Crystalline allyl covalent organic framework material and application thereof in benzamide cyclization reaction

Abstract

The invention relates to preparation of a crystalline allyl covalent organic framework material and application research of the crystalline allyl covalent organic framework material in benzamide cyclization green photocatalytic conversion. The SF-COF material is prepared by adopting a step-by-step synthesis method. The preparation method comprises the following steps: synthesizing a COF precursor by taking 1, 3-benzenetricarboxaldehyde and p-aminophenylacetonitrile as raw materials, and preparing the allylation covalent organic framework material with the electronic push-pull effect from the COF precursor and 5, 5 ', 5'-(benzene-1, 3, 5-triyl) tri (thiophene-2-formaldehyde) through a solvothermal method. The material is applied to the field of photocatalytic organic conversion, and benzamide cyclization and conversion of derivatives of benzamide are achieved under irradiation of a blue light LED. The prepared SF-COF has the advantages of efficient charge separation and electron conduction performance, good structural stability and chemical stability and the like. And a catalyzed organic reaction substrate has the advantages of wide universality range, good cycle stability and the like, and shows excellent photocatalytic conversion capability.

Description

Technical Field

[0001] This invention pertains to the preparation of covalent organic framework materials and their application in the field of photocatalytic organic conversion. Specifically, it relates to a method for preparing a crystalline allyl covalent organic framework material. Background Technology

[0002] 1,2,4-Thiadiazoles are an important class of heterocyclic compounds with biological and therapeutic applications ranging from anticancer to neuroprotective activities. However, the preparation of these valuable organic compounds using traditional synthetic methods faces significant challenges, often requiring strong oxidants (such as high-valence metal oxides and peroxides) or harsh reaction conditions (such as high temperature, high pressure, and strong acid / base environments). These processes are not only energy-intensive and risky, but also generate large amounts of toxic and harmful byproducts and waste, causing significant environmental pollution, which contradicts the principles of green chemistry and sustainable development.

[0003] To address the aforementioned challenges, photocatalysis technology has shown immense research potential. Its core concept is to mimic natural photosynthesis, utilizing clean, renewable solar energy as a driving force to efficiently and selectively drive chemical reactions under mild conditions (normal temperature and pressure). This significantly reduces dependence on fossil fuels and energy consumption, while avoiding the use of hazardous reagents, providing a green pathway to atom-economical and environmentally friendly organic synthesis.

[0004] Among numerous photocatalytic materials, covalent organic frameworks (COFs) have attracted significant attention due to their unique structural characteristics. COFs are a class of polymers with high crystallinity and porosity, composed of organic building blocks with well-defined pore structures and highly tunable photoelectric properties. They exhibit excellent thermal stability, high structural designability, and superior light-harvesting and carrier generation capabilities. However, traditional COFs suffer from insufficient separation efficiency of photogenerated electrons and holes, coupled with a rapid recombination rate, leading to an inadequate number of effective carriers participating in the catalytic reaction, thus limiting quantum efficiency and reaction rate. Therefore, we designed a crystalline allyl covalent organic framework material to effectively address the limitations of traditional COF materials. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of traditional COF (carbon-based composite materials) which suffer from fast recombination speeds and low charge separation efficiency, and to synthesize 1,2,4-thiadiazole and its derivatives under mild conditions. First, a COF precursor material was prepared via the Brainwell reaction, and then a crystalline allyl covalent organic framework material was synthesized via solvothermal synthesis. The inherent ordered electron donor-acceptor (DA) structure in SF-COF promotes the separation of photogenerated electrons and holes. The method for preparing SF-COF includes the following steps: (1) Preparation of COF precursor materials: A certain amount of trimesin and p-aminophenylacetonitrile were weighed and mixed in a certain amount of sodium hydroxide solution. The mixture was heated to 60-90℃ under reflux for 2-6 h. After the reaction was completed, the mixture was washed with sodium hydroxide solution, ethanol, and water, and dried overnight at 80℃ to obtain a yellow allyl-linked covalent organic framework precursor (BTAC) solid sample.

[0006] The molar ratio of pyromellitic acetonitrile to p-aminophenylacetonitrile in step (1) is 1-4:1-4, wherein 1:3 is preferred; The reaction temperature in step (1) is 60-90 ℃, preferably 85 ℃, and the reaction time is 2-6 h, preferably 2 h.

[0007] (2) Preparation of SF-COF: A certain amount of BTAC was weighed and mixed with 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) in a certain proportion. In addition, a certain amount of acetic acid was added to the reactor and dispersed in a certain volume of solvent. The mixture was then heated in a sealed environment to 120-180℃ for 3-7 days. After the reaction was completed, the mixture was washed with organic reagents, filtered, and vacuum dried at 80℃ to obtain a yellow SF-COF powder sample.

[0008] The solvents are n-butanol and o-dichlorobenzene.

[0009] The ratio of BTAC to 5,5',5''-(benzene-1,3,5-triyl)tri(thiophene-2-carboxaldehyde) is 1-4:1-4, preferably 1:1.

[0010] In step (2), the reaction temperature of SF-COF is heated to 120-180℃ and maintained for 3-7 days, wherein the preferred reaction temperature is 120℃ and the reaction time is 3 days.

[0011] (3) A procedure for synthesizing 1,2,4-thiadiazole using SF-COF: First, a certain amount of benzamide and its derivatives, along with the SF-COF photocatalyst, were weighed into a light-transmitting glass bottle. Then, a certain volume of reaction solvent was measured and fully dissolved. Next, a certain amount of gas was introduced to maintain the stability of the reaction system. The glass bottle was placed under a light source and stirred for a certain period of time at a specific temperature. After the experiment, the reaction system was processed, the products were collected, and analyzed to determine the success of the reaction and the catalytic effect of the catalyst. The reaction formula is as follows:

[0012] The oxidant is a highly reactive oxygen species that can be generated during organic transformation reactions and intervene in the aerobic organic reaction process.

[0013] The R is any one of alkyl, alkoxy, or halogen; The alkyl group is C1-C 10 The alkoxy group is a straight-chain alkane or a branched-chain alkane; the alkoxy group includes one of methoxy, ethoxy, or propoxy; and the halogen is any one of F, Cl, Br, or I.

[0014] The catalyst dosage is 1-10% of the benzamide mass, and the solvent is any one of ACE, MeCN, DCM, MeOH, and EtOH, with DCM being preferred. The introduced gas is air or oxygen; the light source is ultraviolet LED, blue LED, white LED, green LED, or orange LED, with blue LED being preferred; the reaction temperature is at room temperature, and the irradiation time is 3-24 h, with 6 h being preferred.

[0015] After obtaining benzamide and its derivatives, SF-COF is recovered, reactivated, and the preparation of benzamide and its derivatives is repeated to achieve... N Preparation in multiple cycles. N Greater than or equal to 3.

[0016] The specific beneficial effects of this material are manifested as follows: (1) The allyl covalent organic framework SF-COF structure synthesized in this invention contains DA-type structural units, which significantly improves the separation efficiency of photogenerated carriers.

[0017] (2) It maintains high catalytic activity and low catalyst loss in multiple cycles and has good stability.

[0018] (3) In this invention, blue light is used as the light source and allyl covalent organic framework SF-COF is used as the photocatalyst to perform photocatalytic aerobic oxidation of benzamide and its derivatives, namely 1,2,4-thiadiazole and its derivatives. The yield of the product 1,2,4-thiadiazole and its derivatives can reach more than 60% (72% in Example 3-1), showing excellent photocatalytic activity. Attached Figure Description

[0019] Figure 1 This is a synthesis route diagram for BTAC and SF-COF materials.

[0020] Figure 2 This is a powder X-ray diffraction pattern of SF-COF material.

[0021] Figure 3 This is the Fourier transform infrared spectrum of BTAC material.

[0022] Figure 4 This is the Fourier transform infrared spectrum of the SF-COF material.

[0023] Figure 5 The image shows the 1H NMR spectrum of 1,2,4-thiadiazole.

[0024] Figure 6 The NMR spectrum of 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole is shown in the 1H NMR spectrum.

[0025] Figure 7 The NMR spectrum of 5-(4-fluorophenyl)-3-(4-methylphenyl)-1,2,4-thiadiazole is shown in the 1H NMR spectrum.

[0026] Figure 8 The NMR spectrum of 5-(4-chlorophenyl)-3-(4-methylphenyl)-1,2,4-thiadiazole is shown in the 1H NMR spectrum.

[0027] Figure 9 The graph shows the cyclic stability test results for the covalent organic framework SF-COF.

[0028] Figure 10 The image shows the XRD patterns of the covalent organic framework SF-COF before and after cycling. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0030] Example 1 Synthesis of BTAC: Weigh 81.1 mg (0.5 mmol) of trimesin, 198.2 mg (1.5 mmol) of p-aminophenylacetonitrile, and 500 mg (12.5 mmol) of sodium hydroxide into a round-bottom flask. Heat at 85 °C for 2 h. After cooling to room temperature, collect the solid, wash with sodium hydroxide solution, ethanol, and water to remove impurities, and then place the washed solid in a vacuum drying oven at 80 °C and dry overnight. Collect the product to obtain BTAC.

[0031] Example 2 Synthesis of SF-COF: BATC (20.4 mg, 0.05 mmol) and 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) (20.4 mg, 0.05 mmol) were weighed and dispersed in ampoules containing n-butanol and o-dichlorobenzene (2 mL / 2 mL, v / v). The ampoules were then flame-sealed under vacuum and heated at 120°C for 3 days. After cooling to room temperature, the solids were collected and washed with DMF and EtOH. Finally, the material was dried overnight under vacuum at 80°C, and the product was collected to obtain SF-COF.

[0032] Figure 1This is a synthesis route diagram for BTAC and SF-COF materials.

[0033] Figure 2 The image shows the powder X-ray diffraction pattern of BTAC material. The X-ray powder diffraction pattern of SF-COF material shows two peaks at 3.6°, 6.28°, 7.4°, and 9.58°. θ The angular signal peaks are attributed to the 100, 210, 200, and 310 crystal planes, respectively. The presence of characteristic peaks at small angles indicates the successful preparation of this crystalline material.

[0034] Figure 3 Fourier transform infrared spectrum of BTAC material; 2213 cm⁻¹ -1 A C≡N stretching vibration peak appears at 1619 cm⁻¹. -1 A stretching vibration peak of the benzene ring appears at 1590 cm⁻¹. -1 A C=C stretching vibration peak appears at 1183 cm⁻¹. -1 1242 cm -1 1294 cm -1 The peak at 828 cm⁻¹ is attributed to the bending vibration of the CH bond on the benzene ring. -1 A skeletal vibration peak of the benzene ring appears at this location.

[0035] Figure 4 Fourier transform infrared spectrum of SF-COF material; at 1656 cm⁻¹ -1 No peaks related to aldehyde stretching were observed at 3355 cm⁻¹. -1 No peaks related to -NH stretching were observed, which is characteristic of the precursor compound, demonstrating the successful preparation of the COF material.

[0036] Example 3 Synthesis of 1,2,4-thiadiazole:

[0037] 0.2 mmol of benzamide and 8 mg of photocatalyst (SF-COF) were weighed into a light-transmitting glass bottle, and 1 mL of DCM was added. A certain amount of O2 was introduced, and the glass bottle was stirred at room temperature for 6 h under light-protected conditions. No 1,2,4-thiadiazole product was obtained.

[0038] Weigh 0.2 mmol benzamide and 8 mg photocatalyst (SF-COF) into a light-transmitting glass bottle, add 2 mL of DCM, introduce a certain amount of O2, place the glass bottle in a blue light reactor, and stir at room temperature for 6 h to obtain 1,2,4-thiadiazole product (16.4 mg, 69%, separation yield).

[0039] Figure 5The 1H NMR spectrum of 1,2,4-thiadiazole is shown. 1 ¹H NMR (400 MHz, CDCl₃-d), δ 8.42 – 8.38 (m, 2H), 8.08 – 8.04 (m, 2H), 7.58 – 7.46 (m, 6H); The figure shows that we successfully synthesized 1,2,4-thiadiazole.

[0040] Example 3-1 Synthesis of 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole:

[0041] Weigh 0.2 mmol of 3-tolylthiocarboxamide and 8 mg of photocatalyst (SF-COF) into a light-transmitting glass bottle, add 1 mL of DCM, introduce a certain amount of O2, place the glass bottle in a blue light reactor, and stir at room temperature for 6 h to obtain 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole (19.2 mg, 72%, separation yield).

[0042] Figure 6 The 1H NMR spectrum of 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole is shown. 1 ¹H NMR (400 MHZ, CDCl₃-d), δ 8.30 – 8.23 ​​(m, 2H), 7.98 – 7.90 (m, 2H), 7.31 (dd, J = 7.9, 5.6 Hz, 4H), 2.43 (d, J = 3.8 Hz, 6H); The figure shows that we successfully synthesized 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole.

[0043] Example 3-2 Synthesis of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole:

[0044] Weigh 0.2 mmol of 3-fluorothiocarboxamide and 8 mg of photocatalyst (SF-COF) into a light-transmitting glass bottle, add 1 mL of DCM, introduce a certain amount of O2, place the glass bottle in a blue light reactor, and stir at room temperature for 6 h to obtain the 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole product.

[0045] Figure 7 The image shows the 1H NMR spectrum of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole. 1¹H NMR (400 MHz, CDCl₃-d), δ 8.41 – 8.35 (m, 2H), 8.07 – 8.02 (m, 2H), 7.25 – 7.15 (m, 4H); The figure shows that 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole (17.3 mg, 63%, isolated yield) was successfully synthesized.

[0046] Example 3-3 Synthesis of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole:

[0047] Weigh 0.2 mmol of 3-chlorothiocarboxamide and 8 mg of photocatalyst (SF-COF) into a light-transmitting glass bottle, add 1 mL of DCM, introduce a certain amount of O2, place the glass bottle in a blue light reactor, and stir at room temperature for 6 h to obtain 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole (18.6 mg, 66%, separation yield).

[0048] Figure 8 The 1H NMR spectrum of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole 1 ¹H NMR (400 MHZ, CDCl₃-d), δ 8.34 – 8.28 (m, 2H), 8.00 – 7.95 (m, 2H), 7.53 – 7.45 (m, 4H); As shown in the figure, we have successfully synthesized 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole.

[0049] Example 4 Cyclic stability test: Using SF-COF as a photocatalyst, the photocatalytic organic conversion of benzamide and its derivatives in Example 3 was carried out to generate 1,2,4-thiadiazole and its derivatives. After the reaction, the SF-COF catalyst was separated from the reaction solution by simple filtration, then thoroughly washed with dichloromethane and vacuum dried at room temperature. It could be directly used in the next round of reaction without additional activation. The cycle was repeated at least 3 times under the conditions of Example 3 to systematically evaluate its cycling stability.

[0050] Figure 9 Cyclic stability test results for the covalent organic framework SF-COF and Figure 10The figures show the PXRD patterns of the covalent organic framework SF-COF before and after cycling. Experimental results indicate that the SF-COF maintains high photocatalytic activity for the aforementioned reactions after three cycles. Furthermore, the PXRD of SF-COF remains essentially unchanged after three cycles, demonstrating the good stability of the SF-COF photocatalyst.

[0051] In summary, this method provides a crystalline allyl covalent organic framework photocatalyst and its application in photocatalytic organic conversion. The prepared SF-COF was applied to the organic conversion of benzamide and its derivatives, catalyzing the production of 1,2,4-thiadiazole and its derivatives, with a maximum separation efficiency of 72%. This catalyst exhibits excellent photocatalytic performance and good stability.

[0052] The above description is merely a preferred embodiment of the present invention, but the invention is not limited to the disclosed content. Therefore, any modifications or equivalents made without departing from the scope of the present invention fall within the protection scope of the present invention.

Claims

1. A crystalline allyl covalent organic framework material, characterized in that, X-ray powder diffraction of crystalline allyl covalent organic framework materials showed 2 at 3.6°, 6.28°, 7.4°, and 9.58°. θ The angular signal peaks are attributed to the 100, 210, 200, and 310 crystal planes, respectively.

2. The method for preparing the crystalline allyl covalent organic framework material according to claim 1, characterized in that, Includes the following steps: (a) Prepare COF precursor by reacting trimesin with p-aminophenylacetonitrile under alkaline conditions; (b) The crystalline allyl covalent organic framework material SF-COF is prepared by solvothermal reaction of the COF precursor with 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) in the presence of an organic solvent and an acidic catalyst.

3. The preparation method according to claim 1, characterized in that, In step (a), the molar ratio of pyromellitic acetonitrile to p-aminophenylacetonitrile used as raw materials is 1-4:1-4, wherein 1:3 is preferred. The alkali includes sodium hydroxide, potassium hydroxide, and calcium hydroxide, with sodium hydroxide being preferred.

4. The preparation method according to claim 1, characterized in that, In step (b), the ratio of BTAC to 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) is 1-4:1-4, preferably 1:1; The acetic acid concentration ranges from 3 M to 12 M, with 6 M being preferred.

5. The preparation method according to claim 1, characterized in that, The solvents in step (b) include n-butanol and o-dichlorobenzene.

6. The preparation method according to claim 1, characterized in that, The solvothermal reaction described in step (b) is maintained at 120-180°C for 3-7 days; preferably at 120°C for 3 days.

7. A photocatalyst for the photocatalytic conversion of benzamide to thiadiazole, characterized in that, The catalyst is the crystalline allyl covalent organic framework material according to claim 1, or the crystalline allyl covalent organic framework material prepared by the preparation method according to any one of claims 2-6.

8. A method for preparing 1,2,4-thiadiazole compounds by cyclization of benzamide or its derivatives using the photocatalyst described in claim 7, characterized in that... Includes the following steps: At a certain temperature, benzamide or benzamide derivatives are added to a certain amount of organic solvent, followed by a certain amount of crystalline allyl covalent organic framework material. Under light irradiation and with an atmosphere introduced, the reaction proceeds for a period of time to obtain the product of organic transformation. The reaction formula is as follows: The R is any one of alkyl, alkoxy, or halogen; The alkyl group is C1-C 10 The alkoxy group is a straight-chain alkane or a branched-chain alkane; the alkoxy group includes one of methoxy, ethoxy, or propoxy; and the halogen is any one of F, Cl, Br, or I.

9. The method according to claim 8, characterized in that, The organic solvent includes any one of acetone, acetonitrile, dichloromethane, methanol, and ethanol.

10. The method according to claim 8, characterized in that, The amount of catalyst used is 1-10% of the mass of benzamide; the atmosphere introduced is air or oxygen; the light source used in the illumination process is ultraviolet LED, blue LED, white LED, green LED, or orange LED, with blue LED being preferred; the reaction temperature is at room temperature and the illumination time is 3-24 h, with 6 h being preferred.

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