CN112851593B

CN112851593B - Amino-bridged hexacarboxylic acid ligand, metal organic framework material, and preparation methods and applications thereof

Info

Publication number: CN112851593B
Application number: CN202110019307.6A
Authority: CN
Inventors: 郑柏树; 汪冠宇; 王莹; 廖俊雄; 汪朝旭; 张少伟
Original assignee: Hunan University of Science and Technology
Current assignee: Hunan University of Science and Technology
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2022-06-28
Anticipated expiration: 2041-01-07
Also published as: CN112851593A

Abstract

The invention relates to the field of metal organic framework materials, and discloses an amino-bridged hexacarboxylic acid ligand, a metal organic framework material, and a preparation method and application thereof. The amino-bridged hexacarboxylic acid ligand has a structure shown in formula (I). The method for preparing the amino modified metal organic framework material has the characteristics of easily obtained synthetic raw materials, mild synthetic conditions, simple operation, few byproducts and easy mass preparation; the amino-modified metal organic framework material provided by the invention has good thermal stability, and can keep a porous framework structure unchanged after guest molecules are removed.

Description

Amino-bridged hexacarboxylic acid ligand, metal organic framework material, and preparation methods and applications thereof

Technical Field

The invention relates to the field of metal organic framework materials, in particular to an amino-bridged hexacarboxylic acid ligand, a metal organic framework material, and a preparation method and application thereof.

Background

With the rapid development of the social industry, a great deal of fossil fuels such as coal, petroleum, natural gas and the like are combusted, resulting in CO in the atmosphere₂Increased concentration of CO₂As greenhouse gas pairClimate and ecological environment cause serious impact and endanger the sustainable development of human society.

At present, organic amine is mainly used for treating CO in industrial waste gas in industry₂The capture is carried out, and then the desorption is carried out under the high-temperature condition, but the method has the disadvantages of high energy consumption, high cost, serious corrosion to equipment and the like in the desorption process. The adsorption separation based on the porous material is a separation means which is relatively energy-saving and high in selectivity, and is expected to solve a plurality of problems in the traditional separation process. Therefore, the research and development of the method can effectively adsorb and separate CO₂The novel porous material has important significance.

Metal Organic Frameworks (MOFs) are porous materials with a periodic network structure formed by self-assembly of organic ligands and metal ions or metal clusters through complexation. The nano-porous silicon dioxide has the characteristics of high specific surface area, adjustable pore size, high density of active sites, easiness in functionalization and the like, and is widely applied to the fields of gas storage, separation, catalysis, drug slow release, fluorescence recognition and the like.

Many MOF materials have been designed and constructed by scientists to enhance CO by modifying MOF channels with the introduction of metal active sites (OMSs) and polar groups₂Interaction force between the material and the frame material, thereby promoting the selective adsorption and separation of CO from the material₂The ability of the cell to perform. However, many MOF materials currently suffer from poor framework stability and tend to partially or fully collapse when exposed to high temperatures or water vapor.

Therefore, a CO with better stability is developed₂Novel porous materials with high adsorption selectivity are in the spotlight.

Disclosure of Invention

The invention aims to overcome the defect of poor stability of a metal organic framework material in the prior art, and provides a novel amino modified metal organic framework material with stable performance and a preparation method thereof.

In order to achieve the above object, a first aspect of the present invention provides an amino-bridged hexacarboxylic acid ligand having a structure represented by formula (I),

a second aspect of the present invention provides a method of preparing a ligand according to the first aspect, the method comprising:

(1) reacting a compound shown as a formula (II) with cyanuric chloride in a 1, 4-dioxane solution to obtain a reaction product;

(2) under the alkaline condition, carrying out hydrolysis reaction on the reaction product, sequentially acidifying, filtering, washing with water to be neutral, washing with hot methanol for 2-3 times, and drying to obtain a ligand shown in a formula (I);

the third aspect of the present invention provides an amino-modified metal-organic framework material, wherein the molecular formula of the amino-modified metal-organic framework material is: [ Cu ]₃(C₄₅H₂₄N₆O₁₂)]_nWherein n is a positive integer; the amino modified metal organic framework material belongs to a tetragonal system, I4/m space group, and the unit cell parameters are respectively as follows:

α＝90.00°，β＝90.00°，γ＝90.00°。

the fourth aspect of the present invention provides a method for preparing an amino-modified metal-organic framework material, comprising: in the presence of a solvent, a ligand shown as a formula (I) and CuSO₄·5(H₂O) performing coordination reaction, wherein the solvent is at least one of DMF (N, N-dimethylformamide), DMSO (dimethyl sulfoxide), water and acetonitrile;

the fifth aspect of the present invention provides an amino-modified metal-organic framework material prepared by the method described in the fourth aspect.

A sixth aspect of the present invention provides the use of the amino-modified metal-organic framework material of the third and fifth aspects for selective adsorptive separation of CO₂/CH₄And/or CO₂/N₂The use of (1).

A seventh aspect of the invention provides a selective adsorptive separation of CO₂/CH₄And/or CO₂/N₂The method of (1), the method comprising:

(a) activating the amino-modified metal organic framework material to obtain an activated amino-modified metal organic framework material;

(b) reacting the activated amino modified metal organic framework material with a catalyst containing CO₂/CH₄And/or CO₂/N₂The gas (a) is contacted;

wherein, in the step (a), the amino-modified metal-organic framework material is the amino-modified metal-organic framework material described in the third aspect and the fifth aspect.

The method for preparing the amino modified metal organic framework material has the characteristics of easily obtained synthetic raw materials, mild synthetic conditions, simple operation, few byproducts and easy mass preparation.

The amino-modified metal organic framework material provided by the invention has good thermal stability, and can keep the framework structure unchanged after the guest molecules are removed.

Drawings

FIG. 1 is a diagram showing the coordination environment of an amino-bridged hexacarboxylic acid ligand and a metal node in preparation example 1;

FIGS. 2a-c are three different types of cages in the framework of the amino-modified metal organic framework material of example 1; FIG. 2d is a three-dimensional crystal structure diagram of an amino-modified metal-organic framework material in example 1;

FIG. 3 is a photograph of an optical photograph of a sample of the amino-modified metal-organic framework material of example 1;

FIG. 4 is an infrared spectrum of the amino-modified metal organic framework material of example 1; in FIG. 4, a is an infrared spectrum curve of an amino-bridged hexacarboxylic acid ligand shown in formula (I), b is an infrared spectrum curve of an amino-modified metal organic framework material, c is an infrared spectrum curve of an amino-modified metal organic framework material after acetone soaking treatment, and d is an infrared spectrum curve of an activated amino-modified metal organic framework material;

FIG. 5 is a thermogravimetric analysis of the amino-modified metal-organic framework material of example 1; in FIG. 5, a is the thermogravimetric curve of the amino-modified metal-organic framework material after activation; b is a thermogravimetric curve of the amino modified metal organic framework material; c is a thermogravimetric curve of the amino modified metal organic framework material after the acetone soaking treatment;

FIG. 6 is an X-ray powder diffraction pattern of the amino-modified metal-organic framework material of example 1; in FIG. 6, a is the X-ray powder diffraction curve of the amino-modified metal-organic framework material after activation; b is an X-ray powder diffraction curve of the amino modified metal organic framework material; c is an X-ray powder diffraction curve of the amino modified metal organic framework material after the acetone soaking treatment;

FIG. 7 shows the amino-modified metal-organic framework material of example 1 for N at 77K₂Adsorption isotherm curve of (d);

FIG. 8a shows the amino-modified metal organic framework material prepared in example 1 at 0-1.1bar and 273K for CO₂、N₂、CH₄The gas adsorption isotherm diagram of (a);

FIG. 8b is the amino-modified metal organic framework material prepared in example 1 under the conditions of 0-1.1bar and 298K for CO₂、N₂、CH₄The gas adsorption isotherm diagram of (a);

FIG. 9a is a diagram of the amino-modified organometallic framework material of example 1 in CO at 273K₂、 CH₄、N₂Isothermally fitting an initial slope curve graph;

FIG. 9b is a diagram of the amino-modified organometallic framework material of example 1 under the condition of 298K in CO₂、 CH₄、N₂Isothermally fitting an initial slope curve graph;

FIG. 10 shows that the amino-modified metal-organic framework material in example 1 is based on 273K and 298K conditionsCO calculated from adsorption isotherm curves₂、CH₄Adsorption heat profile;

FIG. 11 shows the amino-modified metal organic framework material prepared in example 1 at 298K and 1bar for a binary mixed gas CO₂/N₂(V/V＝2:8)、CO₂/CH₄(V/V ═ 2:8) graph of penetration experiments;

FIG. 12 is a nuclear magnetic map of an amino-bridged hexacarboxylic acid ligand in preparation example 1.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values are understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

As previously mentioned, a first aspect of the present invention provides an amino-bridged hexacarboxylic acid ligand having the structure of formula (I),

when the amino-bridged hexacarboxylic acid ligand provided by the invention is used for preparing an amino-modified metal framework material, few byproducts are generated, the prepared amino-modified metal framework material has better thermal stability, and the framework structure can be kept unchanged after the guest molecules are removed.

The preparation method for preparing the amino-bridged hexacarboxylic acid ligand is not particularly limited, and the amino-bridged hexacarboxylic acid ligand can be prepared by selecting a synthetic route according to a structural formula and combining a known method in the field of organic synthesis by a person skilled in the art. However, in order to obtain higher yields and purities, according to a preferred embodiment, as previously described, the second aspect of the present invention provides a process for preparing a ligand according to the first aspect, comprising:

in the present invention, the structural formula of cyanuric chloride is as follows:

preferably, the compound shown in the formula (II) and cyanuric chloride are used in a molar ratio of 1: 0.3-0.4.

In the present invention, it is preferable that the alkaline condition is formed by at least one substance selected from the group consisting of potassium hydroxide, sodium hydroxide, and lithium hydroxide; particularly preferably, the alkaline conditions are provided by sodium hydroxide.

Preferably, in step (1), the reaction conditions at least satisfy: the temperature is 70-120 ℃, and the time is 6-12 h. More preferably, the conditions of the contact reaction at least satisfy: the temperature is 90-100 ℃ and the time is 8-10 h. The inventors of the present invention found that the reaction conditions at least satisfy: when the temperature is 90-100 ℃ and the time is 8-10h, fewer by-products are obtained, and the yield and the purity are higher.

Preferably, in step (2), the conditions of the hydrolysis reaction at least satisfy: the temperature is 40-90 ℃ and the time is 4-10 h.

As previously mentioned, a third aspect of the invention provides an amino modificationThe amino-modified metal organic framework material has the molecular formula as follows: [ Cu ]₃(C₄₅H₂₄N₆O₁₂)]_nWherein n is a positive integer; the amino modified metal organic framework material belongs to a tetragonal system, I4/m space group, and the unit cell parameters are respectively as follows:

α＝90.00°，β＝90.00°，γ＝90.00°。

as described above, the fourth aspect of the present invention provides a method for preparing an amino-modified metal-organic framework material, the method comprising: in the presence of a solvent, a ligand shown as a formula (I) and CuSO₄·5(H₂O) carrying out coordination reaction, wherein the solvent is at least one of DMF, DMSO, water and acetonitrile;

preferably, the solvent is a combination of DMF and DMSO.

Further preferably, the volume ratio of the DMF to the DMSO is 1: 0.8-1.2. The inventor of the invention finds that the volume ratio of the DMF to the DMSO is 1:1, the prepared amino modified metal organic framework material has better thermal stability.

Preferably, the amount of DMF is 0.1-0.3mL per 1mg of the ligand of formula (I).

Preferably, the ligand represented by the formula (I) and the CuSO₄·5(H₂O) is 1: 2-8. More preferably, the ligand represented by the formula (I) is reacted with the CuSO₄·5(H₂O) is 1: 2-4.

Preferably, the coordination reaction satisfies at least the following conditions: the reaction temperature is 70-120 ℃, and the reaction time is 48-120 h. More preferably, the coordination reaction satisfies at least the following condition: the reaction temperature is 80-110 ℃, and the reaction time is 48-96 h.

According to a preferred embodiment, the method further comprises:

before the coordination reaction is carried out, the solvent, the ligand shown in the formula (I) and the CuSO are firstly contained₄·5(H₂And the reaction system of O) is contacted with an acidic substance at the temperature of not higher than 35 ℃ to carry out acidification, and then the temperature of the acidified reaction system is raised to carry out the coordination reaction, wherein the acidic substance is at least one of fluoboric acid, hydrochloric acid and phosphoric acid.

Preferably, the acidic substance is fluoroboric acid.

The preparation method of the present invention may further include various post-treatment methods conventionally used in the art such as filtration, washing, purification, drying, etc. The step of the post-treatment is not particularly limited in the present invention. For example, the present invention may be such that the mixture obtained after the completion of the contact reaction is first filtered to remove the residue, and then the filtrate obtained is concentrated, purified by distillation, and dried.

As mentioned above, the fifth aspect of the present invention provides the amino-modified metal-organic framework material prepared by the method of the fourth aspect.

As mentioned above, the sixth aspect of the present invention provides the use of the amino-modified metal-organic framework material of the third and fifth aspects for selective adsorptive separation of CO₂/CH₄And/or CO₂/N₂The use of (1).

As previously mentioned, a seventh aspect of the invention provides a selective adsorptive separation of CO₂/CH₄And/or CO₂/N₂The method of (1), the method comprising:

According to another preferred embodiment, in the step (1), the step of activating treatment comprises a soaking treatment and a degassing treatment, wherein the soaking treatment is performed in a solution containing anhydrous acetone, and the soaking treatment time is 70-90 h.

Preferably, in the soaking treatment, the anhydrous acetone is used in an amount of 0.1 to 0.5mL per 1mg of the amino-modified metal-organic framework material.

Preferably, the degassing treatment conditions at least satisfy: the temperature is 80-130 ℃ and the time is 5-20 h. Further preferably, the degassing treatment is performed under conditions at least satisfying: the temperature is 100 ℃ and 110 ℃, and the time is 10-15 h.

The amino-modified metal organic framework material provided by the invention can better selectively adsorb CO₂Thereby being capable of better selecting and separating CO₂/CH₄And/or CO₂/N₂. Therefore, the amino modified metal organic framework material provided by the invention can be used for CO in exhaust gas discharged by factories₂The fields of capture separation, natural gas purification and the like, and has wide industrial application prospect.

The present invention will be described in detail below by way of examples.

In the following examples, all of the amino-modified metal-organic framework materials are abbreviated as MOF materials and room temperature is 25. + -. 3 ℃ unless otherwise specified, and the various starting materials used are commercially available.

Cyanuric chloride: from Aladdin reagent, Inc.

A process for preparing a compound of formula (II):

0.344g of p-bromoaniline was dissolved in 40mL of toluene, and then a mixed solution of 0.6g of 3, 5-dimethoxycarbonylphenylboronic acid and 12mL of ethanol was added, followed by 0.74g of Na₂CO₃Mixing with 8mL of water, and introducing N for 10min₂Then 0.2g of Pd (PPh) is added₃)₄N for another 5min₂Then the obtained reactant is mixedThe system is stirred at 80 ℃ for 9h, cooled to room temperature, purified by a silica gel column and spin-dried by a rotary evaporator to obtain 0.82g of the compound shown in the formula (II).

Preparation example 1: preparation of amino-bridged hexacarboxylic acid ligands

In an ice-water bath, 0.855g of the compound represented by the formula (II) was added to 60mL of 1, 4-dioxane and poured into a 200mL round-bottom flask, and 1.1mL of 1, 4-dioxane solution of 1M cyanuric chloride was slowly added dropwise thereto, followed by 1 hour and reaction at 95 ℃ for 8 hours. And (4) after the reaction is finished, spin-drying to obtain a reaction product.

0.8826g of NaOH solid were weighed out and dissolved in 20mL of H₂Adding the mixture into 30mL of methanol solution in which the reaction product is dissolved, and hydrolyzing for 7h at 70 ℃; then acidified to pH of about 2 with 1M hydrochloric acid, filtered, washed with water to neutrality, dried at 75 ℃ for 6h to obtain a crude product, and finally refluxed with methanol 3 times to obtain 0.755g of an amino-bridged hexacarboxylic acid ligand represented by formula (I) as a brown yellow solid in 89.10% yield.

Preparation example 2: preparation of amino-bridged hexacarboxylic acid ligands

Similar to the preparation method of preparation example 1, except that:

the mixed solution containing the compound of formula (II) was heated at 80 ℃ for 11 hours to give 0.733g of the amino-bridged hexacarboxylic acid ligand of formula (I) as a tan solid.

As a result: the yield of amino-bridged hexacarboxylic acid ligands was 86.52%.

Example 1: preparation of MOF materials

8.5mg of the amino-bridged hexacarboxylic acid ligand of the formula (I) prepared in preparation example 1 and 25mg of CuSO were added₄·5(H₂O), 2mL of DMF and 2mL of LDMSO were completely dissolved and mixed in a 20mL glass bottle, and 0.375mL of HBF was added₄And acidifying the solution, sealing the glass bottle, placing the glass bottle in a constant-temperature oven at 85 ℃ for reacting for 48 hours, cooling to room temperature after the reaction is finished, washing with DMF, filtering, and naturally airing to obtain a blue polyhedral crystal, namely the MOF material.

Example 2: preparation of MOF materials

Adding into8.5mg of the amino-bridged hexacarboxylic acid ligand of formula (I) prepared in preparation example 1, 40mg of CuSO₄·5(H₂O), 2mL of DMF and 1.8mL of LDMSO were completely dissolved and mixed in a 20mL glass bottle, and 0.375mL of HBF was added₄And acidifying the solution, sealing the glass bottle, placing the glass bottle in a constant-temperature oven at 90 ℃ for reaction for 72 hours, cooling to room temperature after the reaction is finished, washing with DMF, filtering and drying to obtain a blue polyhedral crystal, namely the MOF material.

Example 3: preparation of MOF materials

Similar to the preparation process of example 1, except that: the amount of DMF was 2mL and the amount of DMSO was 3mL, giving a MOF material.

Example 4: activation of MOF materials

The MOF materials of examples 1-4 were activated separately, as follows:

soaking 200mg of MOF material in 40mL of anhydrous acetone for 80h (replacing the anhydrous acetone every 8h, wherein the dosage is 4mL each time) to exchange high-boiling-point DMF molecules in pore channels, degassing at 105 ℃ for 12h, and removing the DMF molecules in the pore channels to obtain the activated amino modified metal organic framework material.

Test example 1: characterization of the Crystal Structure

The MOF material of example 1 was purified at room temperature using Mo/ka radiation monochromatized with a graphite monochromator (where,

) Crystal data were collected on a Bruker Smart ApexII model X-ray single crystal diffractometer. The crystal structure was refined using Olex2 software and the results are shown in Table 1.

Test example 2: infrared spectral property characterization

The MOF material of example 1 was mixed with KBr and ground into a pressed sheet, and the sheet was measured by an IR Prestige-21, Shimadzu type FTIR Infrared spectrometer having a wavelength range of 400-4000cm^-1. The specific results are shown in FIG. 4.

Test example 3: characterization of Heat stability Properties

The MOF material of example 1 was subjected to a soaking treatmentThe MOF material of example 1 (40mL dry acetone soak 80h) and the MOF material of example 1 activated using the method of example 4 were subjected to thermogravimetric analysis (TGA) by: in N₂Under protection, DSC/TG pan Al is adopted₂O₃The thermogravimetric analyzer scans the sample and increases the temperature from 30 ℃ to 650 ℃ at a rate of 10 ℃/min to obtain a TG curve, and the specific result is shown in FIG. 5.

Test example 4: x-ray powder diffraction Spectroscopy characterization

The MOF material of example 1 and the MOF material of example 1 activated with the method of example 4 were subjected to PXRD analysis on a D8-a25, Bruker-AXS model X-ray powder diffractometer with an angle range of 5-30 °, specific results are shown in fig. 6.

Test example 5: characterization of the adsorption Properties

The MOF material prepared in example 1 was subjected to a specific surface area analyzer model ASAP 2020 of Micromeritics (manufactured by Michkoku corporation) to determine N at 77K₂Adsorption capacity, N at 273K and 298K₂、CH₄And CO₂See fig. 7-10 for specific results.

FIG. 7 shows the amino-modified metal-organic framework material of example 1 for N at 77K₂Adsorption isotherm curve of (d); as can be seen from FIG. 7, the specific surface area of the MOF material is relatively high in both Langmuir and BET values.

FIG. 8a shows the amino-modified metal organic framework material prepared in example 1 at 0-1.1bar and 273K for CO₂、N₂、CH₄The gas adsorption isotherm diagram of (a); FIG. 8b is the amino-modified metal organic framework material prepared in example 1 under the conditions of 0-1.1bar and 298K for CO₂、N₂、CH₄The gas adsorption isotherm diagram of (a); as can be seen from FIG. 8, all adsorption isotherms in the graph are completely reversible and there is no hysteresis. In addition, the MOF material can well adsorb and store CO₂。

FIG. 9a is a CO atmosphere at 273K condition of the amino-modified metal-organic framework material in example 1₂、 CH₄、N₂Isothermally fitting an initial slope curve graph; FIG. 9b is a schematic diagram of an embodimentExample 1 amino-modified Metal-organic framework Material CO at 298K₂、CH₄、N₂Isothermally fitting an initial slope curve graph; as can be seen from FIG. 9, CO was observed at 273K and 298K₂/CH₄And CO₂/N₂The adsorption selectivity is higher, which indicates that the MOF material can be applied to CO₂/CH₄And CO₂/N₂And (4) adsorbing and separating the gas.

FIG. 10 shows CO calculated based on adsorption isotherms at 273K and 298K for the amino-modified metal-organic framework material in example 1₂、CH₄Adsorption heat profile; from FIG. 10, it can be seen that CO is present₂The heat of adsorption of (A) is 22.9kJ^-1And CH₄Has a heat of adsorption of only 14.2kJ^-1Far less than CO₂Illustrating the MOF material of the invention with CO₂Has stronger interaction and can be used for adsorbing and separating CO₂。

FIG. 11 shows the amino-modified metal organic framework material prepared in example 1 at 298K and 1bar for a binary mixed gas CO₂/N₂(V/V＝2:8)、CO₂/CH₄(V/V ═ 2:8) graph of penetration experiments; FIG. 11 shows that the MOF material of the invention can be used as an adsorbent for flue gas (CO)₂/N₂) Or natural gas (CO)₂/CH₄) Middle adsorption CO separation₂A gas. .

FIG. 12 is a nuclear magnetic diagram of an amino-bridged hexacarboxylic acid ligand in production example 1, and it can be seen from FIG. 12 that the compound represented by formula (I) is produced in production example 1.¹H NMR(400MHz,CDCl₃)δ9.82 (s,3H,NH),8.44(s,3H,ArH),8.39(d,6H,ArH),8.01(s,6H,ArH),7.75(d,6H,ArH)。

The same tests were carried out on the products of examples 2 to 3 in the same manner as in test examples 1 to 5 described above, and the test results are shown in Table 2.

TABLE 1

TABLE 2

Note: CO 2₂/CH₄Penetration time¹(min) represents: CO 2₂/CH₄A time interval of complete separation; CO 2₂/N₂Penetration time²(min) represents: CO 2₂/N₂Time interval of complete separation.

FIG. 1 is a diagram showing the coordination environment of an amino-bridged hexacarboxylic acid ligand and a metal node in preparation example 1; FIGS. 2a-c are three different types of cages in the framework of the amino-modified metal organic framework material of example 1; FIG. 2d is a three-dimensional crystal structure diagram of an amino-modified metal-organic framework material in example 1; as can be seen from FIGS. 1-2, the structure contains a slurry-wheel shape [ Cu ]₂(CO₂)₄]A secondary building block in which each ligand molecule (i.e., the amino-bridged hexacarboxylic acid ligand of formula (I)) is identical to six [ Cu [ -Cu ]₂(CO₂)₄]The secondary structural units are connected, each [ Cu ]₂(CO₂)₄]The secondary building block is connected with 6 ligand molecules to form the MOF material with rht-type topological structure. In this MOF material, there are three polyhedral cages of different sizes: from 12 pieces of [ Cu ]₂(CO₂)₄]Cuboctahedra formed by secondary structural units and a part of 24 isophthalic acids (as shown in figure 2 a); from 12 pieces of [ Cu ]₂(CO₂)₄]Truncated tetrahedrons formed by the secondary building blocks and 4 ligand molecules (see FIG. 2 b); from 24 pieces of [ Cu ]₂(CO₂)₄]Truncated octahedra formed by secondary building blocks and 8 ligand molecules (as shown in fig. 2 c). The three types of cages were held assembled in a ratio of 1:1:2, forming a non-through-hole (3, 24) MOF material connecting rht-type topologies (see fig. 2 d).

FIG. 3 is an optical photograph of a sample of the amino-modified metal organic framework material of example 1.

FIG. 4 is an infrared spectrum of the amino-modified metal organic framework material of example 1; in FIG. 4, a is an infrared spectrum curve of an amino-bridged hexacarboxylic acid ligand shown in formula (I), b is an infrared spectrum curve of an amino-modified metal organic framework material, c is an infrared spectrum curve of an amino-modified metal organic framework material after acetone soaking treatment, and d is an infrared spectrum curve of an activated amino-modified metal organic framework material; as can be seen from FIG. 4, the ligand molecule was successfully coordinated to the secondary building block, and no residue remained. And DMF molecules were not present in the MOF organic framework material of example 1 after the soaking treatment and activated by the method in example 4.

FIG. 5 is a thermogravimetric analysis of the amino-modified metal-organic framework material of example 1; in FIG. 5, a is the thermogravimetric curve of the amino-modified metal-organic framework material after activation; b is a thermogravimetric curve of the amino modified metal organic framework material; c is a thermogravimetric curve of the amino modified metal organic framework material after the acetone soaking treatment; as can be seen from fig. 5, the MOF material of example 1 after soaking treatment, and the MOF material of example 1 activated by the method of example 4 did not approach a straight line until the curve of the sample after 400 ℃, indicating that the material had decomposed and completely collapsed the framework, indicating that the MOF material of the present invention has good thermal stability.

FIG. 6 is an X-ray powder diffraction pattern of the amino-modified metal-organic framework material of example 1; in fig. 6, a is the X-ray powder diffraction curve of the activated amino-modified metal-organic framework material; b is an X-ray powder diffraction curve of the amino modified metal organic framework material; c is an X-ray powder diffraction curve of the amino modified metal organic framework material after the acetone soaking treatment; as can be seen from fig. 6, the PXRD curve of the MOF material in example 1 substantially coincided with the simulated PXRD curve, indicating that the sample was highly pure and free of impurities. And the MOF material in example 1 activated by the method in example 4 is the same as the MOF and simulated PXRD curve in example 1, indicating that the MOF material has good stability.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the specific features in any suitable way, and the invention will not be further described in relation to the various possible combinations in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.

Claims

1. An amino-bridged hexacarboxylic acid ligand, characterized in that it has the structure of formula (I),

2. a method of preparing the ligand of claim 1, comprising:

3. the method according to claim 2, wherein the compound represented by the formula (II) and cyanuric chloride are used in a molar ratio of 1: 0.3-0.4.

4. The process according to claim 2 or 3, wherein in step (1), the conditions of the reaction are at least such that: the temperature is 70-120 ℃, and the time is 6-12 h.

5. The process according to claim 2 or 3, wherein in step (2), the conditions of the hydrolysis reaction at least satisfy: the temperature is 40-90 ℃ and the time is 4-10 h.

6. An amino-modified metal organic framework material is characterized in that the molecular formula of the amino-modified metal organic framework material is as follows: [ Cu ]₃(C₄₅H₂₄N₆O₁₂)]_nWherein n is a positive integer; the amino modified metal organic framework material is prepared from a ligand shown as a formula (I) and CuSO₄·5(H₂O) carrying out coordination reaction to obtain;

the amino modified metal organic framework material belongs to a tetragonal system, I4/m space group, and the unit cell parameters are respectively as follows:

α＝90.00°，β＝90.00°，γ＝90.00°。

7. a preparation method of an amino modified metal organic framework material is characterized by comprising the following steps: in the presence of a solvent, a ligand represented by the formula (I) and CuSO₄·5(H₂O) carrying out coordination reaction, wherein the solvent is at least one of DMF, DMSO, water and acetonitrile;

α＝90.00°，β＝90.00°，γ＝90.00°。

8. the method of claim 7, wherein the solvent is a combination of DMF and DMSO.

9. The method of claim 7, wherein the DMF and DMSO are used in a volume ratio of 1: 0.8-1.2.

10. The method according to claim 7, wherein the amount of DMF is 0.1-0.3mL per 1mg of the ligand of formula (I).

11. The method according to claim 7, wherein the ligand represented by formula (I) and CuSO₄·5(H₂O) is 1: 2-8.

12. The method of claim 7, wherein the coordination reaction satisfies at least the following conditions: the reaction temperature is 70-120 ℃, and the reaction time is 48-120 h.

13. The method of any of claims 7-12, wherein the method further comprises: before the coordination reaction, the solvent, the ligand shown in the formula (I) and the CuSO are firstly contained₄·5(H₂And the reaction system of O) is contacted with an acidic substance at the temperature of not higher than 35 ℃ to carry out acidification, and then the temperature of the acidified reaction system is raised to carry out the coordination reaction, wherein the acidic substance is at least one of fluoboric acid, hydrochloric acid and phosphoric acid.

14. The method of claim 13, wherein the acidic substance is fluoroboric acid.

15. Amino-modified metal-organic framework material obtainable by the process according to any one of claims 7 to 14.

16. Use of the amino-modified metal-organic framework material of claim 6 or 15 in selective adsorption separation of CO₂/CH₄And/or CO₂/N₂The use of (1).

17. Selective adsorption separation of CO₂/CH₄And/or CO₂/N₂The method of (a), wherein the method comprises:

wherein, in the step (a), the amino-modified metal-organic framework material is the amino-modified metal-organic framework material according to claim 6 or 15.

18. The method according to claim 17, wherein, in the step (1), the step of activating treatment comprises a soaking treatment and a degassing treatment, wherein the soaking treatment is performed in a solution containing anhydrous acetone, and the time of the soaking treatment is 70-90 h.

19. The method of claim 18, wherein the anhydrous acetone is used in an amount of 0.1-0.5mL per 1mg of the amino-modified metal-organic framework material in the soaking treatment.

20. The method of claim 18, wherein the degassing process is conditioned to at least: the temperature is 80-130 ℃ and the time is 5-20 h.