Metal organic framework material, preparation method and application thereof

Abstract

This invention discloses a metal-organic framework material, its preparation method, and its applications, relating to the technical field of metal-organic framework materials. The metal-organic framework material prepared by this invention using specific metal nitrates, organic ligands, and solvents, combined with a solvothermal method, possesses a rigid three-dimensional framework structure and a hierarchical pore structure with periodically alternating narrow windows and larger pores. When used for the separation of C3F6 and C3F8, it exhibits advantages such as high selectivity, excellent low-pressure adsorption performance, good structural stability, low energy consumption, and the ability to be carried out under ambient temperature and pressure conditions. Furthermore, the separation of C3F6 and C3F8 can be achieved simply by passing a mixed gas containing C3F6 and C3F8 through a permeation column packed with the metal-organic framework material. The process is simple and has promising application prospects.

Description

Technical Field

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

[0002] Fluorine-containing specialty gases play a crucial role in semiconductor manufacturing processes, particularly in plasma etching, reaction chamber cleaning, and surface treatment. Perfluoropropane (C3F8) is widely used as an etching and cleaning gas due to its excellent chemical stability and controllable reaction characteristics. In industrial production, C3F8 is typically prepared through the fluorination reaction of hexafluoropropylene (C3F6), inevitably resulting in a small amount of unreacted C3F6 impurities. Since even small amounts of C3F6 can adversely affect etching precision and device performance, deep purification of C3F8 is necessary to meet electronic-grade requirements.

[0003] However, the high similarity between C3F6 and C3F8 in physicochemical properties such as molecular size, polarity, and boiling point makes their separation process quite challenging. Currently, industrial methods typically employ cryogenic distillation to separate them. This method relies on the difference in volatility between the two, but due to the small difference, it often requires operation under low temperature and high pressure conditions, resulting in high energy consumption, significant equipment investment, and a complex process flow. Furthermore, the separation efficiency is low, especially when dealing with low concentrations of C3F6 impurities.

[0004] To reduce energy consumption and simplify separation processes, adsorption separation technology has gradually gained attention. This type of method relies on the selective adsorption capacity of porous materials for different gas molecules to achieve separation. Currently commonly used adsorption materials include activated carbon, molecular sieves, and some porous coordination materials. However, traditional adsorption materials generally suffer from insufficient selectivity or limited adsorption capacity, making it difficult to achieve efficient separation of C3F6 and C3F8.

[0005] In recent years, metal-organic frameworks (MOFs) have been widely used in gas adsorption and separation due to their tunable pore structure and surface chemical environment. Some MOFs have been reported for the separation of fluorine-containing gases, but existing MOFs still have the following shortcomings in separating C3F6 and C3F8: Firstly, due to the small difference in molecular size between the two gases, existing materials struggle to achieve precise size sieving, leading to easy co-adsorption of C3F6 and C3F8 and reduced separation selectivity. Secondly, although some materials can enhance the adsorption of C3F6 through strong interactions, their adsorption capacity remains limited under low partial pressure conditions, failing to meet the practical needs of trace impurity removal. Furthermore, while some porous materials based on flexible frameworks can achieve a certain degree of separation through structural response, their separation performance often depends on external conditions such as temperature and pressure, exhibiting poor stability and controllability, which is detrimental to practical industrial applications.

[0006] In summary, current technologies lack an adsorption material that can simultaneously achieve high adsorption capacity for C3F6 and effective repulsion of C3F8 under mild conditions, while also possessing good structural stability. Therefore, it is necessary to develop a novel porous material that can achieve efficient separation of C3F6 and C3F8 through precise control of pore size structure and pore environment.

[0007] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0008] Based on the shortcomings of the prior art, the purpose of this invention is to provide a metal-organic framework material, its preparation method and application, aiming to solve the problem of the lack of existing metal-organic framework materials that can effectively separate C3F6 and C3F8 under mild conditions.

[0009] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a metal-organic framework material, comprising the following steps: Metal nitrate, organic ligand, and solvent are mixed to obtain a mixture; The metal-organic framework material is obtained by subjecting the mixture to a solvothermal reaction. The metal nitrate includes at least one of aluminum nitrate, iron nitrate, cobalt nitrate, and gallium nitrate; The solvent includes N,N-dimethylformamide, formic acid, and water; The organic ligand is 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylic acid.

[0010] Optionally, the volume ratio of N,N-dimethylformamide, formic acid and water is (2~6):(2~6):(2~6).

[0011] Optionally, the mass ratio of the metal nitrate to the organic ligand is (2~6):(1~4).

[0012] Optionally, the mass ratio of the metal nitrate to the organic ligand is (1.5~3.0):1.

[0013] Optionally, the ratio of the metal nitrate to the solvent is (20~60) mg: (6~36) mL.

[0014] Optionally, the temperature of the solvothermal reaction is 180~200 ℃, and the time of the solvothermal reaction is 3~5 days.

[0015] In a second aspect, the present invention provides a metal-organic framework material, wherein it is prepared by the preparation method of the present invention as described above.

[0016] Optionally, the molecular formula of the metal-organic framework material is [M3( μ 3-O)(H2O)3(L)]NO3, M represents Al, Fe, Cr or Ga, L represents 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylate ion; The pore window size of the metal-organic framework is 4.5~5.5 Å, and the cavity size of the metal-organic framework is 8.0~11.0 Å.

[0017] A third aspect of the present invention provides the application of the metal-organic framework material of the present invention as described above in the separation of binary mixtures of C3F6 and C3F8.

[0018] Optionally, the method of application is as follows: passing a binary mixture of C3F6 and C3F8 through a penetrating column containing the metal-organic framework material to obtain C3F8.

[0019] Beneficial effects: The metal-organic framework material prepared by this invention using specific metal nitrates, organic ligands, and solvents, combined with a solvothermal method, possesses a rigid three-dimensional framework structure constructed from trinuclear metal (aluminum, iron, or gallium) clusters, wherein the metal center is... μ 3-O bridging forms stable, unstructured building blocks, which in turn form multi-linked coordination structures with organic ligands (i.e., hexacarboxylic acid ligands), thereby constructing a stable three-dimensional PCU topological framework. This material exhibits excellent thermal and chemical stability, which helps it maintain structural integrity under complex operating conditions.

[0020] On the one hand, the prepared metal-organic framework material has a hierarchical pore structure with a periodic alternation of narrow pore windows and larger pore cavities. The size of the narrow pore windows is approximately 4.5–5.5 Å, and the size of the pore cavities is approximately 8.0–11.0 Å. A suitable narrow pore window can effectively achieve the sieving of a mixture of C3F6 and C3F8 under mild conditions (room temperature and pressure). Specifically, C3F6 preferentially enters the pores of the material and is adsorbed, while C3F8, due to its larger molecular size, cannot enter the pores and is selectively excluded by the material. Therefore, the metal-organic framework material provided by this invention can achieve effective separation of C3F6 and C3F8. Simultaneously, the larger pores in the structure can provide more adsorption space, thereby achieving a higher C3F6 adsorption capacity.

[0021] On the other hand, the inner walls of the pores in the metal-organic framework material prepared by this invention are provided with hydrogen-rich surfaces by organic ligands, thereby forming a locally positively charged environment. This environment can generate favorable weak interactions with fluorine-containing gas molecules, which helps to improve the material's adsorption capacity for C3F6 under low partial pressure conditions. Therefore, this material not only has a high adsorption capacity at atmospheric pressure, but also exhibits excellent C3F6 adsorption performance under low pressure conditions, making it suitable for the removal of trace impurities such as C3F6.

[0022] In summary, this invention, through synergistic regulation of pore structure, pore environment, and framework stability, enables the metal-organic framework material prepared by this invention to exhibit advantages such as high selectivity, excellent low-pressure adsorption performance, good structural stability, low energy consumption, and the ability to be processed under ambient temperature and pressure conditions when used for the separation of C3F6 and C3F8. Furthermore, the separation of C3F6 and C3F8 can be achieved simply by passing a mixed gas of C3F6 and C3F8 through a permeation column containing the metal-organic framework material, resulting in a simple process with promising application prospects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the preparation process of the metal-organic framework material in an embodiment of the present invention.

[0024] Figure 2 The diagram shows the crystal structure and pore structure of HIAM-344 in Example 1, where a is a diagram of the building blocks of HIAM-344; b is a diagram of the three-dimensional framework structure of HIAM-344; and c is a diagram of NO3. - Location diagram in the HIAM-344 framework (Connolly surface calculated using Materials Studio, probe radius 1.3 Å); d is a magnified view of the pore structure (where A represents the narrow pore window and B represents the pore cavity); e is a schematic diagram of the shape matching between the C3F6 molecule and the HIAM-344 pores.

[0025] Figure 3The images show the simulated PXRD pattern of HIAM-344 in Example 1 and its measured PXRD patterns before and after adsorption.

[0026] Figure 4 The images show isotherms of HIAM-344 adsorbing C3F6 and C3F8 at 273 K and 298 K in Example 1. In the images, a is an isotherm with the horizontal axis on a normal coordinate system and b is an isotherm with the horizontal axis on an exponential coordinate system.

[0027] Figure 5 The diagram shows the penetration curves of a C3F6 and C3F8 (1:99, v:v) mixture at a flow rate of 5.0 mL / min through HIAM-344 in Example 1 at 298 K and 1 bar. In the diagram, a is the single penetration curve and b is the five-pass penetration curve. Detailed Implementation

[0028] This invention provides a metal-organic framework material, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0030] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0031] This invention provides a method for preparing a metal-organic framework material, wherein, as shown in the embodiments of the present invention... Figure 1 As shown, it includes the following steps: S1. A metal nitrate, an organic ligand, and a solvent are mixed to obtain a mixture; the metal nitrate includes at least one of aluminum nitrate, iron nitrate, chromium nitrate, and gallium nitrate; the solvent includes N,N-dimethylformamide, formic acid, and water; the organic ligand is 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylic acid; S2. After subjecting the mixture to a solvothermal reaction, the metal-organic framework material is obtained.

[0032] This invention utilizes specific metal nitrates, organic ligands, and solvents, combined with a solvothermal method, to prepare metal-organic framework materials with a rigid three-dimensional framework structure composed of trinuclear metal (aluminum, iron, chromium, or gallium) clusters. This ensures stable pore size during use, preventing significant structural deformation with temperature or pressure changes. Compared to some flexible metal-organic framework materials that rely on a "breathing effect" for separation, the rigid structure of this invention's metal-organic framework material offers better stability and controllability, guaranteeing consistent separation performance under different operating conditions, making it more suitable for practical industrial applications. The metal centers are... μ 3-O bridging forms stable, unstructured building blocks, which in turn form multi-linked coordination structures with organic ligands (i.e., hexacarboxylic acid ligands), thereby constructing a stable three-dimensional PCU topological framework. This material exhibits excellent thermal and chemical stability, which helps it maintain structural integrity under complex operating conditions.

[0033] On the one hand, the prepared metal-organic framework material has a hierarchical pore structure with a periodic alternation of narrow pore windows and larger pore cavities (i.e., a multi-level pore structure that combines precise size sieving ability with high adsorption capacity). The size of the narrow pore windows is approximately 4.5–5.5 Å, and the size of the pore cavities is approximately 8.0–11.0 Å. A suitable narrow pore window can effectively sieve the mixture of C3F6 and C3F8 under mild conditions (room temperature and pressure). Specifically, C3F6 preferentially enters the pores of the material and is adsorbed, while C3F8, due to its larger molecular size, cannot enter the pores and is selectively excluded by the material. Therefore, the metal-organic framework material provided by this invention can effectively separate C3F6 and C3F8. Simultaneously, the larger pores in the structure can provide more adsorption and storage space, thereby achieving a higher C3F6 adsorption capacity.

[0034] On the other hand, regarding the pore environment, the inner walls of the metal-organic framework material prepared in this invention are provided with hydrogen-rich surfaces by organic ligands, thereby forming a locally positively charged environment. This environment can generate favorable weak interactions with fluorine-containing gas molecules, which helps to improve the material's adsorption capacity for C3F6 under low partial pressure conditions. Therefore, this material not only has a high adsorption capacity at ambient pressure, but also exhibits excellent C3F6 adsorption performance under low pressure conditions, making it suitable for the removal of trace impurities such as C3F6.

[0035] In summary, this invention, through synergistic regulation of pore structure, pore environment, and framework stability, enables the metal-organic framework material prepared by this invention to exhibit advantages such as high selectivity, excellent low-pressure adsorption performance, good structural stability, low energy consumption, and the ability to be processed under ambient temperature and pressure conditions (i.e., mild conditions) when used for the separation of C3F6 and C3F8. Furthermore, the separation of C3F6 and C3F8 can be achieved simply by passing a mixed gas of C3F6 and C3F8 through a permeation column containing the metal-organic framework material, resulting in a simple process with promising application prospects.

[0036] In this invention, the formation of the hierarchical pore structure of narrow-window-large-cavity is jointly determined by the metal cluster configuration, ligand geometry, and the synergistic regulation of anions within the pore channels. Specifically, at the level of raw materials and structural building units, the trinuclear metal cluster, acting as a six-connected inorganic node, forms a six-connected rigid framework with the hexacarboxylic acid ligand, thereby constructing a three-dimensional pore structure with regular periodicity in its topology. The matching of these highly connected nodes with the rigid hexacarboxylic acid ligand makes the framework tend to generate a pore structure with spatially separated characteristics during its formation process. Furthermore, in terms of fine-tuning the pore size, anions within the pore channels play a crucial role, with NO3-... - During crystal growth, the molecules are embedded and stably occupy specific positions within the pores. Their spatial occupancy effect causes the originally large pore opening to shrink, forming an effective narrow pore window with a size of approximately 4.5–5.5 Å. This narrow pore window acts as a confinement unit for molecules entering the pores, and its size is close to the kinetic diameter of C3F6 and C3F8. Smaller C3F6 molecules can enter the pores through the pore window, while larger C3F8 molecules are excluded. This narrow pore window structure directly endows the material with a significant molecular sieving effect, which is key to achieving highly selective separation. Simultaneously, the larger pore size provides ample adsorption space for gas molecules (C3F6) entering the pores, allowing C3F6 to effectively accumulate within the pores, thus significantly increasing the material's adsorption capacity for C3F6. This synergistic "narrow pore window-large pore size" structure overcomes the problem of balancing selectivity and capacity in traditional single-pore size materials.

[0037] In step S1, in some embodiments, the solvent is composed of N,N-dimethylformamide, formic acid, and water.

[0038] In some embodiments, the volume ratio of N,N-dimethylformamide, formic acid and water is (2~6):(2~6):(2~6), for example, it can be 1:1:1, 2:2:3, 1:1:2, 1:1:3, 1:2:1, 1:3:1, 3:2:2, 2:1:1, 3:1:1, 3:2:3, 1:1:2 or 3:1:3, etc.

[0039] In some embodiments, the mass ratio of the metal nitrate to the organic ligand is (2~6):(1~4), for example, it can be 2:1, 1:1, 2:3, 1:2, 3:1, 3:2, 3:4, 4:1, 4:3, 5:1, 5:2, 5:3, 5:4 or 6:1, etc.

[0040] In some embodiments, the mass ratio of the metal nitrate to the organic ligand is (1.5~3.0):1, for example, it can be 1.5:1, 2:1, 2.5:1 or 3:1, etc.

[0041] In some embodiments, the ratio of the metal nitrate to the solvent is (20~60) mg:(6~36) mL, for example, 20 mg:6 mL, 30 mg:6 mL, 40 mg:6 mL, 50 mg:6 mL, 60 mg:6 mL, 20 mg:10 mL, 30 mg:10 mL, 40 mg:10 mL, 50 mg:10 mL, 60 mg:10 mL, etc. 20 mg:12 mL, 30 mg:12 mL, 40 mg:12 mL, 50 mg:12 mL, 60 mg:12 mL, 20 mg:20mL, 30 mg:20 mL, 40 mg:20 mL, 50 mg:20 mL, 60 mg:20 mL, 20 mg:36 mL, 30 mg:36 mL, 40mg:36 mL, 50 mg:36 mL or 60 mg:36 mL, etc.

[0042] In some embodiments, the temperature of the solvothermal reaction is 180~200℃ (e.g., 180℃, 185℃, 190℃, 195℃ or 200℃, etc.), and the time of the solvothermal reaction is 3~5 days (e.g., 3 days, 4 days or 5 days, etc.).

[0043] This invention also provides a metal-organic framework material, which is prepared using the preparation method described above.

[0044] The molecular formula of the metal-organic framework material is [M3( μ 3-O)(H2O)3(L)]NO3, M represents Al, Fe, Cr or Ga, L represents 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylate ion; The pore window size of the metal-organic framework is 4.5~5.5 Å, and the cavity size of the metal-organic framework is 8.0~11.0 Å.

[0045] In this embodiment, the metal-organic framework material has a rigid three-dimensional framework structure constructed from a trinuclear metal (aluminum, iron, chromium, or gallium) cluster, wherein the metal center is located through... μ 3-O bridging forms stable, unstructured building blocks, which in turn form multi-linked coordination structures with organic ligands (i.e., hexacarboxylic acid ligands), thereby constructing a stable three-dimensional PCU topological framework. This material exhibits excellent thermal and chemical stability, which helps it maintain structural integrity under complex operating conditions.

[0046] On the one hand, metal-organic framework materials possess a hierarchical pore structure with a periodic alternation of narrow pore windows and larger pore cavities. The size of the narrow pore windows is approximately 4.5–5.5 Å, and the size of the pore cavities is approximately 8.0–11.0 Å. Suitable narrow pore windows can effectively achieve the sieving of C3F6 and C3F8 mixtures under mild conditions (room temperature and pressure). Specifically, C3F6 preferentially enters the material's pores and is adsorbed, while C3F8, due to its larger molecular size, cannot enter the pores and is selectively excluded by the material. Therefore, the metal-organic framework material provided by this invention can achieve effective separation of C3F6 and C3F8. Simultaneously, the larger pores in the structure provide more adsorption space, thereby achieving a higher C3F6 adsorption capacity.

[0047] On the other hand, regarding the pore environment, the inner walls of the metal-organic framework material provided by this invention have a hydrogen-rich surface provided by organic ligands, thereby forming a locally positively charged environment. This environment can generate favorable weak interactions with fluorine-containing gas molecules, which helps to improve the material's adsorption capacity for C3F6 under low partial pressure conditions. Therefore, this material not only has a high adsorption capacity at ambient pressure, but also exhibits excellent C3F6 adsorption performance under low pressure conditions, making it suitable for the removal of trace impurities such as C3F6.

[0048] In summary, the metal-organic framework material provided by this invention has advantages such as high selectivity, excellent low-pressure adsorption performance, good structural stability, low energy consumption, and can be used for the separation of C3F6 and C3F8. Furthermore, the separation of C3F6 and C3F8 can be achieved simply by passing a mixed gas containing C3F6 and C3F8 through a permeation column packed with the metal-organic framework material. The process is simple and has good application prospects.

[0049] This invention also provides an application of the metal-organic framework material described above in the separation of a binary gas mixture of C3F6 and C3F8. Specifically, the metal-organic framework material can selectively separate C3F8 from a binary gas mixture of C3F6 and C3F8 at room temperature.

[0050] The metal-organic framework material provided by this invention does not adsorb C3F8 at all, but exhibits a high adsorption capacity for C3F6, with adsorption capacities of 75.5 cm⁻¹ for C3F6 at 273 K, 0.01 bar, and 1 bar, respectively. 3 g -1 and 89.9 cm 3 g -1 The adsorption capacities for C3F6 at 298 K, 0.01 bar, and 1 bar were 59.2 cm⁻¹, respectively. 3 g -1 and 78.8 cm 3 g -1 Therefore, the metal-organic framework material in this invention can achieve the separation of C3F6 and C3F8 mixed gases.

[0051] In some embodiments, the method of application is as follows: passing a binary mixture of C3F6 and C3F8 through a penetrating column containing the metal-organic framework material to obtain C3F8.

[0052] In this embodiment, when the mixed gas of C3F6 and C3F8 passes through the permeation column, C3F8 permeates rapidly because it cannot be adsorbed by the metal-organic framework material, while C3F6 is effectively adsorbed, thereby achieving efficient separation of the two gases. This separation process can be carried out at room temperature, significantly reducing energy consumption and simplifying the process flow.

[0053] The present invention will be further described below through specific embodiments.

[0054] In the following embodiments, some symbols have the following meanings: DMF: N,N-dimethylformamide.

[0055] Unless otherwise specified, all raw materials used in the following implementations are commercially available products.

[0056] The structural formula of 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylic acid (H6L) is: .

[0057] Example 1 40 mg of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and 20 mg of the hexacarboxylic acid ligand 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylic acid (H6L) were added to 12 mL of a mixed solvent (composed of 4 mL DMF, 4 mL formic acid, and 4 mL H2O). The mixture was stirred at room temperature for 30 minutes, then transferred to a 25 mL polytetrafluoroethylene (PTFE) reactor and reacted in an oven at 180 °C for 3 days. After cooling to room temperature, the solid was collected by filtration, washed three times with DMF, and finally subjected to solvent exchange 10 times in methanol. After vacuum drying at 200 °C for 12 hours, yellow blocky crystals, i.e., MOF material, with the molecular formula [Al3( μ The MOF material is named HIAM-344, which is composed of 3-O)(H2O)3(L)]NO3.

[0058] The crystal structure and pore structure of HIAM-344 are as follows: Figure 2 As shown, HIAM-344 possesses a rigid three-dimensional framework structure constructed from three-core aluminum clusters, with the metal center passing through... μ 3-O bridging forms stable, unstructured building blocks, which then form multi-linked coordination structures with hexacarboxylic acid ligands, thereby constructing a stable three-dimensional PCU topological framework (e.g., Figure 2 As shown in a and b in the figure. Figure 2 In the diagram 'a', the orange-pink sphere represents Al; the red sphere represents O; the gray sphere represents C; and the blue sphere represents N. (For clarity, hydrogen atoms are omitted.) NO3 - During crystal growth, it is embedded and stably occupies a specific position in the channel. Its space-occupying effect causes the originally large aperture to shrink, thus forming an effective narrow aperture window (such as...). Figure 2 As shown in c). HIAM-344 exhibits an alternating pore structure of narrow windows and larger cavities along the pore direction, where the size of the narrow window (A) is approximately 5.0 Å, while the size of the cavity (B) is approximately 9.5 Å (as shown in c). Figure 2 (As shown in d). Furthermore, the C3F6 molecule exhibits good shape matching with the HIAM-344 channels (e.g., ...). Figure 2 (as shown in e).

[0059] The comparison results of the PXRD (powder X-ray diffraction) pattern obtained from the simulation of the HIAM-344 single crystal structure and the measured PXRD pattern of the HIAM-344 prepared above are as follows: Figure 3As shown in the figure, the positions of the diffraction peaks in the measured spectrum (i.e., before adsorption in the corresponding figure) are highly consistent with the simulated spectrum, indicating that the synthesized material is consistent with the single-crystal structure analysis results, proving that HIAM-344 has good crystallinity and phase purity. Furthermore, after methanol solvent exchange and vacuum heating to 200 °C pretreatment, the prepared HIAM-344 was used to adsorb C3F6. The PXRD pattern of HIAM-344 after C3F6 adsorption was also measured. The results showed that the PXRD pattern of HIAM-344 after C3F6 adsorption was basically consistent with the PXRD pattern of freshly synthesized HIAM-344 (i.e., HIAM-344 before adsorption), indicating that HIAM-344 can maintain its structural integrity during vacuum activation and gas adsorption, demonstrating good structural stability.

[0060] Isotherms of HIAM-344 adsorbing C3F6 and C3F8 at 273 K and 298 K are as follows: Figure 4 As shown, HIAM-344 does not adsorb C3F8 at all, but has a very high adsorption capacity for C3F6, adsorbing 75.5 cm⁻¹ C3F6 at 273 K, 0.01 bar, and 1 bar, respectively. 3 g -1 and 89.9 cm 3 g -1 At 298 K, 0.01 bar, and 1 bar, it can adsorb C3F6 at 59.2 cm⁻¹, respectively. 3 g -1 and 78.8 cm 3 g -1 The single-component adsorption isotherm strongly demonstrates that HIAM-344 can achieve the separation of C3F6 and C3F8 mixed gases.

[0061] HIAM-344 was packed into a permeation column, and the permeation curves and five permeation cycles of a C3F6 and C3F8 (C3F6:C3F8=1:99, volume ratio) mixture were tested at 298 K and 1 bar at a flow rate of 5.0 mL / min. The results are as follows. Figure 5As shown in the breakthrough curve, it can be observed that when the gas flow rate of the mixed C3F6 and C3F8 (C3F6:C3F8=1:99, volume ratio) is 5.0 mL / min, and it passes through a breakthrough column packed with HIAM-344, C3F8 preferentially breaks through, while C3F6 breaks through after being retained for about 194 minutes. This further confirms that HIAM-344 has the ability to separate C3F6 and C3F8, thus obtaining C3F8 with electronic-grade purity (>99.999%). The five-cycle breakthrough curve proves that HIAM-344 can still maintain excellent separation ability after five adsorption-desorption cycles, demonstrating that HIAM-344 has good cycle stability.

[0062] In summary, this invention provides a metal-organic framework material, its preparation method, and its applications. The metal-organic framework material prepared by this invention using specific metal nitrates, organic ligands, and solvents, combined with a solvothermal method, possesses a rigid three-dimensional framework structure constructed from trinuclear metal (aluminum, iron, chromium, or gallium) clusters. This ensures stable pore size during use, preventing significant structural deformation with temperature or pressure changes. Compared to some flexible MOF materials that rely on a "breathing effect" for separation, the rigid structure of this invention offers better stability and controllability, guaranteeing consistent separation performance under different operating conditions, making it more suitable for practical industrial applications. The metal centers are located through… μ 3-O bridging forms stable, unstructured building blocks, which in turn form multi-linked coordination structures with organic ligands (i.e., hexacarboxylic acid ligands), thereby constructing a stable three-dimensional PCU topological framework. This material exhibits excellent thermal and chemical stability, which helps it maintain structural integrity under complex operating conditions.

[0063] On the one hand, the prepared metal-organic framework material has a pore structure with a periodic alternation of narrow pore windows and larger pore cavities. The size of the narrow pore windows is approximately 4.5–5.5 Å, and the size of the pore cavities is approximately 8.0–11.0 Å. A suitable narrow pore window can effectively achieve the sieving of a mixture of C3F6 and C3F8 under mild conditions (room temperature and pressure). Specifically, C3F6 preferentially enters the pores of the material and is adsorbed, while C3F8, due to its larger molecular size, cannot enter the pores and is selectively excluded by the material. Therefore, the metal-organic framework material provided by this invention can achieve effective separation of C3F6 and C3F8. Meanwhile, the larger pores in the structure can provide more adsorption space, thereby achieving a higher C3F6 adsorption capacity (that is, unlike the uniform pore structure commonly found in the prior art, this invention introduces pore structure units of significantly different sizes in the same material, with narrow pore windows serving as limiting units for molecular sieving, and large pores serving as gas adsorption and storage spaces. On the one hand, it can effectively prevent larger C3F8 molecules from entering the pores, significantly improving separation selectivity; on the other hand, it can provide sufficient adsorption space for C3F6 molecules, improving the overall adsorption capacity).

[0064] On the other hand, the inner walls of the pores of the metal-organic framework material prepared by this invention are provided with hydrogen-rich surfaces by organic ligands, thereby forming a locally positively charged environment. This environment can generate favorable weak interactions with fluorine-containing gas molecules, which helps to improve the material's adsorption capacity for C3F6 under low partial pressure conditions. Therefore, this material not only has a high adsorption capacity at atmospheric pressure, but also exhibits excellent C3F6 adsorption performance under low pressure conditions, making it suitable for the removal of trace impurities C3F6 (i.e., improving the material's applicability in trace impurity removal processes).

[0065] In summary, this invention, through the synergistic regulation of pore structure, pore environment, and framework stability, enables the metal-organic framework material prepared by this invention to exhibit advantages such as high selectivity, excellent low-pressure adsorption performance, good structural stability, low energy consumption, and the ability to be processed under ambient temperature and pressure conditions when used for the separation of C3F6 and C3F8. Furthermore, the separation of C3F6 and C3F8 can be achieved simply by passing a mixed gas of C3F6 and C3F8 through a permeation column containing the metal-organic framework material, making the process simple and promising for future applications.

[0066] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a metal-organic framework material, characterized in that, Includes the following steps: Metal nitrate, organic ligand, and solvent are mixed to obtain a mixture; The metal-organic framework material is obtained by subjecting the mixture to a solvothermal reaction. The metal nitrate includes at least one of aluminum nitrate, iron nitrate, chromium nitrate, and gallium nitrate; The solvent includes N,N-dimethylformamide, formic acid, and water; The organic ligand is 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylic acid.

2. The preparation method according to claim 1, characterized in that, The volume ratio of N,N-dimethylformamide, formic acid and water is (2~6):(2~6):(2~6).

3. The preparation method according to claim 1, characterized in that, The mass ratio of the metal nitrate to the organic ligand is (2~6):(1~4).

4. The preparation method according to claim 1, characterized in that, The mass ratio of the metal nitrate to the organic ligand is (1.5~3.0):

1.

5. The preparation method according to claim 1, characterized in that, The ratio of the metal nitrate to the solvent is (20~60) mg: (6~36) mL.

6. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction is 180~200℃, and the reaction time is 3~5 days.

7. A metal-organic framework material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The metal-organic framework material according to claim 7, characterized in that, The molecular formula of the metal-organic framework material is [M3( μ 3-O)(H2O)3(L)]NO3, M represents Al, Fe, Cr or Ga, L represents 2'-amino-5'-(3,5-dicarboxyphenyl)-[1,1':3',1”-terphenyl]-3,3”,5,5”-tetracarboxylate ion; The pore window size of the metal-organic framework is 4.5~5.5 Å, and the cavity size of the metal-organic framework is 8.0~11.0 Å.

9. The use of a metal-organic framework material according to any one of claims 7-8 in the separation of a binary mixture of hexafluoropropylene and perfluoropropane.

10. The application according to claim 9, characterized in that, The method of application is as follows: passing a binary mixture of hexafluoropropylene and perfluoropropane through a permeation column containing the metal-organic framework material to obtain perfluoropropane.

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