A chlorophyll-modified CdS / UiO-67-NH2 artificial photosynthetic catalyst and a preparation method thereof

Abstract

The application discloses a chlorophyll-modified CdS / UiO-67-NH2 artificial photocatalyst and a preparation method thereof, and belongs to the field of photochemical energy conversion and photocatalytic degradation. The application relates to the preparation of an artificial photocatalyst composite material, and mainly solves the problems of poor catalytic performance of the material, fast carrier recombination and complicated preparation. The application has the following steps: firstly, zirconium tetrachloride, 2-amino-4,4'-biphenyldicarboxylic acid and acetic acid are added into a N,N-dimethylformamide solvent and stirred, and then heated; after cooling, the product is cleaned with ethanol, and vacuum drying is conducted to obtain UiO-67-NH2 powder; secondly, the UiO-67-NH2 is dispersed in deionized water, and then cadmium nitrate tetrahydrate and thioacetamide are added and dissolved, and then heated and continuously stirred; after cooling, the product is cleaned with deionized water, and vacuum drying is conducted to obtain CdS / UiO-67-NH2 powder; thirdly, spinach is ground in ethanol, and then a large amount of ethanol is added and stirred, and then centrifuged, and then the upper liquid is taken to obtain a chlorophyll solution; and fourthly, a proper amount of CdS / UiO-67-NH2 powder is taken into a mortar, the chlorophyll solution is added, and then ground until dry to obtain Chl@CdS / UiO-67-NH2 composite material powder.

Description

Technical Field

[0001] This invention belongs to the field of photochemical energy conversion and photocatalytic degradation. Background Technology

[0002] All-solid-state direct Z-scheme photocatalysts have attracted increasing attention from researchers because their composition requires only two photocatalysts, a reduction photocatalyst PSI and an oxidation photocatalyst PSI, with compatible Fermi level and band structure edges, forming an effective interfacial contact. Photogenerated electrons then migrate along a Z-shaped path from the conduction band of PSI to the valence band of PSI under the influence of the built-in electric field in the space charge region, thus achieving effective separation of photogenerated electrons and holes. This photogenerated carrier transfer process maximizes the retention of the thermodynamic driving force of the redox reaction between the two catalysts. With the continuous advancement of related research in recent years, the range of materials has expanded from inorganic semiconductors to emerging metal-organic frameworks (MOFs). MOFs are porous crystalline materials composed of a central metal ion or metal oxide cluster and organic ligands, possessing extremely high specific surface area, well-defined structure, and tunable porosity, enabling them to accommodate nanoscale catalysts. In early research, MOFs have been applied to various fields such as gas adsorption, separation, and catalysis. With the development of photoresponsive MOFs, their application in photocatalysis is becoming increasingly widespread. Its high porosity allows it to effectively load other nanoscale photocatalysts, and its ordered structure facilitates the transfer of photogenerated electrons. Cadmium sulfide (CdS) is a typical narrow bandgap inorganic semiconductor with a bandgap of approximately 2.4 eV, and it can exist in hexagonal and cubic crystal structures at room temperature. Its application in photocatalysis has been extensively studied in recent years, mainly due to its broad-spectrum solar response characteristics and highly active hydrogen evolution reaction sites. In summary, considering the kinetics and thermodynamic requirements of photocatalytic reactions, and pursuing higher solar energy conversion efficiency, a direct Z-type heterojunction was constructed using CdS, which exhibits excellent hydrogen production performance but insufficient stability, and the emerging MOF material UiO-67-NH2. Furthermore, chlorophyll molecules were loaded onto the surface of the heterojunction as photosensitizers to enhance the catalyst's light absorption capacity and charge transfer driving force. Summary of the Invention

[0003] This invention relates to solving the problems of high-quality synthesis and innovative surface modification of organic-inorganic hybrid artificial photosynthetic heterojunction catalysts to improve catalyst performance. It proposes a low-temperature, rapid method for preparing organic-inorganic hybrid artificial photosynthetic catalysts and a simple chlorophyll extraction and catalyst surface modification strategy. To solve the above problems, the chlorophyll-modified CdS / UiO-67-NH2 artificial photosynthetic catalyst and its preparation method are completed through the following steps.

[0004] Step 1: Zirconium tetrachloride and 2-amino-4,4'-biphenyl dicarboxylic acid were added to N,N-dimethylformamide solvent and stirred. Then, acetic acid was added and stirred. The solution was transferred to the lining of a reaction vessel and heated. After cooling to room temperature, the product was washed with ethanol and dried in a vacuum drying oven to obtain UiO-67-NH2 powder.

[0005] Step 2: Disperse UiO-67-NH2 in deionized water, then add cadmium nitrate tetrahydrate and thioacetamide, heat and stir, and after the reaction is complete, cool to room temperature. Wash the product with deionized water and dry it in a vacuum drying oven to obtain CdS / UiO-67-NH2 powder.

[0006] Step 3: Take fresh spinach leaves, wash them, cut them into small pieces, add ethanol and grind them. Then transfer them to anhydrous ethanol, stir and extract chlorophyll. Centrifuge and collect the supernatant to obtain a chlorophyll solution.

[0007] Step 4: Grind CdS / UiO-67-NH2 powder, chlorophyll solution and anhydrous ethanol under infrared lamp irradiation until dry to obtain CdS / UiO-67-NH2 powder with surface chlorophyll modification.

[0008] Further specifying that in step one, 46.90~87.10 mg of zirconium tetrachloride and 50.40~93.60 mg of 2-amino-4,4'-biphenyl dicarboxylic acid are added to 14~26 mL of N,N-dimethylformamide solvent, and the stirring and dissolution time is 30 min.

[0009] Further specify that the amount of acetic acid added in step one is 0.9~1.8 mL.

[0010] Further specified, the heating temperature in step one is 80~160 ℃, and the vacuum drying temperature is 60 ℃.

[0011] Further specifying, in step two, 70~130 mg of UiO-67-NH2 powder is dispersed in 35~65 mL of deionized water.

[0012] Further specifying, in step two, 404.88~751.92 mg of cadmium nitrate tetrahydrate and 98.35~182.65 mg of thioacetamide are added.

[0013] Further specify that the heating and stirring temperature in step two is 70~100 ℃, and the heating reaction time is 2~4 h.

[0014] Further specify that the amount of spinach leaves used in step three is 70-130 g, and the amount of anhydrous ethanol used is 70-130 mL.

[0015] Further specifying, the stirring time in step three is 10 hours.

[0016] Further specifying, in step four, 80-120 mg of UiO-67-NH2 powder, 1.5-2.5 mL of chlorophyll solution, and 5-15 mL of anhydrous ethanol are mixed and ground.

[0017] The chlorophyll-modified artificial photosynthetic heterojunction catalyst CdS / UiO-67-NH2 prepared by the method of this invention is a Chl@CdS / UiO-67-NH2 composite material formed by good coupling of a stable UiO-67-NH2 metal-organic framework and CdS nanoparticles, and further surface modification with chlorophyll. This enables photogenerated charge carriers to be effectively separated in the space charge region under the action of the built-in electric field at the interface, ultimately achieving an effective improvement in photocatalytic performance. Attached Figure Description

[0018] Figure 1 These are the XRD patterns of UiO-67-NH2, CdS, CU, Chl@CU, and the standard PDF card; Figure 2 These are SEM images of UiO-67-NH2 and CdS, TEM image of Cu, and elemental distribution energy spectrum of Chl@Cu; Figure 3 These are the UV-Vis absorption spectra of UiO-67-NH2, CdS, Cu, and Chl@Cu; Figure 4 The optical band gaps of UiO-67-NH2, CdS, CU, and Chl@CU are; Figure 5 These are the Mott-Schottky spectra of UiO-67-NH2, CdS, CU, and Chl@CU; Figure 6 These are the electrochemical impedance spectra of UiO-67-NH2, CdS, Cu, and Chl@Cu; Figure 7 The photocatalytic reduction degradation curves of potassium dichromate indicator solution are shown for the blank control group, UiO-67-NH2, CdS, CU and Chl@CU. Figure 8 The results are the first-order kinetic fits of the photocatalytic reduction degradation of potassium dichromate indicator solution by the blank control group, UiO-67-NH2, CdS, CU and Chl@CU; Figure 9 The photocatalytic reduction degradation rates of potassium dichromate indicator solution were compared with those of the blank control group, UiO-67-NH2, CdS, CU, and Chl@CU. Figure 10 The photocatalytic reduction degradation cycle curve of potassium dichromate indicator solution by Chl@CU is shown.

[0019] Example 1: The use of UiO-67-NH2 in this example was carried out according to the following steps: 67 mg of zirconium tetrachloride and 72 mg of 2-amino-4,4'-biphenyl dicarboxylic acid were added to 20 ml of N,N-dimethylformamide solvent and stirred for 30 min. Then, 1.4 mL of acetic acid was added, and the solution was transferred to a 50 mL reaction vessel liner. The reaction was carried out at 120 °C for 24 h. After cooling to room temperature, the product was washed 5 times with ethanol and dried in a vacuum drying oven at 60 °C for 12 h.

[0020] The chlorophyll-modified CdS / UiO-67-NH2 artificial photosynthetic catalyst and its preparation method in this embodiment are accomplished through the following steps.

[0021] Step 1: Add 67 mg of zirconium tetrachloride and 72 mg of 2-amino-4,4'-biphenyl dicarboxylic acid to 20 mL of N,N-dimethylformamide solvent, stir for 30 min, add 1.4 mL of acetic acid, transfer to a 50 mL reaction vessel liner, react at 120 °C for 24 h, cool to room temperature, wash the product 5 times with ethanol, and dry in a vacuum drying oven at 60 °C for 12 h to obtain metal-organic framework UiO-67-NH2 powder.

[0022] Step 2: 100 mg UiO-67-NH2 was dispersed in 50 mL of deionized water by stirring for 30 min. Then, 578.4 mg of cadmium nitrate tetrahydrate and 140.5 mg of thioacetamide were added. The mixture was heated and stirred at 80 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature. The product was washed three times with deionized water and dried in a vacuum drying oven at 60 °C for 12 h to obtain the CdS / UiO-67-NH2 composite material, named CU.

[0023] Step 3: Take 100 g of fresh spinach leaves, wash them, cut them into small pieces, add an appropriate amount of ethanol and grind them. Add 100 mL of ethanol to the ground mixture and stir for 10 h. Then centrifuge the mixture and take the supernatant to obtain a chlorophyll solution, named Chl.

[0024] Step 4: Take 100 mg of CU powder, 2 mL of chlorophyll solution and 10 mL of anhydrous ethanol and grind them until dry under infrared lamp irradiation to obtain chlorophyll-modified CdS / UiO-67-NH2 powder, named Chl@CU.

[0025] The photocatalytic reduction degradation of Cr(VI) was performed using a 300 W xenon lamp to simulate sunlight. 10 mg of the catalyst and 30 mL of a 20 mg / L potassium dichromate indicator solution were placed in a 100 mL beaker. The beaker was fixed 5 cm in front of the light source, and the reaction was continuously stirred magnetically at a constant speed. The absorbance of the reaction solution was measured at equal time intervals, and the concentration of the reaction solution was calculated. A curve showing the degradation rate versus illumination time was plotted to analyze and evaluate the photocatalytic activity of the sample. Figure 7 As shown.

[0026] from Figure 9 As can be seen, the performance of the CdS / UiO-67-NH2 composite photocatalyst in the photocatalytic reaction is higher than that of the reference CdS and UiO-67-NH2 catalysts. Furthermore, Chl@CdS / UiO-67-NH2 shows a significant performance improvement over the CdS / UiO-67-NH2 composite material, degrading all the potassium dichromate indicator solution in just 5 minutes (see details). Figure 7 The degradation rate reached 39.38 μmol·min. -1 ·g cat -1 It also exhibits good cyclic stability, maintaining a degradation rate of over 95% even after three consecutive reactions, such as... Figure 10 As shown in the illustration, the above performance results demonstrate that the unique photogenerated electron migration pathway of artificial photosynthetic catalysts creates favorable conditions for space charge separation, which not only prolongs the lifetime of photogenerated electrons but also effectively increases the reaction thermodynamic potential energy of photogenerated electrons, macroscopically manifested as a significant improvement in the photocatalytic degradation performance of the material.

Claims

1. A chlorophyll-modified A method for preparing an artificial photosynthetic catalyst, characterized in that... The preparation method is accomplished through the following steps: Step 1: Zirconium tetrachloride and 2-amino-4,4'-biphenyl dicarboxylic acid were added to N,N-dimethylformamide solvent and stirred. Then, acetic acid was added and stirred. The solution was transferred to the lining of a reaction vessel and heated. After cooling to room temperature, the product was washed with ethanol and dried in a vacuum drying oven to obtain the desired product. powder; Step 2, The product was dispersed in deionized water and stirred until dispersed. Cadmium nitrate tetrahydrate and thioacetamide were then added and stirred until fully dissolved. The mixture was then heated and stirred continuously. After cooling to room temperature, the product was washed with deionized water and dried in a vacuum drying oven. powder; 70~130mg The powder was dispersed in 35-65 mL of deionized water; Add 404.88~751.92 mg of cadmium nitrate tetrahydrate and 98.35~182.65 mg of thioacetamide; The heating temperature is 70~100℃, and the holding time is 2~4 hours; Step 3: Take fresh spinach leaves, wash them, cut them into small pieces, add ethanol and grind them. Then transfer them to anhydrous ethanol, stir and extract chlorophyll. Centrifuge and collect the supernatant to obtain a chlorophyll solution. Step 4: The powder, chlorophyll solution, and anhydrous ethanol were ground until dry under infrared light irradiation to obtain a chlorophyll-modified surface. powder.

2. The preparation method according to claim 1, characterized in that... In step one, 46.90~87.10 mg of zirconium tetrachloride and 50.40~93.60 mg of 2-amino-4,4'-biphenyl dicarboxylic acid were added to 14~26 mL of N,N-dimethylformamide solvent, and the mixture was stirred and dissolved for 30 min.

3. The preparation method according to claim 1, characterized in that... The amount of acetic acid added in step one is 0.9~1.8mL.

4. The method according to claim 1, characterized in that... In step one, the heating temperature is 80~160℃, and the vacuum drying temperature is 60℃.

5. The preparation method according to claim 1, characterized in that... In step three, the amount of spinach leaves used is 70-130g, and the amount of anhydrous ethanol used is 70-130mL.

6. The preparation method according to claim 1, characterized in that... The stirring time in step three is 10 hours.

7. The preparation method according to claim 1, characterized in that... In step four, 80-120mg Mix and grind the powder, 1.5~2.5mL of chlorophyll solution, and 5~15mL of anhydrous ethanol.

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