MOF (Metal Organic Framework) compound with carbon dioxide-nitrogen-methane ternary mixture adsorption separation function under wide-temperature condition as well as preparation method and application of MOF compound

Abstract

The invention discloses an MOF compound with a carbon dioxide-nitrogen-methane ternary mixture adsorption separation function under a wide-temperature condition as well as a preparation method and application thereof, and relates to the field of inorganic chemistry, the chemical formula of the compound is [Zn (btzip) (H2btzip)]. 2DMF. 2H2O, in the formula, H2btzip is 4, 6-bis (triazole-1-yl) isophthalic acid, btzip is deprotonated 4, 6-bis (triazole-1-yl) isophthalic acid, DMF is N, N-dimethylformamide, and N, N-dimethylformamide is N, N-dimethylformamide. And N, N-dimethylformamide is used as a solvent. The invention also discloses a preparation method of the compound. The MOF compound prepared by adopting an azole-carboxylic acid difunctional coordination group ligand is of a three-dimensional frame structure containing a one-dimensional pore channel, and the material shows relatively high adsorption capacity on carbon dioxide, but has relatively low adsorption capacity on nitrogen and methane, so that the material has relatively high adsorption capacity on carbon dioxide. Therefore, the adsorbent has an excellent function of adsorbing and separating a carbon dioxide-nitrogen-methane ternary mixture.

Description

Technical Field

[0001] The present invention relates to the field of inorganic chemistry and material chemistry, and in particular to a MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under a wide temperature range, and a preparation method and application thereof. Background Art

[0002] In industrial production, carbon dioxide, nitrogen and methane are common gas components, and they often exist in the form of a mixture. In natural gas extraction, natural gas often contains a certain amount of carbon dioxide and nitrogen; in biogas production, the main component of biogas is methane, but it also contains a certain amount of carbon dioxide. Improving the purity of methane in natural gas increases its calorific value and utilization efficiency, and reduces energy waste. At the same time, carbon dioxide and nitrogen separated from the mixture can be used as chemical raw materials or in other fields. Therefore, separating these gases from the mixture has important application value in fields such as natural gas purification and chemical production.

[0003] Metal-organic frameworks, or MOFs for short, are crystalline materials formed by chemical bonds between metal ions or metal clusters and organic ligands. This type of material has the advantages of high specific surface area, pore structure, and controllability, and has broad application prospects in gas adsorption, separation, catalysis, drug delivery, and other fields. Among the many MOF structures, the coordination bonds formed by azole ligands and metal ions are usually stronger than those formed by carboxylic acid ligands. Combined with the diversity of carboxylic acid ligands, the structural types of MOFs are further enriched, making azole-carboxylic acid MOFs have higher structural stability, which is crucial for the long-term stability and durability of MOFs in practical applications. Azoles-carboxylic acid MOFs usually have high specific surface areas and rich pore structures, which enable them to adsorb a large number of gas molecules. In particular, for some small molecular gases such as carbon dioxide, nitrogen, and methane, azole-carboxylic acid MOFs exhibit excellent adsorption performance. In addition, by regulating the pore structure and surface functionalization of azole-carboxylic acid MOFs, selective adsorption of specific gas molecules can be achieved. The synthesis of related materials is of great significance. Summary of the invention

[0004] The object of the present invention is to provide a MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under wide temperature conditions, and a preparation method and application thereof.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under wide temperature conditions, wherein the chemical formula of the compound is [Zn(btzip)(H2btzip)]·2DMF·2H2O, wherein H2btzip is 4,6-bis(triazole-1-yl)isophthalic acid, btzip is deprotonated 4,6-bis(triazole-1-yl)isophthalic acid, and DMF is N,N-dimethylformamide.

[0007] Preferably, the MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide-nitrogen-methane has a three-dimensional framework structure, contains one-dimensional quadrilateral channels, and has a porosity of 39.2%.

[0008] The present invention also provides a method for preparing a MOF compound having a carbon dioxide-nitrogen-methane ternary mixture adsorption and separation function under wide temperature conditions, which adopts a solvent thermal synthesis method, uses Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid as raw materials, and specifically comprises the following steps:

[0009] (1) adding Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid to a mixed solvent of N,N-dimethylformamide-acetonitrile-hydrochloric acid to obtain a mixed solution;

[0010] (2) placing the mixed solution obtained in step (1) in a reaction kettle, heating it to 120-140° C. in a sealed state and maintaining it for 70-75 hours;

[0011] (3) cooling the temperature in the reaction kettle to room temperature at a rate of 5 to 7° C. / hour to obtain colorless block crystals;

[0012] (4) The colorless block crystals obtained in step (3) are exchanged in methanol, then activated under vacuum conditions, and naturally cooled to room temperature to obtain a MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under a wide temperature range.

[0013] Preferably, the molar ratio of Zn(NO3)2·6H2O to 4,6-bis(triazole-1-yl)isophthalic acid is 2:1.

[0014] Preferably, in the mixed solvent, the volume ratio of N,N-dimethylformamide:acetonitrile:hydrochloric acid is 4:4:0.05.

[0015] Preferably, in step (4), the exchange time of the colorless block crystals in methanol is 70 to 80 hours.

[0016] Preferably, in step (4), the activation temperature is 150-160° C., and the activation time is 6-8 hours.

[0017] The present invention also provides the use of the above MOF compound in the adsorption and separation of a ternary mixture of carbon dioxide-nitrogen-methane.

[0018] Preferably, the conditions for the adsorption separation are: under a wide temperature range of 273-333K and a pressure of 100KPa.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention uses a ligand with a bifunctional azole-carboxylic acid coordination group to prepare a novel porous metal organic framework material for adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane, which has simple steps, is easy to operate, and has low equipment requirements;

[0021] (2) The prepared metal organic framework material is a three-dimensional framework structure containing one-dimensional channels. The channel surface contains uncoordinated carboxyl O atoms and triazole N atoms, etc. It has a high adsorption capacity for carbon dioxide, but a low adsorption capacity for nitrogen and methane. It has excellent adsorption and separation function for carbon dioxide-nitrogen-methane ternary mixture. The adsorption capacity for carbon dioxide, nitrogen and methane is 133.2-65.9 cm 3 g -1 、14.5~6.7cm 3 g -1 and 46.1~14.3cm 3 g -1 , which has important application value in the fields of natural gas purification and chemical production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Zn in the MOF compound described in Example 1 of the present invention 2+ Coordination environment diagram of the ion;

[0023] Figure 2 The layered structure of the MOF compound described in Example 1 of the present invention;

[0024] Figure 3 It is the three-dimensional framework structure of the MOF compound described in Example 1 of the present invention;

[0025] Figure 4 The adsorption isotherms of carbon dioxide, nitrogen and methane of the MOF compound described in Example 1 of the present invention at 273K;

[0026] Figure 5 The adsorption isotherms of carbon dioxide, nitrogen and methane of the MOF compound described in Example 1 of the present invention at 298K;

[0027] Figure 6The adsorption isotherms of carbon dioxide, nitrogen and methane of the MOF compound described in Example 1 of the present invention at 313K;

[0028] Figure 7 The adsorption isotherms of carbon dioxide, nitrogen and methane of the MOF compound described in Example 1 of the present invention at 333K;

[0029] Figure 8 The carbon dioxide / methane adsorption selectivity curve of the MOF compound at 273K to 333K calculated by ideal adsorption solution theory in Example 1 of the present invention;

[0030] Fig. 9 The carbon dioxide / nitrogen adsorption selectivity curve of the MOF compound at 273K to 333K calculated by the ideal adsorption solution theory in Example 1 of the present invention;

[0031] Fig.10 The dynamic breakthrough curve of the MOF compound described in Example 1 of the present invention at 273K in a ternary mixture of carbon dioxide-nitrogen-methane with a volume ratio of 5:5:5;

[0032] Fig.11 The dynamic breakthrough curve of the MOF compound described in Example 1 of the present invention at 298K in a ternary mixture of carbon dioxide-nitrogen-methane with a volume ratio of 5:5:5;

[0033] Fig.12 The dynamic breakthrough curve of the MOF compound of Example 1 of the present invention at 313K in a ternary mixture of carbon dioxide-nitrogen-methane with a volume ratio of 5:5:5;

[0034] Fig.13 This is the dynamic breakthrough curve of a ternary mixture of carbon dioxide-nitrogen-methane in a volume ratio of 5:5:5 at 333K of the MOF compound described in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] The invention provides an MOF compound with carbon dioxide, nitrogen and methane adsorption and separation functions under wide temperature conditions, wherein the chemical formula is [Zn(btzip)(H2btzip)]·2DMF·2H2O, wherein H2btzip is 4,6-bis(triazole-1-yl)isophthalic acid, btzip is deprotonated 4,6-bis(triazole-1-yl)isophthalic acid, and DMF is N,N-dimethylformamide.

[0037] The structural formula of H2btzip is as follows:

[0038]

[0039] The structure of btzip is as follows:

[0040]

[0041] The MOF compound of the present invention has a three-dimensional framework structure and contains one-dimensional quadrilateral channels. The MOF compound is crystallized in the orthorhombic Pbcm space group in crystallography, and the unit cell parameters are: α=90°, β=90°, γ=90°, Its asymmetric unit contains a Zn 2+ ion, a completely deprotonated btzip ligand, and a non-deprotonated H2btzip ligand. Zn 2+ The ion is a hexacoordinated octahedral configuration, in which the six coordinated atoms come from two triazole N atoms of the two btzip ligands, two carboxyl O atoms of the btzip ligands, and two triazole N atoms of the H2btzip ligands, such as Figure 1 As shown. Each Zn 2+ Ionically connects four btzip ligands to form a two-dimensional (2D) layer, such as Figure 2 The layers are connected by triazole on the H2btzip ligand to form a three-dimensional framework structure, as shown in Figure 3 The porosity of the framework is 39.2%, and the surface of the channel mainly contains uncoordinated carboxyl O atoms and triazole N atoms.

[0042] The present invention also provides a method for preparing a MOF compound having the adsorption and separation function of carbon dioxide, nitrogen and methane under wide temperature conditions, which adopts a solvent thermal synthesis method, uses Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid as raw materials, and specifically comprises the following steps:

[0043] (1) adding Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid to a mixed solvent of N,N-dimethylformamide-acetonitrile-hydrochloric acid to obtain a mixed solution; the molar ratio of Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid is preferably 2:1, and the volume ratio of N,N-dimethylformamide:acetonitrile:hydrochloric acid in the mixed solvent is preferably 4:4:0.05;

[0044] (2) placing the mixed solution obtained in step (1) in a reaction kettle, heating it to 120-140° C. in a sealed state and maintaining it for 70-75 hours;

[0045] (3) cooling the temperature in the reaction kettle to room temperature at a rate of 5 to 7° C. / hour to obtain colorless block crystals;

[0046] (4) exchanging the colorless block crystals obtained in step (3) in methanol, the exchanging time is preferably 70 to 80 hours, and then heating and activating under vacuum conditions, the activation temperature is preferably 150 to 160° C., and the activation time is preferably 6 to 8 hours; naturally cooling to room temperature to obtain a MOF compound having carbon dioxide, nitrogen and methane adsorption and separation functions.

[0047] The present invention also provides the use of the above MOF compound in the adsorption separation of a ternary mixture of carbon dioxide, nitrogen and methane. The conditions for the adsorption separation are preferably: under a wide temperature range of 273 to 333 K and a pressure of 100 KPa. The experimental results show that the adsorption amounts of carbon dioxide, nitrogen and methane are 133.2 to 65.9 cm 3 g -1 、14.5~6.7cm 3 g -1 and 46.1~14.3cm 3 g -1 .

[0048] The present invention is further described in detail below with reference to specific examples, and the raw materials involved in the examples are all commercially available.

[0049] Example 1

[0050] A method for preparing a MOF compound having the adsorption and separation function of carbon dioxide, nitrogen and methane under wide temperature conditions, specifically comprising the following steps:

[0051] (1) Zn(NO3)2·6H2O (0.0297 g, 0.10 mmol) and 4,6-bis(triazol-1-yl)isophthalic acid (0.0150 g, 0.05 mmol) were added to a mixed solvent of N,N-dimethylformamide (4 mL)-acetonitrile (4 mL)-hydrochloric acid (0.05 mL) at a molar ratio of 2:1;

[0052] (2) placing the mixed solution obtained in step (1) in a 25 mL reaction kettle, heating to 130° C. and maintaining the temperature for 72 hours;

[0053] (3) cooling the temperature in the reactor to room temperature at a rate of 5°C / hour to obtain colorless block crystals;

[0054] (4) exchanging the colorless block crystals obtained in step (3) in methanol for 70 hours, then heating to 150° C. under vacuum conditions for activation for 6 hours; and naturally cooling to room temperature to obtain a MOF compound having carbon dioxide, nitrogen and methane adsorption and separation functions.

[0055] Example 2

[0056] A method for preparing a MOF compound having the adsorption and separation function of carbon dioxide, nitrogen and methane under wide temperature conditions, specifically comprising the following steps:

[0057] (1) Zn(NO3)2·6H2O (0.0445 g, 0.15 mmol) and 4,6-bis(triazol-1-yl)isophthalic acid (0.0225 g, 0.075 mmol) were added to a mixed solvent of N,N-dimethylformamide (8 mL)-acetonitrile (8 mL)-hydrochloric acid (0.1 mL) at a molar ratio of 2:1;

[0058] (2) placing the mixed solution obtained in step (1) in a 50 mL reaction kettle, heating to 120° C. and maintaining for 75 hours;

[0059] (3) cooling the temperature in the reactor to room temperature at a rate of 6°C / hour to obtain colorless block crystals;

[0060] (4) exchanging the colorless block crystals obtained in step (3) in methanol for 72 hours, and then heating to 150° C. for activation for 8 hours under vacuum conditions; and naturally cooling to room temperature to obtain a MOF compound having carbon dioxide, nitrogen and methane adsorption and separation functions.

[0061] Example 3

[0062] A method for preparing a MOF compound having the adsorption and separation function of carbon dioxide, nitrogen and methane under wide temperature conditions, specifically comprising the following steps:

[0063] (1) Zn(NO3)2·6H2O (0.0594 g, 0.20 mmol) and 4,6-bis(triazol-1-yl)isophthalic acid (0.0300 g, 0.10 mmol) were added to a mixed solvent of N,N-dimethylformamide (8 mL)-acetonitrile (8 mL)-hydrochloric acid (0.10 mL) at a molar ratio of 2:1;

[0064] (2) placing the mixed solution obtained in step (1) in a 50 mL reaction kettle, heating to 140° C. and maintaining for 75 hours;

[0065] (3) cooling the temperature in the reactor to room temperature at a rate of 7° C. / hour to obtain colorless block crystals;

[0066] (4) exchanging the colorless block crystals obtained in step (3) in methanol for 80 hours, then heating to 155° C. for activation for 6 hours under vacuum conditions; and naturally cooling to room temperature to obtain a MOF compound having carbon dioxide, nitrogen and methane adsorption and separation functions.

[0067] The MOF compound prepared in Example 1 was subjected to adsorption separation test, and the results were as follows:

[0068] The obtained MOF compound was used for gas adsorption separation test. The adsorption isotherms of the MOF compound for carbon dioxide, nitrogen and methane at 273-333K were measured using ASAP2020M physical adsorption instrument. Figures 4 to 7 At 273K and 100kPa, the adsorption capacities of the MOF compound for carbon dioxide, nitrogen, and methane were 133.2, 14.5, and 46.1 cm 3 g -1 At 298K and 100kPa, the adsorption capacity of the MOF compound for carbon dioxide, nitrogen and methane was 102.7, 27.6 and 9.1 cm, respectively. 3 g -1 At 313K and 100kPa, the adsorption capacity of the MOF compound for carbon dioxide, nitrogen and methane was 83.1, 18.8 and 8.8 cm, respectively. 3 g -1 At 333K and 100kPa, the adsorption capacity of the MOF compound for carbon dioxide, nitrogen and methane was 65.9, 14.3 and 6.7 cm, respectively. 3 g -1 ; Under wide temperature (273-333K) conditions, the MOF compound has a high adsorption capacity for carbon dioxide, and the adsorption of carbon dioxide is much higher than that of nitrogen and methane. The adsorption selectivity of the MOF compound for carbon dioxide mainly comes from the presence of uncoordinated carboxyl O atoms and triazole N atoms on the surface of the compound pores, which can form a strong interaction with carbon dioxide.

[0069] According to the gas adsorption isotherms tested at 273-333K, the separation selectivity of the MOF compound for mixed gases at different pressures was calculated using the ideal adsorption solution theory. Figure 8As shown, for a mixture of carbon dioxide and methane with equal components, in the pressure range of 1 to 100 kPa, the carbon dioxide / methane selectivity values ​​are approximately 11.2 to 17.7, 8.6 to 10.2, 7.1 to 7.8, and 7.3 to 6.2 at 273K, 298K, 313K, and 333K, respectively. Fig. 9 As shown, for a mixture of carbon dioxide and nitrogen with equal components, within the pressure range of 1 to 100 kPa, the carbon dioxide / nitrogen selectivity values ​​are approximately 45.1 to 172.4, 25.4 to 53.1, 18.2 to 15.9, and 16.4 to 16.3 at 273 K, 298 K, 313 K, and 333 K. Therefore, the MOF compound exhibits excellent separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures under wide temperature conditions, and has important application value in the separation and purification of carbon dioxide in the fields of natural gas purification and chemical production.

[0070] Dynamic separation test results:

[0071] The dynamic penetration experiment of the MOF compound on the carbon dioxide-nitrogen-methane ternary mixture was studied using the Quantachrome dynaSorb BT equipment of Quantachrome Corporation of the United States. At a temperature of 273-333K, a mixture of carbon dioxide / nitrogen / methane / argon with a volume ratio of 5 / 5 / 5 / 90 was passed through a packed column filled with 1g of the MOF compound, and the total flow rate of the mixed gas was 8mL·min -1 .like Figures 10 to 13As shown, the MOF compound can effectively separate the carbon dioxide-nitrogen-methane ternary mixture, wherein, at 273K, nitrogen is first detected through the packed column at 2 minutes, and methane is secondly detected through the packed column at 8 minutes, while carbon dioxide begins to flow out of the packed column after 85 minutes; at 298K, nitrogen is first detected through the packed column at 2 minutes, and methane is secondly detected through the packed column at 5 minutes, while carbon dioxide begins to flow out of the packed column after 30 minutes; at 313K, nitrogen is first detected through the packed column at 2 minutes, and methane is secondly detected through the packed column at 5 minutes, while carbon dioxide begins to flow out of the packed column after 30 minutes; At 333K, nitrogen was first detected flowing out through the packed column at 1 minute, followed by methane flowing out through the packed column at 2 minutes, while carbon dioxide began to flow out from the packed column after 9 minutes. This shows that the MOF compound can efficiently separate the carbon dioxide-nitrogen-methane ternary mixture under a wide temperature (273-333K) condition. Therefore, the MOF compound exhibits excellent separation functions of carbon dioxide, nitrogen and methane, and has important application value in the separation and purification of carbon dioxide in the fields of natural gas purification and chemical production.

[0072] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under wide temperature conditions, characterized in that: The chemical formula of the compound is [Zn(btzip)(H2btzip)]·2DMF·2H2O, wherein H2btzip is 4,6-bis(triazole-1-yl)isophthalic acid, btzip is deprotonated 4,6-bis(triazole-1-yl)isophthalic acid, and DMF is N,N-dimethylformamide.

2. The MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under wide temperature conditions according to claim 1, characterized in that: The MOF compound having the function of adsorbing and separating the carbon dioxide-nitrogen-methane ternary mixture has a three-dimensional framework structure, contains one-dimensional quadrilateral channels, and has a porosity of 39.2%.

3. The method for preparing a MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under wide temperature conditions according to claim 1 or 2, characterized in that: The solvent thermal synthesis method is adopted, with Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid as raw materials, and specifically includes the following steps: (1) adding Zn(NO3)2·6H2O and 4,6-bis(triazole-1-yl)isophthalic acid to a mixed solvent of N,N-dimethylformamide-acetonitrile-hydrochloric acid to obtain a mixed solution; (2) placing the mixed solution obtained in step (1) in a reaction kettle, heating it to 120-140° C. in a sealed state and maintaining it for 70-75 hours; (3) cooling the temperature in the reaction kettle to room temperature at a rate of 5 to 7° C. / hour to obtain colorless block crystals; (4) The colorless block crystals obtained in step (3) are exchanged in methanol, then activated under vacuum conditions, and naturally cooled to room temperature to obtain a MOF compound having the function of adsorbing and separating a ternary mixture of carbon dioxide, nitrogen and methane under a wide temperature range.

4. The preparation method according to claim 3, characterized in that: The molar ratio of Zn(NO3)2·6H2O to 4,6-bis(triazole-1-yl)isophthalic acid is 2:

1.

5. The preparation method according to claim 3, characterized in that: In the mixed solvent, the volume ratio of N,N-dimethylformamide:acetonitrile:hydrochloric acid is 4:4:0.

05.

6. The preparation method according to claim 3, characterized in that: In step (4), the exchange time of the colorless block crystals in methanol is 70 to 80 hours.

7. The preparation method according to claim 3, characterized in that: In step (4), the activation temperature is 150-160° C. and the activation time is 6-8 hours.

8. Use of the MOF compound according to claim 1 or 2 in the adsorption separation of a carbon dioxide-nitrogen-methane ternary mixture.

9. Use of the MOF compound according to claim 8 in the adsorption separation of a carbon dioxide-nitrogen-methane ternary mixture, characterized in that: The conditions for adsorption separation are: under a wide temperature range of 273-333K and a pressure of 100KPa.

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