Preparation method and photocatalytic application of Pd-Ace-COF

Abstract

The invention provides a preparation method and photocatalytic application of Pd-Ace-COF.The preparation method of Pd-Ace-COF comprises the steps that acenaphthequinone and 2, 4, 6-tri (4-aminophenyl)-1, 3, 5-triazine are covalently bonded to form a nanometer layered stacking material of a porous structure, and PdCl2 is coordinated with two adjacent nitrogen atoms and evenly dispersed in the COF material. The invention provides a method for applying a novel monatomic catalyst to photocatalysis, iodobenzene and phenylboronic acid are driven to be subjected to coupling reaction through illumination, and reaction conditions such as high temperature and high pressure are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials and relates to a preparation method of Pd-Ace-COF and a photocatalytic application thereof. Background Art

[0002] Suzuki-Miyauea, Sonogashira and other cross-coupling reactions are the most classic and widely used CC bond construction strategies, playing an important role in the pharmaceutical industry, natural product synthesis and fine chemicals. These coupling reactions generally rely on high temperature conditions and palladium salt catalysts, resulting in high energy consumption and high reaction costs, which is not in line with the concept of green organic synthesis. Recently, in order to improve the utilization efficiency of catalysts, researchers have confined palladium nanoparticles to metal organic frameworks or modified them to the surface of two-dimensional materials to achieve the recycling of catalysts. However, in this type of material, only the palladium on the surface of the nanoparticles has catalytic activity, resulting in low atomic utilization of precious metal catalysts. Therefore, how to develop atomic-level palladium heterogeneous catalysts for room temperature coupling reactions is an important scientific challenge facing this field.

[0003] Covalent Organic Frameworks (COF) materials are crystalline organic porous polymer materials with regular structure, low density, large specific surface area, adjustable pore size, and strong modifiability, which have great application potential. In particular, the preparation of atomic-level metal catalysts can be achieved by introducing vacancies into COFs materials in a targeted manner, thereby confining single-site metal catalytic centers. In addition, studies have shown that COFs have excellent visible light absorption capabilities and are widely used in the field of photosynthesis.

[0004] Based on this, the present invention provides a simple preparation method of a Pd single-atom COF catalyst for cross-coupling reaction, and realizes the efficient driving of the CC coupling reaction of iodobenzene and phenylboronic acid at room temperature and visible light irradiation conditions, greatly reducing the reaction energy consumption and significantly improving the utilization rate and stability of the catalyst.

[0005] After searching, two patent documents with similar contents to this case were found, among which the Chinese patent with publication number CN117643880A disclosed a porous organic cage-supported palladium catalyst, its preparation method and its application in the selective hydrogenation reaction of acetylenic compounds. A porous organic cage FT-RCC3 was prepared as a carrier, and Pd was fixed in the skeleton successfully loaded into FT-RCC3 by a reverse double solvent method to prepare a Pd@FT-RCC3 composite catalyst. The porous organic cage-supported palladium catalyst of the present invention includes a carrier and an active component, the carrier includes a porous organic cage FT-RCC3, and the active component includes palladium Pd nanoclusters. Based on the total mass of the catalyst, the loading amount of palladium is 0.3 to 3wt%, and the size of the Pd nanoclusters is 0.5 to 2nm.

[0006] The Chinese patent with publication number CN116510776A provides a COF-based photocatalytic material with oxygen vacancies and a preparation method thereof, which relates to the technical field of COF-based photocatalytic materials. The COF-based photocatalytic material with oxygen vacancies and a preparation method thereof include a single-atom-loaded TpPa-1 photocatalytic material containing oxygen vacancies, wherein the single-atom-loaded TpPa-1 photocatalytic material containing oxygen vacancies includes a raw material for synthesizing TpPa-1, a synthetic solvent, glacial acetic acid, hydrofluoric acid (HF), tetrahydrofuran, methanol, and a metal salt of Cu, Co, Zn, Ni, Fe, or Mn. The base metal single-atom catalyst of the invention does not need a co-catalyst and can have a hydrogen production performance that is not inferior to that of a COFs-based material using a precious metal as a co-catalyst.

[0007] After analysis and comparison, it is found that the above two patent documents have obvious differences from the patent application of the present invention in terms of the raw materials used in the preparation methods and the reaction mechanism, and there are also differences in the specific application directions. Summary of the invention

[0008] The present invention aims to solve the limitations of the prior art. To this end, a method for preparing Pd-Ace-COF is provided, wherein the porous structure of the photosensitive Ace-COF (acenaphthenequinone covalent organic framework powder) framework can effectively limit the aggregation of Pd atoms during the catalytic process, thereby enhancing the utilization rate of Pd and the stability of the catalyst, and significantly improving the photocatalytic performance of Pd-Ace-COF. As a photocatalyst, Pd-Ace-COF can effectively absorb visible light and drive iodobenzene and phenylboric acid to undergo a coupling reaction to generate biphenyl.

[0009] A Pd-Ace-COF photocatalyst is a nano-layered stacking material with a porous structure formed by covalently bonding acenaphthenequinone and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, wherein PdCl2 is coordinated with two adjacent nitrogen atoms and uniformly dispersed in the COF material. The specific preparation method is as follows:

[0010] (1) Take a 10 mL Shrek tube and slowly pass argon gas into it to expel the air from the tube.

[0011] (2) Under exhaust conditions, 35.4 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 27.3 mg of acenaphthenequinone were added to a Shrek tube and 0.5 mL of 1,4-dioxane, 0.5 mL of acetonitrile and 0.1 mL of 6 M acetic acid were added.

[0012] (3) Take 77K liquid nitrogen, place the Shrek tube containing the mixture into it, and perform three freeze-degassing-thawing pump cycles.

[0013] (4) After returning to room temperature, the Shrek tube was vacuum-sealed and placed in an oven for reaction at 120°C for 72 h.

[0014] (5) After the reaction is completed and cooled to room temperature, the mixture is taken out and centrifuged.

[0015] (6) After centrifugation, add anhydrous methanol and soak for 72 hours, replacing with fresh anhydrous methanol every 24 hours.

[0016] (7) After centrifugation, add acetone and tetrahydrofuran to wash three times each.

[0017] (8) After washing, the mixture was placed under vacuum at 120 °C overnight to obtain a reddish-brown Ace-COF powder (acenaphthenequinone covalent organic framework intermediate).

[0018] (9) Take 20 mg of palladium chloride and place it in a 50 mL round-bottom flask. Add 10 mL of acetonitrile and stir in a 65 °C oil bath until the palladium chloride is completely dissolved. Take 30 mg of the Ace-COF powder in step (8) and add it to the hot solution. Continue stirring for 12 h.

[0019] (10) Cool to room temperature and wash with acetonitrile three times.

[0020] Preferably, in step (2), the ratio of 1,4-dioxane to acetonitrile is 1:9, 3:7, 5:5, 7:3, 9:1, respectively, and the total volume is 1 mL, and the ratio is preferably 5:5.

[0021] Preferably, in step (2), acetic acid is used in amounts of 0.1 mL, 0.2 mL, 0.3 mL, 0.4 mL, and 0.5 mL, preferably 0.1 mL.

[0022] Preferably, the temperature in step (4) is 80°C, 90°C, 100°C, 120°C, 150°C, preferably 120°C.

[0023] Preferably, the time in step (4) is 36 h, 48 h, 72 h, 96 h, 120 h, preferably 72 h.

[0024] Preferably, in step (9), palladium chloride and Ace-COF powder are reacted in 50°C acetone, 65°C acetonitrile, 80°C methanol, 100°C toluene, and 150°C N,N-dimethylformamide solution, respectively, preferably in 65°C acetonitrile solution.

[0025] The present invention also provides an application of the above-mentioned Pd-Ace-COF in the field of photocatalysis, using Pd-Ace-COF as a photocatalyst to drive the coupling reaction of iodobenzene and phenylboric acid to prepare biphenyl. The specific operation steps are as follows:

[0026] 2 mg of Pd-Ace-COF was added into a 15 mL transparent quartz tube.

[0027] Furthermore, 0.1 mmol iodobenzene, 0.12 mmol phenylboric acid, 0.2 mmol potassium carbonate and 5 mL ethanol were added into the reaction.

[0028] Further, the vent valve was opened slowly to pass argon gas into the mixed solution. It was observed that small bubbles emerged from the solution one by one. The vent valve was fixed and the solution was ventilated for 15 minutes.

[0029] Furthermore, the reaction was carried out under irradiation with a xenon lamp (λ>400nm) with a power of 300W and a light intensity of 100mW / cm 2 .

[0030] Furthermore, the reaction environment temperature is 20-30°C.

[0031] Furthermore, the reaction time of the reaction is 6 hours.

[0032] Furthermore, after the reaction is completed, the catalyst is separated by centrifugation for reuse.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention provides a method for using a novel single-atom catalyst for photocatalysis, which drives the coupling reaction between iodobenzene and phenylboric acid by light, thereby avoiding reaction conditions such as high temperature and high pressure.

[0035] (2) The Pd-Ace-COF material of the present invention utilizes the porous structure of the organic framework COF and introduces redox-active quinone-type polycyclic aromatic hydrocarbons through synthesis, which effectively limits the aggregation of Pd atoms into metal nanoparticles, significantly improves the utilization rate of Pd, and reduces the reaction cost.

[0036] (3) The present invention can realize the recovery of precious metal catalysts by centrifugation. The recovery method is simple and does not affect the catalytic activity of the catalyst itself. The catalyst can be recycled for multiple times. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the PXRD diffraction pattern of the Pd-Ace-COF catalyst and the Ace-COF intermediate in the present invention.

[0038] Figure 2 It is a schematic structural diagram of the Pd-Ace-COF catalyst and the Ace-COF intermediate involved in the present invention.

[0039] Figure 3 It is a Fourier transform infrared spectrum diagram of the Pd-Ace-COF catalyst and the Ace-COF intermediate involved in the present invention.

[0040] Figure 4 It is a transmission electron microscope image of the Pd-Ace-COF catalyst involved in the present invention.

[0041] Figure 5 It is a schematic diagram of the structure of the photocatalytic CC coupling product of the Pd-Ace-COF catalyst involved in the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0043] Example 1

[0044] The present invention provides a method for synthesizing a Pd single-atom photocatalyst for a photocatalytic coupling reaction, and the preparation method thereof comprises the following steps:

[0045] (1) 35.4 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 27.3 mg of acenaphthenequinone were added to a Shrek tube, followed by 0.5 mL of 1,4-dioxane, 0.5 mL of acetonitrile and 0.1 mL of 6 M acetic acid.

[0046] (2) The Shrek tube containing the mixture was placed in 77K liquid nitrogen and subjected to three freeze-degassing-thawing pump cycles. After the mixture was heated to room temperature, it was sealed in a vacuum and reacted at 120°C for 72 hours.

[0047] (3) The mixture was taken out and centrifuged, and then the solvent was exchanged with anhydrous methanol and washed with acetone and tetrahydrofuran three times each. Then, the mixture was dehydrated at 120° C. overnight under vacuum conditions to synthesize Ace-COF.

[0048] (4) Take 20 mg of palladium chloride and place it in a 50 mL round-bottom flask, add 10 mL of acetonitrile, and stir in a 65°C oil bath until the palladium chloride is completely dissolved. Take 30 mg of the Ace-COF powder in step (3) and add it to the hot solution. After continuing to stir for 12 hours, cool it to room temperature and filter it to obtain a reddish brown powder. After washing the above powder with acetonitrile, dry it in a vacuum drying oven at 60°C for 12 hours to obtain the final product Pd-Ace-COF.

[0049] Structural characterization:

[0050] The Pd-Ace-COF prepared in step (4) was characterized and the results were as follows:

[0051] 1) Nanosheet AA stacking morphology

[0052] For example, the PXRD diffraction patterns of Pd-Ace-COF and Ace-COF ( Figure 1), the obtained pattern is in good agreement with the simulated AA stacking PXRD diffraction pattern, proving that the synthesized Pd-Ace-COF presents a nanosheet AA stacking morphology.

[0053] 2) Figure 2 The structure diagrams of Ace-COF and Pd-Ace-COF.

[0054] 3) Figure 3 The Fourier transform infrared spectra of Pd-Ace-COF and Ace-COF are shown in the figure. As shown in the figure, the peaks of Ace-COF and Pd-Ace-COF are similar, 1714cm -1 , 1518cm -1 and 1366cm -1 The vibration absorption peaks are respectively attributed to the C=C bond and the imine bond (C=N), confirming the covalent bond connection mode of the material.

[0055] 4) Figure 4 This is an electron microscope image of Pd-Ace-COF. As shown in the figure, Pd single atoms are evenly distributed in the framework network of Ace-COF.

[0056] Example 2

[0057] The present invention also applies the palladium single-atom catalyst Pd-Ace-COF prepared above to a photocatalytic CC coupling reaction.

[0058] The specific method is as follows:

[0059] Add 2mg Pd-Ace-COF, 0.1mmol iodobenzene, 0.12mmol phenylboric acid, 0.1mmol K2CO3 and 5mL ethanol to a quartz tube. Seal with a rubber tube and slowly pass argon for 15 minutes. After ventilation, irradiate with a 300W xenon lamp for 6 hours. After the reaction is completed, centrifuge the reaction solution, take the supernatant, filter it with a filter membrane, and detect the biphenyl production by gas chromatography. The yield is 99%. In addition, by replacing different substrates with the above method for expansion experiments, the following can be obtained: Figure 5 Various coupling products are shown.

[0060] Studies have shown that Pd-Ace-COF can efficiently drive the photocatalytic coupling of iodobenzene and phenylboronic acid to produce biphenyl. However, due to the lack of palladium catalytic active sites on Ace-COF, the catalytic yield of biphenyl is almost zero, proving that Pd is the active site for the cross-coupling reaction.

[0061] The above embodiment is a preferred embodiment of the present invention, and Pd-Ace-COF catalyst has been successfully synthesized according to this method. However, the embodiments of the present invention are not limited to the above embodiment, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing Pd-Ace-COF, characterized in that: Acenaphthenequinone and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine are covalently bonded to form a nano-layered stacking material with a porous structure. PdCl2 is coordinated with two adjacent nitrogen atoms and uniformly dispersed in the COF material. The specific preparation method is as follows: (1) Add acenaphthenequinone and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine into a 10 mL Shrek tube under a nitrogen atmosphere; (2) adding 1,4-dioxane, acetonitrile and 6 M acetic acid to the Shrek tube prepared in step (1), exhausting the air in the Shrek tube and vacuum sealing the tube; (3) The sealed Shrek tube in step (2) was subjected to freeze-degassing-thawing cycle operation three times at 77K, and then placed in an oven, heated to 80-120°C, and reacted for 36-72h; (4) After step (3), the mixture was cooled to room temperature, and the obtained red solid powder was washed with acetone and tetrahydrofuran in turn, and placed in a vacuum drying oven at 120° C. overnight to obtain an acenaphthenequinone covalent organic framework intermediate, i.e., Ace-COF powder; (5) Place PdCl2 in a 50 mL round-bottom flask, add solvent, and stir in an oil bath at 50-150°C until palladium chloride is completely dissolved; (6) Take the Ace-COF powder in step (4) and add it to the hot solution. Continue stirring for 12 hours. After the reaction is completed, cool it to room temperature and filter it to obtain a reddish brown powder. After washing with acetonitrile, place it in a vacuum drying oven at 60°C overnight to obtain the target product Pd-Ace-COF.

2. The method for preparing Pd-Ace-COF according to claim 1, characterized in that: In step (1), the weight ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to acenaphthenequinone is 1.3-1.5:

1.

3. The method for preparing Pd-Ace-COF according to claim 1, characterized in that: In step (2), the volume ratio of 1,4-dioxane, acetonitrile and acetic acid is 5:5:1-5, and the usage ratio of acenaphthenequinone to 1,4-dioxane is 50-60:1 (w / v).

4. The method for preparing Pd-Ace-COF according to claim 1, characterized in that: In step (5), the ratio of palladium chloride to solvent is 4-5:2 (w / v), and the solvent is acetone, acetonitrile, methanol, toluene or N,N-dimethylformamide.

5. The method for preparing Pd-Ace-COF according to claim 1, characterized in that: The weight ratio of the Ace-COF powder described in step (6) to the palladium chloride described in step (5) is 2 to 3:

2.

6. A Pd-Ace-COF photocatalyst, characterized in that: The catalytic sites formed by the Pd-Ace-COF photocatalyst are all in the form of Pd single atoms, and PdCl2 is anchored in the Ace-COF pores as a catalytic active site to form Pd-Ace-COF, which is prepared by the preparation method of Pd-Ace-COF according to any one of claims 1 to 6.

7. An application of a Pd-Ace-COF photocatalyst, characterized in that: the method for photocatalytic Suzuki coupling reaction of the Pd-Ace-COF photocatalyst as described in claim 6 is used to drive the coupling reaction of iodobenzene and phenylboric acid to prepare biphenyl.

8. The use of the Pd-Ace-COF photocatalyst according to claim 7, characterized in that: the method for photocatalytic Suzuki coupling reaction is performed in the following steps: (1) Add 2 mg of Pd-Ace-COF into a 15 mL transparent quartz tube and add 0.1 mmol of iodobenzene, 0.12 mmol of phenylboric acid, 0.2 mmol of potassium carbonate, and 5 mL of ethanol in sequence; (2) Slowly open the vent valve and introduce argon into the mixed solution. When small bubbles are observed to emerge from the solution, fix the vent valve and ventilate for 15 minutes. (3) The reaction was carried out under irradiation with a xenon lamp of 300 W and a wavelength of λ>400 nm with an illumination intensity of 100 mW / cm 2 , biphenyl was prepared.

9. The use of the Pd-Ace-COF photocatalyst according to claim 8, characterized in that the reaction environment temperature in step (3) is 20-30°C and the reaction time is 6 hours.

10. The use of the Pd-Ace-COF photocatalyst according to claim 8, characterized in that after the reaction is completed, the catalyst is separated by centrifugation for reuse.

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