Metal covalent organic framework Cu3-PA-MCOF photocatalyst and application thereof in thioamide derivative synthesis

Abstract

The invention relates to a metal covalent organic framework Cu3-PA-MCOF photocatalyst and application of the metal covalent organic framework Cu3-PA-MCOF photocatalyst in synthesis of thioamide derivatives. A cyclic trinuclear copper cluster unit Cu3L is synthesized from copper nitrate and 1H-pyrazole-4-formaldehyde, a Cu3-PA-MCOF material is prepared from p-phenylenediamine through a solvothermal method, and a (100) crystal face diffraction peak appears at the position of 2theta = 3.15 degrees through XRD (X-Ray Diffraction) of the Cu3-PA-MCOF material. Under visible light irradiation, the Cu3-PA-MCOF material serves as a photocatalyst to be applied to conversion of thioamide and derivatives thereof, the prepared Cu3-PA-MCOF material shows excellent photocatalytic conversion capacity, efficient and high-selectivity conversion of thioamide and derivatives thereof to 1, 2, 4-thiadiazole compounds can be achieved, and the universality range of a substrate is wide. Through the technology provided by the invention, the efficiency and selectivity of photocatalytic organic conversion reaction can be improved, and a new technical scheme is provided for developing an environment-friendly and sustainable chemical synthesis method.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a trinuclear copper cluster metal covalent organic framework (Cu3-PA-MCOF) photocatalyst, and its catalytic application in thioamide aerobic conversion reactions. The technical solution can effectively improve the efficiency and product selectivity of photocatalytic reactions, and is helpful to promote the development of green and sustainable chemical processes. BACKGROUND

[0002] Metal covalent organic framework (MCOF) is a new type of material with crystalline state and porosity. It has high stability and regular channels of covalent organic framework (COF), as well as rich functions and designable active sites of metal organic framework (MOF), creating a new multifunctional material platform of "1+1>2". With its unique hybrid structure, it has wide application potential in the fields of heterogeneous catalysis, energy storage and conversion, intelligent sensing and photoelectricity, and efficient gas separation.

[0003] Photocatalytic technology can convert solar energy into chemical energy for environmental purification and energy production, and the performance of photocatalysts is the core of this technology. Current photocatalysts still face some common challenges: low efficiency of photogenerated carrier separation, limited range of solar light utilization, and difficulty in balancing catalytic activity and stability. Therefore, researchers have introduced MCOF into the field of photocatalysts, using highly designable structures to precisely customize the excellent performance of catalysts from the molecular level.

[0004] Cu3-PA-MCOF, as a new type of metal covalent organic framework material, combines wide spectrum light absorption ability, efficient charge separation mechanism and customizable active channels, thereby achieving high activity, high selectivity and good recyclability in photocatalytic organic transformation reactions, providing an ideal material platform for developing more efficient, precise and sustainable catalytic processes. Although there have been reports on the synthesis of Cu3-PA-MCOF and its preliminary application in photocatalysis, the optimization of its preparation process and the in-depth exploration of its application in specific organic transformation reactions remain to be explored. Therefore, the present application proposes a method for efficiently preparing Cu3-PA-MCOF metal organic covalent framework photocatalyst, and systematically studies its novel application in photocatalytic organic transformation, aiming to expand the functional boundaries of this material in the field of photocatalysis and provide new ideas and experimental basis for the development and application of related technologies. SUMMARY

[0005] The present application provides a preparation method of efficient Cu3-PA-MCOF photocatalyst, which aims to solve the core problems of low efficiency and low visible light utilization of existing metal covalent organic framework materials in photocatalytic organic transformation, thereby obtaining materials with excellent photocatalytic performance.

[0006] The technical purpose of the present application is to provide a Cu3-PA-MCOF metal photocatalyst, which comprises a Cu3-PA-MCOF crystal structure with a space group of P-1 and a lattice parameter of a = 1. 2 θ= 3. 15°, the appearance of a small-angle characteristic diffraction signal, which confirms that the material has a regular crystal structure and is direct evidence of the successful synthesis thereof. Marked as (100) crystal face.

[0007] To determine the product of the present scheme, in the Fourier infrared spectrum detection, the photocatalyst comprises a C=N stretching vibration peak observed at about 1620 cm -1 -1 of Cu3-PA-MCOF, indicating the successful formation of an imine bond. At the same time, no N-H stretching vibration peak is detected at 3307 cm -1 and 3377 cm -1 -1 of Cu3-PA-MCOF, and a stretching vibration peak attributed to aldehyde group C=O at about 1670 cm -1 -1, further confirming the complete reaction of the precursor.

[0008] Another technical purpose of the present application is to provide an efficient preparation method of Cu3-PA-MCOF metal photocatalyst, which mainly comprises the following steps: (a) allowing copper nitrate to react with 1H-pyrazole-4-carboxaldehyde in a solvent to prepare a trinuclear copper cluster Cu3L; (b) allowing the Cu3L to react with p-phenylenediamine in an acid catalyst in an organic solvent, and performing solvent thermal treatment, washing and drying to obtain Cu3-PA-MCOF.

[0009] The solvent in step (a) is a mixed solvent of N,N-dimethylformamide, water and ethanol, the reaction temperature is 60-120°C, and the reaction time is 12-48 h.

[0010] In some preferred cases, the preparation of the trinuclear copper cluster unit Cu3L comprises: A certain amount of copper nitrate and 1H-pyrazole-4-carboxaldehyde are mixed in a mixed solvent of N,N-dimethylformamide, deionized water and ethanol, the reaction system is loaded into a polytetrafluoroethylene-lined high-pressure reaction kettle, heated to 60-120°C under airtight conditions, and the reaction time is 12-48 h. After the reaction is completed, washing is performed with H2O, and drying is performed at 120°C overnight to obtain a light yellow crystal trinuclear copper cluster unit Cu3L.

[0011] The acid catalyst in step (b) is trifluoroacetic acid, and the concentration is 3-12 M, preferably 6 M; The molar ratio of Cu3L to p-phenylenediamine is 1:1 to 3:3, preferably 2:3.

[0012] The organic solvent in step (b) is a mixed solvent of 1,2-dichlorobenzene and 1-butanol, with a volume ratio of 1:1 to 8:8, preferably 7:3; the reaction temperature is 80-160℃, and the reaction time is 60-72 h, preferably 120℃ and 72 h.

[0013] Preparation of Cu3-PA-MCOF: In some preferred cases, the preparation steps of the Cu3-PA-MCOF are as follows: a certain mass of the trinuclear copper cluster unit Cu3L and p-phenylenediamine are weighed into a reactor, a certain amount of trifluoroacetic acid catalyst is added, and a certain amount of a solvent of 1,2-dichlorobenzene and 1-butanol is added to the reaction system, which is mixed and shaken until the solution is uniform. Under a certain temperature, the "freezing-vacuumizing-thawing" cycle is used for degassing treatment. Then the glass tube is sealed, the temperature is heated to the specified reaction temperature, and the reaction is kept for a period of time to ensure that the reaction is fully carried out. After the reaction is completed, the obtained solid product needs to be washed and filtered in different solvents for several times to remove impurities in the product. After washing, the solid product is placed in a vacuum drying oven for drying, and the target product is finally obtained after drying.

[0014] The washing step in step (2) is sequential washing with N,N-dimethylformamide, methanol, ethanol and dichloromethane, which is repeated for 3-5 times, preferably 3 times.

[0015] The product in step (2) is dried in a vacuum drying oven, with a set temperature of 60-120℃, preferably 80℃, and for no less than 12 h.

[0016] The application also provides a photocatalyst for photocatalytic conversion of thioamide organic compounds to thiadiazoles, which is the crystalline covalent organic framework material or the crystalline covalent organic framework material prepared by the preparation method.

[0017] The application also provides an application of the Cu3-PA-MCOF photocatalyst in photocatalytic synthesis of 1,2,4-thiadiazole compounds.

[0018] The application also provides a method for generating thiadiazoles from thioamides by using a Cu3-PA-MCOF metal photocatalyst, which comprises the following steps: First, a certain amount of thioamide derivative and photocatalyst are weighed, a certain volume of reaction solvent is measured, and is placed in a light-permeable glass bottle. Dissolve thoroughly to ensure uniform dispersion. Then, control the flow of gas to maintain stable reaction conditions. Place the glass bottle under the light source and continuously stir the mixed solution to facilitate the reaction. Carry out the catalytic reaction at a certain temperature for a certain time, which is determined by the experimental design. After the experiment is completed, the reaction system is treated, the product is collected and analyzed to confirm the success of the reaction and the catalytic effect of the photocatalyst. The reaction formula is as follows: .

[0019] The oxidant is a high active oxygen species that can be generated during organic conversion reactions and intervene in aerobic organic reactions.

[0020] The solvent is methanol, ethanol, acetonitrile, ethyl acetate, dichloromethane, preferably methanol; The gas introduced into the middle is air, oxygen and air, preferably oxygen.

[0021] The light source is white light, blue light, green light, ultraviolet light, orange light or xenon lamp, preferably white light.

[0022] The reaction temperature is room temperature to 60 DEG C, and the reaction time is 3-36 h, preferably 18 h.

[0023] The solvent used for washing is methanol, ethanol, acetonitrile, ethyl acetate, dichloromethane, preferably ethanol.

[0024] The general formula of the thioamide derivative is R-C(S)NH2, wherein R is alkyl, aryl, halogenated aryl, alkoxy or heteroaryl, and the amount of the photocatalyst is 1-10% of the mass of the reactant.

[0025] The specific beneficial effects of the material are as follows: The preparation of the Cu3-PA-MCOF photocatalyst and its application in the field of photocatalytic organic conversion have the following beneficial effects: 1. High efficient and precise catalytic performance: the Cu3-PA-MCOF photocatalyst can realize efficient activation and conversion of thioamide to thiazole under the driving of mild visible light (especially white light), and through optimization of reaction conditions, high conversion rate and high selectivity of target product can be obtained, reducing the generation of side reactions.

[0026] 2. Synergistic effect and efficient separation of photo-generated carriers: The synergistic effect between the conjugated skeleton formed by Cu and PA ligand in Cu3-PA-MCOF is the key to its performance beyond. This synergistic effect can effectively regulate the electronic structure of the material, as an internal electron transfer channel, significantly promote the separation of photo-generated electron-hole pairs, and prolong their lifetime, thereby converting more light energy into chemical energy to drive the efficient progress of the catalytic reaction.

[0027] 3. The preparation method is simple and has the potential for large-scale production: Cu3-PA-MCOF catalyst can be synthesized by a mild and simple solvothermal method, and the route has good potential for large-scale production. It shows high activity and universality in the conversion of a variety of thioamide derivatives. This synergistic advantage of "easy to prepare" and "widely applicable" lays a solid foundation for its industrial application.

[0028] 4. Green system, mild conditions: The catalytic system integrates multiple green elements, using clean visible light as energy, air as green oxidant, low-toxicity alcohol as solvent, and operating at room temperature / normal pressure. The system systematically gets rid of the dependence on noble metals, high temperature and pressure, and toxic reagents, fundamentally meets the principle of atom economy, and has both operational safety and process economy. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The synthesis route map of Cu3L material.

[0030] Figure 2 The synthesis route map of Cu3-PA-MCOF material.

[0031] Figure 3 The powder X-ray diffraction spectrum of Cu3L.

[0032] Figure 4 The powder X-ray diffraction spectrum of Cu3-PA-MCOF material.

[0033] Figure 5 The Fourier transform infrared spectrum of Cu3-PA-MCOF and PA, Cu3L.

[0034] Figure 6 The nuclear magnetic resonance hydrogen spectrum of 3,5-di-p-tolyl-1,2,4-thiadiazole.

[0035] Figure 7 The nuclear magnetic resonance hydrogen spectrum of 3,5-di(4-fluorophenyl)-1,2,4-thiadiazole.

[0036] Figure 8 The nuclear magnetic resonance hydrogen spectrum of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole.

[0037] Figure 9 The NMR spectrum of 3,5-di-m-tolyl-1,2,4-thiadiazole. DETAILED DESCRIPTION

[0038] The application will be further described in conjunction with the following examples, but the application is not limited to the following examples.

[0039] Example 1 Synthesis of Cu3L: Copper nitrate (0.83 mmol, 0.20 g) and 1H-pyrazole-4-carboxaldehyde (1.0 mmol, 0.096 g) were weighed into a Teflon-lined autoclave, and a mixture of N,N-dimethylformamide (6.7 mL), H2O (5.0 mL), and ethanol (6.7 mL) was added. Subsequently, the reaction system was placed in an oven set at 100 °C and heated for 24 h. After the reaction was completed, the autoclave was returned to room temperature, washed with H2O, filtered, and transferred to a 120 °C oven for drying overnight. The product was collected, and light yellow crystalline Cu3L was obtained.

[0040] Figure 1 The synthetic route for preparing Cu3L in Example 1.

[0041] Figure 3 The PXRD spectrum of Cu3L. The PXRD spectrum of Cu3L prepared by the method of Example 1 was compared with the PXRD spectrum of Cu3L by simulating the PXRD spectrum of Cu3L (the Cu3L single crystal structure CIF file with the accession number 2026064 from the Cambridge Crystallographic Data Centre (CCDC) was used to fit the PXRD spectrum of the experimental sample, so as to verify the phase purity and crystal structure of the synthesized material). It was found that the diffraction peak positions of the two were basically coincident and no other impurity peaks were found, that is, Cu3L could be successfully prepared by the method of Example 1.

[0042] Example 2 Synthesis of Cu3-PA-MCOF: Weigh out the cyclic trinuclear copper cluster unit Cu3L (0.05 mmol, 23.7 mg) and p-phenylenediamine (PA) (0.075 mmol, 23.7 mg) prepared in Example 1, mix them thoroughly, add trifluoroacetic acid (6 M, 0.1 mL) catalyst, and add 1,2-dichlorobenzene (0.7 mL) and 1-butanol (0.3 mL) to the reaction system. Mix thoroughly and shake until the solution reaches a homogeneous state. Flame seal under dynamic vacuum. After sealing, heat at 120 °C for 72 h. After the reaction is complete, the obtained solid product is washed in sequence with N,N-dimethylformamide, methanol, ethanol and dichloromethane. After washing, the solid product is placed in a vacuum drying oven at 80 °C and dried for 24 h. After drying, a black powdery Cu3-PA-MCOF material is obtained.

[0043] Figure 2 The synthetic route for preparing Cu3-PA-MCOF is shown in Example 2.

[0044] Figure 4 The powder X-ray diffraction pattern of Cu3-PA-MCOF material; the powder X-ray diffraction pattern of Cu3-PA-MCOF material at 2 θ= The presence of characteristic diffraction peaks of the (100) and (110) crystal planes at 3.15° and 5.42° indicates that the material has successfully constructed a highly ordered two-dimensional channel structure and has good crystallinity.

[0045] Figure 5 Fourier transform infrared spectra of Cu3-PA-MCOF and its precursors PA and Cu3L. Cu3-PA-MCOF exhibits Fourier transform infrared spectra at approximately 1620 cm⁻¹. -1 The observation of the C=N stretching vibration peak at 3307 cm⁻¹ indicates successful imine bond formation. Meanwhile, the peak at 3307 cm⁻¹ was not detected in Cu₃-PA-MCOF. -1 and 3377 cm -1 The NH stretching vibration peak at approximately 1670 cm⁻¹, and the peak at approximately 1670 cm⁻¹. -1 The peak attributable to the stretching vibration of the aldehyde group C=O further confirms the complete reaction of the precursor. Cu3-PA-MCOF was successfully prepared using the method described in Example 1, and its structure was confirmed by characterization.

[0046] Example 3 Synthesis of 3,5-di-p-tolyl-1,2,4-thiadiazole:

[0047] In a transparent glass reactor, 0.2 mmol of 4-tolylthiocarboxamide and 8 mg of photocatalyst Cu3-PA-MCOF were added. Acetonitrile (2 mL) was then injected as a solvent, and oxygen was introduced into the reaction system. The reactor was placed in a white light reaction apparatus and stirred at room temperature for 18 h. After the reaction was complete, the product 3,5-di-p-tolyl-1,2,4-thiadiazole (17.1 mg, 77%, separation yield) was obtained after separation and purification.

[0048] Figure 6 The figure shows the 1H NMR spectrum of 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole, indicating that 3,5-bis(4-methylphenyl)-1,2,4-thiadiazole was successfully synthesized.

[0049] Example 3-1 Synthesis of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole:

[0050] In a transparent glass reaction flask equipped with a magnetic stir bar, 0.2 mmol of 4-fluorophenyl thiocarboxamide and 5 mg of photocatalyst Cu3-PA-MCOF were accurately weighed. Then, 1.5 mL of N,N-dimethylformamide (DMF) was injected as a solvent using a pipette, and O2 was continuously bubbled into the reaction mixture. The flask was sealed and placed in a white LED reactor, where it was stirred vigorously at a constant temperature of 40°C for 10 h. After the reaction was complete, the entire reaction mixture was transferred to a centrifuge tube, and the catalyst was completely recovered by centrifugation for 5 minutes. The supernatant was subjected to rotary evaporation to remove the solvent, and the crude product was purified by silica gel column chromatography to obtain white flaky crystals of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole (16.9 mg, 78%, isolated yield).

[0051] Figure 7 The figure shows the 1H NMR spectrum of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole, indicating that 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole was successfully synthesized.

[0052] Example 3-2 Synthesis of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole:

[0053] In a pressure-resistant transparent glass tube, 0.2 mmol of 4-chlorophenylthiocarboxamide, 12 mg of photocatalyst Cu3-PA-MCOF, and 2.5 mL of 1,4-dioxane were added sequentially. The glass tube was connected to a double-tube vacuum system, and three cycles of freezing-vacuuming-thawing were performed to remove air, with a suitable amount of oxygen added under vacuum. The sealed glass tube was placed in a multifunctional photochemical reactor, and the reaction was stirred at room temperature for 36 h under blue LED illumination. After the reaction was complete, the glass tube was carefully opened, and the reaction solution was filtered through a polytetrafluoroethylene microporous membrane to separate the catalyst. The filtrate was concentrated and recrystallized using an ethanol / water mixed solvent to obtain a white powdery solid 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole (17.3 mg, 75%, separation yield).

[0054] Figure 8 The figure shows the 1H NMR spectrum of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole, indicating that 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole was successfully synthesized.

[0055] Example 3-3 Synthesis of 3,5-di-m-tolyl-1,2,4-thiadiazole:

[0056] In a 50 mL round-bottom flask, 0.2 mmol of 3-tolylthioformamide and 8 mg of photocatalyst Cu3-PA-MCOF were added. Then, a mixture of 3.0 mL of tert-butanol and 0.5 mL of toluene was injected. Air was continuously and slowly bubbled into the reaction system. The flask was placed under a xenon lamp (equipped with a 420 nm filter to simulate visible light), and the reaction was carried out under electromagnetic stirring at room temperature for 12 h. After the reaction was complete, the reaction mixture was filtered directly through a sintered glass funnel, and the solid catalyst was washed three times with a small amount of dichloromethane. The filtrate and washings were combined, concentrated under reduced pressure, and purified by preparative thin-layer chromatography to obtain a colorless, transparent oily substance, which solidified upon standing to form 3,5-di-m-tolyl-1,2,4-thiadiazole (16.2 mg, 74%, separation yield).

[0057] Figure 9 The figure shows the 1H NMR spectrum of 3,5-dimethyl-p-tolyl-1,2,4-thiadiazole, indicating that 3,5-di-m-tolyl-1,2,4-thiadiazole was successfully synthesized.

[0058] In summary, this invention successfully prepared a highly efficient Cu3-PA-MCOF metal photocatalyst and pioneered its innovative application in photocatalytic organic synthesis. In the catalytic synthesis of 1,2,4-thiadiazole from thioamides and their derivatives, this catalyst exhibits excellent catalytic efficiency, with a maximum conversion rate of 78%. Furthermore, the catalyst possesses excellent high conversion and high selectivity, effectively generating the target product and reducing the generation of side reactions. It provides a reliable catalyst solution for achieving green and economical organic synthesis processes.

[0059] 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 metal covalent organic framework Cu3-PA-MCOF photocatalyst, characterized in that, The powder X-ray diffraction pattern of the covalent organic framework is shown in 2. θ At 3.15°, there is a characteristic diffraction peak belonging to the (100) crystal plane, and its structural formula is as follows: 。 2. The photocatalyst according to claim 1, characterized in that, Its Fourier transform infrared spectrum is at 1620 cm⁻¹ -1 The peak of C=N stretching vibration is displayed at this location.

3. A method for preparing the Cu3-PA-MCOF photocatalyst as described in claim 1 or 2, characterized in that, Includes the following steps: (a) Prepare cyclic trinuclear copper cluster Cu3L by thermally reacting copper nitrate with 1H-pyrazole-4-carboxaldehyde in a solvent; (b) The Cu3L is reacted with p-phenylenediamine in an organic solvent under acid catalysis, followed by solvothermal treatment, washing and drying to obtain Cu3-PA-MCOF.

4. The preparation method according to claim 3, characterized in that, The solvent in step (a) is a mixture of N,N-dimethylformamide, water and ethanol, the reaction temperature is 60-120℃, and the reaction time is 12-48 h.

5. The preparation method according to claim 3, characterized in that, The acid catalyst mentioned in step (b) is trifluoroacetic acid at a concentration of 3-12 M; The molar ratio of Cu3L to p-phenylenediamine is 1~3:1~3; The organic solvent mentioned in step (b) is a mixed solvent of 1,2-dichlorobenzene and 1-butanol, with a volume ratio of 1~8:1~8; The reaction temperature is 80-160℃, and the reaction time is 60-72 h.

6. The preparation method according to claim 5, characterized in that, The acid catalyst mentioned in step (b) is trifluoroacetic acid at a concentration of 6 M; The molar ratio of Cu3L to p-phenylenediamine is 2:3; The organic solvent mentioned in step (b) is a mixed solvent of 1,2-dichlorobenzene and 1-butanol in a volume ratio of 7:3; The reaction temperature was 120℃ and the reaction time was 72 h.

7. A photocatalyst for the organic conversion of thioamides or their derivatives into thiadiazoles, characterized in that, The catalyst is the metal covalent organic framework Cu3-PA-MCOF as described in claim 1 or 2, or the metal covalent organic framework Cu3-PA-MCOF prepared by the preparation method described in any one of claims 3-6.

8. The application of the Cu3-PA-MCOF photocatalyst as described in claim 1 or 2 in the photocatalytic synthesis of 1,2,4-thiadiazole compounds.

9. A method for photocatalytic synthesis of 1,2,4-thiadiazole compounds, characterized in that, This includes reacting thioamides or their derivatives with oxygen in an organic solvent under light irradiation, in the presence of the Cu3-PA-MCOF photocatalyst as described in claim 1 or 2, with the following reaction formula: The R is alkyl, aryl, haloaryl, alkoxy, or heteroaryl.

10. The method according to claim 9, characterized in that, The organic solvent is selected from one or more of methanol, ethanol, acetonitrile, acetone, dichloromethane, N,N-dimethylformamide, 1,4-dioxane, tert-butanol or toluene; the light source is white light, blue light or xenon lamp; the reaction temperature is room temperature to 60°C; and the reaction time is 3-36 h. The general formula of the thioamide derivative is RC(S)NH2, where R is alkyl, aryl, haloaryl, alkoxy, or heteroaryl, and the amount of the photocatalyst is 1-10% of the reactant mass.

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