A bimetallic organic framework nanomaterial with enzyme-like properties, its preparation method and application

Abstract

The present invention provides a bimetallic organic framework nanomaterial with enzyme-like properties, a preparation method thereof, and an application thereof, belonging to the technical field of mimetic enzymes. In the present invention, ferric chloride hexahydrate is used as an iron source, cobalt chloride hexahydrate is used as a cobalt source, and 1,3,5-benzenetricarboxylic acid is used as an organic ligand. A bimetallic organic framework nanomaterial with enzyme-like properties is prepared by a hydrothermal reaction and applied to the visual detection of benzenethiol. The preparation method of the bimetallic organic framework nanomaterial of the present invention is simple, has good selectivity and stability for the detection of benzenethiol, the detection process is carried out in a neutral environment at room temperature, and has the advantages of rapidity, sensitivity, convenience, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of mimetic enzymes, and particularly relates to a bimetallic organic framework nanomaterial with enzyme-like characteristics, a preparation method thereof, and an application thereof. Background Art

[0002] Benzenethiol is a type of aromatic thiol, represented by 4-methylbenzenethiol, which has been widely used in the preparation of pesticides, polymers, and medical drugs in recent years. However, benzenethiol has strong biological toxicity and can cause serious impacts on human health. Therefore, the development of timely, rapid, and efficient detection and monitoring of benzenethiol is of great significance for maintaining human health and protecting the ecological environment. Currently, most methods for detecting benzenethiol and its derivatives rely on large-scale instrument equipment, which is not conducive to on-site rapid detection. In order to achieve rapid portable on-site detection of benzenethiol and its derivatives, detection technologies based on colorimetry have gradually attracted people's attention. Commonly used colorimetric methods generally use nanomaterials as catalytic elements, with H 2 O 2 as the enzyme substrate and TMB as the chromogenic medium. Through the catalysis of nanomaterials on H 2 O 2 to generate ·OH, and further oxidize TMB, the solution of the reaction system shows a color change from "colorless - blue". After adding thiol-containing benzenethiol substances, they will compete with TMB for ·OH, and then produce a color difference proportional to the target concentration. Although this technology has a mature method route, the preparation of complex nanocomposites has certain randomness, and the property of H 2 O 2 is unstable, which affects the accuracy, stability, and repeatability of this technical method to a certain extent.

[0003] In order to effectively solve the problems of material preparation and unstable enzyme substrate in general colorimetric detection methods, organometallic framework materials (MOF) with enzyme-like activity and persulfate (PMS) are introduced. MIL-100(Fe) is an iron-based MOF material, whose preparation process is relatively simple, the product forming rate is high, and it has a high specific surface area and stability, so it is widely used in fields such as catalytic degradation of pollutants and new energy processes. However, the catalytic activity of single-metal MOF is generally limited by the inherent metal ions. At the same time, for the emerging enzyme substrate PMS, it can be catalyzed by transition metals at room temperature and can also be excited under specific light conditions, so it has dual properties of enzyme-like catalysis and photocatalysis, and it is more stable than H 2 O 2 itself. Therefore, if the catalytic activity of single-metal MOF materials can be improved and combined with PMS, a new, more efficient, and stable colorimetric detection method may be established. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a bimetallic organic framework nanomaterial with enzyme-like properties, a preparation method thereof, and an application thereof. The bimetallic organic framework nanomaterial prepared by the present invention can catalyze persulfate at room temperature. A colorimetric method based on this reaction can be used for visual detection of benzenethiol, providing a convenient and rapid approach for trace detection of benzenethiol.

[0005] To achieve the above object, the present invention provides a bimetallic organic framework nanomaterial with enzyme-like properties, using 1,3,5-benzenetricarboxylic acid as an organic ligand, ferric chloride hexahydrate as an iron source, cobalt chloride hexahydrate as a cobalt source, and water as a solvent for hydrothermal synthesis. The bimetallic organic framework nanomaterial has a 3D rhombic octahedron shape, a particle size of 0.5 - 1.5 μm, belongs to a porous material, and has more active sites, which is beneficial to the transfer of electrons and free radicals. Compared with other iron sources and cobalt sources, the advantage of the iron source and cobalt source used in the present invention is that they are more conducive to forming an octahedral three-dimensional cone structure. Using water as the reaction solvent is safe and convenient.

[0006] The present invention provides a preparation method of a bimetallic organic framework nanomaterial with enzyme-like properties, comprising the following steps:

[0007] (1) Mix ferric chloride hexahydrate, cobalt chloride hexahydrate, 1,3,5-benzenetricarboxylic acid, and water to obtain a mixed solution;

[0008] (2) Place the mixed solution in a reaction kettle for hydrothermal reaction to obtain the bimetallic organic framework nanomaterial with enzyme-like properties, namely MIL-100(Fe,Co).

[0009] Furthermore, the molar ratio of ferric chloride hexahydrate to 1,3,5-benzenetricarboxylic acid is 1 - 2:1, and the molar ratio of ferric chloride hexahydrate to cobalt chloride hexahydrate is 4 - 12:1.

[0010] Furthermore, the dosage ratio of ferric chloride hexahydrate to water is (10 - 20) mmol:(50 - 64) mL.

[0011] Furthermore, the temperature of the hydrothermal reaction is 120 - 200 °C, and the time is 12 - 24 h.

[0012] Furthermore, the preparation method of the bimetallic organic framework nanomaterial with enzyme-like properties of the present invention further comprises the steps of cooling, solid-liquid separation, washing, and drying the system in sequence after the hydrothermal reaction.

[0013] The present invention also provides an application of the bimetallic organic framework nanomaterial in the visual detection of benzenethiol.

[0014] Furthermore, the bimetallic organic framework nanomaterial serves as an enzyme mimic.

[0015] Furthermore, it includes the following steps:

[0016] (1) Dissolve the bimetallic organic framework nanomaterial in water to obtain a bimetallic organic framework dispersion;

[0017] (2) Mix the bimetallic organic framework dispersion, the solution to be measured, a persulfate solution (PMS), a 3,3',5,5'-tetramethylbenzidine solution (TMB), and an acetic acid-sodium acetate buffer solution, and conduct an oxidation reaction to obtain a reaction solution;

[0018] (3) Measure the absorbance of the reaction solution at λ = 652 nm;

[0019] (4) Obtain the content of benzenethiol in the solution to be measured according to the absorbance and the benzenethiol standard curve.

[0020] Furthermore, the detection limit of benzenethiol is 1 - 60 μM, that is, the content of benzenethiol in the solution to be measured is 1 - 60 μM, or the linear range of the benzenethiol standard curve.

[0021] Even further, the concentration of the bimetallic organic framework dispersion is 0.05 - 0.2 mg / mL, the concentration of the 3,3',5,5'-tetramethylbenzidine solution is 0.4 - 1.2 mmol / L, the pH value of the acetic acid-sodium acetate buffer solution is 3 - 6, and the concentration is 100 - 300 mmol / L.

[0022] Even further, the volume ratio of the total volume of the solution to be measured, the bimetallic organic framework dispersion, the persulfate solution, and the 3,3',5,5'-tetramethylbenzidine solution to the volume of the acetic acid-sodium acetate buffer solution is 1:10 - 500.

[0023] Even further, the oxidation reaction is carried out in a neutral environment at room temperature, the oxidation reaction temperature is 20 - 50 °C, and the time is 1 - 6 min.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] (1) The present invention prepares a Co(II)-doped MIL-100(Fe) bimetallic MOF material (MIL-100(Fe,Co)), and combines it with PMS to construct a new colorimetric method for the rapid detection of benzenethiol. This method uses PMS as the substrate and TMB as the colorimetric medium. In the presence of persulfate, the MIL-100(Fe,Co) prepared by the present invention can catalyze PMS to generate SO 4 -·, and further oxidize TMB to generate blue oxTMB, producing a visual color change, which has a characteristic ultraviolet absorption at 652 nm. When benzenethiol is present, it can compete with TMB for SO 4 - ·, resulting in a decrease in the amount of oxidized TMB, thus causing a difference in the color change of the system. By measuring the color difference value, benzenethiol is quantitatively detected according to the absorbance at 652 nm.

[0026] (2) The preparation method of the bimetallic organic framework nanomaterial provided by the present invention is simple, has good selectivity and stability for the detection of benzenethiol. The detection process is carried out in a neutral environment at room temperature, and has good application prospects, as well as advantages such as fast, sensitive and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0028] Figure 1 For the morphology and elemental composition diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention, see Figure 1 , where (a) is the HRTEM image, (b)-(e) are the EDS elemental distribution diagrams of C, O, Fe, and Co respectively, and (f) is the EDS energy spectrum diagram;

[0029] Figure 2 For the elemental valence state analysis diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention, see Figure 2 , where (a) is the full spectrum diagram, (b) is C1s, (c) is O1s, (d) is Fe 2p, and (e) is Co 2p;

[0030] Figure 3 For the enzyme kinetics analysis diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention, see Figure 3 , where (a) is the steady-state kinetic curve of the bimetallic organic framework nanomaterial for PMS, (b) is the steady-state kinetic curve of the bimetallic organic framework nanomaterial for TMB, (c) is the double-reciprocal linear equation of PMS, and (d) is the double-reciprocal equation of TMB;

[0031] Figure 4 For the ultraviolet absorption spectrum diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention under different pH values and reaction times, see Figure 4 , where (a) is the absorption signal diagram related to the influence of pH on the enzyme activity of the bimetallic organic framework nanomaterial, and (b) is the absorption signal diagram related to the influence of the oxidation reaction time on the enzyme activity of the bimetallic organic framework nanomaterial;

[0032] Figure 5 Visual colorimetric map, ultraviolet absorption spectrum and absorbance linear curve of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention for detecting 4-methylthiophenol, where (a) is the ultraviolet-visible spectrum and colorimetric detection results (upper left inset) of groups a-e in Application Example 4, and (b) is the relative absorbance at λ = 652 nm and the linear curve of detecting MTP at different MTP (1-60 μM) in Application Example 5 (lower right inset);

[0033] Figure 6 Stability determination results of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention stored at room temperature for 1, 2, 3, 4, 5, and 6 weeks;

[0034] Figure 7 Selectivity test results of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention for MTP detection;

[0035] Figure 8 Schematic process diagram for preparing the bimetallic organic framework nanomaterial in Example 2. Detailed implementation manners

[0036] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be regarded as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0037] It should be understood that the terms used in the present invention are only for describing particular implementation manners and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0038] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0039] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0040] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0041] The present invention provides a bimetallic organic framework nanomaterial with enzyme-like properties. Using 1,3,5-benzenetricarboxylic acid as the organic ligand, ferric chloride hexahydrate as the iron source, cobalt chloride hexahydrate as the cobalt source, and water as the solvent for hydrothermal synthesis. The shape of the bimetallic organic framework nanomaterial is a 3D rhombic octahedron, with a particle size of 0.5 - 1.5 μm. It belongs to porous materials, has a larger specific surface area and more active sites, which is beneficial to the transfer of electrons and free radicals. The advantage compared with other iron sources and cobalt sources is that the iron source and cobalt source used in the present invention are more conducive to the formation of an octahedral three-dimensional cone structure. Using water as the reaction solvent is safe and convenient.

[0042] The present invention provides a preparation method of a bimetallic organic framework nanomaterial with enzyme-like properties, including the following steps:

[0043] (1) Mix ferric chloride hexahydrate, cobalt chloride hexahydrate, 1,3,5-benzenetricarboxylic acid with water to obtain a mixed solution;

[0044] (2) Place the mixed solution in a reaction kettle for hydrothermal reaction to obtain the bimetallic organic framework nanomaterial with enzyme-like properties, namely MIL-100(Fe,Co).

[0045] In some preferred embodiments of the present invention, the iron source is ferric chloride hexahydrate (FeCl 3 ·6H 2 O), the cobalt source is cobalt chloride hexahydrate (CoCl 2 ·6H 2 O), and 1,3,5-benzenetricarboxylic acid is used as the organic ligand at the same time. The advantage compared with other iron sources and cobalt sources is that the iron source and cobalt source used in the embodiments of the present invention are more conducive to the formation of an octahedral three-dimensional cone structure. Using ultrapure water as the reaction solvent is safer and more convenient.

[0046] The amounts of iron source, cobalt source, 1,3,5-benzenetricarboxylic acid and water have an impact on the enzyme-like properties of the bimetallic organic framework nanomaterials. In order to further improve the enzyme activity of the bimetallic organic framework nanomaterials, in some embodiments of the present invention, the molar ratio of the iron source to 1,3,5-benzenetricarboxylic acid is 1-2:1, preferably 1.5:1; the molar ratio of the iron source to the cobalt source is 4-12:1, preferably 9:1; the dosage ratio of the iron source to water is (10-20) mmol:(50-64) mL, preferably 15 mmol:54 mL.

[0047] In the embodiments of the present invention, the temperature of the hydrothermal reaction is 120-200 °C and the time is 12-24 h. In some preferred embodiments, the temperature of the hydrothermal reaction is 150 °C and the time is 16 h.

[0048] The preparation method of the bimetallic organic framework nanomaterials with enzyme-like properties of the present invention further includes the steps of cooling, solid-liquid separation, washing and drying the system in sequence after the hydrothermal reaction. Specifically:

[0049] In the embodiments of the present invention, the cooling is preferably natural cooling to room temperature (in the embodiments of the present invention, unless otherwise specified, room temperature refers to 25±2 °C); the method of solid-liquid separation is preferably centrifugation.

[0050] In the embodiments of the present invention, the solid matter obtained by centrifugation is washed and dried. The washing preferably includes ethanol washing and water washing alternately; the water washing is preferably distilled water washing. In some preferred embodiments of the present invention, the number of alternate washings is preferably 3 times, specifically preferably washing alternately with absolute ethanol and distilled water 3 times. The drying is preferably vacuum drying, the drying temperature is preferably 60-90 °C, more preferably 70-80 °C; the drying time is preferably 12-24 h, more preferably 15-20 h.

[0051] The present invention also provides the application of the above bimetallic organic framework nanomaterials in the visual detection of benzenethiol. The bimetallic organic framework nanomaterials are used as enzyme-like substances. In the embodiments of the present invention, the benzenethiol is 4-methylbenzenethiol, and specifically includes the following steps:

[0052] (1) Dissolve the bimetallic organic framework nanomaterials in water to obtain a bimetallic organic framework dispersion, and the water is preferably ultrapure water;

[0053] (2) Mix the bimetallic organic framework dispersion, the solution to be tested, persulfate solution (PMS), 3,3',5,5'-tetramethylbenzidine solution (TMB) and acetic acid-sodium acetate buffer solution, and carry out an oxidation reaction to obtain a reaction solution;

[0054] (3) The absorbance of the reaction solution at λ = 652 nm was measured by ultraviolet spectrophotometry;

[0055] (4) According to the absorbance and the standard curve of benzenethiol, the content of benzenethiol in the solution to be measured was obtained.

[0056] In the embodiment of the present invention, the detection limit of benzenethiol is 1 - 60 μM, that is, the content of benzenethiol in the solution to be measured is 1 - 60 μM, or the linear range of the standard curve of benzenethiol. In some preferred embodiments of the present invention, the detection limit of benzenethiol is 5 - 50 μM.

[0057] In the embodiment of the present invention, the concentration of the bimetallic organic framework dispersion is 0.05 - 0.2 mg / mL, preferably 0.1 mg / mL.

[0058] In the embodiment of the present invention, the concentration of the 3,3',5,5'-tetramethylbenzidine solution is 0.4 - 1.2 mmol / L, preferably 0.8 mmol / L, and the solvent of the 3,3',5,5'-tetramethylbenzidine solution is preferably dimethyl sulfoxide.

[0059] In the embodiment of the present invention, the pH value of the acetic acid - sodium acetate buffer solution is 3 - 6, preferably 4; the concentration is 100 - 300 mmol / L, preferably 200 mmol / L.

[0060] In the embodiment of the present invention, the volume ratio of the total volume of the solution to be measured, the bimetallic organic framework dispersion, and the 3,3',5,5'-tetramethylbenzidine solution to the volume of the acetic acid - sodium acetate buffer solution is 1:10 - 500, preferably 1:50 - 60.

[0061] In the embodiment of the present invention, the preferred mixing method of the solution to be measured, the bimetallic organic framework dispersion, the persulfate solution, the 3,3',5,5'-tetramethylbenzidine solution, and the acetic acid - sodium acetate buffer solution is: the bimetallic organic framework dispersion, the 3,3',5,5'-tetramethylbenzidine solution, and the solution to be measured are sequentially added to the acetic acid - sodium acetate buffer solution for an oxidation reaction to obtain a reaction solution.

[0062] In the embodiment of the present invention, the oxidation reaction is carried out in a neutral environment at room temperature, the oxidation reaction temperature is 20 - 50 °C, and the time is 1 - 6 min. More preferably, the temperature is 25 - 35 °C and the time is 3 - 5 min.

[0063] All the raw materials used in the embodiments of the present invention were obtained by purchasing commercially.

[0064] The technical solution of the present invention will be further described below through examples.

[0065] Example 1

[0066] (1) Measure 54 mL of ultrapure water into a 100 mL beaker. Weigh 0.015 mol (1.35 g) of ferric chloride hexahydrate and 0.0017 mol (0.204 g) of cobalt chloride hexahydrate (the molar ratio of iron source to cobalt source is 9:1), mix and add them to the beaker, stir for 10 min, then add 0.01 mol (0.70 g) of 1,3,5-benzenetricarboxylic acid to the beaker, and stir for 1 h to obtain a mixed solution;

[0067] (2) Transfer the mixed solution in the beaker to a 100 mL autoclave and carry out a hydrothermal reaction at 150 °C for 16 h;

[0068] (3) After the hydrothermal reaction, cool it to room temperature, centrifuge and extract the lower-layer solid, wash it 3 times alternately with deionized water and ethanol, then dry it in an oven at 60 °C for 10 h, and finally dry it under vacuum at 80 °C for 10 h, and grind it thoroughly to obtain a bimetallic organic framework nanomaterial.

[0069] The morphology and elemental composition diagrams of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention are shown in Figure 1 , where (a) is the HRTEM diagram, (b)-(e) are the EDS elemental distribution diagrams of C, O, Fe, and Co respectively, and (f) is the EDS energy spectrum diagram. It can be seen from Figure 1 that the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention contains Fe, Co, C, and O elements, is a 3D rhombic octahedron, and the particle size is 0.5-1.5 μm.

[0070] The elemental valence state analysis diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention is shown in Figure 2 , where (a) is the full-spectrum diagram, (b) is C1s, (c) is O1s, (d) is Fe 2p, and (e) is Co 2p. It can be seen from Figure 2 that the elements in the prepared bimetallic organic framework nanomaterial are combined by covalent bonds, rather than the simple superposition of each single substance.

[0071] Application Example 1

[0072] (1) Dissolve 10 mg of the bimetallic organic framework nanomaterial prepared in Example 1 in 100 mL of ultrapure water to obtain a bimetallic organic framework dispersion;

[0073] (2) Mix the bimetallic organic framework dispersion obtained in step (1) with 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L). Then, sequentially add 3,3',5,5'-tetramethylbenzidine solution (TMB) and persulfate solution (PMS) to make their final concentrations 0.8 mmol / L and 0.05 mmol / L, respectively. After that, add the test solution (4-methylbenzenethiol concentrations are 1, 3, 5, 7, 9, 10, 20, 30, 40, 50, 60 μM) and shake well to mix. Conduct an oxidation reaction at 25 °C for 5 min to obtain a reaction solution;

[0074] (3) Use ultraviolet spectrophotometry to measure the absorbance of the reaction solution at λ = 652 nm.

[0075] Keep other conditions unchanged and only change the concentrations of the persulfate solution (PMS) to 0.02, 0.03, 0.06, 0.09, and 0.10 mol / L, respectively, and repeat the experiment.

[0076] The enzyme kinetic analysis diagram of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention is shown in Figure 3 , where (a) is the steady-state kinetic curve of the bimetallic organic framework nanomaterial for PMS, (b) is the steady-state kinetic curve of the bimetallic organic framework nanomaterial for TMB, (c) is the double-reciprocal linear equation of PMS, and (d) is the double-reciprocal equation of TMB. According to Figure 3 the results of calculation, the Michaelis constant of the bimetallic organic framework nanomaterial prepared in Example 1 is 0.25 mmol / L, and the maximum reaction rate Vmax value is 14.79×10 -8 mol / s.

[0077] Application Example 2

[0078] The same as Application Example 1, the only difference is that the pH values of the acetic acid-sodium acetate buffer solution are changed to 2.0, 3.0, 4.0, 5.0, and 6.0, respectively, and the concentration of the persulfate solution (PMS) is fixed at 0.05 mmol / L.

[0079] Application Example 3

[0080] The same as Application Example 1, the only difference is that the oxidation reaction times are changed to 1, 2, 3, 4, and 6 min, respectively, and the concentration of the persulfate solution (PMS) is fixed at 0.05 mmol / L.

[0081] Under the conditions of Application Example 2 and Application Example 3, the ultraviolet absorption spectra of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention at different pH values and reaction times are shown in Figure 4, where (a) is the absorption signal diagram related to the effect of pH on the enzyme activity of the bimetallic organic framework nanomaterial, and (b) is the absorption signal diagram related to the effect of the oxidation reaction time on the enzyme activity of the bimetallic organic framework nanomaterial. It is determined by Figure 4 that the optimal pH value is 4.0 and the optimal oxidation reaction time is 5 min.

[0082] Application Example 4

[0083] Visual detection of 4-methylbenzenethiol was carried out, and five groups a-e were set:

[0084] Group a: 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L) was mixed with TMB to make its concentration 0.8 mmol / L;

[0085] Group b: 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L) was mixed with TMB and PMS to make their concentrations 0.8 mmol / L and 0.5 mmol / L respectively;

[0086] Group c: 10 mg of the bimetallic organic framework nanomaterial prepared in Example 1 was dissolved in 100 mL of ultrapure water to obtain a bimetallic organic framework dispersion. The obtained bimetallic organic framework dispersion was mixed with 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L), and then TMB and PMS were added successively to make their concentrations 0.8 mmol / L and 0.5 mmol / L respectively;

[0087] Group d: 10 mg of the bimetallic organic framework nanomaterial prepared in Example 1 was dissolved in 100 mL of ultrapure water to obtain a bimetallic organic framework dispersion. The obtained bimetallic organic framework dispersion was mixed with 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L), and then TMB and PMS were added successively to make their concentrations 0.8 mmol / L and 0.5 mmol / L respectively. Then, the test solution (4-methylbenzenethiol concentration is 10 μM) was added and shaken well;

[0088] Group e: 10 mg of the bimetallic organic framework nanomaterial prepared in Example 1 was dissolved in 100 mL of ultrapure water to obtain a bimetallic organic framework dispersion. The obtained bimetallic organic framework dispersion was mixed with 20 mL of acetic acid-sodium acetate buffer solution (pH = 4, 0.3 mol / L), and then TMB and PMS were added successively to make their concentrations 0.8 mmol / L and 0.5 mmol / L respectively. Then, the test solution (4-methylbenzenethiol concentration is 50 μM) was added and shaken well;

[0089] The absorbance of the reaction solutions in groups a-b at λ = 652 nm was measured by ultraviolet spectrophotometry.

[0090] Application Example 5

[0091] Similar to Application Example 1, the concentration of the persulfate solution (PMS) was fixed at 0.05 mmol / L. The only difference was that the concentrations of 4-methylthiophenol (MTP) in the test solution were set to 1, 3, 5, 7, 9, 10, 20, 30, 40, 50, and 60 μM respectively. After shaking well and mixing, the oxidation reaction was carried out at 25 °C for 5 min to obtain the reaction solution.

[0092] And the ultraviolet spectrophotometry was used to measure the absorbance of different reaction solutions at λ = 652 nm.

[0093] Under the conditions of Application Example 4 and Application Example 5, the visual colorimetric map, ultraviolet absorption spectrum, and absorbance linear curve of the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention for detecting 4-methylthiophenol are shown in Figure 5 , where (a) is the ultraviolet-visible spectrum and colorimetric detection results (upper left inset) of groups a-e in Application Example 4, and (b) is the relative absorbance at λ = 652 nm and the linear curve graph for detecting MTP (lower right inset) in Application Example 5 under different MTP (1-60 μM).

[0094] According to Figure 5 It can be seen that the absorbance standard curve range of 4-methylthiophenol in the present invention is 5.0-50 μM, and the linear equation is ΔA = 0.0137C MTP + 0.046.

[0095] Application Example 5

[0096] Similar to Application Example 1, the only difference was that the concentration of the persulfate solution (PMS) was fixed at 0.05 mmol / L. Then, the absorbance was measured once a week for a total of 6 repetitions, and the result data were recorded. The results are shown in Figure 6 .

[0097] Application Example 6

[0098] Similar to Application Example 1, the only difference was that the concentration of the persulfate solution (PMS) was fixed at 0.05 mmol / L, and the test solution was successively replaced with test solutions containing rhodamine B (RhB), tetracycline hydrochloride (TCHC), oxytetracycline (OCHC), bisphenol A (BPA), copper ions (Cu 2+ ) and 4-methylthiophenol (MTP) so that their final concentrations were all 40 μM. Then, the absorbance test was carried out, and the test results are shown in Figure 7 .

[0099] Comprehensively Figure 6 and Figure 7It can be seen from the experimental results that the colorimetric method constructed based on the bimetallic organic framework nanomaterial prepared in Example 1 of the present invention has good stability and selectivity.

[0100] Example 2

[0101] The schematic process diagram for preparing the bimetallic organic framework nanomaterial in Example 2 is shown in Figure 8 , specifically:

[0102] (1) Measure 64 mL of ultrapure water into a 100 mL beaker, weigh 0.01 mol (1.35 g) of ferric chloride hexahydrate and 0.0025 mol (0.3 g) of cobalt chloride hexahydrate (the molar ratio of the iron source to the cobalt source is 4:1), mix and add them to the beaker and stir for 10 min, then add 0.01 mol (0.70 g) of 1,3,5-benzenetricarboxylic acid to the beaker and stir for 1 h to obtain a mixed solution;

[0103] (2) Transfer the mixed solution in the beaker to a 100 mL reaction kettle and carry out a hydrothermal reaction at 150 °C for 12 h;

[0104] (3) After the hydrothermal reaction is completed, cool it to room temperature, centrifuge and extract the lower-layer solid, wash it 3 times alternately with deionized water and ethanol, and then dry it in an oven at 80 °C for 10 h and grind it thoroughly to obtain the bimetallic organic framework nanomaterial.

[0105] Example 3

[0106] (1) Measure 50 mL of ultrapure water into a 100 mL beaker, weigh 0.02 mol (1.35 g) of ferric chloride hexahydrate and 0.001 mol (0.24 g) of cobalt chloride hexahydrate (the molar ratio of the iron source to the cobalt source is 10:1), mix and add them to the beaker and stir for 10 min, then add 0.01 mol (0.70 g) of 1,3,5-benzenetricarboxylic acid to the beaker and stir for 1 h to obtain a mixed solution;

[0107] (2) Transfer the mixed solution in the beaker to a 100 mL reaction kettle and carry out a hydrothermal reaction at 120 °C for 24 h;

[0108] (3) After the hydrothermal reaction is completed, cool it to room temperature, centrifuge and extract the lower-layer solid, wash it 3 times alternately with deionized water and ethanol, and then dry it in an oven at 60 °C for 24 h and grind it thoroughly to obtain the bimetallic organic framework nanomaterial.

[0109] Example 4

[0110] (1) Measure 60 mL of ultrapure water into a 100 mL beaker. Weigh 0.012 mol (1.35 g) of ferric chloride hexahydrate and 0.001 mol (0.12 g) of cobalt chloride hexahydrate (the molar ratio of the iron source to the cobalt source is 12:1), mix and add them to the beaker, stir for 10 min, then add 0.01 mol (0.70 g) of 1,3,5-benzenetricarboxylic acid to the beaker, and stir for 1 h to obtain a mixed solution;

[0111] (2) Transfer the mixed solution in the beaker to a 100 mL autoclave and carry out a hydrothermal reaction at 200 °C for 12 h;

[0112] (3) After the hydrothermal reaction, cool to room temperature, centrifuge and extract the lower-layer solid, wash it 3 times alternately with deionized water and ethanol, then dry it in an oven at 90 °C for 12 h and grind it thoroughly to obtain the bimetallic organic framework nanomaterial.

[0113] Comparative Example 1

[0114] Same as Example 1, the only difference is that ferric chloride hexahydrate is replaced with iron nitrate in equal mass, and cobalt chloride hexahydrate is replaced with cobalt nitrate in equal mass.

[0115] Comparative Example 2

[0116] Same as Example 1, the only difference is that the temperature of the hydrothermal reaction is 100 °C and the time is 10 h.

[0117] Comparative Example 3

[0118] Same as Example 1, the only difference is that 54 mL of ultrapure water is measured into a 100 mL beaker, and 0.015 mol (1.35 g) of ferric chloride hexahydrate and 0.0075 mol (0.9 g) of cobalt chloride hexahydrate (the molar ratio of the iron source to the cobalt source is 2:1) are weighed.

[0119] Performance test

[0120] Accuracy comparison: After testing, after the comparative examples were replaced with different conditions and the detection of 4-methylthiophenol was carried out according to the method of Application Example 1, the difference from the detection results of the examples was 5% - 15%, indicating that the bimetallic organic framework nanomaterial prepared by the technical solution of the present invention is more suitable for the detection of thiophenol and has higher accuracy.

[0121] The above is only the preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A bimetallic organic framework nanomaterial with enzyme-like properties, characterized in that using 1,3,5-benzenetricarboxylic acid as the organic ligand, ferric chloride hexahydrate as the iron source, cobalt chloride hexahydrate as the cobalt source, and water as the solvent for hydrothermal synthesis. The shape of the bimetallic organic framework nanomaterial is a 3D rhombic octahedron, and the particle size is 0.5 - 1.5 μm; The preparation method of the bimetallic organic framework nanomaterial with enzyme-like properties includes the following steps: (1) Mix ferric chloride hexahydrate, cobalt chloride hexahydrate, 1,3,5-benzenetricarboxylic acid and water to obtain a mixed solution; (2) Carry out hydrothermal reaction on the mixed solution to obtain the bimetallic organic framework nanomaterial with enzyme-like properties; The molar ratio of ferric chloride hexahydrate to 1,3,5-benzenetricarboxylic acid is 1 - 2:1, and the molar ratio of ferric chloride hexahydrate to cobalt chloride hexahydrate is 4 - 12:1; The dosage ratio of ferric chloride hexahydrate to water is (10 - 20) mmol:(50 - 64) mL; The temperature of the hydrothermal reaction is 120 - 200 °C, and the time is 12 - 24 h.

2. The application of the bimetallic organic framework nanomaterial according to claim 1 in the visual detection of benzenethiol, characterized in that the bimetallic organic framework nanomaterial serves as an enzyme-like substance.

3. According to the application described in claim 2, characterized in that it includes the following steps: (1) Dissolve the bimetallic organic framework nanomaterial according to claim 1 in water to obtain a bimetallic organic framework dispersion; (2) Mix the bimetallic organic framework dispersion, the solution to be measured, a persulfate solution, a 3,3',5,5'-tetramethylbenzidine solution and an acetic acid - sodium acetate buffer solution to obtain a reaction solution; (3) Measure the absorbance of the reaction solution at λ = 652 nm; (4) According to the absorbance and the benzenethiol standard curve, obtain the content of benzenethiol in the solution to be measured; The concentration of benzenethiol in the solution to be measured is 1 - 60 μM, the concentration of the persulfate solution is 0.02 - 0.10 mol / L, the pH value of the acetic acid - sodium acetate buffer solution is 3 - 6, and the concentration is 100 - 300 mmol / L; After the bimetallic organic framework dispersion, the solution to be measured, the persulfate solution, the 3,3',5,5'-tetramethylbenzidine solution and the acetic acid - sodium acetate buffer solution are mixed, an oxidation reaction is carried out under a neutral environment at room temperature; The temperature of the oxidation reaction is 20 - 50 °C, and the time is 1 - 6 min.

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