Defect-state MOFs derived trimanganese tetraoxide material and preparation method and application thereof

Abstract

The application discloses a kind of defect state MOFs derived trivalent manganese tetroxide materials and its preparation method and application.Preparation method includes: using valine as competitive ligand, by coordination competition effect inhibits 1,3,5-benzene tricarboxylic acid and manganese ion complete coordination, to build Mn-MOFs precursor with high defect concentration in hydrothermal synthesis process;Subsequently, obtain Mn3O4 catalyst rich in oxygen vacancy by pyrolysis treatment.The catalyst can efficiently activate persulfate to generate various active oxygen species, realize the efficient degradation of norfloxacin.Experiments show that the prepared catalyst shows excellent catalytic activity in the range of pH 3~11, and the influence of environmental factors is small.After repeated use test, the catalyst can still maintain stable catalytic performance after multiple cycles, showing good practical application potential, and providing an effective solution for the treatment of antibiotic pollutants in wastewater.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a defect-state MOFs-derived manganese tetroxide material, its preparation method, and its application. Background Technology

[0002] Recent environmental science research has shown that the persistent detection of new pollutants in aquatic environments has become a major global environmental challenge. These pollutants, due to their persistence, bioaccumulation, and potential ecotoxicity, pose an irreversible threat to human health and ecosystem stability. Of particular concern are emerging antibiotic pollutants, whose environmental residues may significantly disrupt the structure and function of microbial communities by inducing the spread of antibiotic resistance genes, thereby profoundly impacting the long-term sustainability of ecosystems.

[0003] Based on sulfate free radicals (SO4• - AOPs (SR-AOPs), including SO4• as a reactive oxygen species (ROS). - •OH radicals are considered a more efficient and promising technology than traditional hydroxyl radical (•OH)-based AOPs. Hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), and peroxydisulfate (PDS) (collectively referred to as persulfates) can directly degrade certain pollutants, but with low removal rates. Therefore, various activation strategies involving energy inputs (e.g., ultraviolet light, heat, microwaves, and ultrasound) and catalysts have been widely introduced into persulfate-based AOPs to trigger highly reactive substances.

[0004] Numerous studies have found that transition metal ions (including Co) can facilitate this process. 2+ Fe 2+ Mn 2+ Ni 2+ Ce 3+ Manganese oxide (MnO4) and related heterogeneous catalysts can efficiently activate PMS. Among various transition metal oxides, manganese oxide (MnO4) is the most efficient. x Due to its relatively low toxicity, natural abundance, diverse valence, and environmental friendliness, manganese-based catalysts are considered promising catalysts for PMS activation. However, traditional manganese-based catalysts (such as MnO2, Mn2O3, and Mn3O4) still contain Mn during the activation of PMS to degrade organic pollutants. 2+ High dissolution rates lead to insufficient catalyst stability; limited exposure of active sites results in low PMS activation efficiency; and insufficient oxygen vacancy concentration affects the continuous generation of free radicals. This invention significantly improves the PMS activation performance of manganese-based catalysts through MOF defect engineering strategies, solving the problems of poor stability and low activation efficiency of traditional manganese-based catalysts in practical applications, and has significant environmental application value. Summary of the Invention

[0005] This invention addresses the technical bottlenecks of existing manganese-based catalysts, such as insufficient stability, low exposure of active sites, limited oxygen vacancy concentration, and poor PMS activation efficiency. It innovatively proposes a method for preparing a Mn3O4 catalyst derived from defective MOFs and develops its application in activating PMS to degrade the antibiotic norfloxacin. By precisely controlling the structural defects of the MOF precursor, this invention successfully prepares a Mn3O4 catalyst with abundant active sites and a high concentration of oxygen vacancies, significantly improving PMS activation efficiency and antibiotic degradation performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing Mn3O4 material derived from defect-state MOFs includes the following steps:

[0008] Step 1. Add 2.4 mmol of manganese chloride to 50 mL of N,N-dimethylformamide and 10 mL of H2O to obtain a mixed solution. Then add a certain amount of valine to the mixed solution and transfer it to an ultrasonic reactor. After ultrasonication, heat at 85°C to obtain solution A.

[0009] Step 2. Add a certain amount of 1,3,5-benzenetricarboxylic acid to 5 mL of N,N-dimethylformamide and stir for a period of time to obtain solution B;

[0010] Step 3. Add solution B to solution A obtained in step 1, heat at 85°C for 30 min, and then transfer to a hydrothermal reactor for hydrothermal reaction;

[0011] Step 4. After cooling the mixture obtained in Step 3, centrifuge, wash, and dry it. Place the product in a tube furnace and calcine it in an air atmosphere at a calcination temperature of 550°C to obtain Mn3O4 material derived from defective MOFs.

[0012] Furthermore, in the above preparation method, in step 1, the reaction time after sonication is 60 min at 85°C.

[0013] Furthermore, in the above preparation method, in step 1, the molar ratio of manganese chloride to valine is (2~3):1.

[0014] Furthermore, in the above preparation method, in step 2, the molar ratio of valine to 1,3,5-benzenetricarboxylic acid is (0.8~1.2):1.

[0015] Furthermore, in the above preparation method, in step 3, the hydrothermal reaction temperature is 120℃ and the reaction time is 8 h.

[0016] Furthermore, in the above preparation method, in step 4, the calcination temperature is 550℃ and the calcination time is 2 h.

[0017] The above-mentioned defective MOFs-derived Mn3O4 materials are used in the removal of norfloxacin from wastewater using advanced persulfate oxidation technology.

[0018] Further, the above application is carried out as follows: the catalyst is added to 100 mL of wastewater containing norfloxacin, and persulfate is added to initiate the reaction.

[0019] Furthermore, in the above applications, the catalyst addition amount is 0.25~2.0 g / L.

[0020] Furthermore, in the above applications, the concentration of norfloxacin in the wastewater is 10 mg / L, and the amount of persulfate is 0.25~2 mmol / L.

[0021] Furthermore, in the above applications, the pH of the water body is 3 to 11.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention uses a valine coordination regulation strategy to precisely control the defect concentration of Mn-MOFs precursors, and obtains a Mn3O4 catalyst with an abundant oxygen vacancy structure after pyrolysis, which significantly improves the activation efficiency and catalytic performance of the material for persulfate.

[0024] 2. The defect-state MOFs-derived Mn3O4 catalyst provided by this invention is synthesized by a two-step hydrothermal-calcination method, which is simple, energy-efficient, and uses inexpensive raw materials. The preparation process is also environmentally friendly and has the feasibility for industrial-scale production.

[0025] 3. The defect-state MOFs-derived Mn3O4 catalyst provided by this invention can efficiently activate persulfate to generate a variety of reactive oxygen species, exhibiting excellent degradation efficiency for organic pollutants.

[0026] 4. The defect-state MOFs-derived Mn3O4 catalyst provided by this invention has excellent pH adaptability (pH 3~11) and good cycling stability. It maintains high catalytic activity even after repeated use and has significant practical application value. Attached Figure Description

[0027] Figure 1 Scanning electron microscope (SEM) images of the Mn3O4, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3 catalysts prepared in this invention.

[0028] Figure 2The XRD patterns of the Mn3O4, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3 catalysts prepared in this invention are shown.

[0029] Figure 3 The graph shows the degradation effect of the Mn3O4, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3 catalysts prepared in this invention on norfloxacin.

[0030] Figure 4 The graph shows the effect of different pH values ​​on the degradation of norfloxacin by PMS catalytic activation using Mn3O4-V2 prepared in this invention.

[0031] Figure 5 The graph shows the effect of different PMS concentrations on the degradation of norfloxacin by Mn3O4-V2-catalyzed activated PMS prepared in this invention.

[0032] Figure 6 The figure shows the effect of different Mn3O4-V2 catalyst dosages on the catalytic activation of PMS for the degradation of norfloxacin.

[0033] Figure 7 The image shows the degradation effect of norfloxacin on the Mn3O4-V2 catalyst prepared in this invention after recycling. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to examples, which will demonstrate its outstanding features and significant advancements. These examples are for illustrative purposes only and are not intended to limit the invention to its specific aspects. Norfloxacin (NOR) was selected as the target pollutant in the examples.

[0035] Example 1

[0036] The preparation method is as follows:

[0037] 2.4 mmol of manganese chloride was dissolved in a mixed solution of 10 mL H₂O and 50 mL N,N-dimethylformamide. The solution was stirred for 30 min to ensure uniform dispersion. Valine was then added to the above solution at concentrations of 0, 0.8, 1.0, and 1.2 mmol, respectively. After ultrasonic dispersion, the solution was stirred at 85 °C for 1 h to obtain solution A. 1.0 mmol of 1,3,5-benzenetricarboxylic acid was dissolved in 5 mL N,N-dimethylformamide to obtain solution B. Solution B was added to solution A and stirred again at 85 °C for 30 min. The mixture was then transferred to a 100 mL hydrothermal reactor and reacted at 120 °C for 8 h. After the reaction solution cooled to room temperature, it was centrifuged at 8000 rpm for 8 min. The solution was washed three times with N,N-dimethylformamide and methanol, and the resulting white powder was reserved for use.

[0038] The obtained white powder was placed in a tube furnace and calcined in air at a temperature of 550℃ for 1 h and a holding time of 2 h. After the reaction in the tube furnace was completed, the powder sample was cooled to room temperature and collected to obtain defect-state MOFs-derived Mn3O4 catalysts, which were named Mn3O4, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3, respectively.

[0039] Characteristic such as Figure 1 As shown, Figure 1(a) is a 2000x magnified SEM image of Mn3O4 prepared in Example 1; Figure 1(b) is a 5000x magnified SEM image of Mn3O4 prepared in Example 1; Figure 1(c) is a 10000x magnified SEM image of Mn3O4 prepared in Example 1; Figure 1(d) is a 2000x magnified SEM image of Mn3O4-V1 prepared in Example 1; Figure 1(e) is a 5000x magnified SEM image of Mn3O4-V1 prepared in Example 1; Figure 1(f) is a 10000x magnified SEM image of Mn3O4-V1 prepared in Example 1; Figure 1(g) is a 2000x magnified SEM image of Mn3O4-V2 prepared in Example 1; Figure 1 Figure 1(h) shows a 5000x magnified SEM image of Mn3O4-V2 prepared in Example 1; Figure 1(i) shows a 10000x magnified SEM image of Mn3O4-V2 prepared in Example 1; Figure 1(j) shows a 2000x magnified SEM image of Mn3O4-V3 prepared in Example 1; Figure 1(k) shows a 5000x magnified SEM image of Mn3O4-V3 prepared in Example 1; Figure 1(l) shows a 10000x magnified SEM image of Mn3O4-V3 prepared in Example 1. The Mn3O4 samples exhibit a micron-rod-like structure. The three samples, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3, are micron-sphere structures composed of uniform triangular nanosheets, and the presence of nanoporous structures is clearly visible.

[0040] Figure 2 These are the XRD patterns of the Mn3O4, Mn3O4-V1, Mn3O4-V2, and Mn3O4-V3 catalysts prepared in Example 1 of this invention. Mn3O4-V xThe sample and the Mn3O4 sample exhibited similar characteristic diffraction peaks. The XRD pattern conformed to the crystal characteristics of tetragonal Mn3O4 (JCPDS No. 24-0734). The diffraction peaks at 18.0°, 28.8°, 31.0°, 32.3°, 36.1°, 37.9°, 44.6°, 50.7°, 58.6° and 59.8° corresponded to the (101), (112), (200), (103), (211), (004), (220), (105), (303) and (224) crystal planes of Mn3O4, respectively.

[0041] Example 2

[0042] 100 mL of a 10 mg / L NOR aqueous solution was placed in a beaker, and 0.050 g of the Mn3O4 series catalysts (Mn3O4, Mn3O4-V1, Mn3O4-V2, Mn3O4-V3) prepared in Example 1 were added. After pre-adsorption for 30 min under magnetic stirring at 400 r / min, PMS was added to a concentration of 1 mmol / L to initiate the catalytic reaction. 2 mL samples were taken at time points of 10, 20, 30, 40, 50, and 60 min after the start of the reaction, and an equal volume of methanol was immediately added to quench the reaction. After filtration through a 0.22 μm polytetrafluoroethylene (PTFE) membrane, the residual NOR concentration was determined by UV-Vis spectrophotometry. The norfloxacin degradation rate was calculated using Equation 1:

[0043] Formula 1: Norfloxacin degradation rate (%) = (norfloxacin concentration in the solution before reaction - norfloxacin concentration in the solution after reaction) / norfloxacin concentration in the solution before reaction × 100%;

[0044] The results are as follows Figure 3 The results showed that within 60 min, the degradation rate of NOR using only 1.0 mmol / L PMS was 52.13%. In contrast, the Mn3O4 series catalysts prepared in Example 1 exhibited significantly enhanced catalytic activity, with NOR degradation rates as follows: Mn3O4 (74.82%), Mn3O4-V1 (81.46%), Mn3O4-V2 (92.01%), and Mn3O4-V3 (86.59%). Among them, Mn3O4-V2 exhibited the best catalytic performance, confirming that the Mn3O4-V2 material prepared by regulating the defect concentration of MOF precursors through valine and then calcining can efficiently activate the PMS oxidation system and significantly improve the degradation efficiency of NOR in water. This result clearly reveals the key role of defect engineering strategies in enhancing the activation performance of Mn3O4 catalysts for persulfate.

[0045] Example 3

[0046] This example compares the effect of different pH values ​​on the degradation of NOR by Mn3O4-V2-catalyzed PMS.

[0047] 100 mL of a 10 mg / L NOR aqueous solution was placed in a beaker, and the pH was adjusted to 3, 5, 7, 9, and 11 using 0.1 M HCl and 0.1 M NaOH solutions, respectively. 0.050 g of the Mn3O4-V2 catalyst prepared in Example 1 was added to the reaction system at each pH condition. After pre-adsorption for 30 min under magnetic stirring at 400 r / min, PMS was added to achieve a concentration of 1 mmol / L to initiate the catalytic reaction. 2 mL samples were taken at time points of 10, 20, 30, 40, 50, and 60 min after the start of the reaction. An equal volume of methanol was immediately added to quench the reaction. After filtration through a 0.22 μm PTFE membrane, the residual NOR concentration was determined by UV-Vis spectrophotometry.

[0048] The results are as follows Figure 4 The results show that the Mn3O4-V2 / PMS system exhibits excellent NOR degradation efficiency under different pH conditions. Within the pH range of 3-11, the NOR degradation rate remains between 82.88% and 96.86%, with the optimal degradation efficiency (96.86%) achieved under weakly acidic conditions (pH 5). Specifically, the degradation rates are as follows: pH 3 (92.01%), pH 5 (96.86%), pH 7 (88.92%), pH 9 (87.37%), and pH 11 (82.88%). These data indicate that the Mn3O4-V2 catalyst can exhibit good catalytic performance over a wide pH range, with higher reaction efficiency under weakly acidic conditions, demonstrating good applicability for treating complex real-world aquatic environments.

[0049] Example 4

[0050] This example compares the effects of different concentrations of PMS (0.25, 0.5, 1.0, 1.5, 2.0 mmol / L) on the catalytic reaction.

[0051] 100 mL of a 10 mg / L NOR aqueous solution was placed in a beaker, and the pH was adjusted to 5.0 using 0.1 M hydrochloric acid and 0.1 M NaOH solution. Then, 0.050 g of the Mn3O4-V2 catalyst prepared in Example 1 was added to the solution, and pre-adsorption was performed for 30 min under magnetic stirring at 400 r / min. Subsequently, PMS was added to achieve concentrations of 0.25, 0.5, 1.0, 1.5, and 2.0 mmol / L. 2 mL samples were taken at time points of 10, 20, 30, 40, 50, and 60 min after the start of the reaction. An equal volume of methanol was immediately added to quench the reaction. After filtration through a 0.22 μm PTFE membrane, the residual NOR concentration was determined by UV-Vis spectrophotometry.

[0052] Figure 5 The NOR degradation performance of the Mn3O4-V2 catalyst under different PMS concentrations was demonstrated. Experimental data showed that when the PMS concentration increased from 0.25 mmol / L to 1.0 mmol / L, the NOR degradation rate significantly increased from 81.06% to 96.86%, indicating that the oxidant concentration has a significant impact on the degradation efficiency. However, when the PMS concentration was further increased to 1.5–2.0 mmol / L, the degradation rate only increased slightly to 97.40–97.50%, showing a clear plateau effect. This phenomenon may be attributed to the saturation of active sites on the catalyst surface, where excess PMS cannot be effectively activated. The results indicate that 1.0 mmol / L PMS is close to the optimal oxidant concentration for this catalytic system, and further increasing the PMS concentration does not significantly improve the degradation efficiency. This has important guiding significance for the optimized addition of oxidants in practical applications.

[0053] Example 5

[0054] This example compares the effects of different Mn3O4-V2 dosages (0.25, 0.50, 1.0, 2.0 g / L) on the catalytic reaction.

[0055] 100 mL of a 10 mg / L NOR aqueous solution was placed in a beaker, and the pH was adjusted to 5.0 using 0.1 M hydrochloric acid and 0.1 M NaOH solution. Then, 0.025, 0.050, 0.100, and 0.200 g (corresponding to dosages of 0.25–2.0 g / L) of the Mn3O4-V2 catalyst prepared in Example 1 were added to the solution, respectively. The mixture was then stirred at 400 r / min for 30 min on a magnetic stirrer. PMS was added to a concentration of 1 mmol / L to initiate the catalytic reaction. 2 mL samples were taken at time points of 10, 20, 30, 40, 50, and 60 min after the start of the reaction. An equal volume of methanol was immediately added to quench the reaction. After filtration through a 0.22 μm PTFE membrane, the residual NOR concentration was determined by UV-Vis spectrophotometry.

[0056] Figure 6 This paper describes the degradation effect of the Mn3O4-V2 catalyst prepared in this invention on NOR under different catalyst dosages. Experimental data show that the degradation rates of NOR at catalyst dosages of 0.25, 0.50, 1.0, and 2.0 g / L are 81.17%, 96.86%, 96.63%, and 96.58%, respectively. The results indicate that when the catalyst dosage is increased from 0.25 g / L to 0.50 g / L, the NOR degradation rate significantly increases from 81.17% to 96.86%. However, further increasing the dosage to 1.0 g / L~2.0 g / L only maintains the degradation rate between 96.58% and 96.86%, without a significant increase. This result suggests that after the catalyst dosage reaches a certain level, there may be limiting factors such as active site saturation or enhanced free radical recombination effects; excessive catalyst does not significantly change the NOR degradation rate.

[0057] Example 6

[0058] This example examines the cycling performance of the Mn3O4-V2 catalyst prepared in Example 1 in the Mn3O4-V2 / PMS reaction system for NOR degradation.

[0059] A 100 mL NOR aqueous solution with a concentration of 10 mg / L was placed in a beaker. The pH was adjusted to 5.0 using 0.1 M hydrochloric acid and 0.1 M NaOH solution. Then, 0.100 g of the Mn3O4-V2 catalyst prepared in Example 1 was added to the solution, and pre-adsorption was performed for 30 min under magnetic stirring at 400 r / min. PMS was added to a concentration of 1 mmol / L to initiate the catalytic reaction. 2 mL samples were taken at time points of 10, 20, 30, 40, 50, and 60 min after the start of the reaction. An equal volume of methanol was immediately added to quench the reaction. After filtration through a 0.22 μm PTFE membrane, the residual NOR concentration was determined by UV-Vis spectrophotometry.

[0060] After the reaction, the Mn3O4-V2 catalyst was centrifuged, washed, and dried. The experimental conditions and methods were the same as those in the above oxidative degradation experiment, and the experiment was repeated three times.

[0061] Figure 7 To assess the degradation effect of the Mn3O4-V2 catalyst prepared in this invention on NOR after recycling, the Mn3O4-V2 catalyst prepared in Example 1 showed NOR degradation rates of 96.63%, 87.29%, and 83.63% after three cycles of PMS catalysis. After three reuses, the NOR degradation rate of Mn3O4-V2 remained above 80%, which fully demonstrates that the Mn3O4-V2 / PMS system possesses stable catalytic activity, good structural integrity, and sustainable active site retention. Experimental data show that the valine-modified Mn3O4-V2 catalyst not only has a highly efficient ability to activate PMS but also exhibits significant reusability, providing an important guarantee for its application in practical wastewater treatment.

Claims

1. A method of preparing a defective-state MOFs-derived Mn304 material, characterized in that, The method comprises the following steps: Step 1. 2.4 mmol of manganese chloride is added into 50 mL of N, N-dimethylformamide and 10 mL of H2O to obtain a mixed solution, and then a certain amount of valine is added into the mixed solution and transferred into an ultrasonic reactor for ultrasonic treatment and heating at 85℃ to obtain solution A; Step 2. A certain amount of 1, 3, 5-benzene tricarboxylic acid is added into 5 mL of N, N-dimethylformamide and stirred to obtain solution B; Step 3. Solution B is added into solution A obtained in step 1, and after heating at 85℃ for 30 min, the mixture is transferred into a hydrothermal kettle for hydrothermal reaction; Step 4. After the reaction in step 3, the mixture is cooled, centrifuged, washed and dried, and then the obtained product is calcined in a tube furnace under the condition of an air atmosphere and a calcination temperature of 550℃ to obtain a defective MOFs derived Mn3O4 material.

2. The production method according to claim 1, characterized by, In step 1, the reaction time is 60 min after ultrasonic treatment and heating at 85℃.

3. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of manganese chloride to valine is (2-3):

1.

4. The method of claim 1, wherein, In step 2, the molar ratio of valine to 1, 3, 5-benzene tricarboxylic acid is (0.8-1.2):

1.

5. The preparation method according to claim 1, characterized in that, In step 3, the hydrothermal reaction temperature is 120℃, and the reaction time is 8 h.

6. The method of claim 1, wherein, In step 4, the calcination time is 2 h.

7. A defect-state MOFs derived trimanganese tetraoxide material, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

8. The use of the defective-state MOFs derived trimanganese tetraoxide material according to claim 7 for the removal of norfloxacin from wastewater in catalytic persulfate advanced oxidation technology, characterized in that, A certain amount of persulfate and the defective MOFs derived Mn3O4 material are added into wastewater, and the mixture is stirred and mixed uniformly.

9. Use according to claim 8, characterized in that, The addition amount of the defective MOFs derived Mn3O4 material is 0.25-2.0 g / L.

10. Use according to claim 8, characterized in that, When the concentration of norfloxacin in the wastewater is 10 mg / L, the amount of persulfate is controlled to be 0.25-2 mmol / L.

11. Use according to claim 8, characterized in that, The pH of the wastewater should be 3-11.

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