CN113461955A

CN113461955A - High-stability metal organic framework material, and preparation method and application thereof

Info

Publication number: CN113461955A
Application number: CN202010248149.7A
Authority: CN
Inventors: 龚奇菡; 陈毅飞; 崔佳; 姜浩锡; 吕雉; 董秀芹; 胡长禄; 耿中峰; 张上; 李兆飞; 马安
Original assignee: Tianjin University; Petrochina Co Ltd
Current assignee: Tianjin University; Petrochina Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2021-10-01
Anticipated expiration: 2040-03-31
Also published as: CN113461955B

Abstract

The invention discloses a high-stability metal organic framework material, which contains a modified UiO-66 structure of 2-amino terephthalic acid and has a specific surface area of 600m²/g～1000m²The pore diameter is 2.0 to 2.3nm, and the porosity is 0.35 to 0.55 ml/g. The invention also discloses a preparation method and application of the high-stability metal organic framework material.

Description

High-stability metal organic framework material, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of metal organic framework materials applied to aspects of gas storage, adsorption separation, catalysis and the like, and particularly relates to a metal organic framework material for adsorption separation of C6 isomer.

Background

Metal-Organic Frameworks (MOFs) are a new type of hybrid nanomaterial that has been developed in recent years. The material consists of two parts, namely an inorganic metal ion part and an oxygen and nitrogen-containing aromatic carboxylic acid or alkali, ester and other organic ligand parts, wherein the two parts are connected together in a self-assembly mode. The material has a porous structure similar to activated carbon and molecular sieve, and has adjustable pore size and certain flexibility, so that the material has unique adsorption performance, catalytic performance and gas storage performance. However, the stability of MOFs materials has been a bottleneck limiting their widespread use. The material UiO-66 is simple to synthesize, has the characteristics of high porosity, large effective specific surface area, high stability and the like, and has potential commercial and industrial application values.

The method for separating the C5/C6 isomerization products mainly comprises a rectification method and an adsorption separation method, and the method has the advantages that the C5-C6 alkane fraction is lighter, the boiling points of isomers are close, the precision of rectification separation is limited, the purity of separated normal alkane is lower, and the method is smaller in the range of improving the octane number. The adsorption separation method is to selectively adsorb normal paraffin by using the selective adsorption performance of molecular sieve pore channels on adsorbed substances, so that the normal paraffin is separated from isoparaffin. The adsorption separation method has high separation efficiency, low energy consumption and high purity of separated products, and can greatly improve the octane number of C5/C6 isomerized products.

The adsorbents used in the existing adsorption separation method are 5A molecular sieve adsorbents. The effective pore size of the 5A molecular sieve is about

The normal alkane molecule has an equivalent diameter of about

While the equivalent diameter of the non-normal hydrocarbons is greater than

The normal alkane can enter the micro channel of the 5A molecular sieve, thereby being separated from the hydrocarbon mixture. However, the existing 5A molecular sieves have limited adsorption capacity and only adsorb. Of the 5 isomers of C6, the n-hexane octane number was lowest (RON 25), the branched alkanes 2-methylpentane and 3-methylpentane were slightly higher (RONs 73 and 74, respectively), and the unbranched alkanes 2, 2-dimethylbutane and 2, 3-dimethylbutane were the highest (RONs 92 and 103.6, respectively). Adsorption of only straight chain paraffins results in the raffinate including all branched paraffins, with monobranched paraffins resulting in an average octane number of the raffinate below 90; while the octane number of the raffinate is increased if the adsorbent material is capable of adsorbing a portion of the monobranched paraffins simultaneously. In order to increase the capacity or to allow the adsorbent material to adsorb both straight-chain paraffins and mono-branched paraffins, new materials are required. And because the traditional inorganic porous materials are complex in synthesis and preparation processes, and the structures, properties and functions of the materials, such as pore shapes and sizes, are not easy to realize the structurization and functionalization of the materials by a molecular cutting method, the further development of the materials is restricted.

CN109317104A discloses a mercapto-functionalized metal-organic framework material, preparation and application thereof, wherein ammonia is describedRadical functionalized metal-organic framework UiO-66-NH₂The synthesis of (2): mixing zirconium chloride, 2-aminoterephthalic acid, N-dimethylformamide solution and concentrated hydrochloric acid solution, transferring the mixture after ultrasonic treatment to a reaction kettle with a polytetrafluoroethylene lining, screwing the mixture, and reacting the mixture in an oven at 200-250 ℃ for 8-20 hours, preferably 220 ℃ and 16 hours. The sulfhydryl functionalized metal-organic framework material, the preparation and the application thereof belong to the technical field of metal-organic framework materials. The compound has a structural formula that UiO-66-SH is used as a heavy metal ion adsorbent in an aqueous solution for adsorbing and removing heavy metal ions in the aqueous solution, and adsorption data show that UiO-66-SH can well adsorb and remove mercury ions (Hg (II)) in the aqueous solution and UiO-66-NH₂Compared with the prior art, the adsorption performance is greatly improved, and the adsorption capacity can reach 490.98 mg/g. In addition, UiO-66-SH can selectively adsorb and remove mercury ions under multi-ion conditions.

The prior art mainly comprises a rectification method and an adsorption separation method for separating C5/C6 isomerization products, and the method has the advantages that the C5-C6 alkane fraction is light, the boiling points of isomers are close, the precision of rectification separation is limited, the purity of separated normal alkane is low, and the method is small in octane number improvement amplitude. The adsorption separation method is to selectively adsorb normal paraffin by using the selective adsorption performance of molecular sieve pore channels on adsorbed substances, so that the normal paraffin is separated from isoparaffin. The adsorption separation method has high separation efficiency, low energy consumption and high purity of separated products, and can greatly improve the octane number of C5/C6 isomerized products.

The normal alkane molecule has an equivalent diameter of about

While the equivalent diameter of the non-normal hydrocarbons is greater than

The normal alkane can enter 5A minutesAnd sieving the inside of the micro-channel so as to separate the hydrocarbon mixture. However, the existing 5A molecular sieves have limited adsorption capacity and only adsorb. Of the 5 isomers of C6, the n-hexane octane number was lowest (RON 25), the branched alkanes 2-methylpentane and 3-methylpentane were slightly higher (RONs 73 and 74, respectively), and the unbranched alkanes 2, 2-dimethylbutane and 2, 3-dimethylbutane were the highest (RONs 92 and 103.6, respectively). Adsorption of only straight chain paraffins results in the raffinate including all branched paraffins, with monobranched paraffins resulting in an average octane number of the raffinate below 90; while the octane number of the raffinate is increased if the adsorbent material is capable of adsorbing a portion of the monobranched paraffins simultaneously. In order to increase the capacity or to allow the adsorbent material to adsorb both straight-chain paraffins and mono-branched paraffins, new materials are required. And because the traditional inorganic porous materials are complex in synthesis and preparation processes, and the structures, properties and functions of the materials, such as pore shapes and sizes, are not easy to realize the structurization and functionalization of the materials by a molecular cutting method, the further development of the materials is restricted.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a high-stability metal organic framework material, a preparation method and application thereof, wherein the metal organic framework material can be applied to the aspects of gas storage, adsorption separation, catalysis and the like, and particularly relates to the adsorption separation of C6 isomer.

Therefore, the invention provides a high-stability metal organic framework material, which contains a modified UiO-66 structure of 2-amino terephthalic acid and has a specific surface area of 600m²/g～1000m²(ii) per gram, pore diameter of 2.0-2.3nm, and porosity of 0.35-0.55 ml/g.

The metal-organic framework material according to the present invention preferably has a specific surface area of 700m²/g～900m²The pore diameter is 2.1-2.2 nm, and the porosity is 0.40-0.45 ml/g.

The invention also provides a preparation method of the metal organic framework material, which comprises the following steps:

(1) mixing a zirconium source-containing metal salt, 2-amino terephthalic acid and a solvent to form an intermediate solution, and further mixing the intermediate solution with glacial acetic acid to form a mixed solution, wherein the molar ratio of the zirconium source-containing metal salt to the 2-amino terephthalic acid is 1-1.7: 1.5-1;

(2) reacting the mixed solution, wherein the reaction temperature is 40-160 ℃, and the reaction time is 12-24 h;

(3) after the reaction is finished, cooling to 15-35 ℃;

(4) removing the upper mother liquor, washing the reaction product, filtering, and naturally drying at 15-35 ℃ to obtain the powdery adsorbent material.

In the step (1), the adding mode and sequence of the raw materials include but are not limited to respectively dissolving metal salt and 2-amino terephthalic acid in DMF, mixing, and adding glacial acetic acid; or metal salt and 2-amino terephthalic acid are mixed and then dissolved in DMF or glacial acetic acid solution, and the like.

In the step (1), ultrasonic waves are preferably used in the mixing process (which can also include the dissolution process of the solute), the recommended frequency is 20-50 KHz, the time is preferably 5-30 min, and the ultrasonic mode is higher than the magnetic stirring strength, so that the reaction liquid is easier to mix uniformly.

In step (1) of the present invention, the metal salt containing a zirconium source is preferably ZrCl₄，ZrCl₄And 2-aminoterephthalic acid are preferably in a molar ratio of 1:1.5 to 1.5: 1.

In step (1) of the present invention, ZrCl₄The addition amount of (B) is preferably not less than 0.03 mol.

The method of "washing the reaction product" in step (4) of the present invention is not particularly limited, and any method commonly used in the art may be used, and the washing solution is usually DMF, dichloromethane, methanol, ethanol, etc., and the preferred washing method is washing with DMF, followed by washing with methanol and ethanol. The specific further preferable method of the invention is as follows: removing the upper mother liquid of the crystals obtained by the reaction, respectively soaking the crystals in DMF (dimethyl formamide) and methanol, filtering the solution, and adding fresh ethanol to repeatedly wash the crystals.

In the preparation method of the metal organic framework material, the solvent is preferably at least one selected from DMF, DMA and methanol.

In the preparation method of the metal organic framework material, the solvent is preferably DMF.

In the preparation method of the metal-organic framework material, the ratio of the metal salt containing a zirconium source to the glacial acetic acid is preferably 1mol:2.5L to 1mol: 5L.

In the preparation method of the metal-organic framework material, the ratio of the metal salt containing a zirconium source to the glacial acetic acid is preferably 1mol: 3L.

In the preparation method of the metal organic framework material, the reaction temperature in the step (2) is preferably 100-120 ℃.

The preparation method of the metal organic framework material according to the present invention preferably further comprises, between step (2) and step (3): and carrying out ultrasonic treatment on the mixed solution, wherein the ultrasonic treatment time is 5-60 min.

In the preparation method of the metal organic framework material, preferably, in the step (4), the washing is: and sequentially soaking the reaction product in DMF and methanol, filtering, and adding fresh ethanol for repeated washing.

The invention also provides an application of the metal organic framework material in separation of hexane isomers.

UiO-66-NH provided by the invention₂The material can be applied to the separation of C6 isomer. The inventors have found that selective adsorption of linear and mono-branched paraffins results from the modification of the pore size of the structure by amino modification, resulting in higher adsorption of linear and mono-branched paraffins than for di-branched paraffins.

The inventor finds that the metal organic framework material UiO-66-NH can be improved by adding glacial acetic acid with a proper proportion into the reaction mother liquor₂The crystallinity of (2). Preparation of UiO-66-NH₂(Zr) wherein, in addition to the reaction raw materials and the solvent DMF, concentrated hydrochloric acid (e.g. CN109317104A), formic acid (e.g. CN108295825A), hydrochloric acid (e.g. CN106861627A) or the like is added during the preparation processNo other reagent (such as CN108636454A) is added in the process, and the functions are different. The addition of acid generally helps to adjust the pH of the solution to a pH value more suitable for crystallization; compared with concentrated hydrochloric acid, formic acid and glacial acetic acid contain carboxyl, can coordinate with metal ions, and have an occupying effect, and then the organic ligand slowly replaces formic acid/glacial acetic acid to form a target structure, so that the crystallization process is slower, and the crystal growth is more ordered. The materials are used in different purposes and are selected to be long.

The inventor also unexpectedly finds that, compared with formic acid, glacial acetic acid not only plays a role in occupying space, but also partially plays a role in supporting the pore channels of the framework, and is more favorable for forming crystals with perfect structures; in addition, the larger the amount of glacial acetic acid added, the more obvious the space occupying effect, and when the ratio of the metal salt to the glacial acetic acid is more than 1mol:2.5L, especially more than 1mol:3L, the crystallinity is obviously improved. The characteristic lies in that UiO-66-NH₂The material is particularly effective in separating isomers of C6.

Compared with the prior art, the invention has the following advantages:

1. the functional group modified UiO-66 prepared by the method has better crystallinity;

2. the functional group modified UiO-66 prepared by the method has larger adsorption capacity and better selectivity on hexane isomers.

3. The functional group modified UiO-66 prepared by the process of the present invention provides adsorptive selectivity to straight and mono-branched paraffins over di-branched paraffins. Compared with a 5A molecular sieve, the adsorbent has excellent adsorption capacity, and the adsorption capacity can reach 2.3 times of that of a 5A molecular sieve adsorbent.

Drawings

FIG. 1 shows the powder X-ray diffraction patterns of example 1(A) and comparative example 1(B)

FIG. 2 is the powder X-ray diffraction patterns of example 2(C) and comparative example 2(D)

FIG. 3 is the powder X-ray diffraction patterns of example 3(E) and comparative example 3(F)

FIG. 4 is the powder X-ray diffraction patterns of example 4(G and comparative example 4(H))

FIG. 5 is the adsorption curve for the C6 isomer on example 1.

FIG. 6 is an adsorption curve for the C6 isomer on comparative example 1.

FIG. 7 is the adsorption curve for the C6 isomer on comparative example 4.

Figure 8 is an adsorption and desorption isotherm for n-hexane at 25 ℃ for the 5A molecular sieve, comparative example 4 and example 2.

Detailed Description

The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.

Example 1

(1) 350mL of DMF was weighed into a 500mL beaker, and 9.790g of ZrCl was weighed₄Adding into DMF, and performing ultrasonic treatment for about 10 min;

(2) 6.972g of 2-amino terephthalic acid is weighed and added into the solution, and then 150mL of glacial acetic acid is added and stirred until the solution is completely dissolved;

(3) transferring the mixed solution in the step (2) to a hydrothermal reaction kettle with a polytetrafluoroethylene lining;

(4) loading a reaction kettle, and placing the reaction kettle in an oven, wherein the reaction temperature is 120 ℃, and the reaction time is 24 hours;

(5) after the reaction is finished, taking out the reaction kettle, and naturally cooling to 25 ℃;

(6) pouring out the mother liquor on the upper layer to obtain a light yellow product, adding 200mL of DMF into the light yellow product, fully stirring the mixture by using a glass rod, and standing and soaking the mixture for 12 hours; pouring out the upper layer liquid, then adding 200mL of methanol, fully stirring by using a glass rod, standing and soaking for 12 h;

(7) performing suction filtration, adding 200mL of fresh ethanol into the obtained product, fully stirring by using a glass rod, and standing; after 12h, replacing fresh ethanol, repeating the steps, and washing for four times in two days;

(8) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample A.

The powder X-ray diffraction pattern of sample A is shown in FIG. 1, and its specific surface area, pore size and porosity are shown in Table 1.

Comparative example 1

(2) 6.972g of 2-amino terephthalic acid is weighed and added into the solution, and then 150mL of hydrochloric acid is added and stirred until the solution is completely dissolved;

(6) pouring out the mother liquor on the upper layer to obtain a light yellow product, adding 200mL of DMF into the light yellow product, fully stirring the mixture by using a glass rod, standing and soaking the mixture for 12 hours, pouring out the liquid on the upper layer, adding 200mL of methanol into the mixture, fully stirring the mixture by using the glass rod, standing and soaking the mixture for 12 hours;

(8) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample B.

The powder X-ray diffraction pattern of sample B is shown in FIG. 1.

Example 2

(1) 9.790g of ZrCl were weighed out₄Adding into DMF, weighing 6.972g of 2-amino terephthalic acid, adding into a 500mL beaker, adding 350mL of DMF, adding 150mL of glacial acetic acid, and stirring until the mixture is completely dissolved; performing ultrasonic treatment for about 10 min;

(2) transferring the mixed solution in the step (1) into a glass bottle with a plastic cover;

(3) filling a reaction bottle, and placing the reaction bottle in an oven, wherein the reaction temperature is 120 ℃, and the reaction time is 24 hours;

(4) after the reaction is finished, taking out the reaction bottle, and naturally cooling to 25 ℃;

(5) pouring out the mother liquor on the upper layer to obtain a light yellow product, adding 200mL of DMF into the light yellow product, fully stirring the mixture by using a glass rod, and standing and soaking the mixture for 12 hours; pouring out the upper layer liquid, then adding 200mL of methanol, fully stirring by using a glass rod, standing and soaking for 12 h;

(6) performing suction filtration, adding 200mL of fresh ethanol into the obtained product, fully stirring by using a glass rod, and standing; after 12h, replacing fresh ethanol, repeating the steps, and washing for four times in two days;

(7) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample C.

The powder X-ray diffraction pattern of sample C is shown in FIG. 2, and its specific surface area, pore size and porosity are shown in Table 1.

Comparative example 2

(1) 9.790g of ZrCl were weighed out₄Adding into DMA, weighing 6.972g of 2-amino terephthalic acid, adding into a 500mL beaker, adding 350mL of DMA, adding 150mL of formic acid, and stirring until the mixture is completely dissolved; performing ultrasonic treatment for about 10 min;

(5) pouring out the mother liquor on the upper layer to obtain a light yellow product, adding 200mL of DMA into the light yellow product, fully stirring the mixture by using a glass rod, and standing and soaking the mixture for 12 hours; pouring out the upper layer liquid, then adding 200mL of methanol, fully stirring by using a glass rod, standing and soaking for 12 h;

(7) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample D.

The powder X-ray diffraction pattern of sample D is shown in FIG. 2.

Example 3

(1) Measure 192mL of DMA inIn a 250mL beaker, 3.356g of ZrCl were weighed₄Adding the mixture into DMA;

(2) 3.913g of 2-aminoterephthalic acid are weighed and added into the solution, stirred until the solution is completely dissolved, and 48ml of glacial acetic acid is added;

(4) loading a reaction kettle, and placing the reaction kettle in an oven, wherein the reaction temperature is 100 ℃, and the reaction time is 12 hours;

(5) after the reaction is finished, taking out the reaction kettle, and naturally cooling to room temperature;

(6) centrifuging to remove the upper mother liquor to obtain a light yellow product, adding 200mL of DMA into the light yellow product, fully stirring by using a glass rod, and standing and soaking for 12 hours; pouring out the upper layer liquid, then adding 200mL of methanol, fully stirring by using a glass rod, standing and soaking for 12 h;

(8) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample E.

The powder X-ray diffraction pattern of sample E is shown in FIG. 3, and its specific surface area, pore size and porosity are shown in Table 1.

Comparative example 3

(1) 192mL of DMF was weighed into a 250mL beaker, and 3.356g of ZrCl was weighed₄Adding into DMF;

(2) 3.913g of 2-aminoterephthalic acid is weighed and added into the solution, stirred until the solution is completely dissolved, and 28.8ml of glacial acetic acid is added;

(6) centrifuging to remove the upper mother liquor to obtain a light yellow product, adding 200mL of DMF, fully stirring with a glass rod, standing and soaking for 12 h; pouring out the upper layer liquid, then adding 200mL of methanol, fully stirring by using a glass rod, standing and soaking for 12 h;

(8) filtered and naturally dried at room temperature to give a pale yellow powder, which was designated sample F.

The powder X-ray diffraction pattern of sample F is shown in FIG. 3.

Example 4

(2) 6.972g of 2-amino terephthalic acid is weighed and added into the solution, and then 120mL of glacial acetic acid is added and stirred until the solution is completely dissolved;

(8) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample G.

The powder X-ray diffraction pattern of sample G is shown in FIG. 4, and its specific surface area, pore size and porosity are shown in Table 1.

Comparative example 4

(1) Measuring and taking 350mL of DMF in a 500mL beaker, 9.790g of ZrCl were weighed₄Adding into DMF, and performing ultrasonic treatment for about 10 min;

(2) 6.972g of terephthalic acid is weighed and added into the solution, and then 120mL of glacial acetic acid is added and stirred until the terephthalic acid is completely dissolved;

(8) filtered and naturally dried at room temperature to obtain a light yellow powder product, which is named sample H.

The powder X-ray diffraction pattern of sample H is shown in FIG. 4, and its specific surface area, pore size and porosity are shown in Table 1.

TABLE 1

As shown in Table 1, the BET specific surface areas of the samples A, C, E, G were all 600-1000m²The average pore diameter is between 2.0 and 2.3 nm; the porosity is between 0.35 and 0.55 ml/g. Also, as shown in FIGS. 1, 2 and 3, the powder X-ray diffraction pattern of sample A, C, E was all stronger than the peaks in sample B, D, F, indicating better crystallinity; as shown in FIG. 4, the peaks of sample G and sample H are strong, but sample H has a hetero-peak between 8 and 10 degrees, indicating that sample G is more crystalline.

Adsorption application test:

example 5

The UiO-66-NH in example 1 was added₂The material is taken to place about 50mg of adsorbent into a sample disk of an adsorption analyzer and then is vacuumized to 10 DEG^-5Pa, and then vacuumizing and activating for 6-12 h at 150 ℃. Adsorption isotherms at 25 ℃ were tested using n-hexane as representative of the linear C6 isomer, 2-methylpentane as representative of the mono-branched C6 isomer, and 2, 2-dimethylbutane as representative of the di-branched hexane isomer, as shown in fig. 5.

Comparative example 5

About 50mg of the adsorbent was placed in the sample pan of the adsorption analyzer for the UiO-66 material obtained in comparative example 1, and then vacuum was applied to 10 deg.C^-5Pa, and then vacuumizing and activating for 6-12 h at 150 ℃. Adsorption isotherms at 25 ℃ were tested using n-hexane as representative of the linear C6 isomer, 2-methylpentane as representative of the mono-branched C6 isomer, and 2, 2-dimethylbutane as representative of the di-branched hexane isomer, as shown in fig. 6.

Comparative example 5-1

About 50mg of the adsorbent was placed in the sample pan of the adsorption analyzer for the UiO-66 material obtained in comparative example 4, and then vacuum was applied to 10 deg.C^-5Pa, and then vacuumizing and activating for 6-12 h at 150 ℃. Adsorption isotherms at 25 ℃ were tested using n-hexane as representative of the linear C6 isomer, 2-methylpentane as representative of the mono-branched C6 isomer, and 2, 2-dimethylbutane as representative of the di-branched hexane isomer, as shown in fig. 7.

Example 6

The UiO-66-NH in example 2₂The material is taken to place about 50mg of adsorbent into a sample disk of an adsorption analyzer and then is vacuumized to 10 DEG^-5Pa, and then vacuumizing and activating for 6-12 h at 150 ℃. The adsorption isotherm at 25 ℃ was tested using n-hexane as representative of the linear C6 isomer, as shown in figure 8.

Comparative example 6

About 50mg of the adsorbent was placed in the sample pan of the adsorption analyzer for the UiO-66 material obtained in comparative example 4, and then vacuum was applied to 10 deg.C^-5Pa, then at 15Vacuumizing and activating for 6-12 h at 0 ℃. The adsorption isotherm at 25 ℃ was tested using n-hexane as representative of the linear C6 isomer, as shown in figure 8.

Comparative example 7

Taking 50mg of adsorbent from 5A molecular sieve material, placing the adsorbent into a sample tray of an adsorption analyzer, and vacuumizing to 10 DEG^-5Pa, and then vacuumizing and activating for 6-12 h at 150 ℃. The adsorption isotherm at 25 ℃ was tested using n-hexane as representative of the linear C6 isomer, as shown in figure 8.

As shown in FIG. 8, by subjecting 5A molecular sieves, UiO-66 and UiO-66-NH₂The n-hexane adsorption isotherm test of (A) compared with 5A molecular sieves, UiO-66 and UiO-66-NH₂The adsorption capacity of the adsorbent is greatly improved. The adsorption capacity of UiO-66 to n-hexane is 2.3 times of that of 5A molecular sieve at 25 ℃ and 80 mbar; UiO-66-NH₂The adsorption capacity for n-hexane was 1.9 times that of 5A molecular sieve. As can be seen from FIGS. 2 and 3, UiO-66 did not exhibit thermodynamic adsorptive separation properties for hexane isomers, but passed through NH₂Modified UiO-66-NH₂UiO-66-NH can be seen in the adsorption isotherm of₂The adsorption capacity of the straight chain hexane and the single straight chain hexane is higher than that of the double branched chain hexane, and certain separation property is presented. Known as NH₂The modified UiO-66 has the function of improving the separation performance of hexane isomer.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.

Claims

1. The high-stability metal organic framework material is characterized by comprising a modified UiO-66 structure of 2-amino terephthalic acid, and the specific surface area of the metal organic framework material is 600m²/g～1000m²The pore diameter is 2.0 to 2.3nm, and the porosity is 0.35 to 0.55 ml/g.

2. The metal organic bone according to claim 1A framework material, characterized in that the metal-organic framework material has a specific surface area of 700m²/g～900m²The pore diameter is 2.1-2.2 nm, and the porosity is 0.40-0.45 ml/g.

3. A method for preparing a metal-organic framework material according to claim 1, comprising the steps of:

(3) after the reaction is finished, cooling to 15-35 ℃;

4. The method of claim 3, wherein the solvent is at least one selected from DMF, DMA, and methanol.

5. The method of claim 3, wherein the solvent is DMF.

6. The method of claim 3, wherein the ratio of the zirconium-source-containing metal salt to the glacial acetic acid is from 1mol:2.5L to 1mol: 5L.

7. The method of claim 6, wherein the ratio of the zirconium-source containing metal salt to the glacial acetic acid is 1mol: 3L.

8. The method for preparing a metal-organic framework material according to claim 3, wherein the reaction temperature in step (2) is 100-120 ℃.

9. The method for preparing a metal-organic framework material according to claim 3, further comprising between step (2) and step (3): and carrying out ultrasonic treatment on the mixed solution, wherein the ultrasonic treatment time is 5-60 min.

10. The method for preparing a metal-organic framework material according to claim 3, wherein in step (4), the washing is: and sequentially soaking the reaction product in DMF and methanol, filtering, and adding fresh ethanol for repeated washing.

11. Use of a metal organic framework material according to claim 1 for the separation of hexane isomers.