A MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, its preparation method and application

Abstract

This invention discloses a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, its preparation method, and its application, belonging to the field of photocatalytic functional materials technology. A method for preparing the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst includes the following steps: mixing ZIF-67 (Co) and MOF-5 (Zn), and calcining at 550~750℃ to obtain the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst; wherein the mass ratio of ZIF-67 (Co) to MOF-5 (Zn) is 1:(3~9). This invention combines ZIF-67 (Co)-derived Co3O4 and MOF-5 (Zn)-derived ZnO at a specific mass ratio. The resulting heterostructure allows the two semiconductors to produce a synergistic effect, increasing the specific surface area of ​​the catalyst, improving its redox capacity, enhancing its persulfate activation rate, and thus improving the photocatalytic efficiency of the catalyst, efficiently degrading organic pollutants. The photocatalyst of this invention exhibits a degradation rate of ≥97% for Rhodamine B within 6 minutes.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic functional materials technology, specifically to a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, its preparation method, and its application. Background Technology

[0002] Metal-organic frameworks (MOFs) have attracted widespread attention in recent years due to their unique properties, such as tunable porosity, high specific surface area, rich physicochemical properties, and potential applications in the energy and environmental fields. Currently, MOFs have been used as templates or precursors for the synthesis of metal oxides to prepare composite functional materials with high porosity, large specific surface area, and low cost. However, MOF materials typically suffer from narrow light absorption ranges and insufficient catalytic active sites, limiting their photocatalytic degradation efficiency. As a strong oxidant, persulfate (PMS) can be activated under light irradiation, generating a variety of highly reactive free radicals. These free radicals possess strong oxidizing capabilities and can rapidly oxidize and decompose organic pollutants into harmless small molecules. Studies have shown that incorporating PMS into MOF-mediated photocatalytic systems, through the synergistic effect of the two, can greatly promote the activation efficiency of PMS, thereby achieving a significant improvement in photocatalytic degradation performance. Existing technology cleverly combines PMS oxidation and MOF photocatalysis to design a Mn3O4 / CuO (CMO-2) composite catalyst. Compared with Mn3O4, its catalytic activity efficiency in activating peroxymonosulfate is increased by nearly six times, enabling more effective degradation of pollutants. However, the degradation rate of the Mn3O4 / CuO (CMO-2) composite catalyst is still relatively slow and cannot meet the requirements for rapid treatment; its catalytic rate needs further optimization. Summary of the Invention

[0003] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing MOF-derived Co3O4 / ZnO heterostructure composite photocatalysts.

[0004] Another object of the present invention is to provide a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst.

[0005] Another object of the present invention is to provide the application of MOF-derived Co3O4 / ZnO heterostructure composite photocatalysts in the degradation of organic matter in wastewater.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst includes the following steps: ZIF-67 (Co) and MOF-5 (Zn) were mixed and calcined at 550~750℃ to obtain the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst. The mass ratio of ZIF-67 (Co) to MOF-5 (Zn) is 1:(3~9).

[0007] This invention involves calcining ZIF-67(Co)MOF-5(Zn) at a specific temperature in a specific mass ratio to achieve the composite formation of ZIF-67(Co)-derived Co3O4 and MOF-5(Zn)-derived ZnO, resulting in a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst. The combination of these two semiconductor materials with different bandgap structures to form a heterostructure improves the separation efficiency of photogenerated electrons and holes, increasing the surface active sites and contact area of ​​this composite photocatalyst material, thereby enhancing its photocatalytic efficiency.

[0008] Preferably, the mixing method is grinding.

[0009] Preferably, the preparation method of ZIF-67(Co) includes: mixing dimethylimidazole, soluble cobalt salt and methanol, reacting to obtain ZIF-67(Co).

[0010] More preferably, the reaction time is 30-60 minutes.

[0011] More preferably, the method for preparing ZIF-67(Co) further includes adding a surfactant.

[0012] The surfactant can reduce the surface tension of the reaction system, thereby facilitating the reaction under milder conditions (such as lower temperatures) and accelerating the reaction rate; it also plays a role in modifying the morphology and guiding the growth of specific crystal faces.

[0013] More preferably, the surfactant is at least one of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and tetradecyltrimethylammonium bromide.

[0014] Preferably, the soluble cobalt salt is at least one of cobalt nitrate hexahydrate, cobalt acetate, and cobalt chloride.

[0015] More preferably, the mass-to-volume ratio of the dimethylimidazole, soluble cobalt salt, methanol and surfactant is 22.4~23.0g: 0.578~0.586g: 390~410mL: 0.0045~0.007g.

[0016] Preferably, the preparation method of MOF-5(Zn) includes: mixing terephthalic acid, soluble zinc salt and polar organic solvent, and performing a solvothermal reaction to obtain MOF-5(Zn).

[0017] More preferably, the solvothermal reaction temperature is 120~140°C.

[0018] More preferably, the solvothermal reaction time is 3-5 hours.

[0019] More preferably, the soluble zinc salt is at least one of zinc acetate, zinc nitrate, and zinc sulfate.

[0020] More preferably, the polar organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0021] More preferably, the polar organic solvent is N,N-dimethylformamide.

[0022] More preferably, the mass-to-volume ratio of the terephthalic acid, the soluble zinc salt, and the polar organic solvent is 0.698~0.710g: 2.440~2.465g: 45~55mL.

[0023] Preferably, the mass ratio of ZIF-67 (Co) to MOF-5 (Zn) is 1:(5~9).

[0024] More preferably, the preparation method of ZIF-67 (Co) and MOF-5 (Zn) further includes washing and vacuum drying.

[0025] More preferably, the vacuum drying further includes vacuum drying at 120~140°C for 12~16 hours.

[0026] More preferably, the washing includes washing 3 to 6 times with an organic solvent and / or water.

[0027] Preferably, the ZIF-67(Co) has a dodecahedral structure.

[0028] Preferably, the MOF-5 (Zn) is a micron-sized, flower-like crystal aggregate. The overall structure consists of irregularly shaped plate-like crystals as a framework, with slender rod-shaped / needle-shaped crystals extending outwards from the surface, arranged radially in a stacked pattern resembling coral or a flower cluster. The surface is smooth, the edges are clear, and it exhibits obvious anisotropic growth characteristics.

[0029] More preferably, the cluster size of the MOF-5 (Zn) is 5~8 μm.

[0030] Preferably, after calcination, the ZnO derived from MOF-5 (Zn) exhibits a rose-like layered structure, while the Co3O4 derived from ZIF-67 (Co) retains its original crystal structure, with Co3O4 adhering to the outer surface of ZnO.

[0031] Preferably, the temperature is increased to the 550-750°C at a heating rate of 2-5°C / min (from room temperature).

[0032] Preferably, the calcination time is 4 to 6 hours.

[0033] Preferably, the calcination is performed in air or in an oxygen-containing atmosphere.

[0034] This invention also protects the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst prepared by the above preparation method.

[0035] This invention also protects the application of the above-mentioned MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst in the degradation of organic matter in wastewater.

[0036] Preferably, the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst degrades organic matter in wastewater by activating persulfate.

[0037] The principle of the MOF-derived heterostructure composite photocatalyst prepared in this invention in degrading organic pollutants is as follows: Under illumination conditions (generally provided by a xenon lamp), the MOF-derived heterostructure composite photocatalyst prepared in this invention comes into full contact with organic pollutants, and the interaction achieves a special catalytic and conversion effect, causing the surrounding oxygen and water molecules to deactivate persulfate, thereby improving the photocatalytic efficiency, and thus achieving the purpose of highly excited free radical negative ions with oxidizing ability to degrade organic pollutants.

[0038] Persulfates mainly include two categories: permonosulfate (PMS) and perdisulfate (PDS). Due to its asymmetric molecular structure (peroxy bond length 1.453 Å), PMS is more reactive and easier to excite than the symmetrical structure of PDS (bond length 1.497 Å). Therefore, the activation of PMS generates sulfate radicals (·SO4). - Advanced oxidation technologies for water have attracted much attention. In photocatalytic degradation systems, persulfate can be directly activated by photogenerated electrons to generate strong oxidizing species such as sulfate radicals. These radicals gradually oxidize and decompose organic pollutants into harmless small molecules through various mechanisms such as electron transfer, addition, and substitution, thereby achieving efficient water purification.

[0039] Preferably, the organic compound is at least one of Rhodamine B, Bisphenol A, Methylene Blue, Tetracycline, Ciprofloxacin, Oxytetracycline Hydrochloride, and Levofloxacin.

[0040] More preferably, the organic compound is Rhodamine B.

[0041] Compared with the prior art, the present invention has the following beneficial effects: This invention constructs a MOF-derived Co3O4 / ZnO composite photocatalyst by combining ZIF-67 (Co)-derived Co3O4 and MOF-5 (Zn)-derived ZnO. The heterostructure formed by the composite of these two semiconductors creates a synergistic effect, improving redox capabilities and enhancing the activation rate of persulfate, thereby increasing the photocatalytic efficiency and efficiently degrading organic pollutants. The photocatalyst of this invention achieves a degradation rate of Rhodamine B ≥97% within 6 minutes. The preparation method of this invention avoids resource waste and secondary pollution, and its low cost and ease of operation provide an efficient, economical, and sustainable solution for the environmental protection field. Attached Figure Description

[0042] Figure 1 The images are XRD patterns of Example 1, Comparative Example 1, and Comparative Example 2.

[0043] Figure 2 SEM image of ZIF-67(Co) prepared in this invention.

[0044] Figure 3 This is the SEM image of Comparative Example 2.

[0045] Figure 4 SEM image of MOF-5 (Zn) prepared in this invention.

[0046] Figure 5 This is the SEM image of Comparative Example 1.

[0047] Figure 6 SEM image of the MOF-derived Co3O4 / ZnO composite photocatalyst prepared in Example 1.

[0048] Figure 7 This is a catalytic activity diagram of the degradation of methylene blue (MB) and tetracycline (TCH) by persulfate PMS in Example 1.

[0049] Figure 8 The diagram shows the catalytic activity of PMS in the degradation of Rhodane B in Examples 1-4 and Comparative Examples 1-4.

[0050] Figure 9 The diagram shows the pseudo-first-order reaction kinetics of the degradation process of Rhodamine B in Examples 1-4 and Comparative Examples 1-3 at a dosage of 10 mg.

[0051] Figure 10 This is a TEM image of Example 1. Detailed Implementation

[0052] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0053] In this invention, ZIF-67(Co) is prepared as follows: 22.7 g of 2-methylimidazole is dissolved in 350 mL of methanol and stirred until homogeneous to form solution A. 2 mmol of Co(NO3)2·6H2O and 5 mg of hexadecyltrimethylammonium bromide (CTAB) are dissolved in 50 mL of methanol and stirred until homogeneous to form solution B. Solution A is then rapidly poured into solution B, and the resulting mixture is stirred for 30 min. Finally, the precursor product is collected by centrifugation, washing three times with ethanol and three times with water, and vacuum drying at 130 °C for 14 h.

[0054] In this invention, MOF-5 (Zn) is prepared as follows: 0.704 g of terephthalic acid (H2BDC) and 2.455 g of zinc acetate hexahydrate (Zn(Ac)2·2H2O) are added to 50 mL of N,N-dimethylformamide (DMF), and stirred at room temperature for 1 h. The colorless, transparent solution is then transferred to a polytetrafluoroethylene-lined autoclave and heated at 130 °C for 4 h. The resulting product is then centrifuged and washed three times with DMF, and then dried under vacuum at 130 °C for 14 h overnight.

[0055] Example 1 This embodiment provides a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, the preparation method of which includes: Preparation of Co3O4 / ZnO: Weigh 0.1g ZIF-67 (Co) and 0.5g MOF-5 (Zn) and grind them in an agate mortar. After grinding, pour the powder into a quartz crucible and place it in a muffle furnace. Under air atmosphere, heat the furnace from room temperature to 750℃ at a heating rate of 2℃ / min. Calcine the furnace at 750℃ for 3 hours and finally cool it to room temperature to obtain the product Co3O4 / ZnO, named Co3O4 / ZnO-5.

[0056] Example 2 This embodiment provides a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, which differs from Example 1 in that the amounts of ZIF-67 (Co) and MOF-5 (Zn) are 0.1 g and 0.3 g, respectively; the rest is the same as in Example 1. It is named Co3O4 / ZnO-3.

[0057] Example 3 This embodiment provides a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, which differs from Example 1 in that the amounts of ZIF-67 (Co) and MOF-5 (Zn) are 0.1 g and 0.7 g, respectively; the rest is the same as in Example 1. It is named Co3O4 / ZnO-7.

[0058] Example 4 This embodiment provides a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, which differs from Example 1 in that the amounts of ZIF-67 (Co) and MOF-5 (Zn) are 0.1 g and 0.9 g, respectively; the rest is the same as in Example 1. It is named Co3O4 / ZnO-9.

[0059] Comparative Example 1 This comparative example provides a MOF-derived ZnO photocatalyst, which differs from Example 1 in that ZIF-67(Co) was not added in S3; otherwise, it is the same as Example 1. ZnO was obtained.

[0060] Comparative Example 2 This comparative example provides a MOF-derived Co3O4 photocatalyst, which differs from Example 1 in that MOF-5(Zn) was not added in S3; otherwise, it is the same as Example 1. The product Co3O4 was obtained.

[0061] Comparative Example 3 This comparative example provides a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, which differs from Example 1 in that the amounts of ZIF-67 (Co) and MOF-5 (Zn) are 0.1 g and 0.1 g, respectively; otherwise, it is the same as Example 1. It is named Co3O4 / ZnO-1.

[0062] Comparative Example 4 This comparative example provides a MOF-derived Co3O4@ZnO photocatalyst, which differs from Example 1 in that MOF-5 (Zn) is replaced with ZIF-8 (Zn); otherwise, it is the same as Example 1. Co3O4@ZnO is obtained.

[0063] The preparation method of ZIF-8 (Zn) includes: adding 1.63 g of p-2-methylimidazole and 2.455 g of zinc acetate hexahydrate (Zn(Ac)2·2H2O) to 50 mL of N,N-dimethylformamide (DMF), stirring at room temperature for 1 h, then transferring the colorless and transparent solution to a polytetrafluoroethylene-lined autoclave and heating at 130 °C for 4 h. The resulting product is then centrifuged and washed three times with DMF, and then dried under vacuum at 130 °C for 14 h overnight.

[0064] Performance testing Figure 1 The figures show the XRD patterns of Example 1, Comparative Example 1, and Comparative Example 2. The results indicate that the characteristic diffraction peaks of ZnO and Co3O4 are essentially consistent with those on the standard cards (PDF#99-0111) and (PDF#43-1003), respectively, and no characteristic peaks of other substances were observed, indicating high purity and successful synthesis. Furthermore, the characteristic peaks of the synthesized Co3O4 / ZnO in the figures completely correspond to the characteristic peaks of ZnO and Co3O4, proving the successful synthesis of the composite.

[0065] Figure 2 The image shows a SEM image of ZIF-67(Co) prepared according to the present invention. As can be seen from the image, the ZIF-67(Co) prepared according to the present invention has a regular dodecahedral structure and a relatively smooth surface.

[0066] Figure 3 The image shown is a SEM image of Comparative Example 2. The ZIF-67(Co)-derived Co3O4 prepared in Comparative Example 2 retains the original crystal structure, but due to the collapse of the metal framework after calcination, the surface of Co3O4 becomes rough and has many pores, which is beneficial to improving the absorption rate of visible light, thereby improving the photocatalytic performance.

[0067] Figure 4 This is a SEM image of the MOF-5(Zn) prepared according to the present invention. The MOF-5(Zn) prepared by the present invention exhibits micron-sized flower-like crystal aggregates. The overall structure consists of irregular plate-like crystals as the framework, with slender rod-shaped / needle-shaped crystals extending outward from the surface, stacked radially, resembling coral or flower clusters. The cluster size is approximately 5~8 μm, with a smooth surface, clear edges, and obvious anisotropic growth characteristics.

[0068] Figure 5 The image shown is a SEM image of Comparative Example 1. The MOF-5(Zn)-derived ZnO prepared in Comparative Example 1 has a thinner overall framework after calcination, exhibiting a rose-like layered microstructure composed of numerous ultrathin nanosheets rolled and stacked layer by layer, with increased interlayer spacing. This is beneficial for increasing the specific surface area and improving the absorption rate of visible light, thereby enhancing photocatalytic performance.

[0069] Figure 6 The image shows a SEM image of the MOF-derived Co3O4 / ZnO composite photocatalyst prepared in Example 1. As can be seen from the image, the Co3O4 / ZnO composite photocatalyst prepared in this invention maintains the same crystal structure as Co3O4 and ZnO, with Co3O4 attached to the outer surface of ZnO.

[0070] Adsorption activity test The experiment was conducted using a UV-1800 UV-Vis spectrophotometer (purchased from Shanghai Meixi Instrument Co., Ltd.), without turning on the light source. 100 mL of Rhodamine B (concentration of 50 mg / L) simulating dye wastewater was added to the reactor and its initial value was measured. Then, 10 mg of photocatalyst was added. The reactor was magnetically stirred for 30 min without turning on the light source. Samples were taken for analysis. After centrifugation, the supernatant was taken and its concentration was measured at λ=554 nm using a UV spectrophotometer. The degradation rate Dr was calculated using the formula: Q=(C0-C)V / m, where C0 is the initial concentration of the Rhodamine B solution, C is the concentration of the Rhodamine B solution when adsorption equilibrium is reached, V is the volume of the solution, and m is the mass of the added catalyst.

[0071] Depend on Figure 8 It can be seen that all samples were tested after the dark reaction lasted for 30 minutes (i.e., Figure 8 During the period from 30 minutes before the start of the experiment to 0 minutes before the start of illumination (i.e., the -30 to 0 minute period), the adsorption of Rhodamine B reaches equilibrium, and the ratio of its equilibrium concentration C to the initial concentration C0 of the Rhodamine B solution is ≥0.9. This ensures that the decrease in Rhodamine B concentration during subsequent illumination experiments is attributable to photocatalytic effects, guaranteeing the accuracy of the experiment.

[0072] Photocatalyst catalytic efficiency test The experiment was conducted using a UV-1800 UV-Vis spectrophotometer (purchased from Shanghai Meixi Instrument Co., Ltd.) and irradiated with a 420nm xenon lamp (purchased from Zhenjiang Yinzhu Chemical Technology Co., Ltd.) at a power of 50W. 100 mL of Rhodamine B (concentration 50 mg / L) simulating dye wastewater was added to the reactor, and its initial concentration was measured. Then, 10 mg of the prepared photocatalyst was added, and the mixture was magnetically stirred for 30 min. Samples were taken for analysis, and after centrifugation, the supernatant was measured at λ=554 nm using a UV spectrophotometer. The sample was returned to the reactor, and 10 mg of PMS was added. Irradiation with a 420 nm light source was then initiated. Samples were taken for analysis every 2 min during the irradiation process. After centrifugation, the supernatant was measured at λ=554 nm using a UV spectrophotometer. The absorbance was measured at nm, and the degradation rate Dr was calculated using the formula: Dr = (C0 - C) × 100 / C0, where C0 is the concentration after adsorption equilibrium is reached, C is the concentration of Rhodamine B solution measured at time t, and t is the reaction time. In photocatalytic reactions, the catalyst that generates electron-hole pairs upon light excitation is limited. As the light intensity increases, more catalyst will join the reaction, but when the light intensity increases to a certain value, there is no excess catalyst to generate electron-hole pairs, and it has almost no effect on catalytic performance. Conversely, excessively strong light intensity will cause the reaction system temperature to rise, resulting in catalyst aggregation and thus reducing catalytic performance.

[0073] Figure 7 This is a catalytic activity diagram for the degradation of methylene blue and tetracycline by persulfate PMS in Example 1. Figure 7 It can be seen that after 25 minutes, the degradation rates of 10 mg / L methylene blue and tetracycline by PMS activated by the Co3O4 / ZnO-5 catalyst were 100% and 79.6%, respectively.

[0074] Figure 8The figures show the catalytic activity of PMS activation for the degradation of Rhodamine B in Examples 1-4 and Comparative Examples 1-4. As can be seen from the figures, different mass ratios of Co3O4 / ZnO resulted in different photodegradation efficiencies. With increasing ZnO mass ratio in the composite, the degradation rate of Rhodamine B activated by the Co3O4 / ZnO catalyst in PMS showed a trend of first increasing and then decreasing. Compared to single semiconductor photocatalysts, the overall degradation rate of the Co3O4 / ZnO catalyst of this invention was higher. When the mass ratio of Co3O4 / ZnO photocatalyst was 1:5, the Co3O4 / ZnO-5 catalyst in Example 1 showed the highest degradation efficiency for Rhodamine B activated by PMS, reaching 100% within 6 minutes of illumination. The photodegradation efficiencies of Co3O4 / ZnO-1, Co3O4 / ZnO-3, Co3O4 / ZnO-7, and Co3O4 / ZnO-9 within 6 minutes were 65%, 98%, 98%, and 97%, respectively. Compared to ZIF-67(Co)-derived Co3O4, which exhibits a 34% degradation rate within 6 minutes of illumination, and MOF-5(Zn)-derived ZnO, which shows a 17% degradation rate within the same timeframe, this invention demonstrates that the composite of ZIF-67(Co)-derived Co3O4 and MOF-5(Zn)-derived ZnO exhibits synergistic effects, resulting in a photocatalyst with excellent photocatalytic efficiency. Comparative Example 4 prepared a Co3O4@ZnO photocatalyst by combining ZIF-67(Co)-derived Co3O4 and ZIF-8(Zn)-derived ZnO, achieving a 57% degradation rate of Rhodamine B within 6 minutes. The comparison shows that the catalytic efficiency of the Co3O4@ZnO photocatalyst derived from ZIF-67(Co) and ZIF-8(Zn) is significantly lower than that of the Co3O4@ZnO photocatalyst derived from ZIF-67(Co) and MOF-5(Zn) in this invention. This may be because ZIF-8, with 2-methylimidazole as a ligand, undergoes rapid pyrolysis and complete oxidation during calcination, resulting in highly crystalline ZnO with almost no defects and very few oxygen vacancies. Consequently, it cannot quickly and effectively break the O-O bonds to generate sulfate radicals (·SO4). - This leads to its low catalytic efficiency.

[0075] Experimental data were fitted using first-order reaction kinetic equations to quantitatively analyze the degradation rate of Rhodamine B by the photocatalyst. Figure 9 As shown, under the action of PMS, the reaction rate constants of Examples 1-4 are 115 × 10⁻⁶, respectively. -2 min -1 73×10 -2 min -1 58×10 -2 min -1 and 50×10 -2 min-1 In contrast, the reaction rate constant of ZnO with Co3O4 in Comparative Examples 1 and 2 is 0.74 × 10⁻⁶. -2 min -1 and 2.5×10 -2 min -1 As shown in the figure, under the same conditions, the reaction rate constant of Example 1 was the largest under the action of PMS, which was significantly higher than that of Comparative Example 1 (0.74 × 10⁻⁶). -2 min -1 ) and Comparative Example 2 (2.5 × 10 -2 min -1 155 times and 46 times.

[0076] Figure 10 The TEM image for Example 1 shows that, in Figure (b), the lattice fringes corresponding to ZnO (101) and Co3O4 (220) intersect closely at the edges of the regions, with no obvious interfacial voids or separation layers observed. This indicates that there is an atomic-level close contact or intercalation interface between Co3O4 and ZnO, suggesting that Co3O4 and ZnO form a heterostructure. The low-magnification TEM image in Figure (a) shows that the material surface exhibits a dense agglomeration of nanoparticles, rather than large, independently dispersed particles. This morphological feature of symbiotic growth or close loading strongly supports the formation of a composite structure, rather than a simple physical-mechanical mixture.

[0077] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst, characterized in that, Includes the following steps: ZIF-67 (Co) and MOF-5 (Zn) were mixed and calcined at 550~750℃ to obtain the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst. The mass ratio of ZIF-67 (Co) to MOF-5 (Zn) is 1:(3~9).

2. The preparation method according to claim 1, characterized in that, The preparation method of ZIF-67(Co) includes: mixing dimethylimidazole, soluble cobalt salt and methanol, reacting to obtain ZIF-67(Co).

3. The preparation method according to claim 2, characterized in that, The preparation method of ZIF-67(Co) also includes the step of adding a surfactant.

4. The preparation method according to claim 1, characterized in that, The preparation method of MOF-5 (Zn) includes: mixing terephthalic acid, soluble zinc salt and polar organic solvent, and reacting them with a solvothermal agent to obtain MOF-5 (Zn).

5. The preparation method according to claim 1, characterized in that, The mass ratio of ZIF-67 (Co) to MOF-5 (Zn) is 1:(5~9).

6. The preparation method according to claim 1, characterized in that, The calcination time is 4-6 hours.

7. The preparation method according to claim 1, characterized in that, The calcination is performed in air or in an oxygen-containing atmosphere.

8. The MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst prepared by any of the preparation methods described in claims 1 to 7.

9. The application of the MOF-derived Co3O4 / ZnO heterostructure composite photocatalyst of claim 8 in the degradation of organic matter in wastewater.

10. The application according to claim 9, characterized in that, The organic compound is at least one of Rhodamine B, Bisphenol A, Methylene Blue, Tetracycline, Ciprofloxacin, Oxytetracycline Hydrochloride, and Levofloxacin.

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