2D nanosheet cobalt-based catalyst, and preparation method and application thereof

Abstract

This invention discloses a 2D nanosheet cobalt-based catalyst, its preparation method, and its applications, relating to the field of catalytic material preparation technology. The method precisely controls the carbonization process of ZnCo-ZIF through polar dispersion and lattice etching effects in a molten salt medium, preparing 2D nanosheets with micron-sized lateral dimensions and well-developed mesoporous structures. This catalyst possesses highly exposed Co active centers and excellent mass transfer kinetics. In the reaction system of activated peroxy-sulfate (PMS) degradation of ciprofloxacin (CIP), it exhibits significant catalytic activity and stability, mainly through singlet oxygen (…). 1 The O2 non-radical mechanism enables rapid removal of pollutants. This preparation process is characterized by low cost and strong scalability, and the resulting product exhibits excellent catalytic performance over a wide pH range and in real water bodies, demonstrating promising prospects for practical applications.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a 2D nanosheet cobalt-based catalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of the modern pharmaceutical industry and animal husbandry, the use of antibiotics has exploded globally. CIPs (Chemical Inhibitors) are widely used in clinical treatment and agricultural production due to their broad-spectrum antibacterial properties. However, antibiotics are often difficult to completely absorb and metabolize in organisms, resulting in large amounts of untreated or incompletely treated antibiotics entering natural water bodies with wastewater discharge. These emerging pollutants (ECs) not only have environmental persistence but may also induce the development of antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs), posing a serious potential threat to ecological security and human health. Among numerous advanced wastewater treatment technologies, PMS-based advanced oxidation processes (AOPs) have attracted widespread attention due to their strong oxidation capacity, wide pH range applicability, and the ease of activation of PMS molecules due to their asymmetric structure. Traditional activation methods include photoactivation, thermal activation, and transition metal ion activation, among which heterogeneous metal catalytic activation has become a research hotspot due to its simple equipment, high efficiency, and lack of secondary pollution. Cobalt (Co)-based materials are widely recognized as one of the most effective catalysts for activating PMS, especially in that they can generate highly efficient reactive oxygen species (ROS) through electron transfer or free radical / non-free radical pathways during the activation process.

[0003] In recent years, carbon-based catalysts derived from metal-organic frameworks (MOFs) have gained significant attention due to their high specific surface area and tunable active centers. Zeolite imidazole frameworks (ZIFs), as a type of MOF, are ideal precursors for preparing nitrogen-doped carbon-supported metal catalysts (M-NC). However, ZIF-derived catalysts prepared by conventional pyrolysis methods typically retain their original 3D rhombic dodecahedral structure, with particle sizes usually on the order of hundreds of nanometers. The dense carbon framework encapsulates a large number of metal active sites within the bulk phase, resulting in poor accessibility of the active centers. Furthermore, the 3D bulk structure faces mass transfer resistance in liquid-phase catalytic reactions, making it difficult for reactant molecules to diffuse rapidly into the particle interior, thus limiting the macroscopic degradation rate. During high-temperature pyrolysis, metal atoms are prone to thermal migration and aggregation, forming large-sized metal nanoparticles, reducing atom utilization and increasing the risk of metal leaching.

[0004] To address the aforementioned challenges, developing carbon-based catalysts with 2D morphology is considered an effective solution. Chinese patent application CN111545235A discloses a 2D / 2D g-C3N4 / CoAl-LDH hydrogen-generating heterojunction material, its preparation method, and its applications. This technology utilizes a layer-by-layer self-assembly method to construct heterojunctions to promote charge separation. However, its preparation involves multiple exfoliation and recombination processes, making the process complex and difficult to scale up for industrial production. Furthermore, LDHs have limited chemical stability under acidic or strongly alkaline environments, limiting their application in wastewater treatment across a wide pH range.

[0005] Chinese Patent Publication No. CN112323089B discloses a method for synthesizing doped carbon nanosheet catalysts using an all-solid-phase molten salt process: Solid 2-methylimidazole, zinc oxide, and sodium chloride powders are uniformly mixed and subjected to a chemical steam reaction in a hydrothermal reactor; the sample after the steam reaction is ground and washed with ethanol; the washed sample is centrifuged and vacuum-dried to obtain a powder sample; the powder sample is calcined at high temperature in a nitrogen atmosphere, and after cooling, a powder sample containing sodium chloride is obtained; the powder sample is washed with deionized water; the washed powder sample is filtered and vacuum-dried to obtain the doped carbon nanosheet catalyst. This method primarily focuses on the graphitization process, enabling the catalyst to exhibit excellent electrocatalytic performance. Summary of the Invention

[0006] The present invention aims to provide a 2D nanosheet cobalt-based catalyst and its preparation method, which significantly improves the catalyst's activation efficiency for PMS and degradation rate of pollutants.

[0007] This invention also discloses the application of a 2D nanosheet cobalt-based catalyst in the activation of PMS for the degradation of organic pollutants.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a 2D nanosheet cobalt-based catalyst includes the following steps: S1. Mix ZnCo-ZIF precursor powder with eutectic point halide salt and grind thoroughly to obtain mixed powder. Then place the mixed powder under an inert atmosphere for heat treatment. Utilize the molten liquid phase environment of halide salt at high temperature to guide the carbon substrate to grow in the 2D direction, and the vapor phase etching effect of halide ions to obtain cobalt-based products loaded on 2D nanosheets. The eutectic halide salts form eutectic molten salts at 220~240 °C; S2. The cobalt-based product loaded on 2D nanosheets obtained in step S1 is placed in a strong acid solution, heated and stirred at a constant temperature, filtered, washed until neutral and dried to obtain a 2D nanosheet cobalt-based catalyst.

[0009] Preferably, the eutectic halide salt forms a eutectic molten salt at 225~235 °C.

[0010] This invention utilizes the liquid-phase confinement effect and chemical ablation of molten salt to reshape traditional 3D ZIF particles into 2D nanosheets with high specific surface area and abundant mesopores, thereby significantly improving the activation efficiency of the catalyst for PMS and the degradation rate of pollutants.

[0011] Eutectic point halides begin to melt at 220–240 °C to form highly polar media. Utilizing the electrostatic induction and liquid-phase confinement effect of salt ions, carbon layer stacking along the Z-axis is suppressed earlier and more effectively, allowing carbon fragments generated by the pyrolysis of the ZIF framework to dissolve and disperse. Under the induction of salt ions, the carbon fragments recombine into 2D micron-sized nanosheets, effectively breaking the mass transfer barrier of traditional 3D structures. Simultaneously, the high-temperature evaporation of Zn and Cl... - The strong chemical etching effect of ions constructs a well-developed multi-level pore system of "micropores-mesopores" in a 2D plane. This invention provides a new approach to resolving the triangular contradiction of "oxidizing capacity-site utilization-environmental safety" and promotes the practical application of non-radical catalytic systems.

[0012] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows: In step S1, the eutectic halide salt comprises potassium chloride and zinc chloride in a mass ratio of 3~5:6~8; preferably 4~5:7~8. More preferably, the eutectic halide salt comprises potassium chloride and zinc chloride in a mass ratio of 4:7~8. The introduction of the molten salt-assisted strategy utilizes its highly polar liquid phase environment at high temperatures to induce two-dimensional epitaxial growth of ZIF fragments. + The electrostatic induction of ions and the confinement effect of salt crystal planes effectively suppressed the stacking of carbon supports along the Z-axis, forming ultrathin nanosheets with micron-scale lateral dimensions.

[0013] In one preferred embodiment, in step S1, the mass ratio of ZnCo-ZIF powder to eutectic point halide salt is 1:3~5; preferably 1:4~5.

[0014] In one preferred embodiment, in step S1, the heat treatment involves heating to 850–950 °C at a heating rate of 4–8 °C / min and holding for 2–4 h; preferably, to 900–950 °C and holding for 3–4 h. This temperature range ensures effective evaporation of Zn atoms (boiling point 907 °C) and sufficient liquefaction of the eutectic salt. An appropriate heating rate helps to firmly anchor the Co active sites in the two-dimensional carbon nanosheet matrix, preventing excessive aggregation of cobalt species.

[0015] In one preferred embodiment, in step S1, the inert atmosphere is high-purity argon gas with a flow rate of 80~120 sccm; preferably 100~120 sccm.

[0016] In one preferred embodiment, in step S2, the heating temperature is 60~90 ℃, and the stirring is carried out at a constant temperature for 8~15 h. Preferably, the heating temperature is 70~90 ℃, and the stirring is carried out at a constant temperature for 10~15 h.

[0017] In one preferred embodiment, the strong acid solution is a sulfuric acid solution with a concentration of 0.5~2.5 M, preferably 1.0~2.0 M. This effectively removes recrystallized salts adhering to the product surface, as well as any metal elemental or oxide particles that may form.

[0018] In one preferred embodiment, the method for preparing the ZnCo-ZIF powder includes the following steps: (1) Mix zinc nitrate hexahydrate, cobalt nitrate hexahydrate, 2-methylimidazole and methanol solution evenly. The molar ratio of zinc nitrate hexahydrate to cobalt nitrate hexahydrate is 1:0.1~0.2, and the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:3~5.

[0019] (2) The mixed solution was stirred at room temperature for 3-5 h, followed by centrifugation, washing, and drying to obtain ZnCo-ZIF powder. ZnCo-ZIF was selected as the precursor, taking advantage of its natural template with atomic-level metal dispersion, combined with Zn high-temperature volatilization to create pores and imidazole ligand-rich nitrogen source, and morphology reshaping induced by molten salt medium, thereby constructing a 2D porous catalyst with ultra-high specific surface area, abundant Co active sites and excellent mass transfer performance.

[0020] The grinding time in step S1 is 10~20 min.

[0021] In step S2, the drying temperature is 55~65℃.

[0022] This invention also discloses a 2D nanosheet cobalt-based catalyst, which exhibits a 2D ultrathin nanosheet morphology and has a specific surface area of ​​2300~2400 m². 2 g -1 The total pore volume is 1.2~1.3 cm³. 2 g -1 It exhibits a distinct mesoporous distribution within the range of 3.5 to 5 nm; preferably, the proportion of mesopores in the pore structure is 20% to 40%.

[0023] Preferably, the catalyst has a specific surface area of ​​2300~2350 m². 2 g -1The total pore volume is 1.2~1.26 cm³. 2 g -1 .

[0024] In one preferred embodiment, the catalyst has a Co loading of 0.6-0.7 wt.% and a CN / CC ratio of 0.30-0.50. The CN / CC ratio of the catalyst is higher than that of Co-NC (0.19), increasing the defect concentration in the carbon matrix.

[0025] Conventional ZIFs-derived 3D cobalt-based catalysts typically exhibit a rhombic dodecahedral bulk structure. A large number of metal active sites within the catalyst are deeply encapsulated by organic ligands and a carbon substrate, preventing the active sites from being effectively exposed. Furthermore, the compact structure, dominated by micropores, restricts the entry of reactants, resulting in problems such as insufficient mass transfer in the catalyst layer, low utilization of active sites, and susceptibility to passivation.

[0026] The Co-NC-2D catalyst prepared in this invention achieves morphological reshaping through molten salt-assisted pyrolysis. Its 2D sheet-like structure with a lateral size of up to micrometers greatly increases the exposed area of ​​surface active sites, combined with a maximum 2348 μm... 2 The specific surface area is 1.25 cm³ / g and the well-developed hierarchical pore structure is 1.25 cm³ / g. 3 The method significantly shortens the ion diffusion path and accelerates the interfacial charge transfer. At the same time, by increasing the carbon matrix defect concentration and optimizing the electronic localization of Co sites, the intrinsic catalytic activity and mass transfer efficiency are simultaneously enhanced.

[0027] This invention also discloses the application of the aforementioned 2D nanosheet cobalt-based catalyst or the 2D nanosheet cobalt-based catalyst prepared according to the aforementioned method in the degradation of organic pollutants by activated PMS. The catalyst is added to wastewater containing organic pollutants, followed by the addition of PMS to initiate the reaction. The reaction is achieved by catalytically activating PMS to generate reactive oxygen species dominated by singlet oxygen, thereby realizing the oxidative degradation of organic pollutants. Preferably, the catalyst dosage is 0.02~0.05 g / L, the initial concentration of PMS is 0.5~2.0 mM, and the applicable pH range is 3.0~11.0.

[0028] The catalyst exhibits excellent degradation performance over a wide pH range of 3 to 11.

[0029] The organic pollutants include one or more of CIP, sulfamethoxazole, carbamazepine, sulfadiazine, and tetracycline-rich electron-rich pollutants. The catalyst system of this invention, dominated by a singlet oxygen non-radical pathway, can specifically target and rapidly extract electrons from electron-rich pollutants.

[0030] The preparation principle of the catalyst of this invention is as follows: A morphology control strategy was achieved through molten salt-assisted pyrolysis, utilizing the synergistic effects of liquid-phase confinement, morphology remodeling, and vapor-phase etching. When the system temperature exceeded the eutectic point, the halide salt transformed into a highly polar liquid molten salt medium, confining the nitrogen-containing carbon fragments generated by the pyrolysis of ZnCoZIF at the droplet interface for two-dimensional coupling and arrangement, thereby inducing the formation of 2D nanosheet structures. Simultaneously, the high-temperature Cl... - The strong corrosiveness of ions enables vapor-phase etching of the carbon substrate, generating abundant defects through controlled atomic exfoliation. This, combined with in-situ evaporation of Zn atoms in ZnCo-ZIF at 900 °C, creates numerous interconnected micropores and mesopores within the carbon layer. Ultimately, stable Co sites formed under molten salt protection are efficiently anchored on the surface of extremely thin 2D nanosheets (less than 10 nm thick), significantly improving the accessibility of active sites and catalytic mass transfer efficiency, thereby optimizing the overall catalytic performance of the reaction system.

[0031] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes vapor-phase etching in molten salt and in-situ evaporation of Zn atoms to construct well-developed microporous-mesoporous interconnected channels in 2D nanosheets, increasing the density of accessible active sites on the catalyst, significantly accelerating the transport efficiency of reaction substrates and catalytic products on the catalyst surface, and greatly improving the reaction rate of PMS activation.

[0032] Precise electronic structure control: The molten salt environment significantly increased the content of pyridine nitrogen (pN), effectively regulated the electron cloud distribution of the Co active center, and reduced the energy barrier for activating PMS.

[0033] Highly selective degradation pathway: The system uses singlet oxygen ( 1 With O2 as the dominant active species, it has a strong anti-interference ability and can maintain high efficiency in degradation when facing coexisting anions, cations and humic acids in complex water bodies.

[0034] The precursor raw materials used in this invention are inexpensive and readily available, and the preparation process is simple and easy to control precisely. Due to the strong coordination between the Co sites and the carbon substrate, the catalyst exhibits excellent chemical stability and outstanding practical application potential, belonging to an environmentally friendly catalytic technology. Attached Figure Description

[0035] Figure 1 The images show the XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1.

[0036] Figure 2 This is a SEM image of the catalyst prepared in Example 1.

[0037] Figure 3 The image shows the SEM image of the catalyst prepared in Comparative Example 1.

[0038] Figure 4 The pore size distribution diagrams are for the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 3.

[0039] Figure 5 The images show the XPS high-resolution spectra of the catalysts prepared in Example 1 and Comparative Example 1.

[0040] Figure 6 The catalysts prepared in Example 1 and Comparative Example 1 were used to test their performance in catalytic degradation of CIP.

[0041] Figure 7 The catalysts prepared in Examples 1, 2, and 3 were used to test their performance in catalytic degradation of CIP.

[0042] Figure 8 The performance of the catalyst obtained in Example 1 in catalytic degradation of CIP was tested for different quenchers.

[0043] Figure 9 The effect of pH on the catalytic degradation performance of CIP by the catalyst prepared in Example 1 was tested.

[0044] Figure 10 The effect of coexisting ions on the catalytic degradation performance of CIP by the catalyst prepared in Example 1 was tested.

[0045] Figure 11 The effect of actual water bodies on the catalytic degradation performance of CIP by the catalyst prepared in Example 1 was tested.

[0046] Figure 12 The performance of the catalyst prepared in Example 1 in catalytic degradation of CIP, sulfamethoxazole, carbamazepine, sulfamethoxazole and tetracycline was tested. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0048] Example 1: A method for preparing a 2D nanosheet cobalt-based catalyst includes the following steps: Precursor synthesis: 1.674 g Zn(NO3)2·6H2O and 0.103 g Co(NO3)2·6H2O were weighed and dissolved in 45 mL methanol (beaker 1). Separately, 1.848 g 2-methylimidazole was weighed and dissolved in 45 mL methanol (beaker 2). The contents of beaker 1 were poured into beaker 2 under vigorous stirring, and the mixture was sonicated for 10 min to ensure homogeneity. The mixture was stirred continuously at 25 °C for 4 h. The purple solid was collected by centrifugation (10000 rpm, 3 min), washed three times alternately with anhydrous methanol and deionized water, and dried under vacuum at 60 °C for 12 h to obtain the ZnCo-ZIF precursor.

[0049] Molten salt modification and pyrolysis: Take 500 mg of the above ZnCo-ZIF, add 720 mg KCl and 1.28 g ZnCl2. Grind the three components finely in a mortar for 15 min until the mixture turns a uniform light purple color. Load the mixed powder into a porcelain boat and place it in the center of a tube furnace. Under argon protection at a flow rate of 100 sccm, heat to 900 ℃ at a heating rate of 5 ℃ / min, hold at that temperature for 3 h, and remove the black powder after cooling.

[0050] Acid washing: The pyrolysis product was added to a 2.0 M H2SO4 solution and stirred at 80 °C for 12 h. Residual salts, excess oxides, and any possible zero-valent cobalt particles were removed by strong acid washing. Finally, the product was filtered, washed until neutral, and dried at 60 °C, denoted as Co-NC-2D.

[0051] Comparative Example 1: The difference between this comparative example and Example 1 is that no halide salts are added in the pyrolysis step 2). The ZnCo-ZIF precursor is directly pyrolyzed at 900 °C for 3 h, followed by the same acid washing treatment, and is denoted as Co-NC.

[0052] Comparative Example 2: The difference between this comparative example and Example 1 is that the eutectic point halide salts added in pyrolysis step 2) are NaCl and ZnCl2, and the same pyrolysis and acid washing treatment are performed. It is denoted as Co-NC-2D-1.

[0053] Comparative Example 3: The difference between this comparative example and Example 1 is that the mass ratio of KCl and ZnCl2 eutectic point halide salts added in pyrolysis step 2) is 1:1, and the same pyrolysis and acid washing treatment is performed. It is denoted as Co-NC-2D-2.

[0054] Figure 1The XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 show that both materials only exhibit characteristic peaks of graphitic carbon at ~22° and ~44°, and no obvious metal-related peaks were found, indicating that the cobalt species are highly dispersed in the carbon substrate.

[0055] Figure 2 SEM images of the catalyst prepared in Example 1 show that Co-NC-2D exhibits a typical 2D nanosheet morphology with lateral dimensions reaching the micrometer scale. In contrast, Figure 3 The SEM images show that the Comparative Example 1 Co-NC without added molten salt retains the original rhombic dodecahedral structure of the ZIF-8 precursor, which strongly demonstrates the decisive promoting effect of eutectic halide salts on the formation of 2D morphology during pyrolysis.

[0056] Figure 4 The pore size distribution diagrams are shown for the catalysts prepared in Example 1, Comparative Examples 1 and 3. The results show that Co-NC-2D exhibits a significant hysteresis loop, indicating the coexistence of micropores and mesopores. Its specific surface area and total pore volume are as high as 2348 m². 2 g -1 and 1.25 cm 3 g -1 It is much higher than that of Comparative Example 1 Co-NC (1299 m 2 g -1 0.67 cm 3 g -1 ) and Comparative Example 3 Co-NC-2D-2 (1876 m 2 g -1 0.94 cm 3 g -1 This significantly increased specific surface area and well-developed porous system provide excellent structural support for the exposure of active sites and rapid mass transfer of reactants. However, when the mass ratio of KCl to ZnCl2 becomes 1:1, the system deviates from the lowest eutectic point of 230℃, leading to the condensation of the liquid phase environment during bond pyrolysis, which hinders the KCl-ZnCl2 exchange process. + The uniform intercalation of the catalyst limited the exfoliation process, resulting in a significant decrease in specific surface area.

[0057] Figure 5 XPS results for the catalysts prepared in Example 1 and Comparative Example 1. Co-NC-2D exhibits a higher CN / CC ratio (0.40), confirming the increased defect concentration. N 1s spectra show the presence of Co-N coordination, and the increased pyridine nitrogen (pN) content contributes to enhanced activity at the Co-N4 sites. A small amount of Co was detected in the Co 2p spectra. 0 This indicates that the molten salt strategy introduces trace amounts of cobalt nano-agglomerates.

[0058] The Co-NC mesoporous ratio obtained in Comparative Example 1 was approximately 5% to 10%. The Co-NC-2D-2 mesoporous ratio obtained in Comparative Example 3 was approximately 15% to 25%. The Co-NC-2D mesoporous ratio obtained in Example 1 was approximately 25% to 35%. Example 1 of the present invention constructed well-developed micropore-mesopore interconnected channels in 2D nanosheets.

[0059] The application of this method will be tested below, taking into account the above embodiments and comparative examples.

[0060] Application Example 2: Performance test of Co-NC-2D activated PMS for CIP degradation.

[0061] This example is used to evaluate the efficiency of the 2D nanosheet cobalt-based catalyst (Co-NC-2D) prepared in Example 1 and Comparative Example 1 (Co-NC) in activating PMS to degrade CIP. The specific experimental procedure is as follows: Reaction system construction: All degradation reactions were carried out in 250 mL beakers, and the total volume of the reaction solution was 50 mL.

[0062] Initial concentration setting: The initial concentration of CIP in the reaction solution was set to 20 mg / L. -1 Catalyst addition: Add 0.04 g L to the system. -1 Catalyst.

[0063] Initiation of the reaction: The reaction system was placed in a dark environment, and 2 mM PMS solution was added to the system to trigger the oxidative degradation reaction, and the start time was recorded simultaneously.

[0064] Sampling and solid-liquid separation: At preset time points (0, 0.5, 1, 1.5, 2, 3, 5, 7, 10 min), accurately aspirate 0.5 mL of the reaction solution using a micropipette.

[0065] Quenching and Detection: Immediately after sampling, solid-liquid separation was performed using a 0.22 μm hydrophilic polytetrafluoroethylene (PTFE) filter membrane, and residual oxidizing substances were quenched using methanol solution. The instantaneous concentration of CIP was determined by high-performance liquid chromatography (HPLC).

[0066] All experiments were repeated twice, and the average value was taken to obtain the test results as follows: Figure 6As shown, the removal rate of CIP after 10 min was only 8.0% when PMS was added alone. After adding Co-NC-2D, CIP was completely removed within 10 min, reaching nearly 100%. In contrast, the removal rate of the Co-NC / PMS system in Comparative Example 1 was only 57% in the same time, while the degradation rates of pure carbon substrate and conventional Co3O4 were only 28% and 17%, respectively, indicating that Co-NC-2D has extremely high catalytic activity. This is mainly due to the morphology control and structural optimization achieved through the molten salt-assisted pyrolysis strategy. The micron-sized 2D layered material of Co-NC-2D has an electronic confinement effect and a very large lateral size, which can significantly shorten the ion diffusion path and solve the problems of low utilization of active sites and insufficient mass transfer caused by the deep encapsulation of internal metal sites in 3D structures. At the same time, the molten salt etching effect endows the material with an ultra-high specific surface area and a well-developed micro-mesoporous system, providing a richer effective exposure area for catalytic reactions. In addition, a higher concentration of defect sites and N doping is introduced into the carbon matrix. In particular, the increased pyridine nitrogen content reduced the electron localization around the Co site, thereby enhancing the adsorption capacity for oxygen-containing species, lowering the reaction energy barrier, and significantly improving the activation performance of the Co site. This demonstrates that the molten salt etching strategy is very effective in improving catalyst performance.

[0067] Application Example 3: The catalysts obtained in Example 1 (Co-NC-2D), Comparative Example 2 (Co-NC-2D-1), and Comparative Example 3 (Co-NC-2D-2) were used to activate the PMS degradation performance of CIP. The specific experimental process is as follows.

[0068] The difference between this application example and application example 2 is that the catalysts prepared in example 1, comparative examples 2, and comparative examples 3 are tested. The results are as follows... Figure 7 As shown. Figure 7 The results show that changing the type or mass ratio of eutectic halide salts affects the catalytic effect. This is because, on the one hand, Na... + Size not as good as K + The steric hindrance and intercalation stripping effect of the carbon layer are greatly reduced, and the internal carbon skeleton is more prone to agglomeration during pyrolysis shrinkage, resulting in an increase in the thickness of the final product and a significant reduction in catalytic efficiency. On the other hand, when the mass ratio of KCl to ZnCl2 becomes 1:1, the eutectic point deviates significantly, the 2D morphology degrades and agglomerates, causing a decrease in the specific surface area and porosity of the catalyst, burying the core Co-N active sites deep and reducing surface defects, resulting in a significant decline in overall performance.

[0069] Application Example 4: The quenching experiment for active species recognition in the Co-NC-2D / PMS system is described in detail below.

[0070] The difference between this embodiment and application embodiment 2 is that only the Co-NC-2D prepared in embodiment 1 is used as the catalyst; before adding PMS to the system to start the reaction, specific concentrations of chemical quenchers, including those for capturing ·OH and SO4, are added to the reaction solution in advance. ·- Methanol (MeOH), tert-butanol (TBA) for capturing ·OH, and O2 for capturing ·- chloroform (CHCl3) and its use in capturing 1 The degradation of CIP by furfuryl alcohol (FFA) with O2 was investigated by comparing the degree of inhibition of CIP degradation efficiency after the addition of different quenchers to identify the main active species in the system. The results are shown in Figure 8. The results show that after adding excess MeOH and TBA, the CIP degradation rate only decreased slightly by about 7.5%, and the degradation rate only decreased by 12.5% ​​after adding CHCl3, indicating that ·OH and SO42- quenching agents inhibited the degradation of CIP. ·- and O2 ·- Playing only a secondary role in this system; on the contrary, joining 1 After O2 scavenging agent FFA was applied, the CIP removal efficiency decreased significantly by approximately 70%, which, combined with the significant inhibition of the kinetic constant, strongly demonstrates... 1 O2 is the dominant active species in this system that enables efficient degradation of pollutants.

[0071] Application Example 5: The catalytic degradation performance of the catalyst obtained in Example 1 on CIP was tested under different initial pH values ​​of the reaction solution. The specific experimental procedure is as follows.

[0072] The difference between this application example and application example 2 is that only the Co-NC-2D catalyst prepared in example 1 was added for testing; before adding the catalyst and PMS to the system, the pH value of the initial CIP solution was adjusted using dilute H2SO4 or NaOH solution to reach 3.16, 4.93, 7.00, 9.71 and 11.12 respectively, and then the degradation efficiency of the catalyst on CIP under different acid and alkaline conditions was investigated. The results are as follows. Figure 9 As shown, the catalyst exhibits excellent and stable degradation performance over a wide initial pH range, with removal rates exceeding 98.2%.

[0073] Application Example 6: The effect of coexisting ions on the catalytic degradation performance of CIP by the catalyst obtained in Example 1 was tested, and the specific experimental procedure is as follows.

[0074] The difference between this application example and application example 2 is that only the Co-NC-2D catalyst prepared in example 1 was added for testing; before starting the reaction, a certain amount of inorganic salt (NaCl, NaNO3, NaHCO3) or humic acid (HA) was added to the CIP solution to reduce the concentration of anions (Cl-) in the system.- NO3 - HCO3 - The concentration of ) was set to a predetermined value, or the HA concentration was set to a specific level, to simulate a complex water quality background and examine the degree of interference of each component on the catalytic efficiency. The results are as follows: Figure 10 As shown, various coexisting substances exhibit only a weak inhibitory effect on the removal of CIP, demonstrating the system's extremely strong anti-interference ability.

[0075] Application Example 7: The performance of the catalyst obtained in Example 1 in catalytic degradation of CIP was tested in natural water bodies. The difference between this application example and Application Example 2 is that only the Co-NC-2D catalyst prepared in Example 1 was added for testing; the reaction solution was not prepared using deionized water, but instead used water collected from tap water, Xiangjiang River in Changsha, and Taozi Lake in Changsha (all actual water samples were filtered to remove sediment before use) to evaluate the catalyst's application potential in real-world water bodies. The results are as follows... Figure 11 As shown, Co-NC-2D can achieve a high efficiency removal rate of over 98% of CIP within 10 minutes in various actual water bodies.

[0076] Application Example 8: The performance test of the catalyst obtained in Example 1 for catalytic degradation of different electron-rich pollutants is as follows: The difference between this application example and application example 2 is that only the catalyst prepared in example 1 is tested; the degraded antibiotic contaminants include: CIP, sulfamethoxazole, carbamazepine, sulfamethoxazole, and tetracycline electron-rich contaminants, all at a concentration of 20 mg / L. -1 Samples were taken at 0, 0.5, 1, 1.5, 2, 3, 5, 7, and 10 mins of the reaction. The results are as follows: Figure 12 As shown. Figure 12 The results show that Co-NC-2D has good catalytic degradation performance for these electron-rich pollutants, achieving removal of more than 80% within 10 minutes. This indicates that the singlet oxygen non-radical pathway dominated by this system can specifically target and rapidly extract electrons from electron-rich pollutants.

[0077] The above-described facts are merely illustrative of this application and are not intended to limit this application. Any modifications or alterations made to the above embodiments within the spirit and principles of this application should be included within the scope of protection of this invention.

Claims

1. A method for preparing a 2D nanosheet cobalt-based catalyst, characterized in that, Includes the following steps: S1. Mix ZnCo-ZIF precursor powder with eutectic point halide salt and grind thoroughly to obtain mixed powder. Place the mixed powder under an inert atmosphere for heat treatment. Utilize the molten liquid phase environment of halide salt at high temperature to guide the carbon substrate to grow in the 2D direction, and the vapor phase etching effect of halide ions to obtain cobalt-based products loaded on 2D nanosheets. The eutectic halide salts form eutectic molten salts at 220~240 °C; S2. The cobalt-based product loaded on 2D nanosheets obtained in step S1 is placed in a strong acid solution, heated and stirred at a constant temperature, filtered, washed until neutral and dried to obtain a 2D nanosheet cobalt-based catalyst.

2. The method for preparing the 2D nanosheet cobalt-based catalyst according to claim 1, characterized in that, In step S1, the eutectic point halide salt comprises potassium chloride and zinc chloride in a mass ratio of 3~5:6~8; preferably 4~5:7~8.

3. The method for preparing the 2D nanosheet cobalt-based catalyst according to claim 1, characterized in that, In step S1, the mass ratio of ZnCo-ZIF powder to eutectic point halide salt is 1:3~5; preferably 1:4~5.

4. The method for preparing the 2D nanosheet cobalt-based catalyst according to claim 1, characterized in that, In step S1, the heat treatment involves heating to 850-950 ℃ at a heating rate of 4-8 ℃ / min and holding for 2-4 h; preferably 900-950 ℃ and holding for 3-4 h.

5. The method for preparing the 2D nanosheet cobalt-based catalyst according to claim 1, characterized in that, In step S1, the inert atmosphere is high-purity argon gas with a flow rate of 80~120 sccm; preferably 100~120 sccm.

6. The method for preparing the 2D nanosheet cobalt-based catalyst according to any one of claims 1-5, characterized in that, In step S2, the heating temperature is 60~90 ℃, and the mixture is stirred at a constant temperature for 8~15 h.

7. The method for preparing the 2D nanosheet cobalt-based catalyst according to any one of claims 1-5, characterized in that, In step S2, the strong acid solution is a sulfuric acid solution with a concentration of 0.5~2.5 M, preferably 1.0~2.0 M.

8. A 2D nanosheet cobalt-based catalyst, characterized in that, The catalyst exhibits a 2D ultrathin nanosheet morphology, and its specific surface area is 2300~2400 m². 2 g -1 The total pore volume is 1.2~1.3 cm³. 2 g -1 It exhibits a distinct mesoporous distribution within the range of 3.5 to 5 nm; preferably, the proportion of mesopores in the pore structure is 20% to 40%.

9. The 2D nanosheet cobalt-based catalyst according to claim 8, characterized in that, The catalyst has a Co loading of 0.6-0.7 wt.%; the catalyst surface has abundant edge defect sites; and the CN / CC ratio is 0.30-0.

50.

10. The application of a 2D nanosheet cobalt-based catalyst according to claim 8 or 9, or a 2D nanosheet cobalt-based catalyst prepared by the preparation method according to any one of claims 1-7, in the activation of PMS for the degradation of organic pollutants, characterized in that: The catalyst is added to wastewater containing organic pollutants, followed by the addition of PMS to initiate the reaction. The PMS is catalytically activated to generate reactive oxygen species dominated by singlet oxygen, thereby achieving the oxidative degradation of organic pollutants. Preferably, the catalyst dosage is 0.02~0.05 g / L, the initial concentration of PMS is 0.5~2.0 mM, and the applicable pH range is 3.0~11.0.

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