A thiophene-based COF material, its synthesis method, and iodine adsorption application

Abstract

The present invention belongs to the technical field of functional compound applications and discloses a thienyl COF material with the chemical formula [(TAPB)2(DTTA)3] n ; Wherein, TAPB is 1,3,5-tris(4-aminophenyl)benzene, DTTA is 2,5-di(2-thienyl)terephthalaldehyde, and n is a positive integer. The material is a 2D polygonal sheet structure, each polygon has multiple exposed thiophene groups, and adjacent sheets are stacked layer by layer through π-π forces to form a multilayer network structure with ordered 1D channels. The material has a high specific surface area and can serve as a good storage channel for iodine molecules; the pores contain thiophene groups with electron-donating properties, which have a high affinity for electron-deficient iodine. Thiphenyl-COF is made into solid particles or sheets and can be used as an efficient capture agent in iodine-containing flowing gases.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional compound applications, and in particular relates to a thienyl COF material, a synthesis method thereof, and iodine adsorption application thereof. Background Art

[0002] Steadily developing green renewable energy and replacing traditional thermal power with more alternatives is a key way to effectively reduce carbon emissions. Currently, hydropower (accounting for 16%) is fully developed. However, renewable energy sources such as solar (accounting for less than 2%), wind, tidal, and geothermal energy are in very limited supply, significantly affected by natural conditions, making continuous high-load and stable power supply difficult and costly. While energy transition is urgent, the world still places its hopes on developing nuclear power. In fact, nuclear power is one of the most efficient and cleanest energy sources.

[0003] Safety is the primary consideration for nuclear power. Iodine isotopes account for about 0.69% of the uranium-235 fission products in the nuclear fuel cycle and are one of the main radioactive wastes produced in nuclear waste. The main isotopes of iodine include 129 I(1.6×10 7 years) and with high specific activity 131 I (8.02d). Radioactive iodine, which evaporates from gaseous and aqueous phases, accumulates in the atmosphere and can be inhaled by the human body and deposited in the thyroid gland, exhibiting extremely strong biotoxicity and radiotoxicity. Therefore, capturing highly volatile radioactive iodine during nuclear fuel reprocessing and in the event of a nuclear accident is crucial for nuclear safety, environmental protection, public health, and ultimately the sustainable development of nuclear energy.

[0004] Under the existing technology, waste gas treatment mainly uses traditional adsorbents, such as activated carbon, metal oxides (220 mg / g), zeolite and its modified adsorbents (196 mg / g), resins (200-1000 mg / g), etc., to capture iodine vapor through physical effects (there is competition between water and iodine for adsorption sites, and high humidity and high temperature affect adsorption efficiency) and chemical effects (metal iodide blocks the pores and limits high adsorption). However, due to the complex conditions of fuel post-treatment waste gas, such as high system temperature, high ambient humidity, high radiation intensity, extremely low iodine concentration and small system partial pressure, there are a large number of coexisting acidic gases (such as NO x , HNO3), etc., so these solid adsorbents have poor capture efficiency for low-concentration iodine. The preferential adsorption of water at high humidity seriously damages the adsorbent performance. Therefore, under the dual pressures of accelerated nuclear power development and environmental protection, there is an urgent need to explore new porous adsorption materials that can efficiently capture low-concentration iodine in the gas / liquid phase under strong competition from water molecules and minimize the volume of nuclear waste. This is the most important challenge in this field. Summary of the Invention

[0005] The present invention aims to disclose a thiophene-based COF material, a synthesis method thereof, and an iodine adsorption application thereof, which solves the problem that traditional adsorbents have poor efficiency in capturing low-concentration iodine and that water is preferentially adsorbed and damages the adsorbent under high humidity.

[0006] The present invention is achieved through the following technical solutions:

[0007] A thienyl COF material, wherein the chemical formula of the thienyl COF material is [(TAPB)2(DTTA)3] n ;

[0008] Wherein, TAPB is 1,3,5-tris(4-aminophenyl)benzene, DTTA is 2,5-di(2-thienyl)terephthalaldehyde, and n is a positive integer.

[0009] Furthermore, the thiophene-based COF material has a 2D polygonal sheet structure, each polygon has multiple exposed thiophene groups, and adjacent sheets are stacked layer by layer through π-π forces to form a multilayer network structure with ordered 1D channels.

[0010] Furthermore, the thiophene-based COF material is mainly microporous, and when the relative pressure is 0.99, the N2 adsorption capacity can reach 514.45 cm 3 / g, and the BET specific surface area and Langmuir specific surface area are 1421.98 m 2 / g and 2007.75m 2 / g.

[0011] The present invention also discloses a method for synthesizing the thiophene-based COF material, comprising the following steps:

[0012] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,5-di(2-thienyl)terephthalaldehyde and a reaction solvent are uniformly mixed, a catalyst is added, and ultrasonic dispersion is performed to obtain a reactant;

[0013] (2) subjecting the reactants to multiple cycles of freezing and thawing under inert gas conditions, and then reacting at 100-140° C. for 48-120 hours, and cooling to obtain a crude product;

[0014] (3) After purifying the crude product, a thienyl COF material is obtained.

[0015] Furthermore, the molar ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-di(2-thienyl)terephthalaldehyde is 1:1-2.

[0016] Furthermore, in step (1), the reaction solvent is one or two of o-dichlorobenzene, mesitylene, 1,4-dioxane, methanol and n-butanol;

[0017] The catalyst is acetic acid, trifluoroacetic acid, or HCl.

[0018] Furthermore, in step (2), the specific operation of multiple cycles of freezing-thawing is: under inert gas conditions, the reactant is degassed multiple times through freeze-pump-thaw cycles.

[0019] Furthermore, in step (3), the specific purification operation is: the crude product is ultrasonically soaked in tetrahydrofuran for multiple times, and after the unreacted monomer substances are completely removed, methanol is used for Soxhlet extraction, and the solid is vacuum dried for 12 to 24 hours to obtain a thienyl COF material.

[0020] The present invention also discloses the application of the thiophene-based COF material as an adsorbent in the field of iodine adsorption, which is characterized in that the thiophene-based COF material is used as a solid adsorbent to capture iodine molecules.

[0021] Furthermore, the thiophene-based COF material is used as a solid adsorbent in the following steps: the thiophene-based COF material is taken, ground evenly, and then filled into a glass tube, and the waste gas containing radioactive iodine passes through the glass tube and is captured.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The present invention discloses a thienyl COF material and a synthesis method thereof. A COF material having a 2D polygonal layer structure is synthesized from 1,3,5-tris(4-aminophenyl)benzene and 2,5-di(2-thienyl)terephthalaldehyde. The chemical formula of the thienyl COF material is [(TAPB)2(DTTA)3] n , a polyphenyl ring system with strong hydrophobic properties that resists damage to the adsorbent even in high humidity environments. Each polygon contains multiple exposed thiophene groups, and adjacent layers stack through π-π interactions to form a multilayer network structure with ordered 1D channels. Its synthetic route is simple, cost-effective, and amenable to large-scale production.

[0024] By molecular customization, i.e., functional group modification, COF is endowed with a special strong effect on iodine, i.e., by introducing thiophene functional groups on the aldehyde linking monomer, it is expected to achieve higher iodine capture. 2D COF can obtain confined 1D nanopores, in which isolated iodine molecules adsorbed tend to spontaneously aggregate to form more stable polyiodine chains. The stronger host-guest interaction between the polyiodine chains and the framework achieves high iodine capture. In this case, low-concentration iodine molecules first bind to and migrate to specific strong adsorption sites within the one-dimensional pores of COF. Further, multiple host-guest interactions between the framework-iodine and iodine-iodine synergistically induce iodine aggregation and framework deformation, and sequentially attract more iodine molecules to subsequently enter the pores smoothly, achieving both low-concentration iodine adsorption and maximizing the use of high porosity to achieve large-scale iodine capture.

[0025] The present invention also discloses that the thiophene-based COF material has excellent iodine adsorption performance, which is due to the following reasons: (1) the thiophene-based COF material itself has a high specific surface area. The BET specific surface area and the Langmuir specific surface area can reach 1421.98 m 2 / g and 2007.75m 2 / g. (2) Electron-rich groups in the pores. The overall electron-donating properties of the thiophene group and the lone pair electron properties of sulfur give it a high affinity for electron-deficient iodine, which enables the material to have a strong adsorption effect on iodine, and thus is expected to be used for iodine waste gas treatment in nuclear power plants under real working conditions.

[0026] The present invention also discloses the use of the thienyl COF material as an adsorbent in the field of iodine adsorption. The material can be placed in a 70°C iodine vapor chamber as a solid adsorbent and can obtain an iodine adsorption capacity of 3.770 g / g in 630 minutes. The thienyl COF material can be filled into a glass pipe, and iodine is captured after the radioactive iodine-containing waste gas passes through the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a synthetic spectrum of the thienyl COF material;

[0028] Figure 2 The powder diffraction comparison patterns of the thienyl COF material and two reactive monomers;

[0029] Figure 3 The infrared comparison spectrum of the thienyl COF material and two reactive monomers;

[0030] Figure 4 N2 adsorption-desorption curves of the thiophene-based COF material at different activation temperatures;

[0031] Figure 5 is a pore size distribution diagram of the thienyl COF material;

[0032] Figure 6 are photos of the thienyl COF material before and after adsorption in iodine vapor;

[0033] Figure 7 is the iodine adsorption curve of the thienyl COF material to iodine vapor at 70° C.;

[0034] Figure 8 is a thermogravimetric curve of the thienyl COF material after saturated adsorption in iodine vapor;

[0035] Figure 9 is the adsorption curve of the thienyl COF material in a dynamic iodine vapor flow. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0037] The detailed description of the embodiment of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. All other embodiments derived by those skilled in the art based on the figures and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0038] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0039] Example 1

[0040] The present invention discloses a method for synthesizing a thiophene-based COF material, comprising the following steps:

[0041] 0.03 mmol of 2,5-di(2-thienyl)terephthalaldehyde and 0.02 mmol of 1,3,5-tris(4-aminophenyl)benzene were accurately weighed, 1.0 mL of o-dichlorobenzene was added as a reaction solvent, and the mixture was uniformly dispersed by ultrasonication to prepare a mixed solution.

[0042] Subsequently, 0.1 mL of 6 M acetic acid was added and ultrasonication was continued for 30 min to obtain the reactant;

[0043] The reactant was transferred to a 10 mL Pyrex tube, and subjected to multiple liquid nitrogen freeze-thaw cycles under vacuum conditions. The mixture was then kept at 120° C. for 72 h, and then slowly cooled to room temperature and filtered to obtain a crude product.

[0044] The crude product was placed in fresh tetrahydrofuran and methanol and ultrasonically immersed multiple times, and then vacuum-dried for 12 hours to obtain a yellow powder, which is the thienyl COF material.

[0045] Example 2

[0046] The synthesis steps are the same as those in Example 1, except that 1 mL of o-dichlorobenzene solution is replaced by 1 mL of mesitylene solution.

[0047] Example 3

[0048] The synthesis steps are the same as those in Example 1, except that 1 mL of o-dichlorobenzene solution is replaced by 1 mL of 1,4-dioxane solution.

[0049] Example 4

[0050] The synthesis steps are the same as those in Example 1, except that 1 mL of o-dichlorobenzene solution is replaced by 1 mL of n-butanol solution.

[0051] Example 5

[0052] The synthesis steps were the same as those in Example 1, except that 0.1 mL of 6 M acetic acid was replaced with 0.1 mL of 6 M trifluoroacetic acid.

[0053] Example 6

[0054] The synthesis steps were the same as those in Example 1, except that 0.1 mL of 6 M acetic acid was replaced with 0.1 mL of 6 M hydrochloric acid.

[0055] Example 7

[0056] The synthesis steps are the same as those in Example 1, except that 0.03 mmol of 2,5-di(2-thienyl)terephthalaldehyde is replaced by 0.02 mmol.

[0057] Example 8

[0058] The synthesis steps are the same as those in Example 1, except that 0.03 mmol of 2,5-di(2-thienyl)terephthalaldehyde is replaced by 0.04 mmol.

[0059] Example 9

[0060] The synthesis steps are the same as those in Example 1, except that the reaction temperature of 120°C is replaced by 100°C.

[0061] Example 10

[0062] The synthesis steps are the same as those in Example 1, except that the reaction temperature of 120°C is replaced by 140°C.

[0063] Example 11

[0064] The synthesis steps are the same as those in Example 1, except that the reaction time 72 h is replaced by 48 h.

[0065] Example 12

[0066] The synthesis steps are the same as those in Example 1, except that the reaction time 72 h is replaced by 96 h.

[0067] Example 13

[0068] The synthesis steps are the same as those in Example 1, except that the reaction time 72 h is replaced by 120 h.

[0069] Examples 1-13, using different reaction solvents, catalysts, reaction temperatures, reaction times, and monomer ratios, all yielded thiophene-based COF materials with good crystallinity and high yield. The resulting thiophene-based COF materials exhibited excellent iodine adsorption properties and possessed significant application value in environmental protection.

[0070] The thiophene-based COF material prepared by the present invention has the chemical formula [(TAPB)2(DTTA)3] n ;

[0071] Wherein, TAPB is 1,3,5-tris(4-aminophenyl)benzene, DTTA is 2,5-di(2-thienyl)terephthalaldehyde, and n is a positive integer.

[0072] The thiophene-based COF material is a powder crystalline substance with a 2D polygonal sheet structure. Each polygon has multiple exposed thiophene groups, and adjacent sheets are stacked layer by layer through π-π forces to form a multilayer network structure with ordered 1D channels.

[0073] The application of the thienyl COF material of the present invention in iodine capture is specifically as follows:

[0074] Application Example 1

[0075] (1) 5 g of the prepared thienyl COF material was ground evenly and a tablet press was used to obtain a thin flake sample with a diameter of 4.8 cm and a thickness of 1 cm;

[0076] (2) The above sample was placed inside a glass tube with an inner diameter of 5 cm and a length of 10 cm to form a gas filter column;

[0077] (3) Connect the filter column containing the thienyl COF material adsorbent to the tail gas treatment pipeline of iodine-containing waste gas to achieve effective iodine capture.

[0078] Application Example 2

[0079] (1) Take 10 g of the prepared thienyl COF material, grind it evenly, and sieve it to obtain a uniform granular sample with a mesh size of 200-500;

[0080] (2) Fill the sample into a glass tube with an inner diameter of 5 cm and a length of 10 cm, and compact the thienyl COF material to form a packed column;

[0081] (3) Connecting the packed column containing the thienyl COF material adsorbent to the tail gas treatment pipeline of iodine-containing waste gas to achieve effective iodine capture.

[0082] The above two methods can be used to make flake or granular samples as solid adsorbents to achieve effective iodine capture.

[0083] Figure 1 This is a synthesis diagram of thienyl COF materials, showing the dehydration of 2,5-di(2-thienyl)terephthalaldehyde and 1,3,5-tri(4-aminophenyl)benzene to form a Schiff base-type thienyl COF material.

[0084] Figure 2 The powder diffraction comparison patterns of the two reaction monomers, thiophene-based COF material, 1,3,5-tris(4-aminophenyl)benzene and 2,5-di(2-thiophenyl)terephthalaldehyde, show a new diffraction peak at 2θ=3.627°, while no obvious monomer diffraction peak appears, proving that the thiophene-based COF material was successfully synthesized.

[0085] Figure 3 This is the infrared comparison spectrum of the two reaction monomers of thiophene-based COF material, 1,3,5-tris(4-aminophenyl)benzene and 2,5-di(2-thienyl)terephthalaldehyde, where the appearance of -C=N proves the successful synthesis of the material.

[0086] Figure 4 The N2 adsorption and desorption curves of the thiophene-based COF material at 77K after activation at 25℃ and 120℃ are shown. The solid points are the adsorption curves and the hollow points are the desorption curves. First, it can be seen that the material has good porosity stability. The N2 adsorption amounts obtained at different activation temperatures are basically the same, and the material can be completely adsorbed and desorbed. Secondly, the adsorption curve of the material is a typical IV type isotherm with certain microporous characteristics. At a relative pressure of 0.99, the N2 adsorption amount can reach 514.45 cm 3 / g, and its BET specific surface area and Langmuir specific surface area are 1421.98 m 2 / g and 2007.75m 2 / g.

[0087] Figure 5 The pore size distribution of thiophene-based COF materials calculated using the non-local density functional theory (NLDFT) method is 1.10 to 3.39 nm.

[0088] Figure 6 Photos of the thienyl COF material before and after iodine vapor adsorption. The color change of the material (from yellow to black) demonstrates its iodine vapor adsorption capacity.

[0089] Figure 7 This is the iodine adsorption curve of the thiophene-based COF material for iodine vapor at 70°C. Using the weighing method, a high iodine adsorption capacity of 3770 mg / g was obtained in 630 minutes, demonstrating the material's high iodine capture efficiency.

[0090] Figure 8This is the thermogravimetric curve of a thienyl COF material after saturated adsorption in iodine vapor. The figure shows a negligible weight loss of 1.26% before 100°C, demonstrating that the thienyl COF material has relatively few iodine molecules adhering to its surface. The inflection point at 347°C, where the weight loss ends, indicates strong charge transfer interaction between the thienyl COF material and iodine, requiring higher temperatures for complete release of the captured iodine. Calculated weight loss indicates that 1g of thienyl COF material can capture 2460mg of vapor-phase iodine.

[0091] Figure 9 The adsorption curve for a thienyl COF sheet material at 30°C, a carrier gas (argon) flow rate of 20 mL / min, and an iodine concentration of 26.8 mg / h (circles represent iodine flow without sample, squares represent flow with sample). DMF was used as the tail gas receiving liquid, and the signal at the point was monitored by UV light. No iodine signal was detected within 70 minutes, and only a small amount was detected starting at 80 minutes. This demonstrates that the material can effectively capture iodine in the flowing airstream.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A thienyl COF material, characterized in that: The chemical formula of the thienyl COF material is [(TAPB)2(DTTA)3] n ; Wherein, TAPB is 1,3,5-tris(4-aminophenyl)benzene, DTTA is 2,5-di(2-thienyl)terephthalaldehyde, and n is a positive integer.

2. A thienyl-based COF material according to claim 1, characterized in that: The thiophene-based COF material is a 2D polygonal sheet structure, each polygon has multiple exposed thiophene groups, and adjacent sheets are stacked layer by layer through π-π forces to form a multilayer network structure with ordered 1D channels.

3. A thienyl COF material according to claim 1, characterized in that: The thiophene-based COF material is mainly microporous, and the N2 adsorption capacity can reach 514.45 cm at a relative pressure of 0.

99. 3 / g, and the BET specific surface area and Langmuir specific surface area are 1421.98 m 2 / g and 2007.75m 2 / g.

4. The method for synthesizing the thienyl COF material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) 1,3,5-tris(4-aminophenyl)benzene, 2,5-di(2-thienyl)terephthalaldehyde and a reaction solvent are uniformly mixed, a catalyst is added, and ultrasonic dispersion is performed to obtain a reactant; (2) subjecting the reactants to multiple cycles of freezing and thawing under inert gas conditions, and then reacting at 100-140° C. for 48-120 hours, and cooling to obtain a crude product; (3) After purifying the crude product, a thienyl COF material is obtained.

5. The method for synthesizing the thienyl COF material according to claim 4, characterized in that: The molar ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-di(2-thienyl)terephthalaldehyde is 1:1-2.

6. The method for synthesizing the thienyl COF material according to claim 4, characterized in that: In step (1), the reaction solvent is one or two of o-dichlorobenzene, mesitylene, 1,4-dioxane, methanol and n-butanol; The catalyst is acetic acid, trifluoroacetic acid, or HCl.

7. The method for synthesizing a thienyl COF material according to claim 4, wherein: In step (2), the specific operation of multiple cycles of freezing-thawing is: under inert gas conditions, the reactant is degassed multiple times through freeze-pump-thaw cycles.

8. The method for synthesizing a thienyl COF material according to claim 4, wherein: In step (3), the specific operation of purification is: the crude product is ultrasonically soaked in tetrahydrofuran for multiple times, and after the unreacted monomer substances are completely removed, methanol is used for Soxhlet extraction, and the solid is vacuum dried for 12 to 24 hours to obtain a thienyl COF material.

9. Use of the thienyl COF material according to any one of claims 1 to 3 as an adsorbent in the field of iodine adsorption, characterized in that: The thienyl COF material is used as a solid adsorbent to capture iodine molecules.

10. The use according to claim 9, characterized in that The thiophene-based COF material is used as a solid adsorbent in the following steps: the thiophene-based COF material is taken, ground evenly, and then filled into a glass tube; waste gas containing radioactive iodine passes through the glass tube and is captured.

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