Nitro-modified metal organic framework material as well as preparation and application thereof

Abstract

The invention relates to the technical field of metal organic framework materials, in particular to a nitro-modified metal organic framework material and preparation and application thereof.The nitro-modified metal organic framework material is prepared by the steps that zinc nitrate hexahydrate, 3-amino-1, 2, 4-triazole and 5-nitro-1, 3-phthalic acid are dissolved in a solvent, then the mixture is transferred into a reaction kettle, a heating reaction is conducted, white powder is obtained through filtering, and the nitro-modified metal organic framework material is obtained; and washing, exchanging overnight by using methanol for Soxhlet extraction, activating the crystal in dynamic vacuum under a heating condition, and removing the solvent in crystal pore channels to obtain the activated nitro-modified metal organic framework material. The method provided by the invention is expected to replace the existing methane enrichment mode with high energy consumption, is a promising low-concentration methane purification adsorbent, and has great application potential in industrial application of adsorption separation of low-concentration coal bed gas. The compound provides a proper pore diameter and pore channel chemical environment for CH4 molecular adsorption, and provides a new idea for separation of CH4 / N2.

Description

Technical Field

[0001] This invention relates to the field of organometallic framework materials technology, and in particular to a nitro-modified organometallic framework material, its preparation and application. Background Technology

[0002] Methane (CH4) is the main component of natural gas, a clean energy source with high calorific value, and is widely used. Driven by the increasing pursuit of clean energy, coalbed methane now accounts for as much as 23.5% of primary energy consumption. China possesses abundant coalbed methane reserves, which, as a typical unconventional natural gas, serve as an important supplement to natural gas.

[0003] However, due to air dilution, large quantities of coalbed methane have very low methane concentrations (typically <30%), and its main component is nitrogen (N2). This low-concentration coalbed methane (methane content <30%) cannot be used as fuel and is usually released into the atmosphere, having a significant impact on the greenhouse effect.

[0004] Therefore, enriching methane and separating nitrogen from low-concentration coalbed methane offers significant economic and environmental benefits. Currently, the mature separation process for CH4 purification is cryogenic distillation, which consumes a relatively high amount of energy. Adsorption separation based on physical adsorbents, due to its lower energy consumption, has become an effective alternative to cryogenic distillation. However, because CH4 and N2 have very similar physicochemical properties, achieving efficient separation between them remains a formidable challenge. Summary of the Invention

[0005] In order to enrich methane from a methane / nitrogen mixture using adsorption separation, this invention provides a nitro-modified metal-organic framework material, its preparation, and its application.

[0006] This invention is achieved through the following technical solution: Firstly, a nitro-modified metal-organic framework material with the chemical formula C 12 H9N9O6Zn2 belongs to space group I4. The lengths of the crystal axes a, b, and c in the unit cell parameters are 13.1316(8) Å, 13.1316(8) Å, and 25.865(3) Å, respectively. The axial angles α, β, and γ are 90°, 90°, and 90°, respectively. The unit cell volume is 4460.1(7) Å. 3 .

[0007] Secondly, a method for preparing a nitro-modified metal-organic framework material includes the following steps: Zinc nitrate hexahydrate, 3-amino-1,2,4-triazole, and 5-nitro-1,3-phthalic acid were dissolved in a solvent, and then the mixture was transferred to a reaction vessel and heated to react. A white powder was obtained by filtration, washed, and then subjected to Soxhlet extraction with methanol exchange overnight. The crystals were activated in a dynamic vacuum under heating conditions to remove the solvent from the crystal channels, thus obtaining the activated nitro-modified metal-organic framework material.

[0008] As a further improvement to the preparation method of the present invention, the molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:0.5~1.5:0.5~1.5.

[0009] As a further improvement to the preparation method of the present invention, the molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:1:1.

[0010] As a further improvement to the preparation method of the present invention, the solvent is a mixed solvent of DMF and water, wherein the volume ratio of DMF to water in the mixed solvent is 0.8~1.2:1.

[0011] As a further improvement to the preparation method of this invention, the heating reaction temperature of the reactor is 130-170℃.

[0012] As a further improvement to the preparation method of the present invention, the heating temperature of the activated crystal in the dynamic vacuum is 100-140 ℃.

[0013] As a further improvement to the preparation method of the present invention, the heating temperature of the activated crystal in the dynamic vacuum is 120 °C.

[0014] Thirdly, the present invention provides an application of nitro-modified metal-organic framework materials as adsorbents in the selective separation of CH4 / N2.

[0015] Fourthly, this invention provides a method for preparing nitro-modified metal-organic framework materials, and the application of the prepared nitro-modified metal-organic framework materials as adsorbents in the selective separation of CH4 / N2.

[0016] The nitro-modified metal-organic framework materials, their preparation, and their applications provided by this invention have the following advantages compared to existing technologies: This invention introduces a nitro (-NO2) functional group onto a ligand and utilizes this compound to enrich methane from a methane / nitrogen mixture, effectively improving the selectivity of CH4 / N2 and achieving highly efficient separation of CH4 / N2. This invention holds promise as a replacement for current energy-intensive methane enrichment methods and represents a promising low-concentration methane purification adsorbent with significant application potential in the industrial adsorption and separation of low-concentration coalbed methane. This compound provides a suitable pore size and pore chemistry environment for CH4 molecule adsorption, offering a novel approach to CH4 / N2 separation. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the compound's structure.

[0020] Figure 2 The X-ray diffraction patterns are shown for Examples 1, 2, 3, and the comparative sample. The samples synthesized in Examples 1, 2, and 3 are named compound, compound-2, and compound-3, respectively. Figure 2 It can be seen that the powder X-ray diffraction pattern of the compound synthesized in Example 1 is highly consistent with the simulation pattern, and the peak intensity is the highest, proving that the synthesized sample has high purity when the reaction time is 48 h.

[0021] Figure 3 The TGA diagrams for Example 1 and the control sample are provided by [the relevant authority / organization]. Figure 3 It can be seen that the compound exhibits good thermal stability up to 200 °C.

[0022] Figure 4 The figures show the CO2 desorption isotherm and pore size distribution of Example 1 and the control sample at 196 K. As can be seen from the figures, both the compound and the control sample are microporous materials. The pore size of the control sample is concentrated at 5.10 Å, while that of the compound is concentrated at 4.35 Å, showing a significant reduction.

[0023] Figure 5 The adsorption isotherms of methane and nitrogen at 298 K for Example 1 and the control sample are shown below. Figure 5 It can be seen that the compound exhibits a higher adsorption capacity for methane than for nitrogen, proving that the material preferentially adsorbs methane.

[0024] Figure 6 The adsorption heat of methane and nitrogen in Example 1 and the comparative sample is given by... Figure 6 It can be seen that the methane adsorption heat of the compound in Example 1 is higher than that of the control sample, indicating that the introduction of the functional group -NO2 enhances the attraction to methane.

[0025] Figure 7 This is a selectivity chart for methane / nitrogen for Example 1 and the control sample. (Source: [Insert chart here]) Figure 7 It can be seen that the compound of Example 1 achieved a selectivity of 10.91 at 298 K and 1 bar, which is higher than the 5.23 of the control sample, demonstrating that the introduction of the functional group -NO2 resulted in better selectivity for methane / nitrogen.

[0026] Figure 8 Example 1 compares the CH4 / N2 selectivity of some typical MOFs at 298 K and 1 bar, and its selectivity exceeds that of most current materials.

[0027] Figure 9 The dynamic penetration curve (CH4 / N2, V / V=50:50) obtained in Example 1 is shown. Figure 9 It can be seen that nitrogen gas exits before methane gas and can maintain its performance within 4 cycles, which proves that it has a good and stable methane-nitrogen separation effect. Detailed Implementation

[0028] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0030] This invention provides a specific embodiment of a method for preparing nitro-modified metal-organic framework materials, comprising the following steps: Zinc nitrate hexahydrate, 3-amino-1,2,4-triazole, and 5-nitro-1,3-phthalic acid were dissolved in a solvent, and then the mixture was transferred to a reaction vessel and heated to react. A white powder was obtained by filtration, washed, and then subjected to Soxhlet extraction with methanol exchange overnight. The crystals were activated in a dynamic vacuum under heating conditions to remove the solvent from the crystal channels, thus obtaining the activated nitro-modified metal-organic framework material.

[0031] In one example provided by the present invention, the molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:0.5~1.5:0.5~1.5.

[0032] In another example provided by the present invention, the molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:1:1.

[0033] In one example provided by the present invention, the solvent is a mixture of DMF and water, wherein the volume ratio of DMF to water in the mixture is 0.8 to 1.2:1, and preferably, the volume ratio of DMF to water in the mixture is 1:1.

[0034] In another example provided by the present invention, the heating reaction temperature of the reactor is 130-170 °C. Preferably, the heating reaction temperature is 150 °C. The heating reaction time is 36-60 h, preferably 48 h.

[0035] In one example provided by the present invention, the heating temperature of the activated crystal in the dynamic vacuum is 100-140°C.

[0036] In another example provided by the present invention, the heating temperature of the activated crystal in the dynamic vacuum is 120°C.

[0037] This invention also provides the application of nitro-modified metal-organic framework materials as adsorbents in the selective separation of CH4 / N2.

[0038] The present invention further provides a method for preparing nitro-modified metal-organic framework materials and the application of the prepared nitro-modified metal-organic framework materials as adsorbents in the selective separation of CH4 / N2.

[0039] The specific embodiments of the present invention will be described in detail below. Example 1

[0040] Zn(NO3)3·6H2O (0.5 mmol), 3-amino-1,2,4-triazole (0.5 mmol), and 5-nitro-1,3-phthalic acid (0.5 mmol) were dissolved in a 1 / 1, 6 mL mixture of DMF and water. The mixture was then transferred to a Teflon-lined stainless steel reactor and placed in an oven at 150 °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 five times each with fresh DMF and water, followed by Soxhlet extraction with methanol exchange overnight. The resulting crystalline powder was then activated under vacuum at 120 °C for 12 h to obtain the activated adsorbent.

[0041] Table 1 Crystal Data Example 2

[0042] Zn(NO3)3·6H2O (0.5 mmol), 3-amino-1,2,4-triazole (0.5 mmol), and 5-nitro-1,3-phthalic acid (0.5 mmol) were dissolved in a 1 / 1, 6 mL mixture of DMF and water. The mixture was then transferred to a Teflon-lined stainless steel reactor and placed in an oven at 150 °C for 36 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed five times each with fresh DMF and water, followed by Soxhlet extraction with methanol exchange overnight. The resulting crystalline powder was then activated under vacuum at 120 °C for 12 h to obtain the activated adsorbent. Example 3

[0043] Zn(NO3)3·6H2O (0.5 mmol), 3-amino-1,2,4-triazole (0.5 mmol), and 5-nitro-1,3-phthalic acid (0.5 mmol) were dissolved in a 1 / 1, 6 mL mixture of DMF and water. The mixture was then transferred to a Teflon-lined stainless steel reactor and reacted in a 150 °C oven for 60 h. After the reaction was complete, the mixture was cooled to room temperature and filtered to obtain the compound. The compound was then washed five times each with fresh DMF and water, followed by Soxhlet extraction with methanol exchange overnight. The resulting crystalline powder was then activated under vacuum at 120 °C for 12 h to obtain the activated adsorbent.

[0044] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A nitro-modified metal-organic framework material, characterized in that, Its chemical formula is C 12 H9N9O6Zn2 belongs to space group I4. The lengths of the crystal axes a, b, and c in the unit cell parameters are 13.1316(8) Å, 13.1316(8) Å, and 25.865(3) Å, respectively. The axial angles α, β, and γ are 90°, 90°, and 90°, respectively. The unit cell volume is 4460.1(7) Å. 3 .

2. A method for preparing a nitro-modified metal-organic framework material, characterized in that, Includes the following steps: Zinc nitrate hexahydrate, 3-amino-1,2,4-triazole, and 5-nitro-1,3-phthalic acid were dissolved in a solvent, and then the mixture was transferred to a reaction vessel and heated to react. A white powder was obtained by filtration, washed, and then subjected to Soxhlet extraction with methanol exchange overnight. The crystals were activated in a dynamic vacuum under heating conditions to remove the solvent from the crystal channels, thus obtaining the activated nitro-modified metal-organic framework material.

3. The method for preparing a nitro-modified metal-organic framework material according to claim 2, characterized in that, The molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:0.5~1.5:0.5~1.

5.

4. The method for preparing a nitro-modified metal-organic framework material according to claim 3, characterized in that, The molar ratio of zinc nitrate hexahydrate, 3-amino-1,2,4-triazole and 5-nitro-1,3-phthalic acid is 1:1:

1.

5. The method for preparing a nitro-modified metal-organic framework material according to claim 2, characterized in that, The solvent is a mixture of DMF and water, with a volume ratio of DMF to water of 0.8 to 1.2:

1.

6. The method for preparing a nitro-modified metal-organic framework material according to claim 5, characterized in that, The heating reaction temperature of the reactor is 130-170 ℃.

7. The method for preparing a nitro-modified metal-organic framework material according to claim 2, characterized in that, The heating temperature for activating the crystal in the dynamic vacuum is 100-140 ℃.

8. The method for preparing a nitro-modified metal-organic framework material according to claim 7, characterized in that, The heating temperature for activating the crystal in the dynamic vacuum is 120 °C.

9. The application of the nitro-modified metal-organic framework material as described in claim 1 as an adsorbent in the selective separation of CH4 / N2.

10. The application of the nitro-modified metal-organic framework material prepared by the method of any one of claims 1 to 8 as an adsorbent in the selective separation of CH4 / N2.

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