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

Abstract

The present invention discloses a preparation method and application of a chiral two-dimensional covalent organic framework material. The present invention obtains a chiral two-dimensional COF photocatalytic material BpyR-COF by solvent thermal polymerization of chiral precursors R-NEA3, 1,3,5-triformyl phloroglucinol and 2,2'-bipyridine-5,5'-diamine, and then introduces Cu by impregnation. 2+ This method forms a Cu-BpyR-COF composite material. By combining chiral induction with a copper (Cu) coordination strategy, the present invention significantly improves the selectivity and stability of photocatalytic CO2 reduction to ethylene and propylene. The preparation process is simple, cost-effective, and has broad industrial application prospects.

Description

Technical Field

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

[0002] Excessive consumption of fossil fuels has led to a continuous rise in atmospheric carbon dioxide (CO2) concentrations, disrupting the dynamic balance of the carbon cycle and triggering a series of ecological crises, including extreme climate change and ocean acidification. Against this backdrop, developing efficient technologies to convert CO2 into high-value-added chemicals (such as ethylene and propylene) has become a key approach to addressing environmental challenges and promoting the upgrading of the green chemical industry.

[0003] The photocatalytic CO2 reduction reaction (CO2RR) mimics natural photosynthesis, utilizing solar energy to drive the conversion of CO2 into fuels or chemical feedstocks. It is considered one of the most promising negative carbon technologies. Currently, research in this field focuses on the development of highly efficient photocatalysts, primarily including the following types of materials:

[0004] 1. Inorganic semiconductors (such as TiO2, ZnO, CdS): Although these materials have wide spectral response characteristics, their band gap structure is difficult to precisely control, resulting in a high recombination rate of photogenerated electrons and holes, and the products are mainly C1 compounds (CO, CH4), C2 + The selectivity of products (such as C2H4 and C3H6) is generally low.

[0005] 2. Metal-organic frameworks (MOFs): With their high specific surface area and modifiable pores, MOFs excel 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 cyclic stability.

[0006] 3. Conjugated polymers: Although the band structure of this type of material can be regulated through molecular design, the disordered polymer network leads to uneven distribution of active sites and the lack of long-range ordered charge transfer channels, which restricts its catalytic efficiency.

[0007] In recent years, covalent organic frameworks (COFs) have attracted considerable 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 and Ni) into the functional groups of COFs, the efficiency of photogenerated carrier separation can be significantly improved. However, existing technologies still face the following bottlenecks:

[0008] (1) Poor metal-COF binding stability: Traditional impregnation methods or in situ synthesis methods are difficult to achieve strong coordination between metal and COF skeleton, which leads to the easy agglomeration or loss of metal nanoparticles during the reaction and short life of active centers.

[0009] (2) Limited product selectivity: The electronic properties of COFs are highly dependent on the local structure, and the existing synthesis strategy is difficult to precisely control its microenvironment, resulting in uncontrollable catalytic pathways. + Product selectivity is generally low.

[0010] (3) Lack of chiral induction mechanism: The high selectivity of enzyme-catalyzed reactions in nature is due to their chiral active centers. However, existing COF materials lack chiral structural design and are unable to guide CC coupling reactions through stereo effects, which restricts the generation of high value-added products.

[0011] Therefore, it is of great significance to develop a new COF-based photocatalyst with high stability, high selectivity and controllable chiral microenvironment. Summary of the Invention

[0012] To address the technical issues of existing photocatalytic CO2 reduction catalysts, such as poor stability, low selectivity, and complex preparation processes, the present invention provides a method for preparing and applying a chiral two-dimensional covalent organic framework material. By combining chiral induction with a copper (Cu) coordination strategy, the present invention designs a chiral two-dimensional Cu-COF material (Cu-BpyR-COF). This improves the stability of the COF-metal bond, enhances the efficiency of photogenerated electron transfer, and suppresses electron-hole recombination, achieving highly selective CO2 reduction to C2H4 and C3H6.

[0013] The technical solution adopted in the present invention is:

[0014] A chiral two-dimensional covalent organic framework material is prepared by solvent thermal polymerization of chiral precursors R-NEA3, 1,3,5-triformyl phloroglucinol and 2,2'-bipyridine-5,5'-diamine to obtain a chiral two-dimensional COF photocatalytic material BpyR-COF, and then Cu is introduced by impregnation. 2+ The Cu-BpyR-COF composite material was formed.

[0015] Furthermore, the preparation method of the above chiral two-dimensional covalent organic framework material comprises the following steps:

[0016] S1. Chiral Precursor Synthesis: 1,3,5-triformylphloroglucinol (Tp) was reacted with (R)-1-(1-naphthyl)ethylamine to prepare the chiral precursor R-NEA3 with a β-ketoenamine structure, thereby endowing the COF with chiral induction ability.

[0017] S2. 2D COF Construction: The chiral precursor R-NEA3 was copolymerized with 1,3,5-triformylphloroglucinol (Tp) and 2,2'-bipyridine-5,5'-diamine (Bpy) via a solvothermal reaction to form a chiral COF with an ordered layered structure, namely BpyR-COF.

[0018] S3. Metallization modification: Cu 2+ The bipyridine sites of BpyR-COF (forming a strong coordination bond N-Cu-N) were introduced to form a Cu-BpyR-COF composite material, which enhanced the electron transport ability.

[0019] Furthermore, 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, and more preferably 1-1.2:3.5-4.

[0020] Furthermore, in step S1, the reaction is carried out in the presence of an organic solvent, and the organic solvent is methanol and / or ethanol, preferably methanol.

[0021] Furthermore, 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.

[0022] Furthermore, 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, and more preferably 1-1.1:1.5-2:1-1.1.

[0023] Furthermore, step S2 is carried out under the combined action of 1,4-dioxane / mesitylene mixed solvent and glacial acetic acid.

[0024] Furthermore, in step S2, the solvent thermal reaction is carried out under vacuum conditions at a temperature of 100-140°C, preferably 110-130°C, more preferably 115-120°C, and for 60-100 hours, preferably 70-80 hours.

[0025] Furthermore, step S2 further includes tetrahydrofuran Soxhlet extraction after the solvent thermal reaction, and the extraction time is 36 to 60 hours, preferably 40 to 48 hours.

[0026] Furthermore, 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, and methanol is used as the solvent and stirred at room temperature for 8-16 hours, preferably 10-14 hours.

[0027] The chiral two-dimensional covalent organic framework material Cu-BpyR-COF is used for the photocatalytic reduction of CO2, and exhibits excellent photocatalytic activity in the 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 mixture of triethanolamine-acetonitrile-water, and performing photocatalytic reduction of CO2 to produce C2H4 or / and C3H6 under visible light irradiation.

[0028] The beneficial effects of the present invention are:

[0029] (1) Highly selective catalysis of C2 + Product formation: The selectivity of Cu-BpyR-COF for ethylene (C2H4) and propylene (C3H6) reached 3.37 μmol·g -1 ·h -1 and 2.17 μmol·g -1 ·h -1 , compared with traditional catalysts (mainly CH4, CO, C2 + Selectivity is generally less than 2 μmol·g -1 ·h -1 ) increased by more than 60%. At the same time, the chiral β-ketoenamine skeleton is induced to form a helical layered structure through the chiral precursor (R-NEA3). Its stereoselective active site can precisely regulate the adsorption configuration of CO2 molecules, promote the CC coupling reaction path, and thus significantly improve C2 + Product proportion.

[0030] (2) Excellent cyclic stability: The strongly coordinated Cu-N active center forms a stable N-Cu-N coordination bond with the bipyridine site through copper ions, effectively inhibiting metal loss and active site agglomeration, while enhancing electron transfer efficiency, significantly extending the catalyst life and improving cyclic stability.

[0031] (3) Coordinated optimization of energy bands and pores: The two-dimensional ordered layered structure gives the material a regular electron transport path. Its band gap (2.1 eV) is highly matched with the redox potential of CO2 reduction to C2H4 (-0.41 V vs. RHE), which reduces the reaction energy barrier and accelerates the separation of photogenerated electrons and holes.

[0032] (4) Green process and low-cost advantages: The chiral COF framework is synthesized in one step using a solvothermal method. The process conditions are mild and no precious metals or complex post-processing are required. The production cost is significantly lower than that of traditional precious metal catalysts. In addition, the entire process uses low-toxic solvents (methanol, 1,4-dioxane, etc.), and no harmful by-products are generated, meeting the requirements of green chemical industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1Figure 2 is the powder diffraction (PXRD) pattern of BpyR-COF and Cu-BpyR-COF, which shows that BpyR-COF and Cu-BpyR-COF have high crystallinity.

[0034] Figure 2 and Figure 3 Scanning electron microscopy (SEM) images of BpyR-COF and Cu-BpyR-COF materials, respectively. It can be seen that both prepared materials exhibit irregular rod-like morphology.

[0035] Figure 4 The Fourier transform infrared spectrum (FTIR) of Cu-BpyR-COF shows that Cu-BpyR-COF has the characteristic functional groups of COF, and the CN 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) indicated the successful synthesis of COFs.

[0036] Figure 5 The photocatalytic activity results of the achiral Bpy0-COF, BpyR-COF and Cu-BpyR-COF characterized by CO2 reduction activity test showed that the prepared Cu-BpyR-COF showed excellent photocatalytic activity in the photocatalytic production of C2H4 and C3H6 under visible light irradiation.

[0037] Figure 6 The photocatalytic activity results of COFs for CO2 reduction obtained by doping BpyR-COF with different metals instead of copper under visible light irradiation. DETAILED DESCRIPTION

[0038] 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.

[0039] Example 1

[0040] Step 1, Synthesis of Chiral Precursor R-NEA3

[0041] 1,3,5-Triformylphloroglucinol (Tp) (210.1 mg, 1.0 mmol), (R)-1-(1-naphthyl)ethanamine (599.0 mg, 3.5 mmol), and CH3OH (70.0 mL) were added to a round-bottom flask. The mixture was stirred and heated to reflux. After 12 hours, the reaction was cooled to room temperature, and the solvent was removed in vacuo to yield a dark red, viscous solid. This solid was washed with copious amounts of ethanol to remove excess ligand and soluble fragments, and then dried under reduced pressure to yield a yellow-green powder, R-NEA3.

[0042] Step 2, Synthesis of Chiral Two-Dimensional COF Photocatalytic Material (BpyR-COF)

[0043] 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 were placed in a glass container and dissolved in a mixture of 1,4-dioxane (10.2 mL) and mesitylene (1.8 mL) as solvent. After sonication for 10 minutes, 0.6 mL of glacial acetic acid was added to the mixture. The mixture was then frozen and thawed three times in a liquid nitrogen bath and sealed with a flame. The reaction mixture was heated in an oven at 120°C for 3 days (72 hours) and gradually cooled to room temperature over 12 hours, yielding an orange-red solid. The solid was washed with tetrahydrofuran, acetone, anhydrous methanol, and anhydrous ethanol, and the precipitate was isolated and dried in vacuum at 65°C for 24 hours. The chiral BpyR-COF was then synthesized by Soxhlet extraction with tetrahydrofuran for 48 hours and drying in vacuum at 65°C for 24 hours.

[0044] Step 3, Synthesis of Cu-doped Chiral Two-Dimensional COF Photocatalytic Material (Cu-BpyR-COF)

[0045] Copper acetate monohydrate and BpyR-COF were mixed in anhydrous methanol at a mass ratio of 1:10 and stirred at room temperature for 12 hours. After the reaction, the solid product was washed with anhydrous methanol to remove any remaining unbound metal salts. Subsequently, the solid product was vacuum-dried at 65°C to obtain Cu-BpyR-COF.

[0046] Example 2

[0047] Step 1: Synthesis of chiral precursor R-NEA3

[0048] Combine 1,3,5-triformylphloroglucinol (Tp) (105.05 mg, 0.5 mmol), (R)-1-(1-naphthyl)ethylamine (437.5 mg, 2.5 mmol), and methanol (35 mL) and heat under reflux for 12 hours. After cooling, remove the solvent in vacuo, wash three times with ethanol, and dry under reduced pressure to obtain a light yellow powder, R-NEA3.

[0049] Step 2: Synthesis of BpyR-COF

[0050] Tp (0.5 mmol), Bpy (0.6 mmol), and R-NEA3 (0.5 mmol) were dissolved in a mixture of 1,4-dioxane (5.1 mL) and mesitylene (0.9 mL). Glacial acetic acid (0.3 mL) was added. After freezing and thawing, the mixture was sealed and reacted at 120°C for 3 days. After cooling, the mixture was washed sequentially with tetrahydrofuran and acetone, extracted with Soxhlet for 36 hours, and dried under vacuum at 65°C to obtain BpyR-COF.

[0051] Step 3: Synthesis of Cu-BpyR-COF

[0052] 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. Wash with methanol and dry at 65°C to obtain Cu-BpyR-COF.

[0053] Example 3

[0054] Step 1: Synthesis of chiral precursor R-NEA3

[0055] Combine Tp (210.1 mg, 1.0 mmol), (R)-1-(1-naphthyl)ethylamine (507.5 mg, 3.5 mmol) and methanol (70 mL) and heat under reflux for 12 hours. Wash with ethanol and dry under reduced pressure to obtain R-NEA3 as a yellow-green powder.

[0056] Step 2: Synthesis of BpyR-COF

[0057] Dissolve Tp (1.1 mmol), Bpy (2.0 mmol), and R-NEA3 (1.1 mmol) in 1,4-dioxane (10.2 mL) and mesitylene (1.8 mL). Add glacial acetic acid (0.6 mL). Seal the container and react at 120°C for 3 days. Soxhlet extraction for 48 hours and drying to obtain BpyR-COF.

[0058] Step 3: Synthesis of Cu-BpyR-COF

[0059] Copper 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. After washing and drying, Cu-BpyR-COF was obtained, and its photocatalytic C2H4 selectivity reached 2.85 μmol·g -1 ·h -1 .

[0060] Example 4

[0061] Step 1: Synthesis of chiral precursor R-NEA3

[0062] Combine Tp (315.15 mg, 1.5 mmol), (R)-1-(1-naphthyl)ethylamine (809.1 mg, 4.5 mmol) and methanol (105 mL) and heat under reflux for 12 hours. Wash with ethanol five times and dry under reduced pressure to obtain R-NEA3 as a dark green powder.

[0063] Step 2: Synthesis of BpyR-COF

[0064] Tp (1.5 mmol), Bpy (2.5 mmol), and R-NEA3 (1.5 mmol) were dissolved in 1,4-dioxane (15.3 mL) and mesitylene (2.7 mL). Glacial acetic acid (0.9 mL) was added. The mixture was sealed and reacted at 120°C for 3 days. Soxhlet extraction was performed for 36 hours, and the mixture was dried to obtain BpyR-COF.

[0065] Step 3: Synthesis of Cu-BpyR-COF

[0066] Copper 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.

[0067] Example 5

[0068] Step 1: Synthesis of chiral precursor R-NEA3

[0069] Combine Tp (252.12 mg, 1.2 mmol), (R)-1-(1-naphthyl)ethylamine (693.0 mg, 4.2 mmol) and methanol (84 mL) and heat under reflux for 12 hours. Wash with ethanol four times and dry to obtain R-NEA3 as a dark yellow powder.

[0070] Step 2: Synthesis of BpyR-COF

[0071] Tp (1.2 mmol), Bpy (2.2 mmol), and R-NEA3 (1.2 mmol) were dissolved in 1,4-dioxane (12.2 mL) and mesitylene (2.1 mL). Glacial acetic acid (0.7 mL) was added. The mixture was sealed and reacted at 120°C for 3 days. Soxhlet extraction was performed for 36 hours, and the mixture was dried to obtain BpyR-COF.

[0072] Step 3: Synthesis of Cu-BpyR-COF

[0073] Copper 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.

[0074] The selectivity of the product C3H6 reached 2.17 μmol·g -1 ·h -1 .

[0075] In order to investigate the photocatalytic CO2 reduction effect 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: 5 mg of the catalyst was ultrasonically dispersed in a mixture of 1 mL of triethanolamine, 2 mL of distilled water and 3 mL of acetonitrile, and then illuminated in a simulated visible light environment.

[0076] Example 1 is a typical example, and its characterization results are as follows Figures 1 to 3 As shown, Figure 1 It shows that BpyR-COF and Cu-BpyR-COF have high crystallinity. Figure 2 and Figure 3 It can be seen that both prepared materials exhibit irregular rod-like morphology; the Fourier transform infrared spectrum (FTIR) of Cu-BpyR-COF is shown in Figure 4 As shown, Cu-BpyR-COF has the characteristic functional groups of COF, CN 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) indicated the successful synthesis of COFs.

[0077] The photocatalytic activity results of achiral Bpy0-COF, BpyR-COF and Cu-BpyR-COF are shown in Figure 2. Figure 5 As shown by Figure 5 It can be seen that the Cu-BpyR-COF material exhibits good performance in photocatalytic CO2 reduction, and the average yields of its photocatalytic CO2 reduction to C2H4 and C3H6 are 3.37 μmol g -1 h -1 , 2.17 μmol g -1 h -1 Meanwhile, the average yields of conventional products CH4, CO and H2 reached 60.96 μmol g -1 h -1 , 4.35 μmol g -1 h -1 and 5.72 μmol g -1 h -1 The photocatalytic activity of COFs doped with BpyR-COF instead of copper under visible light irradiation is shown in the following table. Figure 6 As shown by Figure 6 It can be seen that Cu-BpyR-COF has significant advantages in the photocatalytic reduction of CO2 to C2H4 and C3H6.

[0078] Example 6

[0079] After the photocatalytic CO2 reduction reaction, the Cu-BpyR-COF material obtained in Example 1 was recovered and recycled for the reaction.

[0080] The experimental results show that the activity retention rate is greater than 90% after 10 cycles.

[0081] Comparative Example 1 (Achiral COF)

[0082] The rest of the process was the same as in Example 1, except that the chiral precursor R-NEA3 was omitted and only Tp and Bpy were used to synthesize COF.

[0083] The experimental results show that the C2H4 yield is reduced to 0.8 μmol·g -1 ·h -1 , proving the key role of chiral structure in CC coupling.

[0084] Comparative Example 2 The coordination metal is Fe

[0085] The rest is the same as in Example 1, except that Fe ²+ Substitute for Cu ²+ Carry out coordination.

[0086] The experimental results show that the yield of C2H4 is 1.2 μmol·g -1 ·h -1 , indicating that the d electron orbital characteristics of Cu uniquely regulate the reaction pathway.

[0087] Comparative Example 3 Coordination Metal is Co

[0088] The rest is the same as in Example 1, except that Co ²+ Substitute for Cu ²+ Carry out coordination.

[0089] The experimental results show that the yield of C2H4 is 1.4 μmol·g -1 ·h -1 , indicating that the d electron orbital characteristics of Cu uniquely regulate the reaction pathway.

[0090] Comparative Example 4

[0091] The rest is the same as Example 1, except that the copper loading ratio is adjusted to 1:5.

[0092] The experimental results show that the metal agglomerates seriously and the activity drops by nearly 50%, which proves that appropriate loading conditions such as copper loading ratio are very important.

[0093] Comparative Example 5

[0094] The rest is the same as in Example 1, except that the copper loading ratio is adjusted to 1:15.

[0095] The experimental results show that the metal agglomerates seriously and the activity decreases by more than 50%, which proves the necessity of the copper loading ratio (1:9~11) of the present invention.

[0096] Comparative Example 6

[0097] A mechanical mixing method was used, and the rest was the same as in Example 1, except that the Cu salt and COF were physically mixed without impregnation reaction.

[0098] The experimental results show that Cu is not effectively coordinated, the product is mainly H2 (>80%), and the C2H4 yield is close to 0.

Claims

1. A method for preparing 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+ Forming a Cu-BpyR-COF composite material; the preparation method specifically comprises the following steps: S1. Chiral Precursor Synthesis: 1,3,5-triformylphloroglucinol was reacted with (R)-1-(1-naphthyl)ethylamine at a molar ratio of 0.5-1.5:2.5-4.5 to prepare a chiral precursor with a β-ketoenamine structure, designated R-NEA3. S2. 2D COF construction: The chiral precursor R-NEA3 was copolymerized with 1,3,5-triformylphloroglucinol and 2,2'-bipyridine-5,5'-diamine via a solvothermal reaction. The molar ratio of 1,3,5-triformylphloroglucinol: 2,2'-bipyridine-5,5'-diamine: R-NEA3 was 1-1.5: 1.2-2.5: 1-1.5, forming a chiral COF with an ordered layered structure, namely BpyR-COF. S3. Metallization modification: The mass ratio of copper acetate monohydrate to BpyR-COF is 1:9~11, and Cu is added by post-impregnation method. 2+ Bipyridine sites were introduced into BpyR-COF to form Cu-BpyR-COF composites.

2. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S1, the reaction is carried out in the presence of an organic solvent.

3. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, wherein: 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.

4. 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.

5. 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 a tetrahydrofuran Soxhlet extraction after the solvent thermal reaction for 36-60 hours.

6. The method for preparing a chiral two-dimensional covalent organic framework material according to claim 1, characterized in that: In step S3, methanol is used as the solvent and the mixture is stirred at room temperature for 8 to 16 hours.

7. Use of the chiral two-dimensional covalent organic framework material obtained by the preparation method according to any one of claims 1 to 6 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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