Transition-rare earth metal organic framework compounds, methods of making and uses thereof

Abstract

The application discloses a transition-rare earth metal organic framework compound, which has a minimum asymmetric unit of a chemical formula [RECu(L)2OH], wherein L is 4,4'(pyridine-3,5-diyl) dibenzoate, and RE is a rare earth ion; copper ions and rare earth ions in the asymmetric unit are alternately connected to form a one-dimensional chain-shaped heteronuclear metal cluster secondary structure; the application belongs to an orthorhombic system, a Pca21 space group, and cell parameters are alpha = beta = gamma = 90 degrees. The raw material for synthesizing the heterometal MOFs is low in cost, easy to obtain, stable in structure, has a catalytic effect, and can realize carbon dioxide conversion.

Description

Technical Field

[0001] This invention relates to the field of metal-organic frameworks (MOFs), specifically providing a transition-rare earth metal-organic framework compound, its preparation method, and its uses. Background Technology

[0002] Metal-organic frameworks (MOFs) possess diverse structures and intrinsic properties, such as large specific surface areas, flexible and tunable configurations, and coordinate-unsaturated metal centers. These have facilitated the rapid development and widespread application of coordination chemistry over the past few decades, including in gas adsorption, catalysis, and magnetism. Compared to monometallic MOFs, heterometals occupy unique positions, leading to interesting network topologies. The excellent synergistic effects between different metal ions can effectively enhance physical and chemical properties. Integrating bimetallic nodes into the framework can generate excellent synergistic effects between those metal ions, increasing their functional diversity. For example, heterometallic nanoparticles typically exhibit higher catalytic activity than monometallic nanoparticles. Magnetic and electronic properties can be enhanced by doping a second metal ion into the metal oxide lattice. These not only improve the thermodynamic stability of the framework but also modulate the chemical reactivity of MOFs due to their multimetallic nature. However, the synthesis conditions for heterometallic MOFs are more demanding. The two metals compete with each other, requiring synthesis at suitable temperatures, times, and pH levels, making them more challenging to synthesize than monometallic MOFs. Summary of the Invention:

[0003] The purpose of this invention is to provide a transition-rare earth metal-organic framework compound, its preparation method, and its uses, in order to solve the above-mentioned problems existing in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A transition-rare earth metal-organic framework compound having a minimal asymmetric unit with the chemical formula [RECu(L)2OH], where L is 4,4'-(pyridin-3,5-diyl)dibenzoate and RE is a rare earth ion. The asymmetric unit contains alternating copper and rare earth ions forming a one-dimensional chain-like heteronuclear metal cluster secondary structure, belonging to the orthorhombic crystal system, space group Pca21, with cell parameters of […]. α = β = γ = 90°.

[0006] As a preferred embodiment, the transition-rare earth metal-organic framework compound has a one-dimensional chain-like heteronuclear metal cluster, a three-dimensional framework structure, and uncoordinated Lewis base sites.

[0007] As a preferred option, RE is selected from one of Dy, Gd, Er, Eu, Yb, Pr, Ho, and Tm.

[0008] A method for preparing a transition-rare earth metal-organic framework compound as described above, comprising the following steps:

[0009] RE2O3, 4,4'-(pyridine-3,5-dimethyl)dibenzoic acid and CuCl2·2H2O were added to water, mixed well, and the pH was adjusted to 1.5-2 with acid. The hydrothermal reaction was carried out at 170-190℃. The crystals obtained after the reaction were collected, washed with water, and dried to obtain the transition-rare earth metal-organic framework compound.

[0010] As a preferred embodiment, the molar ratio of RE2O3, 4,4'-(pyridine-3,5-dimethyl)benzoic acid and CuCl2·2H2O is 1:(1.1~1.3):1.

[0011] As a preferred embodiment, the acid is perchloric acid.

[0012] The use of a transition-rare earth metal-organic framework compound as described above in the catalytic preparation of 2-oxazolidinone from carbon dioxide.

[0013] A method for preparing a 2-oxazolidinone derivative as described above, comprising the following steps:

[0014] After uniformly dispersing the transition-rare earth metal-organic framework compound, inorganic base, and propargylamine derivative in an organic solvent, carbon dioxide is introduced at 80–100 °C. After the reaction, since both the raw materials and products dissolve in dichloromethane, they are extracted with water and dichloromethane to obtain the 2-oxazolidinone derivative.

[0015] As a preferred embodiment, the propargylamine derivative is N-(4-methoxybenzyl)propyl-2-yn-1-amine.

[0016] As a preferred embodiment, the inorganic base is potassium hydroxide.

[0017] As a preferred embodiment, the organic solvent is dimethyl sulfoxide.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The raw materials for synthesizing heterometallic MOFs in this invention are inexpensive, readily available, structurally stable, and possess catalytic effects, enabling the conversion of carbon dioxide.

[0020] 2. The method for synthesizing crystalline heterometallic MOFs of the present invention has mild reaction conditions, high yield and purity, and does not require inert gas protection:

[0021] 3. The crystalline material of heterometallic MOFs provided by this invention can synthesize at least eight isomorphic crystals. By comparison, it can be concluded that rare earth metal ions have a synergistic catalytic effect on the conversion reaction of carbon dioxide. Attached Figure Description

[0022] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0023] Figure 1 This is a photograph of the heterometallic MOFs material prepared in Example 1 of this invention;

[0024] Figure 2 for Figure 1 Microscopic magnification;

[0025] Table 1 shows the crystallographic parameters of Example 1 and its series of MOFs;

[0026] Figure 3 This is a structural diagram of the minimum asymmetric structural unit of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention;

[0027] Figure 4 The diagram shows the one-dimensional chain structure formed by alternating dysprosium and copper ions along the a-axis of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention.

[0028] Figure 5 This is the three-dimensional structure along the c-axis of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention;

[0029] Figure 6 The XRD powder diffraction pattern (simulated, synthesized) of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention;

[0030] Figure 7 Thermogravimetric (TG) diagram of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention;

[0031] Figure 8 This is a graph showing the solvent stability of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention.

[0032] Figure 9 This is a stability diagram of the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention in water at different pH values;

[0033] Figure 10 This diagram illustrates the cycloaddition conversion of carbon dioxide and propargylamine derivatives catalyzed by the transition-rare earth metal-organic framework compound prepared in Example 1 of this invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The specific steps for the N2O9CuDy method are as follows:

[0037] S1. Mix Dy2O3 (0.0373 g, 0.1 mmol), 4,4'-(pyridin-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) in 7 mL of water and stir for 20 minutes.

[0038] S2. Add the substance from step S1 to a 25mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.), maintain a constant temperature of 170℃ under autogenous pressure for 72 hours, and then cool to room temperature.

[0039] S3. Filter the product obtained in S2, collect the crystals, wash with water and dry to obtain the blue columnar crystalline compound, namely the transition-rare earth metal-organic framework compound (denoted as M2-Dy for ease of explanation), as shown in the macroscopic photograph. Figure 1 As shown.

[0040] The molecular formula of the transition-rare earth metal-organic framework compound obtained in this embodiment is C2. 38 H 23 N2O9CuDy, elemental analysis: theoretical values ​​(%): C 52.80; H 3.08; N 3.23, measured values: C 52.72; H 3.15; N 3.28.

[0041] The yield was calculated to be 52% based on copper chloride.

[0042] Select a clean, clear, and appropriately sized crystal under a microscope, such as... Figure 2 As shown, single-crystal X-ray diffractometers with Bruker Apex II CCD were used for single-crystal testing at room temperature. The crystal information obtained is as follows: orthorhombic crystal system, space group Pca21, and cell parameters are as follows. α=β=γ=90°. Symmetry operation codes: (i)x,y,z; (ii)-x,-y,z+1 / 2; (iii)-x+1 / 2,y,z+1 / 2; (iv)x+1 / 2,-y,z.

[0043] Depend on Figures 3-5 It is known that the smallest asymmetric unit of transition-rare earth metal-organic framework compounds consists of a binuclear metal Dy and Cu, a hydroxyl group, and two ligands. Metal Dy adopts an octet coordination mode, its coordination environment can be described as coordinating with eight oxygen atoms, six of which originate from the oxygen atoms in the carboxylic acid ligand, and the other two from the oxygen atoms in the hydroxyl group. Metal Cu adopts a hexaton coordination mode, with four coordination sites originating from the oxygen atoms in the carboxylic acid ligand, one from the oxygen atom in the hydroxyl group, and the other coordinating with the nitrogen atom in the ligand. The two ligands in this compound have different coordination modes; in one ligand, the nitrogen atom participates in coordination, while in the other, it does not. The uncoordinated nitrogen atom provides a potential co-catalytic site for the carbon dioxide conversion reaction. Copper and dysprosium ions alternately connect to form a semi-cubic alkyl structure, while dysprosium ions share edges to form a one-dimensional chain-like metal cluster secondary structure. This one-dimensional chain-like metal cluster supports the three-dimensional structure through its connection with the ligands, with the uncoordinated nitrogen atom facing inwards.

[0044] Powder diffraction analysis was performed on M2-Dy, and powder testing experiments were conducted under various conditions for comparison. The test results are as follows: Figure 6 As shown in the figure, the powder diffraction peaks of M2-Dy match its standard simulated peaks, indicating that M2-Dy is a homogeneous, impurity-free pure phase, and the powder diffraction peaks of the synthesized isomorphic crystals all match the simulated peaks.

[0045] The thermal stability of M2-Dy was studied and tested using thermogravimetric analysis (TGA). The experimental results are as follows: Figure 7 As shown in the figure, M2-Dy remained stable at 370℃ during heating, with some guest molecules being lost between 370℃ and 390℃. The compound's framework gradually collapsed after 400℃. These results indicate that the compound possesses good thermal stability.

[0046] Powder diffraction tests were performed after immersing the compound in different common solvents for 6 days, such as... Figure 8 The measured powder diffraction peaks still highly match the simulated peaks, indicating good solvent stability.

[0047] Powder diffraction tests were conducted by immersing the compound in aqueous solutions with different pH values, such as... Figure 9 The measured powder diffraction peaks are highly matched with the simulated peaks, indicating good acid and alkali resistance.

[0048] Example 2

[0049] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuEr involves the following steps: Er2O3 (0.0383 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170 °C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Er.

[0050] Example 3

[0051] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuEu involves the following steps: Eu2O3 (0.0352 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170 °C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Eu.

[0052] Example 4

[0053] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuGd involves the following steps: Gd2O3 (0.0363 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170 °C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Gd.

[0054] Example 5

[0055] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuHo involves the following steps: Ho2O3 (0.0378 g, 0.1 mmol), 4,4'-(pyridin-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170°C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Ho.

[0056] Example 6

[0057] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuPr involves the following steps: Pr2O3 (0.0330 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170 °C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Pr.

[0058] Example 7

[0059] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuTm involves the following steps: Tm2O3 (0.0386 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170°C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Tm.

[0060] Example 8

[0061] This embodiment provides a method for preparing transition-rare earth metal-organic framework compound C at the milligram scale. 38 H 23 The method for obtaining N2O9CuYb involves the following steps: Yb2O3 (0.0394 g, 0.1 mmol), 4,4'-(pyridine-3,5-diyl)benzoic acid (0.0383 g, 0.12 mmol), and perchloric acid (0.385 mmol) are mixed in 7 mL of water and stirred for 20 minutes. This mixture is then added to a 25 mL polytetrafluoroethylene reactor (provided by Shandong Jinan Henghua Co., Ltd.). The reactor is kept at a constant temperature of 170 °C under autogenous pressure for 72 hours. After cooling to room temperature, the product is filtered, the crystals are collected, washed with water, and dried to obtain the blue columnar crystalline compound, denoted as M2-Yb.

[0062] The crystal parameters of the transition-rare earth metal-organic framework compounds obtained in Examples 1 to 8 are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] Comparative Example 1

[0067] The only difference between this comparative example and Example 1 is that the hydrothermal reaction temperature is 160°C, and the product obtained is mainly a precipitate.

[0068] Based on crystal structure information and stability tests, it is preliminarily determined that the target product is thermodynamically stable. Therefore, higher temperatures and longer reaction times are more conducive to the formation of thermodynamically stable products.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 1 is that the pH value is 3, and the products obtained are all precipitates.

[0071] This is because rare earth ions are relatively oxygen-loving elements. Only under suitable acidic pH values ​​can they form crystalline complexes without generating hydroxide precipitates. Therefore, when 18–24 μL of 72% perchloric acid (0.380–0.385 mmol) is added, the target crystals can be obtained; otherwise, the products are all precipitates.

[0072] Comparative Example 3

[0073] The difference between this comparative example and Example 1 is that the acid used to adjust the pH value is nitric acid, and the product obtained is a block powder.

[0074] This is because perchloric acid is more conducive to crystallization and the synthesis of the target crystal, but it is difficult to obtain the target crystal when perchloric acid is replaced with nitric acid. Although the perchlorate ion is not in the structure of the product, it is indispensable in the synthesis process due to its role as a mineralizing agent and template agent.

[0075] Example 9

[0076] This embodiment provides a method for preparing 3-(4-methoxybenzyl)-5-methyleneoxazolidine-2-one using transition-rare earth metal-organic framework compounds prepared in Examples 1-8 as catalysts. The specific steps are as follows:

[0077] Take a clean test tube and add 2.8 mg of a transition-rare earth metal-organic framework compound, 5.6 mg of KOH, 8.9 mg of N-(4-methoxybenzyl)propyl-2-ynyl-1-amine, and 1 mL of DMSO sequentially. After adding a magnetic stir bar, place the test tube in a 90°C oil bath, purge with carbon dioxide, and stir for 10 min. Since both the reactants and products dissolve in dichloromethane, extract with water and dichloromethane to obtain 3-(4-methoxybenzyl)-5-methyleneoxazolidine-2-one. The reaction route is as follows:

[0078] Reaction mechanism such as Figure 10 As shown.

[0079] Copper ions play a major catalytic role in this reaction. Using the obtained isomorphic crystals, the synergistic effect of different rare earth ions on copper catalysis was tested. The results show that isomorphic compounds of different rare earth ions have different catalytic effects on this reaction, proving that rare earth ions participate in catalysis and have a synergistic effect. The results are shown in Table 2. The examples of Dy and Gd showed high yields (63% and 67%) and TOF values ​​(transition frequency) (112 h). -1 and 119h -1 ).

[0080] Table 2

[0081]

[0082] Comparative Example 4

[0083] The only difference between this comparative example and Example 9 is that different bases were used instead of potassium hydroxide. The results are shown in Table 3. KOH alone has no catalytic effect in this reaction, but compared with other bases, KOH has the strongest basicity, thus maximizing the removal of H from N to promote cyclization.

[0084] Table 3

[0085]

[0086]

[0087] Note: Catalyst dosage 5.5 mg

[0088] Comparative Example 5

[0089] The only difference between this comparative example and Example 9 is the use of a different organic solvent instead of dimethyl sulfoxide. The results are shown in Table 4. Screening revealed that DMSO was more favorable as a solvent for the reaction.

[0090] Table 4

[0091]

[0092] Note: Catalyst dosage 2.8 mg

[0093] Comparative Example 6

[0094] The only difference between this comparative example and Example 9 is the use of different reaction temperatures, as shown in Table 5. Suitable temperatures were selected at room temperature (21°C), 30°C, 40°C, 50°C, 70°C, and 90°C. The results show that within the test range, higher temperatures are more conducive to catalysis.

[0095] Table 5

[0096]

[0097] Note: Catalyst dosage: 2.8 mg

[0098] Comparative Example 7

[0099] The only difference between this comparative example and Example 9 is that a different reaction time was used. The results are shown in Table 6. It was found that the catalytic yield of the compound could still reach 99% at 90°C for 10 min.

[0100] Table 6

[0101]

[0102] Copper ions play a major catalytic role in this reaction. Using the obtained isomorphic crystals, the synergistic effect of different rare earth ions on copper catalysis was tested. The results show that isomorphic compounds of different rare earth ions have different catalytic effects on this reaction, proving that rare earth ions participate in catalysis and have a synergistic effect. The results are shown in Table 7. The examples of Dy and Gd showed high yields (63% and 67%) and TOF values ​​(transition frequency) (112 h). -1 and 119h -1 ).

[0103] Table 7

[0104]

[0105] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A transition-rare earth metal-organic framework compound, characterized in that, The smallest asymmetric unit with the chemical formula [RECu(L)2OH], where L is 4,4'(pyridine-3,5-dimethyl)dibenzoate and RE is a rare earth ion, and the copper ion and rare earth ion are alternately connected in the asymmetric unit to form a one-dimensional chain-like heteronuclear metal cluster secondary structure, which belongs to the orthorhombic crystal system, space group Pca21, and the cell parameters are a=29.5356(3) Å, b=14.2185(2) Å, c=7.37110(10) Å, α=β=γ=90°; RE is Dy; The method for preparing the transition-rare earth metal-organic framework compound includes the following steps: Dy2O3, 4,4'-(pyridine-3,5-dimethyl)dibenzoic acid and CuCl2·2H2O were added to water, mixed well, and the pH was adjusted to 1.5-2 with perchloric acid. The hydrothermal reaction was carried out at 170-190℃. The crystals obtained after the reaction were collected, washed with water, and dried to obtain the transition-rare earth metal-organic framework compound.

2. The transition-rare earth metal-organic framework compound as described in claim 1, characterized in that, The molar ratio of Dy2O3, 4,4'(pyridine-3,5-dimethyl)dibenzoic acid and CuCl2·2H2O is 1:(1.1~1.3):

1.

3. Use of a transition-rare earth metal-organic framework compound as described in claim 1 or 2 in the catalytic preparation of 2-oxazolidinone from carbon dioxide.

4. The use as described in claim 3, characterized in that, The preparation method of the 2-oxazolidinone includes the following steps: After uniformly dispersing the transition-rare earth metal-organic framework compound, inorganic base and propargylamine derivative in an organic solvent, carbon dioxide was introduced at 80~100℃. After the reaction, the mixture was extracted with water and dichloromethane to obtain the 2-oxazolidinone. The propargylamine derivative is N-(4-methoxybenzyl)propyl-2-yn-1-amine.

5. The use as described in claim 4, characterized in that, The inorganic base is potassium hydroxide.

6. The use as described in claim 4, characterized in that, The organic solvent is dimethyl sulfoxide.

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