Chiral cationic rare earth-based metal organic framework material, preparation method thereof and carbon dioxide adsorption and conversion

Abstract

The invention relates to a preparation method of a chiral cationic rare-earth-based metal organic framework material based on an amphoteric carboxylic acid ligand and application of the chiral cationic rare-earth-based metal organic framework material in the aspects of carbon dioxide adsorption and conversion. The target product chiral cationic rare earth-based metal organic framework material is a porous material which is prepared through solvothermal and has a novel chiral crystal structure, and the framework of the porous material is positively charged. The target product has good stability and has a pore structure; carbon dioxide can be adsorbed, and the carbon dioxide can be converted into cyclic carbonate under a certain condition. The preparation method of the target product is simple, easy to operate and low in cost, and has potential application value in the directions of adsorption and conversion of carbon dioxide and the like.

Description

Technical Field

[0001] The invention relates to a preparation method of a chiral cationic rare earth-based metal organic framework material based on amphoteric carboxylic acid ligands and its application in carbon dioxide adsorption and conversion. Background Art

[0002] Metal-organic frameworks (MOFs) are a class of porous crystalline materials known for their remarkable molecular tunability. By combining inorganic clusters and organic ligands, MOFs can be designed into functional materials with different properties and structures. Based on the principles of network chemistry, potential MOFs structures can be predicted and synthesized by considering the possible geometries of inorganic and organic building blocks. However, it is extremely challenging to synthetically realize many of these predicted structures. During the MOF crystallization process, most inorganic building blocks are formed in situ under specific reaction conditions, but the specific synthesis conditions that lead to the formation of specific inorganic clusters must first be determined. On the other hand, organic ligands are generally considered to be relatively less variable building blocks with structural integrity and predictable coordination patterns. To date, most MOFs are built with highly symmetric ligands because highly symmetric building blocks have been shown to help form crystalline extended structures. Rather than maintaining geometric rigidity, rationally designed organic ligands can achieve structural flexibility and adapt to more topological structures by changing their geometry (such as torsion, bends, and dihedral angles of adjacent rings) to accommodate incorporation into the MOFs lattice. However, when the energy gained by forming coordination bonds cannot compensate for the energy cost of ligand deformation, the available configurational distortions of the ligands are also limited by the energy distribution of spatial distortions. Therefore, rational design of ligands plays an important role in designing the network chemistry of MOFs and expanding the diversity and complexity of MOFs with customized properties. Amphoteric carboxylic acid ligands can be used to synthesize cationic metal-organic frameworks with specific structures and properties.

[0003] Carbon dioxide adsorption and conversion technology is an integrated technology developed within the framework of carbon capture, utilization and storage. This technology is expected to significantly reduce the cost of emission reduction by directly reacting carbon dioxide from the emission source with co-reactants to convert it into downstream products. It is a new high-efficiency and low-energy carbon dioxide emission reduction technology. Carbon dioxide capture and utilization technology is a technology that captures carbon dioxide from industrial or combustion processes and converts it into new energy, new materials or other useful products. This technology can convert carbon dioxide into energy, such as synthetic natural gas, liquefied natural gas, methanol, diesel, aircraft fuel, etc.; it can also convert carbon dioxide into chemicals, such as ethylene glycol, formic acid, urea, etc.; in addition, carbon dioxide can also be used to produce materials such as concrete, paper, biomass, etc. Carbon dioxide capture and utilization technology can help reduce carbon dioxide emissions, mitigate climate change, and even turn waste into treasure. However, the adsorption and conversion of carbon dioxide using MOFs materials requires further research and development to reduce costs, improve efficiency and ensure its environmental sustainability. Summary of the invention

[0004] The purpose of the present invention is to provide a novel chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands with good stability, a preparation method thereof, and applications in the adsorption and conversion of carbon dioxide.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is as follows:

[0006] The invention discloses a preparation method of a chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands, comprising: adding amphoteric carboxylic acid ligand 1,1'-bis(4-carboxylphenyl)(4,4'-bipyridine) dichloride H2bcbp·2Cl, europium nitrate and lithium perchlorate into a mixed solution consisting of deacetonitrile, deionized water and concentrated nitric acid, stirring for 15 minutes, then transferring the mixture to a polytetrafluoroethylene reactor and heating for a period of time to obtain yellow block crystals, which is a chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands, and the molecular formula of the material is [Eu3(μ3-O)(bcbp)3(NO3)6]n·nClO4·6nH2O.

[0007] Furthermore, the molar ratio of the amphoteric carboxylic acid ligand, europium nitrate and lithium perchlorate is 2:5:10.

[0008] Furthermore, the volume ratio of acetonitrile, deionized water and concentrated nitric acid is 2:1:1.

[0009] Furthermore, the heating temperature is 140° C. and the reaction time is 4 days.

[0010] The present invention also provides a chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands prepared by the above synthesis method; the crystal structure is characterized by crystallization in the chiral space group R 32 and trigonal system.

[0011] The present invention also provides the application of the chiral cationic rare earth-based metal organic framework material based on amphoteric carboxylic acid ligands in the adsorption and conversion of carbon dioxide.

[0012] Furthermore, the target chiral cationic rare earth-based metal-organic framework material has a good adsorption effect on carbon dioxide.

[0013] Furthermore, the target chiral cationic rare earth-based metal organic framework material can catalyze the reaction of adsorbed carbon dioxide with co-reactants to convert it into downstream chemical products such as cyclic carbonates.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands of the present invention has a novel chiral structural feature and a positively charged skeleton, has good stability, and can be stored in the air for a long time;

[0016] The synthesis method of the present invention is simple and fast, low in cost, high in yield, high in repeatability, and easy to mass produce and popularize;

[0017] An example of a target chiral cationic rare earth-based metal organic framework material of the present invention has a three-dimensional chiral framework structure, the skeleton of which carries a positive charge, and the counter anion nitrate is filled in the pores; the target chiral cationic rare earth-based metal organic framework material has a good adsorption effect on carbon dioxide; and can catalyze the adsorbed carbon dioxide to react with a co-reactant to convert it into a downstream chemical product cyclic carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention has been generally described above, and the following drawings are used to illustrate specific embodiments of the present invention.

[0019] Figure 1 Shown is a diagram of the asymmetric unit in the target chiral metal-organic framework;

[0020] Figure 2 Shown is a three-dimensional crystal structure diagram of the target chiral metal organic framework (observed from the c-axis);

[0021] Figure 3 Shown is the PXRD characterization pattern of the target chiral metal organic framework;

[0022] Figure 4Shown is a thermal stability characterization profile of the target chiral metal-organic framework;

[0023] Figure 5 Shown is the CO2 adsorption isotherm of the target chiral metal organic framework at 273K;

[0024] Figure 6 Shown is the catalytic effect of the target chiral metal organic framework on the cycloaddition reaction of carbon dioxide; DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1 Preparation method of target chiral metal organic framework material

[0027] Amphoteric carboxylic acid ligand 1,1'-bis(4-carboxyphenyl)(4,4'-bipyridine) dichloride H2bcbp·2Cl (0.04mmol, 19mg), europium nitrate (44mg, 0.1mmol) and lithium perchlorate (21mg, 0.2mmol) were weighed and added into a mixture of acetonitrile (2mL), deionized water (2mL) and concentrated nitric acid (1mL). After stirring for 15 minutes, the mixture was heated to 140°C in a polytetrafluoroethylene reactor and reacted for 4 days to obtain yellow block crystals, which are chiral cationic rare earth metal organic framework materials based on amphoteric carboxylic acid ligands, and its molecular formula is [Eu3(μ3-O)(bcbp)3(NO3)6]n·nClO4·6nH2O.

[0028] Example 2 Structural Characterization of Target Chiral Metal-Organic Framework Material

[0029] The crystal structure of the target chiral metal organic framework material was obtained by analyzing the X-ray single crystal diffraction data. The X-ray single crystal diffraction data showed that the target chiral cationic rare earth-based metal organic framework material crystallized in the chiral space group R 32 and trigonal system; its asymmetric unit contains 1 Eu 3+ ion, 1 ligand bcbp, two coordinated nitrate ions, 1 μ3-O with 1 / 3 occupancy, and 1 perchlorate ion with 1 / 3 occupancy ( Figure 1 ); μ3-O and 3 Eu 3+ The ions form the Eu3(μ3-O) structural unit; the adjacent Eu 3+The ions are connected to six carboxyl groups in a bidentate single-linked manner by sharing a μ3-O, forming a 6-linked [Eu3(μ3-O)(COO)6] secondary structural unit; 8 secondary structural units are connected to 12 linear bcbp ligands to form a three-dimensional pcu framework with positive charges ( Figure 2 ); The non-centrosymmetric arrangement of the bcbp ligands around the triangular prism-shaped Eu3(μ3-O) structural unit is the key factor leading to the intrinsic chirality of the target cationic rare earth-based metal organic framework material. X-ray powder diffraction data show that the theoretical and experimental data of the target chiral metal organic framework material are consistent ( Figure 3 ), indicating that the target material has good sample purity and crystallinity.

[0030] Example 3 Thermal stability of target chiral metal organic framework materials

[0031] The thermal stability of the target chiral metal organic framework material is characterized by heating the sample to 800°C in a nitrogen environment using a thermogravimetric analyzer, and judging its stable temperature range by the weight loss of the sample during heating. Figure 4 As shown, the skeleton structure of the target material can be stable up to 320°C; after that, the main framework structure of the target material begins to collapse.

[0032] Example 4 Adsorption performance of target chiral metal organic framework material for carbon dioxide

[0033] The target chiral metal organic framework material exhibits good carbon dioxide adsorption performance, and its adsorption capacity for carbon dioxide is 1.37mmol at 273K and 1 atmosphere. . g -1 ( Figure 5 ); attributed to the pore structure of the target material and the pore environment containing pyridinium.

[0034] Example 5 Conversion performance of target chiral metal organic framework material to carbon dioxide

[0035] 1mmol of the ground target chiral metal organic framework material was used as a reaction catalyst to catalyze the conversion of carbon dioxide at different temperatures. The reactant was selected as 2mmol of glycidyl phenyl ether and 1bar of carbon dioxide. The reaction was carried out at 40℃ and 60℃ for 36 hours respectively. The product was determined by nuclear magnetic resonance hydrogen spectrum. The yield of cyclic carbonate reached 75% and 95% respectively ( Figure 6 ); indicating that the target chiral metal organic framework material has a good cycloaddition catalytic effect on the cycloaddition reaction of carbon dioxide. At the same time, at 60°C, the catalytic conversion rate of the target chiral metal organic framework material far exceeds the catalytic conversion rate of the alkaline catalyst (potassium carbonate, n-butyl potassium and potassium hydroxide) and the amphoteric carboxylic acid ligand H2bcbp·2Cl.

Claims

1. A method for preparing a chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands, characterized in that: include: Amphoteric carboxylic acid ligand 1,1'-bis(4-carboxyphenyl)(4,4'-bipyridine) dichloride H2bcbp·2Cl, europium nitrate and lithium perchlorate are added to a mixed solution consisting of acetonitrile, deionized water and concentrated nitric acid, stirred for 15 minutes, transferred to a polytetrafluoroethylene reactor, heated to 140°C and reacted for 4 days to obtain yellow block crystals, which are chiral cationic rare earth-based metal organic framework materials based on amphoteric carboxylic acid ligands, and have a molecular formula of [Eu3(μ3-O)(bcbp)3(NO3)6]n·nClO4·6nH2O; wherein the molar ratio of the above-mentioned amphoteric carboxylic acid ligand, europium nitrate and lithium perchlorate is 2:5:10; and the volume ratio of the acetonitrile, deionized water and concentrated nitric acid is 2:1:

1.

2. The chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands as claimed in claim 1, crystallized in chiral space group R 32 and trigonal system; X-ray single crystal diffraction data show that its asymmetric unit contains 1 Eu 3+ ions, one ligand bcbp, two coordinated nitrate ions, one μ3-O with an occupancy of 1 / 3, and one perchlorate ion with an occupancy of 1 / 3; μ3-O and 3 Eu 3+ The ions form the Eu3(μ3-O) structural unit; the adjacent Eu 3+ The ions are connected to six carboxyl groups in a bidentate single-linked manner by sharing a μ3-O, forming a 6-connected [Eu3(μ3-O)(COO)6] secondary structure unit; 8 secondary structure units are connected to 12 linear bcbp ligands to form a three-dimensional pcu framework with positive charge; the non-centrosymmetric arrangement of bcbp ligands around the triangular prism-shaped Eu3(μ3-O) structure unit is the key factor leading to the inherent chirality of the target cationic rare earth-based metal-organic framework material.

3. The chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands as described in claim 2 has good thermal stability; thermogravimetric data show that its skeleton structure can be stabilized to 320°C.

4. Application of the stable chiral cationic rare earth metal organic framework material based on amphoteric carboxylic acid ligands as described in claim 3 in the adsorption and conversion of carbon dioxide.

5. The use according to claim 4, characterized in that: The target chiral cationic rare earth metal organic framework material has a good adsorption effect on carbon dioxide. Its adsorption capacity for carbon dioxide at 273K and 1 atmosphere is 1.37mmol. . g -1 ; and under certain conditions, carbon dioxide can be converted into cyclic carbonates.

6. The use according to claim 5, characterized in that: 1 mmol of the ground target chiral metal-organic framework material was used as a reaction catalyst to catalyze the conversion of carbon dioxide at different temperatures; the reactant glycidyl phenyl ether reacted with carbon dioxide at 40°C and 60°C for 36 hours, respectively, and the yields reached 75% and 95%, respectively; this shows that the target chiral cationic rare earth-based metal-organic framework material has a good cycloaddition catalytic effect on the cycloaddition reaction of carbon dioxide.

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