A hydrophilic covalent organic framework catalyst for stabilizing and anchoring transition metal ions, its preparation method and application

Abstract

This invention provides a hydrophilic covalent organic framework catalyst for stable anchoring of transition metal ions, its preparation method, and its application. The method includes: preparing a hydrophilic covalent organic framework from an aldehyde monomer and an amino monomer via a Schiff base reaction, followed by a first ammonium ion replacement and a second transition metal ion replacement, and then applying the resulting catalyst to catalyze the degradation of organic pollutants in water using persulfate. The catalyst material obtained by this invention exhibits strong hydrophilicity, high catalytic activity, and strong structural stability. Even with low dosage and interference from coexisting anions, it can efficiently degrade various organic pollutants, demonstrating potential for practical engineering applications and belonging to the field of advanced oxidative degradation of organic pollutants in water.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation technology for degrading organic pollutants in water, specifically relating to a hydrophilic covalent organic framework catalyst that stably anchors transition metal ions, its preparation method, and its application. Background Technology

[0002] Industrial and agricultural wastewater contains large amounts of aromatic hydrocarbons, such as dyes, pharmaceutical intermediates, and pesticides. These substances are widely distributed, structurally complex, and highly toxic. Large quantities entering the aquatic environment will cause the death of aquatic plants and animals, adding to the difficulty of remediation. Domestic pollution includes ingestion of waste products and the use of personal care products. Commonly used personal care products, as well as raw materials, intermediates, and metabolites from antibiotic production processes, are also potential threats to human health. Currently, some countries have detected drug residues, especially antibiotics, in drinking water. Although the concentration is extremely low, they are difficult to completely remove from the environment and accumulate in groundwater and soil over many years, posing a significant threat to human health. The treatment of these pollutants is now urgently needed.

[0003] Advanced persulfate oxidation technology utilizes sulfate free radicals (SO4) ·- This is one of the novel advanced oxidation technologies, primarily based on [the following]. Generally, persulfates are very stable and require activation to break their O2O bonds, generating various reactive species (such as SO42-). ·- ·OH, O2 ·- Persulfate is activated by the oxidation and decomposition of organic pollutants in water. Traditional activation methods using heat, light, and electricity suffer from high energy consumption and low degradation efficiency. Therefore, homogeneous catalytic systems using transition metal ions are more efficient and widely applicable for activating persulfate. However, dispersed transition metal ions in water are toxic and difficult to recycle, severely limiting large-scale application. To address this, transition metal ions are typically loaded onto porous supports, such as porous carbon, zeolites, and metal oxides, to form composite catalysts. However, the interaction between transition metal ions and porous supports is weak, resulting in fewer fixed binding sites. This leads to uneven dispersion and agglomeration of metal ions, resulting in low utilization of active sites, decreased catalytic activity, and secondary pollution caused by metal ion leaching. Furthermore, the hydrophilicity of porous supports significantly affects the adsorption and catalytic degradation efficiency of organic pollutants, which also needs improvement. Therefore, a support capable of maximizing dispersion and stably anchoring transition metal ions is urgently needed to achieve efficient activation of persulfate, thereby improving water treatment efficiency and catalyst lifespan. Summary of the Invention

[0004] Based on this, the present invention provides a hydrophilic covalent organic framework catalyst for stably anchoring transition metal ions, its preparation method, and its application. The catalyst support designed in this invention can achieve stable anchoring of transition metal ions and efficient dispersion and utilization of active sites, while also possessing strong hydrophilicity. It exhibits highly efficient catalytic activity in activating persulfate degradation of organic pollutants at ultra-low dosages, and also has good resistance to anion interference.

[0005] The present invention provides a method for preparing a hydrophilic covalent organic framework catalyst that stably anchors transition metal ions, characterized by comprising the following steps:

[0006] Step (1): Dissolve aldehyde monomers and amino monomers in an organic solvent in a certain ratio, add acetic acid aqueous solution, place the mixed solution in a vacuum environment, and carry out Schiff base polycondensation reaction at 100-150℃ for 72-144h. Then wash and dry to obtain a covalent organic framework carrier with hydrophilic functional groups.

[0007] Step (2) involves mixing the covalent organic framework carrier with an ammonia solution and stirring or sonicating at 20–90°C for 2–30 hours to replace hydrogen ions in the hydrophilic functional groups with ammonium ions, followed by washing and drying.

[0008] Step (3) involves fully dissolving the transition metal salt in deionized water and adding a certain amount of weakly polar solvent to prepare a transition metal ion solution of a certain concentration.

[0009] In step (4), the product from step (2) is mixed with the solution from step (3) and refluxed at 20–90°C to replace the transition metal ions with ammonium ions, thereby obtaining a catalyst with stable anchoring and efficient dispersion of active sites.

[0010] Preferably, the aldehyde monomer in step (1) is one or more of the following: pyromellitic terephthalaldehyde, 1,3,5-trialdehyde-resorcinol, 1,3,5-tris(p-formylphenyl)benzene, 2,4,6-tris(4-aldehyde-phenyl)-1,3,5-triazine, tris(4-formylphenyl)amine, terephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, p-methoxydibenzoyl, and 2,5-dihydroxyterephthalaldehyde.

[0011] Preferably, the amino monomer in step (1) is one or more of 2,5-diaminobenzoic acid, 2,5-diamino-1,4-dihydroxybenzene, 2,5-diaminobenzenesulfonic acid, 4,4'-diamino-3,3'-biphenyldicarboxylic acid, 1,3,5-triaminobenzene, 1,3,5-tris(4-aminophenyl)benzene, and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine.

[0012] Preferably, the molar ratio of the aldehyde monomer and the amino monomer in step (1) is in the range of 0.5 to 1:1.

[0013] Preferably, the organic mixed solvent in step (1) is one or two of the following: mesitylene, 1,4-dioxane, n-butanol, and o-dichlorobenzene; when two mixed solvents are used, the volume ratio ranges from 0.3 to 5:1.

[0014] Preferably, the concentration range of the acetic acid aqueous solution in step (1) is 3 to 6 mol / L; and the volume ratio of the acetic acid aqueous solution to the organic solvent is 0.1 to 0.6:1.

[0015] Preferably, the concentration range of the ammonia solution in step (2) is 0.1 to 3.0 wt%; the ratio of the covalent organic framework carrier to the ammonia solution is 0.5 to 10:1 (mg:mL).

[0016] Preferably, the transition metal salt solution in step (3) is any one or more of cobalt chloride, nickel chloride, manganese chloride, ferric chloride, cobalt nitrate, manganese nitrate, nickel nitrate, ferric nitrate, cobalt acetate, nickel acetate, manganese acetate, and ferric acetate; the molar concentration of the transition metal ion solution is in the range of 0.2 to 3.0 mol / L.

[0017] Preferably, the weakly polar solvent in step (3) is at least one of ethanol, acetone, and methanol; the volume ratio of the weakly polar solvent to deionized water is in the range of 0.1 to 2:1.

[0018] Preferably, the ratio of the product in step (2) to the solution in step (3) is in the range of 4 to 20:1 (mg:mL).

[0019] This invention also provides a method for catalytically activating persulfate to degrade organic pollutants with low catalyst dosage, particularly for aquatic environments with anion interference. The specific process is as follows:

[0020] Step (1) involves dispersing the catalyst in a wastewater solution containing organic pollutants and adding a certain amount of anionic aqueous solution.

[0021] Step (2) involves adding persulfate to the solution obtained in step (1) and stirring the mixture at 30–60°C.

[0022] Step (3): At certain time intervals, take the solution after the reaction in step (2) and quench the free radicals with ethanol, and then use an ultraviolet spectrophotometer to test the degradation of pollutants.

[0023] Preferably, the organic pollutant in step (1) is at least one of tetracycline, methylene blue, rhodamine B, and bisphenol A, and the concentration range of the organic pollutant is 25 to 75 mg / L.

[0024] Preferably, the anionic aqueous solution in step (1) is at least one of sodium chloride solution, sodium bicarbonate solution, and sodium dihydrogen phosphate solution, and the anionic concentration is 5-20 mmol / L.

[0025] Preferably, the amount of catalyst used in step (1) is 0.3 to 1.0 mg / L.

[0026] Preferably, the amount of persulfate used in step (2) is 0.5 to 2.0 mg / L.

[0027] Preferably, the sampling time interval in step (3) is 5 to 10 minutes; the volume of the sampling solution is 0.5 to 2 mL; and the amount of ethanol used is 0.1 to 0.5 mL.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. By employing covalent organic frameworks with hydrophilic functional groups (-OH, -COOH, -SO2OH, -OCH3) and combining them with a two-step ion exchange method, the binding affinity and loading capacity of transition metal ions to the covalent organic framework support are enhanced. On the one hand, the hydrophilic functional groups act as anchoring sites, significantly improving the affinity between polar transition metal ions and the surface of the covalent organic framework; simultaneously, they reduce the AA packing density of the covalent organic framework, increasing its binding space with transition metal ions. On the other hand, the primary ion exchange of ammonium ions (replacing H+ in the hydrophilic functional groups)... + This increases the bond length between the metal ion and the O group in the hydrophilic functional group, reducing the binding energy of the transition metal ion's secondary substitution. Furthermore, the invention adds a weakly polar solvent to the transition metal ion solution, enhancing desolvation capability and further reducing the binding energy between the metal ion and the O group in the hydrophilic functional group. These advantages of the support structure and the loading method ultimately lead to a strong chemical bond between the transition metal ion and the covalent organic framework, and achieve efficient dispersion of the catalytic site.

[0030] 2. From a production perspective, the two-step ion exchange method of this invention is simple, mild, efficient, and non-corrosive.

[0031] 3. From a practical application perspective, the catalyst material of the present invention has highly efficient dispersion and stable anchoring catalytic sites, hydrophilic functional groups that are conducive to adsorbing organic pollutants in water, and high chemical stability. It can efficiently catalyze and activate persulfate with extremely low catalyst dosage, complete the rapid degradation of pollutants, and has a long cycle life with no risk of secondary leaching of metal ions. Attached Figure Description

[0032] Figure 1 This is a flowchart of the catalyst preparation method according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure and synthesis steps of a hydrophilic covalent organic framework loaded with metal ions according to an embodiment of the present invention;

[0034] Figure 3 Transmission electron microscope images of the materials obtained in steps (1), (2), (3), and (4) of Embodiment 2 of the present invention;

[0035] Figure 4 The X-ray diffraction patterns of the material obtained in steps (1), (2), and (3) of Example 3 of the present invention are shown.

[0036] Figure 5 The degradation efficiency of catalyst 1 prepared in Example 1 of this invention in anionized water environment is shown in the figure.

[0037] Figure 6 The diagram shows the efficiency of catalyst 1 prepared in Example 1 of this invention in multiple pollutant degradation processes.

[0038] Figure 7 This is a comparison chart showing the ability of the catalysts prepared in Example 3 and Comparative Example 1 of the present invention to adsorb pollutants. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Finally, it should be noted that the following embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

[0040] Example 1

[0041] 32.43 mg of trimesin and 45.645 mg of 2,5-diaminobenzoic acid (molar ratio = 1:1.5) were dispersed in 2.5 mL of a mixed solvent of n-butanol / o-dichlorobenzene (V / V = 0.5:1), and 0.5 mL of acetic acid aqueous solution (3 mol / L) was added. The mixture underwent a Schiff base condensation reaction at 120 °C under vacuum for 120 h. The mixture was then centrifuged, washed, and vacuum dried at 80 °C for 48 h to obtain a covalent organic framework with hydrophilic functional groups. 50 mg of the covalent organic framework was added to 30 mL of ammonia aqueous solution (0.5 wt%), stirred at 40 °C for 30 h, washed, and dried to obtain an ammonium ion-substituted covalent organic framework. Manganese nitrate was dissolved in a mixed solvent of 1 mL of deionized water and 1 mL of methanol to prepare a 2 mol / L manganese nitrate solution. The covalent organic framework obtained by ammonium ion substitution is mixed with the above manganese nitrate solution and refluxed at 50°C to substitute transition metal ions with ammonium ions, thus obtaining catalyst 1.

[0042] Catalyst 1 was applied to the catalytic degradation of organic pollutants using activated persulfate. The degradation process was as follows: 0.5 mg of catalyst 1 was dispersed in 1 L of wastewater solution containing 65 mg / L Rhodamine B and 20 mmol / L sodium dihydrogen phosphate. Then, 1 mg of persulfate was added and the mixture was stirred at 50 °C. Every 5 min, 0.5 mL of the reaction solution was collected and quenched with 0.2 mL of ethanol. The pollutant degradation was tested using a UV spectrophotometer. The results showed that catalyst 1 in this embodiment had excellent degradation performance: as shown in Table 1, even in the presence of anions (dihydrogen phosphate), the degradation efficiency was as high as 78% within 5 min.

[0043] Table 1. Performance comparison of catalysts 1, 2, and 3 synthesized in the examples of this invention with catalysts 4, 5, and 6 synthesized in the comparative examples.

[0044]

[0045] Figure 2 This is a schematic diagram of the catalyst 1 structure in an example of the present invention. The COF material is mainly synthesized via a Schiff base reaction in step (1), and step (2) involves removing the H group from the hydrophilic group. + Replaced with NH4 + In step (3), metal ions are stably loaded onto the material.

[0046] Figure 5 The catalyst 1 used in this invention catalyzes the degradation of organic pollutants by persulfate in an anionic aqueous solution environment. Even with interference from multiple anions, the catalyst still exhibits good performance, with catalytic efficiencies exceeding 78%.

[0047] Figure 6This is a graph showing the efficiency of catalyst 1 in this invention in degrading pollutants after multiple uses. After three uses, the degradation efficiency is still above 70%.

[0048] Example 2

[0049] 27.08 mg of 1,3,5-trialdehyde phloroglucinol and 36.08 mg of 2,5-diaminobenzenesulfonic acid (molar ratio = 1:1.5) were dispersed in 3 mL of a mixture of mesitylene / 1,4-dioxane (V / V = 1:1), and 1 mL of acetic acid aqueous solution (6 mol / L) was added. The mixture was subjected to Schiff base polycondensation at 140 °C under vacuum for 72 h. After centrifugation and washing, the mixture was vacuum dried at 80 °C for 48 h to obtain a covalent organic framework with hydrophilic functional groups. 50 mg of the material was added to 10 mL of ammonia aqueous solution (1 wt%), stirred at 40 °C for 30 h, washed, and dried to obtain an ammonium ion-substituted covalent organic framework. Cobalt acetate was dissolved in a mixture of 5 mL of deionized water and 10 mL of acetone to prepare a 1 mol / L cobalt acetate solution. The covalent organic framework obtained by ammonium ion substitution is mixed with cobalt acetate solution and refluxed at 90°C to substitute transition metal ions with ammonium ions, thus obtaining catalyst 2.

[0050] Catalyst 2 was applied to the catalytic activation of persulfate for the degradation of organic pollutants. The degradation process was as follows: 0.8 mg of catalyst 2 was dispersed in 1 L of wastewater solution containing 50 mg / L methylene blue and 10 mmol / L sodium chloride, followed by the addition of 0.8 mg of persulfate and stirring at 50 °C. Every 5 min, 1 mL of the reaction solution was collected and quenched with 0.5 mL of ethanol. The degradation of pollutants was tested using a UV spectrophotometer. The test results showed that catalyst 2 in this embodiment had excellent degradation performance: as shown in Table 1, even in the presence of anions (chloride ions), the degradation efficiency was as high as 80% within 5 min.

[0051] Figure 3 The TEM images of the material obtained in steps (1), (2), and (3) of Embodiment 2 of the present invention are obtained by... Figure 3 As can be seen from (a-c), the material structure did not change significantly after the two ion replacements; both remained interwoven strip structures. Figure 3 (d) No cobalt clusters were observed under high magnification, therefore this loading method can achieve uniform dispersion of cobalt ions and maximize the utilization of cobalt ion active sites.

[0052] Example 3

[0053] 78.69 mg of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 42.04 mg of 2,5-diamino-1,4-dihydroxybenzene (molar ratio = 1:1.5) were dispersed in 6 mL of a mixed solvent of o-dichlorobenzene / 1,4-dioxane (V / V = 2:1), and 1 mL of aqueous acetic acid (6 mol / L) was added. The mixture was subjected to Schiff base polycondensation at 150 °C under vacuum for 100 h. The mixture was then centrifuged, washed, and vacuum dried at 80 °C for 48 h to obtain a covalent organic framework with hydrophilic functional groups. 50 mg of the material was added to 10 mL of aqueous ammonia solution (2.5 wt%), stirred at 80 °C for 30 h, washed, and dried to obtain an ammonium ion-substituted covalent organic framework. Ferric chloride was dissolved in 10 mL of methanol and 5 mL of water to prepare a 1.5 mol / L ferric chloride solution. The covalent organic framework obtained by ammonium ion substitution is mixed with ferric chloride solution and refluxed at 50°C to substitute transition metal ions with ammonium ions, thus obtaining catalyst 3.

[0054] Catalyst 3 was applied to the catalytic activation of persulfate for the degradation of organic pollutants. The degradation process was as follows: 0.6 mg of catalyst 3 was dispersed in 1 L of wastewater solution containing 55 mg / L bisphenol A and 10 mmol / L sodium bicarbonate, followed by the addition of 1.5 mg of persulfate and stirring at 55 °C. Every 5 min, 1.5 mL of the reaction solution was taken and quenched with 0.5 mL of ethanol. The degradation of pollutants was tested using a UV spectrophotometer. The test results showed that catalyst 3 in this embodiment had excellent degradation effect: as shown in Table 1, even in the presence of anions (bicarbonate), the degradation efficiency was as high as 82% within 5 min.

[0055] Figure 4 The XRD patterns of the material obtained in steps (1), (2), and (3) of Example 3 of this invention are shown. The material after both ion replacements showed peaks at 4.7° and 27.2°, proving that it still retains the covalent organic framework structure.

[0056] Comparative Example 1

[0057] For comparison, the catalyst was prepared as follows: 32.43 mg of trimesin and 32.40 mg of p-phenylenediamine (molar ratio = 1:1.5) were dispersed in 2.5 mL of a mixed solvent of n-butanol / o-dichlorobenzene (V / V = 0.5:1), and 0.5 mL of an aqueous acetic acid solution (3 mol / L) was added. The mixture was subjected to a Schiff base condensation reaction at 120 °C under vacuum for 120 h. The mixture was then centrifuged, washed, and vacuum dried at 80 °C for 48 h to obtain a covalent organic framework. 50 mg of the covalent organic framework was added to 30 mL of an aqueous ammonia solution (0.5 wt%), stirred at 40 °C for 30 h, washed, and dried to obtain an ammonium ion-substituted covalent organic framework. A 2 mol / L manganese nitrate solution was prepared by dissolving manganese nitrate in a mixed solvent of 1 mL deionized water and 1 mL methanol. The covalent organic framework obtained by ammonium ion substitution is mixed with the above-mentioned manganese nitrate solution and refluxed at 50°C to allow for the substitution of transition metal ions with ammonium ions, thus yielding catalyst 4. The preparation method of catalyst 4 is the same as in Example 1, except that the selected amino monomer has no hydrophilic functional groups.

[0058] The degradation process is the same as in Example 1, and the degradation effect is as follows: Figure 7 The adsorption capacity of catalyst 4 is lower than that of catalyst 1 because catalyst 4 lacks hydrophilic functional groups, limiting its contact range with pollutants in water. As shown in Table 1, the degradation efficiency of organic matter by catalyst 4 is lower than that of catalyst 1 synthesized in Example 1 because the H+ in the hydrophilic functional groups of catalyst 4 is lower. + Without undergoing a primary conversion of ammonium ions, the binding energy between catalyst 4 and the transition metal was not reduced, resulting in a low metal content on catalyst 4. Consequently, the utilization rate of active sites in the subsequent catalytic activation of persulfate was low, leading to low organic matter degradation efficiency.

[0059] Comparative Example 2

[0060] 27.08 mg of 1,3,5-trialdehyde phloroglucinol and 36.08 mg of 2,5-diaminobenzenesulfonic acid (molar ratio = 1:1.5) were dispersed in 3 mL of a mixed solvent of mesitylene / 1,4-dioxane (V / V = 1:1), and 1 mL of an aqueous acetic acid solution (6 mol / L) was added. The mixture underwent Schiff base polycondensation at 140 °C under vacuum for 72 h. After centrifugation and washing, the mixture was vacuum dried at 80 °C for 48 h to obtain a covalent organic framework with hydrophilic functional groups. Cobalt acetate was dissolved in a mixed solvent of 5 mL of deionized water and 10 mL of acetone to prepare a 1 mol / L cobalt acetate solution. The covalent organic framework obtained by ammonium ion substitution was mixed with the cobalt acetate solution and refluxed at 90 °C to allow for the substitution of transition metal ions with ammonium ions, thus obtaining catalyst 2. The preparation method of catalyst 5 is the same as that of Example 2, except that catalyst 5 does not undergo an ammonium ion replacement before loading metal ions, but instead uses a direct impregnation method to load metal ions.

[0061] The degradation process is the same as in Example 2, and the degradation effect is as follows: As shown in Table 1, after the catalyst 5 without ammonium ion replacement catalyzes the activation of persulfate, the amount of cobalt ions leached is greater than that of the catalyst 2 with ammonium ion replacement, indicating that the covalent organic framework without ammonium ion replacement cannot firmly and stably support metal ions.

[0062] Comparative Example 3

[0063] 78.69 mg of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 42.04 mg of 2,5-diamino-1,4-dihydroxybenzene (molar ratio = 1:1.5) were dispersed in 6 mL of a mixed solvent of o-dichlorobenzene / 1,4-dioxane (V / V = 2:1), and 1 mL of acetic acid aqueous solution (6 mol / L) was added. The mixture was subjected to Schiff base polycondensation at 150 °C under vacuum for 100 h. The mixture was then centrifuged, washed, and vacuum dried at 80 °C for 48 h to obtain a covalent organic framework with hydrophilic functional groups. 50 mg of the material was added to 10 mL of ammonia aqueous solution (2.5 wt%), stirred at 80 °C for 30 h, washed, and dried to obtain an ammonium ion-substituted covalent organic framework. Ferric chloride was dissolved in 5 mL of water to prepare a 1.5 mol / L ferric chloride solution. The covalent organic framework obtained by ammonium ion substitution is mixed with a ferric chloride solution and refluxed at 50°C to allow for the substitution of transition metal ions with ammonium ions, thus yielding catalyst 3. Catalyst 6 is prepared using the same method as in Example 3, except that a weakly polar solvent is not added to the transition metal ion solution prepared when loading the metal into catalyst 6.

[0064] The degradation process is the same as in Example 3, and the degradation effect is as follows: As shown in Table 1, the degradation efficiency of catalyst 3 is 88%, while the degradation efficiency of the synthesized catalyst 6 is 75%. The metal loading is lower than that of catalyst 3 synthesized in Example 3. The reason is that a metal ion solution prepared with a weakly polar solvent was not added, and the binding energy between the metal ions and O in the hydrophilic functional group was not reduced.

[0065] The embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above embodiments, and any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a hydrophilic covalent organic framework catalyst that stably anchors transition metal ions, characterized in that, Includes the following steps: Step (1): Dissolve aldehyde monomers and amino monomers in an organic solvent in a certain ratio, add an aqueous acetic acid solution, place the mixed solution under vacuum, and carry out a Schiff base condensation reaction at 100~150℃ for 72~144h. Then wash and dry to obtain a covalent organic framework support with hydrophilic functional groups; the hydrophilic functional groups include at least one of -OH, -COOH, and -SO2OH. Step (2): The covalent organic framework carrier is mixed with an ammonia solution and stirred or sonicated at 20-90°C for 2-30 hours to replace the hydrogen ions of the hydrophilic functional groups with ammonium ions. Then the mixture is washed and dried. Step (3): Dissolve the transition metal salt fully in deionized water and add a certain amount of weakly polar solvent to prepare a transition metal ion solution of a certain concentration; the weakly polar solvent is at least one of ethanol, acetone and methanol. In step (4), the product from step (2) is mixed with the solution from step (3) and refluxed at 20~90℃ to replace the transition metal ions with ammonium ions, thereby obtaining a catalyst with stable anchoring and efficient dispersion of active sites.

2. The preparation method according to claim 1, characterized in that: In step (1), the aldehyde monomer is one or more of the following: pyromellitic pyrophoryl methyl methacrylate (PMM), 1,3,5-trialdehyde-1,3,5-phloroglucinol (PMM), 1,3,5-tris(4-aldehyde-phenyl)-1,3,5-triazine (PMM), tris(4-formylphenyl)amine, terephthalaldehyde (PMM), 2,5-dimethoxyterephthalaldehyde (PMM), and 2,5-dihydroxyterephthalaldehyde (PMM); the amino monomer is 2,5-diaminobenzoic acid (DBA), 2,5-diamino-1,4-dihydroxybenzene (DBA), and 2,5-diaminobenzoic acid (DBA). The organic solvent is one or more of benzenesulfonic acid and 4,4'-diamino-3,3'-biphenyl dicarboxylic acid; the molar ratio of the aldehyde monomer to the amino monomer is in the range of 0.5 to 1:1; the organic solvent is one or a mixture of two of mesitylene, 1,4-dioxane, n-butanol, and o-dichlorobenzene; when two mixed solvents are used, the volume ratio is in the range of 0.3 to 5:1; the concentration of the aqueous acetic acid solution is in the range of 3 to 6 mol / L; the volume ratio of the acetic acid solution to the organic solvent is in the range of 0.1 to 0.6:

1.

3. The preparation method according to claim 1, characterized in that: In step (2), the concentration of the ammonia solution ranges from 0.1 to 3.0 wt%; the ratio of the covalent organic framework carrier to the ammonia solution ranges from 0.5 to 10 mg: 1 mL.

4. The preparation method according to claim 1, characterized in that: In step (3), the transition metal salt is any one or more of cobalt chloride, nickel chloride, manganese chloride, ferric chloride, cobalt nitrate, manganese nitrate, nickel nitrate, ferric nitrate, cobalt acetate, nickel acetate, manganese acetate, and ferric acetate; the molar concentration of the transition metal ion solution is in the range of 0.2~3.0 mol / L; and the volume ratio of the weakly polar solvent to deionized water is in the range of 0.1~2:

1.

5. The preparation method according to claim 1, characterized in that: In step (4), the ratio of the product from step (2) to the solution from step (3) is 4~20 mg: 1 mL.

6. A hydrophilic covalent organic framework catalyst for stably anchoring transition metal ions, characterized in that... The transition metal ion is prepared by the preparation method described in any one of claims 1 to 5; the molar ratio of the transition metal ion to the hydrophilic functional group is in the range of 0.1 to 1.5:

1.

7. The application of the hydrophilic covalent organic framework catalyst for stabilizing and anchoring transition metal ions according to claim 6 in the catalytic activation of persulfate degradation of organic pollutants in water, characterized in that, It can efficiently degrade a variety of organic pollutants even with low catalyst dosage and interference from coexisting anions in the water.

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