Preparation method and application of graphdiynyl N-impurity fully-conjugated COFs (Covalent Organic Frameworks) material

Abstract

The invention provides a preparation method of a graphdiynyl N-heterocyclic fully-conjugated COFs (Covalent Organic Frameworks) material, and the material is prepared by carrying out Aldol Condensation reaction on a nitrogen-containing heterocyclic ring monomer 2, 4, 6-trimethyl-1, 3, 5-triazine and an alkynyl-containing aldehyde monomer 4, 4 ', 4'-[benzene-1, 3, 5-triyl-tri (acetylene-2, 1-diyl)] tribenzaldehyde. The N-impurity full-conjugate COFs material prepared on the basis of the graphdiynyl building block is used for adsorption separation of thorium ions for the first time. The adsorption capacity of the prepared graphdiynyl N-impurity full-conjugate COFs material can reach 1949 mg / g, the adsorption dynamic equilibrium time is only 60 min, and meanwhile, the material has excellent chemical stability and regeneration cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to an N-doped fully conjugated COFs material based on graphyne building blocks for fast and efficient adsorption of thorium ions and a preparation method thereof. Background Art

[0002] Nuclear energy is a clean, efficient, low-carbon energy source that plays an important role in ensuring energy security, promoting energy transformation, and helping to achieve carbon peak and carbon neutrality goals. However, spent fuel in the nuclear industry contains a large amount of unreacted radioactive substances, which pose a serious threat to human health and the ecological environment. Separating and recovering radioactive nuclides from nuclear wastewater is of great significance to the sustainable development of nuclear energy.

[0003] Thorium is an important nuclear energy resource and a strategic reserve for the nuclear industry. Liquid phase extraction is usually used in industry to separate and recover thorium and uranium. However, liquid phase extraction has the disadvantages of large solvent consumption, easy environmental pollution and cumbersome operation, and the separation efficiency is low. Solid-state adsorption methods have become a hot topic of current research due to their advantages such as simple operation, considerable cost-effectiveness and less secondary waste. Traditional adsorption materials, such as activated carbon, ion exchange resins, natural minerals, biomass, etc., have the disadvantages of low adsorption capacity, slow adsorption rate and poor selectivity. Therefore, there is an urgent need to develop a new functional material with high capacity, fast and effective adsorption and separation of thorium.

[0004] Covalent organic frameworks (COFs) are a new class of crystalline porous polymers, which are composed of light elements (such as C, N, O, B, etc.) connected by covalent bonds. They have unique advantages such as highly ordered skeleton structure, adjustable porosity and easy functional modification, and show great potential in the adsorption and separation of metal ions. However, although some pioneering results of COFs for radionuclide adsorption have been reported, COFs materials that show efficient adsorption of Th(IV) in practical applications are still very rare. This is mainly due to the following two reasons: First, the stability of the material is poor. For example, the main covalent bonds (such as BO and C=N) commonly used to construct COFs are intolerant to acids, alkalis and radiation, which greatly limits the practical application of COFs; second, the material lacks adsorption sites with high coordination ability for thorium ions, resulting in low adsorption capacity and adsorption selectivity.

[0005] Compared with borate ester bonds and imine bonds, sp 2 The electron delocalization effect of C=C double bond COFs can reduce the energy of the system, making it more stable in strong acids / bases and different solvents. 2The new carbon allotrope formed by hybridization has abundant carbon chemical bonds, large specific surface area and uniform pore structure. Theoretical studies have shown that graphyne has huge ultimate tensile strength and strain strength, and the acetylene bonds in it have a strong interaction with thorium ions. In addition, the nitrogen atoms on the triazine ring can form multiple forms of interaction with thorium ions, such as coordination bonds and hydrogen bonds, and have a unique high affinity for thorium. Summary of the invention

[0006] In view of this, the present invention proposes a graphyne-based N-doped fully conjugated COFs material and a preparation method thereof for rapid and efficient adsorption and separation of thorium. Introducing graphyne into the COFs skeleton structure to prepare N-doped fully conjugated COFs connected by carbon-carbon double bonds can not only solve the key scientific problem that material defects in the graphyne field cannot be repaired, but also provide a new method and new approach for the development of new ultra-stable fully conjugated COFs materials, and at the same time provide an excellent material basis for the separation and recovery of thorium ions in nuclear wastewater.

[0007] The technical solution of the present invention:

[0008] A method for preparing a graphene-based N-hetero fully conjugated COFs material. The raw materials are prepared by reacting a nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine and an aldehyde monomer containing an alkynyl group 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde.

[0009] Furthermore, the molar ratio of the nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine to the alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde is 1:1-1:3.5.

[0010] A method for preparing a graphene-based N-doped fully conjugated COFs material, the specific steps comprising:

[0011] S1, adding a nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine, an alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde, an organic solvent and a catalyst into a Pyrex tube, and mixing by ultrasonication to obtain a mixture;

[0012] S2, immersing the bottom of the Pyrex tube containing the mixture into liquid nitrogen for freezing;

[0013] S3. Degas the frozen Pyrex tube three times under nitrogen protection, and seal the Pyrex tube with a flame gun under vacuum;

[0014] S4. Place the sealed Pyrex tube in an oven, heat and crystallize it, filter the COFs powder, wash it with an anhydrous organic solvent, heat it, and vacuum dry it to obtain the target graphene-based N-hybrid fully conjugated COFs material.

[0015] Furthermore, in step S1, the organic solvent is a mixed solution of mesitylene and 1,4-dioxane in a volume ratio of 1:1-1:6, a mixed solution of methanol and mesitylene in a volume ratio of 1:1-1:5, a mixed solution of o-dichlorobenzene and mesitylene in a volume ratio of 1:1-1:10, and a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1:1-1:8.

[0016] Furthermore, in step S1, the volume ratio of the sum of the masses of the nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine and the alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde to the organic solvent is 1:6.8-1:33.3 mg / mL.

[0017] Furthermore, in step S1, the catalyst is trifluoroacetic acid or potassium hydroxide; and the volume ratio of the catalyst mass to the organic solvent is 1 mg:10-28 mL.

[0018] Furthermore, in step S1, the ultrasonic treatment time is 15-40 minutes; and in step S4, the heating crystallization temperature is 120-200° C. and the time is 3-9 days.

[0019] Furthermore, in step S4, the anhydrous solvent is at least one of anhydrous tetrahydrofuran, anhydrous acetone, and anhydrous methanol.

[0020] Furthermore, in step S4, the vacuum drying temperature is 100° C.-120° C., and the drying time is 8 h-20 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The COFs material prepared by introducing acetylene groups in the present invention has excellent thorium ion adsorption performance, wherein the maximum adsorption amount is 1949 mg / g within 1 hour under the conditions of initial concentration C0=400 ppm and pH=4.

[0023] (2) The Graphene-based N-hybrid fully conjugated COFs material prepared in the present invention has high stability and excellent regeneration cycle performance, and its adsorption capacity remains almost unchanged after 5 cyclic adsorption experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The PXRD (X-ray powder diffraction) spectra of Examples 1-4, the ordinate Intensity represents the intensity, and 2θ (double θ) refers to the angle between the incident X-ray beam and the diffraction detector

[0025] Figure 2 The adsorption principle diagram of Example 1, the vertical axis Intensity represents the intensity, and the horizontal axis represents the atomic binding energy

[0026] Figure 3 This is the adsorption effect diagram under different cycle times of Example 1, the ordinate q e represents the equilibrium adsorption capacity, and the horizontal axis represents the number of cycles DETAILED DESCRIPTION

[0027] In order to better understand the technical content of the present invention, the technical solution is clearly and completely described, and specific embodiments are provided below to further illustrate the present invention. The following are only some embodiments of the present invention.

[0028] The materials, reagents, etc. used in the embodiments of the present invention, unless otherwise specified, can be obtained from commercial sources. The experimental methods used in the embodiments of the present invention, unless otherwise specified, are conventional methods. In order to better understand the technical content of the present invention, specific embodiments, comparative examples and specific tests are provided below to further illustrate the present invention.

[0029] The 2,4,6-trimethyl-1,3,5-triazine, 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde and 4-[3,5-di(4-formylphenyl)phenyl]benzaldehyde of the present invention were all purchased from Utop Technology Suzhou Co., Ltd.; 4,4'-(benzofurazan-4,7-diyl)benzaldehyde was synthesized according to reported literature; 4,4'-(benzothiadiazole-4,7-diyl)benzaldehyde was purchased from Shanghai Boka Chemical Technology Co., Ltd.

[0030] Table 1 Abbreviation table

[0031] Abbreviation Chinese name TMT 2,4,6-Trimethyl-1,3,5-triazine BTE 4,4',4"-[Benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde TFPB 4-[3,5-Bis(4-formylphenyl)phenyl]benzaldehyde BO 4,4'-(Benzofurazan-4,7-diyl)benzaldehyde BS 4,4'-(Benzothiadiazole-4,7-diyl)benzaldehyde

[0032] Example 1

[0033] TMT (12 mg, 0.1 mmol) and BTE (46.25 mg, 0.1 mmol) were added to a 10 mL Pyrex tube, and then added to a mixed organic solvent (0.9 mL of mesitylene and 0.9 mL of 1,4-dioxane), ultrasonically mixed for 30 min, trifluoroacetic acid (0.4 mL) and acetonitrile (50 μL) were added, liquid nitrogen was frozen, evacuated, flame-sealed, heated at 150 ° C for 3 days, extracted with anhydrous methanol for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain an orange powder covalent organic framework COFs material, named TBT-COF-1.

[0034] The structural formula of TBT-COF-1 is:

[0035]

[0036] Example 2

[0037] TMT (12 mg, 0.1 mmol) and BTE (46.25 mg, 0.1 mmol) were added to a 10 mL Pyrex tube, and then added to a mixed organic solvent (1.2 mL of mesitylene and 1.2 mL of methanol), ultrasonically mixed for 30 min, potassium hydroxide (10 mg) was added, liquid nitrogen was frozen, evacuated, flame-sealed, heated at 180 ° C for 3 days, extracted with anhydrous acetone Soxhlet for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain an orange powder covalent organic framework COFs material, named TBT-COF-2, and the structural formula diagram is the same as that in Example 1.

[0038] Example 3

[0039] TMT (4.92 mg, 0.04 mmol) and BTE (23.12 mg, 0.05 mmol) were added to a 10 mL Pyrex tube, and then added to a mixed organic solvent (0.45 mL of mesitylene and 0.45 mL of o-dichlorobenzene), ultrasonically mixed for 30 min, trifluoroacetic acid (0.2 mL) and acetonitrile (25 μL) were added, liquid nitrogen was frozen, evacuated, flame-sealed, heated at 150 ° C for 3 days, extracted with anhydrous methanol for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain an orange powder covalent organic framework COFs material, named TBT-COF-3, and the structural formula diagram is the same as that in Example 1.

[0040] Example 4

[0041] TMT (4.92 mg, 0.04 mmol) and BTE (23.12 mg, 0.05 mmol) were added to a 10 mL Pyrex tube, and then added to a mixed organic solvent (0.7 mL of o-dichlorobenzene and 0.3 mL of n-butanol), ultrasonically mixed for 30 min, potassium hydroxide (10 mg) was added, liquid nitrogen was frozen, evacuated, flame-sealed, heated at 180 ° C for 3 days, extracted with anhydrous tetrahydrofuran Soxhlet for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain an orange powder covalent organic framework COFs material, named TBT-COF-4, and the structural formula diagram is the same as that in Example 1.

[0042] Comparative Example 1

[0043] TMT (12 mg, 0.1 mmol) and TFPB (38.4 mg, 0.1 mmol) were added to a 10 mL Pyrex tube, and then added to a mixed organic solvent (0.9 mL of mesitylene and 0.9 mL of 1,4-dioxane), ultrasonically mixed for 30 min, trifluoroacetic acid (0.4 mL) and acetonitrile (50 μL) were added, liquid nitrogen was frozen, evacuated, flame-sealed, heated at 150 ° C for 3 days, extracted with anhydrous methanol for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain a covalent organic framework COFs material in the form of a yellow powder, named TBB-COF.

[0044] The structural formula of TBB-COF is:

[0045]

[0046] Comparative Example 2

[0047] TMT (19.7 mg, 0.16 mmol), BO (78.74 mg, 0.24 mmol) and benzoic anhydride (217.6 mg, 0.96 mmol) were added to a 10 mL Pyrex tube and ultrasonically mixed for 30 min. Liquid nitrogen was frozen, vacuumed, flame-sealed, heated at 180 ° C for 5 days, extracted with anhydrous methanol for 24 h, washed, and vacuum dried at 100 ° C for 12 h to obtain an orange-yellow powder of covalent organic framework COFs material, named TBO-COF.

[0048] The structural formula of TBO-COF is:

[0049]

[0050] Comparative Example 3

[0051] TMT (19.7 mg, 0.16 mmol), BS (85.52 mg, 0.24 mmol) and benzoic anhydride (217.6 mg, 0.96 mmol) were added to a 10 mL Pyrex tube and ultrasonically mixed for 30 min. Liquid nitrogen was frozen, vacuumed, flame-sealed, heated at 180°C for 5 days, extracted with anhydrous methanol for 24 h, washed, and vacuum dried at 100°C for 12 h to obtain an orange-yellow powder of covalent organic framework COFs material, named TBS-COF.

[0052] The structural formula of TBS-COF is:

[0053]

[0054] Test Example 1

[0055] 1.5 mg of the covalent organic framework material COFs prepared in Example 1 and Comparative Examples 1-3 were respectively weighed and added into 9 mL of thorium solution for adsorption experiment (initial concentration C0=100 ppm, pH=4), the rotation speed was 410 rpm, and the adsorption time was 1-36 h.

[0056]

[0057] where q e is the adsorption capacity, in mg / g; C0 is the initial concentration of thorium ions, in ppm; C e is the concentration of thorium ions after adsorption, in ppm; V is the volume of the thorium solution, in L; m is the mass of the prepared COFs material adsorbent, in g. The results are shown in Table 2.

[0058] Table 2

[0059] name Adsorption equilibrium time (h) Example 1 (TBT-COF-1) 1 Comparative Example 1 (TBB-COF) 16 Comparative Example 2 (TBO-COF) 12 Comparative Example 3 (TBS COF) 12

[0060] As can be seen from Table 2, under the conditions of an initial concentration of 100 ppm and a pH of 4, the adsorption equilibrium time of the graphene-based N-hybrid fully conjugated COFs material of the present invention is faster.

[0061] Test Example 2

[0062] 1.5 mg of COFs materials prepared in Example 1 and Comparative Examples 1-3 were weighed respectively and added into 9 mL of thorium solution for adsorption experiment (initial concentration C0=400 ppm, pH=4) at a rotation speed of 410 rpm. The adsorption capacity was calculated after 1 hour. The results are shown in Table 3.

[0063] Table 3

[0064] name Saturated adsorption capacity (mg / g) Example 1 (TBT-COF-1) 1949 Comparative Example 1 (TBB-COF) 346 Comparative Example 2 (TBO-COF) 354 Comparative Example 3 (TBS COF) 312

[0065] As can be seen from Table 2, under the conditions of an initial concentration of 100 ppm and a pH of 4, the adsorption performance of the graphene-based N-hybrid fully conjugated COFs material of the present invention is the most excellent, with a maximum adsorption capacity of 1949 mg / g.

[0066] like Figure 1 The X-ray diffraction pattern of the synthesized graphene-based N-mixed fully conjugated COFs material (TBT-COF-1-4) can determine that the COFs material is successfully synthesized using the method of the present invention.

[0067] like Figure 2 The XPS spectra of TBT-COF-1 before and after Th(IV) adsorption. After adsorption, the sample showed the presence of Th4f 7 / 2 and Th 4f 5 / 2 The orbital peak of Th(IV) on TBT-COF-1 confirms the successful adsorption of Th(IV) on TBT-COF-1. Furthermore, compared with the Th 4f XPS spectrum of Th(NO3)4 (a), the Th 4f peak on TBT-COF-1 after adsorption shifts to the lower electron binding energy. 7 / 2 and Th4f 5 / 2 The binding energy of Th(IV) decreased from 335.7eV and 345.1eV to 335.0eV and 344.0eV, respectively, indicating that electron transfer occurred between Th(IV) and TBT-COF-1, the density of Th outer electron cloud increased, and the shielding effect was enhanced.

[0068] Similarly, it can be seen from the N1s XPS (b) and C1s XPS (c) spectra that the electron binding energy of the orbital peaks corresponding to the triazine N and alkynyl C atoms in the sample increased after adsorption, from 399.1 and 284.8 to 399.3 and 284.9, respectively, which is favorable for proving the coordination interaction between the N atoms and alkynyl groups in TBT-COF-1 and Th(IV), and revealing the adsorption mechanism of TBT-COF-1 for Th(IV).

[0069] like Figure 3 The adsorption effect diagram of TBT-COF-1 under different cycle times is shown in Figure 1. It can be seen that after 5 cycles of adsorption experiments, its adsorption capacity remains almost unchanged, indicating that the graphene-based N-mixed fully conjugated COFs material prepared by the present invention has excellent cyclic performance.

[0070] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a graphene-based N-doped fully conjugated COFs material, characterized in that: The preparation raw materials include nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine and alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde, which are reacted to obtain the product.

2. The method for preparing a graphene-based N-hetero fully conjugated COFs material according to claim 1, characterized in that: The molar ratio of the nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine to the alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde is 1:1-1:3.

5.

3. The method for preparing a graphene-based N-hetero fully conjugated COFs material according to claim 1, characterized in that: The specific steps include: S1, adding a nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine, an alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde, an organic solvent and a catalyst into a Pyrex tube, and mixing by ultrasonication to obtain a mixture; S2, immersing the bottom of the Pyrex tube containing the mixture into liquid nitrogen for freezing; S3, degas the frozen Pyrex tube three times, and seal the Pyrex tube with a flame gun under vacuum; S4. Place the sealed Pyrex tube in an oven, heat and crystallize it, filter the COFs powder, wash it with an anhydrous organic solvent, heat it, and vacuum dry it to obtain the target graphene-based N-hybrid fully conjugated COFs material.

4. The method for preparing a graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: In step S1, the organic solvent is a mixed solution of mesitylene and 1,4-dioxane in a volume ratio of 1:1-1:6, a mixed solution of methanol and mesitylene in a volume ratio of 1:1-1:5, a mixed solution of o-dichlorobenzene and mesitylene in a volume ratio of 1:1-1:10, and a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1:1-1:

8.

5. The method for preparing a Graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: In step S1, the volume ratio of the sum of the masses of the nitrogen-containing heterocyclic monomer 2,4,6-trimethyl-1,3,5-triazine and the alkynyl-containing aldehyde monomer 4,4',4"-[benzene-1,3,5-triyltris(acetylene-2,1-diyl)]tribenzaldehyde to the organic solvent is 1:6.8-1:33.3 mg / mL.

6. The method for preparing a Graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: In step S1, the catalyst is trifluoroacetic acid or potassium hydroxide; the volume ratio of the catalyst mass to the organic solvent is 1 mg:10-28 mL.

7. The method for preparing a Graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: In step S1, the ultrasonic treatment time is 15-40 minutes; in step S4, the heating crystallization temperature is 120° C.-200° C. and the time is 3-9 days.

8. The method for preparing a Graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: In step S4, the anhydrous solvent is at least one of anhydrous tetrahydrofuran, anhydrous acetone, and anhydrous methanol.

9. The method for preparing a Graphene-based N-hetero fully conjugated COFs material according to claim 3, characterized in that: Step S4, the vacuum drying temperature is 100°C-120°C, and the drying time is 8h-20h.

10. Use of the graphene-based N-doped fully conjugated COFs material obtained by the preparation method according to any one of claims 3 to 9 in the adsorption of thorium ions.

Images