Ammonia-sensitive materials based on covalent organic frameworks, their preparation methods and applications

Abstract

The present application relates to covalent organic framework-based ammonia-sensitive materials, and a preparation method and application thereof. The present application obtains metalized or hydrogen-modified covalent organic framework-based ammonia-sensitive materials by modifying transition metals or hydrogen on the covalent organic framework, and prepares the ammonia-sensitive materials into an ammonia detection device, which can realize high-sensitivity, high-selectivity and rapid-response NH3 sensing, and the ammonia detection device has excellent repeat stability, thereby providing a new material for the design of a high-performance ammonia detection device in the future.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and in particular to ammonia-sensitive materials based on covalent organic frameworks, their preparation methods, and applications. Background Technology

[0002] Ammonia, a colorless, odorless gas with a pungent smell, is widely used in chemical, light industry, fertilizer, pharmaceutical, and synthetic fiber industries, and can also be used as a biofuel. When ammonia is released into the air, it combines with nitrogen oxides (NOx) and sulfur oxides (SOx) to form PM2.5 particles, causing severe air pollution. Furthermore, ammonia not only corrodes and irritates human skin and mucous membranes, but also denatures tissue proteins and damages cells. Inhaling a certain amount of ammonia can induce poisoning symptoms, with severe cases leading to blindness or even death. Therefore, from the perspective of public health and environmental protection, real-time monitoring of ammonia is essential.

[0003] Currently, the main methods for measuring ammonia content in the air include optical methods, calorimetry, gas chromatography, and acoustic methods. These methods require specialized instruments and equipment, and suffer from problems such as high cost, large size, inconvenience of use, inability to monitor in real time, and difficulty in widespread application. In recent years, rapidly developing gas sensors can effectively overcome the problems of the above-mentioned traditional methods and are a promising method for ammonia detection. Ammonia sensors are mainly divided into semiconductor sensors, electrochemical sensors, optical sensors, and mass sensors. Among them, the Quartz Crystal Microbalance (QCM) gas sensor is a typical mass-type gas sensor. It is based on the mass sensitivity of piezoelectric quartz crystal wafers. A sensitive film material modified on the surface of the quartz crystal wafer captures the analyte gas, and the detection of the analyte gas is achieved by measuring the change in the frequency of the quartz crystal. Compared with other gas sensors, QCM-based sensors have the advantages of low cost, high sensitivity, fast response time, good selectivity, and room temperature operation. Therefore, they have received widespread attention from researchers in recent years and have been applied in various fields. However, the key to developing QCM-type ammonia sensors lies in developing high-performance ammonia-sensitive materials.

[0004] Currently, various materials have been used to fabricate QCM-type ammonia sensors, including metal oxides, polymers, and composite materials. Metal oxides include TiO2, ZnO2, SnO2, and Fe3O4. Commonly used polymers include polyaniline (PANI), polyvinyl acetate (PVAc), and polyacrylonitrile (PAN), all of which are conductive polymers with excellent chemical stability and gas sensitivity. Composite materials often combine oxides and polymers, or porous carbon materials and polymers. While these materials each have their advantages, they also face some drawbacks, such as complex preparation processes, limited structural adjustability, poor selectivity, low repeatability, high operating temperatures, and poor chemical stability. Therefore, further development of novel ammonia-sensitive materials is needed.

[0005] Covalent organic frameworks (COFs), as a new class of porous crystalline materials, have potential applications in many fields such as sensing, catalysis, and energy storage due to their low density, high stability, and tunable pore structure. However, currently, COFs are commonly used in fluorescence sensors and electrochemical gas sensors, and research on mass-type gas sensors is still in its early stages and faces challenges. Because COF structures often exhibit close packing or interleaving, the utilization rate of active sites is low or mass transfer is slow, thus failing to fully develop their performance. Therefore, it is necessary to design and synthesize COFs with different special morphologies to fully expose active sites and improve their performance for wider application. Therefore, there is an urgent need to design an ammonia-sensitive material using COFs to achieve specific detection of ammonia. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems of poor adjustability, high operating temperature, narrow response range of NH3 concentration and low sensitivity of the existing ammonia detection device.

[0007] To address the aforementioned technical problems, this invention synthesizes an activated product (H2-TPCOF) using 5,10,15,20-tetratetra(4-aminophenyl)porphyrin (TAPP) and 2,6-dicarboxypyridine (PCBA). Utilizing the coordination reaction principle, different transition metals are modified onto the covalent organic framework by forming coordination bonds between the nitrogen atom on the pyrrole ring of the porphyrin molecule and metal ions, resulting in metallized M-TPCOF (M = Co, Cu, Ni, or Ag) ammonia-sensitive materials. These materials are then used to fabricate ammonia detection devices, achieving highly sensitive, ultra-high selective, and rapid-response NH3 sensing with excellent repeatability and stability. The ammonia-sensitive materials modified with different transition metals exhibit different detection performances under the same testing conditions, indicating that different metal centers in the materials have different binding characteristics with NH3 gas molecules. It is worth noting that the Co-TPCOF modified ammonia detection device exhibited the highest response (155Hz), the fastest response / recovery time (61s / 90s), ultra-high selectivity, and excellent reusability for NH3 sensing, providing a new material for the design of future high-performance ammonia detection devices.

[0008] The first objective of this invention is an ammonia-sensitive material having the following general structural formula:

[0009]

[0010] M represents a transition metal element or hydrogen.

[0011] Furthermore, the transition metal element is selected from one or more of cobalt, copper, nickel, and silver.

[0012] The second objective of this invention is to provide a method for preparing the above-mentioned ammonia-sensitive material in which M is hydrogen, wherein a porphyrin derivative is reacted with pyridine-2,6-dicarboxaldehyde in the presence of an organic solvent, the mixture is degassed by freezing in a liquid N2 bath, then heated, and washed to obtain the ammonia-sensitive material in which M is hydrogen.

[0013] The third objective of this invention is to provide a method for preparing an ammonia-sensitive material in which M is a transition metal element, comprising the following steps:

[0014] S1. Porphyrin derivatives are reacted with pyridine-2,6-dicarboxaldehyde in the presence of an organic solvent to prepare the ammonia-sensitive material in which M is hydrogen.

[0015] S2. The ammonia-sensitive material containing a transition metal element is prepared by mixing and reacting an acetate solution containing a transition metal element with the ammonia-sensitive material in which M is hydrogen.

[0016] Furthermore, the porphyrin derivative includes 5,10,15,20-tetra(4-aminophenyl)porphyrin.

[0017] Furthermore, the organic solvent is a mixed solution of solvent and catalyst.

[0018] Furthermore, the solvent is selected from one or more of ethanol, o-dichlorobenzene, butanol, toluene, and dioxane; the catalyst is selected from one or more of acetic acid and scandium trifluoromethanesulfonate.

[0019] Furthermore, the reaction described in step S2 is carried out under an inert atmosphere, at a temperature of 30-60°C, and for a time of 12-36 hours.

[0020] A fourth objective of this invention is to provide an ammonia detection device, comprising the aforementioned ammonia-sensitive material or an ammonia-sensitive material prepared by the aforementioned method.

[0021] Furthermore, the ammonia detection device is implemented using a quartz crystal microbalance. The quartz crystal microbalance includes a quartz crystal wafer and a high-frequency oscillator inductively connected to the quartz crystal wafer. The quartz crystal wafer is coated with the ammonia-sensitive material. When the ammonia-sensitive material adsorbs ammonia, the surface mass of the quartz crystal changes. The quartz crystal microbalance utilizes the piezoelectric effect of the quartz crystal to convert the change in the surface mass of the quartz crystal electrode into a frequency change in the electrical signal output by the quartz crystal oscillation circuit, thereby achieving the detection of ammonia.

[0022] The beneficial effects of this invention are:

[0023] The ammonia-sensitive material described in this invention exhibits extremely high sensitivity to ammonia gas. Ammonia sensors made from this material demonstrate high sensitivity, high selectivity, and rapid response to ammonia gas, along with excellent repeatability. Ammonia-sensitive materials modified with different transition metals showed varying detection performance under the same testing conditions, indicating that different metal centers in the materials have different binding characteristics to ammonia molecules. Among them, the ammonia sensor modified with Co-TPCOF nanosheets showed the highest response for NH3 sensing.

[0024] (155Hz), the fastest response / recovery time (61s / 90s), ultra-high selectivity and excellent reusability provide new materials for the design of future high-performance NH3 sensors. Attached Figure Description

[0025] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0026] Figure 1 These are SEM images of H2-TPCOF (left) and Co-TPCOF (right);

[0027] Figure 2The images show the nitrogen adsorption-desorption curve (left) and pore size distribution diagram (right) of the ammonia-sensitive material.

[0028] Figure 3 This is the response value of the ammonia detection device to 100 ppm NH3;

[0029] Figure 4 The response / recovery curves of Co-TPCOF(a), H2-TPCOF(b), Ni-TPCOF(c), Cu-TPCOF(d), and Ag-TPCOF(e) ammonia detection devices to 100 ppm NH3 are shown; the response time of different ammonia detection devices to 100 ppm NH3 is compared (f).

[0030] Figure 5 This is a curve showing the change in response value of the Co-TPCOF ammonia detection device with NH3 concentration;

[0031] Figure 6 This is the repeatability test curve of the Co-TPCOF ammonia detection device for 100ppm NH3;

[0032] Figure 7 The Co-TPCOF ammonia detection device exhibits selectivity for 100 ppm of different gases.

[0033] Figure 8 This is a synthesis pathway diagram for ammonia-sensitive materials. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0035] Example 1: Synthesis of H2-TPCOF

[0036] 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP, 27.1 mg, 0.04 mmol) and pyridine-2,6-dicarboxaldehyde (10.8 mg, 0.08 mmol) were added to a mixed solution of ethanol (0.1 mL), 1,2-dichlorobenzene (0.9 mL), and acetic acid (6 M, 0.3 mL). After sonication for 25 min, the solution was transferred to a Pyrex tube. The tube was immediately frozen in a liquid N2 bath at 77 K and degassed to an internal pressure of -100 mTorr. After the temperature returned to room temperature, the Pyrex tube was heated at 120 °C for 5 days. After cooling to room temperature, the sample was filtered and transferred to a Soxhlet extractor, and washed with tetrahydrofuran for 24 h. Finally, the sample was vacuum-degassed at 120 °C for 24 h to obtain the activated sample H2-TPCOF ammonia-sensitive material.

[0037] Example 2: Synthesis of Co-TPCOF

[0038] 330 mg of cobalt acetate was added to a 250 mL glass bottle, dissolved in 100 mL of ethanol solution, and then 110 mg of activated H2-TPCOF was added. The mixture was sonicated for 2 min to disperse the cobalt acetate, and then stirred at 45 °C for 24 h under Ar inert gas protection. After the reaction was complete, the product was filtered and thoroughly washed three times each with water, methanol, and acetone. The solid product was dried in a vacuum oven for 12 h to obtain the Co-TPCOF ammonia-sensitive material derivative.

[0039] Example 3: Synthesis of Cu-TPCOF

[0040] 330 mg of copper acetate was added to a 250 mL glass bottle, dissolved in 100 mL of ethanol solution, and then 110 mg of activated H2-TPCOF was added. The mixture was sonicated for 2 min to disperse the H2-TPCOF, and the reaction was carried out under Ar inert gas protection at 45 °C with stirring for 24 h. After the reaction was completed, the product was filtered and thoroughly washed three times each with water, methanol, and acetone. The solid product was dried in a vacuum oven for 12 h to obtain the Cu-TPCOF ammonia-sensitive material derivative.

[0041] Example 4: Synthesis of Ni-TPCOF

[0042] 330 mg of nickel acetate was added to a 250 mL glass bottle, dissolved in 100 mL of ethanol solution, and then 110 mg of activated H2-TPCOF was added. The mixture was sonicated for 2 min to disperse the nickel acetate, and then reacted under Ar gas protection at 45 °C with stirring for 24 h. After the reaction was complete, the product was filtered and thoroughly washed three times each with water, methanol, and acetone. The solid product was then dried in a vacuum oven for 12 h to obtain the Ni-TPCOF ammonia-sensitive material derivative.

[0043] Example 5: Synthesis of Ag-TPCOF

[0044] 330 mg of silver acetate was added to a 250 mL glass bottle, dissolved in 100 mL of ethanol solution, and then 110 mg of activated H2-TPCOF was added. The mixture was sonicated for 2 min to disperse the H2-TPCOF, and then stirred at 45 °C for 24 h under Ar inert gas protection. After the reaction was complete, the product was filtered and thoroughly washed three times each with water, methanol, and acetone. The solid product was dried in a vacuum oven for 12 h to obtain the Ag-TPCOF ammonia-sensitive material derivative.

[0045] Example 6: Preparation and Detection of Ammonia Gas Detection Device

[0046] This embodiment of the ammonia detection device utilizes a sensitive film material on the surface of a quartz crystal to capture the target gas. Based on the mass sensitivity of the electro-quartz crystal, and leveraging the mass-frequency relationship of the quartz crystal, the ammonia concentration signal is converted into a frequency signal output. The quartz crystal microbalance (QCM) substrate was cleaned with ethanol and deionized water. The cleaned substrate was then fixed on a horizontal plane. Porphyrin-based COF nanosheets were dispersed in methanol to prepare a 1 mg / mL solution. Then, 3.5 μL of the solution was dropped onto the center of the QCM substrate, and the prepared QCM sensor was dried at room temperature for 2 hours.

[0047] (1) Morphological characterization of ammonia-sensitive materials

[0048] Taking H2-TPCOF and Co-TPCOF as examples, the morphology of the ammonia-sensitive materials was characterized by SEM, and the results are as follows: Figure 1 As shown. Both have a sheet-like network structure and, after post-metallization, the structure of the ammonia-sensitive material was not changed.

[0049] (2) Specific surface area of ​​ammonia-sensitive materials

[0050] like Figure 2 As shown, nitrogen adsorption-desorption tests were performed on the ammonia-sensitive material. Figure 2 It can be seen that the specific surface areas of H2-TPCOF, Ni-TPCOF, Co-TPCOF, Cu-TPCOF, and Ag-TPCOF decrease sequentially, reaching 871.7 m². 2 / g, 809.5m 2 / g、682.0m 2 / g, 510.1m 2 / g and 424.2m 2 / g, this is because the introduction of metal ions significantly reduces the specific surface area of ​​the material, but the pore size of the material does not change significantly.

[0051] (3) The performance of the ammonia detection device modified with ammonia-sensitive material in detecting NH3

[0052] The performance of ammonia detection devices modified with ammonia-sensitive materials for NH3 detection was compared, and the results are as follows: Figure 3As shown, under room temperature and 60% RH conditions, the Co-TPCOF-modified ammonia detection device exhibits the best detection performance with a response of approximately 155 Hz to 100 ppm NH3. While the pore sizes of the various COF materials are not significantly different, their specific surface areas vary considerably. Generally, a larger specific surface area indicates more NH3 adsorption sites. However, the response values ​​of these materials do not change with the specific surface area. Conversely, the metallized COF materials, despite having a smaller specific surface area, show a greater response to NH3. This indicates that the metal centers promote rapid contact and adsorption of NH3, resulting in superior sensing performance.

[0053] (4) Response time of the ammonia detection device modified with ammonia-sensitive material to 100 ppm NH3. The results of the response time of the ammonia detection device modified with ammonia-sensitive material to 100 ppm NH3 are as follows: Figure 4 As shown, the response and recovery times of Co-TPCOF ammonia-sensitive material to 100ppm NH3 are 61s and 90s, respectively, which are significantly faster than other materials, with Ag-TPCOF being the slowest.

[0054] (5) Effect of NH3 concentration on the response value of Co-TPCOF ammonia detection device

[0055] Figure 5 The linear fitting curve of the response value versus concentration of the Co-TPCOF ammonia detector within the NH3 concentration range of 10-300 ppm is shown. The frequency and concentration of the ammonia detector can be fitted using the equation y = 0.29x - 125.33, and the linear correlation coefficient R obtained after fitting is given. 2 =0.97, indicating that the Co-TPCOF ammonia detection device has good linearity.

[0056] (6) Repeatability of NH3 detection by the Co-TPCOF ammonia detection device

[0057] Based on the performance test results for NH3 above, the Co-TPCOF-modified ammonia detection device exhibits a large and rapid response value for NH3, making it the most promising candidate for practical applications. However, the ammonia detection device requires long-term stability during use; therefore, further testing of the repeatability of the Co-TPCOF-modified ammonia detection device for NH3 detection is necessary. Figure 6 As shown, the ammonia detection device exhibits good response and recovery characteristics to 100 ppm NH3 after 17 cycles.

[0058] (7) Selectivity of Co-TPCOF ammonia detection device for NH3 detection

[0059] Figure 7The results show the response values ​​of the Co-TPCOF ammonia detection device in 100 ppm of different interfering gases, namely ammonia, trimethylamine, formaldehyde, toluene, and hydrogen sulfide. The results indicate that the response value of the Co-TPCOF ammonia detection device to ammonia is significantly higher than that to other gases, indicating that the ammonia detection device has good selectivity and anti-interference ability.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A covalent organic framework-based ammonia-sensitive material, characterized in that, The ammonia-sensitive material has the following general structure formula: ， wherein M is cobalt.

2. A method for producing the ammonia-sensitive material according to claim 1, characterized by, The method comprises the following steps: S1. reacting 5,10,15,20-tetra(4-aminophenyl)porphyrin with pyridine-2,6-dicarboxaldehyde in the presence of an organic solvent and a catalyst to obtain the ammonia-sensitive material with M being hydrogen; S2. mixing and reacting a cobalt acetate solution with the ammonia-sensitive material with M being hydrogen to obtain the ammonia-sensitive material with M being cobalt.

3. The production method according to claim 2, characterized by, The organic solvent is selected from one or more of ethanol, o-dichlorobenzene, butanol, toluene, and dioxane; and the catalyst is selected from one or more of acetic acid and scandium triflate.

4. The preparation method according to claim 2, characterized in that, The reaction in step S2 is carried out under an inert atmosphere, at a temperature of 30-60°C, and for a time period of 12-36 hours.

5. An ammonia detection device, characterized by, The ammonia-sensitive material of claim 1 or the ammonia-sensitive material prepared by the method of any one of claims 2-4.

6. The ammonia detection device of claim 5, wherein, The ammonia detection device is realized by a quartz crystal microbalance, which comprises a quartz crystal wafer and a high-frequency oscillator in inductive connection with the quartz crystal wafer, and the quartz crystal wafer is modified with the ammonia-sensitive material.

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