Preparation method and application of chiral two-dimensional covalent organic framework material

Abstract

The invention discloses a preparation method and application of a chiral two-dimensional covalent organic framework material. According to the preparation method, chiral precursors R-NEA3, 1, 3, 5-triformyl phloroglucinol and 2, 2 '-bipyridine-5, 5'-diamine are polymerized through a solvothermal method to obtain a chiral two-dimensional COF photocatalytic material BpyR-COF, and then Cu < 2 + > is introduced through impregnation to form the Cu-BpyR-COF composite material. According to the method, chiral induction and a copper (Cu) coordination strategy are combined, so that the selectivity and the stability of photocatalytic reduction of CO2 into ethylene and propylene are remarkably improved. The preparation method is simple in preparation process and low in cost, and has a wide industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of covalent organic framework materials, and specifically relates to a preparation method and application of a chiral two-dimensional covalent organic framework material. Background Art

[0002] The excessive consumption of fossil fuels has led to a continuous increase in the concentration of carbon dioxide (CO2) in the atmosphere, disrupting the dynamic balance of the carbon cycle and triggering a series of ecological crises such as extreme climate and ocean acidification. Against this background, developing efficient CO2 conversion technologies to fix it into high-value chemicals (such as ethylene and propylene) has become an important way to address environmental problems and promote the upgrading of the green chemical industry.

[0003] Photocatalytic CO2 reduction reaction (CO2RR), by mimicking natural photosynthesis and using solar energy to drive the conversion of CO2 into fuels or chemical raw materials, is regarded as one of the most promising negative carbon technologies. Currently, the research in this field focuses on developing efficient photocatalysts, mainly including the following types of materials: 1. Inorganic semiconductors (such as TiO2, ZnO, CdS): Although these materials have broad spectral response characteristics, their band gap structures are difficult to accurately regulate, resulting in a high recombination rate of photo-generated electrons and holes, and the products are mainly C1 compounds (CO, CH4), and the selectivity of C2 + products (such as C2H4, C3H6) is generally low.

[0004] 2. Metal-organic frameworks (MOFs): With a high specific surface area and modifiable pore channels, MOFs perform excellently in CO2 adsorption. However, the weak coordination bonds between their metal nodes and organic ligands are easily broken during the photocatalytic process, causing structural collapse and poor cycling stability.

[0005] 3. Conjugated polymers: Although the energy band structures of these materials can be regulated through molecular design, the disordered polymerization network leads to uneven distribution of active sites and the lack of long-range ordered charge transport channels, restricting their catalytic efficiency.

[0006] In recent years, covalent organic frameworks (COFs) have attracted much attention in CO2RR due to their highly ordered crystal structures, designable pore systems, and excellent chemical stability. By introducing metal active centers (such as Co, Ni) into the functional groups of COFs, the separation efficiency of photo-generated carriers can be significantly improved. However, the existing technologies still have the following bottlenecks: (1) Poor binding stability of metal-COF: It is difficult to achieve strong coordination between metals and the COF framework by traditional impregnation methods or in-situ synthesis methods, resulting in easy agglomeration or loss of metal nanoparticles during the reaction and a short lifespan of active centers.

[0007] (2)Limited product selectivity: The electronic properties of COFs highly depend on the local structure, and it is difficult to precisely regulate their microenvironment with existing synthesis strategies, resulting in uncontrollable catalytic pathways and generally low C2 + product selectivity.

[0008] (3)Lack of chiral induction mechanism: The high selectivity of enzymatic catalytic reactions in nature stems from their chiral active centers. However, existing COF materials lack chiral structure design and cannot guide C-C coupling reactions through steric effects, restricting the generation of high-value-added products.

[0009] Therefore, it is of great significance to develop a new type of COF-based photocatalyst with high stability, high selectivity, and a controllable chiral microenvironment. Summary of the Invention

[0010] In view of the above technical problems of poor stability, low selectivity, and complex preparation process of existing photocatalytic CO2 reduction reaction catalysts, the present invention provides a preparation method and application of a chiral two-dimensional covalent organic framework material. By combining chiral induction with copper (Cu) coordination strategy, the present invention designs a chiral two-dimensional Cu-COF material (Cu-BpyR-COF), thereby enhancing the binding stability between COF and metal, improving the efficiency of photo-generated electron transfer, and suppressing electron-hole recombination, realizing the highly selective reduction of CO2 to C2H4 and C3H6.

[0011] The technical solution adopted by the present invention is as follows: A chiral two-dimensional covalent organic framework material is obtained by polymerizing a chiral precursor R-NEA3, 1,3,5-triformylphloroglucinol, and 2,2'-bipyridine-5,5'-diamine through a solvothermal method to obtain a chiral two-dimensional COF photocatalytic material BpyR-COF, and then introducing Cu 2+ by impregnation to form a Cu-BpyR-COF composite material.

[0012] Furthermore, the preparation method of the above chiral two-dimensional covalent organic framework material includes the following steps: S1. Chiral precursor synthesis: React 1,3,5-triformylphloroglucinol (Tp) with (R)-1-(1-naphthyl)ethylamine to prepare a chiral precursor R-NEA3 with a β-ketoenamine structure, thereby endowing the COF with chiral induction ability; S2. Two-dimensional COF construction: The chiral precursor R-NEA3, 1,3,5-triformylphloroglucinol (Tp), and 2,2'-bipyridine-5,5'-diamine (Bpy) are copolymerized through a solvothermal reaction to form a chiral COF with an ordered layered structure, namely BpyR-COF; S3. Metallization modification: Cu is introduced by post-impregnation 2+Introduce the bipyridine site of BpyR-COF (forming a strong coordination bond N-Cu-N) to form a Cu-BpyR-COF composite material, enhancing the electron transport ability.

[0013] Further, in step S1, the molar ratio of Tp to (R)-1-(1-naphthyl)ethylamine is 0.5~1.5:2.5~4.5, preferably 0.8~1.2:2.8~4.2, more preferably 1~1.2:3.5~4.

[0014] Further, in step S1, the reaction is carried out in the presence of an organic solvent, and the organic solvent is methanol or / and ethanol, preferably methanol.

[0015] Further, in step S1, the reaction conditions are: heating under reflux for 10~12 hours, and it also includes ethanol washing and vacuum drying after the reflux reaction.

[0016] Further, in step S2, the molar ratio of Tp, Bpy, and R-NEA3 is 1~1.5:1.2~2.5:1~1.5, preferably 1~1.2:1.5~2.2:1~1.2, more preferably 1~1.1:1.5~2:1~1.1.

[0017] Further, step S2 is carried out under the combined action of a 1,4-dioxane / mesitylene mixed solvent and glacial acetic acid.

[0018] Further, in step S2, the solvothermal reaction is carried out under vacuum conditions, the temperature is 100~140 °C, preferably 110~130 °C, more preferably 115~120 °C, and the time is 60 - 100 hours, preferably 70~80 hours.

[0019] Further, in step S2, it also includes Soxhlet extraction with tetrahydrofuran after the solvothermal reaction, and the extraction time is 36~60 hours, preferably 40~48 hours.

[0020] Further, in step S3, the mass ratio of copper acetate monohydrate to BpyR-COF is 1:9~11, preferably 1:9.5~10.5, more preferably 1:9.8~10.2. Using methanol as the solvent, stir at room temperature for 8~16 hours, preferably 10~14 hours.

[0021] The above chiral two-dimensional covalent organic framework material Cu-BpyR-COF is used for photocatalytic reduction of CO2 and exhibits excellent photocatalytic activity in photocatalytic production of C2H4 or / and C3H6 under visible light irradiation. The specific steps include: dispersing the chiral two-dimensional covalent organic framework material Cu-BpyR-COF in a mixed solution of triethanolamine-acetonitrile-water, and carrying out photocatalytic reduction of CO2 to produce C2H4 or / and C3H6 under visible light irradiation.

[0022] The beneficial effects of the present invention are as follows: (1) High-selectivity catalysis of C2 + Product formation: The selectivities of Cu-BpyR-COF for ethylene (C2H4) and propylene (C3H6) reach 3.37 μmol·g -1 ·h -1 and 2.17 μmol·g -1 ·h -1 respectively, which are more than 60% higher than those of traditional catalysts (mainly CH4 and CO, with the selectivity of C2 + generally < 2 μmol·g -1 ·h -1 ). At the same time, the chiral β-ketoenamine skeleton induces a helical layered structure through a chiral precursor (R-NEA3), and its stereoselective active sites can precisely regulate the adsorption configuration of CO2 molecules, promote the C-C coupling reaction path, and thus significantly increase the proportion of C2 + products.

[0023] (2) Excellent cyclic stability: The strong coordination Cu-N active center forms stable N-Cu-N coordination bonds through copper ions and bipyridine sites, effectively inhibiting metal loss and agglomeration of active sites, while enhancing the electron transfer efficiency, significantly prolonging the catalyst life and improving the cyclic stability.

[0024] (3) Synergistic optimization of energy band and pore channel: The two-dimensional ordered layered structure endows the material with a regular electron transfer path, and its band gap (2.1 eV) highly matches the redox potential (-0.41 V vs. RHE) for reducing CO2 to C2H4, reducing the reaction energy barrier and accelerating the separation of photo-generated electrons and holes.

[0025] (4) Green process and low-cost advantages: The chiral COF skeleton is synthesized in one step by the solvothermal method, with mild process conditions, without the need for precious metals or complex post-treatment, and the production cost is significantly lower than that of traditional precious metal catalysts. And low-toxic solvents (such as methanol, 1,4-dioxane, etc.) are used throughout the process, without the generation of harmful by-products, meeting the requirements of green chemical industrialization. Brief Description of the Drawings

[0026] Figure 1 are the powder diffraction (PXRD) patterns of BpyR-COF and Cu-BpyR-COF, showing that BpyR-COF and Cu-BpyR-COF have high crystallinity.

[0027] Figure 2 and Figure 3 are the scanning electron micrographs (SEM) of BpyR-COF and Cu-BpyR-COF materials respectively. It can be seen that the two prepared materials both exhibit an irregular rod-like morphology.

[0028] Figure 4 This is the Fourier transform infrared spectrum (FTIR) of Cu-BpyR-COF, showing the characteristic functional groups of COF in Cu-BpyR-COF. The C-N stretching peak (1257 cm -1 , which is consistent with the structure of β-ketoenamine) and the appearance of C=C (1617 cm -1 , which is consistent with the structure of β-ketoenamine) indicate the successful synthesis of COFs.

[0029] Figure 5 These are the photocatalytic activity results of achiral Bpy0-COF, BpyR-COF, and Cu-BpyR-COF for CO2 reduction activity tests. The prepared Cu-BpyR-COF exhibits excellent photocatalytic activity in the photocatalytic production of C2H4 and C3H6 under visible light irradiation.

[0030] Figure 6 These are the photocatalytic activity results of COFs obtained by doping BpyR-COF with different metals instead of copper under visible light irradiation for the reduction of CO2. Detailed implementation mode

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0032] Example 1

[0033] Step 1, Synthesis of chiral precursor R-NEA3 Add 1,3,5-triformylphloroglucinol (Tp) (210.1 mg, 1.0 mmol), (R)-1-(1-naphthyl)ethylamine (599.0 mg, 3.5 mmol), and CH3OH (70.0 mL) to a round-bottom flask. Stir the mixture and heat it to reflux. After 12 hours, cool the reactant to room temperature, remove the solvent under vacuum, obtain a dark red viscous solid, wash it with a large amount of ethanol to remove excess ligands and soluble fragments, and dry it under reduced pressure to obtain a yellow-green powder, namely R-NEA3.

[0034] Step 2, Synthesis of chiral two-dimensional COF photocatalytic material (BpyR-COF) Dissolve 0.36 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.54 mmol of 2,2'-bipyridine-5,5'-diamine (Bpy), and 0.36 mmol of R-NEA3 in a glass container in a mixture of 1,4-dioxane (10.2 mL) and mesitylene (1.8 mL) as the solvent. Sonicate for 10 minutes, and add 0.6 mL of glacial acetic acid to the mixture. Then freeze-thaw three times in a liquid nitrogen bath and seal it with a flame. Heat the reactant in an oven at 120 °C for 3 days (72 hours) and gradually cool it to room temperature within 12 hours to obtain an orange-red solid. Wash it with tetrahydrofuran, acetone, absolute methanol, and absolute ethanol, and separate the precipitate. Dry it under vacuum at 65 °C for 24 hours. Then, perform Soxhlet extraction with tetrahydrofuran for 48 hours and dry it under vacuum at 65 °C for 24 hours to synthesize chiral BpyR-COF.

[0035] Step 3: Synthesis of copper-doped chiral two-dimensional COF photocatalytic material (Cu-BpyR-COF) Mix copper acetate monohydrate and BpyR-COF in a mass ratio of 1:10 in an absolute methanol solvent and stir at room temperature for 12 hours. After the reaction is completed, wash the solid product with absolute methanol to ensure the removal of residual unbound metal salts. Subsequently, perform vacuum drying at 65 °C to obtain Cu-BpyR-COF.

[0036] Example 2

[0037] Step 1: Synthesis of chiral precursor R-NEA3 Mix 1,3,5-triformylphloroglucinol (Tp) (105.05 mg, 0.5 mmol), (R)-1-(1-naphthyl)ethylamine (437.5 mg, 2.5 mmol) with methanol (35 mL), and heat under reflux for 12 hours. After cooling, remove the solvent under vacuum, wash with ethanol 3 times, and dry under reduced pressure to obtain a light yellow powder R-NEA3.

[0038] Step 2: Synthesis of BpyR-COF Take Tp (0.5 mmol), Bpy (0.6 mmol), R-NEA3 (0.5 mmol), dissolve in a mixed solvent of 1,4-dioxane (5.1 mL) and mesitylene (0.9 mL), and add glacial acetic acid (0.3 mL). After freeze-thawing, seal it and react at 120 °C for 3 days. After cooling, wash successively with tetrahydrofuran and acetone, perform Soxhlet extraction for 36 hours, and dry under vacuum at 65 °C to obtain BpyR-COF.

[0039] Step 3: Synthesis of Cu-BpyR-COF Dissolve copper acetate monohydrate and BpyR-COF in methanol (50 mL) at a mass ratio of 1:10 and stir at room temperature for 12 hours. After washing with methanol, dry at 65 °C to obtain Cu-BpyR-COF.

[0040] Example 3

[0041] Step 1: Synthesis of chiral precursor R-NEA3 Mix Tp (210.1 mg, 1.0 mmol), (R)-1-(1-naphthyl)ethylamine (507.5 mg, 3.5 mmol) with methanol (70 mL) and reflux at heated for 12 hours. After washing with ethanol, dry under reduced pressure to obtain a yellow-green powder R-NEA3.

[0042] Step 2: Synthesis of BpyR-COF Take Tp (1.1 mmol), Bpy (2.0 mmol), R-NEA3 (1.1 mmol), dissolve them in 1,4-dioxane (10.2 mL) and mesitylene (1.8 mL), and add glacial acetic acid (0.6 mL). Seal and react at 120 °C for 3 days. Perform Soxhlet extraction for 48 hours and dry to obtain BpyR-COF.

[0043] Step 3: Synthesis of Cu-BpyR-COF Dissolve copper acetate monohydrate and BpyR-COF in methanol (50 mL) at a mass ratio of 1:10 and stir at room temperature for 12 hours. After washing and drying, obtain Cu-BpyR-COF, whose photocatalytic C2H4 selectivity reaches 2.85 μmol·g -1 ·h -1 .

[0044] Example 4

[0045] Step 1: Synthesis of chiral precursor R-NEA3 Mix Tp (315.15 mg, 1.5 mmol), (R)-1-(1-naphthyl)ethylamine (809.1 mg, 4.5 mmol) with methanol (105 mL) and reflux at heated for 12 hours. Wash with ethanol 5 times and dry under reduced pressure to obtain a dark green powder R-NEA3.

[0046] Step 2: Synthesis of BpyR-COF Take Tp (1.5 mmol), Bpy (2.5 mmol), R-NEA3 (1.5 mmol), dissolve them in 1,4-dioxane (15.3 mL) and mesitylene (2.7 mL), and add glacial acetic acid (0.9 mL). Seal and react at 120 °C for 3 days, perform Soxhlet extraction for 36 hours and dry to obtain BpyR-COF.

[0047] Step 3: Synthesis of Cu-BpyR-COF Copper(II) acetate monohydrate and BpyR-COF were dissolved in methanol (50 mL) at a mass ratio of 1:10 and stirred at room temperature for 12 hours.

[0048] Example 5

[0049] Step 1: Synthesis of chiral precursor R-NEA3 Tp (252.12 mg, 1.2 mmol), (R)-1-(1-naphthyl)ethylamine (693.0 mg, 4.2 mmol) and methanol (84 mL) were mixed and heated under reflux for 12 hours. After washing 4 times with ethanol and drying, dark yellow powder R-NEA3 was obtained.

[0050] Step 2: Synthesis of BpyR-COF Take Tp (1.2 mmol), Bpy (2.2 mmol), R-NEA3 (1.2 mmol), dissolve them in 1,4-dioxane (12.2 mL) and mesitylene (2.1 mL), and add glacial acetic acid (0.7 mL). After sealing, react at 120 °C for 3 days, perform Soxhlet extraction for 36 hours, and dry to obtain BpyR-COF.

[0051] Step 3: Synthesis of Cu-BpyR-COF Copper(II) acetate monohydrate and BpyR-COF were dissolved in methanol (50 mL) at a mass ratio of 1:10 and stirred at room temperature for 12 hours.

[0052] The selectivity of product C3H6 reached 2.17 μmol·g -1 ·h -1 .

[0053] To investigate the photocatalytic CO2 reduction performance of the Cu-BpyR-COF material, the photocatalytic CO2 reduction performance of the catalyst obtained in the above example was tested according to the following method: Weigh 5 mg of the catalyst and ultrasonically disperse it in a mixed solution of 1 mL of triethanolamine, 2 mL of distilled water and 3 mL of acetonitrile, and irradiate it under a simulated visible light environment.

[0054] Taking Example 1 as a typical representative, its characterization results are as Figures 1 to 3 shown Figure 1 indicating that BpyR-COF and Cu-BpyR-COF have high crystallinity. As can be seen from Figure 2 and Figure 3 , both of the prepared materials exhibit an irregular rod-like morphology; The Fourier transform infrared spectrum (FTIR) of Cu-BpyR-COF is as Figure 4As shown, the characteristic functional groups of the COF are shown in Cu-BpyR-COF, and the C-N stretching peak (1257 cm -1 , consistent with the structure of β-ketoenamine) and C=C (1617 cm -1 , consistent with the structure of β-ketoenamine) indicate the successful synthesis of COFs.

[0055] The photocatalytic activity results of achiral Bpy0-COF, BpyR-COF, and Cu-BpyR-COF are as Figure 5 shown. As Figure 5 can be seen, the Cu-BpyR-COF material exhibits good photocatalytic performance for CO2 reduction. The average yields of photocatalytic CO2 reduction to C2H4 and C3H6 reach 3.37 μmol g -1 h -1 and 2.17 μmol g -1 h -1 , respectively. Meanwhile, the average yields of the conventional products CH4, CO, and H2 reach 60.96 μmol g -1 h -1 , 4.35 μmol g -1 h -1 and 5.72 μmol g -1 h -1 , respectively. Under visible light irradiation, the photocatalytic activity results of COFs obtained by doping BpyR-COF with different metals instead of copper for CO2 reduction are as Figure 6 shown. As Figure 6 can be seen, Cu-BpyR-COF shows significant advantages in the photocatalytic reduction of CO2 to C2H4 and C3H6.

[0056] Example 6

[0057] After the photocatalytic CO2 reduction reaction, the Cu-BpyR-COF material obtained in Example 1 was recovered and recycled for the reaction.

[0058] The experimental results show that the activity retention rate is >90% after 10 cycles.

[0059] Comparative Example 1 (Achiral COF) The rest is the same as in Example 1, except that: the chiral precursor R-NEA3 was omitted, and COF was synthesized only with Tp and Bpy.

[0060] The experimental results show that: the C2H4 yield decreased to 0.8 μmol·g -1 ·h -1 , proving the key role of the chiral structure in C-C coupling.

[0061] Comparative Example 2: The coordinated metal is Fe The rest is the same as in Example 1, except that: Fe ²+ is used to replace Cu ²+ for coordination.

[0062] The experimental results show that: the C2H4 yield is 1.2 μmol·g -1 ·h -1 , indicating the unique regulation of the reaction path by the d-electron orbital characteristics of Cu.

[0063] Comparative Example 3: The coordinated metal is Co The rest is the same as in Example 1, except that: Co ²+ is used to replace Cu ²+ for coordination.

[0064] The experimental results show that: the C2H4 yield is 1.4 μmol·g -1 ·h -1 , indicating the unique regulation of the reaction path by the d-electron orbital characteristics of Cu.

[0065] Comparative Example 4 The rest is the same as in Example 1, except that: the copper loading ratio is adjusted to 1:5.

[0066] The experimental results show that: serious metal agglomeration occurs and the activity decreases by nearly 50%, proving that suitable loading conditions such as the copper loading ratio are very important.

[0067] Comparative Example 5 The rest is the same as in Example 1, except that: the copper loading ratio is adjusted to 1:15.

[0068] The experimental results show that: serious metal agglomeration occurs and the activity decreases > 50%, proving the necessity of the copper loading ratio (1:9 - 11) of the present invention.

[0069] Comparative Example 6 The mechanical mixing method is adopted. The rest is the same as in Example 1, except that: the Cu salt and COF are physically mixed and the impregnation reaction is not carried out.

[0070] The experimental results show that: Cu is not effectively coordinated, and the product is mainly H2 (> 80%), and the C2H4 yield approaches 0.

Claims

1. A chiral two-dimensional covalent organic framework material, characterized in that: The chiral two-dimensional COF photocatalytic material BpyR-COF was synthesized by solvothermal polymerization of chiral precursors R-NEA3, 1,3,5-triformylphloroglucinol and 2,2'-bipyridine-5,5'-diamine, and then Cu was introduced by impregnation. 2+ The Cu-BpyR-COF composite material was formed.

2. The method for preparing the chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: The steps include: S1. Chiral precursor synthesis: 1,3,5-triformylphloroglucinol was reacted with (R)-1-(1-naphthyl)ethylamine to prepare the chiral precursor R-NEA3 with β-ketoenamine structure; S2. Construction of two-dimensional COF: The chiral precursor R-NEA3 was copolymerized with 1,3,5-triformylphloroglucinol and 2,2'-bipyridine-5,5'-diamine through solvothermal reaction to form a chiral COF with an ordered layered structure, namely BpyR-COF. S3. Metallization modification: Cu 2+ The bipyridine sites of BpyR-COF were introduced to form the Cu-BpyR-COF composite.

3. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 2, characterized in that: In step S1, the molar ratio of 1,3,5-triformylphloroglucinol to (R)-1-(1-naphthyl)ethylamine is 0.5-1.5:2.5-4.

5.

4. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 2, characterized in that: In step S1, the reaction is carried out in the presence of an organic solvent.

5. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S1, the reaction conditions are: heating reflux reaction for 10 to 12 hours, and also including ethanol washing and vacuum drying after the reflux reaction.

6. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S2, the molar ratio of 1,3,5-triformylphloroglucinol, 2,2'-bipyridine-5,5'-diamine, and R-NEA3 is 1-1.5:1.2-2.5:1-1.

5.

7. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: Step S2 is carried out under the combined action of 1,4-dioxane / mesitylene mixed solvent and glacial acetic acid.

8. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S2, the solvent thermal reaction is carried out under vacuum conditions at a temperature of 100-140° C. for 60-100 hours; and further comprises tetrahydrofuran Soxhlet extraction after the solvent thermal reaction for 36-60 hours.

9. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S3, the mass ratio of BpyR-COF to copper acetate monohydrate is 1:9-11, methanol is used as solvent, and stirring is performed at room temperature for 8-16 hours.

10. Use of the chiral two-dimensional covalent organic framework material according to claim 1 or the chiral two-dimensional covalent organic framework material obtained by the preparation method according to any one of claims 2 to 9 in CO2 photocatalytic reduction, characterized in that: The chiral two-dimensional covalent organic framework material Cu-BpyR-COF is dispersed in a mixture of triethanolamine-acetonitrile-water, and CO2 is photocatalytically reduced to produce C2H4 and / or C3H6 under visible light irradiation.

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