Carborane hybridized two-dimensional porous metal organic supramolecular framework as well as preparation and application thereof

Abstract

The invention discloses a carborane hybridized two-dimensional porous metal organic supramolecular framework as well as a preparation method and application thereof. The two-dimensional porous metal organic supramolecular framework is composed of para-carborane dicarboxylate ions, metal ions Zn < 2 + > and protonated organic nitrogen-containing ligand 4, 4-dipyridylamine, and through tight ABAB filling, a two-dimensional framework structure with Z-shaped 1D channel holes is formed. The preparation method comprises the following steps: reacting Zn < 2 + >-containing salt, 4, 4-dipyridylamine and p-carborane dicarboxylic acid in an acidic solution at 50-100 DEG C to obtain a solid product; and placing the solid product in methanol for one or more times of solvent exchange to remove solvent molecules, and then vacuumizing, degassing and activating to remove methanol molecules in pore channels to obtain the two-dimensional porous metal organic supramolecular framework. The two-dimensional porous metal organic supramolecular framework has high separation selectivity on C2H2 / CO2, and has preferential carbon dioxide adsorption selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis of porous materials and carbon dioxide adsorption and separation, and in particular to a carborane hybridized two-dimensional porous metal-organic supramolecular framework, a preparation method and application thereof. Background Art

[0002] Acetylene (C2H2) is an important raw material for the synthesis of various organic chemicals and polymers. It is mainly produced by catalytic cracking of hydrocarbons or partial combustion of natural gas. These processes always produce a pollutant carbon dioxide (CO2).

[0003] Given that acetylene and carbon dioxide have very similar physical properties, such as similar boiling points (acetylene: 189.3K, carbon dioxide: 194.7K), the same kinetic molecular diameter and the same linear shape, purification of C2H2 / CO2 mixtures is considered one of the most challenging separations and is currently mainly achieved through conventional cryogenic distillation or solvent extraction.

[0004] The development of adsorptive separation techniques using porous solid adsorbents has attracted great interest due to their lower energy consumption and higher environmental friendliness.

[0005] Metal-organic frameworks (MOFs) and supramolecular organic frameworks (SOFs) (or hydrogen-bonded organic frameworks (HOFs)) have emerged as a new class of crystalline porous materials with pore size and environmental tunability, showing great potential in various gas separation applications.

[0006] Since acetylene reacts with carbon dioxide (29.1×10 -25 cm 3 and -13.4×10 -40 C m 2 ) compared to acetylene, which has a larger polarizability (33.3-39.3×10 -25 cm 3 ) and quadrupole moment (+20.5×10 -40 C m 2 ), most materials show preferential adsorption of acetylene by forming stronger interactions at the pore surface. Materials with Lewis acidic sites, such as open metal sites, can form π complexes with acetylene, leading to stronger acetylene binding affinity. Materials with Lewis basic sites, such as free nitrogen atoms, oxygen atoms, and fluorine atoms, can form hydrogen bonds with acetylene, enhancing acetylene adsorption.

[0007] CO2 selective physical adsorption materials can achieve the production of pure acetylene by directly removing carbon dioxide impurities, which is more conducive to the purification process of acetylene. In this regard, research on CO2 selective adsorbents is still lacking.

[0008] In previous studies, we have been working on designing boron cluster hybrid porous materials for C2H2 / CO2 separation. By adjusting the pore size, we obtained two dodecaboron cluster anion pillared MOFs (BSF-3 and BSF-3-Co), which have high acetylene adsorption capacities (80.4 and 86.2 cm 3 g -1 ) and good C2H2 / CO2 selectivity (16.3 and 12.7) [Angew.Chem.Int.Ed.2020,59,17664-17669]. By adjusting the interpenetrating symmetry, we designed the benchmark C2H2 / CO2 separation adsorbent ZNU-1 with an acetylene absorption of 76.3 cm 3 g -1 , C2H2 / CO2 selectivity is 56.6 [Angew.Chem.Int.Ed.2021,60,22865-22870]. Recently, we reported a hydrogen-bonded organic framework BSF-11 constructed by BH···HC dihydrogen bonds, which showed selective gate-opening adsorption of acetylene [Chem.Mater.2024,16,8123-8130].

[0009] However, all of the above boron cluster hybrid porous materials preferentially adsorb acetylene. If the preferential adsorption of carbon dioxide in the acetylene-carbon dioxide mixture can be achieved, it will be more conducive to the industrial application of acetylene purification. Summary of the invention

[0010] Considering the opposite quadrupole moments of C2H2 / CO2, the present invention envisions that appropriate reduction of pore size and pore electronegativity can form a synergistic interaction between the framework and carbon dioxide to promote the adsorption of carbon dioxide. In addition, if we can further modify some electropositive sites to recognize the O atoms of carbon dioxide, more reverse selective adsorption of carbon dioxide can be achieved. The present invention replaces the boron cluster anion with carborane (C2B 10 H 12 ) to change the pore size and pore surface chemistry of porous materials to purify acetylene from C2H2 / CO2 in one step. 10 H 12 Porous materials with carbon skeletons for C2H2 / CO2 inverse separation have never been reported so far.

[0011] Here, the present invention reports a novel carborane hybrid metal organic supramolecular framework ZNU-13, which realizes the one-step purification of acetylene from C2H2 / CO2 by rationally adjusting the pore size and pore surface chemistry of the boron cluster hybrid framework material and designing the selective recognition site of carbon dioxide. ZNU-13 is composed of p-carborane dicarboxylic acid, metal Zn2+ ions and protonated 4,4-dipyridylamine ([dpa-H] + ) were synthesized by compact ABAB filling to form a zigzag one-dimensional (1D) channel, and both static adsorption experiments and dynamic penetration experiments demonstrated good C2H2 / CO2 adsorption and separation performance.

[0012] [1] A two-dimensional porous metal-organic supramolecular framework (ZNU-13) hybridized with carborane for selective adsorption of carbon dioxide from a mixture of acetylene and carbon dioxide, composed of carborane dicarboxylate ions, metal ions Zn 2+ It is composed of a protonated organic nitrogen-containing ligand 4,4-dipyridylamine, and through tight ABAB packing, a two-dimensional framework structure with a zigzag 1D channel hole is formed;

[0013] The expression of p-carborane dicarboxylic acid is p-C2B 10 H 10 (COOH)2, having the structure shown in the following formula (I):

[0014]

[0015] The chemical structure corresponding to the 4,4-dipyridylamine (dpa) is shown below:

[0016]

[0017] [2] The method for preparing a two-dimensional porous metal-organic supramolecular framework according to [1] comprises the following steps:

[0018] (1) Containing Zn 2+ A salt of 4,4-dipyridylamine and p-carboranedicarboxylic acid are reacted in an acidic solution at 50 to 100° C. (e.g., 80° C.) to obtain a solid product;

[0019] (2) placing the solid product in methanol and performing one or more solvent exchanges to remove solvent molecules, and then vacuum degassing and activating to remove methanol molecules in the pores to obtain the two-dimensional porous metal-organic supramolecular framework.

[0020] In step (1), the Zn 2+ The salt may be selected from at least one of nitrates, chlorides, carbonates and sulfates.

[0021] In step (1), the Zn 2+ Zn in salt 2+ The molar ratio of the 4,4-dipyridylamine to the p-carboranedicarboxylic acid may be 2:1 to 3:1 to 3 (eg, 2:2:2, etc.). 2+The 4,4-dipyridylamine is protonated during the reaction and becomes monovalent, while the carborane dicarboxylate ion is divalent. In order to achieve charge balance, the molar ratio of the three is preferably 2:2:3.

[0022] In another preferred embodiment, in step (1), in order to fully react the more expensive carborane dicarboxylic acid, the Zn 2+ Zn in salt 2+ The molar ratio of the 4,4-dipyridylamine to the p-carborane dicarboxylic acid is 1:1:1.

[0023] In step (1), the acid in the acidic solution can be selected from at least one of tetrafluoroboric acid, hydrochloric acid and nitric acid.

[0024] In step (1), the solvent in the acidic solution can be selected from at least one of methanol, DMF (N,N-dimethylformamide), water, DMA (N,N-dimethylacetamide), ethanol, acetone, and acetonitrile.

[0025] In step (1), the reaction time may be 4 to 48 hours, such as 24 hours.

[0026] In step (2), the time for each solvent exchange may be 5 to 8 hours.

[0027] In step (2), the temperature of the vacuum degassing activation can be room temperature to 75° C., and the time can be 12 to 24 hours.

[0028] [3] Application of the two-dimensional porous metal-organic supramolecular framework according to [1] for adsorbing gas. Further, the gas may be acetylene, carbon dioxide, etc.

[0029] [4] Application of the two-dimensional porous metal-organic supramolecular framework according to [1] for adsorbing carbon dioxide and / or acetylene.

[0030] [5] The two-dimensional porous metal-organic supramolecular framework according to [1] is used for selectively adsorbing carbon dioxide from a mixture containing carbon dioxide and acetylene to achieve separation of carbon dioxide and acetylene.

[0031] [6] A method for separation of carbon dioxide and acetylene by adsorption, comprising: using the two-dimensional porous metal organic supramolecular framework described in [1] to selectively adsorb carbon dioxide from a mixture containing carbon dioxide and acetylene to separate carbon dioxide and acetylene.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The present invention designs and synthesizes a novel carborane hybridized two-dimensional porous metal organic supramolecular framework ZNU-13. The framework of ZNU-13 is a mortise and tenon structure, with a convex [dpa-H] + Part of it acts as a tenon, and the hexagonal network based on carborane dicarboxylic acid-Zn acts as a mortise and tenon, and the tenons and mortise bite together to play a connecting role. The two-dimensional layers are strongly interlocked, giving ZNU-13 good thermal and water stability.

[0034] 2) ZNU-13 realizes C2H2 / CO2 reverse adsorption separation and is currently the only carborane hybrid porous material with carbon dioxide preferential adsorption selectivity.

[0035] 3) The present invention uses cage-like polyhedral carborane as a skeleton, which exhibits stronger thermal stability, water stability and hydrophobicity, and is expected to be applied to more gas separations.

[0036] 4) The porous framework material based on the carborane skeleton designed and synthesized by the present invention has high separation selectivity for C2H2 / CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the crystal structure of the porous framework material ZNU-13 based on the carborane skeleton in Example 1;

[0038] Figure 2 The in-situ single crystal and DFT calculation diagram of ZNU-13 adsorbed with acetylene or carbon dioxide molecules in Example 2;

[0039] Figure 3 77K nitrogen and 195K carbon dioxide adsorption curves of ZNU-13 in Example 3;

[0040] Figure 4 The single component adsorption curves of acetylene and carbon dioxide of ZNU-13 measured at 278K and 298K in Example 3;

[0041] Figure 5 The IAST selectivity diagram of the separation of acetylene / carbon dioxide mixed gas obtained by ZNU-13 according to the isotherm in Example 4;

[0042] Figure 6 4 is a graph showing the adsorption heat of acetylene and carbon dioxide of ZNU-13 calculated based on the isotherms in Example 4;

[0043] Figure 7 is a breakthrough curve of acetylene and carbon dioxide in equal molar proportions of ZNU-13 in Example 5;

[0044] Figure 8 This is the water contact angle test diagram of ZNU-13 in Example 6;

[0045] Fig. 9 This is the thermogravimetric (TGA) curve of ZNU-13 in Example 6. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0047] Example 1

[0048] In a 20 mL bottle, 15.0 mg (0.05 mmol) Zn(NO3)2·6H2O, 11.6 mg (0.05 mmol) p-C2B 10 H 10 (COOH)2 and 8.6 mg (0.05 mmol) of 4,4-dipyridylamine were dissolved in a mixture of 4 mL of DMF / methanol / water (2 / 1 / 1 mL), and then 10 μL of tetrafluoroboric acid solution (48 wt%) was added. After ultrasonic treatment for 10 min, the vial was sealed and the mixture was reacted at 80 °C for 24 h to obtain colorless and transparent ZNU-13 crystals. The colorless and transparent crystals were collected by filtration and washed with methanol (3 mL × 3). The above crystals were soaked in anhydrous methanol and solvent exchanged with anhydrous methanol three times (3 × 8 h) before preservation. Before gas adsorption measurement, the synthesized ZNU-13 was vacuum activated at room temperature for 2 h and then activated at 75 °C for 10 h to completely remove the methanol molecules.

[0049] Figure 1 This is a schematic diagram of the crystal structure of ZNU-13. In ZNU-13, each Zn(II) atom is coordinated with three oxygen atoms of the carboxyl group and one nitrogen atom of the pyridine group to form a carborane dicarboxylate ion [C2B 10 H 10 (COO)2] 2- Connection and Zn 2+ The nodes form a hexagonal lattice network ( Figure 1 a-1c). Topological analysis shows that ZNU-13 belongs to the hcb network. The protonated dpa linker is perpendicular to the hexagonal network and interacts with the adjacent 2D network through multiple C(Py)-H···O=C bonds. In addition, there are multiple BH···HC interactions between adjacent layers. ( Figure 1 d). It is worth noting that there are also multiple N(Py)-H···O=C and C(Py)-H···O=C hydrogen bonds between the first and third layers ( Figure 1e) This layer packing pattern can be described as ABAB packing, which is common in many 2D covalent organic frameworks. This structure is also like a mortise and tenon structure. Convex [dpa-H] + Parts act as tenons, while the carborane-based hexagonal mesh acts as mortise and tenon, with the tenon and mortise interlocking to create a connection, allowing the two-dimensional layers to strongly interlock.

[0050] Porosity analysis showed that ZNU-13 exhibited a Z-like one-dimensional channel pore with a pore space of approximately 19% ( Figure 1 f). The narrowest dimension of the channel hole is approximately Along the direction almost perpendicular to the hexagonal network ( Figure 1 g) Such constricted pore channels with multiple O and BH interaction sites on the pore surface have a high potential for CO2 selective adsorption. The maximum size of the pore channel is The hole channel is parallel to the axis and can also be regarded as a large cavity ( Figure 1 h).

[0051] Example 2

[0052] In addition to the highly stable ZNU-13 single crystals, we further obtained and studied the single crystal structures of ZNU-13 loaded with carbon dioxide and acetylene (referred to as CO2@ZNU-13 and C2H2@ZNU-13, respectively). Figure 2 We found that CO2 molecules are mainly adsorbed in narrow channel pores ( Figure 2 a), while acetylene molecules are mainly adsorbed in the spacious cage cavity ( Figure 2 b) If Figure 2 a. Figure 2 As shown in b, after the adsorption of carbon dioxide, the pores expanded significantly, while the cage cavity remained almost unchanged. For each carbon dioxide molecule, multiple close contacts with the framework were observed, such as C(Py)-H···O=C(2.90 and )、CO···C=O and BH···O=C The interaction ( Figure 2 c). In contrast, there is less interaction between the ZNU-13 pore surfaces of adsorbed acetylene ( Figure 2 d). Based on the single crystal structures of CO2@ZNU-13 and C2H2@ZNU-13, the binding energy ΔE was calculated using density functional theory (DFT), which showed that the interaction force between the framework and carbon dioxide (-57.8 kJ / mol) was greater than that between acetylene (-47.3 kJ / mol).

[0053] Example 3

[0054] The permanent porosity of ZNU-13 was confirmed by N2 adsorption at 77K and CO2 adsorption at 195K. Figure 3 The results show that when P / P0 is 0.99, the adsorption capacity of ZNU-13 for N2 is 97.1 cm 3 g -1 , the adsorption capacity of carbon dioxide is 51cm 3 g -1 Gas adsorption isotherms of acetylene and carbon dioxide were then collected on ZNU-13 at 298K and 278K ( Figure 4 ). The adsorption capacity of ZNU-13 for carbon dioxide is much higher than that for acetylene. At 298K and 1 bar, the carbon dioxide adsorption capacity of ZNU-13 is 26.7 cm 3 g -1 , exceeding its 23.8cm 3 g -1 The acetylene adsorption capacity of 1.5 cm2 / s is 1.5 cm2. At low pressure, the difference in adsorption between carbon dioxide and acetylene is more obvious. At 5 kPa, the carbon dioxide adsorption capacity is 9.5 cm2 / s. 3 g -1 , more than three times the acetylene adsorption capacity (3.0 cm 3 g -1 ). At 278K and 1.0 bar, the absorption capacity of carbon dioxide is 32.3 cm 3 g -1 , which is much higher than the acetylene adsorption capacity of 28.8 cm 3 g -1 .

[0055] Example 4

[0056] The adsorption selectivity was evaluated using the ideal adsorption solution selectivity (IAST) theory ( Figure 5 ). In the pressure range of 1-100 kPa of ZNU-13 and at 298 K, its C2H2 / CO2 selectivity is 3.8-2.9, respectively.

[0057] Using the Clausius–Clapeyren equation ( Figure 6 ) Calculate the adsorption enthalpy (Q) of acetylene and carbon dioxide st ). ZNU-13 CO2 Q st 36.1 kJ mol -1 . Q of acetylene in ZNU-13 st Only 17.8 kJ mol -1 , which indicates that the binding force of acetylene in the pore space is much weaker than that of carbon dioxide. st The difference is 18.3 kJ mol -1, further indicating that the adsorption affinity is quite different.

[0058] Example 5

[0059] In order to evaluate the dynamic separation performance of C2H2 / CO2, we conducted a dynamic penetration experiment in a fixed bed. Figure 7 As shown, it was demonstrated that ZNU-13 can effectively purify acetylene from C2H2 / CO2 mixture. Figure 7 The breakthrough curve of ZNU-13 is shown. At 298K, a mixture of CO2 / C2H2 / Ar (5 / 5 / 90 volume ratio) is passed through the breakthrough chamber. Acetylene is first detected from the outlet, reaching high purity. No carbon dioxide is detected. The breakthrough time of acetylene is about 4.9 min g -1 , while the penetration time of carbon dioxide is about 13.1min g -1 Therefore, ZNU-13 can be used at 4.9~13.1min g -1 Pure acetylene is produced in a one-step separation process within a certain period of time.

[0060] Example 6

[0061] Figure 8 The water contact angle test showed that ZNU-13 is a hydrophobic material (contact angle (CA) = 109.605°). Thermogravimetric analysis results showed that the crystal has good thermal stability at 210°C ( Fig. 9 ). These experimental results further confirmed the good stability of ZNU-13.

[0062] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A carborane-hybridized two-dimensional porous metal-organic supramolecular framework capable of selectively adsorbing carbon dioxide from a mixed system containing acetylene and carbon dioxide, characterized in that: The carborane dicarboxylate ion and metal ion Zn 2+ It is composed of a protonated organic nitrogen-containing ligand 4,4-dipyridylamine, and through tight ABAB packing, a two-dimensional framework structure with a zigzag 1D channel hole is formed; The expression of p-carborane dicarboxylic acid is p-C2B 10 H 10 (COOH)2, having the structure shown in the following formula (I):

2. The method for preparing a two-dimensional porous metal-organic supramolecular framework according to claim 1, characterized in that: Includes steps: (1) Containing Zn 2+ The salt of 4,4-dipyridylamine and p-carborane dicarboxylic acid are reacted in an acidic solution at 50-100° C. to obtain a solid product; (2) placing the solid product in methanol and performing one or more solvent exchanges to remove solvent molecules, and then vacuum degassing and activating to remove methanol molecules in the pores to obtain the two-dimensional porous metal-organic supramolecular framework.

3. The preparation method according to claim 2, characterized in that: In step (1): The Zn 2+ The salt is selected from at least one of nitrate, chloride, carbonate and sulfate; The Zn 2+ Zn in salt 2+ The molar ratio of the 4,4-dipyridylamine to the p-carborane dicarboxylic acid is 2:1 to 3:1 to 3.

4. The preparation method according to claim 2, characterized in that: In step (1): The acid in the acidic solution is selected from at least one of tetrafluoroboric acid, hydrochloric acid and nitric acid; The solvent in the acidic solution is selected from at least one of methanol, DMF, water, DMA, ethanol, acetone and acetonitrile.

5. The preparation method according to claim 2, characterized in that: In step (1), the reaction time is 4 to 48 hours.

6. The preparation method according to claim 2, characterized in that: In step (2); The time for each solvent exchange is 5 to 8 h; The temperature of the vacuum degassing activation is room temperature to 75° C., and the time is 12 to 24 hours.

7. Use of the two-dimensional porous metal-organic supramolecular framework according to claim 1 for adsorbing gases.

8. Use of the two-dimensional porous metal-organic supramolecular framework according to claim 1 for adsorbing carbon dioxide and / or acetylene.

9. Use of the two-dimensional porous metal-organic supramolecular framework according to claim 1 for selectively adsorbing carbon dioxide from a mixture containing carbon dioxide and acetylene to achieve separation of carbon dioxide and acetylene.

10. A method for separating carbon dioxide and acetylene by adsorption, characterized in that: include: The two-dimensional porous metal-organic supramolecular framework according to claim 1 is used to selectively adsorb carbon dioxide from a mixture containing carbon dioxide and acetylene to achieve separation of carbon dioxide and acetylene.

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