Preparation method of benzothiadiazole-based zn-mof near-infrared fluorescent material

Abstract

The application discloses a preparation method of a benzothiadiazole-based Zn-MOF near-infrared fluorescent material, and specifically comprises the following steps: mixing 4,4'-(6-(pyridine-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl) dimethyl dibenzoate, NaOH and a solvent, and performing a reflux reaction to obtain an organic ligand SN; and mixing a metal salt, the organic ligand SN, an organic acid and an organic solvent, and performing a self-assembly reaction.The application uses benzothiadiazole as a parent body due to high chemical stability, easy modification and strong electron affinity, synthesizes a donor-acceptor-donor type organic ligand SN, and further constructs a near-infrared fluorescent MOF. The space confinement fixation of the MOF is used to inhibit molecular structure rotation, reduce the excitation state energy non-radiation transition decay probability, and further improve the fluorescence quantum yield.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework (MOF) material preparation technology, specifically relating to a method for preparing benzothiadiazole-based Zn-MOF near-infrared fluorescent materials. Background Technology

[0002] Metal-organic frameworks (MOFs), as a new class of porous materials, possess advantages such as large specific surface area, high porosity, and strong designability. Among them, fluorescent MOFs have been extensively explored as chemical sensors and photosensitizers. The development of these MOFs can be carried out in two ways: firstly, by conjugating lanthanide luminescent or photosensitive metal ions to endow MOFs with fluorescence properties; secondly, by ligand modification to obtain fluorescent MOFs. It is worth noting that ligand modification has a broader selectivity than metal ion modification, allowing for the endowment of target MOFs with specific structures or new functions, and has already been applied in fields such as ion detection and bioimaging.

[0003] 2,1,3-benzothiadiazole (BTD) derivatives, as ideal small molecule groups for visible light, possess large rigid conjugated planes and strong electron-deficient properties, allowing them to act as electron acceptors and couple with electron donors to form DAD-type charge characteristics. This induces a large-scale intramolecular electron transfer tendency, resulting in a redshift of the emitted molecular fluorescence wavelength. However, studies have found that the quantum yield of most organic fluorescent small molecules decreases sharply with the redshift of the emission wavelength. This is because excited-state energy is dissipated through molecular motion, collisions, stacking, and environmental interactions, leading to an increased probability of nonradiative energy loss and a significant decrease in quantum yield. MOFs, as a class of crystalline porous materials, can spatially isolate organic molecules and fix them into a framework, thereby suppressing molecular rotation, reducing the probability of nonradiative transition decay of excited-state energy, and effectively reducing intermolecular π-π stacking and environmental energy interactions, thus improving their quantum yield. Therefore, assembling fluorescent MOFs with benzothiadiazole derivatives having donor-acceptor-donor (DAD) structures and utilizing the spatial immobilization of MOFs can improve their quantum yield. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing benzothiadiazole-based Zn-MOF near-infrared fluorescent materials, thereby improving the fluorescence performance of Zn-MOF near-infrared fluorescent materials.

[0005] The technical solution adopted in this invention is a method for preparing benzothiadiazole-based Zn-MOF near-infrared fluorescent materials, which is specifically implemented according to the following steps:

[0006] Step 1: Synthesize 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid ester;

[0007] Step 2: The 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid ester obtained in Step 1 is mixed with NaOH and solvent and subjected to reflux reaction to prepare organic ligand SN;

[0008] Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, place them in a hydrothermal reactor for self-assembly reaction, cool, and obtain benzothiadiazole-based Zn-MOF material.

[0009] The invention is further characterized in that,

[0010] Step 1 specifically involves:

[0011] Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, and then trifluoroacetic acid and DMSO were added. The mixture was refluxed and heated and stirred under N2 protection. After the reaction was completed, deionized water was added, and a red solid precipitated. The solid was filtered, dried, and washed with methanol to obtain dimethyl 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

[0012] The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid, and DMSO was 1:1:17:256; the stirring reaction temperature was 80-100℃, and the reaction time was 6-8h.

[0013] Step 2 specifically involves:

[0014] 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate was mixed with NaOH, and a mixed solvent of THF / MeOH / H2O was added. The mixture was refluxed and heated and stirred under N2 protection. After the reaction was completed, THF and MeOH were evaporated to dryness, deionized water was added, hydrochloric acid solution was added dropwise until the pH was 1 and stirred for 2-4 hours, filtered, and washed until neutral to obtain the organic ligand SN.

[0015] The molar ratio of 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate, NaOH, THF, MeOH and H2O was 1:12:124:615:278; the reaction temperature was 80-90℃ and the reaction time was 6-8h.

[0016] In step 3, the metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; the organic acid is water-soluble eosin Y; and the molar ratio of the metal salt, organic ligand, organic acid and organic solvent is 3:2:1:52.

[0017] In step 3, the temperature of the self-assembly reaction is 80-100℃, and the self-assembly time is 48-72h.

[0018] The beneficial effects of this invention are as follows: Utilizing benzothiadiazole, which exhibits high chemical stability, ease of modification, and strong electron affinity, as the parent compound, a donor-acceptor-donor (DAD) type organic ligand SN was designed and synthesized, thereby constructing a near-infrared fluorescent MOF (SN-Zn). By leveraging the spatial confinement and immobilization effect of MOFs, molecular rotation is suppressed, reducing the probability of non-radiative transition decay in excited states, thus enhancing its fluorescence quantum yield and expanding its applications for precise visualization detection in biological systems and clinical samples. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of the organic ligand SN prepared by the method of this invention.

[0020] Figure 2 This is a single-crystal structure diagram of SN-Zn prepared by the method of this invention;

[0021] Figure 3 These are the XRD powder spectra of SN-Zn prepared by the method of this invention and single-crystal simulated SN-Zn;

[0022] Figure 4 These are the Fourier transform infrared spectra of SN and SN-Zn prepared by the method of this invention;

[0023] Figure 5 This is the thermogravimetric spectrum of SN-Zn prepared by the method of this invention;

[0024] Figure 6 This is the XRD powder pattern of SN-Zn prepared by the method of this invention after being soaked in various organic solvents for 24 hours;

[0025] Figure 7 These are solid-state fluorescence emission spectra of SN and SN-Zn prepared by the method of this invention;

[0026] Figure 8 This is the solid ultraviolet absorption spectrum of SN and SN-Zn prepared by the method of this invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] The preparation method of the benzothiadiazole-based Zn-MOF near-infrared fluorescent material of the present invention is specifically implemented according to the following steps:

[0029] Step 1: Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, followed by the addition of trifluoroacetic acid and DMSO. The mixture was refluxed under N2 protection and heated with stirring. After the reaction was complete, deionized water was added, resulting in the precipitation of a red solid. The solid was filtered, dried, and washed with methanol to remove excess impurities, yielding the product 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

[0030] The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid and DMSO is 1:1:17:256;

[0031] The stirring reaction temperature is 80-100℃, and the reaction time is 6-8 hours;

[0032] Step 2: Mix 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate with NaOH, add THF / MeOH / H2O mixed solvent, reflux under N2 protection, heat and stir under N2 protection, reaction temperature 80-90℃, reaction time 6-8h. After the reaction is completed, use THF and MeOH in the rotary dry flask, add deionized water, add hydrochloric acid solution dropwise until the pH of the reaction solution is 1, and stir at room temperature for 2-4h. A solid precipitates in the solution. Filter to obtain a red product and wash with distilled water until neutral to obtain the product organic ligand SN.

[0033] 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate, NaOH, THF, MeOH and H2O molar ratio 1:12:124:615:278;

[0034] Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, and place them in a hydrothermal reactor for self-assembly reaction. After the reaction is completed, cool to room temperature to obtain pale yellow cubic transparent crystals, which are benzothiadiazole-based Zn-MOF materials (SN-Zn).

[0035] The metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; the organic acid is water-soluble eosin Y; the molar ratio of the metal salt, organic ligand, organic acid and organic solvent is 3:2:1:52;

[0036] The temperature for the self-assembly reaction is 80-100℃, and the self-assembly time is 48-72h.

[0037] Example 1

[0038] The preparation method of the benzothiadiazole-based Zn-MOF near-infrared fluorescent material of the present invention is specifically implemented according to the following steps:

[0039] Step 1: Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, followed by the addition of trifluoroacetic acid and DMSO. The mixture was refluxed under N2 protection and heated with stirring. After the reaction was complete, deionized water was added, resulting in the precipitation of a red solid. The solid was filtered, dried, and washed with methanol to remove excess impurities, yielding the product 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

[0040] The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid and DMSO is 1:1:17:256;

[0041] The stirring reaction temperature was 100℃, and the reaction time was 8 hours.

[0042] The product data are as follows:

[0043] 1 H NMR (400MHz, CF3OOD) δ: 9.23 (d, J = 6.7 Hz, 2H), 8.95 (d, J = 6.7 Hz, 2H), 8.41 (d, J = 8.2 Hz, 4H), 7.97 (d, J = 8.2 Hz, 4H), 4.14 (s, 6H). 13C NMR (101MHz, CF3OOD) δ: 169.8, 151.8, 151.4, 143.6, 139.6, 135.9, 132.4, 131.3, 130.9, 130.6, 128.1, 119.3, 53.1. HRMS(ESI)m / z:[M+H] + calcd for C 28 H 19 N5O4S: 522.1192; found: 522.1205.

[0044] Step 2: 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate was mixed with NaOH, and a THF / MeOH / H2O mixed solvent was added. The mixture was refluxed and heated under N2 protection with stirring at 85°C for 6 hours. After the reaction was complete, the THF and MeOH in the rotary evaporator were removed, deionized water was added, and hydrochloric acid solution was added dropwise until the pH of the reaction solution reached 1. The mixture was stirred at room temperature for 2 hours. A solid precipitated from the solution. The solid was filtered to obtain a red product, which was washed with distilled water until neutral to obtain the organic ligand SN. Figure 1 As shown;

[0045] 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate, NaOH, THF, MeOH and H2O molar ratio 1:12:124:615:278;

[0046] The product data are as follows:

[0047] 1 H NMR (400MHz, DMSO-d6) δ: 8.89 (d, J = 5.3 Hz, 2H), 8.45 (d, J = 5.3 Hz, 2H), 8.18 (d, J = 7.5 Hz, 8H). 13 C NMR (101MHz, DMSO-d6) δ: 167.2, 154.8, 150.5, 144.4, 141.4, 138.3, 131.2, 130.2, 129.1, 124.2. HRMS(ESI)m / z:[M+H] + calcd for C 26 H 15 N5O4S: 494.0918; found: 494.0934.

[0048] Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, and place them in a hydrothermal reactor for self-assembly reaction. After the reaction is completed, cool to room temperature to obtain pale yellow cubic transparent crystals, which are benzothiadiazole-based Zn-MOF materials (SN-Zn).

[0049] The metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; and the organic acid is water-soluble eosin Y.

[0050] The molar ratio of metal salt, organic ligand, organic acid, and organic solvent is 3:2:1:52;

[0051] The self-assembly reaction temperature is 80℃, and the self-assembly time is 48h.

[0052] Example 2

[0053] The present invention relates to a method for preparing benzothiadiazole-based Zn-MOF near-infrared fluorescent materials, such as... Figure 1 As shown, please follow these steps:

[0054] Step 1: Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, and then trifluoroacetic acid and DMSO were added. The mixture was refluxed and heated and stirred under N2 protection. After the reaction was completed, deionized water was added, and a red solid precipitated. The solid was filtered, dried, and washed with methanol to remove excess impurities, yielding the product 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

[0055] The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid and DMSO is 1:1:17:256;

[0056] The stirring reaction temperature was 100℃, and the reaction time was 8 hours.

[0057] Step 2: 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate was mixed with NaOH, and a THF / MeOH / H2O mixed solvent was added. The mixture was refluxed and heated under N2 protection for stirring at 85°C for 6 hours. After the reaction was completed, the THF and MeOH in the rotary evaporator were used to add deionized water, and hydrochloric acid solution was added dropwise until the pH of the reaction solution was 1. The mixture was stirred at room temperature for 4 hours. A solid precipitated in the solution. The product was filtered to obtain a red product and washed with distilled water until neutral to obtain the organic ligand SN.

[0058] 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate, NaOH, THF, MeOH and H2O molar ratio 1:12:124:615:278;

[0059] Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, and place them in a hydrothermal reactor for self-assembly reaction. After the reaction is completed, cool to room temperature to obtain pale yellow cubic transparent crystals, which are benzothiadiazole-based Zn-MOF materials (SN-Zn).

[0060] The metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; and the organic acid is water-soluble eosin Y.

[0061] The molar ratio of metal salt, organic ligand, organic acid, and organic solvent is 3:2:1:52;

[0062] The self-assembly reaction temperature is 80℃, and the self-assembly time is 48h.

[0063] Example 3

[0064] The method for preparing benzothiadiazole-based Zn-MOF materials of the present invention, as follows: Figure 1 As shown, please follow these steps:

[0065] Step 1: Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, followed by the addition of trifluoroacetic acid and DMSO. The mixture was refluxed under N2 protection and heated with stirring. After the reaction was complete, deionized water was added, resulting in the precipitation of a red solid. The solid was filtered, dried, and washed with methanol to remove excess impurities, yielding the product 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

[0066] The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid and DMSO is 1:1:17:256;

[0067] The stirring reaction temperature was 100℃, and the reaction time was 8 hours.

[0068] Step 2: 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate was mixed with NaOH, and a mixed solvent of THF / MeOH / H2O was added. The mixture was refluxed and heated and stirred under N2 protection. After the reaction was completed, the THF and MeOH in the rotary dry flask were evaporated, deionized water was added, and hydrochloric acid solution was added dropwise until the pH of the reaction solution was 1. The mixture was stirred at room temperature for 3 hours. A solid precipitated in the solution. The product was filtered to obtain a red product and washed with distilled water until neutral to obtain the product organic ligand SN.

[0069] 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid dicarboxylate, NaOH, THF, MeOH and H2O molar ratio 1:12:124:615:278;

[0070] The reaction temperature was 85℃, and the reaction time was 6 hours.

[0071] Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, and place them in a hydrothermal reactor for self-assembly reaction. After the reaction is completed, cool to room temperature to obtain pale yellow cubic transparent crystals, which are benzothiadiazole-based Zn-MOF materials (SN-Zn).

[0072] The metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; and the organic acid is water-soluble eosin Y.

[0073] The molar ratio of metal salt, organic ligand, organic acid, and organic solvent is 3:2:1:52;

[0074] The self-assembly reaction was carried out at a temperature of 100℃ for 48 hours.

[0075] Figure 2 This is a single-crystal structure diagram of the benzothiadiazole-based Zn-MOF material (SN-Zn) of this invention. As shown in the diagram, SN-Zn has a 3D porous structure and belongs to the monoclinic crystal system, space group C2 / c. Its asymmetric unit contains a crystallographically independent metallic center, Zn. 2 +A completely deprotonated SN 2- Ligands. Zn 2+ It is 5-coordinated, consisting of 5 deprotonated SNs. 2- The ligand's four oxygen atoms and one nitrogen atom are coordinated, forming a tetrapyramidal coordination configuration. Two Zn1 atoms connect with a carboxylic acid group to form a paddle-shaped Zn2 (μ2-η) group. 1 :η 1 -COO)4 bimetallic cluster. In this structure, the Zn1 propeller cluster, which serves as 5 connection points, forms a 2D mesh surface through carboxylic acid linkages on 4 SN ligands, and then the nitrogen atom of 1 SN ligand links the layers to form a 3D framework with open channels.

[0076] Figure 3 The figure shows a comparison of the XRD powder spectra of SN-Zn prepared by the method of this invention and the single-crystal simulated SN-Zn. It can be seen from the figure that the SN-Zn powder is consistent with the single-crystal simulated data, indicating that the synthesis purity of SN-Zn is high.

[0077] Figure 4 This is a comparison of the Fourier transform infrared spectra of SN and SN-Zn in this invention. Infrared (IR) spectroscopy tests show that SN-Zn has a wavelength of 3400 cm⁻¹. -1 The disappearance of the peak indicates that the carboxylic acid group has been successfully coordinated with the metal ion.

[0078] Figure 5 The thermogravimetric spectrum of SN-Zn prepared by the method of this invention shows that SN-Zn has good thermal stability, and the framework only begins to collapse when the temperature is raised to 420℃. Figure 6 The XRD powder spectra of SN-Zn prepared by the method of this invention after being soaked in various organic solvents for 24 hours show that SN-Zn can be stably present in different solvents for at least 24 hours. Figure 7 The solid-state fluorescence emission spectra of SN and SN-Zn prepared by the method of this invention show that SN-Zn has a wider visible light absorption range compared to the ligand. Figure 8 The following are the solid-state ultraviolet absorption spectra of SN and SN-Zn prepared by the method of this invention. It can be seen that the absorption range of SN-Zn is basically the same as that of SN.

Claims

1. A method for preparing benzothiadiazole-based Zn-MOF near-infrared fluorescent materials, characterized in that, The specific steps are as follows: Step 1: Synthesize dimethyl 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate; Step 2: The 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoic acid ester obtained in Step 1 is mixed with NaOH and solvent and subjected to reflux reaction to prepare organic ligand SN; Step 3: Mix the metal salt, organic ligand SN, organic acid, and organic solvent, place them in a hydrothermal reactor for self-assembly reaction, cool, and obtain benzothiadiazole-based Zn-MOF material; In step 3, the metal salt is Zn(NO3)2·6H2O; the organic solvent is N,N-dimethylformamide; the organic acid is water-soluble eosin Y; and the molar ratio of the metal salt, organic ligand, organic acid and organic solvent is 3:2:1:

52.

2. The method for preparing the benzothiadiazole-based Zn-MOF near-infrared fluorescent material according to claim 1, characterized in that, In step 1, specifically: Dimethyl 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate was mixed with 4-pyridinecarboxaldehyde, and then trifluoroacetic acid and DMSO were added. The mixture was refluxed and heated and stirred under N2 protection. After the reaction was completed, deionized water was added, and a red solid precipitated. The solid was filtered, dried, and washed with methanol to obtain dimethyl 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dibenzoate.

3. The method for preparing the benzothiadiazole-based Zn-MOF near-infrared fluorescent material according to claim 2, characterized in that, The molar ratio of 4,4'-(5,6-diaminobenzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoate, 4-pyridinecarboxaldehyde, trifluoroacetic acid, and DMSO was 1:1:17:256; the stirring reaction temperature was 80-100℃, and the reaction time was 6-8h.

4. The method for preparing the benzothiadiazole-based Zn-MOF near-infrared fluorescent material according to claim 1, characterized in that, Step 2 specifically involves: Dimethyl dibenzoate (4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl) was mixed with NaOH, and a mixed solvent of THF / MeOH / H2O was added. The mixture was refluxed and heated under N2 protection. After the reaction was completed, THF and MeOH were evaporated to dryness, deionized water was added, and hydrochloric acid solution was added dropwise until the pH reached 1. The mixture was stirred for 2-4 hours, filtered, and washed until neutral to obtain the organic ligand SN.

5. The method for preparing the benzothiadiazole-based Zn-MOF near-infrared fluorescent material according to claim 4, characterized in that, The molar ratio of 4,4'-(6-(pyridin-4-yl)-5H-imidazo[4',5':4,5]benzo[1,2-c][1,2,5]thiadiazole-4,8-diyl)dimethyl dibenzoate, NaOH, THF, MeOH and H2O was 1:12:124:615:278; the reaction temperature was 80-90℃ and the reaction time was 6-8h.

6. The method for preparing the benzothiadiazole-based Zn-MOF near-infrared fluorescent material according to claim 1, characterized in that, In step 3, the temperature of the self-assembly reaction is 80-100℃, and the self-assembly time is 48-72h.

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