Supramolecular network material as well as preparation method and application thereof

Abstract

The invention discloses a supramolecular network material as well as a preparation method and application thereof. The supramolecular network material is formed by self-assembling zinc ions and 2-mercaptonicotinic acid. The supramolecular network material provided by the invention not only has the characteristics of large specific surface area, flexible and adjustable structure and the like, but also contains a large amount of pyridine nitrogen sites with strong adsorption activity, and has excellent gas-phase I2 steam and gas-phase CH3I steam adsorption performance and liquid-phase I3-adsorption performance; by means of charge transfer interaction with iodine species, sublimated iodine and sublimated methyl iodide in air and triiodide ions in an aqueous solution can be powerfully removed, the adsorption capacity can reach 4500 mg.g <-1 > when gas-phase I2 steam is adsorbed for 24 h at the temperature of 55 DEG C, and great application potential is achieved in the field of radioactive iodine removal. The method can be used for solving the problems of recovery and treatment of the radioactive iodine elementary substance in the nuclear waste in the future.

Description

Technical Field

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

[0002] Nuclear leakage can produce a variety of radioactive isotopes that pose serious hazards to the human body. Among them, iodine-131, one of the radioactive nuclides produced by nuclear leakage, has attracted strong attention from the scientific community because it is easy to accumulate in the human thyroid gland and induce thyroid cancer. Therefore, the development of iodine adsorption materials has become one of the important research topics for humans to prevent the hazards of nuclear leakage. Although there have been theoretical reports on the charge transfer interaction between the lone pair electron sites as electron donors and iodine species as electron acceptors, the applied research on realizing the strong adsorption of iodine species using this mechanism still needs to be further explored.

[0003] Common methods for removing radioactive iodine can be divided into two categories: wet methods and dry methods. The wet method uses a solvent to wash iodine in the gas, including alkaline washing, electrolytic washing, and mercuration and iodination processes, fluorocarbon absorption, etc., to remove radioactive iodine in the waste gas through a disproportionation reaction. The dry method mainly uses a solid adsorbent to directly adsorb radioactive iodine. 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. In addition, the high production cost of activated carbon also limits its large-scale use. In addition, activated carbon mainly relies on a large specific surface area to achieve physical adsorption of iodine species. Due to the lack of strong chemisorption sites, the adsorption capacity of activated carbon is relatively limited, and it is difficult to achieve higher adsorption performance. Summary of the Invention

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

[0005] In order to achieve the above purposes, the technical solutions adopted by the present invention are as follows:

[0006] Coordination supramolecular networks (CSNs) are formed by the self-assembly of central metal ions and ligands. Their characteristics such as rich active sites, large specific surface area, and flexible and adjustable structures have attracted extensive attention in adsorption separation. CSNs formed by the self-assembly of the functional groups of ligand molecules and central metal ions greatly improve chemical stability, avoiding problems such as sublimation, decomposition, and dissolution in water that may occur in ligand molecules, effectively increasing the storage life of the material, and ensuring that the adsorption material can still be effectively used after long-term storage. The present invention uses a coordination supramolecular network as a solid iodine adsorbent, and its rich active sites are conducive to achieving excellent adsorption effects.

[0007] In the first aspect of the present invention, a supramolecular network material is provided, and the supramolecular network material is a supramolecular network material formed by the self-assembly of zinc ions and 2-mercaptonicotinic acid.

[0008] The supramolecular network material of the present invention is formed by the self-assembly of zinc ions and 2-mercaptonicotinic acid. The network material has a one-dimensional non-porous network structure, and a large number of pyridine nitrogen sites with strong adsorption activity are contained on the network, and it has excellent gas-phase I 2 vapor, gas-phase CH 3 I vapor adsorption performance and liquid-phase I 3 – adsorption performance, and can strongly remove sublimated iodine, iodomethane, and triiodide ions in aqueous solution in the air through charge transfer interactions occurring with iodine species.

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

[0010]

[0011] Preferably, the supramolecular network material is a crystal material, satisfying at least one of the following conditions:

[0012] a) The crystal material is of micro-nano scale;

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

[0014] c) The structure of the crystal 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] In the second aspect of the present invention, a preparation method of the supramolecular network material described in the first aspect is provided, including the following steps: mixing 2-mercaptonicotinic acid and an alkaline substance in a solvent, then adding a zinc source, and carrying out a coordination reaction to obtain the supramolecular network material.

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

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

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

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

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

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

[0023] Preferably, the solvent is water.

[0024] Currently, the reported CSNs adsorption materials generally use the solvothermal method with organic solvents under high temperature and high pressure environments for reactions, which can cause environmental pollution and high energy consumption, and is not conducive to environmental protection. By using deionized water as the solvent and using NaOH to remove the hydrogen atoms of the coordination groups, the deprotonation method that realizes the rapid coordination reaction of organic ligands in water has the advantages of high yield, short reaction time, low energy consumption, and environmental friendliness. Moreover, the CSNs obtained by the deprotonation method often have a crystal structure different from that of the CSNs obtained by the solvothermal method, which makes it an effective way to develop new CSNs materials.

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

[0026] More preferably, the concentration of 2-mercaptonicotinic acid 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 °C.

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

[0031] Preferably, it further includes the following steps: after the coordination reaction, the supernatant is removed by centrifugation, washed with water and ethanol, and finally dried to obtain a pale 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 duration is 5–10 min.

[0034] The third aspect of the present invention provides an application of the supramolecular network material described in the first aspect in adsorbing iodine.

[0035] Preferably, the iodine is gaseous I 2 vapor, gaseous CH 3 I vapor or liquid-phase I 3 – .

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

[0037] The 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 under the condition of 25-75 °C.

[0039] The beneficial effects of the present invention are as follows:

[0040] (1) The present invention provides a supramolecular network material, which is self-assembled from zinc ions and 2-mercaptonicotinic acid. Compared with traditional activated carbon, the supramolecular network material not only has characteristics such as a large specific surface area and a flexible and adjustable structure, but also its network contains a large number of pyridine nitrogen sites with strong adsorption activity, and has excellent gaseous I 2 vapor, gaseous CH 3 I vapor adsorption performance and liquid-phase I 3 – adsorption performance. It can strongly remove sublimated iodine, gaseous CH 3 I vapor in the air and iodine triions in aqueous solution through charge transfer interactions with iodine species. When adsorbing gaseous I 2 vapor at 55 °C for 24 h, the adsorption capacity can reach 4500 mg·g -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 preparation method of the above supramolecular network material, which uses an alkaline substance to deprotonate and remove the hydrogen atoms of the coordination groups, realizing the rapid coordination of the organic ligand in the solvent. It has the advantages of short reaction time, low energy consumption, environmental friendliness, etc. Moreover, the CSNs obtained by the deprotonation method often have a crystal structure different from that of the CSNs obtained by the solvothermal method, which makes it an effective way to develop new CSNs materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is the Zn-MNA coordination structure of Example 1;

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

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

[0045] Figure 4 It is the quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I 2 ;

[0046] Figure 5 It is the quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing CH 3 I;

[0047] Figure 6 It is the quantum chemical calculation optimized model structure of Zn-MNA of Example 1 after adsorbing I 3 – ;

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

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

[0050] Figure 9 It is the adsorption amount result of the steam I 2 adsorption experiment of Zn-MNA of Example 1 at different temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0051] The content of the present invention will be further described in detail through specific examples below. The raw materials used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or prepared and separated by simple synthesis; the processes used, unless otherwise specified, are all conventional processes in the art.

[0052] Example 1

[0053] This example provides a supramolecular network material and its preparation method. The preparation process steps are as follows:

[0054] At room temperature, 1 mmol of 2-mercaptonicotinic acid is added to 30 mL of deionized water, and then 1 mmol of NaOH is added thereto and stirred until the solution becomes clear. Subsequently, 1 mmol of ZnSO 4 ·7H 2 O is added and the solution is stirred for 10 min to form a pale yellow solid. Subsequently, centrifugation is carried out at 8000 rpm for 5 min to remove the supernatant. Then, it is washed once with deionized water and once with absolute ethanol, and vacuum dried at 80 °C for 12 h to obtain a pale yellow powder, denoted as Zn-MNA.

[0055] Material Characterization

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

[0057] Figure 4 is the optimized model structure of quantum chemical calculation after Zn-MNA in Example 1 adsorbs I 2 ; Figure 5 is the optimized model structure of quantum chemical calculation after Zn-MNA in Example 1 adsorbs CH 3 I; Figure 6 is the optimized model structure of quantum chemical calculation after Zn-MNA in Example 1 adsorbs I 3 – ;

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

[0059] Figure 8SEM image of Zn-MNA in Example 1. Zn-MNA is a crystal material with micro-nano scale dimensions, in the form of rectangular rod-shaped crystals. The length of the rectangular rod-shaped crystals is 1–3 μm, and the width is 0.3–0.6 μm.

[0060] Characterization of iodine adsorption experiment

[0061] Weigh out 10 mg of Zn-MNA (denoted as m) and place it in a 2 mL vial (denoted as m a ). Then, place 200 mg of I 2 in another 2 mL vial. Finally, place the two vials at the bottom of a 20 mL vial, seal the vial, set up multiple experimental groups, and place the sealed 20 mL vials in an oven at 25 °C, 35 °C, 45 °C, and 55 °C respectively, with normal pressure. After adsorption for 24 h, weigh the mass of the vial containing Zn-MNA (denoted as m b1 , m b2 ,..., m bn ) until the mass of the vial containing Zn-MNA changes by less than 0.1 mg in three weighings and stop the measurement. Calculate the adsorption capacity qe of gaseous I 2 vapor at an adsorption time of 24 h according to the formula (mb - ma) / m.

[0062] Figure 9 Adsorption capacity results of Zn-MNA in Example 1 for vapor I 2 adsorption experiments at different temperatures. At temperatures of 25 °C, 35 °C, 45 °C, and 55 °C, the adsorption capacities qe of gaseous I 2 vapor at an adsorption time of 24 h are 600, 1015, 2910, and 4500 mg·g -1 respectively, indicating that Zn-MNA has good iodine storage capacity and high stability, and shows a high adsorption capacity in the iodine vapor adsorption experiment.

[0063] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A supramolecular network material, characterized in that: The supramolecular network material is a supramolecular network material formed by self-assembly of zinc ions and 2-mercaptonicotinic acid.

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

3. The method for preparing the supramolecular network material according to claim 1 or 2, characterized in that: The method comprises the following steps: mixing 2-mercaptonicotinic acid and alkaline substances in a solvent, adding a zinc source, and performing coordination reaction to obtain the supramolecular network material.

4. The method for preparing a supramolecular network material according to claim 3, characterized in that: The zinc source is selected from at least one of zinc nitrate, zinc sulfate and zinc chloride; And / or, the alkaline substance is selected from sodium hydroxide.

5. The method for preparing the supramolecular network material according to claim 3, characterized in that: The molar ratio of the 2-mercaptonicotinic acid to the zinc source is 1:(0.5-2); And / or, the molar ratio of the 2-mercaptonicotinic acid to the alkaline substance is 1:(0.5-2).

6. The method for preparing a supramolecular network material according to claim 3, 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.

7. The method for preparing a supramolecular network material according to claim 3, characterized in that: The reaction time of the coordination reaction is 5 to 20 minutes; And / or, the coordination reaction is carried out under stirring conditions.

8. Use of the supramolecular network material according to claim 1 or 2 in adsorbing iodine.

9. A method for adsorbing iodine vapor, characterized in that: The supramolecular network material according to claim 1 or 2 is used as an adsorbent.

10. The method for adsorbing iodine vapor according to claim 9, characterized in that: The adsorption of iodine vapor is carried out at a temperature of 25 to 75°C.

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