Preparation method and application of spinel-covalent organic framework composite material

Abstract

The application discloses a preparation method and application of a spinel-covalent organic framework composite material. The spinel-covalent organic framework composite material is obtained by introducing the spinel in a reaction process of synthesizing the COFs by a solvent thermal method. The composite material obtained by the application takes the spinel as a cocatalyst, provides active sites for a photocatalytic reaction, and combines the good visible light response capability of the COFs, promotes the separation and transportation of photo-generated carriers through the strong interface effect of the spinel and the COFs, and thus improves the activity of the photocatalytic reaction.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, specifically relating to the preparation of a spinel-covalent organic framework (COF) composite material and its application in the field of photocatalysis. Background Technology

[0002] Energy crisis and environmental pollution are two major challenges facing humanity in the 21st century. Hydrogen energy, as a renewable and clean energy source, is an important industrial raw material and energy carrier, possessing advantages such as high energy density, environmental friendliness, and zero carbon emissions, making it an ideal choice for future sustainable energy development. Photocatalytic hydrogen production driven by solar energy is considered one of the most promising technologies for converting solar energy into green hydrogen. Although many semiconductor materials are used as photocatalysts, most photocatalytic systems have low utilization rates of visible light, low photogenerated carrier separation efficiency, and slow photogenerated electron transfer rates. Therefore, designing efficient and stable photocatalytic materials is currently a major challenge.

[0003] Covalently linked organic materials (COFs) are a class of crystalline porous organic materials developed in recent years. They consist of organic building blocks connected by covalent bonds and possess advantages such as broad visible light absorption, strong tunability of band structure, large specific surface area, open pore channels, and diverse monomer selectivity. These advantages make COFs highly promising for photocatalytic hydrogen desorption from water. However, most COFs are prepared via Schiff base reactions, and the resulting imines, hydrazones, and other organic linking units have high polarity, which is detrimental to the separation and migration of photogenerated carriers within the COFs. Furthermore, most COFs lack metal centers and typically require metal-containing cocatalysts to improve photocatalytic efficiency. Although cocatalysts are inherently inactive, they can provide active sites for proton-to-hydrogen conversion. The migration of photogenerated electrons from COFs to the cocatalyst inhibits the recombination of photogenerated electrons and holes, thereby inducing the photocatalytic reaction. Currently, many photocatalytic systems use noble metals such as platinum, gold, ruthenium, and palladium as cocatalysts, but their high cost and resource scarcity greatly limit their practical application. Therefore, selecting a suitable co-catalyst as a substitute for the noble metal co-catalyst to achieve rapid transfer of photogenerated electrons from COFs to the active site of the co-catalyst is a necessary condition for improving photocatalytic efficiency.

[0004] Spinel materials have attracted widespread attention in the field of photocatalysis due to their high stability, excellent photoelectric properties, low cost, and abundant resources. Zhao et al. (X. Zhao, D. Han, M. Dai, Y. Fan, Z. Wang, D. Han, L. Niu, Direct Z-scheme FeV2O4 / g-C3N4 binary catalyst for highly selective reduction of carbon dioxide, Chem. Eng. J., 2022, 436, 132051.) reported a spinel-based heterojunction composite photocatalyst, FeV2O4 / g-C3N4, which exhibited high selectivity for CO in the photocatalytic CO2 reduction reaction, with CO and CH4 production rates of 9.58 and 0.715 μmol g, respectively. -1 h -1 Subsequently, Wang et al. (R.Wang, W.Yu, N.Fang, P.Wang, Y.Chu, S.Wu, J.Liang, Constructing fast charge separation of ZnIn2S4@CuCo2S4 pn heterojunction for efficient photocatalytic hydrogen energy recovery from quinolone antibiotic wastewater, Appl. Catal. B-Environ. 341(2024)123284.) reported that the ZnIn2S4@CuCo2S4 heterojunction photocatalyst achieved an optimal hydrogen evolution rate of 0.36 mmol g in ofloxacin solution. -1 h -1 Although these spinel-based composite materials can improve photocatalytic activity, they cannot effectively promote the separation and transfer of photogenerated carriers, which greatly limits their photocatalytic performance. Designing and synthesizing novel photocatalytic materials is key to achieving efficient photocatalytic hydrogen evolution. COFs and transition metal oxides have good compatibility; the built-in electric field generated at their interface enables photogenerated carriers to rapidly transfer from COFs to the active sites of transition metal oxides, accelerating the separation of photogenerated electrons and holes. Spinel, as a typical bimetallic oxide, exhibits superior conductivity and electrochemical performance compared to monometallic oxides, and is expected to replace the noble metal platinum as a cocatalyst for COFs. Currently, there are no reports on the formation of composite materials between spinel and COFs using spinel as a cocatalyst. Therefore, developing spinel-COF composite materials with high stability, simple preparation, and low cost is crucial for expanding photocatalytic applications. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of current photocatalytic reactions by providing a method for preparing a spinel-covalent organic framework composite material and applying it to photocatalytic reactions such as hydrogen evolution. This method introduces spinel into the solvothermal synthesis of COFs, resulting in a spinel-covalent organic framework composite material. The composite material obtained by this invention uses spinel as a cocatalyst, providing active sites for the photocatalytic reaction. Combined with the excellent visible light response of COFs, their strong interfacial effects promote the separation and transport of photogenerated carriers, thereby improving the activity of the photocatalytic reaction.

[0006] The technical solution of this invention is as follows:

[0007] A method for preparing a spinel-covalent organic framework composite material, the method comprising the following steps:

[0008] (1) Add spinel, COF precursor, first organic solvent and inorganic acid aqueous solution to reaction tube, sonicate the resulting mixture for 10-60 minutes, remove air and seal, and react under vacuum at 100-200℃ for 3-7 days; wash the generated solid powder 3-6 times and vacuum dry at 60-120℃ to obtain the crude spinel-covalent organic framework composite material;

[0009] The mass ratio of spinel to COF precursor is 1:1 to 50; 1 to 20 mL of the first organic solvent is added for every 1 mmol of COF precursor; and the volume ratio of inorganic acid to the first organic solvent is 1:3 to 10.

[0010] (2) The crude spinel-covalent organic framework composite material obtained in step (1) is added to the second organic solvent and extracted by Soxhlet at 60-110℃ for 1-3 days. The obtained solid powder is collected and vacuum dried at 60-120℃ to obtain the purified spinel-covalent organic framework composite material.

[0011] For every 150 mg of composite material, 100–400 mL of a second organic solvent is added.

[0012] The COF precursors mentioned in step (1) are classified according to their functional groups, including aromatic aldehydes, aromatic amines, aromatic hydrazides, aromatic anhydrides, or aromatic nitrile compounds. Among them, aromatic aldehyde compounds are 2,4,6-tricarboxymethyl-resorcinol, 1,3,5-tricarboxyphenyl, 2,2'-bipyridine-5,5'-dicarboxaldehyde, or 1,3,6,8-tetra(4-formylphenyl)pyrene; aromatic amine compounds are 2,5-dimethyl-p-phenylenediamine, 1,4-phenylenediamine, 2,5-dichloro-1,4-phenylenediamine, 1,3,5-tris[4-amino(1,1-biphenyl-4-yl)]benzene, tetra(4-aminophenyl)porphyrin, or 1,3,5-tris(4-aminophenyl)benzene; aromatic hydrazides are 2,5-dimethoxy-p-phthalylhydrazine, 2,5-diethoxy-p-phenylenediamine, etc. Benzyl hydrazide, dihydrazide p-benzoic acid, or p-aminobenzoyl hydrazide; aromatic anhydrides include 1,4,5,8-naphthoic acid anhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, pyromellitic acid dianhydride, or triphenylhexacarboxylic acid trihydride; aromatic nitrile compounds include 1,4-dicyanobenzene, 2,2'-([1,1'-biphenyl]-4,4'-diyl)acetonitrile, 2,2'-([1,1':4',1”-terphenyl]-4,4”-diyl)acetonitrile, 2,2'-([2,2'-bipyridine]-5,5'-diyl)acetonitrile, or 2,4,6-trimethylbenzene-1,3,5-tricarboxynitrile.

[0013] The spinel mentioned in step (1) is a normal spinel structure or an anti-spinel structure; the normal spinel structure specifically includes CuCo2O4, NiCo2O4 or FeCo2O4; the anti-spinel structure specifically includes TiMg2O4, CoFe2O4 or NiFe2O4.

[0014] The first organic solvent mentioned in step (1) is any one or more of mesitylene, 1,4-dioxane, o-dichlorobenzene, n-butanol, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and N-methylpyrrolidone; the second organic solvent mentioned in step (2) is any one or more of acetone, methanol, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, or dioxane.

[0015] The inorganic acid aqueous solution mentioned in step (1) is hydrochloric acid, acetic acid, and nitric acid, with a concentration of 1–10 mol / L. -1 .

[0016] The spinel-covalent organic framework composite material obtained by the method can be applied to photocatalytic reactions, such as photocatalytic hydrogen evolution reaction, photocatalytic carbon dioxide reduction reaction, or photocatalytic oxygen evolution reaction.

[0017] The steps are as follows: Weigh the spinel-covalent organic framework composite material and sacrificial reagent into a reaction flask, add deionized water to the above system, and irradiate with visible light for 1 to 10 hours under an inert gas or reaction atmosphere.

[0018] The mass ratio of spinel-covalent organic framework composite material to sacrificial reagent is 1:5 to 50; 1 to 20 mg of spinel-covalent organic framework composite material is added to every 10 mL of deionized water.

[0019] The visible light mentioned refers to light emitted by sunlight, xenon lamps, mercury lamps, halogen lamps, or neon lamps;

[0020] The sacrificial agent is any one of L-ascorbic acid, sodium ascorbate, triethylamine, triethanolamine, ethanol, lactic acid, and methanol;

[0021] The inert gas mentioned refers to nitrogen or argon, and the corresponding reaction in an inert atmosphere is photocatalytic hydrogen evolution reaction or photocatalytic oxygen evolution reaction; the reaction atmosphere mentioned is carbon dioxide, and the corresponding reaction is photocatalytic carbon dioxide reduction reaction.

[0022] The essential features of this invention are:

[0023] Most current spinel-based composite materials are composed of different inorganic materials.

[0024] This invention prepares a spinel-covalent organic framework composite material via a solvothermal method while maintaining the crystal structure of COFs. The unique electronic configuration and strong electron enrichment capacity of the divalent metal in this composite material enable photogenerated electrons to rapidly transfer from COFs to the active sites of spinel through interfacial interactions. The large specific surface area of ​​COFs facilitates the exposure of catalytic active sites, promoting contact between the reaction substrate and the active sites. Furthermore, the good compatibility between COFs and spinel allows for the generation of an internal electric field in their interfacial space, thereby reducing the activation energy for electron transfer. Spinel materials are characterized by low cost and good stability; compared to single-metal divalent metal oxides, spinel materials exhibit superior electrical conductivity and electrochemical properties. The composite of COFs and spinel integrates their advantages in incident light absorption efficiency, photoinduced carrier migration, and abundant catalytic active sites, thus synergistically achieving high photocatalytic activity in the hydrogen evolution reaction. Its photocatalytic hydrogen evolution activity is superior to most currently reported photocatalytic systems and can serve as a substitute for noble metal cocatalysts.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) This invention provides a method for preparing spinel-covalent organic framework composite materials. The well-defined structure of spinel and COFs provides an ideal platform for understanding the relationship between the structure and photocatalytic performance of composite materials.

[0027] (2) The spinel-covalent organic framework composite material provided by this invention exhibits a hydrogen evolution rate as high as 8113 μmol g / L under visible light irradiation. -1 h -1 Compared with standalone COF analogs (0.95 μmol g) -1 h -1 The hydrogen evolution performance of the composite material was improved by 8540 times, which also exceeded the hydrogen evolution rate of the Pt-loaded counterpart (5561 μmol g). -1 h -1 Its co-catalyst can be used as a substitute for the precious metal platinum.

[0028] (3) The spinel-covalent organic framework composite material provided by the present invention has photochemical stability and cycle stability. After five consecutive photocatalytic hydrogen evolution experiments for a total of 25 hours, no loss of activity or structural change was detected. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the preparation of the CuCo2O4 / TpPa-COF composite material formed by spinel CuCo2O4 and TpPa-COF in Example 1.

[0030] Figure 2 This is a scanning electron microscope image of the CuCo2O4 / TpPa-COF composite material formed by spinel CuCo2O4 and TpPa-COF in Example 1;

[0031] Figure 3 The hydrogen evolution rate graphs are for TpPa-COF in Comparative Example 1 and CuCo2O4, CuCo2O4 / TpPa-COF composite material and Pt / TpPa-COF in Example 1.

[0032] Figure 4 The image shows the cyclic test results of the CuCo2O4 / TpPa-COF composite material in Example 1.

[0033] Figure 5 The UV-Vis diffuse reflectance spectra of TpPa-COF in Comparative Example 1 and CuCo2O4 / TpPa-COF composite material in Example 1 are shown.

[0034] Figure 6 Electrochemical impedance spectroscopy of TpPa-COF in Comparative Example 1 and CuCo2O4 / TpPa-COF composite material in Example 1. Detailed Implementation

[0035] To further illustrate the method of the present invention, specific embodiments are described below with reference to the accompanying drawings. The following embodiments are merely specific preparation methods of the present invention and do not limit the scope of the invention.

[0036] Comparative Example 1

[0037] 2,4,6-Tricarboxymethyl phloroglucinol (63 mg, 0.3 mmol), 2,5-dimethyl-p-phenylenediamine (61.3 mg, 0.45 mmol), mesitylene (1.5 mL), dioxane (1.5 mL), and an aqueous solution of acetic acid (0.5 mL, 3 M) were added to a Schlenk tube and sonicated for 10 minutes to ensure uniform dispersion. The air in the tube was then removed by a three-cycle "freeze-vacuum-thaw" process using liquid nitrogen. The Schlenk tube was sealed and heated at 120 °C for 3 days. The solid powder was collected by filtration and washed several times with tetrahydrofuran. It was then vacuum-dried at 60 °C for 12 h to obtain a separate COF analogue, namely TpPa-COF.

[0038] Example 1

[0039] Cu(NO3)2·3H2O (0.483 g, 2.0 mmol), Co(NO3)2·6H2O (1.164 g, 4.0 mmol), and urea (1.08 g, 18 mmol) were added to 60 mL of deionized water and stirred at room temperature for 20 minutes. The solution was then transferred to a reaction vessel and placed in a temperature-programmed oven. The temperature was increased to 120 °C at a rate of 3 °C / min and held for 6 hours. The mixture was then allowed to cool naturally to room temperature. The solution was filtered and washed 3–6 times with water / ethanol. After drying at 80 °C for 12 hours, the precursor was obtained. The precursor was placed in a crucible and placed in a muffle furnace. The temperature was increased to 300 °C at a rate of 5 °C / min and held for 3 hours. Finally, the mixture was allowed to cool naturally to room temperature. The resulting black powder was CuCo2O4. (X.Chen,S.Cai,E.Yu,J.Li,J.Chen,H.Jia,Photothermocatalytic performance of ACo2O4 type spinel with light-enhancedmobilizable active oxygen species for toluene oxidation,Appl.Surf.Sci.484(2019)479-488.)

[0040] 2,4,6-tricarboxymethyl phloroglucinol (63 mg, 0.3 mmol), 2,5-dimethyl-p-phenylenediamine (61.3 mg, 0.45 mmol), CuCo₂O₄ (5 mg, 0.02 mmol), mesitylene (1.5 mL), and 1,4-dioxane (1.5 mL) were added to a Schlenk tube and sonicated for 60 minutes. Then, acetic acid aqueous solution (0.5 mL, 3 M) was added, and the mixture was sonicated for 10 minutes to ensure uniform dispersion. The air in the tube was then removed by three cycles of "freezing-vacuuming-thawing" with liquid nitrogen. The Schlenk tube was sealed and heated at 120 °C for 3 days. The solid powder was collected by filtration and washed several times with tetrahydrofuran. Finally, it was vacuum dried at 60 °C for 12 h to obtain the spinel-β-ketoenamine COFs composite material, namely CuCo₂O₄ / TpPa-COF.

[0041] The freezing temperature is -196℃, the vacuum pressure is -0.1MPa, the thawing temperature is 25℃, and the freezing, vacuuming, and thawing times are all two minutes.

[0042] The obtained spinel-β-ketoenamine COFs composite material (200 mg) was added to tetrahydrofuran (150 mL), and after Soxhlet extraction for 2 days, the obtained solid powder was vacuum dried to obtain the purified spinel-β-ketoenamine COFs composite material.

[0043] Figure 1 The diagram below illustrates the preparation of the spinel-β-ketoenamine COFs composite material in Example 1 of this invention. CuCo2O4 is added to the synthesis system of β-ketoenamine COFs, such as COFs (TpPa-COFs) obtained by the condensation reaction of 2,4,6-tricarboxymethyl-resorcinol and 2,5-dimethyl-p-phenylenediamine, to obtain the spinel-β-ketoenamine COFs composite material CuCo2O4 / TpPa-COF.

[0044] Figure 2 The image shows a scanning electron microscope (SEM) image of the CuCo2O4 / TpPa-COF composite material in Example 1 of this invention. The SEM image was tested on a TESCAN MIRALMS. The image reveals that CuCo2O4 / TpPa-COF has a rough-surfaced nanosheet structure. This sheet-like structure enhances the interfacial effect, promotes the separation and transport of photogenerated carriers, and thus improves the activity of the photocatalytic reaction.

[0045] Figure 3In this invention, the hydrogen evolution rates of TpPa-COF in Comparative Example 1 and CuCo2O4, CuCo2O4 / TpPa-COF composite material, and Pt / TpPa-COF in Example 1 were measured on a GC9790 PIUS instrument equipped with a TCD detector. The composite material (10 mg), L-ascorbic acid (100 mg), and deionized water (10 mL) were added sequentially to the reaction flask. The mixture was irradiated at room temperature under nitrogen and a xenon lamp MC-PF300C (Beijing Merry Change) (wavelength ≥ 420 nm) at a distance of approximately 12 cm. Samples were taken every hour for qualitative and quantitative analysis of the generated gas. Under the same conditions, the hydrogen evolution rate of the pure TpPa-COF sample obtained in Comparative Example 1 was 0.95 μmol g / L. -1 h -1 The hydrogen evolution rate of the pure CuCo2O4 sample was 0.23 μmol g. -1 h -1 ,Pt / TpPa-COF(Y.Li,L.Yang,H.He,L.Sun,H.Wang,X.Fang,Y.Zhao,D.Zheng,Y.Qi,Z.Li,W.Deng,In situ photodeposition of platinum clusters on a covalent organicframework for photocatalytic hydrogen production,Nature The hydrogen evolution rate of Chem.13(2022)1355.) is 5561 μmol g -1 h -1 The hydrogen evolution rate of CuCo2O4 / TpPa-COF is as high as 8113 μmol g. -1 h -1 .

[0046] Figure 4 In Example 1 of this invention, the cyclic test of the CuCo2O4 / TpPa-COF composite material was conducted on a GC9790 PIUS instrument equipped with a TCD detector. The figures show that the composite material exhibits excellent durability and photochemical stability; after five consecutive photocatalytic hydrogen evolution experiments totaling 25 hours, no loss of activity or structural change was detected.

[0047] Figure 5In this invention, the UV-Vis diffuse reflectance spectra of the TpPa-COF composite material in Comparative Example 1 and the CuCo2O4 / TpPa-COF composite material in Example 1 were measured on a UV-26001 (Shimadzu, China) instrument with BaSO4 as a reference. As can be seen from the figures, both Comparative Example 1 and Example 1 exhibit strong visible light response, indicating that the response to visible light is mainly contributed by the COFs, with the spinel merely acting as a co-catalyst. Comparative Example 1, however, has relatively lower performance due to the lack of a co-catalyst, resulting in slower separation and transport of photogenerated carriers.

[0048] Figure 6 The electrochemical impedance spectroscopy (EIS) diagrams of the TpPa-COF in Comparative Example 1 and the CuCo2O4 / TpPa-COF composite material in Example 1 are shown in the figure. The separation and transport of photogenerated carriers are crucial to the photoelectric properties of materials. The size of the semicircle radius in the EIS diagram indicates the magnitude of the electron transport impedance; a smaller semicircle radius indicates a smaller electron transport impedance, which is more conducive to the separation and transport of photogenerated carriers. Since the spinel-β-ketoenamine COFs composite material exhibits a smaller semicircle radius compared to pure TpPa-COF, its interfacial electron transport impedance is lower. Therefore, the spinel-β-ketoenamine COFs composite material is more favorable for the separation and transport of photogenerated carriers. The EIS test was performed on a Chenhua CHI 760E workstation. 2 mg of photocatalyst was weighed and dispersed in 900 μL of ethanol and 100 μL of Nafion dispersion to prepare a uniform slurry. Then, 50 μL of the slurry was transferred and coated onto a conductive glass plate, covering an area of ​​approximately 1 cm². 2 The remaining area was then coated with epoxy resin. After drying, a test was conducted.

[0049] Example 2

[0050] NiCo2O4 (5 mg, 0.02 mmol), tetrakis(4-aminophenyl)porphyrin (5 mmol, 33.7 mg), 3,4,9,10-perylenetetracarboxylic dianhydride (10 mmol, 39.2 mg), mesitylene (1 mL), and N-methylpyrrolidone (1 mL) were added to a Schlenk tube and sonicated for 60 minutes. Then, isoquinoline (0.1 mL) was added and sonicated for 10 minutes to ensure uniform dispersion. The air in the tube was then removed by three cycles of "freezing-vacuuming-thawing" with liquid nitrogen. The Schlenk tube was sealed and heated at 180 °C for 4 days. The resulting solid powder was washed multiple times with tetrahydrofuran, and the collected powder was dried under vacuum at 65 °C for 24 h to obtain the spinel-imide COFs composite material.

[0051] The freezing temperature is -196℃, the vacuum pressure is -0.1MPa, the thawing temperature is 25℃, and the freezing, vacuuming, and thawing times are all two minutes.

[0052] The composite material (200 mg) was added to tetrahydrofuran (150 mL), and after Soxhlet extraction for 2 days, the obtained solid powder was vacuum dried to obtain the purified spinel-imide COFs composite material.

[0053] Example 3

[0054] TiMg2O4 (5 mg, 0.03 mmol), 1,3,6,8-tetra(4-formylphenyl)pyrene (0.024 mmol, 15.0 mg), 2,2'-([1,1'-biphenyl]-4,4'-diyl)acetonitrile (0.048 mmol, 11.26 mg), and 1,4-dioxane (1 mL) were added to a Schlenk tube and sonicated for 60 minutes. Then, KOH (4 M, 0.1 mL) was added and sonicated for 10 minutes to ensure uniform dispersion. The air in the tube was then removed by three cycles of "freezing-vacuuming-thawing" with liquid nitrogen. The Schlenk tube was sealed and heated at 110 °C for 3 days. The resulting solid powder was washed multiple times with water and tetrahydrofuran. The collected powder was dried under vacuum at 120 °C for 12 h to obtain the spinel-olefin COFs composite material.

[0055] The freezing temperature is -196℃, the vacuum pressure is -0.1MPa, the thawing temperature is 25℃, and the freezing, vacuuming, and thawing times are all two minutes.

[0056] The composite material (200 mg) was added to tetrahydrofuran (150 mL), and after Soxhlet extraction for 2 days, the obtained solid powder was vacuum dried to obtain the purified spinel-olefin COFs composite material.

[0057] Matters not covered in this invention are common knowledge.

Claims

1. The application of a spinel-covalent organic framework composite material in photocatalytic reactions, characterized in that, Used for photocatalytic hydrogen evolution reaction, photocatalytic carbon dioxide reduction reaction or photocatalytic oxygen evolution reaction; The preparation method of the spinel-covalent organic framework composite material includes the following steps: (1) Add spinel, COF precursor, first organic solvent, and inorganic acid aqueous solution to a reaction tube. Sonicate the resulting mixture for 10-60 minutes to remove air, then seal the tube and incubate under vacuum at 100-200°C. o The reaction takes 3 to 7 days; the resulting solid powder is washed 3 to 6 times, at a temperature of 60 to 120°C. o Vacuum drying at C yields crude spinel-covalent organic framework composite material; The mass ratio of spinel to COF precursor is 1:1 to 50; 1 to 20 mL of the first organic solvent is added for every 1 mmol of COF precursor; the volume ratio of inorganic acid to the first organic solvent is 1:3 to 10. The COFs include aromatic aldehydes, aromatic amines, aromatic hydrazines, aromatic anhydrides, or aromatic nitriles. The spinel is a normal spinel structure or an inverse spinel structure; the normal spinel structure is CuCo2O4, NiCo2O4 or FeCo2O4; the inverse spinel structure is TiMg2O4, CoFe2O4 or NiFe2O4. (2) Add the crude spinel-covalent organic framework composite material obtained in step (1) to a second organic solvent at 60~110 °C. o After Soxhlet extraction for 1-3 days, the resulting solid powder is collected and diluted to 60-120 mg / L. o Vacuum drying at C yields purified spinel-covalent organic framework composite material; In this process, 100 to 400 mL of a second organic solvent is added to every 150 mg of crude composite material. Aromatic aldehydes include 2,4,6-tricarboxyloylphloroglucinol, 1,3,5-tricarboxyphenyl, 2,2'-bipyridine-5,5'-dicarboxaldehyde, or 1,3,6,8-tetra(4-formylphenyl)pyrene; aromatic amines include 2,5-dimethyl-p-phenylenediamine, 1,4-phenylenediamine, 2,5-dichloro-1,4-phenylenediamine, 1,3,5-tris[4-amino(1,1-biphenyl-4-yl)]benzene, tetra(4-aminophenyl)porphyrin, or 1,3,5-tris(4-aminophenyl) Benzene; aromatic hydrazides include 2,5-dimethoxyterephthalohydrazide, 2,5-diethoxyterephthalohydrazide, dihydrazide p-dibenzoic acid, or p-aminobenzoylhydrazide; aromatic anhydrides include 1,4,5,8-naphthalenetetracarboxylic anhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, pyromellitic dianhydride, or benzohexacarboxylic trihydride; aromatic nitrile compounds include 1,4-dicyanobenzene, 2,2'-([1,1'-biphenyl]-4,4'-diyl)acetonitrile, 2,2'-([1,1':4',1''-terphenyl]-4,4''-diyl)acetonitrile, 2,2'-([2,2'-bipyridine]-5,5'-diyl)acetonitrile, or 2,4,6-trimethylbenzene-1,3,5-tricarboxylic acid; The first organic solvent mentioned in step (1) is any one or more of mesitylene, 1,4-dioxane, o-dichlorobenzene, n-butanol, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and N-methylpyrrolidone; the second organic solvent mentioned in step (2) is any one or more of acetone, methanol, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, or dioxane. The inorganic acid aqueous solution mentioned in step (1) is hydrochloric acid, acetic acid, and nitric acid, with a concentration of 1 ~ 10 mol L. -1 .

2. The application as described in claim 1, characterized in that, The process includes the following steps: weighing the spinel-covalent organic framework composite material and sacrificial reagent into a reaction flask, adding deionized water to the system, and irradiating it with visible light for 1 to 10 hours under an inert gas or reaction atmosphere. The mass ratio of spinel-covalent organic framework composite material to sacrificial reagent is 1:5 ~ 50; 1 ~ 20 mg of spinel-covalent organic framework composite material is added to every 10 mL of deionized water; The sacrificial agent is L-ascorbic acid, sodium ascorbate, triethylamine, triethanolamine, ethanol, lactic acid, or methanol; The inert gas mentioned refers to nitrogen or argon; the reaction atmosphere is carbon dioxide.

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