Aggregation-induced emission metal-organic frameworks, methods of making the same, and fluorescent / colorimetric dual-mode smart detection for trace hcl

Abstract

The application discloses an aggregation-induced emission metal organic framework, a preparation method thereof and fluorescent / colorimetric dual-mode intelligent detection for trace HCl. 2+ The aggregation-induced emission metal organic framework is prepared by providing Zn(NO3)3.6H2O as Zn 2+ , imidazole-2-formaldehyde and an AIE molecule HDBB as organic ligands, and through a solvothermal method to obtain ZIF-90-HDBB, which can change the aggregation state fluorescence from yellow green to orange red after being contacted with HCl gas; the ZIF-90-HDBB is uniformly loaded on cellulose filter paper to obtain a paper-based sensor for portable detection of HCl, and through combination with a color recognition APP of a smart phone, the HCl can be rapidly and sensitively detected on site in a fluorescent / colorimetric dual mode. Since the HDBB molecule is prone to protonation under acidic conditions, the fluorescence color changes, and therefore the material can be accurately and efficiently used for detection of acidic gas, and the material can be recycled.

Description

Technical Field

[0001] This invention belongs to the technical field of fluorescent sensing materials, specifically aggregation-induced emission metal-organic coordination polymers, and more specifically to aggregation-induced emission metal-organic frameworks and their preparation methods, as well as fluorescent / colorimetric dual-mode intelligent detection of trace amounts of HCl. Background Technology

[0002] Excessive concentrations of toxic chemical gases can cause significant damage to the environment and human health, making efficient detection of toxic gases an increasingly important concern. One such important and highly hazardous gas is hydrogen chloride (HCl), which is produced in large quantities in fertilizer production, electroplating, textiles, and the rubber industry. Sudden exposure to this gas can cause hoarseness, respiratory ulcers, and pulmonary edema. Furthermore, as a highly toxic and corrosive substance, the workplace exposure limit for HCl is 5 ppm. The human exposure limit is 50-100 ppm of HCl vapor, and exposure to 1300-2000 ppm of HCl vapor can be fatal. Therefore, the ability to detect toxic HCl in real-world environments is of practical significance. Traditional methods for detecting HCl include gas chromatography, chromatography-mass spectrometry, and electrochemical detection. However, these methods require expensive and sophisticated large-scale instruments and specialized technical personnel, making efficient and rapid on-site detection difficult. Efficient and intuitive methods for detecting HCl have become a growing concern.

[0003] Photochemical sensing methods have attracted widespread attention from researchers due to their advantages such as high sensitivity, fast response speed, simple instrumentation, and visualization capabilities. Among photochemical sensing materials, the luminescent properties of luminescent metal-organic frameworks (MOFs) are mainly due to the fluorescence properties of organic ligands and the specificity of metal ions or metal clusters. Therefore, a novel fluorescent material can be obtained by rationally adjusting the ligands in MOFs. Summary of the Invention

[0004] The purpose of this invention is to provide a metal-organic framework material based on aggregation-induced emission (AIE), its preparation method, and its applications. This preparation method requires minimal equipment and is simple to operate; the obtained materials, HDBB and ZIF-90-HDBB, exhibit excellent AIE properties and can sensitively detect hydrogen chloride gas.

[0005] An aggregation-induced emission metal-organic framework, provided by Zn(NO3)3.6H2O. 2+ Using imidazole-2-carboxaldehyde and AIE molecule HDBB as organic ligands, the aggregation-induced emission metal-organic framework material ZIF-90-HDBB was obtained by solvothermal method.

[0006] The above-mentioned method for preparing an aggregation-induced emission metal-organic framework involves dissolving imidazole-2-formaldehyde (ICA) and polyvinylpyrrolidone (PVP) in deionized water and heating in a water bath to obtain solution 1. HDBB is then dissolved in Tris-HCl solution and sonicated to obtain solution 2. After solution 1 cools to room temperature, solution 2 is added to solution 1 and gently shaken. Zn(NO3)2·6H2O solution is then added dropwise to the above mixed solution. After standing, centrifugation and washing, the aggregation-induced emission metal-organic framework material ZIF-90-HDBB is obtained.

[0007] In the above-mentioned method for preparing an aggregation-induced luminescent metal-organic framework, the water bath heating is performed at 80°C for 0-20 minutes.

[0008] In the above-mentioned method for preparing an aggregation-induced emission metal-organic framework, the molar ratio of Zn(NO3)2.6H2O to ICA is 1:4.

[0009] The above-mentioned method for preparing aggregation-induced emission metal-organic frameworks, specifically the method for preparing HDBBs, includes the following steps:

[0010] 4-Aldehyde-3-hydroxybenzoic acid was dissolved in methanol, and hydrazine hydrate was added after dissolution. The mixture was refluxed in an oil bath at 75°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, washed with methanol, and dried under vacuum to obtain a yellow HDBB solid product.

[0011] A probe dispersion is prepared by dissolving the above-mentioned ZIF-90-HDBB in a methanol / DMSO solution and ultrasonically dispersing it to obtain a probe dispersion with a concentration of 1 mg / mL.

[0012] The preparation of the aforementioned aggregation-induced emission metal-organic framework and its application in the fluorescence detection of trace amounts of HCl solution are described below.

[0013] 1) Add the above-mentioned 1 mg / mL probe dispersion to a solution containing 0-0.4 μM HCl, and perform fluorescence testing. The linear relationship between HCl concentration and fluorescence intensity was obtained: y = 2.9933C - 0.2799, R0 2 =0.9958,

[0014] 2) Add the above-mentioned 1 mg / mL probe dispersion to the HCl solution to be tested, and perform fluorescence testing. Based on the fluorescence intensity,

[0015] Substitute these values ​​into the linear equation obtained in step 1) to calculate the concentration of the HCl solution.

[0016] The preparation of the aforementioned aggregation-induced emission metal-organic framework and its application in the fluorescence detection of trace HCl gas are described below.

[0017] 1) Place the above-mentioned 1 mg / mL probe dispersion in a sealed container. The injected HCl solution evaporates upon heating, generating 0-50 ppm HCl gas in the device. After 10 minutes, remove the probe solution and perform fluorescence testing. The linear relationship between HCl gas concentration and fluorescence intensity is obtained: y = 0.01536c + 0.02353, R0 2 =0.9921;

[0018] 2) Place the above 1 mg / mL probe dispersion in a sealed container, place the HCl gas to be tested in the sealed device, and take out the probe solution after 10 min for fluorescence testing. Calculate the concentration of HCl gas based on the fluorescence intensity, the linear equation obtained in step 1), and pV = nRT.

[0019] A paper-based sensor is obtained by dissolving the above-mentioned ZIF-90-HDBB in a nitrogen-methylpyrrolidone solution to obtain a probe dispersion with a concentration of 1 mg / mL, immersing cellulose filter paper in the probe dispersion for 12 h, and then drying it to obtain the paper-based sensor.

[0020] The preparation of the aforementioned aggregation-induced emission metal-organic framework and its application in the colorimetric dual-mode intelligent detection of trace HCl gas are described below.

[0021] 1) Place the paper-based sensor described above in a sealed container. Injecting HCl solution and heating it will generate 0-100 ppm HCl gas within the device. After 10 minutes, remove the paper-based sensor. Under a 360 nm UV lamp, its R / G value can be obtained using a color recognition app. The linear equation between the R / G value and the HCl gas is then derived: y = 0.07248c + 0.8865, R... 2 =0.9650;

[0022] 2) Place the paper-based sensor described above in a sealed container, place the HCl gas to be measured in the sealed device, take it out after 10 minutes, and obtain its R / G value under a 360nm ultraviolet lamp through a color recognition APP. Calculate the concentration of HCl gas according to the linear equation in step 1).

[0023] The aggregation-induced emission metal-organic framework material has a HCl concentration range of 0.1-0.4 μM (detecting HCl solution) and 0-100 ppm (detecting HCl gas).

[0024] The aggregation-induced emission metal-organic framework material ZIF-90-HDBB of the present invention has the advantages of good stability and high fluorescence intensity. Due to the introduction of the ligand AIE molecule HDBB, this material has potential applications in the detection of acidic gases.

[0025] This invention uniformly loads ZIF-90-HDBB onto cellulose filter paper to prepare a portable paper-based sensor for detecting HCl gas. By connecting it to a smartphone color recognition app, it enables rapid and sensitive on-site detection of HCl gas in both fluorescence and colorimetric modes. This invention utilizes the aggregation-induced emission (AIE) properties of aggregation-induced emission molecules to obtain an AIE metal-organic framework material. Because HDBB molecules readily undergo protonation under acidic conditions, resulting in a fluorescence color change, this material can be used accurately and efficiently for the detection of acidic gases. Furthermore, this material is recyclable. Attached Figure Description

[0026] Figure 1 A schematic diagram of the aggregation-induced emission metal-organic framework ZIF-90-HDBB for the detection of HCl.

[0027] Figure 2 This is a schematic diagram of the synthesis of the AIE molecule HDBB.

[0028] Figure 3 The proton NMR spectrum of the AIE molecule HDBB ( 1 H-NMR and carbon NMR spectrum ( 1 C-NMR).

[0029] Figure 4 A schematic diagram of the synthesis of aggregation-induced emission metal-organic framework ZIF-90-HDBB.

[0030] Figure 5 The FT-IR spectrum (a) and XRD spectrum (b) of the AIE molecule HDBB, metal-organic framework ZIF-90, and aggregation-induced emission metal-organic framework ZIF-90-HDBB are shown.

[0031] Figure 6 XPS spectra of synthesized metal-organic framework ZIF-90 and aggregation-induced emission metal-organic framework ZIF-90-HDBB.

[0032] Figure 7 Solid-state fluorescence spectra of AIE molecule HDBB and aggregation-induced emission metal-organic framework ZIF-90-HDBB.

[0033] Figure 8 Fluorescence emission spectra of the aggregation-induced emission metal-organic framework ZIF-90-HDBB with different ligand ratios for synthesis.

[0034] Figure 9 SEM images of different ligand ratios for the synthesis of aggregation-induced emission metal-organic framework ZIF-90-HDBB.

[0035] Figure 10TEM image showing the optimal ligand ratio for the synthesis of aggregation-induced emission metal-organic framework ZIF-90-HDBB.

[0036] Figure 11 Thermogravimetric curves of ZIF-90-HDBB, a metal-organic framework with the optimal ligand ratio, for synthesis of aggregation-induced emission.

[0037] Figure 12 To characterize the aggregation-induced emission properties of the aggregation-induced emission metal-organic framework ZIF-90-HDBB, (a) and (c) show the fluorescence spectra of HDBB and ZIF-90-HDBB in different aggregation states; (b) and (d) show the fluorescence intensity variation curves of HDBB and ZIF-90-HDBB in different aggregation states.

[0038] Figure 13 N2 adsorption diagram of aggregation-induced luminescent metal-organic framework ZIF-90-HDBB.

[0039] Figure 14 The UV-Vis absorption spectra (a) and optimal excitation / emission spectra (b) of the AIE molecule HDBB, the metal-organic framework ZIF-90, and the aggregation-induced emission metal-organic framework ZIF-90-HDBB are shown. The inset in (a) is an optical image of ZIF-90-HDBB under fluorescent light (left) and 365nm UV light (right).

[0040] Figure 15 The response of ZIF-90-HDBB to different acidic gases (a) and the changes in emission wavelength and intensity of ZIF-90-HDBB to different acidic gases (b).

[0041] Figure 16 The linear relationship between the fluorescence emission spectrum of aggregation-induced luminescent metal-organic framework ZIF-90-HDBB in 0-0.4 μM HCl solution and HCl concentration.

[0042] Figure 17 The linear relationship between the fluorescence emission spectrum of the aggregation-induced emission metal-organic framework ZIF-90-HDBB after detecting 0-50 ppm HCl gas and the HCl gas concentration.

[0043] Figure 18 XRD patterns of aggregation-induced emission metal-organic framework ZIF-90-HDBB after detecting 0-1000ppm HCl gas.

[0044] Figure 19 The response time and cycling performance of the aggregation-induced emission metal-organic framework ZIF-90-HDBB for HCl gas detection were evaluated.

[0045] Figure 20 Photographs and scanning electron microscope images of a paper-based sensor prepared by loading aggregation-induced emission metal-organic framework ZIF-90-HDBB onto cellulose filter paper.

[0046] Figure 21 The linear relationship between actual photographs of paper-based sensors detecting 0-100ppm HCl gas and the HCl gas concentration.

[0047] Figure 22 This involves using a paper-based sensor combined with a smartphone color recognition app to detect HCl gas. Detailed Implementation

[0048] Example 1: Aggregation-induced emission molecules HDBB

[0049] (a) such as Figure 2 As shown, the preparation method is as follows:

[0050] 166.2 mg of 4-aldehyde-3-hydroxybenzoic acid was dissolved in 10 mL of methanol. After complete dissolution, 24 μL of hydrazine hydrate was added, and the mixture was refluxed at 75 °C for 12 h. After the reaction was completed, the product was washed with methanol to obtain a yellow HDBB product.

[0051] (II) Characterization of HDBB

[0052] For the 1H NMR spectroscopy of HDBB, approximately 10 mg of vacuum-dried HDBB was dissolved in deuterated DMSO. The sample was ready for testing after complete dissolution. For the 1C NMR spectroscopy of HDBB, approximately 100 mg of HDBB was dissolved in deuterated DMSO. The sample was ready for testing after complete dissolution. The test results are as follows: Figure 3 As shown in (a), the two singlets at chemical shifts δ of 13.25 and 11.15 are typical characteristic peaks of hydrogen on the carboxyl group and hydrogen on the hydroxyl group, respectively. The singlet at 9.04 is a characteristic peak of hydrogen in a carbon-hydrogen bond connected to a nitrogen atom. The hydrogen on the benzene ring has a δ value in the range of 7.88-7.50. Figure 3 As shown in (b), the results of the carbon NMR spectrum corroborate the results of the hydrogen NMR spectrum, confirming the successful synthesis of HDBB.

[0053] Example 2: Aggregation-induced emission metal-organic framework ZIF-90-HDBB

[0054] (a) such as Figure 4 As shown, the preparation method is as follows:

[0055] 5.00 mmol of imidazole-2-carboxaldehyde (ICA) and 0.43 mmol of polyvinylpyrrolidone (PVP) were dissolved in 25 mL of deionized water and heated in a water bath at 80 °C for 10 min to obtain solution 1. 0-0.1 mmol of HDBB was dissolved in 40 μL of Tris-HCl solution and sonicated for 10 min to obtain solution 2. After solution 1 cooled to room temperature, solution 2 was added to solution 1 and gently shaken for 20 min. 5 mL of Zn(NO3)2·6H2O solution (molar ratio of Zn(NO3)2·6H2O to ICA 1:4) was added dropwise to the above mixed solution, and the mixture was allowed to stand for 24 h. After centrifugation and washing with deionized water, the aggregation-induced emission metal-organic framework material ZIF-90-HDBB was obtained.

[0056] Screening for the optimal ratio of test solvents for HDBB and ZIF-90-HDBB: To verify the effect of solvent properties on the aggregation-induced emission properties of HDBB and ZIF-90-HDBB, 10 mg of HDBB molecules prepared in Example 1 and 5 mg of ZIF-90-HDBB molecules prepared in Example 2 were dissolved in 5 mL of methanol, respectively, to obtain solutions with concentrations of 2 mg / mL and 1 mg / mL. 0.5 mL of each of these solutions was then taken, and different volume ratios of methanol and DMSO mixed solutions were added to ensure a final test solution volume of 5 mL, thus obtaining test solutions of HDBB (0.2 mg / mL) and ZIF-90-HDBB (0.1 mg / mL) with different methanol ratios.

[0057] (II) Characterization of ZIF-90-HDBB

[0058] Figure 5 FT-IR spectra of HDBB, ZIF-90, and ZIF-90-HDBB (a) and XRD spectra of ZIF-90 and ZIF-90-HDBB (b). From Figure 5 As can be seen from (a), the main characteristic peak of HDBB is at 1623 cm⁻¹. -1 The C=O vibration peak at 3346 cm⁻¹ and the peak at 3346 cm⁻¹ -1 The OH vibration peak at 1600 cm⁻¹, and the peak at 1600 cm⁻¹ -1 1564cm -1 The characteristic peak of the benzene ring at [location]; the characteristic peak of ZIF-90 is at 2850 cm⁻¹. -1 CH tensile vibration and 1675cm -1 The stretching vibration peak at C=O is observed. Comparing the FT-IR spectra of ZIF-90 and ZIF-90-HDBB, a peak at 1675 cm⁻¹ is visible in ZIF-90-HDBB. -1The C=O stretching vibration peak indicates that ZIF-90-HDBB has a similar functional group structure to ZIF-90. However, the C=O and OH vibration peaks of HDBB are not present in ZIF-90-HDBB because they are bound to zinc ions and are shielded by ZIF-90. This suggests that the HDBB in AIE molecules is encapsulated within the ZIF-90 framework rather than simply adsorbed on its surface. Figure 5 (b) The X-ray diffraction comparison between ZIF-90 and ZIF-90-HDBB shows that each diffraction peak of ZIF-90-HDBB corresponds one-to-one with that of ZIF-90, confirming that ZIF-90-HDBB retains the crystal structure of ZIF-90 and proving the successful synthesis of ZIF-90-HDBB.

[0059] Figure 6 X-ray photoelectron spectroscopy (XPS) of ZIF-90 and ZIF-90-HDBB is shown. Further analysis of the chemical composition of ZIF-90-HDBB was performed using XPS, and the characterization results are as follows: Figure 6 As shown. Figure 6 (a) High-resolution Zn 2p XPS spectra of ZIF-90 and ZIF-90-HDBB. Compared with ZIF-90, the characteristic peaks of ZIF-90-HDBB are shifted, indicating that the coordination environment of Zn has changed. This is mainly due to the introduction of the new ligand HDBB into ZIF-90, forming a new framework ZIF-90-HDBB. The high-resolution C1s XPS spectrum of ZIF-90-HDBB has three peaks at 288.43 eV, 285.99 eV, and 284.58 eV, corresponding to C≡N, CN, and CC / C=O, respectively. Compared with ZIF-90, the C1s peaks in ZIF-90-HDBB are shifted to varying degrees, indicating that the chemical environment of the C atom in ZIF-90-HDBB has changed, further proving the synthesis of ZIF-90-HDBB.

[0060] Figure 7 The solid-state fluorescence spectra of HDBB and ZIF-90-HDBB are shown. Figure 7 It is known that both HDBB and ZIF-90-HDBB possess certain fluorescence properties. Since HDBB molecules can act as organic ligands for forming metal-organic frameworks, they will interact with Zn. 2+ Coordination, through the coordination of metal ions and the stereostructure of the metal-organic framework, restricts the rotation of the N-N bonds in the HDBB molecule of the AIE molecule, resulting in a significantly stronger fluorescence intensity for ZIF-90-HDBB compared to HDBB. This demonstrates that effectively introducing AIE molecules into the metal-organic framework can yield solid-state fluorescent materials with stronger luminescence.

[0061] Figure 8 The fluorescence emission spectra are shown for different ligand ratios during the synthesis of ZIF-90-HDBB. To further improve the fluorescence performance of ZIF-90-HDBB, the synthesis conditions were optimized. The effects of adding different ratios of HDBB and imidazole-2-carboxaldehyde on the fluorescence intensity of ZIF-90-HDBB were investigated. The fluorescence spectra show that the fluorescence emission is weak when the ratio of HDBB to 2-methylimidazole is 2.1:1 and 4.1:1. When the ratio is 16.4:1, the fluorescence intensity is close to its maximum. Further increasing the HDBB content, when the ratio reaches 32.8:1, the increase in fluorescence intensity is minimal.

[0062] Figure 9 SEM images of ZIF-90-HDBB with different ligand ratios are shown. Image 9(a) shows that ZIF-90 has a regular dodecahedral morphology with an average diameter of approximately 2-5 μm. With the addition of HDBB molecules, the morphology of ZIF-90-HDBB gradually deteriorates, and the material's growth becomes increasingly irregular. Based on the fluorescence emission spectra of the material with different ligand ratios, a ratio of HDBB to imidazole-2-carboxaldehyde of 16.4:1 was selected as the optimal addition amount. Subsequent performance and characterization tests of ZIF-90-HDBB synthesized at this ligand ratio were also conducted.

[0063] Figure 10 TEM images of ZIF-90 and aggregation-induced emission metal-organic framework ZIF-90-HDBB. Figure 10 (a) is a TEM image of ZIF-90. Figure 10 (b) is a TEM image of ZIF-90-HDBB. It can be seen from the image that ZIF-90-HDBB exhibits the growth of a destroyed dodecahedron, with an average diameter that is similar to that of ZIF-90.

[0064] Figure 11 Thermogravimetric curves for HDBB, ZIF-90, and ZIF-90-HDBB. From... Figure 11 (c) It can be seen that ZIF-90 does not exhibit weight loss before 300℃, but the organic ligand molecules exhibit weight loss between 350-400℃. When the temperature rises to 400℃, the ZIF-90 skeleton collapses. Figure 11(b) It can be seen that HDBB molecules exhibit weight loss due to water molecules before 100℃. For ZIF-90-HDBB molecules, the weight loss before 100℃ is caused by water molecules, while the weight loss between 100-350℃ and the partial weight loss between 420-800℃ are caused by doped HDBB molecules. The effective doping amount of HDBB molecules is calculated to be approximately 20.07%.

[0065] Figure 12 To characterize the aggregation-induced emission (AIE) properties of the metal-organic framework ZIF-90-HDBB, (a) and (c) show the fluorescence spectra of HDBB and ZIF-90-HDBB in different aggregation states; (b) and (d) show the fluorescence intensity variation curves of HDBB and ZIF-90-HDBB in different aggregation states. DMSO is a good solvent for both HDBB and ZIF-90-HDBB, while methanol is a poor solvent. As can be seen from the figures, the fluorescence intensity of HDBB and ZIF-90-HDBB gradually increases with increasing methanol 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 the maximum fluorescence intensity when the methanol / DMSO ratio is 9:1; for ZIF-90-HDBB molecules, the maximum fluorescence intensity is achieved when the methanol / DMSO ratio is 7:1.

[0066] Figure 13 The N2 adsorption-desorption isotherms for ZIF-90 and ZIF-90-HDBB 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 ZIF-90 and ZIF-90-HDBB were measured. Figure 13 As shown, the adsorption isotherms of ZIF-90 and ZIF-90-HDBB are clearly Type IV isotherms, and the materials exhibit abundant mesoporous structures. However, there is a slight difference in the hysteresis type between ZIF-90 and ZIF-90-HDBB; compared to ZIF-90, ZIF-90-HDBB shows a slight saturation adsorption plateau at (P / P0) ≥ 0.6. These results indicate that the pore structure of ZIF-90-HDBB exhibits randomness, attributed to the introduction of HDBB molecules into the metal-organic framework material. The BET specific surface areas of ZIF-90 and ZIF-90-HDBB are 175.41 m², respectively. 2 / g and 220.54m 2 / g, pore volume is 0.28cm³ 3 / g and 0.34cm 3 / g. The changes in surface area and pore volume after modification are consistent with previous reports. This is mainly due to the longer molecular chains of the introduced HDBB. For metal-organic framework materials, longer ligand molecules lead to larger pore structures, resulting in a larger specific surface area.

[0067] Figure 14 UV-Vis absorption spectra (a) and optimal excitation / emission spectra (b) for HDBB, ZIF-90, and ZIF-90-HDBB. Inset in (a) shows optical images of ZIF-90-HDBB under fluorescent (left) and 365nm UV (right) illumination. Figure 14 As can be seen from (a), HDBB exhibits n-π at 320nm and 400nm. * and π-π * The ZIF-90-HDBB exhibits an absorption peak at 280 nm, characteristic of ZIF-90, and an absorption peak at 400 nm, representing the π-π transition absorption of the HDBB molecule. * Transition absorption peak. ZIF-90-HDBB exhibits yellow-green emission in the aggregated state. From Figure 14 As shown in (b), the fluorescence emission intensity of ZIF-90-HDBB is much higher than that of HDBB molecules. This is mainly because the organic ligand molecule HDBB is immobilized in the backbone of ZIF-90-HDBB, indicating that the formation of ZIF-90-HDBB after coordination with metal ions can effectively suppress the rotation of the NN bond in HDBB. The optimal excitation and emission wavelengths of ZIF-90-HDBB are 446 nm and 532 nm, respectively.

[0068] Figure 15 The figures show the response of ZIF-90-HDBB to different acidic gases (a) and (b). As can be seen from the figures, the fluorescence intensity of ZIF-90-HDBB significantly decreases after detecting 100 ppm HCl gas, while the emission wavelength shifts towards longer wavelengths. ZIF-90-HDBB exhibits negligible changes in fluorescence intensity for other acidic volatile gases at 100 ppm, indicating good selectivity for HCl gas.

[0069] Example 3: Recognition of HCl by the aggregation-induced luminescent metal-organic framework ZIF-90-HDBB

[0070] Test solution preparation: Take 20 mg of ZIF-90-HDBB prepared in Example 2, dissolve it in 20 mL of 9:1 methanol / DMSO solution, and ultrasonically disperse it to obtain a probe dispersion with a concentration of 1 mg / mL.

[0071] Detection of HCl solution: Prepare a 0.01 mol / L HCl stock solution, then dilute it to 0.1-0.4 μM. Add 50 μL of the diluted HCl solution of different concentrations to 5 mL of 1 mg / mL probe solution, and then perform fluorescence detection.

[0072] HCl gas detection: HCl gas detection was performed in a self-made 18L sealed container. An HCl 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 element inside the container evaporated the HCl solution into gaseous HCl. A 1 mg / mL, 5 mL probe dispersion was placed in the sealed container. After 10 minutes, the container was removed for fluorescence testing. The concentration of HCl gas can be calculated using the ideal gas law pV = nRT.

[0073] Figure 16 The graphs show the fluorescence emission spectra of the probe response after the addition of 0-0.4 μM HCl solution (a) and the linear relationship between probe fluorescence intensity and HCl concentration (b). Figure 16 As shown in (a), the fluorescence intensity of the probe gradually decreases with increasing HCl concentration. Figure 16 As shown in (b), the fluorescence intensity of the sensing system exhibits a good linear relationship with the HCl concentration in the range of 0-0.40 μM, R 2 =0.9958. The detection limit was calculated using the formula D = 3σ / K (σ is the standard deviation of the fluorescence intensity of the fluorescent material ZIF-90-HDBB itself, with no less than 20 measurements, and K is the fluorescence intensity change coefficient of the fluorescent material ZIF-90-HDBB when detecting HCl solution). The detection limit of this fluorescent probe for HCl is as low as 0.04 μM.

[0074] Figure 17 The fluorescence emission spectrum (a) of the ZIF-90-HDBB probe after detecting 0-50 ppm HCl gas and the linear relationship between probe fluorescence intensity and HCl gas concentration (b) are shown. Figure 17 As shown in (a), the fluorescence intensity of the probe gradually decreases with increasing HCl gas concentration. Figure 17 As shown in (b), the fluorescence intensity of this sensing system exhibits a good linear relationship with the HCl concentration in the range of 0-50 ppm. 2 =0.9921, using the formula D=3σ / K (σ is the standard deviation of the fluorescence intensity of the fluorescent material ZIF-90-HDBB itself, with no less than 20 measurements, and K is the fluorescence intensity variation coefficient of the fluorescent material ZIF-90-HDBB when detecting HCl gas), the detection limit of this fluorescent probe for HCl gas is calculated to be as low as 3.39ppm.

[0075] Figure 18The changes in XRD patterns after detecting 0-1000 ppm HCl gas using a ZIF-90-HDBB were observed. Figure 18 As can be seen, the prepared fluorescent probe ZIF-90-HDBB has good stability, and its structure is only destroyed under HCl gas with a concentration as high as 1000ppm, which shows the potential for further practical applications. Figure 18 To assess the cyclic performance and response time of the ZIF-90-HDBB probe for HCl gas detection, the material was heated at 100°C for 30 minutes after detecting 40 ppm HCl gas, allowing the HCl gas to dissipate from the pores under heating conditions. After five cycles, the fluorescence intensity of the material decreased by only 6.5%, demonstrating its excellent cyclic performance. Furthermore, the material can detect 50 ppm HCl gas within 10 minutes, confirming the feasibility of this probe for rapid on-site detection of HCl gas.

[0076] Example 4: Fabrication of a paper-based sensor

[0077] Preparation of the paper-based sensor: 20 mg of ZIF-90-HDBB prepared in Example 2 was dissolved in 20 mL of N-methylpyrrolidone solution to obtain a probe dispersion with a concentration of 1 mg / mL. A circular qualitative filter paper with a diameter of approximately 1.2 cm was immersed in the probe dispersion for 12 h, then removed and dried at 30 °C for 6 h to obtain the paper-based sensor.

[0078] HCl gas detection: HCl gas detection was performed in a self-made 18L sealed container. An HCl 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 HCl solution into gaseous HCl. The concentration of HCl gas could be calculated using the ideal gas law pV = nRT. The prepared paper-based sensor was placed in the sealed container and removed after 10 minutes. Its R / G value could be obtained under a 360nm ultraviolet lamp using a color recognition app. Figure 20 Photograph (a) of the paper-based sensor and its scanning electron microscope image (b). From Figure 20 As can be seen from (a), the prepared paper-based sensor appears yellow under fluorescent light. Figure 20 As can be seen in (b), the ZIF-90-HDBB material is uniformly loaded onto the cellulose filter paper.

[0079] Figure 21This image shows a photograph (a) of the paper-based sensor after detecting 0-100 ppm HCl gas, and the linear relationship between the material and the HCl gas concentration. When the HCl gas concentration increases from 0 to 100 ppm, the paper-based sensor exhibits a continuous color change from yellow to yellow-green to orange-red under a 360 nm UV lamp. Since slight color changes are not easily observed with the naked eye, we digitally analyzed the color information (RGB values) of the fluorescence photographs using a color recognition application (Color Grab). After the paper-based sensor detected 0-100 ppm HCl gas, a series of photographs with colors ranging from yellow to yellow-green to orange-red were taken using a mobile phone camera under a 360 nm UV lamp. The RGB values ​​corresponding to these photographs were obtained through the color recognition app, and further statistical analysis yielded the linear relationship curve. The results are as follows... Figure 21 As shown in (b), there is a good linear relationship between the RGB ratio (R / G) and the HCl gas concentration, R 2 =0.9650, with a detection limit as low as 3.0 ppm. These results demonstrate that the prepared paper-based sensor can achieve semi-quantitative, convenient, intuitive, and sensitive intelligent detection of trace HCl gas.

[0080] Figure 22 This is a bar chart showing the R / G changes of the paper-based sensor for different acidic gases. To demonstrate the selectivity of this material for HCl gas detection, the prepared paper-based sensor was tested against 40 ppm HCl and other types of acidic gases. The R / G value of the paper-based sensor showed only slight changes, indicating that the material has good selectivity for HCl gas.

[0081] 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: Imidazole-2-formaldehyde (ICA) and polyvinylpyrrolidone (PVP) are dissolved in deionized water and heated in a water bath at 80 °C for 10 min to obtain solution 1. HDBB is dissolved in Tris-HCl solution and sonicated to obtain solution 2. After solution 1 is cooled to room temperature, solution 2 is added to solution 1 and gently shaken. Zn(NO3)2·6H2O solution is added dropwise to the above mixed solution. After standing, centrifugation and washing, aggregation-induced emission metal-organic framework material ZIF-90-HDBB can be obtained. The mass ratio of HDBB:imidazolium-2-formaldehyde is 16.4:

1.

2. The aggregation-induced emission metal-organic framework according to claim 1, characterized in that, The molar ratio of Zn(NO3)2.6H2O to ICA is 1:

4.

3. The aggregation-induced emission metal-organic framework according to claim 1, characterized in that, The preparation method of HDBB specifically includes the following steps: 4-Aldehyde-3-hydroxybenzoic acid was dissolved in methanol, and hydrazine hydrate was added after dissolution. The mixture was refluxed in an oil bath at 75°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, washed with methanol, and dried under vacuum to obtain a yellow HDBB solid product.

4. A probe dispersion, characterized in that, The ZIF-90-HDBB of claim 1 was dissolved in a methanol / DMSO solution and ultrasonically dispersed to obtain a probe dispersion with a concentration of 1 mg / mL.

5. The probe dispersion according to claim 4 for fluorescence detection of trace HCl solutions in the environment, characterized in that, The method is as follows: 1) In a solution containing 0-0.4 μM HCl, add the 1 mg / mL probe dispersion described in claim 4, and perform fluorescence testing to obtain a linear relationship between HCl concentration c and fluorescence intensity y: y = 2.9933c - 0.2799, R 2 =0.9958, 2) Add the 1 mg / mL probe dispersion described in claim 4 to the HCl solution to be tested, perform fluorescence testing, and calculate the concentration of the HCl solution by substituting the fluorescence intensity into the linear equation obtained in step 1).

6. The probe dispersion according to claim 4 for fluorescence detection of trace HCl gas in the environment, characterized in that, The method is as follows: 1) In a sealed container, the 1 mg / mL probe dispersion as described in claim 4 is placed. The injected HCl solution evaporates upon heating, generating 0-50 ppm HCl gas in the device. After 10 min, the probe solution is removed, and fluorescence testing is performed. The linear relationship between the HCl gas concentration c and the fluorescence intensity y is obtained: y = 0.01536c + 0.02353, R 2 =0.9921; 2) Place the 1 mg / mL probe dispersion as described in claim 4 into a sealed container, place the HCl gas to be tested in the sealed device, take out the probe solution after 10 min, and perform fluorescence testing. Calculate the concentration of HCl gas based on the fluorescence intensity, the linear equation obtained in step 1), and pV=nRT.

7. A paper-based sensor, characterized in that, The ZIF-90-HDBB of claim 1 was dissolved in a nitrogen-methylpyrrolidone solution to obtain a probe dispersion with a concentration of 1 mg / mL. Cellulose filter paper was soaked in the probe dispersion for 12 h and then dried to obtain a paper-based sensor.

8. A paper-based sensor according to claim 7 for colorimetric dual-mode intelligent detection of trace HCl gas, characterized in that, The method is as follows: 1) Place the paper-based sensor as described in claim 7 into a sealed container. Inject HCl solution, which evaporates upon heating, to generate 0-100 ppm HCl gas in the device. After 10 minutes, remove the paper-based sensor. Under a 360 nm ultraviolet lamp, its R / G value can be obtained through a color recognition APP. A linear equation is obtained between the R / G value y and the HCl gas concentration c: y = 0.07248c + 0.8865, R... 2 =0.9650; 2) Place the paper-based sensor as described in claim 7 into a sealed container, place the HCl gas to be measured in the sealed device, take it out after 10 min, and obtain its R / G value under a 360 nm ultraviolet lamp by color recognition APP. Calculate the concentration of HCl gas according to the linear equation in step 1).

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