CN111004398A

CN111004398A - Microporous Cu-MOF material and preparation method and application thereof

Info

Publication number: CN111004398A
Application number: CN201911338978.8A
Authority: CN
Inventors: 石娜; 梁林锋; 张献明
Original assignee: Shanxi University
Current assignee: Shanxi University
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2020-04-14
Anticipated expiration: 2039-12-23
Also published as: CN111004398B

Abstract

The invention discloses a microporous Cu-MOF material and a preparation method and application thereof, wherein the chemical formula of the microporous Cu-MOF material is CuTIPA.n (DMF) (n is 1-3), wherein TIPA^2‑Is 5- (triazole-1-yl) isophthalic acid anion, DMF is N, N-dimethylformamide, and the microporous Cu-MOF material has better water vapor stability and organic solvent stability. The gas adsorption test result shows that the material is used for treating CO₂Has better selective adsorption performance to CO₂/N₂And CO₂/CH₄Has better selective separation performance, and can be applied to CO in the exhaust gas discharged by a power plant₂The capture separation of natural gas and the purification of natural gas.

Description

Microporous Cu-MOF material and preparation method and application thereof

Technical Field

The invention relates to the technical field of metal-organic framework material preparation, in particular to a microporous Cu-MOF material and a preparation method and application thereof.

Background

Since the industrial revolution, with the development of the social industry, people have more and more depended on the combustion of fossil fuels such as coal, oil and natural gas to obtain energy,this also results in atmospheric CO₂The concentration of the compound is increased sharply, and the compound has great influence on climate and ecosystem, which endangers the sustainable development of human society. According to statistics, sixty percent of the CO is currently worldwide₂From exhaust gases discharged from power plants, the main constituent of the exhaust gases being CO₂、N₂And other small amounts of contaminant gases such as water vapor. So that an efficient and selective CO installation is made in a coal or gas power plant₂A capture device is necessary, and the measure can greatly reduce the emission of carbon dioxide in the world. At present, organic amine is mainly used for treating CO in exhaust gas of power plant in industry₂The capture is carried out, and then the desorption is carried out under the high-temperature condition, but the method has the problems of serious corrosion of equipment, high energy consumption in the desorption process and the like. Therefore, the search for new materials capable of selectively capturing carbon dioxide is urgent.

Over the past few decades, several classes of materials including Ionic Liquids (ILS), zeolites, porous carbons, porous organic polymers, Covalent Organic Frameworks (COFs) and metal-organic frameworks (MOFs) have been developed for CO in power plant exhaust₂Capture and transformation of (2). Among them, Metal Organic Frameworks (MOFs), also known as Porous Coordination Polymers (PCPs), are a crystalline porous material having a periodic network structure formed by self-assembly of metal centers (metal ions or clusters) and bridged organic ligands. Compared with the traditional porous materials such as activated carbon, molecular sieve and the like, the MOFs material has the characteristics of rich topological types, adjustable pore diameter, high porosity, easy functionalization and the like. Therefore, the porous metal organic framework is widely applied to the fields of gas storage, separation, catalysis, drug delivery, fluorescence identification and the like. The MOFs have good application prospect in the field of gas storage and separation due to the advantages of designability of the structure, harmony of pore channel environment, simple synthesis process, reversibility of adsorption and desorption, low energy requirement, strong gas capture capacity and the like. Over the past decades, scientists have designed and constructed a large number of new MOF materials. Scientists can use open metal vacant sites (OMSs) and N, O, Cl, -NH₂Modification of MOF materials with polar atoms and groups, such as-COOHTo enhance CO₂Interaction between gas molecules and the framework, thereby promoting selective CO capture₂And made good progress. These excellent properties are not comparable to those of the conventional porous materials. However, the stability of the framework of many MOFs materials is at a disadvantage compared to traditional porous materials, and most of the newly reported MOFs have poor stability in water vapor, and partial or even total collapse of the framework is likely to occur after contact with water vapor. In addition, some MOFs with better water vapor stability reported at present face CO₂The problem of low adsorption quantity and selectivity severely limits the practical CO₂The application of capture separation.

Disclosure of Invention

In view of the above, the present invention aims to provide a microporous Cu-MOF material, and a preparation method and application thereof, aiming to overcome the existing selective CO capture₂The existing equipment is seriously corroded, the energy consumption of the desorption process is high, and the existing method for selectively capturing CO₂The MOFs material does not simultaneously have high stability of frame water vapor and CO₂High adsorption quantity and selectivity, etc.

In order to achieve the purpose of the invention, the technical scheme is as follows:

a microporous Cu-MOF material having the formula CuTIPA n (dmf) (n ═ 1-3), wherein TIPA^2-Is 5- (triazol-1-yl) isophthalic acid anion, DMF is N, N-dimethylformamide, TIPA^2-The structural formula of (1) is as follows:

a method of making a microporous Cu-MOF material as described above, comprising the steps of:

mixing a mixture of 1: adding 0.9-1.1 parts of copper salt and ligand into the mixed solvent, performing ultrasonic treatment until the ligand and the copper salt are uniformly mixed, and reacting at 80-150 ℃ for 1-5 days to obtain a microporous Cu-MOF material;

the copper salt is copper nitrate trihydrate;

the ligand is 5- (triazole-1-yl) isophthalic acid (H)₂TIPA)；

The mixed solvent is water, DMF and N, N-Dimethylacetamide (DMA) according to a volume ratio of 1: 0.5-5: 1 or water and DMF in a volume ratio of 1: 1-5, or mixing water and DMA according to the volume ratio of 1: 1-5, and mixing.

Selective separation of CO from microporous Cu-MOF materials as described above₂/N₂And CO₂/CH₄The use of (1).

Selective separation of CO from microporous Cu-MOF materials as described above₂/N₂And CO₂/CH₄The application method comprises the following steps: soaking the microporous Cu-MOF material in ethanol for 72h to exchange high-boiling-point DMF molecules in pore channels, degassing the exchanged microporous Cu-MOF material at 100 ℃ for 8h, removing the DMF molecules in the pore channels, and filling the material into a container for storing CO₂In a sorbent plant.

The invention has the beneficial effects that:

(1) the synthetic raw materials are cheap and easy to obtain, the conditions are mild, and the preparation method is easy for mass production;

(2) the microporous Cu-MOF material prepared by the method has better thermal stability, water vapor stability and organic solvent stability, and can still keep an original framework structure after guest molecules are removed;

(3) the microporous Cu-MOF material prepared by the invention has CO at 273K₂The adsorption capacity of the adsorbent can reach 99cm³g^-1And N is₂The adsorption capacity of (2) is only 6.8cm³g^-1The IAST selectivity can reach 71.7 at most; 298K CO₂The maximum adsorption capacity of the adsorbent can reach 56.6cm³g^-1And N is₂The adsorption capacity of (2) is only 3.5cm³g^-1According to IAST theoretical calculation, the selectivity can reach 129 at most; in addition to this, Cu-MOF is not only directed to CO₂Has better selective adsorption performance and CO adsorption₂/CH₄Has better selective separation performance. In conclusion, the Cu-MOF can be applied to CO in exhaust gas discharged by a power plant₂Capture separation and natural gas purification ofAnd the like, and has bright industrial application prospect.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a diagram of the coordination environment of ligands and metal nodes of a microporous Cu-MOF material;

FIG. 2 is a diagram of a diamond channel structure of a microporous Cu-MOF material;

FIG. 3 is a zigzag type channel structure diagram of a microporous Cu-MOF material;

FIG. 4 is an X-ray powder diffraction pattern of the microporous Cu-MOF material of the present invention, wherein a is a comparison of XRD pattern of the synthesized microporous Cu-MOF material and XRD pattern obtained from CIF file simulation of Cu-MOF, and b is XRD pattern obtained after the microporous Cu-MOF material is treated in different atmosphere;

FIG. 5 is a graph of the adsorption of a gas by a microporous Cu-MOF material, wherein graph a is 77K N₂FIG. b is CO at 273K₂、N₂、CH₄Graph c is the IAST selectivity at different ratios of carbon dioxide to nitrogen at 273K; panel d is 298K CO₂、N₂、CH₄Gas adsorption profile of (a); panel f is a calculated adsorption heat curve based on the 273K and 298K adsorption curves;

FIG. 6 is a graph of CO calculated according to IAST theory for a microporous Cu-MOF material of the present invention₂/CH₄Selectivity diagram, wherein diagram a is 273K CO₂/CH₄Selectivity at different ratios; panel b is 298K CO₂/CH₄Selectivity at different ratios.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In order to construct the MOF with better selective adsorption, the microporous Cu-MOF material prepared by the invention adopts 5- (triazole-1-yl) isophthalic acid (H) containing two carboxyl groups and triazole at meta positions on 1, 3 and 5 positions on a benzene ring₂TIPA) as ligand, the design concept is based on the following points: on the one hand, the carboxylic acid group at the meta position on the ligand shows strong metal coordination capacity and is easy to coordinate with binuclear copper to construct a main body framework. Meanwhile, triazole at the 5-position has stronger coordination capacity with copper ions, and the water vapor stability of the copper can be obviously improved by occupying the axial position of binuclear copper. In addition, the uncoordinated nitrogen atoms on the triazole can provide polar sites for the framework, which can obviously improve CO₂Gas adsorption capacity. Based on such design concept, we designed and synthesized a microporous Cu-MOF material in the present invention, the Cu-MOF material is composed of ligand (H)₂TIPA) and the metal salt Cu (NO)₃)₂Synthesized by a solvothermal method. As shown in fig. 1-3, in this structure, four carboxyl groups from different ligands coordinate with binuclear copper to form a classical wheel-paddle structure, and the axial site of the binuclear copper is occupied by the nitrogen atom of triazole on the ligand, extending into a three-dimensional network structure. Compared with the traditional binuclear copper structure with an exposed axial position, the metal node cannot be attacked by object molecules (such as water molecules) due to the coordination of the axial position of the binuclear copper structure by nitrogen atoms on triazole, so that the main body frame has excellent water vapor stability. In addition, as shown in FIG. 2, in the structure, a large number of non-coordinated polar N atoms are distributed on one-dimensional pore channel wall, which is favorable for promoting CO₂The capture and separation of the MOF material have great application potential.

Example 1

example 2

A method of making a microporous Cu-MOF material according to example 1, comprising the steps of:

11.6mg of H₂TIPA was placed in a 20mL vial with a Teflon cap, 11.6mg of a mixed solvent of 1mL of water, 2mL of DMF and 1mL of DMA was added thereto, 50uL of a 1mol/L solution of copper nitrate was added thereto and added thereto, and sonication was performed to copper nitrate trihydrate and H₂TIPA was mixed well, and then the vial was covered with a lid and placed in an oven at 85 ℃ for reaction for three days to obtain a blue rod-like crystal, i.e., a microporous Cu-MOF material.

Example 3

Selective separation of CO from microporous Cu-MOF materials as described in example 2₂/N₂And CO₂/CH₄The use of (1).

Example 4

Selective separation of CO from microporous Cu-MOF materials as described in example 3₂/N₂And CO₂/CH₄The application method comprises the following steps: soaking the microporous Cu-MOF material in ethanol for 72h to exchange high boiling point DMF molecules in the pore channels (during which fresh ethanol solvent is exchanged for three times), degassing the exchanged microporous Cu-MOF material at 100 deg.C for 8h, removing DMF molecules in the pore channels, and filling into a container for storing CO₂In a sorbent plant.

Example 5 Crystal Structure determination

Selecting a microporous Cu-MOF material, and selecting a single crystal with proper size and good crystal quality under a polarizing microscope to perform an X-ray single crystal diffraction test at room temperature. Using Rigaku type X-raysSingle crystal diffractometer using graphitized Mo-Ka rays

Is a source of incident radiation, in

Collecting diffraction points by scanning, resolving the structure by using SHELXT program via OLEX2 interface program, and performing ray dispersion on the ray obtained by | F²The method performs full matrix least squares refinement. All non-hydrogen atoms are refined anisotropically, and all hydrogen atoms are estimated according to the riding model, calculated in geometric position, fixed and refined.

As shown in fig. 1-3, fig. 1 is a coordination environment diagram of ligands and metal nodes of a microporous Cu-MOF material structure, in the Cu-MOF structure, four carboxyl groups from different ligands coordinate with binuclear copper to form a wheel-paddle structure, and the axial position of the binuclear copper is occupied by one nitrogen atom of triazole on the ligand and then further extended to form a three-dimensional network structure. Compared with the traditional binuclear copper structure with an exposed axial position, other object molecules (such as water molecules) and the like cannot attack metal nodes after the axial position is coordinated by nitrogen atoms, so that the main body framework has excellent water vapor stability. FIG. 2 is a diagram of rhombohedral channels of a microporous Cu-MOF material with a large number of non-coordinated polar N atoms decorated on the channel surfaces, which would be beneficial for CO promotion₂Adsorption of (3). FIG. 3 is a side view of a zig-zag type channel of a microporous Cu-MOF material.

Example 6 stability testing

And respectively soaking 40mg of microporous Cu-MOF material samples in N, N-dimethylacetamide, N-dimethylformamide, carbon tetrachloride, isopropanol, diethyl ether and N-hexane for 24 hours, filtering and then carrying out an X-ray powder diffraction test.

Samples of 40mg of microporous Cu-MOF material were exposed to air for 30 days and X-ray powder diffraction measurements were performed every 7 days.

The results of the tests are shown in fig. 4, fig. 4 being an X-ray powder diffraction pattern (XRD) in which: the figure a is a comparison graph of XRD patterns of the synthesized microporous Cu-MOF material and simulated XRD patterns of a CIF file, and the figure a shows that: the XRD pattern newly synthesized by the microporous Cu-MOF material is well consistent with the XRD pattern obtained by simulation, which shows that the Cu-MOF pure phase is successfully synthesized; and the figure b is a stability test chart of the microporous Cu-MOF material, and the obtained XRD pattern and the simulated XRD pattern can be well fitted after the microporous Cu-MOF material is exposed in the air for 30 days or soaked in an organic solvent for 24 hours, so that the Cu-MOF material has good organic solvent stability and water vapor stability. Similarly, the powder diffraction of the sample after the organic solvent in the pores is removed is not obviously changed, which shows that the framework structure of the microporous Cu-MOF material is well maintained.

Example 7 gas adsorption test

And (3) measuring a gas adsorption and desorption curve on a Kangta chemical adsorption instrument, degassing the activated microporous Cu-MOF material sample on the adsorption instrument at 120 ℃ for 8 hours, and performing subsequent gas adsorption analysis and test after degassing is finished. The test results are shown in fig. 5 and 6.

FIG. 5 is a graph of the adsorption profile of the microporous Cu-MOF material of the present invention to a single component gas, wherein FIG. a is 77K N₂The specific surface area of the material is 635m according to the calculation of the isothermal adsorption curve²g^-1. Panel b is CO at 273K₂、N₂、CH₄At 273K, 1 atmosphere, CO₂The adsorption capacity of the adsorbent can reach 99cm³g^-1(ii) a FIG. c shows different ratios of carbon dioxide to nitrogen at 273K (wherein different ratios refer to CO:₂：N₂the gas volume ratio of (A) is: 0.85: 0.15,0.2: 0.8 and 0.10: 0.9), calculating the obtained selectivity result according to an IAST theory (ideal solution adsorption theory); panel d is 298K CO₂、N₂、CH₄Gas adsorption graph of (1), showing CO₂The maximum adsorption capacity of the adsorbent can reach 56.6cm³g^-1(ii) a FIG. e is the calculated selectivity results according to IAST theory at different ratios of carbon dioxide to nitrogen at 298K; FIG. f is a calculated adsorption heat curve from the 273K and 298K adsorption curves, from 16kJ mol^-1Increased to 43kJ mol^-1Such an increasing trend indicates that there is a difference between the preferentially adsorbed carbon dioxide and the subsequently adsorbed carbon dioxideStronger interaction.

FIG. 6 is a schematic representation of the microporous Cu-MOF material CO of the present invention₂/CH₄Graph of selective separation performance test, graph a is 273K CO₂/CH₄Calculating selectivity results according to IAST theory under different proportion conditions; b is 298K CO₂/CH₄And (4) calculating selectivity results according to IAST theory under different proportion conditions.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement or combination made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

1. A microporous Cu-MOF material, characterized by: the chemical formula is CuTIPA.n (DMF) (n ═ 1-3), wherein TIPA^2-Is 5- (triazol-1-yl) isophthalic acid anion, DMF is N, N-dimethylformamide, TIPA^2-The structural formula of (1) is as follows:

2. a method of making the microporous Cu-MOF material of claim 1, comprising the steps of:

mixing a mixture of 1: copper salt of 0.9-1.1 and H₂Adding a TIPA ligand into a mixed solvent, performing ultrasonic treatment until the ligand is completely mixed with copper salt, and reacting at 80-150 ℃ for 1-5 days to obtain a microporous Cu-MOF material;

the copper salt is copper nitrate trihydrate;

the ligand is 5- (triazole-1-yl) isophthalic acid (H)₂TIPA)；

The mixed solvent is water, DMF and N, N-Dimethylacetamide (DMA) according to a volume ratio of 1: 0.5-5: 1 or mixing water and DMF according to the volume ratio of 1: 1-5, or mixing water and DMA according to the volume ratio of 1: 1-5, and mixing.

3. The microporous Cu-MOF material of claim 1, in selective separation of CO₂/N₂And CO₂/CH₄The use of (1).

4. Use of the microporous Cu-MOF material of claim 3 in the selective separation of CO₂/N₂And CO₂/CH₄The method is characterized by comprising the following steps: soaking the microporous Cu-MOF material in ethanol for 72h to exchange high-boiling-point DMF molecules in pore channels, degassing the exchanged microporous Cu-MOF material at 100 ℃ for 8h, removing the DMF molecules in the pore channels, and filling the material into a container for storing CO₂In a sorbent plant.