A two-dimensional nickel porphyrin MOF modified graphene electrode and a preparation method and application thereof

Abstract

The application discloses a preparation method of a two-dimensional nickel porphyrin MOF material, and the method comprises the following steps: placing nickel porphyrin (Ni-TCPP), trifluoroacetic acid, polyvinylpyrrolidone and divalent copper salt in a mixed solution of ethanol and N,N-dimethylformamide, and performing a solvothermal reaction at 70000 DEG C to obtain the two-dimensional nickel porphyrin MOF material. The two-dimensional nickel porphyrin MOF material is prepared into a two-dimensional nickel porphyrin MOF modified graphene electrode through a laser direct writing device, and the electrode is used for quantitative detection of p-nitrophenol in an aqueous solution. The electrode has a large linear range, high sensitivity, fast response speed, low detection limit, strong specificity, certain anti-interference property, and can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical analysis technology, specifically relating to a graphene electrode based on nickel porphyrin MOF modification, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] p-Nitrophenol is a common chemical industrial raw material characterized by high chemical stability, low biodegradability, and high toxicity. During industrial treatment, incomplete decomposition and residues are often observed, necessitating the detection of p-nitrophenol in treated wastewater. Researchers commonly employ methods such as liquid chromatography, high-performance liquid chromatography, ultra-high-performance liquid chromatography, capillary electrophoresis, spectrophotometry, and fluorescence methods to detect p-nitrophenol in water. However, these existing methods require specialized researchers and are costly and time-consuming. Currently, electrochemical detection methods are gaining popularity due to their high sensitivity, selectivity, rapid response, and ease of operation. Summary of the Invention

[0004] To overcome the above problems, this invention provides a graphene electrode based on nickel porphyrin MOF modification, its preparation method, and its application. In this invention, the two-dimensional nickel porphyrin MOF can catalyze the oxidation of p-nitrophenol to nitrosophenol, thereby generating an electrochemical signal and enabling the instantaneous detection of p-nitrophenol.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a two-dimensional nickel porphyrin MOF material, the method comprising: placing nickel porphyrin (Ni-TCPP), trifluoroacetic acid (TFA), polyvinylpyrrolidone (PVP), and divalent copper salt in a mixed solution of ethanol and N,N-dimethylformamide (DMF), and carrying out a solvothermal reaction at 70,000°C to obtain the two-dimensional nickel porphyrin MOF material.

[0007] In a second aspect, the present invention provides a two-dimensional nickel porphyrin MOF material prepared by the above-described preparation method.

[0008] A third aspect of the present invention provides a method for preparing a graphene electrode based on two-dimensional nickel porphyrin MOF modification, the method comprising:

[0009] S1. Prepare CS Au(III) precursor solution by mixing HAuCl4 solution with chitosan solution;

[0010] S2. The precursor solution prepared in S1 is coated on the surface of the PI film, and a graphene electrode is prepared by laser direct writing equipment.

[0011] S3. Disperse the two-dimensional nickel porphyrin MOF material provided in the second aspect above in ethanol, take an appropriate amount of solution and drop it onto the graphene electrode prepared in S2, and after natural drying, obtain the graphene electrode modified with two-dimensional nickel porphyrin MOF.

[0012] A fourth aspect of the present invention provides a two-dimensional nickel porphyrin MOF-modified graphene electrode prepared by the above-described preparation method.

[0013] In a fifth aspect, the present invention provides a graphene electrode modified with the above-described two-dimensional nickel porphyrin MOF for quantitative detection of the concentration of p-nitrophenol in an aqueous solution.

[0014] A sixth aspect of the present invention provides a method for quantitatively detecting p-nitrophenol in an aqueous solution, the method comprising:

[0015] Different concentrations of p-nitrophenol solutions were added dropwise to the graphene electrode modified with the above two-dimensional nickel porphyrin MOF. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve at 0.40-0.8 V and / or the response current value of the differential pulse voltammetry (DPV) curve at 0.40-0.3 V were detected by electrochemical detection to obtain the linear relationship between the response current and the concentration.

[0016] The sample solution to be tested was dropped onto the graphene electrode modified with the above two-dimensional nickel porphyrin MOF. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve at 0.40-0.8 V and / or the response current value of the differential pulse voltammetry (DPV) curve at 0.40-0.3 V was detected by electrochemical detection. The response current value was then substituted into the linear relationship between response current and concentration to obtain the concentration of p-nitrobenzene in the aqueous solution.

[0017] (1) The two-dimensional nickel porphyrin MOF-modified graphene electrode prepared by this invention has a simple synthesis method and the raw materials are inexpensive and readily available. When applied to the detection of p-nitrophenol in wastewater, it exhibits a wide linear detection range, high sensitivity, fast response speed, low detection limit, and strong specificity, and can also be recycled.

[0018] (2) The detection method of the present invention does not require professional researchers to operate, and the detection method is simple and low in cost. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 The image shows a SEM image of the two-dimensional nickel porphyrin MOF material prepared in Example 1 of this invention.

[0021] Figure 2 This is the cyclic voltammetry (CV) curve for detecting p-nitrophenol in an aqueous solution using a graphene electrode in Example 3 of this invention. Figure 2 The small images in the image are magnified views of specific areas;

[0022] Figure 3 This is the cyclic voltammetry (CV) curve of the graphene electrode modified with two-dimensional nickel porphyrin MOF in Example 3 of the present invention for detecting p-nitrophenol in aqueous solution. Figure 3 The small images in the image are magnified views of specific areas;

[0023] Figure 4 The diagram shows the structure of the two-dimensional nickel porphyrin MOF-modified graphene electrode and the catalytic sensing mechanism of p-nitrophenol in Example 3 of this invention.

[0024] Figure 5 The cyclic voltammetry (CV) curves of different concentrations of p-nitrophenol at 0.40-0.8 V are shown in Example 4 of this invention, using a two-dimensional nickel porphyrin MOF-modified graphene electrode. Figure 5 The smaller graphs show the CV linear equations;

[0025] Figure 6 The differential pulse voltammetry (DPV) curves of different concentrations of p-nitrophenol in the range of 0.40-0.3 V are shown in Example 4 of this invention, using a two-dimensional nickel porphyrin MOF-modified graphene electrode. Figure 6 The smaller graphs show the linear equations of the DPV;

[0026] Figure 7 This is a diagram showing the recycling of the two-dimensional nickel porphyrin MOF-modified graphene electrode in Example 5. Detailed Implementation

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] The first typical embodiment of the present invention provides a method for preparing a two-dimensional nickel porphyrin MOF material, the method comprising: placing nickel porphyrin (Ni-TCPP), trifluoroacetic acid, polyvinylpyrrolidone, and divalent copper salt in a mixed solution of ethanol and N,N-dimethylformamide, and carrying out a solvothermal reaction at 70,000°C to obtain the two-dimensional nickel porphyrin MOF material.

[0030] In one or more embodiments, the divalent copper salt is one of copper nitrate, copper chloride, and copper acetate, preferably copper nitrate trihydrate.

[0031] In one or more embodiments, the mass ratio of nickel porphyrin, trifluoroacetic acid, polyvinylpyrrolidone, and divalent copper salt is 14016:1500160:20030:507, preferably 15:153:25:6.

[0032] In one or more embodiments, the volume ratio of ethanol to N,N-dimethylformamide is 1:204, preferably 1:3.

[0033] In one or more embodiments, the concentration of the divalent copper salt in a mixed solution of ethanol and N,N-dimethylformamide is 13% to 17%, preferably 15%.

[0034] In one or more embodiments, the solvothermal temperature is 80°C; the reaction time is 406 h, preferably 5 h.

[0035] In one or more embodiments, after the solvothermal reaction is completed, the material is cooled to room temperature and then centrifuged, washed with ethanol, and vacuum dried to obtain a two-dimensional nickel porphyrin MOF material. The preferred centrifugation power is 60000-8000 r / min, more preferably 7000 r / min; the number of ethanol washings is 406 times, more preferably 5 times; the vacuum drying temperature is 400-60℃, preferably 50℃; and the time is 700 h, preferably 8 h.

[0036] A second typical embodiment of the present invention provides a two-dimensional nickel porphyrin MOF material prepared by the above preparation method.

[0037] A third typical embodiment of the present invention provides a method for preparing a graphene electrode based on two-dimensional nickel porphyrin MOF modification, the method comprising:

[0038] S1. Prepare CS Au(III) precursor solution by mixing HAuCl4 solution with chitosan solution;

[0039] S2. The precursor solution prepared in S1 is coated on the surface of the PI film, and a graphene electrode is prepared by laser direct writing equipment.

[0040] S3. Disperse the two-dimensional nickel porphyrin MOF material provided in the second aspect above in ethanol, take an appropriate amount of solution and drop it onto the graphene electrode prepared in S2, and after natural drying, obtain the graphene electrode modified with two-dimensional nickel porphyrin MOF.

[0041] In one or more embodiments, the HAuCl4 solution is prepared by dissolving HAuCl4 in 1 mol / L HCl, wherein the concentration of the HAuCl4 solution is 15025 mmol / L, preferably 20 mmol / L.

[0042] In one or more embodiments, the chitosan solution is an aqueous solution of chitosan, and the mass fraction of the chitosan solute is 0.001.1%, preferably 1%.

[0043] In one or more embodiments, the volume ratio of the HAuCl4 solution to the chitosan solution is 2:5.

[0044] In one or more embodiments, the thickness of the PI film is 0.40-0.5 mm, preferably 0.5 mm; the width of the PI film is 2 cm and the length is 3 cm.

[0045] In one or more embodiments, the PI membrane is completely coated with the precursor solution.

[0046] In one or more embodiments, the parameters of the laser direct writing device are: laser wavelength 1064nm, output power 20W, laser intensity 30%, and direct writing speed 20cm / s.

[0047] In one or more embodiments, the mass-to-volume ratio of the two-dimensional nickel porphyrin MOF to ethanol is 0.80-1.2 mg:1 mL, preferably 1 mg:1 mL.

[0048] In one or more embodiments, the amount of the appropriate solution is 406 μL, preferably 5 μL.

[0049] A fourth typical embodiment of the present invention provides a two-dimensional nickel porphyrin MOF-modified graphene electrode prepared by the above preparation method.

[0050] A fifth typical embodiment of the present invention provides a graphene electrode modified with the above-mentioned two-dimensional nickel porphyrin MOF for quantitative detection of the concentration of p-nitrophenol in an aqueous solution.

[0051] A sixth typical embodiment of the present invention provides a method for quantitatively detecting p-nitrophenol in an aqueous solution, the method comprising:

[0052] Different concentrations of p-nitrophenol solutions were added dropwise to the graphene electrode modified with the above two-dimensional nickel porphyrin MOF. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve at 0.40-0.8 V and / or the response current value of the differential pulse voltammetry (DPV) curve at 0.40-0.3 V were detected by electrochemical detection to obtain the linear relationship between the response current and the concentration.

[0053] The sample solution to be tested was dropped onto the graphene electrode modified with the above two-dimensional nickel porphyrin MOF. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve at 0.40-0.8 V and / or the response current value of the differential pulse voltammetry (DPV) curve at 0.40-0.3 V was detected by electrochemical detection. The response current value was then substituted into the linear relationship between response current and concentration to obtain the concentration of p-nitrobenzene in the aqueous solution.

[0054] In one or more embodiments, the linear relationship between the response current and concentration in the cyclic voltammetry (CV) curve is I(10) -4 A) = 0.004C(μA) + 1.525.

[0055] In one or more embodiments, the linear relationship between the response current and concentration in the differential pulse voltammetry (DPV) curve is I(10 -4 A) = 4.332C(μA) + 1.150.

[0056] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0057] Example 1: Preparation of Two-Dimensional Nickel Porphyrin MOF

[0058] Dissolve 6 mg of copper nitrate trihydrate, 100 μL of trifluoroacetic acid, and 25 mg of polyvinylpyrrolidone in a mixture of 22.5 mL of DMF and 7.5 mL of ethanol.

[0059] Dissolve 15 mg NiTCPP in a mixture of 10 mL DMF and 3.3 mL ethanol.

[0060] The two solutions were ultrasonically mixed at a power of 180W for 5 minutes. The well-mixed solution was then placed in an oil bath at 80°C and reacted for 5 hours.

[0061] After cooling to room temperature, the mixture was centrifuged (7000 r / min), washed five times with ethanol, and vacuum dried at 50℃ for 8 h to obtain a two-dimensional nickel porphyrin MOF.

[0062] Figure 1 Scanning electron microscope image of the two-dimensional nickel porphyrin MOF prepared in this embodiment.

[0063] Example 2 (Preparation of nickel porphyrin MOF-modified graphene electrode)

[0064] Preparation of precursor solution: Dissolve HAuCl4 in 1 mol / L HCl solution to prepare 20 mmol / L HAuCl4 solution; dissolve 50 mg chitosan in 5 mL of ultrapure water; mix 2 mL of HAuCl4 solution and 5 mL of chitosan solution to prepare CS Au(III) precursor solution.

[0065] The above-mentioned CS Au(III) precursor solution was coated on the surface of a PI film with a thickness of 0.5 mm, a width of 2 cm, and a length of 3 cm; and the entire PI film was completely coated with the precursor solution; graphene microelectrodes were printed using a laser direct writing device. The parameters of the laser direct writing device were: laser wavelength 1064 nm, output power 20 W, laser intensity 30%, and direct writing speed 20 cm / s.

[0066] 10 mg of the nickel porphyrin MOF material prepared in Example 1 was dissolved in 10 mL of ethanol, and 5 μL was added dropwise to the graphene microelectrode. After natural drying, the nickel porphyrin MOF-modified graphene electrode was obtained.

[0067] Example 3 (Detection of nitrophenol using a nickel porphyrin MOF-modified graphene electrode and a graphene electrode)

[0068] Prepare 100 μM p-nitrophenol solution (standard solution) and 100 μM potassium chloride solution respectively.

[0069] 100 μL of the p-nitrophenol solution and potassium chloride solution prepared above were respectively added dropwise to the graphene microelectrode prepared in Example 2, and its cyclic voltammetry (CV curve) from 0.4 to -0.8 V was measured. The results are as follows. Figure 2 As shown.

[0070] 100 μL of the p-nitrophenol solution and potassium chloride solution prepared above were respectively added dropwise to the nickel porphyrin MOF-modified graphene electrode prepared in Example 2, and its cyclic voltammetry (CV curve) from 0.4 to -0.8 V was measured. The results are as follows. Figure 3 As shown.

[0071] from Figure 2 and Figure 3 The images show that the graphene microelectrode alone has a weak signal response to p-nitrophenol, while the addition of a two-dimensional nickel porphyrin MOF results in a stronger signal response to p-nitrophenol.

[0072] Figure 4The diagram shows the structure of the graphene electrode modified with two-dimensional nickel porphyrin MOF and the catalytic sensing mechanism of p-nitrophenol. As can be seen from the diagram, the two-dimensional nickel porphyrin MOF can catalyze the oxidation of p-nitrophenol to nitrosophenol, thereby generating an electrochemical signal and realizing the instantaneous detection of p-nitrophenol.

[0073] Example 4 (Linear relationship between response current and concentration)

[0074] Different concentrations of p-nitrophenol solutions (0.0 μM, 3 μM, 10 μM, 20 μM, 30 μM, 60 μM, 0.8 μM, 150 μM, 102 μM, 283 μM, and 300 μM, respectively) were added dropwise to the nickel porphyrin MOF-modified graphene electrode prepared in Example 2. Cyclic voltammetry (CV) curves at 0.40–0.8 V and differential pulse voltammetry (DPV) curves at 0.40–0.3 V were measured. The results are shown below. Figure 5 and Figure 6 As shown. From Figure 5 and Figure 6 The images show that the electrochemical signal continuously increases with increasing p-nitrophenol concentration. (From...) Figure 5 and Figure 6 The linear equation for CV can be derived as: I(10 -4 A) = 0.004C(μA) + 1.525, the limit of detection is 0.02 μM, and the detection range is 0.0-300 μM; the linear equation for DPV is I(10 -4 A) = 4.332C(μA) + 1.150, with a detection limit of 0.003 μM and a detection range of 0.5-200 μM. This indicates that the two-dimensional nickel porphyrin MOF graphene electrode has a low detection limit and a wide detection range for the electrochemical detection of p-nitrophenol, and has great application value.

[0075] The sample solution to be tested was dropped onto the graphene electrode modified with two-dimensional nickel porphyrin MOF prepared in Example 2. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve at 0.40-0.8 V and / or the response current value of the differential pulse voltammetry (DPV) curve at 0.40-0.3 V was detected by electrochemical detection. The response current value was then substituted into the linear relationship between response current and concentration to obtain the concentration of p-nitrobenzene in the aqueous solution.

[0076] Example 5 (Cyclic Experiment)

[0077] The two-dimensional nickel porphyrin MOF-modified graphene electrode prepared in Example 2 was subjected to cyclic testing, as detailed below:

[0078] A 100 μM p-nitrophenol solution was added dropwise to the two-dimensional nickel porphyrin MOF-modified graphene electrode prepared in Example 2. After reacting for 203 min, the response current value of the cyclic voltammetry (CV) curve in the range of 0.40–0.8 V was detected electrochemically. After detection, the electrode was rinsed 405 times with deionized water to remove the added p-nitrophenol solution. Another 100 μM p-nitrophenol solution was added dropwise to the electrode for detection. This process was repeated 20 times to obtain the desired result. Figure 7 The current images shown indicate that the two-dimensional nickel porphyrin MOF-modified graphene electrode still exhibits good measurement performance after 20 tests.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene electrode based on two-dimensional nickel porphyrin MOF modification, characterized in that, The method includes: S1. Prepare CS Au(III) precursor solution by mixing HAuCl4 solution with chitosan solution; S2. The precursor solution prepared in S1 is coated on the surface of the PI film, and a graphene electrode is prepared by laser direct writing equipment. S3. Disperse the two-dimensional nickel porphyrin MOF material in ethanol, take an appropriate amount of solution and drop it onto the graphene electrode prepared in S2, and after natural drying, the graphene electrode modified by the two-dimensional nickel porphyrin MOF is obtained. The preparation method of the two-dimensional nickel porphyrin MOF material includes: placing nickel porphyrin Ni-TCPP, trifluoroacetic acid, polyvinylpyrrolidone, and divalent copper salt in a mixed solution of ethanol and N,N-dimethylformamide, and carrying out a solvothermal reaction at 70~90℃ to obtain the two-dimensional nickel porphyrin MOF material.

2. The preparation method according to claim 1, characterized in that, The divalent copper salt is one of copper nitrate, copper chloride, and copper acetate; Alternatively, the mass ratio of nickel porphyrin, trifluoroacetic acid, polyvinylpyrrolidone, and divalent copper salt is 14~16:150~160:20~30:5~7; Alternatively, the volume ratio of ethanol to N,N-dimethylformamide is 1:2~4; Alternatively, the concentration of the divalent copper salt in the mixed solution of ethanol and N,N-dimethylformamide is 13% to 17%; Alternatively, the solvothermal temperature is 80°C; the reaction time is 4-6 hours. Alternatively, after the solvothermal reaction is completed, the material is cooled to room temperature and then centrifuged, washed with ethanol, and vacuum dried to obtain a two-dimensional nickel porphyrin MOF material; the number of ethanol washings is 4 to 6 times; the temperature of the vacuum drying is 40 to 60°C; and the time is 7 to 9 hours.

3. The preparation method according to claim 1, characterized in that, The divalent copper salt is copper nitrate trihydrate.

4. The preparation method according to claim 1, characterized in that, The mass ratio of nickel porphyrin, trifluoroacetic acid, polyvinylpyrrolidone, and divalent copper salt is 15:153:25:

6.

5. The preparation method according to claim 1, characterized in that, The volume ratio of ethanol to N,N-dimethylformamide is 1:

3.

6. The preparation method according to claim 1, characterized in that, The concentration of the divalent copper salt in the mixed solution of ethanol and N,N-dimethylformamide is 15%.

7. The preparation method according to claim 1, characterized in that, The solvothermal temperature is 80°C; the reaction time is 5 hours.

8. The preparation method according to claim 2, characterized in that, The centrifugation power is 6000~8000 r / min.

9. The preparation method according to claim 2, characterized in that, The centrifugation power is 7000 r / min.

10. The preparation method according to claim 2, characterized in that, The ethanol washing was performed 5 times.

11. The preparation method according to claim 2, characterized in that, The vacuum drying temperature is 50°C.

12. The preparation method according to claim 2, characterized in that, The vacuum drying time is 8 hours.

13. The preparation method according to claim 1, characterized in that, The HAuCl4 solution is prepared by dissolving HAuCl4 in 1 mol / L HCl, and the concentration of the HAuCl4 solution is 15~25 mmol / L. Alternatively, the chitosan solution is an aqueous solution of chitosan, wherein the mass fraction of the chitosan solute is 0.9-1.1%; Alternatively, the volume ratio of the HAuCl4 solution to the chitosan solution is 2:

5.

14. The preparation method according to claim 1, characterized in that, The concentration of the HAuCl4 solution was 20 mmol / L.

15. The preparation method according to claim 13, characterized in that, The mass fraction of the chitosan solute is 1%.

16. The preparation method according to claim 1, characterized in that, The PI film has a thickness of 0.4~0.5mm; the PI film has a width of 2cm and a length of 3cm; Alternatively, the PI membrane may be completely coated with the precursor solution; Alternatively, the parameters of the laser direct writing device are: laser wavelength 1064nm, output power 20W, laser intensity 30%, and direct writing speed 20 cm / s; Alternatively, the mass-to-volume ratio of the two-dimensional nickel porphyrin MOF to ethanol is 0.8~1.2 mg:1 mL; Alternatively, the amount of the appropriate solution is 4~6 μL.

17. The preparation method according to claim 1, characterized in that, The thickness of the PI film is 0.5 mm.

18. The preparation method according to claim 1, characterized in that, The mass ratio of the two-dimensional nickel porphyrin MOF to ethanol is 1 mg: 1 mL.

19. The preparation method according to claim 1, characterized in that, The amount of the appropriate solution is 5 μL.

20. A two-dimensional nickel porphyrin MOF-modified graphene electrode prepared by any one of claims 1 to 19.

21. The two-dimensional nickel porphyrin MOF-modified graphene electrode of claim 20 is used for quantitative detection of the concentration of p-nitrophenol in an aqueous solution.

22. A method for quantitatively detecting p-nitrophenol in an aqueous solution, characterized in that, The method includes: Different concentrations of p-nitrophenol solutions were dropped onto the two-dimensional nickel porphyrin MOF-modified graphene electrode as described in claim 20. After reacting for 2-3 minutes, the response current value of the cyclic voltammetry curve CV at 0.4 to -0.8 V and / or the response current value of the differential pulse voltammetry curve DPV at 0.4 to -0.3 V were detected by electrochemical methods to obtain the linear relationship between the response current and the concentration. The sample solution to be tested is dropped onto the graphene electrode modified with two-dimensional nickel porphyrin MOF as described in claim 20. After reacting for 2-3 minutes, the response current value of the cyclic voltammetry curve CV at 0.4 to -0.8 V and / or the response current value of the differential pulse voltammetry curve DPV at 0.4 to -0.3 V are detected by electrochemical detection. The response current value is then substituted into the linear relationship between response current and concentration to obtain the concentration of p-nitrobenzene in the aqueous solution.

23. The detection method as described in claim 22, characterized in that, In the cyclic voltammetry curve CV, the linear relationship between the response current and the concentration is as follows: I (10 -4 A) = 0.004 C (µA) + 1.525; The linear relationship between response current and concentration in the differential pulse voltammetry (DPV) curve is as follows: I (10 -4 A) = 4.332 C (µA) +1.150.

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