A cationic indium-based metal-organic framework material, its preparation method, and its application in sulfur dioxide capture and storage.

Abstract

This invention belongs to the field of crystalline porous material preparation and gas adsorption and separation technology, specifically relating to a cationic indium-based metal-organic framework material, its preparation method, and its application in sulfur dioxide capture and storage. The chemical formula is [In3O(TMTPB)(ADC)3], and the material exhibits a novel and stable structure, with both cylindrical and spindle-shaped cages. The specific surface area is 2391.3 m². 2 / g, with a pore size distribution of 10.2–15.4 Å. The permanent channels, suitable pore size, hydroxyl-modified pore environment, and strong electrostatic interactions between the cationic framework and SO2 molecules make this material suitable for SO2 capture and storage.

Description

Technical Field

[0001] This invention belongs to the field of crystalline porous material preparation and gas adsorption and separation technology, specifically relating to a cationic indium-based metal-organic framework material, its preparation method, and its application in sulfur dioxide capture and storage. Background Technology

[0002] Sulfur dioxide (SO2) is a major anthropogenic air pollutant, posing a threat to the ecological environment and human health. It is also an important industrial raw material for the production of elemental sulfur, sulfuric acid, and high-value-added sulfur-containing fine chemicals. However, high-capacity storage and low-energy transportation of SO2 under mild conditions still face technological bottlenecks. Achieving efficient and reversible adsorption and desorption not only helps reduce energy consumption during storage and transportation but is also a key step in promoting the transformation of sulfur dioxide from "pollutant control" to "resource utilization." Compared with traditional wet flue gas desulfurization technology, regenerable solid porous adsorbents have advantages such as low water consumption, low energy consumption, and less secondary waste, providing a new path for low-energy storage and transportation of SO2. Therefore, developing novel porous solid materials with both high storage capacity and low regeneration energy consumption is of great significance for achieving effective storage, transportation, and resource utilization of SO2. However, constructing SO2 adsorbents with high operating capacity under mild conditions still faces challenges. Summary of the Invention

[0003] One objective of this invention is to provide a cationic indium-based metal-organic framework material with the chemical formula [In3O(TMTPB)(ADC)3], wherein one of the ligands is 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine (TMTPB), CAS number: 2027486-17-3, and the second ligand is (E)-azobenzene-4,4'-dicarboxylic acid (H2ADC), CAS number: 71987-42-3. It is named DZU-79.

[0004] From the perspective of framework connection and construction, the crystal structure of DZU-79 belongs to the hexagonal crystal system, with space group [missing information]. P6 3 / mcm The unit cell parameters are: a =17.155(5)Å, b =17.155(5)Å, c =30.226(11)Å, α = β= 90 o , γ= 120 o .

[0005] In the three-dimensional framework structure of DZU-79, its crystallographic asymmetric structural unit contains one In(III) ion, one-third of a µ3-O group, one ADC ligand, and one-third of a TMTPB ligand. The In(III) ion is coordinated with six atoms in an octahedral configuration, including four carboxyl O atoms from different ADC ligands, one O atom from a µ3-O group, and one N atom from a TMTPB ligand. Three adjacent In(III) ions are bridged by one µ3-O group and six carboxyl groups from different ADC ligands to form a typical trinuclear metal cluster [In3(μ3-O)(COO)6]. Each metal cluster is alternately connected with an ADC ligand to form a three-dimensional porous structure with an acs topology.

[0006] The chemical formula of this MOF material is [In3O(TMTPB)(ADC)3]. Charge calculation shows that the framework carries a positive charge of +9 and a negative charge of -8. Therefore, the MOF framework is positively charged, i.e., a cationic framework.

[0007] Furthermore, in the three-dimensional structural network, there are two types of cage-like structures: spindle-shaped and cylindrical. The spindle-shaped cage has one [In3(μ3-O)(COO)6] cluster at each of its top and bottom vertices, and three [In3(μ3-O)(COO)6] clusters distributed in the middle. The vertices and the middle clusters are connected by ADC ligands, and the three middle [In3(μ3-O)(COO)6] clusters are connected by TMTPB ligands. The distance between the vertices of the spindle-shaped cage is approximately 30.2 Å, and the diameter at the middle position is approximately 14.5 Å. The cylindrical cage has three [In3(μ3-O)(COO)6] clusters and one TMTPB ligand in its top and bottom planes, respectively. The walls of the cylinder are occupied by six ADCs, and the diameter and height of the base of the cylindrical cage are 14.5 Å and 15.1 Å, respectively.

[0008] At 77 K, the nitrogen isothermal adsorption curve of DZU-79 is of type I, and the maximum nitrogen adsorption capacity at P / P0 pressure is 649.9 cm⁻¹. 3 / g, the specific surface area calculated from the adsorption curve is 2391.3m². 2 / g, with a pore size distribution of 10.2–15.4 Å obtained from adsorption data analysis. This permanent pore structure and suitable pore size make this metal-organic framework suitable for SO2 capture and storage.

[0009] This invention also provides a method for preparing cationic indium-based metal-organic framework materials, comprising the following steps: Under sealed conditions, the organic ligands 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine (TMTPB), (E)-azobenzene-4,4'-dicarboxylic acid (H2ADC), and indium nitrate tetrahydrate (In(NO3)3·4H2O) dissolved in N , N DZU-79 metal-organic framework crystal material was obtained by solvothermal reaction of DMA with an appropriate amount of 52wt% tetrafluoroboric acid.

[0010] Furthermore, the molar ratio of 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine (TMTPB) to (E)-azobenzene-4,4'-dicarboxylic acid (H2ADC) is 1:(2.5-3).

[0011] Furthermore, the molar ratio of In(NO3)3·4H2O to 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine (TMTPB) is (3-5):1.

[0012] Furthermore, the addition ratio of DMA to tetrafluoroboric acid aqueous solution is 1 ml: 5-30 μL.

[0013] Furthermore, the addition ratio of DMA to total ligands was 1 ml: (0.035-0.065) mmol.

[0014] Furthermore, the temperature of the solvothermal reaction is 90~110℃, and the reaction time is 12~48 hours.

[0015] Based on the above scheme, the obtained DZU-79 metal-organic framework crystal material was activated using the following method: First, the synthesized material was thoroughly washed twice with DMA. Then, the washed sample was immersed in fresh ethanol solution for 48 hours, with continuous stirring and ethanol replacement four times during this period. The sample was filtered and then dried in a vacuum oven at 100℃ for 4 hours to obtain the activated sample.

[0016] The present invention also provides the application of the aforementioned cationic indium-based metal-organic framework material in SO2 capture and storage.

[0017] The beneficial technical effects of this invention are as follows: The cationic indium-based metal-organic framework material of this invention has a novel structure and stable framework, and exists in both cylindrical and spindle-shaped cages. The specific surface area of ​​the metal-organic framework material DZU-79 is 2391.3 m². 2 / g, with a pore size distribution of 10.2–15.4 Å. This permanent pore structure, suitable pore size, and hydroxyl-modified pore environment make this metal-organic framework suitable for SO2 capture and storage.

[0018] SO2 molecules exhibit significant charge separation characteristics, with negatively charged oxygen atoms and positively charged sulfur atoms, giving them a strong dipole moment. This allows for strong electrostatic interactions with cationic framework materials, providing a molecular-level basis for designing highly efficient adsorbents. Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal nodes and organic ligands. Due to their high porosity, diverse structures, and precisely tunable pore environments, they show application potential in gas storage and separation. For the demand for low-pressure, high-density SO2 storage, adjusting the framework charge properties, matching pore size, and modifying functional sites are the core strategies for MOF structural design. Based on the molecular size and polarity characteristics of SO2, this invention employs a dual-ligand synergistic strategy to construct cationic indium-based MOF materials: the cationic framework enhances the electrostatic interaction between the MOF host and SO2 molecules; the trimethyl-modified ligand 4,4',4''-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine (TMTPB) improves the structural stability and resistance to water molecule competitive adsorption; and the azobenzene-4,4'-dicarboxylic acid ligand (H2ADC) expands the porosity of the MOF. The synergistic effect of these three components aims to achieve high-capacity SO2 capture and storage. Test results show that the prepared MOF material exhibits high SO2 capture capacity and storage performance, demonstrating potential application as a medium for SO2 capture and storage. Attached Figure Description

[0019] Figure 1 Microscopic image of the crystal of DZU-79; Figure 2 Photograph of the powder state of DZU-79; Figure 3 Diagram showing the coordination environment and coordination mode of the In metal center in DZU-79; Figure 4 The three-dimensional frame structure diagram of DZU-79 includes: (4a) a partial enlarged view of the two-dimensional layered structure and metal secondary building unit (SBU) along a specific direction; (4b) a two-dimensional projection view (or topology) of the skeleton along the

[010] direction; and (4c) a perspective view of the three-dimensional frame structure along the

[001] direction. Figure 5 Structural diagrams of the spindle-shaped cage and cylindrical cage in DZU-79; Figure 6 The images show the synthesized DZU-79 and its powder X-ray diffraction patterns after treatment under different conditions. Figure 7 Thermogravimetric curve of DZU-79; Figure 8 The infrared spectrum of DZU-79 at room temperature; Figure 9The diagram shows the nitrogen adsorption isotherm of DZU-79 at 77K. Figure 10 Aperture distribution diagram of DZU-79; Figure 11 The adsorption-desorption isotherms of SO2 in DZU-79 at 298K and 323K are shown. Figure 12 A comparison of adsorption-desorption isotherms of SO2 and CO2 for DZU-79 at 298K; Figure 13 A comparison of adsorption-desorption isotherms of SO2 and CO2 in DZU-79 at 323K; Figure 14 The IAST selectivity curve of DZU-79 at 298K; Figure 15 Adsorption heat curves of SO2 and CO2 calculated for DZU-79. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0021] Example 1 The organic ligand TMTPB (0.01 mmol), H2ADC (0.03 mmol), and metal salt In(NO3)3·4H2O (0.03 mmol) were weighed and placed in a glass bottle. 1.0 mL of DMA and 10 μL of tetrafluoroboric acid aqueous solution (52 wt%) were added sequentially, and the bottle was sealed. The metal-organic framework crystals were obtained by thermal reaction at 90 °C for 36 hours.

[0022] Example 2 The organic ligand TMTPB (0.02 mmol), H2ADC (0.06 mmol), and metal salt In(NO3)3·4H2O (0.08 mmol) were weighed and placed in a glass bottle. 2.0 mL of DMA and 40 μL of tetrafluoroboric acid aqueous solution (52 wt%) were added sequentially, and the bottle was sealed. The metal-organic framework crystals were obtained by thermal reaction at 110 °C for 12 hours.

[0023] Example 3 The organic ligand TMTPB (0.03 mmol), H2ADC (0.09 mmol), and metal salt In(NO3)3·4H2O (0.15 mmol) were weighed and placed in a glass bottle. Then, 2 mL of DMA and 60 μL of tetrafluoroboric acid aqueous solution (52 wt%) were added sequentially, and the bottle was sealed. The metal-organic framework crystals were obtained by thermal reaction at 100 °C for 24 hours.

[0024] Example 4 The organic ligand TMTPB (0.2 mmol), H2ADC (0.5 mmol), and metal salt In(NO3)3·4H2O (0.6 mmol) were weighed and placed in a glass bottle. 20 mL of DMA and 100 μL of tetrafluoroboric acid aqueous solution (52 wt%) were added sequentially, and the bottle was sealed. The metal-organic framework crystals were obtained by thermal reaction at 100 °C for 48 hours.

[0025] The test results of the DZU-79 products obtained in the above embodiments are the same, and the single crystals are orange ( Figure 1 ), the microcrystalline powder appears red ( Figure 2 ).

[0026] (1) Crystal structure determination: Single crystals of appropriate size were selected under a microscope, and data were collected using a Bruker SMART APEXIICCD diffractometer. Absorption correction was performed using the SADABS program. The structure data for F2 were refined using direct and full-matrix least squares methods with SHELXL-2014. The crystallography program used was the single-set Olex2 integrated system. All non-hydrogen atoms were anisotropically refined. The positions and thermal parameters of hydrogen atoms were determined, and the structure was refined through geometric calculations. The contribution of disordered solvent molecules was handled using the SQUEEZE program implemented on PLATON. The structure diagram is shown below. Figure 1-4 Crystallographic data are shown in Table 1.

[0027] Table 1 Crystallographic data of metal-organic framework materials molecular weight 1516.57 temperature 293.0K Crystal system Six-sided Space Group <![CDATA[P63 / mcm]]> Unit cell parameters a=17.155(5)Å, b=17.155(5)Å, c=30.226(11)Å, =90°, =90°, =120° Unit cell volume <![CDATA[7703(5)Å 3 ]]> Density (calculated) <![CDATA[0.654g / cm 3 ]]> 2θ angle range 3.844-53.104° Absorption correction Semi-experience Refinement Methods Least squares method F2-based fit 1.076 Final R factor (I>2σ(I)) <![CDATA[R1=0.0333,wR2=0.1030]]> R factor (all data) <![CDATA[R1=0.0401,wR2=0.1068]]> Figure 3 The structural diagram shows that the In(III) ion in the DZU-79 structure is octahedral and coordinated with six atoms, including four carboxyl O atoms from different ADC ligands, one O atom from the μ3-O group in the water molecule, and one N atom from the TMTPB ligand. Each dicarboxylic acid has four carboxyl O atoms connected to four In atoms, all in μ2-η configurations. 1 η 1 The coordination mode.

[0028] Figure 4 The three-dimensional framework diagram shows that in DZU-79, three adjacent In(III) ions are bridged by one -OH group and six carboxyl groups of six different ADC ligands to form a typical trinuclear metal cluster [In3(μ3-O)(COO)6]. These trinuclear metal clusters are alternately linked with TMTPB ligands to form a three-dimensional framework.

[0029] Figure 5The schematic diagram shows that the DZU-79 structure contains two cage-like structures: a spindle-shaped one and a cylindrical one. In the spindle-shaped cage, each of the top and bottom vertices is occupied by a [In3(μ3-O)(COO)6] cluster, while the middle portion has three [In3(μ3-O)(COO)6] clusters evenly distributed. The vertices and the middle clusters are connected by ADC ligands, and the three middle [In3(μ3-O)(COO)6] clusters are connected by TMTPB ligands. The distance between the vertices of the spindle-shaped cage is approximately 30.2 Å, and the diameter at the middle position is approximately 14.5 Å. The cylindrical cage contains three [In3(μ3-O)(COO)6] clusters and one TMTPB ligand on its top and bottom planes, respectively. The walls of the cylinder are occupied by six ADCs, and the diameter and height of the base of the cylindrical cage are 14.5 Å and 15.1 Å, respectively.

[0030] Figure 6 The X-ray powder diffraction pattern showed that the measured diffraction peaks almost completely overlapped with the simulated peaks, proving that the synthesized material has the target crystal structure and no obvious impurity phases. After ethanol treatment and gas adsorption activation, the diffraction peak positions did not shift significantly, indicating that the material structure is thermodynamically stable under these treatment conditions.

[0031] Figure 7 The thermogravimetric curves show that the thermal stability of the DZU-79 skeleton reaches 380℃.

[0032] Figure 8 The infrared spectrum shows that for the H2ADC ligand, there is a broad OH peak (3300-2500 cm⁻¹) in its carboxylic acid. -1 ) and C=O stretching vibration peak (~1680cm) -1 It disappeared in DZU-79, and at ~1600cm -1 and ~1400cm -1 The presence of asymmetric and symmetric stretching vibration peaks of the carboxyl group indicates that H2ADC interacts with In via carboxyl group deprotonation in a bidentate coordination mode. 3+ Connection. For TMTPB ligands, the vibrational peaks of its pyridine ring skeleton (~1600, ~1500, ~1450 cm⁻¹) -1 ) and methyl CH stretching vibration peaks (~2920, ~2850 cm⁻¹) -1 The pyridine ring structure is retained in DZU-79, but the peak position shifts and the relative intensity changes, indicating that the pyridine nitrogen atom and In are intact. 3+ Coordination caused a change in the electronic environment. Furthermore, at ~3400 cm⁻¹... -1A broad and strong absorption peak appears at [value], which is attributed to the OH stretching vibration of air water molecules. These results indicate that both H2ADC and TMTPB ligands participate in the skeletal structure of DZU-79: H2ADC, as a carboxylic acid linker, coordinates with the metal node via the carboxylate group, while TMTPB, as a nitrogen-containing second ligand, coordinates via pyridine nitrogen. Together, they form a dual-ligand In-MOF structure.

[0033] (2) Characterization of specific surface area Figure 9 The DZU-79 frame material of this invention is in P / P N2 adsorption isotherms at 0=1 K and 77 K. The figure shows that the saturated N2 absorption capacity of DZU-79 reaches 649.9 cm⁻¹. 3 / g(STP). Through fitting and analysis of the adsorption data, the specific surface area of ​​DZU-79BET was found to be 2391.3 m² / g. 2 / g.

[0034] Figure 10 The image shows the pore size distribution of the DZU-79 of this invention. As can be seen from the image, the pore size is distributed in the range of 10.2-15.4 Å.

[0035] (3) Characterization of adsorption and separation performance: Figure 11 For the present invention DZU-79 at temperatures of 298K and 323K, P / P The adsorption isotherm of SO2 at a value of 1.0 is shown. A 100 mg sample of activated adsorbent was placed under vacuum at 100 °C for 4 h. After degassing, gas adsorption isotherms were measured at 298 K and 323 K. The graph shows that at 298 K, the maximum adsorption capacity of SO2 by DZU-79 crystals is 21.9 mmol / g. At 323 K, the maximum adsorption capacity of SO2 by DZU-79 crystal material is 16.8 mmol / g.

[0036] Figure 12 and Figure 13 This is a comparison of the adsorption-desorption isotherms of SO2 and CO2 by DZU-79 of the present invention at 298K and 323K. The figure shows that the adsorption capacity of DZU-79 for SO2 and CO2 differs significantly between 298K and 323K.

[0037] Figure 14 The figure shows the IAST selectivity curve of the SO2 / CO2 mixed gas of DZU-79 of the present invention at 298K. The figure shows that the IAST selectivity of DZU-79 for SO2 / CO2 is between 6.03 and 22.4 under the condition of 298K.

[0038] Figure 15The adsorption heats for SO2 and CO2 are calculated based on the SO2 and CO2 isotherms at 298 K and 323 K, respectively, within the DZU-79 framework. Specifically, Q for SO2... st The value is greater than 23.3 kJ / mol, significantly higher than the Q of CO2. st The value (12.2~13.5kJ / mol) indicates that the material has a stronger affinity for SO2 than for CO2.

Claims

1. A cationic indium-based metal-organic framework material, characterized in that: The chemical formula is [In3O(TMTPB)(ADC)3], in which one of the ligands is 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridineTMTPB, and the second ligand is (E)-azobenzene-4,4'-dicarboxylic acid H2ADC; From the perspective of framework connection construction, the crystal structure of the cationic indium-based metal-organic framework material belongs to the hexagonal crystal system, with space group [missing information]. P6 3 / mcm The unit cell parameters are: a =17.155(5)Å, b =17.155(5)Å, c =30.226(11)Å, α = β= 90 o , γ= 120 o ; In the structure of the cationic indium-based metal-organic framework material, the crystallographic asymmetric structural unit comprises one In(III) ion, one / 3 µ3-O group, one ADC ligand, and one / 3 TMTPB ligand; the In(III) ion is coordinated with six atoms in an octahedral configuration, including four carboxyl O atoms from different ADC ligands, one O atom from the µ3-O group, and one N atom from the TMTPB ligand; three adjacent In(III) ions are bridged by one µ3-O group and six carboxyl groups from different ADC ligands to form a typical trinuclear metal cluster [In3(μ3-O)(COO)6]; each metal cluster is alternately connected with the ADC ligand to form a three-dimensional porous structure with an acs topology.

2. The cationic indium-based metal-organic framework material according to claim 1, characterized in that: In the three-dimensional porous structure, there are two types of cage-like structures: spindle-shaped and cylindrical. The top and bottom vertices of the spindle-shaped cage are each occupied by one [In3(μ3-O)(COO)6] cluster, and the middle part is distributed with three [In3(μ3-O)(COO)6] clusters. The vertices and the middle clusters are connected by ADC ligands, and the three middle [In3(μ3-O)(COO)6] clusters are connected by TMTPB ligands. The distance between the vertices of the spindle-shaped cage is 30.2 Å, and the diameter at the middle position is 14.5 Å. The top and bottom planes of the cylindrical cage contain three [In3(μ3-O)(COO)6] clusters and one TMTPB ligand, respectively. The walls of the cylinder are occupied by six ADCs. The bottom diameter and height of the cylindrical cage are 14.5 Å and 15.1 Å, respectively.

3. The cationic indium-based metal-organic framework material according to claim 1, characterized in that: At 77 K, the nitrogen isotherm adsorption curve of the cationic indium-based metal-organic framework material is of type I, and the maximum nitrogen adsorption capacity at the P / P0 pressure is 649.9 cm⁻¹. 3 / g, the specific surface area calculated from the adsorption curve is 2391.3m². 2 / g, with a pore size distribution of 10.2-15.4Å.

4. A method for preparing a cationic indium-based metal-organic framework material as described in any one of claims 1-3, characterized in that: Includes the following steps: Under sealed conditions, 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine, (E)-azobenzene-4,4'-dicarboxylic acid, and indium nitrate tetrahydrate dissolved in N , N DZU-79 metal-organic framework crystal material was obtained by adding 52wt% tetrafluoroboric acid to dimethylacetamide and then reacting it with a solvothermal agent.

5. The method for preparing the cationic indium-based metal-organic framework material according to claim 4, characterized in that: The molar ratio of 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine to (E)-azobenzene-4,4'-dicarboxylic acid is 1:(2.5-3); the molar ratio of indium nitrate tetrahydrate to 4,4',4'-(2,4,6-trimethylbenzene-1,3,5-triphenyl)tripyridine is (3-5):

1.

6. The method for preparing the cationic indium-based metal-organic framework material according to claim 4, characterized in that: N , N The addition ratio of dimethylacetamide and the two ligands was 1 mL: (0.035-0.065) mmol; N , N The addition ratio of dimethylacetamide to tetrafluoroboric acid aqueous solution is 1 mL: 5-30 μL.

7. The method for preparing the cationic indium-based metal-organic framework material according to claim 4, characterized in that: The temperature of the solvothermal reaction is 90~110℃, and the reaction time is 12~48 hours.

8. The application of a cationic indium-based metal-organic framework material according to any one of claims 1-3 in the selective capture and storage of SO2.

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