Gas-sensitive sensing material with porous framework as well as preparation method and application of gas-sensitive sensing material

Abstract

The invention belongs to the technical field of gas sensing materials, and discloses a gas-sensitive sensing material with a porous skeleton and a preparation method and application thereof, and the preparation method comprises the following steps: carrying out immersion treatment on a natural wood chip by using a conductive carbon material solution to obtain a conductive wood chip; the preparation method comprises the following steps: dispersing cMOFs in ethanol to obtain a suspension containing cMOFs; dispensing the suspension containing the cMOFs on the wood chip with conductivity, and drying to obtain the wood chip with gas-sensitive performance; depositing silver monatomic on the surface of the wood chip with the gas-sensitive property by using a chemical deposition method, and drying to obtain the gas-sensitive sensing material with a porous framework, according to the invention, a self-supporting pore structure of natural wood is used as a base material for loading the gas-sensitive material, cMOFs is used as a main gas-sensitive material to prepare a pore-in-pore structure, and silver monatomic is deposited, so that the recovery speed of the gas-sensitive material is effectively increased, and effective detection of low-concentration ammonia gas at room temperature is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensing materials, and particularly relates to a gas-sensitive sensing material with a porous skeleton, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of modern industry, environmental pollution problems have attracted increasing attention; the large-scale emission of polluting gases not only causes serious damage to the natural environment, but also poses a great threat to human health and safety; among them, ammonia, as a harmful gas to the human body, is colorless and has a strong pungent odor, and at low concentrations, it can cause throat discomfort, nasal irritation, and dryness, stinging or redness of the eyes in humans, and even lead to the occurrence of bronchitis or asthma; in this context, gas sensors have shown significant advantages compared with traditional fixed gas chromatographs, such as high portability, rapid detection, and low cost; therefore, the importance of gas sensors in ammonia monitoring has become increasingly prominent.

[0003] In order to achieve real-time, accurate, and efficient monitoring of ammonia concentration, gas sensing materials need to have high sensitivity, rapid response and recovery capabilities, excellent selectivity, and stability under high-temperature conditions; currently, a variety of gas sensing materials have been studied and developed, such as metal oxides, carbon materials, conductive polymers, metal-organic framework materials, rare-earth oxides, etc.; among many sensing materials, conductive metal-organic frameworks (cMOFs), due to their extremely high specific surface area and rich pore structures, can provide more adsorption sites for monitoring gases and enhance the adsorption ability of target gas molecules; in addition, their excellent structural tunability and excellent conductivity compared with other metal-organic frameworks make them a research hotspot of current gas-sensitive materials.

[0004] However, the existing cMOFs generally have great difficulty in desorption. The main reasons are as follows: The materials have an extremely high specific surface area and a rich pore structure, which enhances the interaction force between them and ammonia, resulting in an increase in desorption difficulty; Secondly, ammonia is prone to accumulate in the pores of cMOFs, causing pore blockage and further exacerbating the desorption difficulty; In addition, during the adsorption process, ammonia may react chemically with cMOFs. For example, the nitrogen atoms in ammonia coordinate with the metal nodes of cMOFs to form stable chemical bonds, or ammonia, as a basic gas, reacts with acidic sites in cMOFs in an acid-base reaction. The above reactions will not only change the chemical properties of cMOFs but may also cause irreversible deformation or even collapse of their structures, thus significantly affecting the desorption effect; Finally, due to kinetic limitations, the diffusion rate of ammonia in the pores of cMOFs is slow, which also prolongs the desorption time; Due to the phenomenon of great desorption difficulty in existing cMOFs, the response time and recovery time of gas-sensitive sensing materials based on metal-organic framework materials are relatively long, thereby reducing the detection performance of gas sensors. Summary of the Invention

[0005] Aiming at the technical problems existing in the prior art, the present invention provides a gas-sensitive sensing material with a porous skeleton, its preparation method and application, so as to solve the technical problems that the existing cMOFs have great difficulty in desorption, resulting in relatively long response time and recovery time of gas-sensitive sensing materials based on metal-organic framework materials.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of a gas-sensitive sensing material with a porous skeleton, including: Impregnating natural wood chips with a conductive carbon material solution to obtain conductive wood chips; Disperse cMOFs in ethanol to obtain a suspension containing cMOFs; Drop the suspension containing cMOFs onto the conductive wood chips, and after drying, obtain wood chips with gas-sensitive properties; Using a chemical deposition method, deposit silver single atoms on the surface of the wood chips with gas-sensitive properties, and after drying, obtain a gas-sensitive sensing material with a porous skeleton.

[0007] Further, the natural wood chips are cross-cut wood chips of eucalyptus, pine, fir or balsa wood; the mass ratio of the conductive carbon material to water in the conductive carbon material solution is (1-3):(2-4), and the conductive carbon material is carbon nanotubes.

[0008] Further, the preparation process of the cMOFs includes: Copper sulfate is mixed with N,N-dimethylacetamide to obtain a copper sulfate suspension; the HITP•6HCl dispersion is mixed with the sodium acetate solution to obtain a mixed solution; the copper sulfate suspension is mixed with the mixed solution, heated and stirred, and after centrifugation, washing, and drying, cMOFs are obtained.

[0009] Furthermore, the concentration of the copper sulfate suspension is 2 - 2.5 mg / mL; the concentration of the HITP•6HCl dispersion is 3 - 3.5 mg / mL; the mass ratio of the HITP•6HCl dispersion to the sodium acetate solution is 1:1 - 2; wherein, the concentration of the sodium acetate solution is 164 - 170 mg / mL.

[0010] Furthermore, the mass ratio of the copper sulfate suspension to the mixed solution is 1:2 - 3.

[0011] Furthermore, in the process of mixing the copper sulfate suspension with the mixed solution, heating and stirring, and after centrifugation, washing, and drying to obtain the conductive organic framework powder with gas-sensing performance, the heating and stirring temperature is 65 - 75 °C, and the heating and stirring time is 2.5 - 4.5 h; during washing, deionized water and methanol are used for washing.

[0012] Furthermore, the concentration of the suspension containing cMOFs is 10 - 20 mg / mL.

[0013] Furthermore, in the process of depositing silver single atoms on the surface of the wood chip with gas-sensing performance by chemical deposition method and drying to obtain the gas-sensing material with porous framework, the steps are as follows: The silver single atom metal precursor is dissolved in deionized water to obtain an electrolyte solution with the silver single atom metal precursor; The wood chip with gas-sensing performance is immersed in the electrolyte solution with the silver single atom metal precursor, and by electrochemical deposition method, silver single atoms are deposited on the surface of the wood chip with gas-sensing performance, washed, and dried to obtain the gas-sensing material with porous framework.

[0014] The present invention also provides a gas-sensing material with porous framework, which is prepared by using the preparation method of the gas-sensing material with porous framework described above.

[0015] The present invention also provides an application of the gas-sensing material with porous framework, which is used for the preparation of gas sensors.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The preparation method of the gas-sensing material with a porous skeleton provided by the present invention utilizes the highly porous skeleton of wood and the high specific surface area of cMOFs, significantly improving the sensor sensitivity, realizing the effective monitoring of 3 ppm ammonia gas, and reducing the energy consumption and cost. Secondly, by using the chemical deposition method, silver single atoms are deposited on the surface of the wood chips with gas-sensing properties to introduce silver single atoms as SACs, optimizing the adsorption / desorption kinetics of cMOFs for ammonia gas, and increasing the recovery speed of the gas-sensing material by more than 30%. In addition, the suspension containing cMOFs is drop-coated on the conductive wood chips, combining the macroporous structure of wood with the microporous structure of cMOFs to form a "pore-in-pore" hierarchical pore structure, which not only provides more adsorption sites but also accelerates the gas diffusion rate, shortening the sensor response time to within 10 s, especially suitable for the rapid detection of low-concentration gases. Secondly, the natural wood chips are impregnated with a conductive carbon material solution to form a coating of the conductive carbon material on the natural wood, which not only endows the wood with conductivity but also provides conditions for the material to respond to ammonia gas at room temperature. The present invention uses the self-supporting pore structure of natural wood as the matrix material for loading the gas-sensing material, prepares a pore-in-pore structure with cMOFs as the main gas-sensing material, and deposits silver single atoms, effectively improving the recovery speed of the gas-sensing material and realizing the effective detection of low-concentration ammonia gas at room temperature. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is the microscopic morphology diagram of the natural eucalyptus wood chips in Example 1; Figure 2 It is the microscopic morphology diagram of the cMOFs (cMOF) prepared in Example 1; Figure 3 It is the microscopic morphology diagram of the wood chips with gas-sensing properties (cMOF / NW) in Example 1; Figure 4 It is the microscopic morphology diagram of the gas-sensing material with a porous skeleton (Ag-cMOF / NW) in Example 1; Figure 5 It is the scanning energy spectrum diagram of Ag-cMOF / NW in Example 1; among them, Figure 5 a is the C element distribution diagram of Ag-cMOF / NW, Figure 5 b is the O element distribution diagram of Ag-cMOF / NW, Figure 5c is the Cu element distribution map of Ag-cMOF / NW, Figure 5 d is the Ag element distribution map of Ag-cMOF / NW; Figure 6 It is the response recovery curve diagram of the conductive wood chips (CNT / NW), cMOF / NW, and Ag-cMOF / NW in Example 1 after introducing 3 ppm ammonia at room temperature. Specific implementation manners

[0019] In order to make the technical problems, technical solutions, and beneficial effects solved by this application clearer and more understandable, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application; obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

[0020] The present invention provides a preparation method of a gas-sensitive sensing material with a porous structure, including the following steps: Step 100: Immerse natural wood (Nature Wood, NW) with a conductive carbon material solution to obtain conductive wood chips.

[0021] Step 200: Mix copper sulfate with N,N-dimethylacetamide to obtain a copper sulfate suspension; mix a HITP•6HCl dispersion with a sodium acetate solution to obtain a mixed solution; mix the copper sulfate suspension with the mixed solution, heat and stir, and after centrifugation, washing, and drying, obtain cMOFs; Step 300: Disperse the cMOFs in ethanol to obtain a suspension containing cMOFs; Step 400: Drop the suspension containing cMOFs onto the conductive wood chips, and after drying, obtain wood chips with gas-sensitive properties; Step 500: Use a chemical deposition method to deposit silver single atoms on the surface of the wood chips with gas-sensitive properties, and after drying, obtain a gas-sensitive sensing material with a porous framework.

[0022] Preparation principle: The preparation method of the gas-sensing material with porous estimation described in the present invention uses the self-supporting pore structure of natural wood as the matrix material for loading the gas-sensing material. Natural wood, as a sustainable biomass material, has a unique hierarchical pore structure (micropore-mesopore-macropore through-network) and abundant surface functional groups (-OH, -COOH), which provide important channels for ammonia diffusion and adsorption detection. Specifically, the natural vertical pores of wood (pore diameter 10 - 50 μm) and the transverse pits form a three-dimensional through-network, and the gas diffusion rate is 3 - 5 times higher than that of traditional porous silicon-based materials, which can reduce the response time to ammonia. The porous structure of wood provides a uniform loading platform for gas-sensing materials such as cMOFs and conductive carbon materials, exposing more gas action sites. The characteristics of green and low-cost manufacturing of wood enable the prepared gas-sensing material to directly use the wood pores as a "self-template" without template pore formation or high-temperature sintering, which can significantly reduce both the process steps and manufacturing costs and broaden the application scenarios of natural wood. Coating natural wood with carbon nanotubes not only endows the wood with conductivity but also provides conditions for the material to respond to ammonia at room temperature. The suspension containing cMOFs is drop-coated on the conductive wood chips to prepare a pore-in-pore structure with cMOF material as the main gas-sensing material. Among them, cMOFs have a higher specific surface area and porosity, excellent conductivity, and the high active sites and strong host-guest interactions on their surfaces contribute to the efficient operation of the sensor at room temperature without high-temperature conditions, thereby reducing energy consumption and improving the stability of the sensor. In addition, the metal nodes and organic ligands of cMOFs can be combined and regulated in various ways, enabling subsequent customized design for pore size, chemical properties, and surface activity, achieving the characteristic of one-to-one matching between the pore size and the size of the monitored gas molecules, and thus realizing the effective monitoring of the gas to be measured. Using the chemical deposition method, silver single atoms are deposited on the surface of the wood chips with gas-sensing performance to load single-atom catalyst (SAC) silver single atoms on the cMOFs. While ensuring the porosity of the cMOF / NW gas-sensing material, it further improves the monitoring performance of the material for low-concentration ammonia. The single-atom sites have specific adsorption with gas molecules NH3, triggering charge transfer or redox reactions, thereby enhancing the resistance change signal of the sensor, optimizing the adsorption / desorption kinetics of the MOF material for ammonia, and increasing the sensor recovery speed by more than 30%.

[0023] The gas-sensitive sensing material with porous estimation described in the present invention is based on the mechanism of gas adsorption-conductivity change. By combining the porous structure of natural wood, the high adsorption performance of cMOF material, and the catalytic effect of silver ions, high-sensitivity detection of ammonia at room temperature is achieved. Among them, when the ammonia to be detected contacts the surface of the gas-sensitive sensing material, it first rapidly diffuses to the interior through the natural macroporous structure of the wood. Subsequently, the gas enters the microporous structure of the cMOF material with a pore size of 0.5-2 nm. Due to the extremely high specific surface area and abundant adsorption sites of the cMOF material, ammonia molecules are efficiently captured and adsorbed on the surface of the PN heterojunction formed by the cMOF material and carbon nanotubes.

[0024] It should be noted that cMOF and carbon nanotubes have P-type and N-type semiconductor characteristics respectively. When combined, they form a PN heterojunction, generating a built-in electric field at the interface, which significantly improves the charge separation efficiency and conductivity of the material. Carbon nanotubes have high conductivity, good mechanical strength and chemical stability, providing an efficient electron transport channel for the PN heterojunction. The network structure formed by coating on the wood chip substrate provides good support for the loading of cMOF, helps to form a uniform heterojunction interface, and at the same time enhances the overall stability of the material. cMOF has an extremely high specific surface area and a tunable pore structure, which can efficiently adsorb ammonia and enhance the selectivity for ammonia through chemical bonding or acid-base interaction. After ammonia adsorption, the electron transport characteristics of the PN heterojunction change, and this change can be sensitively detected through the resistance signal, thereby improving the response speed and sensitivity of the sensor. The interface effect of the PN heterojunction further amplifies the electrical signal change caused by ammonia adsorption, enabling the sensor to achieve accurate and rapid monitoring at an ammonia concentration as low as 3 ppm. Therefore, the combination of the high adsorption capacity of cMOF and the rapid electron transport characteristics of carbon nanotubes significantly improves the sensitivity of ammonia detection.

[0025] In the present invention, the introduced silver ions as single-atom catalysts (SACs) not only enhance the adsorption capacity of the cMOF material for ammonia but also optimize the desorption process. Specifically, silver ions accelerate the reaction between ammonia molecules and the cMOF material through catalytic action, and at the same time promote the rapid desorption of the adsorbed ammonia molecules after detection, thereby improving the response speed and recovery performance of the sensor. Secondly, the macroporous structure of natural wood provides a rapid gas diffusion channel, while the microporous structure of cMOF ensures high-density gas adsorption. The combination of the two forms a hierarchical pore structure of "pore-in-pore", significantly enhancing the sensitivity and response speed of the sensor. Utilizing the synergistic effect of wood and the gas-sensitive material enables the gas-sensitive sensing material to achieve efficient detection at room temperature without additional heating or cooling devices, reducing energy consumption and operation complexity.

[0026] Example 1 Embodiment 1 provides a method for preparing a gas-sensing material with a porous skeleton, including the following steps: Step 1: Cut cross-cut wood chips of a preset size from the cross-section of eucalyptus wood to obtain natural eucalyptus wood chips; wherein, the size characteristics of the natural eucalyptus wood chips are length × width × thickness = 5 cm × 5 cm × 500 μm; Mix carbon nanotubes (CNT) and water in a mass ratio of 2:3 to obtain a conductive carbon material solution; Immerse the natural eucalyptus wood chips with the conductive carbon material, and after drying, obtain conductive wood chips (CNT / NW); wherein, the number of impregnation and drying times is 6 times, the impregnation time for each time is 5 min, and the drying time is 10 min.

[0027] Step 2: Disperse CuSO4•5H2O powder in N,N-dimethylacetamide and perform ultrasonic treatment for 10 min to obtain a copper sulfate suspension with a concentration of 2.3 mg / mL (denoted as suspension A).

[0028] Step 3: Disperse HITP•6HCl powder in deionized water to obtain a HITP•6HCl dispersion with a concentration of 3.3 mg / mL (denoted as dispersion B).

[0029] Step 4: Mix dispersion B and an aqueous sodium acetate solution with a concentration of 164 mg / mL in a mass ratio of 1:1.3 to obtain a mixed solution (denoted as mixed solution C).

[0030] Step 5: Mix suspension A and mixed solution C in a mass ratio of 1:2.3 to obtain suspension D.

[0031] Step 6: Stir suspension D at room temperature for 5 min, then place it in an open glass bottle, heat it to 65 °C, and stir for 3.5 h to obtain suspension D1.

[0032] Step 7: Place suspension D1 in a centrifuge and centrifuge it at 6000 r / min for 10 min. After removing the supernatant, wash it twice with water and methanol respectively to obtain powder E.

[0033] Step 8: Dry powder E overnight at room temperature in a vacuum oven to obtain a conductive organic framework powder with gas-sensing performance, that is, obtain cMOFs (denoted as powder E1).

[0034] Step 9: Disperse powder E1 in ethanol to obtain a cMOF-containing suspension with a concentration of 10 mg / mL (denoted as suspension F).

[0035] Step 10: Divide the suspension F into five equal - mass portions; by means of drop - coating in batches, drop - coat the five equal - mass portions of the suspension F on the four corners and the preset central area of the conductive wood chip respectively to obtain a wood chip with gas - sensing performance (cMOF / NW, denoted as wood chip G); among them, a drying time of 10 min is reserved after each drop - coating.

[0036] Step 11: Dissolve 0.2 mM of silver nitrate in deionized water to obtain an electrolyte solution with silver single - atom metal precursor (denoted as electrolyte solution H).

[0037] Step 12: Immerse the wood chip G into the electrolyte solution H, and deposit the silver single - atoms in the electrolyte solution H on the wood chip G by electro - chemical deposition method; among them, during the electro - chemical deposition process, the potential of the cathode deposition is scanned from 0.513 V to 0.013 V for deposition, and a scanning rate of 5 mV s -1 is used, and the deposition process is repeated 10 times; after deposition, wash twice with deionized water and once with methanol; after washing, centrifuge and dry in vacuum to obtain a gas - sensing material with a porous skeleton (Ag - cMOF / NW).

[0038] Test results show that: Testing the Ag - cMOF / NW prepared in Example 1, it can be found that the prepared Ag - cMOF / NW has an initial measurement response time of 135.59 s, a recovery time of 6.47 s, and a response value of 5.15% in an ammonia atmosphere of 3 ppm at room temperature, meeting the monitoring of low - concentration ammonia.

[0039] Example 2 This Example 2 provides a preparation method of a gas - sensing material with a porous skeleton, including the following steps: Step 1: Cut a cross - cut wood chip of a preset size from the cross - section of pine wood to obtain a natural pine wood chip; among them, the size characteristics of the natural pine wood chip are length×width×thickness = 5 cm×5 cm×500 μm; mix CNT and water in a mass ratio of 1:2 to obtain a conductive carbon material solution; impregnate the natural pine wood chip with the conductive carbon material and dry it to obtain a conductive wood chip (CNT / NW); among them, the number of impregnation and drying times is 4 times, each impregnation time is 5 min, and the drying time is 10 min.

[0040] Step 2: Disperse CuSO4•5H2O powder in N,N - dimethylacetamide and ultrasonically treat for 10 min to obtain a suspension A with a concentration of 2 mg / mL.

[0041] Step 3: Disperse HITP•6HCl powder in deionized water to obtain dispersion B with a concentration of 3 mg / mL.

[0042] Step 4: Mix dispersion B with an aqueous sodium acetate solution with a concentration of 168 mg / mL in a mass ratio of 1:1 to obtain mixture C.

[0043] Step 5: Mix the suspension A and the mixture C in a mass ratio of 1:2 to obtain suspension D.

[0044] Step 6: Stir the suspension D at room temperature for 5 min, then place it in an open glass bottle, heat it to 70 °C and stir for 2.5 h to obtain suspension D1.

[0045] Step 7: Centrifuge the suspension D1 at 6000 r / min for 10 min in a centrifuge. After removing the supernatant, wash it twice with water and methanol respectively to obtain powder E.

[0046] Step 8: Dry the powder E overnight at room temperature in a vacuum oven to obtain a conductive organic framework powder with gas-sensing properties, that is, obtain powder E1.

[0047] Step 9: Disperse the powder E1 in ethanol to obtain suspension F with a concentration of 15 mg / mL.

[0048] Step 10: Divide the suspension F into five equal masses; by means of fractional dropwise coating, dropwise coat the five equal masses of the suspension F on the four corners and the middle preset area of the conductive wood chip respectively to obtain wood chip G; among them, leave a drying time of 10 min after each dropwise coating.

[0049] Step 11: Dissolve 0.2 mM of silver nitrate in deionized water to obtain electrolyte solution H.

[0050] Step 12: Immerse the wood chip G in the electrolyte solution H, and deposit silver single atoms in the electrolyte solution H on the wood chip G by electrochemical deposition method; during the electrochemical deposition process, scan the cathode deposition potential from 0.513 V to 0.013 V for deposition, and use a scanning rate of 5 mV s -1 and repeat the deposition process 10 times; after deposition, wash it twice with deionized water and once with methanol; after washing, centrifuge and dry it in vacuum to obtain Ag-cMOF / NW.

[0051] Test results description: Testing the Ag-cMOF / NW prepared in Example 2, it can be found that the prepared Ag-cMOF / NW has an initial measurement response time of 212.67 s, a recovery time of 8.25 s, and a response value of 4.07% in an ammonia atmosphere of 3 ppm at room temperature.

[0052] Example 2 Example 2 of the present invention provides a preparation method of a gas-sensitive sensing material with a porous framework, including the following steps: Step 1: Cut a cross-cut wood chip with a preset size from the cross-section of Chinese fir to obtain a natural Chinese fir wood chip; wherein, the size characteristics of the natural Chinese fir wood chip are length×width×thickness = 5 cm×5 cm×600 μm; mix CNT and water in a mass ratio of 1:2 to obtain a conductive carbon material solution; impregnate the natural Chinese fir wood chip with the conductive carbon material, and after drying, obtain a conductive wood chip (CNT / NW); wherein, the impregnation and drying are carried out 6 times, each impregnation time is 5 min, and the drying time is 10 min.

[0053] Step 2: Disperse CuSO4•5H2O powder in N,N-dimethylacetamide and ultrasonically treat for 10 min to obtain suspension A with a concentration of 2.5 mg / mL.

[0054] Step 3: Disperse HITP•6HCl powder in deionized water to obtain dispersion B with a concentration of 3.5 mg / mL.

[0055] Step 4: Mix dispersion B and an aqueous sodium acetate solution with a concentration of 170 mg / mL in a mass ratio of 1:2 to obtain mixture C.

[0056] Step 5: Mix suspension A and mixture C in a mass ratio of 1:2.5 to obtain suspension D.

[0057] Step 6: Stir suspension D at room temperature for 5 min, then place it in an open glass bottle, heat it to 75 °C and stir for 3.0 h to obtain suspension D1.

[0058] Step 7: Centrifuge suspension D1 in a centrifuge at 6500 r / min for 10 min, remove the supernatant, and wash it twice with water and methanol respectively to obtain powder E.

[0059] Step 8: Dry powder E in a vacuum oven at room temperature overnight to obtain a conductive organic framework powder with gas-sensitive properties, that is, obtain powder E1.

[0060] Step 9: Disperse powder E1 in ethanol to obtain suspension F with a concentration of 20 mg / mL.

[0061] Step 10: Divide the suspension F into five equal - mass portions; by means of drop - coating in batches, drop - coat the five equal - mass portions of the suspension F on the four corners and the middle preset area of the conductive wood chip respectively to obtain wood chip G; wherein, a drying time of 10 min is reserved after each drop - coating.

[0062] Step 11: Dissolve 0.2 mM of silver nitrate in deionized water to obtain electrolyte solution H.

[0063] Step 12: Immerse the wood chip G in the electrolyte solution H, and deposit silver single atoms in the electrolyte solution H on the wood chip G by electrochemical deposition; wherein, during the electrochemical deposition process, the potential of the cathode deposition is scanned from 0.513 V to 0.013 V for deposition, and a scanning rate of 5 mV s -1 is used, and the deposition process is repeated 10 times; after deposition, wash twice with deionized water and once with methanol; after washing, centrifuge and dry in vacuum to obtain Ag - cMOF / NW.

[0064] Test results show that: Testing the Ag - cMOF / NW prepared in Example 3 reveals that, in an ammonia atmosphere of 3 ppm at room temperature, the initial measurement response time of the prepared Ag - cMOF / NW is 197.46 s, the recovery time is 8.92 s, and the response value reaches 4.21%.

[0065] Example 4 This Example 4 provides a preparation method of a gas - sensitive sensing material with a porous framework, including the following steps: Step 1: Cut a cross - cut wood chip of a preset size from the cross - section of balsa wood to obtain a natural balsa wood chip; wherein, the size characteristics of the natural balsa wood chip are length×width×thickness = 5 cm×5 cm×700 μm; mix CNT and water in a mass ratio of 3:4 to obtain a conductive carbon material solution; impregnate the natural balsa wood chip with the conductive carbon material, and after drying, obtain a conductive wood chip (CNT / NW); wherein, the number of impregnation and drying times is 4 times, each impregnation time is 5 min, and the drying time is 10 min.

[0066] Step 2: Disperse CuSO4•5H2O powder in N,N - dimethylacetamide and ultrasonically treat for 10 min to obtain a suspension A with a concentration of 2 mg / mL.

[0067] Step 3: Disperse HITP•6HCl powder into deionized water to obtain a dispersion B with a concentration of 3 mg / mL.

[0068] Step 4: Mix dispersion B and an aqueous sodium acetate solution with a concentration of 164 mg / mL in a mass ratio of 1:1 to obtain mixture C.

[0069] Step 5: Mix the suspension A and the mixture C in a mass ratio of 1:2 to obtain suspension D.

[0070] Step 6: Stir the suspension D at room temperature for 5 min, then place it in an open glass bottle, heat it to 70 °C, and stir for 3.5 h to obtain suspension D1.

[0071] Step 7: Centrifuge the suspension D1 at 6000 r / min for 10 min, remove the supernatant, and wash it twice with water and methanol respectively to obtain powder E.

[0072] Step 8: Dry the powder E in a vacuum oven at room temperature overnight to obtain a conductive organic framework powder with gas-sensing performance, i.e., obtain powder E1.

[0073] Step 9: Disperse the powder E1 in ethanol to obtain a suspension F with a concentration of 20 mg / mL.

[0074] Step 10: Divide the suspension F into five equal-mass portions; by means of dropwise coating in batches, dropwise coat the five equal-mass portions of the suspension F on the four corners and the middle preset area of the conductive wooden chip respectively to obtain wooden chip G; among them, leave a drying time of 10 min after each dropwise coating.

[0075] Step 11: Dissolve 0.1 mM of silver nitrate in deionized water to obtain electrolyte solution H.

[0076] Step 12: Immerse the wooden chip G in the electrolyte solution H, and deposit silver single atoms in the electrolyte solution H on the wooden chip G by electrochemical deposition; among them, during the electrochemical deposition process, scan the potential of the cathode deposition from 0.513 V to 0.013 V for deposition, and use a scanning rate of 5 mV s -1 ; repeat the deposition process 10 times; after deposition, wash it twice with deionized water and once with methanol; after washing, centrifuge and dry it in vacuum to obtain Ag-cMOF / NW.

[0077] Test results description: Testing the Ag-cMOF / NW prepared in Example 4 shows that the prepared Ag-cMOF / NW has an initial measurement response time of 235.63 s, a recovery time of 10.21 s, and a response value of 2.07% in an ammonia atmosphere of 3 ppm at room temperature.

[0078] Example 5 This embodiment 5 provides a method for preparing a gas-sensitive sensor material having a porous skeleton, comprising the following steps: Step 1, cutting a cross-cut wood chip of a preset size from the cross-section of eucalyptus to obtain a natural eucalyptus wood chip; wherein the size characteristic of the natural eucalyptus wood chip is length×width×thickness=5cm×5cm×500μm; mixing CNT and water in a mass ratio of 2:3 to obtain a conductive carbon material solution; impregnating the natural eucalyptus wood chip with the conductive carbon material, and obtaining a conductive wood chip (CNT / NW) after drying; wherein the number of impregnation and drying is 6 times, each impregnation time is 5 minutes, and the drying time is 10 minutes.

[0079] Step 2: Disperse CuSO4•5H2O powder in N,N-dimethylacetamide and treat by ultrasonic for 10 min to obtain a suspension A with a concentration of 2.3 mg / mL.

[0080] Step 3: Disperse HITP•6HCl powder into deionized water to obtain dispersion B with a concentration of 3.3 mg / mL.

[0081] Step 4: Mix dispersion B with a sodium acetate aqueous solution having a concentration of 164 mg / mL in a mass ratio of 1:2 to obtain a mixed solution C.

[0082] Step 5: Mix the suspension A and the mixed solution C in a mass ratio of 1:3 to obtain a suspension D.

[0083] Step 6: Stir the suspension D at room temperature for 5 min, then place it in an open glass bottle, heat it to 65° C., and stir it for 4.5 h to obtain suspension D1.

[0084] Step 7: Place the suspension D1 in a centrifuge and centrifuge at 6000 r / min for 10 min. After removing the supernatant, wash twice with water and methanol respectively to obtain powder E.

[0085] Step 8: Dry the powder E in a vacuum oven at room temperature overnight to obtain a conductive organic framework powder with gas-sensitive properties, that is, obtain powder E1.

[0086] Step 9: Disperse the powder E1 in ethanol to obtain a suspension F with a concentration of 20 mg / mL.

[0087] Step 10, dividing the suspension F into five equal parts; dripping the five equal parts of the suspension F onto the four corners and the middle preset area of ​​the conductive wood chip by dripping in batches to obtain the wood chip G; wherein, after each dripping, a drying time of 10 minutes is reserved.

[0088] Step 11: Dissolve 0.1 mM silver nitrate in deionized water to obtain electrolyte solution H.

[0089] Step 12: Immerse the wood chip G into the electrolyte solution H, and deposit silver single atoms in the electrolyte solution H on the wood chip G by electrochemical deposition method; wherein, during the electrochemical deposition process, the potential of cathode deposition is scanned from 0.513 V to 0.013 V for deposition, and a scanning rate of 5 mV s -1 is adopted, and the deposition process is repeated 10 times; after deposition, wash twice with deionized water and once with methanol; after washing, centrifuge and dry under vacuum to obtain Ag-cMOF / NW.

[0090] Test results show that: Testing the Ag-cMOF / NW prepared in Example 5 reveals that the prepared Ag-cMOF / NW has an initial measurement response time of 164.27 s, a recovery time of 8.54 s, and a response value of 4.47% in an ammonia atmosphere of 3 ppm at room temperature.

[0091] As shown in the Figure 1 attachment, the microscopic morphology diagram of the natural eucalyptus wood chip in Example 1 is given; it can be seen from the Figure 1 attachment that the microscopic surface of the natural eucalyptus wood chip is composed of many micron-sized pores, and the surface of the wood chip presents a smooth state, which is conducive to the rapid diffusion of ammonia. Figure 1 As shown in the

[0092] attachment, the microscopic morphology diagram of the cMOFs (cMOF) prepared in Example 1 is given; it can be seen from the Figure 2 attachment that the cMOF has a nanorod-like structure, which can increase the contact area with ammonia, thus facilitating the subsequent ammonia adsorption. Figure 2 As shown in the Figure 2 attachment, the microscopic morphology diagram of the wood chip with gas sensing performance (cMOF / NW) in Example 1 is given; it can be seen from the

[0093] attachment that the cMOF grows tightly on the surface of the wood chip coated with carbon nanotubes, which is conducive to the formation of the CNT-cMOF heterojunction. Figure 3 As shown in the Figure 3 attachment, the microscopic morphology diagram of the gas sensing material with a porous framework (Ag-cMOF / NW) in Example 1 is given; it can be seen from the Figure 3 attachment that the cMOF grows tightly on the surface of the wood chip coated with carbon nanotubes, which is conducive to the formation of the CNT-cMOF heterojunction.

[0094] As shown in the Figure 4 attachment, the microscopic morphology diagram of the gas sensing material with a porous framework (Ag-cMOF / NW) in Example 1 is given; it can be seen from the Figure 4 attachment that the Ag-cMOF / NW has a porous framework structure, which is conducive to the adsorption and diffusion of ammonia. Figure 4It can be seen that the deposited silver is randomly distributed on the surface of cMOF / NW, and the morphology of silver is variable, with spherical and flaky shapes, enriching the microscopic conformation of the material and further increasing the contact surface between the material and ammonia.

[0095] As shown in the Figure 5 appendix, the Figure 5 scanning energy spectrum of Ag-cMOF / NW in Example 1 is given; among them, Figure 5 a is the C element distribution map of Ag-cMOF / NW, Figure 5 b is the O element distribution map of Ag-cMOF / NW, Figure 5 c is the Cu element distribution map of Ag-cMOF / NW, Figure 5 d is the Ag element distribution map of Ag-cMOF / NW; it can be seen from the Figure 5 appendix that cMOF and Ag ions are evenly distributed on the matrix composed of C and O elements.

[0096] As shown in the Figure 6 appendix, the Figure 6 response-recovery curve graphs of the conductive wood chip (CNT / NW), cMOF / NW, and Ag-cMOF / NW in Example 1 after introducing 3 ppm ammonia at room temperature are given; it can be seen from the Figure 6 appendix that after introducing 3 ppm ammonia at room temperature, the gas-sensing performance of the Ag-cMOF / NW material is better, the response value reaches 5.15%, and the response time is calculated to be 139.59 s, and the recovery time is shorter, only 6.47 s; the reasons are analyzed as follows: silver atoms solve the problem of difficult desorption of the composite material and amplify the resistance change of the composite material; among them, the recovery degree of the cMOF / NW material is increased from the original 84.75% to 100%, and the response value to ammonia is also increased from the original 4.13% to 5.15%.

[0097] It should be noted that when testing and calculating the gas-sensing performance of the Ag-cMOF / NW, a JF02F gas-sensing sensor test system produced by Kunming SinoPlatinum Metals Co., Ltd. is used for testing.

[0098] The preparation method of the gas-sensing material with a porous skeleton provided by the present invention utilizes the high-porosity skeleton of wood and the high specific surface area of MOF materials, significantly improving the sensor sensitivity, achieving effective monitoring of 3 ppm ammonia gas, reducing energy consumption and costs; by introducing silver ions as SACs, the adsorption / desorption kinetics of MOF materials for ammonia gas is optimized, increasing the sensor recovery speed by more than 30%, and solving the key bottleneck in the practical application of MOF materials; combining the macroporous structure of wood with the microporous structure of MOF to form a "pore-in-pore" hierarchical pore structure not only provides more adsorption sites but also accelerates the gas diffusion rate, shortening the sensor response time to within 10 seconds, especially suitable for the rapid detection of low-concentration gases; using natural wood as the skeleton reduces costs, utilizes renewable resources, develops environmentally friendly materials, and promotes the development of gas sensors towards low-cost and green sustainable directions; in the present invention, by combining natural wood with MOF materials, a new application scenario of biomass materials in the field of gas sensing is created, providing new ideas for the development of high-performance and multifunctional gas-sensing materials and promoting the cross-integration of biomass materials and advanced functional materials.

[0099] The above embodiments are merely one of the implementation manners capable of realizing the technical solutions of the present invention. The scope of protection required by the present invention is not only limited by this embodiment, but also includes any changes, substitutions, and other implementation manners that are easily conceivable by those skilled in the art within the technical scope disclosed by the present invention.

Claims

1. A method for preparing a gas-sensitive sensing material having a porous skeleton, characterized in that: include: The natural wood chips are impregnated with a conductive carbon material solution to obtain conductive wood chips; dispersing cMOFs in ethanol to obtain a suspension containing cMOFs; The cMOFs-containing suspension is drop-coated on the conductive wood chip, and after drying, a wood chip with gas-sensing properties is obtained; Silver single atoms are deposited on the surface of the wood chip with gas-sensing performance by using a chemical deposition method, and a gas-sensitive sensing material with a porous skeleton is obtained after drying.

2. The method for preparing a gas-sensitive sensing material having a porous skeleton according to claim 1, characterized in that: The natural wood chips are cross-cut wood chips of eucalyptus, pine, fir or balsa; the mass ratio of the conductive carbon material to water in the conductive carbon material solution is (1-3): (2-4), and the conductive carbon material is carbon nanotubes.

3. The method for preparing a gas-sensitive sensor material having a porous skeleton according to claim 1, characterized in that: The preparation process of the cMOFs comprises: Copper sulfate is mixed with N,N-dimethylacetamide to obtain a copper sulfate suspension; HITP•6HCl dispersion is mixed with sodium acetate solution to obtain a mixed solution; the copper sulfate suspension is mixed with the mixed solution, heated and stirred, and centrifuged, washed and dried to obtain cMOFs.

4. The method for preparing a gas-sensitive sensor material having a porous skeleton according to claim 3, characterized in that: The concentration of the copper sulfate suspension is 2-2.5 mg / mL; the concentration of the HITP•6HCl dispersion is 3-3.5 mg / mL; the mass ratio of the HITP•6HCl dispersion to the sodium acetate solution is 1:1-2; wherein the concentration of the sodium acetate solution is 164-170 mg / mL.

5. The method for preparing a gas-sensitive sensor material having a porous skeleton according to claim 4, characterized in that: The mass ratio of the copper sulfate suspension to the mixed solution is 1:2-3.

6. The method for preparing a gas-sensitive sensing material having a porous skeleton according to claim 1, characterized in that: The copper sulfate suspension is mixed with the mixed solution, heated and stirred, and after centrifugation, washing and drying, a conductive organic framework powder with gas-sensitive properties is obtained. The heating and stirring temperature is 65-75° C. and the heating and stirring time is 2.5-4.5 hours. When washing, deionized water and methanol are used for washing.

7. The method for preparing a gas-sensitive sensor material having a porous skeleton according to claim 1, characterized in that: The concentration of the cMOFs-containing suspension is 10-20 mg / mL.

8. The method for preparing a gas-sensitive sensor material having a porous skeleton according to claim 1, characterized in that: The process of depositing silver atoms on the surface of the wood chip with gas-sensitive properties by chemical deposition method and obtaining a gas-sensitive sensing material with a porous skeleton after drying is as follows: dissolving a silver single atom metal precursor in deionized water to obtain an electrolyte solution having the silver single atom metal precursor; The wood chip with gas-sensing property is immersed in the electrolyte solution with silver single atom metal precursor, and the silver single atom is deposited on the surface of the wood chip with gas-sensing property by electrochemical deposition method, and then washed and dried to obtain the gas-sensitive sensing material with porous skeleton.

9. A gas-sensitive sensing material having a porous skeleton, characterized in that: The gas-sensitive sensing material having a porous skeleton is prepared by the preparation method of any one of claims 1 to 8.

10. The use of a gas-sensitive sensing material having a porous skeleton as claimed in claim 9, characterized in that: Used for the preparation of gas sensors.

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