Preparation method of COFs adsorbent and negative pressure gas steel cylinder filled with COFs adsorbent

Abstract

The invention belongs to the technical field of gas adsorption, and particularly relates to a preparation method of a COFs adsorbent and a negative pressure gas steel cylinder filled with the COFs adsorbent. The COFs adsorbent disclosed by the invention is prepared by the following steps: dissolving 2, 4, 6-trihydroxy benzaldehyde and benzidine in ethanol, and carrying out ultrasonic treatment to obtain a mixed solution A; dissolving glucose and ethylenediamine in deionized water, and stirring until the glucose and the ethylenediamine are dissolved to obtain a mixed solution B; mixing the mixed solution A and the mixed solution B while stirring and heating for reaction; finally, cooling, centrifuging, collecting a solid product, washing and drying to obtain the COFs adsorbent. The negative pressure gas steel cylinder comprises a steel cylinder body, a valve arranged on the steel cylinder body and a protective cover arranged above the steel cylinder body, wherein the steel cylinder body is filled with a COFs adsorbent. The adsorbent provided by the invention contains rich porosity and high specific surface area, so that the adsorption capacity to gas is improved, the effect that the high-purity toxic gas COFs adsorbent is stored in a safe and reliable manner is ensured, efficient gas adsorption is realized, and the adsorbent has a good development prospect.

Description

Technical Field

[0001] This application belongs to the technical field of gas adsorption, and specifically relates to a preparation method of a COFs adsorbent and a negative-pressure gas cylinder equipped with the COFs adsorbent. Background Art

[0002] High-purity toxic gases are important raw materials in the emerging microelectronics manufacturing process, so they must be stored and used reasonably. The traditional storage method is to use seamless high-pressure-resistant gas cylinders, but the high pressure inside the cylinders poses safety hazards and is prone to accidents such as leakage of toxic gases. In the prior art, the manufacturing process of high-pressure-resistant gas cylinders is complex and the cost is high, which is not conducive to large-scale production and application.

[0003] The negative-pressure packaging technology has high safety characteristics. Some semiconductor processes, such as ion implantation procedures, mostly use negative-pressure gas supply cylinders. At present, there are two forms of negative-pressure gas cylinders. One is a gas cylinder that uses an adsorption material to adsorb gas; the other is a negative-pressure pressure regulating valve that adjusts the gas pressure inside the gas cylinder to below negative pressure for gas supply. The method of using an adsorption material to adsorb gas is simple and feasible. At present, activated carbon has been widely and long-term used as an adsorption material, but there is a problem of low adsorption efficiency. For example, the SDS gas cylinder system developed by Entegris uses Brightblack porous carbon material as an adsorbent to fix gas molecules in the pores through van der Waals forces. The gas supply pressure of such adsorption gas cylinders is lower than atmospheric pressure, and even if there is a leak, it will not reach a dangerous concentration, and the safety is significantly better than that of traditional high-pressure gas cylinders. However, traditional adsorption materials such as activated carbon have problems of low adsorption efficiency and poor selectivity and cannot be applied to the storage of mixed gases.

[0004] Covalent organic framework materials (COFs) are organic porous crystalline materials formed by light elements connected by covalent bonds. Compared with traditional adsorption materials, they have advantages such as high specific surface area, high porosity, adjustable pore size, and surface modifiability, and have great advantages in the field of toxic gas adsorption, filtration, and storage. For example, the application with the publication number CN108939814A discloses a gas cylinder containing a MOFs adsorbent. By using a gas cylinder containing a MOFs adsorbent, the adsorbent is a metal-organic framework material. However, the selected MOFs adsorbent contains metal ions. Compared with MOFs, COFs do not contain metal ions, avoiding the potential environmental toxicity problems caused by metal ions.

[0005] In summary, in the prior art, carbon adsorption materials have problems such as low adsorption efficiency, poor selectivity, inability to be applied to the storage of mixed gases, and potential environmental toxicity caused by metal ions in MOFs. Summary of the Invention

[0006] In view of the problems in the prior art that the carbon adsorption material has low adsorption efficiency, poor selectivity, and cannot be applied to the storage of mixed gases, and MOFs contain metal ions, which may cause environmental toxicity, etc., this application proposes an adsorbent with high adsorption efficiency and no environmental pollution and uses it in a negative-pressure gas cylinder. The COFs material is filled in the gas cylinder, and the rich porosity and high specific surface area improve the gas adsorption capacity, ensuring the storage of high-purity toxic gases in a safe and reliable manner.

[0007] To solve the above technical problems, the technical solution of this application is as follows:

[0008] On the one hand, this application provides a preparation method of a COFs adsorbent, and the preparation method is as follows:

[0009] Step S1. Dissolve 2,4,6-trihydroxybenzaldehyde and benzidine in ethanol at a molar ratio of 2:3, and perform ultrasonic treatment for 10 min to obtain a mixed solution A;

[0010] Step S2. Dissolve glucose and ethylenediamine at a ratio of 500 mL of ethylenediamine per 1 kg of glucose in 2.5 L of deionized water, and stir until dissolved to obtain a mixed solution B;

[0011] Step S3. Mix the mixed solution A and the mixed solution B at a volume ratio of 1:1, heat and react while stirring, and finally cool and centrifuge to collect the solid product, wash and dry to obtain the COFs adsorbent.

[0012] By adopting the above technical solution, ethanol and water are used as solvents to avoid highly toxic organic reagents. At the same time, the reaction conditions of the technical solution of this application are mild and the operation steps are simple; raw materials such as glucose, ethylenediamine, and ethanol are all cheap and easily available. 2,4,6-Trihydroxybenzaldehyde provides rich phenolic hydroxyl groups, and benzidine provides a rigid aromatic ring structure, which helps to enhance the π-π interaction of COFs while maintaining the strength of the porous structure; glucose and ethylenediamine form a nitrogen-doped carbon dot precursor in deionized water, with rich amino (-NH2) and hydroxyl (-OH) functional groups, enhancing the adsorption sites of the subsequent composite material.

[0013] Preferably, in the step S1, the molar ratio of the sum of 2,4,6-trihydroxybenzaldehyde and benzidine to ethanol is 0.75:17.2.

[0014] By adopting the above technical solution, controlling the molar ratio of the mixture of 2,4,6-trihydroxybenzaldehyde and benzidine to ethanol can dissolve the aldehyde group and amino monomers while suppressing side reactions, ensuring the efficient progress of the subsequent polycondensation reaction.

[0015] Preferably, in the step S3, the heating reaction is a gradient heating reaction, first heating to 120 °C and holding for 2 h, and then heating to 160 °C and holding for 16 h.

[0016] Through the optimized design of gradient heating reaction (120℃ for 2h → 160℃ for 16h), the reaction kinetics and thermodynamics are regulated in stages. The condensation of aldehyde amine is promoted under mild conditions (120℃) to form an imine bond precursor, and then long-term annealing at high temperature (160℃) is used to improve the crystallinity and structural stability of covalent organic frameworks (COFs), while inducing orderly growth of pores. Ultimately, a balance between high specific surface area, strong adsorption capacity and excellent chemical stability is achieved, taking into account both reaction efficiency and material performance optimization.

[0017] Preferably, the washing in step S3 is performed with anhydrous ethanol for 3 times, with 30 ml of anhydrous ethanol being used for every 1 g of the solid product.

[0018] By washing with anhydrous ethanol, residual reactants and small molecule by-products are removed, while hydrolysis or pore collapse problems that may be caused by water washing are avoided. The rapid volatility of ethanol ensures the integrity and high purity of the porous structure of the material.

[0019] Preferably, the COFs adsorbent adsorbs any one or two of carbon monoxide (CO), hydrogen sulfide (H2S), diborane (B2H6), hydrogen chloride (HCl), hydrogen fluoride (HF), hydrogen bromide (HBr), sulfur dioxide (SO2), phosphine (PH3), arsine (AsH3), nitrogen oxides (NOx), sulfur oxides (SOx), chlorine (Cl2), and phosgene (COCl2).

[0020] The adsorbent prepared by the present application can not only achieve efficient and broad-spectrum adsorption of a variety of high-risk gases, but also has the potential to expand the scope of potential applications.

[0021] On the other hand, the present application provides a negative pressure gas cylinder filled with COFs adsorbent, the negative pressure gas cylinder comprising a cylinder body, a valve arranged on the cylinder body and a protective cover arranged above the cylinder body, the cylinder body being filled with COFs adsorbent.

[0022] The negative pressure gas cylinder has a built-in high specific surface area COFs adsorbent, combined with the negative pressure environment and protective cover design of the cylinder to improve the adsorption and sealing efficiency of high-risk gases. The negative pressure state can accelerate the diffusion of gas molecules to the adsorbent surface, while the protective cover effectively isolates external impacts and pollutants.

[0023] Preferably, the ratio of the COFs adsorbent filling volume to the volume of the negative pressure gas cylinder is (0.1-1):1.

[0024] Further preferably, the ratio of the COFs adsorbent filling volume to the volume of the steel cylinder is (0.2-0.6):1.

[0025] By optimizing the ratio of the loading volume of the COFs adsorbent to the volume of the steel cylinder, while ensuring sufficient adsorbent to efficiently capture the gas, a reasonable space is reserved to maintain a negative pressure environment and promote uniform gas diffusion, avoiding the accumulation of the adsorbent or the obstruction of gas flow caused by overloading, so as to achieve the best balance among the adsorption efficiency, the utilization rate of the steel cylinder capacity, and the gas dynamic response performance, and improve the overall gas storage safety and service efficiency of the steel cylinder.

[0026] Preferably, the pressure of the negative pressure gas steel cylinder is -0.05 to 0 MPa.

[0027] By setting the pressure range of the negative pressure gas steel cylinder to -0.05 to 0 MPa, the diffusion and adsorption of gas molecules to the surface of the COFs adsorbent are accelerated through a moderate negative pressure environment, while avoiding the structural stress or safety hazards of the steel cylinder caused by too high negative pressure, and achieving a balance between ensuring high adsorption performance and the mechanical stability of the steel cylinder.

[0028] Preferably, the valve of the negative pressure gas steel cylinder is also connected to a filter and a pressure gauge through a pipeline. The filter is used to filter impurities in the gas, and the pressure gauge is used to monitor the pressure of the negative pressure gas steel cylinder.

[0029] By configuring a pneumatic or manual valve and connecting a filter and a pressure gauge, the negative pressure gas steel cylinder realizes precise control of gas flow, efficient removal of impurities, and real-time monitoring of pressure, ensuring the safety and controllability of the gas adsorption and release process.

[0030] The beneficial effects of this application are as follows:

[0031] (1) This application adopts gradient heating reaction to ensure the uniform composite of COFs and carbon dots, and improve the specific surface area and porosity of the adsorbent. Adopting gradient heating (120°C to 160°C) can also optimize the crystallinity of COFs, while avoiding the aggregation of carbon dots and improving the material stability.

[0032] (2) The COFs adsorbent of this application has a high specific surface area and can efficiently adsorb a variety of toxic gases. Ethylenediamine is introduced into the reaction system as a nitrogen-containing compound. Its molecule contains two amino groups (-NH2), providing an abundant nitrogen source for nitrogen doping. Nitrogen-doped carbon dots enhance the gas adsorption ability, and the adsorbent has excellent regeneration performance and can be recycled multiple times, reducing the operation and maintenance costs. This application uses ethanol and water as solvents, avoiding the use of toxic organic solvents, which conforms to the principles of green chemistry.

[0033] (3) This application has the advantages of simple adsorption process, safety and reliability, high adsorption capacity, and the ability to store mixed gases. It is suitable for the adsorption and storage of a variety of toxic gases and meets the requirements such as industrial waste gas absorption. Description of the Drawings

[0034] AppendixFigure 1 This is a schematic diagram of the overall structure of the negative pressure gas cylinder of this application.

[0035] Explanation of the attached drawing labels:

[0036] 1. Gas cylinder body; 2. Filter; 3. Pressure gauge; 4. Protective cover; 5. Valve. Specific implementation manners

[0037] To further elaborate on the technical means and effects adopted by this application to achieve the intended invention purpose, the following, in combination with preferred embodiments, details the specific implementation manners, structures, features, and their effects of this application as follows.

[0038] Device embodiment

[0039] As shown in the attached Figure 1 drawing, this embodiment provides a negative pressure gas cylinder for filling COFs adsorbent. The negative pressure gas cylinder includes a gas cylinder body 1, a valve 5 provided on the gas cylinder body 1, and a protective cover 4 provided above the gas cylinder body 1. The gas cylinder body 1 is filled with COFs adsorbent, and the ratio of the filling volume of the COFs adsorbent to the volume of the negative pressure gas cylinder is controlled to be (0.1 - 1):1. The pressure of the negative pressure gas cylinder is controlled to be (-0.05 to 0) MPa. The types of gases adsorbed by the COFs adsorbent are any one or two of carbon monoxide (CO), hydrogen sulfide (H2S), diborane (B2H6), hydrogen chloride (HCl), hydrogen fluoride (HF), hydrogen bromide (HBr), sulfur dioxide (SO2), phosphine (PH3), arsine (AsH3), nitrogen oxides (NOx), sulfur oxides (SOx), chlorine (Cl2), phosgene (COCl2).

[0040] Among them, the valve 5 is a pneumatic valve or a manual valve, and the corresponding valve 5 can be selected according to actual needs.

[0041] The valve 5 of the negative pressure gas cylinder is also connected to the filter 2 and the pressure gauge 3 through a pipeline. The filter 2 filters the adsorbent to avoid pollution during use, and the pressure gauge 3 shows the gas pressure inside the negative pressure gas cylinder.

[0042] When the pressure in the negative pressure gas cylinder is greater than the external pressure, the gas inside the negative pressure gas cylinder can be used, and the connection between the gas inside the negative pressure gas cylinder and the outside is controlled by opening or closing the valve 5. The toxic gas inside the cylinder is adsorbed in the pore channels of the COFs adsorbent. When the valve 5 is opened, under the action of pressure, the toxic gas desorbs from the COFs adsorbent. After closing the cylinder valve 5, the toxic gas continues to be sealed in the COFs adsorbent.

[0043] Principle of the device embodiment:

[0044] Confirm that components such as the cylinder body 1, valve 5, protective cover 4, filter 2, and pressure gauge 3 are in good condition without leakage or damage.

[0045] Vacuum-dry the COFs adsorbent at 60 °C for 12 hours to remove the adsorbed moisture and impurities. Open the protective cover 4 at the top of the cylinder, and evenly load the adsorbent into the cylinder, avoiding accumulation or blockage. After loading is completed, reinstall the protective cover 4 and tighten the bolts. Connect the filter 2 to the outlet of the cylinder valve 5 through a pipeline, ensuring that the connection is sealed and leak-free. Install a pressure gauge 3 at the outlet of the filter 2 for real-time monitoring of the pressure inside the cylinder. Select a pneumatic valve 5 or a manual valve 5 according to actual needs, and ensure that the valve 5 is firmly connected to the cylinder.

[0046] Close the cylinder valve 5 to ensure a negative pressure inside the cylinder, and use the pressure gauge 3 to confirm whether the pressure inside the cylinder meets the requirements. Open the cylinder valve 5 to allow the toxic gas to enter the cylinder. After the gas removes particulate matter and impurities through the filter 2, it is captured by the COFs adsorbent and stored in the pores. Observe the pressure gauge 3, and when the pressure approaches 0 MPa, close the valve 5 to stop the gas intake.

[0047] When the gas needs to be used, open the valve 5, and under the action of pressure, the toxic gas desorbs from the COFs adsorbent. The gas is transported to the using equipment through a pipeline.

[0048] During use, monitor the pressure gauge 3 in real time to ensure stable gas supply. After use, close the cylinder valve 5 to cut off the gas supply. Check the pressure inside the cylinder to ensure it is in a negative pressure state.

[0049] Adsorbent Preparation Example 1

[0050] Step S1: Prepare mixture A

[0051] Weigh 0.3 mol of 2,4,6-trihydroxybenzaldehyde and 0.45 mol of benzidine, add the two to 2.5 L of ethanol, and transfer to an ultrasonic instrument after preliminary dissolution by magnetic stirring. Perform ultrasonic treatment for 10 minutes, with a power of 300 W and a frequency of 40 kHz. Ultrasonic treatment breaks the intermolecular hydrogen bonds, promotes the uniform dispersion of 2,4,6-trihydroxybenzaldehyde and benzidine, and avoids the formation of prepolymers caused by excessive local concentration. The ethanol solvent can dissolve the aldehyde group and amino monomers, and at the same time inhibit side reactions, ensuring the efficient progress of the subsequent polycondensation reaction.

[0052] Step S2: Prepare mixture B

[0053] Weigh 1 kg of glucose and 500 mL of ethylenediamine, and add them to 2.5 L of deionized water. Stir magnetically at room temperature (rotation speed 800 rpm) until completely dissolved to form a transparent brownish-yellow solution. Glucose and ethylenediamine form a nitrogen-doped carbon dot precursor in deionized water, which is rich in amino (-NH2) and hydroxyl (-OH) functional groups, enhancing the adsorption sites of the subsequent composite material.

[0054] Step S3: Mixing and gradient heating reaction

[0055] Slowly pour 1 L of mixture A into 1 L of mixture B while stirring (rotation speed 500 rpm). After mixing, continue stirring for 10 minutes. Transfer to a reaction kettle, seal it, and heat it according to the gradient: heat it to 160 °C at a rate of 5 °C / min and keep it warm for 2 hours to promote the imine bond polycondensation of COFs. Subsequently, continue heating to 160 °C and keep it warm for 16 hours to complete the crystallization of COFs and simultaneously carbonize to generate nitrogen-doped carbon dots. The COFs framework skeleton is preferentially formed in the low-temperature stage to avoid premature carbonization of the carbon dot precursor blocking the pores. The high-temperature stage promotes the formation of carbon dots and their embedding into the COFs pores to form a hierarchical pore structure. The carbon dots and COFs are tightly combined through hydrogen bonds and π-π stacking to avoid pore blockage caused by post-modification.

[0056] Step S4: Product separation and washing

[0057] After the reaction is completed, naturally cool it to room temperature, open the reaction kettle, and transfer the reaction solution to a centrifuge tube. Centrifuge at 8000 rpm for 10 minutes, discard the supernatant, and collect the solid product. Wash it 3 times according to the ratio of 30 mL of absolute ethanol per 1 g of solid product, and remove the washing solution after each centrifugation. Washing with absolute ethanol effectively removes unreacted 2,4,6-trihydroxybenzaldehyde, benzidine monomers, and oligomers to avoid impurity blockage of the COFs pores. The weak polar solvent property of ethanol retains the imine bond stability of COFs and prevents hydrolysis.

[0058] Step S5: Drying and storage

[0059] Lay the washed solid product flat in a petri dish, place it in a vacuum drying oven, and dry it under vacuum at 60 °C and -0.1 MPa for 12 hours. After drying, seal it and store it in a nitrogen-filled dryer to avoid moisture absorption.

[0060] Vacuum drying at low temperature avoids the collapse of the COFs framework or the oxidation of carbon dots caused by high temperature, maintaining the structural integrity of the material.

[0061] Adsorbent preparation comparative example 1

[0062] The difference between this comparative example and adsorbent preparation example 1 is that there is no gradient heating, and it is directly heated to 160 °C.

[0063] Adsorbent preparation comparative example 2

[0064] The difference between this comparative example and Adsorbent Preparation Example 1 is as follows: In the first 4 hours, the temperature is raised to 120 °C at a rate of 5 °C / min to promote the polycondensation of imine bonds in COFs. In the subsequent 14 hours, the temperature is maintained at 160 °C to complete the crystallization of COFs and simultaneously carbonize to generate nitrogen-doped carbon dots.

[0065] Adsorbent Preparation Comparative Example 3

[0066] The difference between this example and Adsorbent Preparation Example 1 is that 2,4,6-trihydroxybenzaldehyde, benzidine, glucose, and ethylenediamine are added to a mixed solution of 2.5 L of deionized water and 2.5 L of ethanol, and ultrasonic treatment is carried out for 10 minutes with a power of 300 W and a frequency of 40 kHz; finally, magnetic stirring (rotation speed 800 rpm) is carried out at room temperature until completely dissolved.

[0067] Example 1

[0068] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.1:1, and the adsorbed gas is carbon monoxide.

[0069] Example 2

[0070] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.2:1, and the adsorbed gases are carbon monoxide and hydrogen sulfide with a volume ratio of 1:1.

[0071] Example 3

[0072] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.3:1, and the adsorbed gas is arsine.

[0073] Example 4

[0074] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.4:1, and the adsorbed gas is phosphine.

[0075] Example 5

[0076] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.5:1, and the adsorbed gas is sulfur dioxide.

[0077] Example 6

[0078] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.6:1. The adsorbed gas is hydrogen bromide.

[0079] Example 7

[0080] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.7:1. The adsorbed gas is hydrogen fluoride.

[0081] Example 8

[0082] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.8:1. The adsorbed gas is hydrogen chloride.

[0083] Example 9

[0084] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 0.9:1. The adsorbed gas is diborane.

[0085] Example 10

[0086] This example provides a negative-pressure gas cylinder filled with a COFs adsorbent. The adsorbent prepared in Adsorbent Preparation Example 1 is selected, and the ratio of the filling volume of the adsorbent to the volume of the negative-pressure gas cylinder is 1:1. The adsorbed gas is hydrogen sulfide.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is that the selected adsorbent is a commercially available COFs adsorbent.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that the selected adsorbent is the adsorbent of Adsorbent Preparation Comparative Example 1.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 1 is that the selected adsorbent is the adsorbent of Adsorbent Preparation Comparative Example 2.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 1 is that the selected adsorbent is the adsorbent of Adsorbent Preparation Comparative Example 3.

[0095] Performance detection

[0096] (1) The specific surface areas of Adsorbent Preparation Example 1, Adsorbent Preparation Comparative Example 1, Adsorbent Preparation Comparative Example 2 and commercially available COFs adsorbent were measured by BET nitrogen adsorption, and the results are shown in Table 1.

[0097] Table 1

[0098] Sample <![CDATA[Specific surface area (m 2 / g)]]> Adsorbent Preparation Example 1 6341.17 Adsorbent Preparation Comparative Example 1 4819.98 Adsorbent Preparation Comparative Example 2 4967.42 Adsorbent Preparation Comparative Example 3 4796.85 Commercially Available COFs Adsorbent 4529.35

[0099] (2) When the adsorption pressure of the steel cylinder reached 0 MPa, the volume (L) of the adsorbed gas was measured, and the results are shown in Table 2. It should be noted that the volume of the selected negative pressure gas steel cylinder was 5 L.

[0100] Table 2

[0101]

[0102]

[0103] As can be seen from Table 1, by using the preparation method of the present application, the specific surface area of the adsorbent is larger than that of Adsorbent Preparation Examples 1 to 3 and commercially available COFs adsorbent. This may be because the gradient heating reaction is adopted in the present application to ensure the uniform composite of COFs and carbon dots, thereby improving the specific surface area and porosity of the adsorbent. This may mean that the adsorbent prepared by the method of the present application may enrich the pore size of the COFs adsorbent and increase the adsorption sites. It can also be seen from Example 1 and Comparative Examples 1 to 4 that the adsorption performance of the adsorbent prepared by the present application for the same gas is better than that of the commercially available adsorbent and the adsorbent prepared outside the protection scope of the present application; it can be seen from Examples 1 to 10 that as the loading volume of the COFs adsorbent increases, the gas adsorption performance continuously enhances. However, it can be found that when the ratio of the loading volume of the COFs adsorbent to the volume of the negative pressure steel cylinder increases to 0.6:1, the growth rate of the adsorption performance of the COFs adsorbent slows down. In the preferred reasonable space to maintain the negative pressure environment and promote the uniform diffusion of gas, the adsorption performance is relatively high. However, as the adsorbent accumulates, the gas flow is blocked, resulting in a decrease in the adsorption growth rate.

[0104] The above is only a preferred embodiment of the present application, and does not impose any form of limitation on the present application. Although the present application has been disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical content of the present application, any modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application still fall within the scope of the technical solution of the present application.

Claims

1. A preparation method of a COFs adsorbent, characterized in that, The preparation method is as follows: Step S1. Dissolve 2,4,6-trihydroxybenzaldehyde and benzidine in ethanol at a molar ratio of 2:3, and ultrasonically treat for 10 min to obtain a mixed solution A; Step S2. Dissolve glucose and ethylenediamine at a ratio of 500 mL of ethylenediamine per 1 kg of glucose in 2.5 L of deionized water, and stir until dissolved to obtain a mixed solution B; Step S3. Mix the mixed solution A and the mixed solution B at a volume ratio of 1:1, heat and react while stirring, and finally cool and centrifuge to collect the solid product, wash and dry to obtain the COFs adsorbent.

2. The preparation method of a COFs adsorbent according to claim 1, characterized in that, In the step S1, the molar ratio of the sum of 2,4,6-trihydroxybenzaldehyde and benzidine to ethanol is 0.75:17.

2.

3. The preparation method of a COFs adsorbent according to claim 1, characterized in that, In the step S3, the heating reaction is a gradient heating reaction. First, heat up to 120 °C and keep warm for 2 h, and then heat up to 160 °C and keep warm for 16 h.

4. The preparation method of a COFs adsorbent according to claim 1, characterized in that In the step S3, the washing is carried out with anhydrous ethanol 3 times, and each 1 g of the solid product is washed with 30 ml of anhydrous ethanol.

5. The preparation method of a COFs adsorbent according to claim 1, wherein, The types of gases adsorbed by the COFs adsorbent are any one or two of carbon monoxide, hydrogen sulfide, diborane, hydrogen chloride, hydrogen fluoride, hydrogen bromide, sulfur dioxide, phosphine, arsine, nitrogen oxides, sulfur oxides, chlorine, and phosgene.

6. A negative-pressure gas cylinder filled with the COF adsorbent prepared by any one of the methods recited in claims 1 to 5, characterized in that, The negative pressure gas cylinder includes a cylinder body (1), a valve (5) provided on the cylinder body (1), and a protective cover (4) provided above the cylinder body (1). The cylinder body (1) is filled with the COFs adsorbent.

7. A negative pressure gas cylinder equipped with a COF adsorbent according to claim 6, characterized in that, The ratio of the filling volume of the COFs adsorbent to the volume of the negative pressure gas cylinder is (0.1-1):

1.

8. A negative-pressure gas cylinder equipped with a COFs adsorbent according to claim 6, characterized in that, The pressure of the negative pressure gas cylinder is -0.05 to 0 MPa.

9. A negative-pressure gas cylinder equipped with a COFs adsorbent according to claim 6, characterized in that The valve (5) of the negative pressure gas cylinder is also connected to a filter (2) and a pressure gauge (3) through a pipeline. The filter (2) is used to filter impurities in the gas, and the pressure gauge (3) is used to monitor the pressure of the negative pressure gas cylinder.

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