Double-metal MOF (Metal Organic Framework) catalyst based on waste plastic as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of metal organic framework materials and catalytic oxidation, and particularly relates to a bimetallic MOF catalyst based on waste plastics and a preparation method and application thereof. Adding the PET plastic bottle fragments and metal salt into a solvent, heating to a specified temperature, reacting for a preset time, then cooling to room temperature, centrifugally separating, cleaning and drying to obtain the bimetallic MOF catalyst. The preparation method is simple in step, and a large amount of time can be saved. The bimetallic MOF catalyst can effectively catalyze and degrade various dyes, antibiotics and phenol pollutants, and has a good cyclic catalysis effect, a good cyclic catalysis effect and excellent stability. The bimetallic MOF catalyst is prepared from the waste plastics, so that the raw material cost in the MOF synthesis process can be reduced, and the environmental problem of the waste plastics is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework materials and catalytic oxidation technology, specifically relating to a bimetallic MOF catalyst based on waste plastics, its preparation method and application. Background Technology

[0002] With the acceleration of industrialization and modernization, pollution from dyes, antibiotics, and phenolic compounds has become increasingly serious, becoming one of the main components of water pollution. While their widespread use brings convenience to production, it also poses a severe challenge to the environment and human health. The discharge of dyes, antibiotics, and phenolic compounds not only disrupts the ecological balance of aquatic bodies but may also have long-term negative impacts on organisms through the food chain. Therefore, studying the characteristics, hazards, and efficient removal methods of these pollutants is an important topic in environmental science today.

[0003] With the increasing severity of global plastic pollution, the recycling and reuse of waste plastics has become a crucial issue in environmental protection. Waste plastics are typically difficult to degrade, and plastic waste can persist for hundreds of years. These plastics decompose slowly in the natural environment, and their long-term accumulation causes serious pollution to soil, air, and water sources. The non-biodegradable nature of plastics leads to the accumulation of large amounts of plastic waste in the environment, placing severe pressure on ecosystems. Therefore, developing innovative waste plastic recycling technologies can not only reduce environmental pollution but also provide sustainable resources for the preparation of new materials.

[0004] In recent years, the synthesis of bimetallic MOF materials from waste plastics has become an emerging research direction. MOFs are a class of porous materials formed by the coordination bonding of metal ions or metal clusters with organic ligands. MOF materials possess high porosity, good tunability, and large specific surface area, thus demonstrating great application potential in many fields. For example, Mustafa T. Yagub et al. explored the use of biomass-based activated carbon from industrial waste and agricultural byproducts, using these low-cost materials as adsorbents to treat wastewater. Zhang et al. investigated the synthesis methods and applications of water pollutant removal, providing a pathway for the effective utilization of water-stable MOFs in material design and environmental remediation. The application prospects of MOFs in pollutant remediation are also discussed.

[0005] In the prior art, Chinese invention patent application number 202410043044.6 discloses a MOF adsorbent prepared from waste PET plastic, its preparation method, and its application. First, PET is depolymerized to obtain terephthalic acid. Then, a one-pot method is used to disperse metal ions into the resin channels using a complexing agent to prepare a MOF-supported resin composite adsorbent. This adsorbent exhibits excellent performance in adsorbing Congo red. Chinese invention patent application number 202510124819.7 discloses a method for preparing a MOF catalyst using waste PET plastic as a ligand source and its application. The method involves obtaining terephthalic acid from depolymerized PET, using it as the organic framework for preparing MOF, and then adding metal salts, organic solvents, and regulators to the reaction system. The reaction is carried out under heating or room temperature conditions. After the reaction, the MOF catalyst is finally obtained through centrifugation, washing, and drying. The obtained catalyst exhibits good thermal stability below 400℃ and good catalytic performance in oxidizing olefins to epoxides.

[0006] The above-mentioned preparation methods all employ a two-step process: first, PET is depolymerized to obtain terephthalic acid, and then it is synthesized through heating. This process is relatively cumbersome and the reaction time is excessively long. Furthermore, the MOF catalysts in the existing technologies can only effectively catalyze a specific type of pollutant, such as Congo red or olefins, and cannot meet the requirement of achieving good adsorption effects on common pollutants such as dyes, antibiotics, and phenolic compounds, thus limiting their application scope. Summary of the Invention

[0007] Based on this, this application provides a bimetallic MOF catalyst based on waste plastics, its preparation method and application, to solve the technical problems of the existing MOF catalyst preparation process being relatively cumbersome and the reaction time being too long. At the same time, the MOF catalysts prepared can only effectively catalyze a certain type of pollutant and cannot achieve good adsorption effect on common pollutants such as dyes, antibiotics and phenolic compounds, thus limiting their application scope.

[0008] The technical solution to the above-mentioned technical problems in this application is as follows: A method for preparing a bimetallic MOF catalyst based on waste plastics, comprising: PET plastic bottle fragments, a first metal salt, and a second metal salt are added to a solvent, heated to a specified temperature, reacted for a predetermined time, then cooled to room temperature, centrifuged, washed, and dried to obtain the bimetallic MOF catalyst.

[0009] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the first metal salt includes either copper nitrate pentahydrate or copper sulfate, and the second metal salt includes either manganese nitrate hexahydrate or manganese sulfate.

[0010] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the sum of the masses of the first metal salt and the second metal salt is a, and the mass of the PET plastic bottle fragments is b, where a:b = 5:(2 to 6).

[0011] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the molar ratio of the first metal salt to the characteristic metal in the second metal salt is (1 to 9):1.

[0012] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the solvent is a mixture of DMF and water in a volume ratio of (1 to 4):1.

[0013] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the specified temperature is 150°C to 250°C.

[0014] Preferably, in the above-mentioned method for preparing bimetallic MOF catalysts based on waste plastics, the predetermined time is 3 h to 6 h.

[0015] A bimetallic MOF catalyst based on waste plastics is prepared by any of the above-described methods for preparing bimetallic MOF catalysts based on waste plastics.

[0016] Preferably, the above-mentioned bimetallic MOF catalyst based on waste plastics is used in the degradation of organic dyes, antibiotics and phenolic compounds.

[0017] Preferably, in the above application, a bimetallic MOF catalyst and an oxidant are added to wastewater containing organic dyes, antibiotics, or phenolic compounds for degradation.

[0018] Compared with the prior art, this application has at least the following advantages: This application discloses a method for preparing a bimetallic MOF catalyst based on waste plastics. By reacting waste PET plastics with metal salts and organic ligands under appropriate conditions, a bimetallic MOF catalyst was successfully synthesized. This application uses a one-step microwave hydrothermal synthesis method to synthesize Cu / Mn-MOF catalysts. Compared with traditional synthesis methods, such as two-step methods and ordinary hydrothermal synthesis methods, this method is simpler and can save a significant amount of time.

[0019] The bimetallic MOF catalyst prepared by the method described in this application, namely the Cu / Mn-MOF catalyst, can effectively catalyze the degradation of various dyes, antibiotics, and phenolic pollutants, such as CR, MB, MeBe, Rh B, CIPRO, TC, and 4-NP, with degradation rates exceeding 80%. In particular, the residue rates of MB, MeBe, and Rh B almost reached 0% after 24 minutes of reaction; the degradation rates of TC, CIPRO, and 4-NP reached over 98% after 24 minutes. In addition to its excellent catalytic degradation effect, it maintains high catalytic activity even after six cycles, demonstrating good cyclic catalytic performance. Furthermore, the Cu / Mn-MOF catalyst exhibits good salt tolerance, showing potential for application in complex organic wastewater treatment; and the Cu / Mn-MOF catalyst showed no significant color change after being soaked in water for one week, indicating its good stability.

[0020] This application proposes a method for preparing bimetallic MOF catalysts using waste plastics. This method not only reduces the raw material cost in the MOF synthesis process but also endows MOF materials with certain mechanical strength and chemical stability. Furthermore, it effectively solves the environmental problems associated with waste plastics, provides an innovative recycling pathway for waste plastics, and opens up new avenues for the preparation and application of MOF materials. This approach has significant implications for environmental protection and resource utilization. Attached Figure Description

[0021] Figure 1 The images show the morphology of the prepared MOF catalysts under electron microscopy; where (ae) represents a fixed Cu:Mn molar ratio of 9:1 with varying PET mass; and (fj) represents a fixed PET mass with varying Cu:Mn molar ratio in the metal salt.

[0022] Figure 2 (a) is the FT-IR spectrum; (b) is the XPS spectrum; (c) is the TG analysis diagram; (d) is the surface potential diagram.

[0023] Figure 3 (a) Degradation of Rh B with and without bimetallic MOF (Co=30 mg / L, pH=7, 1 ml 90 mM PMS); (b) Degradation of dyes by Cu / Mn-MOF catalyst (Co=30 mg / L, pH=7, 1 ml 90 mM PMS); (c) Degradation of antibiotics by Cu / Mn-MOF catalyst (Co=30 mg / L, pH=7, 1 ml 90 mM PMS); (d) Degradation of phenols by Cu / Mn-MOF catalyst (Co=30 mg / L, pH=7, 1 ml 90 mM PMS).

[0024] Figure 4(a) shows the reusability of the Cu / Mn-MOF catalyst; (b) shows the effect of different metal salts on the catalytic efficiency.

[0025] Figure 5 (a) is a SEM image of the catalyst after soaking for one week; (b) is an optical photograph of the MOF catalyst after soaking for one week. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. The technical solutions of the present invention will be further described below with reference to the accompanying drawings of the embodiments of the present invention. The present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] In one specific embodiment of this application, a method for preparing a bimetallic MOF catalyst based on waste plastics includes: PET plastic bottle fragments, a first metal salt, and a second metal salt are added to a solvent, heated to a specified temperature, reacted for a predetermined time, then cooled to room temperature, centrifuged, washed, and dried to obtain the bimetallic MOF catalyst.

[0029] Waste plastics contain abundant carbon and hydrogen, which can serve as fundamental raw materials for MOF synthesis. Through appropriate treatment and reaction, waste plastics can be converted into MOF catalysts, reducing synthesis costs and effectively addressing the environmental problems associated with waste plastics. Furthermore, MOF catalysts derived from waste plastics often possess unique structures and properties, making them suitable for the adsorption and degradation of environmental pollutants. Using MOF catalysts for water treatment offers high treatment efficiency and low environmental burden, effectively removing harmful substances from water. Bimetallic MOF catalysts have significant advantages over monometallic MOF catalysts, as the bimetallic element can enhance the overall activity of the catalyst through synergistic effects. For example, Cu can provide electrons, while Mn helps enhance the catalyst's adsorption and activation capabilities for reactants. This synergistic effect makes bimetallic catalysts more efficient than monometallic catalysts in certain reactions. Monometallic catalysts may undergo oxidation or degradation during catalysis, leading to a decrease in catalytic activity. The other metal in a bimetallic catalyst (such as Mn) may help prevent excessive oxidation of Cu metal, improving the catalyst's stability and durability. Therefore, the first metal salt includes either copper nitrate pentahydrate or copper sulfate, and the second metal salt includes either manganese nitrate hexahydrate or manganese sulfate. Preferably, the first metal salt is copper nitrate pentahydrate, and the second metal salt is manganese nitrate hexahydrate.

[0030] When the relative contents of PET and metal salt in the reaction were changed, the morphology of the resulting bimetallic MOF catalyst changed significantly. Preferably, the sum of the masses of the first and second metal salts is *a*, and the mass of the PET plastic bottle fragments is *b*, where a:b = 5:(2 to 6). For example, if the sum of the masses of the first and second metal salts is 10g, then the mass of the PET plastic bottle fragments is 4g to 12g. Further, a:b = 5:5, that is, the ratio of the sum of the masses of the first and second metal salts to the mass of the PET plastic bottle fragments is 5:5, resulting in the most regular morphology of the bimetallic MOF catalyst.

[0031] Preferably, the molar ratio of the characteristic metal in the first metal salt to that in the second metal salt is (1 to 9):1. For example, when the first metal salt is copper nitrate pentahydrate or copper sulfate, its characteristic metal is copper (Cu), and when the second metal salt is manganese nitrate hexahydrate or manganese sulfate, its characteristic metal is manganese (Mn). These two characteristic metals enhance the overall activity of the catalyst through a synergistic effect. Cu can provide electrons, while Mn helps to enhance the catalyst's adsorption and activation capacity for reactants. The synergistic effect of both makes bimetallic catalysts more efficient than monometallic catalysts in certain reactions.

[0032] Preferably, the solvent is a mixture of DMF and water in a volume ratio of (1 to 4):1.

[0033] Furthermore, the specified temperature is 150°C to 250°C, and the predetermined duration is 3 hours to 6 hours.

[0034] For example, PET plastic bottles are cut into fragments and added to a solvent (DMF and water are mixed in a volume ratio of 1 to 4) at a mass ratio of (2 to 6): 5) with metal salts. The metal salts include Mn(NO3)2·6H2O and Cu(NO3)2·5H2O, and the molar ratio of copper to manganese in the metal salts is (1 to 9): 1. The mixture is then transferred to a microwave reactor and heated at 150 ℃ to 250 ℃ for 3 h to 6 h. After the temperature drops to room temperature, the mixture is centrifuged and washed sequentially with DMF, H2O, and ethanol. Finally, it is placed in a forced-air drying oven and dried at 90 ℃ for 8 h to obtain Cu / Mn-MOF material, which is the bimetallic MOF catalyst based on waste plastics.

[0035] This scheme utilizes a one-step microwave hydrothermal synthesis method to synthesize large quantities of Cu / Mn-MOF materials from waste PET, which can then be used as a catalyst for the catalytic degradation of wastewater. Compared to traditional synthesis methods, such as two-step methods and conventional hydrothermal synthesis methods, the two-step method first requires converting waste plastics into terephthalic acid, which is cumbersome, while the conventional hydrothermal method has an excessively long reaction time. This scheme chooses the microwave hydrothermal synthesis method, which can save a significant amount of time.

[0036] The preparation of bimetallic MOF catalysts using waste plastics can not only reduce the raw material cost in the MOF synthesis process, but also endow MOF materials with certain mechanical strength and chemical stability. At the same time, it can not only effectively solve the environmental problems of waste plastics and provide an innovative way to recycle waste plastics, but also open up new ideas for the preparation and application of MOF materials, providing a low-cost and sustainable method, which has important environmental protection and resource utilization significance.

[0037] In another specific embodiment of this application, a bimetallic MOF catalyst based on waste plastic is prepared by the preparation method of the bimetallic MOF catalyst based on waste plastic described in any of the above claims.

[0038] The bimetallic MOF catalyst used in this scheme for water treatment exhibits high treatment efficiency and low environmental impact, effectively removing harmful substances from water. It can effectively catalyze the degradation of various dyes, antibiotics, and phenolic pollutants, such as CR, MB, MeBe, Rh B, CIPRO, TC, and 4-NP, achieving degradation rates exceeding 80%. In particular, MB, MeBe, and Rh B show almost 0% residue after 24 minutes of reaction; TC, CIPRO, and 4-NP show degradation rates exceeding 98% after 24 minutes. Besides its excellent catalytic degradation effect, it maintains high catalytic activity even after six cycles, demonstrating good cyclic catalytic performance. Furthermore, the Cu / Mn-MOF catalyst exhibits good salt tolerance, showing potential for application in complex organic wastewater treatment; and the Cu / Mn-MOF catalyst showed no significant color change after soaking in water for one week, indicating good stability.

[0039] In another specific embodiment of this application, the above-mentioned bimetallic MOF catalyst based on waste plastics is used in the degradation of organic dyes, antibiotics or phenolic compounds.

[0040] Preferably, in the above applications, a bimetallic MOF catalyst and an oxidant are added to wastewater containing organic dyes, antibiotics, or phenolic compounds for degradation. For example, a bimetallic MOF is used as the catalyst and PMS as the oxidant; both are added to the wastewater containing pollutants, mixed and stirred, to degrade the organic dyes, antibiotics, or phenolic compounds in the wastewater.

[0041] It is worth noting that the process temperature and process time involved in the above embodiments are all temperatures or times used in the experiment. Any reasonable adjustments made by those skilled in the art based on the process temperature and process time provided by the present invention, within the error range, should be included within the protection scope of the present invention.

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through experimental examples.

[0043] 1.1 Materials and Reagents The PET waste plastic bottles came from Wahaha mineral water bottles. N,N-dimethylformamide was purchased from Xuzhou Tianhong Chemical Co., Ltd. Manganese nitrate hexahydrate and copper nitrate pentahydrate were supplied by Maclean and Bailingwei companies, respectively. Terephthalic acid (PTA) was supplied by Yuanye Biotechnology Co., Ltd. Potassium persulfate (PMS) was purchased from Shanghai Aladdin Co., Ltd. Rhodamine b, Congo red, methylene blue, methylene blue, tetracycline, ciprofloxacin, and p-nitrophenol were purchased from Shanghai Guangnuo Chemical Technology Co., Ltd., Shuangshuang Chemical Co., Ltd., Yuanye Biotechnology Co., Ltd., Bailingwei Technology Co., Ltd., Aladdin Technology Co., Ltd., Ron Chemical Reagent Co., Ltd., and Keyuan Biochemical Co., Ltd., respectively.

[0044] 1.2 Preparation of MOF catalysts 1.2.1 Preparation of Cu / Mn-MOF catalyst from waste PET bottles PET plastic bottles were cut into 3 mm × 3 mm fragments. Then, 0.3111 g of Mn(NO3)2·6H2O, 2.2693 g of Cu(NO3)2·5H2O, and 2.57 g of PET flakes were added to 26.66 ml of DMF and 13.33 ml of H2O. The mixture was transferred to a microwave reactor and heated at 180 °C with 500 W for 4 h. After cooling to room temperature, Cu / Mn-MOF material was obtained by centrifugation. The material was then washed sequentially with DMF, H2O, and ethanol, and finally dried in a forced-air drying oven at 90 °C for 8 hours. During this preparation process, different Cu / Mn-MOF materials were prepared by varying the contents of PET, Mn(NO3)2·6H2O, and Cu(NO3)2·5H2O.

[0045] 1.2.2 Preparation of MOF catalysts without bimetallic addition PET plastic bottles were cut into 3 mm × 3 mm pieces and added to 26.66 ml DMF and 13.33 ml H2O. The mixture was then transferred to a microwave reactor and heated at 180 °C with 500 W for 4 h. After the temperature dropped to room temperature, the MOF material without added bimetallic compounds was obtained by centrifugation. The MOF material was then washed sequentially with DMF, H2O, and ethanol. Finally, it was placed in a forced-air drying oven and dried at 90 °C for 8 hours to obtain the MOF material without added bimetallic compounds.

[0046] Characterization of Cu / Mn-MOF catalysts The microstructure of the material surface was observed using a thermal field emission scanning electron microscope (SEM) system (Zeiss SIGMA 500, Germany) and a transmission electron microscope (TEM) (FEI Talos F200x, USA); X-ray diffraction (XRD) measurements were performed using a Shimadzu XRD-6000 (Japan); X-ray photoelectron spectroscopy (XPS) analysis was performed using a Thermo Scientific K-Alpha; the surface area, pore size distribution, and pore volume (BET) of the catalyst were measured using a 3H-2000PM1 (China) with N as the adsorbent; the thermal stability of the catalyst was tested using a STA 6000 (PerkinElmer, USA); particle size and potential analysis were performed using a Zetasizer NanoZS90 (UK); and the chemical structure and composition of the catalyst were analyzed using a Fourier transform infrared spectroscopy (FTIR) system (WQF-520A, China).

[0047] Evaluation of Cu / Mn-MOF catalytic performance To evaluate the catalytic performance of the prepared Cu / Mn-MOF material, 25 mL each of methylene blue (MB), methylene blue (MeBe), rhodamine b Rh B, Congo red (CR), tetracycline (TC), ciprofloxacin (CIPRO), and p-nitrophenol (4-NP) at an initial concentration of 30 mg / L, along with a certain amount of catalyst, were measured into 100 mL Erlenmeyer flasks. 1 mL of 90 mM PMS was added, and the flasks were placed in a shaker. The reaction process was monitored at 200 rpm and 25 °C to investigate the effects on the degradation of different pollutants. The concentrations of various pollutants at different time points in the reaction system were determined using UV-Vis spectroscopy (TU-1810DSPC, China).

[0048] After the catalytic reaction was completed, the catalyst in the solution was separated and recovered by centrifugation, then washed with pure water and dried at 60°C. The catalyst was then subjected to a recycling test under the previous conditions to evaluate its recyclability. Finally, to explore the reaction mechanism of the catalytic process, free radical quenching experiments were conducted. Different quenchers were added to the catalytic system, and the contributions of sulfate radicals, hydroxyl radicals, and singlet oxygen were investigated using methanol (MeOH), tert-butanol (TBA), and furfuryl alcohol (FFA), respectively. The above experiments included parallel samples and repeated experiments, each performed independently at least three times.

[0049] Results and Discussion 2.1 Characterization of Cu / Mn-MOF catalysts The morphology of the prepared MOF catalyst was characterized by scanning electron microscopy, such as... Figure 1As shown, changing the relative contents of PET and metal salt in the reaction significantly altered the morphology of the resulting MOF. Decreasing PET content resulted in an irregular shape, while increasing PET content led to a more regular morphology. Only when the mass ratio of PET to metal salt was 5:5 did the MOF exhibit the most regular morphology. Then, by fixing the PET and metal salt contents and changing the relative contents of Cu and Mn, it was found that as the Cu content increased, the structure of the Cu / Mn-MOF became increasingly regular. Even at lower Cu contents (e.g., 50% and 60%), significant phase separation was observed in the prepared material, with smaller nanoparticles attached to larger particles. Therefore, we selected a 5:5 mass ratio of PET to metal salt and a Cu content of 90% in the bimetallic salt as the optimal preparation conditions for Cu / Mn-MOF.

[0050] Infrared spectroscopy is highly sensitive to conformational changes in polymer molecular regions; therefore, it is used for chemical structure analysis of MOFs. For example... Figure 2 As shown in (a), Cu / Mn-MOF in and The main characteristic peaks obtained at the location correspond to the stretching vibrations of the C=O and CO groups, respectively. The benzene ring structure of the PTA ligand in PET will... Characteristic absorption peaks of C=C stretching vibrations appear on both sides. These peaks represent the vibrational modes of the aromatic ring and can help confirm the presence of PTA ligands. The stretching vibrations of CH were observed, including those of the methyl (-CH3) and methylene (-CH2) groups. The bending vibrations of the OH group were also observed. The vicinity is represented by a broad peak. The characteristic absorption peaks of Cu / Mn-O also appear nearby.

[0051] XPS characterization was performed to further understand the surface composition and chemical state of Cu / Mn-MOF materials. Figure 2 (b) The XPS wide-angle measurement spectrum shows that C, N, O, Mn, and Cu are all present in the Cu / Mn-MOF material. The characteristic peaks of C appear at 284 eV–292 eV, N at 401 eV–402 eV, O at 531 eV–534 eV, Mn at 642 eV–650 eV, and Cu at 932 eV–955 eV. It can be seen that no obvious characteristic peaks appear in the blank spectrum. The characteristic peak of N also appears in the Cu / Mn-MOF material. This may be because N in the DMF solution coordinates with some other element, or it may be due to the presence of the metal nitrate precursor NO3. - Residual.

[0052] To investigate the thermal stability of this material, the thermal stability (TG) of this MOF material was measured, and the results are as follows: Figure 2 As shown in (c), the test results show that the Cu / Mn-MOF material remains stable at 800℃ with almost no weight loss. This confirms that the thermal stability of bimetallic MOF materials is much superior.

[0053] like Figure 2 As shown in (d), the Zeta potential values ​​of the Cu / Mn-MOF catalyst solution under different pH conditions are displayed. The Zeta potential decreases as the solution pH increases, reaching its lowest value of -45.73 mV at pH=9. As the pH continues to increase, the Zeta potential increases, remaining negative at -27.93 mV even at the highest pH. Measurements of the potential of the Cu / Mn-MOF catalyst solution with varying pH values ​​reveal that pH has a significant impact on the potential of the same solution, and the solution exhibits the highest negative potential under strongly acidic conditions. Therefore, different pH values ​​may lead to different effects on the subsequent catalytic dyes and contaminants, resulting in significant differences in catalytic performance.

[0054] 2.2 Evaluation of the catalytic performance of MOF catalysts 2.2.1 Catalytic effect of MOF catalyst on different pollutants To verify the catalytic effect of MOF materials, MOFs without and with bimetallic additives were used to catalyze the degradation of Rh B. Figure 3 As shown in (a), the catalytic effect of bimetallic MOF materials is significantly better than that of MOF materials without bimetal.

[0055] To further evaluate the catalytic performance of the Cu / Mn-MOF catalyst, degradation experiments were conducted on different dyes (CR, MB, MeBe, RhB), different antibiotics (CIPRO, TC), and phenolic contaminants (4-NP). Figure 3 As shown in (b), after 24 min of reaction, the residual rates of MB, MeBe, and RhB were almost 0%, while the residual rate of CR was relatively high, around 20%. This is presumably because the pore structure of the MOF is relatively narrow or mismatched with the molecular size of Congo red, preventing dye molecules from entering the MOF channels and resulting in poor catalytic effect. Furthermore, the interaction between the sulfonic acid groups of Congo red and certain active sites on the MOF material surface may be weak, which could also affect the catalytic effect. Congo red and methylene blue are anionic dyes, while Rhodamine B and methylene blue are cationic dyes. The prepared MOF material is negatively charged, thus exhibiting better catalytic effect on cationic dyes. Among the anionic dyes, Congo red has the largest molecular size, resulting in the lowest degradation efficiency for Congo red.

[0056] like Figure 3 As shown in (c) and (d), the catalyst also has a good catalytic effect on TC, CIPRO and 4-NP. After 24 min of reaction, the degradation rate can reach almost 98% or more.

[0057] 2.2.2 Cyclic performance and stability of Cu / Mn-MOF catalyst The cycle stability of a catalyst is one of the key indicators for measuring its practical application potential. In this study, the prepared Cu / Mn-MOF catalyst was subjected to multiple cycle tests to explore its performance in the long-term operation process.

[0058] During the experiment, after each catalytic reaction, the catalyst was efficiently recovered from the reaction system by centrifugation (8000 rpm for 5 min). The recovered catalyst was then washed, dried, and used in the next round of catalytic reaction.

[0059] like Figure 4 As shown in (a), during initial use, the catalyst exhibited excellent catalytic performance in catalyzing Rh B, TC, and 4-NP, with degradation rates all exceeding 95%. With increasing cycle number, the catalytic activity decreased slightly after the first cycle, with the TC degradation rate dropping to 90%, while the degradation rates of Rh B and 4-NP were 97% and 93%, respectively. However, the degradation rates remained at a relatively high level. Until the sixth cycle, except for 4-NP which dropped below 70%, the degradation rates of Rh B and TC remained around 80%. Overall, Cu / Mn-MOF demonstrated good reusability.

[0060] Furthermore, the effects of different metal salts on the catalytic activity of Cu / Mn-MOF were investigated, such as... Figure 4 As shown in (b), the introduction of different metal salts also affected the activity of pollutants to varying degrees. Compared with other metal salts, NaCl, CaCl2, and CaSO4 had a greater inhibitory effect on the reaction process. For different pollutants, the introduction of metal salts had the most significant effect on nitrophenol, followed by TC, while it had almost no effect on RhB. Furthermore, the removal rate of TC was reduced to a minimum of 92%, while the removal rate of 4-NP was reduced to a minimum of 82%. This indicates that Cu / Mn-MOF has good salt tolerance and has the potential to be applied to complex organic wastewater.

[0061] To further analyze the stability of the catalyst structure during the cycle, only the data of Cu / Mn-MOF will be retained, and its structural properties will be characterized after soaking in water for one week. Figure 5(a) SEM images of the MOF catalyst after soaking show that the morphology of Cu / Mn-MOF did not change significantly. Furthermore, macroscopic photographs of the catalyst... Figure 5 (b) It can be seen that the appearance color of the bimetallic Cu / Mn-MOF did not change significantly. This further demonstrates that its catalyst has good stability.

[0062] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a bimetallic MOF catalyst based on waste plastics, characterized in that, include: PET plastic bottle fragments, a first metal salt, and a second metal salt are added to a solvent, heated to a specified temperature, reacted for a predetermined time, then cooled to room temperature, centrifuged, washed, and dried to obtain the bimetallic MOF catalyst.

2. The method for preparing a bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The first metal salt includes either copper nitrate pentahydrate or copper sulfate, and the second metal salt includes either manganese nitrate hexahydrate or manganese sulfate.

3. The method for preparing a bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The sum of the masses of the first metal salt and the second metal salt is a, and the mass of the PET plastic bottle fragment is b, where a:b = 5:(2 to 6).

4. The method for preparing the bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The molar ratio of the first metal salt to the characteristic metal in the second metal salt is (1 to 9):

1.

5. The method for preparing a bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The solvent is a mixture of DMF and water in a volume ratio of (1 to 4):

1.

6. The method for preparing the bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The specified temperature is 150 ℃ to 250 ℃.

7. The method for preparing the bimetallic MOF catalyst based on waste plastics as described in claim 1, characterized in that, The predetermined duration is 3 to 6 hours.

8. A bimetallic MOF catalyst based on waste plastics, characterized in that, It is prepared by the method for preparing bimetallic MOF catalyst based on waste plastics according to any one of claims 1 to 7.

9. The application of the bimetallic MOF catalyst based on waste plastics as described in claim 8 in the degradation of organic dyes, antibiotics and phenolic compounds.

10. The application as described in claim 9, characterized in that, Bimetallic MOF catalysts and oxidants are added to wastewater containing organic dyes, antibiotics, or phenolic compounds for degradation.

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