CN111992185A - A kind of Cu-MOF and its modified adsorption material and preparation method - Google Patents

Abstract

The invention mainly relates to the technical field of metal-organic framework materials, and specifically discloses a Cu-MOF and its modified adsorption material and a preparation method. The preparation method of the modified Cu-MOF is as follows: placing the Cu-MOF in a solution containing Fe ³⁺ and Fe ²⁺ , and modifying the Cu-MOF to obtain the modified Cu-MOF; the modified Cu-MOF is obtained; -MOF specific surface area≥150.85m ² /g; the maximum adsorption amount of As(III) by the modified Cu-MOF prepared by the present invention is 66.12mg/g, which shows excellent adsorption performance of heavy metal ions.

Description

A kind of Cu-MOF and its modified adsorption material and preparation method

technical field

The invention mainly relates to the technical field of metal-organic framework materials, in particular to a Cu-MOF and its modified adsorption material and preparation method.

Background technique

Heavy metal pollution is an unavoidable environmental problem in the current industrial development process. Heavy metals are not biodegradable and have bioaccumulation. Even if the concentration is low, their toxicity is also very high, which has irreversible harm to the ecological environment. The Minamata disease incident in Japan, the Osteopathy incident and the Shimen arsenic contamination incident all sounded the alarm for us.

Metal-organic frameworks (MOFs) are a newly emerging heavy metal ion adsorption material. Since Kitagawa's research group first reported the adsorption properties of MOF materials in 1997, a large number of coordination polymers have been studied as porous adsorption materials. Due to the different surface structures of MOFs, their ability to remove heavy metal ions is also different. Therefore, MOFs are usually modified to increase the specific surface area, increase the effective functional groups, enhance the hydrophobic/hydrophilic properties and surface charge, thereby improving their adsorption capacity for heavy metal ions.

Among the heavy metal ions, the pollution situation of As(III) is particularly severe. Although there are related papers reported in the prior art, the adsorption effect of this type of MOF adsorption materials for As(III) is relatively limited, such as Zheng X. The maximum adsorption capacity of As is 33.91 mg/g by GUT-3, the maximum adsorption capacity of As by Li Z.-Q. is 24.83 mg/g by MOF-808, and the maximum adsorption capacity of As by VuT. MIL-53(Fe) is 21.3 mg/g, so it is an urgent need to prepare a MOF material with excellent adsorption performance for heavy metal ions; such as a patent (CN111004398A) a microporous Cu-MOF material and its preparation method and application, which discloses a Cu-MOF material -MOF material, its chemical formula is CuTIPA·n(DMF) (n=1-3), wherein TIPA2- is 5-(triazol-1-yl)isophthalate anion, DMF is N,N-dimethyl formamide, but the microporous Cu-MOF material has limited adsorption capacity for heavy metals in liquid.

SUMMARY OF THE INVENTION

1. The problem to be solved

The object of the present invention is to provide a kind of Cu-MOF and its modified adsorption material and preparation method in view of the technical problems of small specific surface area of MOF material and poor adsorption effect on heavy metal ions in the prior art. , in order to achieve better adsorption effect of heavy metal ions. The maximum adsorption capacity of the modified Cu-MOF of the present invention for As(III) is 66.12 mg/g, which is higher than that of the MOF materials that have been developed so far. For example, the maximum adsorption capacity of GUT-3 is 33.91 mg/g. The maximum adsorption capacity of -808 is 24.83mg/g, and the maximum adsorption capacity of MIL-53(Fe) is 21.3mg/g.

2. Technical solutions

The invention provides a method for preparing a modified Cu-MOF adsorption material, which specifically includes placing Cu-MOF in a solution containing Fe ³⁺ and Fe ²⁺ to modify the Cu-MOF to obtain a modified Cu-MOF. MOF; the specific surface area of the modified Cu-MOF is ≥150.85 m ² /g. The modification of Cu-MOF materials by Fe ³⁺ and Fe ²⁺ is mainly to load Fe ³⁺ and Fe ²⁺ and S on the Cu-MOF material at the same time, thereby greatly improving the specific surface area and adsorption performance of the material .

Preferably, the ligand of the Cu-MOF used is 5-bromosalicylaldehyde 4-amino-1,2,4-triazole.

Preferably, its specific steps are:

Step 1: Prepare a solution containing Fe ³⁺ and Fe ²⁺ , add Cu-MOF into the solution for stirring, and load the two ions on the material;

Step 2, adding an alkaline reagent to the system obtained in step 1, and adjusting the pH of the solution to 10-11, so that two kinds of iron ions form Fe(OH) ₂ and Fe(OH) ₃ and are loaded on the material;

Step 3, adding NH ₄ Cl solution to the system obtained in step 2; stirring the system;

In step 4, the system obtained in step 3 is sequentially filtered, washed and dried to obtain a modified Cu-MOF adsorption material.

Preferably, the solution containing Fe ³⁺ and Fe ²⁺ in step 1 includes one or more of sulfate, nitrate, chloride and perchlorate;

And/or the alkaline reagent in step 2 is one or more of alkaline solution, strong base and weak acid salt solution.

Preferably, in step 1, the stirring temperature is 45-65° C., and the stirring time is 20-40 min;

And/or in step 3, the stirring temperature is 70-90°C, and the stirring time is 1.5-2.5h;

And/or the drying temperature in step 4 is 50-60°C.

Preferably, its detailed steps are:

Add 25.00-50.00mL of 0.3-0.5mol/L ferric sulfate solution and 100-200mL of 0.04-0.08mol/L ferrous sulfate solution to the beaker containing 10.00-20.00g of the Cu-MOF, 45-65°C After stirring for 20-40min, add 8-12mol/L sodium hydroxide solution, adjust the pH of the solution to be between 10-11, then add 0.04-0.06mol/L ammonium chloride solution 200-400mL, 70- Stir at 90°C for 1.5-2.5h, then filter and wash the precipitate until neutral, and dry at 50-60°C to obtain the modified Cu-MOF adsorption material.

The present invention also provides the modified Cu-MOF adsorption material prepared by any of the aforementioned preparation methods.

The invention also provides a preparation method of the Cu-MOF before modification: dissolving 5-bromosalicylaldehyde 4-amino-1,2,4-triazole ligand and copper ion salt in a solvent, and carrying out The Cu-MOF was prepared by heating.

Preferably, its detailed steps are:

Weigh 0.15-0.30g of 5-bromosalicylaldehyde acetal 4-amino-1,2,4-triazole ligand and 0.121-0.242g of copper nitrate trihydrate and place them in a reaction flask, add 3-6mL of DMF and 3-6mL of secondary distilled water were stirred for 10-20min, then the reaction flask was tightened and then placed in an oven at 80-100°C for 24-48h to obtain dark green needle-like crystals, which were filtered. The Cu-MOF is obtained by washing with distilled water and drying.

The present invention also provides the Cu-MOF prepared by any of the aforementioned preparation methods, and its main coordination mode is:

The Cu-MOF is composed of seven Cu atoms, four deprotonated 5-bromosalicylaldehyde 4-amino-1,2,4-triazole ligands and six water molecules. Cu1 coordinates with N3, N4, N7 from three ligands and O2, O3 from two water molecules, forming a four-coordinate planar configuration. The coordination environment of Cu3 and Cu3a is the same as that of Cu1. Cu2 coordinates with O1, O1a, N1, and N1a from two ligands, forming a five-coordinated tetragonal pyramid configuration. The coordination environment of Cu2a, Cu4 and Cu4a is the same as that of Cu2.

3. Beneficial effects

Compared with the prior art, the beneficial effects of the present invention are:

(1) In a modified Cu-MOF adsorption material of the present invention, Fe ³⁺ and Fe ²⁺ are used to dope the Cu-MOF material, so that Fe ³⁺ and Fe ²⁺ can be loaded on the surface of the material in the form of ions, It is beneficial to expand the specific surface area of Cu-MOF materials, and at the same time, it is easier to form complexes with heavy metal ions to achieve the effect of removing heavy metal ions. The adsorption capacity is 66.12mg/g, which is higher than the adsorption capacity of MOF materials that have been developed so far. ) The maximum adsorption capacity is 21.3 mg/g.

(2) A modified Cu-MOF adsorption material of the present invention, which uses 5-bromosalicylaldehyde acetal 4-amino-1,2,4-triazole as a ligand, on the one hand, can form a pore size of about 11.93 The nanometer spatial network structure provides a certain structural basis for the subsequent loading of Fe ³⁺ and Fe ²⁺ , thereby realizing the preparation of modified Cu-MOF adsorbents with high specific surface area. The surface area is increased from 7.16m ² /g to 150.85m ² /g; on the other hand, the bromine element it contains can replace the heavy metal ion As(III), and its substitution rate after modification by Fe ³⁺ and Fe ²⁺ It can reach 71.3%, showing excellent adsorption performance of heavy metal ions.

(3) The preparation method of a modified Cu-MOF adsorption material of the present invention has the advantages of simple process, low cost, easy control of chemical components, good repeatability and high yield.

Description of drawings

FIG. 1 is an application diagram of the modified Cu-MOF adsorption and removal of As(III) of the present invention.

Fig. 2 is the SEM scanning electron microscope images of the Cu-MOF (left) of the present invention, the modified Cu-MOF (middle) and the modified Cu-MOF with adsorbed As(III) (right)

Figure 3 shows the EDS spectra of the Cu-MOF of the present invention (left), the modified Cu-MOF (middle), and the modified Cu-MOF with adsorbed As(III) (right).

Figure 4 shows the XPS full spectrum and As(III) fine spectrum before and after the modified Cu-MOF of the present invention adsorbs As(III).

Figure 5 shows the adsorption rates of As(III) by modified Cu-MOF, Cu-MOF and Cu-MOF-2 at different pH values.

Detailed ways

Example 1

The present embodiment provides a preparation method of a Cu-MOF material, specifically:

Weigh 0.20g of 5-bromosalicylaldehyde acetal 4-amino-1,2,4-triazole ligand and 0.16g of copper nitrate trihydrate, put them in a 20mL micro-reaction flask, add 5mL DMF and 4mL secondary Stir in distilled water for 10 min, tighten the cap of the reaction flask and put it in an 80°C oven for 24 hours to obtain dark green needle-like crystals, which are filtered, washed with distilled water, and dried to obtain the Cu-MOF.

This embodiment also provides a Cu-MOF prepared by the above-mentioned preparation method, and the pore diameter of the Cu-MOF is about 11.93 nm, which is obtained by detecting its XRD pattern and calculating.

The present embodiment provides a preparation method of a modified Cu-MOF adsorption material, specifically:

Add 30.00mL of 0.4mol/L ferric sulfate solution and 150mL of 0.06mol/L ferrous sulfate solution to the beaker containing 15.00g of the Cu-MOF, stir at 55°C for 30min, add 10mol/L of hydrogen Sodium oxide solution was adjusted to pH 11, then 300 mL of 0.05 mol/L ammonium chloride solution was added, stirred at 80 °C for 2 h, the precipitate was filtered and washed until neutral, and dried at 60 °C to obtain The modified Cu-MOF adsorption material.

This embodiment also provides a modified Cu-MOF adsorption material prepared by the above-mentioned preparation method.

In order to explore the maximum adsorption capacity of modified Cu-MOF for As(III), different initial concentrations of arsenic ions were set in this example, as shown in Figure 1. The study shows that modified Cu-MOF has excellent adsorption capacity for As(III). Adsorption performance, its maximum adsorption capacity is 66.12mg/g, which is higher than that of MOF materials that have been developed so far. The maximum adsorption capacity of MIL-53(Fe) is 21.3mg/g.

Comparative Example 1

This comparative example provides a preparation method of a Cu-MOF material, and the specific preparation method is the same as that of the first embodiment.

This comparative example also provides a Cu-MOF prepared by the above-mentioned preparation method. The difference from Example 1 is that the Cu-MOF is not subjected to subsequent modification treatment, but the Cu-MOF is directly subjected to various treatments. item performance test.

The present invention uses BET method to detect the specific surface area of Cu-MOF (Comparative Example 1) and modified Cu-MOF (Example 1). The specific data are shown in Table 1. It can be seen that the specific surface area of Cu-MOF before modification is 7.16 m ² /g, while the specific surface area of the modified Cu-MOF material is 150.85 m ² /g, the specific surface area of the modified Cu-MOF material is 20 times higher than that of the Cu-MOF material, which is more conducive to the adsorption and removal of heavy metal ions.

In order to compare the changes of the surface morphology of the Cu-MOF before and after modification and the adsorption of As(III) of the modified Cu-MOF, the present invention uses a JMS-7900 scanning electron microscope to analyze the Cu-MOF before modification ( Comparative Example 1), modified Cu-MOF (Example 1), and the modified Cu-MOF material after adsorbing As(III) were analyzed by SEM, EDS and XPS, and the results are shown in Figures 2, 3, and 4:

From the SEM images in Figure 2, it can be seen that the surface morphology of the material before and after modification has changed significantly. After the modification of the Cu-MOF before modification, the smooth surface becomes wrinkled and rough and porous. Such a porous structure is The adsorption of As(III) provides a certain structural basis, and the surface of the modified Cu-MOF material after adsorption of As(III) becomes smoother, which may be due to the adsorption of As(III) on the pores and rough surfaces, Thereby reducing the roughness of the material;

From the EDS analysis in Figure 3, it can be seen that the modified Cu-MOF has significantly more Fe, S, and Cl elements than the Cu-MOF, which proves that the modification successfully loads the Fe, S, and Cl elements into the Cu-MOF. On the surface of the material, the modified Cu-MOF material after adsorption of As(III) has significantly more As elements than before modification, which proves that As(III) is successfully adsorbed into the modified Cu-MOF material. ;

Similar results to EDS can be seen from the XPS analysis in Fig. 4, Cu 2p, C 1s, N 1s, O 1s, Br 3d appear in the XPS broad scan spectrum of the Cu-MOF before modification; the modified Cu- Fe 2p, Cl 2p and S2p peaks were added in the XPS broad scan spectrum of MOF; As(Ⅲ) was added to the modified Cu-MOFXPS broad scan spectrum after adsorption of As(Ⅲ), which confirmed that As(Ⅲ) was adsorbed onto the modified Cu-MOF.

Comparative Example 2

This comparative example provides a preparation method of a Cu-MOF material, and its specific preparation method is basically the same as that of the first embodiment, and the difference is:

The synthesized Cu-MOF was immersed in a ferrous ammonium sulfate solution with a concentration of 0.14 mol/L, and the ratio of Cu-MOF to ferrous ammonium sulfate was 5:4. After ultrasonication at room temperature for 20 min, the precipitate was taken out and filtered. And washed until neutral, and dried at 60 °C to obtain the sample Cu-MOF-2.

The present comparative example also provides a Cu-MOF prepared by the aforementioned preparation method.

In order to verify the excellent adsorption performance of the two iron ion-modified Cu-MOFs of the present invention, the modified Cu-MOF (Example 1) and unmodified Cu-MOF prepared by the two iron ion modification were compared respectively. (Comparative example 1) and ferrous ion modified Cu-MOF-2 (comparative example 2) for the adsorption rate of As(III) at different pH values, the specific test method is: set a solution containing As(III) The initial concentration is 10mg/L, the dosage of the selected adsorbent is 0.1g/25mL, the adsorption temperature is T=25℃, the adsorption time is t=24h, the rotating speed of the shaking table is 180r/min, and the pH of the solution is adjusted with HCl and NaOH solutions. value, and the results are shown in Figure 5.

It can be seen from Figure 5 that the adsorption rate of As(III) to As(III) of the modified Cu-MOFs prepared by the modification of two kinds of iron ions in the pH range of 3-11 is basically maintained above 95%, which is far The adsorption rate of As(III) is higher than that of the unmodified Cu-MOF and the Cu-MOF-2 prepared by ferrous ion modification, which indicates that the adsorption effect of the two ferrous modified Cu-MOF materials is better than The Cu-MOF material before modification is better than the single Fe ²⁺ modified Cu-MOF-2 material;

At the same time, it can also be seen that the modified Cu-MOF material has a significant increase in the adsorption rate of As(III) in the pH range of 3-10, and the highest value is reached when the pH reaches 11. When the pH value exceeds 11, the modified Cu-MOF material The adsorption capacity of -MOF gradually decreased, so the pH range of the modified Cu-MOF material for the effective adsorption of As(III) was 3-11, and the adsorption performance was optimal when the pH was 11.

In addition, it can be seen from the EDS analysis of the present invention that the percentage of Br after adsorption is significantly reduced, which may be due to the substitution of Br by As(III). The substitution rate of As for Br in -MOF is as high as 71.3%, which is much higher than that of Cu-MOF and Cu-MOF-2 before modification, showing excellent As(III) adsorption performance.

Table 1 Effect comparison table

Example 1 Comparative Example 1 Comparative Example 2 Types of adsorption materials Modified Cu-MOF Cu-MOF Cu-MOF-2 Specific surface area (m²/g) 150.85 7.16 — The substitution rate of As to Br 71.3% 23.0% 39.8%

The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the present invention as defined by the appended claims. The detailed description and drawings are to be regarded in an illustrative rather than a restrictive sense, and if any such modifications and variations exist, they will fall within the scope of the invention described herein. In addition, the background art is intended to illustrate the research and development status and significance of the present technology, and is not intended to limit the present invention or the application and application fields of the present invention.

More particularly, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments, but includes modifications, omissions, Any and all embodiments of combinations, adaptations, and/or substitutions (eg, among the various embodiments), and combinations between the various embodiments of the present invention may be made as desired. The definitions in the claims are to be construed broadly according to the language used in the claims, and are not limited to the examples described in the foregoing detailed description or during the practice of this application, which examples are to be considered non-exclusive. Any steps recited in any method or process claims may be performed in any order and are not limited to the order presented in the claims. Accordingly, the scope of the invention should be determined only by the appended claims and their legal equivalents, rather than by the description and examples given above.

Claims (10)

1. a preparation method of modified Cu-MOF adsorbent material, it is characterized in that, Cu-MOF is placed in the solution containing Fe ³⁺ and Fe ²⁺ , and Cu-MOF is modified to obtain modified Cu-MOF -MOF; the specific surface area of the modified Cu-MOF is ≥150.85 m ² /g. 2. the preparation method of a kind of modified Cu-MOF adsorbent material according to claim 1, is characterized in that, the ligand of used Cu-MOF is 5-bromosalicylaldehyde acetal 4-amino-1,2, 4-Triazole. 3. the preparation method of a kind of modified Cu-MOF adsorbent material according to claim 1, is characterized in that, its concrete steps are: Step 1: Prepare a solution containing Fe ³⁺ and Fe ²⁺ , add Cu-MOF into the solution for stirring, and load the two ions on the material; Step 2, adding an alkaline reagent to the system obtained in step 1, and adjusting the pH of the solution to 10-11, so that two kinds of iron ions form Fe(OH) ₂ and Fe(OH) ₃ and are loaded on the material; Step 3, adding NH ₄ Cl solution to the system obtained in step 2; stirring the system; In step 4, the system obtained in step 3 is sequentially filtered, washed and dried to obtain a modified Cu-MOF adsorption material. 4. the preparation method of a kind of modified Cu-MOF adsorption material according to claim 3, is characterized in that, the solution containing Fe ³⁺ and Fe ²⁺ described in step 1 comprises sulfate, nitrate, chlorine One or more of salt and perchlorate; And/or the alkaline reagent in step 2 is one or more of alkaline solution, strong base and weak acid salt solution. 5. the preparation method of a kind of modified Cu-MOF adsorption material according to claim 3, is characterized in that, in step 1, stirring temperature is 45-65 ℃, and stirring time is 20-40min; And/or in step 3, the stirring temperature is 70-90°C, and the stirring time is 1.5-2.5h; And/or the drying temperature in step 4 is 50-60°C. 6. The preparation method of a modified Cu-MOF adsorbent material according to any one of claims 1-5, wherein 25.00-50.00 g of Cu-MOF is added to the beaker containing 10.00-20.00 g of the Cu-MOF. mL of 0.3-0.5mol/L ferric sulfate solution and 100-200mL of 0.04-0.08mol/L ferrous sulfate solution, stir at 45-65°C for 20-40min, add 8-12mol/L sodium hydroxide solution, Adjust the pH of the solution to 10-11, then add 200-400 mL of 0.04-0.06 mol/L ammonium chloride solution, stir at 70-90 ° C for 1.5-2.5 h, and then filter and wash the precipitate until neutral , and drying at 50-60° C. to obtain the modified Cu-MOF adsorption material. 7. A modified Cu-MOF adsorption material, characterized in that, the modified Cu-MOF adsorption material prepared by any one of the preparation methods of claims 1-6. 8. the preparation method of a kind of modified Cu-MOF adsorbent material according to claim 1, is characterized in that, the preparation method of Cu-MOF before modification is: 5-bromosalicylaldehyde acetal 4-amino-1 , 2,4-Triazole ligand and copper ion salt are dissolved in a solvent and heated to prepare Cu-MOF. 9. the preparation method of a kind of modified Cu-MOF adsorption material according to claim 8, take by weighing 0.15-0.30g of 5-bromosalicylaldehyde acetal 4-amino-1,2,4-triazole compound. body and 0.121-0.242g of copper nitrate trihydrate and placed in the reaction flask, add 3-6mL of DMF and 3-6mL of double distilled water and stir for 10-20min, tighten the cap of the reaction flask and put it in an oven at 80-100℃ After standing for 24-48 hours, dark green needle-like crystals are obtained, and the dark-green needle-like crystals are filtered, washed with distilled water, and dried to obtain the Cu-MOF. 10. A Cu-MOF, characterized by the Cu-MOF obtained by the preparation method of any one of claims 8-9.

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