A nitrogen-doped carbon-modified graphene paper-based material, its preparation method and applications

Abstract

This invention provides a nitrogen-doped carbon-modified graphene paper-based material, its preparation method, and its applications. The graphene paper is a nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous carbon nanoparticles, with a mass percentage of 5-30% based on the total mass of the nitrogen-doped carbon-modified graphene paper-based material. The preparation process of this graphene paper-based material is simple and controllable, and it is not only resistant to acids and alkalis and high-temperature detection environments, but also has high extraction efficiency, making it suitable for applications of paper spray extraction technology in oilfield pollution detection.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a nitrogen-doped carbon-modified graphene paper-based material, its preparation method, and its applications. Background Technology

[0002] Paper spray extraction (PSI) technology uses a paper substrate as a carrier. Solid or liquid samples are placed on the paper substrate surface, and a high-voltage electric current drives the solvent to dissolve analytes in the complex sample, causing them to migrate and ionize. Finally, an electrospray occurs at the tip of the paper substrate, enabling real-time online monitoring. The process is simple, efficient, and inexpensive. It is currently used to determine various compounds in a variety of complex samples, such as food, blood, urine, and biological tissue samples. Based on a similar ionization principle to paper spray-mass spectrometry, many other types of open-loop direct ionization techniques have also been developed, such as leaf spray, tissue spray, pen tip spray, and ballpoint pen spray. Specifically, the sample is loaded into the center of a small triangular paper substrate, a solvent (usually a mixture of methanol and water) is added, and a DC voltage is applied. Driven by the electricity, the analyte is extracted and transported by the solvent. When the solvent reaches the tip of the paper, it is electrosprayed under the influence of a strong electric field and enters the mass spectrometer for analysis. With the increasing analytical requirements of paper spray mass spectrometry (PSMS), more and more new paper spray methods have been developed, such as solid-phase extraction paper spray, zero-volt paper spray, electrostatic paper spray, microfluidic paper spray, and various paper-based modified paper spray methods. These methods are currently widely used in many fields. However, the limited types of paper available on the market and the diverse and complex types of oilfield pollutants limit the application of PMS in oilfield pollution detection. Therefore, it is necessary to modify the paper base to meet different experimental needs.

[0003] The development of modifications to paper-based materials is receiving increasing attention. To date, various porous materials, such as graphene, MXene, metal oxide nanoparticles, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and polymeric ionic liquids, have been used in the synthesis of functionalized paper-based materials.

[0004] For example, CN106970138B discloses a paper base modified with metal oxide nanoparticles and its application in sample detection. The paper base modified with metal oxide nanoparticles is prepared by the following method: 0.5-1g of Co3O4 nanoparticles are weighed, ground for 20-30 minutes, dispersed in 30-50mL of anhydrous ethanol, and stirred for 10-20 minutes to obtain a Co3O4 dispersion. Chromatographic paper is laid flat on a polytetrafluoroethylene (PTFE) plate with uniform voids underneath for filtering the solution. The Co3O4 dispersion is uniformly dispersed on the PTFE plate and allowed to stand at room temperature for 8-10 hours until the anhydrous ethanol solution has completely evaporated, resulting in a dry paper base modified with metal oxide nanoparticles. Furthermore, this patent describes the use of paper spray mass spectrometry to detect prohibited dyes in children's toy samples using a paper substrate modified with dried metal oxide nanoparticles. The specific steps include: cutting a triangular piece from the metal oxide nanoparticle-modified paper substrate; loading the children's toy sample onto the triangular paper substrate; clamping the base of the triangular paper substrate with a metal clip connected to an external high-voltage power supply; and placing the triangular paper substrate near the sample inlet of the mass spectrometer detector. An extraction solvent is then added dropwise to the triangular paper substrate, and high pressure is applied. The extraction solvent extracts the prohibited dye components from the children's toy sample, forming an electrospray at the tip of the triangular paper substrate, and the mass spectrometer detector receives a corresponding response signal. However, in this patent, the metal oxide nanoparticle-modified paper substrate has limited adsorption capacity, and its detection sensitivity and extraction capacity for complex organic compounds are not yet sufficient.

[0005] CN104849370B discloses a method for enriching and analyzing phenolic substances in vegetable oils using a filter paper-supported benzylimidazole solid-phase microextraction membrane, belonging to the field of trace organic phenolic substance detection technology in vegetable oils. The technical solution of this patent includes steps such as plotting a standard curve, enriching and analyzing the sample to be tested, and preparing the filter paper-supported benzylimidazole solid-phase microextraction membrane. The preparation process of the benzylimidazole solid-phase microextraction membrane supported on filter paper is as follows: 25 mmol of benzylimidazole and 25 mmol of 3-chloropropyltriethoxysilane are placed in a round-bottom flask and stirred at 80℃ for 24 h to obtain benzylimidazole ionic liquid. The filter paper is cut into strips and washed with acetone 5-6 times and dried at room temperature. The filter paper is then sprayed with the same mass of distilled water and placed in a round-bottom flask. 5 mL of benzylimidazole ionic liquid is added, and 40 mL of toluene and 10 mL of anhydrous ethanol are used as solvents. The mixture is heated and stirred under reflux at 105℃ for 24 h. After cooling to room temperature, the filter paper is washed 3 times with a mixed solution of toluene and anhydrous ethanol at a volume ratio of 4:1, and then washed 3 times with anhydrous ethanol. Finally, the filter paper is placed in a drying oven and dried at 60℃ for 10 h to obtain the benzylimidazole solid-phase microextraction membrane supported on filter paper. However, the patent still has some drawbacks. First, the filter paper is not heat-resistant and is flammable above 200°C, making it impossible to extract high-temperature products. Second, the filter paper itself has poor adsorption capacity, and the adsorbed organic molecules are easy to escape again, leading to deviations in experimental data. Furthermore, the loaded benzylimidazole is expensive and not conducive to large-scale preparation, and this paper-based material is not resistant to acids and alkalis or high temperatures and cannot be recycled.

[0006] However, existing paper-based materials suffer from drawbacks such as low extraction efficiency, poor selectivity, poor stability, and limited lifespan. Therefore, addressing the issues of low extraction efficiency, poor stability, and low recyclability in functionalized paper-based materials has become an urgent problem to be solved. Summary of the Invention

[0007] To address the problems of existing technologies, this invention provides a nitrogen-doped carbon-modified graphene paper-based material with excellent extraction capability, stability, and separation performance. The preparation process of this graphene paper-based material is simple and controllable. It is not only resistant to acids and alkalis and high-temperature detection environments, but also possesses high extraction efficiency. This overcomes the shortcomings of existing substrate materials, such as high cost, poor adsorption capacity, poor high-temperature resistance, and inability to be repeatedly recycled. Therefore, it is suitable for the application of paper spray extraction technology in oilfield pollution detection.

[0008] The technical solution of the present invention is as follows:

[0009] This invention provides a nitrogen-doped carbon-modified graphene paper-based material, wherein the graphene paper is nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous nano-carbon, wherein the mass percentage of the nitrogen-doped porous nano-carbon is 5-30%, based on the total mass of the nitrogen-doped carbon-modified graphene paper-based material.

[0010] Furthermore, the specific surface area of ​​the nitrogen-doped carbon-modified graphene paper-based material is 50-400 cm². 2 / g.

[0011] More preferably, the nitrogen-doped porous carbon nanotubes have a mass percentage of 5-20%, based on the total mass of the graphene paper-based material modified with the nitrogen-doped carbon.

[0012] Furthermore, in the nitrogen-boron co-doped graphene paper, the molar ratio of nitrogen to boron is 2:1.

[0013] Furthermore, the nitrogen-doped carbon-modified graphene paper-based material exhibits the characteristic X-ray diffraction peaks of reduced graphene (RGO) at 26°±0.2.

[0014] Furthermore, the nitrogen-doped carbon-modified graphene paper-based material exhibits absorption peaks of nitrogen-doped porous carbon nanofibers at wavelengths of 1574, 1489, 1303, and 1142, representing C=N, CN, NN, and C=C.

[0015] Furthermore, the area of ​​the nitrogen-doped carbon-modified graphene paper-based material is completely controllable, and the thickness is between 2 and 5 μm.

[0016] The present invention also provides a method for preparing the aforementioned nitrogen-doped carbon-modified graphene paper-based material, the method comprising the following steps:

[0017] Step 1: Prepare graphene oxide solution (GO);

[0018] Step 2: Preparation of ionic liquid (IL) modified graphene oxide paper (IL-GOP);

[0019] The graphene oxide solution obtained in step 1 is mixed with an ionic liquid solution and coated onto a substrate. After acid treatment, peeling, and drying, the IL-GOP can be obtained.

[0020] Step 3: Prepare Cu-MOF (IL-GOP@Cu-MOF) supported on graphene oxide paper modified with ionic liquid;

[0021] The IL-GOP obtained in step 2 was cut into small paper pieces, immersed in a mixed solution of copper salt and organic ligand, incubated at room temperature for 3-6 hours, washed and dried to obtain the precursor IL-GOP@Cu-MOF;

[0022] Step 4: Prepare nitrogen-doped carbon-coated copper nanoparticle-modified nitrogen-boron co-doped graphene paper (N,B-GP@CuNPs-NC);

[0023] The precursor IL-GOP@Cu-MOF obtained in step 3 was placed in a tube furnace and pyrolyzed and calcined at 500-1000°C for 1-3 hours under an inert atmosphere to obtain the N,B-GP@Cu NPs-NC.

[0024] Step 5: Prepare nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper (N,B-GP@NC);

[0025] In step 4, N,B-GP@Cu NPs-NC is thoroughly washed with acid to remove Cu nanoparticles (NPs) to obtain nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper (N,B-GP@NC), which is the nitrogen-doped carbon modified graphene paper-based material.

[0026] Furthermore, in step 1, the concentration of the graphene oxide solution is 2-7 mg / mL.

[0027] Furthermore, in step 1, the graphene oxide solution is obtained using expanded graphite as raw material via the Hummer method.

[0028] Furthermore, in step 1, the Hummer method specifically includes the following steps:

[0029] Step S1: After the expanded graphite powder is oxidized and exfoliated by strong acid, an acidic initial solution of graphene oxide is obtained.

[0030] Step S2: Wash the initial graphene oxide solution repeatedly with ultrapure water until it becomes neutral;

[0031] Step S3: After washing the initial graphene oxide solution to neutral, mix it thoroughly and centrifuge to remove carbon black, to obtain the graphene oxide solution from step 1.

[0032] Further, in step S1, the strong acid includes at least one of sulfuric acid and nitric acid.

[0033] Furthermore, in step 2, the concentration of the graphene oxide solution is 2-7 mg / mL.

[0034] Furthermore, in step 2, the concentration of the ionic liquid solution is 2-5 mM.

[0035] Further, in step 2, the ionic liquid is at least one of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), 1-vinyl-3-ethylimidazolium tetrafluoroborate, or 1-butyl-3-methylimidazolium hexafluorophosphate.

[0036] Further, in step 2, the molar ratio of the graphene oxide solution to the ionic liquid solution is 20:1 to 5:1.

[0037] Furthermore, in step 2, the substrate is a smooth and clean glass substrate.

[0038] Furthermore, in step 2, the graphene oxide solution is mixed with the ionic liquid solution, coated onto the substrate, and then allowed to air dry naturally.

[0039] Furthermore, in step 2, the acid treatment is carried out in a 0.2 mol / L 37% concentrated hydrochloric acid solution.

[0040] Furthermore, in step 3, the IL-GOP is cut into paper pieces with a size of 1×3cm.

[0041] Furthermore, in step 3, the copper salt includes copper nitrate trihydrate.

[0042] Furthermore, in step 3, the organic ligand includes 1,2,4-triazole.

[0043] Further, in step 3, the mass ratio of the copper salt to the organic ligand is 1:1 to 1:8.

[0044] Further, in step 3, the mixed solution is obtained by dissolving 3 mmol of copper nitrate trihydrate and 24 mmol of 1,2,4-triazole in 60 mL of deionized water.

[0045] Further, in step 4, the precursor IL-GOP@Cu-MOF is IL-GOP@Cutrz. Here, IL-GOP represents ionic liquid-modified graphene oxide paper, and Cutrz represents a copper-based metal-organic framework.

[0046] In step 4, the Cutrz is calcined in situ at high temperature in an inert atmosphere to generate nitrogen-doped porous carbon nanoparticles coated with copper nanoparticles. The copper nanoparticles are uniformly embedded in the surface of the graphene paper. At the same time, the graphene oxide paper is further completely reduced at high temperature to obtain nitrogen-boron co-doped graphene paper (N,B-GP). This allows the nitrogen-doped porous carbon nanoparticles coated with copper nanoparticles (Cu NPs-NC) to modify the nitrogen-boron co-doped graphene paper (N,B-GP), thus obtaining N,B-GP@Cu NPs-NC.

[0047] Furthermore, in step 5, the pickling is performed using at least one of ferric chloride and nitric acid.

[0048] This invention also provides the use of the aforementioned nitrogen-doped carbon-modified graphene paper-based material for paper spray extraction-ionization mass spectrometry (SPME-MS), wherein the paper spray extraction-ionization mass spectrometry is used to detect benzene series compounds in wastewater, and the detection includes the following steps:

[0049] Step T1: Cut the nitrogen-doped carbon-modified graphene paper-based material into triangles, and then immerse the nitrogen-doped carbon-modified graphene paper-based material into a sample solution containing benzene compounds, so that the benzene compounds are adsorbed onto the nitrogen-doped carbon-modified graphene paper-based material.

[0050] Step T2: After thoroughly drying the nitrogen-doped carbon-modified graphene paper-based material, wash it with deionized water to remove benzene compounds adsorbed on the surface of the nitrogen-doped carbon-modified graphene paper-based material, and then dry it to obtain N,B-GP@NC adsorbed with benzene compounds.

[0051] Then, the benzene series compounds are eluted from N,B-GP@NC by continuously adding elution solvent. The benzene series compounds to be tested are ionized by an external power supply and then detected by a mass spectrometer.

[0052] Further, in step T1, the nitrogen-doped carbon-modified graphene paper-based material is immersed in a sample solution containing benzene compounds for 5 minutes. Because nitrogen-doped porous carbon nanotubes have a good specific surface area and active sites, benzene compounds can be effectively adsorbed onto the nitrogen-doped carbon-modified graphene paper-based material, achieving their extraction and enrichment.

[0053] Further, in step T2, paper spray mass spectrometry is used to detect sample solutions containing benzene series compounds of different concentrations (1nM-1000nM) and internal standards of the same concentration (20μM). A standard curve is obtained by plotting the ratio of the concentrations of benzene series compounds to the internal standard on the x-axis and the ratio of the intensity of the detected benzene series compounds to the intensity of the internal standard sample on the y-axis.

[0054] Further, in step T2, the nitrogen-doped carbon-modified graphene paper-based material is washed with deionized water for 15 seconds.

[0055] Furthermore, the elution solvent is an elution solvent commonly used in the art, such as at least one of dichloromethane, methanol, and formic acid. For example, a mixture of dichloromethane and methanol, or a mixture of dichloromethane and formic acid, etc., and the specific mixing ratio can be adjusted according to the properties of the benzene series compound to be tested.

[0056] Further, in step T2, the specific operation is as follows: the bottom edge of the triangular nitrogen-doped carbon-modified graphene paper-based material is clamped with a metal clip, the metal clip is connected to an external high-voltage power supply, and the triangular nitrogen-doped carbon-modified graphene paper-based material is placed near the injection port of the mass spectrometer detector; an elution solvent is dropped onto the triangular nitrogen-doped carbon-modified graphene paper-based material, high pressure is applied, the elution solvent extracts benzene compounds in the triangular nitrogen-doped carbon-modified graphene paper-based material, and an electrospray is formed at the tip of the triangular nitrogen-doped carbon-modified graphene paper-based material, and the mass spectrometer detector obtains a corresponding response signal.

[0057] Furthermore, the mass spectrometry conditions of the mass spectrometer detector are set as follows:

[0058] Capillary voltage: 3.2kV;

[0059] Extraction voltage: 3V;

[0060] RF lens voltage: 0.1V;

[0061] Ion source temperature: 120℃;

[0062] Desolvation gas temperature: 350℃.

[0063] The present invention has the following significant technical effects:

[0064] 1. This invention uses graphene oxide solution and ionic liquid as raw materials to prepare IL-GOP, and further grows Cutrz in situ on IL-GOP. The N,B-GP@NC material prepared with Cutrz as a precursor has high stability, good extraction performance and separation performance.

[0065] 2. The N,B-GP@NC material prepared by this invention has a large specific surface area (50-400 cm²). 2 / g), nitrogen-doped porous carbon nanotubes have excellent adsorption properties, which can greatly extract volatile benzene series organic molecules and prevent the adsorbed molecules from leaking out; in addition, nitrogen-doped porous carbon nanotubes can withstand high temperatures up to 500°C. Therefore, the N,B-GP@NC of the present invention can extract various organic molecules in a wide range of extraction temperatures, and also has the ability to extract non-volatile high-boiling-point organic compounds.

[0066] 3. Since the paper-based material is a high-temperature annealed and acid-washed product, it can withstand acids, alkalis and high temperatures. Therefore, the extracted N,B-GP@NC can be washed away by acid and alkali washing, and then dried at high temperature to remove the solvent and maintain its porosity again, so it can be recycled repeatedly.

[0067] 4. The N,B-GP@NC material prepared by this invention is generated in situ by high-temperature pyrolysis in an inert atmosphere. It has high stability and large specific surface area, which is due to the high stability of N,B-GP, the large porosity of NC, the synergistic effect of multiple sites, and its unique structure and mechanical properties.

[0068] 5. This invention combines high-performance functionalized graphene paper with N-doped porous carbon, opening up a new avenue for the rapid and effective detection of pollutants in oilfield wastewater and providing a novel approach to the modification of paper using paper spray extraction correction ionization mass spectrometry technology. This is of great significance for the pollution control of water resources in the oilfield ecological environment.

[0069] 6. The wrinkled and N,B-doped GP synthesized in this invention not only has a superior surface area to support high-load functional nanomaterials, but also provides abundant exposed anchoring sites for the growth of Cutrz nanocrystals on it.

[0070] 7. Porous carbon nanomaterials possess excellent physicochemical properties, including large specific surface area, high thermal stability, good mechanical properties, and scalable low-cost synthesis, enabling them to maintain stable extraction capabilities in harsh environments. Graphene paper has a large specific surface area, high chemical stability, and unique tensile strength due to its macroscopic fibrous structure. Its surface also contains abundant oxygen functional groups, which facilitates functionalization and makes it promising for applications in paper spray extraction correction ionization mass spectrometry. GP exhibits excellent thermal and solvent stability, as well as superior surface modification properties, thus holding great potential as a novel paper-based material. Directly constructing porous carbon coating materials through calcination of precursors can further provide new functions and possibilities. However, the rational design and engineered assembly of functionalized paper-based materials on GP without sacrificing its inherent advantages has been quite limited to date. Metal-organic frameworks (MOFs) are an emerging class of porous materials that exhibit significant advantages as precursors due to their highly diverse chemical compositions and the formation of customized structures. Using IL-GOP@Cu-MOF as a precursor, porous nano-carbon compounds can be generated in situ through high-temperature calcination in an inert atmosphere. MOF-derived porous carbon nanotubes also possess the excellent properties of MOF-derived materials, such as tunable chemical structure, large specific surface area, uniform pore distribution, and diverse morphology. This makes MOF-derived microporous carbon nanotubes an ideal candidate material for functionalized paper-based materials. Attached Figure Description

[0071] Figure 1 This is a scanning electron microscope image of the IL-GOP prepared in Example 1 of the present invention.

[0072] Figure 2 The image shows a scanning electron microscope image of IL-GP@Cutrz prepared in Example 1 of this invention.

[0073] Figure 3 A scanning electron microscope image of N,B-GP@Cu NP-NC prepared in Example 1 of this invention.

[0074] Figure 4 A scanning electron microscope of N,B-GP@NC prepared in Example 1 of the present invention.

[0075] Figure 5 The diffraction peak positions of ionic liquid-modified graphene oxide in the X-ray diffraction pattern of IL-GOP prepared in Example 1 of this invention; and the diffraction peak positions of reduced graphene in the X-ray diffraction pattern of N,B-GP@Cu NPs-NC prepared in Example 1.

[0076] Figure 6 Infrared spectra of IL-GOP, N,B-GP@Cu NPs-NC and N,B-GP@NC prepared in Example 1 of this invention.

[0077] Figure 7 This is a nitrogen adsorption curve of N,B-GP@NC in Example 1 of the present invention. Detailed Implementation

[0078] The technical solutions in the embodiments of the present invention will be clearly and completely described below. The described embodiments are only some embodiments of the present invention, and not all embodiments. All embodiments improved or replaced by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0079] Example 1

[0080] A nitrogen-doped carbon-modified graphene paper-based material is disclosed. The graphene paper is nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous carbon nanoparticles with a mass percentage of 18%. Based on the total mass of the nitrogen-doped carbon-modified graphene paper-based material, the specific surface area of ​​the material is 314 cm³. 2 / g.

[0081] The preparation method is as follows:

[0082] Step 1: Prepare graphene oxide solution (GO);

[0083] Graphene oxide (GO) was prepared using expanded graphite as raw material and a modified Hummer method.

[0084] Step 2: Preparation of ionic liquid (IL) modified graphene oxide paper (IL-GOP);

[0085] Mix the GO solution with 2 mM [BMIM]BF4 solution and coat it onto a smooth and clean glass substrate. Let it air dry naturally, treat it with 0.2 mol / L 37% concentrated hydrochloric acid solution, peel it off, and dry it to obtain IL-GOP.

[0086] Step 3: Prepare Cu-MOF (IL-GOP@Cu-MOF) supported on graphene oxide paper modified with ionic liquid;

[0087] After air drying, IL-GOP was cut into paper pieces with a size of 1×3cm, suspended in 60mL of deionized water containing 3mM Cu(NO3)2·3H2O and 24mmol 1,2,4-triazole, and incubated at room temperature for 4 hours. After washing and drying, the precursor IL-GOP@Cutrz was obtained.

[0088] Step 4: Prepare nitrogen-doped carbon-coated copper nanoparticle-modified nitrogen-boron co-doped graphene paper (N,B-GP@CuNPs-NC);

[0089] The precursor IL-GOP@Cutrz was then placed in a tube furnace and calcined under an argon atmosphere at a temperature of 700℃ for 2 hours. During the high-temperature pyrolysis process, Cutrz was converted into copper nanoparticles coated with N-doped porous carbon. The graphene paper modified with ionic liquid was further completely reduced at high temperature to obtain N,B-GP.

[0090] Step 5: Prepare nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper (N,B-GP@NC);

[0091] Subsequently, the N,B-GP@Cu NPs-NC from step 4 was washed with 5 mM FeCl3 to remove copper nanoparticles and obtain N-doped porous carbon (NC), which then modifies the GP with an ordered mesoporous carbon nanotube array (NC), thus obtaining N,B-GP@NC.

[0092] Figure 1 The image shows a scanning electron microscope image of the IL-GOP prepared in Example 1.

[0093] Figure 2 The image shows a scanning electron microscope image of the prepared IL-GP@Cutrz. Figure 2 The Cu-MOF can be seen densely growing on nitrogen-doped carbon-modified graphene paper.

[0094] Figure 3 Scanning electron microscope image of N,B-GP@Cu NP-NC prepared in Example 1. Figure 3 As can be seen, after IL-GOP@Cu-MOF is reduced by high-temperature pyrolysis, Cu nanoparticles (white dots) are uniformly embedded into the surface of graphene paper.

[0095] Figure 4 A scanning electron microscope of N,B-GP@NC prepared in Example 1. Figure 4 The results show that the N,B-GP@NC surface has many pores, exhibiting extremely high porosity. Because the N,B-GP@Cu NP-NC surface has numerous channels after acid removal, this greatly enhances its specific surface area, providing abundant sites for the extraction of organic matter.

[0096] Figure 5The diffraction peak positions of ionic liquid-modified graphene oxide in the X-ray diffraction pattern of IL-GOP prepared in Example 1, and the diffraction peak positions of reduced graphene in the X-ray diffraction pattern of N,B-GP@Cu NPs-NC prepared in Example 1. The nitrogen-doped carbon-modified graphene paper-based material shows the characteristic X-ray diffraction peaks of reduced graphene (RGO) at 26° ± 0.2.

[0097] Figure 6 Infrared spectra of IL-GOP, N,B-GP@Cu NPs-NC, and N,B-GP@NC prepared in Example 1. The nitrogen-doped carbon-modified graphene paper-based materials exhibit absorption peaks of nitrogen-doped porous carbon nanofibers at wavelengths of 1574, 1489, 1303, and 1142 nm, representing C=N, CN, NN, and C=C, respectively.

[0098] Figure 7 The nitrogen adsorption curve of N,B-GP@NC prepared in Example 1 is shown.

[0099] Example 2

[0100] A nitrogen-doped carbon-modified graphene paper-based material is disclosed. The graphene paper is nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous carbon nanoparticles with a mass percentage of 22%. Based on the total mass of the nitrogen-doped carbon-modified graphene paper-based material, the specific surface area of ​​the material is 343 cm³. 2 / g.

[0101] The preparation method is as follows:

[0102] Step 1: Prepare graphene oxide solution (GO);

[0103] Graphene oxide (GO) was prepared using expanded graphite as raw material and a modified Hummer method.

[0104] Step 2: Preparation of ionic liquid (IL) modified graphene oxide paper (IL-GOP);

[0105] Mix the GO solution with a 2mM ([BMIM]BF4) solution and coat it onto a smooth and clean glass substrate. Let it air dry naturally, treat it with a 0.2mol / L 37% concentrated hydrochloric acid solution, peel it off, and dry it to obtain IL-GOP.

[0106] Step 3: Prepare Cu-MOF (IL-GOP@Cu-MOF) supported on graphene oxide paper modified with ionic liquid;

[0107] After air drying, IL-GOP was cut into paper pieces with a size of 1×3cm, suspended in 60mL of deionized water containing 3mM Cu(NO3)2·3H2O and 24mmol 1,2,4-triazole, and incubated at room temperature for 4 hours. After washing and drying, the precursor IL-GOP@Cutrz was obtained.

[0108] Step 4: Prepare nitrogen-doped carbon-coated copper nanoparticle-modified nitrogen-boron co-doped graphene paper (N,B-GP@CuNPs-NC);

[0109] The precursor IL-GOP@Cutrz was then placed in a tube furnace and calcined under an argon atmosphere at a temperature of 800°C for 2 hours. During the high-temperature pyrolysis process, Cutrz was converted into copper nanoparticles coated with N-doped porous carbon. The graphene paper modified with ionic liquid was further completely reduced at high temperature to obtain N,B-GP.

[0110] Step 5: Prepare nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper (N,B-GP@NC);

[0111] Subsequently, the N,B-GP@Cu NPs-NC from step 4 was washed with 5 mM FeCl3 to remove copper nanoparticles and obtain N-doped porous carbon (NC), which then modifies the GP with an ordered mesoporous carbon nanotube array (NC), thus obtaining N,B-GP@NC.

[0112] Example 3

[0113] A nitrogen-doped carbon-modified graphene paper-based material is disclosed. The graphene paper is nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous carbon nanoparticles with a mass percentage of 28%. Based on the total mass of the nitrogen-doped carbon-modified graphene paper-based material, the specific surface area is 372 cm³. 2 / g.

[0114] The preparation method is as follows:

[0115] Step 1: Prepare graphene oxide solution (GO);

[0116] Graphene oxide (GO) was prepared using expanded graphite as a raw material and a modified Hummer method.

[0117] Step 2: Preparation of ionic liquid (IL) modified graphene oxide paper (IL-GOP);

[0118] Mix the GO solution with a 2mM ([BMIM]BF4) solution and coat it onto a smooth and clean glass substrate. Let it air dry naturally, treat it with a 0.2mol / L 37% concentrated hydrochloric acid solution, peel it off, and dry it to obtain IL-GOP.

[0119] Step 3: Prepare Cu-MOF (IL-GOP@Cu-MOF) supported on graphene oxide paper modified with ionic liquid;

[0120] After air drying, IL-GOP was cut into paper pieces with a size of 1×3cm, suspended in 60mL of deionized water containing 3mM Cu(NO3)2·3H2O and 24mmol 1,2,4-triazole, and incubated at room temperature for 4 hours. After washing and drying, the precursor IL-GOP@Cutrz was obtained.

[0121] Step 4: Prepare nitrogen-doped carbon-coated copper nanoparticle-modified nitrogen-boron co-doped graphene paper (N,B-GP@CuNPs-NC);

[0122] The precursor IL-GOP@Cutrz was then placed in a tube furnace and calcined under an argon atmosphere at a temperature of 900℃ for 2 hours. During the high-temperature pyrolysis process, Cutrz was converted into copper nanoparticles coated with N-doped porous carbon.

[0123] Step 5: Prepare nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper (N,B-GP@NC);

[0124] Subsequently, the N,B-GP@Cu NPs-NC from step 4 was washed with 5 mM FeCl3 to remove copper nanoparticles and obtain N-doped porous carbon (NC), which then modifies the GP with an ordered mesoporous carbon nanotube array (NC), thus obtaining N,B-GP@NC.

[0125] Test case

[0126] The nitrogen-doped carbon-modified graphene paper-based material obtained in Example 1 was applied to paper spray extraction-ionization mass spectrometry to detect benzene series compounds in wastewater, including the following steps:

[0127] Step T1: Cut the nitrogen-doped carbon-modified graphene paper-based material into triangles, and then immerse the nitrogen-doped carbon-modified graphene paper-based material in three sample solutions containing benzene compounds (including domestic sewage, laboratory wastewater and oilfield wastewater with concentrations of 5 μg / L and 255 μg / L) for 5 min, so that the benzene compounds are adsorbed on the nitrogen-doped carbon-modified graphene paper-based material.

[0128] Step T2: After thoroughly drying the nitrogen-doped carbon-modified graphene paper-based material, wash it with deionized water for 15 seconds to remove benzene compounds adsorbed on the surface of the nitrogen-doped carbon-modified graphene paper-based material. Then dry it to obtain N,B-GP@NC adsorbed with benzene compounds.

[0129] Then, benzene compounds were eluted from N,B-GP@NC by continuous dropwise addition of elution solvent. The benzene compounds were then ionized by an external power source and detected by a mass spectrometer.

[0130] In this process, the bottom edge of a triangular nitrogen-doped carbon-modified graphene paper-based material is held by a metal clip, which is connected to an external high-voltage power supply. The triangular nitrogen-doped carbon-modified graphene paper-based material is placed near the sample inlet of the mass spectrometer detector. An elution solvent is dropped onto the triangular nitrogen-doped carbon-modified graphene paper-based material, and high pressure is applied. The elution solvent extracts benzene compounds from the triangular nitrogen-doped carbon-modified graphene paper-based material, and an electrospray is formed at the tip of the triangular nitrogen-doped carbon-modified graphene paper-based material. The mass spectrometer detector obtains the corresponding response signal (as shown in Table 1).

[0131] The mass spectrometry conditions for the mass spectrometer detector are set as follows:

[0132] Capillary voltage: 3.2kV;

[0133] Extraction voltage: 3V;

[0134] RF lens voltage: 0.1V;

[0135] Ion source temperature: 120℃;

[0136] Desolvation gas temperature: 350℃.

[0137] Table 1. Determination results of benzene series compounds in actual water samples.

[0138]

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-modified graphene paper-based material, characterized in that, The method includes the following steps: Step 1: Prepare graphene oxide solution; Step 2: Preparation of ionic liquid-modified graphene oxide paper IL-GOP; The graphene oxide solution obtained in step 1 is mixed with an ionic liquid solution and coated onto a substrate. After acid treatment, peeling, and drying, the IL-GOP can be obtained. Step 3: Prepare Cu-MOF supported on ionic liquid-modified graphene oxide paper; The IL-GOP obtained in step 2 is cut into small paper pieces, immersed in a mixed solution of copper salt and organic ligand, incubated at room temperature for 3-6 hours, washed and dried to obtain the precursor - ionic liquid modified graphene oxide paper-supported Cu-MOF, namely IL-GOP@Cu-MOF. Step 4: Prepare nitrogen-boron co-doped graphene paper modified with nitrogen-doped carbon-coated copper nanoparticles; The precursor IL-GOP@Cu-MOF obtained in step 3 is placed in a tube furnace and pyrolyzed and calcined at 500-1000℃ for 1-3 hours under an inert atmosphere to obtain N,B-GP@Cu NPs-NC, i.e. N,B-GP@Cu NPs-NC. Step 5: Prepare nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper; The N,B-GP@Cu NPs-NC from step 4 is thoroughly washed with acid to remove Cu nanoparticles, resulting in nitrogen-doped porous carbon nanofiber modified nitrogen-boron co-doped graphene paper N,B-GP@NC, which is the nitrogen-doped carbon modified graphene paper-based material.

2. The preparation method according to claim 1, characterized in that, The concentration of the graphene oxide solution is 2-7 mg / mL.

3. The preparation method according to claim 1 or 2, characterized in that, In step 2, the concentration of the ionic liquid solution is 2-5 mM.

4. The preparation method according to claim 3, characterized in that, In step 2, the ionic liquid is at least one of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-ethylimidazolium tetrafluoroborate, or 1-butyl-3-methylimidazolium hexafluorophosphate.

5. The preparation method according to claim 4, characterized in that, In step 2, the molar ratio of the graphene oxide solution to the ionic liquid solution is 20:1 to 5:

1.

6. The preparation method according to claim 5, characterized in that, In step 3, the mixed solution is obtained by dissolving 3 mmol of copper nitrate trihydrate and 24 mmol of 1,2,4-triazole in 60 mL of deionized water.

7. A nitrogen-doped carbon-modified graphene paper-based material prepared by the method according to any one of claims 1 to 6, characterized in that, The graphene paper is nitrogen-boron co-doped graphene paper, and the nitrogen-doped carbon is nitrogen-doped porous nano-carbon. The mass percentage of the nitrogen-doped porous nano-carbon is 5-30%, based on the total mass of the graphene paper-based material modified with the nitrogen-doped carbon.

8. The nitrogen-doped carbon-modified graphene paper-based material according to claim 7, characterized in that, The nitrogen-doped carbon-modified graphene paper-based material has a specific surface area of ​​50-400 cm². 2 / g.

9. The nitrogen-doped carbon-modified graphene paper-based material according to claim 8, characterized in that, The nitrogen-doped carbon-modified graphene paper-based material exhibits the characteristic X-ray diffraction peaks of reduced graphene at 26°±0.

2.

10. Use of a nitrogen-doped carbon-modified graphene paper-based material according to any one of claims 7 to 9 for paper spray extraction-ionization mass spectrometry, wherein the paper spray extraction-ionization mass spectrometry is used to detect benzene series compounds in wastewater.

Images