A porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material, a preparation method and application thereof

Abstract

The present application relates to a kind of preparation and its application based on 5,10,15,20-tetraaminophenyl nickel porphyrin composite material. Due to the excellent electron transport capacity of multi-walled carbon nanotubes and the good synergistic effect of MWCNTs and composite COF-366-Ni, COF-366-Ni@MWCNTs has very low detection limit for toluene gas at room temperature, and has good selectivity and stability. The present application obtains a sensor with excellent gas sensing performance, which has good responsiveness, high sensitivity, fast response and recovery time, good reproducibility and strong selectivity for different concentrations of toluene. It is simple to prepare, low in production cost, green and environmentally friendly, and can be used for detection of low concentration toluene in the environment.

Description

Technical Field

[0001] This invention relates to the field of preparation and application technology of interfacial reactions of composite materials, and particularly to a method for preparing a porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material (COF-366-Ni@MWCNTs) and its application in detecting toluene. Background Technology

[0002] Toluene is a volatile organic compound, a colorless, volatile liquid with a characteristic aromatic odor. It is miscible with ethanol, ether, acetone, chloroform, carbon disulfide, and glacial acetic acid, and very slightly soluble in water. It is flammable, and its vapor can form explosive mixtures with air. In indoor pollution, toluene primarily originates from the paint in furniture. Toluene is toxic and can be harmful to humans through the respiratory tract. Toluene, along with formaldehyde, constitutes the most significant source of modern indoor pollution. Toluene primarily harms the human body through inhalation, ingestion, and skin absorption, and is irritating to the skin and mucous membranes. Inhaling high concentrations of toluene in a short period can cause dizziness, nausea, vomiting, and even coma. Studies have found that the concentration of toluene in the breath of non-small cell lung cancer patients is closely related to smoking behavior and is several orders of magnitude higher than that in the breath of healthy individuals. Therefore, in non-invasive medical diagnosis, simple breath sensors play a crucial role, avoiding inconvenience and discomfort for the patient and eliminating the need for expensive invasive testing equipment.

[0003] Currently, methods such as gas chromatography, activated carbon adsorption, and colorimetry are commonly used to detect toluene gas in the environment. However, their large size, high cost, and inability to detect in real time limit their application in practical situations. Meanwhile, various chemical impedance gas sensors based on metal oxide semiconductors typically require high operating temperatures, which restricts their practical application. For metal oxide gas sensors, ambient humidity is also a challenge, as it can produce erroneous responses and unreliable results. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a covalent organic framework-multi-walled carbon nanotube composite material for detecting toluene, characterized by the following steps: Multi-walled carbon nanotubes (MWCNTs) are uniformly dissolved in ethanol by ultrasonication for 4 h; subsequently, 5,10,15,20-tetraaminophenyl nickel porphyrin (Ni-TAPP), terephthalaldehyde, m-trimethylbenzene, and acetic acid are added to the MWCNTs / ethanol dispersion in the carbon nanotubes at high temperature; followed by a three-cycle degassing process of "vacuuming-freezing-thawing"; then, a heat-resistant glass tube is flame-sealed, and the system is heated at 110-130 °C for 60-84 °C. After the reaction was completed, the crude product was obtained by centrifugation, and then washed sequentially with 1,4-dioxane, tetrahydrofuran and acetone to obtain the purified product COF-366-Ni@MWCNTs composite material, wherein the mass ratio of MWCNTs, Ni-TAPP and terephthalaldehyde was 1:2.2:0.9-1; and the volume ratio of anhydrous ethanol, mesitylene and acetic acid was 10:0.5:0.1-0.3.

[0005] Among them, the porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material, abbreviated as COF-366-Ni@MWCNTs, has the structural formula shown in Formula 1; Formula 1 The application of the porphyrin-based covalent organic framework multi-walled carbon nanotube composite material in the preparation of toluene gas sensors.

[0006] A gas sensor for detecting toluene synthesizes a COF-366-Ni@MWCNT composite material through in-situ growth and loads it onto the surface of the hand-drawn interdigitated electrode, thereby achieving highly sensitive detection of toluene gas.

[0007] The method for preparing the gas sensor for detecting toluene is as follows: (1) The experiment used a 6B pencil to directly draw the flexible interdigitated electrodes on a standard A4 office paper. The hand-drawn interdigitated electrodes consisted of 6 pairs of graphite electrodes with the following dimensions: electrode width 1.0 mm, spacing 0.85 mm, and overlap length 7.5 mm. Subsequently, the composite material was dissolved in a mixed solution of ethanol and water in a certain proportion to prepare a solution of COF-366-Ni@MWCNTs with a concentration of 5 mg / mL; (2) The prepared solution of COF-366-Ni@MWCNTs with a concentration of 5 mg / mL was carefully dropped onto the hand-drawn interdigital electrode. After drying, the composite material was tightly attached to the surface of the interdigital electrode to form a toluene gas sensor.

[0008] The present invention provides a gas sensor for the determination of toluene. The material used is a porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material COF-366-Ni@MWCNTs, which is composed of Ni-TAPP, terephthalaldehyde, and MWCNTs. COF-366-Ni@MWCNTs exhibits good responsiveness, high sensitivity, fast response and recovery time, good reproducibility, and strong selectivity for toluene in the range of 1-500 ppm at room temperature. This covalent organic framework carbon nanotube composite material demonstrates excellent gas-sensing performance.

[0009] Advantages of this invention: (1) The method for preparing nanomaterials for detecting toluene used in this invention is simple and has relatively low energy consumption; (2) Due to the excellent electron transport capability of multi-walled carbon nanotubes and the good synergistic effect of MWCNTs and the composite material COF-366-Ni, this gas sensor has an extremely low detection limit for toluene gas at room temperature, while also exhibiting good selectivity and stability. In addition, the paper-based gas sensor can still detect toluene gas sensitively, efficiently, and stably under mechanical deformation of different intensities. Attached Figure Description

[0010] Figure 1 This is a scanning electron microscope cross-sectional image of COF-366-Ni@MWCNTs; Figure 2 This is the Fourier transform infrared spectrum of COF-366-Ni@MWCNTs; Figure 3 This is the X-ray photoelectron spectroscopy (XPS) spectrum of COF-366-Ni@MWCNTs; Figure 4 This is the long-term stability curve of the toluene gas sensor against 100 ppm toluene over 100 days (at room temperature). Figure 5 This is the response / recovery time curve of the toluene gas sensor to toluene (at room temperature). Figure 6 This is the reproducibility test curve of the toluene gas sensor (at room temperature). Figure 7 This is the response-time curve of a toluene gas sensor to different concentrations of toluene (at room temperature). Figure 8 This is a schematic diagram of the selectivity of a toluene gas sensor for different gases.

[0011] Specific implementation steps

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. However, the content of the present invention is not limited to the following embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0013] It should be understood that the terminology used in the examples of this invention is for describing specific implementations and not for limiting the scope of protection of this invention. Methods not specified in the following examples are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0014] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, the two endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the prior art mastery of those skilled in the art and the description of the present invention. The present invention may also be implemented using any prior art methods, devices and materials similar to or equivalent to the methods, devices and materials described in the embodiments of the present invention.

[0015] Example 1: Preparation method of covalent organic framework-multi-walled carbon nanotube composite material COF-366-Ni@MWCNTs: 1.1: (1) MWCNTs (6.2 mg) were uniformly dissolved in 10.0 mL of ethanol by sonication for 4 h. Subsequently, Ni-TAPP (13.5 mg), terephthalaldehyde (5.6 mg), m-trimethylbenzene (0.5 mL), and acetic acid (0.1 mL, 6 M) were added to the MWCNTs / ethanol dispersion in high-temperature carbon nanotubes. After three refrigeration-thawing cycles, it was flame-sealed. Then, it was heated at 120 °C for 72 h to form a deep purple COF-366-Ni@MWCNTs precipitate. Finally, the crude product was separated by centrifugation and then washed sequentially with 1,4-dioxane, tetrahydrofuran, and acetone to obtain the purified product COF-366-Ni@MWCNTs. (2) The obtained product was fully characterized. Figure 1 This is a scanning electron microscope cross-sectional image of COF-366-Ni@MWCNTs. The surface of the COF-366-Ni@MWCNTs composite material has a COF-366-Ni coating of approximately 2-3 nm, showing a bilayer structure with a crystalline and rough outer surface. Figure 2 As shown, the Fourier transform infrared spectrum reveals that, compared to the original material, the original multi-walled carbon nanotubes exhibit a higher density at 1632 cm⁻¹. -1The region exhibits a strong spectral band corresponding to the C=C stretching vibration. Conversely, the C=C peak in COF-366-Ni@MWCNTs redshifts to 1618 cm⁻¹. -1 This indicates that electron delocalization occurred due to π-π interactions. Simultaneously, the 1374, 1356, 984, and 799 cm⁻¹ values ​​of the COF-366-Ni@MWCNTs composite material... -1 New characteristic peaks of COF-366-Ni were also found at the surface, indicating that COF-366-Ni was successfully attached to the surface of MWCNTs. Figure 3 As shown, the XPS-measured spectra reveal the coexistence of C, N, O, and Ni elements in the COF-366-Ni@MWCNTs structure; 1.2: (1) MWCNTs (6.2 mg) were uniformly dissolved in 10.0 mL of ethanol by sonication for 4 h. Subsequently, Ni-TAPP (13.5 mg), terephthalaldehyde (6.7 mg), m-trimethylbenzene (0.5 mL), and acetic acid (0.1 mL, 6 M) were added to the MWCNTs / ethanol dispersion in high-temperature carbon nanotubes. After that, it was subjected to three refrigeration pump-thaw cycles. Then, it was flame-sealed. Then, it was heated at 120 °C for 72 h to form a deep purple COF-366-Ni@MWCNTs precipitate. Finally, the crude product was separated by centrifugation and then washed with 1,4-dioxane, tetrahydrofuran, and acetone in sequence to obtain the purified product COF-366-Ni@MWCNTs; (2) The obtained composite product was fully characterized: the results were consistent with 1.1; 1.3: (1) MWCNTs (6.2 mg) were uniformly dissolved in 10.0 mL of ethanol by sonication for 4 h. Subsequently, Ni-TAPP (13.5 mg), terephthalaldehyde (8.0 mg), m-trimethylbenzene (0.5 mL), and acetic acid (0.1 mL, 6 M) were added to the MWCNTs / ethanol dispersion in high-temperature carbon nanotubes. After that, it was subjected to three refrigeration pump-thaw cycles. Then, it was flame-sealed. Then, it was heated at 120 °C for 72 h to form a deep purple COF-366-Ni@MWCNTs precipitate. Finally, the crude product was separated by centrifugation and then washed with 1,4-dioxane, tetrahydrofuran, and acetone in sequence to obtain the purified product COF-366-Ni@MWCNTs; (2) The obtained composite product was fully characterized: the results were consistent with 1.1.

[0016] Example 2: Fabrication of a toluene gas sensor The composite material was dissolved in a mixed solution of ethanol and water in a certain proportion to prepare a COF-366-Ni@MWCNTs solution with a concentration of 5 mg / mL. The prepared solution was carefully dropped onto a hand-drawn interdigitated electrode. After drying, the composite material was tightly adhered to the surface of the interdigitated electrode to form a toluene gas sensor.

[0017] Example 3 Performance Testing of Toluene Gas Sensor A gas-sensitive testing device was constructed using the covalent organic framework-multi-walled carbon nanotube composite material COF-366-Ni@MWCNTs obtained in Example 2, and gas-sensitive testing experiments were conducted. The gas-sensitive performance was tested in a relatively mild environment (room temperature, ambient atmospheric pressure, and dry air) with a fixed bias voltage of 5 V between the two electrodes. The testing instrument used was an Agilent B290a precision source / measuring unit. Specifically, the gas sensor fabricated using COF-366-Ni@MWCNTs prepared in Example 2 was tested, and the test results were consistent; all were as shown in the figure. Figure 4-8 As shown. Figure 5 As shown, the response / recovery times are 32s and 116s, respectively; Figure 4 and Figure 6 As shown, the long-term stability of the COF-366-Ni@MWCNTs gas sensor over 100 days and its repeatability against 100, 200, and 500 ppb toluene are basically consistent, indicating that the gas sensor has good stability; Figure 7 As shown, the COF-366-Ni@MWCNTs gas sensor exhibits good response to toluene concentrations of 1-500 ppm, with a detection limit reaching 33 ppb; Figure 8 As shown, to determine the selectivity of the paper-based gas sensor, the sensor's response to toluene gas and various interfering gases was experimentally tested. By injecting interfering gases such as CO, CO2, NH3, acetone, methanol, NO2, and ethanol, it can be seen that COF-366-Ni@MWCNTsP exhibits the largest response to toluene among all test gases, demonstrating that the paper-based sensor has good selectivity for toluene gas.

[0018] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material, abbreviated as COF-366-Ni@MWCNTs, has the structural formula shown in Figure 1, and its preparation method includes the following steps: Multi-walled carbon nanotubes (MWCNTs) were uniformly dissolved in anhydrous ethanol by ultrasonication for 4-6 h. Subsequently, 5,10,15,20-tetraaminophenyl nickel porphyrin, terephthalaldehyde, m-trimethylbenzene, and acetic acid were added to the MCCNT / anhydrous ethanol dispersion in a heat-resistant glass tube. Degassing was then performed through three cycles of "evacuation-freezing-thawing." The heat-resistant glass tube was then flame-sealed and heated at 110-130 °C for 60-84 °C. After the reaction was completed, the crude product was obtained by centrifugation, and then washed sequentially with 1,4-dioxane, tetrahydrofuran and acetone to obtain the purified product COF-366-Ni@MWCNTs composite material, wherein the mass ratio of multi-walled carbon nanotubes, 5,10,15,20-tetraaminophenyl nickel porphyrin and terephthalaldehyde was 1:2.2:0.9-1.3; and the volume ratio of anhydrous ethanol, m-trimethylbenzene and acetic acid was 10:0.5:0.1-0.

3. Example 1.

2. The porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material according to claim 1, characterized in that: COF-366-Ni is tightly bonded to the multi-walled carbon nanotube, and a thin layer of COF-366-Ni with a thickness of 1.5-2.5 nm is deposited around the multi-walled carbon nanotube.

3. The method for preparing a porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material according to claim 1, characterized in that, The process includes the following steps: Multi-walled carbon nanotubes (MWCNTs) are uniformly dissolved in anhydrous ethanol by ultrasonication for 4-6 hours. Subsequently, 5,10,15,20-tetraaminophenyl nickel porphyrin, terephthalaldehyde, m-trimethylbenzene, and acetic acid are added to the MCCNT / anhydrous ethanol dispersion in a heat-resistant glass tube. Degassing is then performed through three cycles of "evacuation-freezing-thawing." The heat-resistant glass tube is then flame-sealed and heated at 110-130 °C for 60-84 °C. After the reaction was completed, the crude product was obtained by centrifugation, and then washed sequentially with 1,4-dioxane, tetrahydrofuran and acetone to obtain the purified product COF-366-Ni@MWCNTs composite material, in which the mass ratio of multi-walled carbon nanotubes, 5,10,15,20-tetraaminophenyl nickel porphyrin and terephthalaldehyde was 1:2.2:0.9-1.3; and the volume ratio of anhydrous ethanol, m-trimethylbenzene and acetic acid was 10:0.5:0.1-0.

3.

4. The use of the porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material according to claim 2, characterized in that: Within the concentration range of 1-500 ppm, the response current gradually decreases as the toluene concentration decreases.

5. The use of the porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material according to claim 4, characterized in that: The detection limit for toluene is 33 ppb.

6. The use of the porphyrin-based covalent organic framework-multi-walled carbon nanotube composite material according to claim 4, characterized in that: The response and recovery times to toluene were 32 s and 116 s, respectively.

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