Aggregation-induced emission metal-organic frameworks, methods of making and use thereof for portable detection of low concentrations of nitrobenzene

Abstract

The application discloses an aggregation-induced emission metal organic framework, a preparation method thereof and application of the aggregation-induced emission metal organic framework in portable detection of low-concentration nitrobenzene. 4+ The aggregation-induced emission metal organic framework is prepared by providing Zr by ZrCl4, using 2-sulfo terephthalic acid and AIE molecule 2,3,5,6-tetra(4-carboxyphenyl)pyrazine as organic ligands, and obtaining an aggregation-induced emission fluorescent material by a solvothermal method. The material shows bright blue fluorescence due to a coordination effect and intramolecular rotation restriction, and the aggregation state fluorescence of the material can be significantly quenched after being contacted with nitrobenzene. The application utilizes the aggregation-induced emission performance of the aggregation-induced emission molecule to obtain the aggregation-induced emission metal organic framework material. The material has good detection capacity for nitrobenzene, can rapidly and efficiently detect nitrobenzene in a solution, and has good cycle performance. Meanwhile, the material can also realize multiple detection of nitrobenzene gas, and has good sensitivity and practicability.

Description

Technical Field

[0001] This invention belongs to the technical field of fluorescent sensing materials, and relates to aggregation-induced emission metal-organic coordination polymers, specifically to aggregation-induced emission metal-organic frameworks and their preparation methods, and their application in portable detection of low concentrations of nitrobenzene. Background Technology

[0002] Nitroaromatic compounds are prominent environmental pollutants due to their potential toxicity and exceptional explosiveness. Their widespread use in weapons manufacturing, metal etching, and leather manufacturing industries not only pollutes groundwater but also harms human health. Nitrobenzene (NB) is a highly toxic, mutagenic, and carcinogenic nitroaromatic compound widely used in paint additives, pesticides, and pharmaceutical synthesis. NB can cause serious harm to human health through accumulation in water; long-term exposure can lead to anemia, leukemia, abnormal liver function, and kidney disease. Due to its high volatility, accidental inhalation of NB can cause nausea and vomiting, and in severe cases, damage to the lungs and nervous system. To date, numerous conventional analytical techniques have been used to detect NB, such as mass spectrometry, electrochemical methods, surface-enhanced Raman spectroscopy, and energy-dispersive X-ray diffraction. However, these traditional methods have limitations and drawbacks, such as complex operation, high technical requirements for operators, and difficulty in achieving rapid on-site detection. Therefore, developing a simple, rapid, and portable NB detection technology is essential.

[0003] Among a range of detection methods, fluorescence detection has attracted widespread attention from researchers due to its advantages such as low cost, high sensitivity, fast response time, and portability. In fluorescent sensing materials, the fluorescence performance of luminescent metal-organic frameworks (MOFs) often depends on the fluorescence properties of their organic ligands or the fluorescence properties of their metal ions and clusters. Therefore, by effectively designing the organic ligands of MOF materials, a fluorescent sensing material with a specific response can be obtained. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a highly sensitive aggregation-induced emission metal-organic framework material for the detection of nitrobenzene. This method has low equipment requirements and is simple to operate. Based on the prepared metal-organic framework material, a portable flexible aggregation-induced emission film for detecting nitrobenzene gas is prepared. The prepared materials H4TCPP and UiO-66-H4TCPP have good aggregation-induced emission properties, and the UiO-66-H4TCPP and UiO-66-H4TCPP@PVDF film can rapidly and sensitively detect nitrobenzene.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: an aggregation-induced emission metal-organic framework is prepared by dissolving ZrCl4 in N,N-dimethylformamide solution and performing the reaction under ultrasonic conditions. Subsequently, BDC-SO3H and AIE molecule H4TCPP are added, and the mixture is then treated under ultrasonic conditions to obtain a transparent solution. A certain amount of acetic acid is added to the solution, and the mixed solution is placed in a polytetrafluoroethylene reactor and heated for reaction. After the reaction is completed, the aggregation-induced emission metal-organic framework material UiO-66-H4TCPP can be obtained by centrifugation and washing.

[0006] The above-mentioned aggregation-induced emission metal-organic framework, H4TCPP, is prepared as follows: Vitamin B1 is added to a mixed solvent of CH3OH and H2O to adjust the pH to 9-10. Methyl 4-toluene is added, and the reaction mixture is stirred in an ice-water bath for 1 hour. Then, it is heated to form a precipitate, which is filtered to obtain the product. Acetic anhydride is added to the product and a solution of ammonium acetate, and the mixture is stirred at 120 °C under N2 conditions for 12 hours to obtain a solid product. The product is filtered and washed with water and diethyl ether to obtain a yellow solid 2,3,5,6-tetra(4-methoxycarbonyl)phenyl)pyrazine. NaOH is added to 2,3,5,6-tetra(4-(methoxycarbonyl)phenyl)pyrazine in a THF-H2O solution, and the mixture is refluxed for about 12 hours. Tetrahydrofuran is evaporated, and the pH is adjusted to 4-5. The precipitate is filtered and washed with water to obtain the yellow solid H4TCPP.

[0007] The above-mentioned aggregation-induced light-emitting metal-organic framework is heated at 60 °C for 1 hour and at 85 °C for 1 hour.

[0008] The above-mentioned aggregation-induced emission metal-organic framework has a mass ratio of BDC-SO3H to ZrCl4 of 0-0.67:1 and a mass ratio of BDC-SO3H to H4TCPP of 1:0-1.4.

[0009] The above-mentioned aggregation-induced emission metal-organic framework, wherein the heating reaction is carried out at 0-120 °C for 0-24 h.

[0010] The application of the above-mentioned aggregation-induced emission metal-organic framework in the fluorescence detection of nitrobenzene in water is described below.

[0011] 1) In a solution containing 0-200 nM nitrobenzene, 1 mg / mL UiO-66-H4TCPP solution was added, and fluorescence was measured. The linear relationship between nitrobenzene concentration and fluorescence intensity was obtained: y = 0.04710. c +1.09875, R 2 =0.99111;

[0012] 2) Add 1 mg / mL UiO-66-H4TCPP solution to the nitrobenzene solution to be tested, and perform fluorescence testing. Based on the fluorescence intensity, substitute it into the linear equation obtained in step 1) to calculate the concentration of nitrobenzene in water.

[0013] The above-mentioned application of an aggregation-induced emission metal-organic framework in the fluorescence detection of nitrobenzene gas is described below.

[0014] 1) In a sealed container, 15 mg of UiO-66-H4TCPP powder was placed. Nitrobenzene gas (0-50 ppm) was generated in the device through heating and volatilization. After 20 minutes, the solid powder material was removed, and solid-state fluorescence was measured. The linear relationship between nitrobenzene gas concentration and fluorescence intensity was obtained: y = 0.03108. c +0.85508, R 2 =0.99289;

[0015] 2) Place 15 mg of UiO-66-H4TCPP powder in a sealed container, place the nitrobenzene gas to be tested in the sealed device, and take out the solid powder material after 20 min for solid fluorescence test. The concentration of nitrobenzene gas can be calculated based on the fluorescence intensity, the linear equation obtained in step 1), and pV=nRT.

[0016] A portable UiO-66-H4TCPP@PVDF membrane for detecting nitrobenzene gas was obtained by adding PVDF to a DMF solution and heating until the PVDF was completely dissolved. The UiO-66-H4TCPP powder was then added to the PVDF solution and stirred until homogeneous. The mixture was then poured onto a glass mold and placed in deionized water. The UiO-66-H4TCPP@PVDF membrane detached from the glass mold, thus obtaining the portable UiO-66-H4TCPP@PVDF membrane for detecting nitrobenzene gas.

[0017] The above-mentioned portable UiO-66-H4TCPP@PVDF film for detecting nitrobenzene gas has a mass ratio of UiO-66-H4TCPP to PVDF of 0.2:1, and the heating reaction is carried out at 70 °C for 0-30 min.

[0018] The above-mentioned portable UiO-66-H4TCPP@PVDF film for detecting nitrobenzene gas is described in the following method: The UiO-66-H4TCPP@PVDF film is placed in a sealed container. Nitrobenzene gas of 0-50 ppm is generated in the device by the volatilization of nitrobenzene upon heating. After 20 min, the film is removed, and the blue fluorescence of the film can be observed to be effectively quenched under a 360 nm ultraviolet lamp.

[0019] The aggregation-induced emission metal-organic framework material UiO-66-H4TCPP and the aggregation-induced emission flexible film UiO-66-H4TCPP@PVDF film of the present invention have advantages such as good stability, high fluorescence intensity and portability. Due to the introduction of the ligand AIE molecule H4TCPP, this material has potential applications for the detection of nitrobenzene gas. Attached Figure Description

[0020] Figure 1 The synthesis roadmap for UiO-66-H4TCPP.

[0021] Figure 2 This is a schematic diagram of the synthesis of the AIE molecule H4TCPP.

[0022] Figure 3 The images show the 1H-NMR spectra of the products from each step in the synthesis of the AIE molecule H4TCPP.

[0023] Figure 4 A schematic diagram of the synthesis of aggregation-induced luminescent metal-organic framework UiO-66-H4TCPP.

[0024] Figure 5 The FT-IR spectrum (a) and XRD spectrum (b) of the AIE molecule H4TCPP, the metal-organic framework UiO-66-SO3H, and the aggregation-induced emission metal-organic framework UiO-66-H4TCPP are shown.

[0025] Figure 6 XPS spectra of synthesized metal-organic frameworks UiO-66-SO3H and aggregation-induced emission metal-organic frameworks UiO-66-H4TCPP.

[0026] Figure 7 Fluorescence emission spectra of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP with different ligand ratios for synthesis.

[0027] Figure 8 SEM images of different ligand ratios for the synthesis of aggregation-induced emission metal-organic framework UiO-66-H4TCPP.

[0028] Figure 9 XRD patterns of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP with different ligand ratios.

[0029] Figure 10 N2 adsorption diagram of aggregation-induced luminescent metal-organic framework UiO-66-H4TCPP.

[0030] Figure 11 Thermogravimetric curves for the synthesis of aggregation-induced emission metal-organic framework UiO-66-H4TCPP.

[0031] Figure 12 To characterize the aggregation-induced emission properties of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP, (a) and (c) show the fluorescence spectra of H4TCPP and UiO-66-H4TCPP in different aggregation states; (b) and (d) show the fluorescence intensity variation curves of H4TCPP and UiO-66-H4TCPP in different aggregation states.

[0032] Figure 13 The UV-Vis absorption spectra (a) and optimal excitation / emission spectra (b) of the AIE molecule H4TCPP, the metal-organic framework UiO-66-SO3H, and the aggregation-induced emission metal-organic framework UiO-66-H4TCPP are shown.

[0033] Figure 14 The fluorescence response of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP to different volatile organic compounds is shown in (a) and the bar graph showing the changes in fluorescence intensity is shown in (b).

[0034] Figure 15 The fluorescence response of aggregation-induced emission metal-organic framework UiO-66-H4TCPP to different volatile organic compounds in the range of 0-200 nM (a) and the anti-interference test of UiO-66-H4TCPP for the detection of nitrobenzene (b).

[0035] Figure 16 The fluorescence emission spectrum (a) of 0-200 nM nitrobenzene solution detected by aggregation-induced emission metal-organic framework UiO-66-H4TCPP and the linear relationship between probe fluorescence intensity and nitrobenzene concentration (b) are shown.

[0036] Figure 17 The fluorescence emission spectrum (a) of 0-50 ppm nitrobenzene gas detected by aggregation-induced emission metal-organic framework UiO-66-H4TCPP and the linear relationship between probe fluorescence intensity and nitrobenzene concentration (b) are shown.

[0037] Figure 18 The response time diagram (a) and cycle performance diagram (b) of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP for the detection of nitrobenzene are shown.

[0038] Figure 19 Photograph (a) and optical photograph (b) of a flexible UiO-66-H4TCPP@PVDF film for portable detection of nitrobenzene gas, prepared by blending aggregation-induced emission metal-organic framework UiO-66-H4TCPP with polyvinylidene fluoride (PVDF).

[0039] Figure 20 Photographs (a) of UiO-66-H4TCPP@PVDF film after detecting 0-50ppm nitrobenzene gas, graph (b) showing the change in nitrobenzene gas concentration and fluorescence intensity, and graph (c) showing the linear relationship between the fluorescence intensity of UiO-66-H4TCPP@PVDF film and nitrobenzene concentration. Detailed Implementation

[0040] Example 1: Aggregation-induced luminescence molecule H4TCPP

[0041] (a) such as Figure 2 As shown, the preparation method is as follows:

[0042] Vitamin B1 (0.27 mmol) was added to a mixed solvent of CH3OH (6.00 mL) and H2O (2.00 mL), followed by the dropwise addition of NaOH (1.00 mL, 2 M) to adjust the pH to 9-10. Then, methyl 4-toluene (18.29 mmol) was added. The reaction mixture was stirred in an ice-water bath for 1 hour, then heated at 60 °C for 1 hour and 85 °C for 1 hour to form a precipitate. The precipitate was obtained by filtration. Acetic anhydride (7.50 mmol) was then added to a solution of the product (5.00 mmol) and ammonium acetate (15.00 mmol). The mixture was stirred at 120 °C under N2 conditions for 12 hours to obtain a solid product. The product was washed with water and diethyl ether to give a yellow solid, 2,3,5,6-tetra(4-methoxycarbonyl)phenyl)pyrazine (1.35 mmol).

[0043] 2,3,5,6-Tetra(4-(methoxycarbonyl)phenyl)pyrazine (0.88 mmol) was added to a THF-H2O (1:1, 15.00 mL) solution with NaOH (9.95 mmol). The mixture was refluxed for about 12 hours, tetrahydrofuran was evaporated, and the solution was acidified to pH 4-5 with hydrochloric acid (2M). The precipitate was filtered and washed with water to obtain H4TCPP as a yellow solid (0.81 mmol).

[0044] (ii) Characterization of HDBB

[0045] For the 1H NMR spectroscopy of H4TCPP, approximately 10 mg of the first-step product, the second-step product, and H4TCPP, after vacuum drying, were dissolved in deuterated chloroform and deuterated DMSO, respectively. After complete dissolution, the samples were analyzed. The test results are as follows: Figure 3 As shown, the successful synthesis of the AIE molecule H4TCPP can be confirmed by proton nuclear magnetic resonance spectroscopy.

[0046] Example 2: Aggregation-induced emission metal-organic framework UiO-66-H4TCPP

[0047] (a) such as Figure 4 As shown, the preparation method is as follows:

[0048] 0.106 g of zirconium tetrachloride (ZrCl4) was dissolved in 20 mL of N,N-dimethylformamide (DMF) under ultrasonic conditions. Subsequently, 0-71.17 mg of 2-sulfonic acid terephthalic acid (BDC-SO3H) and 50.83-122 mg of H4TCPP molecules were added, followed by ultrasonic treatment to obtain a clear solution. The solution was mixed with acetic acid and crystallized in an oven at 120 °C for 24 hours. The precipitate was separated by centrifugation, washed four times with DMF and five times with acetone, and the resulting white powder was air-dried overnight and activated under dynamic vacuum at 90 °C for 24 hours to obtain the aggregation-induced emission metal-organic framework material UiO-66-H4TCPP.

[0049] (II) Characterization of UiO-66-H4TCPP

[0050] Figure 5 FT-IR spectra of H4TCPP, UiO-66-SO3H, and UiO-66-H4TCPP (a) and XRD spectra of UiO-66-SO3H and UiO-66-H4TCPP (b). From Figure 5 As can be seen in (a), 1025 cm -1 and 1079 cm -1 The peak at 1170 cm⁻¹ is due to the stretching vibration of the S=O double bond and the n-plane framework vibration caused by the substitution of hydrogen atoms on the benzene ring with sulfonic acid groups. -1 The peak at that point can be attributed to the tensile vibration of the O=S=O bond.

[0051] In the AIE molecule H4TCPP, 1726 cm -1 The peak of the stretching vibration of C=O is located at 3450 cm⁻¹. -1 The peak at 1726 cm⁻¹ represents the vibrational peak of the OH group. In the UiO-66-H4TCPP molecule, the characteristic peak of the sulfonic acid group still exists, but at 1726 cm⁻¹... -1 The disappearance of the C=O vibrational peak at this point proves the successful coordination of the carboxyl group and zirconium ion in H4TCPP. From Figure 5 (b) The X-ray diffraction comparison of UiO-66 and UiO-66-SO3H shows that the diffraction peak at 8.48° is destroyed due to the introduction of the sulfonic acid group of terephthalic acid, but diffraction peaks at 7.36° and 25.68° still exist. Under the action of the H4TCPP molecule, its crystal structure changed and new diffraction peaks appeared, which confirms the successful synthesis of UiO-66-H4TCPP.

[0052] Figure 6X-ray photoelectron spectroscopy (XPS) of UiO-66-SO3H and UiO-66-H4TCPP were performed. The chemical composition of UiO-66-H4TCPP was further analyzed using XPS, and the characterization results are as follows: Figure 6 As shown. Figure 6 (a) High-resolution Zr 3d XPS spectra of UiO-66-SO3H and UiO-66-H4TCPP. Compared with UiO-66-SO3H, the characteristic peaks of Zr-O bonds in 3d3 / 2 and 3d5 / 2 at 184.73 eV and 182.37 eV of UiO-66-H4TCPP shift to the lower field, indicating that the coordination environment of Zr has changed. This is mainly due to the introduction of a new ligand H4TCPP into UiO-66-H4TCPP, forming a new framework UiO-66-H4TCPP. The high-resolution C1s XPS spectrum of UiO-66-H4TCPP contains four peaks at 288.35 eV, 285.74 eV, 284.72 eV, and 284.20 eV, which are C=O / CO, CS, C=C / CC, and CN, respectively. The presence of the C1s characteristic peak strongly confirms the successful synthesis of UiO-66-H4TCPP. Compared with UiO-66-SO3H, the characteristic peak of C1s in UiO-66-H4TCPP shifts to a lower field, indicating that the chemical environment of C atoms in UiO-66-H4TCPP has changed. The introduction of H4TCPP leads to an increase in the electron cloud density around it, causing the binding energy to shift to a lower field.

[0053] Figure 7 Fluorescence emission spectra of UiO-66-H4TCPP with different ligand addition mass ratios are shown. To further improve the fluorescence performance of UiO-66-H4TCPP, the synthesis conditions were optimized. The effects of adding different mass ratios of H4TCPP and BDC-SO3H on the fluorescence intensity of UiO-66-H4TCPP were investigated. The fluorescence spectra show that when the mass ratio of H4TCPP to BDC-SO3H is 1:0.8, the fluorescence emission is weak. When the mass ratio of H4TCPP to BDC-SO3H is 1:1, the fluorescence intensity of the material increases significantly. Further increasing the amount of H4TCPP molecules, until the mass ratio of H4TCPP to BDC-SO3H is 1:1.4, does not significantly increase the fluorescence intensity.

[0054] Figure 8SEM images of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP with different ligand mass ratios are shown in Figure 8(a). As can be seen from Figure 8(a), the morphology of UiO-66 is a regular octahedron with an average diameter of approximately 100-150 nm. Without the addition of BDC-SO3H, the morphology of Zr-H4TCPP is a regular ellipse with an average diameter of approximately 150-200 nm. With increasing H4TCPP molecule content, the morphology of UiO-66-H4TCPP gradually transforms into an elliptical shape. Based on the fluorescence emission spectra of the material with different ligand ratios, a mass ratio of H4TCPP to BDC-SO3H of 1:1 was selected as the optimal addition amount. Subsequent performance and characterization tests of the material were also conducted using UiO-66-H4TCPP synthesized with this ligand ratio.

[0055] Figure 9 XRD patterns of the aggregation-induced emission metal-organic framework UiO-66-H4TCPP with different ligand mass ratios were obtained. XRD analysis showed that UiO-66-H4TCPP exhibited a different crystal structure from UiO-66-SO3H. When the mass ratio of H4TCPP to BDC-SO3H was greater than 1:0.8, changing the amount of H4TCPP added had little effect on the crystallinity of UiO-66-H4TCPP, and different diffraction peaks appeared at 8.75°, 10.40°, and 11.45°. When the mass ratio of H4TCPP to BDC-SO3H was 1:1, the material exhibited good crystallinity, and UiO-66-H4TCPP synthesized with this ligand ratio was selected for subsequent performance and characterization tests.

[0056] Figure 10 The N2 adsorption-desorption isotherms for UiO-66-SO3H and UiO-66-H4TCPP are shown. The specific surface area and pore structure of a material are crucial to its sensing performance; therefore, the N2 adsorption-desorption isotherms of UiO-66-SO3H and UiO-66-H4TCPP were measured. The pore size distribution of UiO-66-SO3H and UiO-66-H4TCPP is mainly in the range of 3-10 nm, classifying them as mesoporous materials. The specific surface area and pore volume of UiO-66-H4TCPP range from 117.941 m² / m³. 2 / g, decreased from 0.551 cc / g to 63.683 m 2 / g, 0.356 cc / g. This result is thought to be due to the introduction of the AIE molecule H4TCPP occupying the pore structure of the UiO-66-SO3H framework. However, the introduction of the H4TCPP molecule into the MOF is beneficial for the detection of nitrobenzene gas.

[0057] Figure 11Thermogravimetric curves for H4TCPP, UiO-66-SO3H, and UiO-66-H4TCPP. From... Figure 11 As can be seen, in the first stage, the mass loss of materials UiO-66-SO3H and UiO-66-H4TCPP before 100℃ can be attributed to water evaporation, with a mass loss of 10.76% for both. In the second stage, the mass loss of UiO-66-SO3H is mainly due to solvent evaporation in the MOF pores and the dehydroxylation of the zirconium oxide cluster, with a mass loss of approximately 22.23%. UiO-66-H4TCPP exhibits two mass losses in this stage, which can be attributed to solvent evaporation in the MOF pores, the dehydroxylation of the zirconium oxide cluster, and the mass loss of H4TCPP. In the third stage, structural collapse occurs. UiO-66-SO3H begins to decompose at 370℃, while UiO-66-H4TCPP decomposes at 500℃, indicating that the introduction of H4TCPP molecules significantly improves the thermal stability of the materials.

[0058] Figure 12 To characterize the aggregation-induced emission (AIE) properties of the metal-organic framework UiO-66-H4TCPP, (a) and (c) show the fluorescence spectra of H4TCPP and UiO-66-H4TCPP in different aggregation states; (b) and (d) show the fluorescence intensity variation curves of H4TCPP and UiO-66-H4TCPP in different aggregation states. DMF is a good solvent for H4TCPP and UiO-66-H4TCPP, and H2O is a poor solvent for H4TCPP and UiO-66-H4TCPP. As can be seen from the figures, the fluorescence intensity of H4TCPP and UiO-66-H4TCPP gradually increases with increasing H2O content. This is mainly because in poor solvents, the materials tend to form aggregates, restricting molecular motion and releasing energy in the form of fluorescence. The material exhibits maximum fluorescence intensity when the H2O / DMF ratio is 1:1; for the UiO-66-H4TCPP molecule, the material exhibits maximum fluorescence intensity when the H2O / DMF ratio is 9:1.

[0059] Figure 13 The UV-Vis absorption spectra (a) and optimal excitation / emission spectra (b) of H4TCPP, UiO-66-SO3H, and UiO-66-H4TCPP are shown. Figure 13(a) It can be seen that, compared with the UV absorption peaks of H4TCPP and UiO-66-SO3H, the largest UV absorption peak of UiO-66-H4TCPP shows a significant blue shift. The shift in absorption peak indicates that the coordination environment of Zr has changed, thus proving that coordination may have occurred between H4TCPP and the central metal ion in UiO-66-SO3H, and demonstrating the formation of the metal-organic framework of UiO-66-H4TCPP.

[0060] Example 3: Recognition of nitrobenzene by the aggregation-induced emission metal-organic framework UiO-66-H4TCPP

[0061] Test solution preparation: Take 20 mg of UiO-66-H4TCPP prepared in Example 2, dissolve it in 20 mL of deionized water, and ultrasonically disperse it to obtain a probe dispersion with a concentration of 1 mg / mL.

[0062] Detection of nitrobenzene solution: Prepare a nitrobenzene stock solution with a concentration of 0.01 mol / L, and then dilute it to 0-200 nM. Add 100 μL of the diluted nitrobenzene solution of different concentrations to 5 mL of probe solution with a concentration of 1 mg / mL, and then perform fluorescence detection.

[0063] Detection of nitrobenzene gas: The detection of nitrobenzene gas was performed in a self-made 18 L sealed container. A nitrobenzene solution was injected into the container through a small hole with a rubber stopper at the top of the apparatus using a syringe. A heating device inside the container evaporated the nitrobenzene solution into gaseous nitrobenzene. 15 mg of UiO-66-H4TCPP was placed in the sealed container, and after 20 minutes, it was removed for solid-state fluorescence testing. The concentration of nitrobenzene gas can be calculated using the ideal gas law pV=nRT.

[0064] Figure 14 The results (a) and histogram (b) show the response of UiO-66-H4TCPP to different aromatic compounds and volatile organic compounds (formaldehyde, 1-Butanol, EtOAc, Ph-Cl, Benzene, Toluene, Isopropyl alcohol, o-Xylene, Styrene, NB) and their fluorescence intensity changes. Figure 14 (a) It can be seen that the fluorescence intensity of the material decreases significantly after detecting 500 nM nitrobenzene, proving that UiO-66-H4TCPP can detect nitrobenzene with high sensitivity. Figure 14 As shown in (b), UiO-66-H4TCPP exhibits good selectivity for nitrobenzene.

[0065] Figure 15 The response of UiO-66-H4TCPP to different aromatic compounds and volatile organic compounds ranging from 0 to 200 nM is shown in (a), and the anti-interference performance of UiO-66-H4TCPP in detecting nitrobenzene is shown in (b). Considering the complexity of real-world environments, other potential interfering substances that may exist when UiO-66-H4TCPP detects nitrobenzene are further considered. In the presence of formaldehyde, n-butanol, ethyl acetate, chlorobenzene, benzene, toluene, isoamyl alcohol, xylene, styrene, etc., UiO-66-H4TCPP still exhibits a good fluorescence quenching response to nitrobenzene. The above results indicate that UiO-66-H4TCPP has satisfactory anti-interference performance in the detection of nitrobenzene.

[0066] Figure 16 The graph shows the fluorescence emission spectrum of the probe response after adding 0-200 nM nitrobenzene solution (a) and the linear relationship between probe fluorescence intensity and nitrobenzene concentration (b). Figure 16 As shown in (a), the fluorescence intensity of the probe gradually decreases with increasing nitrobenzene concentration. Figure 16 As shown in (b), the fluorescence intensity of the sensing system exhibits a good linear relationship with the nitrobenzene concentration in the range of 20-200 nM. R 2 =0.99111, using the formula D=3 / K ( It is the standard deviation of the fluorescence intensity of the fluorescent material UiO-66-H4TCPP itself, and the number of measurements is not less than 20. K The detection limit was calculated using the fluorescence intensity change coefficient of the fluorescent material UiO-66-H4TCPP when detecting nitrobenzene solution. The detection limit of this fluorescent probe for nitrobenzene is as low as 2.71 nM.

[0067] Figure 17 The fluorescence emission spectrum (a) of UiO-66-H4TCPP after detecting 0-50 ppm nitrobenzene gas and the linear relationship between probe fluorescence intensity and nitrobenzene gas concentration (b) are shown. Figure 17 As shown in (a), the fluorescence intensity of the probe gradually decreases with increasing nitrobenzene gas concentration. Figure 17 As shown in (b), the fluorescence intensity of this sensing system exhibits a good linear relationship with the nitrobenzene concentration in the range of 5-50 ppm. R 2 =0.99289, according to the formula D=3 / K ( It is the standard deviation of the fluorescence intensity of the fluorescent material UiO-66-H4TCPP itself, and the number of measurements is not less than 20. KThe fluorescence intensity variation coefficient of the fluorescent material UiO-66-H4TCPP when detecting nitrobenzene gas was used to calculate the detection limit of the fluorescent probe for nitrobenzene gas as low as 4.11 ppm.

[0068] Figure 18 The response time and cycling performance of UiO-66-H4TCPP for p-nitrobenzene detection were tested. The material can detect 50 nM and 100 nM nitrobenzene within 8 minutes, demonstrating its rapid detection capability. The cycling performance of UiO-66-H4TCPP for p-nitrobenzene gas detection was also tested. After detecting 20 ppm nitrobenzene gas, heating at 200 °C for 30 min allowed the nitrobenzene gas to escape from the pores under heating conditions. After five cycles, the fluorescence intensity of the material decreased by only 5.9%, demonstrating its excellent recyclability.

[0069] Example 4: Preparation of UiO-66-H4TCPP@PVDF Thin Film

[0070] Preparation of UiO-66-H4TCPP@PVDF film: 200 mg of PVDF was added to 2 mL of DMF solution and heated to 70 °C until the PVDF was completely dissolved. 60 mg of UiO-66-H4TCPP powder prepared in Example 2 was added to the PVDF solution and stirred evenly. The mixture was then poured onto a glass mold and placed in deionized water. The UiO-66-H4TCPP@PVDF film could be detached from the glass mold, thus obtaining a flexible aggregation-induced emission film capable of detecting nitrobenzene.

[0071] Detection of nitrobenzene gas: The detection of nitrobenzene gas was performed in a self-made 18 L sealed container. A nitrobenzene solution was injected into the container through a small hole with a rubber stopper at the top of the device using a syringe. A heating device inside the container evaporated the nitrobenzene solution into gaseous nitrobenzene. A UiO-66-H4TCPP@PVDF film was placed in the sealed container and removed after 20 minutes for solid-state fluorescence testing. The concentration of nitrobenzene gas could be calculated using the ideal gas law pV=nRT.

[0072] Figure 19 Photographs of a portable flexible UiO-66-H4TCPP@PVDF film for detecting nitrobenzene gas, prepared by blending aggregation-induced emission metal-organic framework UiO-66-H4TCPP with polyvinylidene fluoride (PVDF), and optical photographs under a 365 nm UV lamp. The UiO-66-H4TCPP@PVDF film is white in appearance and exhibits blue fluorescence emission under a 365 nm UV lamp, mainly due to the blue fluorescence of the introduced UiO-66-H4TCPP molecules.

[0073] Figure 20 The image shows the linear relationship between the actual fluorescence intensity of the UiO-66-H4TCPP@PVDF film after detecting nitrobenzene gas from 0 to 50 ppm and the nitrobenzene gas concentration. To achieve portable detection of nitrobenzene gas, a UiO-66-H4TCPP@PVDF film was prepared, and its detection capability for nitrobenzene gas was tested. When the concentration of nitrobenzene gas increased from 0 to 50 ppm, the fluorescence intensity of the film was gradually quenched. Figure 20 (a) A photograph of the UiO-66-H4TCPP thin film after detecting 0-50 ppm nitrobenzene gas. Figure 20 (b) and (c) show the fluorescence intensity change curves and linear relationship, y=0.01595. c +1.10278, R 2 =0.91935.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aggregation-induced emission metal-organic framework, characterized in that, The preparation method is as follows: ZrCl4 is dissolved in N,N-dimethylformamide solution and subjected to ultrasonic treatment. Subsequently, 2-sulfonic acid terephthalic acid BDC-SO3H and AIE molecule 2,3,5,6-tetra(4-carboxyphenyl)pyrazine H4TCPP are added, and the mixture is then treated under ultrasonic conditions to obtain a transparent solution. A certain amount of acetic acid is added to the solution, and the mixed solution is placed in a polytetrafluoroethylene reactor and heated for reaction. After the reaction is completed, the aggregation-induced emission metal-organic framework material UiO-66-H4TCPP can be obtained by centrifugation and washing. The mass ratio of BDC-SO3H to H4TCPP is 1:0.8-1.

4.

2. The aggregation-induced emission metal-organic framework according to claim 1, characterized in that, The preparation method of H4TCPP is as follows: Vitamin B1 is added to a mixed solvent of CH3OH and H2O to adjust the pH to 9-10. Methyl 4-toluene is added, and the reaction mixture is stirred in an ice-water bath for 1 hour. Then, it is heated to form a precipitate. After filtration, the product is obtained. Acetic anhydride is added to the product and a solution of ammonium acetate. The mixture is stirred at 120 °C under N2 conditions for 12 hours to obtain a solid product. The product is filtered and washed with water and diethyl ether to obtain a yellow solid 2,3,5,6-tetra(4-methoxycarbonyl)phenyl)pyrazine. NaOH is added to 2,3,5,6-tetra(4-(methoxycarbonyl)phenyl)pyrazine in a THF-H2O solution. The mixture is refluxed for 12 hours, tetrahydrofuran is evaporated, and the pH is adjusted to 4-5. The precipitate is filtered and washed with water to obtain a yellow solid H4TCPP.

3. The aggregation-induced emission metal-organic framework according to claim 2, characterized in that, The heating process involves heating at 60°C for 1 hour and heating at 85°C for 1 hour.

4. The aggregation-induced emission metal-organic framework according to claim 1, characterized in that, The heating reaction was carried out at 120 °C for 24 h.

5. The application of an aggregation-induced emission metal-organic framework according to any one of claims 1-4 in the fluorescence detection of nitrobenzene in water, characterized in that, The method is as follows: 1) In a solution containing 0-200 nM nitrobenzene, 1 mg / mL UiO-66-H4TCPP solution was added, and fluorescence was measured. The linear relationship between the nitrobenzene concentration c and the fluorescence intensity y was obtained, y = 0.04710. c +1.09875, R 2 =0.99111; 2) Add 1 mg / mL UiO-66-H4TCPP solution to the nitrobenzene solution to be tested, and perform fluorescence testing. Based on the fluorescence intensity, substitute it into the linear equation obtained in step 1) to calculate the concentration of nitrobenzene in water.

6. The application of the aggregation-induced emission metal-organic framework according to claim 1 in the fluorescence detection of nitrobenzene gas, characterized in that, The method is as follows: 1) In a sealed container, 15 mg of UiO-66-H4TCPP powder was placed. Nitrobenzene gas (0-50 ppm) was generated in the device through heating and volatilization. After 20 minutes, the solid powder material was removed, and solid-state fluorescence was tested. The linear relationship between the nitrobenzene gas concentration c and the fluorescence intensity y was obtained: y = 0.03108. c +0.85508, R 2 =0.99289; 2) Place 15 mg of UiO-66-H4TCPP powder in a sealed container, place the nitrobenzene gas to be tested in the sealed device, and take out the solid powder material after 20 min for solid fluorescence test. The concentration of nitrobenzene gas can be calculated based on the fluorescence intensity, the linear equation obtained in step 1), and pV=nRT.

7. A portable UiO-66-H4TCPP@PVDF thin film for detecting nitrobenzene gas, characterized in that, PVDF is added to a DMF solution and heated until the PVDF is completely dissolved. UiO-66-H4TCPP powder as described in any one of claims 1-5 is added to the PVDF solution and stirred evenly. The mixture is then poured onto a glass mold and placed in deionized water. The UiO-66-H4TCPP@PVDF membrane is detached from the glass mold to obtain a portable UiO-66-H4TCPP@PVDF thin film for detecting nitrobenzene gas.

8. The UiO-66-H4TCPP@PVDF thin film for portable detection of nitrobenzene gas according to claim 7, wherein the mass ratio of UiO-66-H4TCPP to PVDF is 0.2:1, and the heating reaction is carried out at 70 °C for 30 min.

9. A portable UiO-66-H4TCPP@PVDF thin film for detecting nitrobenzene gas according to claim 7 or 8, characterized in that, The method is as follows: UiO-66-H4TCPP@PVDF film is placed in a sealed container. Nitrobenzene gas of 0-50 ppm is generated in the device by the volatilization of nitrobenzene upon heating. After 20 min, the film is removed and the blue fluorescence of the film can be observed to be effectively quenched under a 360 nm ultraviolet lamp.

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