An organic framework material for purification of fluorine-containing electronic special gas and a preparation method thereof

Abstract

The present application relates to a kind of organic framework material for fluorine-containing electronic special gas purification and its preparation method, belong to electronic special gas purification material technical field.The material is formed by cyanonitrile and fluorine-containing amide monomer through nitrile group cyclotrimization to form covalent triazine skeleton, the molar ratio of two kinds of monomers is 1:0.12-0.18;The fluorine-containing amide monomer is obtained by the reaction of p-aminobenzonitrile and trifluoroacetic anhydride, then it is reacted by microwave heating under the action of trifluoromethanesulfonic acid with cyanonitrile, and the organic framework material is obtained after treatment;The obtained material can be dry premixed with fibrillatable polytetrafluoroethylene, shear fibrillation and pressing to form purification product;Fluorine-containing amide structure can strengthen trace hydrogen fluoride adsorption, improve the capacity retention rate when trace water exists;The interface adaptation of fluorine-containing skeleton and polytetrafluoroethylene is conducive to reducing the loss of forming pore, improving the effective capacity per bed volume, and is suitable for the deep removal of hydrogen fluoride impurities in various fluorine-containing electronic special gas.

Description

Technical Field

[0001] This invention belongs to the field of electronic specialty gas purification materials technology, specifically, it relates to an organic framework material for purifying fluorine-containing electronic specialty gases and its preparation method. Background Technology

[0002] Fluorinated electronic specialty gases are widely used in processes such as semiconductor etching, thin film deposition, and cavity cleaning. Due to factors such as raw material residues, synthesis side reactions, and desorption from storage and transportation equipment surfaces, fluorinated electronic specialty gases such as nitrogen trifluoride, carbon tetrafluoride, hexafluoroethane, trifluoromethane, and sulfur hexafluoride often contain trace amounts of hydrogen fluoride. Hydrogen fluoride is highly corrosive and reactive; even at low concentrations, it can corrode pipelines and process equipment, affecting the stability of electronic specialty gases in etching and deposition processes. Therefore, it is necessary to thoroughly remove trace amounts of hydrogen fluoride from fluorinated electronic specialty gases before use.

[0003] Existing hydrogen fluoride purification materials mainly include inorganic adsorbents such as activated alumina and metal oxides, as well as organic porous materials such as metal-organic frameworks and covalent organic frameworks. These materials are typically packaged directly into purification columns as powders, or formed into granules, columns, or tablets after being combined with polymer binders for use in fixed-bed purification. Inorganic adsorbents can immobilize hydrogen fluoride through surface reactions; however, some activated alumina materials may produce water during the fluorination reaction. Water itself is an impurity in fluorinated electronic gases that requires strict control, potentially leading to increased moisture content after hydrogen fluoride removal.

[0004] Organic framework materials possess advantages such as tunable pore structure and low inorganic dust generation, enabling the adsorption of hydrogen fluoride using framework nitrogen atoms or introduced polar groups. However, hydrogen fluoride in electronic specialty gases is typically at a low partial pressure, making it difficult to obtain sufficient adsorption driving force solely through high specific surface area or ordinary pore physical adsorption. While adding polar groups such as amides, hydroxyl groups, or amino groups to the framework can enhance the effect on hydrogen fluoride, these groups also readily adsorb moisture. When trace amounts of water are present in the feed gas, moisture occupies polar sites or forms a hydration layer within the pores, reducing the available adsorption sites for hydrogen fluoride. Therefore, simply adding hydrophilic polar groups makes it difficult to simultaneously achieve both hydrogen fluoride adsorption capacity and capacity retention under humid conditions.

[0005] Furthermore, organic framework materials are typically fine powders with low bulk density. Direct packing of powders can easily lead to problems such as uneven bed porosity, airflow short-circuiting, and powder entrainment. Adding molding materials such as polytetrafluoroethylene (PTFE) can further cause these materials to cover the pores, agglomerate framework particles, or reduce the effective framework material content per unit volume. Therefore, a high mass adsorption capacity of powder materials does not necessarily translate to a high purification capacity per unit bed volume in a molded fixed bed. Evaluating materials solely based on their 77K nitrogen specific surface area or static adsorption capacity is also insufficient to fully reflect their actual performance under dynamic purification of trace hydrogen fluoride and molded packing conditions.

[0006] Therefore, existing technologies still need to address the problem that organic framework materials have insufficient adsorption capacity under low hydrogen fluoride partial pressure and trace water coexistence conditions, and that their mass adsorption performance is difficult to effectively convert into the volumetric purification capacity of the fixed bed. At the same time, it is also necessary to reduce the risk of moisture generation and loss of the main fluorinated electronic special gas during the purification process. Summary of the Invention

[0007] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide an organic framework material for the purification of fluorine-containing electronic special gases and a method for preparing the same.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] An organic framework material for purifying fluorinated electronic special gases is a covalent triazine framework material obtained by the cyclotrimerization reaction of terephthalonitrile and a fluorinated amide monomer. The structural formula of the fluorinated amide monomer can be represented as CF3CONH-C6H4-CN. Terephthalonitrile, as a dinitrile monomer, constitutes a continuously cross-linked covalent triazine framework. The fluorinated amide monomer contains only one nitrile group and mainly participates in the formation of some triazine nodes, introducing a fluorinated amide structure into the framework.

[0010] The preparation method of the fluorinated amide monomer is as follows: p-aminobenzonitrile, triethylamine and anhydrous dichloromethane are mixed, dried under nitrogen protection and cooled, and trifluoroacetic anhydride is slowly added to perform nucleophilic acyl substitution, thus preparing the fluorinated amide monomer.

[0011] Furthermore, the molar ratio of p-aminobenzonitrile, trifluoroacetic anhydride, and triethylamine is 1:1.04-1.08:1.15-1.2.

[0012] Preferably, the temperature during the addition of trifluoroacetic anhydride is not higher than 5°C, and the reaction temperature after complete addition is not higher than 30°C; triethylamine is used to bind the generated trifluoroacetic acid, reducing the influence of the conversion of p-aminobenzonitrile into ammonium salt on the reaction rate, and the low-temperature reaction environment is conducive to the full progress of nucleophilic acyl substitution.

[0013] The preparation method of the organic framework material is as follows: terephthalonitrile and fluorinated amide monomers are ground and mixed, and trifluoromethanesulfonic acid is added under dry nitrogen protection, mixed and heated to carry out cyclotrimerization reaction to obtain the organic framework material.

[0014] Furthermore, the molar ratio of terephthalonitrile to fluorinated amide monomer is 1:0.12-0.18, and the volume of trifluoromethanesulfonic acid, based on the total amount of terephthalonitrile and fluorinated amide monomer, is 0.6-0.72 L / mol.

[0015] Preferably, the cyclotrimerization reaction is carried out using microwave heating at a temperature of 90-105℃.

[0016] Furthermore, the organic framework material is sequentially dry-premixed with fibrillable polytetrafluoroethylene, sheared fibrillated, and pressed into shape, which can be used for the purification of hydrogen fluoride impurities in fluorinated electronic specialty gases, including nitrogen trifluoride, carbon tetrafluoride, hexafluoroethane, trifluoromethane, and sulfur hexafluoride.

[0017] Preferably, the amount of fibrillable polytetrafluoroethylene used is 4.7-5.5 wt% of the organic framework material.

[0018] The beneficial effects of this invention are:

[0019] This invention employs a cyclotrimerization reaction between terephthalonitrile and a fluorinated amide monomer. The terephthalonitrile forms a continuously cross-linked covalent triazine framework, while the fluorinated amide monomer participates in the formation of some triazine nodes and introduces the fluorinated amide structure into the framework pore walls. The triazine ring nitrogen atom, amide carbonyl group, and amide hydrogen can form hydrogen bonds and polar interactions with hydrogen fluoride from different directions, thereby improving the adsorption driving force of the material under low hydrogen fluoride partial pressure. Compared with ordinary covalent triazine framework materials, this structure can reduce the outlet HF concentration in the initial stage of purification and increase the dynamic HF capacity, solving the problem of insufficient trace HF binding capacity when relying solely on pore physical adsorption.

[0020] The amide group in the fluorinated amide structure primarily provides HF binding sites, while the trifluoromethyl group helps regulate the local polarity and fluorinated surface characteristics around these sites, reducing the tendency for water to continuously accumulate near strongly polar sites and obscure the pores. Therefore, this structure does not simply increase hydrophilic hydrogen-bonding groups, nor does it merely improve hydrophobicity through the trifluoromethyl group alone; rather, it improves the availability of adsorption sites in the presence of trace amounts of water while retaining a strong HF binding capacity. In the test results, Comparative Example 2 showed improved wet-state capacity retention after introducing the trifluoromethyl group alone, but the dynamic HF capacity was still lower than that of the example, indicating that the regulation of water competitive adsorption by the trifluoromethyl group cannot replace the directional effect of the amide site on HF; the coexistence of both can balance HF adsorption capacity and wet-state adsorption stability.

[0021] The fluorinated amide structure can also modulate the surface properties of the organic framework material particles. Its fluorinated portion has similar fluorinated surface characteristics to polytetrafluoroethylene (PTFE), which is beneficial for improving the contact state between the framework particles and the PTFE molding phase. This reduces local aggregation of PTFE, ineffective large voids between framework particles, and concentrated coverage of the pores by the molding material. As a result, the obtained product maintains gas channels while increasing the utilization rate of effective adsorption sites per unit bed volume. Therefore, this invention not only improves the HF capacity of the material by mass but also converts its adsorption advantage into effective volumetric capacity in the molded fixed bed, compensating for the low bulk density of the organic framework powder and the decrease in pore utilization after molding.

[0022] The material of this invention mainly uses HF adsorption and fixation within pores, and has a stable purification effect on trace amounts of HF in common fluorine-containing electronic specialty gases such as NF3, CF4, C2F6, CHF3 and SF6, with minimal loss of the main gas. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: Preparation of an organic framework material for the purification of fluorine-containing electronic special gases, specifically including the following:

[0025] 1) Preparation of fluoroamide monomer: 14.18 g of p-aminobenzonitrile, 13.96 g of triethylamine and 300 mL of anhydrous dichloromethane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel and dry nitrogen inlet. Dry nitrogen was introduced for 10 min and stirred. The system was cooled to 0 °C. 26.21 g of trifluoroacetic anhydride was dissolved in 60 mL of anhydrous dichloromethane and added dropwise to the flask over 30 min. During the dropwise addition, the temperature of the reaction solution was controlled not to exceed 5 °C. After the dropwise addition was completed, the temperature was raised to 20 °C and the reaction was allowed to proceed for 2.5 h.

[0026] After the reaction was completed, the reaction solution was cooled back to below 5°C, and 300 mL of ice water was slowly added with stirring to hydrolyze the remaining trifluoroacetic anhydride. After standing and separating the layers, the organic phase was retained, and the aqueous phase was extracted twice with dichloromethane, 100 mL each time. The organic phases were combined and washed twice with 5 wt% sodium bicarbonate aqueous solution, twice with ultrapure water, and once with saturated sodium chloride aqueous solution, 200 mL each time. The organic phase was then dried with anhydrous sodium sulfate for 4 h, filtered, and dried under reduced pressure at a temperature not exceeding 35°C and an absolute pressure not exceeding 10 kPa to obtain the fluoroamide monomer.

[0027] 2) Preparation of organic framework material: In this example, the total amount of the two nitrile monomers is 0.6 mol, and the molar ratio of terephthalonitrile to fluorinated amide monomer is 1:0.12. Take 68.64 g of terephthalonitrile and 13.77 g of fluorinated amide monomer, grind them in an agate mortar for 30 min, transfer them to a microwave reaction vessel resistant to strong acid, and purge with dry nitrogen for 15 min; take 360 ​​mL of trifluoromethanesulfonic acid and slowly add it over 10 min while stirring, then use a microwave reactor with temperature feedback control to raise the temperature to 90 °C and maintain it at this temperature for 35 min;

[0028] After the reaction was completed, the mixture was naturally cooled to below 30°C, and 1 L of 20% (v / v) ethanol aqueous solution was added for washing. The pH was adjusted to 6 with triethylamine, filtered, washed with water and dried. Then, the mixture was extracted with methanol by Soxhlet for 12 h and dried under vacuum to constant weight to obtain the organic framework material.

[0029] 3) Preparation of gas purification samples: Take more than 50g of the prepared organic framework material and 2.35g of fibrillable polytetrafluoroethylene (Teflon 6-J) and dry mix for 10min. Then raise the mixing temperature to 55℃ and shear mix at 1200rpm for 15min to fibrillate the polytetrafluoroethylene. Press the mixture into a columnar product under 10MPa and hold the pressure for 60s. After demolding, vacuum devolatilize at 98℃ and absolute pressure not exceeding 1kPa for 10h. After cooling, seal and store in dry nitrogen.

[0030] Example 2: Preparation of an organic framework material for the purification of fluorine-containing electronic special gases, specifically including the following:

[0031] 1) Preparation of fluoroamide monomers: 14.18 g of p-aminobenzonitrile, 14.27 g of triethylamine and 320 mL of anhydrous dichloromethane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel and dry nitrogen inlet. Dry nitrogen was introduced for 10 min and stirred. The system was cooled to 0 °C. 26.72 g of trifluoroacetic anhydride was dissolved in 60 mL of anhydrous dichloromethane and added dropwise to the flask over 30 min. During the addition, the temperature of the reaction solution was controlled not to exceed 5 °C. After the addition was completed, the temperature was raised to 25 °C and the reaction was carried out for 3 h. The purification process was the same as above.

[0032] Preparation of organic framework material: In this example, the total amount of the two nitrile monomers was 0.6 mol, and the molar ratio of terephthalonitrile to fluorinated amide monomer was 1:0.15. 66.85 g of terephthalonitrile and 16.76 g of fluorinated amide monomer were ground in an agate mortar for 35 min, transferred to a microwave reaction vessel resistant to strong acid, and purged with dry nitrogen for 15 min. 396 mL of trifluoromethanesulfonic acid was slowly added and stirred over 12 min, and then the temperature was raised to 98 °C using a microwave reactor with temperature feedback control and maintained at that temperature for 30 min. The purification process was the same as above.

[0033] 3) Preparation of gas purification samples: Take more than 50g of the prepared organic framework material and 2.55g of fibrillable polytetrafluoroethylene (Teflon 6-J) and dry mix for 10min. Then raise the mixing temperature to 55℃ and shear mix at 1500rpm for 12min to fibrillate the polytetrafluoroethylene. Press the mixture into a columnar product under 10MPa and hold the pressure for 60s. After demolding, vacuum devolatilize at 98℃ and absolute pressure not exceeding 1kPa for 10h. After cooling, seal and store in dry nitrogen.

[0034] Example 3: Preparation of an organic framework material for the purification of fluorine-containing electronic special gases, specifically including the following:

[0035] 1) Preparation of fluoroamide monomers: 14.18 g of p-aminobenzonitrile, 14.57 g of triethylamine and 350 mL of anhydrous dichloromethane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel and dry nitrogen inlet. Dry nitrogen was introduced for 10 min and stirred. The system was cooled to 0 °C. 27.22 g of trifluoroacetic anhydride was dissolved in 70 mL of anhydrous dichloromethane and added dropwise to the flask over 30 min. During the addition, the temperature of the reaction solution was controlled not to exceed 5 °C. After the addition was completed, the temperature was raised to 30 °C and the reaction was allowed to proceed for 3.5 h. The purification process was the same as above.

[0036] Preparation of organic framework material: In this example, the total amount of the two nitrile monomers was 0.6 mol, and the molar ratio of terephthalonitrile to fluorinated amide monomer was 1:0.18. 65.15 g of terephthalonitrile and 19.6 g of fluorinated amide monomer were ground in an agate mortar for 40 min, transferred to a microwave reaction vessel resistant to strong acid, and purged with dry nitrogen for 15 min. 432 mL of trifluoromethanesulfonic acid was slowly added and stirred over 15 min, and then the temperature was raised to 105 °C using a microwave reactor with temperature feedback control and maintained at that temperature for 25 min. The purification process was the same as above.

[0037] 3) Preparation of gas purification samples: Take more than 50g of the prepared organic framework material and 2.75g of fibrillable polytetrafluoroethylene (Teflon 6-J) and dry mix for 20min. Then raise the mixing temperature to 55℃ and shear mix at 1500rpm for 25min to fibrillate the polytetrafluoroethylene. Press the mixture into columnar products under 10MPa and hold the pressure for 60s. After demolding, vacuum devolatilize at 98℃ and absolute pressure not exceeding 1kPa for 10h. After cooling, seal and store in dry nitrogen.

[0038] Comparative Example 1: No fluorinated amide monomer was added for co-cyclic trimerization reaction; the specific implementation process is the same as in Example 3.

[0039] Comparative Example 2 uses p-trifluoromethylbenzonitrile instead of fluorinated amide monomers for co-cyclic trimerization. The specific implementation process is the same as in Example 3, with equal substitution of nitrile molar amounts.

[0040] Comparative Example 3, using commercially available AxTrap TM Type 612 HF remover.

[0041] The material used for purifying fluorine-containing electronic specialty gases was loaded into a fixed bed. N2 containing 50 ppmv of HF was introduced at 25℃ and 0.10 MPa at a flow rate of 500 mL / min. A laser absorption HF analyzer calibrated with standard gas was used to detect the outlet HF. The outlet HF concentration was recorded after 30 minutes of operation. The dynamic HF capacity was calculated by integrating the difference between the inlet and outlet HF concentrations, with the outlet HF reaching 0.10 ppmv as the breakthrough point. Additionally, 10 ppmv of moisture was added to the feed gas, and the wet capacity retention rate was calculated as the ratio of wet capacity to dry capacity. The effective capacity per unit bed volume was calculated based on the actual sample packing mass and bed volume. Specific test results are shown in Table 1.

[0042] Table 1

[0043]

[0044] Based on the above tests, the product containing the organic framework material prepared in Example 3 was selected as the purification material. NF3, CF4, C2F6, CHF3, and SF6 containing 5.0 ppmv HF were introduced at 25℃ and 0.10 MPa, respectively, at a flow rate of 500 mL / min. After continuous operation for 60 min, the outlet HF was measured, and the HF removal rate was calculated. The main gas recovery rate was calculated based on the ratio of the inlet and outlet standard volume flow rates. Specific test results are shown in Table 2.

[0045] Table 2

[0046]

[0047] As shown in Table 1, the 30-minute outlet HF concentration, dry dynamic HF capacity, and wet capacity retention rate of Examples 1-3 are all better than those of Comparative Example 1. Although the wet retention rate was improved by introducing only trifluoromethyl groups in Comparative Example 2, its HF capacity was still significantly lower than that of Examples 1-3. This indicates that when amide sites and fluorinated groups coexist, both HF binding strength and site availability under humid conditions can be taken into account.

[0048] As the proportion of fluorinated amide monomers increases within the scope of this application, the mass capacity and wet state retention rate of Examples 1-3 gradually increase; at the same time, their effective capacity per unit bed volume also increases significantly. This result indicates that the fluorinated amide structure effectively increases the effective action sites for HF, while the increase in Examples 2 to 3 slows down, which also shows that a higher proportion of functional monomers is not necessarily better.

[0049] As shown in Table 2, when Example 2 was used for five representative fluorine-containing electronic specialty gases, the outlet HF was 12-26 ppbv, the HF removal rate was 99.48%-99.76%, and the main gas recovery rate was 99.7%-99.9%. This indicates that the material has a stable purification effect on trace amounts of HF in different fluorine-containing electronic specialty gases, and the loss of the main gas is small.

[0050] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. An organic framework material for purifying fluorine-containing electronic special gases, characterized in that, It is prepared by the cyclotrimerization reaction of terephthalonitrile and a fluorinated amide monomer, wherein the structural formula of the fluorinated amide monomer can be represented as CF3CONH-C6H4-CN, and the preparation method is as follows: p-Aminobenzonitrile, triethylamine, and anhydrous dichloromethane are mixed, dried under nitrogen protection, and cooled. Trifluoroacetic anhydride is then slowly added to perform nucleophilic acyl substitution, thus preparing a fluoroamide monomer.

2. The organic framework material for purifying fluorine-containing electronic special gases according to claim 1, characterized in that, The molar ratio of p-aminobenzonitrile, trifluoroacetic anhydride and triethylamine is 1:1.04-1.08:1.15-1.

2.

3. The organic framework material for purifying fluorine-containing electronic special gases according to claim 2, characterized in that, The temperature during the addition of trifluoroacetic anhydride should not exceed 5°C, and the reaction temperature after complete addition should not exceed 30°C.

4. The method for preparing an organic framework material for purifying fluorine-containing electronic special gases according to claim 3, characterized in that, The specific method is as follows: Terephthalonitrile and fluorinated amide monomers were ground and mixed evenly, and trifluoromethanesulfonic acid was added under dry nitrogen protection and stirred evenly. The mixture was then heated to carry out a cyclotrimerization reaction to obtain an organic framework material.

5. The method for preparing an organic framework material for purifying fluorine-containing electronic special gases according to claim 4, characterized in that, The molar ratio of terephthalonitrile to fluorinated amide monomer is 1:0.12-0.18, and the volume of trifluoromethanesulfonic acid, based on the total amount of terephthalonitrile and fluorinated amide monomer, is 0.6-0.72 L / mol.

6. The method for preparing an organic framework material for purifying fluorine-containing electronic special gases according to claim 5, characterized in that, The cyclotrimerization reaction is carried out using microwave heating at a temperature of 90-105℃.

7. The organic framework material for purifying fluorine-containing electronic special gases prepared by the method according to claim 6, characterized in that, Organic framework materials are sequentially dry-premixed with fibrillable polytetrafluoroethylene, sheared fibrillated, and pressed into shape for use in the purification of fluorine-containing electronic specialty gases.

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