Preparation method and application of a Cu-BTC / indusium biomass carbon composite

Abstract

A preparation method and application of a Cu-BTC / parapleurolobus bark biomass carbon composite material, which belongs to the technical field of room temperature gas sensing materials. The purpose of the present invention is to solve the problems of high synthesis cost, complex synthesis process, easy accumulation and small pore size of existing MOFs nanomaterials, which may lead to large gas mass transfer resistance and limit the sensing efficiency. In the present invention, parapleurolobus bark is used to prepare parapleurolobus bark porous carbon by chemical activation combined with calcination process. This biomass carbon material retains the natural tubular structure of biomass, which is beneficial to the adsorption or diffusion of the gas to be measured. For the first time, the present invention prepares a Cu-BTC / parapleurolobus bark biomass carbon composite material from parapleurolobus bark-derived biomass carbon and successfully applies it to NO2 gas sensing to solve the problems of low sensitivity, high detection limit, poor recovery and high cost when detecting NO2. The present invention has the characteristics of simple operation and high NO2 sensing efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of room temperature gas sensing materials, and particularly relates to a preparation method and application of a Cu-BTC / Chinese parasol fluff biomass carbon composite material. Background Art

[0002] Nitrogen dioxide (NO2) is a toxic and harmful air pollutant. It not only corrodes industrial production equipment and shortens its service life, but may also cause serious respiratory diseases. NO2 often coexists with other gases in the environment, and these gas molecules are extremely likely to interact with the surface of gas sensing materials, affecting the selectivity of the sensor. Effective environmental monitoring and health protection first require efficient and convenient detection means and detection equipment. Therefore, developing a highly selective and sensitive NO2 gas sensor under room temperature conditions has important practical significance.

[0003] As a kind of intelligent sensor, the gas sensor plays an important role in the field of intelligent sensing. The chemiresistive gas sensor promotes the innovative development of the gas sensing field with the detection of harmful gases with low power consumption, low cost and high sensitivity. The existing gas sensing mainly detects gases through two forms: chemical adsorption and physical adsorption. Chemical adsorption enhances the sensing response and selectivity by forming covalent bonds, but this binding method may lead to irreversible chemical changes; physical adsorption is suitable for real-time monitoring but has problems of insufficient stability and lack of selectivity. Therefore, exploring gas sensing materials that are compatible with high selectivity and high sensitivity has important application value.

[0004] Due to its unique structural characteristics and functionality, metal-organic framework materials (MOFs) show great application potential in the field of gas sensing. The structural diversity and large specific surface area of MOF nanomaterials provide a large number of adsorption sites for gas molecules, which helps to improve the sensitivity and selectivity of the sensor. By regulating the pore size and geometric shape of MOF nanomaterials, selective adsorption of specific gas molecules can be achieved, thereby enhancing the specificity of the sensor. Although MOF nanomaterials have great potential in gas sensing, their chemical stability, thermal stability and mechanical stability are relatively poor, resulting in challenges in their practical applications. In addition, the synthesis cost of MOF nanomaterials is high, the synthesis process is complex, they are easy to stack and the pore size is small, which may lead to large gas mass transfer resistance, limiting the sensing efficiency. In view of this, it greatly hinders the practical application of MOF nanomaterials in the field of gas sensors. Summary of the Invention

[0005] The object of the present invention is to solve the problems that the synthesis cost of existing MOFs nanomaterials is relatively high, the synthesis process is complex, they are prone to accumulation and the pore size is relatively small, which may lead to relatively large gas mass transfer resistance and limit the sensing efficiency, and to provide a preparation method and application of a Cu-BTC / Chinese parasol tree floss biomass carbon composite material.

[0006] The present invention provides a preparation method and application of a Cu-BTC / Chinese parasol tree floss biomass carbon composite material with a special hierarchical porous structure based on a host-guest coupling construction strategy. The preparation conditions of the present invention require low, the operation is simple, the energy consumption is low, it is environmentally friendly, there is a tight interfacial combination between the two components of the obtained gas sensing material, it has excellent room temperature NO2 gas sensing performance and stability, and the phase and morphology structure of the composite material are easy to regulate, providing important technical support for the development and application of efficient room temperature NO2 gas sensing materials.

[0007] A preparation method of a Cu-BTC / Chinese parasol tree floss biomass carbon composite material is specifically completed according to the following steps:

[0008] I. Preparation of Chinese parasol tree floss porous carbon with a porous thin-layer tubular structure:

[0009] ①. Wash the collected Chinese parasol tree floss, and then dry it to obtain pretreated Chinese parasol tree floss;

[0010] ②. Immerse the pretreated Chinese parasol tree floss in a NaOH solution, stir at room temperature for a period of time, then stand and soak for a period of time, then dry, and finally heat to the calcination temperature in a carbonization atmosphere and calcine for a period of time at the calcination temperature to obtain a reaction product;

[0011] ③. Wash the reaction product and then dry it to obtain Chinese parasol tree floss porous carbon with a porous thin-layer tubular structure;

[0012] II. Preparation of a Cu-BTC / Chinese parasol tree floss biomass carbon composite material:

[0013] ①. Dissolve a copper salt in deionized water to obtain solution I;

[0014] ②. Add an organic ligand and polyvinylpyrrolidone to a mixed solution of N,N-dimethylformamide and absolute ethanol, first perform ultrasonic treatment, and then perform magnetic stirring to obtain solution II;

[0015] ③. Mix solution I and solution II to obtain a mixed solution; immerse the Chinese parasol tree floss porous carbon with a porous thin-layer tubular structure in the mixed solution, stand for a period of time, then transfer it to a stainless steel autoclave with a polytetrafluoroethylene liner, and then heat at 80°C to 120°C for 10h to 12h, cool to room temperature, wash, then centrifuge, collect the precipitate after centrifugation, and finally dry it to obtain a Cu-BTC / Chinese parasol tree floss biomass carbon composite material.

[0016] A Cu-BTC / indusium platanifolium biomass carbon composite material is used for preparing a gas sensor element.

[0017] Principle of the present invention:

[0018] The present invention provides a simple solvothermal method for preparing a composite material with biomass carbon anchored with Cu-BTC and its application in NO2 gas sensing at room temperature; the present invention prepares a Cu-BTC material by a simple method to solve the problem of size controllability of MOF-based materials; the present invention provides a simple heat treatment method to prepare a porous tubular biomass carbon using indusium platanifolium as a raw material to solve the problem that a large number of micropores in biomass carbon hinder the diffusion of gas molecules; the present invention uses a composite material with a guest biomass carbon anchored to a host Cu-BTC to support and disperse the Cu-BTC material, obtaining a gas sensing material with a large specific surface area and rich active sites, increasing the contact between the gas to be detected and the sensing material, shortening the carrier transport path, and improving the sensitivity and selectivity of gas sensing.

[0019] The present invention has the following beneficial effects:

[0020] (1) The Cu-BTC / indusium platanifolium biomass carbon composite material provided by the present invention has a porous hierarchical nanoscale tubular structure in the form of biomass. The porous hierarchical nanostructure can effectively reduce the working temperature and obtain higher NO2 gas sensitivity and response speed.

[0021] (2) In the Cu-BTC / indusium platanifolium biomass carbon composite material provided by the present invention, Cu-BTC is an organometallic framework nanomaterial, forming a metal framework material structure of a regular hexahedron. The narrow and high XRD diffraction peaks indicate that the material has good crystallinity, so its anti-interference ability against the external environment is increased, making its performance stable.

[0022] (3) The Cu-BTC / indusium platanifolium biomass carbon composite material and pure Cu-BTC provided by the present invention are used as gas sensing materials to detect NO2 gas in the air. No heating system is required, and detection can be carried out at room temperature. The working temperature is low and the operating conditions are mild.

[0023] (4) The Cu-BTC / Chinese parasol tree fluff biochar composite material provided by the present invention is used as a gas sensing material to detect NO2 gas in the air, and can be operated at room temperature, i.e., 20°C to 35°C, and a humidity of 20% to 50%. Under these conditions, the sensitivity of the composite material to NO2 gas with a concentration of 50 ppm is as high as 39.54, and the sensitivity to NO2 gas with a concentration as low as 0.03 ppm is 1.27, showing excellent gas sensing performance; the time taken for the resistance of the sensitive film to start changing from when 50 ppm to 1 ppm of NO2 gas is injected until its resistance is completely stable is less than 20 s, with a fast response speed, and good adsorption reversibility without external influence, and the usage method is simple;

[0024] (5) The preparation method of the Cu-BTC / Chinese parasol tree fluff biochar composite material provided by the present invention is simple to operate, low in cost, and convenient for popularization. Description of the Drawings

[0025] Figure 1 It is an electron scanning electron microscope image of Cu-BTC prepared in Comparative Example 1;

[0026] Figure 2 It is an electron scanning electron microscope image of the biochar prepared in Comparative Example 2 and the Chinese parasol tree porous carbon with a porous thin-layer tubular structure prepared in Step 1 of Example 1. In the figure, (a) and (b) are the biochar prepared in Comparative Example 2, and (c) and (d) are the Chinese parasol tree porous carbon with a porous thin-layer tubular structure prepared in Step 1 of Example 1;

[0027] Figure 3 It is an electron scanning electron microscope image of the Cu-BTC / Chinese parasol tree fluff biochar composite material prepared in Example 1;

[0028] Figure 4 For Figure 3 Local enlarged electron scanning electron microscope image;

[0029] Figure 5 It is an X-ray diffraction pattern of Cu-BTC prepared in Comparative Example 1 and the Cu-BTC / Chinese parasol tree fluff biochar composite material prepared in Example 1;

[0030] Figure 6 It is a thermogravimetric curve of Chinese parasol tree fluff in an air atmosphere;

[0031] Figure 7 It is a sensitivity curve graph of detecting NO2 with different concentrations by using the gas sensor element prepared with Cu-BTC prepared in Comparative Example 1 as the sensitive material in Comparative Application Example 1;

[0032] Figure 8The sensitivity curve graph of the gas sensor prepared with the Cu-BTC / parasol fluff biomass carbon composite material prepared in Example 1 as the sensitive material in Application Example 1 for detecting NO2 at different concentrations. Specific implementation method

[0033] Specific implementation manner 1: A preparation method of a Cu-BTC / parasol fluff biomass carbon composite material is specifically completed according to the following steps:

[0034] I. Prepare porous thin-layer tubular structure parasol fluff porous carbon:

[0035] ①. Wash the collected parasol fluff, and then dry it to obtain pretreated parasol fluff;

[0036] ②. Immerse the pretreated parasol fluff in a NaOH solution, stir at room temperature for a period of time, then stand for impregnation for a period of time, then dry, and finally heat to the calcination temperature in a carbonization atmosphere and calcine for a period of time at the calcination temperature to obtain a reaction product;

[0037] ③. Wash the reaction product and then dry it to obtain porous thin-layer tubular structure parasol fluff porous carbon;

[0038] II. Prepare Cu-BTC / parasol fluff biomass carbon composite material:

[0039] ①. Dissolve the copper salt in deionized water to obtain Solution I;

[0040] ②. Add the organic ligand and polyvinylpyrrolidone to the mixed solution of N,N-dimethylformamide and absolute ethanol, first perform ultrasonic treatment, and then perform magnetic stirring to obtain Solution II;

[0041] ③. Mix Solution I and Solution II to obtain a mixed solution; immerse the porous thin-layer tubular structure parasol fluff porous carbon in the mixed solution, stand for a period of time, then transfer it to a stainless steel autoclave with a polytetrafluoroethylene liner, and then heat at 80°C to 120°C for 10h to 12h, cool to room temperature, wash, then centrifuge, collect the centrifuged precipitate, and finally dry to obtain the Cu-BTC / parasol fluff biomass carbon composite material.

[0042] Specific implementation manner 2: The difference between this implementation manner and Specific implementation manner 1 is: in step I ①, the collected parasol fluff is washed 2 to 4 times with absolute ethanol and then dried at 60°C to 80°C for 10h to 12h; in step I ②, the concentration of the NaOH solution is 0.5mol / L to 3mol / L; in step I ②, the pretreated parasol fluff is immersed in the NaOH solution, stirred at room temperature for 1h to 2h, then stood for impregnation for 8h to 10h, and then dried at 60°C to 80°C for 10h to 12h. Other steps are the same as those in Specific implementation manner 1.

[0043] Embodiment 3: The difference between this embodiment and Embodiment 1 or Embodiment 2 is as follows: The carbonization atmosphere described in Step 1② is air, nitrogen or argon; in Step 1②, the temperature is raised from room temperature to 300°C - 450°C at a heating rate of 5°C / min - 10°C / min under the carbonization atmosphere, and calcined at 300°C - 450°C for 30 min - 240 min; in Step 1③, the reaction product is washed with deionized water until neutral, and then dried at 60°C - 80°C for 10 h - 12 h to obtain the sycamore floss porous carbon with a porous thin-layer tubular structure. Other steps are the same as those in Embodiment 1 or Embodiment 2.

[0044] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is as follows: The copper salt described in Step 2① is copper nitrate or copper sulfate; the mass ratio of the copper salt to the volume of deionized water in Step 2① is (2.5 g - 4.5 g):30 mL. Other steps are the same as those in Embodiments 1 to 3.

[0045] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is as follows: The organic ligand described in Step 2② is 1,4-benzenedicarboxylic acid, 1,3,5-benzenetricarboxylic acid or 1,2-dimethylimidazole; the molecular weight of the polyvinylpyrrolidone described in Step 2② is 58000, 24000 or 1300000; the volume ratio of N,N-dimethylformamide to absolute ethanol in the mixed solution of N,N-dimethylformamide and absolute ethanol described in Step 2② is (20 - 50):(20 - 50). Other steps are the same as those in Embodiments 1 to 4.

[0046] Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is as follows: The mass-volume ratio of the organic ligand, polyvinylpyrrolidone and the mixed solution of N,N-dimethylformamide and absolute ethanol described in Step 2② is (1 g - 2 g):(1 g - 2 g):60 mL; the ultrasonic treatment time described in Step 2② is 5 min - 10 min, the magnetic stirring time is 15 min - 60 min, and the magnetic stirring speed is 500 r / min - 800 r / min. Other steps are the same as those in Embodiments 1 to 5.

[0047] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is as follows: The volume ratio of Solution Ⅰ to Solution Ⅱ described in Step 2③ is 1:2; the standing time described in Step 2③ is 10 h - 12 h; the washing in Step 2③ is to wash 2 - 4 times successively with deionized water and absolute ethanol; the drying temperature described in Step 2③ is 60°C - 80°C, and the drying time is 5 h - 10 h. Other steps are the same as those in Embodiments 1 to 6.

[0048] Embodiment 8: This embodiment is about using a Cu-BTC / Chinese parasol tree floss biochar composite material to prepare a gas sensor element.

[0049] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: The specific steps for using a Cu-BTC / Chinese parasol tree floss biochar composite material to prepare a gas sensor element are as follows: Add the Cu-BTC / Chinese parasol tree floss biochar composite material to absolute ethanol and disperse it by ultrasonic treatment to obtain a uniformly dispersed suspension; Spin-coat the uniformly dispersed suspension on the Au interdigital electrode and dry it at room temperature to obtain the gas sensor element; The mass ratio of the Cu-BTC / Chinese parasol tree floss biochar composite material to the volume of absolute ethanol is (0.01 g - 0.05 g):(0.3 mL - 1.0 mL); The volume ratio of the uniformly dispersed suspension to the surface area of the Au interdigital electrode is (0.03 mL - 0.15 mL):0.25 cm 2 . Other steps are the same as those in Embodiments 1 to 8.

[0050] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is as follows: The gas sensor element is used at room temperature to detect low-concentration NO2 gas in the air, and the detection limit is as low as 30 ppb. Other steps are the same as those in Embodiments 1 to 9.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Comparative Example 1: The preparation method of Cu-BTC is specifically completed according to the following steps:

[0053] Dissolve 4.25 g of copper nitrate in 30 mL of deionized water and stir to form a transparent solution; Then, mix 2.0 g of 1,3,5-benzenetricarboxylic acid (H3BTC) and 2.0 g of PVP (molecular weight 1,300,000) in a mixed solution of 30 mL of N,N-dimethylformamide (DMF) and 30 mL of absolute ethanol, then perform 5 min of ultrasonic treatment and 30 min of magnetic stirring, and mix the two solutions to form a precursor mixed solution; Transfer the precursor mixed solution to a polytetrafluoroethylene-lined stainless steel autoclave (100 mL) and heat it at 100 °C for 10 hours. After cooling to room temperature, centrifuge the blue Cu-BTC crystals and dry them at 60 °C for 7 h to obtain Cu-BTC.

[0054] Comparative Example 2: Biochar prepared by an unactivated method is specifically completed according to the following steps:

[0055] ①. Wash the collected Chinese parasol tree floss 3 times with absolute ethanol, and then dry it at 80 °C for 12 h to obtain pretreated Chinese parasol tree floss;

[0056] ②. Heat the pretreated phoenix tree catkins to 400 °C at a heating rate of 5 °C / min under an air atmosphere and calcine at 400 °C for 120 min to obtain a reaction product;

[0057] ③. Wash the reaction product with deionized water until neutral, and then dry at 80 °C to obtain biomass carbon.

[0058] Example 1: A preparation method of a Cu-BTC / phoenix tree catkin biomass carbon composite material is specifically completed according to the following steps:

[0059] I. Prepare phoenix tree porous carbon with a porous thin-layer tubular structure:

[0060] ①. Wash the collected phoenix tree catkins 3 times with absolute ethanol, and then dry at 80 °C for 12 h to obtain pretreated phoenix tree catkins;

[0061] ②. Immerse the pretreated phoenix tree catkins in a NaOH solution with a concentration of 1 mol / L, stir at room temperature for 1 h, then let it stand for impregnation for 10 h, then dry at 80 °C for 12 h, and finally heat from room temperature to 400 °C at a heating rate of 5 °C / min under an air atmosphere and calcine at 400 °C for 120 min to obtain a reaction product;

[0062] ③. Wash the reaction product with deionized water until neutral, and then dry at 80 °C to obtain phoenix tree porous carbon with a porous thin-layer tubular structure;

[0063] II. Prepare a Cu-BTC / phoenix tree catkin biomass carbon composite material:

[0064] ①. Dissolve 4.25 g of copper nitrate in 30 mL of deionized water to obtain solution I;

[0065] ②. Mix 2.0 g of 1,3,5-benzenetricarboxylic acid (H3BTC) and 2.0 g of PVP (molecular weight 1,300,000) in a mixed solution of 30 mL of N,N-dimethylformamide (DMF) and 30 mL of absolute ethanol, first perform ultrasonic treatment for 5 min, and then perform magnetic stirring for 30 min at a magnetic stirring speed of 500 r / min to obtain solution II;

[0066] ③. Mix solution I and solution II to obtain a mixed solution; immerse the phoenix tree porous carbon with a porous thin-layer tubular structure into the mixed solution, let it stand for 12 h, then transfer it to a stainless steel autoclave with a polytetrafluoroethylene inner lining (100 mL), then heat at 100 °C for 10 h, cool to room temperature, wash 3 times with deionized water and absolute ethanol in sequence, then centrifuge, collect the centrifuged precipitate, and finally dry at 60 °C for 8 h to obtain a Cu-BTC / phoenix tree catkin biomass carbon composite material.

[0067] Figure 1 This is a scanning electron microscopy image of Cu-BTC prepared in Comparative Example 1;

[0068] Depend on Figure 1 It can be seen that Cu-BTC has a regular hexahedral structure and a particle size of 1-2 microns.

[0069] Figure 2 The electron scanning electron micrographs of the biomass charcoal prepared in Comparative Example 2 and the porous thin-layer tubular structure of the tung oil linden porous charcoal prepared in Step 1 of Example 1, wherein (a) and (b) are the biomass charcoal prepared in Comparative Example 2, and (c) and (d) are the porous thin-layer tubular structure of the tung oil linden porous charcoal prepared in Step 1 of Example 1;

[0070] Depend on Figure 2 (a) and (b) show that the unactivated biochar presents a smooth tubular structure with an inner diameter of about 40-60 μm; while the activated biochar tube wall becomes significantly thinner and presents a distinct sparse pore structure ( Figure 2 (c) and (d)).

[0071] Figure 3 This is a scanning electron micrograph of the Cu-BTC / Phoenix tung blossom biomass carbon composite material prepared in Example 1;

[0072] from Figure 3 It can be seen that Cu-BTC nanoparticles are evenly wrapped on the surface of biochar.

[0073] Figure 4 for Figure 3 A local magnified electron scanning electron microscope image;

[0074] from Figure 4 It can be seen that the composite Cu-BTC still retains a complete hexahedral structure, but some round particles are produced on its surface.

[0075] Figure 5 X-ray diffraction patterns of Cu-BTC prepared in Comparative Example 1 and Cu-BTC / Putong fluff biomass carbon composite material prepared in Example 1;

[0076] Figure 5 This can prove the successful preparation of Cu-BTC material; the X-ray diffraction peak of Cu-BTC / biomass carbon composite material is lower in intensity than that of Cu-BTC, and the (111) and (200) diffraction peaks of Cu element appear.

[0077] Figure 6 This is the thermogravimetric curve of sycamore fluff in air atmosphere;

[0078] Figure 6It can be observed that when the phoenix tree floss material is calcined in an air atmosphere, an obvious weight loss and carbonization process occurs at 300 °C to 450 °C. Therefore, the carbonization temperatures selected in Example 1 and Example 5 are 300 °C, 350 °C, 400 °C, and 450 °C.

[0079] Comparative Application Example 1: The gas sensor element prepared with the Cu-BTC prepared in Comparative Example 1 as the sensitive material was completed according to the following steps:

[0080] 0.05 g of the Cu-BTC prepared in Comparative Example 1 was ultrasonically dispersed in 0.5 mL of absolute ethanol to obtain a uniformly dispersed suspension, and then the suspension was spin-coated on the Au interdigitated electrode and dried at room temperature to obtain the gas sensor element; the volume ratio of the uniformly dispersed suspension to the surface area of the Au interdigitated electrode was 0.05 mL:0.25 cm 2 .

[0081] The gas sensor element prepared in Application Example 1 was used to detect its sensitivity to NO2 in the air environment. The results are shown in Table 1 and Figure 7 as shown.

[0082] Table 1 Results of detecting NO2 with the gas sensor element prepared in Comparative Application Example 1

[0083]

[0084]

[0085] Figure 7 It is a sensitivity curve graph of the gas sensor element prepared with the Cu-BTC prepared in Comparative Example 1 as the sensitive material in Comparative Application Example 1 to detect NO2 at different concentrations;

[0086] From Table 1 and Figure 7 it can be seen that the gas sensor element prepared in Application Example 1 has a sensitivity as high as 3.63 to 1 ppm NO2 gas, that is, the gas sensor element has certain response and recovery characteristics to NO2; the time taken for the resistance of the sensitive film to change from when 1 ppm NO2 gas is injected until its resistance is completely stable is less than 20 s, the response speed is fast, the adsorption reversibility is good, and the usage method is simple.

[0087] Among them, the sensitivity S = R a / R g , R a is the initial resistance of the gas sensor element in the air environment, and R g is the resistance of the gas sensor element in the NO2 atmosphere.

[0088] Application Example 1: The gas sensor element prepared with the Cu-BTC / phoenix tree floss biomass carbon composite material prepared in Example 1 as the sensitive material was completed according to the following steps:

[0089] 0.05 g of the Cu-BTC / Tung Blossom Biomass Carbon Composite Material prepared in Example 1 was ultrasonically dispersed in 0.5 mL of anhydrous ethanol to obtain a uniformly dispersed suspension, which was then spin-coated on an Au interdigital electrode and dried at room temperature to obtain a gas sensor; the ratio of the volume of the uniformly dispersed suspension to the surface area of ​​the Au interdigital electrode was 0.05 mL:0.25 cm 2 .

[0090] The gas sensor prepared in Example 1 was used to detect its sensitivity to NO2 in the air environment. The results are shown in Tables 2 and Figure 8 shown.

[0091] Table 2 Results of using the gas sensor prepared in Example 1 to detect NO2

[0092]

[0093]

[0094] Figure 8 The sensitivity curve diagram of the gas sensor prepared by using the Cu-BTC / Pu Tong cotton wool biomass carbon composite material prepared in Example 1 as the sensitive material to detect different concentrations of NO2;

[0095] From Table 2 and Figure 8 It can be seen that the sensitivity of the gas sensor prepared in Example 1 to NO2 gas with a concentration of 50ppm is as high as 39.54, that is, the gas sensor has good response and recovery characteristics to NO2; the time taken for the sensitive membrane to change from the beginning of the NO2 gas resistance change when the NO2 gas is injected from 50ppm to 1ppm to the complete stabilization of its resistance is less than 15s, with fast response speed, good adsorption reversibility and simple use.

[0096] Example 2: The difference between this example and Example 1 is that the difference between this embodiment and the specific embodiment 1 is that: in step 1①, the collected sycamore cotton wool is washed 3 times with anhydrous ethanol and then dried at 60℃ for 12h; the concentration of the NaOH solution described in step 1② is 0.5mol / L; in step 1②, the pretreated sycamore cotton wool is immersed in the NaOH solution, stirred at room temperature for 1h, then allowed to stand and soak for 8h, and then dried at 60℃ for 12h. The other steps are the same as the specific embodiment 1.

[0097] Application Example 2: The difference between this application example and application example 1 is that the Cu-BTC / Phoenix tung blossoms biomass carbon composite material prepared in example 1 is replaced by the Cu-BTC / Phoenix tung blossoms biomass carbon composite material prepared in example 2. The other steps and parameters are the same as those in application example 1.

[0098] Example 3: The difference between this example and Example 1 is as follows: The difference between this embodiment and one of the Specific Embodiments 1 or 2 is that: the carbonization atmosphere described in Step 1 ② is nitrogen; in Step 1 ②, the temperature is raised from room temperature to 450 °C at a heating rate of 5 °C / min under the carbonization atmosphere, and calcined at 450 °C for 120 min; in Step 1 ③, deionized water is used to wash the reaction product until neutral, and then dried at 60 °C for 12 h to obtain the phoenix floss porous carbon with a porous thin-layer tubular structure. Other steps are the same as those in Specific Embodiment 1 or 2.

[0099] Application Example 3: The difference between this application example and Application Example 1 is that: the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 1 is replaced by the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 3. Other steps and parameters are the same as those in Application Example 1.

[0100] Example 4: The difference between this example and Example 1 is that: the copper salt described in Step 2 ① is copper sulfate; the mass ratio of the copper sulfate described in Step 2 ① to the volume of deionized water is 3.2 g:30 mL. Other steps and parameters are the same as those in Example 1.

[0101] Application Example 4: The difference between this application example and Application Example 1 is that: the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 1 is replaced by the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 4. Other steps and parameters are the same as those in Application Example 1.

[0102] Example 5: The difference between this example and Example 1 is that: 1,2-dimethylimidazole is used to replace 1,3,5-benzenetricarboxylic acid (H3BTC) in Step 2 ②; the molecular weight of the polyvinylpyrrolidone (PVP) described in Step 2 ② is 58000. Other steps and parameters are the same as those in Example 1.

[0103] Application Example 5: The difference between this application example and Application Example 1 is that: the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 1 is replaced by the Cu-BTC / phoenix floss biomass carbon composite material prepared in Example 5. Other steps and parameters are the same as those in Application Example 1.

[0104] The sensitivity results of the gas sensors prepared in Comparative Application Example 1 and Application Examples 1 to 5 for detecting 50 ppm of NO2 are shown in Table 3;

[0105] Table 3

[0106] Number Sensitivity Response Time (s) Comparison with Application Example 1 3.63 17.4 Application Example 1 39.54 9.4 Application Example 2 6.2 47.4 Application Example 3 4.5 28.9 Application Example 4 17.6 12.5 Application Example 5 15.9 28

[0107] In summary, when the Cu-BTC / Chinese parasol tree floss biomass carbon composite provided by the present invention is used as a gas-sensitive material for detecting the concentration of NO2 in the air, it does not require a heating system, can operate at room temperature, has a fast response speed, good recovery reversibility, a simple usage method, and a low manufacturing cost.

[0108] The Cu-BTC / Chinese parasol tree floss biomass carbon composite prepared by the present invention can be operated at room temperature, i.e., 20°C to 35°C, and a humidity of 20% to 40%, indicating that environmental humidity has no significant effect on the gas-sensing performance of the composite material. And under this condition, the sensitivity of the composite material to NO2 gas with a concentration of 50 ppm is as high as 39.54, that is, the gas-sensitive element has good response and recovery characteristics to NO2 and a relatively high sensitivity; when the concentration of NO2 is 0.03 ppm, the sensitivity is 1.27, and at the same time, the actual detection limit of the gas-sensitive element can reach 23 ppb. The time taken for the resistance of the sensitive film to start changing to its complete stability when injecting NO2 gas from 50 ppm to 1 ppm is less than 20 s. It has a fast response speed, good adsorption reversibility, and a simple usage method. Therefore, compared with the single-component Cu-BTC material, the Cu-BTC / Chinese parasol tree floss biomass carbon composite has greater advantages such as higher sensitivity, faster response time, and lower detection limit, laying a foundation for the efficient detection of low-concentration nitrogen dioxide at room temperature.

Claims

1. A method for preparing a Cu-BTC / Pu Tong cotton fiber biomass carbon composite material, characterized in that The Cu-BTC / Phoenix tung oil biomass carbon composite material prepared by the preparation method is used to prepare a gas sensor; the gas sensor is used to detect low-concentration NO2 gas in the air at room temperature, and the detection limit is as low as 30ppb; The preparation method is specifically completed according to the following steps:

1. Preparation of porous thin-layer tubular structure of tung oil cotton wool porous carbon: ①, washing the collected tung oil cotton wool, and then drying it to obtain pre-treated tung oil cotton wool; ②, soak the pretreated tung oil floss in NaOH solution, stir at room temperature for 1h to 2h, then stand and soak for 8h to 10h, then dry at 60℃ to 80℃ for 10h to 12h, finally heat to calcination temperature in a carbonization atmosphere, calcine at calcination temperature for a period of time to obtain a reaction product; The concentration of the NaOH solution described in step 1② is 0.5mol / L to 3mol / L; The carbonization atmosphere in step 1② is air, nitrogen or argon; in step 1②, the temperature is raised from room temperature to 300℃~450℃ at a heating rate of 5℃ / min~10℃ / min under the carbonization atmosphere, and calcined at 300℃~450℃ for 30min~240min; ③, washing the reaction product and drying it to obtain porous thin-layer tubular structure of tung oil linden fiber porous carbon; 2. Preparation of Cu-BTC / Pu Tong Floc Biomass Carbon Composite Material: ① Dissolve copper salt in deionized water to obtain solution Ⅰ; ②, adding the organic ligand and polyvinyl pyrrolidone to the mixture of N,N-dimethylformamide and anhydrous ethanol, firstly ultrasonically treating, then magnetically stirring, to obtain solution II; ③. Mix solution I and solution II to obtain a mixed solution; immerse the porous thin-layer tubular structure of the tung oil tree fiber porous carbon into the mixed solution, let it stand for 10 h to 12 h, then transfer it to a polytetrafluoroethylene-lined stainless steel high-pressure reactor, and then heat it at 80°C to 120°C for 10 h to 12 h, cool to room temperature, wash, and centrifuge again, collect the precipitate after centrifugation, and finally dry it to obtain the Cu-BTC / tung oil tree fiber biomass carbon composite material.

2. The method for preparing a Cu-BTC / Phoenix tung oil biomass carbon composite material according to claim 1, characterized in that In step 1①, the collected sycamore fluff is washed 2 to 4 times with anhydrous ethanol, and then dried at 60°C to 80°C for 10 hours to 12 hours.

3. The method for preparing a Cu-BTC / Phoenix tung oil biomass carbon composite material according to claim 1, characterized in that In step 1③, the reaction product is washed with deionized water until it becomes neutral, and then dried at 60°C to 80°C for 10h to 12h to obtain a porous thin-layer tubular structure of tung oil linden porous carbon.

4. The method for preparing a Cu-BTC / Phoenix tung oil biomass carbon composite material according to claim 1, characterized in that The copper salt described in step 2① is copper nitrate or copper sulfate; the mass ratio of the copper salt described in step 2① to deionized water is (2.5g~4.5g):30mL.

5. The method for preparing a Cu-BTC / Phoenix tung oil fiber biomass carbon composite material according to claim 1, characterized in that The organic ligand described in step 2② is 1,4-phthalic acid, 1,3,5-benzenetricarboxylic acid or 1,2-dimethylimidazole; the molecular weight of the polyvinyl pyrrolidone described in step 2② is 58000, 24000 or 1300000; the volume ratio of N,N-dimethylformamide and anhydrous ethanol in the mixed solution of N,N-dimethylformamide and anhydrous ethanol described in step 2② is (20-50):(20-50).

6. The method for preparing a Cu-BTC / Phoenix tung oil fiber biomass carbon composite material according to claim 1, characterized in that The mass volume ratio of the mixed solution of the organic ligand, polyvinyl pyrrolidone, N,N-dimethylformamide and anhydrous ethanol described in step 2② is (1g~2g):(1g~2g):60mL; the time of ultrasonic treatment described in step 2② is 5min~10min, the time of magnetic stirring is 15min~60min, and the speed of magnetic stirring is 500r / min~800r / min.

7. The method for preparing a Cu-BTC / Phoenix tung oil biomass carbon composite material according to claim 1, characterized in that The volume ratio of solution I and solution II described in step 2③ is 1:2; the washing described in step 2③ is washing with deionized water and anhydrous ethanol in sequence for 2 to 4 times; the drying temperature described in step 2③ is 60°C to 80°C, and the drying time is 5h to 10h.

8. The method for preparing a Cu-BTC / Phoenix tung oil biomass carbon composite material according to claim 1, characterized in that A Cu-BTC / Phoenix tung blossom biomass carbon composite material is used to prepare a gas sensor, which is specifically completed in the following steps: adding the Cu-BTC / Phoenix tung blossom biomass carbon composite material to anhydrous ethanol, ultrasonically dispersing, and obtaining a uniformly dispersed suspension; spin-coating the uniformly dispersed suspension on an Au interdigital electrode, and drying at room temperature to obtain a gas sensor; the mass ratio of the Cu-BTC / Phoenix tung blossom biomass carbon composite material to the volume of anhydrous ethanol is (0.01g-0.05g):(0.3mL-1.0mL); the volume ratio of the uniformly dispersed suspension to the surface area of ​​the Au interdigital electrode is (0.03mL-0.15mL):0.25cm 2 .

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