Scandium-based MOF crystal material, preparation method and application thereof

Abstract

The application discloses a scandium-based MOF crystal material, a preparation method and application thereof. The MOF crystal is formed by [Sc3(mu2-OH)3(CO2)4O6] n The three-dimensional porous framework structure is formed by the mutual connection of an inorganic metal chain, 2,5-thiophene dicarboxylic acid and a nitrate ion, is directly synthesized by a solvothermal reaction with a metal Sc based on the ligand 2,5-thiophene dicarboxylic acid, and has relatively mild, simple and easy reaction conditions. The MOF crystal has high crystallinity, excellent thermal stability, water stability, solvent stability and wide pH stability. Under normal temperature and pressure, C3H6 is preferentially adsorbed, then C2H6, and finally C2H4, and the MOF crystal has good C3H6 / C2H4 and C2H6 / C2H4 separation performance, thereby obtaining high-purity C2H4 and recovering C3H6, and can be applied to the effective separation of C2H4 and C3H6 in a methanol-to-olefin (MTO) mixture.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of porous organic materials, and particularly relates to a porous scandium-based MOF crystal material constructed by [Sc3(μ2-OH)3(CO2)4O6] n The inorganic metal chain is constructed with an organic ligand 2, 5-thiophene dicarboxylic acid (H2Tdc) to form a porous scandium-based MOF crystal material with excellent stability. BACKGROUND

[0002] Ethylene (C2H4) and propylene (C3H6) are important basic raw materials in modern manufacturing and petrochemical products, and occupy an important position in the petrochemical industry and energy field, so their demand is increasing year by year. At present, the methanol-to-olefins (MTO) technology is the core technology for developing non-petroleum resources to produce C2H4 and C3H6 and other light hydrocarbons, and has become the focus of development in recent years. In the MTO products, the contents of C2H4 and C3H6 can reach 51.1wt% and 20.9wt%, respectively, but it is inevitable to contain ethane (C2H6, 6-10%) as the main impurity. Therefore, in order to obtain polymer-grade C2H4 and C3H6, it is crucial to separate C2H6 and C2H4 efficiently and recover C3H6. Since the traditional low-temperature distillation technology has the disadvantages of high energy consumption and high cost, the adsorption separation technology using porous materials is favored due to its low energy consumption, high efficiency and flexible operation. Therefore, developing new and efficient porous materials has become the core and key of the adsorption separation technology.

[0003] Metal-Organic Framework (MOF), a new emerging organic-inorganic hybrid material, is a porous crystalline material with periodic network structure formed by self-assembly of metal ions or metal clusters and organic ligands. Due to its high specific surface area and porosity, adjustable components and structure, etc., it has a wide application prospect in the field of gas adsorption and separation, and has become an ideal choice for purifying C2H4 by separating light hydrocarbon mixtures. At present, although a small number of MOFs adsorbents for separating C2H6 and C2H4 have been reported, they are still in the early stage of research, and there are still some deficiencies in selectivity, stability, etc. (Small 2023, 19, 2300821. Chinese J. Chem. Eng. 2022, 42, 35-41.). Therefore, designing and synthesizing new and efficient MOFs for separating C2H6 and C2H4 and recovering C3H6 is still a great challenge. SUMMARY

[0004] The application aims to provide a stable scandium-based MOF crystal material. The scandium-based MOF crystal material has high crystallinity, excellent thermal stability, water stability, solvent stability and wide pH stability. Under normal temperature and pressure, C3H6 is preferentially adsorbed, then C2H6, and finally C2H4, and the scandium-based MOF crystal material has good C3H6 / C2H4 and C2H6 / C2H4 separation performance, can well separate C2H4 and C2H6, thereby obtaining high-purity C2H4 and recovering C3H6, and the yield of C2H4 and C3H6 is 13.04 L / kg and 28.01 L / kg, respectively.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical solutions.

[0006] In a first aspect, the application provides a stable scandium-based MOF crystal material, which has a chemical formula: {[Sc3(OH)2(Tdc)3(NO3)]·H2O} ∞ .

[0007] Further, the scandium-based MOF crystal material is constructed by connecting an inorganic metal chain [Sc3(μ2-OH)3(CO2)6O2] n with an organic ligand 2,5-thiophenedicarboxylic acid and a nitrate ion to form a scandium-based MOF with a microporous structure.

[0008] Further, the [Sc3(μ2-OH)3(CO2)6O2] n inorganic metal chain has two independent Sc ions, namely Sc1 and Sc2, both of which are hexacoordinated, six coordination oxygen atoms of Sc1 come from four different 2,5-thiophenedicarboxylic acid ligands, one μ2-OH and one nitrate ion, and six coordination oxygen atoms of Sc2 come from four different 2,5-thiophenedicarboxylic acid ligands and two μ2-OH.

[0009] Further, the scandium-based MOF crystal material belongs to a monoclinic crystal system and has a space group I2 / m.

[0010] Further, the crystallographic data of the scandium-based MOF crystal material is as follows: cell parameters: α = 90°, β = 96.642(3)°, γ = 90°, Z = 4.

[0011] Further, the scandium-based MOF crystal material is a colorless transparent block crystal, which has excellent thermal stability, water stability, solvent stability and wide pH stability.

[0012] In a second aspect, the present application provides a preparation method of the stable scandium-based MOF crystal material of the first aspect, which is directly synthesized by a solvothermal reaction of 2,5-thiophene dicarboxylic acid and metal Sc, and specifically comprises the following steps:

[0013] (1) 2,5-thiophene dicarboxylic acid 17.5 mg and template 1,2,4-triazole 10 mg are added into 2.5 ml of acetonitrile, and ultrasonic is applied for a period of time to mix them thoroughly, which is recorded as a first solution;

[0014] (2) Scandium nitrate hydrate 46 mg is dissolved in 1.8 ml of H2O, which is recorded as a second solution;

[0015] (3) The first solution and the second solution are mixed, and then 60-90 μL of concentrated nitric acid is added to obtain a transparent mixed solution;

[0016] (4) The mixed solution is placed in an oven for a solvothermal reaction to obtain a colorless transparent block crystal, which is a scandium-based MOF crystal material.

[0017] Further, the solvothermal reaction temperature is 100°C, and the reaction time is 72 h.

[0018] In a third aspect, the present application further provides an application of the scandium-based MOF crystal material of the first aspect in separating and purifying C2H4 from a light hydrocarbon mixture.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. The scandium-based MOF crystal material provided by the present application is directly synthesized by a simple solvothermal reaction of 2,5-thiophene dicarboxylic acid and metal Sc, and the reaction conditions are relatively mild and simple.

[0021] 2. The scandium-based MOF crystal material provided by the present application has high crystallinity, excellent thermal stability, water stability, solvent stability and wide pH stability, and is convenient for practical application research.

[0022] 3. The scandium-based MOF crystal material provided by the present application preferentially adsorbs C3H6, then C2H6, and finally C2H4 at normal temperature and pressure, has good C3H6 / C2H4 and C2H6 / C2H4 separation performance, can well separate C2H4 and C2H6, thereby obtaining high-purity C2H4 in one step and recovering C3H6, and has excellent application prospect in purifying C2H4 and recovering C3H6 from an MTO mixture. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is an optical microscope image of the scandium-based MOF crystal material of the present application.

[0024] Figure 2 Structure schematic diagram of the scandium-based MOF crystal material of the present application, wherein (a) coordination mode of Sc1 atom; (b) coordination mode of Sc2 atom; (c) one-dimensional metal chain [Sc3(μ2-OH)3(CO2)4O6] n Structure schematic diagram; (d) three-dimensional network structure diagram along a-axis direction; (e) three-dimensional network structure diagram along a-c-axis direction.

[0025] Figure 3 PXRD diagram of the scandium-based MOF crystal material of the present application.

[0026] Figure 4 PXRD diagram of the scandium-based MOF crystal material of the present application soaked in HCl and KOH aqueous solution with different pH for 24 h.

[0027] Figure 5 PXRD diagram of the scandium-based MOF crystal material of the present application soaked in water for different time.

[0028] Figure 6 PXRD spectrum diagram of the scandium-based MOF crystal material of the present application soaked in different organic solvents for 24 h.

[0029] Figure 7 Thermogravimetric curve diagram of the scandium-based MOF crystal material of the present application.

[0030] Figure 8 Normal pressure isothermal adsorption curve of C2H4, C2H6 and C3H6 at 288 K of the scandium-based MOF crystal material of the present application.

[0031] Figure 9 Normal pressure isothermal adsorption curve of C2H4, C2H6 and C3H6 at 298 K of the scandium-based MOF crystal material of the present application.

[0032] Figure 10 Normal pressure isothermal adsorption curve of C2H4, C2H6 and C3H6 at 308 K of the scandium-based MOF crystal material of the present application.

[0033] Figure 11 Adsorption enthalpy of C2H4, C2H6 and C3H6 of the scandium-based MOF crystal material of the present application.

[0034] Figure 12 Adsorption selectivity of mixed gas C2H6 / C2H4 (v / v, 1 / 9) at 298 K of the scandium-based MOF crystal material of the present application.

[0035] Figure 13 Adsorption selectivity of mixed gas C3H6 / C2H4 (v / v, 2 / 5) at 298 K of the scandium-based MOF crystal material of the present application.

[0036] Figure 14 Breakthrough curve of the scandium-based MOF crystalline material of the present application for the three-component gas mixture C2H6 / C3H6 / C2H4 (2 / 10 / 25, v / v / v) at 298 K.

[0037] Figure 15 Shown are the desorption plots of C2H4, C2H6 and C3H6 (He purge rate 4 mL / min) for the scandium-based MOF crystalline material of the present application at 338 K.

[0038] Figure 16 Shown are the desorption plots of C3H6 (He purge rate 4 mL / min) for the scandium-based MOF crystalline material of the present application at 338 K.

[0039] Figure 17 PXRD pattern of the scandium-based MOF crystalline material prepared in Example 2. DETAILED DESCRIPTION

[0040] In order to make the content of the present application more convenient to understand, the technical solutions described in the present application will be further described below in combination with specific embodiments, but the present application is not limited thereto.

[0041] I. Preparation of samples

[0042] The raw materials in the examples of the present application are all purchased through commercial channels, for example, scandium nitrate hydrate (Cas No: 13465-60-6) is a brand of chemical reagent from Macklin.

[0043] Example 1

[0044] At room temperature, 2,5-thiophenedicarboxylic acid (17.5 mg), 1,2,4-triazole (10 mg) were dissolved in 2.5 ml of acetonitrile (MeCN) solution, and ultrasonic was applied for 1 h to make them fully mixed, obtaining a white suspension S1. Scandium nitrate hydrate (46 mg) was dissolved in 1.8 ml of H2O, and ultrasonic was applied to make them fully mixed, obtaining a clear colorless clear solution S2. The S1 solution and the S2 solution were mixed, 40 μL of concentrated nitric acid was added, and the mixture was placed in a 100°C oven for reaction for 72 h. Then it was taken out and cooled to room temperature, and washed with MeCN. It was observed that there was a precipitate deposited at the bottom of the reaction bottle, but no crystals were produced.

[0045] Example 2

[0046] Scandium nitrate hydrate (46 mg) was dissolved in 1.8 ml H2O and sonicated to give a clear colourless solution S2. The S1 solution and S2 solution were mixed and 60 μL of concentrated nitric acid was added. The mixture was placed in a 100 °C oven for 72 h. The mixture was then removed, allowed to cool to room temperature and washed with MeCN. A small amount of colourless transparent block crystals were observed to have deposited at the bottom of the reaction vessel. PXRD analysis of the crystals showed them to be scandium-based MOF crystalline material as shown in Figure 1. Figure 17

[0047] Example 3

[0048] Scandium nitrate hydrate (46 mg) was dissolved in 1.8 ml H2O and sonicated to give a clear colourless solution S2. The S1 solution and S2 solution were mixed and 60 μL of concentrated nitric acid was added. The mixture was placed in a 100 °C oven for 72 h. The mixture was then removed, allowed to cool to room temperature and washed with MeCN. A small amount of colourless transparent block crystals were observed to have deposited at the bottom of the reaction vessel. PXRD analysis of the crystals showed them to be scandium-based MOF crystalline material as shown in Figure 1. Figure 3

[0049] Example 4

[0050] Scandium nitrate hydrate (46 mg) was dissolved in 1.8 ml H2O and sonicated to give a clear colourless solution S2. The S1 solution and S2 solution were mixed and 60 μL of concentrated nitric acid was added. The mixture was placed in a 100 °C oven for 72 h. The mixture was then removed, allowed to cool to room temperature and washed with MeCN. A small amount of colourless transparent block crystals were observed to have deposited at the bottom of the reaction vessel. PXRD analysis of the crystals showed them to be scandium-based MOF crystalline material as shown in Figure 1.

[0051] Example 5

[0052] ​​At room temperature, 17.5 mg of 2,5-thiophene dicarboxylic acid was dissolved in 2.5 mL of acetonitrile (MeCN) solution and sonicated for 1 h to obtain a white suspension S1. 46 mg of scandium nitrate hydrate was dissolved in 1.8 mL of H₂O and sonicated to obtain a clear, colorless solution S2. Solutions S1 and S2 were mixed, and 90 μL of concentrated nitric acid was added. The mixture was then placed in an oven at 100 °C for 72 h. After cooling to room temperature, the solution was washed with MeCN; no crystals were deposited at the bottom of the reaction flask. Therefore, scandium-based MOF crystalline materials cannot be generated without the structure-directing agent 1,2,4-triazole.

[0053] Example 6

[0054] At room temperature, 17.5 mg of 2,5-thiophene dicarboxylic acid and 10 mg of 1,2,4-triazole were dissolved in 2.5 mL of acetonitrile (MeCN) solution and sonicated for 1 h to obtain a white suspension S1. 46 mg of scandium nitrate hydrate was dissolved in 1.8 mL of H₂O and sonicated to obtain a clear, colorless solution S2. Solutions S1 and S2 were mixed, and 90 μL of concentrated nitric acid was added. The mixture was placed in a 100 °C oven for 48 h. After cooling to room temperature, the solution was washed with MeCN; no crystals were deposited at the bottom of the reaction flask. Therefore, scandium-based MOF crystalline materials could not be formed at a reaction time of 48 h.

[0055] II. Structural Characterization of Samples

[0056] like Figure 1 The image shown is an optical microscope image of the scandium-based MOF crystal prepared in the above embodiments, with the sample prepared in Example 3 as an example. The prepared scandium-based MOF exhibits a regular geometric shape and is a colorless, transparent, blocky crystal.

[0057] like Figure 2 The diagram shows the structural schematic of the scandium-based MOF crystal prepared in the above embodiments, with the sample prepared in Example 3 as an example. Two independent Sc ions (Sc1, Sc2) exist in this MOF, both six-coordinated, with the coordination mode as shown below. Figure 2 (a) and Figure 2 As shown in (b), the four coordination sites of Sc1 are occupied by O atoms on the carboxyl groups of four different ligands, and the other two coordination sites are occupied by a μ2-OH ion and a nitrate ion, respectively; the six coordination sites of Sc2 are occupied by O atoms on the carboxyl groups of four different ligands and two μ2-OH ions, forming an infinitely long one-dimensional chain [Sc3(μ2-OH)3(CO2)4O6]. n ,like Figure 2 (c) of these [Sc3(μ2-OH)3(CO2)4O6] nThe chains are further connected to each other by ligand 2,5-thiophenedicarboxylic acid, nitrate ions to form a three-dimensional porous framework structure Figure 2 (d) and Figure 2 (e) in

[0058] III. PXRD characterization of the samples

[0059] As shown in Figure 3 PXRD patterns of the scandium-based MOF crystals prepared in the above examples, with the sample prepared in Example 3 as a representative example. The experimental PXRD curve of the scandium-based MOF crystal is in good agreement with the simulated PXRD curve (simulated using single crystal structure data), indicating that the scandium-based MOF crystal is a pure phase and does not contain other impurities.

[0060] IV. Stability analysis of the samples

[0061] As shown in Figure 4 PXRD patterns of the scandium-based MOF crystals prepared in the above examples after being immersed in aqueous HCl and KOH solutions with different pH values for 24 h, with the sample prepared in Example 3 as a representative example. The scandium-based MOF crystal can be stable in aqueous solutions with pH = 2 to pH = 12, indicating that it has a wide pH stability.

[0062] As shown in Figure 5 PXRD patterns of the scandium-based MOF crystals prepared in the above examples after being immersed in water for different times, with the sample prepared in Example 3 as a representative example. The scandium-based MOF crystal can maintain the integrity of its own framework after being immersed in water for 1 month at room temperature, indicating that it has good water stability.

[0063] As shown in Figure 6 PXRD patterns of the scandium-based MOF crystals prepared in the above examples after being immersed in different organic solvents for 24 h, with the sample prepared in Example 3 as a representative example. The scandium-based MOF crystal can exist stably in various organic solvents, indicating that it has excellent solvent stability.

[0064] As shown in Figure 7 TG curve of the scandium-based MOF crystal prepared in the above examples, with the sample prepared in Example 3 as a representative example. The scandium-based MOF crystal begins to decompose at 450°C, indicating that it has high thermal stability.

[0065] In summary, the scandium-based MOF crystal has excellent thermal stability, water stability, solvent stability, and wide pH stability.

[0066] V. Gas adsorption properties of the samples

[0067] Using the sample prepared in Example 3 as an example, the prepared scandium-based MOF crystals were exchanged with anhydrous methanol for 3 days, 3 times a day, and then activated under vacuum at 120°C for 24 hours to obtain activated scandium-based MOF. Approximately 100 mg of the activated scandium-based MOF was weighed and placed into an adsorption tube of known mass, and the adsorption isotherms of C2H4, C2H6, and C3H6 were tested on a physical adsorption instrument. Assuming that He is not adsorbed at any temperature, He (99.999%) was selected to test the dead volume of the system. The test temperatures were 288 K, 298 K, and 308 K. Approximately 920 mg of activated scandium-based MOF was weighed and packed into a stainless steel column (0.4 cm inner diameter, 15 cm length). The column was purged with helium for 20 min at a flow rate of 10 mL / min and subjected to a dynamic adsorption-breakthrough experiment of a three-component gas mixture C2H6 / C3H6 / C2H4 (2 / 10 / 25, v / v / v) at 298 K.

[0068] like Figure 8 , Figure 9 and Figure 10 The activated scandium-based MOF crystals are shown as atmospheric pressure isothermal adsorption curves for C2H4, C2H6, and C3H6 at 288 K, 298 K, and 308 K, respectively. It can be seen that at extremely low pressures, the adsorption amounts of C2H4 and C2H6 are very small, indicating that C2H4 and C2H6 have difficulty entering the scandium-based MOF channels at extremely low pressures. Furthermore, below 0.8 bar, the adsorption amounts of C2H4, C2H6, and C3H6 are not significantly affected by temperature. At room temperature (T = 298 K), with increasing pressure, the scandium-based MOF crystals preferentially adsorb C3H6, then C2H6, and finally C2H4. At 298 K and 1 bar, the adsorption amounts of C3H6, C2H6, and C2H4 are 98.6 cm⁻¹, respectively. 3 / g, 74.3cm 3 / g and 67.7cm 3 / g.

[0069] like Figure 11 The figure shows the adsorption enthalpy Q of C2H4, C2H6, and C3H6 of the activated scandium-based MOF crystal. st Based on the above atmospheric pressure isothermal adsorption curves, the adsorption enthalpies Q of C2H4, C2H6, and C3H6 at zero loading were calculated to be... st,C2H4 =41.8kJ / mol, Q st,C2H6 =63.3kJ / mol and Q st,C3H6 = 83.7 kJ / mol. This indicates that, compared to C2H4, the scandium-based MOF framework has a stronger interaction with C3H6 and C2H6, resulting in the adsorption of more C3H6 and C2H6. This phenomenon is consistent with the experimental results reflected in the ambient pressure isothermal adsorption curves of C2H4, C2H6, and C3H6.

[0070] As Figure 12 shown is the adsorption selectivity of the activated scandium-based MOF crystals for the mixed gas C2H6 / C2H4(v / v, 1 / 9) at 298 K. Based on the ideal adsorbed solution theory (IAST), it is calculated to have a higher C2H6 / C2H4 adsorption selectivity of 2.32, higher than some famous C2H6-selective MOFs, such as TJT-100 (1.2) (Angew. Chem. Int. Ed., 2018, 57, 16067-16071.), NPU-2 (1.52) (J. Am. Chem. Soc., 2021, 143, 1485-1492.), Azole-Th-1 (1.46) (Nat Commun., 2020, 11, 3163.), JNU-2 (1.6) (J. Am. Chem. Soc., 2019, 141, 20390-20396.) and Zn-BPZ-TATB (1.7) (Angew. Chem. Int. Ed., 2023, 62, e202311654.).

[0071] As Figure 13 shown is the adsorption selectivity of the activated scandium-based MOF crystals for the mixed gas C3H6 / C2H4(v / v, 2 / 5) at 298 K. Based on the ideal adsorbed solution theory (IAST), it is calculated to have a higher C3H6 / C2H4 adsorption selectivity of 7.93, higher than some famous C3H6-selective MOFs, such as PCP 1 (3.6) (Dalton Trans, 2018, 47, 9008-9013.), Cu-BTC (5.8) (J. Chem. Eng. Data, 2017, 62, 417-421.), Mg-MOF-74 (4.7) (Langmuir, 2011, 27, 13554-13562.), spe-MOF (7.7) (Angew. Chem. Int. Ed., 2021, 60, 16521-16528.).

[0072] As Figure 14 shown is the breakthrough curve of the activated scandium-based MOF crystals for the three-component gas mixture C2H6 / C3H6 / C2H4(2 / 10 / 25, v / v / v) at 298 K. The results show that C2H4 is the first to break through, and the breakthrough time is 43 min, and the required high-purity C2H4 is produced at 53 min, with a yield of 13.04 L / kg; compared with C2H4, C2H6 has a stronger interaction with the scandium-based MOF framework (Q st,C2H4 = 41.8 kJ / mol < Q st,C2H6= 63.3 kJ / mol), thus remained for a while, C2H6 started to breakthrough at 59 min; since C3H6 has the strongest interaction with the Sc-based MOF framework (Q st,C2H4 = 41.8 kJ / mol < Q st,C2H6 = 63.3 kJ / mol < Q st,C3H6 = 83.7 kJ / mol), until C3H6 reached breakthrough point at 155 min. This indicates that the Sc-based MOF can well separate C2H4 and C2H6, obtaining high purity C2H4 in one step and recycling C3H6.

[0073] As shown in FIG. 1, the Sc-based MOF crystal was activated at 423 K under vacuum for 8 h, and then saturated with C3H6 at 298 K. Figure 15 、 Figure 16 As shown in FIG. 2, the desorption curves of the activated Sc-based MOF crystal after adsorbing saturated three-component gas mixture (C2H6 / C3H6 / C2H4 (2 / 10 / 25, v / v / v)) and after adsorbing saturated C3H6. Since C3H6 is another target gas that needs to be purified from MTO products, after the fixed bed column reached the equilibrium concentration, the adsorbed saturated Sc-based MOF crystal was subjected to desorption experiment with helium (4 mL / min) at 338 K to produce pure C3H6. The experiment shows that the Sc-based MOF crystal can be easily regenerated, and C2H4 and C2H6 are desorbed faster than C3H6, after 16 min, high purity C3H6 is desorbed, and the yield is 28.01 L / kg.

[0074] The above experimental results show that the Sc-based MOF crystal material of the present application preferentially adsorbs C3H6, then C2H6, and finally C2H4 at normal temperature and pressure, has good C3H6 / C2H4 and C2H6 / C2H4 separation performance, can well separate C2H4 and C2H6 to obtain high purity C2H4 and recycle C3H6, and is expected to realize efficient separation of C2H4 and C3H6 from MTO mixture.

[0075] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with the above preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solution.

Claims

1. A stable scandium-based MOF crystalline material, characterized in that, having the chemical formula: {[Sc3(OH)2(Tdc)3(NO3)]•H2O} ∞ ; The scandium-based MOF crystal material has a microporous structure, which is constructed by [Sc3(μ2-OH)3(CO2)4O6] n The inorganic metal chain is self-assembled with an organic ligand 2,5-thiophene dicarboxylic acid and a nitrate ion. Wherein, the [Sc3(μ2-OH)3(CO2)4O6] n There are two independent Sc ions in the inorganic metal chain, namely Sc1 and Sc2, both of which are hexacoordinated, Sc1 six coordinated oxygen atoms are from four different 2,5-thiophene dicarboxylic acid ligands, one μ 2-OH and one nitrate ion; Sc2 six coordinated oxygen atoms are from four different 2,5-thiophene dicarboxylic acid ligands, two μ 2-OH.

2. The scandium-based MOF crystalline material of claim 1, wherein, The scandium-based MOF crystal material belongs to monoclinic system, I 2 / m space group.

3. The scandium-based MOF crystalline material of claim 1, wherein, The crystallographic data for the scandium-based MOF crystalline material is: a = 10.7483(8) A, b = 17.5676(13) A, c = 21.9285(14) A, α = 90°, β = 96.642(3)°, γ = 90°, V = 4112.8(5) A 3 Z = 4.

4. A method of producing a scandium-based MOF crystalline material as claimed in any one of claims 1 to 3, characterized in that, The Sc-based MOF crystal material is directly synthesized by a solvothermal reaction of 2,5-thiophene dicarboxylic acid and metal Sc, and specifically includes the following steps: (1) 17.5 mg of the organic ligand 2,5-thiophene dicarboxylic acid and 10 mg of a template agent 1,2,4-triazole are added into 2.5 ml of acetonitrile, and ultrasonic is applied for a period of time to mix them thoroughly, denoted as a first solution; (2) 46 mg of hydrated scandium nitrate is dissolved in 1.8 ml of H2O, denoted as a second solution; (3) the first solution and the second solution are mixed, and then 60-90 µL of concentrated nitric acid is added to obtain a transparent mixed solution; (4) the mixed solution is placed in an oven for a solvothermal reaction to obtain the Sc-based MOF crystal material.

5. The method of claim 4, wherein, The solvothermal reaction temperature is 100°C, and the reaction time is 72 h.

6. Application of the stable Sc-based MOF crystal material according to any one of claims 1-3 or the Sc-based MOF crystal material prepared by the method according to any one of claims 4 and 5 in purifying C2H4 in a light hydrocarbon mixture.

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