Ureido covalent organic framework material as well as preparation method and application thereof

Abstract

The invention relates to a ureido covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of covalent organic framework materials. The material has a relatively high specific surface area and a one-dimensional nano channel, urea groups are uniformly distributed in the one-dimensional nano channel, rapid mass transfer and high accessibility of the urea groups serving as an effective chiral hydrogen bond donor catalyst can be realized, and meanwhile, the excellent capability of generating singlet oxygen by combining porphyrin is realized; under the condition that no acid is added into the ureido covalent organic framework material, the photocatalytic semi-synthesis of artemisinin is realized at high conversion rate and yield. The material is obtained by condensation of aldehyde porphyrin and 1, 3-bis (4-aminophenyl) urea.

Description

Technical Field

[0001] The invention relates to a urea-based covalent organic framework material, a preparation method and application thereof, and belongs to the technical field of covalent organic framework materials. Background Art

[0002] Malaria is a parasitic disease caused by infection with Plasmodium and has long been one of the serious public health issues of global concern. Artemisinin is currently the most effective drug for treating malaria parasites, and the World Health Organization has recommended artemisinin-based combination therapy as a first-line drug. Currently, artemisinin is mainly extracted from Artemisia annua. However, unstable plant supply has led to large fluctuations in artemisinin prices. Artificial synthesis of artemisinin provides an alternative method with stable yields to meet market demand. But the total synthesis of artemisinin is very laborious and expensive. Photochemical semi-synthesis of artemisinin using the abundant biosynthetic precursor dihydroartemisinic acid is a promising strategy. The photochemical conversion of dihydroartemisinic acid to artemisinin has been shown to involve the formation of a peroxide intermediate via a singlet oxygen-induced ene reaction, followed by acid-catalyzed Hook cleavage and cyclization reactions. So far, a series of multifunctional combinatorial catalysts have been developed by integrating excellent singlet oxygen generating photosensitizers (i.e., porphyrin, 9, 10-dicyanoanthracene, and terpyridine ruthenium chloride) and acids (i.e., benzenesulfonic acid, trifluoroacetic acid, sulfuric acid), and successfully achieved the photocatalytic synthesis of artemisinin. For example, in the article "Applying green chemistry to the photochemical route to artemisinin", terpyridine ruthenium chloride (photosensitizer) and trifluoroacetic acid (acid catalyst) were used to photocatalytically synthesize artemisinin in a mixed solvent system of tetrahydrofuran and water. In the article "Porphyrinic Metal−Organic Frameworks Installed with Brønsted Acid Sites for Efficient Tandem Semisynthesis of Artemisinin", Brønsted acid sites (sulfuric acid) were installed into a series of porphyrin metal-organic frameworks (MOFs) for the bifunctional solid acid / photocatalyst catalysis of dihydroartemisinic acid tandem semisynthesis of artemisinin. However, in the above-mentioned reported photocatalytic synthesis of artemisinin, strong acid is required to catalyze Hook cleavage, which makes catalyst recovery and waste acid treatment difficult. In addition, strong acidic conditions may decompose artemisinin, resulting in reduced productivity. Therefore, it is very urgent to develop environmentally friendly and effective catalysts for the photocatalytic synthesis of artemisinin. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a urea-based covalent organic framework material, a preparation method and its application. The material has a high specific surface area and a one-dimensional nanochannel, and the urea groups are evenly distributed in the one-dimensional nanochannel, which can achieve rapid mass transfer and high accessibility of the urea groups as effective chiral hydrogen bond donor (HBD) catalysts. At the same time, combined with the excellent ability of porphyrin to produce singlet oxygen, the urea-based covalent organic framework material can achieve photocatalytic semi-synthesis of artemisinin with high conversion rate and yield without adding acid. The material is obtained by condensation of aldehyde porphyrin and 1,3-bis(4-aminophenyl)urea.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows.

[0005] A urea-based covalent organic framework material, the structural formula of the material is: ; Wherein, M is 2H or a fourth period transition metal element.

[0006] Preferably, the fourth period transition metal element is Fe, Co, Ni, Cu or Zn.

[0007] Preferably, M is 2H, Cu or Zn.

[0008] A method for preparing the urea-based covalent organic framework material of the present invention comprises the following steps: (1) Dispersing aldehyde porphyrin and 1,3-bis(4-aminophenyl)urea uniformly in a mixed solvent, then adding a catalyst, and after being uniformly dispersed, freezing with liquid nitrogen and vacuum degassing; reacting at 60-100° C. for more than 72 hours, cooling, and obtaining a crude product; (2) purifying and drying the crude product to obtain a urea-based covalent organic framework material; Among them, the structural formula of aldehyde porphyrin is: , M is 2H or a fourth period transition metal element; The structural formula of 1,3-bis(4-aminophenyl)urea is: .

[0009] Preferably, in step (1), the molar ratio of the aldehyde porphyrin to 1,3-bis(4-aminophenyl)urea is 1:2 to 1:2.5.

[0010] Preferably, in step (1), the mixed solvent is o-phthalic acid dichloride and alcohol in a volume ratio, and the alcohol is ethanol or n-butanol. More preferably, the volume ratio of o-phthalic acid dichloride and alcohol is 1:1 to 1:9; and the molar ratio of aldehyde porphyrin to the mixed solvent is 1:200 to 1:1000.

[0011] Preferably, in step (1), the catalyst is acetic acid or trifluoroacetic acid. More preferably, the concentration of acetic acid is 5-7 mol / L, the concentration of trifluoroacetic acid is 2-4 mol / L, and the molar ratio of aldehyde porphyrin to catalyst is 1:20-1:100.

[0012] Preferably, in step (2), the crude product is subjected to Soxhlet extraction with tetrahydrofuran and acetone respectively, and then dried in vacuum at 60-70°C.

[0013] An application of the urea-based covalent organic framework material of the present invention comprises the following steps: dispersing dihydroartemisinic acid and the urea-based covalent organic framework material uniformly in a solvent under an oxygen atmosphere, stirring and reacting for 6 to 12 hours under a light condition at -10 to 10°C, and filtering, washing, drying, concentrating and recrystallizing to obtain artemisinin after the reaction is completed.

[0014] Preferably, the amount of the urea-based covalent organic framework material is 0.5 mol% to 10 mol% of dihydroartemisinic acid.

[0015] Preferably, the solvent is dichloromethane or toluene.

[0016] Beneficial Effects The present invention provides a urea-based covalent organic framework material, a preparation method and an application thereof. The material has a high specific surface area and a one-dimensional nanochannel. The urea groups are evenly distributed in the one-dimensional nanochannel, which can achieve rapid mass transfer and improve catalytic efficiency. When the material is used for the photocatalytic semi-synthesis of artemisinin, there is an obvious hydrogen bond interaction between the urea-based covalent organic framework material and dihydroartemisinic acid. The urea group can effectively activate the reaction substrate and reduce the reaction energy barrier. The hook cleavage reaction can be catalyzed without the use of a strong acid. At the same time, the urea group is evenly distributed in the one-dimensional nanochannel, which can avoid the self-quenching phenomenon. The urea group and the porphyrin structure have a synergistic effect, so that the urea-based covalent organic framework material can achieve the photocatalytic semi-synthesis of artemisinin with a high conversion rate and yield without adding acid. The material is prepared by condensation of aldehyde porphyrin and 1,3-bis(4-aminophenyl)urea, has a periodic structure, and the preparation method is simple to operate. The reaction equation is as follows: . BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Fourier transform infrared (FT-IR) spectra of the urea-based covalent organic framework material of Example 1, 5,10,15,20-tetrakis(4-formylphenyl)-21H,23H-porphyrin and 1,3-bis(4-aminophenyl)urea.

[0018] Figure 2 The solid state of the urea-based covalent organic framework material of Example 1 13C cross-polarization / magic angle spinning NMR spectrum.

[0019] Figure 3 This is the powder X-ray diffraction pattern of the urea-based covalent organic framework material of Example 1.

[0020] Figure 4 This is a nitrogen adsorption-desorption curve of the urea-based covalent organic framework material of Example 1.

[0021] Figure 5 This is the nuclear magnetic hydrogen spectrum of the photocatalytic synthesis of artemisinin by the urea-based covalent organic framework material of Example 3. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments.

[0023] Example 1 Step 1: Weigh 0.02 mmol (14.5 mg) of 5,10,15,20-tetrakis(4-formaldehydephenyl)-21H,23H-porphyrin and 0.04 mmol (9.7 mg) of 1,3-bis(4-aminophenyl)urea and place them in a pyrex tube (sealed at one end, 20 cm long, 0.8 cm inner diameter, 1.2 cm outer diameter), add 0.5 mL of o-dichlorobenzene and 0.5 mL of n-butanol solvent, and place the pyrex tube in an ultrasonic generator for 15 minutes; Step 2: Take out the pyrex tube, add 0.1 mL of 6 mol / L acetic acid solution into it, and then place the pyrex tube in an ultrasonic generator for 15 minutes to form a uniformly dispersed system; Step 3: Take out the pyrex tube and place it in a Dewar flask containing liquid nitrogen to freeze it quickly, then connect the pyrex tube to a vacuum pump for degassing, take it out and thaw it, and then freeze and degas it again, and repeat this process three times; Step 4: Under vacuum conditions, use an alcohol torch flame to melt the glass-sealed pyrex tube. The length of the sealed tube is 12 cm. Step 5: After the pyrex tube returns to room temperature, place it in a 100°C oven for 72 hours to produce a brown precipitate, then take out the pyrex tube and cool it to room temperature; Step 6: Break the pyrex tube, filter to obtain a brown fluffy precipitate, wash it three times with N,N-dimethylformamide and tetrahydrofuran respectively, then wrap the precipitate with filter paper and place it in Soxhlet extraction, extract it in tetrahydrofuran and acetone for 24 hours respectively; Step 7: After the Soxhlet extraction is completed, the brown precipitate is taken out and vacuum dried at 60° C. for 24 hours to obtain 19.7 mg of a urea-based covalent organic framework material with a yield of 86.4%.

[0024] like Figure 1As shown, in the Fourier transform infrared (FT-IR) spectrum, a peak at 1622 cm -1 The characteristic peak of C=N double bond vibration is at 1700 cm in 5,10,15,20-tetrakis(4-formylphenyl)-21H,23H-porphyrin. -1 The C=O double bond stretching vibration peak at 3298-3403 cm in 1,3-bis(4-aminophenyl)urea -1 The NH stretching peak of 5,10,15,20-tetrakis(4-formylphenyl)-21H,23H-porphyrin was successfully connected with the amino group of 1,3-bis(4-aminophenyl)urea. 13 The signal due to the imine bond carbon was observed at 157 ppm in the C cross-polarization / magic angle spinning NMR spectrum, further proving the formation of the imine bond, such as Figure 2 shown.

[0025] Through powder X-ray diffraction (PXRD) testing, it was found that the urea-based covalent organic framework material had a series of peaks at 2.78°, 5.58°, 8.38°, 11.20° and 21.10°, indicating its high crystallinity. Figure 3 shown.

[0026] The nitrogen adsorption-desorption isotherm data of the urea-based covalent organic framework were recorded at 77K. Figure 4 It can be observed that the material shows a typical type IV adsorption curve with a specific surface area of ​​1732 m 2 g -1 , through non-local density functional theory (NLDFT) analysis, the average pore size of the material is 3.1 nm, which is consistent with the theoretical value.

[0027] After testing, it was determined that the structural formula of the urea-based covalent organic framework material is: , M is 2H.

[0028] The urea-based covalent organic framework material was immersed in a dihydroartemisinic acid solution and then tested by Fourier transform infrared spectroscopy. The urea-based covalent organic framework material immersed in dihydroartemisinic acid solution had a wavelength of 2980-2830 cm -1 The CH stretching vibration peak of dihydroartemisinic acid was observed at 1669 cm-1. In addition, compared with the urea-based covalent organic framework material before immersion, the urea-based covalent organic framework material after immersion showed a significant shift of the NH stretching vibration of the urea group to a lower frequency, and the peak at 1669 cm-1 was observed. -1 A new peak appears at . This peak is attributed to the protonated imine C=NH + The characteristic signal of 1623 cm -1The disappearance of C=N stretching vibration at the position of the urea group indicates that there is an obvious hydrogen bonding interaction between the urea-based covalent organic framework material and dihydroartemisinic acid, indicating that the urea group can effectively activate the reaction substrate, reduce the reaction energy barrier, and catalyze the hook cleavage reaction without using strong acid.

[0029] Example 2 In this embodiment, 5,10,15,20-tetrakis(4-formaldehyde benzene)-21H, 23H-porphyrin is replaced by 5,10,15,20-tetrakis(4-formaldehyde benzene)-iron-porphyrin, 5,10,15,20-tetrakis(4-formaldehyde benzene)-cobalt-porphyrin, 5,10,15,20-tetrakis(4-formaldehyde benzene)-nickel-porphyrin, 5,10,15,20-tetrakis(4-formaldehyde benzene)-copper-porphyrin or 5,10,15,20-tetrakis(4-formaldehyde benzene)-zinc-porphyrin, respectively, and the rest is the same as in Example 1.

[0030] After testing, the structural formula of the urea-based covalent organic framework material is: , M is Fe, Co, Ni, Cu or Zn.

[0031] The urea-based covalent organic framework material was immersed in a dihydroartemisinic acid solution and then subjected to Fourier transform infrared spectroscopy testing. The results showed that there was an obvious hydrogen bond interaction between the urea-based covalent organic framework material and dihydroartemisinic acid.

[0032] Example 3 Step 1, weigh 0.1 mmol (23.6 mg) of dihydroartemisinic acid and 5 mg of the urea-based covalent organic framework material prepared in Example 1 and place them in a 25 mL test tube, and add 5 mL of dichloromethane to the test tube; Step 2: Place the test tube in an ice bath and slowly bubble oxygen into it for 10 minutes to saturate the solution with oxygen, and seal the test tube with a latex stopper; Step 3: Place the test tube in the photoreactor, set the ambient temperature to 5 degrees, and turn on the light source (420-650nm LED light source, 200 mW cm -2 ) irradiation for 12 hours; Step 4: After the irradiation, take out the test tube, spin dry the dichloromethane under reduced pressure and low temperature, and add 0.1mmol (15.4mg) of biphenyl (internal standard). Add 0.5mL of deuterated chloroform to perform nuclear magnetic resonance hydrogen spectrum test. Figure 5 As shown, the conversion rate and yield of the urea-based covalent organic framework material in Example 1 for photocatalytic synthesis of artemisinin from dihydroartemisinic acid were 99% and 73%, respectively.

[0033] To obtain purified artemisinin, the reaction solution in the test tube after the illumination is completed can be filtered, washed with dichloromethane, the filtrate is collected, dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain a crude product. The crude product is recrystallized in ethanol and n-hexane to obtain the artemisinin product.

[0034] Example 4 The urea-based covalent organic framework material in Example 3 was replaced by the urea-based covalent organic framework material in Example 2, and the rest was the same as in Example 3.

[0035] When M is nickel, the conversion rate and yield of urea-based covalent organic framework materials for photocatalytic synthesis of artemisinin from dihydroartemisinic acid are 75% and 26%, respectively.

[0036] When M is copper, the conversion rate and yield of urea-based covalent organic framework materials for photocatalytic synthesis of artemisinin from dihydroartemisinic acid are 99% and 47%, respectively.

[0037] When M is zinc, the conversion rate and yield of urea-based covalent organic framework materials for photocatalytic synthesis of artemisinin from dihydroartemisinic acid are 99% and 54%, respectively.

[0038] Comparative Example 1 Step 1: Weigh 0.1 mmol (23.6 mg) of dihydroartemisinic acid, 0.005 mmol (3.60 mg) of 5,10,15,20-tetrakis(4-formylphenyl)porphyrin and 0.01 mmol (2.4 mg) of 1,3-bis(4-aminophenyl)urea into a 25 mL test tube, and add 5 mL of dichloromethane into the test tube; Step 2: Place the test tube in an ice bath and slowly bubble oxygen into it for 10 minutes to saturate the solution with oxygen, and seal the test tube with a latex stopper; Step 3: Place the test tube in the photoreactor, set the ambient temperature to 5°C, and turn on the light source (420-650nm LED light source, 200 mW cm -2 ) for 12 hours of light exposure; Step 4: After the irradiation, take out the test tube, spin dry the dichloromethane under reduced pressure and low temperature, and add 0.1mmol (15.4mg) of biphenyl (internal standard). Add 0.5mL of deuterated chloroform to it for nuclear magnetic hydrogen spectrum test. The conversion rate and yield of photocatalytic dihydroartemisinic acid to synthesize artemisinin were 99% and 15%, respectively.

[0039] In summary, the invention includes but is not limited to the above embodiments. Any equivalent substitution or partial improvement made under the spirit and principle of the invention shall be deemed to be within the protection scope of the invention.

Claims

1. A urea-based covalent organic framework material, characterized in that: The structural formula of the material is: ； Wherein, M is 2H or a fourth period transition metal element.

2. A urea-based covalent organic framework material according to claim 1, characterized in that: The fourth period transition metal element is Fe, Co, Ni, Cu or Zn.

3. The urea-based covalent organic framework material according to claim 1, characterized in that: M is 2H, Cu or Zn.

4. A method for preparing a urea-based covalent organic framework material according to any one of claims 1 to 3, characterized in that: The method steps include: (1) Dispersing aldehyde porphyrin and 1,3-bis(4-aminophenyl)urea uniformly in a mixed solvent, then adding a catalyst, and after being uniformly dispersed, freezing with liquid nitrogen and vacuum degassing; reacting at 60-100° C. for more than 72 hours, cooling, and obtaining a crude product; (2) purifying and drying the crude product to obtain a urea-based covalent organic framework material; Among them, the structural formula of aldehyde porphyrin is: , M is 2H or a fourth period transition metal element; The structural formula of 1,3-bis(4-aminophenyl)urea is: .

5. The method for preparing a urea-based covalent organic framework material according to claim 4, characterized in that: In step (1), the molar ratio of the aldehyde porphyrin to 1,3-bis(4-aminophenyl)urea is 1:2 to 1:2.

5.

6. The method for preparing a urea-based covalent organic framework material according to claim 4, characterized in that: In step (1), the mixed solvent is o-phthalic acid and alcohol in a volume ratio, wherein the alcohol is ethanol or n-butanol; the volume ratio of o-phthalic acid and alcohol is 1:1-1:9; and the molar ratio of aldehyde porphyrin to the mixed solvent is 1:200-1:1000.

7. The method for preparing a urea-based covalent organic framework material according to claim 4, characterized in that: In step (1), the catalyst is acetic acid or trifluoroacetic acid; the concentration of acetic acid is 5-7 mol / L, the concentration of trifluoroacetic acid is 2-4 mol / L, and the molar ratio of aldehyde porphyrin to catalyst is 1:20-1:

100.

8. The method for preparing a urea-based covalent organic framework material according to claim 4, characterized in that: In step (2), the crude product is subjected to Soxhlet extraction with tetrahydrofuran and acetone, respectively, and then dried in vacuum at 60-70°C.

9. An application of the urea-based covalent organic framework material according to any one of claims 1 to 3, characterized in that: Under an oxygen atmosphere, dihydroartemisinic acid and the urea-based covalent organic framework material are evenly dispersed in a solvent, and stirred for reaction at -10 to 10° C. under light conditions for 6 to 12 hours. After the reaction is completed, artemisinin is obtained by filtering, washing, drying, concentrating and recrystallizing.

10. The use of a urea-based covalent organic framework material as claimed in claim 9, characterized in that: The amount of the urea-based covalent organic framework material is 0.5 mol% to 10 mol% of dihydroartemisinic acid; the solvent is dichloromethane or toluene.

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