, and the powder D3 finally obtained is 10% F-MIL-100 (Fe, Al).

Images