Composite aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of aerogel, and particularly relates to composite aerogel as well as a preparation method and application thereof. According to the preparation method disclosed by the invention, waste persimmon pomace can be utilized, and 2, 4-diaminobenzene sulfonic acid is added to be doped with nitrogen and sulfur elements to prepare the fluorescent carbon quantum dot with the emission wavelength in a green light region. The carbon quantum dots show that groups such as amino groups and the like can be subjected to Schiff base reaction with formaldehyde to quench fluorescence, so that formaldehyde detection is realized. Similarly, amino groups in the chitosan-acrylamide aerogel can also adsorb formaldehyde in the air through a Schiff base reaction with formaldehyde. The method for preparing the aerogel ball is very mild, simple in process and safe to operate, and is a green and environment-friendly material. Nitrogen and sulfur co-doped carbon quantum dots and chitosan-acrylamide are compounded to form aerogel which is used as a formaldehyde adsorption-detection bifunctional material, whether the material reaches adsorption saturation or not is detected through a carbon quantum dot fluorescence reaction, formaldehyde is fixed through chemical adsorption by utilizing groups of the material, and secondary pollution caused by formaldehyde desorption is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerogels, and in particular relates to a composite aerogel and a preparation method and application thereof. Background Art

[0002] Formaldehyde (HCHO) is a volatile organic compound (VOC) gas that can be released from sources such as wood burning, industrial emissions, and fixatives in resin manufacturing. This colorless gas can irritate the eyes and upper respiratory tract. Long-term exposure to formaldehyde is known to cause numerous adverse reactions, including nasopharyngeal cancer, pregnancy-related complications, brain tumors, and leukemia. Therefore, rapid formaldehyde detection and removal methods have garnered significant research attention.

[0003] Currently, common methods for removing formaldehyde at home include adsorption (activated carbon, etc.), biological filtration (plants), and catalytic decomposition (photocatalysis, thermal catalysis, chlorine dioxide oxidation decomposition, etc.). However, due to the higher cost of catalytic methods and the toxicity of some catalysts, activated carbon adsorption and plant filtration are more commonly used in households. Activated carbon adsorbs formaldehyde through physical bonding mechanisms such as van der Waals forces. While inexpensive, this approach poses significant safety risks due to difficulties determining adsorption saturation and the ease of desorption. Plants have a limited ability to filter formaldehyde and are not suitable for treating excessive formaldehyde levels in the environment. Therefore, developing a dual-functional formaldehyde adsorption and detection material that can simultaneously detect and remove formaldehyde from the environment is highly valuable. Summary of the Invention

[0004] The present invention provides a composite aerogel, its preparation method, and its application. This dual-functional carbon quantum dot / chitosan-acrylamide composite aerogel, which combines both adsorption and sensitive detection, possesses a large specific surface area and amino groups, enabling physical and chemical adsorption of formaldehyde in the air. Furthermore, by doping the carbon quantum dots and allowing formaldehyde to react with them, fluorescence quenching occurs, enabling fluorescent detection of formaldehyde.

[0005] The first aspect of the present application provides a method for preparing a composite aerogel, comprising: Step 1, preparing a nitrogen-sulfur co-doped carbon quantum dot solution using persimmon pomace; Step 2: Add a certain amount of acetic acid to the diluted carbon quantum dot solution and stir evenly; then, add gelatin and chitosan powder, maintain at a certain temperature and stir until uniform; Step 3, adding a certain amount of acrylamide and stirring at room temperature; after forming a stable aqueous mixture, adding glutaraldehyde solution and stirring to crosslink; Step 4, vacuum freeze-drying the solution until the water is completely removed; rinsing the obtained material with ultrapure water until neutral, then soaking and rinsing in acetone several times, and soaking in cyclohexane for a certain period of time; vacuum drying the product at room temperature until the solvent is completely removed to obtain carbon quantum dot / chitosan-acrylamide composite aerogel.

[0006] In one embodiment of the present application, step 1 includes: Step 11, taking persimmon pomace, thoroughly washing it, drying it, and grinding it into powder; the persimmon pomace can be discarded persimmon pomace; Step 12, dispersing the powder in an ethanol solution, adding 2,4-diaminobenzenesulfonic acid and ultrasonically mixing, and then placing the mixture in a hydrothermal reactor for heating and reaction; Step 13: After the reaction is completed, the supernatant in the reactor is centrifuged and filtered to form a nitrogen-sulfur co-doped carbon quantum dot solution, which is stored for later use.

[0007] In one embodiment of the present application, in step 12, the mass ratio of persimmon pomace powder to 2,4-diaminobenzenesulfonic acid is 1:0.5 to 1:2, preferably 1:1; the ethanol concentration of the ethanol solution is 20%-90%, preferably 50%; the mass of persimmon pomace powder: solution volume is 1g:40mL to 1g:60mL, preferably 1g:50mL.

[0008] In one embodiment of the present application, in step 12, the ultrasonic mixing is preferably performed in a polytetrafluoroethylene liner, and the ultrasonic mixing time is 5-30 minutes, preferably 10 minutes.

[0009] In one embodiment of the present application, in step 12, the heating reaction time is 10-15 hours, preferably 12 hours; the heating reaction temperature is 160-200°C, preferably 180°C.

[0010] In one embodiment of the present application, in step 2, the concentration of the carbon quantum dot solution is 0% to 50%; the mass ratio of gelatin to chitosan is 1:5-1:20, preferably 1:10; the volume ratio of acetic acid: carbon quantum dot solution is 1:200; and the ratio of gelatin: chitosan: carbon quantum dot solution is 0.1 g: 1 g: 100 mL.

[0011] In one embodiment of the present application, in step 3: The mass ratio of acrylamide to chitosan is 1:10-1:40, preferably 1:20; The concentration of glutaraldehyde is 5%-50%, preferably 10%; the volume ratio of glutaraldehyde to the aqueous mixture solution is 1:500-1:2000, preferably 1:1000; The stirring cross-linking time is 10h-24h, preferably 12h.

[0012] In one embodiment of the present application, in step 4: The vacuum freeze-drying time is 24-48 hours, and the temperature is -30 to -50°C; preferably, the vacuum freeze-drying time is 48 hours, and the temperature is -50°C; The vacuum drying time is 8 h to 24 h, and the temperature is 20° C. to 30° C.; preferably, the vacuum drying time is 24 h, and the temperature is 25° C.

[0013] A second aspect of the present application provides a composite aerogel prepared using the preparation method described above.

[0014] A third aspect of the present application provides an application of the composite aerogel as described above in the adsorption detection of formaldehyde.

[0015] The beneficial effects of the present invention are as follows: the present invention can utilize discarded persimmon pomace, and prepare a fluorescent carbon quantum dot with an emission wavelength in the green region by adding 2,4-diaminobenzenesulfonic acid to dope nitrogen and sulfur elements. The carbon quantum dots show that there are groups such as amino groups that can react with formaldehyde to undergo a Schiff base reaction to quench its fluorescence, thereby realizing the detection of formaldehyde. Similarly, the amino groups in the chitosan-acrylamide aerogel can also react with formaldehyde through a Schiff base reaction to adsorb formaldehyde in the air. The method for preparing this aerogel ball is very gentle, the process is simple, the operation is safe, and it is a green and environmentally friendly material. The nitrogen and sulfur co-doped carbon quantum dots are composited with chitosan-acrylamide to form an aerogel as a dual-functional material for adsorption and detection of formaldehyde. The fluorescence reaction of the carbon quantum dots is used to detect whether the material has reached adsorption saturation, and the groups of the material are used to fix formaldehyde through chemical adsorption, which greatly reduces the secondary pollution caused by formaldehyde desorption.

[0016] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1: is a fluorescence spectrum diagram of Example 2 of the present invention; wherein, a in the figure is a fluorescence excitation diagram, and b is a fluorescence emission diagram; Figure 2 The SEM images of Comparative Example 1 and Example 2 of the present invention are shown; Figure 3 FTIR spectra of Example 2 and Comparative Example 3 of the present invention, showing the presence of sulfonic acid functional groups in the aerogel (Example 2) after the addition of nitrogen-sulfur co-doped carbon quantum dots. In addition, both Example 2 and Comparative Example 1 have stretching vibration bands of chitosan-derived carbohydrates CH, CH2, and CH3. Figure 4 The formaldehyde adsorption test results of Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 of the present invention show that Example 2 has a better adsorption effect; Figure 5 The static desorption test of Example 2 of the present invention and Comparative Examples 1, 2, 3 and 4 shows that the amount of formaldehyde desorbed by Example 2 after adsorption saturation is quite small and is also significantly lower than that of Comparative Example 1. Figure 6 The fluorescence intensity changes of the aqueous solution of Example 2 of the present invention in formaldehyde solutions of different concentrations are shown. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Carbon dots (CDs) are a new member of the carbon nanomaterial family. They are discrete, quasi-spherical carbon nanoparticles with a particle size of less than 10 nm. Since their discovery in 2004, CDs have theoretically shown great potential as fluorescent probes due to their high solubility, low toxicity, good biocompatibility, and controllable fluorescence, as they can be functionalized to suit different functional requirements. Chitosan, a renewable natural product, contains a large number of amine (-NH2) and hydroxyl (-OH) groups in its molecular chain. These molecules react with formaldehyde through a Schiff base reaction, preventing formaldehyde desorption and making it a good formaldehyde adsorbent. By combining carbon quantum dots with chitosan aerogel to form a dual-functional adsorption and detection material, efficient formaldehyde removal can be achieved.

[0022] Example 1: Preparation of nitrogen-sulfur co-doped persimmon pomace carbon quantum dot solution A certain amount of discarded persimmon pomace was cleaned with deionized water, dried, and ground into powder using a pulverizer. One gram of persimmon pomace powder and one gram of 2,4-diaminobenzenesulfonic acid (2,4-DABS) were dissolved in 50 ml of 50% ethanol and mixed thoroughly by sonication for 10 minutes. The solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 hours. After the reaction, the solution was centrifuged at 10,000 rpm for 5 minutes. The supernatant was filtered through a 0.22 μm filter to prepare a nitrogen-sulfur co-doped persimmon pomace carbon quantum dot solution (hereinafter referred to as persimmon pomace carbon quantum dots). This process was repeated five times to obtain a total of 220 ml of persimmon pomace carbon quantum dot solution.

[0023] Example 2: Preparation of nitrogen-sulfur co-doped persimmon pomace carbon quantum dots / chitosan-acrylamide composite aerogel 50 ml of the persimmon residue carbon quantum dot solution was added to deionized water to prepare 200 ml of a 25% concentration of persimmon residue carbon quantum dot solution. 1 mL of CH3COOH was added to the persimmon residue carbon quantum dot solution and stirred until homogeneous. Then, 200 mg of gelatin and 2 g of chitosan powder were added to a beaker, maintained at 40°C on a magnetic stirrer, and stirred until homogeneous. 100 mg of C3H5NO was then added and stirred at room temperature for 12 hours. After a stable aqueous mixture was formed, glutaraldehyde (200 μL, 10%) was added and stirred for 12 hours to achieve sufficient cross-linking. The solution was then injected into a glass Petri dish and freeze-dried at -50°C for 48 hours using a freeze dryer until the water was completely removed. The resulting material was rinsed with ultrapure water until neutral, then soaked and rinsed three times in acetone and soaked in cyclohexane for 2 hours. The product was dried at 25 °C for 24 h until the solvent was completely removed to obtain nitrogen-sulfur co-doped persimmon pomace carbon quantum dots / chitosan-acrylamide composite aerogel.

[0024] Comparative Example 1 1 mL of CH3COOH was added to 200 mL of ultrapure water and stirred thoroughly. Subsequently, 200 mg of gelatin and 2 g of chitosan powder were added to a beaker, maintained at 40°C on a magnetic stirrer, and stirred until homogeneous. 100 mg of C3H5NO was then added and stirred at room temperature for 12 hours. After a stable mixture was formed, glutaraldehyde (200 μL, 10%) was added and stirred for 12 hours to achieve sufficient cross-linking. The solution was then injected into a glass Petri dish and freeze-dried at -50°C for 48 hours using a freeze dryer until the water was completely removed. The resulting material was rinsed with ultrapure water until neutral, then soaked and rinsed three times in acetone and soaked in cyclohexane for 2 hours. The product was dried at 25°C for 24 hours until the solvent was completely removed to obtain the chitosan-acrylamide aerogel.

[0025] Comparative Example 2 10 ml of the persimmon residue carbon quantum dot solution was added to deionized water to prepare 200 ml of a 5% persimmon residue carbon quantum dot solution. The remaining steps remained the same as in Example 2.

[0026] Comparative Example 3 20 ml of the persimmon residue carbon quantum dot solution was added to deionized water to prepare 200 ml of a 10% persimmon residue carbon quantum dot solution. The remaining steps remained the same as in Example 2.

[0027] Comparative Example 4 100 ml of the persimmon residue carbon quantum dot solution was added to deionized water to prepare 200 ml of a 50% persimmon residue carbon quantum dot solution. The remaining steps remained the same as in Example 2.

[0028] Application Example 1 The following experiments demonstrate the formaldehyde removal effect of the nitrogen-sulfur co-doped persimmon pomace carbon quantum dots / chitosan-acrylamide composite aerogel (hereinafter referred to as aerogel) prepared by the present invention. (1) Formaldehyde adsorption test: Referring to QB / T2761--2006 standard, 1 g of aerogel prepared in Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 of the present invention was taken and placed in a 0.2 m 3 The test was conducted in a glass glove box. The formaldehyde concentration in each group was the same, and the initial formaldehyde release was 60µL of a 1.8% formaldehyde solution. The detection method was phenol reagent spectrophotometry. The test results are shown in Tables 1-1, 1-2, 1-3, and 1-4. Example 2 of the present invention was selected as the one with the best adsorption effect, and a subsequent static desorption test was performed with Comparative Example 1 without doping carbon quantum dots. Figure 4 , are the formaldehyde adsorption test results of Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 of the present invention, showing that Example 2 has a better adsorption effect.

[0029] Table 1-1 Formaldehyde adsorption capacity test of Example 2 0h 2h 4h 6h 24h 36h 48h Adsorption capacity (mg / g) Formaldehyde adsorption rate (%) 0.00 25.12 37.63 58.34 82.22 87.05 91.87 1.071 Table 1-2 Comparative Example 1 Formaldehyde Adsorption Capacity Test 0h 2h 4h 6h 24h 36h 48h Adsorption capacity (mg / g) Formaldehyde adsorption rate (%) 0.00 5.63 16.07 42.69 70.75 76.63 78.96 0.921 Table 1-3 Comparative Example 2 Formaldehyde Adsorption Capacity Test 0h 2h 4h 6h 24h 36h 48h Adsorption capacity (mg / g) Formaldehyde adsorption rate (%) 0.00 18.09 30.05 46.37 71.53 79.14 83.73 0.977 Table 1-4 Comparative Example 3 Formaldehyde Adsorption Capacity Test 0h 2h 4h 6h 24h 36h 48h Adsorption capacity (mg / g) Formaldehyde adsorption rate (%) 0.00 17.67 26.89 46.76 72.94 75.68 85.34 0.995 Table 1-5 Comparative Example 4 Formaldehyde Adsorption Capacity Test 0h 2h 4h 6h 24h 36h 48h Adsorption capacity (mg / g) Formaldehyde adsorption rate (%) 0.00 24.54 38.39 56.56 79.67 84.77 89.40 1.043 (2) Static desorption test after adsorption: 1 g of the aerogels prepared in Example 2 of the present invention and Comparative Examples 1 to 4 after saturation with formaldehyde adsorption was placed in a 0.2 m 3 The test was carried out in a glass glove box to detect the formaldehyde content within 48 hours. The detection method was a formaldehyde sensor. The test results are shown in Table 2-1, Table 2-2, Table 2-3, Table 2-4 and Table 2-5.

[0030] Table 2-1 Static desorption test after adsorption of Example 2 0h 12h 24h 36h 48h <![CDATA[Formaldehyde content (mg / m 3 )]]> 0.002 0.00295 0.0031 0.00351 0.00394 Table 2-2 Static desorption test after adsorption of comparative example 1 0h 12h 24h 36h 48h <![CDATA[Formaldehyde content (mg / m 3 )]]> 0.0023 0.0033 0.00403 0.00481 0.00502 Table 2-3 Static desorption test after adsorption of comparative example 2 0h 12h 24h 36h 48h <![CDATA[Formaldehyde content (mg / m 3 )]]> 0.00221 0.00317 0.00353 0.00385 0.00439 Table 2-4 Static desorption test after adsorption of comparative example 3 0h 12h 24h 36h 48h <![CDATA[Formaldehyde content (mg / m 3 )]]> 0.00207 0.00319 0.00341 0.00377 0.00411 Table 2-5 Static desorption test after adsorption of comparative example 4 0h 12h 24h 36h 48h <![CDATA[Formaldehyde content (mg / m 3 )]]> 0.00199 0.003 0.0033 0.00369 0.004 According to Table 1-1, Table 1-2, Table 1-3, Table 1-4 and Table 1-5, and Figure 5 It can be seen that the aerogel prepared in Example 2 of the present invention has a large formaldehyde adsorption capacity under a certain concentration of formaldehyde. Compared with Comparative Examples 1, 2, 3 and 4, the addition of nitrogen-sulfur co-doped carbon quantum dots prepared in Example 1 significantly increased the adsorption of formaldehyde, so that the adsorption of formaldehyde within 48 hours can reach 1.071 mg / g. It can be seen that the formaldehyde adsorption capacity increases when the addition amount is from 0-25%, and decreases when it reaches 50%, so 25% is the optimal addition amount of persimmon residue carbon quantum dot solution. At the same time, the static desorption test results after adsorption in Tables 2-1, 2-2, 2-3, 2-4 and 2-5 show that the aerogel prepared in Example 2 of the present invention and Comparative Examples 1, 2, 3 and 4 desorbed very little formaldehyde within 48 hours, and the desorption amount of Example 2 is the best. This provides feasibility for its effective removal of formaldehyde in practical applications.

[0031] Application Example 2 The following experiments demonstrate the fluorescence detection effect of formaldehyde by the nitrogen-sulfur co-doped persimmon pomace carbon quantum dots / chitosan-acrylamide composite aerogel (hereinafter referred to as aerogel) prepared by the present invention.

[0032] Take some aerogels prepared in Example 2 of the present invention and grind them into powder, and take 10 mg and disperse them in 100 ml of deionized water and ultrasonicate for 10 minutes to form a fluorescence detection solution. Then take a 36% formaldehyde solution and configure it into a 1~5 mg / L formaldehyde solution. Take 5 ml of formaldehyde solution of different concentrations and add 50 μL of the fluorescence detection solution. After standing at room temperature for 30 minutes, put it into a fluorescence spectrophotometer to record the fluorescence intensity corresponding to the formaldehyde standard solution of different concentrations. The ratio of the fluorescence intensity corresponding to the formaldehyde standard solution of different concentrations to the fluorescence intensity corresponding to the standard solution with a concentration of 0 is used as the vertical coordinate, and the concentration of different formaldehyde standard solutions is used as the horizontal coordinate. Draw a standard curve and solve the fitting equation. See the specific results for details. Figure 6 ,from Figure 6 It can be seen that when the formaldehyde concentration of the solution decreases, the fluorescence intensity of the biochar material is significantly enhanced. The fluorescence intensity ratio F0 / F is linearly related to the formaldehyde concentration. The linear regression equation is: y = 0.1421x 甲醛 + 0.9935 (R 2 = 0.9903). Therefore, the aerogel has the ability to be applied to detect formaldehyde in practical applications.

[0033] See also Figure 2 , is the SEM image of comparative example 1 and embodiment 2 of the present invention, showing the microstructure of both; wherein, Figure 2 Figure a is the image of Comparative Example 1 after magnification 10,000 times; Figure 2 Middle b is the image of comparative example 1 after magnification 200 times; Figure 2 Middle c is the image of comparative example 1 after magnification 40 times; Figure 2 d in the middle is the image of Example 2 after magnification 10000 times; Figure 2 Figure e is the image of Example 2 after magnification 200 times; Figure 2 Figure f is a 40x magnified image of Example 2. Comparing the SEM images of Example 1 and Example 2, it was found that the aerogel without the addition of nitrogen-sulfur co-doped carbon quantum dots folded like a paper ball, while the aerogel with the addition of nitrogen-sulfur co-doped carbon quantum dots exhibited more pores.

[0034] See also Figure 3 , which are FTIR spectra of Example 2 of the present invention and Comparative Example 3, showing that after the addition of nitrogen-sulfur co-doped carbon quantum dots, the aerogel (Example 2) has sulfonic acid functional groups. In addition, both Example 2 and Comparative Example 1 have CH, CH2, and CH3 stretching vibration bands belonging to chitosan carbohydrates.

[0035] Based on the above-mentioned ideal embodiment of the present invention, and through the above description, relevant personnel can make various changes and modifications without departing from the scope of the technical concept of the present invention. The technical scope of the present invention is not limited to the contents of the specification.

Claims

1. A method for preparing a composite aerogel, characterized in that: include: Step 1, preparing a nitrogen-sulfur co-doped carbon quantum dot solution using persimmon pomace; Step 2: Add a certain amount of acetic acid to the diluted carbon quantum dot solution and stir evenly; then, add gelatin and chitosan powder, maintain at a certain temperature and stir until uniform; Step 3, adding a certain amount of acrylamide and stirring at room temperature; after forming a stable aqueous mixture, adding glutaraldehyde solution and stirring to crosslink; Step 4, vacuum freeze-drying the solution until the water is completely removed; rinsing the obtained material with ultrapure water until neutral, then soaking and rinsing in acetone several times, and soaking in cyclohexane for a certain period of time; vacuum drying the product at room temperature until the solvent is completely removed to obtain carbon quantum dot / chitosan-acrylamide composite aerogel.

2. The method for preparing the composite aerogel according to claim 3, wherein: The step 1 comprises: Step 11, taking the persimmon pomace, washing it thoroughly, drying it and grinding it into powder; Step 12, dispersing the powder in an ethanol solution, adding 2,4-diaminobenzenesulfonic acid and ultrasonically mixing, and then placing the mixture in a hydrothermal reactor for heating and reaction; Step 13: After the reaction is completed, the supernatant in the reactor is centrifuged and filtered to form a nitrogen-sulfur co-doped carbon quantum dot solution, which is stored for later use.

3. The method for preparing the composite aerogel according to claim 2, wherein: In step 12, the mass ratio of persimmon pomace powder to 2,4-diaminobenzenesulfonic acid is 1:0.5 to 1:2, the ethanol concentration of the ethanol solution is 20%-90%, and the mass (g) of persimmon pomace powder: volume (mL) of ethanol solution is 1g:40mL to 1g:60mL.

4. The method for preparing the composite aerogel according to claim 2, wherein: In step 12, the ultrasonic mixing is preferably performed in a polytetrafluoroethylene liner, and the ultrasonic mixing time is 5-30 minutes.

5. The method for preparing the composite aerogel according to claim 2, wherein: In step 12, the heating reaction time is 10-15 hours, and the heating reaction temperature is 160-200°C.

6. The method for preparing the composite aerogel according to claim 1, wherein: In step 2: The concentration of the carbon quantum dot solution is 0% to 50%; The mass ratio of gelatin to chitosan is 1:5-1:20; The volume ratio of acetic acid to carbon quantum dot solution is 1:200; The gelatin:chitosan:carbon quantum dot solution is 0.1g:1g:100mL.

7. The method for preparing the composite aerogel according to claim 1, characterized in that: In step 3: The mass ratio of acrylamide to chitosan is 1:10-1:40; The concentration of glutaraldehyde is 5%-50%, and the volume ratio of glutaraldehyde to the aqueous solution of the mixture is 1:500-1:2000; The stirring and cross-linking time is 10h-24h.

8. The method for preparing the composite aerogel according to claim 1, characterized in that: In step 4: The vacuum freeze-drying time is 24-48 h, and the temperature is -30 to -50°C; The vacuum drying time is 8h-24h, and the temperature is 20℃~30℃.

9. A composite aerogel, characterized in that The method is described in any one of claims 1 to 8.

10. Use of the composite aerogel according to claim 9 in adsorption detection of formaldehyde.

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