Imine bond covalent organic framework material as well as preparation method and application thereof

Abstract

The invention provides an imine bond covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of new material preparation. The imine bond covalent organic framework material provided by the invention is a polymer as shown in a formula I, and four amino nitrogen groups of N, N, N ', N'-tetra (p-aminophenyl) p-phenylenediamine in the polymer are respectively connected with aldehyde carbon of terephthalaldehyde through C = N bonds. The imine bond covalent organic framework material provided by the invention is a porous crystalline framework material, gold can be adsorbed and recovered from a gold-containing solution through synergistic electrostatic adsorption and reduction effects of protonated tertiary amine and imine, and meanwhile, the material has an appropriate structure, can have excellent selective adsorption on gold, has excellent stability, and can be applied to the field of gold adsorption. The stability of the adsorption performance can be maintained under different pH value conditions, and particularly, the acid stability is remarkable.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material preparation, and particularly relates to an imine bond covalent organic framework material, a preparation method thereof, and an application thereof. Background Art

[0002] Metallic gold has excellent physical and chemical properties, such as excellent electrical conductivity, corrosion resistance, and biocompatibility, and has wide applications in electronic devices, jewelry making, currency systems, and the medical field. However, the content of gold in the earth's crust is very low, and it is a rare resource. Therefore, it is very important to selectively recover gold from secondary resources, but it is also a challenging task. At present, the relatively mature gold recovery technology is mainly the adsorption method, in which an adsorbent is used to adsorb gold from a gold-containing solution. The adsorbents in the prior art are mainly activated carbon, but its stability is poor, the adsorption performance is greatly reduced under acidic conditions, and the selective adsorption of gold ions is poor.

[0003] Therefore, there is an urgent need for an adsorbent material with good stability and excellent selective adsorption performance for gold ions. Summary of the Invention

[0004] The purpose of the present invention is to provide an imine bond covalent organic framework material, a preparation method thereof, and an application thereof. The imine bond covalent organic framework material provided by the present invention has good stability, still has excellent adsorption performance under acidic conditions, and has excellent selective adsorption for gold ions.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides an imine bond covalent organic framework material having a chemical structure shown in Formula I:

[0007]

[0008] The present invention also provides a preparation method of the imine bond covalent organic framework material described in the above technical solution, including:

[0009] Mixing N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine, terephthalaldehyde, an organic solvent, and an acid solution, and performing a Schiff base condensation reaction to obtain an imine bond covalent organic framework material.

[0010] Preferably, the molar ratio of N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine to terephthalaldehyde is 1:(1.8-2.2).

[0011] Preferably, the organic solvent includes a first organic solvent and a second organic solvent; the first organic solvent includes 1,4-dioxane or o-dichlorobenzene; the second organic solvent includes mesitylene or n-butanol.

[0012] Preferably, the volume ratio of the first organic solvent to the second organic solvent is (4 - 19):1.

[0013] Preferably, the volume ratio of N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine to the first organic solvent is (7 - 14):(19 - 20).

[0014] Preferably, the acid solution includes an acetic acid aqueous solution; the concentration of the acid solution is 6 - 11 mol / L.

[0015] Preferably, the volume ratio of the organic solvent to the acid solution is (2 - 10):1.

[0016] Preferably, the temperature of the Schiff base condensation reaction is 70 - 120 °C, and the time of the Schiff base condensation reaction is 70 - 75 h.

[0017] The present invention also provides the application of the imine bond covalent organic framework material described in the above technical solution or the imine bond covalent organic framework material prepared by the preparation method described in the above technical solution in the recovery of precious metal gold.

[0018] The present invention provides an imine bond covalent organic framework material which is a polymer shown in Formula I. In the polymer, the four amino nitrogens of N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine are respectively connected to the aldehyde carbon of terephthalaldehyde through C=N bonds. The imine bond covalent organic framework material provided by the present invention is a porous, crystalline framework material. Through the synergistic electrostatic adsorption and reduction of protonated tertiary amine - imine, gold can be adsorbed and recovered from a gold-containing solution. At the same time, the material has a suitable structure and can have excellent selective adsorption for gold, and has excellent stability, and can maintain the stability of the adsorption performance under different pH value conditions, especially has remarkable acid stability. The results of the examples show that the imine bond covalent organic framework material provided by the present invention has selective adsorption for gold and still has excellent adsorption performance under acidic conditions. Description of the Drawings

[0019] Figure 1 XRD patterns of the imine bond covalent organic framework materials prepared in Example 2 and Example 3;

[0020] Figure 2 Adsorption amounts of the imine bond covalent organic framework material prepared in Example 2 for gold ions under different acidic conditions;

[0021] Figure 3 Adsorption amounts of the imine bond covalent organic framework material prepared in Example 2 for different metal ions. Detailed Embodiments

[0022] The present invention provides an imine - bonded covalent organic framework material with a chemical structure as shown in Formula I:

[0023]

[0024] The imine - bonded covalent organic framework material provided by the present invention is a polymer as shown in Formula I. In the polymer, the four amino nitrogens of N,N,N',N'-tetrakis(p - aminophenyl) - p - phenylenediamine are respectively connected to the aldehyde - group carbons of terephthalaldehyde through C=N bonds.

[0025] The imine - bonded covalent organic framework material provided by the present invention has excellent selective adsorption properties for gold and excellent stability, and can maintain the stability of adsorption performance under different pH conditions, especially having remarkable acid stability.

[0026] The present invention also provides a preparation method of the imine - bonded covalent organic framework material described in the above technical solution, including:

[0027] Mix N,N,N',N'-tetrakis(p - aminophenyl) - p - phenylenediamine, terephthalaldehyde, an organic solvent and an acid solution, and carry out a Schiff - base condensation reaction to obtain the imine - bonded covalent organic framework material.

[0028] Unless otherwise specified, the present invention has no special limitation on the sources of each raw material, and commercially available products well - known to those skilled in the art can be used.

[0029] In the present invention, the molar ratio of N,N,N',N'-tetrakis(p - aminophenyl) - p - phenylenediamine to terephthalaldehyde is preferably 1:(1.8 - 2.2). As an implementation manner, the molar ratio of N,N,N',N'-tetrakis(p - aminophenyl) - p - phenylenediamine to terephthalaldehyde can be specifically 1:1.8, 1:1.9, 1:2, 1:2.1 or 1:2.2. By controlling the molar ratio of N,N,N',N'-tetrakis(p - aminophenyl) - p - phenylenediamine to terephthalaldehyde within the above range, the present invention can enable the two to react fully.

[0030] In the present invention, the organic solvent preferably includes a first organic solvent and a second organic solvent.

[0031] In the present invention, the first organic solvent preferably includes 1,4 - dioxane or o - dichlorobenzene; the second organic solvent preferably includes mesitylene or n - butanol.

[0032] As an implementation mode, the first organic solvent and the second organic solvent can be used in combination; when the first organic solvent is 1,4-dioxane, the second organic solvent can be mesitylene; when the first organic solvent is o-dichlorobenzene, the second organic solvent can be n-butanol. In the present invention, using the first organic solvent and the second organic solvent in combination can make the polarity of the first organic solvent and the second organic solvent match the solubility of N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine and terephthalaldehyde, and the two dissolve more fully, thus making the Schiff base condensation reaction more complete.

[0033] In the present invention, the volume ratio of the first organic solvent to the second organic solvent is preferably (4-19):1. As an implementation mode, the volume ratio of the first organic solvent to the second organic solvent can be specifically 4:1, 8:1, 10:1, 12:1, 15:1 or 19:1. By controlling the volume ratio of the first organic solvent to the second organic solvent within the above range in the present invention, N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine and terephthalaldehyde can be dissolved more fully, thus making the Schiff base condensation reaction more complete.

[0034] In the present invention, the volume ratio of N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine to the first organic solvent is preferably (7-14):(19-20). As an implementation mode, the volume ratio of N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine to the first organic solvent can be specifically 7:20 or 14:19. By controlling the volume ratio of N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine to the first organic solvent within the above range in the present invention, N,N,N',N'-tetrakis(p-aminophenyl)terephthalenediamine can be dissolved fully.

[0035] In the present invention, the acid solution preferably includes an acetic acid aqueous solution; the concentration of the acid solution is preferably 6-11 mol / L. As an implementation mode, the concentration of the acid solution can be specifically 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 10.5 mol / L or 11 mol / L. By controlling the type and concentration of the acid solution within the above range in the present invention, the progress of the Schiff base condensation reaction can be catalyzed better.

[0036] In the present invention, the volume ratio of the organic solvent to the acid solution is preferably (2-10):1. As an implementation mode, the volume ratio of the organic solvent to the acid solution can be specifically 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1. By controlling the volume ratio of the organic solvent to the acid solution within the above range in the present invention, the progress of the Schiff base condensation reaction can be catalyzed better.

[0037] In the present invention, the mixing of N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine, p-phthalaldehyde, an organic solvent and an acid solution is preferably carried out as follows: N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine, p-phthalaldehyde and the organic solvent are mixed first, and then the mixture is mixed with the acid solution.

[0038] In the present invention, the mixing is preferably carried out under ultrasonic conditions. The present invention has no special limitation on the power and time of the ultrasonic treatment, as long as the raw materials are mixed evenly.

[0039] After the mixing is completed, the present invention preferably performs a degassing treatment on the resulting mixed solution, then seals it, and then performs a Schiff base condensation reaction.

[0040] In the present invention, the degassing treatment is preferably carried out as follows: the mixed solution is frozen, evacuated, and then thawed in sequence.

[0041] In the present invention, the freezing is preferably carried out in a liquid nitrogen bath; the temperature of the liquid nitrogen bath freezing is preferably 70-77K; the time of the liquid nitrogen bath freezing is preferably 4-5 min.

[0042] In the present invention, the pressure of the evacuation is preferably 4-6 Pa, more preferably 5 Pa.

[0043] In the present invention, the temperature of the thawing is preferably room temperature; the time of the thawing is preferably 10-30 min.

[0044] In the present invention, the number of times of the degassing treatment is preferably 2-4 times, more preferably 3 times.

[0045] The present invention has no special limitation on the sealing operation, and the well-known sealing technical solutions in the art can be adopted. The degassing and sealing of the mixed solution in the present invention can remove the oxygen in the mixed solution, which is more beneficial to the progress of the Schiff base condensation reaction.

[0046] In the present invention, the temperature of the Schiff base condensation reaction is preferably 70-120 °C. As an embodiment, the temperature of the Schiff base condensation reaction can be specifically 70 °C, 80 °C, 90 °C, 100 °C, 110 °C or 120 °C.

[0047] In the present invention, the time of the Schiff base condensation reaction is preferably 70-75 h. As an embodiment, the time of the Schiff base condensation reaction can be specifically 70 h, 71 h, 72 h, 73 h, 74 h or 75 h. By controlling the temperature and time of the Schiff base condensation reaction within the above ranges in the present invention, the reaction can proceed sufficiently.

[0048] After the Schiff base condensation reaction is completed, the present invention preferably subjects the product of the Schiff base condensation reaction to first filtration, purification, second filtration, first washing, extraction, second washing, third filtration, and drying in sequence to obtain an imine bond covalent organic framework material.

[0049] The present invention has no special limitation on the operations of the first filtration, second filtration, and third filtration, and the technical solutions of filtration well-known to those skilled in the art can be adopted.

[0050] In the present invention, the purification is preferably: mixing the solid obtained by the first filtration with N,N-dimethylformamide and stirring for 30 - 50 min. The present invention has no special limitation on the dosage of the N,N-dimethylformamide, and it can be selected according to actual needs.

[0051] In the present invention, the detergent for the first washing is preferably anhydrous tetrahydrofuran. The present invention has no special limitation on the dosage of the anhydrous tetrahydrofuran, and it can be selected according to actual needs.

[0052] In the present invention, the extraction is preferably Soxhlet extraction; the reagent for the extraction is preferably anhydrous tetrahydrofuran; the extraction time is preferably 11 - 13 h, more preferably 12 h.

[0053] In the present invention, the detergent for the second washing is preferably methanol.

[0054] In the present invention, the drying temperature is preferably 50 - 70 °C, more preferably 60 °C; the drying time is preferably 10 - 15 h, more preferably 12 h. By adopting the above treatment process, the present invention can fully remove impurities in the product and improve the purity of the product.

[0055] The present invention also provides the application of the imine bond covalent organic framework material described in the above technical solution or the imine bond covalent organic framework material prepared by the preparation method described in the above technical solution in the recovery of precious metal gold.

[0056] The present invention has no special limitation on the operation of the application, and the technical solutions of application well-known to those skilled in the art can be adopted.

[0057] The imine bond covalent organic framework material provided by the present invention has excellent selective adsorption for gold and still has excellent adsorption performance under acidic conditions.

[0058] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the examples in the present invention. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without making creative efforts belong to the scope protected by the present invention.

[0059] Example 1

[0060] An imine - bond covalent organic framework material has a chemical structure as shown in Formula I:

[0061]

[0062] Example 2

[0063] Preparation method of the imine - bond covalent organic framework material in Example 1: Take a 20 - mL Pyrex glass reaction tube, add N,N,N',N'-tetrakis(4 - aminophenyl)terephthalamide, terephthalaldehyde, 4 mL of 1,4 - dioxane and 1 mL of mesitylene (the molar ratio of N,N,N',N'-tetrakis(4 - aminophenyl)terephthalamide to terephthalaldehyde is 1:2, the volume ratio of 1,4 - dioxane to mesitylene is 4:1, and the volume ratio of N,N,N',N'-tetrakis(4 - aminophenyl)terephthalamide to 1,4 - dioxane is 7:20), ultrasonicate for 30 min, then add 2.5 mL of 10.5 mol / L acetic acid aqueous solution (the total volume of 1,4 - dioxane and mesitylene and the volume of acetic acid aqueous solution is 2:1), ultrasonicate for 20 min to obtain a mixed solution. Freeze the obtained mixed solution at 77 K (liquid nitrogen bath) for 4 min, evacuate to 5 Pa, thaw at room temperature for 30 min, repeat the freezing - evacuation - thawing process 3 times, then seal and carry out a Schiff - base condensation reaction at 70 °C for 72 h. Filter the reaction system to obtain a precipitate. Wash the obtained precipitate with N,N - dimethylformamide, stir for 40 min and then filter. Wash the obtained solid with anhydrous tetrahydrofuran 2 times, then carry out Soxhlet extraction with anhydrous tetrahydrofuran as the solvent for 12 h. Finally, wash with methanol and filter by suction. Dry the obtained solid in vacuo at 60 °C for 12 h to obtain a dark red powder, which is the imine - bond covalent organic framework material, denoted as M - COF - TPPD.

[0064] Example 3

[0065] Preparation method of imine-bonded covalent organic framework material in Example 1: Take a 20 mL Pyrex glass reaction tube, add N,N,N',N'-tetrakis(4-aminophenyl)-p-phenylenediamine, terephthalaldehyde, 1.9 mL of o-dichlorobenzene and 0.1 mL of n-butanol (the molar ratio of N,N,N',N'-tetrakis(4-aminophenyl)-p-phenylenediamine to terephthalaldehyde is 1:2, the volume ratio of o-dichlorobenzene to n-butanol is 19:1, and the volume ratio of N,N,N',N'-tetrakis(4-aminophenyl)-p-phenylenediamine to o-dichlorobenzene is 14:19), ultrasonicate for 30 min, then add 0.2 mL of 6 mol / L acetic acid aqueous solution (the total volume of o-dichlorobenzene and n-butanol and the volume of acetic acid aqueous solution have a volume ratio of 10:1), ultrasonicate for 20 min to obtain a mixed solution. Freeze the obtained mixed solution at 77 K (liquid nitrogen bath) for 4 min, evacuate to 5 Pa, thaw at room temperature for 30 min, repeat the freezing-evacuation-thawing process 3 times, then seal, and carry out Schiff base condensation reaction at 120 °C for 72 h. Filter the reaction system to obtain a precipitate. Wash the obtained precipitate with N,N-dimethylformamide and stir for 40 min, then filter. Wash the obtained solid with anhydrous tetrahydrofuran twice, then carry out Soxhlet extraction with anhydrous tetrahydrofuran as the solvent for 12 h, and finally wash with methanol and filter by suction. Dry the obtained solid in vacuum at 60 °C for 12 h to obtain a dark red powder, namely the imine-bonded covalent organic framework material, denoted as O-COF-TPPD.

[0066] The crystallinity of the imine-bonded covalent organic framework materials prepared in Example 2 and Example 3 was tested by X-ray diffraction analysis, and the obtained XRD patterns are as Figure 1 shown. From Figure 1 it can be seen that the stronger signal peaks of M-COF-TPPD prepared in Example 2 are distributed at 2.53°, 4.34°, 4.91°, 6.52° and 8.86°, indicating that M-COF-TPPD has good crystallinity; the signal peaks of O-COF-TPPD prepared in Example 3 are distributed at 2.37°. Compared with Example 2, the peak intensity is significantly reduced, indicating that the crystallinity of O-COF-TPPD prepared in Example 3 is not as good as that of M-COF-TPPD prepared in Example 2.

[0067] Application Example 1

[0068] Use a pipette to take a solution of chloroauric(III) acid trihydrate and put it into a centrifuge tube, then slowly drop in hydrochloric acid to obtain a mixed solution. The total volume of the mixed solution is 30 mL, and the pH values of the mixed solution are 1, 0, -0.3, -0.6, -0.8 respectively. The concentration of chloroauric(III) acid trihydrate in the mixed solution is 200 mg / L, and the gold exists in the form of Au(Cl)4 - form.

[0069] Weigh 3 mg of the imine-bonded covalent organic framework material prepared in Example 2 and add it to the above mixed solution. Ultrasonically mix it evenly, then place it in a shaker and shake. During this period, turn on the ultraviolet lamp of the shaker and adsorb for 12 h at 25 °C and 180 rpm. After the adsorption is completed, use an atomic absorption spectrophotometer to measure the concentration of Au(Cl)4 - in the solution, and calculate the adsorption capacity of the imine-bonded covalent organic framework material prepared in Example 2 for Au(Cl)4 - under different acidic conditions. The results are as Figure 2 shown.

[0070] From Figure 2 it can be seen that when the pH values are 1, 0, -0.3, -0.6, -0.8, the adsorption capacities of the imine-bonded covalent organic framework material prepared in Example 2 for Au(Cl)4 - are 1099.9 mg / g, 1047.3 mg / g, 1690.9 mg / g, 1645.9 mg / g, 1065.7 mg / g respectively. It can be seen that the imine-bonded covalent organic framework material provided by the present invention has excellent adsorption effects on gold under different acidic conditions.

[0071] Application Example 2

[0072] Prepare aqueous solutions (30 mL) with pH values of -0.3 and containing 200 mg / L of Pd(II), Ni(II), Cu(II), Co(II), Cd(II), Pb(II), Cr(III), Fe(III) and Zn(II) respectively. Add 3 mg of the imine-bonded covalent organic framework material prepared in Example 2 to each solution, ultrasonically mix them evenly, then place them in a shaker and shake. During this period, turn on the ultraviolet lamp of the shaker and adsorb for 12 h at 25 °C and 180 rpm. After the adsorption is completed, use an atomic absorption spectrophotometer to measure the concentration of each metal ion in the solution, and calculate the adsorption capacity of the imine-bonded covalent organic framework material prepared in Example 2 for different metal ions. The results are as Figure 3 shown.

[0073] From Figure 3 it can be seen that the adsorption capacity of the imine-bonded covalent organic framework material prepared in Example 2 for Au(Cl)4 - is 1690.9 mg / g, the adsorption capacity for Pd(II) is 47.2 mg / g, and it hardly adsorbs Ni(II), Cu(II), Co(II), Cd(II), Pb(II), Cr(III), Fe(III) and Zn(II). The adsorption capacities of the imine-bonded covalent organic framework material prepared in Example 2 for metal ions other than gold ions are all less than 200 mg / g, which proves that the imine-bonded covalent organic framework material provided by the present invention has excellent adsorption selectivity for gold ions.

[0074] In summary, the imine bond covalent organic framework material provided by the present invention has excellent adsorption selectivity for gold ions and excellent adsorption performance under different acidic conditions.

[0075] The above are only the preferred embodiments 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 should also be regarded as the protection scope of the present invention.

Claims

1. An imine - bond covalent organic framework material has a chemical structure shown in Formula Ⅰ:

2. A preparation method of the imine - bond covalent organic framework material according to Claim 1, comprising: Mixing N,N,N',N'-tetrakis(p - aminophenyl)-p - phenylenediamine, terephthalaldehyde, an organic solvent and an acid solution, and carrying out a Schiff - base condensation reaction to obtain the imine - bond covalent organic framework material.

3. The preparation method according to claim 2, characterized in that, The molar ratio of N,N,N',N'-tetrakis(p - aminophenyl)-p - phenylenediamine to terephthalaldehyde is 1:(1.8 - 2.2).

4. The preparation method according to claim 2, characterized in that, The organic solvent includes a first organic solvent and a second organic solvent; the first organic solvent includes 1,4 - dioxane or o - dichlorobenzene; the second organic solvent includes mesitylene or n - butanol.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the first organic solvent to the second organic solvent is (4 - 19):

1.

6. The preparation method according to claim 5, characterized in that, The volume ratio of N,N,N',N'-tetrakis(p - aminophenyl)-p - phenylenediamine to the first organic solvent is (7 - 14):(19 - 20).

7. The preparation method according to claim 2, characterized in that, The acid solution includes an acetic acid aqueous solution; the concentration of the acid solution is 6 - 11 mol / L.

8. The preparation method according to claim 7, characterized in that, The volume ratio of the organic solvent to the acid solution is (2 - 10):

1.

9. The preparation method according to claim 2, wherein The temperature of the Schiff - base condensation reaction is 70 - 120 °C, and the time of the Schiff - base condensation reaction is 70 - 75 h.

10. Use of the imine - bond covalent organic framework material according to Claim 1 or the imine - bond covalent organic framework material prepared by the preparation method according to any one of Claims 2 - 9 in the recovery of precious metal gold.

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