阅读说明：本技术 一种锌基金属有机骨架及其合成方法与应用 (Zinc-based metal organic framework and synthesis method and application thereof ) 是由 卢治拥 郭如勇 张广豹 于 2021-08-09 设计创作，主要内容包括：本发明公开了一种锌基金属有机骨架及其合成方法与应用,锌基金属有机骨架包括α型和β型两类构型,其化学通式分别为：α型{[Zn-(15)(Ln)-(8)(HCOO)-(2)(H-(2)O)-(8.5)O-(0.25)][(NH-(2)CH-(3)CH-(3))-(6.5)]}-(n),其中,n＝1,2,3,4或5和β型[Zn-(17)(Ln)-(8)(CH-(3)COO)(H-(2)O)-(9.25)O-(0.5)]-(n),其中,n＝1,2,3,4或5；以5-(取代基)-1,3-二(3,5-二羧酸苯基)苯为配体,溶剂为N,N-二甲基甲酰胺或N,N-二乙基甲酰胺,采用溶剂热法,合成具有三重壁笼子特征的三维网络结构。本发明制备的有机金属骨架材料显示出很高的二氧化碳选择吸附性能,能选择性分离二氧化碳,该化合物在热电厂烟道气中的二氧化碳捕获以及天然气纯化领域具有很大的应用价值。(The invention discloses a zinc-based metal organic framework and a synthesis method and application thereof, wherein the zinc-based metal organic framework comprises an alpha type configuration and a beta type configuration, and the chemical general formulas of the two configurations are respectively as follows: alpha form { [ Zn ] 15 (Ln) 8 (HCOO) 2 (H 2 O) 8.5 O 0.25 ][(NH 2 CH 3 CH 3 ) 6.5 ]} n Wherein n ═ 1, 2, 3,4 or 5 and β type [ Zn ] 17 (Ln) 8 (CH 3 COO)(H 2 O) 9.25 O 0.5 ] n Wherein n is 1, 2, 3,4 or 5; 5- (substituent) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene is taken as a ligand, and N, N-dimethylformamide or N, N-diethyl is taken as a solventFormamide, and a solvothermal method is adopted to synthesize a three-dimensional network structure with triple-wall cage characteristics. The organic metal framework material prepared by the invention has high carbon dioxide selective adsorption performance, can selectively separate carbon dioxide, and has great application value in the fields of carbon dioxide capture in thermal power plant flue gas and natural gas purification.)

1. A zinc-based metal organic framework, characterized by: the zinc-based metal organic framework comprises an alpha type and a beta type, a compound shown in a formula (I) is used as a ligand, carboxylic acid groups in the ligand are all involved in coordination, a polynuclear zinc-oxygen cluster is formed by the ligand and divalent zinc ions, and a porous three-dimensional network structure with triple-wall cage characteristics is further constructed;

formula (I) is:

wherein R represents any one of methyl, methoxy, amino, hydroxyl or trifluoromethyl.

2. A zinc-based metal organic framework according to claim 1, characterized in that: the chemical formula of the beta-type metal organic framework is [ Zn ]₁₇(Ln)₈(CH₃COO)(H₂O)_9.25O_0.5]_nWherein n is 1, 2, 3,4 or 5; the crystal of the beta-type metal organic framework belongs to a tetragonal system, I4/mmm space group, and the unit cell parameters are respectively as follows: a ═α＝β＝γ＝90°。

3. A zinc-based metal organic framework according to claim 1, characterized in that: the chemical formula of the alpha-type metal organic framework is { [ Zn ]₁₅(Ln)₈(HCOO)₂(H₂O)_8.5O_0.25][(NH₂CH₃CH₃)_6.5]}_nWherein n is 1, 2, 3,4 or 5; the crystal of the alpha-type metal organic framework belongs to a tetragonal system, I4/mmm space group, and the unit cell parameters are respectively as follows:α＝β＝γ＝90°

4. a method of synthesizing a zinc-based metal organic framework as defined in claim 1, comprising the steps of:

1) dissolving a compound shown in a formula (I) and zinc salt in a mixed solvent of an organic solvent and water, adding concentrated nitric acid, and performing ultrasonic oscillation to assist complete dissolution;

2) transferring and sealing the prepared solution, carrying out solvothermal reaction at a constant temperature, and cooling to room temperature after the solvothermal reaction is finished to obtain a colorless transparent hollow square tubular crystal;

3) finally, washing and drying to obtain a zinc-based metal organic framework;

formula (I) is:

wherein, R represents any one of methyl, methoxy, amino, hydroxyl or trifluoromethyl;

the organic solvent is N, N-dimethylformamide or N, N-diethylformamide.

5. The method of claim 4, wherein the zinc-based metal organic framework comprises: when N, N-dimethylformamide is adopted in the step 1), the obtained zinc-based metal organic framework is alpha type; when N, N-diethylformamide is adopted in the step 1), the obtained zinc-based metal organic framework is beta type.

6. The method of claim 4, wherein the zinc-based metal organic framework comprises: in the step 1), the molar ratio of the compound shown in the formula (I) to the zinc salt is 1: 3-9; wherein the zinc salt is any one of zinc chloride, zinc nitrate hexahydrate and zinc acetate dihydrate.

7. The method of claim 4, wherein the zinc-based metal organic framework comprises: in the step 1), the dosage ratio of the compound shown in the formula (I), the mixed solvent of the organic solvent and water and the concentrated nitric acid is 0.1-0.15 millimole: 20 ml: 0.1-0.5 ml.

8. The method of claim 7, wherein the zinc-based metal organic framework comprises: in the mixed solvent, the volume ratio of the organic solvent to the water is 5: 0.5 to 2.

9. The method of claim 4, wherein the zinc-based metal organic framework comprises: in the step 2), the temperature of the constant-temperature solvothermal reaction is 95-120 ℃, and the reaction time is 1-2 days.

10. Use of a zinc-based metal organic framework according to claim 1 as adsorbent material in carbon dioxide capture or natural gas purification.

Technical Field

The invention belongs to synthesis of metal organic framework materials, and particularly relates to two types of isomorphic zinc-based metal organic framework materials with a triple cage characteristic, which are constructed by five zinc-oxygen clusters and take 5- (substituent) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene as a ligand.

Background

In order to increase the material to CO as much as possible₂The selective affinity of the carbon dioxide molecule is an effective method for constructing a polyhedral cage-shaped pore cavity in Metal-Organic Frameworks (MOFs), and achieving the specific adsorption and selective capture of the carbon dioxide molecule through the synergistic effect of a pore cavity window and specific Metal sites in the pore cavity. The polyhedral cage type structure has good structural stability and can endow the metal organic framework material with high stability, so that the construction of the metal organic framework material containing the polyhedral cage for the selective capture of carbon dioxide is very attractive. Meanwhile, the heterogeneity of the metal clusters is increased, so that a plurality of metal sites with different activities can be constructed in the same metal organic framework system, and the selective adsorption of the gas is also improved. However, in general, the polyhedral cage-type metal-organic framework materials are all constructed by single-layer cages, so that the improvement of stability is limited, and due to the limitation of heterogeneity of metal clusters, the number of the metal clusters for constructing the cage-type metal-organic framework is basically limited to two or less. Therefore, how to effectively construct a metal organic framework material with multiple-wall cages and metal cluster multiple heterogeneous characteristics, which has high carbon dioxide selective adsorption capacity, remains a challenging research topic.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a series of novel isomorphic two zinc-based metal-organic frameworks which are constructed by five metal-oxygen clusters and have triple-wall cage characteristics; the second purpose of the invention is to provide a synthesis method of the zinc-based metal organic framework; the third purpose of the invention is to provide the application of the zinc-based metal organic framework in carbon dioxide capture and natural gas purification.

The technical scheme is as follows: the zinc-based metal organic framework comprises an alpha type and a beta type, a compound shown in a formula (I) is used as a ligand, carboxylic acid groups in the ligand are all involved in coordination, a multinuclear zinc oxygen cluster is formed by the ligand and divalent zinc ions, and a porous three-dimensional network structure with characteristics of a triple-wall cage is further constructed;

formula (I) is:

wherein R represents any one of methyl, methoxy, amino, hydroxyl or trifluoromethyl.

Further, the chemical formula of the beta-type metal organic framework is [ Zn ]₁₇(Ln)₈(CH₃COO)(H₂O)_9.25O_0.5]_nWherein n is 1, 2, 3,4 or 5; the crystal of the beta-type metal organic framework belongs to a tetragonal system, I4/mmm space group, and the unit cell parameters are respectively as follows:α＝β＝γ＝90°。

specifically, when the substituent is methyl, the chemical formula of the beta-type metal organic framework is C₁₈₆H₁₁₄O_75.75Zn₁₇(ii) a When the substituent is methoxy, the chemical formula of the beta-type metal organic framework is C₁₈₆H₁₁₄O_83.75Zn₁₇(ii) a When the substituent is amino, the chemical formula of the beta-type metal organic framework is C₁₇₈H₁₀₆N₈O_75.75Zn₁₇(ii) a When the substituent is hydroxyl, the chemical formula of the beta-type metal organic framework is C₁₇₈H₉₈O_83.75Zn₁₇(ii) a When the substituent is trifluoromethyl, the chemical formula of the beta-type metal organic framework is C₁₈₆H₉₁O_75.75F₂₄Zn₁₇。

Further, the chemical formula of the alpha-type metal organic framework is { [ Zn ]₁₅(Ln)₈(HCOO)₂(H₂O)_8.5O_0.25][(NH₂CH₃CH₃)_6.5]}_nWherein n is 1, 2, 3,4Or 5; the crystal of the alpha-type metal organic framework belongs to a tetragonal system, I4/mmm space group, and the unit cell parameters are respectively as follows:α＝β＝γ＝90°

specifically, when the substituent is methyl, the chemical formula of the alpha-type metal organic framework is C₁₉₉H₁₆₇N_6.50O_76.75Zn₁₅(ii) a When the substituent is methoxy, the chemical formula of the alpha-type metal organic framework is C₁₉₉H₁₆₇N_6.50O_84.75Zn₁₅(ii) a When the substituent is amino, the chemical formula of the alpha-type metal organic framework is C₁₉₁H₁₅₉N_14.50O_76.75Zn₁₅(ii) a When the substituent is hydroxyl, the chemical formula of the alpha-type metal organic framework is C₁₉₁H₁₅₁N_6.50O_84.75Zn₁₅(ii) a When the substituent is trifluoromethyl, the chemical formula of the alpha-type metal organic framework is C₁₉₉H₁₄₃N_6.50O_76.75F₂₄Zn₁₅。

The invention also provides a synthetic method of the zinc-based metal organic framework, which comprises the following steps:

1) dissolving a compound shown in a formula (I) and zinc salt in a mixed solvent of an organic solvent and water, adding concentrated nitric acid, and performing ultrasonic oscillation to assist complete dissolution;

2) transferring and sealing the prepared solution, carrying out solvothermal reaction at a constant temperature, and cooling to room temperature after the solvothermal reaction is finished to obtain a colorless transparent hollow square tubular crystal;

3) finally, washing and drying to obtain a zinc-based metal organic framework;

formula (I) is:

wherein, R represents any one of methyl, methoxy, amino, hydroxyl or trifluoromethyl;

the organic solvent is N, N-dimethylformamide or N, N-diethylformamide.

Further, when N, N-dimethylformamide is adopted in the step 1), the obtained zinc-based metal organic framework is alpha type; when N, N-diethylformamide is adopted in the step 1), the obtained zinc-based metal organic framework is beta type.

Further, the molar ratio of the compound shown in the formula (I) to the zinc salt is 1: 3-9; wherein the zinc salt is any one of zinc chloride, zinc nitrate hexahydrate and zinc acetate dihydrate.

Further, the dosage ratio of the compound shown in the formula (I), the mixed solvent of the organic solvent and water and the concentrated nitric acid is 0.1-0.15 millimole: 20 ml: 0.1 to 0.5 ml, preferably 0.12 mmol: 20 ml: 0.3 ml

Further, in the mixed solvent, the volume ratio of the organic solvent to the water is 5: 0.5-2, preferably 5: 1.

further, in the step 2), the temperature of the constant-temperature solvothermal is 95-120 ℃, and the reaction time is 1-2 days.

The invention further protects the application of the zinc-based metal organic framework as an adsorption material in carbon dioxide capture or natural gas purification.

In the invention, the ligand is 5- (substituent) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene (formula (I)), and the substituents are respectively methyl, methoxy, amino, hydroxyl and trifluoromethyl with hydrogen bond acceptors, which are mainly because the substituents have the characteristic of forming R-H- - -Pi bonds with benzene rings, thereby determining the formation of a triple-wall cage structure to a certain extent.

In the invention, two types of zinc-based metal organic frameworks with the same structure but different zinc cores can be obtained by adjusting the types of solvents in the reaction process, mainly because the decomposition products of two different solvents (N, N-dimethylformamide and N, N-dimethylacetamide) under the acidic condition are different in the solvothermal reaction process. For example, when N, N-dimethylformamide is used, the solvent is partially decomposed, the products are formate and dimethylamine cations, respectively, and the formate interacts with the zinc ion and the organic ligand to form five zinc oxygen clustersZn of one₄(HCOO)₂(COO)₈(H₂O)₄(SBU-5) to form an alpha-Zn with further construction together with other zinc oxygen clusters₂₄@Zn₁₂@Zn₁₀₄A characteristic metal organic framework; when N, N-diethylformamide is used, the solvent is partially decomposed and the products are acetate and dimethylamine cations. Acetate has one more methyl group than formate, and cannot interact with zinc ions and organic ligands to form SBU-5 due to steric hindrance, but forms Zn with similar structure, same connectivity and different zinc core numbers₈(COO)₈(H₂O)₆(SBU-5 s). The zinc-oxygen cluster is further constructed together with other zinc-oxygen clusters to form beta-type Zn isomorphic with alpha-type₂₄@Zn₁₂@Zn₁₃₆A characteristic metal organic framework.

The preparation principle of the invention is that carboxylic acid groups in ligands are all involved in coordination, five zinc-oxygen clusters with completely different structures are formed with divalent zinc ions, wherein the zinc-oxygen cluster structures with alpha type and beta type configurations have slight difference, and then a nested triple-wall cage structure with a rhombic dodecahedron cage as an inner layer, a cubic cage as a sandwich layer and a doughnut-type cage as an outer layer is further constructed through diversified ligand configuration modes and the zinc-oxygen clusters. The triple-wall cage-shaped structure further forms a three-dimensional network structure with discontinuous separation cavities by using zinc-oxygen clusters as joints between two inner layers of polymers to be arranged in a line along the c axis and overlapping the polymers in a staggered manner.

Because the cage structure with triple-wall characteristics exists in the whole structure and zinc-oxygen cluster units participating in construction are diversified, compared with the traditional polyhedral cage-type metal-organic framework material, the preparation method has the characteristic that the metal-organic framework material with a complex and stable structure and diversified carbon dioxide active sites is directly prepared by a simple solvothermal one-pot method, and the carbon dioxide selectivity of the material is improved.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:

1. a series of novel isomorphic zinc-based metal organic framework materials which are constructed by five metal oxygen clusters and have triple-wall cage characteristics and constructed by Zn (II) and 5- (substituent) -1, 3-bis (3, 5-dicarboxylic acid phenyl) benzene prepared by the invention show high carbon dioxide selective adsorption performance, can selectively separate carbon dioxide, and have great application value in the fields of carbon dioxide capture in thermal power plant flue gas and natural gas purification.

2. The invention can obtain two types of zinc-based metal organic framework materials with the same structure but different zinc core numbers by solvothermal reaction and solvent adjustment, has simple integral preparation method and is easy for industrialized production and application.

Drawings

FIG. 1 is a schematic diagram of the synthesis of a zinc-based metal organic framework material of the present invention;

FIG. 2 is an optical microscope image of a hollow square tubular crystal;

FIG. 3 is a schematic view of five zinc-oxygen clusters in example 1 of the present invention;

FIG. 4 is a schematic representation of four conformational ligands in example 1 of the present invention;

FIG. 5 shows a 3,3,4,4,4,4,6,7, 8-connection topology network of a metal organic framework after the nodes of a zinc-oxygen cluster and a ligand are simplified according to connectivity in example 1 of the present invention;

FIG. 6 shows Zn in example 1 of the present invention₂₄@Zn₁₂@Zn₁₀₄A schematic molding diagram;

FIG. 7 shows Zn arranged in line along the c-axis in the metal-organic framework structure in example 1 of the present invention₂₄@Zn₁₂A polymeric body;

FIG. 8 is a graph illustrating the R- -H- - - π interaction present in a zinc-based metal organic framework material according to example 1 of the present invention;

FIG. 9 is a schematic diagram of five kinds of zinc-oxygen clusters and their similarities and differences with the zinc-oxygen clusters of alpha-type structure in example 2 of the present invention;

FIG. 10 is a powder X-ray diffraction pattern of a metal-organic framework prepared in an example of the present invention;

FIG. 11 is a graph of carbon dioxide adsorption isotherms and selectivities for a beta-type zinc-based metal organic framework material of the invention.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and examples.

The experimental methods described in this example are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

Example 1

Novel cage Zn with triple walls and constructed by five metal oxygen clusters₂₄@Zn₁₂@Zn₁₀₄A method for preparing a characteristic zinc-based metal organic framework (alpha type) comprises the following steps:

(1) as shown in fig. 1, the organic ligand 5- (methyl) -1, 3-bis (3, 5-dicarboxyphenyl) benzene (5.04mg), and zinc nitrate hexahydrate (21.42mg) were added to a teflon-lined reaction vessel, and 2mL of a N, N-dimethylformamide/water mixed solution (V/V ═ 5/1) and 30 μ L of concentrated nitric acid were added, and the dissolution was completed with an ultrasonic oscillator;

(2) sealing, reacting at 105 deg.C for 2 days, and cooling to room temperature to obtain colorless transparent hollow square tubular crystal with yield of about 55% as shown in FIG. 2;

(3) and washing the colorless crystal with N, N-dimethylformamide and ethanol, and drying to obtain the metal organic framework material.

The chemical formula of the metal organic framework material is C₁₉₉H₁₆₇N_6.50O_76.75Zn₁₅5- (methyl) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene is used as a ligand, and N, N-dimethylformamide is used as a solvent.

Referring to FIG. 4, the dihedral angles between the central benzene ring and the terminal benzene ring of the four-configuration ligands present in the crystal structure were 25.9 °/25.9 ° (type I), 0 °/0 ° (type II, with the distance between the parallel carboxyl oxygens being 25.9 °/25.9 °, respectively) 52.0 °/35.1 ° (type III), 0 °/0 ° (type IV, distance between parallel carboxyl oxygens is) (ii) a Referring to FIG. 3, the carboxylic acid groups in the ligand and divalent zinc ions form five zinc-oxygen clusters with completely different structures, namely, 4-connectivity paddle-shaped dual-core zinc-oxygen cluster Zn₂(COO)₄(H₂O)₂(SBU-1), a double-wheeled paddle-like tetranuclear zinc oxygen cluster Zn with 4-connectivity₄O(COO)₈(H₂O)₂(SBU-2) bending type double-wheel paddle-shaped tetranuclear zinc-oxygen cluster Zn with 6-connectivity₄(HCOO)(COO)₈(H₂O)₂(SBU-3) trinuclear zinc-oxygen cluster Zn with 7-connectivity₃(COO)₇(H₂O) (SBU-4), and a tetranuclear zinc-oxygen cluster Zn with 8-connectivity₄(HCOO)₂(COO)₈(H₂O)₄(SBU-5)。

See fig. 5 for a simplified 3,3,4,4,4,4,6,7, 8-connecting network of an alpha-type metal-organic framework, see fig. 6, comprising rhombic dodecahedron Zn₂₄A core cage; cubic Zn₁₂An interlayer cage; nested Zn₂₄@Zn₁₂A polymeric body; donut type Zn₁₀₄A housing cage; triple-wall cage-shaped structure Zn₂₄@Zn₁₂@Zn₁₃₆(ii) a The ligands with diversified configurations and the zinc-oxygen clusters further construct a rhombic dodecahedral cage which is surrounded by 4 SBU-1, 2 semi-SBU-2, 8 semi-SBU-4 and 24 isophthalic acid units and contains 24 zinc ions and is used as an inner layer (marked as Zn)₂₄A core cage having an inner bore of size) Cubic cages containing 12 zinc ions formed by 8 semi-SBU-4 and 12 intact Ln ligands as a sandwich (noted as Zn)₁₂Sandwich cage) consisting of 8 SBU-3, 8 semi-SBU-3, 8 SBU-4, 8 SBU-5 and 32 isophthalic acid units and 12 complete Ln ligands, 104 zinc ions in a doughnut-type cage as the outer layer (noted as Zn₁₀₄Outer cage) of a nested triple-walled cage structure Zn₂₄@Zn₁₂@Zn₁₀₄。

Referring to fig. 7, the triple-walled cage structure is shownBy inner two layers of Zn₂₄@Zn₁₂The three-dimensional network structure with discontinuous separation cavities is further formed in a mode that the aggregates are mutually arranged in a line along the c axis by taking SBU-2 as a joint point and are mutually overlapped in a staggered mode, the three-dimensional network can be further simplified into a 3,3,4,4,4,4,6,7, 8-connection network containing 9 topological independent nodes, and the topological point symbol is {4.6 }²}₄{4².6¹³.8⁶}₈{4³.6³}₂₀{4⁴.6¹¹}₄{4⁴.6²}₄{4⁸.6¹⁶.8⁴}₂{6³}₈{6⁴.8²And the method is a brand new topological structure type. After removing the solvent molecules in the pores, the porosity was 30.8% as calculated by the PLATON program. Referring to fig. 8, a characteristic exists in such a structure that R-H-pi interaction exists between a substituent of an organic ligand and an isophthalic acid benzene ring adjacent to the ligand, which is one of the key factors that each organic ligand with different substituents can form a series of isomorphic metal-organic framework materials.

Example 2

Novel cage Zn with triple walls and constructed by five metal oxygen clusters₂₄@Zn₁₂@Zn₁₃₆A process for the preparation of a characteristic zinc-based metal-organic framework (beta-form), comprising the steps of:

(1) as shown in fig. 1, the organic ligand 5- (methyl) -1, 3-bis (3, 5-dicarboxyphenyl) benzene (5.04mg), and zinc nitrate hexahydrate (21.42mg) were added to a teflon-lined reaction vessel, and 2mL of a N, N-dimethylacetamide/water mixed solution (V/V ═ 5/1) and 30 μ L of concentrated nitric acid were added, and the dissolution was completed with an ultrasonic oscillator;

(2) sealing, reacting at 105 ℃ for 2 days, and cooling to room temperature after the reaction is finished to obtain a colorless transparent hollow square tubular crystal with the yield of about 65%;

(3) and washing the colorless crystal with N, N-dimethylacetamide and ethanol, and drying to obtain the metal organic framework material.

The metal is as followsThe chemical formula of the framework material is C₁₈₆H₁₁₄O_75.75Zn₁₇5- (methyl) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene is used as a ligand, and N, N-dimethylacetamide is used as a solvent. The crystal structure has organic ligands with the same configuration as that of the alpha-type series structure, and dihedral angles between central benzene rings and terminal benzene rings of the four configuration ligands are respectively 25.9 degrees/25.9 degrees (type I) and 0 degrees/0 degrees (type II), and the distances between parallel carboxyl oxygen are respectively 25.9 degrees/25.9 degrees (type I) and 0 degrees/0 degrees (type II)) 52.0 °/35.1 ° (type III), 0 °/0 ° (type IV, distance between parallel carboxyl oxygens is)。

Referring to FIG. 9, the carboxylic acid groups in the ligand form five zinc-oxygen clusters with divalent zinc ions, including a 4-linked, paddle-shaped dual-core zinc-oxygen cluster Zn having the same structure as the alpha-type zinc-oxygen cluster₂(COO)₄(H₂O)₂(SBU-1), a double-wheeled paddle-like tetranuclear zinc oxygen cluster Zn with 4-connectivity₄O(COO)₈(H₂O)₂(SBU-2) and a trinuclear zinc-oxygen cluster Zn with 7-connectivity₃(COO)₇(H₂O) (SBU-4), bent double-wheel paddle-shaped tetranuclear zinc-oxygen cluster Zn with 6-connectivity and same structure but different auxiliary ligands₄(CH₃COO)(COO)₈(H₂O)₂(SBU-3s) and a tetranuclear zinc-oxygen cluster Zn with 8-connectivity having the same structure but different numbers of zinc nuclei₈(COO)₈(H₂O)₆(SBU-5s)。

The diversified ligand configuration modes and the zinc-oxygen clusters further construct a nested triple-wall cage structure Zn which has the same alpha-type series structure as that of example 1 but has different zinc nucleus numbers₂₄@Zn₁₂@Zn₁₃₆。

The triple-wall cage structure depends on Zn of inner two layers₂₄@Zn₁₂The polymers are arranged in a line along the c-axis with SBU-2 as the joint point, and are overlapped with each other in a staggered manner, thereby forming a polymer withA three-dimensional network of discrete partitioned cavities. The three-dimensional grid can be further simplified into a 3,3,4,4,4,4,6,7, 8-connection network containing 9 topology independent nodes, and the sign of the topology point is {4.6 }²}₄{4².6¹³.8⁶}₈{4³.6³}₂₀{4⁴.6¹¹}₄{4⁴.6²}₄{4⁸.6¹⁶.8⁴}₂{6³}₈{6⁴.8²And the method is a brand new topological structure type. The same characteristic exists in such structures, namely that the substituent of the organic ligand has R-H- - -Pi interaction with the benzene ring of isophthalic acid adjacent to the ligand, which is also one of the key factors that each organic ligand with different substituents can form a series of isomorphic metal-organic framework materials.

Example 3

The specific preparation method is the same as that of example 1, except that: the organic ligand is 5- (methoxyl) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene, and zinc salt is zinc chloride;

the molar ratio of 5- (methoxy) -1, 3-bis (3, 5-dicarboxyphenyl) benzene to zinc chloride was 1: 3;

the ratio of the N, N-dimethylformamide/water mixed solvent is 5: 0.5;

the temperature of the constant temperature solvothermal reaction is 95 ℃;

the chemical formula of the metal organic framework material is C₁₉₉H₁₆₇N_6.50O_84.75Zn₁₅。

Example 4

The specific preparation method is the same as that of example 1, except that: the organic ligand is 5- (amino) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene, and the zinc salt is zinc acetate dihydrate;

the organic ligand is 5- (amino) -1, 3-bis (3, 5-dicarboxylic acid phenyl) benzene and zinc acetate dihydrate, and the molar ratio of the organic ligand to the zinc acetate dihydrate is 1: 9;

the ratio of the N, N-dimethylformamide/water mixed solvent is 5: 2;

the temperature of the constant temperature solvothermal reaction is 120 ℃;

the chemical formula of the metal organic framework material is C₁₉₁H₁₅₉N_14.50O_76.75Zn₁₅。

Example 5

The specific preparation method is the same as that of example 2, except that: the organic ligand is 5- (hydroxyl) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene; the chemical formula of the metal organic framework material is C₁₇₈H₉₈O_83.75Zn₁₇。

Example 6

The specific preparation method is the same as that of example 2, except that: the organic ligand is 5- (trifluoromethyl) -1, 3-di (3, 5-dicarboxylic acid phenyl) benzene; the chemical formula of the metal organic framework material is C₁₈₆H₉₁O_75.75F₂₄Zn₁₇。

Referring to fig. 10, for the powder X-ray diffraction patterns of the metal organic framework materials prepared in examples 1 to 6, the matching degree of diffraction peaks appearing at various angles is high, and no unnecessary impurity peak appears, compared with the α -single crystal fitting pattern, which indicates that the prepared metal organic framework materials have the same structure and the purity of the sample is very high.

Example 7

Characterization of the metal-organic framework materials obtained in example 1 and example 2

(1) Determination of Crystal Structure

The single crystals were selected under a microscope with the right dimensions, intact appearance and no cracks and data were collected on a single crystal diffractometer using Mo-K α radiation monochromatized with a graphite monochromator at temperatures 173(2) K or 296(2) K. All diffraction data were absorption corrected using the SADABS program; the unit cell parameters are determined by a least square method; data reduction and structure analysis was done using SAINT and SHELXTL programs. Firstly, determining the coordinates of all non-hydrogen atoms by using a difference function method and a least square method, obtaining the hydrogen atom position of a main body framework by using a theoretical hydrogenation method, and then refining the crystal structure by using the least square method. Some of the parameters for crystallographic diffraction point data collection and structure refinement are shown in table 1 below.

TABLE 1 Crystal parameter tables for alpha-and beta-form zinc-based organic frameworks

R₁＝Σ||F_o|-|F_c||/|F_o|；wR₂＝[Σw(ΣF_o ²-F_c ²)²/Σw(F_o ²)²]^1/2

Example 8

Study on adsorption and separation properties of carbon dioxide

A batch of samples of type β prepared in example 2 was subjected to solvent substitution in anhydrous methanol for 72 hours, with the anhydrous methanol being replaced every 8 hours, after which the samples were subjected to supercritical activation using a carbon dioxide supercritical dryer, followed by degassing at room temperature for 2 hours to give fully activated samples.

The activated sample was tested for carbon dioxide adsorption performance at temperatures of 273K and 298K, shown as a in fig. 11. Under the conditions of 298K and 1bar, the carbon dioxide adsorption capacity of the compound is 21.3cm³ g^-1. In FIG. 11 b shows the compound in CO₂:N₂2:8 thermal power plant flue gas simulation mixed gas and CO₂:CH₄Natural gas at 5:5 simulates a selectivity to carbon dioxide gas in a mixed gas as high as 128 and 10, respectively. The zinc-based metal organic framework (beta type) with triple-wall cage characteristics, which is constructed by five metal oxygen clusters, has high selective adsorption capacity on carbon dioxide at normal temperature, and can be applied to carbon dioxide capture and natural gas purification in flue gas of a thermal power plant.