N, s heteroatom-doped two-dimensional covalent organic framework material, preparation method and application thereof

Abstract

The application relates to an N, S heteroatom doped two-dimensional covalent organic framework material, a preparation method and applications thereof in hydrogen evolution reactions and iodine element capturing, and belongs to the technical field of two-dimensional covalent organic framework materials. Two N, S heteroatom doped two-dimensional covalent organic framework materials proposed in the application show excellent catalytic performance under room temperature conditions, and the average hydrogen evolution rate (HER) of JLNU-308 and JLNU-309 can reach 1827.686 mu mol g ‑1 h ‑1 and 2868.5735 mu mol g ‑1 h ‑1 under visible light illumination (420-780 nm) and in the presence of 1wt% Pt cocatalyst. In addition, both of them have excellent adsorption rates for iodine elements within 50h, and the maximum adsorption capacities can reach 3.798 g / g and 3.84 g / g, and the catalytic and adsorption performances are superior to those of porous organic polymers.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional covalent organic framework materials technology, specifically relating to a two-dimensional covalent organic framework material (JLNU-308 or JLNU-309) doped with N and S heteroatoms, its preparation method, and its application in hydrogen evolution reaction and iodine capture. Background Technology

[0002] Hydrogen energy is widely considered a sustainable, pollution-free, high-calorific-value, and high-energy-density green clean energy source, and its combustion products do not cause any environmental pollution. Therefore, hydrogen energy development is one of the ideal ways to solve the energy crisis and environmental pollution problems in the future, and has attracted significant attention in the field of photocatalytic water splitting for hydrogen production. The core issue facing hydrogen energy technology development is how to achieve large-scale and inexpensive hydrogen production, which has become one of the current research hotspots in this field. Among the many methods and approaches to hydrogen energy development, using solar energy for photocatalytic water splitting to produce hydrogen is the most ideal and promising technology.

[0003] While most photocatalysts are based on inorganic semiconductors, some are composed solely of light elements, primarily carbon nitride polymers. However, the main drawbacks of these polymers are poor crystallinity and low surface area. Furthermore, carbon nitrides are mostly composed of heptaazines or triazines, thus offering limited chemical diversity. Covalent organic frameworks (COFs), due to their high crystallinity and porosity, easily overcome these inherent weaknesses of carbon nitrides, and many imine-bonded COFs have been reported for efficient photocatalytic hydrogen production.

[0004] Furthermore, with the increasing severity of global warming, nuclear energy has become one of the most prominent and feasible alternative energy sources for reducing greenhouse gas emissions. However, a pressing issue accompanying the development of nuclear energy is nuclear waste pollution; the reprocessing of spent nuclear fuel produces substances containing iodine isotopes (…). 129 I and 131 I) Volatile radioactive compounds. Due to their long half-life ( 129 I is 1.57 × 10 7 Year, 131 Iodine (with a shelf life of 8 days) is highly volatile and has adverse effects on human metabolism and the environment. Therefore, for the sake of human health and environmental safety, developing effective methods for capturing and storing volatile radioactive isotopes like iodine has become an important goal for researchers.

[0005] Currently reported iodine solid-phase adsorption materials mainly include inorganic porous materials, metal-organic frameworks (MOFs), hypercrosslinked polymers (HCPs), modified carbon materials, and porous organic polymers (POPs). Imine-bonded COFs possess characteristics such as low framework density, large specific surface area, high porosity, and tunable pore structure, making them ideal gas adsorption and storage materials. Furthermore, N and S-rich COFs can enhance the adsorption affinity for iodine, thereby increasing the amount of iodine adsorbed. Summary of the Invention

[0006] This invention addresses the energy crisis and environmental pollution by proposing a two-dimensional covalent organic framework material (JLNU-308 or JLNU-309) doped with N and S heteroatoms, its preparation method, and its applications in hydrogen evolution reaction at room temperature and iodine capture at 75°C. The resulting target catalyst material, which also functions as an adsorbent, exhibits high specific surface area and good thermochemical stability.

[0007] The preparation method of JLNU-308, a two-dimensional covalent organic framework material doped with N and S heteroatoms according to the present invention, comprises the following steps:

[0008] (1) Mix and grind 1,3,5-tris(4-aminophenyl)benzene (TAPB, 17-28 mg) with 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) (BTC, 20-32 mg) and add the mixture to a glass tube. Then add 1-butanol (1-3 mL) and 6 mol / L acetic acid (0.1-0.3 mL) as a mixed solvent and let stand for 2-3 min.

[0009] (2) Place the glass tube that has been left to stand in step (1) in liquid nitrogen and freeze until the solvent is completely frozen and no longer flows. Evacuate the glass tube to make the pressure in the glass tube 0.10-0.20 mmHg. Seal the opening of the glass tube with a flame gun and then react the glass tube at 110-130℃ for 3-7 days.

[0010] (3) After cooling the glass tube in step (2) to room temperature, take out the reaction product, filter it, wash it with acetone 2 to 5 times, and then soak it in acetone for 5 to 10 hours. Replace the acetone 3 to 5 times during the soaking period. Finally, vacuum dry to obtain a light yellow solid product, namely JLNU-308.

[0011] The preparation method of JLNU-309, a two-dimensional covalent organic framework material doped with N and S heteroatoms according to the present invention, comprises the following steps:

[0012] (1) Mix and grind 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT, 17-27 mg) with 5,5',5''-(benzene-1,3,5-triyl)tri(thiophene-2-carboxaldehyde) (BTC, 20-32 mg) and add the mixture to a glass tube. Then add 1-butanol (0.15-0.35 mL), o-dichlorobenzene (0.45-1.05 mL) and 6 mol / L acetic acid (0.1-0.3 mL) as a mixed solvent and let stand for 2-3 min.

[0013] (2) Place the glass tube that has been left to stand in step (1) in liquid nitrogen and freeze until the solvent is completely frozen and no longer flows. Evacuate the glass tube to make the pressure in the glass tube 0.10-0.20 mmHg. Seal the opening of the glass tube with a flame gun and then react the glass tube at 110-130℃ for 3-7 days.

[0014] (3) After cooling the glass tube in step (2) to room temperature, take out the reaction product, filter it, wash it with acetone 2 to 5 times, and then soak it in acetone for 5 to 10 hours. Replace the acetone 3 to 5 times during the soaking period. Finally, vacuum dry to obtain a yellow solid product, namely JLNU-309.

[0015] In the above method, the volume ratio of 1-butanol to o-dichlorobenzene is 1:3.

[0016] A two-dimensional covalent organic framework material (JLNU-308 or JLNU-309) doped with N and S heteroatoms is prepared by the above method.

[0017] The two-dimensional covalent organic framework material (JLNU-308 or JLNU-309) doped with N and S heteroatoms has been applied in hydrogen evolution reaction and iodine capture.

[0018] Compared with existing technologies, this invention has the following innovative features:

[0019] 1. The two metal-free thiophene-based covalent organic framework materials, JLNU-308 and JLNU-309, possess a p-π conjugated structure (e.g., Figure 1 The synthetic schematic diagrams all have the following structures. Such p-π conjugated structures generally result in molecules with good stability.

[0020] 2. The two-dimensional covalent organic framework materials (JLNU-308 or JLNU-309) synthesized in this invention possess excellent crystallinity (e.g., Figure 2 (a) and (b) correspond to the XRD patterns of JLNU-308 and JLNU-309, respectively. The high main peak in the figure proves the excellent crystallinity of the material.

[0021] 3. The JLNU-308 and JLNU-309 obtained in this invention exhibit excellent adsorption rates for elemental iodine within 50 hours. After 5 cycles, the adsorption capacity of the two COFs (i.e., JLNU-308 and JLNU-309 prepared in this invention) for iodine remains essentially consistent with that of the original adsorbent. Figure 6 (c) and (d).

[0022] 4. The material obtained in this invention is a novel photocatalytic hydrogen production catalyst. Under visible light illumination (420–780 nm) and in the presence of 1 wt% Pt co-catalyst, the average hydrogen evolution rate (HER) of JLNU-308 and JLNU-309 can reach up to 1827.686 μmol g. -1 h -1 and 2868.5735 μmol g -1 h -1 (like Figure 5 (b)) and has good reusability. Attached Figure Description

[0023] Figure 1 Example 1 shows the synthesis diagram of the N, S heteroatom-doped JLNU-308 and JLNU-309 materials (where TAPB represents 1,3,5-tris(4-aminophenyl)benzene; TAPT represents 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; BTC represents 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde); n-BuOH represents n-butanol; o-DCB represents o-dichlorobenzene; and HOAc represents acetic acid).

[0024] Figure 2 XRD patterns of N, S heteroatom-doped JLNU-308 and JLNU-309 materials prepared in Example 1 are shown in Figures (a) and (b), respectively, comparing the XRD patterns of JLNU-308 and JLNU-309 with the theoretically simulated AA and AB packing patterns. In Figure (a), curve 1 represents the XRD pattern of JLNU-308, curve 2 represents the XRD pattern of the AA packing of JLNU-308 sample simulated using Materials Studio software, and curve 3 represents the XRD pattern of the AB packing of JLNU-308 sample simulated using Materials Studio software. Similarly, in Figure (b), curve 1 represents the XRD pattern of JLNU-309, curve 2 represents the XRD pattern of the AA packing of JLNU-309 sample simulated using Materials Studio software, and curve 3 represents the XRD pattern of the AB packing of JLNU-309 sample simulated using Materials Studio software.

[0025] Figure 3 Fourier transform infrared (FT-IR) spectra of the N, S heteroatom-doped JLNU-308 material (corresponding to Figure a) and JLNU-309 material (corresponding to Figure b) prepared in Example 1; wherein, in Figure (a), curve 1 represents the infrared spectrum of 1,3,5-tris(4-aminophenyl)benzene monomer, curve 2 represents the infrared spectrum of 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) monomer, and curve 3 represents the infrared spectrum of JLNU-308; in Figure (b), curve 1 represents the infrared spectrum of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine monomer, curve 2 represents the infrared spectrum of 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) monomer, and curve 3 represents the infrared spectrum of JLNU-309.

[0026] Figure 4 SEM images of the N and S heteroatom co-doped JLNU-308 material (corresponding to Figure a) and JLNU-309 material (corresponding to Figure b) prepared in Example 1;

[0027] Figure 5 The hydrogen production rate curves (corresponding to Figure a, where curve 1 represents JLNU-308 and curve 2 represents JLNU-309) of the N and S heteroatom co-doped JLNU-308 and JLNU-309 materials prepared in Example 1, and the hydrogen production rate cycle test graph (corresponding to Figure b, bar graph) within 25 hours are shown. Figure 1 This represents JLNU-308, columnar. Figure 2 This represents JLNU-309;

[0028] Figure 6Example 1 shows the iodine capture test spectra of the N, S heteroatom co-doped JLNU-308 and JLNU-309 materials. Figure (a) represents the gradient-time iodine capture experiment curve of JLNU-308 within 50 hours, and Figure (b) represents the gradient-time iodine capture experiment curve of JLNU-309 within 50 hours. The tests show that both materials have sustained adsorption capacity; JLNU-308 can adsorb 3.798 g / g of elemental iodine in 50 hours, and JLNU-309 can adsorb 3.84 g / g of elemental iodine in 50 hours. Figure (c) shows the bar graph of 5 iodine capture cycle experiments for JLNU-308, and Figure (d) shows the bar graph of 5 iodine capture cycle experiments for JLNU-309. The cycle test results indicate that JLNU-308 and JLNU-309 have excellent cycle stability and recyclability. Figure (e) represents the mass measurement bar chart of iodine retention in the COF pore structure of JLNU-308 at 25℃ and 1 standard atmosphere for 8 days, and Figure (f) represents the mass measurement bar chart of iodine retention in the COF pore structure of JLNU-309 at 25℃ and 1 standard atmosphere for 8 days. The retention experiment proves that both materials have excellent pore structures, which can effectively adsorb iodine inside the pores and prevent iodine volatilization. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0030] Example 1

[0031] (1) Mix and grind 1,3,5-tris(4-aminophenyl)benzene (TAPB, 17.5725 mg, 0.05 mmol) with 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) (BTC, 20.4255 mg, 0.05 mmol) and add the mixture to a 10 mL glass tube. Then add 1-butanol (1 mL) and 6 mol / L acetic acid (0.1 mL) as a mixed solvent and let stand for 3 min.

[0032] (2) Place the glass tube obtained in step (1) in liquid nitrogen and freeze for 1 minute. Evacuate the glass tube to make the pressure in the glass tube 0.15 mmHg. Seal the opening of the glass tube with a flame gun and keep the length of the glass tube about 13 cm. Then react the glass tube at 120°C for 3 days.

[0033] (3) After cooling the glass tube from step (2) to room temperature, the reaction product was taken out, filtered, washed three times with acetone, and then soaked in acetone for 8 hours. The acetone was replaced four times during the soaking period. Finally, the product was dried under vacuum to obtain 32.1 mg of a pale yellow solid product, namely JLNU-308.

[0034] The preparation method of JLNU-309, a two-dimensional covalent organic framework material doped with N and S heteroatoms according to the present invention, comprises the following steps:

[0035] (1) Mix and grind 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT, 17.721 mg, 0.05 mmol) with 5,5',5''-(benzene-1,3,5-triyl)tri(thiophene-2-carboxaldehyde) (BTC, 20.4255 mg, 0.05 mmol) and add the mixture to a 10 mL glass tube. Then add 1-butanol (0.25 mL), o-dichlorobenzene (0.75 mL) and 6 mol / L acetic acid (0.1 mL) as a mixed solvent and let stand for 3 min.

[0036] (2) Place the glass tube obtained in step (1) in liquid nitrogen and freeze for 1 minute. Evacuate the glass tube to make the pressure in the glass tube 0.15 mmHg. Seal the opening of the glass tube with a flame gun and keep the length of the glass tube about 13 cm. Then react the glass tube at 120°C for 3 days.

[0037] (3) After cooling the glass tube from step (2) to room temperature, the reaction product was taken out, filtered, washed three times with acetone, and then soaked in acetone for 8 hours. The acetone was replaced four times during the soaking period. Finally, the product was dried under vacuum to obtain 34.8 mg of yellow solid product, namely JLNU-309.

[0038] Example 2

[0039] The materials prepared in Example 1 were subjected to some structural characterization. Figure 1 This is a schematic diagram of the synthesis of the obtained material; Figure 2 The XRD spectra of the obtained materials JLNU-308 (Fig. a) and JLNU-309 (Fig. b) are shown to prove that the obtained JLNU-308 and JLNU-309 are AA-packed topological framework structures. Figure 3 The Fourier transform infrared (FT-IR) spectra of JLNU-308 (corresponding to Figure a) and JLNU-309 (corresponding to Figure b) further confirm the formation of C=N bonds; Figure 4 The SEM spectra of the obtained materials are shown in Figure a. As can be seen from Figure a, catalyst JLNU-308 exhibits a rod-like structure and has good crystallinity. As can be seen from Figure b, JLNU-309 exhibits an irregular spherical shape.

[0040] (1) The material prepared in Example 1 was subjected to photocatalytic hydrogen production test under visible light (xenon lamp, 300W, λ≥400nm) irradiation, with H2PtCl6 as a co-catalyst and ascorbic acid as a sacrificial agent.

[0041] The specific experimental steps are as follows: 30 mg of JLNU-308 or JLNU-309 catalyst was dispersed in 99 mL of aqueous solution (containing 10 mL of 0.1 M ascorbic acid as a sacrificial agent). The reactant solution was ultrasonically treated for 1 h under visible light (xenon lamp, 300 W, λ≥400 nm), followed by degassing and vacuuming for 30 min to completely remove air from the Pyrex reactor. Simultaneously, 1 mL of H2PtCl6 solution (with a concentration of 1.89 mg / mL) was used as a co-catalyst. Furthermore, the reactant solution in the Pyrex reactor was continuously stirred, and a circulating condensate system maintained the temperature of the entire reaction equipment at a constant 25°C throughout the photocatalytic process. The amount of hydrogen was monitored using a fully automated gas chromatography system (GC9790Ⅱ). The catalyst dosage was 30 mg, the sacrificial agent dosage was 10 mL, and the co-catalyst dosage was 1 mL.

[0042] (2) The materials prepared in Example 1 were washed three times with acetone solvent to obtain samples JLNU-308 and JLNU-309, and dried under vacuum for 5 hours to ensure the removal of solvent molecules and water molecules from the samples before iodine capture experiments. An open vial (2 mL) containing a COF sample (20.0 mg) was placed in a reaction vessel (10 mL) containing iodine (1 g), sealed, and reacted in an oven at 75°C. After 20 hours, the vial containing the COF sample was weighed and returned to the reaction vessel containing iodine. The vessel was sealed and returned to the oven at 75°C to continue adsorption until the mass of the vial containing the COF sample did not change. The sample after iodine adsorption was cooled to room temperature and weighed. The amount of iodine absorbed by the sample was calculated according to formula (1).

[0043] a=(m2-m1) / m1 (1)

[0044] Where a represents the amount of iodine adsorbed, m1 represents the mass of the COF sample before adsorption, and m2 represents the mass of the sample after adsorption of elemental iodine.

[0045] Photocatalytic hydrogen production test:

[0046] like Figure 5 As shown in (a), the catalyst can continuously produce hydrogen during 5 cycles (each cycle lasting 4.5 hours). Figure 5 (b) shows that the highest hydrogen production rate is 1827.686 μmol / g / h for JLNU-308 and 2868.5735 μmol / g / h for JLNU-309.

[0047] Gradient-time iodine capture test:

[0048] like Figure 6As shown in (a) and (b), the adsorption mass of iodine by JLNU-308 and JLNU-309 continued to increase within 50 h, reaching 3.798 g / g for JLNU-308 and 3.84 g / g for JLNU-309 at 50 h.

[0049] Catalytic stability test:

[0050] like Figure 5 As shown in (b), under the same conditions, the catalyst was tested for stability through cyclic use. After 5 cycles, its catalytic performance showed almost no decline. The catalytic and adsorption performance of JLNU-308 and JLNU-309 were superior to those of porous organic polymers.

[0051] Adsorption stability test:

[0052] like Figure 6 As shown in (c) and (d), the cyclic capture experiment revealed that the iodine capture capacity remained almost unchanged after five cycles, indicating that both JLNU-308 and JLNU-309 have good recyclability.

[0053] The above embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes, substitutions and improvements that can be easily conceived by those skilled in the art within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. Use of an N, S heteroatom-doped two-dimensional covalent organic framework material in a hydrogen evolution reaction or in iodine elemental capture, characterized in that: The N, S heteroatom-doped two-dimensional covalent organic framework material was prepared by the following steps. (1) Mix and grind 17-28 mg of 1,3,5-tris(4-aminophenyl)benzene with 20-32 mg of 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) and add it to a glass tube. Then add 1-3 mL of 1-butanol and 0.1-0.3 mL of 6 mol / L acetic acid mixed solvent and let stand for 2-3 min. (2) Place the glass tube that has been left to stand in step (1) in liquid nitrogen and freeze until the solvent is completely frozen and no longer flows. Evacuate the glass tube to make the pressure in the glass tube 0.10~0.20 mmHg. Seal the glass tube opening and then react the glass tube at 110~130 ℃ for 3~7 days. (3) After cooling the glass tube from step (2) to room temperature, take out the reaction product, filter it, wash it with acetone 2 to 5 times, and then soak it in acetone for 5 to 10 hours. Replace the acetone 3 to 5 times during the soaking period. Finally, vacuum dry to obtain a light yellow solid product, namely the two-dimensional covalent organic framework material doped with N and S heteroatoms, denoted as JLNU-308.

2. An application of a two-dimensional covalent organic framework material doped with N and S heteroatoms in hydrogen evolution reaction or in the capture of elemental iodine, characterized in that: The N, S heteroatom-doped two-dimensional covalent organic framework material was prepared by the following steps. (1) Mix and grind 17-27 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 20-32 mg of 5,5',5''-(benzene-1,3,5-triyl)tris(thiophene-2-carboxaldehyde) and add the mixture to a glass tube. Then add 0.15-0.35 mL of 1-butanol, 0.45-1.05 mL of o-dichlorobenzene and 0.1-0.3 mL of 6 mol / L acetic acid mixed solvent and let stand for 2-3 min. The volume ratio of 1-butanol to o-dichlorobenzene is 1:

3. (2) Place the glass tube that has been left to stand in step (1) in liquid nitrogen and freeze until the solvent is completely frozen and no longer flows. Evacuate the glass tube to make the pressure in the glass tube 0.10~0.20 mmHg. Seal the glass tube opening and then react the glass tube at 110~130 ℃ for 3~7 days. (3) After cooling the glass tube from step (2) to room temperature, take out the reaction product, filter it, wash it with acetone 2 to 5 times, and then soak it in acetone for 5 to 10 hours. Replace the acetone 3 to 5 times during the soaking period. Finally, vacuum dry to obtain a yellow solid product, namely the two-dimensional covalent organic framework material doped with N and S heteroatoms, denoted as JLNU-309.

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