Preparation method and application of copper cluster-phenothiazinyl metal organic framework with visible light catalysis C-N bond cross coupling performance

Abstract

The invention belongs to the technical field of photocatalytic materials, and relates to a preparation method and application of a copper cluster-phenothiazinyl metal organic framework with visible light catalysis C-N bond cross coupling performance, and the preparation method comprises the following steps: taking 3, 7-bis (4-pyridyl)-10-(4-(4-pyridyl) phenyl) phenothiazine PyPTH as an organic ligand, taking cuprous iodide as a metal salt, and carrying out hydrothermal reaction to obtain the copper cluster-phenothiazinyl metal organic framework with visible light catalysis C-N bond cross coupling performance. The copper cluster-phenothiazinyl metal organic framework Cu4I4-PyPTH is prepared through a solvothermal method, and the synthesis route of the copper cluster-phenothiazinyl metal organic framework Cu4I4-PyPTH is as follows: PyPTH + CuI-Cu4I4-PyPTH; an LED with the wavelength of 405 nm is used as a light source, inert aryl chloride is activated under the mild condition, and Ullmann coupling reaction is achieved. According to the prepared target material Cu4I4-PyPTH, an LED with the wavelength of 405 nm can be used as a light source, inert aryl chloride is activated under the mild condition, light-copper concerted catalysis C-N coupling reaction is achieved, and the good yield and substrate applicability are achieved.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a copper cluster-phenothiazine-based metal organic framework with visible light catalytic C-N bond cross-coupling performance, belonging to the technical field of photocatalytic materials. Background Art

[0002] The C–N bond is an important building block of organic molecules and is also a basic module that gives biological activity to fine chemicals such as pharmaceuticals and pesticides. The formation reaction of the C–N bond is one of the most basic methods in organic synthetic chemistry and has important application value in fields such as biomedicine. In 1903, Ullmann used the inexpensive transition metal copper as a catalyst to successfully couple aromatic halides with nitrogen-centered nucleophiles. The Ullmann coupling reaction has become one of the most classic methods for constructing aromatic C–N bonds and is widely used in the preparation of fine chemical pharmaceuticals and pesticide intermediates.

[0003] However, the oxidative addition step of Cu(I) to the aryl carbon-halogen bond has a high energy barrier, so it relies on harsh reaction conditions such as high temperature and strong base, and usually requires the use of a substantially equivalent or even equivalent copper catalyst. Even under the above-mentioned enhanced reaction conditions, the Ullmann coupling reaction is usually only applicable to more active but expensive coupling reagents such as aryl iodides and bromides, while the reaction activity is low for more inert and cheap aryl chlorides.

[0004] The synergy of photocatalysis and copper catalysis provides new opportunities for the construction of C–N bonds under mild conditions. The copper complex formed by cuprous halide and organic nitrogen ligand can obtain an excited state with strong reducing ability under the excitation of near-ultraviolet light source, realizing the reductive dehalogenation of inert reagents such as aromatic and alkyl bromides and chlorides to form aromatic / alkyl radicals, and then the in situ generated Cu(II) species captures the radical species to generate Cu(III) intermediates, circumventing the high thermodynamic barriers in the oxidative addition of Cu(I) to carbon-halogen bonds in the copper-catalyzed Ullmann reaction, and can complete C–N cross-coupling at room temperature or even low temperature. However, in the above-mentioned synergistic catalytic system, the catalyst itself lacks a photosensitive unit, and its light absorption in the near-ultraviolet region depends on the coordination of large conjugated aromatic amine nucleophiles, and its light absorption capacity in the visible region is insufficient.

[0005] As a new type of organic and inorganic hybrid material with a long-range ordered structure, Metal-Organic Frameworks (MOFs) can introduce dye photosensitizing sites and transition metal cluster centers into organic ligands and metal nodes, respectively, so that the catalytic system has both visible light absorption ability and transition metal catalytic ability. By carefully designing the linking method between organic ligands and transition metal clusters, the electron transfer process in the photocatalytic cycle and the transition metal catalytic cycle is matched, thus achieving effective synergy between photocatalysis and transition metal catalysis.

[0006] Phenothiazine dyes have strong light absorption in the visible light region, and have a relatively negative excited state reduction potential, high hole mobility, and excellent photostability. Their derivatives exhibit different conformations (axial conformation and equatorial conformation) and photophysical and chemical properties due to different substituents. They are easy to connect coordination groups or expand their conjugated systems through covalent modification, which makes phenothiazine derivatives have the potential to be developed as ligands for MOFs metal organic frameworks. In addition, the non-planar butterfly-shaped bending structure of phenothiazine is also conducive to inhibiting competitive processes such as intermolecular self-aggregation during the coordination self-assembly process. Cheap and readily available cuprous iodide is a common catalyst for the Ullmann coupling reaction. In the reaction process, it is not a monodispersed copper ion, but a Cu n I n The Cu4I4 cluster is the representative smallest structural unit.

[0007] If a MOF catalyst can be constructed using phenothiazine derivatives as ligands and Cu4I4 clusters as nodes, it is expected that the monodisperse and high-density distribution of photocatalytic centers and copper catalytic centers can be taken into account, thereby improving the reactivity of photocatalytic Ullmann coupling.

[0008] The present invention uses the phenothiazine derivative PyPTH as an organic photosensitive ligand, and uses the Cu4I4 cluster as a node to obtain a copper (I) iodine cluster metal organic framework MOF material with a three-dimensional interpenetrating structure by self-assembly of the Cu4I4 cluster and the phenothiazine-based ligand PyPTH. This catalyst takes into account the monodispersity, high-density distribution, and accessibility of the photocatalytic center and the copper catalytic center, as well as the openness of the pores.

[0009] As an inert substrate, aryl halides can effectively enter the pores and achieve activation and anchoring with the photosensitive center PyPTH through weak interactions; the controllable and directional electron transfer between the substrate, the phenothiazine-based photosensitive center, and the copper cluster node effectively coordinates the two processes of photocatalysis and copper catalysis, and can achieve high conversion rates and selectivity under mild conditions. The activation of aryl chlorides in cross-coupling reactions is a long-standing challenge in organic synthesis. This reaction system can be applied to Ullmann-type coupling reactions of aryl chlorides, bromides and nitrogen-centered nucleophiles. The use of copper cluster-phenothiazine-based metal organic frameworks as new photocatalysts greatly reduces the difficulty of C–Cl activation and effectively solves the problems of traditional catalysts. It has distinct innovation and ease of application, and provides new ideas for the synthesis of fine chemicals, medicines and agrochemicals. Summary of the invention

[0010] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a preparation method and application of a copper cluster-phenothiazine-based metal organic framework with visible light catalytic C-N bond cross-coupling performance. In the target material obtained by this preparation method, the phenothiazine derivative ligand can obtain an aromatic halide free radical intermediate by relying on its own excellent photoreduction ability. After excitation, the metal cluster transfers electrons to the ligand and combines with the nucleophilic reagent, thereby realizing the catalytic cycle of the free radical pathway reaction. At the same time, the target material has a wide visible light absorption range and good thermal stability; it can be recycled many times and is easy to recycle. In addition, it has the advantages of simple preparation and easy availability of raw materials.

[0011] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a method for preparing a copper cluster-phenothiazine-based metal organic framework with visible light catalytic C-N bond cross-coupling performance, using 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)phenothiazine PyPTH as an organic ligand and cuprous iodide as a metal salt, and preparing the copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH by a solvothermal method, and the synthesis route is as follows:

[0012] PyPTH + CuI → Cu4I4–PyPTH;

[0013] The organic ligand PyPTH has the following molecular structure formula (A):

[0014]

[0015] The Cu4I4 cluster is connected to the ligand PyPTH and has the following (B) crystal minimum repeating unit,

[0016]

[0017] The preparation method of the copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH comprises the following steps:

[0018] Step 1, add 20-30 g phenothiazine, 30-40 g p-bromoiodobenzene, 20-30 g sodium tert-butoxide, 300-500 mg cuprous iodide to a 500 mL three-necked flask, evacuate and pass nitrogen for 2-3 times, wash the syringe with nitrogen, add 150-250 mL degassed dioxane and 1-2 mL 1,2-cyclohexanediamine to the three-necked flask with a syringe, reflux for 10-20 h under a N2 atmosphere at 100-110 ° C, stir magnetically during the reaction, cool to room temperature after the reaction is completed, add dichloromethane and deionized water in a volume ratio of 1:2-4 to the reaction solution, extract 2-3 times, separate the liquid, dry the lower organic phase with anhydrous sodium sulfate, filter, and spin-dry the filtrate to obtain a crude product, separate the crude product by silica gel column chromatography, and obtain 10-(4-bromophenyl)phenothiazine as a white solid powder;

[0019] Step 2, weigh 5-10 g of the product 10-(4-bromophenyl)phenothiazine of step 1 and add it to a round-bottom flask, and add 4-5 g N-bromosuccinimide, 800-1300 mL of dichloromethane, 10-15 g of 200-300 mesh silica gel, react at room temperature in the dark for 15-20 h, add 200-300 mesh silica gel 20-25 g to the mixed solution after the reaction, spin dry the reaction solution, separate by silica gel column chromatography, dry sample, and obtain a light yellow solid powder 3,7-dibromo-10-(4-bromophenyl)phenothiazine after separation;

[0020] Step 3, weigh 5-10 g of the product of step 2, 3,7-dibromo-10-(4-bromophenyl)phenothiazine, 4-5 g of 4-pyridineboric acid, 500-600 mg of tetrakis(triphenylphosphine)palladium, and 6-7 g of anhydrous potassium carbonate, add them to a three-necked reaction flask, evacuate and pass nitrogen 2-3 times, wash the syringe with nitrogen, and then add 100-200 mL of degassed toluene, 100-150 mL of ethanol, and 30-50 mL of deionized water to the three-necked reaction flask with a syringe, and react at 80-90 ° C for 40-50 minutes at a slight boiling state. h, after the reaction is completed, cool to room temperature, transfer the reaction solution to a separatory funnel, extract 2 to 3 times with dichloromethane and deionized water in a volume ratio of 1:2 to 4, separate the liquids, dry the lower organic phase with anhydrous sodium sulfate, filter, and spin-dry the filtrate to obtain a crude product, which is then separated by silica gel column chromatography to obtain an orange solid powder, i.e., the organic ligand 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)phenothiazine PyPTH;

[0021] Step 4, weigh the organic ligand PyPTH and cuprous iodide (cluster) in a molar ratio of 1:1~2, add them into a heat-resistant glass bottle containing 2~3mL N,N-dimethylacetamide, and disperse them evenly by ultrasonication; add the evenly dispersed raw materials into a hydrothermal reactor with a polytetrafluoroethylene lining and seal it, then put it into an oven with a temperature control program, heat it to 120~130℃, and keep the constant temperature for reaction for 70~75h; after the reaction is completed and cooled to room temperature, remove the supernatant, add ethanol for washing, centrifuge, repeat the operation 2~3 times, collect the bottom crystals, and obtain orange-yellow block crystals, which are the target material copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH.

[0022] The target material copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH prepared by the method is applied in the photocatalytic C-N bond Ullmann-type coupling reaction.

[0023] The invention has the beneficial effects of: a method for preparing a copper cluster-phenothiazine-based metal organic framework with visible light catalytic C-N bond cross-coupling performance, using 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)thiophene PyPTH as an organic ligand and cuprous iodide as a metal salt, and preparing the copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH by a solvothermal method, and the synthesis route is as follows: PyPTH + CuI → Cu4I4-PyPTH; the crystal of the copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH prepared by the method of the invention is a three-dimensional interlaced structure, belongs to the trigonal system, R3c space group, and its minimum asymmetric structural unit is composed of a Cu4I4 cluster, a phenothiazine ligand (PyPTH) and a water molecule. All Cu atoms in the structure are in a tetrahedral four-coordination mode. Each phenothiazine ligand (PyPTH) is connected to three Cu4I4 clusters, and each Cu4I4 cluster node is connected to three phenothiazine ligands (PyPTH) ligands and a water molecule. The copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH with visible light catalytic C–N bond cross-coupling performance prepared by the method has a sufficiently negative excited state potential (E ox * = -2.22 V), and is capable of reducing inert substrates such as aryl chlorides; after PyPTH* reduces aryl halides, the resulting PyPTH ·+The species and the Cu4I4 metal cluster can undergo directional electron transfer from the metal cluster to the ligand. When Cu(II) is generated, the Jahn-Teller effect is accompanied. The tetrahedral configuration of the metal cluster is rapidly distorted and flattened. Its open conformation is conducive to capturing aromatic radical species and combining with nucleophiles. After the subsequent reduction elimination step, the C–N cross-coupling product can be obtained. This process successfully circumvents the high thermodynamic barriers in the "one-step" oxidative addition of carbon-halogen bonds by the traditional catalyst Cu(I). Using a 405 nm wavelength LED as a light source, inert aromatic chlorides are activated under mild conditions to achieve Ullmann coupling reaction. The target material Cu4I4–PyPTH prepared by the present invention can use a 405 nm wavelength LED as a light source to activate inert aromatic chlorides under mild conditions to achieve light-copper synergistic catalytic C–N coupling reaction, with excellent yield and substrate applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the crystal structure of the target material Cu4I4-PyPTH in Example 1.

[0025] Figure 2 This is the infrared spectrum of the target material Cu4I4-PyPTH in Example 2.

[0026] Figure 3 This is the cyclic voltammogram of the target material Cu4I4-PyPTH in Example 3.

[0027] Figure 4 This is the EIS electrochemical impedance diagram of the target material Cu4I4-PyPTH in Example 3.

[0028] Figure 5 This is the photocurrent test spectrum of the target material Cu4I4-PyPTH in Example 3.

[0029] Figure 6 This is the UV-visible absorption spectrum of the target material Cu4I4-PyPTH in Example 4.

[0030] Figure 7 This is the fluorescence emission spectrum of the target material Cu4I4-PyPTH after adding different concentrations of p-chlorobenzonitrile in Example 5.

[0031] Figure 8 This is a schematic diagram of the catalytic cycle yield of the target material Cu4I4-PyPTH in Example 6.

[0032] Fig. 9 This is the PXRD pattern of the target material Cu4I4-PyPTH of Example 6. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the embodiments.

[0034] Example 1

[0035] The preparation of the target material Cu4I4–PyPTH includes the following steps:

[0036] Step 1. Add phenothiazine (21.76 g, 109.2 mmol), p-bromoiodobenzene (37.34 g, 131.8 mmol), sodium tert-butoxide (21.17 g, 220.6 mmol), and cuprous iodide (0.42 g, 2.2 mmol) to a 500 mL three-necked flask, evacuate the mixture and pass nitrogen for 3 times. After eluting the syringe with nitrogen, add degassed dioxane (200 mL) and 1,2-cyclohexanediamine (1.4 mL) into the three-necked flask with a syringe, and reflux the mixture under N2 atmosphere at 105 °C for 12 h with magnetic stirring during the reaction. After the reaction was completed, the mixture was cooled to room temperature, and dichloromethane and deionized water were added to the reaction solution in a volume ratio of 1:3 for extraction three times. The lower organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was spin-dried to obtain a crude product. The crude product was separated by silica gel column chromatography with n-hexane as the developing solvent to obtain 31.31 g of 10-(4-bromophenyl)phenothiazine as a white solid powder with a yield of 81%.

[0037] Step 2, weigh 10-(4-bromophenyl) phenothiazine (5.00 g, 14.1 mmol) and add it to a round-bottom flask, and add dichloromethane (1000 mL), N-bromosuccinimide (4.70 g, 26.4 mmol), 300 mesh silica gel (11.20 g), and react at room temperature in the dark for 18 h. After the reaction, add about 20 g of 300 mesh silica gel to the mixed solution, spin dry the reaction solution, separate it by silica gel column chromatography, dry sample loading, and the developing solvent is n-hexane. After separation, 6.82 g of light yellow solid powder 3,7-dibromo-10-(4-bromophenyl) phenothiazine is obtained, and the yield is 94%.

[0038] Step 3. Weigh 3,7-dibromo-10-(4-bromophenyl)phenothiazine (5.16 g, 10.1 mmol), 4-pyridineboric acid (4.34 g, 35.3 mmol), tetrakis(triphenylphosphine)palladium (589.3 mg, 0.5 mmol), and anhydrous potassium carbonate (6.97 g, 50.4 mmol) into a three-necked reaction flask, evacuate the flask with nitrogen for 3 times, and after eluting the syringe with nitrogen, add degassed toluene (150 mL), ethanol (100 mL), and deionized water (50 mL) into the three-necked reaction flask with a syringe, and react at 85 °C with a slight boiling state for 48 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was transferred to a separatory funnel and extracted three times with deionized water and dichloromethane in a volume ratio of 3:1. The lower organic phase was dried over anhydrous sodium sulfate, filtered, and the filtrate was spin-dried to obtain a crude product, which was then separated by silica gel column chromatography using triethylamine and ethyl acetate in a volume ratio of 1:500 as the developing solvent to obtain an orange solid powder, namely, 4.81 g of the organic ligand 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)thiophene PyPTH, with a yield of 95%.

[0039] Step 4: Weigh the organic ligand PyPTH (2.5 mg, 5.0 µmol) and CuI (2.0 mg, 10.0 µmol) into a heat-resistant glass vial containing 3 mL N,N-dimethylacetamide, disperse them evenly by ultrasonication, and add the evenly dispersed raw materials into a hydrothermal reactor with a polytetrafluoroethylene lining and seal it. Repeat the above proportions and operations for 30 heat-resistant glass vials, then place the 30 heat-resistant glass vials in an oven with a temperature control program, heat them to 120 °C, and keep the constant temperature for 72 hours; after the reaction is completed and cooled to room temperature, remove the supernatant, add ethanol for washing, centrifuge, repeat the operation 3 times, collect the bottom crystals, and obtain orange-yellow block crystals, i.e., the target material copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH 108.9 mg, with a yield of 65%. The obtained crystals were tested on a Bruker D8 Venture single crystal X-ray diffractometer. Single crystal structure analysis showed that the complex crystals belonged to the trigonal system, R3c space group, a = 62.3823(11), b = 62.3823(11), c = 39.5929(9), α = β = 90°, γ = 120°, and the crystal structure diagram is as follows: Figure 1 shown.

[0040] Example 2

[0041] 10.0 mg of the target material Cu4I4–PyPTH and 10.0 mg of the organic ligand PyPTH were weighed, mixed with 100.0 mg of potassium bromide powder, and ground into a mortar. The mixture was fully ground and evenly mixed, and then pressed into transparent discs. The discs were tested on the 6700 Advanced Fourier Transform Infrared Spectrometer of Thermo Fisher Company in the United States. The Fourier Transform Infrared Spectrum is shown in the figure. Figure 2 As shown in the figure, the main absorption peaks were assigned. Compared with the organic ligand PyPTH, the corresponding C=N, C–N, and C–S stretching vibration peaks in Cu4I4–PyPTH were obviously blue-shifted. This is probably due to the fact that after the metal cluster forms a coordination bond with the organic ligand, the lone electron pair on the ligand molecule pyridine N shifts toward Cu(I).

[0042] Example 3

[0043] 2.0 mg of the target material Cu4I4–PyPTH was weighed and added to 0.5 mL of ethanol to make a suspension. Then 0.06 mL of Nafion was added and mixed by ultrasound. 0.2 mL of the suspension was applied to the FTO glass surface with a coating area of ​​1 cm. 2 , dried, and then the FTO glass was clamped on the electrode clamp as the working electrode. The photocurrent test was carried out on a CHI 660E electrochemical workstation using a three-electrode system, with an Ag / AgCl electrode as the reference electrode, a platinum electrode as the counter electrode, and a 0.10 M tetrabutylammonium hexafluorophosphate acetonitrile solution as the electrolyte. The cyclic voltammogram of Cu4I4–PyPTH is shown in Figure 2. Figure 3 As shown. EIS electrochemical impedance spectroscopy of Cu4I4–PyPTH and ligand PyPTH, as shown Figure 4 As shown. The photocurrent test was conducted under 1 atm nitrogen conditions, room temperature, and a 50 W LED light source with a wavelength of 400 nm. The photocurrent test spectra of Cu4I4–PyPTH and ligand PyPTH are shown in Figure 5 Both electrochemical impedance and photocurrent tests show that compared with the ligand PyPTH, Cu4I4–PyPTH has a smaller electrochemical impedance, a stronger photoresponse, and a higher photoinduced charge separation efficiency.

[0044] Example 4

[0045] Weigh 5.0 mg of the target material Cu4I4–PyPTH into an agate mortar and grind it into powder. Then put it into a quartz cuvette and add 3 mL of anhydrous acetonitrile to make a suspension. N2 is bubbled for 5 min to place the system in an inert gas atmosphere. The UV-visible absorption spectrum of the target material Cu4I4–PyPTH is as follows: Figure 6As shown, it reflects the light absorption properties of Cu4I4–PyPTH. Compared with the phenothiazine-based ligand PyPTH, Cu4I4–PyPTH has a wider absorption range, among which the absorption peak near 360 nm is attributed to the charge transfer absorption peak from the metal cluster to the ligand PyPTH. The absorption peak of 400~500 nm is attributed to the absorption of the charge transfer state of the Cu4I4–PyPTH molecule. The broadening of the absorption peak of Cu4I4–PyPTH is conducive to the absorption of light, thereby improving the catalytic efficiency of visible light catalysis.

[0046] Example 5

[0047] Weigh 2.0 mg of Cu4I4–PyPTH and add it to 10 mL of acetonitrile to make a uniform and relatively transparent suspension. Transfer it to a stoppered fluorescence cell and bubble argon for 15 min to ensure that the suspension is in anoxic conditions. Perform a fluorescence titration test on the FLS1000 instrument. Select an excitation wavelength of 385 nm and titrate the suspension with an acetonitrile solution of p-bromobenzonitrile treated with argon. During the titration, an obvious fluorescence emission spectrum of Cu4I4–PyPTH is observed, as shown in Figure 2. Figure 7 This indicates that efficient photoinduced electron transfer occurs from Cu4I4–PyPTH to the radical precursor bromoxynil.

[0048] Example 6

[0049] Add p-bromobenzonitrile (1.5 eq, 0.3 mmol, 54.6 mg), benzimidazole (1 eq, 0.2 mmol, 23.6 mg), Cu4I4–PyPTH (0.01 mmol, 5 mol %, 10.8 mg), and K3PO4 (2 eq, 0.4 mmol, 84.9 mg) to a dry photoreaction tube and seal it with a turn-down stopper. Perform "vacuum / nitrogen" treatment on the reaction system three times to remove oxygen from the solid system. Add dry and degassed acetonitrile (3 mL) to the reaction tube with a long needle; then seal the puncture of the reaction tube with Parafilm sealing film and stir at room temperature for 24 h under 405 nm LED light source. After the catalytic reaction is completed, the reaction mixture is centrifuged and the precipitate at the bottom of the centrifuge tube is placed in a Buchner funnel. The precipitate is rinsed with 20 mL of N,N-dimethylformamide and 20 mL of anhydrous ethanol, respectively. The washed solid powder is vacuum dried at room temperature to obtain the Cu4I4–PyPTH powder recovered after the reaction, and the next reaction cycle is carried out. The schematic diagram of the catalytic cycle yield is shown in FIG. Figure 8 After Cu4I4–PyPTH was repeatedly used for three times, its structure was roughly maintained by X-ray powder diffraction test (PXRD), as shown in Fig. 9 shown.

[0050] Example 7

[0051] Add p-bromobenzonitrile (1.5 eq, 0.3 mmol, 54.60 mg), benzimidazole (1 eq, 0.2 mmol, 23.6 mg), Cu4I4–PyPTH (0.01 mmol, 5 mol %, 10.8 mg), and K3PO4 (2 eq, 0.4 mmol, 84.9 mg) to a dry photoreaction tube and seal it with a turn-down stopper. Perform a "vacuum / nitrogen" treatment three times on the reaction system to remove oxygen from the solid system. Add dry, degassed acetonitrile (3 mL) to the reaction tube with a long needle; then seal the puncture of the reaction tube with a Parafilm sealing film and stir at room temperature for 24 h under 405 nm LED light source. Separate the catalyst with an organic filter membrane, spin dry the filtrate, and separate the crude product by thin layer chromatography. The substrate extension of Cu4I4–PyPTH-catalyzed C–N bond coupling is shown in Table 1.

[0052] Table 1

[0053]

[0054] The copper cluster-phenothiazine-based metal-organic framework Cu4I4–PyPTH exhibits a good substrate range for the Ullmann coupling reaction and is suitable for free radical precursors of various aromatic halides. It helps to solve the problems of harsh reaction conditions and difficult catalyst recovery in traditional catalytic systems. This heterogeneous catalytic photocatalytic system has good application potential in the fields of fine chemicals, medicines and intermediate synthesis.

Claims

1. A method for preparing a copper cluster-phenothiazine-based metal organic framework with visible light catalytic C–N bond cross-coupling performance, characterized in that: The copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH was prepared by solvothermal method using 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)phenolthiophene PyPTH as organic ligand and cuprous iodide as metal salt. The synthesis route is as follows: PyPTH + CuI→ Cu4I4–PyPTH; The organic ligand PyPTH has the following molecular structure formula (A): ； The Cu4I4 cluster is connected to the ligand PyPTH and has the following (B) crystal minimum repeating unit, ； The preparation method of the copper cluster-phenothiazine-based metal organic framework Cu4I4-PyPTH comprises the following steps: Step 1, add 20-30 g phenothiazine, 30-40 g p-bromoiodobenzene, 20-30 g sodium tert-butoxide, 300-500 mg cuprous iodide to a 500 mL three-necked flask, evacuate and pass nitrogen for 2-3 times, wash the syringe with nitrogen, add 150-250 mL degassed dioxane and 1-2 mL 1,2-cyclohexanediamine to the three-necked flask with a syringe, reflux for 10-20 h under a N2 atmosphere at 100-110 ° C, stir magnetically during the reaction, cool to room temperature after the reaction is completed, add dichloromethane and deionized water in a volume ratio of 1:2-4 to the reaction solution, extract 2-3 times, separate the liquid, dry the lower organic phase with anhydrous sodium sulfate, filter, and spin-dry the filtrate to obtain a crude product, separate the crude product by silica gel column chromatography, and obtain 10-(4-bromophenyl)phenothiazine as a white solid powder; Step 2, weigh 5-10 g of the product 10-(4-bromophenyl)phenothiazine of step 1 and add it to a round-bottom flask, and add 4-5 g N-bromosuccinimide, 800-1300 mL of dichloromethane, 10-15 g of 200-300 mesh silica gel, react at room temperature in the dark for 15-20 h, add 200-300 mesh silica gel 20-25 g to the mixed solution after the reaction, spin dry the reaction solution, separate by silica gel column chromatography, dry sample, and obtain a light yellow solid powder 3,7-dibromo-10-(4-bromophenyl)phenothiazine after separation; Step 3, weigh 5-10 g of the product of step 2, 3,7-dibromo-10-(4-bromophenyl)phenothiazine, 4-5 g of 4-pyridineboric acid, 500-600 mg of tetrakis(triphenylphosphine)palladium, and 6-7 g of anhydrous potassium carbonate, add them to a three-necked reaction flask, evacuate and pass nitrogen 2-3 times, wash the syringe with nitrogen, and then add 100-200 mL of degassed toluene, 100-150 mL of ethanol, and 30-50 mL of deionized water to the three-necked reaction flask with a syringe, and react at 80-90 ° C for 40-50 minutes at a slight boiling state. h, after the reaction is completed, cool to room temperature, transfer the reaction solution to a separatory funnel, extract 2 to 3 times with dichloromethane and deionized water in a volume ratio of 1:2 to 4, separate the liquids, dry the lower organic phase with anhydrous sodium sulfate, filter, and spin-dry the filtrate to obtain a crude product, which is then separated by silica gel column chromatography to obtain an orange solid powder, i.e., the organic ligand 3,7-di(4-pyridyl)-10-(4-(4-pyridyl)phenyl)phenothiazine PyPTH; Step 4. Weigh the organic ligand PyPTH and cuprous iodide (cluster) in a molar ratio of 1:1~2, add them into a heat-resistant glass bottle containing 2~3 mL N,N-dimethylacetamide, and disperse them evenly by ultrasonication; add the evenly dispersed raw materials into a hydrothermal reactor with a polytetrafluoroethylene lining and seal it, then put it into an oven with a temperature control program, heat it to 120~130 ℃, and maintain a constant temperature reaction for 70~75 h; after the reaction is completed and cooled to room temperature, remove the supernatant, add ethanol for washing, centrifuge, repeat the operation 2~3 times, collect the bottom crystals, and obtain orange-yellow block crystals, which are the target material copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH.

2. Application of the target material copper cluster-phenothiazine-based metal organic framework Cu4I4–PyPTH prepared by the method according to claim 1 in the photocatalytic C–N bond Ullmann-type coupling reaction.

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