Method for removing carbon dioxide impurity in monofluoromethane electronic gas

Abstract

The invention relates to the technical field of gas purification, in particular to a method for removing carbon dioxide impurities in monofluoromethane electronic gas. The method specifically comprises the following steps: S1, pre-adsorption: introducing monofluoromethane electronic gas containing carbon dioxide impurities into an adsorption tower filled with a first-stage adsorbent, and carrying out pre-adsorption and preliminary impurity removal; and S2, directional adsorption: introducing the gas subjected to primary impurity removal in the step S1 into an adsorption tower filled with a secondary adsorbent, and carrying out directional adsorption on carbon dioxide to obtain the high-purity monofluoromethane electronic gas. Through the synergistic effect of primary micropore screening pre-adsorption and amino chemical adsorption, the purpose of high purity in electron gas purification is achieved, and an efficient and low-consumption CO2 removal solution is provided for a semiconductor industry chain.

Description

Technical Field

[0001] The present application relates to the technical field of gas purification, and in particular to a method for removing carbon dioxide impurities from monofluoromethane electronic gas. Background Art

[0002] As an important electronic gas, monofluoromethane is widely used in fields such as semiconductor manufacturing. However, during the preparation and storage of monofluoromethane, carbon dioxide impurities are often mixed in. The presence of carbon dioxide impurities will seriously affect the purity and performance of monofluoromethane electronic gas, and thus have an adverse effect on related electronic manufacturing processes. As a key electronic specialty gas in advanced processes, monofluoromethane, CO2 impurities will cause defects on the wafer surface (>0.1ppm, which affects the yield). At present, the commonly used technologies for separating and removing CO2 include absorption, membrane separation, and solid adsorption. Traditional adsorption methods have poor selectivity (CH3F loss rate>3%) and high regeneration energy consumption (≥200℃); membrane separation methods are difficult to deal with CO2 / CH3F molecules of similar size (kinetic diameters are vs Solid adsorption has become the primary method for separating and removing CO2 from high-purity gases due to its simplicity, low corrosion to equipment, and low energy consumption for adsorbent recovery and regeneration. However, solid adsorption suffers from low efficiency, high cost, and the introduction of new impurities. Consequently, numerous researchers have attempted to develop an efficient, low-cost method for removing CO2 from monofluoromethane electronic gas without introducing new impurities.

[0003] The technical solution with announcement number CN115448810A discloses a method and system for removing carbon dioxide and nitrous oxide from trifluoromethane. The specific method is: the crude trifluoromethane product is first subjected to a solid alkaline substance absorbent to remove carbon dioxide, then an activated carbon adsorbent to remove nitrous oxide, and finally a molecular sieve adsorbent to further remove carbon dioxide and nitrous oxide, thereby obtaining trifluoromethane with CO2 ≤ 1ppm and N2O ≤ 0.3ppm. The removal method of this technical solution removes carbon dioxide from the crude nitrogen trifluoride product to below 1ppm in a short period of time, greatly improving the subsequent purification effect. However, according to the results disclosed in its specification, the minimum carbon dioxide content after purification is 0.492ppm.

[0004] Chinese patent publication number CN109513421B discloses a method for adsorbing CO2 from gases. This method uses alkali metal ion-modified ZSM-5 molecular sieves as an adsorbent to adsorb the electron gas of low-concentration CO2 gas, where the CO2 concentration in the electron gas is 100 to 1000 ppmv. The alkali metal ion modification allows the ZSM-5 molecular sieve to contain alkaline centers. Through acid-base interactions, the ZSM-5 molecular sieve efficiently adsorbs low-concentration CO2 from high-purity gases, reducing the CO2 impurity concentration in the high-purity gas to less than 0.01 ppmv. However, over time, the carbon dioxide adsorbed in the molecular sieve interacts with the alkali metal ions, potentially destroying the porous framework structure of the molecular sieve.

[0005] Zeolitic imidazolate frameworks (ZIFs) are zeolite-like porous crystalline materials formed by self-assembly of transition metal ions such as zinc and cobalt and imidazole organic ligands. They have the characteristics of high specific surface area, adjustable pore size, uniform pore structure and rich functional sites. They are widely used in gas storage, CO2 capture, heavy metal ion removal, organic pollutant adsorption and drug delivery. However, in low-concentration CO2 environments, (ZIFs) adsorbents mainly rely on physical adsorption, and the adsorption capacity is insufficient, making it difficult to meet the gas purity requirements of electron gas.

[0006] In summary, the existing technology for adsorbing carbon dioxide in electronic gas has problems such as difficulty in meeting purity requirements, insufficient adsorption dosage, and possible introduction of new impurities. It is urgent to propose a method for removing carbon dioxide impurities in monofluoromethane electronic gas to solve the problems existing in the existing technology. Summary of the Invention

[0007] In response to the problems in the existing technology of adsorbing carbon dioxide in electronic gas, such as difficulty in meeting purity requirements, insufficient adsorption dosage and possible introduction of new impurities, this application proposes a method for removing carbon dioxide impurities from monofluoromethane electronic gas to improve the efficiency of carbon dioxide removal.

[0008] The technical solution of this application is as follows:

[0009] A method for removing carbon dioxide impurities from monofluoromethane electronic gas comprises the following steps:

[0010] Step S1. Pre-adsorption: The monofluoromethane electronic gas containing carbon dioxide impurities is passed into an adsorption tower equipped with a primary adsorbent for pre-adsorption and preliminary impurity removal;

[0011] Step S2. Directed adsorption: The gas initially cleaned from step S1 is passed into an adsorption tower containing a secondary adsorbent for directed adsorption of carbon dioxide to obtain high-purity monofluoromethane electronic gas;

[0012] The secondary adsorbent is ZIF-8@amino-treated carbon nanotubes.

[0013] Preferably, the pre-adsorption temperature is 20-50° C., and the pressure is 0.5-1.0 MPa.

[0014] Preferably, the primary adsorbent is a mixed adsorbent of activated alumina, 5A molecular sieve and 3A molecular sieve.

[0015] Preferably, the mass ratio of the activated alumina, 5A molecular sieve and 3A molecular sieve is (2-5):1:1.

[0016] Preferably, the temperature of the directional adsorption is -20°C to 10°C, and the pressure is 0.5 to 1.0 MPa.

[0017] Preferably, the preparation method of the ZIF-8@amino-modified carbon nanotubes is as follows:

[0018] Step S21. adding the carbon nanotubes to a concentrated nitric acid solution and ultrasonically treating the carbon nanotubes, followed by reflux heating for reaction, washing with deionized water by centrifugation until neutral, and drying to obtain functionalized carbon nanotubes;

[0019] Step S22: dispersing the functionalized carbon nanotubes into a methanol solution of zinc nitrate, followed by adding a methanol solution of 2-methylimidazole, heating for reaction, centrifuging to remove methanol, washing three times, and drying to obtain ZIF-8@carbon nanotubes;

[0020] Step S23. Add amino modifier to ZIF-8@ carbon nanotubes and heat under reflux for reaction, wash with methanol three times by centrifugation, and dry to obtain ZIF-8@ amino carbon nanotubes.

[0021] Preferably, in step S21, the mass ratio of carbon nanotubes to concentrated nitric acid is 1:50; the mass fraction of concentrated nitric acid is 65% to 90%; the reflux heating reaction temperature is 80° C. to 120° C., and the time is 6 to 10 hours; and the drying temperature is 60° C., and the time is 12 hours.

[0022] Preferably, in step S22, the concentration of the zinc nitrate methanol solution is 0.5 mol / L, and the concentration of the 2-methylimidazole methanol solution is 4 mol / L; the mass ratio of the functionalized carbon nanotubes: the zinc nitrate methanol solution, and the 2-methylimidazole methanol solution is (1-2):(45-50):(45-50); the heating reaction temperature is 100°C, and the time is 20-24 hours; the drying temperature is 60°C, and the time is 12 hours.

[0023] Preferably, in step S23, the amino modifier is ethylenediamine or aminosilane coupling agent, the mass ratio of ZIF-8@ carbon nanotubes to the amino modifier is (1-2):5, and the reaction conditions are as follows: controlling the pH to 8.5-11.5, the temperature to 50°C to 80°C, and the time to 4-8 hours; the drying temperature is 120°C, and the time is 6 hours.

[0024] Beneficial effects of this application:

[0025] This application uses the synergistic effect of primary microporous screening pre-adsorption and amino chemical adsorption to improve the selective adsorption capacity of amino-modified ZIF-8@ carbon nanotubes for carbon dioxide. The primary adsorption tower uses a mixed adsorption of activated alumina / 5A / 3A molecular sieves to remove a large amount of impurities such as carbon dioxide, creating optimal conditions for secondary directional adsorption. The introduction of an amino modifier (ethylenediamine / aminosilane) as a secondary adsorbent further increases the number of chemical adsorption sites, while concentrated nitric acid pretreatment provides a structural basis for functionalization, ultimately achieving a dual increase in adsorption capacity and selectivity, achieving the high-purity goal of electronic gas purification, and providing an efficient and low-cost CO2 removal solution for the semiconductor industry chain. DETAILED DESCRIPTION

[0026] In order to further illustrate the technical means and effects adopted by this application to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of this application are described in detail below in combination with preferred embodiments.

[0027] Preparation Example 1

[0028] This preparation example provides a method for preparing ZIF-8@amino-modified carbon nanotubes, as follows:

[0029] Step S21: Take 2.0g of carbon nanotubes and add them to 100g of concentrated nitric acid (68% by mass) and ultrasonically disperse them for 30min (power 500W). The mixture is refluxed at 80°C for 6 hours to allow the nitric acid to fully oxidize the surface of the carbon nanotubes to generate carboxyl and hydroxyl groups. After the reaction, centrifuge, wash with deionized water until neutral, and vacuum dry at 60°C for 12 hours to obtain functionalized carbon nanotubes. Concentrated nitric acid oxidation introduces oxygen-containing functional groups on the surface of the carbon nanotubes, significantly enhancing their hydrophilicity and chemical activity. The carboxyl groups can serve as anchor points for the subsequent growth of metal-organic frameworks, while inhibiting carbon nanotube agglomeration and improving dispersion stability.

[0030] Step S22: Disperse 1.5 g of functionalized carbon nanotubes in 45 g of 0.5 mol / L zinc nitrate methanol solution and sonicate for 30 minutes to form a uniform suspension. Add 50 g of 4 mol / L 2-methylimidazole methanol solution and rapidly stir to mix. Transfer the mixture to a reactor and react at 100°C for 20 hours. Collect the solid by centrifugation, wash three times with methanol, and dry at 60°C for 12 hours to obtain ZIF-8@ carbon nanotubes.

[0031] Step S23: Mix 0.5g of ZIF-8@carbon nanotubes with 2.5g of ethylenediamine and adjust the pH to 8.5 with deionized water. Reflux the mixture at 50°C for 4 hours. Collect the solid by centrifugation, wash three times with methanol, and dry under vacuum at 120°C for 6 hours to obtain ZIF-8@amino-modified carbon nanotubes. The amino groups (-NH2) react with CO2 through an acid-base reaction to form carbamates, significantly enhancing adsorption capacity and selectivity.

[0032] Preparation Example 2

[0033] This preparation example provides a method for preparing ZIF-8@amino-modified carbon nanotubes, as follows:

[0034] Step S21: Take 2.0g of carbon nanotubes and add them to 100g of concentrated nitric acid (70% by mass) and ultrasonically disperse them for 30min (power 500W). The mixture is refluxed at 90°C for 7 hours to allow the nitric acid to fully oxidize the surface of the carbon nanotubes to generate carboxyl and hydroxyl groups. After the reaction, centrifuge, wash with deionized water until neutral, and vacuum dry at 60°C for 12 hours to obtain functionalized carbon nanotubes. Concentrated nitric acid oxidation introduces oxygen-containing functional groups on the surface of the carbon nanotubes, significantly enhancing their hydrophilicity and chemical activity. The carboxyl groups can serve as anchor points for the subsequent growth of metal-organic frameworks, while inhibiting carbon nanotube agglomeration and improving dispersion stability.

[0035] Step S22: Disperse 1 g of functionalized carbon nanotubes in 25 g of 0.5 mol / L zinc nitrate methanol solution and sonicate for 30 minutes to form a uniform suspension. Add 45 g of 4 mol / L 2-methylimidazole methanol solution and rapidly stir to mix. Transfer the mixture to a reactor and react at 100°C for 21 hours. Collect the solid by centrifugation, wash three times with methanol, and dry at 60°C for 12 hours to obtain ZIF-8@ carbon nanotubes.

[0036] Step S23: Mix 0.5g of ZIF-8@carbon nanotubes with 2g of ethylenediamine and adjust the pH to 9 with deionized water. Reflux the mixture at 50°C to 80°C for 5 hours. The solid was collected by centrifugation, washed three times with methanol, and dried under vacuum at 120°C for 6 hours to obtain ZIF-8@amino-modified carbon nanotubes. The amino groups (-NH2) react with CO2 through an acid-base reaction to form carbamates, significantly enhancing adsorption capacity and selectivity.

[0037] Preparation Example 3

[0038] This preparation example provides a method for preparing ZIF-8@amino-modified carbon nanotubes, as follows:

[0039] Step S21: Take 2.0g of carbon nanotubes and add them to 100g of concentrated nitric acid (68% by mass) and ultrasonically disperse them for 30min (power 500W). The mixture is refluxed at 100°C for 8 hours to allow the nitric acid to fully oxidize the surface of the carbon nanotubes to generate carboxyl and hydroxyl groups. After the reaction, centrifuge, wash with deionized water until neutral, and vacuum dry at 60°C for 12 hours to obtain functionalized carbon nanotubes. Concentrated nitric acid oxidation introduces oxygen-containing functional groups on the surface of the carbon nanotubes, significantly enhancing their hydrophilicity and chemical activity. The carboxyl groups can serve as anchor points for the subsequent growth of metal-organic frameworks, while inhibiting carbon nanotube agglomeration and improving dispersion stability.

[0040] Step S22: Disperse 1 g of functionalized carbon nanotubes in 45 g of 0.5 mol / L zinc nitrate methanol solution and sonicate for 30 minutes to form a uniform suspension. Add 25 g of 4 mol / L 2-methylimidazole methanol solution and rapidly stir to mix. Transfer the mixture to a reactor and react at 100°C for 23 hours. Collect the solid by centrifugation, wash three times with methanol, and dry at 60°C for 12 hours to obtain ZIF-8@ carbon nanotubes.

[0041] Step S23: Mix 0.5g of ZIF-8@carbon nanotubes with 1.67g of KH570 and adjust the pH to 10.0 with deionized water. Reflux the mixture at 70°C for 7 hours. Collect the solid by centrifugation, wash three times with methanol, and dry under vacuum at 120°C for 6 hours to obtain ZIF-8@amino-modified carbon nanotubes. The amino groups (-NH2) react with CO2 through an acid-base reaction to form carbamates, significantly enhancing adsorption capacity and selectivity.

[0042] Preparation Example 4

[0043] This preparation example provides a method for preparing ZIF-8@amino-modified carbon nanotubes, as follows:

[0044] Step S21, take 2.0g carbon nanotubes and add them to 100g concentrated nitric acid (concentrated nitric acid mass fraction 68%), and ultrasonically disperse them for 30min (power 500W). The mixture is refluxed at 120°C for 10 hours to allow the nitric acid to fully oxidize the surface of the carbon nanotubes to generate carboxyl and hydroxyl groups. After the reaction, centrifugation is performed, the mixture is washed with deionized water until neutral, and vacuum dried at 60°C for 12 hours to obtain functionalized carbon nanotubes. Concentrated nitric acid oxidation introduces oxygen-containing functional groups on the surface of the carbon nanotubes, significantly enhancing their hydrophilicity and chemical activity. The carboxyl groups can serve as anchor points for the subsequent growth of metal-organic frameworks, while inhibiting carbon nanotube agglomeration and improving dispersion stability.

[0045] Step S22: Disperse 1 g of functionalized carbon nanotubes in 50 g of 0.5 mol / L zinc nitrate methanol solution and sonicate for 30 minutes to form a uniform suspension. Add 45 g of 4 mol / L 2-methylimidazole methanol solution and rapidly stir to mix. Transfer the mixture to a reactor and react at 100°C for 24 hours. Collect the solid by centrifugation, wash three times with methanol, and dry at 60°C for 12 hours to obtain ZIF-8@ carbon nanotubes.

[0046] Step S23: Mix 0.5g of ZIF-8@carbon nanotubes with 2.2g of KH550 and adjust the pH to 10.0 with deionized water. Reflux the mixture at 80°C for 8 hours. Collect the solid by centrifugation, wash three times with methanol, and vacuum dry at 120°C for 6 hours to obtain ZIF-8@amino-modified carbon nanotubes. The amino groups (-NH2) react with CO2 through an acid-base reaction to form carbamates, significantly enhancing adsorption capacity and selectivity.

[0047] The preparation methods of ZIF-8@amino-modified carbon nanotubes provided in Preparation Examples 1 to 4 have been tested to have a specific surface area ≥ 2000 m2 / g and a CO2 adsorption capacity ≥ 5 mmol / g (25°C).

[0048] Example 1

[0049] This embodiment provides a method for removing carbon dioxide impurities from monofluoromethane electronic gas, comprising the following steps:

[0050] Step S1. Pre-adsorption:

[0051] First, the adsorption tower is filled with pre-mixed adsorbents (activated alumina, 5A molecular sieve, and 3A molecular sieve) in a 2:1:1 mass ratio. Then, monofluoromethane (HF) electronic gas containing CO2 impurities is passed through the adsorption tower filled with the primary adsorbent for pre-adsorption and initial impurity removal. The pre-adsorption temperature is 20°C and the pressure is 0.5 MPa. This step removes approximately 30%-40% of the CO2 impurity and some macromolecular impurities, reducing the burden of subsequent processing.

[0052] Step S2. Directed adsorption:

[0053] The gas preliminarily cleaned from impurities in step S1 is passed into an adsorption tower filled with a secondary adsorbent to directional adsorb carbon dioxide to obtain high-purity monofluoromethane electronic gas; the secondary adsorbent is ZIF-8@amino-carbon nanotubes prepared in Preparation Example 1, the directional adsorption temperature is 10°C, and the pressure is 0.5 MPa.

[0054] Example 2

[0055] This embodiment provides a method for removing carbon dioxide impurities from monofluoromethane electronic gas, comprising the following steps:

[0056] Step S1. Pre-adsorption:

[0057] First, the adsorption tower is filled with pre-mixed adsorbents (activated alumina, 5A molecular sieve, and 3A molecular sieve) in a 5:1:1 mass ratio. Then, monofluoromethane electronic gas containing carbon dioxide impurities is passed through the adsorption tower filled with the primary adsorbent for pre-adsorption and initial impurity removal. The pre-adsorption temperature is 30°C and the pressure is 1.0 MPa. This step removes approximately 30%-40% of the carbon dioxide impurity and some large molecular impurities, reducing the burden of subsequent processing.

[0058] Step S2. Directed adsorption:

[0059] The gas preliminarily cleaned from impurities in step S1 is passed into an adsorption tower filled with a secondary adsorbent to directional adsorb carbon dioxide to obtain high-purity monofluoromethane electronic gas; the secondary adsorbent is ZIF-8@amino-carbon nanotubes prepared in Preparation Example 2, the directional adsorption temperature is -20°C, and the pressure is 0.7 MPa.

[0060] Example 3

[0061] This embodiment provides a method for removing carbon dioxide impurities from monofluoromethane electronic gas, comprising the following steps:

[0062] Step S1. Pre-adsorption:

[0063] First, the adsorption tower is filled with pre-mixed adsorbents (activated alumina, 5A molecular sieve, and 3A molecular sieve) in a 3:1:1 mass ratio. Then, monofluoromethane electronic gas containing carbon dioxide impurities is passed through the adsorption tower filled with the primary adsorbent for pre-adsorption and initial impurity removal. The pre-adsorption temperature is 25°C and the pressure is 0.8 MPa. This step removes approximately 30%-40% of the carbon dioxide impurity and some large molecular impurities, reducing the burden of subsequent treatment.

[0064] Step S2. Directed adsorption:

[0065] The gas preliminarily cleaned in step S1 is passed into an adsorption tower filled with a secondary adsorbent to directional adsorb carbon dioxide to obtain high-purity monofluoromethane electronic gas; the secondary adsorbent is ZIF-8@amino-carbon nanotubes prepared in Preparation Example 3, the directional adsorption temperature is -15°C, and the pressure is 0.8 MPa.

[0066] Example 4

[0067] This embodiment provides a method for removing carbon dioxide impurities from monofluoromethane electronic gas, comprising the following steps:

[0068] Step S1. Pre-adsorption:

[0069] First, the adsorption tower is filled with pre-mixed adsorbents (activated alumina, 5A molecular sieve, and 3A molecular sieve in a 4:1:1 mass ratio). Then, monofluoromethane electronic gas containing carbon dioxide impurities is passed through the adsorption tower filled with the primary adsorbent for pre-adsorption and initial impurity removal. The pre-adsorption temperature is 50°C and the pressure is 1.0 MPa. This step removes approximately 30%-40% of the carbon dioxide impurity and some large molecular impurities, reducing the burden of subsequent treatment.

[0070] Step S2. Directed adsorption:

[0071] The gas preliminarily cleaned in step S1 is passed into an adsorption tower filled with a secondary adsorbent to directional adsorb carbon dioxide to obtain high-purity monofluoromethane electronic gas; the secondary adsorbent is ZIF-8@amino-carbon nanotubes prepared in Preparation Example 4, the directional adsorption temperature is -20°C, and the pressure is 1.0 MPa.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that the directional adsorbent in this comparative example is carbon nanotubes.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that the directional adsorbent in this comparative example is ZIF-8@carbon nanotubes.

[0076] The CO2 content before and after the adsorption of monofluoromethane was detected, and the results are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] The above description is merely a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application has been disclosed as 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 equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present application. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for removing carbon dioxide impurities from monofluoromethane electronic gas, characterized in that: The steps include: Step S1. Pre-adsorption: The monofluoromethane electronic gas containing carbon dioxide impurities is passed into an adsorption tower equipped with a primary adsorbent for pre-adsorption and preliminary impurity removal; Step S2. Directed adsorption: The gas initially cleaned from step S1 is passed into an adsorption tower containing a secondary adsorbent for directed adsorption of carbon dioxide to obtain high-purity monofluoromethane electronic gas; The secondary adsorbent is ZIF-8@amino-treated carbon nanotubes.

2. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 1, characterized in that: The pre-adsorption temperature is 20-50° C., and the pressure is 0.5-1.0 MPa.

3. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 1, characterized in that: The primary adsorbent is a mixed adsorbent of activated alumina, 5A molecular sieve and 3A molecular sieve.

4. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 4, characterized in that: The mass ratio of the activated alumina, 5A molecular sieve and 3A molecular sieve is (2-5):1:

1.

5. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 1, characterized in that: The temperature of the directional adsorption is -20°C to 10°C, and the pressure is 0.5 to 1.0 MPa.

6. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 1, characterized in that: The preparation method of the ZIF-8@amino-carbon nanotubes is as follows: Step S21. adding the carbon nanotubes to a concentrated nitric acid solution and ultrasonically treating the carbon nanotubes, followed by heating under reflux for reaction, centrifuging, washing with deionized water until neutral, and drying to obtain functionalized carbon nanotubes; Step S22: dispersing the functionalized carbon nanotubes into a methanol solution of zinc nitrate, followed by adding a methanol solution of 2-methylimidazole, heating for reaction, centrifuging, washing with methanol three times, and drying to obtain ZIF-8@carbon nanotubes; Step S23. Add amino modifier to ZIF-8@ carbon nanotubes and heat under reflux for reaction, centrifuge, wash with methanol three times, and dry to obtain ZIF-8@ amino carbon nanotubes.

7. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 6, characterized in that: In step S21, the mass ratio of carbon nanotubes to concentrated nitric acid is 1:50; the mass fraction of concentrated nitric acid is 65% to 90%; the reflux heating reaction temperature is 80° C. to 120° C. for 6 to 10 hours; and the drying temperature is 60° C. for 12 hours.

8. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 6, characterized in that: In step S22, the concentration of the zinc nitrate methanol solution is 0.5 mol / L, and the concentration of the 2-methylimidazole methanol solution is 4 mol / L; the mass ratio of the functionalized carbon nanotubes: the zinc nitrate methanol solution, and the 2-methylimidazole methanol solution is (1-2):(45-50):(45-50); the heating reaction temperature is 100° C. and the time is 20-24 hours; and the drying temperature is 60° C. and the time is 12 hours.

9. The method for removing carbon dioxide impurities from monofluoromethane electronic gas according to claim 6, characterized in that: In step S23, the amino modifier is ethylenediamine or aminosilane coupling agent, the mass ratio of ZIF-8@ carbon nanotubes to the amino modifier is (1-2):5, and the reaction conditions are as follows: controlling the pH to 8.5-11.5, the temperature to 50°C to 80°C, and the time to 4-8 hours; the drying temperature is 120°C and the time is 6 hours.

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