A magnetic pebble-like Cu-Fe bimetallic center MOF and its preparation method and application

Abstract

The present invention discloses a magnetic pebble-like Cu-Fe bimetallic center MOF and its preparation method and application. The magnetic pebble-like Cu-Fe bimetallic center MOF includes magnetic nano-Fe3O4, strongly hydrophilic free metal ions, and strongly hydrophobic aromatic amine-based organic ligand units. The magnetic Fe-based MOF is prepared by a microwave method, and then, using the magnetic Fe-based MOF as a matrix, a hydrophobic aromatic amine-based organic ligand and strongly hydrophilic free metal ions are introduced to in-situ generate the magnetic pebble-like Cu-Fe bimetallic center MOF. Compared with the prior art, the advantages of the present invention are as follows: The magnetic pebble-like Cu-Fe bimetallic center MOF has both amphiphilicity and high adsorption capacity, fundamentally overcoming the problems of easy fragmentation and hydrolysis of MOFs in traditional MOF composites, and having more advantages in the adsorption removal and separation purification of VOCs organic pollutants in environmental water samples.

Description

Technical Field

[0001] The present invention relates to the field of functional materials for the pretreatment of environmental chemical pollutants, and particularly to a magnetic pebble-like Cu-Fe bimetallic center MOF and its preparation method and application. Background Art

[0002] Volatile organic compounds (VOCs) are a class of organic pollutants with boiling points of 50 - 260 °C and saturated vapor pressures exceeding 133.32 Pa at room temperature, mainly including: benzene, toluene, xylene, chloroform, formaldehyde, trichloroethylene, etc. Such pollutants are toxic, and some can cause cancer and birth defects, seriously threatening human life and health. For such organic pollutants, the research focus is on using the adsorption method to remove VOCs in the atmosphere, and the mainstream adsorption materials include: activated carbon, amorphous silica, highly crosslinked polymer resins, and MOFs, etc. Compared with other traditional adsorption materials, MOFs materials have the characteristics of large specific surface area, rich and easily adjustable pore structures, diverse structural compositions, strong regenerability, open metal active sites, and chemical modifiability, and they exhibit excellent performance in the adsorption and removal of VOCs (Xiuquan Li, Li Zhang, Zhongqing Yang, Peng Wang, Yunfei Yan, Jingyu Ran. Adsorption materials for volatile organic compounds (VOCs) and the key factors for VOCs adsorption process: A review. Separation and Purification Technology, 2020, 235, 116213).

[0003] Compared with the adsorption treatment of VOCs organic pollutants in the atmospheric environment, there is less research on the adsorption and removal of VOCs organic pollutants in water environment caused by accidental VOCs leakage. At the same time, due to the poor stability of MOFs materials in water and their easy hydrolysis, the adsorption research on VOCs organic pollutants in the water environment still needs to be further carried out.

[0004] During the preparation of MOFs, the reaction temperature, reaction solvent, system pH, and the types of central ions and organic ligands constituting MOFs have a significant impact on their adsorption performance and microstructure. Considering the hydrophilicity of free metal ions and the hydrophobicity of aromatic amine organic ligands, developing an amphiphilic MOF with both magnetic nano-Fe3O4, strongly hydrophilic free metal ions, and strongly hydrophobic aromatic amine organic ligand units and using it for the rapid adsorption and removal of VOCs in environmental water samples has broad application prospects and certain challenges. Summary of the Invention

[0005] The object of the present invention is to provide a magnetic pebble-like Cu-Fe bimetallic center MOF, a preparation method thereof, and an application thereof, aiming at the deficiencies of the prior art.

[0006] The object of the present invention is achieved by the following technical solutions: A magnetic pebble-like Cu-Fe bimetallic center MOF, comprising: RNH2-Fe3O4·Cu-ArNH2, where ArNH2 represents a strongly hydrophobic aromatic amine organic ligand, and Fe3O4 is magnetic nano-Fe3O4.

[0007] Further, the magnetic nano-Fe3O4 is one of Fe3O4 with a particle size of 10 nm, 100 nm, and 400 nm.

[0008] Further, the strongly hydrophobic aromatic amine organic ligand unit is one of 4,4'-diaminobiphenyl, 2,2'-biphenyldiamine disulfonic acid, and 4,4′-sulfonyldiphenylamine.

[0009] On the other hand, the present specification also provides a preparation method of a magnetic pebble-like Cu-Fe bimetallic center MOF, which includes:

[0010] S1. Prepare magnetic Fe-based MOF by microwave method:

[0011] Add FeCl3•6H2O, ethylene glycol, anhydrous sodium acetate, and tetraethylenepentamine into a thick-walled PTFE pressure-resistant bottle, seal it with a PTFE screw cap, perform ultrasonic dispersion, then transfer it to a microwave reactor for reaction, cool to room temperature, perform magnetic separation, wash it with pure water several times until neutral, and dry it under vacuum to obtain magnetic Fe-based MOF based on Fe3O4;

[0012] S2. Prepare magnetic pebble-like Cu-Fe bimetallic center MOF by microwave method:

[0013] Add magnetic Fe-based MOFs with different particle sizes, copper acetate, aromatic amine organic ligands, strongly hydrophilic free metal ions, and 40 mL of DMF into a thick-walled PTFE pressure-resistant bottle, seal it with a PTFE screw cap, perform ultrasonic dispersion, then transfer it to a microwave reactor for reaction, cool to room temperature, perform magnetic separation, wash it with pure water several times until neutral, and dry it under vacuum to obtain magnetic pebble-like Cu-Fe bimetallic center MOF with both amphiphilicity and strong adsorption performance.

[0014] Further, the strongly hydrophilic free metal ions are Fe2 + 、Fe3 + 、Cu2 +One of the following.

[0015] Further, in the preparation of magnetic Fe-based MOFs by the microwave method, the mass ratio of FeCl3•6H2O to anhydrous sodium acetate is (1~3):3.

[0016] Further, in the preparation of magnetic Fe-based MOFs by the microwave method, the volume ratio of ethylene glycol to tetraethylenepentamine is (20~60):(5~10).

[0017] Further, in the preparation of magnetic pebble-like Cu-Fe bimetallic center MOFs by the microwave method, the mass ratio of magnetic Fe-based MOFs with different particle sizes, copper acetate, aromatic amine organic ligands, and strongly hydrophilic free metal ions is (0.5~1.0):(1.0~3.0):(0.5~5.0):(0.2~2.0).

[0018] Further, the temperature in the microwave reactor is 180 - 220 °C and 110 - 160 °C respectively in the preparation of magnetic Fe-based MOFs and magnetic pebble-like Cu-Fe bimetallic center MOFs.

[0019] On the other hand, this specification also provides an application of magnetic pebble-like Cu-Fe bimetallic center MOFs for the adsorption and removal of VOCs in environmental water samples.

[0020] Advantages of the present invention:

[0021] (1) The preparation method of the magnetic pebble-like Cu-Fe bimetallic center MOFs of the present invention is simple, and the morphology and structure are controllable. More prominently, by in-situ reaction on the surface of Fe-based MOFs, strongly hydrophilic free metal ions and strongly hydrophobic aromatic amine organic ligands are introduced onto the MOFs. The prepared magnetic pebble-like Cu-Fe bimetallic center MOFs not only have good amphiphilic properties, but also have a high adsorption capacity for VOCs in environmental water samples, can be used for the rapid adsorption and removal of VOCs organic pollutants in environmental water samples and achieve one-step separation and purification, greatly improving the pretreatment efficiency of environmental water samples.

[0022] (2) Compared with traditional MOF composites, the present invention fundamentally overcomes the problems of easy fragmentation and hydrolysis of MOFs in MOF composites, and has more advantages in the removal and separation and purification of VOCs organic pollutants in environmental water samples. Description of the Drawings

[0023] Figure 1 It is a scanning electron microscope image of the magnetic pebble-like Cu-Fe bimetallic center MOFs provided by the embodiment of the present invention;

[0024] Figure 2The hysteresis loop of the magnetic pebble-like Cu-Fe bimetallic center MOFs provided by the embodiments of the present invention;

[0025] Figure 3 The X-ray photoelectron spectroscopy diagram of the magnetic pebble-like Cu-Fe bimetallic center MOFs provided by the embodiments of the present invention;

[0026] Figure 4 The X-ray diffraction spectrum of the magnetic pebble-like Cu-Fe bimetallic center MOFs provided by the embodiments of the present invention;

[0027] Figure 5 The adsorption performance results of the magnetic pebble-like Cu-Fe bimetallic center MOFs for VOCs organic pollutants. Specific embodiments

[0028] The following further details the specific embodiments of the present invention with reference to the accompanying drawings.

[0029] A magnetic pebble-like Cu-Fe bimetallic center MOFs provided by the embodiments of the present invention, with the chemical formula RNH2-Fe3O4·Cu-ArNH2, includes magnetic nano-Fe3O4, strongly hydrophilic free metal ions, and strongly hydrophobic aromatic amine organic ligand units.

[0030] In the above solution, the magnetic nano-Fe3O4 is at least one of Fe3O4 with a particle size of 10 nm, 100 nm, and 400 nm.

[0031] The strongly hydrophobic aromatic amine organic ligand units are at least one of 4,4'-diaminobiphenyl, 2,2'-biphenyldiamine disulfonic acid, and 4,4′-sulfonyldianiline.

[0032] The strongly hydrophilic free metal ions are Fe 2+ 、Fe 3+ 、Cu 2+ at least one of them.

[0033] The embodiments of the present invention also provide a preparation method of the magnetic pebble-like Cu-Fe bimetallic center MOFs, including:

[0034] Example 1: Preparation of magnetic pebble-like Cu-Fe bimetallic center MOFs by two-step reaction

[0035] (1) Add 3.0 g of anhydrous sodium acetate, 20 mL of ethylene glycol, 1.0 g of FeCl3•6H2O, and 5 mL of tetraethylenepentamine into a polytetrafluoroethylene pressure-resistant bottle, seal it with a polytetrafluoroethylene screw cap, ultrasonically disperse for 20 min, then transfer it to a microwave reactor and react at 200 °C for 3 h. Cool to room temperature, perform magnetic separation, wash several times with pure water until neutral, and dry in vacuum at 60 °C for 48 h to obtain magnetic Fe-based MOFs.

[0036] (2) Add 0.5 g of the magnetic Fe-based MOFs prepared in step (1), 1.0 g of copper acetate, 0.5 g of aromatic amine organic ligand, 0.2 g of copper sulfate, and 40 mL of DMF into a thick-walled polytetrafluoroethylene pressure-resistant bottle, seal it with a polytetrafluoroethylene screw cap, ultrasonically disperse for 20 min, then transfer it to a microwave reactor and react at 130 °C for 2 h. Cool to room temperature, perform magnetic separation, wash several times with pure water until neutral, and dry in vacuum at 60 °C for 48 h to obtain magnetic pebble-like Cu-Fe bimetallic center MOFs with amphiphilicity and strong adsorption performance.

[0037] The operation steps of Examples 1 to 18 are the same as those of Example 1, and the raw materials, raw material formulas, and preparation condition parameters are shown in Table 1.

[0038] The scanning electron microscope image of the magnetic pebble-like Cu-Fe bimetallic center MOFs with amphiphilicity and strong adsorption performance prepared in Example 1 is as Figure 1 shown. This magnetic Cu-Fe bimetallic center MOFs has a pebble-like structure and its morphology is relatively regular. From the Figure 2 hysteresis loop of the magnetic pebble-like Cu-Fe bimetallic center MOFs, it can be seen that the magnetic pebble-like Cu-Fe bimetallic center MOFs prepared in Example 1 has a strong saturation magnetization intensity (43.98 emu / g), enabling it to achieve efficient directional movement under an external magnetic field, which is conducive to the recycling and reuse of the material. As Figure 3 shown, in the magnetic pebble-like Cu-Fe bimetallic center MOFs obtained in Example 1, the binding energies of the carbon spectrum (C 1s), oxygen spectrum (O 1s), nitrogen spectrum (N 1s), and iron spectrum (Fe2p) are 286.6 eV, 530.2 eV, 399.8 eV, and 710.9 eV respectively, indicating that the hydrophobic aromatic amine group is successfully immobilized in the magnetic Cu-Fe bimetallic center MOFs. In addition, as Figure 4As shown, the XRD pattern of the magnetic pebble-like Cu-Fe bimetallic center MOFs in Example 1 shows that the 2θ angles are 30.1°, 35.5°, 42.9°, 57.1°, and 62.7°, corresponding to the (220), (311), (400), (422), (511), and (440) crystal planes of Fe3O4, respectively; the 2θ angles are 43.8°, 50.8°, and 73.9°, corresponding to the (111), (200), and (220) crystal planes of Cu, respectively, further indicating the successful preparation of the magnetic pebble-like Cu-Fe bimetallic center MOFs.

[0039] Table 1 Raw material components and preparation parameters of Examples 1-18 of the present invention

[0040]

[0041] Example 19: Adsorption performance evaluation of magnetic pebble-like Cu-Fe bimetallic center MOFs

[0042] The adsorption performance of the magnetic pebble-like Cu-Fe bimetallic center MOFs prepared in Example 1 of the present invention was investigated. Accurately weigh 10.0 mg of VOCs standards such as benzene, toluene, xylene, chloroform, formaldehyde, and trichloroethylene into 6 10 mL volumetric flasks respectively. After dissolving with a small amount of methanol, dilute to the scale with methanol to prepare a standard stock solution of 1.0 g / L, and store it in a refrigerator at 4 °C for standby. Prepare 50 mL of a mixed standard solution with a concentration of 100 mg / L using the above VOCs standard stock solutions, add 20 mg of the magnetic pebble-like Cu-Fe bimetallic center MOFs prepared in Example 1, the adsorption temperature is 30 °C, stir magnetically or oscillate at a constant temperature for 24 hours. After the adsorption is completed, perform magnetic separation, and use GC-MS / MS to measure the concentrations of VOCs such as benzene, toluene, xylene, chloroform, formaldehyde, and trichloroethylene in the supernatant, and calculate its adsorption capacity according to formula (1). The results are as Figure 5 shown.

[0043] (1)

[0044] q is the adsorption capacity (mg / g), C0 is the initial concentration of VOCs in the water sample (mg / L), C e is the concentration of VOCs in the water sample at adsorption equilibrium (mg / L), V is the volume of the water sample (mL), and m is the mass (g) of the magnetic pebble-like Cu-Fe bimetallic center MOFs.

[0045] From Figure 5It can be seen that the magnetic pebble-like Cu-Fe bimetallic center MOFs have a high adsorption capacity for VOCs organic pollutants and have great application potential in the adsorption and removal of VOCs organic pollutants in the water environment pollution caused by accidental VOCs leakage.

[0046] On the other hand, the embodiment of the present invention also provides an application of the above-mentioned magnetic pebble-like Cu-Fe bimetallic center MOFs in the adsorption and removal of VOCs organic pollutants in environmental water samples, including: transferring 50-100 mL of water sample into a 250 mL flat-bottom flask, adding 20-50 mg of magnetic pebble-like Cu-Fe bimetallic center MOFs, and performing constant-temperature oscillating adsorption at 25°C - 40°C for 12-24 h. After the adsorption is completed, magnetic separation is carried out to obtain the supernatant; the supernatant is analyzed by gas chromatography-tandem mass spectrometry to obtain the content of residual VOCs in the water sample, and then the adsorption rate of the magnetic pebble-like Cu-Fe bimetallic center MOFs for VOCs in the water sample is calculated.

[0047] After considering the specification and the content disclosed herein, those skilled in the art will readily think of other embodiments of the present application. The present application aims to cover any variations, uses, or adaptive changes of the present application, which follow the general principles of the present application and include the common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and the embodiments are only regarded as exemplary, and the true scope and spirit of the present application are pointed out by the claims.

[0048] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. The present application is not limited to the precise structure already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present application is only limited by the appended claims.

Claims

1. A magnetic pebble-like Cu-Fe bimetallic center MOF, characterized in that, The preparation method includes: S1. Prepare magnetic Fe-based MOFs by microwave method: Add FeCl3•6H2O, ethylene glycol, anhydrous sodium acetate, and tetraethylenepentamine into a thick-walled PTFE pressure-resistant bottle, seal it with a PTFE screw cap, perform ultrasonic dispersion, then transfer it to a microwave reactor for reaction, cool to room temperature, perform magnetic separation, wash it with pure water several times until neutral, and obtain magnetic Fe-based MOFs based on Fe3O4 after vacuum drying. The Fe3O4 is magnetic nano-Fe3O4, and the magnetic nano-Fe3O4 is one of Fe3O4 with a particle size of 10nm, 100nm, and 400nm; S2. Prepare magnetic pebble-like Cu-Fe bimetallic center MOFs by microwave method: Add magnetic Fe-based MOFs, copper acetate, aromatic amine organic ligand, strongly hydrophilic free metal ion, and 40 mL of DMF into a thick-walled PTFE pressure-resistant bottle, seal it with a PTFE screw cap, perform ultrasonic dispersion, then transfer it to a microwave reactor for reaction, cool to room temperature, perform magnetic separation, wash it with pure water several times until neutral, and obtain magnetic pebble-like Cu-Fe bimetallic center MOFs with both amphiphilicity and strong adsorption performance after vacuum drying; The aromatic amine-based organic ligand is a strongly hydrophobic aromatic amine-based organic ligand unit, specifically one of 4,4'-diaminobiphenyl, 2,2'-biphenyldiamine disulfonic acid, and 4,4′-sulfonyldiphenylamine; the strongly hydrophilic free metal ion is , , one of them.

2. The magnetic pebble-like Cu-Fe bimetallic center MOFs according to claim 1, characterized in that, In the preparation of magnetic Fe-based MOFs by microwave method, the mass ratio of FeCl3•6H2O to anhydrous sodium acetate is (1~3):

3.

3. The magnetic pebble-like Cu-Fe bimetallic center MOFs according to claim 1, characterized in that, In the preparation of magnetic Fe-based MOFs by microwave method, the volume ratio of ethylene glycol to tetraethylenepentamine is (20~60):(5~10).

4. The magnetic pebble-like Cu-Fe bimetallic center MOFs according to claim 1, characterized in that, In the preparation of magnetic pebble-like Cu-Fe bimetallic center MOFs by microwave method, the mass ratio of magnetic Fe-based MOFs, copper acetate, aromatic amine organic ligand, and strongly hydrophilic free metal ion is (0.5~1.0):(1.0~3.0):(0.5~5.0):(0.2~2.0).

5. The magnetic pebble-like Cu-Fe bimetallic center MOFs according to claim 2, characterized in that, The temperature in the microwave reactor is 180 - 220°C and 110 - 160°C respectively in the preparation of magnetic Fe-based MOFs and magnetic pebble-like Cu-Fe bimetallic center MOFs.

6. Application of the magnetic pebble-like Cu-Fe bimetallic center MOFs as described in claim 1, characterized in that: It is used for the adsorption and removal of VOCs in environmental water samples.

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