Modified ZIF-8 photocatalyst and preparation method thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a modified ZIF-8 photocatalyst and a preparation method thereof. The preparation method comprises the following steps: soaking a template agent in a precursor solution; sequentially carrying out vacuum degassing, filtering and drying on the soaked mixture to obtain a first intermediate product; soaking the first intermediate product with a mixed solution of methanol and NH3.H2O, and then sequentially carrying out vacuum degassing, standing, filtering and drying to obtain a second intermediate product; and soaking the second intermediate product in DMF (Dimethyl Formamide) to remove the template agent, and then sequentially filtering, washing and drying to obtain the modified ZIF-8 photocatalyst. The modified ZIF-8 photocatalyst prepared by the method effectively solves the problem of low light absorption efficiency of a single ZIF-8 photocatalyst, improves the problem of high recombination rate of photon-generated carriers, improves the photocatalytic reaction rate, and further improves the hydrogen production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, in particular to a modified ZIF-8 photocatalyst and a preparation method thereof. Background Art

[0002] In recent years, while fossil fuels such as coal, oil, and natural gas remain the mainstay of global energy supply, the development and utilization of clean energy sources such as hydrogen has become urgent. Hydrogen, with its high energy content, serves as both an energy carrier and fuel, and is also widely used in industrial production. In industry, solar hydrogen production has gradually developed into a highly efficient, environmentally friendly, and energy-saving hydrogen production technology. Photocatalytic hydrogen production not only achieves pollution-free hydrogen production but also offers the advantages of low cost and low energy consumption, making it a key technological approach for solar hydrogen production.

[0003] A major challenge in photocatalytic water splitting for hydrogen production is designing highly active and stable photocatalysts. ZIF-8 photocatalysts are porous materials formed by coordination bonds between Zn(II) and 2-methylimidazole ligands. They possess a unique microporous structure. Compared to other similar catalysts, ZIF-8 photocatalysts offer advantages such as high surface area, excellent chemical stability, and superior optical properties, resulting in significant photocatalytic hydrogen production from water. Traditional ZIF-8 photocatalysts are synthesized from Zn(NO₃)₂·6H₂O and 2-methylimidazole ligands in anhydrous methanol. The zinc ions bind to the 2-methylimidazole ligands through coordination bonds, forming ZIF-8 crystals with a porous structure. However, current ZIF-8 photocatalysts exhibit a narrow light absorption range and a large band gap (4.9–5.2 eV), limiting their absorption to ultraviolet light. This severely limits their photocatalytic hydrogen production efficiency. Furthermore, the high recombination rate of photogenerated carriers results in a short effective carrier lifetime and reduced catalytic activity, making pure ZIF-8 insufficient for practical hydrogen production. Summary of the Invention

[0004] In order to solve or partially solve the problems existing in the related art, the present invention provides a modified ZIF-8 photocatalyst and a preparation method thereof.

[0005] The present invention provides a method for preparing a modified ZIF-8 photocatalyst, which comprises: Step a), immersing the template in a precursor solution; the precursor solution comprises: a first metal salt, a second metal salt, an organic ligand and an alcohol solvent; the first metal salt is an inorganic salt containing zinc ions, and the second metal salt is an inorganic salt containing doped metal ions; the template is a three-dimensionally ordered array of polystyrene microspheres; Step b), vacuum degassing, filtering and drying the mixture obtained after soaking in step a) to obtain a first intermediate product; Step c), soaking the first intermediate product in a mixed solution of methanol and NH3·H2O, and then sequentially degassing, standing, filtering, and drying to obtain a second intermediate product; Step d), soaking the second intermediate product in DMF to remove the template, and then filtering, washing, and drying in sequence to obtain a modified ZIF-8 photocatalyst.

[0006] Furthermore, the first metal salt is Zn(NO3)2·6H2O, the organic ligand is 2-methylimidazole, and the alcohol solvent is anhydrous methanol.

[0007] Furthermore, the doping metal ions are selected from Cu 2+ , K + 、Ag + 、Na + , Ca 2+ 、Ni 2+ 、Mn 2+ 、Zr 4+ One or more of the .

[0008] Furthermore, the second metal salt is Cu(NO3)2·3H2O, KCl, AgNO3, Na2SO 4、 One or more of CaCl2·2H2O, NiCl2·6H2O, MnCl2·4H2O, and Zr(NO3)4·5H2O.

[0009] Furthermore, the molar ratio of the second metal salt, the first metal salt and the organic ligand is 1:2.5-4:4-10.

[0010] Furthermore, in step a), the soaking time is 0.5-2 hours.

[0011] Furthermore, in the step b), the vacuum degassing time is 8-12 minutes, and the drying temperature is 40-60°C.

[0012] Furthermore, in the step c), the vacuum degassing time is 2-5 minutes, the standing time is 20-30 hours, and the drying is performed at room temperature.

[0013] Furthermore, in step d), the soaking temperature is 60-90°C, anhydrous ethanol is used for washing, and the drying temperature is 50-70°C.

[0014] The present invention also provides a modified ZIF-8 photocatalyst, which is prepared according to any one of the methods described above.

[0015] The modified ZIF-8 photocatalyst and preparation method thereof provided by the present invention can have the following beneficial effects: This preparation method modifies ZIF-8 by combining a three-dimensional ordered macroporous structure with metal ion doping, narrowing the band gap to a certain extent. This effectively addresses the low light absorption efficiency of single ZIF-8 photocatalysts, while also improving the high recombination rate of photogenerated carriers, increasing the photocatalytic reaction rate and further enhancing hydrogen production efficiency. Furthermore, this preparation method is simple, easy to operate, and has a low synthesis cost. The resulting photocatalyst is easy to store, meeting industrial demand for photocatalysts.

[0016] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0018] Figure 1 These are scanning electron microscope images and transmission electron microscope images of some photocatalyst products in the embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The singular forms "a," "the," and "the" used in this invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0022] An embodiment of the present invention provides a method for preparing a modified ZIF-8 photocatalyst, comprising: Step a), immersing the template in a precursor solution; the precursor solution comprises: a first metal salt, a second metal salt, an organic ligand and an alcohol solvent; the first metal salt is an inorganic salt containing zinc ions, and the second metal salt is an inorganic salt containing doped metal ions; the template is a three-dimensionally ordered array of polystyrene microspheres; Step b), vacuum degassing, filtering and drying the mixture obtained after soaking in step a) to obtain a first intermediate product; Step c), soaking the first intermediate product in a mixed solution of methanol and NH3·H2O, and then sequentially degassing, standing, filtering, and drying to obtain a second intermediate product; Step d), soaking the second intermediate product in DMF to remove the template, and then filtering, washing, and drying in sequence to obtain a modified ZIF-8 photocatalyst.

[0023] In the above step a), during the soaking process, Zn 2+ The doped metal ions and organic ligands enter the gaps of the template, and ZIF-8 is formed in the gaps of the template and the metal ion doping is completed, and the formed solid modified ZIF-8 accumulates in the gaps of the template. The immersion time is preferably 0.5-2 hours, and most preferably 1 hour.

[0024] The template used is a three-dimensionally ordered array of polystyrene microspheres, preferably with a diameter of 195-325 nm, more preferably 325 nm. Using polystyrene microspheres as templates has the following advantages: the resulting three-dimensional ordered macroporous structure is uniform in size, rich in pores, and easy to surface modify. The size and arrangement of the polystyrene microspheres can be adjusted to adjust the cavity size and overall dimensions of the hollow structure, resulting in high controllability and a relatively mature preparation method. Furthermore, the polystyrene microspheres can be subsequently dissolved in DMF, making the process simple.

[0025] The template can be prepared as follows: Under nitrogen protection, styrene polymerization is initiated in water using potassium persulfate as an initiator to form polystyrene. The resulting mixture is centrifuged and dried to obtain a polystyrene microsphere template. The centrifugation time is 15-20 hours, more preferably 18 hours.

[0026] In the above preparation method, the centrifugation process is not only for achieving solid-liquid separation, but the longer centrifugation time is also used to allow the formed polystyrene microspheres to rearrange, thereby obtaining three-dimensionally ordered polystyrene microspheres. The reaction temperature is preferably 80-110°C, and the reaction time is 4-6h. The dosage ratio of styrene to potassium persulfate is 100-358 mL:1. More preferably, the reaction temperature is preferably 88-108°C, the reaction time is 5h, and the dosage ratio of styrene to potassium persulfate is 114-343 mL:1. Under these conditions, polystyrene microspheres with a diameter of 195-325nm can be obtained.

[0027] In the above-mentioned precursor solution, the first metal salt is used to provide Zn 2+ , coordinates with the organic ligand, and the second metal salt is used to provide doping metal ions to achieve metal doping. It can be understood by those skilled in the art that the doping metal ions should be 2+ Different metal ions. The first metal salt can be selected from zinc nitrate, zinc acetate, zinc chloride or zinc sulfate. In this application, Zn(NO3)2·6H2O is preferably used. The organic ligand is preferably 2-methylimidazole. The alcohol solvent is used to provide the reaction medium. The alcohol solvent is preferably anhydrous methanol. The doping metal ion is preferably Cu 2+ , K + 、Ag + 、Na + , Ca 2+ 、Ni 2+ 、Mn 2+ 、Zr 4+ Furthermore, the second metal salt is Cu(NO3)2·3H2O, KCl, AgNO3, Na2SO 4、 One or more of CaCl2·2H2O, NiCl2·6H2O, MnCl2·4H2O, and Zr(NO3)4·5H2O. The applicant has found that the doping metal has an important influence on the catalytic activity of the final photocatalyst. The photocatalyst finally prepared by doping with the above metal ions has a higher photocatalytic activity. It is more preferred to use Cu 2+ , or Cu 2+ and other doping metal ions mentioned above, such as Cu 2+ and Ag + The second metal salt is more preferably Cu(NO3)2·3H2O, or KCl, AgNO3, Na2SO 4、A combination of one or more of CaCl2·2H2O, NiCl2·6H2O, MnCl2·4H2O, and Zr(NO3)4·5H2O with Cu(NO3)2·3H2O. The molar ratio of the second metal salt, the first metal salt, and the organic ligand in the precursor solution is preferably 1:2.5-4:4-10, and most preferably 1:3:9.

[0028] Step b) is the step of obtaining the first intermediate product. The applicant has found that the performance of the photocatalyst can be further improved by vacuum degassing. Degassing in this step is conducive to the zinc ions, organic ligands and doping metal ions fully filling the gaps in the template to generate ZIF-8 and complete doping. In this step b), the vacuum degassing time is preferably 8-12 minutes, and the drying temperature is preferably 40-60°C. Most preferably, the vacuum degassing time is 10 minutes and the drying temperature is 50°C. The first intermediate product obtained after step b) includes modified ZIF-8 and the template that has not been removed. At this time, the crystallinity of the modified ZIF-8 is also low. Subsequent steps c) and d) are required.

[0029] Step c) involves a dual-solvent soaking process, which is used to improve crystallinity. Methanol is primarily used as a solvent, allowing ammonia to more easily penetrate the template gaps. The addition of ammonia is primarily intended to enhance crystallinity, ensuring that the sample maintains a three-dimensional, ordered macroporous structure after the PS template is subsequently removed. The volume ratio of methanol to NH3·H2O in the mixed solution of methanol and NH3·H2O is preferably 1:(1-1.5), and most preferably 1:1. Degassing in this step ensures that methanol and ammonia fully penetrate the template, enhancing the crystallinity of the modified ZIF-8. Preferably, the vacuum degassing time is 2-5 minutes, the standing time is 20-30 hours, and the drying is performed at room temperature. Most preferably, the vacuum degassing time is 3 minutes, and the standing time is 24 hours.

[0030] Step d) involves removing the template using DMF as a solvent. In this step, the immersion temperature is preferably 60-90°C, more preferably 80°C. The immersion time is preferably 0.5-2 hours, most preferably 1 hour. Anhydrous ethanol is preferably used for washing. The drying temperature is preferably 50-70°C, more preferably 60°C, and the drying time is preferably 10-15 hours. After step d), the modified ZIF-8 photocatalyst is obtained.

[0031] Another embodiment of the present invention further provides the modified ZIF-8 photocatalyst, which is prepared according to the method of the above embodiment. The specific embodiment is the same as the above content and is not repeated here.

[0032] The preparation method of the modified ZIF-8 photocatalyst provided in the embodiment of the present invention has the following advantages: This preparation method modifies ZIF-8 by combining a three-dimensional ordered macroporous structure with metal ion doping, narrowing the band gap to a certain extent. This effectively addresses the low light absorption efficiency of single ZIF-8 photocatalysts, while also improving the high recombination rate of photogenerated carriers, increasing the photocatalytic reaction rate and further enhancing hydrogen production efficiency. Furthermore, this preparation method is simple, easy to operate, and has a low synthesis cost. The resulting photocatalyst is easy to store, meeting industrial demand for photocatalysts.

[0033] The technical solution of the present invention will be further described below in conjunction with specific embodiments: The polystyrene microsphere templates in the following examples were prepared according to the following method: 1. Weigh 8 g of sodium hydroxide and add 200 mL of distilled water into a 500 mL beaker. Add the sodium hydroxide to the beaker and dissolve it by ultrasonication while stirring with a glass rod to obtain a sodium hydroxide solution.

[0034] 2. Take styrene from the refrigerator and pour it into a separatory funnel. Wash it four times with the sodium hydroxide solution prepared in step 1, with the volume of sodium hydroxide solution used each time being 6.25 times the volume of styrene; then wash it four times with distilled water, with the volume of distilled water used each time being 6.25 times the volume of styrene, to obtain cleaned styrene.

[0035] 3. Take 0.07 g of potassium persulfate and add it to 10 mL of distilled water. Place it in a small conical flask, clamp the small conical flask with a rack, dissolve it by ultrasonication, and heat it to 88°C in an oil bath to obtain a potassium persulfate solution.

[0036] 4. Add 170 mL of distilled water to a 250 mL three-necked flask, pass condensed water, pass nitrogen, mechanically stir, place in a water bath, and control the speed of mechanical stirring at 400 r·min -1 , nitrogen was passed through the solution at a flow rate of 50 mL min -1 Set the water bath to the preset temperature and turn on the magnetic stirring of the water bath at a speed of 600 r·min. -1 .

[0037] 5. Add a preset mass of styrene obtained in step 3 into a three-necked flask. After 60 minutes, quickly add the potassium persulfate aqueous solution prepared in step 3. Under nitrogen protection, conduct the polymerization reaction at a constant temperature for 5 hours.

[0038] 6. After the reaction is complete, stop heating the water bath, magnetic stirring, and mechanical stirring. Raise the 250 mL three-necked flask out of the oil bath. Continue to flow nitrogen and condensed water until the solution cools to room temperature.

[0039] 7. Pour the obtained white solution into a centrifuge tube, put it into the centrifuge, and set the speed to 3000r·min -1 After centrifugation, the supernatant was discarded and the mixture was dried at room temperature for 24 h to obtain a PS microsphere template.

[0040] In the above preparation method, the diameter of the polystyrene microsphere template was adjusted by changing the amount of styrene added (step 5) and the reaction temperature (water bath temperature in step 4). The above reaction conditions and the sizes of the prepared polystyrene microspheres are listed in Table 1: Table 1 Reaction conditions and polystyrene microsphere size

[0041] Example 1 1. Dissolve 8.15 g (0.027 mol) of Zn(NO3)2·6H2O, 6.75 g (0.082 mol) of 2-methylimidazole, and 2.1744 g (0.009 mol) of Cu(NO3)2·3H2O in 50 mL of methanol to obtain a precursor solution.

[0042] 2. Soak the PS-325 template in the above precursor solution for 1 hour, then vacuum degas for 10 minutes, filter, and dry at 50°C for 12 hours to obtain the first intermediate product.

[0043] 3. The first intermediate product was soaked in a methanol / NH3·H2O (v / v 1:1) mixed solution, vacuum degassed for 3 minutes, allowed to stand at room temperature and atmospheric pressure for 24 hours, the obtained fragments were filtered, and then naturally dried at room temperature to obtain the second intermediate product.

[0044] 4. Soak the second intermediate product in DMF and heat it to 80°C for 1 hour to remove the template. Filter the resulting white product, wash it with anhydrous ethanol, and dry it in an oven at 60°C for 12 hours. The resulting photocatalyst product is named Cu-3D-ZIF-8-325.

[0045] Example 2 The only difference from Example 1 is that in step 1, Cu(NO3)2·3H2O was replaced with an equimolar amount of KCl (0.6980 g). The resulting photocatalyst product was named K-3D-ZIF-89-325.

[0046] Example 3 The only differences from Example 1 are: in step 1, the Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of AgNO₃ (1.5288 g). In step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Ag-3D-ZIF-8-248.

[0047] Example 4 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of Na₂SO₄ (1.2783 g). In step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Na-3D-ZIF-8-248.

[0048] Example 5 The only difference from Example 1 is that in step 1, Cu(NO3)2·3H2O was replaced with an equal molar amount of CaCl2·2H2O (1.3231 g). The resulting photocatalyst product was named Ca-3D-ZIF-8-325.

[0049] Example 6 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of NiCl₂·6H₂O (2.1392 g). In step 2, the PS-325 template was replaced with PS-195. The resulting photocatalyst product was named Ni-3D-ZIF-8-195.

[0050] Example 7 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of MnCl₂·4H₂O (1.7812 g). In step 2, the PS-325 template was replaced with PS-195. The resulting photocatalyst product was named Mn-3D-ZIF-8-195.

[0051] Example 8 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of Zr(NO₃)₄·5H₂O (3.8640 g). In step 2, the PS-325 template was replaced with PS-195. The resulting photocatalyst product was named Zr-3D-ZIF-8-195.

[0052] Example 9 The only differences from Example 1 are: in Step 1, the Cu(NO₃)₂·3H₂O was replaced with 0.0045 mol Cu(NO₃)₂·3H₂O (1.0872 g) and 0.0045 mol AgNO₃ (0.7644 g). In Step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Cu / Ag-3D-ZIF-8-248.

[0053] Example 10 The only differences from Example 1 are: in Step 1, Cu(NO₃)₂·3H₂O was replaced with 0.0045 mol Na₂SO₄ (0.6392 g) and 0.0045 mol KCl (0.3490 g). In Step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Na / K-3D-ZIF-8-248.

[0054] Example 11 The only differences from Example 1 are: in Step 1, Cu(NO₃)₂·3H₂O was replaced with 0.0045 mol Zr(NO₃)₄·5H₂O (1.9320 g) and 0.0045 mol CaCl₂·2H₂O (0.6613 g). In Step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Zr / Ca-3D-ZIF-8-248.

[0055] Comparative Example 1 8.15 g (0.027 mol) of Zn(NO3)2•6H2O and 6.75 g (0.082 mol) of 2-methylimidazole were dissolved in 100 mL of anhydrous methanol and stirred at 300 r / min on a magnetic stirrer at room temperature for 5 h. Then, the mixture was centrifuged at 8000 r / min for 5 min, washed three times with anhydrous methanol, and dried at 60°C for 12 h. The obtained photocatalyst product was named ZIF-8.

[0056] Comparative Example 2 The only difference from Example 1 is that Cu(NO3)2·3H2O is not added in step 1. The obtained photocatalyst product is named 3D-ZIF-8-325.

[0057] Comparative Example 3 The only difference from Comparative Example 1 is that 2.1744 g (0.009 mol) of Cu(NO3)2·3H2O is further added to anhydrous methanol. The resulting photocatalyst product is named Cu-ZIF-8.

[0058] Comparative Example 4 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of InCl₃ (1.9906 g). In step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named In-3D-ZIF-8-248.

[0059] Comparative Example 5 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of PbCl₂ (2.5030 g). In step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Pb-3D-ZIF-8-248.

[0060] Comparative Example 6 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of Cr(NO₃)₃·9H₂O (2.5030 g). In step 2, the PS-325 template was replaced with PS-195. The resulting photocatalyst product was named Cr-3D-ZIF-8-195.

[0061] Comparative Example 7 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of Co(NO₃)₂·6H₂O (2.6193 g). In step 2, the PS-325 template was replaced with PS-248. The resulting photocatalyst product was named Co-3D-ZIF-8-248.

[0062] Comparative Example 8 The only differences from Example 1 are: in step 1, Cu(NO₃)₂·3H₂O was replaced with an equal molar amount of Ce(NO₃)₃·6H₂O (3.9082 g). In step 2, the PS-325 template was replaced with PS-225. The resulting photocatalyst product was named Ce-3D-ZIF-8-225.

[0063] The photocatalytic activity of the photocatalyst products prepared in the above comparative examples and embodiments was tested. The test method is as follows: 20 mg of the ground photocatalyst product was added to 100 mL of a solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3. 21.6 μL of 9.519 mg / mL chloroplatinic acid solution was pipetted with a pipette and ultrasonicated for 5 minutes using an ultrasonic cleaner to form a uniform suspension. Subsequently, nitrogen was passed through the reaction system for 20 minutes to exhaust the air. Next, the reactor was placed on a magnetic stirrer and stirred continuously at a speed of 300 r / min. A 300W xenon lamp was used as a light source for 4 hours to ensure that the photocatalyst remained uniformly dispersed and uniformly illuminated during the experiment. The hydrogen content in the gas sample was analyzed by gas chromatograph. The photocatalytic activity of different photocatalyst products is listed in Table 2: Table 2 Photocatalytic activity of different photocatalyst products

[0064] See Figure 1 : Figure 1 In the figure, A and B are scanning electron micrographs of polystyrene templates PS-325 and PS-248, respectively. As can be seen from A and B, the ordered arrangement of PS templates of different sizes provides feasibility for the subsequent synthesis of three-dimensional ordered macroporous modified ZIF-8 with different pore sizes.

[0065] C and D are scanning electron micrographs and transmission electron micrographs, respectively, of the Cu-ZIF-8 photocatalyst prepared in Comparative Example 3. E and F are scanning electron micrographs and transmission electron micrographs, respectively, of the ZIF-8 photocatalyst prepared in Comparative Example 1. It can be seen that the final products prepared without the use of a template did not form a three-dimensional ordered macroporous morphology.

[0066] G and H are scanning electron micrographs and transmission electron micrographs, respectively, of the photocatalyst Cu-3D-ZIF-8-325 prepared in Example 1, and I and J are scanning electron micrographs and transmission electron micrographs, respectively, of the photocatalyst 3D-ZIF-8-325 prepared in Comparative Example 2. Thus, it can be seen that the present application successfully prepared a photocatalyst with a three-dimensional ordered macroporous morphology.

[0067] From the above content, we can know that: The enhanced activity of the metal-doped three-dimensional ordered macroporous modified ZIF-8 provided in this application is primarily due to two key factors: one is the three-dimensional ordered macroporous structure, as can be seen from Comparative Example 3 and Example 1. Both samples are doped with copper, but the activity of Example 1 is more than three times that of Comparative Example 3. The second is metal doping, as can be seen from Comparative Example 2 and Example 1. Both samples have a three-dimensional ordered macroporous structure, but the activity of Example 1 is more than 27 times that of Comparative Example 2.

[0068] The results of the activity analysis of the modified ZIF-8 photocatalysts prepared in the above examples and comparative examples show that the catalytic activity of ZIF-8 can be improved by combining the three-dimensional ordered macroporous structure with metal ion doping. Among them, the effect of doping with metallic copper is the best, with a catalytic activity of up to 2233.2 μmol·g -1 ·h -1 , which is nearly 29 times the activity before modification.

[0069] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a modified ZIF-8 photocatalyst, characterized in that: include: Step a), soaking the template in the precursor solution; The precursor solution comprises: a first metal salt, a second metal salt, an organic ligand and an alcohol solvent; the first metal salt is an inorganic salt containing zinc ions, and the second metal salt is an inorganic salt containing doped metal ions; the template is a three-dimensionally ordered array of polystyrene microspheres; Step b), vacuum degassing, filtering and drying the mixture obtained after soaking in step a) to obtain a first intermediate product; Step c), soaking the first intermediate product in a mixed solution of methanol and NH3·H2O, and then sequentially degassing, standing, filtering, and drying to obtain a second intermediate product; Step d), soaking the second intermediate product in DMF to remove the template, and then filtering, washing, and drying in sequence to obtain a modified ZIF-8 photocatalyst.

2. The preparation method according to claim 1, characterized in that The first metal salt is Zn(NO3)2·6H2O, the organic ligand is 2-methylimidazole, and the alcohol solvent is anhydrous methanol.

3. The preparation method according to claim 1, characterized in that The doping metal ion is selected from Cu 2+ , K + 、Ag + 、Na + , Ca 2+ 、Ni 2+ 、Mn 2+ 、Zr 4+ One or more of the .

4. The preparation method according to claim 3, characterized in that The second metal salt is Cu(NO3)2·3H2O, KCl, AgNO3, Na2SO 4、 One or more of CaCl2·2H2O, NiCl2·6H2O, MnCl2·4H2O, and Zr(NO3)4·5H2O.

5. The preparation method according to claim 1, characterized in that The molar ratio of the second metal salt, the first metal salt and the organic ligand is 1:2.5-4:4-10.

6. The preparation method according to claim 1, characterized in that In the step a), the soaking time is 0.5-2 hours.

7. The preparation method according to claim 1, characterized in that In the step b), the vacuum degassing time is 8-12 minutes, and the drying temperature is 40-60°C.

8. The preparation method according to claim 1, characterized in that In the step c), the vacuum degassing time is 2-5 minutes, the standing time is 20-30 hours, and the drying is done at room temperature.

9. The preparation method according to claim 1, characterized in that In the step d), the soaking temperature is 60-90°C, anhydrous ethanol is used for washing, and the drying temperature is 50-70°C.

10. A modified ZIF-8 photocatalyst, characterized in that: It is prepared according to the method according to any one of claims 1 to 9.

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