A zinc-based mixed imidazole ligand metal-organic framework adsorbent for efficient separation of CF4 / N2 and its preparation method
By preparing zinc-based mixed imidazole ligand metal-organic framework adsorbent materials and constructing a pore structure suitable for CF4 adsorption using a mixed ligand strategy, the problem of low CF4/N2 separation efficiency was solved, achieving efficient CF4 adsorption and selective separation. The material structure is stable and has good recyclability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUZHOU UNIV
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-30
Smart Images
Figure CN122302306A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of gas adsorption and separation, specifically relating to a zinc-based mixed imidazole ligand metal-organic framework adsorbent material for efficient separation of CF4 / N2 and its preparation method. Background Technology
[0002] Carbon tetrafluoride (CF4), commonly known as an electronic specialty gas, plays a crucial role in the current semiconductor industry. Due to its long atmospheric lifetime and high global warming potential (GWP), it must be selectively separated from nitrogen (N2). Current methods for recovering fluorinated gases mainly include cryogenic distillation, liquefaction, and membrane separation, but these methods generally suffer from high losses and low separation efficiency. In contrast, microporous adsorbents can effectively achieve low losses and high separation performance, thus promising for the efficient enrichment of CF4 and the selective separation of CF4 / N2 mixtures.
[0003] Zeolite imidazole materials, as a subclass of metal-organic frameworks, possess the advantages of high specific surface area and permanent porosity, making them highly promising for gas adsorption and separation. Recent studies have found that pore sizes slightly larger than gas molecules in adsorbent materials can improve their adsorption capacity. However, small-pore materials exhibit relatively low CF4 capture rates.
[0004] Therefore, it is of great significance to ensure that the material has a high CF4 adsorption capacity while also taking into account excellent CF4 / N2 separation selectivity for efficient separation and recovery of CF4. Summary of the Invention
[0005] The purpose of this invention is to provide a zinc-based mixed imidazole ligand metal-organic framework adsorbent material for efficient separation of CF4 / N2 and its preparation method. By using a mixed ligand strategy, a series of ZIF materials with different pore sizes are prepared to solve the problems of CF4 adsorption and selective separation of CF4 / N2.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a method for preparing a zinc-based mixed imidazole ligand metal-organic framework adsorbent material for efficiently separating CF4 / N2, comprising the following steps:
[0008] (1) Zinc acetate dihydrate, benzimidazole and 2-nitroimidazole were ultrasonically dissolved in N,N-dimethylformamide, and the resulting benzimidazole solution and 2-nitroimidazole solution were mixed evenly to obtain a pre-reaction mixture;
[0009] (2) Add zinc acetate dihydrate solution dropwise to the pre-reaction mixture obtained in step (1), stir for 10-30 min, transfer to a reaction vessel for hydrothermal reaction, cool to room temperature after the reaction is completed, centrifuge, and wash and dry the product to prepare zinc-based mixed imidazole ligand metal-organic framework adsorbent Zn(bIm). x (nIm) 4-x Where bIm is benzimidazole and nIm is 2-nitroimidazole.
[0010] Furthermore, the molar ratio of zinc acetate dihydrate, benzimidazole and 2-nitroimidazole in step (1) is 1.5 mmol: 0~4 mmol: 0~4 mmol.
[0011] Furthermore, the amount of N,N-dimethylformamide used in step (1) is 30~60 mL.
[0012] Furthermore, the ultrasound time in step (1) is 10~40 min.
[0013] Furthermore, the temperature of the hydrothermal reaction in step (2) is 100~160℃, and the time of the hydrothermal reaction is 8~48h.
[0014] Furthermore, the drying temperature in step (2) is 100~140℃, and the drying time is 24~48h.
[0015] Secondly, the present invention provides a zinc-based mixed imidazole ligand metal-organic framework adsorbent material prepared by the above preparation method.
[0016] Furthermore, the specific surface area of the adsorbent material is 69~755 m². 2 / g, micropore volume is 0.03~0.35 cm³ 3 / g.
[0017] Thirdly, the present invention provides the application of the above-mentioned zinc-based mixed imidazole ligand metal-organic framework adsorbent material in the adsorption of CF4.
[0018] Fourthly, the present invention provides the application of the above-mentioned zinc-based mixed imidazole ligand metal-organic framework adsorbent material in the separation of CF4 / N2.
[0019] This invention selects benzimidazole and 2-nitroimidazole as parent compounds for ligand exchange to capture CF4 gas and selectively separate CF4 / N2. A mixed ligand strategy is employed to leverage the advantageous properties of both ligands. 2-Nitroimidazole possesses the ability to polarize the framework, while benzimidazole provides numerous adsorption sites. The electron-withdrawing effect and relatively long (easily broken) Zn-N bond length of 2-nitroimidazole allow for flexible substitution between the two ligands, constructing porous structures with different adaptability to CF4 adsorption. Furthermore, a slight imbalance in the ligand ratio results in unsaturated coordination, exposing even more adsorption sites in the material.
[0020] The beneficial effects of this invention are as follows:
[0021] (1) Zn(bIm) was synthesized using a highly efficient and convenient hydrothermal method. x (nIm) 4-x The preparation method is simple.
[0022] (2) Mixing benzimidazole and 2-nitroimidazole as ligands, the resulting material has a large specific surface area and a suitable pore structure, which can effectively avoid the imbalance between adsorption capacity and selectivity, so that the material has both good CF4 adsorption capacity and CF4 / N2 separation selectivity.
[0023] (3) Zn(bIm) prepared using a mixed ligand strategy x (nIm) 4-x Applied to the field of gas adsorption and separation, this technology overcomes the shortcomings of traditional adsorption materials, which have a single pore structure and cannot be flexibly adjusted. The resulting material has a stable structure, good porosity, and recyclability, reducing actual losses during application. Attached Figure Description
[0024] Figure 1 Zn(bIm) x (nIm) 4-x XRD and infrared characterization tests of (a~b) and (c~d) respectively.
[0025] Figure 2 Zn(bIm) x (nIm) 4-x (a) Adsorption-desorption curves at 77 K; (b) Pore size distribution of Zn(bIm)4(nIm)0; (c) Zn(bIm) 2.5 (nIm) 1.5 The pore size distribution of (d) Zn(bIm)2(nIm)2, and the pore size distribution of (e) Zn(bIm)2. 1.5 (nIm) 2.5 The pore size distribution of (f)Zn(bIm)0(nIm)4.
[0026] Figure 3 : (a) Zn(bIm)4(nIm)0, (b) Zn(bIm) 2.5 (nIm) 1.5 , (c) Zn(bIm)2(nIm)2, (d) Zn(bIm) 1.5 (nIm) 2.5 Adsorption curves of single-component CF4 and N2 of (e)Zn(bIm)0(nIm)4 at 273 and 298 K.
[0027] Figure 4 Zn(bIm) x (nIm) 4-x For the separation selectivity of CF4 / N2.
[0028] Figure 5 : (a) Zn(bIm)4(nIm)0, (b) Zn(bIm) 2.5 (nIm) 1.5 , (c) Zn(bIm)2(nIm)2, (d) Zn(bIm) 1.5 (nIm) 2.5 The actual breakthrough curves of (e)Zn(bIm)0(nIm)4 for CF4 and N2 at a flow rate of 15 mL / min, and (f)Zn(bIm) 1.5 (nIm) 2.5 Multiple loop test graphs. Detailed Implementation
[0029] To better understand the technical solution of the present invention, a detailed description is provided below in conjunction with specific embodiments and accompanying drawings, but this does not limit the scope of protection of the present invention.
[0030] Example 1 Zn(bIm)4(nIm)0
[0031] 0.708 g of benzimidazole and 0.33 g of zinc acetate dihydrate were dissolved in 60 mL and 30 mL of N,N-dimethylformamide, respectively, and sonicated for 20 min. The zinc acetate dihydrate solution was added dropwise to the benzimidazole solution, and after stirring for 10 min, the mixture was transferred to a reactor for hydrothermal reaction. The mixture was heated to 120 °C and maintained for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed three times with DMF, and finally dried in a vacuum oven at 120 °C for 1 day to prepare Zn(bIm)4(nIm)0.
[0032] Example 2 Zn(bIm) 2.5 (nIm) 1.5
[0033] 0.254 g of 2-nitroimidazole and 0.443 g of benzimidazole were dissolved in 60 mL of N,N-dimethylformamide, and 0.33 g of zinc acetate dihydrate was dissolved in 30 mL of N,N-dimethylformamide. Both solutions were sonicated for 20 min. The 2-nitroimidazole and benzimidazole solutions were first mixed thoroughly to obtain a pre-reaction mixture. Then, the zinc acetate dihydrate solution was added dropwise to the pre-reaction mixture, and the mixture was stirred for 10 min. The mixture was then transferred to a reactor for a hydrothermal reaction, heated to 120 °C, and maintained for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed three times with DMF, and finally dried in a vacuum oven at 120 °C for 1 day to obtain Zn(bIm). 2.5 (nIm) 1.5 .
[0034] Example 3 Zn(bIm)2(nIm)2
[0035] 0.339 g of 2-nitroimidazole and 0.354 g of benzimidazole were dissolved in 60 mL of N,N-dimethylformamide, and 0.33 g of zinc acetate dihydrate was dissolved in 30 mL of N,N-dimethylformamide. The solutions were sonicated for 20 min each. The 2-nitroimidazole and benzimidazole solutions were first mixed thoroughly to obtain a pre-reaction mixture. Then, the zinc acetate dihydrate solution was added dropwise to the pre-reaction mixture, and the mixture was stirred for 10 min. The mixture was then transferred to a reactor for hydrothermal reaction, heated to 120 °C, and maintained for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed three times with DMF, and finally dried in a vacuum oven at 120 °C for 1 day to prepare Zn(bIm)2(nIm)2.
[0036] Example 4 Zn(bIm) 1.5 (nIm) 2.5
[0037] 0.424 g of 2-nitroimidazole and 0.266 g of benzimidazole were dissolved in 60 mL of N,N-dimethylformamide, and 0.33 g of zinc acetate dihydrate was dissolved in 30 mL of N,N-dimethylformamide. Each solution was sonicated for 20 min. The 2-nitroimidazole and benzimidazole solutions were first mixed thoroughly to obtain a pre-reaction mixture. The zinc acetate dihydrate solution was then added dropwise to the pre-reaction mixture, and the mixture was stirred for 10 min. The mixture was then transferred to a reactor for a hydrothermal reaction, heated to 120 °C, and maintained for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed three times with DMF, and finally dried in a vacuum oven at 120 °C for one day to obtain Zn(bIm). 1.5 (nIm) 2.5 .
[0038] Example 5 Zn(bIm)0(nIm)4
[0039] 0.678 g of 2-nitroimidazole was dissolved in 60 mL of N,N-dimethylformamide, and 0.33 g of zinc acetate dihydrate was dissolved in 30 mL of N,N-dimethylformamide. Both solutions were sonicated for 20 min. The zinc acetate dihydrate solution was added dropwise to the 2-nitroimidazole solution, and the mixture was stirred for 10 min. The mixture was then transferred to a reaction vessel for hydrothermal reaction, heated to 120 °C, and maintained for 8 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed three times with DMF, and finally dried in a vacuum oven at 120 °C for 1 day to prepare Zn(bIm)0(nIm)4.
[0040] Table 1 shows the specific surface area and micropore volume of the materials prepared in Examples 1-5. The results indicate that Zn(bIm) 1.5 (nIm) 2.5 It has the largest specific surface area of 755 m² 2 g -1 and micropore volume 0.35 cm³ 3 g -1 .
[0041] Table 1. Specific surface area and micropore volume of the materials prepared in Examples 1-5.
[0042]
[0043] Figure 1 For Zn(bIm) x (nIm) 4-x XRD and infrared characterization tests were performed on (Examples 1-5). XRD results showed that the diffraction peaks of all materials matched the standard cards, indicating successful synthesis. Infrared tests showed peaks at 738, 1241, 1280, and 1469 cm⁻¹. -1 The main characteristic peaks at these locations correspond to out-of-plane bending vibration (CH), stretching vibration (CN), stretching vibration (C=N), and skeletal vibration (CC), respectively, while the peaks at 1363 and 1537 cm⁻¹ correspond to these vibrations. -1 The peak at that location originates from a nitro group, and the presence of related groups further confirms the successful synthesis of the material.
[0044] Figure 2 For Zn(bIm) x (nIm) 4-x (Examples 1-5) N2 adsorption-desorption curves at 77K: After vacuum activation pretreatment, the materials were tested for N2 adsorption-desorption at 77K using a surface area and porosity analyzer to determine the pore size distribution of each material, Zn(bIm). 1.5 (nIm) 2.5It has the smallest and most suitable pore size of approximately 0.73 nm among all materials for CF4 adsorption, and a slight ligand imbalance also makes Zn(bIm) suitable for adsorption. 1.5 (nIm) 2.5 Compared to Zn(bIm)2(nIm)2, it exposes more adsorption sites.
[0045] Figure 3 For Zn(bIm) x (nIm) 4-x The single-component adsorption capacity of CF4 and N2 was assessed by adjusting the test temperatures to 298K and 273K using a surface area and porosity analyzer. All samples were vacuum activated before testing to ensure complete gas desorption within the material pores. Single-component adsorption of CF4 and N2 was performed at both temperatures. Zn(bIm) was optimized using a mixed ligand strategy. 1.5 (nIm) 2.5 It exhibits a higher CF4 adsorption capacity (18.3 cm⁻¹) than other samples. 3 g -1 ).
[0046] Figure 4 For Zn(bIm) x (nIm) 4-x The selective separation capability of CF4 / N2 was assessed by selectively fitting the adsorption data of CF4 and N2 at room temperature using the Langmuir model. The R-squared values of all fitted curves were calculated. 2 All are greater than 0.999. Zn(bIm) 1.5 (nIm) 2.5 Due to the optimized adjustment of the pore structure, the CF4 / N2 separation selectivity is optimal (7.3).
[0047] Figure 5 For Zn(bIm) x (nIm) 4-x At a flow rate of 15 mL / min, the actual breakthrough separation of all materials was simulated using a multi-component adsorption breakthrough curve analyzer. The CF4:N2 mixed gas ratio was set to 0.1:0.9 to simulate the low fluorine gas content during actual separation. The results show that Zn(bIm) x (nIm) 4-x Both can effectively separate CF4 / N2, demonstrating excellent practical separation performance and recyclability.
[0048] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for preparing a zinc-based mixed imidazole ligand metal-organic framework adsorbent for efficient separation of CF4 / N2, characterized in that: Includes the following steps: (1) Zinc acetate dihydrate, benzimidazole and 2-nitroimidazole were ultrasonically dissolved in N,N-dimethylformamide, and the resulting benzimidazole solution and 2-nitroimidazole solution were mixed evenly to obtain a pre-reaction mixture; (2) Add zinc acetate dihydrate solution dropwise to the pre-reaction mixture obtained in step (1), stir for 10-30 min, transfer to a reaction vessel for hydrothermal reaction, cool to room temperature after the reaction is completed, centrifuge, and wash and dry the product to prepare zinc-based mixed imidazole ligand metal-organic framework adsorbent Zn(bIm). x (nIm) 4-x Where bIm is benzimidazole and nIm is 2-nitroimidazole.
2. The preparation method according to claim 1, characterized in that: The molar ratio of zinc acetate dihydrate, benzimidazole and 2-nitroimidazole in step (1) is 1.5 mmol: 0~4 mmol: 0~4 mmol.
3. The preparation method according to claim 1, characterized in that: The amount of N,N-dimethylformamide used in step (1) is 30~60mL.
4. The preparation method according to claim 1, characterized in that: The ultrasound time in step (1) is 10~40 min.
5. The preparation method according to claim 1, characterized in that: The hydrothermal reaction in step (2) is carried out at a temperature of 100~160℃ for 8~48h.
6. The preparation method according to claim 1, characterized in that: The drying temperature in step (2) is 100~140℃ and the drying time is 24~48h.
7. A zinc-based mixed imidazole ligand metal-organic framework adsorbent material prepared by the preparation method according to any one of claims 1 to 6.
8. The zinc-based mixed imidazole ligand metal-organic framework adsorbent material according to claim 7, characterized in that: The specific surface area of the adsorbent material is 69~755 m². 2 / g, micropore volume is 0.03~0.35 cm³ 3 / g.
9. The application of the zinc-based mixed imidazole ligand metal-organic framework adsorbent material as described in claim 7 in the adsorption of CF4.
10. The application of the zinc-based mixed imidazole ligand metal-organic framework adsorbent material as described in claim 7 in the separation of CF4 / N2.