Cobalt-loaded covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a cobalt-loaded covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The cobalt-loaded covalent organic framework material is prepared by taking a carbonized covalent organic framework as a matrix and cobalt nitrate hexahydrate as a cobalt source, reducing by using a sodium borohydride methanol solution, and introducing transition metal cobalt into the framework through room-temperature impregnation and thermal reduction processes. In the material, active components comprise Co0 and Co < 2 + > which are uniformly distributed on a carrier. Moreover, the metal cobalt is stably loaded in a carbon skeleton through the bonding effect of heteroatoms such as nitrogen and carbon, so that the stability, the catalytic activity and the durability of the metal cobalt are effectively improved, the dissolution risk of the metal cobalt is reduced, the hidden danger of environmental pollution is reduced, and efficient catalytic activity is shown in the aspect of catalyzing and activating peroxymonosulfate to degrade organic pollutants; and good recycling stability is achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of catalyst preparation, and specifically relates to a cobalt-loaded covalent organic framework material and a preparation method and application thereof. Background Art

[0002] Advanced oxidation processes based on permonosulfate (PMS) have become one of the effective solutions for treating refractory organic pollutants. However, under normal temperature and pressure conditions, PMS is difficult to react spontaneously with organic pollutants, and usually requires catalytic activation to generate free radicals or other active species to achieve pollutant degradation.

[0003] Metal ions are fixed on covalent organic frameworks (COFs) through chemical bonds, which provides an improved solution for the application of metal-based catalytic materials and overcomes the problems of high dependence on pH, metal leaching and agglomeration. Among transition metals (Fe, Mn, Co, Cu, etc.), cobalt is one of the most effective metals for PMS activation. It can activate PMS through single electron transfer to generate sulfate radicals (SO4·-), hydroxyl radicals (·OH), singlet oxygen ( 1 O 2 ) and direct electron transfer. In addition, cobalt can also form high-valent metals through double electron transfer to further promote the activation of PMS.

[0004] In the prior art, there are a number of patent applications for metal-supported COF catalysts. For example, patent CN114164446A discloses a noble metal platinum-supported COF catalytic material, wherein the preparation of PdCu alloy catalysts involves multiple complex steps, including the synthesis of alloy precursors, metal loading, reduction treatment and subsequent heat treatment. These process steps usually require a variety of chemical reagents, such as metal salts, reducing agents, additives and dispersants, not only the operation process is cumbersome, the reagent purity and reaction conditions are required to be high, but also the preparation cost is significantly increased, especially the high price of noble metal palladium limits the feasibility of its large-scale application. In addition, patent CN108682870A reports a bimetallic single-atom supported catalyst and a preparation method thereof, which utilizes a metal organic framework (MOF) as a carrier and obtains a bimetallic single-atom catalyst by an impregnation method. However, the preparation process of this method is complicated, the cost is high, and due to the poor coordination bond stability of MOF materials, the metal active component is easy to fall off from the carrier, affecting the stability and reusability of the catalyst. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] This application aims to solve the problem that cobalt in the existing cobalt-containing catalyst metal is easily leached out, resulting in a decrease in catalyst performance, and provides a cobalt-loaded covalent organic framework material, its preparation method and application. The cobalt-loaded covalent organic framework material uses carbonized covalent organic framework as the matrix, cobalt hexahydrate nitrate as the cobalt source, and sodium borohydride methanol solution for reduction. Then, through room-temperature impregnation and thermal reduction processes, transition metal cobalt is introduced into the framework to prepare the cobalt-loaded covalent organic framework material. In this material, the active components include Co 0 and Co 2+ , which are evenly distributed on the carrier. This material exhibits high catalytic activity in the catalytic activation of peroxymonosulfate for the degradation of organic pollutants and has good cyclic use stability.

[0007] 2. Technical solutions

[0008] To solve the above problems, the technical solutions adopted in this application are as follows:

[0009] This application provides a cobalt-loaded covalent organic framework material, which includes a carbonized COF skeleton and nano-cobalt. The nano-cobalt is dispersed on the carbonized COF skeleton in the form of zero-valent metal and multiple valence states.

[0010] Further, the above-mentioned multiple valence states include Co(II) and Co(III).

[0011] Further, for the above cobalt-loaded covalent organic framework material, the particle size of the nano-cobalt is mainly distributed in the range of 5 - 10 nm.

[0012] Further, for the above cobalt-loaded covalent organic framework material, the particle size of the nano-cobalt is mainly distributed in the range of 6 - 7 nm.

[0013] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 1 wt% - 7 wt%.

[0014] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 2 wt% - 7 wt%.

[0015] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 2 wt% - 5 wt%.

[0016] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 3 wt% - 5 wt%.

[0017] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 4 wt% - 5 wt%.

[0018] Further, for the above cobalt-loaded covalent organic framework material, the mass fraction of cobalt is 5 wt%.

[0019] Furthermore, in the above cobalt-loaded covalent organic framework material, the nitrogen includes pyrrole nitrogen, pyridine nitrogen, and graphitic nitrogen forms.

[0020] This application also provides a preparation method of the above cobalt-loaded covalent organic framework material, and the method includes the following steps:

[0021] S1, Preparation of COF: Using trimesic aldehyde and p-phenylenediamine as precursors, dissolve them in 1,4-dioxane to form a uniform reaction system, add acetic acid as a catalyst, and after the reaction is completed, vacuum freeze-dry to generate COF;

[0022] S2, Cobalt salt loading: Disperse COF in a methanol solution, add cobalt(II) nitrate hexahydrate to form a uniform dispersion system;

[0023] S3, Reduction of cobalt ions: Slowly drop a sodium borohydride methanol solution into the dispersion system, stir and then heat to cause the reduction reaction of cobalt ions;

[0024] S4, Calcination: Place the solid sample obtained in S3 in a tubular furnace, under a nitrogen atmosphere, heat up to 600 - 850 °C for calcination, keep the temperature for 2 - 4 h, and after cooling, obtain the cobalt-loaded covalent organic framework material.

[0025] Furthermore, in the above step S1, the mass ratio of trimesic aldehyde to p-phenylenediamine is 1:1.

[0026] Furthermore, in the above step S1, dissolving in 1,4-dioxane includes ultrasonic treatment to completely dissolve the precursors.

[0027] Furthermore, in the above step S1, the addition amount of acetic acid is 10% of the total volume of the reaction solution.

[0028] Furthermore, in the above step S1, the reaction includes standing at room temperature for 60 - 84 h.

[0029] Furthermore, in the above step S1, the reaction includes standing at room temperature for 72 h.

[0030] Furthermore, in the above step S1, before vacuum freeze-drying, wash the product with acetone and tetrahydrofuran (THF) 3 - 4 times respectively to remove unreacted monomers and other soluble by-products.

[0031] Furthermore, in the above step S2, relative to 1 mg of COF, the volume of methanol is 1 mL.

[0032] Furthermore, in the above step S2, after adding cobalt(II) nitrate hexahydrate, it also includes ultrasonic treatment for 20 - 40 min to ensure sufficient contact between the cobalt salt and COF and form a uniform dispersion system.

[0033] Further, in the above step S2, the dispersion in the methanol solution includes ultrasonic treatment for 20 - 40 min to ensure the uniform dispersion of COF in the solution.

[0034] Further, in the above step S3, the concentration of NaBH 4 / methanol solution is 10%.

[0035] Further, in the above step S3, relative to 1 mg of cobalt nitrate hexahydrate, the volume of the NaBH 4 / methanol solution is 0.08 - 0.12 mL, and NaBH 4 / methanol is used as a reducing agent to reduce Co 2+ to metallic cobalt nanoparticles.

[0036] Further, in the above step S3, relative to 1 mg of cobalt nitrate hexahydrate, the volume of the NaBH 4 / methanol solution is 0.10 mL.

[0037] Further, in the above step S3, the stirring time is 1.5 - 3 h, and the reaction lasts for 1.5 - 3 h to ensure the full reduction of cobalt ions and their firm loading on the surface of COF.

[0038] Further, in the above step S3, the stirring time is 2 h.

[0039] Further, in the above step S3, the stirring includes magnetic stirring, etc., to keep the system uniformly dispersed.

[0040] Further, in the above step S3, the heating temperature is 70 - 90 °C to promote the evaporation of methanol, causing the precipitation and solidification of the solid cobalt-loaded sample in the COF matrix.

[0041] Further, in the above step S3, the heating temperature is 75 - 85 °C.

[0042] Further, in the above step S3, the heating temperature is 80 °C.

[0043] Further, in the above step S4, the heating rate is 4 - 6 °C / min.

[0044] Further, in the above step S4, the heating rate is 5 °C / min.

[0045] Further, in the above step S4, the calcination temperature is 700 - 850 °C. During the heat preservation (calcination) process, COF undergoes carbonization to form a carbon-based structure rich in micropores. At the same time, cobalt is further stabilized to form metallic cobalt or cobalt oxide, which combines with the carbonized COF matrix, thereby improving the conductivity and structural stability of the catalyst.

[0046] Further, in the above step S4, the calcination temperature is 700 - 800 °C.

[0047] Further, in the above step S4, the calcination temperature is 700 - 750 °C.

[0048] Further, in the above step S4, the calcination temperature is 750 °C.

[0049] Further, in the above step S4, keep warm for 3 h.

[0050] The present application also provides an application of the above cobalt-loaded covalent organic framework material in the activation of persulfate for the degradation of organic pollutants.

[0051] Further, the above organic pollutants include any one or more of levofloxacin, sulfamethoxazole, sulfadiazine, tetracycline hydrochloride, and bisphenol A.

[0052] 3. Beneficial effects

[0053] Compared with the prior art, the beneficial effects of the present application are as follows:

[0054] (1) A cobalt-loaded covalent organic framework material provided by the present application includes a carbonized COF skeleton and metallic cobalt. The cobalt is stably dispersed on the carbonized COF skeleton in the forms of zero-valent metal and multivalent states (including Co(II) and Co(III)). The COF forms a porous carbon-based skeleton through carbonization, which has a large specific surface area, uniform pore structure, and good electrical conductivity, can provide abundant reactive sites, form abundant metal-carbon active centers, and significantly improve the catalytic degradation ability of the material to organic pollutants. At the same time, the nitrogen element in the material significantly optimizes the electron transfer performance, and the active sites on the material surface are further increased, which helps to improve the catalytic degradation efficiency. The stable dispersion of metallic cobalt also effectively reduces the problem of metal agglomeration and the loss of active sites.

[0055] (2) A cobalt-loaded covalent organic framework material provided by the present application has the cobalt stably dispersed on the carbonized COF skeleton in the forms of zero-valent metal and multivalent states. Moreover, the metallic cobalt is stably loaded in the carbon skeleton through the bonding action of heteroatoms such as nitrogen and carbon, effectively improving its stability, catalytic activity and durability, reducing the risk of dissolution of metallic cobalt, and reducing the potential environmental pollution hazard.

[0056] (3) The preparation method of the cobalt-loaded covalent organic framework material provided by this application selects cobalt nitrate hexahydrate as the precursor of metallic cobalt, and uses the COF material as the carrier to load cobalt elements. After the COF is carbonized, a porous carbon-based framework is formed, which not only has a high specific surface area and a uniform pore structure, but also the unique porous structure and large π-electron conjugate system of the COF provide an ideal environment for the uniform dispersion of metallic cobalt. In addition, through the coordination of nitrogen atoms in its framework with metallic cobalt, the loading efficiency and stability of cobalt are enhanced. Moreover, through the high-temperature calcination process, a rich defect structure and active sites are formed on the surface of the catalyst. The doped nitrogen elements mainly exist in the forms of pyrrolic nitrogen, pyridinic nitrogen and graphitic nitrogen, forming stable bonds with cobalt and the carbon framework, and at the same time constructing a vacancy structure on the surface of the material, effectively accelerating electron transfer and the generation of free radicals, thereby improving the catalytic performance of the material. Compared with traditional catalysts, this invention enables the catalyst to have higher chemical stability and reaction activity through the co-doping of non-metallic elements and the high-temperature carbonization process. The dispersion uniformity and binding strength of metallic cobalt in the COF matrix are significantly improved, and the existence of defect structures and multivalent cobalt further enhances the activation ability of peroxides and the degradation performance of organic pollutants.

[0057] (4) The application of a cobalt-loaded covalent organic framework material provided by this application shows excellent performance as a catalyst in the system of activating peroxymonosulfate. Compared with catalysts doped with other metals, the metallic cobalt in this catalyst shows higher activation efficiency in the rate-limiting step of the persulfate reaction, becoming an ideal choice for degrading organic pollutants such as antibiotics, especially suitable for the treatment requirements of complex water environments, providing an efficient path for degrading various organic pollutants. Kinetic experiments verify that the catalytic material prepared by this invention has high reusability. The active components cobalt oxide and cobalt nitride are bonded to the surface of the covalent organic framework through chemical bonds and are not easily dissolved and lost during the reaction process; it has a wide pH application range, and the pH value has little impact on the active components that play an important role in the reaction process; it has broad-spectrum removal of antibiotics, and the active component Co 0 has a relatively high redox potential, reflecting the great potential of the catalytic material for activating peroxymonosulfate in practical applications. Degradation degrees of different pollutants within 60 minutes: levofloxacin (LEV, 100%), sulfamethoxazole (SMX, 100%), sulfadiazine (SDZ, 100%), tetracycline hydrochloride (TCH, 100%), bisphenol A (BPA, 100%). When the catalyst of this invention is applied to activate peroxymonosulfate, the main mechanism is through the multivalent state cycle of cobalt elements on the surface of the catalyst, further promoting the continuous activation of PMS (peroxymonosulfate), thereby improving the catalytic efficiency.

[0058] (5) The cobalt-loaded covalent organic framework material provided by this application, its preparation method and application have the advantages of low preparation cost, simple process, easy scale-up production, etc., and can be widely applied to fields such as wastewater treatment, energy storage and environmental purification, providing an efficient and economical solution for sustainable environmental governance. Description of the Drawings

[0059] Figure 1 are the TEM images of COF and Co@COF-5, where: (a) is COF; (b) and (c) are Co@COF-5.

[0060] Figure 2 are the XRD patterns of COF and Co@COF-5.

[0061] Figure 3 are the Raman spectra of COF and Co@COF-5.

[0062] Figure 4 is the full X-ray photoelectron spectroscopy pattern of Co@COF prepared in Examples 1 - 6.

[0063] Figure 5 are the research results of the catalytic performance of the prepared materials, where: (a) is the kinetic curve of the degradation of levofloxacin (LEV) by cobalt-loaded materials with different ratios; (b) is the kinetic curve of Co@COF-4 degrading different pollutants; (c) is the kinetic curve of different systems degrading the pollutant LEV; (d) is the kinetic curve of the degradation of levofloxacin by the Co@COF / PMS system under different anion interferences.

[0064] Figure 6 is the kinetic curve of the degradation of LEV by Co@COF activating PMS at different pyrolysis temperatures during preparation.

[0065] Figure 7 is the kinetic curve of the degradation of LEV by Co@COF activating PMS at different initial pH values.

[0066] Figure 8 are the research results of the reaction mechanism of the Co@COF material degrading pollutants, where: (a) is the kinetic curve of the quenching experiment of Co@COF-5 degrading levofloxacin; (b) is the i-t curve graph of Co@COF-5 and COF; (c) is the electron paramagnetic resonance spectrum of Co@COF-5 when DMPO is used as the scavenger; (d) is the electron paramagnetic resonance spectrum of Co@COF-5 when TEMP is used as the scavenger.

[0067] Figure 9These are the research results on the magnetic properties and recyclability of Co@COF-5, where: (a) is the degradation efficiency of the cyclic degradation of Co@COF-5; (b) is the hysteresis loop of Co@COF-5. Detailed implementation manners

[0068] The present application will be further described below in conjunction with specific embodiments.

[0069] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" etc. cited in this specification are only for the sake of clarity in narration and are not used to limit the scope that can be implemented. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope that the present application can implement.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0071] For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0072] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. Those skilled in the art can easily determine the degree of flexibility of a specific variable.

[0073] As used herein, the term "at least one of..." is intended to be synonymous with "one or more of...". For example, "at least one of A, B, and C" clearly includes only A, only B, only C, and their respective combinations.

[0074] Concentrations, amounts, and other numerical data may be presented herein in a range format. It should be understood that such a range format is used only for convenience and brevity and should be interpreted flexibly as including not only the numerical values explicitly recited as the range limits but also all individual numerical values or sub-ranges subsumed within the stated range as if each numerical value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted as including not only the explicitly recited limit values of 1 to about 4.5 but also the individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that recite only one numerical value, such as "less than about 4.5", which should be interpreted as including all of the above values and ranges. In addition, this interpretation should apply regardless of the breadth of the range or feature described.

[0075] In this application, unless otherwise specified, the PMS used is potassium persulfate (KHSO 5 ).

[0076] In this application, unless otherwise specified, the catalytic performance evaluation experiment includes: First, add 5 mg of catalyst (such as Co@COF) to a 50 mL solution of pollutant (such as LEV) with a concentration of 10 mg / L, stir at 25 ± 1 °C for 30 min to allow the system to reach adsorption equilibrium. Then add 0.5 mM PMS to initiate the catalytic reaction. At 0, 1, 5, 10, 20, 30, and 60 min, take 1 mL of the reaction solution and add an equal amount of methanol to quench the reaction. Subsequently, the mixture is filtered through a 0.22 μm membrane to obtain a sample for analysis. To study the catalytic mechanism more deeply, different quenchers are used to identify the active species in the system. Specifically, potassium iodide (KI) is used to inhibit the electron transfer pathway, methyl phenyl sulfoxide (PMSO) is used to capture high-valent iron-oxy species, furfuryl alcohol (FFA) is used to identify singlet oxygen ( 1 O 2 ), p-benzoquinone (p-BQ) is used to detect superoxide anion (O 2 ·- ), methanol (MeOH) is used to quench ·OH and SO 4 ·- simultaneously, while tert-butanol (TBA) is mainly targeted at ·OH. Through these experiments, the roles of different active species in the catalytic process can be understood more clearly.

[0077] In this application, unless otherwise specified, the cobalt content in Co@COF is determined by inductively coupled plasma mass spectrometry (ICP-MS). The specific operation is to place 50 mg of the catalyst in a crucible, put it in a digestion instrument, and successively add 6 mL of nitric acid (HNO 3 ), 3 mL of hydrogen peroxide (H 2 O 2 ), 2 mL of hydrofluoric acid (HF), and 2 mL of perchloric acid (HClO 4 ) for digestion. After digestion, the sample is first cooled, then diluted and fixed in volume, and then analyzed using ICP-MS. This application also uses an atomic absorption spectrophotometer to measure the leaching concentration of cobalt ions in the system after the catalytic reaction to evaluate the stability of the catalyst. After the catalytic degradation reaction of the Co@COF / PMS / LEV system is completed, 15 mL of the reaction solution is filtered, and then the cobalt ion concentration is detected using an atomic absorption spectrophotometer.

[0078] In this application, unless otherwise specified, the PMS concentration is determined by potassium iodide colorimetry. The specific method is to use 0.05 M sodium bicarbonate (NaHCO 3) Prepare a 0.5 M high-concentration KI solution. Subsequently, measure 4.9 mL of the high-concentration KI solution and mix it thoroughly with 0.1 mL of the reaction solution by shaking. After the reaction is completed, place the mixture in a light-proof environment for 15 min, and then measure its absorbance at a wavelength of 352 nm using a UV-visible spectrophotometer.

[0079] In this application, unless otherwise specified, a high-performance liquid chromatograph (Waters 2695) is used to detect the concentration of pollutants such as levofloxacin (LEV). The instrument is equipped with an E2695 UV detector and an XDB-C18 chromatographic column. During the test, the flow rate is set to 1.0 mL / min, and the injection volume is determined to be 20 μL. The detailed detection conditions are as follows in the table:

[0080]

[0081] In this application, unless otherwise specified, an electrochemical workstation (CHI600E) is used to test the electrochemical impedance spectroscopy and current-time (i-t) curves to evaluate the electron transfer performance of the material. All electrochemical experiments are carried out under a standard three-electrode system, where the reference electrode is an Ag / AgCl electrode, the counter electrode is a platinum electrode, and the working electrode is an FTO electrode. ① Electrochemical impedance spectroscopy (EIS) test: The electrolyte uses a solution containing 2.5 mmol / L potassium ferricyanide and 0.1 mol / L KCl. By applying an AC voltage amplitude of 5 mV, electrochemical impedance spectroscopy data in the frequency range of 0.1 Hz to 100 kHz are measured. ② i-t curve test: Select 100 mL of 50 mM sodium sulfate solution as the electrolyte, set the experimental time to 800 s, and add PMS and LEV at 200 s and 500 s respectively. Through the recorded i-t curves, the electron transfer mechanism in the system is analyzed, especially the direct electron transfer process.

[0082] In this application, the microstructure of the catalyst is observed with a high-resolution transmission electron microscope (FEI Tecnai G2 F20), which can present fine images at the nanoscale. In this application, a microgrid copper mesh is used as the carrier, and ethanol is selected as the dispersant to ensure that the catalyst is evenly distributed on the support grid and avoid aggregation affecting the imaging effect. Through TEM imaging, the morphological characteristics of the covalent organic framework-derived carbon material can be analyzed, and its pore structure and distribution can be observed. At the same time, the cobalt metal nanoparticles loaded on the material surface can be directly seen, and their particle size, morphology, and dispersion can be analyzed. Further through high-resolution imaging, the lattice fringes of the cobalt nanoparticles can be seen, and combined with Fourier transform analysis (FFT) to determine their crystal structure, and then the specific chemical state of cobalt can be inferred.

[0083] In this application, an X-ray diffractometer (Bruker D2 Phaser) was used to analyze the crystal structure of the catalyst, so as to clarify the crystallization characteristics and phase composition of the material. As a commonly used crystal structure characterization technique, Cu target was selected as the X-ray source in this application to perform diffraction scanning on the sample. To fully cover the main diffraction peaks and ensure obtaining complete crystal structure information, the scanning speed was set at 2° / min, and the scanning range was determined to be 5-90°. Further in-depth analysis of the XRD diffraction pattern can further clarify the phase state of the cobalt compound in the catalyst.

[0084] In this application, a laser micro-Raman spectrometer (inVia TM ) was used to analyze the defect condition and graphitization degree of the catalyst. Raman spectroscopy, as an effective technique, is widely used in the study of molecular structure, chemical bonds, and lattice vibrations, and can also be used to detect phase transitions and morphological changes of samples. Its principle relies on Raman scattering. When light interacts with matter, the frequency of the scattered light will change, and this frequency change is closely related to the vibrational energy of the molecule. The Raman spectrum of the sample can be obtained by measuring the frequency shift.

[0085] In this application, an X-ray photoelectron spectrometer (K-Alpha) was used to analyze the elemental composition and valence band structure of the catalyst, aiming to explore its surface chemical state and electronic structure characteristics. The principle of this analysis technique is that the incident X-ray can excite the photoelectrons on the surface of the sample, and the binding energy information of the elements can be obtained by accurately measuring the energy distribution of the photoelectrons. By analyzing the position, shape, and intensity of the photoelectron peaks, the type, relative content, and chemical valence state of the elements contained on the sample surface can be accurately judged, and finally the key information about the surface electronic structure of the catalyst can be obtained. In this application, the XPS spectra of Co, N, and C elements were mainly analyzed to investigate the valence state distribution of Co species, explore the N doping form and its interaction with Co, and the evolution of the electronic structure of the carbon substrate. By comparing the XPS data of the samples at different temperatures, the chemical environment changes of the materials during the pyrolysis process were revealed, and the structure-activity relationship of the catalyst was further analyzed, providing an important basis for optimizing the catalytic performance.

[0086] In this application, a vibrating sample magnetometer (Lake Shore 7074) was used to test the magnetic properties of the catalyst. The vibrating sample magnetometer, as a key instrument for exploring the magnetism of materials, can be used to measure the characteristics of the hysteresis loop, including core parameters such as saturation magnetization and coercivity. This VSM test has specific parameters. The moment measurement range is between 5×10 -7 emu and 10 3 emu, the scanning speed is 1-200 Gauss / s, and the measurement sensitivity at room temperature reaches 5×10 -7emu. By analyzing the hysteresis loop, the magnetic properties of the material are deeply studied, and then the potential of the material in recycling is evaluated.

[0087] In this application, an electron paramagnetic resonance spectrometer (EMXplus-6 / 1) is used to detect the reactive oxygen species generated in the system. When conducting the EPR test, the sample is placed in a constant magnetic field, and microwave radiation is used to promote the unpaired electrons in the sample to jump to a higher energy level, thereby generating a resonance absorption signal. If there are free radicals in the sample, the unpaired electrons will show characteristic signals on the EPR spectrum, and information about the type, quantity, and environment of the free radicals can be obtained from the shape and intensity of the signals. It can be seen that the EPR technology realizes the identification and analysis of free radicals by detecting the unpaired electrons in the free radicals. In this application, the EPR technology is used to detect the singlet oxygen and superoxide anion radicals generated in the Co@COF / PMS system.

[0088] Example 1

[0089] This example provides a preparation method of a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0090] The preparation method of the cobalt-loaded covalent organic framework material includes the following steps:

[0091] S1, Preparation of COF

[0092] 48 mg of terephthalaldehyde and 48 mg of p-phenylenediamine are added to 4 mL of 1,4-dioxane, and ultrasonicated until the monomers are completely dissolved; 0.6 mL of acetic acid is slowly added dropwise; the reaction mixture is allowed to stand at room temperature for 72 h for reaction; after the reaction is completed, the solid product is separated from the solution by suction filtration, and the product is washed three times with acetone and tetrahydrofuran (THF) respectively to remove unreacted monomers and other soluble by-products; the obtained yellow solid is vacuum freeze-dried to remove residual solvents, and a yellow powdery COF material is obtained. Terephthalaldehyde and p-phenylenediamine are both precursor substances for constructing the COF structure; 1,4-dioxane, as a solvent, can effectively dissolve the reactants and also provide a suitable environment for the subsequent cross-linking reaction; acetic acid, as a catalyst, plays a role in promoting the formation of covalent bonds between carbonyl groups and amino groups during the reaction process; standing for 72 h ensures that the precursors are fully polymerized to form a stable covalent organic framework structure; vacuum freeze-drying is used to remove residual solvents;

[0093] S2, Cobalt salt loading

[0094] Disperse 40 mg of the COF prepared in S1 in 40 mL of methanol and ultrasonically treat for 30 min to ensure that the COF is uniformly dispersed in the solution; then add 9.8 mg of cobalt(II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O), and ultrasonically treat again for 30 min to allow the cobalt salt to come into full contact with the COF and form a uniform dispersion system; methanol not only acts as a solvent to play a dispersing role, but also can improve the adsorption efficiency of the precursor on the COF; cobalt(II) nitrate hexahydrate serves as the cobalt precursor; ultrasonically treating again is to ensure that the cobalt salt is uniformly distributed and attached to the surface of the COF to form a uniform cobalt-loaded dispersion system;

[0095] S3, reduction of cobalt ions

[0096] Slowly add 1 mL of 10% NaBH 4 / methanol solution to the dispersion system in S2. NaBH 4 acts as a reducing agent to reduce cobalt ions and load them onto the COF; place the solution on a magnetic stirrer and stir for 2 h to allow the reaction to proceed completely; heat the solution in a water bath to 80 °C to evaporate the water and ensure that the cobalt ions are fully reduced and firmly loaded on the surface of the COF; heating to 80 °C promotes the evaporation of methanol, causing the solid cobalt-loaded sample to precipitate and solidify in the COF matrix;

[0097] S4, calcination

[0098] Place the solid sample obtained after completely evaporating the water in S3 into a tubular furnace. Under a nitrogen (N 2 ) atmosphere, heat it to 750 °C at a heating rate of 5 °C / min, hold for 3 h, and after cooling, obtain a black cobalt-loaded covalent organic framework material with a cobalt mass fraction of 5 wt%, named Co@COF-5; during the holding (calcination) process, the COF undergoes carbonization to form a carbon-based structure rich in micropores. At the same time, cobalt is further stabilized to form metallic cobalt or cobalt oxide or cobalt nitride and combines with the carbonized COF matrix, thereby improving the conductivity and structural stability of the catalyst.

[0099] Example 2

[0100] This example provides a method for preparing a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0101] Referring to Example 1, the difference is that the addition amount of cobalt(II) nitrate hexahydrate is 1.96 mg, and the usage amount of the NaBH 4 / methanol solution is 0.2 mL. The cobalt mass fraction in the obtained cobalt-loaded covalent organic framework material is 1 wt%, named Co@COF-1.

[0102] Example 3

[0103] This example provides a preparation method of a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0104] Referring to Example 1, the difference is that the addition amount of cobalt(II) nitrate hexahydrate is 3.92 mg, and the usage amount of the NaBH 4 / methanol solution is 0.4 mL. The mass fraction of cobalt in the obtained cobalt-loaded covalent organic framework material is 2 wt%, and it is named Co@COF-2.

[0105] Example 4

[0106] This example provides a preparation method of a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0107] Referring to Example 1, the difference is that the addition amount of cobalt(II) nitrate hexahydrate is 5.88 mg, and the usage amount of the NaBH 4 / methanol solution is 0.6 mL. The mass fraction of cobalt in the obtained cobalt-loaded covalent organic framework material is 3 wt%, and it is named Co@COF-3.

[0108] Example 5

[0109] This example provides a preparation method of a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0110] Referring to Example 1, the difference is that the addition amount of cobalt(II) nitrate hexahydrate is 7.84 mg, and the usage amount of the NaBH 4 / methanol solution is 0.8 mL. The mass fraction of cobalt in the obtained cobalt-loaded covalent organic framework material is 4 wt%, and it is named Co@COF-4.

[0111] Example 6

[0112] This example provides a preparation method of a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0113] Referring to Example 1, the difference is that the addition amount of cobalt(II) nitrate hexahydrate is 13.72 mg, and the usage amount of the NaBH 4 / methanol solution is 1.4 mL. The mass fraction of cobalt in the obtained cobalt-loaded covalent organic framework material is 7 wt%, and it is named Co@COF-7.

[0114] Comparative Example 1

[0115] This example provides a preparation method without a cobalt-loaded covalent organic framework material and the cobalt-loaded covalent organic framework material prepared thereby.

[0116] Referring to Example 1, the difference is that cobalt hexahydrate nitrate is not added during the preparation process. Specifically:

[0117] Dissolve 48 mg of benzene-1,3,5-tricarbaldehyde and 48 mg of p-phenylenediamine in 4 mL of 1,4-dioxane. After ultrasonic dissolution until complete, add 0.6 mL of acetic acid as a catalyst and let it react at room temperature for 72 hours; after the reaction is completed, wash the solid product three times each with acetone and tetrahydrofuran, and then vacuum freeze-dry to obtain a yellow powdery COF material;

[0118] Slowly add 1.0 mL of 10% NaBH 4 / methanol solution, stir and react for 2 hours, then heat the solution to 80 °C to evaporate the water to obtain a cobalt-loaded sample;

[0119] Place the obtained cobalt-loaded sample in a tube furnace, under a nitrogen atmosphere, heat it to 750 °C at a rate of 5 °C / min, hold for 3 h, and after cooling, obtain a black covalent organic framework material (COF).

[0120] Example 7

[0121] This example provides a study on the physical and chemical characterization of cobalt-loaded covalent organic framework materials.

[0122] (1) TEM (transmission electron microscope) images

[0123] The TEM images of COF and Co@COF-5 are as Figure 1 shown, where: (a) is COF; (b) and (c) are Co@COF-5.

[0124] As Figure 1 shown in (a) therein, it can be clearly observed from the TEM image of COF that the material exhibits a uniform nano-spherical structure with a smooth surface and no obvious defects, indicating that the synthesis process of the COF material is relatively stable and controllable. In addition, the particle size distribution is also relatively consistent, and no obvious size deviation is seen, which shows that the COF material has good uniformity and reproducibility at the nano level.

[0125] As Figure 1 shown in (b) and (c) therein, it can be more intuitively found from the TEM image of Co@COF-5 the distribution characteristics of nano-clusters of cobalt atoms or cobalt nitrides on the COF substrate. These clusters are concentrated in size from 6 to 7 nm, showing a high degree of uniformity and no agglomeration phenomenon, which to a certain extent proves that cobalt atoms can be loaded on the COF material with good dispersion. And such distribution characteristics not only reflect the relatively tight and effective binding of cobalt to the COF framework, but also indirectly prove the restrictive effect of the framework structure on the cobalt nano-clusters during the synthesis process, and at the same time provide a strong structural basis for the subsequent study of catalytic performance.

[0126] (2) XRD (X-ray diffraction) pattern

[0127] The XRD patterns of COF and Co@COF-5 are as Figure 2 shown, revealing the crystal structure characteristics of the two samples, COF and Co@COF-5.

[0128] First of all, at 2θ = 26.1°, a significant diffraction peak appears in both samples. Through analysis, this peak corresponds to the (001) crystal plane in the COF material and mainly comes from the structural characteristics of π-π interlayer stacking in the conjugated aromatic system. This π-π stacking indicates that the COF material has a highly ordered layered structure, showing excellent molecular arrangement regularity, providing a good basis for the further modification of the material.

[0129] Secondly, in the XRD pattern of Co@COF, the diffraction peak at 26° still exists and retains the main characteristics of the COF material, indicating that the basic crystal structure of COF is well preserved after the introduction of cobalt. In addition, on this basis, new diffraction peaks also appear in the pattern, indicating that the introduction of cobalt has a certain regulatory effect on the crystal structure. Specifically, the newly added characteristic peak near 26° is attributed to the (002) crystal plane of carbon, indicating that the loading of cobalt may promote the rearrangement or modification of some carbon-based materials. In addition, at 2θ = 44.2°, 51.5° and 76.1°, characteristic peaks of cobalt metal are further observed in the pattern, and these peaks correspond to the (101), (200) and (220) crystal planes of cobalt respectively. Their appearance not only proves the successful loading of cobalt metal in the COF material to obtain Co@COF, but also indicates that the loaded cobalt has a clear metal phase structure.

[0130] (3) Raman spectrum

[0131] The Raman spectra of COF and Co@COF-5 are as Figure 3 shown. Raman spectra reveal the structural characteristics of materials through the G band and D band. The G band reflects the vibration of sp 2 hybridized carbon in the material, which is usually related to the degree of graphitization and lattice order. The D band is closely related to lattice defects and structural irregularities, and the intensity and width can reflect the degree of disorder and the number of defects in the material.

[0132] As Figure 3As shown, the Raman spectrum of the COF material only shows a clear G-band signal, indicating that its carbon-based structure is relatively ordered with fewer defects, reflecting the high crystallinity of the COF framework. In the Raman spectrum of Co@COF, the D-band signal is significantly enhanced, and the ID / IG ratio is 1.04, indicating that after cobalt loading, the disorder of the material increases and the structural defects increase. These defects may be caused by the introduction of cobalt and its interaction with the COF framework. The loading of cobalt not only changes the crystal structure of the material but also improves the reaction activity of the material.

[0133] (4) XPS (X-ray photoelectron spectroscopy) full spectrum

[0134] The X-ray photoelectron spectroscopy full spectra of Co@COF prepared in Examples 1 - 6 are as Figure 4 shown, and the characteristic peaks of each element are clearly visible.

[0135] Taking Co@COF-5 prepared in Example 1 as an example:

[0136] Three main carbon functional groups: C═C (284.7 eV), C-N / C-O (285.4 eV), and C═O (289.3 eV). These carbon functional groups account for 43 at%, 50 at%, and 7 at% of the total carbon in the Co@COF material, respectively (see Table 1).

[0137] In the N1s spectrum, five obvious peaks appear at 398.4 eV, 399.6 eV, 400.7 eV, 401.8 eV, and 403.7 eV, corresponding to five different nitrogen functional groups: pyridine nitrogen (398.4 eV), Co-Nx (399.6 eV), pyrrole nitrogen (400.7 eV), graphitic nitrogen (401.8 eV), and nitrogen oxide (403.7 eV). The contents of these nitrogen functional groups in the Co@COF material are 22 at%, 15 at%, 22 at%, 17 at%, and 24 at%, respectively (see Table 1). The diversity of nitrogen functional groups not only helps to improve the electronic conductivity of the material but also enhances the interaction between the material and reactants, promoting the catalytic process.

[0138] According to the Co 2p spectrum, this spectrum can be divided into Co 2p 1 / 2 and Co 2p 3 / 2 two main peaks, and there is a satellite peak at 782 eV. Specific analysis shows that the peak at 778.4 eV corresponds to Co 0 , and the peaks at 779.8 eV and 797.2 eV are attributed to Co 2+ , and these results indicate the chemical state distribution of Co in the catalyst. Table 1 shows the Co 0 and Co 2+Relative content. The XPS results show that Co 0 As an electron donor, it can effectively provide electrons to PMS, promote the activation of PMS, and thus enhance its degradation efficiency.

[0139] Table 1 Proportion of Co, N, and C elements in Co@COF-5 forming active components in the element

[0140]

[0141]

[0142] Example 8

[0143] This example provides a study on the catalytic performance of cobalt-loaded covalent organic framework materials.

[0144] In this example, unless otherwise specified, the system is 50 mL, the concentration of the catalyst is 0.1 g / L, the concentration of PMS is 0.5 mM, the concentration of each pollutant (such as LEV) is 10 mg / L, the pH is 5.00, and the temperature is 25 °C.

[0145] (1) Effect of different cobalt loadings on catalytic performance

[0146] The results of the effect of different cobalt loadings on catalytic performance are as shown in Figure 5 (a) below, Figure 5 (a) below is the kinetic curve of the degradation of levofloxacin (LEV) by covalent organic framework materials with different cobalt loadings.

[0147] The apparent rate constant K under different cobalt loadings was calculated according to the pseudo-first-order reaction kinetics. As the cobalt loading ratio gradually increased from 1 wt% to 5 wt%, the reaction rate also increased, from 0.016 min -1 to 0.025 min -1 and reached 0.214 min at 5 wt% -1 . However, when the cobalt loading ratio continued to increase to 7 wt%, the reaction rate tended to stabilize at 0.215 min -1 . This may be due to the dilution effect of the catalytic active sites caused by too high a metal loading. Especially at higher cobalt contents, the metal nanoparticles may agglomerate, reducing the effective active sites of the catalyst and thus limiting the further increase in the catalytic reaction rate.

[0148] (2) Effect of different calcination temperatures on catalytic performance

[0149] Referring to Example 1, the difference is that the calcination in step S4 is 650, 700, 750 (i.e., Example 1), 800, and 850 °C respectively to prepare cobalt-loaded covalent organic framework materials.

[0150] Under different calcination temperatures, the degradation kinetic curves of LEV by Co@COF-activated PMS are as Figure 6 shown. When the calcination temperature is 750 °C, the synthesized Co@COF exhibits the best catalytic activity during the activation of PMS. Within 60 min, the degradation rate of LEV by Co@COF750 reaches 100%, and the degradation rate constant is 0.214 min -1 , which is higher than that of Co@COF650 (0.029 min -1 ), Co@COF700 (0.064 min -1 ), Co@COF800 (0.16 min -1 ), and Co@COF850 (0.188 min -1 ). This indicates that the Co@COF synthesized by calcination at 750 °C is significantly superior in catalytic performance to the catalysts synthesized at other temperatures. When the pyrolysis temperature increases from 650 °C to 750 °C, the degradation efficiency of the catalyst for LEV increases significantly. However, when the temperature continues to rise to 850 °C, the degradation efficiency does not continue to increase but instead decreases slightly. This is consistent with the XPS analysis results. At 750 °C, the content of Co(0) in Co@COF reaches the highest (19.6%). As an electron donor, Co(0) can effectively provide electrons to PMS, promote the activation of PMS, and generate free radicals, thereby accelerating the degradation of LEV. In addition, the contents of C-N / C-O and nitrogen oxides in the catalyst also reach the maximum at 750 °C. These functional groups contribute to electron transfer, further enhancing the activation efficiency of PMS and thus increasing the catalytic reaction rate.

[0151] (3) Degradation of different pollutants by cobalt-loaded covalent organic framework materials

[0152] In this example, the cobalt-loaded covalent organic framework material is Co@COF-4 prepared in Example 4.

[0153] In this example, the pollutants include: levofloxacin (LEV), tetracycline hydrochloride (TCH, an antibiotic), bisphenol A (BPA, an endocrine disruptor), sulfadiazine (SD), and sulfamethoxazole (SMX), all of which are persistent organic pollutants commonly present in the environment and have a concentration of 10 mg / L.

[0154] The kinetic curves of Co@COF-4 for degrading different pollutants are as Figure 5As shown in (b), Co@COF-4 showed significant effects in the catalytic degradation of these compounds. Experimental data indicated that the system composed of Co@COF-4 and PMS could completely decompose TCH, BPA, SD, and SMX within 60 minutes, and their corresponding degradation rates were 0.45 min -1 、0.122 min -1 、0.054 min -1 and 0.043 min -1 . These findings confirmed that Co@COF not only had high activation efficiency but also had wide applicability in dealing with diverse refractory organic pollutants.

[0155] (4) Study on the catalytic performance of different systems (materials) for the refractory pollutant LEV

[0156] In this embodiment, the materials included: Co@COF-5; COF; Co 3 O 4 , and the systems were Co@COF / PMS, COF / PMS, Co3O4 / PMS, and pure PMS respectively.

[0157] The kinetic curves of different systems (materials) for degrading the pollutant LEV are as shown in Figure 5 (c). The degradation effects of the COF / PMS and pure PMS systems were poor, and the degradation efficiency of LEV was only 14%, indicating that the activation ability of PMS was very limited without cobalt loading. For the Co 3 O 4 / PMS system, although a 94% degradation effect could be achieved within 60 min, its reaction rate constant was only 0.033 min -1 , which was much lower than that of Co@COF (K obs = 0.214 min -1 ). In addition, there was a relatively high metal leaching problem in the cobalt tetroxide system during the catalytic process, reducing its long-term stability and environmental friendliness. In contrast, the Co@COF / PMS system was significantly superior to other systems in terms of catalytic effect, achieving 100% degradation of LEV within 20 minutes and having a low metal leaching rate, meeting the national environmental standards.

[0158] (5) Influence of common anions on the performance of the Co@COF / PMS system for degrading LEV

[0159] In this embodiment, the common anions included: SO 4 2- 、HCO 3 - 、H 2 PO 4 - 、Cl- and NO 3 - , and their ion concentrations are all 5mM.

[0160] The kinetic curves of levofloxacin degradation by Co@COF / PMS system under different anion interferences are shown in Figure 5 As shown in (d), the results show that SO 4 2- , H 2 PO 4 - , Cl - and NO 3 - All of them have a certain degree of inhibitory effect on LEV degradation, mainly because they compete with pollutants for active substances or directly consume key active species in the reaction.

[0161] NO 3 - The inhibition of degradation is weak, which may be due to the SO generated in the consumption system. 4 ·- However, even so, 90% of LEV can still be degraded within 60 min, and the inhibitory effect is not significant. 2 PO 4 - Then it is possible to 4 ·- The reaction generates less active H 2 PO 4 · , or by reacting with ·OH to generate water, resulting in a slight decrease in degradation efficiency. - The inhibitory effect of SO 4 ·- Cl generated by reaction with OH · and Cl 2 ·- The activity is low and it fails to participate significantly in the degradation process. 4 2- The inhibitory effect of HCO is more obvious, which may be due to its high electronegativity, which leads to the formation of an adsorption layer on the catalyst surface, thereby shielding some active sites and hindering the electron transfer process. 3 - It has a certain promoting effect on the degradation reaction, and the degradation rate constant is 0.216min -1 This promoting effect may be attributed to HCO 3 - The bicarbonate free radical (HCO 3 · ) has a certain oxidation ability and can synergistically participate in the degradation process of pollutants.

[0162] Overall, the influence of these common anions on the degradation kinetics of the Co@COF / PMS / LEV system is relatively limited, indicating that this catalytic system has strong anti-interference ability and still has practical application potential in complex water environments.

[0163] (6) Influence of the initial pH of the degradation system on the performance of LEV degradation

[0164] The performance of the Co@COF / PMS system in the degradation kinetics of LEV was investigated under the conditions of initial pH values of 3, 5, 7, 9, and 10. The results are as Figure 8 shown.

[0165] The results show that this system exhibits excellent catalytic activity in the pH range from 3 to 10. This is mainly due to the chemical stability of the catalyst, which enables it to efficiently activate PMS under acidic, neutral, and weakly alkaline conditions, generate reactive species, and achieve effective degradation of pollutants. The degradation rate of the system reaches the maximum at pH = 5. This may be because under these conditions, the charge state of the active sites on the catalyst surface and the adsorption characteristics of the pollutants are more matched, thus strengthening the interaction between the two and improving the catalytic efficiency.

[0166] Example 9

[0167] This example provides a study on the reaction mechanism of Co@COF for degrading pollutants.

[0168] In this example, through capture experiments, EPR experiments, and electrochemical tests, the mechanism of Co@COF in activating peroxymonosulfate (PMS) and promoting pollutant degradation was revealed.

[0169] The quenching experiment kinetic curve of Co@COF-5 for degrading levofloxacin is as Figure 8 shown in (a) below, showing the changes in the pollutant degradation rate in the presence of different active substance inhibitors (MeOH, p-BQ, KI, PMSO, TBA, FFA). The control group without adding inhibitors showed the fastest degradation rate. After adding p-BQ and FFA, the degradation rate decreased significantly, indicating that superoxide radicals (O 2 -· ·) and singlet oxygen ( 1 O 2 ·) are the main active species in the degradation reaction, while the roles of hydroxyl radicals (·OH) and sulfate radicals (SO 4 - 4·) are relatively small. Therefore, it can be inferred that the Co@COF catalytic system mainly degrades pollutants through O 2 - · and 1 O 2to drive pollutant degradation. However, introducing excessive p-BQ and FFA as scavengers of O 2 - · and 1 O 2 in the catalytic oxidation system did not completely inhibit the degradation of LEV. Therefore, potassium iodide (KI) was selected as a quencher to detect the electron transfer pathway. Importantly, the addition of KI had a significant inhibitory effect on this catalytic oxidation system. Experiments showed that within 60 minutes, the degradation rate of LEV was only 27%. Therefore, in the Co@COF / PMS system, the degradation of LEV was mainly affected by the electron transfer pathway.

[0170] The direct transfer pathway of LEV degradation was further studied by i-t experiments. The i-t curves of Co@COF-5 and COF are shown in Figure 8 (b) therein. The i-t curve shows the change in current density after introducing PMS, indicating that electron transfer occurred between PMS and the catalyst. After adding LEV, a significant change in current density was found. The COF material hardly produced a change in current density, while the current density generated by Co@COF-5 was much higher than that of COF. The results showed that Co@COF could accelerate the electron transfer in the system, which was also consistent with the EIS research results in Figure 8 (c) and (d) therein, Figure 8 (c) therein is the electron paramagnetic resonance spectrum of Co@COF-5 when DMPO (5,5-dimethyl-1-pyrroline-N-oxide) is used as a capturer; Figure 8 (d) therein is the electron paramagnetic resonance spectrum of Co@COF-5 when TEMP (2,2,6,6-tetramethylpiperidine-N-oxide) is used as a capturer.

[0171] Example 10

[0172] This example provides a study on the magnetic properties and recycling performance of Co@COF-5.

[0173] The hysteresis loop of Co@COF-5 is shown in Figure 9 (b) therein, demonstrating its magnetic properties. The loop shows the behavior of a typical ferromagnetic material, and the material has a certain hysteresis phenomenon, indicating that it can be recycled by an external magnetic field. The magnetization intensity reaches saturation, proving that the Co@COF material has good magnetic recycling performance. This means that in practical applications, the catalyst can be easily recycled by magnetic separation technology after use, further improving the practicality and environmental friendliness of the material.

[0174] The degradation efficiency of Co@COF-5 for cyclic degradation of LEV is shown in Figure 9As shown in (a). In each cycle, the degradation efficiency of the material for the target pollutant remained close to 100%, indicating that Co@COF-5 could still maintain high catalytic activity after multiple cycles of use. There was almost no significant decrease in the degradation efficiency, proving that the material had good stability. The broken line in the figure represents the leaching rate of cobalt, and the leaching rate remained at a low level, below about 3%. This indicates that very little cobalt was lost during the use of the Co@COF material, and it had good structural stability, being able to maintain high catalytic performance for a long time without significant failure due to the loss of cobalt.

[0175] The above has schematically described the present invention and its embodiments. This description is not restrictive, and what is shown in the drawings is only one of the embodiments of the present invention. The actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural forms and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A cobalt-loaded covalent organic framework material, characterized in that: The material comprises a carbonized COF skeleton and nano-cobalt, wherein the nano-cobalt is dispersed on the carbonized COF skeleton in the form of zero-valent metal and multivalent state.

2. The cobalt-loaded covalent organic framework material according to claim 1, characterized in that: The multivalent states include Co(II) and Co(III).

3. The cobalt-loaded covalent organic framework material according to claim 2, characterized in that: The particle size of the nano-cobalt is mainly distributed in the range of 5 to 10 nm.

4. The cobalt-loaded covalent organic framework material according to any one of claims 1 to 3, characterized in that: The mass fraction of cobalt in the cobalt-loaded covalent organic framework material is 1 wt% to 7 wt%.

5. The cobalt-loaded covalent organic framework material according to claim 4, characterized in that: In the cobalt-supported covalent organic framework material, nitrogen includes pyrrolic nitrogen, pyridinic nitrogen and graphitic nitrogen.

6. A method for preparing a cobalt-loaded covalent organic framework material, characterized in that: The method comprises the following steps: S1, preparation of COF: trimesaldehyde and p-phenylenediamine are used as precursors, dissolved in 1,4-dioxane to form a uniform reaction system, acetic acid is added as a catalyst, and after the reaction is completed, the mixture is freeze-dried in vacuum to generate COF; S2, cobalt salt loading: COF was dispersed in methanol solution and cobalt nitrate hexahydrate was added to form a uniform dispersion system; S3, cobalt ion reduction: slowly add sodium borohydride methanol solution to the dispersed system, stir and heat to cause the cobalt ions to undergo reduction reaction; S4, calcination: placing the solid sample obtained in S3 in a tubular furnace, heating to 600-850° C. for calcination under a nitrogen atmosphere, keeping the temperature for 2-4 hours, and obtaining a cobalt-loaded covalent organic framework material after cooling.

7. The method for preparing a cobalt-loaded covalent organic framework material according to claim 6, characterized in that: In step S1, the reaction comprises standing for 60 to 84 hours; and / or In the step S2, dispersing in the methanol solution includes ultrasonic treatment for 20 to 40 minutes; and / or adding cobalt nitrate hexahydrate also includes ultrasonic treatment for 20 to 40 minutes; and / or In step S3, the stirring time is 1.5 to 3 hours; and / or the heating temperature is 70 to 90° C.; and / or In the step S4, the heating rate is 4-6°C / min; and the calcination temperature is 700-850°C.

8. The method for preparing a cobalt-loaded covalent organic framework material according to claim 6 or 7, characterized in that: In the step S1, the mass ratio of trimesaldehyde to p-phenylenediamine is 1:

1.

9. Use of the cobalt-loaded covalent organic framework material according to any one of claims 1 to 4 in activating peroxymonosulfate to degrade organic pollutants.

10. The use according to claim 10, characterized in that: The organic pollutants include any one or more of levofloxacin, sulfamethoxazole, sulfadiazine, tetracycline hydrochloride and bisphenol A.

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