Covalent organic framework material and method of making, method for detecting uranyl ions in water

Abstract

The application provides a covalent organic framework material and a preparation method and a detection method of uranium ion in water, and comprises the following steps: uniformly mixing covalent organic framework powder and an alcohol solvent to obtain a mixed solution; the covalent organic framework powder has a carbon-carbon double bond and a cyano group in the structure; the mixed solution, hydroxylamine hydrochloride and triethylamine are mixed and heated to obtain the covalent organic framework material. Compared with the prior art, the covalent organic framework material can be used to detect the content of uranium ion in a water sample to be measured with high specificity and high sensitivity, and has high application value. The preparation method is simple and easy to operate, and the formed covalent organic framework material is stable and is not easy to hydrolyze. When the covalent organic framework material is used to detect the content of uranium ion in the water sample to be measured, the content of uranium ion in the water sample to be measured can be conveniently obtained through the linear relationship between the fluorescence intensity and the concentration of uranium ion.

Description

Technical Field

[0001] This invention relates to the field of uranyl ion detection technology in the environment, and particularly to a covalent organic framework material and its preparation method, and a method for detecting uranyl ions in water. Background Technology

[0002] Nuclear energy, with its advantages of low carbon emissions and high efficiency, plays an irreplaceable role in addressing global climate change and building an economical, sustainable, and efficient energy system. However, with the continuous development of the nuclear industry, large-scale uranium mining, and nuclear accidents, a large amount of radioactive uranium has seeped into our environment. This radioactive harmful uranium element is mainly in the form of hexavalent uranium ions (UO2). 2+ Uranium exists in water bodies in the form of uranium. When uranium-containing wastewater spreads into the environment, soil, and even food and water sources, it will cause serious harm and impact on human health.

[0003] Therefore, developing renewable materials capable of rapidly and efficiently detecting uranyl ions in water is of great significance for environmental protection, monitoring, and public health. Currently, many analytical methods exist, such as atomic absorption spectroscopy, atomic emission spectroscopy, total internal reflection X-ray fluorescence spectroscopy, inductively coupled plasma mass spectrometry, and fluorescence sensing, all of which offer high sensitivity for detecting uranyl ions.

[0004] Fluorescence detection is widely used for real-time monitoring of uranyl ions due to its simplicity and other advantages. However, existing fluorescence sensors suffer from low sensitivity and difficulties in recovering and reusing uranyl ions after dissolution in water. Summary of the Invention

[0005] The main objective of this invention is to provide a covalent organic framework material and its preparation method, as well as a method for detecting uranyl ions in water, aiming to solve the problems of low sensitivity and easy hydrolysis in existing fluorescent sensors.

[0006] To achieve the above objectives, the present invention provides a covalent organic framework material, the structural formula of which is as follows:

[0007]

[0008] The present invention also provides a method for preparing the covalent organic framework material as described above, comprising the steps of: mixing covalent organic framework powder with an alcohol solvent to obtain a mixture; wherein the covalent organic framework powder has carbon-carbon double bonds and cyano groups in its structure.

[0009] The mixture, hydroxylamine hydrochloride, and triethylamine are mixed and heated to obtain the covalent organic framework material.

[0010] Further, the source of the covalent organic framework powder includes: dissolving 3-cyano-4,6-dimethyl-2-hydroxypyridine and 1,3,5-tris(p-formylphenyl)benzene in a mixed solvent to obtain a suspension; subjecting the suspension to freeze treatment and heat treatment in sequence to obtain the covalent organic framework powder.

[0011] Further, the mixing ratio of the 3-cyano-4,6-dimethyl-2-hydroxypyridine, the 1,3,5-tris(p-formylphenyl)benzene, and the mixed solvent is 43-46 mg: 77-80 mg: 4.5-6.6 mL.

[0012] Further, the mixed solvent is o-dichlorobenzene, N,N-dimethylformamide and dimethylamine mixed in a volume ratio of 2-3 mL: 2-3 mL: 0.5-0.6 mL.

[0013] Furthermore, the freezing treatment involves freezing the suspension with liquid nitrogen and evacuating it three times; the heating treatment is performed at a temperature of 170–190°C for a duration of 70–74 hours.

[0014] Furthermore, the heat treatment further includes washing and drying to obtain the covalent organic framework powder.

[0015] Furthermore, the heating temperature of the heating reaction is 70–90°C, and the reaction time is 20–30 h.

[0016] The present invention also provides an application of a method for detecting uranyl ions in water using a covalent organic framework material prepared by the covalent organic framework material described above or by the preparation method described above.

[0017] Further, the method includes the following steps: mixing the covalent organic framework material, N-dimethylformamide solvent, HEPEs buffer, and the water sample to be tested to obtain a detection mixture; measuring the fluorescence intensity of the detection mixture; and determining the content of uranyl ions in the water sample to be tested based on the linear relationship between the fluorescence intensity and the uranyl ion concentration.

[0018] The beneficial effects achieved by this invention are as follows:

[0019] The covalent organic framework material provided by this invention possesses metallo-oxime groups, hydroxyl groups, and pyridyl groups. These functional groups are designed within the channels of the covalent organic carbon framework. The C=N, NO, and -OH groups on the metallo-oxime groups exhibit highly specific coordination recognition with uranyl ions, while the hydroxyl groups facilitate the formation of hydrogen bonds within the covalent organic carbon framework, enhancing its stability. The pyridyl groups not only have an affinity for uranyl ions but also act as Lewis bases to promote the formation of the covalent organic carbon framework. Therefore, the prepared material exhibits a specific affinity for uranyl ions. Using this covalent organic framework material, the content of uranyl ions in water samples can be detected with high specificity and sensitivity, demonstrating significant application value.

[0020] Furthermore, the preparation method of the covalent organic framework material provided by this invention is simple and easy to operate. First, a covalent organic framework powder structure with carbon-carbon double bonds and cyano groups is established. Then, by reacting with hydroxylamine hydrochloride and triethylamine, the amylopyridine groups are modified into the channels of the covalent organic framework to form a stable covalent organic framework material that is not easily hydrolyzed.

[0021] When using this covalent organic framework material to detect the content of uranyl ions in the water sample, the covalent organic framework material can specifically bind to the uranyl ions in the water sample, resulting in high sensitivity; the content of uranyl ions in the water sample can be conveniently obtained through the linear relationship between fluorescence intensity and uranyl ion concentration. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the synthesis process of GC-TFPB and GC-TFPB-AO prepared in Example 1;

[0024] Figure 2 SEM images of GC-TFPB and GC-TFPB-AO obtained in Example 1 are shown below; where (a) is the SEM image of GC-TFPB obtained in Example 1, and (b) is the SEM image of GC-TFPB-AO obtained in Example 1.

[0025] Figure 3 The images show the infrared characterization results of TFPB, GC, GC-TFPB, and GC-TFPB-AO during the preparation process of Example 1; where (a) is a comparison of the infrared characterization of TFPB, GC, and GC-TFPB; and (b) is a comparison of the infrared characterization of GC-TFPB and GC-TFPB-AO.

[0026] Figure 4 Thermogravimetric analysis characterization diagram of GC-TFPB obtained in Example 1;

[0027] Figure 5 The graph shows the linear relationship between fluorescence intensity and uranyl ion concentration in Example 2.

[0028] Figure 6 The fluorescence performance analysis diagram of GC-TFPB-AO prepared in Example 1 is shown.

[0029] Figure 7 This is a comparison of the fluorescence intensity of GC-TFPB-AO prepared in Example 1 before and after its interaction with uranyl ions in water over time.

[0030] Figure 8 This is a comparison of the quenching rate of GC-TFPB-AO prepared in Example 1 before and after its reaction with uranyl ions in water as a function of pH.

[0031] Figure 9 This is a comparison of the fluorescence intensity changes of GC-TFPB and GC-TFPB-AO prepared in Example 1 before and after their interaction with uranyl ions in water.

[0032] Figure 10 This is a graph showing the changes in the cyclic detection results of Example 4.

[0033] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of this invention is for describing specific implementations and not for limiting the scope of protection of this invention.

[0036] Unless otherwise defined, all technical and scientific terms used in this invention are consistent with the prior art known to those skilled in the art and the description of this invention. This invention may also be implemented using any prior art methods, devices and materials similar to or equivalent to those described, used or made by means of methods, devices and materials in the embodiments of this invention. Those skilled in the art should understand that, as an explanation of this application, without affecting the actual understanding of the technical solution of this application, "GC" can represent 3-cyano-4,6-dimethyl-2-hydroxypyridine, "TFPB" can represent 1,3,5-tris(p-formylphenyl)benzene, "o-DCB" can represent o-dichlorobenzene, "DMF" can represent NN-dimethylformamide, "COFs" and "GC-TFPB" can both represent covalent organic framework powder, "AO" can represent a amine oxime group, "GC-TFPB-AO" can represent covalent organic framework material, "SEM" can represent scanning electron microscope, "samples" can represent sample type, "Add" can represent amount added, "found" can represent detection value, "Recovery" can represent recovery rate, "RSD" can represent relative standard deviation, "SD" can represent standard deviation, and "ICP-MS" can represent detection value by inductively coupled plasma mass spectrometry.

[0037] When numerical ranges are given in the examples, it should be understood that, unless otherwise stated in the invention, both endpoints of each range and any value between the two endpoints may be used. Test methods in the following examples that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers. Unless otherwise specified, all materials or reagents required in the following examples are commercially available.

[0038] In the accompanying diagrams of the specification, “Wavenumber” represents the wavelength range, “T” represents the heating temperature of the reaction, “Wt” represents the mass percentage of the covalent organic framework material, “Concentration” represents the uranyl ion concentration, “(I0-I) / I0” represents the quenching rate, “Wavelength” represents the wavelength, “Intensity” represents the fluorescence intensity, “Time” represents the time, and “Cycle Number” represents the number of cycles.

[0039] To address the issues of low sensitivity and instability due to hydrolysis in existing fluorescence sensors, this invention provides a covalent organic framework material. The structural formula of the covalent organic framework material is as follows:

[0040]

[0041] This covalent organic framework material possesses metallo-oxime groups, hydroxyl groups, and pyridyl groups. These functional groups are designed within the channels of the covalent organic carbon framework. The C=N, NO, and -OH groups on the metallo-oxime groups exhibit highly specific coordination recognition with uranyl ions. The hydroxyl groups facilitate the formation of hydrogen bonds within the covalent organic carbon framework, enhancing its stability. The pyridyl groups not only have an affinity for uranyl ions but also act as Lewis bases to promote the formation of the covalent organic carbon framework. Therefore, the prepared material exhibits a specific affinity for uranyl ions. Using this covalent organic framework material, the content of uranyl ions in water samples can be detected with high specificity and sensitivity, demonstrating significant application value.

[0042] The present invention also provides a method for preparing a covalent organic framework material as described above, comprising the steps of: mixing covalent organic framework powder with an alcohol solvent to obtain a mixture; the covalent organic framework powder has carbon-carbon double bonds and cyano groups in its structure.

[0043] The mixture, hydroxylamine hydrochloride, and triethylamine were mixed and heated to obtain a covalent organic framework material.

[0044] Specifically, a covalent organic framework powder containing carbon-carbon double bonds, cyano groups, pyridyl groups, and hydroxyl groups is added to an ethanol solution and ultrasonically mixed to obtain a mixture. Hydroxylamine hydrochloride and triethylamine are then added to the mixture and heated to obtain a covalent organic framework material with functional groups such as amylopyrime groups, hydroxyl groups, and pyridyl groups. The carbon-carbon double bonds and hydroxyl groups endow the covalent organic framework powder with excellent stability and hydrophilicity, while the cyano group can be converted into amylopyrime group, improving the recognition specificity for uranyl ions.

[0045] The preparation method of the covalent organic framework material provided by this invention is simple and easy to operate. First, a covalent organic framework powder structure with carbon-carbon double bonds and cyano groups is established. Then, by reacting with hydroxylamine hydrochloride and triethylamine, the amylopyridine groups are modified into the channels of the covalent organic framework to form a stable covalent organic framework material that is not easily hydrolyzed.

[0046] Furthermore, the sources of the covalent organic framework powder include: dissolving 3-cyano-4,6-dimethyl-2-hydroxypyridine and 1,3,5-tris(p-formylphenyl)benzene in a mixed solvent to obtain a suspension; subjecting the suspension to freeze treatment and heat treatment in sequence to obtain the covalent organic framework powder.

[0047] Specifically, 3-cyano-4,6-dimethyl-2-hydroxypyridine (GC) and 1,3,5-tris(p-formylphenyl)benzene (TFPB) are added to a Pyrex glass tube, followed by the addition of a mixed solvent to form a suspension. After ultrasonically dispersing the suspension for 20 minutes, it is then subjected to sequential freezing and heating treatments to obtain the covalent organic framework powder (COFs). 3-Cyano-4,6-dimethyl-2-hydroxypyridine offers advantages such as simple preparation, high stability, and low cost.

[0048] Furthermore, the mixing ratio of 3-cyano-4,6-dimethyl-2-hydroxypyridine, 1,3,5-tris(p-formylphenyl)benzene and the mixed solvent is 43-46 mg: 77-80 mg: 4.5-6.6 mL.

[0049] Specifically, 43–46 mg of 3-cyano-4,6-dimethyl-2-hydroxypyridine (GC) and 77–80 mg of 1,3,5-tris(p-formylphenyl)benzene (TFPB) were added to a Pyrex glass tube, followed by the addition of 4.5–6.6 mL of a mixed solvent to prepare a suspension. The mixing ratio of 3-cyano-4,6-dimethyl-2-hydroxypyridine (GC) to 1,3,5-tris(p-formylphenyl)benzene (TFPB) was 43–46 mg:77–80 mg, satisfying the molar ratio of 3:2, which meets the design requirements and promotes complete reaction.

[0050] Furthermore, the mixed solvent is o-dichlorobenzene, N,N-dimethylformamide, and dimethylamine mixed in a volume ratio of 2–3 mL: 2–3 mL: 0.5–0.6 mL. The ratio of the mixed solvent affects the yield of the product. When the volume ratio of o-dichlorobenzene, N,N-dimethylformamide, and dimethylamine is 2–3 mL: 2–3 mL: 0.5–0.6 mL, it is beneficial to the synthesis of the material and the yield is the highest.

[0051] Furthermore, the freezing treatment method involves freezing the suspension with liquid nitrogen and evacuating it three times; the heating treatment temperature is 170–190°C; and the heating treatment duration is 70–74 hours.

[0052] Specifically, the suspension, after ultrasonic dispersion for 20 minutes, was subjected to liquid nitrogen freezing and vacuuming, repeated three times; then it was heated at 170–190°C for 70–74 hours. When the heating treatment time was >70 hours, a covalent organic framework with a high degree of polymerization could be formed. When the time was extended to more than 74 hours, the degree of polymerization no longer changed significantly, indicating that the final product had been formed.

[0053] Furthermore, the heat treatment also includes washing and drying to obtain covalent organic framework powder.

[0054] Specifically, the product after heat treatment is washed 2-3 times with acetone, ethanol, and water, and then dried at 100°C for 8 hours to obtain covalent organic framework powder.

[0055] Furthermore, the heating temperature of the heating reaction is 70–90°C, and the reaction time is 20–30 h.

[0056] Specifically, a covalent organic framework powder containing carbon-carbon double bonds and cyano groups is added to an ethanol solution and ultrasonically mixed to obtain a mixture. Hydroxylamine hydrochloride and triethylamine are added to the mixture and stirred at 250-300 rpm at 70-90°C for 20-30 hours. After centrifugation to remove the supernatant, the mixture is washed with ethanol and water in sequence, and then dried at 100°C for 8 hours to obtain the final product, the covalent organic framework material.

[0057] When the mixture, hydroxylamine hydrochloride, and triethylamine are heated at 70–90°C for 20–30 h, the cyano groups on GC-TFPB are completely converted into amylopyridine groups, forming the final product GC-TFPB-AO, a uranyl ion detection material.

[0058] The present invention also provides an application of a method for detecting uranyl ions in water using a covalent organic framework material prepared by the above-described method or a covalent organic framework material prepared by the above-described method.

[0059] Further, the method includes the following steps: mixing covalent organic framework material, N-dimethylformamide solvent, HEPEs buffer, and the water sample to be tested to obtain a detection mixture; measuring the fluorescence intensity of the detection mixture; and determining the content of uranyl ions in the water sample to be tested based on the linear relationship between fluorescence intensity and uranyl ion concentration.

[0060] Specifically, a standard solution was prepared by mixing covalent organic framework material, N-dimethylformamide solvent, HEPEs buffer, and uranyl ions of various standard concentrations. The optimal fluorescence intensity of the system was determined under the conditions of excitation wavelength of 370 nm and emission wavelength of 500 nm, and a linear equation between fluorescence intensity and uranyl ion concentration was obtained.

[0061] The linear equation is:

[0062] Y=(I0-I) / I0=0.0005021x-0.00305

[0063] Where I0 is the fluorescence intensity when 0 μM uranyl ions are added; I is the fluorescence intensity after adding different concentrations of uranyl ions; (I0-I) is the fluorescence intensity change; Y is the quenching rate; x is the uranyl ion concentration, the linear range is from 0 to 500 nM, and the correlation coefficient R is... 2 =0.998.

[0064] When the uranyl ion concentration is between 0 and 500 nM, it exhibits a good linear relationship with fluorescence intensity. Furthermore, this concentration range has a wide detection range and can be used to detect uranyl ion concentrations in most environmental water samples.

[0065] A detection mixture was prepared by mixing a covalent organic framework material, N-dimethylformamide solvent, HEPEs buffer, and the water sample to be tested. The fluorescence intensity of the detection mixture was measured under the conditions of excitation wavelength of 370 nm and emission wavelength of 500 nm. The fluorescence intensity was substituted into the above linear equation to calculate the content of uranyl ions in the water sample to be tested.

[0066] To further illustrate the present invention, the following examples are provided:

[0067] Example 1

[0068] Synthesis of GC-TFPB and GC-TFPB-AO:

[0069] A schematic diagram of the specific material synthesis process is shown below. Figure 1 As shown.

[0070] (1) Synthesis of GC-TFPB:

[0071] Add 44.45 mg of 3-cyano-4,6-dimethyl-2-hydroxypyridine (GC) and 78 mg of 1,3,5-tris(p-formylphenyl)benzene (TFPB) to a Pyrex glass tube, then add 3 mL of o-dichlorobenzene (o-DCB), 3 mL of N-N-dimethylformamide (DMF), and 0.6 mL of dimethylamine to prepare a suspension. Sonicate the suspension for 20 min and set aside. Rapidly freeze the suspension with liquid nitrogen, then evacuate the tube to create a vacuum. After thawing, repeat the liquid nitrogen freezing and vacuuming process three times. Then, heat the material at 180°C for 72 h, wash 2-3 times with acetone, ethanol, and water, and dry at 100°C for 8 h to obtain the product: GC-TFPB (covalent organic framework powder).

[0072] (2) Synthesis of GC-TFPB-AO:

[0073] Weigh 80 mg of the covalent organic framework powder obtained in step (1), add it to 20 mL of ethanol and sonicate it. Then add 500 mg of hydroxylamine hydrochloride and 300 μL of triethylamine solution to obtain a suspension. Place the suspension at 80 °C and stir at 300 rpm for 24 h. After centrifugation to remove the supernatant, wash with ethanol and water in sequence, and dry at 100 °C for 8 h to obtain the product: GC-TFPB-AO (covalent organic framework material).

[0074] Analysis example 1

[0075] Characterization analysis of GC-TFPB and GC-TFPB-AO prepared in Example 1:

[0076] (1) The prepared COFs materials GC-TFPB and GC-TFPB-AO were characterized by scanning electron microscopy (SEM). The SEM images of the two materials are shown below. Figure 2 As shown; where, Figure 2 (a) is a SEM image of the GC-TFPB obtained in Example 1. Figure 2 (b) is a SEM image of GC-TFPB-AO prepared in Example 1.

[0077] according to Figure 2 Observations show that both GC-TFPB and GC-TFPB-AO exhibit irregular porous and fluffy structures, and spherical aggregates of varying sizes can be observed.

[0078] (2) Infrared characterization was performed on the raw material TFPB, raw material GC, intermediate product GC-TFPB, and final product GC-TFPB-AO during the preparation process of Example 1. Specific infrared characterization results are as follows: Figure 3 As shown, where, Figure 3 (a) Comparison of infrared characterization of raw material TFPB, raw material GC, and stage product GC-TFPB; Figure 3 (b) is a comparison of the infrared characterization of the stage product GC-TFPB and the final product GC-TFPB-AO.

[0079] according to Figure 3 (a) Observations show that the intermediate product GC-TFPB, compared to TFBB and GC, has a longer growth rate at approximately 1661 cm⁻¹. -1 and 960cm -1 A vibrational tensile peak of inverse C=C appears at 1689 cm⁻¹ in TFPB. -1 The carbonyl (C=O) peak disappeared at the GC site, while the cyano (CN) group remained in the GC. This indicates that GC-TFPB was successfully synthesized and contains both cyano (CN) and C=C (sp) groups. 2 carbon).

[0080] according to Figure 3 (b) Observations show that GC-TFPB-AO, compared to GC-TFPB, has a lower concentration at 2215 cm⁻¹. -1 The cyano peak disappears at 1655 cm⁻¹; -1 1442cm -1 and 967cm -1 The stretching of C=N, CN and NO bonds can be attributed to the stretching of these bonds, indicating that the intermediate product GC-TFPB has been successfully modified with amine oxime groups, thus obtaining the final product GC-TFPB-AO.

[0081] (3) The final product GC-TFPB-AO obtained in Example 1 was characterized by thermogravimetric analysis, and the characterization results are as follows: Figure 4 As shown.

[0082] according to Figure 4 Observations show that GC-TFPB-AO experiences a mass loss of less than 20% at 400℃, which is likely due to the evaporation of water and solvent molecules. This excellent heat resistance of GC-TFPB-AO is probably due to the good chemical stability of the irreversible C=C and extended π-π fully conjugated system formed by the reaction.

[0083] Example 2

[0084] It should be noted that the water samples to be tested in this invention are all selected from Xiangjiang River water samples.

[0085] (1) Preparation of Xiangjiang River water samples with different concentrations of uranyl ions: The collected Xiangjiang River water samples were filtered and diluted with pure water to prepare 10 μM uranyl nitrate working solution using standard uranyl nitrate solution (1M). 0 mL, 3 mL, 4 mL and 5 mL of uranyl nitrate working solution were added to 100 mL volumetric flasks respectively. The Xiangjiang River water samples were then used to make up the volume to prepare Xiangjiang River spiked water samples with uranyl ion concentrations of 0 μM, 0.3 μM, 0.4 μM and 0.5 μM respectively for testing.

[0086] (2) Determine the fluorescence intensity of the spiked water sample from the Xiangjiang River: Weigh 2 mg of GC-TFPB-AO and add it to 10 mL of ultrapure water. Mix the mixture with ultrasonication to prepare a suspension. Then take 150 μL of the suspension and add 100 μL of HEPEs buffer (pH=7), 100 μL of the spiked water sample from the Xiangjiang River prepared in step (1) at different concentrations, and 650 μL of LDMF solvent (NN-dimethylformamide solvent).

[0087] The fluorescence intensity of the response was detected under conditions of excitation wavelength of 370 nm and emission wavelength of 500 nm, and the fluorescence intensity (I) value at 500 nm was read. A linear equation relating fluorescence intensity to uranyl ion concentration was obtained:

[0088] Y = (I0 - I) / I0 = 0.0005021x - 0.00305; (its linear relationship graph is as follows) Figure 5 (As shown).

[0089] Where I0 is the fluorescence intensity when 0 μM uranyl ions are added; I is the fluorescence intensity; (I0-I) is the change in fluorescence intensity; Y is the quenching rate; x is the uranyl ion concentration, the linear range is from 0 to 500 nM, and the correlation coefficient R is... 2 =0.998.

[0090] The limit of detection (LOD) was 21.25 nM. The specific calculation method used was: LOD = SD (standard deviation of 11 blank values) * 3 / k (slope of the standard curve of the linear equation of fluorescence intensity and uranyl ion concentration).

[0091] (3) Measure the fluorescence intensity of the water samples to be tested (Xiangjiang Water 0, Xiangjiang Water 1, Xiangjiang Water 2, Xiangjiang Water 3), and calculate the concentration of uranyl ions in the corresponding Xiangjiang Water 0, Xiangjiang Water 1, Xiangjiang Water 2, and Xiangjiang Water 3 according to the linear equation obtained in step (2).

[0092] The calculated concentrations of uranyl ions in Xiangjiang River water 0, Xiangjiang River water 1, Xiangjiang River water 2, and Xiangjiang River water 3 were 8.8 nM, 335.7 nM, 403.7 nM, and 536.8 nM, respectively. The specific detection results are shown in Table 1.

[0093] Table 1. Detection and analysis results of the water samples to be tested.

[0094]

[0095] As shown in Table 1, the recovery rate of this system for Xiangjiang River water ranged from 101% to 111%, with relative deviations all less than 4.7%. The good recovery rate demonstrates that the GC-TFPB-AO-based detection system is suitable for rapid and sensitive detection of UO2 in practical samples. 2+ An effective method for (uranyl ion) was used to validate the sample using ICP-MS, and the results showed good consistency and could be mutually verified.

[0096] Analysis example 2

[0097] Analysis of the material properties of GC-TFPB-AO prepared in Example 1 and its interaction with uranyl ions in water

[0098] (1) Fluorescence properties of GC-TFPB-AO before and after interaction with uranyl ions (U) in water

[0099] The fluorescence properties of GC-TFPB-AO prepared in Example 1 were measured. The excitation and emission wavelengths of GC-TFPB-AO and the fluorescence curve quenched after the addition of uranyl ions are shown in the figure below. Figure 6 As shown.

[0100] 2 mg of GC-TFPB-AO prepared in Example 1 was added to 10 mL of ultrapure water and sonicated to prepare a suspension. Then, 150 μL of the suspension was taken, and 100 μL of HEPEs buffer (pH = 7) was added, followed by 650 μL of DMF solvent (NN-dimethylformamide solvent) and 100 μL of pure water or uranyl ions (uranyl ion concentration of 10 μM). The excitation and emission wavelengths, as well as the fluorescence curves quenched upon the addition of uranyl ions, were measured and plotted. Figure 6 .

[0101] exist Figure 6 In the figure, the Em curve represents the emission wavelength; the Ex curve represents the excitation wavelength; and the GC-TFPB-AO+U curve represents the fluorescence curve after the addition of uranyl ions. As can be observed from the figure, the optimal emission wavelength for the prepared covalent organic framework material GC-TFPB-AO is 500 nm; the optimal excitation wavelength is 370 nm.

[0102] Furthermore, the fluorescence was significantly quenched upon the addition of uranyl ions, demonstrating that the material is specific for uranyl ions and can be applied to fluorescence sensing of uranyl ions.

[0103] (2) Material stability analysis before and after the reaction of GC-TFPB-AO with uranyl ions (U) in water

[0104] Two mg of GC-TFPB-AO prepared in Example 1 was added to 10 mL of ultrapure water and sonicated to prepare a suspension. Then, 150 μL of the suspension was taken, and 100 μL of HEPEs buffer (pH = 7) was added, followed by 650 μL of DMF solvent (NN-dimethylformamide solvent) and 100 μL of pure water or uranyl ions (uranyl ion concentration of 10 μM). The fluorescence intensity changes of GC-TFPB-AO and GC-TFPB-AO+U over time from 0 to 250 min are shown in the graph below. Figure 7 As shown.

[0105] according to Figure 7 Observations show that GC-TFPB-AO can achieve stable and sensitive detection results within just ten minutes. Furthermore, the fluorescence intensity and quenching degree remain stable within 250 minutes, demonstrating its excellent detection stability.

[0106] (3) Quenching rate analysis of GC-TFPB-AO under different pH conditions

[0107] 2 mg of GC-TFPB-AO prepared in Example 1 was added to 10 mL of ultrapure water and ultrasonically mixed to prepare a suspension. Then, 150 μL of the suspension was taken, and 100 μL of pure water at different pH values ​​(pH = 2–8) and 100 μL of uranyl ions at different pH values ​​(pH = 2–8) (concentration 10 μM) were added, followed by 650 μL of DMF solvent (NN-dimethylformamide solvent). The quenching rate variation of GC-TFPB-AO under different pH conditions is shown in the graph below. Figure 8 As shown.

[0108] according to Figure 8Observations show that GC-TFPB-AO exhibits fluorescence quenching for uranyl ions at pH values ​​ranging from 2 to 8, demonstrating its wide applicability and effectiveness under both acidic and alkaline conditions. The highest degree of fluorescence quenching and best detection performance are observed at pH 7.

[0109] Example 3

[0110] The uranyl ions in the water sample to be tested were detected using the intermediate product GC-TFPB and the final product GC-TFPB-AO obtained in Example 1, respectively. The specific steps are as follows: 2 mg of GC-TFPB and GC-TFPB-AO were added to 10 mL of ultrapure water and ultrasonically mixed to prepare a suspension. Then, 150 μL of the suspension was taken, 100 μL of HEPEs buffer (pH=7) was added, and 650 μL of DMF solvent (NN-dimethylformamide solvent) was added. The initial fluorescence intensity was measured respectively.

[0111] Then add 100 μL of uranyl ions (concentration of 10 μM) and measure the fluorescence results, such as... Figure 9 As shown.

[0112] according to Figure 9 Observations show that GC-TFPB has a certain responsiveness to uranyl ions. After modification with a methylamine oxime group, its sensitivity is significantly improved, proving that the methylamine oxime-modified GC-TFPB-AO has superior uranyl ion detection performance.

[0113] Example 4

[0114] Cyclic detection experiments were performed on the GC-TFPB-AO obtained in Example 1. 2 mg of GC-TFPB-AO was added to 10 mL of ultrapure water and ultrasonically mixed to prepare a suspension. Then, 150 μL of the suspension was taken, and 100 μL of HEPEs buffer (pH = 7) was added, followed by 650 μL of DMF solvent (NN-dimethylformamide solvent) and 100 μL of uranyl ions (concentration 10 μM). The fluorescence value was then measured. The elution process was as follows: The above system was repeated (note that the uranyl ions need to be replaced with 100 μL of 1 M sodium bicarbonate solution; detecting the fluorescence recovery intensity constitutes one cycle). The above system was repeated 1-2 times. The specific experimental results are shown in the graph below. Figure 10 As shown.

[0115] according to Figure 10 Observations show that GC-TFPB-AO can be eluted by sodium bicarbonate solution and recover its fluorescence intensity after being quenched by uranyl ions. When uranyl ions are added again, it is quenched again, proving that GC-TFPB-AO can be recycled.

[0116] In summary, the above-described technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A covalent organic framework material, characterized in that, The structural formula of the covalent organic framework material is as follows: ； The method for preparing the covalent organic framework material includes the following steps: A covalent organic framework powder is mixed with an alcohol solvent to obtain a mixture; the covalent organic framework powder has carbon-carbon double bonds and cyano groups in its structure. The mixture, hydroxylamine hydrochloride, and triethylamine were mixed and heated to obtain the covalent organic framework material. The covalent organic framework powder is obtained by dissolving 3-cyano-4,6-dimethyl-2-hydroxypyridine and 1,3,5-tris(p-formylphenyl)benzene in a mixed solvent to obtain a suspension; and subjecting the suspension to freezing and heating treatments in sequence to obtain the covalent organic framework powder.

2. A method for preparing a covalent organic framework material as described in claim 1, characterized in that, Including the following steps: A covalent organic framework powder is mixed with an alcohol solvent to obtain a mixture; the covalent organic framework powder has carbon-carbon double bonds and cyano groups in its structure. The mixture, hydroxylamine hydrochloride, and triethylamine are mixed and heated to obtain the covalent organic framework material.

3. The preparation method according to claim 2, characterized in that, The covalent organic framework powder is obtained by dissolving 3-cyano-4,6-dimethyl-2-hydroxypyridine and 1,3,5-tris(p-formylphenyl)benzene in a mixed solvent to obtain a suspension; and subjecting the suspension to freezing and heating treatments in sequence to obtain the covalent organic framework powder.

4. The preparation method according to claim 3, characterized in that, The mixing ratio of the 3-cyano-4,6-dimethyl-2-hydroxypyridine, the 1,3,5-tris(p-formylphenyl)benzene, and the mixed solvent is 43~46 mg: 77~80 mg: 4.5~6.6 mL.

5. The preparation method according to claim 4, characterized in that, The mixed solvent is o-dichlorobenzene, N,N-dimethylformamide and dimethylamine mixed in a volume ratio of 2~3mL:2~3mL:0.5~0.6mL.

6. The preparation method according to claim 3, characterized in that, The freezing process involves freezing the suspension with liquid nitrogen and evacuating it three times. The temperature of the heat treatment is 170~190℃; the duration of the heat treatment is 70~74h.

7. The preparation method according to claim 3, characterized in that, The heat treatment is followed by washing and drying to obtain the covalent organic framework powder.

8. The preparation method according to claim 2, characterized in that, The heating temperature of the heating reaction is 70~90℃, and the reaction time is 20~30h.

9. The application of a method for detecting uranyl ions in water using a covalent organic framework material as described in claim 1 or a covalent organic framework material prepared by any one of the preparation methods described in claims 2 to 8.

10. The detection method according to claim 9, characterized in that, Including the following steps: The covalent organic framework material, N,N-dimethylformamide solvent, HEPES buffer, and the water sample to be tested are mixed to obtain a detection mixture; the fluorescence intensity of the detection mixture is measured, and the content of uranyl ions in the water sample to be tested is determined based on the linear relationship between the fluorescence intensity and the uranyl ion concentration.

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