Zn-MOF material, preparation method thereof and application of Zn-MOF material in Congo red dye adsorption

Abstract

The invention provides a Zn-MOF material, a preparation method thereof and application of the Zn-MOF material in Congo red dye adsorption, and relates to the technical field of metal organic framework materials. The preparation method provided by the invention comprises the following steps: reacting 2-methylimidazole with 3, 6-dichloropyridazine in an alkaline solvent environment to generate 3, 6-bis (2-methylimidazole) pyridazine; the preparation method comprises the following steps: mixing and coordinating 3, 6-bis (2-methylimidazole) pyridazine, isophthalic acid and a zinc source to prepare a Zn-MOF material; the Zn-MOF material prepared by the preparation method disclosed by the invention can be used for effectively adsorbing Congo red.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, and in particular to a Zn-MOF material and a preparation method thereof and application thereof in the adsorption of Congo red dye. Background Art

[0002] In recent years, water pollution and its management have been of great concern. What is worrying is that toxins in wastewater, such as dyes, heavy metals, antimicrobial agents, etc., can have devastating effects on aquatic organisms and humans, and even cause cancer, even at very low concentrations. The pollution of water resources is mainly caused by organic and inorganic wastes generated in industrial and agricultural production and life. Due to the development of the textile industry, the discharge of dye wastewater has increased year by year, and about 10-15% of dyes are discharged from printing production. Congo red (CR) is a classic anionic azo dye, commonly used in the manufacture of textiles, rubber and plastics. It is highly toxic, carcinogenic and antioxidant, posing a real risk to ecosystems and biological health. In addition, the aromatic structure of azo dyes makes them chemically stable and not easily degraded by microorganisms, which makes the treatment of CR dye wastewater more difficult. Therefore, it is urgent to provide a solution to improve the above problems. Summary of the invention

[0003] The purpose of the present invention is to provide a Zn-MOF material and a preparation method thereof and application in the adsorption of Congo red dye.

[0004] In a first aspect, the present invention provides a method for preparing a Zn-MOF material, comprising: in an alkaline solvent environment, 2-methylimidazole and 3,6-dichloropyridazine react to generate 3,6-bis(2-methylimidazole)pyridazine; and 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and coordinated to obtain a Zn-MOF material.

[0005] Optionally, the alkaline solute in the alkaline solvent environment includes one of sodium hydroxide, potassium hydroxide and sodium bicarbonate.

[0006] Optionally, the solvent environment includes one of dimethyl sulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0007] Optionally, the pH of the solvent environment is 8-11.

[0008] Optionally, one of the 2-methylimidazole and the 3,6-dichloropyridazine is provided in excess.

[0009] Optionally, the molar ratio of the 2-methylimidazole to the 3,6-dichloropyridazine is 1:(2-3).

[0010] Alternatively, 2-methylimidazole is reacted with 3,6-dichloropyridazine at 50° C.-70° C. for 3 h-5 h.

[0011] Optionally, an alkaline solute and 2-methylimidazole are added into a solvent environment, refluxed at 50° C.-70° C. for 0.1 h-1 h, and then 3,6-dichloropyridazine is added and stirred for reaction, and after cooling, the mixture is filtered, separated, and dried to obtain 3,6-bis(2-methylimidazole)pyridazine.

[0012] Optionally, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and dissolved in a polar solvent, and then a coordination reaction is carried out to obtain a Zn-MOF material; preferably, the 3,6-bis(2-methylimidazole)pyridazine, the isophthalic acid and the zinc source are mixed and dissolved in a mixture of a polar solvent and deionized water.

[0013] Optionally, the molar ratio of the 3,6-bis(2-methylimidazole)pyridazine to the isophthalic acid is 1:(1-2).

[0014] Optionally, the molar ratio of the 3,6-bis(2-methylimidazole)pyridazine to the zinc ions in the zinc source is 1:(2-3).

[0015] Optionally, the polar solvent includes N,N-dimethylacetamide or N,N-dimethylformamide.

[0016] Optionally, the zinc source includes one of zinc nitrate and a hydrate thereof.

[0017] Optionally, the volume ratio of the polar solvent to the deionized water is (1-6):1.

[0018] Optionally, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and reacted at 80° C.-90° C. for 20 h-28 h.

[0019] Optionally, after mixing and coordination, the Zn-MOF material is washed and dried.

[0020] In a second aspect, the present invention also provides a Zn-MOF material prepared by any of the above optional preparation methods.

[0021] In a third aspect, the present invention also provides an application of a Zn-MOF material prepared by any of the above optional preparation methods in the adsorption of Congo red dye. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for preparing a Zn-MOF material provided by the present invention;

[0023] Figure 2 The hydrogen nuclear magnetic spectrum of 3,6-bis(2-methylimidazole)pyridazine prepared by the present invention;

[0024] Figure 3 The carbon NMR spectrum of 3,6-bis(2-methylimidazole)pyridazine prepared by the present invention;

[0025] Figure 4 A schematic diagram of the three-dimensional structure of a monomer of the Zn-MOF material prepared in the present invention;

[0026] Figure 5 A schematic diagram of the three-dimensional structure of the Zn-MOF material prepared in the present invention;

[0027] Figure 6 is an isothermal adsorption curve of the Zn-MOF material prepared in Example 2 of the present invention to Congo red solution;

[0028] Figure 7 This is a comparison diagram of the Congo red solution before and after the Zn-MOF material prepared in Example 1 of the present invention adsorbs 100 ppm Congo red solution;

[0029] Figure 8 This is a comparison diagram of the Congo red solution before and after the Zn-MOF material prepared in Example 2 of the present invention adsorbs 1000ppm Congo red solution;

[0030] Fig. 9 This is a comparison diagram of the Congo red solution before and after the Zn-MOF material prepared in Example 3 of the present invention adsorbs 100 ppm Congo red solution;

[0031] Fig.10 This is a comparison chart of the Congo red solution before and after the Zn-MOF material prepared in Example 4 of the present invention adsorbs 1000 ppm Congo red solution. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0033] See also Figure 1 The present invention provides a method for preparing a Zn-MOF material, comprising the following steps:

[0034] S1. In an alkaline solvent environment, 2-methylimidazole reacts with 3,6-dichloropyridazine to generate 3,6-bis(2-methylimidazole)pyridazine;

[0035] S2. 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and coordinated to obtain a Zn-MOF material.

[0036] In some embodiments, the alkaline solute in the alkaline solvent environment used includes one of sodium hydroxide, potassium hydroxide, and sodium bicarbonate. In addition, the solvent environment used includes one of dimethyl sulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide. Specifically, when performing step S1 to prepare 3,6-bis(2-methylimidazole)pyridazine, the alkaline environment can promote the reaction to proceed in the forward direction, and the solvent environment can make 2-methylimidazole and 3,6-dichloropyridazine evenly distributed. In fact, the pH in the alkaline solvent environment is 8-11.

[0037] In some embodiments, when performing step S1, one of 2-methylimidazole and 3,6-dichloropyridazine is set in excess, which is conducive to promoting the reaction to proceed in the forward direction, thereby increasing the yield of 3,6-bis(2-methylimidazole)pyridazine. Specifically, the molar ratio of 2-methylimidazole to 3,6-dichloropyridazine during the reaction is 1:(2-3). In addition, to further promote the reaction, 2-methylimidazole and 3,6-dichloropyridazine can be reacted at 50°C-70°C for 3h-5h.

[0038] In some embodiments, when performing step S1, an alkaline solute and 2-methylimidazole are added to a solvent environment, and after reflux reaction at 50°C-70°C for 0.1h-1h, 3,6-dichloropyridazine is added and stirred for reaction, and after cooling, filtration is performed to separate and dry to obtain 3,6-bis(2-methylimidazole)pyridazine. Specifically, when the alkaline solute and 2-methylimidazole are added to the solvent environment, the molar ratio of the alkaline solute to 2-methylimidazole is 1:1.

[0039] In some embodiments, after adding 3,6-dichloropyridazine and stirring the reaction and then cooling, the reaction system is added to an ice-water mixture and refrigerated, 3,6-bis(2-methylimidazole)pyridazine is precipitated, and then the solid phase is separated by solid-liquid separation means, and then the mother liquor is used for washing and drying to obtain 3,6-bis(2-methylimidazole)pyridazine. Specifically, when the reaction system is added to the ice-water mixture, the volume ratio of the reaction system to the ice-water mixture is 1:(10-15).

[0040] In fact, in step S1, the reaction formula for generating 3,6-bis(2-methylimidazole)pyridazine by reacting 2-methylimidazole with 3,6-dichloropyridazine is as follows:

[0041]

[0042] In addition, after NMR characterization of 3,6-bis(2-methylimidazole)pyridazine prepared in step S1, its hydrogen spectrum and carbon spectrum are as follows: Figure 2 and Figure 3 shown.

[0043] In some embodiments, when performing step S2, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and dissolved in a polar solvent, and then a coordination reaction is performed to obtain a Zn-MOF material. In fact, the three reactants can be dissolved and mixed by reacting in a polar solvent. Specifically, the polar solvent used includes N,N-dimethylacetamide or N,N-dimethylformamide.

[0044] In some further embodiments, when performing step S2, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and dissolved in a mixture of a polar solvent and deionized water. Specifically, the volume ratio of the polar solvent to the deionized water in the mixture is (1-6):1. In addition, the molar ratio of 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and zinc ions in the zinc source is 1:(1-2):(2-3).

[0045] In some embodiments, the zinc source used includes one of zinc nitrate and its hydrate. Specifically, the zinc source used must be able to be completely dissolved in a polar solvent. In addition, when preparing the Zn-MOF material, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and the zinc source are mixed, reacted at 80°C-90°C for 20h-28h, and washed and dried after the coordination reaction to obtain the Zn-MOF material.

[0046] In fact, the present invention also provides a Zn-MOF material prepared by the preparation method in any of the above optional embodiments. Figure 4 The monomer of Zn-MOF material is composed of 40 carbon atoms, 32 hydrogen atoms, 12 nitrogen atoms, 2 zinc atoms and 8 oxygen atoms, and its relative molecular mass is 939.51g / mol; it includes an asymmetric unit consisting of 1 Zn(Ⅱ) ion, 1 3,6-bis(2-methylimidazole)pyridazine ligand, 1 deprotonated isophthalic acid ligand and two uncoordinated water molecules, and each 3,6-bis(2-methylimidazole)pyridazine ligand is connected to two Zn(Ⅱ) ions, thus forming a stack of Z-shaped chains and constructing a two-dimensional tetragonal lattice monolayer structure such as Figure 5 shown.

[0047] Example 1

[0048] This embodiment 1 provides a method for preparing a Zn-MOF material, comprising the following steps:

[0049] S1. Mix 0.1402 g of sodium hydroxide and 0.2759 g of 2-methylimidazole and dissolve them in 10 mL of dimethyl sulfoxide. After condensing and refluxing at 60° C. for 0.5 h, add 0.2 g of 3,6-dichloropyridazine (CAS: 141-30-0) and stir at 60° C. for 4 h. After cooling naturally to room temperature, pour into 150 mL of ice-water mixture and refrigerate for 24 h. After suction filtration, rinse with deionized water three times, and dry in a 70° C. oven to constant weight to obtain 3,6-bis(2-methylimidazole)pyridazine.

[0050] S2. Dissolve 3.127 g of zinc nitrate hexahydrate, 1.272 g of 3,6-bis(2-methylimidazole)pyridazine, and 0.8798 g of isophthalic acid in 10.5 mL of N,N-dimethylformamide, respectively. Add 2 mL of N,N-dimethylformamide and 1 mL of deionized water into 50 scintillation vials, and then add 0.2 mL of zinc nitrate hexahydrate N,N-dimethylformamide solution, 0.2 mL of d-HCl, and 0.5 mL of ethanol to each scintillation vial. 0.2mL of N,N-dimethylformamide solution of 3,6-bis(2-methylimidazole)pyridazine and 0.2mL of N,N-dimethylformamide solution of isophthalic acid were sealed and reacted in an oven at 85°C for 24 hours. After natural cooling to room temperature, the mixture was filtered out and rinsed three times with a mixture of N,N-dimethylformamide and deionized water. The mixture was soaked in acetonitrile at room temperature for 48 hours and then dried in vacuum to obtain Zn-MOF material (NCD-123).

[0051] Example 2

[0052] This embodiment 2 provides a method for preparing a Zn-MOF material, comprising the following steps:

[0053] S1. Mix 2.804 g of sodium hydroxide and 5.518 g of 2-methylimidazole and dissolve them in 200 mL of dimethyl sulfoxide. After condensing and refluxing at 60° C. for 0.5 h, add 4 g of 3,6-dichloropyridazine (CAS: 141-30-0) and stir at 60° C. for 4 h. After cooling naturally to room temperature, pour into 3000 mL of ice-water mixture and refrigerate for 24 h. After suction filtration, rinse with deionized water three times, and dry in a 70° C. oven to constant weight to obtain 3,6-bis(2-methylimidazole)pyridazine.

[0054] S2. Dissolve 6.195 g of zinc nitrate hexahydrate, 2.52 g of 3,6-bis(2-methylimidazole)pyridazine, and 1.743 g of isophthalic acid in 21 mL of N,N-dimethylformamide, respectively. Add 2 mL of N,N-dimethylformamide and 1 mL of deionized water into 100 scintillation vials, and then add 0.2 mL of zinc nitrate hexahydrate N,N-dimethylformamide solution, 0.2 mL of deionized water, and 1 mL of ethanol to each scintillation vial. mL of 3,6-bis(2-methylimidazole)pyridazine N,N-dimethylformamide solution and 0.2 mL of isophthalic acid N,N-dimethylformamide solution were sealed and reacted in an oven at 85°C for 24 hours. After natural cooling to room temperature, the mixture was filtered out and rinsed three times with a mixture of N,N-dimethylformamide and deionized water. The mixture was soaked in acetonitrile at room temperature for 48 hours and then vacuum dried to obtain Zn-MOF material (NCD-123).

[0055] Example 3

[0056] This Example 3 provides a method for preparing a Zn-MOF material, which is different from Example 2 in that in step S2, 6 mL of N,N-dimethylformamide and 1 mL of deionized water are respectively added to 100 scintillation vials.

[0057] Example 4

[0058] This Example 4 provides a method for preparing a Zn-MOF material, which is different from Example 1 in that in step S2, 1 mL of N,N-dimethylformamide and 2 mL of deionized water are respectively added to 50 scintillation vials.

[0059] Performance Testing

[0060] The adsorption capacity of the Zn-MOF material (NCD-123) prepared in Example 2 was tested at different CR solution concentrations, and the isothermal adsorption curves were as follows: Figure 6 As shown. Figure 6 It can be seen that as the concentration of CR solution increases, the adsorption capacity of the adsorbent also increases. According to the fitting results, the adsorption capacity of NCD-123 for CR at room temperature (298K) is 13226 mg g -1 .

[0061] 20 mg of the Zn-MOF material (NCD-123) prepared in Example 1 and Example 3 were added to 100 mL of a 100 ppm Congo red solution, and the mixture was stirred at 500 rpm for 4 h before separation. Figure 7 and Fig. 9As shown; 20 mg of the Zn-MOF material (NCD-123) prepared in Example 2 and Example 4 were added to 100 mL of a 1000 ppm Congo red solution, and the mixture was stirred at 500 rpm for 4 hours and then separated. Figure 8 and Fig.10 The results are shown in Table 1 below.

[0062] Table 1 Congo red solution concentration values ​​before and after adsorption

[0063] Before adsorption / ppm After adsorption / ppm Example 1 100 1.2 Example 2 1000 145 Example 3 100 0.7 Example 4 1000 116

[0064] The Zn-MOF material in Example 2 was characterized for its crystal form, and its crystal form result data are shown in Table 2 below:

[0065] Table 2 Crystal structure data of Zn-MOF material obtained in Example 2

[0066]

[0067]

[0068] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A method for preparing a Zn-MOF material, characterized in that: include: In an alkaline solvent environment, 2-methylimidazole reacts with 3,6-dichloropyridazine to generate 3,6-bis(2-methylimidazole)pyridazine; 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and coordinated to obtain a Zn-MOF material.

2. The preparation method according to claim 1, characterized in that: The alkaline solute in the alkaline solvent environment includes one of sodium hydroxide, potassium hydroxide, and sodium bicarbonate; and / or, the solvent environment includes one of dimethyl sulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide; and / or, the pH in the solvent environment is 9-11.

3. The preparation method according to claim 1, characterized in that: One of the 2-methylimidazole and the 3,6-dichloropyridazine is set in excess, preferably the molar ratio of the 2-methylimidazole to the 3,6-dichloropyridazine is 1:(2-3); and / or, 2-methylimidazole and 3,6-dichloropyridazine are reacted at 50°C-70°C for 3h-5h.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Add alkaline solute and 2-methylimidazole into the solvent environment, reflux at 50°C-70°C for 0.1h-1h, then add 3,6-dichloropyridazine and stir to react, cool, filter, separate and dry to obtain 3,6-bis(2-methylimidazole)pyridazine.

5. The preparation method according to claim 1, characterized in that: After 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and dissolved in a polar solvent, a coordination reaction is carried out to obtain a Zn-MOF material; preferably, the 3,6-bis(2-methylimidazole)pyridazine, the isophthalic acid and the zinc source are mixed and dissolved in a mixture of a polar solvent and deionized water.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the 3,6-bis(2-methylimidazole)pyridazine to the isophthalic acid is 1:(1-2); and / or the molar ratio of the 3,6-bis(2-methylimidazole)pyridazine to the zinc ions in the zinc source is 1:(2-3); and / or the polar solvent includes N,N-dimethylacetamide or N,N-dimethylformamide; and / or the zinc source includes one of zinc nitrate and its hydrate.

7. The preparation method according to claim 5, characterized in that: The volume ratio of the polar solvent to the deionized water is (1-6):1; and / or, 3,6-bis(2-methylimidazole)pyridazine, isophthalic acid and a zinc source are mixed and reacted at 80°C-90°C for 20h-28h; and / or, after mixing and coordination, the Zn-MOF material is washed and dried.

8. A Zn-MOF material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the Zn-MOF material prepared by the preparation method according to any one of claims 1 to 7 in the adsorption of Congo red dye.

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