Application of metal organic framework material with open Bi < 3 + > sites in N2O separation
By preparing metal-organic framework materials with open Bi3+ sites, the problem of N2O separation in the presence of multiple competing gases was solved, achieving efficient and stable N2O capture and separation, which is suitable for industrial N2O separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies struggle to efficiently separate and capture nitrous oxide (N2O) in the presence of multiple competing gases, especially in the presence of CO2. Pressure swing adsorption (PSA) technology has low energy consumption but insufficient separation efficiency.
Bi9(C9H3O6)9(H2O)9 was synthesized via a solvothermal method using a metal-organic framework material with open Bi3+ sites. By utilizing the strong interaction between Bi3+ sites and N2O, empty coordination sites were exposed after high-temperature activation, thus achieving highly selective adsorption and regeneration cycling of N2O.
The material achieves highly selective adsorption of N2O in complex gas environments, significantly increases the adsorption capacity of N2O, prolongs the breakthrough time of N2O, and exhibits good thermal stability, making it suitable for industrial applications.
Smart Images
Figure CN121972142A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of gas separation technology, and specifically relates to a gas separation method with open Bi 3+ Application of site-specific metal-organic framework materials in N2O separation. Background Technology
[0002] Nitrous oxide (N₂O) is the world's third-largest greenhouse gas, after carbon dioxide and methane. Although the total emissions of N₂O are relatively low compared to carbon dioxide (CO₂), its warming effect is extremely strong: the warming potential of N₂O over 100 years is approximately 273 times that of CO₂. Furthermore, N₂O has a long atmospheric persistence, approximately 120 years. Nitrous oxide has a wide range of applications, including in food, pharmaceuticals, fuels, and catalysis, and can also serve as a donor of nitrogen or oxygen atoms.
[0003] The largest industrial source of N2O emissions is the tail gas produced by adipic acid, nitric acid, and caprolactam. This gas mainly contains nitrogen (N2), oxygen (O2), and CO2. N2O has significantly different properties from N2 and O2, making it relatively easy to separate. However, N2O and CO2 have very similar properties, so capturing N2O is challenging in the presence of multiple competing gases containing CO2.
[0004] Among the current processes available for N2O treatment, pressure swing adsorption (PSA) technology has the advantages of low energy consumption and simple operation. Therefore, achieving efficient separation of four gases using adsorption separation remains a formidable challenge. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention provides a method with open Bi 3+ Application of metal-organic framework materials at specific sites in N2O separation. The open Bi content in the metal-organic framework material... 3+ The site interacts strongly with N2O molecules, enabling efficient N2O capture even in the presence of multiple competing gases.
[0006] This invention is achieved through the following technical solution: A type with open Bi 3+ The application of a metal-organic framework (MOF) at a specific site in N₂O separation, wherein the MOF has the molecular formula Bi₉(C₉H₃O₆)₉(H₂O)₉, is generated by a solvothermal reaction using bismuth nitrate pentahydrate as the metal source, trimesic acid as the organic ligand, and methanol as the solvent. High-temperature activation of the material is required before use in gas separation.
[0007] Furthermore, the preparation method of the metal-organic framework material includes the following steps: dissolving bismuth nitrate pentahydrate and trimesic acid in methanol, then transferring the mixture to a polytetrafluoroethylene reaction vessel, placing it in an oven for reaction, obtaining a white powder by filtration, washing it three times with methanol, drying it in air, and then activating the crystal in a dynamic vacuum for 12 hours to remove the solvent in the crystal channels, thereby obtaining an activated sample.
[0008] Furthermore, in the structure of the metal-organic framework material, Bi 3+ It is a Bi-O nine-coordinate system, where eight O atoms come from the carboxyl group of the ligand, and the remaining O atom comes from a water molecule. High-temperature activation can remove the water molecule, exposing an empty Bi atom. 3+ Site.
[0009] Furthermore, the molar ratio of bismuth nitrate pentahydrate to trimesic acid is 1:15~20, preferably 1:17.26.
[0010] Furthermore, the reaction temperature is 120-160℃, and the reaction time is 24-72 hours. Preferably, the temperature is 140℃ and the reaction time is 48 hours.
[0011] Furthermore, the activation temperature is 100-200℃, preferably 150℃.
[0012] Furthermore, the metal-organic framework material can be desorbed and regenerated after adsorbing the gas, and can be recycled.
[0013] Beneficial technical effects of the present invention: The beneficial technical effects of this patent are mainly reflected in the following aspects: (1) The metal-organic framework material provided by the present invention has open Bi 3+ The site can generate specific and strong interactions with N2O molecules, achieving highly selective adsorption of N2O even under the coexistence of multiple competing gases such as N2, O2, and CO2. The adsorption capacity of this material for N2O is significantly higher than that for CO2, N2, and O2, and the N2O / CO2 selectivity is significantly better than that of the comparative material, demonstrating excellent N2O capture ability.
[0014] (2) DFT calculations confirmed that there is a shorter interaction distance and a stronger binding energy between the open Bi³⁺ sites in the material and N₂O molecules, which theoretically revealed the mechanism of its highly selective adsorption and provided a clear structural basis for material design.
[0015] (3) Thermogravimetric analysis shows that the material has excellent thermal stability below 400℃. In addition, the material can be regenerated by desorption after adsorbing gas, and has the potential for recycling.
[0016] (4) Dynamic penetration experiments show that the material can effectively delay the penetration time of N2O in N2O / CO2, N2O / N2 binary mixtures and N2 / O2 / CO2 / N2O quaternary mixtures, proving that it still has stable and efficient N2O separation capability in complex gas environments.
[0017] (5) The metal-organic framework material is synthesized in one step by using common bismuth nitrate and trimesic acid as raw materials via a solvothermal method. The process conditions are mild and reproducible, making it suitable for large-scale production and with good industrial application prospects. Attached Figure Description
[0018] Figure 1 The diagram shows the structures of Example 1 and Comparative Example 1.
[0019] Figure 2 The X-ray diffraction patterns are for Example 1 and Comparative Example 1.
[0020] Figure 3 The TGA diagrams are for Example 1 and Comparative Example 1.
[0021] Figure 4 The N2 adsorption-desorption isotherms and pore size distribution diagrams for Example 1(a) and Comparative Example 1(b) at 77 K are shown.
[0022] Figure 5 The adsorption isotherms of nitrous oxide, carbon dioxide, nitrogen and oxygen at 298 K are for Example 1(a) and Comparative Example 1(b).
[0023] Figure 6 The heat of adsorption of nitrous oxide, carbon dioxide, nitrogen and oxygen in Example 1(a) and Comparative Example 1(b) is given.
[0024] Figure 7 The graphs show the selectivity of nitrous oxide / carbon dioxide for Example 1(a) and Comparative Example 1(b), and the selectivity of nitrous oxide / nitrogen and nitrous oxide / oxygen for Example 1.
[0025] Figure 8 For the open Bi in Example 1 3+ The DFT calculations were performed on the site, where (ad) represents nitrous oxide, carbon dioxide, nitrogen, and oxygen in that order.
[0026] Figure 9 The dynamic penetration curves obtained in Example 1 are shown, where (ac) are N2O / CO2, V / V=50:50, N2O / N2, V / V=50:50, and N2 / N2O / O2 / CO2, V / V=60:30:5:5.
[0027] Figure 10 The graph shows the results of five N2O and CO2 adsorption cycle tests performed for Application Example 1. Detailed Implementation
[0028] Example 1
[0029] Bismuth nitrate pentahydrate (0.31 mmol) and trimesic acid (5.35 mmol) were dissolved in a methanol solution (60 mL). The mixture was then transferred to a 100 mL polytetrafluoroethylene (PTFE) reactor and reacted in an oven at 140 °C for 48 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed three times with fresh methanol and dried in air. The resulting crystalline powder was activated under vacuum at 150 °C for 12 h to obtain the activated adsorbent.
[0030] Example 2
[0031] Bismuth nitrate pentahydrate (0.31 mmol) and trimesic acid (4.65 mmol) were dissolved in a methanol solution (60 mL). The mixture was then transferred to a 100 mL polytetrafluoroethylene (PTFE) reactor and placed in an oven at 160 °C for 24 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed three times with fresh methanol and dried in air. The resulting crystalline powder was activated under vacuum at 100 °C for 12 h to obtain the activated adsorbent.
[0032] Example 3
[0033] Bismuth nitrate pentahydrate (0.31 mmol) and trimesic acid (6.2 mmol) were dissolved in a methanol solution (60 mL). The mixture was then transferred to a 100 mL polytetrafluoroethylene (PTFE) reactor and placed in an oven at 120 °C for 72 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed three times with fresh methanol and dried in air. The resulting crystalline powder was activated under vacuum at 200 °C for 12 h to obtain the activated adsorbent.
[0034] Examples 1-3 all yielded Bi9(C9H3O6)9(H2O)9 materials, but Example 1 achieved efficient utilization and conversion of ligands under relatively mild reaction conditions, and the target product had the highest crystallinity and yield, providing the most reliable and reproducible material basis for subsequent adsorption performance studies.
[0035] Comparative Example 1 Preparation method: Bismuth nitrate pentahydrate (0.94 mmol) and trimesic acid (4.60 mmol) were dissolved in 10 mL and 15 mL of N,N-dimethylformamide (DMF) solution, respectively. The mixtures were sonicated at room temperature for 10 min until dissolved. The metal salt solution was then added to the trimesic acid solution. The mixture was then transferred to a 100 mL polytetrafluoroethylene reactor and reacted in a 140 °C oven for 72 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed three times with fresh methanol and dried in air. The resulting crystalline powder was vacuum activated at 150 °C for 12 h to obtain the activated adsorbent.
[0036] The molecular formula of the material obtained in Comparative Example 1 is C 18 Bi 1.50 O 12 It does not have open metal sites.
[0037] Schematic diagrams of the materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown in the figure, Bi in the material 3+ It is a Bi-O nine-coordinate system, where eight O atoms come from the carboxyl groups of the ligands, and one O atom comes from a water molecule. High-temperature activation can remove the water molecule, exposing an empty coordination site; the Bi in the material of Comparative Example 1... 3+ There are two coordination modes: one is Bi-O nine-coordinate and the other is Bi-O ten-coordinate, where the O in both modes comes from the carboxyl group of the ligand.
[0038] Figure 2 X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Example 1. Figure 2 It can be seen that the powder X-ray diffraction pattern of the sample in Example 1 is highly consistent with the simulation pattern, proving that the synthesized sample has high purity. Furthermore, it can be seen that the characteristic peaks of the material prepared in Comparative Example 1 do not match those of the material in Example 1, proving that the two materials were prepared at different temperatures.
[0039] Figure 3 TGA images of the materials prepared in Example 1 and Comparative Example 1. (From...) Figure 3 It is known that the metal-organic framework material exhibits good thermal stability up to 400°C.
[0040] Figure 4 The figures show the N2 adsorption-desorption isotherms and pore size distribution of the materials prepared in Example 1 and Comparative Example 1 at 77 K. As can be seen from the figures, the metal-organic framework material is a microporous material with pore sizes concentrated at 0.80 nm. The pore size of the comparative example material is concentrated at 0.69 nm.
[0041] Figure 5The adsorption isotherms for nitrous oxide, carbon dioxide, nitrogen, and oxygen at 298 K are shown for the materials prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the metal-organic framework material exhibits the following adsorption order: nitrous oxide > carbon dioxide > oxygen > nitrogen, demonstrating that the material preferentially adsorbs nitrous oxide.
[0042] Figure 6 The figure shows the heat of adsorption of nitrous oxide, carbon dioxide, nitrogen, and oxygen for the materials prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the heat of adsorption of nitrous oxide for the material prepared in Example 1 is higher than that for carbon dioxide, indicating that Bi... 3+ The presence of nitrous oxide enhances the interaction force of the material.
[0043] Figure 7 The graphs show the selectivity of the materials prepared in Example 1 and Comparative Example 1 for nitrous oxide / carbon dioxide, and the selectivity of the material prepared in Example 1 for nitrous oxide / nitrogen and nitrous oxide / oxygen. As can be seen from the graphs, the material prepared in Example 1 achieved a nitrous oxide / nitrogen selectivity of 1.4 at 298 K and 1 bar, which is higher than the 1.1 of the material prepared in Comparative Example 1, demonstrating the open Bi content in the structure. 3+ The site has a stronger interaction with N2O.
[0044] Figure 8 For the open Bi in Example 1 3+ DFT calculations were performed at the site. As shown in the figure, compared to other competing gases, the open Bi in Example 1... 3+ The shorter interaction distance between the site and N2O results in a more favorable binding energy, indicating that the open Bi... 3+ There is a stronger interaction between the site and N2O.
[0045] Figure 9 The dynamic breakthrough curves (N2O / CO2, V / V=50:50, N2O / N2, V / V=50:50, N2 / N2O / O2 / CO2, V / V=60:30:5:5) obtained using the material from Example 1 as an adsorbent are shown in the figure. As can be seen from the figure, in the two-component breakthrough test, carbon dioxide exits before nitrous oxide, and nitrogen exits before nitrous oxide, maintaining performance at different flow rates. In the four-component breakthrough test, nitrous oxide exits last, demonstrating that the material still exhibits good and stable N2O capture performance even in the presence of multiple competing gases.
[0046] Figure 10 Five N2O and CO2 adsorption cycles were performed on Example 1. As shown in the figure, the gas adsorption amount remained stable throughout the five cycles, confirming that the material exhibits excellent cycle stability.
Claims
1. A type of open-Bi 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The molecular formula of the metal-organic framework material is Bi9(C9H3O6)9(H2O)9. The metal-organic framework material is generated by a solvothermal reaction using bismuth nitrate pentahydrate as the metal source, trimesic acid as the organic ligand, and methanol as the solvent. When separating gases, the material needs to be activated at high temperature before use.
2. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: In the structure of the metal-organic framework material, Bi 3+ It is a Bi-O nine-coordinate system, where eight O atoms come from the carboxyl group of the ligand, and the remaining O atom comes from a water molecule. High-temperature activation can remove the water molecule, exposing an empty Bi atom. 3+ Site.
3. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The preparation method of the metal-organic framework material includes the following steps: dissolving bismuth nitrate pentahydrate and trimesic acid in methanol, then transferring the mixture to a polytetrafluoroethylene reactor, placing it in an oven for reaction, obtaining a white powder by filtration, washing it three times with methanol, drying it in air, and then activating the crystal in a dynamic vacuum for 12 hours to remove the solvent in the crystal channels, thereby obtaining an activated sample.
4. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The molar ratio of bismuth nitrate pentahydrate to trimesic acid is 1:15~20.
5. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The reaction temperature is 120-160℃, and the reaction time is 24-72 hours.
6. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The activation temperature is 100-200℃.
7. The open Bi as described in claim 1 3+ The application of metal-organic framework materials at specific sites in N2O separation is characterized by: The metal-organic framework material can be desorbed and regenerated after adsorbing gas, and can be recycled.