Cobalt monatomic catalyst with controllable loading and coordination configuration, preparation method and application thereof

Abstract

The application discloses a cobalt monatomic catalyst with controllable loading and coordination configuration and a preparation method and application thereof, relates to the technical field of material engineering and environmental engineering, and the catalyst is prepared by the following method: organic ligands (oxalic acid, ethylenediaminetetraacetic acid, citric acid and the like) are respectively combined with cobalt acetate tetrahydrate to form cobalt-containing complexes, then the cobalt-containing complexes are combined with cyanuric acid and melamine to perform hydrogen bond assembly, and a supramolecular solid is constructed; then pyrolysis is performed under an argon atmosphere; by means of the anchoring mode and the difference between the internal sites of the carbon nitride carrier, the cobalt monatomic catalyst with controllable coordination configuration is prepared; by means of ligand complexation, ion replacement and carrier modification strategies, the cobalt monatomic catalyst with controllable cobalt loading and nitrogen / carbon structure is constructed, the coordination environment of cobalt sites is essentially optimized, the non-radical selectivity generation capacity is improved, and a green, efficient and beneficial technical scheme for improving the biodegradability is provided for the treatment of wastewater containing chlorophenol pollutants.

Description

Technical Field

[0001] This invention belongs to the fields of materials engineering and environmental engineering technology, specifically relating to a cobalt single-atom catalyst with controllable loading and coordination configuration, its preparation method, and its application. Background Technology

[0002] Chlorophenols exhibit strong biotoxicity and chemical inertness due to the synergistic effect of the benzene ring conjugated system and chlorine substituents, leading to bottlenecks in traditional physicochemical-biological combined processes such as low degradation efficiency, low mineralization efficiency, and poor biodegradability. Advanced oxidation processes (AOPs) utilize reactive oxygen species (ROS) to disrupt the molecular structure of pollutants; however, traditional homogeneous Fenton systems suffer from problems such as difficult catalyst recovery and large iron sludge production, while transition metal / carbon-based heterogeneous catalysts are limited by high preparation costs and unstable active sites.

[0003] Single-atom catalysts (SACs) possess multiple advantages, including homogeneity, heterogeneity, and enzyme catalysis. They often exhibit selective non-radical generation pathways in advanced oxidation processes; however, their non-radical-dominated processes generally suffer from insufficient mineralization efficiency. Singlet oxygen (… 1 O2 possesses unoccupied orbitals, allowing it to selectively remove electron-rich contaminants; however, its low redox potential (1.88 V) and short lifetime (≈2–4 μs) easily lead to incomplete oxidation. High-valence metal-oxygen species (M... n+2 =O, E = 2.2–2.8 V, pH = 3) Long lifetime (≈7 s) and steady-state concentration can reach 10 -8 M, while providing sustained oxidizing power at the cost of slow kinetics, offers a different approach. In contrast, hydroxyl and sulfate radicals, by extracting hydrogen atoms from pollutants and stripping electrons, bypass the limitations of low mineralization rates, fundamentally altering the utilization of oxidants. However, due to the lack of transient reaction intermediates and active species, they struggle to maintain selective degradation processes and may instead promote electron depletion of pollutants, thereby clogging catalytic sites. This trade-off between kinetics and thermodynamics stems from the fact that a single active species pathway cannot simultaneously address both activation barriers and oxidation lifetime.

[0004] Therefore, there is an urgent need in this field to design a single-atom catalyst with controllable coordination to selectively generate multiple non-radical species, significantly improve the mineralization efficiency of chlorophenol pollutants, and construct a dynamic degradation network capable of synergistically mineralizing recalcitrant intermediates. This strategy is expected to break the balance between removal efficiency and mineralization efficiency, providing a potentially effective path to overcome current technological bottlenecks. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a cobalt single-atom catalyst with controllable loading and coordination configuration, as well as its preparation method and application.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, a method for synthesizing and applying a cobalt single-atom catalyst with controllable loading and coordination configuration is disclosed, wherein the cobalt single-atom catalyst is prepared through the following steps: S1: Prepare an organic ligand solution by mixing the organic ligand, then add the cobalt salt and stir at room temperature until completely dissolved to obtain the first solution; S2: Prepare a cyanuric acid solution from cyanuric acid; mix and stir the first solution with the cyanuric acid solution to obtain a second solution; S3: Prepare a melamine solution by dissolving melamine in water; add the second solution to the melamine solution, stir to generate a precipitate, and filter to obtain a supramolecular solid; S4: The supramolecular solid obtained in step S3 is subjected to gradient heating, held at the temperature and cooled to room temperature to obtain a cobalt single-atom catalyst with controllable loading and coordination configuration.

[0007] The organic ligands include oxalic acid, ethylenediaminetetraacetic acid, and citric acid; the molar ratio of the organic ligands to cobalt acetate tetrahydrate is 1:1-5:1, the molar ratio of cobalt salt to cyanuric acid is 1:1-1:7, and the molar ratio of melamine to cyanuric acid is 1:0.6-1:1.

[0008] Further, in step S1, the cobalt salt is specifically cobalt acetate tetrahydrate.

[0009] Furthermore, the room temperature is specifically 15-35℃.

[0010] Furthermore, in steps S2 and S3, the temperature of the cyanuric acid solution and the melamine solution is 75-95°C.

[0011] Furthermore, in step S4, the heating rate of the gradient heating is 2-8℃ / minute, and the target temperature is 400-600℃.

[0012] Furthermore, in step S4, the heat preservation time is 2-6 hours.

[0013] Secondly, the present invention provides a cobalt single-atom catalyst prepared by the method described above.

[0014] Thirdly, the present invention provides an application of a cobalt single-atom catalyst prepared according to the method in the removal of chlorophenol pollutants from wastewater.

[0015] Furthermore, the application specifically involves adding the cobalt single-atom catalyst and persulfate together to a solution containing chlorophenol pollutants, and stirring the reaction at a water temperature of 20-25°C for 0-60 minutes to remove the chlorophenol pollutants from the solution.

[0016] Furthermore, the mass ratio of the cobalt single-atom catalyst to chlorophenol pollutants is 30:1-70:1, and the mass ratio of persulfate to chlorophenol pollutants is 10:1-20:1.

[0017] The beneficial effects of this invention are: 1) This invention successfully prepared a cobalt single-atom catalyst Co1 / CN- ligand with controllable loading and coordination configuration by simply changing the type of organic ligand (including oxalic acid, ethylenediaminetetraacetic acid, citric acid, etc.) and the dosage of cobalt salt (cobalt acetate tetrahydrate). 2) This invention achieves simultaneous regulation of cobalt atom loading and ligand configuration, significantly improving the activation efficiency of persulfate and enabling selective generation of singlet oxygen and high-valence cobalt species; for wastewater containing chlorophenol pollutants, this catalyst can achieve high mineralization rate and effectively improve the biodegradability of wastewater; at the same time, this catalyst has good cycle stability. 3) In addition, this invention constructs a cobalt single-atom catalyst with controllable cobalt loading and nitrogen / carbon structure through strategies such as ligand complexation, ion replacement and support modification. This fundamentally optimizes the coordination environment of cobalt sites and enhances the selective generation of non-radicals, providing a green, efficient and biodegradable technical solution for the treatment of wastewater containing chlorophenol pollutants. Attached Figure Description

[0018] Figure 1 The X-ray diffraction patterns are those of the catalysts prepared in Examples 1-3; Figure 2 Fourier transform infrared spectra of the catalysts prepared in Examples 1-3; Figure 3 The images show a comparison of the X-ray photoelectron spectra of the catalysts prepared in Examples 1-3. Figure 3 In the figure, 'a' is a comparison of the X-ray photoelectron C1s spectra of the catalysts prepared in Examples 1-3. Figure 3 In the figure, b is a comparison of the X-ray photoelectron N 1s spectra of the catalysts prepared in Examples 1-3. Figure 3 In the figure, c is a comparison of the X-ray photoelectron Co 2p spectra of the catalysts prepared in Examples 1-3; Figure 4 The Fourier transform Co K-side R-space X-ray extended edge absorption fine structure spectra of the catalysts prepared in Examples 1-3 are shown. Figure 5 The graph shows the degradation performance of p-chlorophenol under conditions such as CN, the catalysts prepared in Examples 1-3 activating the PMS system, etc. Among them, Figure 5 The graph shows the degradation rate of chlorophenol under conditions such as CN, the catalysts prepared in Examples 1-3 activating the PMS system, etc. Figure 5In the figure, b represents CN, and the degradation rate of chlorophenol is shown under the conditions of PMS system activated by catalysts prepared in Examples 1-3. Figure 6 The electron spin resonance spectra of the PMS systems activated by the catalysts prepared in Examples 1-3 are shown below. Figure 6 In the diagram, 'a' represents the electron spin resonance spectrum of the PMS system activated by the catalyst prepared in Example 1. Figure 6 In the diagram, b represents the electron spin resonance spectrum of the PMS system activated by the catalyst prepared in Example 2. Figure 6 In the figure, c represents the electron spin resonance spectrum of the PMS system activated by the catalyst prepared in Example 3; Figure 7 This is a chromatogram showing the analysis of active species in the PMS degradation system of p-chlorophenol activated by the catalyst prepared in Example 1. Figure 7 In Figure 'a', the figure represents the quenching experiment diagram of the PMS degradation of p-chlorophenol system activated by the catalyst prepared in Example 1. Figure 7 In Figure b, the degradation rate comparison diagram of the quenching experiment of the PMS degradation of p-chlorophenol system activated by the catalyst prepared in Example 1 is shown. Figure 8 This is a chromatogram showing the analysis of active species in the PMS degradation system of p-chlorophenol activated by the catalyst prepared in Example 2. Figure 8 In Figure 'a', the figure represents the quenching experiment diagram of the PMS degradation of p-chlorophenol system activated by the catalyst prepared in Example 2. Figure 8 In Example 2, b is a comparison of the degradation rates of the quenching experiment of the PMS activated by the catalyst prepared in Example 2 for the degradation of p-chlorophenol. Figure 9 This is a chromatogram showing the analysis of active species in the PMS degradation system of p-chlorophenol activated by the catalyst prepared in Example 3. Figure 9 In Example 3, 'a' represents the quenching experiment of the catalyst prepared in Example 3 activating PMS to degrade p-chlorophenol. Figure 9 In Example 3, b is a comparison of the degradation rates of the quenching experiment of the PMS activated by the catalyst prepared in Example 3 for the degradation of p-chlorophenol. Figure 10 This is a comparison chart of the high-valent cobalt formation in the PMS system activated by the catalysts prepared in Examples CN and Examples 1-3. Figure 10 In this context, 'a' represents the amount of high-valent cobalt generated in the CN-activated PMS system. Figure 10 In this context, b represents the amount of high-valent cobalt generated in the activated PMS system of Example 1. Figure 10 In this context, 'c' represents the amount of high-valent cobalt generated in the activated PMS system of Example 2. Figure 10 In this context, d represents the amount of high-valent cobalt generated in the activated PMS system of Example 3; Figure 11 This is a comparison graph showing the changes in chloride ion concentration and its theoretical maximum value in the PMS degradation system of the catalyst prepared in Example 1. Figure 12 The graph shows the change in degradation rate of p-chlorophenol in a cyclic experiment using the catalyst prepared in Example 1 to activate PMS. Figure 13 This is an experimental diagram showing the interference of the catalyst prepared in Example 1 on the degradation of p-chlorophenol by PMS. Figure 13 In the graph, 'a' represents the change in the degradation rate of p-chlorophenol by PMS activated by the catalyst prepared in Example 1 under coexisting ions. Figure 13 In the figure, b represents the change in the degradation rate of chlorophenol by PMS activated by the catalyst prepared in Example 1 at different pH values; Figure 14 This is a graph showing the change in total organic carbon removal rate of the PMS system activated by the catalyst prepared in Example 1 for the degradation of various chlorophenol-containing pollutants; Figure 15 The graph shows the changes in bio-oxygen demand / chemical oxygen demand of the PMS system activated by the catalyst prepared in Example 1 for the degradation of various chlorophenol-containing pollutants. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0020] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0021] This invention provides a method for synthesizing and applying a cobalt single-atom catalyst with controllable loading and coordination configuration. By changing the complexation combination of organic ligands (oxalic acid, ethylenediaminetetraacetic acid, citric acid) and cobalt acetate tetrahydrate, the controllable preparation of cobalt single-atom catalyst loading and coordination configuration is achieved, denoted as Co1 / CN- ligand, as shown in Examples 1-3.

[0022] Example 1: A cobalt single-atom catalyst (Co1 / CN-oxalic acid) with controllable loading and coordination configuration was prepared by the following steps: S1: Oxalic acid is dissolved in deionized water to prepare an oxalic acid solution with a molar concentration of 10.7 mmol / L. Then cobalt acetate tetrahydrate is added and stirred at room temperature (25°C) until completely dissolved to obtain the first solution. The molar ratio of oxalic acid to cobalt acetate tetrahydrate is 3:1. S2: Dissolve cyanuric acid in deionized water at 85°C to prepare a cyanuric acid solution with a molar concentration of 37.5 mmol / L; mix the first solution with the cyanuric acid solution and stir to obtain a second solution; S3: Melamine is dissolved in deionized water at 85°C to prepare a melamine solution with a molar concentration of 37.5 mmol / L; the second solution is poured into the melamine solution, stirred to form a precipitate, and filtered to obtain a supramolecular solid; S4: The supramolecular solid obtained in step S3 is subjected to gradient heating (heating rate 5℃ / min, target temperature 500℃), held at the temperature for 4 hours, and then cooled to room temperature to obtain a cobalt single-atom catalyst with controllable loading and coordination configuration.

[0023] The organic ligand for the cobalt single-atom catalyst prepared in Example 1 is oxalic acid, and is therefore denoted as Co1 / CN-oxalic acid.

[0024] Example 2: A cobalt single-atom catalyst (Co1 / CN-ethylenediaminetetraacetic acid) with controllable loading and coordination configuration was prepared by the following steps: S1: Dissolve ethylenediaminetetraacetic acid in deionized water to prepare an ethylenediaminetetraacetic acid solution with a molar concentration of 10.7 mmol / L. Then add cobalt acetate tetrahydrate and stir at room temperature (25°C) until completely dissolved to obtain the first solution. The molar ratio of oxalic acid to cobalt acetate tetrahydrate is 3:1. S2: Dissolve cyanuric acid in deionized water at 85°C to prepare a cyanuric acid solution with a molar concentration of 37.5 mmol / L; mix the first solution with the cyanuric acid solution and stir to obtain a second solution; S3: Melamine is dissolved in deionized water at 85°C to prepare a melamine solution with a molar concentration of 37.5 mmol / L; the second solution is poured into the melamine solution, stirred to form a precipitate, and filtered to obtain a supramolecular solid; S4: The supramolecular solid obtained in step S3 is subjected to gradient heating (heating rate 5℃ / min, target temperature 500℃), held at the temperature for 4 hours, and then cooled to room temperature to obtain a cobalt single-atom catalyst with controllable loading and coordination configuration.

[0025] The ligand for the cobalt single-atom catalyst prepared in Example 2 was ethylenediaminetetraacetic acid, and therefore it was denoted as Co1 / CN-ethylenediaminetetraacetic acid.

[0026] Example 3: A cobalt single-atom catalyst (Co1 / CN-citric acid) with controllable loading and coordination configuration was prepared by the following steps: S1: Dissolve citric acid in deionized water to prepare a citric acid solution with a molar concentration of 10.7 mmol / L, then add cobalt acetate tetrahydrate and stir at room temperature (25°C) until completely dissolved to obtain the first solution; the molar ratio of oxalic acid to cobalt acetate tetrahydrate is 3:1; S2: Dissolve cyanuric acid in deionized water at 85°C to prepare a cyanuric acid solution with a molar concentration of 37.5 mmol / L; mix the first solution with the cyanuric acid solution and stir to obtain a second solution; S3: Melamine is dissolved in deionized water at 85°C to prepare a melamine solution with a molar concentration of 37.5 mmol / L; the second solution is poured into the melamine solution, stirred to form a precipitate, and filtered to obtain a supramolecular solid; S4: The supramolecular solid obtained in step S3 is subjected to gradient heating (heating rate 5℃ / min, target temperature 500℃), held at the temperature for 4 hours, and then cooled to room temperature to obtain a cobalt single-atom catalyst with controllable loading and coordination configuration.

[0027] In Example 3, the ligand for the cobalt single-atom catalyst was citric acid, and therefore it was denoted as Co1 / CN-citric acid.

[0028] Comparative example: A graphitic carbon nitride (CN) is prepared by the following steps: S1: Dissolve cyanuric acid in deionized water at 85°C to prepare a cyanuric acid solution with a molar concentration of 37.5 mmol / L; mix and stir the a solution with the cyanuric acid solution to obtain solution a; S2: Melamine is dissolved in deionized water at 85°C to prepare a melamine solution with a molar concentration of 37.5 mmol / L; the a solution is poured into the melamine solution, stirred to form a precipitate, and filtered to obtain a supramolecular solid; S3: The supramolecular solid obtained in step S2 is subjected to gradient heating (heating rate 5℃ / min, target temperature 500℃), held at the temperature for 4 hours, and then cooled to room temperature to obtain graphitic carbon nitride (CN).

[0029] The catalyst prepared in the comparative example was graphitic carbon nitride, and therefore denoted as CN.

[0030] X-ray diffraction was used to analyze the structure of CN and the cobalt single-atom catalysts prepared in Examples 1-3 (denoted as Co1 / CN-oxalic acid, Co1 / CN-ethylenediaminetetraacetic acid, and Co1 / CN-citric acid, respectively). Figure 1The results showed that diffraction peaks appeared near 12.83° and 27.80° for all catalyst samples, which were attributed to the (100) and (002) crystal plane diffraction of graphitic carbon nitride, indicating that a partially graphitized structure was formed in the material. No characteristic diffraction peaks of metallic cobalt or cobalt oxide were detected in any of the samples, indicating that cobalt atoms did not agglomerate or crystallize during pyrolysis, and it is speculated that they were loaded in a highly dispersed or even single-atom state on graphitic carbon nitride. Further analysis of crystal plane shifts revealed that the characteristic peaks of Co1 / CN-citric acid remained consistent with those of CN. However, the (100) plane diffraction of Co1 / CN-ethylenediaminetetraacetic acid showed a red shift, while the (002) plane diffraction showed a blue shift, indicating that ethylenediaminetetraacetic acid formed unsaturated coordination of nitrogen and carbon at the Co sites. Co1 / CN-oxalic acid not only showed blue shifts in the (100) and (002) plane diffractions but also exhibited more pronounced broad peaks, suggesting that the introduction of cobalt ions promoted the reconstruction of the carbon framework structure, enhanced the disorder of carbon, and may have formed some defect structures, providing favorable electronic active centers for subsequent reactions. XRD analysis showed that Co1 / CN-oxalic acid, Co1 / CN-ethylenediaminetetraacetic acid, and Co1 / CN-citric acid did not form cobalt or oxide crystals during pyrolysis; cobalt atoms were highly dispersed in the carbon-based framework, providing structural assurance for constructing highly efficient cobalt single-atom catalysts.

[0031] Fourier transform infrared spectroscopy was used to test Co1 / CN-oxalic acid, Co1 / CN-ethylenediaminetetraacetic acid, and Co1 / CN-citric acid. Figure 2 (1400–1700 cm) -1 Within this range, absorption peaks due to the C=O stretching vibration of the carboxylic acid group (-COOH) can be clearly observed, located at approximately 1710 cm⁻¹. -1 1650 cm -1 and 1620 cm -1 In Co1 / CN-oxalic acid and Co1 / CN-ethylenediaminetetraacetic acid, the peak intensity decreased significantly and showed a slight shift, indicating that the carboxyl group in the ligand successfully participated in the Co... 2+ Coordination with these coordinates forms stable Co–O or Co–N coordination bonds. Furthermore, at 2000–2200 cm⁻¹... -1 In the wavenumber region, the addition of dual characteristic absorption peaks in Co1 / CN-oxalic acid indicates that a certain cyano defect (-C≡N-) has appeared on the CN support.

[0032] X-ray photoelectron spectroscopy test results are as follows: Figure 3 As shown. C 1s spectrum ( Figure 3a) shows that all three catalysts exhibit three typical carbon-based chemical environments: 284.6 eV corresponds to C–C / C=C bonds; 285.9 eV corresponds to C–N bonds, indicating nitrogen doping in the catalysts; and 288.4 eV belongs to the N–C=N structure. Among them, the N–C=N peak area of ​​the Co1 / CN-oxalic acid sample is relatively large, indicating its complete carbon-nitrogen framework structure; while the C–N peaks are more prominent in the Co1 / CN-ethylenediaminetetraacetic acid and Co1 / CN-citric acid samples, suggesting that they may have formed more Co–N coordination bonds, providing active centers for the catalytic reaction. (N 1s spectrum) Figure 3 b) The fitting results show that the main forms of different types of nitrogen are: 398.5 eV: C=N–C (pyridine N); 399.4 eV: N–(C)3 (triazine N); 400.4 eV: –NH2 (amino N). Among these, C=N–C represents the formation of Co–N. x The active site, a crucial site, significantly contributed in all three catalysts, indicating that nitrogen atoms play a key role in Co single-atom anchoring. The Co1 / CN-ethylenediaminetetraacetic acid sample showed a higher content of amino-type N, possibly related to the residual –NH group in the EDTA molecule. (Co 2p spectrum) Figure 3 c) The chemical valence state and coordination environment of cobalt were further confirmed: 780.5 eV (Co 2p 3 / 2 ) and 796.0 eV (Co 2p 1 / 2 ) for Co 2+ Characteristic peaks; no metallic Co was observed. 0 The characteristic peak (778.1 eV) indicates that no metal clusters or nanoparticles formed in the catalyst. Furthermore, the Co1 / CN-oxalic acid sample exhibits a slightly higher relative intensity of its main peak, indicating a greater number of exposed Co sites on its surface; the Co1 / CN-citric acid sample shows a weaker Co peak, indicating a higher degree of cobalt atom dispersion. XPS analysis results show that all three catalysts successfully constructed high-valence Co single-atom structures with Co–N or Co–O as coordination environments, and formed good nitrogen doping and carbon framework support on the material surface, ensuring stable and efficient active sites in the catalytic reaction.

[0033] X-ray absorption extended edge structure pattern as follows: Figure 4 As shown, the Co foil sample exhibits a strong Co–Co pairing signal at approximately 2.2 Å; the CoO sample shows Co–O and Co–Co coordination peaks near approximately 1.9–2.0 Å and 2.8 Å, respectively. In contrast, none of the three cobalt single-atom catalyst samples showed a significant Co–Co coordination peak near 2.2 Å, indicating that cobalt atoms did not form clusters, consistent with single-atom dispersion characteristics. Their coordination structures are Co–N4O1, Co–N3C1, and Co–N4, respectively.

[0034] To evaluate the degradation performance of the cobalt single-atom catalysts prepared in Examples 1-3 on chlorophenol pollutants, degradation experiments were conducted under the following conditions: 20 mL of deionized water was placed in a beaker, and 10 mg of catalyst was added. The mixture was then sonicated to ensure thorough dispersion. Subsequently, p-chlorophenol and potassium persulfate (PMS) were added to bring the initial concentrations to 10 mg / L and 50 mg / L, respectively. The reaction was carried out at a constant speed using a magnetic stirrer throughout, without adjusting the initial pH. 2.0 mL of the reaction solution was collected at set time points, and the supernatant was used to determine the p-chlorophenol concentration. Figure 5 As shown, the cobalt single-atom catalysts prepared in Examples 1-3 all exhibited certain degradation effects. Among them, Co1 / CN-oxalic acid showed the highest degradation rate, reaching 100%. To eliminate the dual influence of loading and coordination configuration on catalytic performance, the cobalt loading of the three catalysts was determined by inductively coupled plasma mass spectrometry (ICP-MS) (Table 1) and normalized. The results showed that the degradation rate of Co1 / CN-oxalic acid reached 0.017 seconds. -1 The values ​​of Co1 / CN-ethylenediaminetetraacetic acid and Co1 / CN-citric acid were 2.23 times and 45.59 times, respectively, indicating that the Co–N4O1 coordination configuration and -C≡N- defects can significantly enhance the catalytic efficiency of Co sites.

[0035] Table 1: Cobalt loading of catalysts prepared in Examples 1-3 The reactive oxygen species generated during the cobalt single-atom catalytic activation of PMS prepared in Examples 1-3 were investigated using electron paramagnetic resonance (EPR), and the results are as follows: Figure 6 As shown. In the TEMP system, CN / PMS alone will not generate TEMP- 1 The characteristic triplet signal of O2 was observed; however, the triplet signal was significantly enhanced upon the addition of Co1 / CN-citric acid, Co1 / CN-ethylenediaminetetraacetic acid, and Co1 / CN-oxalic acid, respectively, indicating that all three could catalyze the production of PMS. 1 O2. Furthermore, Co1 / CN-ethylenediaminetetraacetic acid can also effectively generate Co. IV =O and O2 •- Co1 / CN-oxalic acid can also generate •OH and SO4. •- .

[0036] Four reactive oxygen species in the Co1 / CN-oxalate activated PMS system were quenched by using methanol, tert-butanol, p-benzoquinone, and sodium azide, respectively. Figure 7 ), and combined with pseudo-first-order kinetic analysis (fitting the sampling points to the time points before reaching reaction equilibrium), the contribution ratios of each reactive oxygen species to the degradation of p-chlorophenol were calculated, in descending order as follows: 1O2 (61.73%), •OH (21.55%), SO4 •- (10.81%), O2 •- (4.60%). Quenching experiment of Co1 / CN-ethylenediaminetetraacetic acid activated PMS system ( Figure 8 Further confirmation showed that only sodium azide exhibited a significant inhibitory effect, while having no significant effect on benzoquinone, consistent with the EPR results. Simultaneously, it was observed that sodium azide had an inhibitory effect on both •OH and SO4. •- The quenching effect was also not significant, indicating that both contributed little to the system. The contributions of each reactive oxygen species in this system, from largest to smallest, are as follows: 1 O2 (49.59%), SO4 •- 12.30%), O2 •- (11.65%), •OH (2.23%). For the quenching experiment of the Co1 / CN-citric acid activated PMS system ( Figure 9 Methanol exhibits the most significant quenching effect, while other quenchers also show some effect. Among reactive oxygen species, SO42- is the most prominent. •- It is mainly composed of •OH, with a small amount of O2. •- The contributions, in descending order, are: SO4 •- (39.86%), •OH (38.31%), O2 •- (17.14%) 1 O2 (4.69%).

[0037] Given that high-valent cobalt can oxidize PMSO to PMSO2 via oxygen atom transfer, PMSO was used instead of p-chlorophenol in the experiment to detect the formation of high-valent cobalt. Figure 10 The results showed that although PMS itself can oxidize PMSO to PMSO2, the rates of PMSO consumption and PMSO2 generation in the Co1 / CN-citric acid / PMS system were higher than those in the CN / PMS system, and the yield of PMSO2 was lower. This indicates the presence of high-valent cobalt in the Co1 / CN-citric acid / PMS system, while other reactive oxygen species oxidize PMSO to other products through mechanisms such as single-electron transfer. Further investigation into the generation of high-valent cobalt in the Co1 / CN-ethylenediaminetetraacetic acid / PMS and Co1 / CN-oxalic acid / PMS systems revealed that PMSO consumption in Co1 / CN-oxalic acid / PMS was slightly higher than in CN / PMS and Co1 / CN-ethylenediaminetetraacetic acid / PMS alone, while PMSO2 generation was similar. This suggests that the small amount of residual cobalt in the Co1 / CN-oxalic acid / PMS system generated a small amount of high-valent cobalt. The changes in chloride ion concentration during the reaction were monitored. Figure 11 It was found that not all degraded p-chlorophenol underwent dechlorination, and there was a gap between the actual chloride ion concentration in the solution and the theoretical maximum value, indicating that there are other degradation pathways besides direct dechlorination.

[0038] To assess the stability of Co1 / CN-oxalic acid by constructing a continuous flow catalytic membrane device. Figure 12 0.2 g of catalyst was filtered to form a film. After 24 cycles of testing, the removal rate of chlorophenol remained above 90%, indicating its good sustainable operation value. To investigate the influence of water chemical factors, the effects of initial solution pH, anions, and humic acid were examined. Figure 13 The results showed that the removal efficiency of chlorophenol was relatively ideal under acidic, neutral, and weakly alkaline conditions; however, under strongly alkaline conditions, PMS decomposed, and Co species may form precipitates, leading to a significant reduction in removal efficiency. No significant inhibitory effect was observed in experiments involving different ions.

[0039] To explore the removal efficiency of Co1 / CN-oxalic acid for other chlorophenolic pollutants, its biodegradability and total organic carbon removal rate for various chlorophenolic pollutants were studied. Figure 14 The results showed that Co1 / CN-oxalic acid achieved a mineralization rate of over 90% for 10 mg / L of 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol, 2,3,5-trichlorophenol, phenol, chlorobenzene, nitrochlorobenzene, and polychlorinated biphenyls. The bio-oxygen demand / chemical oxygen demand ratio after the reaction was consistently higher than 0.5. Figure 15 This indicates that the treated wastewater is beneficial for subsequent advanced biological treatment.

[0040] The above results confirm that the cobalt single-atom catalyst of the present invention, based on controllable loading and coordination configuration, has a highly efficient degradation effect on chlorophenol pollutants. Among them, the Co1 / CN-oxalic acid prepared in Example 1 has the best performance and has good application potential in the actual water treatment of chlorophenol pollutants.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 method for preparing a cobalt single-atom catalyst with controllable loading and coordination configuration, characterized in that, Includes the following steps: S1: Prepare an organic ligand solution by mixing the organic ligand, then add the cobalt salt and stir at room temperature until completely dissolved to obtain the first solution; S2: Prepare a cyanuric acid solution from cyanuric acid; mix and stir the first solution with the cyanuric acid solution to obtain a second solution; S3: Prepare a melamine solution by dissolving melamine in water; add the second solution to the melamine solution, stir to generate a precipitate, and filter to obtain a supramolecular solid; S4: The supramolecular solid obtained in step S3 is subjected to gradient heating, held at the temperature and cooled to room temperature to obtain a cobalt single-atom catalyst with controllable loading and coordination configuration. The organic ligands include oxalic acid, ethylenediaminetetraacetic acid, and citric acid; the molar ratio of the organic ligand to the cobalt salt is 1:1-5:1, the molar ratio of the cobalt salt to cyanuric acid is 1:1-1:7, and the molar ratio of melamine to cyanuric acid is 1:0.6-1:

1.

2. The method of claim 1, wherein, In step S1, the cobalt salt is specifically cobalt acetate tetrahydrate.

3. The method according to claim 1, characterized in that, The room temperature is specifically 15-35℃.

4. The method according to claim 1, characterized in that, In steps S2 and S3, the temperature of the cyanuric acid solution and the melamine solution is 75-95℃.

5. The method according to claim 1, characterized in that, In step S4, the heating rate of the gradient heating is 2-8℃ / minute, and the target temperature is 400-600℃.

6. The method according to claim 1, characterized in that, In step S4, the heat preservation time is 2-6 hours.

7. A cobalt single-atom catalyst prepared by the method according to any one of claims 1-6.

8. The application of a cobalt single-atom catalyst prepared by the method according to any one of claims 1-6 in the removal of chlorophenol pollutants from wastewater.

9. The application according to claim 8, characterized in that, The specific application involves adding the cobalt single-atom catalyst and persulfate together to a solution containing chlorophenol pollutants, and stirring the reaction at a water temperature of 20-25°C for 0-60 minutes to remove the chlorophenol pollutants from the solution.

10. The application according to claim 8, characterized in that, The mass ratio of the cobalt single-atom catalyst to chlorophenol pollutants is 30:1-70:1, and the mass ratio of persulfate to chlorophenol pollutants is 10:1-20:1.

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