One-step synthesis method of cauliflower-like copper coordination polymer by self-assembly of nanowires

Abstract

The present invention discloses a one-step synthesis method of cauliflower-shaped copper coordination polymers by self-assembly of nanowires, which belongs to the technical field of preparation of nanomaterials. The present invention utilizes halogen anions to regulate the coordination of copper ions with trimesic acid and 4,4'-bipyridine at room temperature, thereby obtaining cauliflower-shaped copper coordination polymers formed by self-assembly of one-dimensional nanowires. The synthesis process is simple, the cost is low, it is suitable for large-scale industrial production, and has good economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of nano - material preparation, and particularly relates to a one - step synthesis method of cauliflower - shaped copper coordination polymers with self - assembled nanowires. Background Art

[0002] Coordination polymers are composed of metal ions and organic ligands through coordination, and have advantages such as high specific surface area, ordered pore structures, and adjustable active metal centers. The copper metal centers of copper coordination polymers have variable valence states, can serve as catalytic centers for redox reactions, and have low toxicity and cost, making them ideal, safe, and environmentally friendly catalytic or energy - storage materials. However, the pore structures of most copper coordination polymers are micropores, that is, the pore size is <2 nm, which is not conducive to the rapid transfer of reaction molecules to the metal active centers inside. Therefore, although copper coordination polymers have abundant metal centers, their reaction activity still mainly depends on the atoms exposed on the surface, and their catalytic activity is relatively low. Currently, one of the most common strategies is morphology control: 1) regulating the dimensional morphology of coordination polymers, that is, from bulk materials to 1D or 2D materials, which have more atoms exposed on the surface and shorter distances from the surface to the interior; 2) regulating the exposed surfaces of coordination polymers, that is, exposing crystal planes with more active metal centers.

[0003] 1D copper coordination polymer nanowires are one of the ideal catalytic structures. They have anisotropy on the surface, can expose more unsaturated coordinated metals, and have a high aspect ratio and directional electron transfer, which is conducive to the rapid transfer of reaction molecules to catalytic active centers. However, the current methods for morphology control of coordination polymers mainly use surfactants. Surfactants can adsorb on the surface of coordination polymers, inhibit the growth of this crystal plane, or compete with organic ligands for coordination metal ions to achieve morphology control. However, they have the problem of being difficult to remove, which causes the active metal centers exposed on the surface to be covered, unable to react with reactants, and also blocks the transfer of reaction molecules to the active metal centers inside the coordination polymers, resulting in a significant reduction in catalytic activity. Therefore, it is necessary to develop a simple and surfactant - free method to prepare 1D copper coordination polymers. Summary of the Invention

[0004] In view of the above problems, the present invention provides a simpler and faster method for preparing 1D copper coordination polymers without using surfactants.

[0005] To achieve the above object, the present invention adopts the following technical scheme:

[0006] A one - step synthesis method of cauliflower - shaped copper coordination polymers with self - assembled nanowires, which comprises the following steps:

[0007] (1) Without adding surfactants, add chloride salts or bromide salts to N,N-dimethylformamide containing a copper metal precursor, and stir at room temperature until dissolved uniformly to obtain a metal salt solution;

[0008] (2) Dissolve trimesic acid and 4,4-bipyridine separately in the same amount of N,N-dimethylformamide as in step (1), and stir at room temperature until dissolved uniformly to obtain a trimesic acid solution and a 4,4-bipyridine solution;

[0009] (3) Add the trimesic acid solution to the metal salt solution, stir for a period of time, then add the 4,4-bipyridine solution, continue to stir and react at room temperature, and after washing and drying, obtain a cauliflower-shaped copper coordination polymer self-assembled by nanowires.

[0010] Furthermore, the chloride salt or bromide salt in step (1) is specifically a potassium salt, a sodium salt or a manganese salt, and its dosage is calculated according to the molar ratio of Cl ions or Br ions to Cu ions in the copper metal precursor being (0.06 - 1.8):3.

[0011] Furthermore, the copper metal precursor is specifically CuH6N2O9.

[0012] Furthermore, the dosages of the trimesic acid and 4,4-bipyridine in step (2) are calculated according to the molar ratio to Cu ions in the copper metal precursor being (5 - 5.5):(0.5 - 1):3.

[0013] Furthermore, after adding the trimesic acid solution in step (3), it needs to be stirred for 30 min, and after adding the 4,4-bipyridine solution, it continues to be stirred for 30 - 90 min, and the stirring speed is 300 - 800 rpm.

[0014] The remarkable advantages of the present invention are as follows:

[0015] (1) The present invention uses easily available raw materials, and under the condition of no surfactants and templates, uses halogen metal salts to synthesize a cauliflower-shaped copper coordination polymer assembled by 1D nanowires at room temperature in one step.

[0016] (2) The cauliflower-shaped copper coordination polymer assembled by 1D nanowires in the present invention has anisotropy on the surface, can expose more active metal centers, and has a high aspect ratio and directional electron transfer, which is conducive to the rapid transfer of reaction molecules to the catalytic active center.

[0017] (3) The raw materials of the present invention are green and environmentally friendly, the preparation process is simple, it can be mass-produced, and the obtained copper coordination polymer is an environmentally friendly material and can be applied to different catalytic and environmental fields. Brief Description of the Drawings

[0018] Figure 1 SEM images of cauliflower-like copper coordination polymers synthesized with different molar amounts of Mn salts in Example 1;

[0019] Figure 2 XRD patterns of cauliflower-like copper coordination polymers synthesized with different molar amounts of Mn salts in Example 1;

[0020] Figure 3 Energy spectrum diagrams of cauliflower-like copper coordination polymers synthesized with 0.115 mmol MnCl₂ in Example 1;

[0021] Figure 4 Energy spectrum diagrams of cauliflower-like copper coordination polymers synthesized with 0.288 mmol MnCl₂ in Example 1;

[0022] Figure 5 Energy spectrum diagrams of cauliflower-like copper coordination polymers synthesized with 0.576 mmol MnCl₂ in Example 1;

[0023] Figure 6 SEM images of cauliflower-like copper coordination polymers synthesized in Example 2;

[0024] Figure 7 SEM images of cauliflower-like copper coordination polymers synthesized in Example 3;

[0025] Figure 8 SEM images of copper coordination polymers synthesized in Comparative Example 1;

[0026] Figure 9 SEM images of copper coordination polymers synthesized in Comparative Example 2;

[0027] Figure 10 Performance diagrams of copper coordination polymers prepared in Example 1 and Comparative Example 1 for degrading organic dyes. Detailed implementation manners

[0028] To make the content of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation manners, but the present invention is not limited thereto.

[0029] Preparation of manganese chloride - cauliflower-like copper coordination polymer in Example 1:

[0030] (1)0.058, 0.115, 0.288, 0.403, 0.489, 0.576, and 0.863 mmol of MnCl₂ were separately added to 0.7248 g (3 mmol) of Cu(NO₃)₂·3H₂O in 20 mL of DMF, and stirred at room temperature until completely dissolved to form a metal salt solution; 5.4 mmol of trimesic acid and 0.73 mmol of 4,4-bipyridine were separately dissolved in 20 mL of DMF, and stirred at room temperature until completely dissolved to obtain a trimesic acid solution and a 4,4-bipyridine solution;

[0031] (2)The trimesic acid solution was directly poured into the metal salt solution, stirred at 500 rpm at room temperature for 30 min, then the 4,4-bipyridine solution was poured in, and the reaction was continued to stir at 500 rpm at room temperature for 60 min;

[0032] (3)The obtained precipitate was washed three times with DMF and methanol respectively, centrifuged and then dried in a vacuum drying oven to obtain a manganese chloride-cauliflower-like copper coordination polymer.

[0033] Figure 1 Figure 1 is the SEM image of the cauliflower-like copper coordination polymers synthesized with different molar amounts of MnCl₂. It can be seen from the figure that after adding MnCl₂, the copper coordination polymer self-assembled from 1D nanowires into a cauliflower-like shape.

[0034] Figure 2 Figure 2 is the XRD pattern of the cauliflower-like copper coordination polymers synthesized with different molar amounts of MnCl₂. The figure shows that the amount of MnCl₂ salt used does not change the phase of the copper coordination polymer.

[0035] Figures 3 - 5 Figures 3-5 are the electron energy spectra of the cauliflower-like copper coordination polymers synthesized with 0.115, 0.288, and 0.576 mmol of MnCl₂ respectively. It can be seen from the figures that the Cu, C, N, O, and Cl elements in the obtained polymers are evenly distributed on the nanosheets, indicating that chloride ions are the key to regulating the morphology.

[0036] Example 2 Preparation of potassium chloride-cauliflower-like copper coordination polymer:

[0037] (1)1.126 mmol of KCl and 3 mmol of Cu(NO₃)₂·3H₂O were added to 20 mL of DMF, and stirred at room temperature until completely dissolved to form a metal salt solution; 5.4 mmol of trimesic acid and 0.73 mmol of 4,4-bipyridine were separately dissolved in 20 mL of DMF, and stirred at room temperature until completely dissolved to obtain a trimesic acid solution and a 4,4-bipyridine solution;

[0038] (2) Pour the trimesic acid solution directly into the metal salt solution, stir at room temperature at a speed of 500 rpm for 30 min, then pour in the 4,4'-bipyridine solution, and continue to stir and react at room temperature at a speed of 500 rpm for 60 min;

[0039] (3) Wash the obtained precipitate 3 times with DMF and methanol respectively, centrifuge and place it in a vacuum drying oven for drying to obtain a potassium chloride-cauliflower-like copper coordination polymer.

[0040] Example 3 Potassium bromide-cauliflower-like copper coordination polymer:

[0041] (1) Add 1.126 mmol of KBr and 3 mmol of Cu(NO3)2·3H2O to 20 mL of DMF, stir at room temperature until completely dissolved to form a metal salt solution; dissolve 5.4 mmol of trimesic acid and 0.73 mmol of 4,4'-bipyridine in 20 mL of DMF respectively, stir at room temperature until completely dissolved to obtain a trimesic acid solution and a 4,4'-bipyridine solution;

[0042] (2) Pour the trimesic acid solution directly into the metal salt solution, stir at room temperature at a speed of 500 rpm for 30 min, then pour in the 4,4'-bipyridine solution, and continue to stir and react at room temperature at a speed of 500 rpm for 60 min;

[0043] (3) Wash the obtained precipitate 3 times with DMF and methanol respectively, centrifuge and place it in a vacuum drying oven for drying to obtain a potassium bromide-cauliflower-like copper coordination polymer.

[0044] Figure 6 , 7 are the scanning electron microscope images of the cauliflower-like copper coordination polymers synthesized in Examples 2 and 3 respectively. As can be seen from the figure, the cauliflower-like structures synthesized using potassium chloride and potassium bromide are still composed of 1D nanowires self-assembled, which indicates that a certain amount of halogen ions can drive the self-assembly of copper coordination polymer nanowires to form cauliflower-like structures.

[0045] Comparative Example 1

[0046] (1) Add 1.151 mmol of MnCl2 and 3 mmol of Cu(NO3)2·3H2O to 20 mL of DMF, stir at room temperature until completely dissolved to form a metal salt solution; dissolve 5.4 mmol of trimesic acid and 0.73 mmol of 4,4'-bipyridine in 20 mL of DMF respectively, stir at room temperature until completely dissolved to obtain a trimesic acid solution and a 4,4'-bipyridine solution;

[0047] (2) Pour the trimesic acid solution directly into the metal salt solution, stir at room temperature at a speed of 500 rpm for 30 min, then pour in the 4,4-bipyridine solution, and continue to stir and react at room temperature at a speed of 500 rpm for 60 min;

[0048] (3) Wash the obtained precipitate 3 times with DMF and methanol respectively, centrifuge and wash, and then place it in a vacuum drying oven for drying to obtain a copper coordination polymer.

[0049] Comparative Example 2

[0050] (1) Add 3 mmol of Cu(NO3)2·3H2O to 20 mL of DMF, stir at room temperature until completely dissolved to form a metal salt solution; dissolve 5.4 mmol of trimesic acid and 0.73 mmol of 4,4-bipyridine in 20 mL of DMF respectively, stir at room temperature until completely dissolved to obtain a trimesic acid solution and a 4,4-bipyridine solution;

[0051] (2) Pour the trimesic acid solution directly into the metal salt solution, stir at room temperature at a speed of 500 rpm for 30 min, then pour in the 4,4-bipyridine solution, and continue to stir and react at room temperature at a speed of 500 rpm for 60 min;

[0052] (3) Wash the obtained precipitate 3 times with DMF and methanol respectively, centrifuge and wash, and then place it in a vacuum drying oven for drying to obtain a copper coordination polymer.

[0053] Figure 8 、 9 are the scanning electron microscope images of the copper coordination polymers synthesized in Comparative Examples 1 and 2 respectively. As can be seen from the figure, the polymers formed by adding too much or not adding halogen ions do not have a cauliflower-like morphology.

[0054] Performance Test

[0055] Disperse 20 mg of the sample prepared in Example 1 using 0.403 mmol of MnCl2 and the sample prepared in Comparative Example 1 into 50 mL of a solution containing 10 ppm of congo red and methylene blue respectively, and monitor the concentrations of congo red and methylene blue in the solution by liquid ultraviolet, and the results are shown in Figure 10 .

[0056] From Figure 10 it can be seen that compared with the copper coordination polymer nanowires, the cauliflower-like copper coordination polymer has better degradation activity for organic dyes.

[0057] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A one-step synthesis method of cauliflower-like copper coordination polymer by self-assembly of nanowires, characterized in that: It includes the following steps: (1) Add chloride salt or bromide salt into N,N-dimethylformamide containing copper metal precursor, and stir at room temperature until it is dissolved evenly to obtain a metal salt solution; (2) Dissolve trimesic acid and 4,4'-bipyridine into N,N-dimethylformamide with the same amount as that in step (1) respectively, and stir at room temperature until it is dissolved evenly to obtain a trimesic acid solution and a 4,4'-bipyridine solution; (3) Add the trimesic acid solution into the metal salt solution, stir for a period of time, then add the 4,4'-bipyridine solution, continue to stir and react at room temperature, and after washing and drying, a cauliflower-shaped copper coordination polymer self-assembled by nanowires is obtained; The chloride salt or bromide salt described in step (1) is specifically potassium salt, sodium salt or manganese salt, and its dosage is converted according to the molar ratio of Cl ion or Br ion to Cu ion in the copper metal precursor being (0.06-1.8):3; The copper metal precursor is specifically CuH6N2O9.

2. The one-step synthesis method of a cauliflower-shaped copper coordination polymer by self-assembly of nanowires according to claim 1, characterized in that: The dosages of the trimesic acid and 4,4'-bipyridine described in step (2) are converted according to the molar ratio of (5-5.5):(0.5-1):3 to the Cu ion in the copper metal precursor.

3. The one-step synthesis method of a cauliflower-like copper coordination polymer by self-assembly of nanowires according to claim 1, characterized in that: In step (3), after adding the trimesic acid solution, it needs to be stirred for 30 min, and after adding the 4,4'-bipyridine solution, it continues to be stirred for 30-90 min, and the stirring speed is 300-800 rpm.

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