A cof@mof composite material and a preparation method and application thereof

Abstract

The application discloses a COF@MOF composite material and a preparation method and application thereof, and relates to the technical field of new materials.The preparation method comprises the following steps: introducing a-COOH group into PY-COF through a substitution reaction to obtain PY-COF-COOH; and mixing the PY-COF-COOH with a metal source, an organic ligand and a solvent, and heating to react, so as to obtain the COF@MOF composite material.The application takes PY-COF as a starting COF material, then introduces a-COOH group through a substitution reaction for post-synthesis, so as to provide a growth site of MOF, and then grows MOF on the surface of the PY-COF-COOH through a solvothermal method, so as to obtain the final COF@MOF composite material.The preparation method has high scalability and compatibility, can realize the growth of most MOFs including acid-unstable MOFs on the surface of the PY-COF, and can construct various COF@MOF composite materials.In addition, compared with a single MOF material, the COF@MOF composite material prepared by the application can realize efficient Fenton oxidation degradation of organic pollutants in a water environment and efficient adsorption and separation of a mixed gas of methane / ethane / propane.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a COF@MOF composite material, its preparation method, and its application. Background Technology

[0002] In recent years, covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) have attracted much attention as two novel types of porous materials. COFs, through their conjugated network structure formed by strong covalent bonds, exhibit excellent thermal stability, chemical stability, and organic matter adsorption performance; however, the design and regulation of their functional sites are limited. In contrast, MOFs, with their open metal sites and high specific surface area microporous structure, demonstrate outstanding performance in catalytic reactions, gas adsorption and storage, etc., but their environmental sensitivity restricts their applications.

[0003] To overcome the performance bottlenecks of single materials, the academic community has proposed a composite strategy combining MOFs and COFs. For example, attempts have been made to integrate the advantages of both by constructing MOFs using metal-supported COFs or conjugated units, but these methods suffer from weak interfacial bonding and imprecise control of pore structure. In particular, hierarchical porous materials constructed using COF-on-MOF (MOF@COF) heterostructures can leverage the conjugated network of COFs to enhance material stability while retaining the active sites of MOFs, exhibiting a synergistic effect in controlling the pore structure and electron transport efficiency. However, the existing composite materials suffer from complex fabrication processes and insufficient interfacial compatibility, resulting in limited performance improvements.

[0004] Based on this, developing a structurally stable COF@MOF composite material with tight interfacial coupling and its controllable preparation method is of great significance for promoting the application of functionalized porous materials in catalysis, energy storage, environmental governance and other fields. Summary of the Invention

[0005] The purpose of this invention is to provide a COF@MOF composite material, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention: a method for preparing COF@MOF composite material, comprising the following steps:

[0008] A -COOH group is introduced into PY-COF through a substitution reaction to obtain PY-COF-COOH; the PY-COF-COOH is mixed with a metal source, an organic ligand and a solvent, and heated to react (i.e., to carry out a solvothermal reaction) to obtain the COF@MOF composite material.

[0009] This invention uses PY-COF as a starting material for COF, and then introduces -COOH groups through a substitution reaction for post-synthesis to provide growth sites for MOFs. Subsequently, MOFs are grown on the PY-COF-COOH surface via a solvothermal method to obtain the final COF@MOF composite material. The preparation method of this invention is highly scalable and compatible, enabling the growth of most MOFs, including acid-labile MOFs (such as ZIF-8), on the PY-COF surface, and the construction of various COF@MOF composite materials. Furthermore, compared to standalone MOF materials, the COF@MOF composite material prepared by this invention can achieve highly efficient Fenton oxidation degradation of organic pollutants in aquatic environments and highly efficient adsorption and separation of methane / ethane / propane.

[0010] The method of the present invention has advantages such as flexible and controllable components and tight interface coupling.

[0011] Furthermore, the metal source includes an iron source, a zirconium source, a cobalt source, or a zinc source.

[0012] Furthermore, the ratio of the amount of PY-COF-COOH to the metal source and the solvent is 100mg:0.10-1.00mmol:30mL.

[0013] Furthermore, the heating reaction is carried out at a temperature of 120°C for 24 hours.

[0014] Preferably, when the metal source is an iron source, a zirconium source, or a cobalt source, the organic ligand is 2-aminoterephthalic acid, and the molar ratio of the metal source to the organic ligand is 1:1.

[0015] When the metal source is iron, the MOF grown on the PY-COF-COOH surface is called MIL-101(Fe); when the metal source is cobalt, the MOF grown on the PY-COF-COOH surface is called Co-MOF; and when the metal source is zirconium, the MOF grown on the PY-COF-COOH surface is called UIO-66.

[0016] Preferably, when the metal source is a zinc source, the organic ligand is 2-methylimidazole, and the molar ratio of the metal source to the organic ligand is 1:8.

[0017] When the metal source is zinc, the MOF grown on the PY-COF-COOH surface is called ZIF-8.

[0018] Optionally, the iron source includes ferric chloride hexahydrate, the zirconium source includes zirconium oxychloride octahydrate, the cobalt source includes cobalt acetate hexahydrate, and the zinc source includes zinc acetate dihydrate.

[0019] Optionally, the solvent includes N,N-dimethylformamide (DMF).

[0020] Further, the process of introducing a -COOH group into PY-COF via a substitution reaction to obtain PY-COF-COOH comprises: mixing PY-COF, 4-fluorobenzoic acid (4-FA), potassium carbonate, and a solvent to obtain a mixed solution; and heating the mixed solution to carry out a substitution reaction to obtain the PY-COF-COOH.

[0021] Using PY-COF as the substrate, 4-fluorobenzoic acid as the reactant providing -COOH, and potassium carbonate as the dehydrating agent, in the reaction system, the phenolic hydroxyl group of PY-COF undergoes a substitution reaction with the CF bond of 4-fluorobenzoic acid, thereby introducing -COOH onto the surface of PY-COF.

[0022] This invention enhances the connection between PY-COF and MOF and the stability of the composite material by precisely modifying the carboxyl groups on the surface of PY-COF; and induces structural defects in the MOF on the surface of PY-COF, releasing the active sites of the composite material and enhancing its hydrogen peroxide catalytic performance and methane / ethane / propane adsorption and separation performance.

[0023] Furthermore, the ratio of PY-COF, 4-fluorobenzoic acid, potassium carbonate, and solvent is 100 mg: 1.00 mmol: 1.5 mmol: 40 mL.

[0024] Furthermore, the substitution reaction was carried out at a temperature of 110°C for 72 hours.

[0025] Optionally, the solvent used in the substitution reaction includes N,N-dimethylformamide (DMF).

[0026] Further, the preparation steps of the PY-COF (pyrene-based covalent organic framework material) include: dissolving 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene in a mixed solvent of n-butanol, o-dichlorobenzene and acetic acid, degassing and then carrying out a solvothermal reaction to obtain the PY-COF.

[0027] Further, the ratio of 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene to the mixed solvent is 0.04 mmol:0.02 mmol:1.1 mL.

[0028] Furthermore, the concentration of the acetic acid is 6M.

[0029] Furthermore, the volume ratio of n-butanol, o-dichlorobenzene, and acetic acid in the mixed solvent is 5:5:1.

[0030] Optionally, the degassing operation is carried out by performing three cycles of freezing-evacuation-thawing.

[0031] Furthermore, the solvothermal reaction is carried out at a temperature of 120°C for 72 hours.

[0032] Furthermore, the solvothermal reaction is carried out under sealed conditions.

[0033] The second technical solution of the present invention: a COF@MOF composite material prepared according to the above-mentioned preparation method of COF@MOF composite material.

[0034] The third technical solution of the present invention: an application of the above-mentioned COF@MOF composite material in the Fenton degradation of organic pollutants.

[0035] Preferably, the organic pollutant includes enrofloxacin.

[0036] Furthermore, the application includes adding the COF@MOF composite material as a heterogeneous catalyst to an organic pollutant solution to carry out a Fenton reaction, thereby achieving Fenton oxidation degradation of organic pollutants in the aquatic environment.

[0037] Preferably, the COF@MOF composite material used for Fenton degradation of organic pollutants is a PY-COF@Co-MOF composite material (i.e., a COF@MOF composite material prepared using cobalt source as metal source and 2-aminoterephthalic acid as organic ligand).

[0038] The fourth technical solution of the present invention: an application of the above-mentioned COF@MOF composite material in gas adsorption and separation.

[0039] Furthermore, the gas adsorption separation specifically refers to the adsorption separation of a methane / ethane / propane mixed gas. That is, ethane and propane are adsorbed and removed from the mixed gas of methane, ethane, and propane, leaving methane, thus achieving the separation of methane.

[0040] The COF@MOF composite exhibits stronger adsorption affinity for ethane and propane than PY-COF and ZIF-8 alone, but lower adsorption affinity for methane, thus enabling the separation of methane from methane / ethane / propane mixtures.

[0041] Preferably, the COF@MOF composite material used for gas adsorption and separation is a PY-COF@ZIF-8 composite material (i.e., a COF@MOF composite material prepared using zinc as the metal source and 2-methylimidazole as the organic ligand).

[0042] The present invention discloses the following technical effects:

[0043] (1) This invention uses PY-COF as the starting material for COF, and then introduces -COOH groups through a substitution reaction for post-synthesis to provide growth sites for MOF. Subsequently, MOF is grown on the PY-COF-COOH surface by a solvothermal method to obtain the final COF@MOF composite material. The preparation method of this invention has high scalability and compatibility, and can realize the growth of most MOFs, including acid-labile MOFs, on the PY-COF surface to construct a variety of COF@MOF composite materials.

[0044] (2) The present invention can grow MIL-101(Fe), Co-MOF, UIO-66 and ZIF-8 on the surface of PY-COF respectively.

[0045] (3) The PY-COF@Co-MOF composite material prepared by the present invention can achieve efficient removal of enrofloxacin, specifically achieving an enrofloxacin removal rate of over 99.5%, and has significantly improved stability compared to Co-MOF alone.

[0046] (4) The PY-COF@ZIF-8 composite material prepared by the present invention can effectively adsorb and separate methane / ethane / propane mixed gas, achieving a significant leap compared with pure PY-COF and ZIF-8. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 The NMR spectrum of PY-COF-COOH obtained in step (2) of Example 1 is shown.

[0049] Figure 2 The XRD diffraction patterns are those of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2.

[0050] Figure 3 Scanning electron microscope (SEM) images of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2.

[0051] Figure 4Scanning electron microscope (SEM) images of PY-COF@ZIF-X prepared in Example 2, PY-COF prepared in Comparative Example 2, and ZIF-8 prepared in Comparative Example 3.

[0052] Figure 5 The XRD diffraction patterns are those of PY-COF@ZIF-X prepared in Example 2 and ZIF-8 prepared in Comparative Example 3.

[0053] Figure 6 Enrofloxacin degradation curves of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2.

[0054] Figure 7 The images show the methane, ethane, and propane adsorption curves of PY-COF@ZIF-X prepared in Example 2, PY-COF prepared in Comparative Example 2, and ZIF-8 prepared in Comparative Example 3. Detailed Implementation

[0055] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0056] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0057] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0058] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0059] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0060] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0061] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20-30°C.

[0062] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0063] Example 1

[0064] A COF@MOF composite material is prepared by the following steps:

[0065] (1) Preparation of PY-COF

[0066] 1,4-Dihydroxybenzidine (0.04 mmol, 8.6 mg) and 1,3,6,8-tetra(4-formylphenyl)pyrene (0.02 mmol, 12.3 mg) were dissolved in a mixture of n-butanol / o-dichlorobenzene / 6M acetic acid (volume ratio of 5 / 5 / 1, mixed solvent volume 1.1 mL) and loaded into a 10 mL Pyrex reaction tube. The system was degassed by three freeze-evacuation-thawing cycles, sealed, and heated at 120 °C for 72 h. After the reaction, the precipitate was collected by centrifugation, soaked in DMF for 48 h, washed five times with anhydrous tetrahydrofuran, and washed twice with acetone. Finally, the product powder was vacuum dried at 120 °C for 12 h to obtain PY-COF.

[0067] (2) Preparation of PY-COF-COOH

[0068] 100 mg of the prepared PY-COF was added to a mixed solution prepared with 1.00 mmol (219.00 mg) of 4-fluorobenzoic acid, 1.5 mmol (207.30 mg) of potassium carbonate, and 40 mL of DMF. The mixture was stirred at 200 rpm for 30 min at room temperature to ensure complete dissolution. Subsequently, the reaction system was stirred at 200 rpm for 72 h at 110 °C under a nitrogen atmosphere. After the reaction was complete, the mixture was washed successively with deionized water, DMF, and anhydrous ethanol to remove unreacted raw materials. The resulting solid was vacuum dried at 80 °C for 24 h to obtain PY-COF-COOH, which was then stored at 4 °C for later use.

[0069] (3) Preparation of COF@MOF composite materials

[0070] 100 mg of PY-COF-COOH was added to a 50 mL flask containing 15 mL of DMF, and sonicated for 10 min to ensure complete dispersion, yielding a PY-COF solution. Subsequently, X mmol (X = 0.10, 0.25, 0.50, or 1.00) of cobalt acetate hexahydrate was added to the PY-COF solution, and the mixture was stirred to form a homogeneous mixture. Next, an organic ligand solution prepared from X mmol of 2-aminoterephthalic acid and 15 mL of DMF was added to the flask, and the mixture was heated at 120 °C for 24 h. After the reaction was complete, the product was allowed to cool naturally to room temperature, washed three times sequentially with DMF and anhydrous ethanol, and then vacuum dried at 80 °C for 12 h to obtain the COF@MOF composite material (referred to as PY-COF@Co-MOF-X, where X represents the molar amount of cobalt acetate hexahydrate), which was stored at 4 °C for later use.

[0071] Example 2

[0072] (1) Preparation of PY-COF

[0073] 1,4-Dihydroxybenzidine (0.04 mmol, 8.6 mg) and 1,3,6,8-tetra(4-formylphenyl)pyrene (0.02 mmol, 12.3 mg) were dissolved in a mixture of n-butanol / o-dichlorobenzene / 6M acetic acid (volume ratio of 5 / 5 / 1, mixed solvent volume 1.1 mL) and loaded into a 10 mL Pyrex reaction tube. The system was degassed by three freeze-evacuation-thawing cycles, sealed, and heated at 120 °C for 72 h. After the reaction, the precipitate was collected by centrifugation, soaked in DMF for 48 h, washed five times with anhydrous tetrahydrofuran, and washed twice with acetone. Finally, the product powder was vacuum dried at 120 °C for 12 h to obtain PY-COF.

[0074] (2) Preparation of PY-COF-COOH

[0075] 100 mg of the prepared PY-COF was added to a mixed solution prepared with 1.00 mmol (219.00 mg) of 4-fluorobenzoic acid, 1.5 mmol (207.30 mg) of potassium carbonate, and 40 mL of DMF. The mixture was stirred at 200 rpm for 30 min at room temperature to ensure complete dissolution. Subsequently, the reaction system was stirred at 200 rpm for 72 h at 110 °C under a nitrogen atmosphere. After the reaction was complete, the mixture was washed successively with deionized water, DMF, and anhydrous ethanol to remove unreacted raw materials. The resulting solid was vacuum dried at 80 °C for 24 h to obtain PY-COF-COOH, which was then stored at 4 °C for later use.

[0076] (3) Preparation of COF@MOF composite materials

[0077] 100 mg of PY-COF-COOH was added to a 50 mL flask containing 15 mL of DMF solution, and sonicated for 10 min to ensure complete dispersion, yielding a PY-COF solution. Subsequently, X mmol (X = 0.10, 0.25, 0.50, or 1.00) of zinc acetate dihydrate was added to the PY-COF solution, and the mixture was stirred to form a homogeneous mixture. Next, an organic ligand solution prepared from 8X mmol of 2-methylimidazole and 15 mL of DMF was added to the flask, and the mixture was heated at 120 °C for 24 h. After the reaction was complete, the product was allowed to cool naturally to room temperature, washed three times successively with DMF and anhydrous ethanol, and then vacuum dried at 80 °C for 12 h to obtain the COF@MOF composite material (referred to as PY-COF@ZIF-X, where X represents the molar amount of zinc acetate dihydrate), which was stored at 4 °C for later use.

[0078] Comparative Example 1

[0079] The preparation of Co-MOFs involves the following steps:

[0080] 1.00 mmol of cobalt acetate hexahydrate and 1.00 mmol of 2-aminoterephthalic acid were dissolved separately in 15 mL of DMF and sonicated for 5 min to ensure complete dissolution. The two clear solutions were then transferred to 50 mL solvent bottles and sonicated again for 5 min to ensure homogeneity. The mixture was heated at 120 °C for 24 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation, washed three times successively with DMF and anhydrous ethanol, and finally dried under vacuum at 80 °C for 24 h to obtain Co-MOF.

[0081] Comparative Example 2

[0082] The preparation steps of PY-COF are as follows:

[0083] 1,4-Dihydroxybenzidine (0.04 mmol, 8.6 mg) and 1,3,6,8-tetra(4-formylphenyl)pyrene (0.02 mmol, 12.3 mg) were dissolved in a mixture of n-butanol / o-dichlorobenzene / 6M acetic acid (volume ratio of 5 / 5 / 1, mixed solvent volume 1.1 mL) and loaded into a 10 mL Pyrex reaction tube. The system was degassed by three freeze-evacuation-thawing cycles, sealed, and heated at 120 °C for 72 h. After the reaction, the precipitate was collected by centrifugation, soaked in DMF for 48 h, washed five times with anhydrous tetrahydrofuran, and washed twice with acetone. Finally, the product powder was vacuum dried at 120 °C for 12 h to obtain PY-COF.

[0084] Comparative Example 3

[0085] The preparation of ZIF-8 is as follows:

[0086] 1.00 mmol of zinc acetate dihydrate and 8.00 mmol of 2-methylimidazole were dissolved separately in 15 mL of DMF and sonicated for 5 min to ensure complete dissolution. The two clear solutions were then transferred to 50 mL solvent bottles and sonicated again for 5 min to ensure homogeneity. The mixture was heated at 120 °C for 24 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation, washed three times successively with DMF and anhydrous ethanol, and finally dried under vacuum at 80 °C for 24 h to obtain ZIF-8.

[0087] Test Example 1

[0088] Morphological structure and composition characterization

[0089] Figure 1 The NMR spectrum of PY-COF-COOH obtained in step (2) of Example 1 shows that after the substitution reaction was completed, -CO and -C=O signal peaks at shifts of 150ppm and 162ppm, respectively, were attributed to the -COOH group, proving that the -COOH group was successfully introduced.

[0090] Figure 2 The XRD diffraction patterns of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2 are shown. It can be seen that both individual PY-COF (3.28°) and individual Co-MOF (5.40°, 10.86°, 19.65°, and 26.02°) exhibit unique sharp XRD diffraction peaks. After the composite material is formed, the characteristic peaks of PY-COF are retained, while the characteristic peaks of Co-MOF disappear, suggesting that there are structural defects in the Co-MOF on the PY-COF surface, which is beneficial for the release of catalytically active sites.

[0091] Figure 3 The images show scanning electron microscope (SEM) images of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2. It can be seen that individual PY-COF exhibits a rod-like structure, while individual Co-MOF exhibits a sheet-like structure. After the composite material is formed, Co-MOF grows tightly adhered to the surface of PY-COF, and the number of Co-MOF particles on the PY-COF surface gradually increases with the increase of the amount of Co-MOF raw material added.

[0092] Figure 4The images show scanning electron microscope (SEM) images of PY-COF@ZIF-X prepared in Example 2, PY-COF prepared in Comparative Example 2, and ZIF-8 prepared in Comparative Example 3. It can be seen that individual PY-COF exhibits a rod-like structure, while individual ZIF-8 exhibits aggregated granular structures. After forming the composite material, ZIF-8 grows tightly adheres to the surface of PY-COF, exhibiting good dispersibility. The aggregated granular morphology is significantly improved to a well-defined octahedral structure, and the number of ZIF-8 particles on the PY-COF surface gradually increases with the increase in the amount of ZIF-8 added.

[0093] Figure 5 The XRD diffraction patterns of PY-COF@ZIF-X prepared in Example 2 and ZIF-8 prepared in Comparative Example 3 show that the composite material contains sharp characteristic peaks of ZIF-8 at 7.43°, 10.42° and 12.77° and characteristic peak of PY-COF at 3.28°, proving that the composite material was successfully synthesized.

[0094] Test Example 2

[0095] The specific procedure for the enrofloxacin Fenton oxidation degradation test is as follows:

[0096] Add 20 mg of catalyst (PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, or PY-COF prepared in Comparative Example 2) to 100 mL of enrofloxacin aqueous solution with a concentration of 10 μg / L. Use the experimental group without any catalyst as the blank control group, i.e., KB group) and shake at 25 °C for 60 min to reach adsorption equilibrium. Then add 0.5 mL of hydrogen peroxide with a concentration of 30 wt% to each reaction system (KB group also shakes pure enrofloxacin aqueous solution for 60 min before adding hydrogen peroxide). Perform Fenton reaction at 25 °C. Take samples at different reaction times to detect the concentration of enrofloxacin in the reaction system and calculate the enrofloxacin removal rate according to formula (1).

[0097] Enrofloxacin removal rate (%) = [1-C t / C0]×100% (1);

[0098] In formula (1), C0 is the original concentration of enrofloxacin aqueous solution (i.e., 10 μg / L), C t The concentration of enrofloxacin after a certain reaction time.

[0099] Figure 6The enrofloxacin degradation curves of PY-COF@Co-MOF-X prepared in Example 1, Co-MOF prepared in Comparative Example 1, and PY-COF prepared in Comparative Example 2 are shown (where the -60min to 0min stage represents the adsorption equilibrium stage). It can be seen that the equilibrium removal rate of enrofloxacin by PY-COF@Co-MOF-X exceeds 99.5%, which is significantly better than that of PY-COF (equilibrium removal rate of 62.4%) and Co-MOF (equilibrium removal rate of 35.7%).

[0100] Test Example 3

[0101] The adsorption separation experiment steps are as follows:

[0102] Under the conditions of ambient temperature 25℃, adsorption time of 2h, and degassing time of 6h, the adsorption amounts of PY-COF@ZIF-X prepared in Example 2, PY-COF prepared in Comparative Example 2, and ZIF-8 prepared in Comparative Example 3 for methane (CH4), ethane (C2H6), and propane (C3H8), respectively, were measured by static volumetric method.

[0103] Figure 7 The adsorption curves for methane, ethane, and propane of PY-COF@ZIF-X prepared in Example 2, PY-COF prepared in Comparative Example 2, and ZIF-8 prepared in Comparative Example 3 are shown. It can be seen that at 100 kPa, the saturated adsorption capacities of PY-COF@ZIF-X (X = 1.00) for methane, propane, and ethane are 6.55 cm⁻¹, respectively. 3 / g (methane), 82.48cm 3 / g (propane) and 77.95cm 3 / g (ethane); the saturated adsorption capacity of PY-COF for the three substances was 3.71 cm⁻¹. 3 / g (methane), 13.05 (ethane), and 28.00cm 3 / g (propane); the saturated adsorption capacity of ZIF-8 for the three substances was 5.15cm³. 3 / g (methane), 43.77cm 3 / g (ethane) and 83.61cm 3 / g (propane). It is evident that PY-COF alone exhibits low adsorption capacities for methane, ethane, and propane. ZIF-8 alone shows significantly higher adsorption capacities for ethane and propane than for methane, but its adsorption capacity for ethane remains low compared to methane. After being prepared as a composite material, the morphology and particle size of ZIF-8 grown on the PY-COF surface change, leading to a further reduction in pore size. This facilitates gas adsorption and separation, enhancing the composite material's adsorption capacity for ethane and propane, but the adsorption capacity for methane remains low. Therefore, in the gas adsorption separation results of PY-COF@ZIF-1.00, it can be observed that in the relatively low pressure region (0-20 kPa), the ethane and propane adsorption curves of PY-COF@ZIF-1.00 rise rapidly and reach a plateau, while no similar phenomenon was observed with ZIF-8 alone or PY-COF alone. This indicates that PY-COF@ZIF-1.00 exhibits stronger adsorption affinity for ethane and propane than PY-COF and ZIF-8 alone, while having a low adsorption affinity for methane. Therefore, it can separate methane from the methane / ethane / propane mixture.

[0104] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a COF@MOF composite material, characterized in that, Includes the following steps: -COOH groups are introduced into PY-COF through a substitution reaction to obtain PY-COF-COOH; the PY-COF-COOH is mixed with a metal source, an organic ligand and a solvent, and heated to react to obtain the COF@MOF composite material; The metal source is a cobalt source or a zinc source; The ratio of PY-COF-COOH to the metal source and the solvent is 100 mg: 0.10-1.00 mmol: 30 mL; The heating reaction was carried out at a temperature of 120 °C for 24 h. When the metal source is a cobalt source, the organic ligand is 2-aminoterephthalic acid, and the molar ratio of the metal source to the organic ligand is 1:

1. When the metal source is a zinc source, the organic ligand is 2-methylimidazole, and the molar ratio of the metal source to the organic ligand is 1:8; The process of introducing -COOH groups into PY-COF via a substitution reaction to obtain PY-COF-COOH comprises: mixing PY-COF, 4-fluorobenzoic acid, potassium carbonate, and a solvent to obtain a mixed solution; and heating the mixed solution to carry out a substitution reaction to obtain the PY-COF-COOH. The preparation steps of the PY-COF include: dissolving 1,4-dihydroxybenzidine and 1,3,6,8-tetra(4-formylphenyl)pyrene in a mixed solvent of n-butanol, o-dichlorobenzene and acetic acid, degassing and then carrying out a solvothermal reaction to obtain the PY-COF.

2. The method for preparing the COF@MOF composite material as described in claim 1, characterized in that, The ratio of PY-COF, 4-fluorobenzoic acid, potassium carbonate, and solvent is 100 mg: 1.00 mmol: 1.5 mmol: 40 mL; And / or, the substitution reaction is carried out at a temperature of 110°C for a time of 72 h.

3. The method for preparing the COF@MOF composite material as described in claim 1, characterized in that, The ratio of 1,4-dihydroxybenzidine, 1,3,6,8-tetrakis(4-formylphenyl)pyrene, and the mixed solvent was 0.04 mmol:0.02 mmol:1.1 mL. And / or, the concentration of the acetic acid is 6 M; And / or, the volume ratio of n-butanol, o-dichlorobenzene and acetic acid in the mixed solvent is 5:5:1; And / or, the temperature of the solvothermal reaction is 120 °C and the time is 72 h.

4. A COF@MOF composite material prepared by the method of any one of claims 1-3.

5. The application of the COF@MOF composite material as described in claim 4 in the Fenton degradation of organic pollutants.

6. An application of the COF@MOF composite material as described in claim 4 in gas adsorption separation.

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