Supramolecular network material, preparation method and application thereof

Abstract

The application discloses a supramolecular network material and a preparation method and application thereof, and the supramolecular network material is a supramolecular network material formed by self-assembly of zinc ions and 2-mercapto-nicotinic acid. The supramolecular network material has the characteristics of large specific surface area, flexible and adjustable structure and the like, the network further contains a large number of pyridine nitrogen sites with strong adsorption activity, has excellent gas-phase I2 vapor, gas-phase CH3I vapor adsorption performance and liquid-phase I3 – adsorption performance, and can realize strong removal of sublimated iodine in air, sublimated iodine methane and iodine triion in an aqueous solution through charge transfer interaction with iodine species; the adsorption amount can reach 4500mg.g ‑1 -1.h-1 when adsorbing gas-phase I2 vapor for 24h at 55 DEG C, and has great application potential in the field of removal of radioactive iodine, and can be used for solving the problems of recovery and treatment of radioactive iodine in nuclear waste in the future.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adsorption materials, and particularly relates to a supramolecular network material and a preparation method and application thereof. BACKGROUND

[0002] Nuclear leakage can produce a variety of radioactive isotopes that are harmful to human body, and one of the radioactive isotopes produced by nuclear leakage, iodine-131, has attracted strong attention of the scientific community because it is easy to accumulate in human thyroid and induce thyroid cancer. Therefore, the development of iodine adsorption materials has become one of the important research topics for human to curb the harm of nuclear leakage. Although there have been theoretical reports on the charge transfer interaction between the lone pair electron site as an electron donor and the iodine species as an electron acceptor, the application research of using the interaction mechanism to realize the strong adsorption of iodine species still needs further exploration.

[0003] Common methods for removing radioactive iodine can be divided into two categories: wet method and dry method. The wet method is to wash the iodine in the gas with a solvent, including alkaline washing, electrolytic washing, and mercury and iodine process, fluorocarbon absorption, etc., to remove radioactive iodine in waste gas through disproportionation reaction. The dry method is mainly to directly adsorb radioactive iodine with a solid adsorbent. The mainstream solid adsorbent is generally activated carbon, however, the preparation process of activated carbon is complex, which makes the adsorption activity of the prepared activated carbon unstable, and in addition, the high production cost of activated carbon also limits its large-scale use. In addition, activated carbon mainly relies on large specific surface area to realize physical adsorption of iodine species. Due to the lack of strong chemical adsorption sites, the adsorption capacity of activated carbon is limited, and it is difficult to achieve higher adsorption performance. SUMMARY

[0004] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a supramolecular network material. The second purpose of the present application is to provide a preparation method of the supramolecular network material. The third purpose of the present application is to provide an application of the supramolecular network material. The fourth purpose of the present application is to provide a method for adsorbing iodine vapor.

[0005] In order to achieve the above purposes, the technical scheme adopted by the present application is:

[0006] Coordination supramolecular networks (CSNs) are formed by self-assembly of central metal ions and ligands. The rich active sites, large specific surface area, and flexible and adjustable structure of CSNs have attracted extensive attention in the field of adsorption and separation. The CSNs formed by self-assembly of functional groups of ligand molecules and central metal ions greatly improve the chemical stability, avoid sublimation, decomposition and dissolution of ligand molecules in water, effectively improve the storage life of the material, and ensure that the adsorption material can still be effectively used after long-term storage. The coordination supramolecular network is used as a solid iodine adsorbent in the present application, and the rich active sites are beneficial to achieve excellent adsorption effect.

[0007] The first aspect of the present application provides a supramolecular network material, which is a supramolecular network material formed by self-assembly of zinc ions and 2-mercaptonic acid.

[0008] The supramolecular network material of the present application is formed by self-assembly of zinc ions and 2-mercaptonic acid. The network material has a one-dimensional non-porous network structure, and contains a large number of pyridine nitrogen sites with strong adsorption activity on the network, and has excellent gas-phase I2 vapor, gas-phase CH3I vapor adsorption performance and liquid-phase I3 – adsorption performance, which can realize strong removal of sublimed iodine in air, sublimed iodine methane and iodine trianion in aqueous solution through charge transfer interaction between the adsorbent and iodine species.

[0009] The structural formula of the 2-mercaptonic acid is shown as formula a:

[0010]

[0011] Preferably, the supramolecular network material is a crystalline material, which satisfies at least one of the following conditions:

[0012] a) the crystalline material is of micro-nano size;

[0013] b) the morphology of the crystalline material is a cuboid rod-shaped crystal;

[0014] c) the structure of the crystalline material is a one-dimensional non-porous network structure.

[0015] More preferably, the length of the cuboid rod-shaped crystal is 1-3 μm, and the width is 0.3-0.6 μm.

[0016] The second aspect of the present application provides a preparation method of the supramolecular network material of the first aspect, which comprises the following steps: mixing 2-mercaptonic acid and alkaline substance in a solvent, then adding zinc source to perform coordination reaction, and preparing the supramolecular network material.

[0017] Preferably, the zinc source is selected from at least one of zinc nitrate, zinc sulfate, zinc chloride.

[0018] Preferably, the basic substance is selected from sodium hydroxide.

[0019] Preferably, the molar ratio of 2-mercaptopyridine to zinc source is 1:(0.5-2).

[0020] More preferably, the molar ratio of 2-mercaptopyridine to zinc source is 1:(0.75-1.25).

[0021] Preferably, the molar ratio of 2-mercaptopyridine to basic substance is 1:(0.75-1.25).

[0022] Preferably, the 2-mercaptopyridine is first added to the solvent, then the basic substance is added and stirred until the solution becomes clear.

[0023] Preferably, the solvent is water.

[0024] The currently reported CSNs adsorbent materials generally use organic solvents to carry out the reaction by solvothermal method under high temperature and high pressure environment, which will cause environmental pollution and high energy consumption, which is not conducive to environmental protection. The deprotonation method using deionized water as a solvent and NaOH to remove the hydrogen atoms of the coordination group to realize the rapid coordination reaction of organic ligands in water has the advantages of high yield, short reaction time, low energy consumption and environmental friendliness, and the CSNs obtained by the deprotonation method often have different crystal structures from the CSNs obtained by the solvothermal method, which makes it an effective way to develop new CSNs materials.

[0025] Preferably, the concentration of 2-mercaptopyridine in the solvent is (1-10) mmol:100 mL.

[0026] More preferably, the concentration of 2-mercaptopyridine in the solvent is (2-5) mmol:100 mL.

[0027] Preferably, the reaction time of the coordination reaction is 5-20 min.

[0028] More preferably, the reaction time of the coordination reaction is 7-12 min.

[0029] Preferably, the reaction temperature of the coordination reaction is 15-40℃.

[0030] Preferably, the coordination reaction is carried out under stirring.

[0031] Preferably, it further comprises the following steps: after the coordination reaction, the supernatant is removed by centrifugation, washed with water and ethanol, and finally dried to obtain a light yellow powder.

[0032] More preferably, the drying is carried out under vacuum conditions; the drying temperature is 60–100°C.

[0033] More preferably, the centrifuge speed is 4000–8000 rpm; the centrifugation time is 5–10 min.

[0034] A third aspect of the present invention provides the application of the supramolecular network material described in the first aspect in the adsorption of iodine.

[0035] Preferably, the iodine is gaseous I2 vapor, gaseous CH3I vapor, or liquid I3. – .

[0036] Preferably, the iodine is radioactive iodine-131 or iodine-129.

[0037] A fourth aspect of the present invention provides a method for adsorbing iodine vapor, using the supramolecular network material described in the first aspect as an adsorbent.

[0038] Preferably, the adsorption of iodine vapor is carried out at a temperature of 25–75°C.

[0039] The beneficial effects of this invention are:

[0040] (1) This invention provides a supramolecular network material, which is formed by the self-assembly of zinc ions and 2-mercaptonicotinic acid. Compared with traditional activated carbon, the supramolecular network material not only has the characteristics of large specific surface area and flexible and tunable structure, but its network also contains a large number of pyridine nitrogen sites with strong adsorption activity, and has excellent adsorption performance of gas phase I2 vapor, gas phase CH3I vapor and liquid phase I3. – The adsorption performance is strong, achieving powerful removal of sublimed iodine from the air, gaseous CH3I vapor, and triiodide ions from aqueous solutions through charge transfer interactions with iodine species. At 55℃, the adsorption capacity for gaseous I2 vapor reaches 4500 mg·g⁻¹ after 24 hours. -1 It has great application potential in removing radioactive iodine and can be used in the future to solve problems such as the recovery and treatment of radioactive iodine in nuclear waste.

[0041] (2) The present invention also provides a method for preparing the above-mentioned supramolecular network material, which removes hydrogen atoms of the coordinating group by deprotonation with alkaline substances, thereby achieving rapid coordination of organic ligands in solvent. It has the advantages of short reaction time, low energy consumption, and environmental friendliness. Moreover, CSNs obtained by the deprotonation method often have different crystal structures than CSNs obtained by the solvothermal method, which makes it an effective way to develop new CSNs materials. Attached Figure Description

[0042] Figure 1 The Zn-MNA coordination structure of Example 1;

[0043] Figure 2 one-dimensional chain structure of Zn-MNA of Example 1;

[0044] Figure 3 one-dimensional non-porous network structure of Zn-MNA of Example 1;

[0045] Figure 4 quantum chemistry calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I2;

[0046] Figure 5 quantum chemistry calculation optimized model structure of Zn-MNA of Example 1 after adsorbing CH3I;

[0047] Figure 6 quantum chemistry calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I3 –

[0048] Figure 7 XRD pattern of Zn-MNA of Example 1 and single crystal Zn-MNA (CCDC 818208);

[0049] Figure 8 SEM image of Zn-MNA of Example 1;

[0050] Figure 9 adsorption amount results of Zn-MNA of Example 1 in steam I2 adsorption experiments at different temperatures. DETAILED DESCRIPTION

[0051] The present application will be further described in details by specific examples. In the following examples, the raw materials used, unless otherwise specified, can be obtained from conventional commercial channels or prepared and isolated by simple synthesis; the processes used, unless otherwise specified, are conventional processes in the art.

[0052] Example 1

[0053] This example provides a supramolecular network material and a preparation method thereof, and the preparation process steps are as follows:

[0054] 1 mmol of 2-mercaptopyridine acid was added to 30 mL of deionized water at room temperature, then 1 mmol of NaOH was added and stirred until the solution became clear. Then 1 mmol of ZnSO4·7H2O was added and the solution was stirred for 10 min to form a light yellow solid. Then centrifuged at 8000 rpm for 5 min to remove the supernatant. Then, washed once with deionized water, then washed once with anhydrous ethanol, and dried at 80°C under vacuum for 12 h to obtain a light yellow powder, marked as Zn-MNA.

[0055] ​Material characterization

[0056] Figure 1 Zn-MNA coordination structure of Example 1; Figure 2 One-dimensional chain structure of Zn-MNA of Example 1; Figure 3 One-dimensional non-porous network structure of Zn-MNA of Example 1, the Zn(II) center is a five-coordinated structure, coordinated by two thiol sulfur atoms and three carboxyl oxygen atoms from different MNA ligands, has a highly distorted pyramid structure, extends the one-dimensional zigzag chain through the carboxyl oxygen atom, there are π···π stacking interactions within the chain, and there are N-H···O hydrogen bond interactions between adjacent chains; the Zn-MNA of the application is formed by self-assembly of zinc ions and 2-mercapto-nicotinic acid, the supramolecular network material not only has a large specific surface area, flexible and adjustable structure and other characteristics, and the network also contains a large number of pyridine nitrogen sites with strong adsorption activity.

[0057] Figure 4 Quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I2; Figure 5 Quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing CH3I; Figure 6 Quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I3. –

[0058] Figure 7 XRD pattern of Zn-MNA of Example 1 and single crystal Zn-MNA (CCDC 818208).

[0059] Figure 8 SEM image of Zn-MNA of Example 1, the Zn-MNA is a micro-nano-sized crystal material, the morphology is a cuboid rod-shaped crystal, the length of the cuboid rod-shaped crystal is 1-3 μm, and the width is 0.3-0.6 μm.

[0060] Adsorption iodine experiment characterization

[0061] Put the weighed 10 mg of Zn-MNA (the mass is denoted as m) into a 2 mL vial (the mass is denoted as m a ), then put 200 mg of I2 into another 2 mL vial, and finally put the two vials into the bottom of a 20 mL vial, seal the vial, set multiple experimental groups, and respectively put the sealed 20 mL vial into an oven at 25℃, 35℃, 45℃, and 55℃, the pressure is normal pressure, and the mass of the vial containing Zn-MNA is weighed (denoted as m b1 , m b2 ,..., m bn ​), until the mass of the vial with Zn-MNA changes less than 0.1 mg in 3 weighings, stop the measurement, and calculate the adsorption amount qe of the gas-phase I2 vapor at 24 h according to the formula (mb-ma) / m.

[0062] Figure 9 The adsorption amount results of the steam I2 adsorption experiment of the Zn-MNA of Example 1 at different temperatures. At temperatures of 25℃, 35℃, 45℃, and 55℃, the adsorption amount qe of the gas-phase I2 vapor at 24 h is 600, 1015, 2910, and 4500 mg·g -1 , respectively, indicating that the Zn-MNA has good iodine storage capacity and high stability, and exhibits high adsorption amount in the iodine vapor adsorption experiment.

[0063] The above describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. Use of a supramolecular network material for adsorbing iodine vapor, characterized in that, The supramolecular network material is a supramolecular network material formed by self-assembly of zinc ions and 2-mercaptonicotinic acid; The preparation method of the supramolecular network material comprises the following steps: mixing 2-mercaptonicotinic acid and an alkaline substance in a solvent, then adding a zinc source to perform a coordination reaction, and obtaining the supramolecular network material; The molar ratio of the 2-mercaptonicotinic acid to the zinc source is 1:(0.5-2); the molar ratio of the 2-mercaptonicotinic acid to the alkaline substance is 1:(0.5-2); The reaction time of the coordination reaction is 5-20 min; the reaction temperature of the coordination reaction is 15-40 DEG C.

2. Use according to claim 1, characterized in that, The supramolecular network material is a crystal material, and at least one of the following conditions is satisfied: a) the crystal material is in a micro-nano size; b) the crystal material is in a cuboid rod shape; c) the crystal material is in a one-dimensional non-porous network structure.

3. Use according to claim 1, characterized in that, The zinc source is at least one selected from zinc nitrate, zinc sulfate and zinc chloride; And / or, the alkaline substance is selected from sodium hydroxide.

4. Use according to claim 1, characterized in that, The solvent is water; And / or, the concentration of the 2-mercaptonicotinic acid in the solvent is (1-10) mmol:100 mL.

5. The use according to claim 1, characterized in that, The coordination reaction is performed under stirring.

6. A method of adsorbing iodine vapor, characterized by, The supramolecular network material is used as an adsorbent in the application of any one of claims 1-5.

7. The method of claim 6, wherein the iodine vapor is adsorbed by the adsorbent material at a temperature of 20°C to 30°C. The adsorption of iodine vapor is performed at 25-75 DEG C.

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