Preparation method of ferroferric oxide and fluorine-containing organic framework core-shell structure material

Abstract

The invention belongs to the technical field of functional materials, and particularly provides a preparation method of a ferroferric oxide and fluorine-containing organic framework core-shell structure material, which realizes integration of double functions of core magnetism and shell lipophilicity. According to the invention, by optimizing the type of a functional group X on a benzene ring of terephthalic acid (H2BDC) and regulating and controlling the nucleation and growth behaviors of MOFs in the reaction process of Al ions and H2BDC-X organic ligands, a core-shell structure material which is uniformly dispersed and uniformly coated is obtained. The influence mechanism of a fluorine-containing organic ligand functional group on heterogeneous nucleation of the MOFs shell layer on the surface of the metal oxide is discussed for the first time, and the types of the MOFs shell layer are enriched; the magnetic and oleophylic core-shell structure material obtained by the invention shows excellent performance in oil-water separation.

Description

Technical Field

[0001] The invention belongs to the technical field of functional materials, and specifically relates to a method for preparing a ferroferric oxide@fluorine-containing organic skeleton core-shell structure material. Background Art

[0002] Industrial and domestic oily wastewater and oil leakage not only cause serious environmental problems, but also lead to waste of resources. Therefore, efficient oil-water separation has aroused great interest. Common methods for oil-water separation include centrifugation, gravity, adsorption, flotation, bio-oxidation and chemical methods. Among them, metal organic frameworks (MOFs) have become an excellent class of oil-water separation materials due to their structural advantages such as high specific surface area and high porosity. In particular, the fluorine-carbon chain chemical bonds in fluorine-containing MOFs materials are stable and highly lipophilic, making it easy for the oil phase to diffuse and penetrate in them, which has recently attracted the attention of scientists. Compared with traditional MOFs membrane materials, directly using MOFs powder for oil-water separation has good separation effects, but there are problems such as poor powder reusability and difficulty in oil recovery.

[0003] In order to achieve the reuse of oil-water separation materials, magnetic materials can be introduced into the oil-water separation materials. Among the common magnetic materials, ferroferric oxide has become the most widely used magnetic material due to its low price. However, how to compound ferroferric oxide with fluorine-containing MOFs materials and realize the ferroferric oxide@fluorine-containing MOFs core-shell structure oil-water separation materials with integrated magnetic and lipophilic dual functions through a simple and mild strategy is still a great challenge. Summary of the invention

[0004] Aiming at the potential application of MOFs-based core-shell structure materials with both magnetic and lipophilic properties in oil-water separation, the present invention provides a method for preparing ferroferric oxide @ fluorine-containing organic skeleton core-shell structure materials. Ferroferric oxide, aluminum salt, and fluorine-containing organic ligands are mixed without any sacrificial template or pre-modification of the surface of ferroferric oxide particles. By regulating the type of fluorine-containing organic ligands, a ferroferric oxide @ fluorine-containing organic skeleton core-shell structure material with both magnetic and lipophilic properties is prepared.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing ferroferric oxide@fluorine-containing organic skeleton core-shell structure material, comprising the following steps: The ferroferric oxide, aluminum salt and fluorine-containing organic ligand are ultrasonically dispersed in a mixed solvent, mechanically stirred for reaction, and then cooled, centrifuged, washed and dried to obtain the ferroferric oxide@fluorine-containing organic skeleton core-shell structure material.

[0006] The ferrosoferric oxide is a nano-spherical particle with a particle size of 200-400 nm.

[0007] The aluminum salt is Al(NO 3 ) 3 9H 2 O.

[0008] The fluorine-containing organic ligand is one of 2-fluoroterephthalic acid and 2,5-bis(trifluoromethyl)terephthalic acid.

[0009] The mass ratio of the aluminum salt to the fluorine-containing organic ligand is 1 / 5 to 3 / 5.

[0010] The mass ratio of the fluorine-containing organic ligand to ferrosoferric oxide is 1 / 10 to 1 / 2.

[0011] The mass volume ratio of the fluorine-containing organic ligand to the mixed solvent is 0.5-2.5 mg / mL.

[0012] The mixed solvent is a mixed solvent of water and N,N-dimethylformamide, wherein the volume ratio of N,N-dimethylformamide to water is less than 3, preferably 1 / 4 to 1. When the content of N,N-dimethylformamide is too large, the deprotonation ability changes, resulting in homogeneous nucleation of MOFs.

[0013] The stirring rate of the mechanical stirring is 100-500 rpm, preferably 200 rpm; The mechanical stirring time is 4 to 24 hours, preferably 8 hours; The reaction temperature is 60-90°C, preferably 60°C.

[0014] Considering the types of organic ligand functional groups, especially the fluorine with strong electron-withdrawing effect in fluorinated organic ligands, which has a great influence on the nucleation and growth behavior of MOFs, how to synthesize ferroferric oxide @ fluorinated organic skeleton core-shell structure materials is still a huge challenge. The present invention studies the influence of the types of functional groups on the heterogeneous nucleation of fluorinated MOFs on the surface of ferroferric oxide by regulating the functional groups of fluorinated organic ligands; explores the influence of solvent composition on the nucleation kinetics of MOFs by regulating the content of N,N-dimethylformamide in the mixed solvent; and finally determines the appropriate reaction conditions and organic ligands to prepare ferroferric oxide @ fluorinated organic skeleton core-shell structure materials.

[0015] Beneficial effects: 1. The present invention prepares for the first time a ferroferric oxide @ fluorinated organic framework core-shell structure material with both magnetic and lipophilic functions, proposes the effect of fluorinated organic ligand functional groups on the heterogeneous nucleation of MOFs shell, and enriches the types of MOFs coated on the surface of metal oxides.

[0016] 2. The ferroferric oxide@fluorinated organic framework core-shell structure material prepared by the present invention, the lipophilic fluorinated MOFs endow the core-shell structure material with excellent oil-water separation performance; in addition, the use of magnetic ferroferric oxide as the core is conducive to the recovery of the core-shell structure material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a transmission electron micrograph of the ferroferric oxide@fluorine-containing organic framework core-shell structure material prepared in Example 1; Figure 2 This is a transmission electron micrograph of the ferroferric oxide@fluorine-containing organic framework core-shell structure material prepared in Example 2; Figure 3 It is a comparison diagram of lipophilic properties and a magnetic diagram of the ferroferric oxide@fluorine-containing organic skeleton core-shell structure material prepared in Example 2; Figure 4 This is a transmission electron micrograph of the ferroferric oxide@fluorine-containing organic framework core-shell structure material prepared in Example 3; Figure 5 This is a transmission electron micrograph of the ferroferric oxide@fluorine-containing organic framework core-shell structure material prepared in Comparative Example 1; Figure 6 This is a transmission electron micrograph of the ferroferric oxide@fluorine-containing organic framework core-shell structure material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and examples, which are only used to illustrate the present invention, but do not constitute any limitation to the scope of the present invention. Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available.

[0019] In the following examples and comparative examples, the ferroferric oxide nanoparticles are obtained by hydrothermal reaction of ethylene glycol and ferric chloride. The size of the ferroferric oxide nanoparticles can be changed by changing the amount of the regulating agent anhydrous sodium acetate and polyethylene glycol. The particle size of the ferroferric oxide used in the following examples and comparative examples is 400 nm.

[0020] Example 1 50mg ferroferric oxide, 8mg Al(NO 3 ) 3 9H 2 O, and 20 mg 2-fluoroterephthalic acid (H 2The Al-BDC-F (Al-BDC-F) was ultrasonically dispersed in a mixed solution of 20 mL of deionized water and N,N-dimethylformamide (wherein the volume ratio of deionized water to N,N-dimethylformamide was 1:1), mechanically stirred at 60 °C with a stirring rate of 200 rpm, reacted for 8 h, cooled to room temperature, centrifuged, washed with DMF and ethanol respectively, and vacuum dried at 80 °C overnight to obtain the ferroferric oxide @Al-BDC-F core-shell structure material.

[0021] Figure 1 This is a low-magnification transmission electron micrograph of the ferroferric oxide@Al-BDC-F core-shell structure material. It can be seen from the figure that the Al-BDC-F shell layer is evenly coated on the surface of the ferroferric oxide particles, and the shell material shows a jagged shape.

[0022] Example 2 This embodiment is the same as embodiment 1, except that the functional group in the organic ligand is changed from F to two CF 3 , that is, using 2,5-bis(trifluoromethyl)terephthalic acid as a fluorine-containing organic ligand, and keeping other conditions unchanged, ferroferric oxide@Al-BDC-2CF 3 Core-shell structural materials.

[0023] Figure 2 Display Fe3O4@Al-BDC-2CF 3 Low-magnification transmission electron microscopy image of the core-shell structure material. It can be seen from the image that the MOFs material is evenly coated on the surface of the ferroferric oxide particles, and the jagged surface of the shell layer is more obvious than that of the ferroferric oxide@Al-BDC-F core-shell structure material prepared in Example 1.

[0024] like Figure 3 Shown are ferroferric oxide and ferroferric oxide@Al-BDC-2CF 3 Comparison of the lipophilic properties of core-shell structure materials and FeO4@Al-BDC-2CF 3 Magnetic image of core-shell structure sample. It can be seen from the figure that ferroferric oxide is dispersed in the water phase, while ferroferric oxide@Al-BDC-2CF 3 The core-shell structure material is enriched in the oil phase. Compared with the ferroferric oxide particles, the ferroferric oxide@Al-BDC-2CF prepared in this example is 3 The oleophilic properties of the core-shell structured material have been significantly improved, and the material can be easily recovered by adding an external magnet, so it is expected to have application prospects in oil-water separation.

[0025] Example 3 This embodiment is the same as embodiment 2, except that the volume ratio of the mixed solution of deionized water and N,N-dimethylformamide is 3:1, and other conditions remain unchanged to prepare ferroferric oxide @Al-BDC-2CF3 Core-shell structural materials.

[0026] Figure 4 It shows that when the volume ratio of the mixed solution of deionized water and N,N-dimethylformamide is 3:1, the obtained FeO@Al-BDC-2CF 3 Low-magnification transmission electron microscopy image of the core-shell structure material. It can be seen from the image that the MOFs material is evenly coated on the surface of the ferroferric oxide particles.

[0027] Example 4 This example is the same as Example 2, except that the volume ratio of the mixed solution of deionized water and N,N-dimethylformamide is 10:0, and other conditions remain unchanged to prepare ferroferric oxide @Al-BDC-2CF 3 Core-shell structural materials.

[0028] Comparative Example 1 This comparative example is the same as Example 1, except that the organic ligand is 2-trifluoromethyl terephthalic acid, and other reaction conditions remain unchanged. The low-magnification transmission electron microscopy image of the sample prepared after the reaction is as follows: Figure 5 As shown, MOFs are not uniformly coated on the surface of ferroferric oxide particles. Considering that the electron-withdrawing effect of the functional group 2-trifluoromethyl is between H and 2,5-bis(trifluoromethyl), terephthalic acid and 2,5-bis(trifluoromethyl)terephthalic acid as organic ligands can form core-shell structures, while 2-trifluoromethyl as an organic ligand cannot form a core-shell structure. This may be due to the different electron-withdrawing ability of the two carboxyl groups on the benzene ring, resulting in symmetry destruction, thus causing different nucleation and growth behaviors.

[0029] Comparative Example 2 This comparative example is the same as Example 1, except that the organic ligand is 2,3,5,6-tetrafluoroterephthalic acid, and other reaction conditions remain unchanged. The transmission electron microscopy image of the sample prepared after the reaction is as follows: Figure 6 As shown, MOFs are not evenly coated on the surface of ferroferric oxide particles. This may be because the electron-withdrawing effect of the four Fs connected to the benzene ring is too strong, which affects the nucleation and growth of MOFs on the surface of ferroferric oxide particles.

[0030] Comparative Example 3 This comparative example is the same as Example 1, except that the volume ratio of water to N,N-dimethylformamide in the mixed solvent is 1:3. The low-magnification transmission electron microscopy image of the sample morphology prepared after the reaction shows that MOFs are not coated on the surface of the ferroferric oxide particles, but grow independently by nucleation. The reason is that too much N,N-dimethylformamide changes the growth kinetics of MOFs.

Claims

1. A method for preparing ferroferric oxide @ fluorine-containing organic framework core-shell structure material, characterized in that: The steps include: The ferroferric oxide, aluminum salt and fluorine-containing organic ligand are ultrasonically dispersed in a mixed solvent, mechanically stirred for reaction, and then cooled, centrifuged, washed and dried to obtain the ferroferric oxide@fluorine-containing organic skeleton core-shell structure material; The fluorine-containing organic ligand is one of 2-fluoroterephthalic acid and 2,5-bis(trifluoromethyl)terephthalic acid.

2. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The aluminum salt is Al(NO3)3·9H2O.

3. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The mass ratio of the fluorine-containing organic ligand to ferrosoferric oxide is 1 / 10 to 1 / 2.

4. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The mass ratio of the aluminum salt to the fluorine-containing organic ligand is 1 / 5 to 3 / 5.

5. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The mass volume ratio of the fluorine-containing organic ligand to the mixed solvent is 0.5-2.5 mg / mL.

6. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The mixed solvent is a mixed solvent of water and N,N-dimethylformamide.

7. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 6, characterized in that: The volume ratio of the N,N-dimethylformamide to water is less than 3.

8. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 7, characterized in that: The volume ratio of the N,N-dimethylformamide to water is 1 / 4-1.

9. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The ferrosoferric oxide is a nano-spherical particle with a particle size of 200-400nm.

10. The method for preparing the ferroferric oxide@fluorine-containing organic framework core-shell structure material according to claim 1, characterized in that: The stirring rate of the mechanical stirring is 100-500 rpm; The mechanical stirring time is 4 to 24 hours; The reaction temperature is 60-90°C.

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