Preparation method and application of sulfydryl functionalized metal organic framework

Abstract

The invention belongs to the field of material synthesis, and particularly relates to a preparation method and application of a sulfydryl functionalized metal organic framework, the preparation method comprises the following steps: mixing a metal organic framework ZIF-8, cetyltrimethylammonium bromide, ethanol and ammonia water, stirring for 15-30 minutes, adding deionized water, tetraethoxysilane and 3-mercaptopropyltrimethoxysilane, continuously stirring for reaction for 6-8 hours, filtering, washing and drying to obtain the sulfydryl functionalized metal organic framework. And centrifuging, filtering, washing, centrifuging and filtering to obtain a head product, adding the head product into an ethanol solution of hydrochloric acid, reacting for 4-6 hours at the temperature of 80 DEG C, centrifuging, filtering, washing, centrifuging, filtering, drying and grinding to obtain the sulfydryl functionalized metal organic framework. The ZIF-8 is subjected to sulfydryl functionalization by adopting 3-mercaptopropyltrimethoxysilane, so that the utilization rate of active sites is effectively improved, the structure of a metal organic framework is not influenced, divalent cadmium ions can be quickly adsorbed within a short time, and an excellent photocatalytic degradation effect on organic dyes is also achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of material synthesis, and in particular relates to a preparation method and application of a mercapto-functionalized metal organic framework. Background Art

[0002] ZIF-8 (zeolitic imidazolate framework-8) is a porous crystalline material formed by the self-assembly of Zn(II) and 2-methylimidazole. It shows great potential in the adsorption of heavy metal ions due to its high specific surface area, ordered pore structure, high crystallinity, multiple metal sites, thermal stability and chemical stability. There are some limitations in the practical application of ZIF-8, such as low utilization of active sites, slow adsorption kinetics and poor reusability, which restrict its industrial application. Typical treatment technologies for cadmium-containing wastewater include precipitation, adsorption, ion exchange and membrane separation. Adsorption technology is favored by other methods because of its high feasibility and relatively low cost, especially for contaminated water with high heavy metal concentrations. The water body can meet the national emission standards only after being treated with appropriate adsorbents.

[0003] ZIF-8 has limited adsorption or degradation effects on heavy metal ions, and ZIF-8 usually needs to be modified. Current research focuses on developing new ZIF-8 composite materials, optimizing adsorption conditions, reducing costs, and improving the recyclability of materials. For example, by using poly(p-styrene sulfonate) (PSS) to modify ZIF-8, the adsorption rate of the modified ZIF-8@PSS increased by dozens of times compared with the original ZIF-8, and the adsorption capacity increased by 1.6 times. The addition of PSS improves the agglomeration problem of ZIF-8 nanomaterials, fully exposing its active sites, thereby effectively improving the adsorption capacity. At the same time, PSS carries a large amount of negative charge, which makes ZIF-8 change from hydrophobic to hydrophilic, enhances the diffusion transfer of metal ions to ZIF-8, and the negatively charged PSS has an electrostatic attraction to positively charged metal ions. Although this modification of the ZIF-8 surface greatly improves its adsorption performance, it is far from enough to remove the efficiency of heavy metal ions in wastewater and improve the surface coordination sites.

[0004] Based on this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a preparation method of a thiol-functionalized metal organic framework and its application to solve the above-mentioned problems.

[0006] In a first aspect, a method for preparing a thiol-functionalized metal organic framework comprises the following steps:

[0007] The metal organic framework ZIF-8, hexadecyltrimethylammonium bromide, ethanol and ammonia water are mixed and stirred for 15 to 30 minutes, deionized water, tetraethyl orthosilicate and 3-mercaptopropyltrimethoxysilane are added, and the reaction is continued to be stirred for 6 to 8 hours, centrifuged, filtered, washed, centrifuged and filtered to obtain a primary product, and the primary product is added to an ethanol solution of hydrochloric acid, reacted at a temperature of 80°C for 4 to 6 hours, centrifuged, filtered, washed, centrifuged, filtered, dried and ground to obtain a thiol-functionalized metal organic framework.

[0008] As a further improvement, the metal organic framework ZIF-8 is obtained by stirring 2-methylimidazole and zinc acetate in methanol for 24 to 36 hours.

[0009] In a further improvement, the mass ratio of the 2-methylimidazole, zinc acetate and methanol is (3.2-3.3):(1.8-1.9):(7-7.2).

[0010] As a further improvement, the mass ratio of the metal organic framework ZIF-8, hexadecyltrimethylammonium bromide, ethanol, ammonia water, deionized water, ethyl orthosilicate, 3-mercaptopropyltrimethoxysilane, and ethanol solution of hydrochloric acid is 1:0.6:(110-111):2:140:(6.5-6.6):3.7:8.4.

[0011] In a further improvement, the mass fraction of the aqueous ammonia is 25%.

[0012] As a further improvement, the ethanol solution of hydrochloric acid is composed of a mixture of hydrochloric acid and ethanol aqueous solution, the volume ratio of the hydrochloric acid to the ethanol aqueous solution is 1:9, the mass fraction of the hydrochloric acid is 36%, and the mass fraction of the ethanol aqueous solution is 95%.

[0013] In a second aspect, a thiol-functionalized metal organic framework is prepared by the preparation method of the thiol-functionalized metal organic framework.

[0014] The third aspect is the application of the thiol-functionalized metal organic framework.

[0015] Further improvements are applied to remove divalent cadmium ions from water.

[0016] Further improvements are applied to the removal of organic dyes from water.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention uses 3-mercaptopropyltrimethoxysilane to functionalize ZIF-8 with mercapto groups, which effectively improves the utilization rate of active sites and does not affect the structure of the metal organic framework itself, and can quickly adsorb divalent cadmium ions in a short time. The mercapto-functionalized ZIF-8 can form a stable complex with heavy metal ions.

[0019] 2. The synthesized thiol-functionalized metal-organic framework ZIF-8-SH also has excellent photocatalytic degradation effect on organic dyes, thereby broadening its application range.

[0020] 3. The preparation method of the present invention has the advantages of short synthesis time, simple operation and strong economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the XRD spectra of ZIF-8 obtained in Example 1 and ZIF-8-SH obtained in Example 2;

[0022] Figure 2 is a scanning electron micrograph of ZIF-8;

[0023] Figure 3 is a scanning electron micrograph of ZIF-8-SH;

[0024] Figure 4 It is a graph of the absorbance change of divalent cadmium ion solutions with different concentrations using an ultraviolet spectrophotometer;

[0025] Figure 5 It is the fitting curve diagram between the concentration of cadmium ions and absorbance;

[0026] Figure 6 This is the removal rate change diagram of ZIF-8 for divalent cadmium ion solution with concentrations of 10 mg / L and 15 mg / L;

[0027] Figure 7 This is the removal rate change diagram of ZIF-8-SH for divalent cadmium ion solution with concentrations of 10 mg / L and 15 mg / L;

[0028] Figure 8 It is a comparison chart of the removal efficiency of Cd(II), Cu, and Hg using ZIF-8-SH;

[0029] Fig. 9 This is a comparison chart of the removal rate of Cd(II) heavy metal ions after introducing different thiol functional groups on the surface of ZIF-8;

[0030] Fig.10 This is a comparison chart of the removal rates of organic dyes using ZIF-8-SH and ZIF-8;

[0031] Fig.11This is the change diagram of the removal rate of cadmium (II) ions when the dosage of ZIF-8-SH is 5 mg and 10 mg;

[0032] Fig.12 This is the change diagram of the removal rate of cadmium (II) ions when the dosage of ZIF-8-SH is 10 mg and 20 mg;

[0033] Fig.13 This is a comparison chart of the effects of different pH values ​​on the removal of divalent cadmium ions by ZIF-8 and ZIF-8-SH. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0035] Example 1

[0036] Preparation of Metal-Organic Framework ZIF-8

[0037] 3.2837 g of 2-methylimidazole and 1.8353 g of zinc acetate were placed in 7.155 g of methanol, mixed and stirred at room temperature for 24 hours, and centrifuged using a high-speed centrifuge to obtain a first filter residue. The first filter residue was washed with deionized water and methanol solution, and the centrifugation operation was repeated to obtain a second filter residue. The second filter residue was sent to a vacuum drying oven for drying. The temperature in the vacuum drying oven was set to 70°C and the vacuum degree was set to -0.1 to -0.07 MPa. After drying for 24 hours, the metal organic framework ZIF-8 was obtained.

[0038] Example 2

[0039] Surface modification of metal organic framework ZIF-8 with 3-mercaptopropyltrimethoxysilane

[0040] 1 g of the prepared metal organic framework ZIF-8 (ZIF-8 for short) was added to a mixed solution containing 0.6 g of hexadecyltrimethylammonium bromide, 140 mL of anhydrous ethanol (110.46 g) and 2.2 mL of ammonia water (mass fraction 25%). After magnetic stirring for 15 min, 140 mL of deionized water, 6.531 g of ethyl orthosilicate, and 3.699 g of 3-mercaptopropyltrimethoxysilane, stirring is continued for 6 hours, and then centrifugal filtration is performed to obtain a third filter residue. After the third filter residue is washed with deionized water and ethanol solution, centrifugal filtration is continued to obtain a fourth filter residue. The fourth filter residue is added to 8.39g of hydrochloric acid ethanol solution (the volume ratio of hydrochloric acid and ethanol aqueous solution is 1:9, the mass fraction of hydrochloric acid is 36%, and the mass fraction of ethanol aqueous solution is 95%), and the reaction is carried out in an 80°C oil bath for 4 to 6 hours. The material obtained after the oil bath is centrifuged to obtain a fifth filter residue. After the fifth filter residue is washed with deionized water and ethanol solution, centrifugal filtration is continued to obtain a sixth filter residue. After the sixth filter residue is vacuum dried for 12 hours at a temperature of 85°C and a vacuum degree of -0.1 to -0.07MPa, it is taken out and ground to obtain a thiol-functionalized metal organic framework ZIF-8-SH (abbreviated as ZIF-8-SH).

[0041] Figure 1 The XRD spectra of ZIF-8 obtained in Example 1 and ZIF-8-SH obtained in Example 2 are shown in Figure 1. After ZIF-8 is functionalized with thiol groups, the main diffraction peaks can be aligned with the previous peaks, indicating that the thiol functional groups have not changed their structure, which is as expected. The thiol method used in the present invention only allows thiol groups to attach to its surface, thereby improving its ability to adsorb heavy metal ions.

[0042] Figure 2 This is a scanning electron microscope image of ZIF-8. It can be seen from the image that the ZIF-8 particles are regular dodecahedrons, the particle size is very uniform, and the dispersion between particles is good. Figure 3 The ZIF-8-SH particles in the sample are widely distributed, and their surfaces are completely covered by thiol groups, forming a tight shell, which greatly increases the contact area of ​​the surface and facilitates the subsequent adsorption of cadmium (II) ions.

[0043] Example 3

[0044] Adsorption of cadmium (II) ions by ZIF-8 and ZIF-8-SH

[0045] Deionized water was added to the standard cadmium (II) ion solution (concentration 100 mg / L) to dilute it, and divalent cadmium ion solutions with different concentration gradients of 5, 10, 15, 20, 25, and 30 mg / L were obtained, and tested by ultraviolet spectrophotometer. Figure 4This is a graph of the absorbance change of different concentrations of divalent cadmium ion solutions by ultraviolet spectrophotometer. In order to clearly and intuitively reflect whether the change of cadmium ion concentration can be expressed by ultraviolet spectrophotometer, and also to eliminate errors, a fitting curve between the concentration and absorbance of cadmium ions was fitted, as shown in the figure below: Figure 5 As shown, Figure 5 Medium R 2 The absorbance is close to 1, indicating that the absorbance can be used to represent the changing trend of cadmium ion concentration.

[0046] When the dosage is 10 mg, the removal rate of ZIF-8 for divalent cadmium ion solution with concentrations of 10 mg / L and 15 mg / L is shown in Figure 6 The removal rate of ZIF-8-SH for divalent cadmium ion solution with concentrations of 10 mg / L and 15 mg / L is shown in Figure 7 .

[0047] pass Figure 6 , 7 It can be seen that both ZIF-8 and ZIF-8-SH can be adsorbed and reached dynamic equilibrium after 10 minutes. It is obvious that after the thiol functionalization of ZIF-8, its adsorption performance has been significantly improved. When the concentration of divalent cadmium ion solution is 10 mg / L, the removal rate of ZIF-8 reaches 82.96%, while the removal rate of ZIF-8-SH has reached 98.88% in 20 minutes, which basically completely adsorbs the cadmium ions. The ability to achieve this adsorption effect mainly depends on the thiol group. Since the coordination bonds of ZIF-8 itself are not rich enough, the coordination bonds are formed between the hydrogen bonds on the thiol group and the cadmium ions, increasing the coordination sites on the surface of ZIF-8, thereby achieving an ideal adsorption effect.

[0048] Example 4

[0049] Adsorption of cadmium (II), Cu and Hg ions by ZIF-8-SH

[0050] Take a 10 mg / L divalent cadmium ion solution, a copper ion solution, and a mercury ion solution, and add ZIF-8-SH (the amount added is 10 mg). The removal rate of ZIF-8-SH for Cd(II), Cu, and Hg ions is shown in Figure 8 .exist Figure 8 In the results, when the adsorption equilibrium was reached, the removal rate of Cd(II) by ZIF-8-SH reached 99%, while the removal rates of Cu and Hg were only 69% and 70% respectively, indicating that ZIF-8-SH had a better removal effect on Cd(II), and the thiol groups on the surface had a certain selectivity for the adsorption of different metal ions.

[0051] Example 5

[0052] Thioglycolic acid and lipoic acid functional groups thiolate ZIF-8 and adsorb cadmium (II) ions

[0053] 100 mg zirconium tetrachloride (ZrCl4), 10 mg ZIF-8 and 340 μL thioglycolic acid (MAA) were dissolved in 3 mL N, N dimethylformamide (DMF), and the mixture was placed in an oven at 120°C for 24 h. After cooling to room temperature, centrifugation was performed, and then washed three times with DMF and methanol respectively, and dried in vacuum at 120°C to obtain ZIF-8-MAA.

[0054] 50 mg zirconium tetrachloride (ZrC14), 10 mg ZIF-8 and 500 mg lipoic acid (ALA) were dissolved in 3 mL DMF, and the mixture was placed in an oven at 120°C for 24 h. After cooling to room temperature, the mixture was centrifuged, washed three times with DMF and methanol respectively, and dried under vacuum at 120°C to obtain ZIF-8-ALA.

[0055] Fig. 9 It is a diagram showing the changes in the adsorption of cadmium (II) ions after the introduction of different thiol functional groups. As shown in FIG9 , the removal rate of ZIF-8 after thiol functionalization with 3-mercaptopropyltrimethoxysilane is 98.99%, while the removal rates of ZIF-8 after thiol functionalization with two thiol groups, thioglycolic acid and thioctic acid, are only 71.23% and 64.83% respectively. The comparison further illustrates that the ZIF-8-SH of the present invention has better adsorption performance for cadmium (II) ions.

[0056] Example 6

[0057] Photocatalytic degradation of organic dyes by ZIF-8 and ZIF-8-SH

[0058] First, a certain concentration of organic dye solution was prepared, and a rhodamine B solution, a malachite green solution, and a methylene blue solution with a concentration of 10 mg / L were selected. 20 mg of ZIF-8-SH was added to 50 mL of the above three organic dye solutions. In order to be evenly dispersed, ultrasonic oscillation was performed for 30 minutes under luminescence conditions. Afterwards, a xenon lamp with a power of 300 W was used to simulate a solar light source, which was arranged at a position 30 cm away from the reaction vessel (with a wavelength of 735 W / m 2 The irradiation intensity was 2000 nm (0.17 W) for photodegradation experiment. During the 90-minute light reaction time, samples were collected from the reaction system every 10 minutes to monitor the degradation progress of the dye. After sampling, the solid and liquid were quickly separated by centrifuge, and the supernatant was extracted. The concentration of residual dye was measured and recorded by UV-Vis spectrophotometer. The removal rate of rhodamine B, malachite green and methylene blue by ZIF-8-SH was compared. Fig.10 .

[0059] Depend on Fig.10 It can be seen that equilibrium was reached after 80 minutes of illumination, and the removal rates of rhodamine B, malachite green, and methylene blue by ZIF-8-SH were 96.36%, 95.48%, and 72.36%, respectively. Fig.10 The curve corresponding to "ZIF-8" refers to the photocatalytic degradation curve of ZIF-8 for methylene blue, which only reaches 62.19%. The above shows that the thiol functionalization of ZIF-8 can improve its removal of organic dyes, especially non-azo dyes.

[0060] Example 7

[0061] Optimal delivery amount screening

[0062] Weigh 5 mg, 10 mg, and 20 mg of ZIF-8-SH using an electronic balance, and place them into a 10 mg / L divalent cadmium ion solution, respectively. Use a magnetic stirrer to stir thoroughly, and perform a UV spectrophotometer test every 1 minute in the first 5 minutes. Perform a UV spectrophotometer test every 5 minutes after 5 minutes. Fig.11 , 12 It can be found that the removal rate is best when the dosage is 10 mg. Fig.11 It can be seen that when the amount of addition is small, although it can quickly reach adsorption equilibrium, the removal rate will drop significantly; Fig.12 It can be seen that when the dosage is too much, the removal rate can quickly reach the highest, but as time goes by, the removal rate decreases rapidly and the removal effect is not stable enough; from the above conclusions, it can be concluded that the optimal dosage of ZIF-8-SH is 10 mg.

[0063] Example 8

[0064] Optimal pH screening

[0065] Concentrated hydrochloric acid was added dropwise to a 10 mg / L divalent cadmium ion solution to adjust the pH to 3, 4, 5, and 6. 10 mg of ZIF-8 and ZIF-8-SH were weighed using an electronic balance and added to the solution, and then stirred thoroughly using a magnetic stirrer. The removal rates of divalent cadmium ions by ZIF-8 and ZIF-8-SH at different pH values ​​were shown in Table 1. Fig.13 .from Fig.13 It can be seen that the optimal pH range of ZIF-8 and ZIF-8-SH is 6, and their removal rate reaches the highest; it can be found that under acidic conditions, the coordination and combination of thiol groups and divalent cadmium ions will be promoted, mainly because their hydrogen bonds and metal ions are combined together through coordination, thereby achieving the adsorption effect.

[0066] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a thiol-functionalized metal organic framework, characterized in that: The following steps are involved: The metal organic framework ZIF-8, hexadecyltrimethylammonium bromide, ethanol and ammonia water are mixed and stirred for 15 to 30 minutes, deionized water, tetraethyl orthosilicate and 3-mercaptopropyltrimethoxysilane are added, and the reaction is continued to be stirred for 6 to 8 hours, centrifuged, filtered, washed, centrifuged and filtered to obtain a primary product, and the primary product is added to an ethanol solution of hydrochloric acid, reacted at a temperature of 80°C for 4 to 6 hours, centrifuged, filtered, washed, centrifuged, filtered, dried and ground to obtain a thiol-functionalized metal organic framework.

2. The method for preparing a thiol-functionalized metal organic framework according to claim 1, characterized in that: The metal organic framework ZIF-8 is obtained by stirring 2-methylimidazole and zinc acetate in methanol for 24 to 36 hours.

3. The method for preparing a thiol-functionalized metal organic framework according to claim 2, characterized in that: The mass ratio of the 2-methylimidazole, zinc acetate and methanol is (3.2-3.3):(1.8-1.9):(7-7.2).

4. The method for preparing a thiol-functionalized metal organic framework according to claim 1, characterized in that: The mass ratio of the metal organic framework ZIF-8, hexadecyltrimethylammonium bromide, ethanol, ammonia water, deionized water, ethyl orthosilicate, 3-mercaptopropyltrimethoxysilane, and ethanol solution of hydrochloric acid is 1:0.6:(110-111):2:140:(6.5-6.6):3.7:8.

4.

5. The method for preparing a thiol-functionalized metal organic framework according to claim 4, characterized in that: The mass fraction of the ammonia water is 25%.

6. The method for preparing a thiol-functionalized metal organic framework according to claim 4, characterized in that: The ethanol solution of hydrochloric acid is formed by mixing hydrochloric acid and ethanol aqueous solution, the volume ratio of the hydrochloric acid to the ethanol aqueous solution is 1:9, the mass fraction of the hydrochloric acid is 36%, and the mass fraction of the ethanol aqueous solution is 95%. 7 . The thiol-functionalized metal organic framework prepared by the method for preparing the thiol-functionalized metal organic framework according to claim 1 .

8. Use of the thiol-functionalized metal organic framework as claimed in claim 7.

9. The use according to claim 8, characterized in that: Used to remove divalent cadmium ions in water.

10. The use according to claim 8, characterized in that: Used to remove organic dyes from water.

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