Metal-organic framework cu3-pa-mcof photocatalyst and its application in synthesis of thioamide derivatives

Abstract

The present application relates to metal covalent organic framework Cu3-PA-MCOF photocatalyst and its application in synthesis of thioamide derivatives. θ =3.15° appears (100) crystal face diffraction peak. Under visible light irradiation, it is applied to the conversion of thioamide and its derivatives as a photocatalyst, the prepared Cu3-PA-MCOF material exhibits excellent photocatalytic conversion capacity, can realize the efficient and high-selectivity conversion of thioamide and its derivatives to 1,2,4-thiadiazole compounds, and the substrate has wide universality. Through the technology of the present application, the efficiency and selectivity of photocatalytic organic conversion reaction can be improved, which provides a new technical scheme for developing environment-friendly and sustainable chemical synthesis method.

Description

Technical Field

[0001] This invention relates to a method for preparing a trinuclear copper cluster metal covalent organic framework (Cu3-PA-MCOF) photocatalyst and its catalytic application in the aerobic conversion reaction of thioamides. This technical solution can effectively improve the efficiency and product selectivity of photocatalytic reactions, contributing to the development of green and sustainable chemical processes. Background Technology

[0002] Metal-covalent organic frameworks (MCOFs) are a novel type of porous material with a crystalline state. They combine the high stability and well-defined pores of covalent organic frameworks (COFs) with the rich functionality and designable active sites of metal-organic frameworks (MOFs), creating a novel multifunctional material platform where "1+1>2". With their unique hybrid structure, they have broad application potential in heterogeneous catalysis, energy storage and conversion, smart sensing and optoelectronics, and efficient gas separation.

[0003] Photocatalysis converts 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 photogenerated carrier separation efficiency, limited solar light utilization range, and the difficulty of balancing catalytic activity and stability. Therefore, researchers have introduced molecularly-coated free radicals (MCOFs) into the field of photocatalysis, utilizing their highly designable structure to precisely customize the superior performance of the catalyst at the molecular level.

[0004] Cu3-PA-MCOF, as a novel metal-organic covalent framework material, combines broad-spectrum absorption, efficient charge separation mechanism, and customizable active channels, thus achieving high activity, high selectivity, and good recyclability in photocatalytic organic conversion reactions. This provides an ideal material platform for developing more efficient, precise, and sustainable catalytic processes. Although previous studies have reported the synthesis of Cu3-PA-MCOF and its preliminary applications in photocatalysis, further research is needed to optimize its preparation process and explore its application in specific organic conversion reactions. Therefore, this invention proposes a method for efficiently preparing Cu3-PA-MCOF metal-organic covalent framework photocatalysts and systematically studies its novel applications in photocatalytic organic conversion, 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 of the Invention

[0005] This invention provides a method for preparing a highly efficient Cu3-PA-MCOF photocatalyst, aiming to solve the core problems of low efficiency and low visible light utilization in existing metal covalent organic framework materials in photocatalytic organic conversion, thereby obtaining a material with excellent photocatalytic performance.

[0006] The technical objective of this invention is to provide a Cu3-PA-MCOF metal photocatalyst, wherein the catalyst comprises approximately 2 θ= A small-angle peak is observed at 3.15°. The presence of this small-angle characteristic diffraction signal confirms that the material has a regular crystalline structure, which is direct evidence of its successful synthesis. It is marked as the (100) crystal plane.

[0007] To determine the product of this scheme, in the Fourier transform infrared spectroscopy detection of this invention, the photocatalyst includes Cu3-PA-MCOF 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 The peak attributable to the stretching vibration of the aldehyde group C=O further confirms that the precursor reaction was complete.

[0008] Another technical objective of this invention is to provide a highly efficient method for preparing Cu3-PA-MCOF metal photocatalysts. The method for preparing Cu3-PA-MCOF metal photocatalysts mainly includes the following steps:

[0009] (a) Prepare cyclic trinuclear copper cluster Cu3L by thermally reacting copper nitrate with 1H-pyrazole-4-carboxaldehyde in a solvent;

[0010] (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.

[0011] 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.

[0012] In some preferred embodiments, the preparation of the cyclic trinuclear copper cluster unit Cu3L is as follows:

[0013] A certain amount of copper nitrate was weighed and mixed with 1H-pyrazole-4-carboxaldehyde in a mixed solvent of N,N-dimethylformamide, deionized water, and ethanol. The reaction system was placed in a high-pressure reactor lined with polytetrafluoroethylene and heated to 60-120 °C under sealed conditions for 12-48 h. After the reaction was completed, the mixture was washed with H2O and dried overnight at 120 °C to obtain pale yellow crystalline trinuclear copper cluster units Cu3L.

[0014] The acid catalyst mentioned in step (b) is trifluoroacetic acid with a concentration of 3-12 M, preferably 6 M;

[0015] The molar ratio of Cu3L to p-phenylenediamine is 1:1 to 3:3, preferably 2:3.

[0016] 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.

[0017] Preparation of Cu3-PA-MCOF:

[0018] In some preferred embodiments, the preparation steps of Cu3-PA-MCOF involve weighing a certain mass of cyclic trinuclear copper cluster unit Cu3L and p-phenylenediamine into a reactor, adding a certain amount of trifluoroacetic acid catalyst, and adding a certain amount of solvent of 1,2-dichlorobenzene and 1-butanol to the reaction system. The mixture is thoroughly mixed and shaken until the solution reaches a homogeneous state. At a certain temperature, a "freezing-vacuuming-thawing" cycle is performed to remove gas. Subsequently, the glass tube is sealed, and the temperature is heated to the specified reaction temperature and maintained for a period of time to ensure the reaction proceeds fully. After the reaction, the obtained solid product needs to be washed and filtered multiple times in different solvents to remove impurities. After washing, the solid product is placed in a pre-set vacuum drying oven for drying. Once drying is complete, the target product is finally obtained.

[0019] The washing step (2) involves sequentially washing with N,N-dimethylformamide, methanol, ethanol and dichloromethane, repeating 3-5 times, preferably 3 times.

[0020] In step (2), the product is placed in a vacuum drying oven and dried at a temperature of 60-120°C, preferably 80°C, for no less than 12 hours.

[0021] The present invention also provides a photocatalyst for the photocatalytic organic conversion of thioamides to thiadiazoles, wherein the catalyst is the crystalline covalent organic framework material described above, or the crystalline covalent organic framework material prepared by the preparation method described above.

[0022] The present invention also provides the application of the Cu3-PA-MCOF photocatalyst in the photocatalytic synthesis of 1,2,4-thiadiazole compounds.

[0023] This invention also provides a method for the formation of thiadiazole from thioamides catalyzed by a Cu3-PA-MCOF metal photocatalyst, characterized by comprising the following steps:

[0024] First, weigh out a certain amount of the thioamide derivative and the photocatalyst, and measure out a certain volume of the reaction solvent, placing them in a light-transmitting glass bottle. Ensure complete dissolution and uniform dispersion. Then, control the gas flow rate to maintain stable reaction conditions. Place the glass bottle under a light source and continuously stir the mixture to promote the reaction. Irradiate at a certain temperature for a certain time to carry out the catalytic reaction; the specific time depends on the experimental design. After the experiment, process the reaction system, collect the products, and analyze them to confirm the success of the reaction and the catalytic effect of the photocatalyst. The reaction formula is as follows:

[0025] .

[0026] The oxidant is a highly reactive oxygen species that can be generated during organic transformation reactions and intervene in the aerobic organic reaction process.

[0027] The solvent is methanol, ethanol, acetonitrile, ethyl acetate, or dichloromethane, with methanol being preferred;

[0028] The gas introduced into the process is air, oxygen, or air, preferably oxygen.

[0029] The light source is white light, blue light, green light, ultraviolet light, orange light, or a xenon lamp, with white light being preferred.

[0030] The reaction temperature is from room temperature to 60°C, and the reaction time is 3-36 h, preferably 18 h.

[0031] The solvent used for washing is methanol, ethanol, acetonitrile, ethyl acetate, or dichloromethane, with ethanol being preferred.

[0032] 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.

[0033] The specific beneficial effects of this material are manifested as follows:

[0034] The preparation of a Cu3-PA-MCOF photocatalyst according to the present invention and its application in the field of photocatalytic organic conversion have the following beneficial effects:

[0035] 1. Highly efficient and precise catalytic performance: The Cu3-PA-MCOF photocatalyst can achieve efficient activation and conversion of thioamides to thiadiazoles under mild visible light (especially white light). By optimizing the reaction conditions, it is possible to obtain the target product with high conversion rate and high selectivity at the same time, and reduce the generation of side reactions.

[0036] 2. Synergistic Effect and Efficient Separation of Photogenerated Carriers: Compared with single-metal COFs, the synergistic effect between the conjugated framework formed by Cu and PA ligands in Cu3-PA-MCOF is the key to its superior performance. This synergistic effect can effectively regulate the electronic structure of the material, acting as an internal electron transfer channel, significantly promoting the separation of photogenerated electron-hole pairs and extending their lifetime, thereby converting more light energy into chemical energy and driving the catalytic reaction to proceed efficiently.

[0037] 3. The preparation method is simple and has the potential for large-scale production: The Cu3-PA-MCOF catalyst can be synthesized via a mild and simple solvothermal method, which has good potential for large-scale production. It exhibits high activity and versatility in the conversion of various thioamide derivatives. This synergistic advantage of "easy preparation" and "wide applicability" lays a solid foundation for its industrial application.

[0038] 4. Green System and Mild Conditions: This catalytic system integrates multiple green elements, using clean visible light as energy, air as a green oxidant, and low-toxicity alcohols as solvents, and operates at room temperature / normal pressure. It systematically eliminates dependence on precious metals, high temperatures and pressures, and toxic reagents, fundamentally conforming to the principle of atom economy, and combining operational safety with process economy. Attached Figure Description

[0039] Figure 1 This is a synthesis route diagram for Cu3L materials.

[0040] Figure 2 This is a synthesis route diagram for Cu3-PA-MCOF materials.

[0041] Figure 3 The image shows the powder X-ray diffraction pattern of Cu3L.

[0042] Figure 4 The powder X-ray diffraction pattern of Cu3-PA-MCOF material.

[0043] Figure 5 Fourier transform infrared spectra of Cu3-PA-MCOF and PA, Cu3L.

[0044] Figure 6 The 1H NMR spectrum of 3,5-di-p-tolyl-1,2,4-thiadiazole.

[0045] Figure 7 The 1H NMR spectrum of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole.

[0046] Figure 8 The NMR spectrum of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole is shown in the 1H NMR spectrum.

[0047] Figure 9 The 1H NMR spectrum of 3,5-di-m-tolyl-1,2,4-thiadiazole. Detailed Implementation

[0048] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0049] Example 1

[0050] Synthesis of Cu3L, a trinuclear copper cluster unit:

[0051] Copper nitrate (0.83 mmol, 0.20 g) and 1H-pyrazole-4-carboxaldehyde (1.0 mmol, 0.096 g) were weighed and placed in a polytetrafluoroethylene-lined high-pressure reactor. A mixed solution of N,N-dimethylformamide (6.7 mL), H2O (5.0 mL), and ethanol (6.7 mL) was added. The reaction system was then placed in an oven set to 100 °C and heated for 24 h. After the reaction was complete, the reactor was brought to room temperature, washed with H2O, filtered, and dried overnight in an oven at 120 °C. The product was collected, finally yielding pale yellow crystalline trinuclear copper cluster unit Cu3L.

[0052] Figure 1 The synthetic route for preparing Cu3L is shown in Example 1.

[0053] Figure 3 The image shows the powder X-ray diffraction (PXRD) pattern of Cu3L. The simulated PXRD pattern of Cu3L (CIF file number 2026064, obtained from the Cambridge Crystallography Data Centre (CCDC), was used to fit the PXRD pattern of the experimental sample to verify the phase purity and crystal structure of the synthesized material) was compared with the PXRD pattern of the Cu3L sample prepared using the method in Example 1. The results showed that the diffraction peak positions of both patterns largely overlapped and there were no other impurity peaks, indicating that Cu3L could be successfully prepared using Example 1.

[0054] Example 2

[0055] Synthesis of Cu3-PA-MCOF:

[0056] 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.

[0057] Figure 2 The synthetic route for preparing Cu3-PA-MCOF is shown in Example 2.

[0058] 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.

[0059] 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.

[0060] Example 3

[0061] Synthesis of 3,5-di-p-tolyl-1,2,4-thiadiazole:

[0062]

[0063] 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.

[0064] 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.

[0065] Example 3-1

[0066] Synthesis of 3,5-bis(4-fluorophenyl)-1,2,4-thiadiazole:

[0067]

[0068] 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).

[0069] 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.

[0070] Example 3-2

[0071] Synthesis of 3,5-bis(4-chlorophenyl)-1,2,4-thiadiazole:

[0072]

[0073] 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).

[0074] 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.

[0075] Example 3-3

[0076] Synthesis of 3,5-di-m-tolyl-1,2,4-thiadiazole:

[0077]

[0078] 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).

[0079] 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.

[0080] 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.

[0081] 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. The application of a Cu3-PA-MCOF photocatalyst in the photocatalytic synthesis of 1,2,4-thiadiazole compounds, characterized in that, This includes the reaction of thioamides with oxygen in an organic solvent under light conditions, in the presence of a Cu3-PA-MCOF photocatalyst with a metal covalent organic framework, as shown in the following reaction formula: The R is alkyl, aryl, haloaryl, alkoxy, or heteroaryl; Powder X-ray diffraction patterns of Cu3-PA-MCOF photocatalysts 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: Its Fourier transform infrared spectrum is at 1620 cm⁻¹ -1 The peak of C=N stretching vibration is displayed at this location.

2. The application according to claim 1, 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 a xenon lamp. The reaction temperature is from room temperature to 60°C, and the reaction time is 3-36 h.

3. The application according to claim 1, characterized in that, The amount of the photocatalyst used is 1-10% of the reactant mass.

Images