Preparation method and application of Cu / Eu bimetal MOF (Metal Organic Framework) material with mixed valence states

Abstract

The invention belongs to the field of crystalline materials, and relates to a CuI / CuII mixed valence bimetallic Cu / Eu-MOF catalyst, a preparation method and catalytic application. The catalyst is a metal-organic framework catalyst constructed based on pyridine carboxylic acid ligands and copper / europium bimetal ions, the chemical formula is {[(CuI3I2) 4 (CuII2EuIII) 3L24 (H2O) 6] (NO3)} n, L is an organic ligand 5-chloronicotinic acid, and the catalyst is specifically formed by further connecting nanocages assembled by two different cluster base nodes of [Cu3I2] and [Cu2Eu (COO) 8] through organic ligands, the catalyst has complex mixed valence and Cu / Eu bimetallic synergistic catalytic sites, is high in porosity and large in specific surface area, is high in conversion yield of catalyzing reaction of CO2 and terminal alkynol compounds under mild conditions, and can be recycled for multiple times.

Description

Technical Field

[0001] This application belongs to the field of crystalline materials and relates to metal-organic framework materials. Specifically, it relates to a mixed-valence bimetallic Cu / Eu-MOF material, its preparation method, and its catalytic application. Background Technology

[0002] With the global climate change situation becoming increasingly severe, carbon dioxide (CO2) emission reduction and resource utilization have become one of the core pathways to achieving carbon neutrality. Carbon Dioxide Utilization (CDU) not only helps mitigate the greenhouse effect but also converts CO2 into high-value-added chemicals such as methanol, formic acid, and cyclic carbonates, effectively promoting the development of carbon cycling and green industries.

[0003] While traditional carbon capture and storage (CCS) technology can effectively reduce emissions, it faces challenges such as high costs and uncertain long-term safety.

[0004] α-Methylene cyclic carbonates are important intermediates in organic synthesis and medicinal chemistry. The carboxylic acid cyclization reaction of propargyl alcohol and carbon dioxide successfully introduces unsaturated methylene functional groups while preparing α-methylene cyclic carbonates, making them more favorable intermediates for subsequent reactions. However, CO2, due to its unique... Electron-delocalized structures possess high chemical inertness and thermodynamic stability. In catalytic conversion, they typically require reactions under conditions such as noble metal catalysts, high pressure, high temperature, and co-catalysts, which leads to increased energy consumption and reaction costs.

[0005] Based on this, the present invention develops a Cu Ⅰ / Cu Ⅱ Mixed valence states and Cu / Eu bimetallic MOF materials were developed to achieve efficient catalysis of the cycloaddition reaction of terminal alkynols with carbon dioxide under mild conditions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a metal-organic framework catalyst based on pyridine carboxylic acid ligands and copper / europium bimetallic ions, and to solve the problems mentioned in the background art through the following technical solutions.

[0007] The primary objective of this application is to provide a metal-organic framework catalyst based on pyridine carboxylic acid ligands and copper / europium bimetallic ions, with the chemical formula {[(Cu I 3I2)4(Cu Ⅱ 2Eu Ⅲ 3L 24 (H2O)6](NO3)} nL is the organic ligand 5-chloronicotinic acid, and n is a non-zero natural number.

[0008] Furthermore, this metal-organic framework catalyst belongs to the cubic crystal system with space group I. 432 The unit cell parameters are a=b=c=22.6979(2), α=β=γ=90°, and the topology is a novel topological network structure with (6,2,8)-connection.

[0009] Furthermore, the metal-organic framework catalyst is a three-dimensional framework structure formed by connecting nanocages assembled from two different cluster-based nodes, [Cu3I2] and [Cu2Eu(COO)8], through organic ligands. The nanocage is an 84-core copper / europium bimetallic nanocage formed by connecting sixteen hexa-linked [Cu3I2N6] clusters and twelve [Cu2Eu(COO)8] clusters through ninety-six organic ligands. The window size of the nanocage is 6 Å × 6 Å and the cavity diameter is 14 Å.

[0010] The second objective of this application is to provide a method for preparing the metal-organic framework catalyst, comprising the following steps: reacting 5-chloronicotinic acid, cuprous iodide, copper salt and europium salt in a mixed solution of N,N-dimethylformamide and acetonitrile with acid as a modifier via a solvothermal reaction to obtain crystals of the metal-organic framework material.

[0011] Furthermore, the preparation method shall satisfy at least one of the following: (1) the molar ratio of 5-chloronicotinic acid, cuprous iodide, copper salt and europium salt is 1:(1-5):(0.1-1):(0.5-5) on a molar basis; (2) the amount of 5-chloronicotinic acid, N,N-dimethylformamide (DMF), acetonitrile and regulator added is 0.1mmol:1mL-9mL:0.5mL-5mL:10μL-100μL.

[0012] Furthermore, the preparation method shall satisfy at least one of the following: (1) the copper salt is copper nitrate, copper chloride or copper bromide; (2) the europium salt is europium nitrate, europium chloride, europium oxide or europium perchlorate; (3) the regulator is glacial acetic acid, formic acid, propionic acid or nitric acid.

[0013] Furthermore, the solvothermal reaction temperature is 80°C-140°C and the reaction time is 10h-96h.

[0014] The third objective of this application is to provide an application of a metal-organic framework catalyst with a three-dimensional framework structure prepared according to the above preparation method, wherein the metal-organic framework catalyst is used to catalyze the conversion reaction of CO2 with terminal alkynols.

[0015] Compared with the prior art, this application has the following beneficial effects:

[0016] (1) This application provides a metal-organic framework catalyst based on pyridine carboxylic acid ligands and copper / europium bimetallic ions, wherein the metal-organic framework has a complex Cu I / Cu II This study utilizes mixed valence states and Cu / Eu bimetallic synergistic catalytic sites, constructing a nanocage structure with a window size of 6 Å × 6 Å and a cavity diameter of 14 Å. The nanocage structure is repeatedly stacked and connected by organic ligands to form a metal-organic framework catalyst with a three-dimensional framework structure. Compared to traditional disordered porous materials, this structure has advantages such as well-defined structure, large specific surface area, easily modifiable pore structure, and uniformly dispersed active sites. MOFs with this structure have broad applications in catalyzing the conversion of CO2 with terminal alkynols under mild conditions.

[0017] (2) This application provides an application of a metal-organic framework catalyst that can efficiently catalyze CO2 and terminal alkynols under mild conditions, and can catalyze the reaction of low concentration CO2 and terminal alkynols in simulated flue gas. Not only is the catalytic yield very high for a single use, but it can also be reused at least 5 times after recovery. Its use in industrial production can greatly reduce production costs. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0019] Figure 1 For the secondary building blocks of the metal-organic framework of this application, (a) is a coordination environment diagram of the [Cu3I2N6] cluster, (b) is a coordination environment diagram of the organic ligand 5-chloronicotinic acid, and (c) is a coordination environment diagram of the organic ligand and Cu / Eu ions.

[0020] Figure 2 This is a schematic diagram of the 84-core copper / europium bimetallic cubic nanocage structure and three-dimensional framework corresponding to the metal-organic framework of this application.

[0021] Figure 3 The PXRD pattern of the metal-organic framework material of this application;

[0022] Figure 4 This is a diagram showing the catalytic cycle performance of the metal-organic framework material in this application;

[0023] Figure 5 The image shows the PXRD pattern of the metal-organic framework material of this application after five catalytic cycles.

[0024] Figure 6 This is a schematic diagram illustrating the application and catalytic rate of the Cu / Eu-MOF catalyst in this application. Figure 6[a] represents the yield of the reaction between CO2 at atmospheric pressure and terminal alkynol compounds. Figure 6 [b] The yield of the simulated reaction between flue gas (CO2 volume fraction of 15%) and terminal alkynol compounds. Detailed Implementation

[0025] The present application will be further described below with reference to specific embodiments. These embodiments are only used to more clearly illustrate the technical solutions of the present application and should not be construed as limiting the scope of protection of the present application. Anything not described in detail in this patent application is considered common knowledge in the art.

[0026] The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized by conventional methods and are ready for use without further processing, as are the instruments used in the examples. All technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0027] Metal-organic framework materials, as a class of porous organic-inorganic hybrid materials, have the characteristics of high specific surface area, adjustable pore structure and large porosity, and have been rapidly developed in many fields such as catalysis, adsorption separation and sensing.

[0028] Based on the fact that pyridine carboxylic acid ligands possess both pyridine nitrogen and carboxyl oxygen atoms as coordinating atoms, according to the hard and soft acid-base theory, the N atom preferentially coordinates with low-valence monovalent copper ions, while the O atom can coordinate with high-valence rare-earth europium ions and divalent copper ions, thus constructing MOF materials with different metal ions. Ⅰ / Cu Ⅱ The synergistic effect of mixed valence states and Cu / Eu bimetallic MOF materials can greatly expand the application of MOF materials in the field of catalysis.

[0029] In some embodiments, a metal-organic framework catalyst based on pyridine carboxylic acid ligands and copper / europium bimetallic ions is provided, specifically a heterogeneous three-dimensional bivalent mixed-metal Cu / Eu-MOF material based on 5-chloronicotinic acid, with the chemical formula {[(Cu I 3I2)4(Cu Ⅱ 2Eu Ⅲ 3L 24 (H2O)6](NO3)} n L is the organic ligand 5-chloronicotinic acid, and n is a non-zero natural number.

[0030] The organic ligand 5-chloronicotinic acid has both a basic pyridine N atom that can coordinate with monovalent copper ions and an acidic carboxyl group that can coordinate with rare earth europium ions and divalent copper ions to form bonds, with an angle of 120° between the two groups and a chlorine atom at the meta position. The specific structural formula is as follows:

[0031] .

[0032] This metal-organic framework structure contains three different coordination forms of metal ions: monovalent copper ions (Cu). I Divalent copper ions Cu Ⅱ trivalent europium ions Eu III Among them, every three Cu I It coordinates with two iodide ions to form [Cu3I2]. + A cation cluster, in which Cu I Each ligand coordinates with two pyridine nitrogen atoms from two ligands, forming a six-linked [Cu3I2N6] cluster with three copper ions, six coordinated pyridine nitrogen atoms, and two iodide ions. Each ligand then coordinates with neighboring divalent copper and europium ions via its carboxyl oxygen atom at the other end, forming a [Cu2Eu(COO)8] trinuclear heterometallic cluster structure. The trivalent europium ion coordinates with eight carboxyl oxygen atoms from eight ligands, and the oxygen atoms at the other end of the carboxyl group bridge two divalent copper ions. Each divalent copper ion is terminated by an oxygen atom from a water molecule, resulting in two five-linked divalent copper ions, ultimately forming an eight-linked [Cu2Eu(COO)8(H2O)2] cluster. Ultimately, sixteen [Cu3I2N6] clusters and twelve [Cu2Eu(COO)8] clusters are connected by ninety-six organic ligands to form an 84-core copper / europium bimetallic cubic nanocage. This copper / europium bimetallic cubic nanocage has a window size of 6 Å × 6 Å and a cavity diameter of 14 Å. The nanocages are further assembled into a long-range ordered three-dimensional framework structure through organic ligands. In this topological structure, the organic ligands, [Cu3I2N6] clusters, and [Cu2Eu(COO)8] clusters can be considered as 2-connected, 6-connected, and 8-connected nodes, respectively. The alternating connections of these three types of nodes form a novel (6,2,8)-connected topological network.

[0033] This metal-organic framework catalyst belongs to the cubic crystal system and has space group I. 432 The unit cell parameters are a=b=c=22.6979(2), α=β=γ=90°, which can be simplified to a three-dimensional framework structure of a novel topological network structure with (6,2,8)-connection.

[0034] In some embodiments, a method for preparing the above-mentioned metal-organic framework catalyst is provided, comprising the following steps: adding 5-chloronicotinic acid, cuprous iodide, copper salt, and europium salt to a mixed solution of N,N-dimethylformamide and acetonitrile in a molar ratio of 1:(1-5):(0.1-1):(0.5-5), using acid as a regulator, and obtaining crystals of the metal-organic framework material via a solvothermal reaction. This preparation method has mild reaction conditions, precise reactant ratios, and is easy to control during production, making it suitable for industrial applications. In some embodiments, the amounts of 5-chloronicotinic acid, N,N-dimethylformamide (DMF), acetonitrile, and glacial acetic acid added are 0.1 mmol:1 mL-9 mL:0.5 mL-5 mL:10 μL-100 μL. In one embodiment, the copper salt may be copper nitrate, copper chloride, or copper bromide; the europium salt may be europium nitrate, europium chloride, europium oxide, or europium perchlorate; and the regulator may be glacial acetic acid, formic acid, propionic acid, or nitric acid. In one embodiment, the solvothermal reaction temperature is 80°C-140°C and the reaction time is 10h-96h.

[0035] In some embodiments, the obtained metal-organic framework catalyst is used to catalyze the conversion reaction of CO2 with terminal alkynols. In one embodiment, the reaction equation for CO2 with 2-methyl-3-butyn-2-ol is as follows:

[0036] .

[0037] In other embodiments, such as Figure 6 As shown, Cu / Eu-MOF metal-organic framework catalysts can be used to catalyze the reaction of CO2 with 2-methyl-3-butyn-2-ol (product structure shown in figure). Figure 6 The conversion reactions of terminal alkyne alcohols, including those shown in Figure 2a), 3-methyl-1-pentyn-3-ol (product structure formula 2b), 3-ethyl-1-pentyn-3-ol (product structure formula 2c), 3,5-dimethyl-1-hexyn-3-ol (product structure formula 2d), 3,6-dimethyl-1-heptyyn-3-ol (product structure formula 2e), 1-ethynylcyclopentanol (product structure formula 2f), ethynylcyclohexanol (product structure formula 2g), and ethinylprogesterone (product structure formula 2h).

[0038] In some embodiments, the Cu / Eu-MOF catalyst after the reaction is recovered according to the following steps: After the reaction is completed, the reaction mixture is collected and centrifuged, and then... 1 The product yield in the liquid phase was determined by 1H NMR analysis. The collected Cu / Eu-MOF solid catalyst was washed with ethanol solvent and centrifuged three times, and then dried in a vacuum drying oven at 45°C-80°C for 6-24 hours. The recovered Cu / Eu-MOF catalyst can be reused in a new round of reaction.

[0039] Example 1

[0040] This embodiment provides a Cu I / Cu Ⅱ The mixed-valence state Cu / Eu bimetallic MOF material catalyst was prepared as follows: 3 mL of N,N-dimethylformamide, 2 mL of acetonitrile, and 25 μL of glacial acetic acid were added sequentially to copper nitrate pentahydrate (0.05 mmol), cuprous iodide (0.1 mmol), europium nitrate pentahydrate (0.1 mmol), and 5-chloronicotinic acid (0.1 mmol). After stirring evenly, the mixture was placed in a 120°C oven and reacted at a constant temperature for 72 h, then naturally cooled to room temperature. The mixture was washed three times each with N,N-dimethylformamide and anhydrous ethanol. The resulting crystals were then dried in a 60°C oven for 12 h to obtain a green powder, which is the mixed-valence state bimetallic Cu / Eu-MOF material.

[0041] Example 2

[0042] This embodiment provides a Cu I / Cu Ⅱ The mixed-valence state Cu / Eu bimetallic MOF material catalyst was prepared as follows: 3 mL of a mixed solution of N,N-dimethylformamide (containing 0.03 mmol of copper nitrate pentahydrate) and 2 mL of acetonitrile (containing 0.15 mmol of europium nitrate pentahydrate) was added to cuprous iodide (0.2 mmol) and the organic ligand 5-chloronicotinic acid (0.1 mmol). 40 μL of glacial acetic acid was added dropwise to the above mixed solution. After stirring evenly, the mixture was placed in an oven at 110°C and reacted at a constant temperature for 96 h. The temperature was then lowered to room temperature at a rate of 1.25°C / h. The reaction solution was removed by centrifugation, and the mixture was washed three times each with N,N-dimethylformamide and acetonitrile. After centrifugation, the upper acetonitrile solution was removed, and the precipitate was dried in an oven at 60°C for 12 h to obtain a green powder, which is the mixed-valence state bimetallic Cu / Eu-MOF material.

[0043] Example 3

[0044] This embodiment provides a Cu I / Cu ⅡThe mixed-valence state Cu / Eu bimetallic MOF catalyst was prepared as follows: 8 mL of N,N-dimethylformamide, 3 mL of acetonitrile, and 50 μL of glacial acetic acid were added sequentially to copper nitrate pentahydrate (0.05 mmol), cuprous iodide (0.3 mmol), europium nitrate pentahydrate (0.3 mmol), and the organic ligand 5-chloronicotinic acid (0.2 mmol). After stirring evenly, the mixture was placed in a 90°C oven and reacted at a constant temperature for 96 h, then naturally cooled to room temperature. The reaction solution was removed by centrifugation, and the mixture was washed three times each with N,N-dimethylformamide and acetonitrile. After centrifugation, the upper acetonitrile solution was removed, and the precipitate was dried in a 60°C oven for 12 h to obtain a green powder, which is the mixed-valence state bimetallic Cu / Eu-MOF material.

[0045] Example 4

[0046] This embodiment provides a Cu I / Cu Ⅱ The mixed-valence state Cu / Eu bimetallic MOF material catalyst was prepared as follows: 3 mL of N,N-dimethylformamide, 2 mL of acetonitrile, and 25 μL of propionic acid were added sequentially to copper chloride (0.05 mmol), cuprous iodide (0.1 mmol), europium perchlorate (0.1 mmol), and 5-chloronicotinic acid (0.1 mmol). After stirring evenly, the mixture was placed in a 120°C oven and reacted at a constant temperature for 72 h, then naturally cooled to room temperature. The mixture was washed three times each with N,N-dimethylformamide and anhydrous ethanol. The resulting crystals were then dried in a 60°C oven for 12 h to obtain a green powder, which is the mixed-valence state Cu / Eu-MOF material.

[0047] To further verify the technical solution of this application and its beneficial effects, Examples 1-4 were verified.

[0048] Experimental Example 1: Characterization Test

[0049] Select hexagonal, green, transparent Cu / Eu-MOF crystals of suitable size and good crystal quality. Collect crystal data using Mo-Kα rays (λ=0.71073Å) as the light source on a SuperNova X-ray single crystal diffractometer under a nitrogen atmosphere at 120K. Analyze the structure of the collected crystal data using Olex2 software and refine the data using the full matrix least squares method. Specific parameters are shown in Table 1.

[0050] Table 1. Crystallographic data of Cu / Eu-MOF

[0051] Formula sum <![CDATA[C 144 H 72 Cl 24 With 18 Eu3I8N 24 A 48 ]]> Formula weight g / mol 6372.07 Temperature / K 120 Crystal system Cubic Space-group I432 a / Å 22.6979(2) b / Å 22.6979(2) c / Å 22.6979(2) α / ° 90 β / ° 90 γ / ° 90 <![CDATA[Cell volume / Å 3 ]]> 11693.9(3) Z 2 <![CDATA[Calc.density g / cm 3 ]]> 1.875 F(000) 6277.0 R(int) 0.0301 <![CDATA[GOF on F 2 ]]> 0.947 <![CDATA[R1 / wR2[I >2 (I)]]]> 0.0375 / 0.0902 <![CDATA[R1 / wR2(all data)]]> 0.0462 / 0.0969

[0052] The results show that, Figure 1As shown, the framework structure contains two inorganic metal cluster nodes, [Cu3I2N6] and [Cu2Eu(COO)8], and the organic ligand is 5-chloronicotinic acid. Figure 2 As shown, the mixed-valence bimetallic Cu / Eu-MOF material possesses an 84-core copper / europium bimetallic cubic nanocage, which extends to form a three-dimensional framework structure. (PXRD pattern) Figure 3 The results show that the experimental data spectrum of the mixed-valence bimetallic Cu / Eu-MOF material matches well with the spectrum simulated by single-crystal data, confirming that the synthesized sample has high phase purity.

[0053] Application Example 1

[0054] Take 20 mg of the heterogeneous metal-organic framework catalyst obtained in Examples 1-4 and place it in a 20 ml reaction tube. Add 2 mmol of 2-methyl-3-butyn-2-ol and 500 μL of DMF solvent containing 10 μL of DBU. After adding a magnetic stir bar, seal the reaction tube and introduce 1 atm of CO2 gas. Place the prepared reaction tube in a 50°C water bath and stir for 5 h. Weigh 0.5 mmol of 1,3,5-trimethoxybenzene as an internal standard and add it to the reaction tube. After mixing evenly, remove the reaction mixture and centrifuge. Take the supernatant and analyze the product by 1H NMR spectroscopy.

[0055] The reacted Cu / Eu-MOF catalyst was washed three times with acetonitrile, dried in an oven at 60°C, and recycled for use in the next round of catalytic reaction.

[0056] The results showed that in the cycloaddition reaction of CO2 with 2-methyl-3-butyn-2-ol, the yield of methylene cyclic carbonates was as high as 99%; for example... Figure 4 As shown, this Cu / Eu-MOF material exhibits excellent recyclability, maintaining a catalytic yield of 95% even after five reuses; and from Figure 5 As can be seen, the powder diffraction data of the Cu / Eu-MOF material did not show significant changes after five catalytic cycles, indicating that the catalyst has good stability and can be efficiently recycled and reused.

[0057] Application Example 2

[0058] like Figure 6As shown in [a], Cu / Eu-MOF material was used to catalyze the reaction of CO2 with a series of terminal alkynols. The reaction conditions were: 2 mmol of substrate, 20 mg of Cu / Eu-MOF catalyst, 10 μL of DBU, 500 μL of DMF, and 1 atm of CO2, reacted at 50°C for 5 h. The conversion yields were all no less than 60%, especially when Cu / Eu-MOF material catalyzed the reaction of CO2 with 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, and ethinylprogesterone, the conversion yields were as high as 99%. The yields were based on 1,3,5-trimethoxybenzene as an internal standard. 1 The results were obtained from H NMR calculations.

[0059] Application Example 3

[0060] like Figure 6 As shown in [b], Cu / Eu-MOF material was used to catalyze the reaction of low-concentration CO2 with a series of terminal alkynols. The reaction conditions were as follows: 2 mmol of substrate, 20 mg of Cu / Eu-MOF catalyst, 10 μL of DBU, and 500 μL of DMF were added. The reaction tube was sealed and filled with 1 MPa of simulated flue gas (CO2 concentration of 15%), and the reaction was carried out at 50°C for 5 h. The results showed that the Cu / Eu-MOF catalyst had good versatility for a variety of substrates. Based on 1,3,5-trimethoxybenzene as an internal standard, the reaction was successfully completed. 1 The yield was obtained by 1H NMR calculation, and the corresponding yield of methylene cyclic carbonate was as follows: Figure 6 As shown, the yields of most of these reactions are above 95%.

[0061] Based on the preferred embodiments of this application, and through the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A metal-organic framework catalyst based on pyridine carboxylic acid ligands and copper / europium bimetallic ions, with the chemical formula {[(Cu I 3I2)4(Cu Ⅱ 2Eu Ⅲ 3L 24 (H2O)6](NO3)} n L is the organic ligand 5-chloronicotinic acid, and n is a non-zero natural number.

2. The metal-organic framework catalyst according to claim 1, wherein the metal-organic framework catalyst belongs to the cubic crystal system and has space group I. 432 The unit cell parameters are a=b=c=22.6979(2), α=β=γ=90°, and the topology is a novel topological network structure with (6,2,8)-connection.

3. The metal-organic framework catalyst according to claim 1 or 2, wherein, The metal-organic framework catalyst is a three-dimensional framework structure formed by assembling nanocages of two different cluster-based nodes, [Cu3I2] and [Cu2Eu(COO)8], through organic ligands, and further connecting them through organic ligands. The nanocage is an eighty-four-core copper / europium bimetallic nanocage formed by connecting sixteen hexa-linked [Cu3I2N6] clusters and twelve [Cu2Eu(COO)8] clusters through ninety-six organic ligands. The window size of the nanocage is 6 Å × 6 Å and the cavity diameter is 14 Å.

4. A method for preparing a metal-organic framework catalyst according to any one of claims 1-3, comprising the following steps: Crystals of metal-organic framework materials were obtained by solvothermal reaction of 5-chloronicotinic acid, cuprous iodide, copper salt, and europium salt in a mixed solution of N,N-dimethylformamide and acetonitrile with acid as a regulator.

5. The preparation method according to claim 4, wherein at least one of the following is satisfied: (1) On a molar basis, the molar ratio of the 5-chloronicotinic acid, the cuprous iodide, the copper salt and the europium salt is 1:(1-5):(0.1-1):(0.5-5); (2) The amount of 5-chloronicotinic acid, N,N-dimethylformamide (DMF), acetonitrile and the regulator added is 0.1 mmol: 1 mL - 9 mL: 0.5 mL - 5 mL: 10 μL - 100 μL.

6. The preparation method according to claim 5, wherein at least one of the following is satisfied: (1) The copper salt is copper nitrate, copper chloride, or copper bromide; (2) The europium salt is europium nitrate, europium chloride, europium oxide, or europium perchlorate; (3) The regulator is glacial acetic acid, formic acid, propionic acid or nitric acid.

7. The preparation method according to claim 5 or 6, wherein the solvothermal reaction temperature is 80°C-140°C and the reaction time is 10h-96h.

8. The application of a metal-organic framework catalyst prepared according to any one of claims 4-7, wherein the structure is as described in any one of claims 1-3, the metal-organic framework catalyst being used to catalyze the conversion reaction of CO2 with terminal alkynols.

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