Preparation method and application of meso-tetra (5-carboxylthiophenyl) porphyrin and corresponding zirconium-based metal organic framework material

Abstract

This invention successfully synthesized meso-tetra(5-carboxythiophene-2-carboxylate)porphyrin by reflux of methyl 5-aldehydethiophene-2-carboxylate and pyrrole in a propionic acid system, and further hydrolyzed it to obtain meso-tetra(5-carboxythiophene-2-carboxylate)porphyrin. Using this carboxyporphyrin as a ligand, it was reacted with anhydrous ZrCl4 under solvothermal conditions to successfully prepare a novel metal-organic framework material, NKU-222. The prepared meso-tetra(5-carboxythiophene-2-carboxylate)porphyrin molecule exhibits a characteristic red-shifted absorption band compared to meso-position carboxyphenyl-substituted porphyrin compounds. Benefiting from the larger dipole moment of the tabletop meso-tetra(5-carboxythiophene-2-carboxylate)porphyrin molecule, NKU-222 exhibits superior carrier separation efficiency compared to PCN-222. NKU-222 can be used in visible light photocatalysis to efficiently achieve the oxidative coupling of benzylamine to generate imine, and exhibits good structural stability and reusability. It significantly expands the types of Zr-based porphyrin MOFs and demonstrates their potential in visible light photocatalysis applications.

Description

Technical Field

[0001] This invention relates to the field of metal-organic framework materials and photocatalysis, specifically to a method for preparing meso-tetra(5-carboxythienyl)porphyrin and its corresponding zirconium-based porphyrin metal-organic framework materials and their photocatalytic applications. Background Technology

[0002] Imines, as an important class of functional intermediates, possess unique chemical reactivity and excellent biological and pharmacological activities, demonstrating significant research value and broad application prospects in fields such as medicine, catalysis, and advanced functional materials. In recent years, the visible-light-catalyzed oxidative coupling reaction of benzylamine has provided a green and sustainable route for the synthesis of imines due to its mild conditions, low energy consumption, and environmental friendliness. The efficiency of oxidative coupling largely depends on the design and synthesis of efficient photocatalysts. Metal-organic frameworks (MOFs) are a class of crystalline porous materials with atomically precise structures assembled from metal nodes and organic ligands through coordination bonds. Due to their highly tunable composition and structure, and easily modifiable pore environment, MOFs have become an ideal platform for the design and construction of photocatalytic materials. Among them, zirconium-based porphyrin MOFs have attracted widespread attention in the field of visible-light photocatalysis due to their excellent structural stability, outstanding visible light absorption capacity of porphyrin units, long triplet lifetime, and high triplet quantum yield. However, the types of carboxylic acid ligands currently available for constructing Zr-based porphyrin MOFs are still relatively limited, with related research mainly focusing on carboxyphenyl-substituted porphyrin systems. The relatively symmetrical electronic structure of these ligands results in limited charge polarization of the system, making it easy for photogenerated carriers to recombine after separation, thus limiting further improvement in photocatalytic performance.

[0003] For porphyrin molecules, the carbon atom at the meso position is a key node connecting pyrrole units and constructing a highly conjugated macrocyclic structure. Changes in its substituents can significantly affect the molecule's dipole moment and electronic distribution characteristics. Therefore, the rational design of substituents at the meso position is crucial for regulating the electronic structure and carrier segregation and transport properties of porphyrin molecules and corresponding Zr-based porphyrin MOFs. Compared to benzene ring structures, the thiophene unit, as a typical electron-rich heterocycle, not only possesses stronger π-electron delocalization capabilities and superior electron transport characteristics, but the introduction of sulfur atoms can also enhance the intramolecular charge asymmetry distribution and increase the system's dipole moment. This increased degree of local polarization facilitates the construction of a stronger built-in molecular electric field, thereby improving the carrier segregation and transport dynamics. Therefore, designing and synthesizing thiophene-functionalized carboxylic acid porphyrin ligands, and achieving their orderly assembly with zirconium clusters to construct well-defined Zr-based porphyrin MOFs, thereby optimizing their photoelectrochemical properties and applying them to visible light-catalyzed oxidative coupling of benzylamine to generate imines and their derivatives, remains a challenging technical problem. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art, and to provide a carboxylic acid porphyrin molecule with a meso position thiophene carboxyl group substituted and a method for preparing the corresponding Zr-MOFs, which can be used for the visible light photocatalytic coupling reaction of benzylamine to synthesize imine derivatives.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The structural formula of meso-tetra(5-carboxythienyl)porphyrin (abbreviated as H2TCTP) is: .

[0006] The synthetic method of meso-tetra(5-carboxythienyl)porphyrin (abbreviated as H2TCTP) includes the following steps: (1) Add meso-tetra(5-carboxymethyl thiophene)porphyrin and potassium hydroxide to distilled water, methanol and tetrahydrofuran, and sonicate until the solid is completely dissolved; (2) Then heat under reflux until the reaction is complete; (3) After the reaction system is cooled to room temperature, a solid crude product is obtained by rotary evaporation under reduced pressure; (4) Add distilled water until the solid product is fully dissolved, and then acidify until a precipitate is formed; (5) Collect the precipitate and wash it until the filtrate is neutral; (6) Finally, the product is dried to obtain a blue-purple solid product, namely meso-tetra(5-carboxythiophene)porphyrin.

[0007] In step (1), the molar ratio of meso-tetra(5-carboxymethylthiophene)porphyrin and potassium hydroxide is between 1:65 and 1:35; the volume ratio of distilled water, methanol and tetrahydrofuran is 1:1:1.

[0008] In step (2), the reflux temperature is 80-100℃, and the reaction time is determined by thin-layer chromatography (TLC) to ensure that the reactants are completely consumed.

[0009] In step (4), acidification is performed using dilute hydrochloric acid, with a molar concentration of 1-3M.

[0010] In step (5), the precipitate is washed with distilled water.

[0011] The synthesis method of meso-tetra(5-carboxymethyl thiophene)porphyrin is as follows: ① Methyl 5-aldehyde thiophene-2-carboxylate and propionic acid are mixed and ultrasonically treated until the solid is completely dissolved; ② Pyrrole is then slowly added dropwise under light-protected conditions, and the reaction system is heated under ambient atmosphere and refluxed until the reaction is complete; ③ After the reaction mixture is cooled to room temperature, the precipitate is collected by vacuum filtration; ④ The precipitate is washed successively with tetrahydrofuran, ethyl acetate and methanol until the color of the filtrate disappears; ⑤ Finally, the product is dried to obtain a purple solid product, namely meso-tetra(5-carboxymethyl thiophene)porphyrin.

[0012] The molar ratio of methyl 5-aldehydethiophene-2-carboxylate to pyrrole is 1:1; the amount of propionic acid used is sufficient to fully dissolve methyl 5-aldehydethiophene-2-carboxylate.

[0013] In step ②, the reflux temperature is 130-160℃, and the reaction time is determined by thin-layer chromatography (TLC) to ensure that the reactants are completely consumed.

[0014] The structural formula of meso-tetra(5-carboxymethyl thiophene)porphyrin (abbreviated as H2TTPCOOMe) is: .

[0015] By testing the UV-Vis absorption spectra of H2TCTP and meso-tetra(5-carboxyphenyl)porphyrin (abbreviated as H2TCPP), it was found that the Soret band of H2TCPP appeared at 425 nm, while the Soret band of H2TCTP red-shifted to 434 nm, indicating that its conjugated system was enhanced and its light absorption capacity was improved.

[0016] Density functional theory (DFT) was used to calculate and analyze the optimized structures of the two porphyrin molecules. The results showed that the dipole moment of tabletop H2TCTP was 8.542 Debye, which was significantly higher than that of H2TCPP (4.508 Debye). This indicates that the introduction of thiophene substituents significantly enhanced the polarity and asymmetric electronic distribution of the molecules.

[0017] A method for preparing a zirconium-based porphyrin metal-organic framework material NKU-222 includes the following steps: Organic ligand H2TCTP, zirconium salt, and template agent were added to an organic solvent; the mixture was subjected to a solvothermal reaction; after the reaction system was cooled to room temperature, purple hexagonal prism crystals were obtained; subsequently, the crystal material NKU-222 was obtained after washing with organic solvent and drying.

[0018] The zirconium salt is selected from anhydrous ZrCl4 or ZrOCl2·8H2O; the organic solvent is selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), or N,N-diethylformamide (DEF); the template agent is selected from benzoic acid, acetic acid, trifluoroacetic acid, or o-fluorobenzoic acid.

[0019] The molar concentration ratio of the organic ligand H2TCTP to the zirconium metal salt is 1:10-1:60; the molar concentration ratio of the organic ligand H2TCTP to the template agent is 1:500-1:2000; and the molar ratio of the organic solvent to the zirconium metal salt is 1-4 ml: 20 mg.

[0020] The reaction temperature of the solvothermal reaction is 110-140℃; the reaction time is 24-72 hours.

[0021] The crystal structure of a zirconium-based porphyrin metal-organic framework material NKU-222 has a (4,8)-connected csq topology. The framework structure is composed of Zr6 clusters connected by H2TCTP ligands. Each Zr6 cluster is coordinated with eight carboxylate groups from H2TCTP ligands to form an approximately cubic coordination configuration, with four located above the equatorial plane and four located below the equatorial plane. The structure exhibits hierarchical porosity.

[0022] An activation method for a zirconium-based porphyrin metal-organic framework material NKU-222 includes the following steps: Zirconium-based porphyrin metal-organic framework (MOF) material NKU-222 was placed in a DMF solution and heated for soaking, during which it was exchanged with fresh DMF. The MOF material was then collected by vacuum filtration, transferred to acetone solvent, heated for soaking, and exchanged with fresh acetone solvent. The solid was then collected by vacuum filtration and degassed for activation to obtain the activated NKU-222 material.

[0023] The temperature for heating and soaking should be room temperature or no higher than the boiling point of the solvent. The degassing and activation temperature is 80-120℃; The degassing and activation time is 8-24 hours; The DMF and acetone solvent exchange is performed 3-5 times; The DMF and acetone are heated and soaked for 1-2 days.

[0024] Application of a zirconium-based porphyrin metal-organic framework material NKU-222 for visible light-catalyzed benzylamine oxidative coupling.

[0025] After activation, the zirconium-based porphyrin metal-organic framework material NKU-222 catalyzes the oxidative coupling reaction of benzylamine under visible light excitation to produce an imine.

[0026] Compared with existing technologies, the advantages of this invention are as follows: Addressing the limitations of available ligand types and the number of frameworks in existing Zr-based porphyrin MOF systems, particularly the limitation of carboxylic acid ligands used for framework construction to carboxyphenyl-substituted porphyrins at the meso position, this invention, for the first time, successfully synthesized meso-tetra(5-carboxythienyl)porphyrin by reflux of methyl 5-aldehydethiophene-2-carboxylate and pyrrole in a propionic acid system, and further obtained meso-tetra(5-carboxythienyl)porphyrin after hydrolysis. The prepared meso-tetra(5-carboxythienyl)porphyrin molecule exhibits a characteristic red-shifted absorption band compared to meso-position carboxyphenyl-substituted porphyrin compounds. Using this carboxyporphyrin as a ligand and reacting it with zirconium metal salt under solvothermal conditions, a novel metal-organic framework material, NKU-222, was successfully prepared. Thanks to the larger dipole moment of the tabletop meso-tetra(5-carboxythienyl)porphyrin molecule compared to meso-position carboxyphenyl-substituted porphyrin compounds, NKU-222 exhibits superior carrier separation efficiency compared to PCN-222, showing higher photocurrent density and lower impedance after illumination in photocurrent and impedance tests. This MOF material, when applied to visible light photocatalysis, can efficiently achieve the oxidative coupling reaction of benzylamine to generate imine, exhibiting good structural stability and reusability. It significantly expands the types of Zr-based porphyrin MOFs and demonstrates their potential in visible light photocatalysis applications. Attached Figure Description

[0027] Figure 1 The example is a meso-tetra(5-carboxythienyl)porphyrin structure.

[0028] Figure 2 The synthetic route for meso-tetra(5-carboxythienyl)porphyrin is given.

[0029] Figure 3The 1H NMR spectrum of meso-tetra(5-carboxymethyl thiophene)porphyrin is shown.

[0030] Figure 4 The 1H NMR spectrum of meso-tetra(5-carboxythienyl)porphyrin is shown.

[0031] Figure 5 The UV-Vis absorption spectra of meso-tetra(5-carboxythienyl)porphyrin and meso-tetra(5-carboxyphenyl)porphyrin are shown.

[0032] Figure 6 The surface electrostatic potential distribution diagrams are for tabletop meso-tetra(5-carboxythienyl)porphyrin and meso-tetra(5-carboxyphenyl)porphyrin.

[0033] Figure 7 This is a structural diagram of the NKU-222 material.

[0034] Figure 8 PXRD patterns of experimental and simulated NKU-222 material and results of structural refinement.

[0035] Figure 9 PXRD patterns of NKU-222 material immersed in different organic solvents (a) and aqueous solutions with different pH values ​​(b).

[0036] Figure 10 Nitrogen adsorption-desorption isotherms and pore size distribution diagram for NKU-222 material (inset).

[0037] Figure 11 Photocurrent density and impedance diagrams for NKU-222 and PCN-222 materials.

[0038] Figure 12 The kinetic curves for the visible light-catalyzed oxidative coupling of NKU-222 material to generate imine from benzylamine.

[0039] Figure 13 Five-cycle diagram of NKU-222 material used for visible light-catalyzed oxidative coupling of benzylamine to imine. Detailed Implementation

[0040] The specific embodiments of the present invention will now be described in further clear and complete detail with reference to the accompanying drawings: (1) meso-tetra(5-carboxythienyl)porphyrin (abbreviated as H2TCTP) (e.g. Figure 1 Synthesis method (as shown) Figure 2 (As shown), including the following steps: The first step involved the synthesis of meso-tetra(5-methyl carboxylate thiophene)porphyrin: Methyl 5-aldehyde thiophene-2-carboxylate (5.10 g, 30 mmol) and propionic acid (300 mL) were added to a 1000 mL three-necked flask and sonicated for 5 minutes until completely dissolved. Then, pyrrole (2010 µL, 30 mmol) was added dropwise, and the mixture was refluxed at 140 °C for 12 hours in the dark. After the reaction mixture cooled to room temperature, the precipitate was collected by filtration. The precipitate was washed successively with 600 mL each of tetrahydrofuran, ethyl acetate, and methanol, and further dried in a vacuum drying oven to obtain a purple meso-tetra(5-methyl carboxylate thiophene)porphyrin solid product (1.76 g, 2.02 mmol), with a yield of 26.9%. Based on the solid product's reaction in deuterated chloroform... 1 H NMR (CDCl3, 400MHz) data: 9.06 (s, 8H), 8.21 (d, 4H), 7.92 (d, 4H), 4.06 (s, 12H), -2.75 (s, 2H), as shown Figure 3 It can be deduced that the obtained solid product is meso-tetra(5-carboxymethyl thiophene)porphyrin.

[0041] The second step involved the synthesis of meso-tetra(5-carboxythienyl)porphyrin (H2TCTP): 0.87 g (1.0 mmol) of meso-tetra(5-carboxymethyl thienyl)porphyrin and 3.00 g (53.6 mmol) of potassium hydroxide were added to a mixed solvent of 25 mL each of distilled water, methanol, and tetrahydrofuran. The mixture was heated under reflux at 85 °C for 12 hours. After the reaction system cooled to room temperature, the crude solid product was obtained by rotary evaporation under reduced pressure. The solid product was dissolved in 50 mL of distilled water and acidified with an aqueous HCl solution (pH=1) until a precipitate formed. The precipitate was collected by centrifugation and washed with distilled water until the filtrate was neutral. The resulting filter cake was dried under vacuum to obtain carboxyporphyrin H2TCTP, with a yield of 93.6%. The solid product was dissolved in DMSO-d6. 1 H NMR (DMSO-d6, 400MHz) data: 13.50 (br, 4H), 9.15 (s, 8H), 8.19 (t, 4H), 8.13 (t, 4H), -2.88 (s, 2H), as shown Figure 4 It can be deduced that the solid product obtained is H2TCTP.

[0042] (2) Light absorption capacity of H2TCTP and H2TCPP: H2TCTP and H2TCPP were dissolved in DMF to prepare a solution with a concentration of 4 × 10⁻⁶. -6 A solution of M was prepared, and its UV-Vis absorption spectra were measured, such as... Figure 5As shown in the figure, the results indicate that H2TCPP exhibits a Soret absorption band at 425 nm and four Q absorption bands at 521 nm, 555 nm, 596 nm, and 651 nm. In contrast, the Soret absorption band of H2TCTP is red-shifted to 434 nm, while its Q absorption bands appear at 528 nm, 565 nm, 600 nm, and 667 nm. These results demonstrate that H2TCTP exhibits an overall red-shift in its absorption spectrum compared to H2TCPP, indicating a higher degree of conjugation.

[0043] (2) Electrostatic potential distribution of H2TCTP and H2TCPP: The structures of tabletop H2TCTP and H2TCPP were optimized using density functional theory, and electrostatic potential distribution analysis was performed, such as... Figure 6 As shown in the figure. The results show that the dipole moment of the tabletop H2TCTP is 8.542 Debye, which is significantly higher than that of H2TCPP (4.508 Debye), indicating that the introduction of the thiophene substituent significantly enhances the polarity and asymmetric electronic distribution of the molecule.

[0044] (3) Synthesis of NKU-222 material: 20 mg of anhydrous ZrCl4, 10 mg of H2TCTP, 800 mg of benzoic acid, and 2 mL of DMF were added to a 10 mL glass vial, and the mixture was sonicated for 20 minutes until the solid was completely dissolved. The vial was then placed in a 120°C oven and heated for 48 hours. After the reaction was complete and the mixture cooled to room temperature, purple hexagonal prism crystals were collected, filtered, and dried to obtain the preliminary crystalline material, namely NKU-222.

[0045] (4) Activation of NKU-222 material: The obtained MOF material NKU-222 was placed in a glass vial containing 10 mL of DMF and immersed in a 120°C oven for one day, during which time it was exchanged with fresh DMF solvent three times. The MOF material was then transferred to a glass vial containing 10 mL of acetone and immersed in a 40°C oven for three days, during which time it was exchanged with fresh acetone three times daily. Finally, it was activated at 120°C for 12 hours in a degassing station to obtain activated NKU-222.

[0046] (5) Characterization and performance testing of NKU-222 material: A schematic diagram of the crystal structure of the NKU-222 material is shown below. Figure 7As shown, the framework has a (4,8)-connected csq topology. The skeleton structure consists of Zr6 clusters linked by H2TCTP ligands. Each Zr6 cluster is coordinated with eight carboxylate groups from the H2TCTP ligands, forming an approximately cubic coordination configuration, with four located above the equatorial plane and four below. Further analysis reveals that the structure exhibits hierarchical porosity, with triangular micropores of 13.0 Å and hexagonal mesopores of 28.3 Å along the c-axis.

[0047] By comparing the experimental PXRD patterns with the corresponding simulation patterns, it can be confirmed that the synthesized NKU-222 has good phase purity. Based on the structural model obtained from the diffraction data, the experimental PXRD patterns were structurally refined. The resulting fit results are highly consistent with the experimental patterns, and the R-factor and weighted profile R-factor are 3.49% and 5.65%, respectively, further indicating that the obtained bulk material is a single-phase product. Figure 8 Stability tests show that NKU-222 material maintains a good crystalline structure in common organic solvents (ethanol, methanol, acetonitrile, acetic acid, 1,4-dioxane, acetone), 8M hydrochloric acid, and aqueous solutions at pH=10. Figure 9 a, Figure 9 b.

[0048] Nitrogen adsorption experiments were conducted at 77 K to characterize the permanent pore structure of NKU-222. NKU-222 exhibited a typical Type IV adsorption isotherm, indicating a hierarchical pore structure composed of both micropores and mesopores. At a relative pressure P / P0 = 0.90, the nitrogen adsorption capacity of NKU-222 reached 756 cm⁻¹. 3 ·g -1 The corresponding total pore volume is 1.17 cm³. 3 ·g -1 The specific surface area of ​​Brunauer-Emmett-Teller (BET) calculated based on adsorption isotherms is 1997 m². 2 ·g -1 Nonlocal density functional theory was used to analyze the pore size distribution. The results showed that two types of channels exist in the material, with pore sizes of 12.4 Å and 28.3 Å, corresponding to triangular micropores and hexagonal mesopores, respectively. Figure 10 .

[0049] To test the photogenerated carrier separation efficiency of the NKU-222 and PCN-222 materials, photocurrent density and impedance were measured using a Shanghai Chenhua electrochemical workstation (CHI-760E). A standard three-electrode system was used for photoelectrochemical testing, with a platinum sheet (1×1 cm²) as the electrode. 2The Nafion electrode was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. For the preparation of the working electrode, 2.0 mg of the material was added to a mixed solution consisting of 20 μL of Nafion solution and 1.0 mL of ethanol, and sonicated for 30 minutes to ensure thorough dispersion. Then, 200 μL of the suspension was drop-coated onto a surface approximately 1.0 cm thick. 2 The NKU-222 material was placed on an indium tin oxide (ITO) conductive glass substrate and allowed to air dry before use. Furthermore, a 0.1M Na₂SO₄ solution was used as the electrolyte in the experiment. The results show that under the same test conditions, the NKU-222 material exhibits a higher photocurrent density and lower impedance than the PCN-222 material, indicating that its photogenerated carrier separation efficiency is better. Figure 11 a, Figure 11 b.

[0050] To test the performance of the NKU-222 material in the visible-light catalytic oxidative coupling reaction of benzylamine, an amine substrate (0.1 mmol) and a catalyst (1.0 mol%) were added to a 10 mL round-bottom Schlenk tube equipped with a magnetic stirrer, using 1.0 mL of deuterated acetonitrile as the solvent. After sonication for 2 minutes, the reaction system was irradiated with an LED light source at a wavelength of 420 nm under air atmosphere. The reaction conversion and selectivity were determined by analyzing the crude product. 1 ¹H NMR was used for determination, and 1,3,5-trimethylbenzene was used as an internal standard for quantitative analysis. First, the time-dependent curve of conversion was studied, such as… Figure 12 Irradiation for 30 minutes can completely convert benzylamine into imine with near 100% selectivity, and no byproducts were detected.

[0051] To test the cyclic stability of the catalyst, after the reaction was complete, the solid catalyst was separated from the reaction mixture by centrifugation and washed with fresh acetonitrile, followed by re-degassing and reactivation of the material. The recovered catalyst was then added to fresh benzylamine and deuterated acetonitrile for the next round of reaction. This process was repeated for five consecutive cycles to evaluate the reusability of the heterogeneous catalyst; Figure 13 During all five cycles of use, the NKU-222 material was able to efficiently oxidize benzylamine to imine.

Claims

1. Meso-tetra(5-carboxythienyl)porphyrin, characterized in that... Its structural formula is: 。 2. A method for synthesizing meso-tetra(5-carboxythienyl)porphyrin, characterized by comprising the following steps: (1) Add meso-tetra(5-carboxymethyl thiophene)porphyrin and potassium hydroxide to distilled water, methanol and tetrahydrofuran, and sonicate until the solid is completely dissolved; (2) Then heat under reflux until the reaction is complete; (3) After the reaction system is cooled to room temperature, a solid crude product is obtained by rotary evaporation under reduced pressure; (4) Add distilled water until the solid product is fully dissolved, and then acidify until a precipitate is formed; (5) Collect the precipitate and wash it until the filtrate is neutral; (6) Finally, the product is dried to obtain a blue-purple solid product, namely meso-tetra(5-carboxythiophene)porphyrin.

3. The method for synthesizing meso-tetra(5-carboxythienyl)porphyrin according to claim 2, characterized in that... In step (1), the molar ratio of meso-tetra(5-carboxymethyl thiophene)porphyrin to potassium hydroxide is between 1:65 and 1:35; the volume ratio of distilled water, methanol and tetrahydrofuran is 1:1:

1. The reflux temperature in step (2) is 80-100℃, and the reaction time is determined by thin-layer chromatography (TLC) to ensure that the reactants are completely consumed. In step (4), acidification is performed using dilute hydrochloric acid, with a molar concentration of 1-3M. In step (5), the precipitate is washed with distilled water.

4. The method for synthesizing meso-tetra(5-carboxythienyl)porphyrin according to claim 2 or 3, characterized in that... The synthesis method of meso-tetra(5-carboxymethyl thiophene)porphyrin is as follows: ① Methyl 5-aldehyde thiophene-2-carboxylate and propionic acid are mixed and ultrasonically treated until the solid is completely dissolved; ② Pyrrole is then slowly added dropwise under light-protected conditions, and the reaction system is heated under ambient atmosphere and refluxed until the reaction is complete; ③ After the reaction mixture is cooled to room temperature, the precipitate is collected by vacuum filtration; ④ The precipitate is washed successively with tetrahydrofuran, ethyl acetate and methanol until the color of the filtrate disappears; ⑤ Finally, the product is dried to obtain a purple solid product, namely meso-tetra(5-carboxymethyl thiophene)porphyrin.

5. The method for synthesizing meso-tetra(5-carboxythienyl)porphyrin according to claim 4, characterized in that... The molar ratio of methyl 5-aldehydethiophene-2-carboxylate to pyrrole is 1:1; the amount of propionic acid used is sufficient to fully dissolve methyl 5-aldehydethiophene-2-carboxylate. In step ②, the reflux temperature is 130-160℃, and the reaction time is determined by thin-layer chromatography (TLC) to ensure that the reactants are completely consumed.

6. A method for preparing a zirconium-based porphyrin metal-organic framework material NKU-222, characterized in that... It includes the following steps: Organic ligand meso-tetra(5-carboxythienyl)porphyrin, zirconium salt and template agent were added to an organic solvent; the mixture was heated to carry out a solvothermal reaction; after the reaction system was cooled to room temperature, purple hexagonal prism crystals were obtained; then washed with organic solvent and dried to obtain the crystalline material NKU-222.

7. The preparation method of the zirconium-based porphyrin metal-organic framework material NKU-222 according to claim 6, characterized in that... The zirconium salt is selected from anhydrous ZrCl4 or ZrOCl2·8H2O; the organic solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide or N,N-diethylformamide; the template agent is selected from benzoic acid, acetic acid, trifluoroacetic acid or o-fluorobenzoic acid. The molar concentration ratio of the organic ligand meso-tetra(5-carboxythienyl)porphyrin to the metal salt anhydrous ZrCl4 or ZrOCl2·8H2O is 1:10-1:60; the molar concentration ratio of the organic ligand meso-tetra(5-carboxythienyl)porphyrin to the template agent benzoic acid, acetic acid, trifluoroacetic acid or o-fluorobenzoic acid is 1:500-1:2000; the molar ratio of the organic solvent N,N-dimethylformamide, N,N-dimethylacetamide or N,N-diethylformamide to the zirconium metal salt is 1-4 mL: 20 mg; The reaction temperature of the solvothermal reaction is 110-140℃; the reaction time is 24-72 hours.

8. A crystal structure of a zirconium-based porphyrin metal-organic framework material NKU-222, characterized in that... Its framework has a (4,8)-connected csq topology, and the skeleton structure is composed of Zr6 clusters connected by H2TCTP ligands. Each Zr6 cluster is coordinated with eight carboxylate groups from H2TCTP ligands to form an approximately cubic coordination configuration, with four located above the equatorial plane and four located below the equatorial plane; the structure exhibits hierarchical porosity.

9. An activation method for a zirconium-based porphyrin metal-organic framework material NKU-222, characterized in that... It includes the following steps: Zirconium-based porphyrin metal-organic framework (MOF) material NKU-222 was placed in a DMF solution and heated for soaking, during which it was exchanged with fresh DMF. The MOF material was then collected by vacuum filtration, transferred to acetone solvent, heated for soaking, and exchanged with fresh acetone solvent. The solid was then collected by vacuum filtration and degassed for activation to obtain the activated NKU-222 material.

10. An application of a zirconium-based porphyrin metal-organic framework material NKU-222, characterized in that... Used for visible light-catalyzed benzylamine oxidative coupling reaction.

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