A multi-metal active site covalent organic framework material, a preparation method thereof and application of the material in activated PMS degradation of pollutants

Abstract

The application discloses a kind of multi-metal active site covalent organic framework materials and its preparation method and the application of activated PMS degradation pollutant, the multi-metal active site covalent organic framework material includes metal porphyrin and bipyridine group, while loading metal in porphyrin, utilize two nitrogen atoms of bipyridine and connect metal atom, constitute multi-metal active site;Increase metal active site, adjust the distance between metal, so that the framework material shows excellent catalytic activity.Covalent organic framework material is prepared by solvothermal reaction, continue to react with metal precursor can be loaded on metal, preparation method is simple, without complex reaction process and harsh reaction conditions, can be mass-produced.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalytic materials technology, specifically relating to a multi-metal active site covalent organic framework material, its preparation method, and its application in activating PMS to degrade pollutants. Background Technology

[0002] With industrial development, the amount of recalcitrant organic pollutants in water is increasing, threatening the ecological environment and human health. Advanced oxidation technologies that generate highly reactive oxidizing species have attracted attention for removing recalcitrant organic pollutants. In the field of environmental catalysis, advanced oxidation technologies based on persulfate (PMS) activation can efficiently degrade recalcitrant organic pollutants in water; however, PMS often requires activation to achieve its oxidative degradation effect.

[0003] Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have become ideal catalyst supports for activating phosphorus-containing microstructures (PMS) due to their regular pore structures, high specific surface areas, and tunable chemical compositions. In particular, COFs incorporating metals can generate highly oxidizing active species (such as sulfate radicals and hydroxyl radicals) through the interaction between the metal active sites and PMS, thereby achieving rapid degradation of pollutants.

[0004] However, COF is formed by the covalent connection of organic ligands according to certain rules to form a fixed structure, and its fixed structure depends on the structure of the ligands. When a COF with a fixed structure is used as a carrier to load metal, the fixed spatial arrangement of the ligands in the carrier makes it difficult to load metal or the amount of metal loaded is limited. As a result, the interaction between the metal active site and PMS is weak, making it difficult to efficiently activate PMS to achieve rapid degradation of pollutants.

[0005] Therefore, developing a metal COF material with high metal loading and simple loading method is of great significance for improving the activation efficiency of PMS and expanding its application in pollutant degradation. Summary of the Invention

[0006] For the reasons mentioned above, the first objective of this invention is to provide a covalent organic framework material with multiple metal active sites, comprising a metalloporphyrin and a bipyridine group, wherein the two nitrogen atoms of the bipyridine are coordinated to connect to the metal atom, forming a multiple metal active site with the metal of the metalloporphyrin, thus successfully achieving metal loading in the COF structure; thereby enabling the framework material to exhibit excellent catalytic activity.

[0007] The second objective of this invention is to provide a method for preparing a multi-metal active site covalent organic framework material. The COF material provides metal coordination sites through ligand groups, and the metal loading can be achieved through the coordination reaction between COF and metal precursors. The preparation method is simple, does not require complex reaction processes and harsh reaction conditions, and can be prepared on a large scale.

[0008] The fourth objective of this invention is to provide an application of a multi-metallic active site covalent organic framework material in the degradation of pollutants by room-temperature activated PMS. The enzyme-mimicking properties of the metalloporphyrin itself enhance the catalytic activity of COF, while the multi-metallic sites further enable highly efficient catalysis.

[0009] The first objective of this invention can be achieved by adopting the following technical solution:

[0010] A multi-metallic active site covalent organic framework material having the molecular structure shown in Formula I:

[0011]

[0012] Where M is any one of Fe, Co, Ni, Mn, Pt, Au, and Pd.

[0013] Furthermore, the BET specific surface area of ​​the multi-metal active site covalent organic framework material is 500-800 m². 2 g -1 The metal loading is 1-1.5 wt%.

[0014] The second objective of this invention can be achieved by adopting the following technical solution:

[0015] A method for preparing multi-metal active site covalent organic framework materials includes the following steps:

[0016] The COF structure shown in Formula II reacts with the M metal precursor in a solvent to obtain the multi-metal active site covalent organic framework material.

[0017]

[0018] Furthermore, the solvent is a mixture of alcohol and water, with a volume ratio of alcohol to water of (3-10):1.

[0019] Furthermore, the alcohol is methanol or ethanol.

[0020] Furthermore, the M metal precursor is an acetate, chloride, sulfate, nitrate, or hydrate of the M metal.

[0021] Furthermore, the mass ratio of COF to the M metal precursor in the structure shown in Formula II is (1-5):1.

[0022] Furthermore, the reaction conditions are 20-45℃ for 12-72 hours.

[0023] Furthermore, the reaction includes a post-processing step: solid-liquid separation, in which the solid product is washed with water and ethanol and then vacuum dried to obtain the multi-metal active site covalent organic framework material.

[0024] Furthermore, the COF structure shown in Formula II is prepared by a solvothermal reaction of 5,10,15,20-tetra(4-aminophenyl)porphyrin and 2,2'-bipyridine-5,5'-dicarboxaldehyde under vacuum.

[0025] Furthermore, the solvent is a mixture of 1,2-dichlorobenzene and n-butanol; the volume ratio of 1,2-dichlorobenzene to n-butanol is (2-10):1.

[0026] Furthermore, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to 2,2'-bipyridine-5,5'-dicarboxaldehyde is 1:(2-2.2).

[0027] Furthermore, the molar-volume ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to the solvent is 1 mmol:(50-100) mL.

[0028] Furthermore, the reaction is carried out in the presence of acetic acid, the concentration of which is 1-6 M; the volume ratio of acetic acid to solvent is 1:(5-20).

[0029] Furthermore, the reaction conditions are: 100-140℃ for 48-144 hours.

[0030] Furthermore, it also includes post-processing steps: after the end of the solubility heat reaction, cooling, solid-liquid separation, and washing the solid product sequentially with N,N-dimethylformamide, tetrahydrofuran, dichloromethane and ethanol; purification by Soxhlet extraction in tetrahydrofuran.

[0031] The third objective of this invention can be achieved by adopting the following technical solution:

[0032] Application of polymetallic active site covalent organic framework materials in the degradation of pollutants by activated PMS.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention provides a covalent organic framework material with multiple metal active sites, which utilizes the ability of ligands to bind metal atoms to load metal atoms on the basis of COF material structure; the high specific surface area and abundant porosity of the framework material are combined with multiple metal active sites to enhance catalytic oxidation ability.

[0035] 2. The present invention discloses a method for preparing a multi-metal active site covalent organic framework material. The metal coordination sites are provided by the ligand groups of the COF material, and metal loading can be achieved through the coordination reaction between COF and the metal precursor. The preparation method is simple, requiring no complex reaction process or harsh reaction conditions, and can be prepared on a large scale. Furthermore, COF materials can be prepared through a solvothermal reaction, enabling large-scale production.

[0036] 3. The multi-metal active site covalent organic framework material of this application, metalloporphyrin, possesses enzyme-mimicking properties that enhance the catalytic activity of COF, while the multi-metal sites further improve the catalytic efficiency. Therefore, the multi-metal active site covalent organic framework material can effectively degrade apap by activating PMS at room temperature. obs The value reached 0.039 min⁻¹. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the reaction for preparing Fe-COF-367 in Example 4;

[0038] Figure 2 X-ray powder diffraction patterns of COF-367 and Fe-COF-367;

[0039] Figure 3 Infrared spectra of COF-367 and Fe-COF-367;

[0040] Figure 4 The graph shows the BET test results for COF-367 and Fe-COF-367.

[0041] Figure 5 The activity diagram of COF-367, Fe-COF-367 and Fe-COF-biphenyl in degrading pollutants apap;

[0042] Figure 6 The kJ of COF-367, Fe-COF-367 and Fe-COF-biphenyl degradation pollutant apap obs value;

[0043] Figure 7 The graph shows the adsorption test results of COF-367 and Fe-COF-367. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] The coordination environment of metals is a core factor influencing the catalytic performance of metal-COF materials, and the coordination distance between metal atoms is one of the key parameters. Studies have shown that differences in metal coordination distance directly affect electron transfer efficiency, the activation pathway of PMS, and the adsorption and oxidation capacity for target pollutants. For example, when the metal coordination distance is within a specific range, such as with iron, it can promote Fe²⁺… + With Fe³ + The cyclic transformation accelerates the decomposition of PMS, thereby increasing the degradation rate of pollutants; if the distance is too far, it will hinder electron transfer and weaken catalytic activity.

[0046] However, significant challenges remain in the control of metal coordination distances in metal-COF materials using existing technologies. On the one hand, traditional preparation methods often rely on single ligands or supports, making it difficult to achieve precise adjustment of metal coordination distances through simple means. The limited coordination environment of metals restricts the broad applicability of the materials. On the other hand, some control methods require complex template agents or harsh reaction conditions (such as high-temperature calcination or high-pressure treatment), which not only increases preparation costs but may also damage the framework structure of COF materials, leading to a decrease in specific surface area or loss of active sites.

[0047] Therefore, this application provides a multi-metal active site covalent organic framework material having the molecular structure shown in Formula I:

[0048]

[0049] Where M is any one of Fe, Co, Ni, Mn, Pt, Au, and Pd.

[0050] Multimetallic active site covalent organic framework materials contain porphyrin groups, which can bind to metals to form metalloporphyrins. However, the macrocyclic structure of porphyrins and the linking groups between porphyrins result in excessively large distances between metal atoms, affecting electron transfer efficiency. This application uses 2,2'-bipyridine as the linking group. The two nitrogen atoms on 2,2'-bipyridine can coordinate to and connect to metal atoms. This increases the number of metal active sites and halves the distance between metal atoms, thus enhancing catalytic activity.

[0051] As one implementation method, the BET specific surface area of ​​the multi-metal active site covalent organic framework material is 500-800 m². 2 g -1 The metal loading is 1-1.5 wt%. COF itself has abundant porosity, which is conducive to metal ions entering the framework for coordination; it also provides a large specific surface area, which is beneficial for contact with the substrate and improves catalytic performance. The metal loading provides sufficient reactive sites without clogging the porosity.

[0052] This application also provides a method for preparing a multi-metal active site covalent organic framework material, comprising the following steps:

[0053] The COF structure shown in Formula II reacts with the M metal precursor in a solvent to obtain the multi-metal active site covalent organic framework material; as shown in Formula II. Figure 1 As shown.

[0054]

[0055] The four nitrogen atoms of the porphyrin ring in the COF structure shown in Formula II readily coordinate with metals to form metalporphyrins; the two nitrogen atoms on the 2,2'-bipyridine also provide coordination sites. This allows the COF structure shown in Formula II to react with metal precursors, simultaneously coordinating metal atoms onto both the porphyrin and bipyridine groups, forming a multi-metal active site covalent organic framework material. While maintaining the properties of the COF, the catalytic performance is enhanced by loading metal atoms.

[0056] In one embodiment, the solvent is a mixture of alcohol and water, with a volume ratio of alcohol to water of (3-10):1. Water and ethanol are miscible, and the COF structure shown in Formula II is soluble in ethanol. Since the metal precursor is water-soluble, the COF can fully contact and react with the metal ions in the metal precursor. Preferably, the alcohol is methanol or ethanol.

[0057] In one embodiment, the precursor of metal M is an acetate, chloride, sulfate, nitrate, or hydrate of metal M. Preferably, when metal M is Fe, the precursor is ferrous acetate, ferrous chloride, ferrous sulfate, ferrous nitrate, or hydrate; when the metal is Co, Ni, Mn, Pt, Au, or Pd, the precursor is its acetate, chloride, sulfate, nitrate, or hydrate.

[0058] In one implementation, the mass ratio of COF to the M metal precursor in the structure shown in Formula II is (1-5):1. The iron is in excess to ensure sufficient reaction at the COF coordination sites; on the other hand, the iron is limited to prevent metal agglomeration within the COF and blockage of the channels.

[0059] In one implementation method, the reaction conditions are 20-45℃ for 12-72 hours. Room temperature coordination can directly anchor the metal without triggering other side reactions that affect the COF structure. Preferably, the reaction is performed by shaking, a relatively gentle method that promotes metal adsorption and coordination reactions.

[0060] In one embodiment, the reaction includes a post-processing step: solid-liquid separation, whereby the solid product is washed with water and ethanol, and then vacuum dried to obtain the multi-metal active site covalent organic framework material. Preferably, the obtained solid product is repeatedly washed with ultrapure water (50 mL × 3) and ethanol (3 mL × 3), and then dried in a vacuum oven at 50-80°C for 6-24 hours.

[0061] As one embodiment, the COF structure shown in Formula II is prepared by a solvothermal reaction of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and 2,2'-bipyridine-5,5'-dicarboxaldehyde under vacuum.

[0062] The COF structure shown in Formula II is formed by the covalent linkage of 5,10,15,20-tetra(4-aminophenyl)porphyrin and 2,2'-bipyridine-5,5'-dicarboxaldehyde through an amine-aldehyde condensation. This reaction can be achieved using a solvothermal reaction.

[0063] One implementation method involves freezing the reaction vessel in a liquid nitrogen bath, evacuating it, and then sealing it. This effectively removes air and creates a vacuum environment.

[0064] In one embodiment, the solvent is a mixture of 1,2-dichlorobenzene and n-butanol; the volume ratio of 1,2-dichlorobenzene to n-butanol is (2-10):1. 1,2-Dichlorobenzene has a high boiling point and can provide a high reaction temperature.

[0065] In one embodiment, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to 2,2'-bipyridine-5,5'-dicarboxaldehyde is 1:(2-2.2).

[0066] In one embodiment, the molar-volume ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to the solvent is 1 mmol:(50-100) mL.

[0067] In one embodiment, the reaction is carried out in the presence of acetic acid, the concentration of which is 1-6 M; the volume ratio of acetic acid to solvent is 1:(5-20).

[0068] As one implementation method, the reaction conditions are: 100-140℃ for 48-144 hours.

[0069] One implementation method includes a post-processing step: after the heat of dissolution reaction ends, cooling is performed, solid-liquid separation is carried out, and the solid product is washed sequentially with N,N-dimethylformamide, tetrahydrofuran, dichloromethane, and ethanol; purification is then performed by Soxhlet extraction in tetrahydrofuran. The purified COF is then used for metal loading.

[0070] Preferably, the solid product is washed sequentially with N,N-dimethylformamide (50 mL × 3), tetrahydrofuran (50 mL × 3), dichloromethane (3 mL × 3), and ethanol (3 mL × 3). Further purification is performed by Soxhlet extraction in tetrahydrofuran for 24 h.

[0071] This application provides the application of multimetallic active site covalent organic framework materials in the degradation of pollutants by activated PMS.

[0072] The following provides a further explanation using specific implementation methods.

[0073] Example 1: Preparation of COF-367:

[0074] 0.025 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, 0.05 mmol of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 1.6 mL of 1,2-dichlorobenzene, 0.4 mL of n-butanol, and 0.2 mL of 3M anhydrous acetic acid solution were added to 12 mL of [amount not specified]. The mixture was placed in a Pyrex tube; after sonication for 10 min, the tube was placed in a liquid nitrogen bath for freezing, evacuated, and sealed with a flame; then the reaction mixture was heated at 120 °C for 120 h; after the system cooled to room temperature, the solid product was collected by filtration, and the obtained solid product was washed thoroughly with N,N-dimethylformamide (50 mL × 3), tetrahydrofuran (50 mL × 3), dichloromethane (3 mL × 3), and ethanol (3 mL × 3); the obtained solid product was further purified by Soxhlet extraction in tetrahydrofuran for 24 h, and the obtained solid product was dried in a vacuum oven at 120 °C for 12 h; the COF with the structure shown in Formula II was obtained and named COF-367.

[0075] Example 2 Preparation of COF-367:

[0076] 0.025 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, 0.055 mmol of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 2.27 mL of 1,2-dichlorobenzene, 0.23 mL of n-butanol, and 0.125 mL of 3M anhydrous acetic acid solution were added to a 12 mL Plyrex tube; after sonication for 10 min, the tube was placed in a liquid nitrogen bath for freezing, evacuated, and flame-sealed; then the reaction mixture was heated at 100 °C for 14 minutes. After 4 hours, the solid product was collected by filtration and washed thoroughly with N,N-dimethylformamide (50 mL × 3), tetrahydrofuran (50 mL × 3), dichloromethane (3 mL × 3), and ethanol (3 mL × 3) in sequence. The solid product was further purified by Soxhlet extraction in tetrahydrofuran for 24 hours and dried in a vacuum oven at 120 °C for 12 hours to obtain COF with the structure shown in Formula II, named COF-367.

[0077] Example 3 Preparation of COF-367:

[0078] 0.025 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, 0.053 mmol of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 0.83 mL of 1,2-dichlorobenzene, 0.42 mL of n-butanol, and 0.25 mL of 3M anhydrous acetic acid solution were added to 12 mL of [amount not specified]. The mixture was placed in a Pyrex tube; after sonication for 10 min, the tube was frozen in a liquid nitrogen bath, evacuated, and sealed with a flame; then the reaction mixture was heated at 140 °C for 48 h; after the system cooled to room temperature, the solid product was collected by filtration, and the obtained solid product was washed thoroughly with N,N-dimethylformamide (50 mL × 3), tetrahydrofuran (50 mL × 3), dichloromethane (3 mL × 3), and ethanol (3 mL × 3); the obtained solid product was further purified by Soxhlet extraction in tetrahydrofuran for 24 h, and the obtained solid product was dried in a vacuum oven at 120 °C for 12 h; the COF with the structure shown in Formula II was obtained and named COF-367.

[0079] Example 4 Preparation of Fe-COF-367

[0080] 100 mg of COF-367 prepared in Example 1 was added to 10 mL of ethanol, followed by 2 mL of a 10 mg / mL ferrous acetate aqueous solution. The solution was shaken and reacted at room temperature for 24 h. The solution was then filtered, and the resulting solid product was repeatedly washed with ultrapure water (50 mL × 3) and ethanol (3 mL × 3). The product was then dried in a vacuum oven at 80 °C for 12 h to obtain a metal-active site covalent organic framework material with the structure shown in Formula I, named Fe-COF-367.

[0081] Comparative Example 1

[0082] 0.025 mmol of 5,10,15,20-tetra(4-aminophenyl)porphyrin, 0.05 mmol of 4,4′-biphenyldicarboxaldehyde, 1.6 mL of 1,2-dichlorobenzene, 0.4 mL of n-butanol, and 0.2 mL of 3M anhydrous acetic acid solution were added to a 12 mL Pyrex tube. After sonication for 10 min, the tube was placed in a liquid nitrogen bath for freezing, evacuated, and flame-sealed. The reaction mixture was then heated at 120 °C for 120 h. After the system cooled to room temperature, the solid product was collected by filtration. The obtained solid product was washed thoroughly with N,N-dimethylformamide (50 mL × 3), tetrahydrofuran (50 mL × 3), dichloromethane (3 mL × 3), and ethanol (3 mL × 3). The obtained solid product was further purified by Soxhlet extraction in tetrahydrofuran for 24 h. The obtained solid product was then dried in a vacuum oven at 120 °C for 12 h to obtain COF-biphenyl.

[0083] 100 mL of the COF-biphenyl prepared above was added to 10 mL of ethanol, followed by 2 mL of 10 mg / mL ferrous acetate aqueous solution. The solution was reacted with shaking at room temperature for 24 h, then filtered. The resulting solid product was repeatedly washed with ultrapure water (50 mL × 3) and ethanol (3 mL × 3). The product was then dried in a vacuum oven at 80 °C for 12 h to obtain a metal-active site covalent organic framework material with the structure shown in Formula III, named Fe-COF-biphenyl.

[0084]

[0085] Material characterization:

[0086] (1) X-ray powder diffraction tests were performed on COF-367 prepared in Example 1 and Fe-COF-367 prepared in Example 4. The X-ray powder diffraction patterns are shown below. Figure 2 As shown.

[0087] from Figure 2 As can be seen from the results, after the reaction of COF-367 with the metal precursor, the 3.5° characteristic peak in the PXRD of the prepared Fe-COF-367 did not shift, indicating that the COF structure maintained its complete crystal form.

[0088] (2) The COF-367 prepared in Example 1 and the Fe-COF-367 prepared in Example 4 were subjected to infrared spectroscopy tests, and the results are as follows: Figure 3 As shown.

[0089] Figure 3 In the middle, BBD, 1690cm -1 The C=O peak at 1622 cm⁻¹ almost disappears in COF-367, while it is still present at 1622 cm⁻¹ in COF-367. -1The presence of a C=N peak at 1622 cm⁻¹ indicates that the porphyrin amino group reacted with the aldehyde group of bipyridine to form COF. COF-367 and Fe-COF-367 show peaks at 1622 cm⁻¹. -1 The C=N peak showed almost no change, indicating that the COF connection structure was stable.

[0090] (3) The COF-367 prepared in Example 1 and the Fe-COF-367 prepared in Example 4 were subjected to N2 adsorption-desorption tests. The N2 adsorption-desorption curves (top left), pore volume distribution diagram (top right), and specific surface area calculation (bottom) are shown below. Figure 4 As shown.

[0091] Based on the pore volume distribution diagram, both COF-367 and Fe-COF-367 are microporous materials; after loading with metal, the pore size of Fe-COF-367 is reduced compared to COF-367. However, based on specific surface area calculations, COF-367 has a pore size of 1064 μm. 2 g -1 The specific surface area of ​​Fe-COF-367 decreased to 605 m² after being loaded with metal. 2 g -1 .

[0092] (4) The Fe loading of Fe-COF-367 prepared in Example 4 and Fe-COF-biphenyl prepared in Comparative Example 1 was calculated by ICP, and the results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As can be seen from Table 1, the Fe loading of Fe-COF-367 in Example 4 is about 50% higher than that of Fe-COF-biphenyl in Comparative Example 1, indicating that in addition to the porphyrin ring, the bipyridine group is also coordinated to connect Fe atoms.

[0096] Example 5

[0097] Activation of PMS to degrade acetaminophen (APAP): Weigh 5 mg of Fe-COF-367 into an Erlenmeyer flask, add 25 ml of deionized water, and sonicate until the catalyst and water are completely mixed. Add 50 μL of acetaminophen (APAP) into the Erlenmeyer flask and immediately place it in a magnetic stirrer and stir for 15 min until adsorption equilibrium is reached. At this point, take 1 ml of the mixed liquid, filter it, and measure the phenol content using liquid chromatography, recording it as 0s. Then, add PMS (0.5 mM) and immediately start timing. Take 1 ml of samples at 0s, 15s, 30s, 45s, 60s, 75s, 90s, 105s, and 120s, filter them, and measure the APAP content using liquid chromatography. The results are as follows: Figure 5 As shown; the Kobs value of the degradation pollutant APAP is as follows. Figure 6 As shown.

[0098] Comparative Example 2 The COF-367 prepared in Example 1 was tested according to the method in Example 5; the results are as follows. Figure 5 As shown; the Kobs value of the degradation pollutant APAP is as follows. Figure 6 As shown.

[0099] Comparative Example 3 The Fe-COF-biphenyl prepared in Comparative Example 1 was tested according to the method in Example 5; the results are as follows. Figure 5 As shown; the Kobs value of the degradation pollutant APAP is as follows. Figure 6 As shown.

[0100] from Figure 5 As can be seen, Fe-COF-367 activated PMS has a higher efficiency and more thorough degradation of apap, followed by Fe-COF-biphenyl, while COF-367 without iron loading has the worst effect.

[0101] Comparative Example 4 Following the method in Example 5, COF-367 / apap, Fe-COF-367 / apap, and PMS / apap were added respectively. The adsorption performance of COF and the change of apap under PMS without activation were detected. The results are as follows: Figure 7 As shown.

[0102] from Figure 7 As can be seen from the data, the concentration of apap did not change significantly under the three conditions, indicating that COF adsorption is not the main pathway for apap degradation, and PMS did not catalyze activation, so the degradation performance was not activated.

[0103] In summary, the multi-metal active site covalent organic framework material of this application comprises a metalloporphyrin and a bipyridine group. While the metal is supported by the porphyrin, the metal atoms are connected by the two nitrogen atoms of the bipyridine group to form a multi-metal active site. This increases the number of metal active sites and adjusts the distance between the metals, enabling the framework material to exhibit excellent catalytic activity.

[0104] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. The application of a multi-metallic active site covalent organic framework material in the degradation of pollutants by activated PMS, characterized in that, The multi-metal active site covalent organic framework material has the molecular structure shown in Formula I: ； Where M is Fe; The preparation method includes the following steps: The COF structure shown in Formula II reacts with ferrous acetate in a solvent to obtain the polymetallic active site covalent organic framework material. 。 2. The application of the multi-metal active site covalent organic framework material according to claim 1 in the activation of PMS for pollutant degradation, characterized in that, The BET specific surface area of ​​multi-metal active site covalent organic framework materials is 500-800 m². 2 g -1 The metal loading is 1-1.5 wt%.

3. The application of the multi-metal active site covalent organic framework material according to claim 1 in the activation of PMS for pollutant degradation, characterized in that, The solvent is a mixture of alcohol and water, with a volume ratio of alcohol to water of (3-10):1; the alcohol is methanol or ethanol. The mass ratio of COF to ferrous acetate in the structure shown in Formula II is (1-5):1; The reaction conditions are 20-45℃ for 12-72 hours.

4. The application of the multi-metal active site covalent organic framework material according to claim 1 in the activation of PMS for pollutant degradation, characterized in that, The reaction includes a post-processing step: solid-liquid separation, in which the solid product is washed with water and ethanol and then vacuum dried to obtain the multi-metal active site covalent organic framework material.

5. The application of the multi-metal active site covalent organic framework material according to claim 1 in the activation of PMS for pollutant degradation, characterized in that, The COF structure shown in Formula II is prepared by a solvothermal reaction of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and 2,2'-bipyridine-5,5'-dicarboxaldehyde under vacuum.

6. The application of the multi-metal active site covalent organic framework material according to claim 5 in the activation of PMS for pollutant degradation, characterized in that, The solvent is a mixture of 1,2-dichlorobenzene and n-butanol; the volume ratio of 1,2-dichlorobenzene to n-butanol is (2-10):1; The molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to 2,2'-bipyridine-5,5'-dicarboxaldehyde is 1:(2-2.2). The molar-volume ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin to solvent is 1 mmol:(50-100) mL.

7. The application of the multi-metal active site covalent organic framework material according to claim 5 in the activation of PMS for pollutant degradation, characterized in that, The reaction is carried out in the presence of acetic acid, the concentration of which is 1-6 M; the volume ratio of acetic acid to solvent is 1:(5-20). The reaction conditions are: 100-140℃ for 48-144 hours.

8. The application of the multi-metal active site covalent organic framework material according to claim 5 in the activation of PMS for pollutant degradation, characterized in that, It also includes post-processing steps: after the end of the solubility heat reaction, cooling, solid-liquid separation, and washing the solid product sequentially with N,N-dimethylformamide, tetrahydrofuran, dichloromethane and ethanol; purification by Soxhlet extraction in tetrahydrofuran.

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