Silicon-boron-carbon-nitrogen gel-reduced graphene-zeolite three-dimensional structure composite material as well as preparation method and application thereof

Abstract

The invention discloses a silicon-boron-carbon-nitrogen gel-reduced graphene-zeolite three-dimensional structure composite material as well as a preparation method and application thereof.The structural design that reduced graphene oxide is used for modifying SiBCN aerogel and a molecular sieve is compounded is adopted, and assembly of the SiBCN aerogel is promoted and assisted through the powerful self-assembly capacity of rGO; the rGO is filled in macroporous structures of the SiBCN aerogel to relieve collapse of pores and reduce the number of the macroporous structures, and meanwhile, a carbon-rich phase and a graphene phase generated in situ during preparation of the SiBCN aerogel are beneficial to adsorption and filtration of interference gas. By controlling the heat treatment system, the prepared composite material has a more stable three-dimensional pore structure, can be applied to various complex gas monitoring environments, is beneficial to stable work of a combustible gas sensor, and is not influenced by various interference gases.

Description

Technical Field

[0001] This invention relates to the field of materials chemistry, and in particular to a silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional structure composite material, its preparation method, and its application. Background Technology

[0002] In the context of the "carbon neutrality" era, natural gas (mainly composed of methane) and hydrogen, as clean, efficient, and environmentally friendly gaseous energy sources, play an increasingly important role in today's energy system. Methane and hydrogen are colorless, odorless, flammable, and explosive. Their explosive limits in air are 4.9-16% and 4-75%, respectively, making them prone to leakage, which can lead to gas explosions and fires. Given the potential hazards of methane and hydrogen, real-time monitoring using combustible gas sensors in production and daily life is crucial. However, in their detection environment, combustible gas sensors are susceptible to interference from other gases such as ethanol, acetic acid, and formaldehyde, easily causing false alarms. To improve the selectivity of combustible gas sensors, a protective layer can be formed by introducing protective materials. This allows interfering gases to undergo catalytic degradation and adsorption filtration with the protective layer, preventing the sensitive material from responding to interfering gases.

[0003] Currently, improving the anti-interference performance of combustible gas sensors by using protective materials as a protective layer still faces many challenges. Combustible gas sensors are widely used in gas monitoring. Utilizing protective materials can not only effectively improve the anti-interference performance and stability of combustible gas sensors, but also significantly reduce their development costs. However, in order to broadly and effectively improve the anti-interference performance of combustible gas sensors and ensure the sensing performance of target gases, it is necessary to design protective materials with hierarchical porous structures and good gas adsorption properties. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the related art; therefore,

[0005] One object of the present invention is to provide a method for preparing a composite material of silicon boron carbon nitrogen aerogel combined with reduced graphene and zeolite molecular sieve.

[0006] Another object of the present invention is to provide a composite material with a three-dimensional structure formed by combining silicon boron carbon nitrogen aerogel with reduced graphene and zeolite molecular sieve prepared by the above preparation method.

[0007] Another objective of this invention is to provide the application of silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional structure composite materials.

[0008] The technical objective of this invention is achieved through the following technical solution.

[0009] A three-dimensional composite material of silicon boron carbon nitrogen aerogel-reduced graphene-zeolite and its preparation method are disclosed, comprising the following steps:

[0010] Step 1: Composite reduced graphene, silicon boron carbon nitride wet gel and zeolite molecular sieve.

[0011] Reduced graphene solution, silicon boron carbon nitride wet gel and ZSM-5 zeolite molecular sieve were placed in a mixer for pulverization and mixing to obtain a uniformly mixed rGO / PBSZ / ZSM-5 slurry. After molding, the slurry was freeze-dried to form rGO / PBSZ / ZSM-5 precursor aerogel. The slurry contained, by mass, 1-5 parts of reduced graphene solution, 10 parts of silicon boron carbon nitride wet gel and 20-40 parts of ZSM-5 molecular sieve.

[0012] The reduced graphene solution was prepared using the optimized Hummer method, with oleylamine as a surface modifier and ethylenediamine as a reducing agent to reduce graphene oxide. GO, oleylamine, and EDA were mixed and dispersed in cyclohexane, and a uniform rGO solution was formed by ultrasonic dispersion. By mass fraction, there were 15-20 parts of graphene oxide, 1-5 parts of oleylamine, 13-15 parts of ethylenediamine, and 4000 parts of cyclohexane.

[0013] Polyborosilazane and divinylbenzene were added to cyclohexane and stirred to obtain a uniformly dispersed PBSZ solution. The solution was then transferred to a high-pressure reaction vessel and reacted at 110-120℃ for 20-24 hours to carry out a solvothermal reaction, resulting in a wet PBSZ gel. The mass fractions were 2-4 parts of polyborosilazane, 1-2 parts of divinylbenzene, and 15-20 parts of cyclohexane.

[0014] In step 1, 2-4 parts of reduced graphene solution and 20-30 parts of ZSM-5 molecular sieve are used.

[0015] In step 1, the crushing and mixing time is 5 to 15 minutes, preferably 10 to 15 minutes.

[0016] In step 1, the GO / PBSZ / ZSM-5 slurry is transferred to a mold of suitable size and freeze-dried for 40-48 hours.

[0017] In step 1, the reduced graphene solution is prepared using the optimized Hummer method, with 18-20 parts of graphene oxide, 1-3 parts of oleylamine, and 15 parts of ethylenediamine.

[0018] In step 1, polyborosilazane (PBSZ) and divinylbenzene (DVB) are used as precursor raw materials, with 2 parts by mass of PBSZ, 1 part of divinylbenzene, and 16-18 parts of cyclohexane.

[0019] In step 1, after obtaining the PBSZ wet gel, the wet gel is then replaced with cyclohexane to remove the residual unreacted PBSZ and DVB, resulting in the SiBCN wet gel.

[0020] In step 1, the ZSM-5 zeolite molecular sieve used has a particle size of 1 to 10 μm and an internal pore size of 0.5 to 20 nm. More preferably, the ZSM-5 molecular sieve has a particle size of 1 to 5 μm and an internal pore size of 1 to 10 nm.

[0021] In step 1, before use, the ZSM-5 zeolite molecular sieve is subjected to multiple ultrasonic water washings and a final alcohol washing before being put into use.

[0022] Step 2: The rGO / PBSZ / ZSM-5 precursor aerogel prepared in Step 1 is placed in an inert protective atmosphere for calcination, and then cooled to room temperature in the furnace to form rGO / SiBCN / ZSM-5 composite aerogel; wherein, the calcination temperature is 1000-1200℃, and the temperature is maintained at the calcination temperature for 1-3 hours.

[0023] In step 2, the inert protective atmosphere is nitrogen, helium, or argon.

[0024] In step 2, the temperature is increased from room temperature (20-25 degrees Celsius) to calcination temperature (1000-1100 degrees Celsius) at a rate of 3-5 degrees Celsius / min and held for 1-2 hours.

[0025] In the preparation of the three-dimensional composite material in this invention, a structural design is adopted that modifies SiBCN aerogel with reduced graphene oxide and combines it with molecular sieves. The strong self-assembly ability of rGO promotes and assists the assembly of SiBCN aerogel. rGO filling the macroporous structure of SiBCN aerogel alleviates pore collapse and reduces the number of macroporous structures. Simultaneously, the carbon-rich phase and graphene phase generated in situ during the preparation of SiBCN aerogel are beneficial for the adsorption and filtration of interfering gases. This invention uses zeolite molecular sieves with micron-sized particles and nano-sized internal pores as fillers, further composited with SiBCN aerogel to form a SiBCN-graphene-zeolite three-dimensional structure, which can better achieve the adsorption and filtration of large molecular interfering gases. By controlling the heat treatment process, this invention makes the three-dimensional pore structure of the prepared composite material more stable, enabling its application in various complex gas monitoring environments. This is beneficial for the stable operation of combustible gas sensors and makes them unaffected by various interfering gases.

[0026] The present invention discloses a silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional structure composite material, in which the three materials are interwoven to form a three-dimensional spatial interconnected structure and a porous structure with a porosity ranging from nanometer to micrometer.

[0027] In composite materials, the three materials exist as independent phases. Silicon-boron-carbon-nitrogen aerogels mostly exist in the form of cross-linked particles, reduced graphene mostly exists in the form of sheet-like networks, and zeolite materials mostly exist in the form of cross-linked particles.

[0028] The composite material is a porous structure formed by the interweaving of three materials, with a porosity consisting of macropores, mesopores, and micropores, with scales of 50-500 nm, 15-25 nm, and 0.5-2 nm, respectively. Among these material characteristics, a composite material with a macropore scale of 50-100 nm, a mesopore scale of 10-20 nm, and a micropore scale of 0.5-1 nm is further preferred. Even more preferred is a composite material with a macropore scale of 100 nm, a mesopore scale of 10 nm, and a micropore scale of 1 nm.

[0029] The application of a silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material of the present invention as a protective material in the following (1) or (2):

[0030] (1) Application as a protective material in methane gas sensors;

[0031] (2) Application as a protective material in hydrogen sensors.

[0032] The silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional structure composite material is used as a protective material in methane gas sensors to improve their anti-interference performance.

[0033] The composite material with screening protection function obtained by this invention was assembled as a protective material onto a combustible gas sensor for gas sensitivity performance testing. The sensitivity (R0.05) to the interfering gas 2000 ppm ethanol was measured. a / R g The sensitivity is 1.04 for acetic acid at 6000 ppm, 1.05 for acetone at 2000 ppm, 11.56 for methane at 4000 ppm, and 7.36 for hydrogen at 1000 ppm.

[0034] In assembling the gas sensor, the rGO / SiBCN / ZSM-5 composite aerogel material of this invention is pulverized, sieved, and then filled into the sensor protective shell. The protective shell is then assembled with the gas sensor to form a sensor assembly with a protective shell. The rGO / SiBCN / ZSM-5 composite aerogel material of this invention can be pulverized mechanically, such as by ball milling; a 100-200 mesh sieve can be used for sieving. The protective shell can be made of PP, ABS, PC, or metal, adapted to the sensor, and features a top opening. The filling thickness of the composite material in the protective shell is 1.5–2.0 mm. More preferably, a PP protective shell is selected, sieved through a 200 mesh sieve, and the filling thickness is 1.5 mm.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] (1) The silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional composite material prepared by the method of the present invention has abundant pore structure, high specific surface area and stability, and excellent adsorption and filtration performance. In the presence of interfering gases such as ethanol and acetic acid, it can make the methane sensor almost unresponsive, while ensuring that the methane sensor has a sensitivity of 11.56 and a response time of 3s for 4000ppm methane gas; and ensures that the hydrogen sensor has a sensitivity of 7.36 and a response time of 3s for 1000ppm hydrogen gas.

[0037] (2) The preparation process of this invention is simple, low in cost, and easy to industrialize.

[0038] (3) The silicon boron carbon nitrogen aerogel-reduced graphene-zeolite three-dimensional structure composite material prepared by the present invention can improve the anti-interference performance of hydrogen sensors. Attached Figure Description

[0039] Figure 1 These are scanning electron microscope images of the SiBCN-graphene-zeolite three-dimensional composite material samples obtained in Examples 1-4 of this invention.

[0040] Figure 2 This is a graph showing the sensitivity characteristics of the methane sensor from Example 1 to ethanol and acetic acid.

[0041] Figure 3 This is a graph showing the sensitivity characteristics of the methane sensor from Example 1 to methane.

[0042] Figure 4 This is a bar chart showing the selective test results of the methane sensor from Example 1 on interfering gases such as methane and ethanol.

[0043] Figure 5 This is a graph showing the sensitivity characteristics of the hydrogen sensor in Example 1 to hydrogen. Detailed Implementation

[0044] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0045] Example 1:

[0046] The specific preparation method of the SiBCN-graphene-zeolite three-dimensional structure composite material in this embodiment is as follows:

[0047] (1) Preparation of rGO: rGO was prepared by the optimized Hummer method. 0.2 g of GO, 0.02 g of oleylamine and 0.15 g of EDA were weighed and dispersed in 40 g of cyclohexane, and a homogeneous GO solution was formed by ultrasonic dispersion.

[0048] (2) Preparation of SiBCN wet gel: 1.8 g of PBSZ and 0.9 g of DVB were weighed and added to 17 g of cyclohexane. The mixture was stirred at room temperature for 30 min to obtain a homogeneous PBSZ solution. The solution was then transferred to a Teflon-lined autoclave and heated at 120 °C for 20 h to carry out a solvothermal reaction, obtaining a PBSZ wet gel. Subsequently, the wet gel was replaced with cyclohexane to remove residual unreacted PBSZ and DVB.

[0049] (3) Pretreatment of ZSM-5 zeolite molecular sieve: ZSM-5 zeolite molecular sieve with a size of 5 micrometers and an internal pore size of 2 nanometers was selected, and was subjected to multiple ultrasonic water washings and a final alcohol washing before use.

[0050] (4) Formation of the three-dimensional structure of rGO / SiBCN / ZSM-5: 0.4 g of the GO solution from step (1), 1 g of the PBSZ wet gel from step (2), and 2 g of the ZSM-5 molecular sieve from step (3) were weighed and placed in a high-efficiency mixer for pulverization and mixing for 10 min to obtain a uniformly mixed GO / PBSZ / ZSM-5 slurry. The slurry was then transferred to a mold of suitable size and freeze-dried for 48 h to form the rGO / PBSZ / ZSM-5 precursor aerogel.

[0051] (5) The precursor aerogel is placed in an atmosphere furnace for calcination. During the calcination process, it is necessary to carry out the process under an inert atmosphere. The calcination temperature is 1000℃ and the heating rate is 5℃ / min. After maintaining the sintering temperature for 2 hours, it is cooled with the furnace to form the rGO / SiBCN / ZSM-5 composite material.

[0052] (6) Assembly of gas sensor: The rGO / SiBCN / ZSM-5 composite material obtained in step (4) is tightly filled into the PP material sensor protective shell with a top opening at a thickness of 1.5mm, and the protective shell is assembled with the methane sensor to obtain a sensor assembly with a protective shell.

[0053] Microstructure of composite materials, such as Figure 1 As shown in Figure (a), the sensor's gas sensitivity characteristics are as follows: Figure 2 As shown in Figures 3 and 5, the sensor characteristics are presented in Table 1. The composite material possesses a rich porous structure and a high specific surface area, demonstrating sensitivity to methane and hydrogen gases.

[0054] Example 2:

[0055] The experimental procedure is the same as in Example 1, but the difference is:

[0056] In step (1), 0.15 g of GO, 0.05 g of oleylamine and 0.13 g of EDA were weighed and dispersed in 40 g of cyclohexane, and a uniform GO solution was formed by ultrasonic dispersion.

[0057] In step (2), 4 grams of PBSZ and 2 grams of DVB were weighed and added to 20 grams of cyclohexane, and stirred at room temperature for 30 minutes to obtain a homogeneous PBSZ solution.

[0058] In step (3), ZSM-5 molecular sieve with a size of 10 micrometers and an internal pore size of 20 nanometers is selected.

[0059] In step (4), 0.5 g of the GO solution from step (1), 1 g of the PBSZ wet gel from step (2) and 4 g of the ZSM-5 molecular sieve from step (3) are weighed and placed into a high-efficiency mixer for pulverization and mixing for 15 min to obtain a uniformly mixed GO / PBSZ / ZSM-5 slurry.

[0060] In step (5), the calcination temperature is 1100℃, the heating rate is 5℃ / min, and the temperature is maintained at the sintering temperature for 2 hours before being cooled with the furnace to form rGO / SiBCN / ZSM-5 composite aerogel.

[0061] In step (6), the composite material is tightly packed into the PC material sensor protective shell with a top opening to a thickness of 2.0 mm.

[0062] Microstructure of composite materials, such as Figure 1 As shown in (b), the sensor characteristics are shown in Table 1.

[0063] Example 3:

[0064] The experimental procedure is the same as in Example 1, but the difference is:

[0065] In step (1), 0.18 g of GO, 0.03 g of oleylamine and 0.15 g of EDA were weighed and dispersed in 40 g of cyclohexane, and a uniform GO solution was formed by ultrasonic dispersion.

[0066] In step (2), 2 grams of PBSZ and 1 gram of DVB were weighed and added to 18 grams of cyclohexane, and stirred at room temperature for 30 minutes to obtain a homogeneous PBSZ solution.

[0067] In step (3), ZSM-5 molecular sieve with a size of 5 micrometers and an internal pore size of 10 nanometers is selected.

[0068] In step (4), 0.4 g of the GO solution from step (1), 1 g of the PBSZ wet gel from step (2) and 3 g of the ZSM-5 molecular sieve from step (3) are weighed and placed into a high-efficiency mixer for pulverization and mixing for 10 min to obtain a uniformly mixed GO / PBSZ / ZSM-5 slurry.

[0069] In step (5), the calcination temperature is 1000℃, the heating rate is 5℃ / min, and the temperature is maintained at the sintering temperature for 2.5h before being cooled with the furnace to form rGO / SiBCN / ZSM-5 composite aerogel.

[0070] In step (6), the composite material is tightly packed into the metal sensor protective shell with a top opening to a thickness of 2.0 mm.

[0071] The microstructure of the composite material is shown in the attached figure. Figure 1 As shown in (c), the sensor characteristics are shown in Table 1.

[0072] Example 4:

[0073] The experimental procedure is the same as in Example 1, but the difference is:

[0074] In step (1), 0.20 g of GO, 0.03 g of oleylamine and 0.15 g of EDA were weighed and dispersed in 40 g of cyclohexane, and a uniform GO solution was formed by ultrasonic dispersion.

[0075] In step (2), 3 grams of PBSZ and 2 grams of DVB were weighed and added to 16 grams of cyclohexane, and stirred at room temperature for 30 minutes to obtain a homogeneous PBSZ solution.

[0076] In step (3), ZSM-5 molecular sieve with a size of 5 micrometers and an internal pore size of 5 nanometers is selected.

[0077] In step (4), 0.5 g of the GO solution from step (1), 1 g of the PBSZ wet gel from step (2) and 2 g of the ZSM-5 molecular sieve from step (3) are weighed and placed into a high-efficiency mixer for pulverization and mixing for 10 min to obtain a uniformly mixed GO / PBSZ / ZSM-5 slurry.

[0078] In step (5), the calcination temperature is 1200℃, the heating rate is 5℃ / min, and the temperature is maintained at the sintering temperature for 1.5h before being cooled with the furnace to form rGO / SiBCN / ZSM-5 composite aerogel.

[0079] In step (6), the composite material is tightly packed into the ABS sensor protective shell with a top opening at a thickness of 1.5mm.

[0080] The microstructure of the composite material is shown in the attached figure. Figure 1 As shown in (d), the sensor characteristics are shown in Table 1.

[0081] Comparative example:

[0082] The experimental procedure is the same as in Example 1, but the difference is:

[0083] In step (4), ZSM-5 molecular sieve is not added.

[0084] The characteristics of composite material sensors are shown in Table 1.

[0085] From the appendix Figure 1 Scanning electron microscope (SEM) images of the SiBCN-graphene-zeolite three-dimensional composite material samples prepared in Examples 1-4 show that SiBCN, rGO and ZSM-5 form a three-dimensional complementary porous structure, indicating that SiBCN-graphene-zeolite three-dimensional composite materials can be prepared by following the preparation method and by changing the ZSM-5 molecular sieve material with different particle size and pore size.

[0086] Table 1 shows the sensing performance parameters of the three-dimensional structural composite materials prepared in Examples 1-4 and the comparative examples used in methane and hydrogen sensors.

[0087] Table 1 shows the sensor response characteristics.

[0088]

[0089] The aerogel-graphene-zeolite molecular sieve composite material prepared by this invention possesses a three-dimensional, multi-level complementary pore structure. While not affecting the methane gas response, it can effectively isolate or adsorb interfering gases, thereby improving the sensor's selectivity for methane gas. The material preparation process of this invention is simple, and the raw material cost is low, making it an ideal material for sensor protective layers.

[0090] Adjusting the process parameters according to the present invention can achieve the preparation of the aerogel-graphene-zeolite molecular sieve composite material of the present invention. Testing has shown that the performance is essentially the same as that of the present invention. The present invention has been described above as exemplary. It should be noted that any simple modifications, alterations, or other equivalent substitutions that can be made by those skilled in the art without creative effort, without departing from the core of the present invention, fall within the protection scope of the present invention.

Claims

1. A three-dimensional composite material of silicon boron carbon nitride aerogel-reduced graphene-zeolite, characterized in that, The three materials are interwoven to form a three-dimensional interconnected and porous structure with porosity ranging from nanometers to micrometers. In the composite material, each material exists as an independent phase: the silicon-boron-carbon-nitrogen aerogel exists primarily as cross-linked particulate matter, the reduced graphene exists primarily as a network of sheet-like structures, and the zeolite material exists primarily as cross-linked particulate matter. The porous structure formed by the interweaving of these three materials exhibits a simultaneous presence of macropores, mesopores, and micropores, with scales of 50-500 nm, 15-25 nm, and 0.5-2 nm, respectively. The process is as follows: Step 1: Composite reduced graphene, silicon boron carbon nitride wet gel and zeolite molecular sieve. Reduced graphene solution, silicon boron carbon nitride wet gel and ZSM-5 zeolite molecular sieve were placed in a mixer for pulverization and mixing to obtain a uniformly mixed rGO / PBSZ / ZSM-5 slurry. After molding, the slurry was freeze-dried to form rGO / PBSZ / ZSM-5 precursor aerogel. The slurry contained, by mass, 1-5 parts of reduced graphene solution, 10 parts of silicon boron carbon nitride wet gel and 20-40 parts of ZSM-5 molecular sieve. The reduced graphene solution was prepared using the optimized Hummer method, with oleylamine as a surface modifier and ethylenediamine as a reducing agent to reduce graphene oxide. GO, oleylamine, and EDA were mixed and dispersed in cyclohexane, and a uniform rGO solution was formed by ultrasonic dispersion. By mass fraction, there were 15-20 parts of graphene oxide, 1-5 parts of oleylamine, 13-15 parts of ethylenediamine, and 4000 parts of cyclohexane. Polyborosilazane and divinylbenzene were added to cyclohexane and stirred to obtain a uniformly dispersed PBSZ solution. The solution was then transferred to a high-pressure reaction vessel and reacted at 110-120℃ for 20-24 hours to carry out a solvothermal reaction, resulting in a wet PBSZ gel. The mass fractions were 2-4 parts of polyborosilazane, 1-2 parts of divinylbenzene, and 15-20 parts of cyclohexane. Step 2: The rGO / PBSZ / ZSM-5 precursor aerogel prepared in Step 1 is placed in an inert protective atmosphere for calcination, and then cooled to room temperature in the furnace to form rGO / SiBCN / ZSM-5 composite aerogel; wherein, the calcination temperature is 1000-1200℃, and the temperature is maintained at the calcination temperature for 1-3 hours.

2. The silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 1, characterized in that, The porous structure material formed by the interweaving of three materials in the composite material has a porosity in which macropores, mesopores and micropores coexist, with scales of 50-100 nm for macropores, 10-20 nm for mesopores and 0.5-1 nm for micropores, preferably 100 nm for macropores, 10 nm for mesopores and 1 nm for micropores.

3. The silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 1, characterized in that, In step 1, 2-4 parts of reduced graphene solution and 20-30 parts of ZSM-5 molecular sieve are added; the pulverization and mixing time is 5-15 min, preferably 10-15 min; the GO / PBSZ / ZSM-5 slurry is transferred to a mold of suitable size and freeze-dried for 40-48 h.

4. The silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 1, characterized in that, In step 1, the reduced graphene solution is prepared using the optimized Hummer method, with 18-20 parts graphene oxide, 1-3 parts oleylamine, and 15 parts ethylenediamine. Polyborosilazane and divinylbenzene are used as precursor raw materials, with 2 parts polyborosilazane, 1 part divinylbenzene, and 16-18 parts cyclohexane by mass. After obtaining the PBSZ wet gel, the wet gel is then replaced with cyclohexane to remove residual unreacted PBSZ and DVB, yielding the SiBCN wet gel. ZSM-5 zeolite molecular sieves with particle sizes of 1-10 μm and internal pore sizes of 0.5-20 nm are used for molecular sieve selection; more preferably, ZSM-5 molecular sieves with particle sizes of 1-5 μm and internal pore sizes of 1-10 nm are selected. Before use, the ZSM-5 zeolite molecular sieves are subjected to multiple ultrasonic water washes and a final alcohol wash before use.

5. The silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 1, characterized in that, In step 2, the inert protective atmosphere is nitrogen, helium or argon; the temperature is increased from room temperature (20-25 degrees Celsius) to the calcination temperature (1000-1100 degrees Celsius) at a rate of 3-5 degrees Celsius / min and held for 1-2 hours.

6. A method for preparing a three-dimensional composite material of silicon boron carbon nitride aerogel-reduced graphene-zeolite, characterized in that, Follow these steps: Step 1: Composite reduced graphene, silicon boron carbon nitride wet gel and zeolite molecular sieve. Reduced graphene solution, silicon boron carbon nitride wet gel and ZSM-5 zeolite molecular sieve were placed in a mixer for pulverization and mixing to obtain a uniformly mixed rGO / PBSZ / ZSM-5 slurry. After molding, the slurry was freeze-dried to form rGO / PBSZ / ZSM-5 precursor aerogel. The slurry contained, by mass, 1-5 parts of reduced graphene solution, 10 parts of silicon boron carbon nitride wet gel and 20-40 parts of ZSM-5 molecular sieve. The reduced graphene solution was prepared using the optimized Hummer method, with oleylamine as a surface modifier and ethylenediamine as a reducing agent to reduce graphene oxide. GO, oleylamine, and EDA were mixed and dispersed in cyclohexane, and a uniform rGO solution was formed by ultrasonic dispersion. By mass fraction, there were 15-20 parts of graphene oxide, 1-5 parts of oleylamine, 13-15 parts of ethylenediamine, and 4000 parts of cyclohexane. Polyborosilazane and divinylbenzene were added to cyclohexane and stirred to obtain a uniformly dispersed PBSZ solution. The solution was then transferred to a high-pressure reaction vessel and reacted at 110-120℃ for 20-24 hours to carry out a solvothermal reaction, resulting in a wet PBSZ gel. The mass fractions were 2-4 parts of polyborosilazane, 1-2 parts of divinylbenzene, and 15-20 parts of cyclohexane. Step 2: The rGO / PBSZ / ZSM-5 precursor aerogel prepared in Step 1 is placed in an inert protective atmosphere for calcination, and then cooled to room temperature in the furnace to form rGO / SiBCN / ZSM-5 composite aerogel; wherein, the calcination temperature is 1000-1200℃, and the temperature is maintained at the calcination temperature for 1-3 hours.

7. The method for preparing a silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 6, characterized in that, In step 1, 2-4 parts of reduced graphene solution and 20-30 parts of ZSM-5 molecular sieve are added; the pulverization and mixing time is 5-15 min, preferably 10-15 min; the GO / PBSZ / ZSM-5 slurry is transferred to a mold of suitable size and freeze-dried for 40-48 h.

8. The method for preparing a silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 6, characterized in that, In step 1, the reduced graphene solution is prepared using the optimized Hummer method, with 18-20 parts graphene oxide, 1-3 parts oleylamine, and 15 parts ethylenediamine. Polyborosilazane and divinylbenzene are used as precursor raw materials, with 2 parts polyborosilazane, 1 part divinylbenzene, and 16-18 parts cyclohexane by mass. After obtaining the PBSZ wet gel, the wet gel is then replaced with cyclohexane to remove residual unreacted PBSZ and DVB, yielding the SiBCN wet gel. ZSM-5 zeolite molecular sieves with particle sizes of 1-10 μm and internal pore sizes of 0.5-20 nm are used for molecular sieve selection; more preferably, ZSM-5 molecular sieves with particle sizes of 1-5 μm and internal pore sizes of 1-10 nm are selected. Before use, the ZSM-5 zeolite molecular sieves are subjected to multiple ultrasonic water washes and a final alcohol wash before use.

9. The method for preparing a silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material according to claim 6, characterized in that, In step 2, the inert protective atmosphere is nitrogen, helium or argon; the temperature is increased from room temperature (20-25 degrees Celsius) to the calcination temperature (1000-1100 degrees Celsius) at a rate of 3-5 degrees Celsius / min and held for 1-2 hours.

10. The application of the silicon boron carbon nitride aerogel-reduced graphene-zeolite three-dimensional structure composite material as a protective material in a methane gas sensor or a hydrogen gas sensor, as described in any one of claims 1-5, is characterized in that... In assembling the gas sensor, the composite aerogel material is pulverized, sieved, and then filled into the sensor protective shell. The protective shell is then assembled with the gas sensor to form a sensor assembly with a protective shell. The composite aerogel material can be pulverized mechanically, such as by ball milling. A 100-200 mesh sieve is used for sieving. The protective shell can be made of PP, ABS, PC, or metal, adapted to the sensor, and features a top opening. The filling thickness of the composite material in the protective shell is 1.5–2.0 mm. More preferably, a PP protective shell is selected, sieved through a 200 mesh sieve, and filled with a thickness of 1.5 mm. This protective material is then assembled onto the combustible gas sensor for gas sensitivity testing, specifically the sensitivity (R0) to the interfering gas 2000 ppm ethanol. a / R g The sensitivity is 1.04 for acetic acid at 6000 ppm, 1.05 for acetone at 2000 ppm, 11.56 for methane at 4000 ppm, and 7.36 for hydrogen at 1000 ppm.

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