Preparation method and application of carbon-supported copper-cobalt MOF nanosheet

Abstract

The invention discloses a preparation method and application of a carbon-loaded copper-cobalt MOF nanosheet, and relates to the field of environment-friendly materials, the material is obtained by carbonizing a copper-cobalt bimetallic MOF two-dimensional nanosheet precursor and is a two-dimensional sheet-shaped carbon material distributed with copper and cobalt bimetallic species, the width-to-thickness ratio is larger than 40, and the thickness is smaller than 10 nm. The preparation method comprises the following steps: preparing a solution A of copper salt and cobalt salt and a solution B of terephthalic acid dissolved in DMF; mixing the solution A and the solution B, adding triethylamine, stirring and reacting, centrifuging, washing and drying to obtain a precursor; and finally carbonizing under a protective atmosphere. The material can be used for treating organic pollutant wastewater such as antibiotics and the like, and is combined with oxidants such as persulfate and the like to realize efficient catalytic degradation of pollutants. The material disclosed by the invention has high catalytic activity, excellent stability and recycling performance.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly materials, and in particular to a method for preparing carbon-supported copper-cobalt MOF nanosheets and their applications. Background Technology

[0002] Metal-organic frameworks (MOFs), as an emerging type of porous crystalline material, have shown great application potential in environmental fields such as adsorption, separation, and catalysis due to their structural diversity and high specific surface area. Recently, MOFs have received widespread attention as materials for environmental protection and pollution control. MOFs are crystalline three-dimensional materials formed by coordination bonds between inorganic metal ions and bi- or multi-aryl aromatic ligands. MOFs possess highly porous structures and chemical properties, making them widely applicable in adsorption, catalysis, luminescent materials, optical thin films, and drug delivery. However, high production costs and poor stability (structural collapse and aggregation) limit their scalability and market penetration.

[0003] However, the stability of MOFs under different environmental conditions, especially their performance in the face of natural stresses such as water, acids, alkalis, and bacteria, remains a major obstacle to their widespread application. MOFs, composed of metallic nodes and organic ligands, possess high porosity and adjustable pore sizes, making them suitable for various environmental applications. However, many MOFs are prone to structural decomposition upon contact with water, acids, and alkalis, limiting their practical applications. For example, the classic MOF-5 decomposes rapidly in water, while HKUST-1 undergoes a structural transformation in alkaline environments.

[0004] By employing a series of treatments on MOFs, their structural advantages can be effectively utilized to prepare MOF-derived materials with excellent performance, which can be widely used in electrochemical energy storage, photoelectrocatalysis, and adsorption separation. For example, through pyrolysis strategies, organic ligands in MOFs can be transformed in situ into porous carbon materials. These porous carbons can effectively load metals in MOFs, preventing excessive metal aggregation, thereby preparing single-atom or highly dispersed catalytic materials. Furthermore, the metal centers in MOFs can also serve as catalytic centers, forming diverse carbon structures during pyrolysis, endowing MOF-derived materials with diverse application scenarios. Summary of the Invention

[0005] To overcome the problems existing in the prior art, one objective of this invention is to provide a carbon-supported copper-cobalt MOF nanosheet. A second objective is to provide a method for preparing such a carbon-supported copper-cobalt MOF nanosheet. A third objective is to provide applications of such a carbon-supported copper-cobalt MOF nanosheet.

[0006] This application provides a carbon-supported copper-cobalt MOF nanosheet, which is obtained by carbonization of a copper-cobalt bimetallic MOF two-dimensional nanosheet precursor. The material is a two-dimensional sheet-like carbon material with copper and cobalt bimetallic species distributed thereon. The aspect ratio of the two-dimensional sheet-like carbon material is greater than 40 and the thickness is less than 10 nm.

[0007] Preferably, the molar ratio of copper to cobalt in the material is 1:(0.2-2).

[0008] A method for preparing carbon-supported copper-cobalt MOF nanosheets includes the following steps: Preparation of solution A: Dissolve the soluble copper salt and soluble cobalt salt in ultrapure water, then add ethanol and mix well; Preparation of solution B: Dissolve terephthalic acid in N,N-dimethylformamide; Mixing and reaction: Mix solution A and solution B, then add triethylamine to the mixture and stir at room temperature for more than 12 hours; Centrifugation, washing and drying: The solid product was collected by centrifugation, washed with ethanol and then dried under vacuum to obtain the copper-cobalt MOF nanosheet precursor. Carbonization treatment: The precursor is carbonized under a protective atmosphere to obtain the carbon-supported copper-cobalt MOF nanosheets.

[0009] Preferably, the carbonization process parameters are: heating to 600-900℃ at a heating rate of 5-15℃ / min and holding at that temperature for 1-3 hours; the protective atmosphere is nitrogen or an inert gas.

[0010] Preferably, after obtaining the copper-cobalt MOF nanosheet precursor in the centrifugation, washing and drying steps, and before the carbonization step, the process further includes a step of modifying the precursor with polyaniline: dispersing the precursor in hydrochloric acid solution, adding aniline monomer, and adding ammonium persulfate dropwise under ice-water bath conditions to carry out an in-situ polymerization reaction. After the reaction, the precursor is centrifuged, washed and dried to obtain the polyaniline-modified copper-cobalt MOF nanosheet precursor.

[0011] Preferably, the amount of aniline monomer added is 10%-50% of the mass of the precursor powder.

[0012] Preferably, the carbonization process involves: dividing the polyaniline-modified copper-cobalt MOF nanosheet precursor into at least two portions, carbonizing them at different temperatures to obtain at least two carbonized materials; and physically mixing the at least two carbonized materials.

[0013] Preferably, the carbonization at different temperatures includes low-temperature carbonization at 600°C and high-temperature carbonization at 800°C; the mass ratio of the physical mixture is: low-temperature carbonization material : high-temperature carbonization material = 1 : (1-4).

[0014] Application of carbon-supported copper-cobalt MOF nanosheets in the treatment of polluted wastewater.

[0015] Preferably, the application is as follows: the carbon-supported copper-cobalt MOF nanosheets and an oxidant are added together to polluted wastewater to carry out a catalytic oxidation reaction; the oxidant is selected from at least one of persulfate, perdisulfate, hydrogen peroxide, peracetic acid or ozone; the pollutant in the polluted wastewater is an antibiotic.

[0016] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1) This invention provides a carbon-supported copper-cobalt MOF nanosheet composite material. The bimetallic MOF nodes can synergistically alter the electronic structure and chemical properties of the MOF, thereby improving its catalytic activity, adsorption, and activation capabilities. During calcination, the organic ligands in the MOF undergo decomposition and carbonization reactions. The metal nodes recombine with the carbonized ligands or the newly formed phase to form materials with stable crystal structures, such as metal oxides and carbides. This significantly improves the thermal and chemical stability of the material, enabling its application in more demanding environments.

[0017] 2) Increased porosity and specific surface area of ​​MOF obtained after carbonization: Calcination can adjust the pore structure of the material to a certain extent, producing more uniformly sized mesopores or micropores, increasing porosity and specific surface area, thereby improving the material's adsorption capacity for gases, liquids or reactants, and providing more active sites and transport channels for catalysis, storage and other applications.

[0018] 3) This invention employs high-temperature carbonization to prepare carbon-supported copper-cobalt MOF nanosheet composite materials. The calcination process is relatively simple, easy to operate and control, and can achieve continuous production to a certain extent, which helps reduce the preparation cost of MOF materials and improve their economic feasibility in large-scale industrial applications. The calcined material typically exhibits better mechanical strength and processing performance, and can be produced in various forms such as powder, granules, and films, facilitating subsequent molding and integration with other materials to meet the processing needs of different application scenarios.

[0019] 4) By introducing polyaniline for surface modification and combining it with materials carbonized at different temperatures, the stability of the material was improved through chemical anchoring. Furthermore, the interfacial electron transfer process was optimized by constructing a conductive and active composite system, thereby achieving a simultaneous improvement in catalytic activity and material stability on a macroscopic level. This provides an effective way to solve the bottleneck problem of MOF-derived materials in practical water treatment applications. Attached Figure Description

[0020] Figure 1 This is a comparison diagram of the removal effect of MOF on norfloxacin before and after carbonization in Application Example 1 of the present invention. Figure 2 The experiment illustrates the influence of conditions on the activation of persulfate for norfloxacin removal using the carbon-supported copper-cobalt MOF nanosheet composite material of Example 1 of this invention. (a) represents materials prepared at different carbonization temperatures; (b) represents different initial pH values; (c) represents different PMS dosages; and (d) represents different reaction temperatures. Figure 3 The following is an evaluation of the long-term effectiveness and ion resistance of the carbon-supported copper-cobalt MOF nanosheet composite material in Application Example 1 of the present invention, wherein (a) is the reusability efficiency of the carbon-supported copper-cobalt MOF nanosheet composite material in activating PMS to remove norfloxacin; and (b) is the effect of anions in the system on the norfloxacin removal efficiency. Figure 4 The image shows the morphology of the copper-cobalt MOF nanosheet composite material of Comparative Example 1 of the present invention, where (a) is a SEM image and (b) is a TEM image. Figure 5 This is a TEM image of the copper-cobalt MOF nanosheet composite material of Comparative Example 1 of the present invention; Figure 6 This is a TEM image of the carbon-supported copper-cobalt MOF nanosheet composite material of Example 2 of the present invention; Figure 7 The image shown is an HR-TEM image of the carbon-supported copper-cobalt MOF nanosheet composite material of Example 1 of this invention. Figure 8 XPS image of carbon-supported copper-cobalt MOF nanosheet composite material of Example 1 of the present invention; Figure 9 The comparison of the physical properties of the carbon-supported copper-cobalt MOF nanosheet composite material before and after the reaction in Application Example 1 of the present invention is shown in (a) FTIR image and (b) XRD image. Figure 10 The diagram shows the generation of free radicals and non-free radicals in PMS activated by the carbon-supported copper-cobalt MOF nanosheet composite material in Application Example 1 of this invention. (a) is the quenching experiment with quencher; (b) is the EPR signal of singlet oxygen in the system; (c) is the EPR signal of superoxide radical; and (d) is the EPR signal of hydroxyl radical. Detailed Implementation

[0021] 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 invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] A carbon-supported copper-cobalt MOF nanosheet is obtained by carbonization of a copper-cobalt bimetallic MOF two-dimensional nanosheet precursor. It is a two-dimensional sheet-like carbon material with copper and cobalt bimetallic species distributed in it. The aspect ratio of the two-dimensional sheet-like carbon material is greater than 40, and the thickness is less than 10 nm. In the material, the molar ratio of copper to cobalt is 1:(0.2~2); preferably, the molar ratio of copper to cobalt is 1:0.5. The carbonization process is carried out under a protective atmosphere, with a carbonization temperature of 600~900℃, a heating rate of 5~15℃ / min, and a holding time of 1~3h.

[0023] The preparation method of the carbon-supported copper-cobalt MOF nanosheets specifically includes the following steps: Preparation of Solution A: Dissolve soluble copper salt and soluble cobalt salt in ultrapure water, then add ethanol to the solution and mix well to form Solution A; The copper salt is selected from copper sulfate and copper nitrate; the cobalt salt is selected from cobalt sulfate and cobalt nitrate; preferably, copper and cobalt salts with the same anion are used.

[0024] The molar ratio of copper ions to cobalt ions is 1:(0.2~2).

[0025] The molar ratio of the metal ions, ultrapure water and ethanol is (5~10):1:1.

[0026] Preparation of Solution B: Dissolve terephthalic acid in N,N-dimethylformamide (DMF) and stir until completely dissolved to form Solution B; The molar ratio of terephthalic acid to DMF is 1:(300~400); preferably 1:325.

[0027] Mixing and reaction: Mix solution A and solution B, then add triethylamine to the mixture and stir at room temperature for more than 12 hours; The amount of triethylamine added is determined by adjusting the pH of the mixture to neutral.

[0028] The mixing is achieved by magnetic stirring or mechanical stirring.

[0029] Centrifugation, washing and drying: After the reaction is completed, the mixture is centrifuged and the solid product is collected; the solid product is washed with ethanol 3 to 5 times, and then vacuum dried at 65 to 85 °C to obtain a light blue copper cobalt MOF nanosheet precursor.

[0030] Carbonization treatment: The dried precursor is placed in a tube furnace and carbonized under a protective atmosphere. The protective atmosphere is nitrogen or other inert gas; The carbonization process is as follows: the temperature is increased to 600-900℃ at a rate of 5-15℃ / min, and held at this temperature for 1-3 hours; preferably, the heating rate is 5℃ / min, the reaction temperature is 700℃, and the holding time is 2 hours. After carbonization, the material is naturally cooled to room temperature, and the resulting black powder is carbon-supported copper-cobalt MOF nanosheets.

[0031] The pollutants in the polluted wastewater are organic pollutants, preferably antibiotics; the antibiotics include at least one of norfloxacin, metronidazole, florfenicol, tetracycline, and oxytetracycline.

[0032] A method for treating antibiotic-contaminated wastewater specifically includes the following steps: adding the above-mentioned carbon-supported copper-cobalt MOF nanosheets and oxidant to the antibiotic-contaminated wastewater, mixing and carrying out in-situ catalytic oxidation remediation; The oxidant is selected from at least one of persulfate, perdisulfate, hydrogen peroxide, peracetic acid, or ozone; preferably persulfate. When the mass concentration of antibiotics in the polluted wastewater is 1~100 mg / L, the dosage of the carbon-supported copper-cobalt MOF nanosheets is 0.5~5 g / L, and the dosage of the oxidant is 0.5~5 mM; The repair time is 1~120 minutes.

[0033] Example 1: Preparation of carbon-supported copper-cobalt MOF nanosheet composite material; S1: First, prepare solution A: Accurately weigh CuSO4·5H2O (1.50 mM) and Co(NO3)2·6H2O (0.75 mM), dissolve them in 6 mL of ultrapure water, and then add 6 mL of ethanol to the solution. Next, prepare solution B: Weigh 0.2491 g of C8H6O4 and dissolve it in 42 mL of DMF. After thoroughly mixing solutions A and B, add 1.6 mL of triethylamine. Finally, stir the mixture at room temperature for 12 h. The reacted sample is centrifuged at 4000 r / min for 5 min, washed three times with 35 mL of ethanol, and then vacuum dried at 353 K for 48 h. Finally, the light blue product is removed, ground, and stored in a dry container for subsequent experiments. S2: Two-dimensional Cu-Co nanosheets were uniformly deposited inside a quartz boat and placed in a tube furnace. Before calcination, nitrogen gas was continuously purged for 30 minutes. The temperature inside the tube furnace was gradually increased from room temperature to 700℃, 800℃, and 900℃, and maintained at this temperature for 2 hours. After the temperature naturally cooled to room temperature, the nitrogen gas was turned off, and the quartz boat was removed. The material inside the quartz boat was transferred to a mortar and ground to obtain a black powdery material, which is Cu-Co / C, and stored for subsequent experiments.

[0034] Example 2: Preparation of carbon-supported copper-cobalt MOF nanosheet composite material; S1: First, prepare solution A: Accurately weigh CuSO4·5H2O (1.0 mM) and Co(NO3)2·6H2O (1.0 mM), dissolve them in 6 mL of ultrapure water, and then add 6 mL of ethanol to the solution. Next, prepare solution B: Weigh 0.2491 g of C8H6O4 and dissolve it in 42 mL of DMF. After thoroughly mixing solutions A and B, add 1.6 mL of triethylamine. Finally, stir the mixture at room temperature for 24 h. The reacted sample is centrifuged at 3000 r / min for 10 min, washed three times with 35 mL of ethanol, and then vacuum dried at 353 K for 48 h. Finally, the light blue product is removed, ground, and stored in a dry container for subsequent experiments. S2: Two-dimensional Cu-Co nanosheets were uniformly deposited inside a quartz boat and placed in a tube furnace. Nitrogen gas was continuously purged for 30 minutes before calcination. The temperature inside the tube furnace was gradually increased from room temperature to 700℃ and maintained at this temperature for 2 hours. After the temperature naturally cooled to room temperature, the nitrogen gas was turned off, and the quartz boat was removed. The material inside the quartz boat was transferred to a mortar and ground to obtain a black powdery material, which is Cu-Co / C, and stored for subsequent experiments.

[0035] Comparative Example 1: Preparation of copper-cobalt MOF nanosheet composite material; First, prepare solution A: accurately weigh CuSO4·5H2O (1.0 mM) and Co(NO3)2·6H2O (1.0 mM), dissolve them in 6 mL of ultrapure water, and then add 6 mL of ethanol to the solution. Next, prepare solution B: weigh 0.2491 g of C8H6O4 and dissolve it in 42 mL of DMF. After thoroughly mixing solutions A and B, add 1.6 mL of triethylamine. Finally, stir the mixture at room temperature for 24 h. The reacted sample is centrifuged at 3000 r / min for 10 min, washed three times with 35 mL of ethanol, and then vacuum dried at 353 K for 48 h. Finally, the light blue product is removed, ground, and stored in a dry container for subsequent experiments.

[0036] Experimental Example 1: Microstructure analysis and characterization of samples from Examples 1 and 2 and Comparative Example 1; Figure 4 , Figure 5 These are the SEM and TEM images of the Cu-Co MOF nanosheets of Comparative Example 1 of this invention; Figure 4 a and Figure 4b illustrates the morphology of Cu-Co MOF nanosheets. Both SEM and TEM images show that the Cu-Co MOF nanosheets possess thin, flat, sheet-like structures with dimensions ranging from 300 to 500 nm. The sample surface is smooth, and the nanosheet structure has a thickness of 7.5 nm. The smooth surface and clear edge contours of the Cu-Co MOF two-dimensional nanosheets, formed by the stacking of ultrathin nanosheets, are particularly evident in high-resolution images, where the surface of the nanosheets shows no obvious particles or pores. The multiple thin, transparent sheet-like structures further confirm the synthesis of the nanosheets.

[0037] Figure 6 and Figure 7 This is a TEM image of the carbon-supported copper-cobalt MOF nanosheet composite material of the present invention. After calcination, the Cu-Co / C nanosheets show obvious shrinkage, wrinkling, and fracture on their surface, while some nanosheets still retain their original two-dimensional sheet structure to a certain extent. This phenomenon fully demonstrates that calcined Cu-Co MOF as a precursor material possesses good thermal stability. Figure 7 The lattice fringes of the nanosheets can be clearly seen. The lattice spacing is 0.220 nm, corresponding to the (111) crystal plane of Cu. Furthermore, the lattice spacing is 0.202 nm, consistent with the theoretical lattice spacing of the (400) crystal plane of Co. This indicates that the lattice fringes observed in the TEM image are in high agreement with the XRD analysis results. Figure 10 (b) further confirmed the crystal structures of Cu and Co in the sample.

[0038] Figure 8 This is an XPS plot of the carbon-supported copper-cobalt MOF nanosheet composite material of the present invention. The XPS shows the bonding of various elements in the material. For Co 2p, 780.8 and 796.45 eV correspond to Co 2+ The Co 2p3 / 2 and Co 2p1 / 2. For Cu2p, 951.66 eV and 931.77 eV correspond to Cu 2p. 0 The Cu 2p1 / 2 and Cu 2p3 / 2, at 953.99 and 934.01 eV respectively, correspond to Cu 2+ 2p1 / 2, and Cu 2+ The characteristic peak of 2p3 / 2 indicates that Cu 0 Both Cu(II) and CO are present on the surface of these two synthesized materials. The fitted C 1s bands show binding energies at 284.0, 284.82, 286.50 eV, and 288.5 eV, corresponding to sp2, sp3, CO, and C=O bonds, respectively. The O 1s bands show two peaks near 533.7, 531.8, 530.5 eV, and 529.32 eV, which may be attributed to CO and the MO structure of the metal oxide.

[0039] Figure 9 The images show the FTIR and XRD patterns of the carbon-supported copper-cobalt MOF nanosheet composite material of this invention. No characteristic peaks corresponding to the band vibrations of the organic linker were found in the FTIR spectrum of Cu-Co / C. Figure 9 a) This is because high-temperature calcination caused the ablation of the organic ligands. The FTIR spectrum of Cu-Co / C showed no characteristic peaks corresponding to band stretching of the organic ligands, indicating that the sample had high purity. From Figure 9 The characteristic peaks of Cu-Co / C after the reaction can be clearly observed in a, among which, at 3500 cm⁻¹ -1 There is a strong stretching vibration absorption peak of H2O nearby, caused by the vibration of the hydroxyl group (OH), at 1400 cm⁻¹. -1 The absorption peak at 1000 cm⁻¹ belongs to the vibration of the protonated amine matrix in piperazine and the deformation vibration of the OH group bound to the carboxylic acid group. -1 The nearby peaks are attributed to the stretching vibrations of the CO bond. In the XRD pattern, Cu-Co / C exhibits strong diffraction peaks at 2θ = 43.3°, 50.4°, and 74.3°, corresponding to the (111), (200), and (220) diffraction planes of metallic copper (JCPDF card number 85-1326), while the diffraction peaks at 44.2°, 51.2°, and 75.9° belong to the (111), (200), and (220) crystal planes of face-centered cubic cobalt. However, when Cu-Co / C comes into contact with a solution containing norfloxacin, the intensity of all XRD peaks decreases significantly. This may be due to the interaction between the material and the contaminant, with residual norfloxacin or certain intermediate products occupying the active sites. However, the peak positions remain almost unchanged, indicating that the material has a stable crystal structure. The characteristic peak at 2θ=36.49° corresponds to the standard card for Cu₂O (PDF#01-073-6237). Cu₂O forms because, in the efficient multi-valence redox cycle, Cu regulates charge balance through valence state changes, thereby promoting the efficient generation of free radicals from persulfate. In Cu-Co / C composites, the presence of variable-valence Cu is beneficial for the catalytic reaction.

[0040] Application Example 1: 1. Carbon-supported copper-cobalt MOF nanosheet composite material and copper-cobalt MOF nanosheets activated to remove antibiotics from persulfate; 0.1 g / L of Cu-Co / C composite material and Cu-Co MOF were added to a solution contaminated with 20 mg / L norfloxacin (NOR). Sodium persulfate (PMS) was then added to the reaction system as an oxidant. The corresponding reaction conditions were: 20 mg / L norfloxacin, 0.1 g / L of the material, 0.2 mM PMS, room temperature, and shaking at 250 rpm. Samples were taken at various time points, and the concentration of norfloxacin was analyzed by high-performance liquid chromatography (HPLC). The results are as follows. Figure 1 .

[0041] from Figure 1 It can be seen that the removal rates of NOR by Cu-Co MOF and Cu-Co / C are only 11.70% and 21.60%, respectively. In contrast, the removal rates of Cu-Co MOF+PMS and Cu-Co / C+PMS materials are significantly improved, reaching 66.00% and 80.60%, respectively. Considering the presence or absence of calcination, Cu-Co / C and Cu-Co / C+PMS show significantly higher removal efficiencies compared to Cu-Co MOF and Cu-Co MOF+PMS. In summary, the presence of PMS plays a significant role in improving removal efficiency, and calcination treatment further enhances this effect. Further analysis shows that the introduction of the oxidant PMS can effectively enhance the material's pollutant removal performance.

[0042] 2. Experiments on the removal of norfloxacin by activated sodium persulfate (PMS) using carbon-supported copper-cobalt MOF nanosheet composites prepared at different temperatures and the effect of reaction parameters on norfloxacin removal; Carbon-supported copper-cobalt MOF nanosheet composites were prepared at different temperatures by adding 0.1 g / L of different carbon-supported copper-cobalt MOF nanosheets to a solution contaminated with 20 mg / L norfloxacin (catalyst group: 600℃ Cu-Co / C, 700℃ Cu-Co / C, 800℃ Cu-Co / C, Cu-Co / C; no catalyst group: 600℃ Cu-Co / C, 700℃ Cu-Co / C, 800℃ Cu-Co / C, Cu-Co / C). Sodium persulfate (PMS) was then added to the reaction system as an oxidant. The corresponding reaction conditions were: 20 mg / L norfloxacin, 0.1 g / L of different carbon-supported copper-cobalt MOF nanosheets, 0.2 mM PMS, room temperature, and shaking at 250 rpm. Samples were taken at different time points, and the concentration of norfloxacin was analyzed by high-performance liquid chromatography (HPLC). The results are as follows: Figure 2 a.

[0043] The effect of calcination temperature on the degradation of NOR by activated PMS in materials, such as Figure 2As shown in Figure a, within a 120-minute reaction time, the removal rates of pollutants in the experimental group without oxidant were 11.68%, 11.50%, 21.64%, and 25.53%, respectively. In contrast, the removal rates of pollutants in the experimental group with oxidant at different temperatures were significantly higher, reaching 64.28%, 64.56%, 80.58%, and 75.12%, respectively. This indicates that adding PMS can effectively improve the treatment effect of pollutants. Furthermore, different calcination temperatures resulted in different NOR removal rates. Higher temperatures led to improved removal efficiency, with the catalyst reaching its peak degradation efficiency at 700℃. However, when the temperature continued to rise to 800℃, the efficiency of PMS activation in degrading NOR decreased. This is because calcination at 800℃ may have altered the microstructure of the composite material, leading to differences in catalytic efficiency. Therefore, 700℃ is the optimal calcination temperature for activating PMS to degrade NOR.

[0044] The results are as follows Figure 2 As shown in b, at a pH of 4.40, the removal rate of NOR by Cu-Co / C reached 58.51% at the reaction endpoint. When the pH was increased to 6.86, the removal efficiency further increased to 80.58%. However, when the pH continued to increase to 8.64, the removal efficiency decreased to 70.94%. Analysis suggests this is because, under acidic conditions, H+... + The formation of hydrogen bonds with the OO bonds of PMS increases the difficulty of breaking the OO bonds, thereby inhibiting the release of •SO4. - The decomposition of PMS produces reactive species such as •OH. Under alkaline conditions, the main reactive free radicals generated by PMS decomposition include •SO4. - And •OH. However, the redox potential of •OH generated under alkaline conditions is relatively low, significantly lower than that under acidic conditions.

[0045] Figure 2 c shows that when the PMS dosage was increased from 0.2 mM to 0.4 mM, the removal rate of NOR reached 80.58% or even higher within a 120-minute reaction time. This phenomenon can be attributed to the increased reactive free radicals (e.g., SO42-) generated in the system due to the increased PMS dosage. - The amount of (•OH) radicals increased. These free radicals, due to their strong oxidizing properties, can more effectively attack NOR, thereby improving its degradation efficiency. Further increasing the PMS dosage from 0.4 mM to 0.6 mM did not result in a significant increase in NOR removal rate.

[0046] When the reaction temperatures were 20℃, 30℃, and 40℃, the removal rates of NOR reached 75.03%, 80.86%, and 83.27%, respectively. Figure 2d). This is because the thermal activation process of PMS is significantly affected by temperature, and increasing the temperature within a certain range can enhance the efficiency of thermal activation.

[0047] 3. Reusability of Carbon-Supported Copper-Cobalt MOF Nanosheet Composites for Activating Sodium Persulfate (PMS) to Remove Norfloxacin Add 0.1 g / L of 700℃ Cu-Co / C to a solution contaminated with 20 mg / L norfloxacin. Then add sodium persulfate (PMS) as an oxidant to the reaction system. The corresponding reaction conditions are: 20 mg / L norfloxacin, 0.1 g / L material, 0.2 mM PMS, room temperature, and shaking at 250 rpm. Samples were taken at various time points, and the norfloxacin concentration was analyzed by high-performance liquid chromatography (HPLC). After each experiment, the material was collected, dried, and the experiment was repeated. The results are as follows. Figure 3 a.

[0048] Under three cycles, the removal rates of NOR by the Cu-Co / C+PMS system were 77.60%, 77.40%, and 74.50%, respectively. After three cycles, the removal rate of Cu-Co / C remained high, indicating that Cu-Co / C has the advantage of long-term cyclic use. This also demonstrates that the catalyst maintains high catalytic activity and exhibits excellent stability during multiple cycles.

[0049] 4. Effect of anions on the removal of norfloxacin by activated sodium persulfate (PMS) from carbon-supported copper-cobalt MOF nanosheets Add 0.1 g / L of 700℃ Cu-Co / C to a solution contaminated with 20 mg / L norfloxacin. Add sodium persulfate (PMS) as an oxidant to the reaction system, and then add 1 mM, 10 mM, and 50 mM Cl to the reaction system respectively. - SO4 2- CO3 2- The corresponding reaction conditions were: 20 mg / L norfloxacin, 0.1 g / L material, 0.2 mM PMS, room temperature, and shaking at 250 rpm. Samples were taken at various time points, and the concentration of norfloxacin was analyzed by high-performance liquid chromatography (HPLC). The results are as follows: Figure 3 a.

[0050] The results showed that introducing Cl into the solution - It only slightly inhibited the removal rate of NOR. Furthermore, SO4... 2- It also has a slight inhibitory effect on NOR-based pollutant removal processes. CO3 2- As the concentration increases, the removal rate of NOR decreases.

[0051] 5. Activation mechanism; To further identify the active ingredients in the system, an EPR test was performed, and the results are as follows: Figure 10 When only Cu-Co / C is available, TEMP is used as the... 1 No signal was detected with the O2 scavenger; however, the spectrum after adding PMS showed that it was detected. 1 The triplet (1:1:1) characteristic peak of O2 indicates that there is a large amount of O2 in the Cu-Co system. 1 O2 is generated. DMPO is used as the source of O2. - No signal was detected with the trapping agent, but after the addition of PMS, a six-line intensity characteristic peak with a peak intensity of (1:2:1:2:1:2:1) was observed in the EPR spectrum, confirming the presence of •O2. - The presence of . •OH was detected in the Cu-Co / C system, exhibiting four typical characteristic peaks with an intensity ratio of (1:2:2:1), indicating the formation of •OH in the Cu-Co / C system. Based on the free radical quenching experiment and EPR spectral analysis results, the free radical (•SO4) was... - and •OH) and non-free radicals ( 1 O2 is simultaneously generated in the reaction system and synergistically contributes to the degradation of NOR. Furthermore, XRD revealed the presence of Cu2O, a multivalent metal that facilitates redox cycles. Cu2O can regulate charge balance through valence state transitions, thereby efficiently activating PMS to generate free radicals.

[0052] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: Despite their high specific surface area and tunable structure, metal-organic frameworks (MOFs) are prone to hydrolysis of their metal-organic coordination bonds in practical water treatment applications, especially in aquatic, acidic, or alkaline environments. This leads to crystal structure collapse, and their metal active centers are susceptible to migration and aggregation during reactions, resulting in a reduction of active sites and a rapid decline in catalytic performance. These inherent chemical and structural instabilities severely limit their large-scale industrial applications.

[0053] To address this issue, this embodiment provides a carbon-supported bimetallic nanosheet with both high catalytic activity and excellent structural stability, along with its preparation method. A two-dimensional copper-cobalt bimetallic MOF is constructed as a precursor, followed by precisely controlled carbonization under a protective atmosphere. Utilizing the pyrolysis process, unstable organic ligands are transformed in situ into a robust and conductive porous carbon matrix, while atomically dispersed copper and cobalt metal nodes are converted into highly dispersed nanocrystalline species, which are then firmly embedded within the carbon framework.

[0054] In this composite material, copper and cobalt exhibit a synergistic catalytic effect, primarily manifested in the following aspects: During the activation of persulfate, a highly efficient electron transfer cycle is formed between the cobalt and copper centers. Specifically, the Co(III) species, acting as a strong oxidant, can acquire electrons from adjacent Cu(I) species and be reduced to active Co(II), while Cu(I) is oxidized to Cu(II). The generated Co(II) can efficiently activate persulfate, generating sulfate radicals and regenerating them back to Co(III). Cu(II) can then be reduced by reducing agents in the system or by electrons transferred from the carbon matrix, reforming Cu(I), thus completing and sustaining this catalytic cycle. This cycle significantly lowers the reaction energy barrier in the persulfate activation stage and improves the utilization efficiency of the oxidant. Furthermore, the highly graphitized carbon matrix not only acts as a physical barrier to prevent the aggregation and leaching of metal nanoparticles, but its excellent conductivity also serves as an electron channel, promoting the interfacial electron transfer rate between metal centers and between the catalyst and reactants, further optimizing the kinetics of the aforementioned redox cycle. Characterization results show that this synergistic system can simultaneously stimulate both free radical and non-free radical pathways, working together to degrade organic pollutants.

[0055] The carbon-supported copper-cobalt MOF nanosheets prepared in this embodiment effectively overcome the defects of poor stability of traditional MOF materials. They exhibit high removal efficiency, excellent cycle stability and good environmental adaptability when degrading antibiotic pollutants in water.

[0056] Example 3: Addressing the technical bottlenecks of insufficient chemical stability and easy deactivation of active sites in metal-organic framework (MOF) materials for water treatment applications, the root cause lies in the hydrolytic instability of coordination bonds and the tendency of metal centers to migrate and aggregate. The above example constructs a bimetallic carbon-based composite material in which metal nanocrystals are firmly encapsulated by a carbon framework by designing a two-dimensional copper-cobalt bimetallic MOF precursor and combining it with a controllable carbonization process. The core mechanism of this material lies in the synergistic activation of persulfate through efficient valence cycling between the copper and cobalt bimetals. Combined with the electron conduction and physical protection of the carbon matrix, this jointly promotes the generation and reaction process of active and non-radical species, thereby achieving a highly efficient and stable catalytic degradation effect on organic pollutants on a macroscopic scale. Further improvements are made based on the aforementioned examples to enhance its overall effect.

[0057] 1. Preparation of polyaniline-modified copper-cobalt MOF nanosheet precursors; After synthesizing the light blue copper-cobalt MOF nanosheet precursor, it was modified with polyaniline. The specific modification steps are as follows: The dried precursor powder was dispersed in 100 mL of 0.1 M hydrochloric acid solution and sonicated for 30 minutes to form a uniform suspension. Add aniline monomer to the suspension, the amount of which is 10%-50% (preferably 30%) of the precursor powder mass. Under ice-water bath (0-5℃) and continuous stirring conditions, slowly add ammonium persulfate (dissolved in 20mL of 0.1M hydrochloric acid) with a molar ratio of 1:1 to aniline to carry out in-situ polymerization reaction. After the reaction continued for 6-12 hours, the dark green solid product was collected by centrifugation and washed three times alternately with deionized water and ethanol. The product was then dried under vacuum at 60°C to obtain the polyaniline-modified copper-cobalt MOF nanosheet precursor.

[0058] 2. High and low temperature gradient carbonization treatment; The polyaniline-modified copper-cobalt MOF nanosheet precursor was evenly divided into two parts; The two precursors were placed separately in a tube furnace and carbonized under nitrogen protection. The carbonization parameters were as follows: Low-temperature carbonized component: The low-temperature carbonized component is obtained by heating to 600℃ at 5℃ / min, holding at that temperature for 2 hours, and then naturally cooling. High-temperature carbonized component: The temperature is increased to 800℃ at 5℃ / min, held for 2 hours, and then naturally cooled to obtain the high-temperature carbonized component.

[0059] 3. Combination of high and low temperature carbonization materials; The materials obtained by carbonization at two different temperatures are physically mixed at a dry mass ratio of 1:(1-4) (the preferred ratio is low-temperature carbonized part: high-temperature carbonized part = 1:2).

[0060] Experiments were conducted on the technical solution of this embodiment; Detection conditions (consistent with application example 1): Contaminant: 20 mg / L norfloxacin (NOR) solution; Catalyst dosage: 0.1 g / L; Oxidizing agent: Persulfate (PMS), dosage 2.0 mM; Reaction temperature: room temperature (approximately 25°C); Reaction time: 120 minutes; The grouping is shown in Table 1 below, and the detection results are shown in Table 2 below: Table 1

[0061] Table 2

[0062] The experimental results of this embodiment show that the norfloxacin removal rate of the combined material in Example 3 reached 85.5%, which is not only higher than that of the two single components (68.5% and 72.0%), but also exceeds its theoretical average value of 70.8%. Simultaneously, the metal leaching concentration of this combined material is lower than that of either single component, and its performance retention rate is higher after three cycles. These results collectively indicate that the combination of high- and low-temperature materials and polyaniline modification produced a synergistic effect, achieving improvements in both catalytic activity and structural stability.

[0063] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: By introducing the conductive polymer polyaniline and using a combination of materials carbonized at different temperatures, the technical problems of traditional metal-organic framework materials in catalytic applications, such as easy leaching of metal active centers, limited electron conduction efficiency, and insufficient long-term stability, are synergistically solved.

[0064] The introduction of the conductive polymer polyaniline leverages the amino and imino functional groups in its molecular chain to form stable nitrogen-metal coordination bonds with copper and cobalt metals. This chemical interaction effectively anchors the active metal sites, inhibiting their dissolution from the carbon support during catalytic reactions, thereby reducing the risk of secondary pollution and improving the structural integrity of the material. Simultaneously, polyaniline itself possesses certain redox activity and conductivity, allowing it to serve as an auxiliary catalytic phase in the activation process of persulfate.

[0065] Combinations of carbonized materials at different temperatures were developed based on the structural and property differences of the carbonized materials obtained under different heat treatment conditions. Low-temperature carbonized materials retain more nitrogen- and oxygen-containing functional groups and carbon layer defects. These sites have adsorption and enrichment effects on pollutants and can serve as active centers for catalytic reactions; however, their carbon matrix has a lower degree of graphitization, resulting in limited electronic conductivity. High-temperature carbonized materials, on the other hand, have a higher degree of graphitization, forming a highly conductive carbon framework. This framework can serve as a highly efficient electron transport channel, but its surface functional groups are relatively fewer, reducing the accessibility of active sites.

[0066] Together, they construct a functionally complementary integrated catalytic system. The anchoring effect of polyaniline provides a more stable metal-support interface for the entire system, while the physical mixing of high- and low-temperature carbonization materials creates a microscopic close contact between a highly conductive carbon network and highly surface-active regions. This structure allows electrons generated by the active sites provided by the low-temperature carbonization material after activating persulfate to be rapidly transferred through the conductive network constructed by the high-temperature carbonization material, thereby significantly accelerating the redox cycle kinetics of the metal active centers. This synergistic mechanism effectively promotes the co-occurrence of free radical and non-free radical pathways, thereby improving the utilization efficiency of the oxidant and the degradation rate of pollutants.

[0067] This approach improves material stability through chemical anchoring by introducing polyaniline for surface modification and combining it with materials carbonized at different temperatures. Furthermore, it optimizes the interfacial electron transfer process by constructing a conductive-active composite system, thereby achieving a simultaneous improvement in catalytic activity and material stability on a macroscopic level. This provides an effective way to solve the bottleneck problem of MOF-derived materials in practical water treatment applications.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., 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 carbon supported copper cobalt MOF nanosheet, characterized in that, The material is obtained by carbonization treatment of copper-cobalt bimetallic MOF two-dimensional nanosheet precursor, and the material is a two-dimensional sheet-shaped carbon material with copper and cobalt bimetallic species distributed therein; the two-dimensional sheet-shaped carbon material has a width-to-thickness ratio greater than 40 and a thickness less than 10 nm.

2. The carbon-supported copper-cobalt MOF nanoplatelets of claim 1, wherein, The molar ratio of copper to cobalt in the material is 1:(0.2-2).

3. A method of preparing carbon-supported copper-cobalt MOF nanosheets as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: Preparation of solution A: dissolving a soluble copper salt and a soluble cobalt salt in ultrapure water, then adding ethanol and mixing uniformly; Preparation of solution B: dissolving terephthalic acid in N,N-dimethylformamide; Mixing and reaction: mixing solution A and solution B, then adding triethylamine to the mixed solution, and stirring and reacting at room temperature for 12 h or more; Centrifugal washing and drying: collecting the solid product by centrifugation, washing with ethanol, and vacuum drying to obtain a copper-cobalt MOF nanosheet precursor; Carbonization treatment: carbonizing the precursor under a protective atmosphere to obtain the carbon-supported copper-cobalt MOF nanosheet.

4. The method of claim 3, wherein the carbon-supported copper cobalt MOF nanosheets are prepared by the method comprising: The process parameters of the carbonization treatment are as follows: increasing the temperature to 600-900℃ at a heating rate of 5-15℃ / min, and maintaining the temperature for 1-3 h; the protective atmosphere is nitrogen or an inert gas.

5. The method of claim 3, wherein the carbon-supported copper cobalt MOF nanosheets are prepared by the method comprising: After obtaining the copper-cobalt MOF nanosheet precursor in the centrifugal washing and drying step, a step of polyaniline modification of the precursor is further included before the carbonization treatment step: dispersing the precursor in a hydrochloric acid solution, adding aniline monomers, and performing in-situ polymerization reaction by dropwise adding ammonium persulfate under ice water bath conditions, and then centrifuging, washing, and drying after the reaction to obtain a polyaniline-modified copper-cobalt MOF nanosheet precursor.

6. The method of claim 5, wherein the carbon-supported copper cobalt MOF nanosheets are prepared by the method comprising: The amount of aniline monomers added is 10%-50% of the mass of the precursor powder.

7. The method of claim 5, wherein the carbon-supported copper cobalt MOF nanosheets are prepared by the method comprising: The carbonization treatment step is: dividing the polyaniline-modified copper-cobalt MOF nanosheet precursor into at least two portions, and carbonizing the portions at different temperatures to obtain at least two carbonized materials; and physically mixing the at least two carbonized materials.

8. The method of claim 7, wherein the carbon-supported copper cobalt MOF nanosheets are prepared by the method comprising: The different temperature carbonization includes low-temperature carbonization at 600℃ and high-temperature carbonization at 800℃; and the mass ratio of the physical mixing is: low-temperature carbonized material: high-temperature carbonized material = 1:(1-4).

9. Use of the carbon-supported copper-cobalt MOF nanosheet according to claim 1 or 2 in treating contaminated wastewater.

10. Use of the carbon supported copper cobalt MOF nanoplatelets according to claim 9 for the treatment of contaminated wastewater, characterized in that, The use is: co-adding the carbon-supported copper-cobalt MOF nanosheet and an oxidizing agent to the contaminated wastewater to perform a catalytic oxidation reaction; the oxidizing agent is at least one selected from the group consisting of peroxymonosulfate, peroxodisulfate, hydrogen peroxide, peroxyacetic acid, and ozone; and the pollutants in the contaminated wastewater are antibiotics.

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