Lanthanum-based MOF crystal material, preparation method and application method in natural gas decarbonization

Abstract

The present invention relates to a lanthanum-based MOF crystal material, a preparation method and an application method in natural gas decarbonization. The chemical formula of the lanthanum-based MOF crystal material is: (C 54 H 43 La3N3O 22 3‑ ) n ,1(C2H8N1 1+ ), the organic ligand is 3,3',5'-biphenyltricarboxylic acid; the structure of the lanthanum-based MOF crystal material is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and the three-dimensional porous structure has metal vacancies; La in the lanthanum-based MOF crystal material 3+ The ions have a coordination geometry. The metal vacancies, La 3+ Ionic metal sites, Me2NH2 + The combination of lanthanum-based MOF crystal materials and three-dimensional porous structure gives them excellent adsorption capacity, which can be used as a catalyst to catalyze the cycloaddition reaction of CO2 and epoxides. It shows good catalytic performance for the carbon dioxide cycloaddition reaction of epoxides. The reaction conditions are mild, the energy consumption is low, and the cost is low, thus achieving the purpose of continuous flow separation of CH4 / CO2 and converting the captured CO2 into valuable final products.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal organic framework materials, and specifically relates to a lanthanum-based MOF crystal material, a preparation method and an application method in natural gas decarbonization. Background Art

[0002] Natural gas is a high-quality fuel and chemical feedstock. However, extracted natural gas often contains excessive amounts of CO2, which can reduce the calorific value of natural gas and corrode pipelines and equipment. Before natural gas is delivered to users, CO2 must be removed. Common removal methods include CO2 amine chemical adsorption, cryogenic distillation, and solvent extraction. These technologies suffer from high energy consumption and solvent waste. Metal-organic frameworks (MOFs), due to their highly ordered pore structure and tunable chemical properties, offer broad application prospects in gas storage, adsorption separation, and catalysis, and are expected to be used for the purification of natural gas with high CO2 content. Directly discharging the CO2 in the permeate gas would inevitably increase carbon emissions.

[0003] The cycloaddition reaction of CO₂ with epichlorohydrin to produce propylene chlorocarbonate offers opportunities for addressing environmental challenges and maximizing resource utilization. Currently, catalysts such as ionic liquids and certain MOF materials have been developed for this reaction. However, existing catalysts for converting CO₂ into high-value chemical products require high pressure and temperature, resulting in high energy consumption, solvent waste, and excessive cost. Therefore, the development of MOF materials that can combine natural gas purification with CO₂ capture and utilization has become a pressing technical challenge. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention provides a lanthanum-based MOF crystal material, a preparation method, and an application method for natural gas decarbonization. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0005] The embodiment of the present invention provides a lanthanum-based MOF crystal material, the chemical formula of the lanthanum-based MOF crystal material is: (C 54 H 43 La3N3O 22 3- ) n ,1(C2H8N1 1+ ), the organic ligand is 3,3',5'-biphenyltricarboxylic acid;

[0006] The structure of the lanthanum-based MOF crystal material is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and the three-dimensional porous structure has metal vacancies;

[0007] The lanthanum-based MOF crystal material contains La 3+ Ions have coordination geometry.

[0008] In one embodiment of the present invention, the crystal structure of the lanthanum-based MOF crystal material belongs to the monoclinic system, and the space group is The unit cell parameters are α=90°, β=90°, γ=120°.

[0009] In one embodiment of the present invention, there is an asymmetric unit in the three-dimensional porous structure, and the asymmetric unit is composed of a La 3+ ion, an organic ligand 3,3',5'-biphenyltricarboxylic acid, a coordinated N,N-dimethylformamide molecule, and one-third μ3-OH - and one third Me2NH2 + Cation composition, the La 3+ Ions pass through oxygen atoms and the 3,3',5'-biphenyltricarboxylic acid, the N,N-dimethylformamide molecule, the μ3-OH - Connect respectively, the Me2NH2 + The cation is attracted to the oxygen atom of the 3,3',5'-biphenyltricarboxylic acid by electrostatic forces.

[0010] In one embodiment of the present invention, the three-dimensional porous structure is formed by adjacent trinuclear metal clusters [La3(COO)9(μ3-OH)] connected along the target direction through the organic ligand; the trinuclear metal cluster [La3(COO)9(μ3-OH)] is composed of three La 3+ Between ions through μ3-OH - Bond formation; each La 3+ The ionic center presents a nine-coordinate geometric structure, wherein the nine coordinated geometric structures are seven carboxyl oxygen atoms from the organic ligand, one oxygen atom from the N,N-dimethylformamide molecule and one oxygen atom from μ3-OH. - 1 oxygen atom.

[0011] In one embodiment of the present invention, the carboxyl oxygen atom in the organic ligand has three coordination modes: μ3-η 1 :η 2 、μ2-η 1 :η 1 and μ1-η 1 :η 1 .

[0012] Another embodiment of the present invention provides a method for preparing a lanthanum-based MOF crystal material, which is used to prepare the lanthanum-based MOF crystal material as described in the above embodiment, comprising the steps of:

[0013] S1, dissolving 3,3',5'-biphenyltricarboxylic acid and benzoic acid in N,N-dimethylformamide to obtain a first solution, dissolving lanthanum chloride heptahydrate in water to obtain a second solution, and mixing the first solution and the second solution to obtain a mixed solution;

[0014] S2. Using a hydrothermal synthesis method, the mixed solution is subjected to a thermal reaction to obtain a lanthanum-based MOF crystal material.

[0015] In one embodiment of the present invention, the molar ratio of the 3,3',5'-biphenyltricarboxylic acid to the benzoic acid is 1:1;

[0016] The molar ratio of the 3,3',5'-biphenyltricarboxylic acid to the lanthanum chloride heptahydrate is 1:1;

[0017] The ratio of the 3,3',5'-biphenyltricarboxylic acid, the benzoic acid, and the N,N-dimethylformamide is 0.1 mmol: 0.1 mmol: 3 ml;

[0018] The ratio of the lanthanum chloride heptahydrate to the water is 0.1 mmol:2 ml.

[0019] In one embodiment of the present invention, step S2 includes:

[0020] The mixed solution is heated to 120-180°C at a heating rate of 0.5-1.5°C / min using a hydrothermal synthesis method, and the reaction time is 48-96h at 120-180°C, and then cooled to room temperature at a rate of 0.05-0.15°C / min to obtain the lanthanum-based MOF crystalline material.

[0021] Another embodiment of the present invention provides a method for using a lanthanum-based MOF crystal material in natural gas decarbonization, comprising: placing an epoxide, a catalyst, and a co-catalyst in an environment containing carbon dioxide and heating them, so that the epoxide and the carbon dioxide undergo an addition reaction to remove the carbon dioxide;

[0022] The catalyst uses the lanthanum-based MOF crystal material described in the above embodiment.

[0023] In one embodiment of the present invention, the epoxide includes epichlorohydrin, and the co-catalyst includes tetrabutylammonium bromide; the ratio of the epoxide, the catalyst, and the co-catalyst is: 21 mmol: 70 mg: 0.21 mmol;

[0024] The reaction temperature of the addition reaction is 50-70° C., and the reaction time is 32-60 h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The lanthanum-based MOF crystal material of the present invention is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and the three-dimensional porous structure has metal vacancies. 3+ The ion has a coordination geometry to form La 3+ Ionic metal sites, metal vacancies, La 3+ Ionic metal sites, Me2NH2 + The combination of the lanthanum-based MOF crystal material with a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels gives it excellent adsorption capacity, and can be used as a catalyst to catalyze the cycloaddition reaction of CO2 and epoxides. It exhibits good catalytic performance for the carbon dioxide cycloaddition reaction of epoxides, and the reaction conditions are mild, with low energy consumption and low cost, achieving the purpose of continuous flow separation of CH4 / CO2 and converting the captured CO2 into valuable final products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a three-dimensional porous framework of a lanthanum-based MOF crystal material according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic structural diagram of an organic ligand mentioned in an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of an asymmetric unit of a lanthanum-based MOF crystal material provided in an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of a trinuclear metal cluster [La3(COO)9(μ3-OH)] provided in an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of a synthesis process of a lanthanum-based MOF crystal material provided in an embodiment of the present invention;

[0032] Figure 6 BET test curve of La-MOF provided in an embodiment of the present invention;

[0033] Figure 7 The pore size distribution diagram of La-MOF provided in an embodiment of the present invention;

[0034] Figure 8 FT-IR characterization diagram of La-MOF provided in an embodiment of the present invention;

[0035] Figure 9 The XRD pattern of La-MOF provided in an embodiment of the present invention;

[0036] Figure 10 A morphology diagram of La-MOF provided in an embodiment of the present invention;

[0037] Figure 11 The particle size distribution diagram of La-MOF provided in an embodiment of the present invention;

[0038] Figure 12 Schematic diagram of the mechanism of La-MOF catalytic conversion of CO2 provided in an embodiment of the present invention;

[0039] Figure 13 The adsorption isotherm of La-MOF provided in an embodiment of the present invention;

[0040] Figure 14 Adsorption selectivity diagram of La-MOF provided by an embodiment of the present invention;

[0041] Figure 15 This is a comparison chart of the yields of different catalytic systems provided in the examples of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0043] Example 1

[0044] See Figure 1 , Figure 1 This is a schematic diagram of a three-dimensional porous framework of a lanthanum-based MOF crystal material mentioned in an embodiment of the present invention.

[0045] The chemical formula of the lanthanum-based MOF (La-MOF) crystal material provided in this embodiment is: (C 54 H 43 La3N3O 22 3- ) n ,1(C2H8N1 1+ ), the organic ligand is 3,3',5'-biphenyltricarboxylic acid, named FMU-101.

[0046] See Figure 2 , Figure 2 This is a schematic structural diagram of an organic ligand mentioned in an embodiment of the present invention.

[0047] The structure of the lanthanum-based MOF crystal material is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and there are metal vacancies in the three-dimensional porous structure.

[0048] Specifically, a metal vacancy refers to a defect structure in a crystal, where one or more atoms are missing from an atomic position in the crystal, forming a vacancy or hole. In a crystal structure, metal atoms are typically present in the vacant sites of the crystal lattice, and a metal vacancy is the unoccupied position within these vacancies.

[0049] La in lanthanum-based MOF crystal materials 3+ The ions have a coordination geometry that forms metal sites.

[0050] Specifically, the metal site refers to the central atom in the coordination compound formed by the metal ion and one or more coordination groups. 3+ ions have a coordination geometry, forming La 3+ Ionic metal sites.

[0051] Furthermore, from the perspective of framework connection construction, the crystal structure of lanthanum-based MOF crystal materials belongs to the monoclinic system, and the space group is The unit cell parameters are α=90°, β=90°, γ=120°.

[0052] See Figure 3 , Figure 3 A schematic diagram of an asymmetric unit of a lanthanum-based MOF crystal material provided in an embodiment of the present invention.

[0053] Lanthanum-based MOF crystal material FMU-101 is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels. There is an asymmetric unit in the three-dimensional framework of FMU-101. The asymmetric unit consists of a La 3+ ion, an organic ligand 3,3',5'-biphenyltricarboxylic acid (C 15 H 10 O6), a coordinated N,N-dimethylformamide (DMF) molecule, one-third of μ3-OH - and one third Me2NH2 + Cation composition. Among them, La 3+ The ion is connected to 3,3',5'-biphenyltricarboxylic acid, N,N-dimethylformamide molecule, μ3-OH-, Me2NH2 respectively through oxygen atoms + The cation is attracted to the oxygen atom of 3,3',5'-biphenyltricarboxylic acid by electrostatic forces.

[0054] In the above asymmetric unit, the dimethylamine cation (Me2NH2 + ) is composed of DMF in the solvent and free ions in the solution. The dimethylamine cation and the negatively charged unsaturated sites are attracted by electrostatic attraction. Furthermore, the asymmetric unit is not a planar structure, but a distorted structure.

[0055] See Figure 4 , Figure 4 Schematic diagram of a trinuclear metal cluster [La3(COO)9(μ3-OH)] provided in an embodiment of the present invention.

[0056] In FMU-101, the three-dimensional porous structure is formed by adjacent trinuclear metal clusters [La3(COO)9(μ3-OH)] connected along the target direction through organic ligands; the trinuclear metal cluster [La3(COO)9(μ3-OH)] consists of three La 3+ Between ions through μ3-OH - Bonding is formed. The target direction may be the c-axis (where the a-axis is horizontal, the b-axis is vertical, and the c-axis is perpendicular to the paper).

[0057] Specifically, three La 3+ ions, two adjacent La 3+ ions are μ3-OH - Bonded together, three La 3+ The ion is replaced by a μ3-OH - Bonding to form a trinuclear metal cluster [La3(COO)9(μ3-OH)]. Adjacent trinuclear metal clusters are connected along the c-axis by organic ligands to form a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, such as Figure 1 It can be understood that since the asymmetric unit is a non-planar twisted structure, the asymmetric unit of the twisted structure further extends in all directions according to the repetition of the space group, forming a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels.

[0058] Furthermore, each La 3+ The ionic center presents a nine-coordinate geometric structure, which includes seven carboxyl oxygen atoms from organic ligands, one oxygen atom from N,N-dimethylformamide molecule and one oxygen atom from μ3-OH-.

[0059] Furthermore, in the three-dimensional organic framework of FMU-101, the carboxylic acid groups in the ligands exhibit three coordination modes: μ3-η 1 :η 2 ,μ2-η 1 :η 1 and μ1-η 1 :η 1 Among them, η n The n in μ represents the number of atoms coordinated with the metal atom. Generally speaking, these coordinated atoms are directly connected. n For bridging ligands, the subscript n indicates how many metals a ligand is connected to. Generally speaking, if n = 2, it can be omitted.

[0060] The lanthanum-based MOF crystal material of this embodiment is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and there are metal vacancies in the three-dimensional porous structure. 3+ The ion has a coordination geometry to form La 3+Ionic metal sites, metal vacancies, La 3+ Ionic metal sites, Me2NH2 + The combination of the lanthanum-based MOF crystal material with a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels gives it excellent adsorption capacity, and can be used as a catalyst to catalyze the cycloaddition reaction of CO2 and epoxides. It exhibits good catalytic performance for the carbon dioxide cycloaddition reaction of epoxides, and the reaction conditions are mild, with low energy consumption and low cost, achieving the purpose of continuous flow separation of CH4 / CO2 and converting the captured CO2 into valuable final products.

[0061] Example 2

[0062] On the basis of Example 1, this example provides a method for preparing a lanthanum-based MOF crystal material, which is used to prepare the lanthanum-based MOF crystal material of Example 1.

[0063] See Figure 5 , Figure 5 A schematic diagram of a synthesis process of a lanthanum-based MOF crystal material provided in an embodiment of the present invention, the synthesis process comprising:

[0064] S1. Dissolving 3,3',5'-biphenyltricarboxylic acid and benzoic acid in N,N-dimethylformamide to obtain a first solution, dissolving lanthanum chloride heptahydrate in water to obtain a second solution, and mixing the first solution and the second solution to obtain a mixed solution.

[0065] Specifically, the organic ligand 3,3',5'-biphenyltricarboxylic acid and the auxiliary ligand benzoic acid are simultaneously dissolved in N,N-dimethylformamide (DMF) to form a first solution, and lanthanum chloride heptahydrate (LaCl3·7H2O) is dissolved in H2O to form a second solution. After the first and second solutions are thoroughly dissolved under ultrasonic conditions, the dissolved solutions are mixed to form a mixed solution.

[0066] Specifically, the molar ratio of the organic ligand 3,3',5'-biphenyltricarboxylic acid to the auxiliary ligand benzoic acid is 1:1, and the molar ratio of the organic ligand 3,3',5'-biphenyltricarboxylic acid to lanthanum chloride heptahydrate is 1:1. The amount of DMF added is 3 ml of DMF for every 0.1 mmol of 3,3',5'-biphenyltricarboxylic acid and every 0.1 mmol of benzoic acid, i.e., the ratio of 3,3',5'-biphenyltricarboxylic acid, benzoic acid, and N,N-dimethylformamide is 0.1 mmol:0.1 mmol:3 ml. The amount of H2O added is 2 ml of H2O for every 0.1 mmol of lanthanum chloride heptahydrate, i.e., the ratio of lanthanum chloride heptahydrate to water is 0.1 mmol:2 ml.

[0067] S2. Using a hydrothermal synthesis method, the mixed solution is subjected to a thermal reaction to obtain a lanthanum-based MOF crystal material.

[0068] Specifically, the mixed solution is sealed and placed in an oven, and a lanthanum-based MOF crystal material is obtained after a solvent thermal reaction. Further, a hydrothermal synthesis method is used to seal the mixed solution and place it in an oven, and then the mixed solution is heated to 120-180°C at a heating rate of 0.5-1.5°C / min, and the reaction time is 48-96h at 120-180°C, and then cooled to room temperature at a rate of 0.05-0.15°C / min, and then the product is washed and dried to obtain a lanthanum-based MOF crystal material. Exemplarily, the mixed solution is heated to 150°C at a heating rate of 1°C / min, and the reaction time is 72h at 150°C, and then cooled to room temperature at a rate of 0.1°C / min.

[0069] Based on the above preparation method, this example uses a hydrothermal synthesis method to prepare La-MOF and test the performance of La-MOF.

[0070] The hydrothermal synthesis method for preparing La-MOF mainly includes the following experimental contents:

[0071] 3,3',5'-Biphenyltricarboxylic acid (0.1 mmol, 28.6 mg) and benzoic acid (0.1 mmol, 12.2 mg) were dissolved in 3 mL of DMF, and LaCl3·7H2O (0.1 mmol, 37.1 mg) was dissolved in 2 mL of H2O. The two solutions were sonicated until the solids dissolved. After mixing, the two solutions were transferred to a Teflon-lined stainless steel reactor, heated to 150°C over 2 hours, maintained at 150°C for 72 hours, and then cooled to room temperature at a rate of 0.1°C / minute. The hexagonal crystals were collected and washed several times with DMF, then immersed in DMF, decanted and replenished with DMF three times a day for three consecutive days, and finally dried under vacuum at room temperature for 6 hours to obtain La-MOF.

[0072] See Figure 6 , Figure 6 The BET test curve of La-MOF provided in the embodiment of the present invention. After calculation, it can be obtained that the specific surface area (Brunauer-Emmett-Teller, BET) of La-MOF is 236.16m 2 g-1.

[0073] See Figure 7 , Figure 7 The pore size distribution diagram of La-MOF provided in the embodiment of the present invention. The pore size distribution span of La-MOF is approximately This facilitates the unimpeded passage of gas molecules; data analysis demonstrates the successful design of MOF materials with persistent porosity.

[0074] See Figure 8 , Figure 8 FT-IR characterization of La-MOF provided in the embodiment of the present invention. 780cm -1 The adsorption band at 1400 cm represents the partial distribution of COO- groups in [1,1'-biphenyl]-3,3',5-tricarboxylic acid. -1 (COO-symmetric vibration) and 1600cm -1 The adsorption band at 3410 cm (COO- asymmetric vibration) highlights the presence of CH and COO- groups in La-MOF. -1 (NH stretching vibration) and 1360 cm -1 The single band of (CN stretching vibration) provides evidence for the presence of dimethylamine cation in the structure.

[0075] See Figure 9 , Figure 9 The XRD pattern of La-MOF provided in the embodiment of the present invention is shown in FIG. Figure 9 The diffraction peaks of La-MOF observed in the experiment were consistent with those of single crystal simulations, confirming the material's continued crystallinity and unchanged structure under different pH conditions, highlighting its chemical stability.

[0076] See Figure 10 , Figure 10 This is a morphology diagram of La-MOF provided in an embodiment of the present invention. Figure 10 It shows that La-MOF exhibits a uniformly dispersed hexagonal prism structure.

[0077] See Figure 11 , Figure 11 The particle size distribution diagram of La-MOF provided in an embodiment of the present invention. As can be seen from the figure, the particle size of La-MOF is about 480nm.

[0078] In this example, organic ligand 3,3',5'-biphenyltricarboxylic acid and metallic lanthanum were selected to prepare lanthanum-based MOF crystal materials by solvent thermal method. The preparation method is simple and easy to implement. The obtained lanthanum-based MOF structure contains metal vacancies. Metal vacancies, La 3+ Ionic metal sites, Me2NH2 + The combination of a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels gives the lanthanum-based MOF crystal material excellent adsorption capacity, which can adsorb carbon dioxide in natural gas.

[0079] Example 3

[0080] Based on Examples 1 and 2, this example provides a method for applying a lanthanum-based MOF crystal material in natural gas decarbonization. Specifically, the lanthanum-based MOF crystal material FMU-101 can be used as a catalyst in the carbon dioxide cycloaddition catalytic reaction of an epoxide. Specifically, the epoxide, catalyst, and co-catalyst are placed in a carbon dioxide-containing environment and heated, causing the epoxide and carbon dioxide to undergo an addition reaction to remove the carbon dioxide. The catalyst is the lanthanum-based MOF crystal material FMU-101 of Example 1.

[0081] Specifically, the epoxide includes epichlorohydrin, and the co-catalyst includes tetrabutylammonium bromide (TBAB); the ratio of epoxide, catalyst, and co-catalyst is 21 mmol:70 mg:0.21 mmol; the reaction temperature of the addition reaction is 50-70° C., and the reaction time is 32-60 hours. Exemplarily, the reaction temperature of the addition reaction is 60° C., and the reaction time is 48 hours.

[0082] See Figure 12 , Figure 12 Schematic diagram of the process of La-MOF catalytic conversion of CO2 provided in an embodiment of the present invention. Specifically, the reaction equation of epichlorohydrin and CO2 is:

[0083]

[0084] Specifically, after La-MOF is prepared, the corresponding separation performance test is performed by the following method:

[0085] 21 mmol of epoxide, 70 mg of catalyst and 0.21 mmol of co-catalyst were placed in a 10 ml flask with a magnetic stirrer. CO2 gas was introduced into the flask for 30 minutes, and pure CO2 gas was completely replaced into the reaction flask. After the gas exchange was completed, a balloon filled with CO2 gas was connected to ensure sufficient CO2 supply during the reaction. Finally, the reaction flask was placed in a 60°C water bath for 48 hours and the reaction was continued. 1 The product structure was analyzed by HNMR (deuterated DMSO).

[0086] See Figure 13 , Figure 13 The adsorption isotherm of La-MOF provided in the embodiment of the present invention is shown in the figure. The adsorption isotherm of FMU-101 on CO2 (109.5 cm2) at 273K is shown in the figure. 3 g -1 ) showed excellent adsorption performance, and its adsorption capacity was CH4 (11.4 cm 3 g -1 ) is 9.6 times.

[0087] See Figure 14 , Figure 14This is a diagram of the adsorption selectivity of La-MOF provided by an embodiment of the present invention. Figure 14 The selectivity of La-MOF for CO2 / CH4 mixtures at 273 K and 298 K was demonstrated. For an equimolar CO2 / CH4 mixture, the selectivity of FMU-101 at 1 atm was 1.6, indicating the high selectivity of FMU-101a for CO2 adsorption.

[0088] See Figure 15 , Figure 15 The yield comparison chart of different catalytic systems provided in the embodiments of the present invention is shown in FIG. Figure 15 As shown, the catalytic efficiency of La-MOF exhibits significantly higher levels when juxtaposed with metal salts and ligands.

[0089] In this embodiment, the lanthanum-based MOF can be used as a catalyst to catalyze the cycloaddition reaction of CO2 and epichlorohydrin to prepare propylene chlorocarbonate, showing good catalytic performance for the carbon dioxide cycloaddition reaction of epoxides. In addition, the reaction conditions are mild, the energy consumption is low, and the amount of solvent used is small. The continuous flow separation of CH4 / CO2 and the conversion of captured CO2 into valuable end products are achieved, providing opportunities for solving environmental problems and resource utilization.

[0090] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A lanthanum-based MOF crystal material, characterized in that: The chemical formula of the lanthanum-based MOF crystal material is: (C 54 H 43 La3N3O 22 3- ) n ,1(C2H8N1 1+ ), the organic ligand is 3,3',5'-biphenyltricarboxylic acid; The structure of the lanthanum-based MOF crystal material is a three-dimensional porous structure with regular unidirectional hexagonal honeycomb channels, and the three-dimensional porous structure has metal vacancies; The lanthanum-based MOF crystal material contains La 3+ Ions have coordination geometry.

2. The lanthanum-based MOF crystal material according to claim 1, characterized in that The crystal structure of the lanthanum-based MOF crystal material belongs to the monoclinic system, and the space group is The unit cell parameters are α=90°, β=90°, γ=120°.

3. The lanthanum-based MOF crystal material according to claim 1, characterized in that There is an asymmetric unit in the three-dimensional porous structure, and the asymmetric unit consists of a La 3+ ion, an organic ligand 3,3',5'-biphenyltricarboxylic acid, a coordinated N,N-dimethylformamide molecule, and one-third μ3-OH - and one third Me2NH2 + Cation composition, the La 3+ Ions pass through oxygen atoms and the 3,3',5'-biphenyltricarboxylic acid, the N,N-dimethylformamide molecule, the μ3-OH - Connect respectively, the Me2NH2 + The cation is attracted to the oxygen atom of the 3,3',5'-biphenyltricarboxylic acid by electrostatic forces.

4. The lanthanum-based MOF crystalline material according to claim 1, characterized in that The three-dimensional porous structure is formed by connecting adjacent trinuclear metal clusters [La3(COO)9(μ3-OH)] along the target direction through the organic ligand; the trinuclear metal cluster [La3(COO)9(μ3-OH)] is composed of three La 3+ Between ions through μ3-OH - Bond formation; each La 3+ The ionic center presents a nine-coordinate geometric structure, wherein the nine coordinated geometric structures are seven carboxyl oxygen atoms from the organic ligand, one oxygen atom from the N,N-dimethylformamide molecule and one oxygen atom from μ3-OH. - 1 oxygen atom.

5. The lanthanum-based MOF crystal material according to claim 4, characterized in that The carboxyl oxygen atom in the organic ligand has three coordination modes: μ3-η 1 :η 2 、μ2-η 1 :η 1 and μ1-η 1 :η 1 .

6. A method for preparing a lanthanum-based MOF crystal material, characterized in that: The method for preparing the lanthanum-based MOF crystal material according to any one of claims 1 to 5 comprises the following steps: S1, dissolving 3,3',5'-biphenyltricarboxylic acid and benzoic acid in N,N-dimethylformamide to obtain a first solution, dissolving lanthanum chloride heptahydrate in water to obtain a second solution, and mixing the first solution and the second solution to obtain a mixed solution; S2. Using a hydrothermal synthesis method, the mixed solution is subjected to a thermal reaction to obtain a lanthanum-based MOF crystal material.

7. The method for preparing the lanthanum-based MOF crystal material according to claim 6, characterized in that: The molar ratio of the 3,3',5'-biphenyltricarboxylic acid to the benzoic acid is 1:1; The molar ratio of the 3,3',5'-biphenyltricarboxylic acid to the lanthanum chloride heptahydrate is 1:1; The ratio of the 3,3',5'-biphenyltricarboxylic acid, the benzoic acid, and the N,N-dimethylformamide is 0.1 mmol: 0.1 mmol: 3 ml; The ratio of the lanthanum chloride heptahydrate to the water is 0.1 mmol:2 ml.

8. The method for preparing the lanthanum-based MOF crystal material according to claim 6, characterized in that: Step S2 includes: The mixed solution is heated to 120-180°C at a heating rate of 0.5-1.5°C / min using a hydrothermal synthesis method, and the reaction time is 48-96h at 120-180°C, and then cooled to room temperature at a rate of 0.05-0.15°C / min to obtain the lanthanum-based MOF crystalline material.

9. A method for applying a lanthanum-based MOF crystal material in natural gas decarbonization, characterized in that: include: placing an epoxide, a catalyst, and a co-catalyst in an environment containing carbon dioxide and heating the epoxide so that an addition reaction occurs between the epoxide and the carbon dioxide to remove the carbon dioxide; The catalyst adopts the lanthanum-based MOF crystal material according to any one of claims 1 to 5.

10. The method for using the lanthanum-based MOF crystal material in natural gas decarbonization according to claim 9, characterized in that: The epoxide includes epichlorohydrin, and the co-catalyst includes tetrabutylammonium bromide; the ratio of the epoxide, the catalyst, and the co-catalyst is: 21 mmol: 70 mg: 0.21 mmol; The reaction temperature of the addition reaction is 50-70° C., and the reaction time is 32-60 h.

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