A copper-based metal-organic framework material, its preparation method and application

Abstract

This invention discloses a copper-based metal-organic framework material, its preparation method, and its applications. This copper-based metal-organic framework material uses 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] as a ligand coordinated with copper ions to form a metal-organic framework, exhibiting good photocatalytic performance and stability. As a catalyst, it is used in the photocatalytic reaction to prepare hydrogen peroxide in a two-phase system of benzyl alcohol and potassium dihydrogen phosphate aqueous solution. The catalyst is stable, has high catalytic efficiency, and the hydrogen peroxide generation rate can reach 1570.3 μmol / g / h. The copper-based metal-organic framework material can be prepared by a solvothermal reaction between the organic ligand and the metal ion precursor. The synthesis is simple and convenient, allowing for large-scale production without cumbersome procedures; the production cycle is short, effectively saving production time.

Description

Technical Field

[0001] This invention belongs to the field of organic framework functional materials technology, and relates to a copper-based metal-organic framework material, its preparation method and application. Background Technology

[0002] Hydrogen peroxide, as a mild and environmentally friendly oxidant, is widely used in chemical synthesis, textile bleaching, batteries, sterilization, and wastewater purification. Currently, industrial hydrogen peroxide production mainly relies on the energy-intensive anthraquinone process. Furthermore, concentrated hydrogen peroxide leads to additional costs and potential risks in storage and transportation. To address these issues, the direct conversion of water and oxygen into hydrogen peroxide via photosynthesis, driven by solar energy, is considered a promising alternative technology. Given that the amount of hydrogen peroxide produced during photosynthesis is at the millimole level, this method can directly meet the needs of small-scale household applications. However, problems remain in the photosynthesis process for converting water and oxygen into hydrogen peroxide, namely, the mismatch in valence band relationships between the kineticly slow water oxidation half-reaction (WOR) and the faster kinetic oxygen reduction half-reaction (ORR); moreover, a proton transfer equilibrium needs to be reached between the ORR and WOR half-reactions, but the protons used for ORR can only come from WOR, and the proton concentration in pure water or natural water is limited (c at pH=7). (H+) =10 -7 (mol / L); these all severely limit the overall efficiency of the photocatalytic reaction. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a copper-based metal-organic framework material, which uses 4,4',4”-(9H-carbazole-3,6,9-trimethyl)tri[benzoic acid] as a ligand to coordinate with copper ions to form a metal-organic framework, exhibiting excellent photocatalytic performance and stability.

[0004] The second objective of this invention is to provide a method for preparing the aforementioned copper-based metal-organic framework material.

[0005] A third objective of this invention is to provide an application of the aforementioned copper-based metal-organic framework material.

[0006] The first objective of this invention can be achieved by adopting the following technical solution:

[0007] A copper-based metal-organic framework material is formed by coordinating the ligand 4,4',4”-(9H-carbazole-3,6,9-trimethyl)tri[benzoic acid] with copper ions.

[0008] Furthermore, the two copper ions are linked by four carboxyl groups, with two water molecules axially coordinated.

[0009] The four carboxyl groups are respectively derived from benzoic acid attached to the carbazole nitrogen atom in the four ligands, forming the first binuclear copper paddle-shaped structure;

[0010] The four carboxyl groups are respectively derived from benzoic acid at the 3 or 6 position of carbazole in the four ligands, forming a second binuclear copper paddle-shaped structure;

[0011] The first dual-core copper paddle-shaped structure is the same as the second dual-core copper paddle-shaped structure.

[0012] Furthermore, among the four first dinuclear copper paddle-shaped structures adjacent to the first dinuclear copper paddle-shaped structure, the benzoic acid at the 3 or 6 position of the carbazole ligand of two adjacent first dinuclear copper paddle-shaped structures is connected to two identical copper ions to form a second dinuclear copper paddle-shaped structure surrounding the first dinuclear copper paddle-shaped structure.

[0013] Furthermore, the metal-organic framework material belongs to the tetragonal crystal system with space group P42 / nmc; its cell parameters are: α = β = γ = 90°.

[0014] The second objective of this invention can be achieved by adopting the following technical solution:

[0015] A method for preparing a copper-based metal-organic framework material involves a solvothermal reaction of ligand 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] with a copper ion precursor to obtain the copper-based metal-organic framework material.

[0016] Furthermore, the copper ion precursor is one or a combination of two of copper nitrate, copper sulfate, copper chloride, copper acetate, and their hydrates.

[0017] Furthermore, the molar ratio of copper ions to ligands is (2-2.5):1.

[0018] Furthermore, the solvothermal reaction is carried out in a solvent containing acetic acid, wherein the solvent is a mixture of DMF and / or DEF with methanol.

[0019] Furthermore, the volume ratio of DMF and / or DEF, methanol, and acetic acid is (0.5-2):1:(0.01-0.1).

[0020] Furthermore, the molar volume ratio of the ligand 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] to the solvent is (0.001-0.01) mmol:1 mL.

[0021] Furthermore, the solvothermal reaction conditions are a closed reaction at 70-120℃ for 6-72 hours.

[0022] The third objective of this invention can be achieved by adopting the following technical solution:

[0023] Application of the copper-based metal-organic framework material or the copper-based metal-organic framework material prepared by the preparation method of the copper-based metal-organic framework material in the photocatalytic synthesis of hydrogen peroxide.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention provides a copper-based metal-organic framework material, which uses 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] as a ligand to coordinate with copper ions to form a metal-organic framework. The carbazole nitrogen atom and the benzene rings connected at the 3 and 6 positions form a large conjugated structure with a wide light absorption band, which is beneficial to light absorption and charge transfer, and has good photocatalytic performance. Furthermore, the benzene rings connected at the 3 and 6 positions are close to 90 degrees, and the carboxyl groups on the benzene rings connected at the 3 and 6 positions can coordinate with the same copper ion, as can the carboxyl groups on the benzene rings connected with the carbazole nitrogen atom coordinate with the same copper ion, forming a regular topological structure and a stable metal-organic framework structure.

[0026] 2. The present invention provides a method for preparing a copper-based metal-organic framework material, which can be prepared by a solvothermal reaction of an organic ligand and a metal ion precursor. The synthesis is simple and convenient, and it can be mass-produced without complicated operations. The production cycle is short, which effectively saves production time.

[0027] 3. An application of a copper-based metal-organic framework material of the present invention, wherein the copper-based metal-organic framework material is dispersed in an organic phase formed by benzyl alcohol, and potassium dihydrogen phosphate aqueous solution is used instead of water to solve the problem of catalyst instability of water, and the two half-reactions of oxygen reduction to hydrogen peroxide and benzyl alcohol oxidation to benzaldehyde are combined, thereby increasing the utilization rate of photogenerated electron / hole pairs; the hydrogen peroxide generation rate can reach 1570.3 μmol / g / h. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the copper-based metal-organic framework material of the present invention;

[0029] Figure 2 This is a schematic diagram of a double-interlaced structure;

[0030] Figure 3 This is a schematic diagram of a partially interlaced structure;

[0031] Figure 4 This is a partial structural diagram of the copper-based metal-organic framework material of the present invention, wherein a is a schematic diagram of the dinuclear copper paddle-like structure; b is a coordination mode diagram from the perspective of the dinuclear copper paddle; and c is a coordination mode diagram from the perspective of organic ligands.

[0032] Figure 5 This is an X-ray powder diffraction pattern of the copper-based metal-organic framework material of the present invention;

[0033] Figure 6 The infrared spectrum of the copper-based metal-organic framework material of this invention is shown below.

[0034] Figure 7 The ultraviolet absorption curves of hydrogen peroxide aqueous solutions of different concentrations are shown.

[0035] Figure 8 The graph shows the fitted relationship between hydrogen peroxide concentration and its absorbance at 350 nm.

[0036] Figure 9 The UV absorption curve of the reaction solution after 1 hour of reaction using the copper-based metal-organic framework material of the present invention as a catalyst is shown.

[0037] Figure 10 The image shows the 1H NMR spectrum of the organic phase in the lower layer of the reaction solution after the copper-based metal-organic framework material of the present invention has been reacted as a catalyst for 1 hour.

[0038] Figure 11 The image shows the X-ray powder diffraction pattern of the recovered copper-based metal-organic framework material after reacting with the copper-based metal-organic framework material of the present invention as a catalyst for 1 hour.

[0039] Figure 12 The infrared spectrum of the recovered copper-based metal-organic framework material after reacting with the copper-based metal-organic framework material of the present invention as a catalyst for 1 hour is shown.

[0040] Figure 13 The UV absorption curve of the reaction solution after 1 hour of reaction with ZnCTBA as catalyst. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] Most reported copper-based metal-organic frameworks exhibit poor stability, particularly instability with water; therefore, their catalysts suffer from instability and poor catalytic efficiency in the catalytic reaction of water and oxygen to hydrogen peroxide. To address these issues, this invention provides a copper-based metal-organic framework material, its preparation method, and its applications.

[0043] A copper-based metal-organic framework material is formed by coordinating the ligand 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] with copper ions. The structure of the copper-based metal-organic framework material is as follows: Figure 1 As shown.

[0044] The valence electron configuration of the copper ion is [Ar]d. 9 Its d orbital electrons are neither half-filled nor completely empty or completely filled. The 3d orbital occupied by a single electron can easily hybridize with the 4s and 4p orbitals to form an inner orbital complex.

[0045] With 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] as the ligand, the carbazole nitrogen atom and the benzene ring linked at the 3,6 positions form a large conjugated structure with a wide light absorption band, which is beneficial for light absorption and charge transfer, and has good photocatalytic performance; the metal-organic framework structure formed by the coordination of the carboxyl group on the organic ligand with copper ions is stable.

[0046] In one embodiment, the two copper ions are linked by four carboxyl groups, with two water molecules axially coordinated upwards.

[0047] The four carboxyl groups are respectively derived from benzoic acid attached to the carbazole nitrogen atom in the four ligands, forming the first binuclear copper paddle-shaped structure;

[0048] The four carboxyl groups are respectively derived from benzoic acid at the 3 or 6 position of the four ligands carbazole; forming a second binuclear copper paddlewheel structure;

[0049] The first dual-core copper paddle-shaped structure is the same as the second dual-core copper paddle-shaped structure. The dual-core copper paddle-shaped structure is as follows: Figure 4 As shown in a; the organic ligand is connected to the binuclear copper paddle-like structure as follows: Figure 4 b and Figure 4 As shown in c.

[0050] Copper ions exist in a binuclear copper paddlewheel structure, with good charge transfer ability between the binuclei and a more stable coordination structure with the carboxyl group on the ligand. The nodes of the metal-organic framework structure are also more robust.

[0051] In one embodiment, between the four first binuclear copper paddle-shaped structures adjacent to the first binuclear copper paddle-shaped structure, the benzoic acid at the 3 or 6 position of the carbazole ligand of two adjacent first binuclear copper paddle-shaped structures is connected to two identical copper ions to form a second binuclear copper paddle-shaped structure surrounding the first binuclear copper paddle-shaped structure.

[0052] The carboxyl groups on the benzene rings linked by the nitrogen atom of carbazole coordinate to the same copper ion. The benzene rings at positions 3 and 6 are at approximately 90 degrees. The carboxyl groups on the benzene rings linked by the ligands at positions 3 and 6 can coordinate to the same copper ion, forming a regular topological structure. Adjacent carbazole groups are arranged back-to-back, with the carboxyl groups on the benzene rings linked by the nitrogen atom of carbazole connected to two different first binuclear copper paddlewheel structures in a back-to-back manner. This results in the benzene rings linked by adjacent carbazole groups at positions 3 and 6 extending in opposite directions, with the carboxyl groups connected to them respectively connecting to second binuclear copper paddlewheel structures, forming a stable metal-organic framework structure with double interpenetration. Figure 1-3 As shown; where Figure 2 This is a schematic diagram of a double-interlaced structure; Figure 3 This is a schematic diagram of the double-interlaced part of the structure.

[0053] As one embodiment, the base metal-organic framework material belongs to the tetragonal crystal system with space group P42 / nmc; the cell parameters are: α = β = γ = 90°.

[0054] This invention provides a method for preparing a copper-based metal-organic framework material, wherein the ligand 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] is subjected to a solvothermal reaction with a copper ion precursor to prepare the copper-based metal-organic framework material.

[0055] Copper-based metal-organic framework materials can be prepared by solvothermal reaction of organic ligands with copper ion precursors. The solvothermal reaction is mature, the synthesis is simple and convenient, and it can be mass-produced without complicated operation processes; the production cycle is short, which effectively saves production time.

[0056] In one embodiment, the copper ion precursor is one or a combination of two of copper nitrate, copper sulfate, copper chloride, copper acetate, and their hydrates.

[0057] In one embodiment, the molar ratio of copper ions to ligands is (2-2.5):1. Preferably, the molar ratio of copper ions to ligands is 2.2:1.

[0058] In one embodiment, the solvothermal reaction is carried out in a solvent containing acetic acid, wherein the solvent is a mixture of DMF and / or DEF with methanol. DMF or DEF serves as a good solvent for the organic ligands, and both DMF and DEF are capable of dissolving the copper ion precursor, allowing for sufficient contact between the organic ligands and copper ions for reaction. Acetic acid acts as a modifier or acid catalyst, which is beneficial for crystal formation. Preferably, the solvent is a mixture of DMF and methanol.

[0059] As one embodiment, the volume ratio of DMF and / or DEF, methanol, and acetic acid is (0.5-2):1:(0.01-0.1).

[0060] In one embodiment, the molar volume ratio of ligand 4,4',4”-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] to solvent is (0.001-0.01) mmol:1 mL.

[0061] As one implementation method, the solvothermal reaction is carried out under closed conditions at 70-120°C for 6-72 hours.

[0062] As one implementation method, the solvothermal reaction is followed by cooling, which is carried out under natural conditions to a temperature of 10-30°C.

[0063] As one implementation method, the cooling process further includes: performing solid-liquid separation on the system obtained after cooling, and then washing and drying the obtained solid material in sequence to obtain a copper-based metal-organic framework material.

[0064] In one embodiment, the washing process uses DMF and acetone as reagents.

[0065] As one implementation method, the drying is air drying under natural conditions.

[0066] This invention also provides an application of a copper-based metal-organic framework material, which serves as a photocatalyst for photocatalytic reactions in the photocatalytic synthesis of hydrogen peroxide.

[0067] The following is a further explanation using specific embodiments.

[0068] Example 1

[0069] Weigh 2 mg of H3CTBA ligand and 2 mg of Cu(NO3)2·3H2O and add them to a glass tube; add 5 μL of acetic acid, 0.3 mL of DMF and 0.3 mL of MeOH in sequence; seal the glass tube with a hydrogen-oxygen flame; place the glass tube in an ultrasonic machine and sonicate for 5 min; place the glass tube in an oven and heat at 90 °C for 24 h; after cooling to room temperature, open the glass tube and collect the solid product by centrifugation; wash the solid product with DMF and acetone several times; after drying, the copper-based metal-organic framework material is obtained, which is a green octahedron and named CuCTBA.

[0070] Example 2

[0071] Weigh 2 mg of H3CTBA ligand and 1 mg of CuCl2 and add them to a glass tube; add 13 μL of acetic acid, 1.2 mL of DMF, 1.3 mL of DEF and 1.3 mL of MeOH in sequence; seal the glass tube with a hydrogen-oxygen flame; place the glass tube in an ultrasonic machine and sonicate for 5 min; place the glass tube in an oven and heat at 70 °C for 72 h; after cooling to room temperature, open the glass tube and collect the solid product by centrifugation; wash the solid product with DMF and acetone several times; after drying, the copper-based metal-organic framework material is obtained, which is a green octahedron and named CuCTBA.

[0072] Example 3

[0073] Weigh 2 mg of H3CTBA ligand and 2.4 mg of CuSO4·5H2O and add them to a glass tube; add 25 μL of acetic acid, 0.13 mL of DMF and 0.25 mL of MeOH in sequence; seal the glass tube with a hydrogen-oxygen flame; place the glass tube in an ultrasonic machine and sonicate for 5 min; place the glass tube in an oven and heat at 100 °C for 48 h; after cooling to room temperature, open the glass tube and collect the solid product by centrifugation; wash the solid product with DMF and acetone several times; after drying, the copper-based metal-organic framework material, which is a green octahedron, is obtained and named CuCTBA.

[0074] Example 4

[0075] Weigh 2 mg of H3CTBA ligand and 1.8 mg of Cu(CO2CH3)2·H2O and add them to a glass tube; add 10 μL of acetic acid, 1.3 mL of DMF and 1 mL of MeOH in sequence; seal the glass tube with a hydrogen-oxygen flame; place the glass tube in an ultrasonic machine and sonicate for 5 min; place the glass tube in an oven and heat at 120 °C for 6 h; after cooling to room temperature, open the glass tube and collect the solid product by centrifugation; wash the solid product with DMF and acetone several times; after drying, the copper-based metal-organic framework material, which is a green octahedron, is obtained and named CuCTBA.

[0076] Example 5

[0077] 100 mg of H3CTBA ligand was dissolved in 15 mL of DMF, and 100 mg of Cu(NO3)2·3H2O was dissolved in 15 mL of MeOH. After sonication for 5 min each, the solutions were poured into a 50 mL reaction vessel and mixed. Then, 250 μL of acetic acid was added. The reaction vessel was sealed and placed in a 90 °C constant temperature drying oven for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed several times with DMF and acetone, and then dried to obtain the copper-based metal-organic framework material.

[0078] Comparative Example 1

[0079] Synthesis of ZnCTBA: 2 mg H3CTBA ligand and 2.5 mg Zn(NO3)2·6H2O were weighed into a glass tube, followed by the addition of 5 μL acetic acid, 0.3 mL DMF, and 0.3 mL MeOH. The glass tube was then flame-sealed and sonicated for 5 min to dissolve the solid. The glass tube was placed in a 90℃ oven for 24 h. After cooling to room temperature, a white needle-like / cluster-like solid was formed. The glass tube was opened, and the solid product was collected by centrifugation. The solid product was washed several times with DMF and ethanol. After drying at room temperature, the MOF product was obtained and named ZnCTBA.

[0080] Test example:

[0081] 1. X-ray powder diffraction test

[0082] The copper-based metal-organic framework material prepared in Example 1 was subjected to X-ray powder diffraction testing. The X-ray powder diffraction pattern is shown below. Figure 5 As shown.

[0083] from Figure 5 The X-ray powder diffraction test results show that the peak positions of the synthesized CuCTBA diffraction pattern are basically consistent with those of the simulated diffraction pattern, indicating that the synthesized CuCTBA is a pure phase; the diffraction pattern shows that the diffraction peaks are strong, indicating that the synthesized MOF has good crystallinity.

[0084] 2. Infrared spectroscopy test

[0085] The copper-based metal-organic framework material prepared in Example 1 was subjected to infrared spectroscopy testing. The infrared spectrum is shown in the figure below. Figure 6 As shown.

[0086] from Figure 6 The infrared spectrum shows that the synthesized CuCTBA has a wavelength of 1657 cm⁻¹. -1 The C=O peak at 1695 cm⁻¹ contrasts with that of ligand H₃CTBA. -1 The C=O peak at that point shifted significantly, indicating that the carboxyl group in the ligand reacted with Cu. 2+ The participation of ions in coordination demonstrates the successful synthesis of CuCTBA.

[0087] Photocatalytic performance test:

[0088] The concentration of hydrogen peroxide in the aqueous phase was determined by iodometric titration.

[0089] Iodometric method: in H + In its presence, hydrogen peroxide will react with I - Reaction occurs: The generated I3 -The ion has a characteristic absorption peak at 350 nm. Based on the above principle, using ultraviolet-visible spectrophotometry, 0.5 mL of hydrogen peroxide aqueous solution or reaction solution of different concentrations were added to 2 mL of 0.1 mol / L potassium hydrogen phthalate aqueous solution and 2 mL of 0.4 mol / L potassium iodide aqueous solution. After the reaction was allowed to proceed for 24 h, the absorbance at 350 nm was measured.

[0090] A series of standard curves were obtained by preparing aqueous solutions of hydrogen peroxide at known concentrations, such as... Figure 7 As shown; by fitting the standard curve to the hydrogen peroxide concentration and the absorbance at 350 nm, a relationship curve was obtained, as shown. Figure 8 As shown. By Figure 8 It can be seen that its R 2 The value is 0.99932, indicating a high degree of fit.

[0091] 1.0 mg of CuCTBA photocatalyst was weighed and added to a 50 mL photocatalytic reaction flask. Then, 5 mL of benzyl alcohol and 3 mL of 0.01 mol / L KH₂PO₄ aqueous solution were added successively. The mixture was bubbled with high-purity oxygen for 30 min, followed by irradiation with a 300 W xenon lamp for 1 h. The concentration of hydrogen peroxide in the aqueous phase was determined by iodometric titration; the results are as follows. Figure 9 As shown.

[0092] Depend on Figure 9 It can be seen that after 1 hour of photocatalysis, the ultraviolet absorption intensity of the upper reaction solution after iodometric treatment is 2.045. Substituting this into... Figure 8 The relationship yields a hydrogen peroxide concentration of 785.17 μmol / L, which translates to a rate of 1570.3 μmol / g / h.

[0093] The yield of benzaldehyde was characterized by 1H NMR spectroscopy with the addition of 1,2,4,5-tetramethylbenzene as an internal standard. 1H NMR spectroscopy: 500 μL of the lower reaction layer and 500 μL of deuterated DMSO were mixed, and 1,2,4,5-tetramethylbenzene (4.3 mg, 32.03 μmol) was added as an internal standard. The results are as follows: Figure 10 As shown. Calculations using internal standards yielded a benzaldehyde content of 4.04 μmol, which translates to a rate of 4046 μmol / g / h.

[0094] The reaction solution after the photocatalytic reaction was centrifuged, and the solid residue was collected. The solid product was washed multiple times with DMF and acetone. After drying, the recovered copper-based metal-organic framework material was obtained. X-ray powder diffraction analysis was performed on the recovered copper-based metal-organic framework material, and the results are as follows: Figure 11 As shown; infrared spectroscopy tests were performed, and the results are as follows. Figure 12 As shown.

[0095] from Figure 11 PXRD characterization showed that the diffraction peaks of CuCTBA remained basically consistent before and after photocatalysis, especially before 2θ = 10°, with no significant changes in peak position and intensity, indicating that CuCTBA material can still maintain framework stability after photocatalysis experiments; from Figure 12 The infrared spectrum shows that the photocatalyzed CuCTBA has a wavelength of 1657 cm⁻¹. -1 The C=O peak at that location (and Cu) 2 + The presence of carboxyl groups after coordination also demonstrates the high stability of the CuCTBA metal-organic framework material.

[0096] 2.5 mg of ZnCTBA was weighed and added to a 50 mL photocatalytic reaction flask, followed by the addition of 5 mL of benzyl alcohol and 3 mL of 0.01 mol / L KH₂PO₄ aqueous solution. The mixture was bubbled with high-purity oxygen for 30 min, then irradiated with a 300 W xenon lamp for 1 h. The concentration of hydrogen peroxide in the aqueous phase was determined by iodometric titration. The results are as follows: Figure 13 As shown.

[0097] Depend on Figure 13 It can be seen that the concentration of hydrogen peroxide produced by ZnCTBA after 1 hour of photocatalysis was 79.04 μmol / L, which translates to a rate of 94.84 μmol / g / h. Based on the experimental results, the performance of ZnCTBA is far inferior to that of CuCTBA mentioned in this invention. The valence electron configuration of zinc ions is [Ar]d. 10 Its d orbital electrons are fully filled, which means it can only form outer orbital complexes; therefore, the structure of the metal-organic framework material formed is different from that of the copper-based metal-organic framework material of this application, and the photocatalytic hydrogen peroxide production effect is also poor.

[0098] In summary, the copper-based metal-organic framework material of this invention, when used as a photocatalyst in a two-phase system, overcomes the disadvantage of the catalyst's inherent instability in water; furthermore, by using KH2PO4 aqueous solution instead of pure water, the problem of insufficient proton source in the reduction half-reaction is solved; and by combining the two half-reactions of oxygen reduction to hydrogen peroxide and benzyl alcohol oxidation to benzaldehyde, the utilization rate of photogenerated electron / hole pairs is increased; thus exhibiting excellent photocatalytic performance.

[0099] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A copper-based metal-organic framework material, characterized in that the ligands... 4,4',4''-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] coordinates with copper ions to form a metal-organic framework material; The copper-based metal-organic framework material belongs to the tetragonal crystal system with space group P42 / nmc; the cell parameters are: a=b=32.4494 Å; c=25.508 Å; α=β=γ=90°.

2. The copper-based metal-organic framework material according to claim 1, characterized in that, The two copper ions are linked by four carboxyl groups, with two water molecules coordinated axially upwards. The four carboxyl groups are respectively derived from benzoic acid attached to the carbazole nitrogen atom in the four ligands, forming the first binuclear copper paddle-shaped structure; The four carboxyl groups are respectively derived from benzoic acid at the 3 or 6 position of carbazole in the four ligands, forming a second binuclear copper paddle-shaped structure; The first dual-core copper paddle-shaped structure is the same as the second dual-core copper paddle-shaped structure.

3. The copper-based metal-organic framework material according to claim 2, characterized in that, Between the four first binuclear copper paddle-shaped structures adjacent to the first binuclear copper paddle-shaped structure, the benzoic acid at the 3 or 6 position of the carbazole ligand of two adjacent first binuclear copper paddle-shaped structures is connected to two identical copper ions to form a second binuclear copper paddle-shaped structure surrounding the first binuclear copper paddle-shaped structure.

4. A method for preparing a copper-based metal-organic framework material according to any one of claims 1-3, characterized in that, The copper-based metal-organic framework material was prepared by solvothermal reaction of ligand 4,4',4''-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] with a copper ion precursor.

5. The method for preparing the copper-based metal-organic framework material according to claim 4, characterized in that, The copper ion precursor is one or a combination of two of copper nitrate, copper sulfate, copper chloride, copper acetate and their hydrates; the molar ratio of copper ions to ligands is (2-2.5):

1.

6. The method for preparing the copper-based metal-organic framework material according to claim 4, characterized in that, The solvothermal reaction is carried out in a solvent containing acetic acid, wherein the solvent is a mixture of DMF and / or DEF and methanol; wherein the volume ratio of DMF and / or DEF, methanol and acetic acid is (0.5-2):1:(0.01-0.1).

7. The method for preparing the copper-based metal-organic framework material according to claim 4, characterized in that, The molar volume ratio of ligand 4,4',4''-(9H-carbazole-3,6,9-triyl)tri[benzoic acid] to solvent is (0.001-0.01) mmol:1 mL.

8. The method for preparing the copper-based metal-organic framework material according to claim 4, characterized in that, The conditions for the solvothermal reaction are: a closed reaction at 70-120℃ for 6-72 h.

9. The application of the copper-based metal-organic framework material prepared by the preparation method of the copper-based metal-organic framework material according to any one of claims 1-3 or any one of claims 4-8 in the photocatalytic synthesis of hydrogen peroxide.

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