Three-dimensional metal organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a three-dimensional metal organic framework material as well as a preparation method and application thereof. The chemical general formula of the three-dimensional metal organic framework material is {Zn2 (bpydb) 2 (bpyb) 2 (H2O) 6} n, and n is larger than or equal to 1; the three-dimensional metal organic framework material is constructed by interpenetrating and interweaving two-dimensional double-layer structures. The invention provides a unique three-dimensional metal organic framework material. The material is formed by interlacing and constructing a two-dimensional double-layer structure; the activated MOF material shows unprecedented acetylene adsorption performance, the adsorption capacity of the activated MOF material is increased along with temperature rise, the adsorption heat of the activated MOF material to acetylene is as high as 102 kJ / mol, the MOF material can be subjected to single-crystal-to-single-crystal structural transformation, and when a coordinate bond is broken, the adsorption capacity of the activated MOF material is increased, and the adsorption capacity of the activated MOF material is increased. The two-dimensional double-layer structure can be converted into a two-dimensional single-layer structure.

Description

Technical Field

[0001] This invention belongs to the field of MOF material technology, specifically relating to a three-dimensional metal-organic framework material, its preparation method, and its application. Background Technology

[0002] Three-dimensional metal-organic frameworks (MORFs) are crystalline porous materials formed by the self-assembly of metal ions / clusters and organic ligands through coordination bonds. With their core advantages such as ultra-high specific surface area, ordered pores, strong structural designability, and easy functional modification, they have become a hot topic in materials science research over the past 20 years. Tens of thousands of structures have been reported to date, demonstrating enormous application potential in fields such as gas adsorption and separation (CO2, H2, CH4), energy storage (battery electrodes, supercapacitors), heterogeneous catalysis, fluorescence sensing, and drug delivery. This application utilizes a bifunctional rigid ligand (bpydb) 2- (bpyb) and Zn 2+ Precise assembly systematically overcomes traditional shortcomings from four dimensions: skeleton stability, electronic conduction, pore structure, and synthesis process, providing a brand-new solution for the practical application of high-performance 3D-MOFs in fields such as luminescence, sensing, gas separation, and catalysis. Summary of the Invention

[0003] The main objective of this invention is to provide a three-dimensional metal-organic framework material, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0005] This invention provides a three-dimensional metal-organic framework material with the general chemical formula {Zn2(bpydb)2(bpyb)2(H2O)6}. n Where n≥1; the three-dimensional metal-organic framework material is constructed by interlacing two-dimensional double-layer structures.

[0006] This invention also provides a method for preparing the aforementioned three-dimensional metal-organic framework material, comprising:

[0007] The H2bpydb ligand and bpyb ligand were reacted with Zn using a solvothermal method. 2+ The source is reacted to obtain a three-dimensional metal-organic framework material.

[0008] This invention also provides a method for single-crystal structure transformation of a three-dimensional metal-organic framework material, which includes: heating the aforementioned three-dimensional metal-organic framework material at 293~298 K in a nitrogen atmosphere to achieve single-crystal structure transformation of the three-dimensional metal-organic framework material.

[0009] This invention also provides a method for preparing an activated three-dimensional metal-organic framework material, comprising: immersing the aforementioned three-dimensional metal-organic framework material in dichloromethane or trichloromethane for 3-5 days, and then heating it at 80-90°C for 12-18 hours to obtain the activated three-dimensional metal-organic framework material. This invention also provides the application of the aforementioned three-dimensional metal-organic framework material or the activated three-dimensional metal-organic framework material in the selective separation of acetylene / carbon dioxide.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) This invention provides a unique three-dimensional metal-organic framework (MOF) material, which is constructed from a two-dimensional bilayer structure. The activated MOF material exhibits unprecedented acetylene adsorption performance, and its adsorption capacity increases with increasing temperature. The adsorption capacity at four temperature conditions of 298 K, 273 K, 263 K, and 195 K satisfies V 298 K > V 273 K > V 263 K > V 195 The relationship with K; however, the adsorption of other gases such as carbon dioxide and ethylene did not show this trend;

[0012] (2) The adsorption heat of acetylene by the activated three-dimensional metal-organic framework material in this invention is as high as 102 kJ / mol, which is also a breakthrough in the field of metal-organic framework materials.

[0013] (3) The MOF material in this invention can undergo a single-crystal to single-crystal structural transformation. At the same time as the coordination bond breaks, its two-dimensional bilayer structure can be transformed into a two-dimensional monolayer structure. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a crystal structure diagram of target product 1 in Embodiment 1 of the present invention;

[0016] Figures 2a-2b Thermogravimetric analysis curves and X-ray diffraction patterns of target product 1 and activated product 1a in Example 1 of this invention;

[0017] Figure 3 This is the adsorption isotherm diagram of activated product 1a in Example 1 of the present invention;

[0018] Figure 4 This is a graph showing the gas adsorption performance of activated product 1a near room temperature in Example 1 of the present invention;

[0019] Figures 5a-5b This is the adsorption heat of acetylene by activated product 1a in Example 1 of the present invention, and the IAST separation selectivity of the acetylene / carbon dioxide system at different temperatures;

[0020] Figure 6 This is a repeatability test curve of the acetylene adsorption isotherm of activated product 1a in Example 1 of the present invention;

[0021] Figure 7 This is a structural comparison diagram of target product 1 and product 2 in Embodiment 1 of the present invention. Detailed Implementation

[0022] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] Specifically, as one aspect of the technical solution of this invention, the chemical formula of a three-dimensional metal-organic framework material is {Zn2(bpydb)2(bpyb)2(H2O)6}. n Where n≥1; the three-dimensional metal-organic framework material is constructed by interlacing two-dimensional double-layer structures.

[0024] In some preferred embodiments, the three-dimensional metal-organic framework material belongs to the triclinic crystal system, and the crystal structure of the three-dimensional metal-organic framework material is a three-dimensional skeleton formed by interlacing two-dimensional double-layer structures.

[0025] In some preferred embodiments, the asymmetric structural unit of the three-dimensional metal-organic framework material comprises two crystallographically independent Zn atoms. 2+ Two bpydbs 2- The ligand ([4,4'-([4,4'-bipyridinyl]-2,6-diyl)dibenzoate]) and a bpyb ligand ([(1,4-bis(p-pyridyl)benzene]), wherein the two crystallographically independent Zn 2+ Both adopt a five-coordinate [ZnO3N2] tetragonal pyramidal coordination configuration, Zn 2+ Each with two bpydb 2- The three carboxyl oxygen atoms of the ligand and the one from bpydb2- The two nitrogen atoms of the ligand and the bpyb ligand are coordinated and bonded, with each Zn 2+ Ions form a honeycomb-like monolayer structure through coordination with three different ligands. The monolayer structure is then further bridged by bpyb ligands to form a two-dimensional bilayer framework structure.

[0026] In some preferred embodiments, the two six-membered rings of the three-dimensional metal-organic framework material are connected (6... 3 The single-layer structure is arranged in parallel and does not completely overlap, with two six-element rings connected (6 3 The monolayer structure is connected to Zn-N bonds between bpyb columnar ligands and Zn²⁺, and the spacing between zinc atoms in the bilayer framework is 15.516 Å.

[0027] In some preferred embodiments, the pores of the three-dimensional metal-organic framework material are one-dimensional through-hole structures.

[0028] Another aspect of the present invention provides a method for preparing the aforementioned three-dimensional metal-organic framework material, comprising:

[0029] Using a solvothermal method, H2bpydb ligand ([4,4'-([4,4'-bipyridine]-2,6-dimethyl)dibenzoic acid]), bpyb ligand, and Zn were reacted. 2+ The source is reacted to obtain a three-dimensional metal-organic framework material.

[0030] In some preferred embodiments, the Zn 2+ The source includes any one or more combinations of zinc nitrate, zinc sulfate, and zinc chloride, but is not limited thereto.

[0031] In some preferred embodiments, the H2bpydb ligand, bpyb ligand, and Zn 2+ The molar ratio of the sources is 1~2.5:1~2.5:1~3.

[0032] In some preferred embodiments, the reaction is carried out at a temperature of 150-180°C for a time of 12-24 hours.

[0033] Another aspect of the present invention provides a method for single-crystal structure transformation of a three-dimensional metal-organic framework material, comprising: heating the aforementioned three-dimensional metal-organic framework material at 293~298 K in a nitrogen atmosphere to achieve single-crystal structure transformation of the three-dimensional metal-organic framework material.

[0034] In some preferred embodiments, the heat treatment time is 2 to 3 hours.

[0035] Another aspect of the present invention provides a method for preparing an activated three-dimensional metal-organic framework material, comprising: immersing the aforementioned three-dimensional metal-organic framework material in dichloromethane or trichloromethane for 3-5 days, and then heating it at 80-90°C for 12-18 hours to obtain the activated three-dimensional metal-organic framework material.

[0036] In some preferred embodiments, the pores of the activated three-dimensional metal-organic framework material are one-dimensional through-pore structures.

[0037] Another aspect of the present invention provides the application of the aforementioned three-dimensional metal-organic framework material or activated three-dimensional metal-organic framework material in the selective separation of acetylene / carbon dioxide.

[0038] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0039] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0040] Example 1

[0041] By using a solvothermal method, H2bpydb ligand, bpyb ligand and zinc nitrate hexahydrate were reacted to successfully prepare the target product 1, a yellow crystal, which is a three-dimensional metal-organic framework material.

[0042] The target product 1 was soaked in dichloromethane and left to stand for 3 days, and then heated at 80 °C for 12 h to obtain the activated product 1a, which is the activated three-dimensional metal-organic framework material.

[0043] Characterization: The crystal structure of target product 1 is as follows Figure 1 As shown in Figure 2a, the thermogravimetric analysis curves of target product 1 and activated product 1a are shown in Figure 2a, and the X-ray diffraction patterns are shown in Figure 2a. Figure 2b As shown.

[0044] Based on single-crystal X-ray diffraction data, elemental analysis results, and thermogravimetric analysis results, the chemical formula of target product 1 was determined to be {Zn2(bpydb)2(bpyb)2(H2O)6}. n X-ray diffraction analysis revealed that target product 1 belongs to the triclinic crystal system, with a three-dimensional framework formed by the interweaving of two-dimensional bilayer structures. The asymmetric structural unit of this crystal contains two crystallographically independent Zn atoms. 2+ Ions, two bpydb 2-Both Zn1 and Zn2 adopt a five-coordinate [ZnO3N2] tetragonal pyramidal coordination configuration, with the central Zn... 2+ Ions from two bpydb 2- The ligand has three carboxyl oxygen atoms, and comes from a bpydb 2- The two nitrogen atoms of the ligand and the bpyb ligand are coordinated and bonded. Each Zn 2+ Ions, through coordination with three different ligands, first construct a honeycomb-like monolayer structure. These monolayer structures are then further bridged by bpyb ligands, ultimately forming a two-dimensional bilayer framework structure. The two six-membered rings of target product 1 are connected by (6... 3 The monolayer structures are arranged in parallel and are not completely overlapping. They are connected to Zn ions via Zn-N bonds through bpyb pillar ligands, forming a bilayer framework with an inter-zinc atom spacing of 15.516 Å. Each two-dimensional bilayer structure interweaves with two adjacent bilayer structures, thus forming a three-dimensional interwoven framework. To simplify the structural analysis of target product 1, bpydb can be used... 2- The ligands are considered as three-node connectors, and the bpyb ligands as two-node bridging ligands. Therefore, the overall crystal framework of this material can be classified as a 3,4L88 type topological network with two (3,4) nodes. Calculations using PLATON single-crystal structure analysis software show that the solvent-accommodating volume of the crystal channels in target product 1 is 1780.7 Å. 3 It accounts for 44.1% of the total unit cell volume. The pore characteristics were calculated using PoreBlazer_v3.0.2_d pore analysis software. The results show that the pores in this material are one-dimensional continuous pores, with a limiting diameter of 6.17 Å and a maximum diameter of 7.05 Å. The calculated contactable specific surface area is 1101 m². 2 / g.

[0045] Thermogravimetric analysis (TGA) of activated product 1a confirmed that the material was fully activated—no mass loss was observed in the sample before its framework structure collapsed. Figure 2a Powder X-ray diffraction (PXRD) tests showed that the crystal structures of target product 1, the intermediate product soaked in dichloromethane, and the activated product 1a were all different, indicating that the crystal structure of target product 1 was dynamically variable during the above treatment process.

[0046] To investigate the pore characteristics of activated product 1a, its nitrogen adsorption isotherm was measured at 77 K. Figure 3 As shown, activated product 1a exhibits only surface adsorption behavior, with a maximum nitrogen adsorption capacity of only 6 cm³. 3The low pore size ( / g) may be due to its small pore size, insufficient to accommodate nitrogen guest molecules. However, at 195 K, the adsorption of carbon dioxide by activated product 1a exhibits typical type I isotherm characteristics, with a maximum adsorption capacity of 68.6 cm⁻¹. 3 / g, corresponding to an experimental BET specific surface area of ​​110 m² 2 The specific surface area is significantly lower than the theoretically calculated value from single-crystal data, indicating that the framework structure of activated product 1a has significantly shrunk compared to target product 1. To compare with the carbon dioxide adsorption performance, the adsorption isotherm of activated product 1a for acetylene was also tested at 195 K. Under the same conditions, the adsorption capacity of this material for acetylene is much lower than that for carbon dioxide. For example, at 0.5 bar and 195 K, the adsorption capacity of activated product 1a for acetylene is 7.5 cm³. 3 / g, while the adsorption capacity for carbon dioxide can reach 62 cm⁻¹. 3 / g. Considering the molecular size of acetylene and carbon dioxide (carbon dioxide molecular size: 3.4 × 3.4 × 5.3 Å). 3 Acetylene molecular size: 3.4 × 3.4 × 5.5 Å 3 The adsorption properties and boiling points (carbon dioxide boiling point: 194.7 K; acetylene boiling point: 189.3 K) are quite similar, making this adsorption difference particularly anomalous. These results also indicate that activated product 1a exhibits adsorption selectivity for carbon dioxide under low-temperature conditions.

[0047] Figure 4 The graph shows the gas adsorption performance of activated product 1a near room temperature. The study revealed that this material exhibits unique temperature-dependent adsorption behavior for acetylene: as the temperature increases from 263 K to 313 K, the acetylene adsorption gradually increases, reaching a maximum at 298 K; when the temperature rises to 303 K, the acetylene adsorption decreases by only 6 cm⁻¹. 3 The adsorption capacity was / g, and the adsorption amount did not decrease further after heating to 313 K. According to literature reports, the gas adsorption capacity of metal-organic framework materials usually decreases with increasing temperature; therefore, this adsorption phenomenon exhibited by activated product 1a is reported for the first time. For comparison, adsorption isotherms of activated product 1a for carbon dioxide, ethylene, ethane, and methane were simultaneously tested near room temperature. Carbon dioxide showed a stepped adsorption isotherm at 263 K and 273 K, accompanied by adsorption lag, indicating a "gate-opening effect" in its adsorption process. When the temperature rose to 283 K, the "gate-opening effect" disappeared, and the adsorption capacity decreased significantly. The adsorption capacities of ethylene, ethane, and methane all showed a decreasing trend with increasing temperature.

[0048] Existing literature indicates that the increase in gas adsorption capacity with increasing temperature can be attributed to chemisorption. To investigate the interaction energy between acetylene molecules and the material framework, the isosmotic adsorption enthalpy Q of acetylene was calculated based on adsorption data at 298 K and 303 K. st .like Figure 5a The results showed that the isochoric adsorption enthalpy of acetylene at zero coverage was 51.8 kJ / mol, indicating a very strong interaction between acetylene molecules and the material framework; furthermore, with increasing acetylene adsorption, the Q of the activation product 1a increased. st The value continues to rise, reaching 102 kJ / mol under high adsorption conditions. Such a high enthalpy of adsorption is unprecedented in the field of metal-organic framework materials, confirming the possible chemisorption of acetylene by the activated product 1a. To verify the feasibility of this material in separating acetylene / carbon dioxide mixtures, its separation selectivity for equimolar acetylene-carbon dioxide mixtures was calculated using the Ideal Adsorption Solution Theory (IAST) based on the pure component adsorption isotherms at 298 K and 313 K. Figure 5b The results showed that the acetylene / carbon dioxide separation selectivity of activated product 1a at 298 K and 313 K was 18.6 and 27, respectively, which is a relatively high level among metal-organic framework-based porous materials.

[0049] To further investigate the correlation between the adsorption behavior of activated product 1a for acetylene and temperature, supplementary adsorption tests were conducted in the temperature range of 273 K to 298 K (e.g., ...). Figure 6 The experiment first measured the adsorption isotherm of acetylene at 273 K, then the adsorption isotherm at 298 K, and finally the adsorption isotherm at 273 K again. The experimental results show that the adsorption behavior of this material for acetylene is completely reversible.

[0050] To further investigate this anomalous temperature-dependent adsorption behavior, a variable-temperature single-crystal structure analysis was conducted on target product 1. First, the crystal of target product 1 was heated at 298 K for 2 h under a nitrogen atmosphere, followed by single-crystal diffraction data acquisition at a set temperature. Experimental results showed that target product 1 underwent a single-crystal-to-single-crystal structural transformation: one N-Zn coordination bond in the bpyb ligand broke, and two six-membered rings connected (6... 3 Single-layer structures undergoing phase-to-phase displacement (e.g.) Figure 7Correspondingly, the effective solvent-accessible pore volume of the crystal decreased from 44.1% to 12%. Calculations using PoreBlazer software showed that nitrogen molecules could not diffuse into the channels of the newly formed compound (denoted as product 2). The channels of product 2 are one-dimensional through-holes with a limiting diameter of 2.42 Å and a maximum diameter of 3.95 Å, indicating a significant shrinkage in the crystal structure of product 2 compared to target product 1. Cooling the crystal of product 2 at 120 K for one day did not alter its crystal structure, demonstrating the irreversibility of this single-crystal-to-single-crystal structural transformation.

[0051] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0052] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A three-dimensional metal-organic framework material, characterized in that, The general chemical formula of the three-dimensional metal-organic framework material is {Zn2(bpydb)2(bpyb)2(H2O)6} n Where n≥1; the three-dimensional metal-organic framework material is constructed by interlacing two-dimensional double-layer structures.

2. The three-dimensional metal-organic framework material according to claim 1, characterized in that: The three-dimensional metal-organic framework material belongs to the triclinic crystal system, and the crystal structure of the three-dimensional metal-organic framework material is a three-dimensional skeleton formed by interlacing two-dimensional double-layer structures.

3. The three-dimensional metal-organic framework material according to claim 1, characterized in that: The asymmetric structural unit of the three-dimensional metal-organic framework material includes two crystallographically independent Zn atoms. 2+ Two bpydbs 2- The ligand and one bpyb ligand, wherein both crystallographically independent Zn²⁺ ligands adopt a five-coordinate [ZnO₃N₂] tetragonal pyramidal coordination configuration, Zn 2+ Each with two bpydb 2- The three carboxyl oxygen atoms of the ligand and the one from bpydb 2- The two nitrogen atoms of the ligand and the bpyb ligand are coordinated and bonded, with each Zn 2+ Ions form a honeycomb-like monolayer structure through coordination with three different ligands. The monolayer structure is then further bridged by bpyb ligands to form a two-dimensional bilayer framework structure.

4. The three-dimensional metal-organic framework material according to claim 1, characterized in that: The two six-membered rings connected by the three-dimensional metal-organic framework material (6) 3 The single-layer structure is arranged in parallel and does not completely overlap, with two six-element rings connected (6... 3 The monolayer structure is connected to Zn-N bonds between bpyb columnar ligands and Zn²⁺, and the spacing between zinc atoms in the bilayer framework is 15.516 Å.

5. The three-dimensional metal-organic framework material according to claim 1, characterized in that: The pores of the three-dimensional metal-organic framework material are one-dimensional through-pore structures.

6. The method for preparing the three-dimensional metal-organic framework material according to any one of claims 1-5, characterized in that, include: The H2bpydb ligand bpyb ligand was reacted with Zn using a solvothermal method. 2+ The source is reacted to obtain a three-dimensional metal-organic framework material; Preferably, the Zn 2+ The source includes any one or more combinations of zinc nitrate, zinc sulfate, and zinc chloride; Preferably, the H2bpydb ligand, bpyb ligand, and Zn 2+ The molar ratio of the sources is 1~2.5:1~2.5:1~3; Preferably, the reaction temperature is 150~180℃ and the time is 12~24 h.

7. A method for single-crystal structure transformation of a three-dimensional metal-organic framework material, characterized in that, include: In a nitrogen atmosphere, the three-dimensional metal-organic framework material according to any one of claims 1-5 is heated at 293-298 K to achieve the single-crystal structure transformation of the three-dimensional metal-organic framework material.

8. A method for preparing an activated three-dimensional metal-organic framework material, characterized in that, include: The three-dimensional metal-organic framework material according to any one of claims 1-5 is immersed in dichloromethane or trichloromethane for 3-5 days, and then heated at 80-90°C for 12-18 hours to obtain the activated three-dimensional metal-organic framework material.

9. The activated three-dimensional metal-organic framework material prepared by the preparation method according to claim 8, characterized in that: The pores of the activated three-dimensional metal-organic framework material are one-dimensional through-pore structures.

10. The application of the three-dimensional metal-organic framework material according to any one of claims 1-5 or the activated three-dimensional metal-organic framework material according to claim 9 in the selective separation of acetylene / carbon dioxide.

Images