Preparation method and application of nitrogen and oxygen co-doped COF adsorbent

Abstract

The present invention relates to a preparation method and application of a nitrogen-oxygen co-doped carbon-fiber (COF) adsorbent, belonging to the technical field of composite materials. The functionalized nitrogen-oxygen co-doped COF adsorbent, N-PTBT, is obtained by reacting 2,3,4-trihydroxybenzaldehyde with 2,4,6-triaminopyrimidine. The structural formula is #imgabs0#. The functionalized nitrogen-oxygen co-doped COF adsorbent can be used for efficient and selective adsorption of gold ions from solution, and the COF material has strong recyclability.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a nitrogen and oxygen co-doped COF adsorbent, belonging to the technical field of composite materials. Background Art

[0002] Currently, commonly used methods for extracting gold ions include solvent extraction, redox methods, membrane separation, and adsorption. Adsorption, due to its cleanliness, economy, simplicity, and convenience, offers significant advantages for efficient gold ion extraction. Gold ion adsorbents with promising market applications include activated carbon, silicate minerals, and resins. However, while these adsorbents exhibit considerable adsorption performance, they also suffer from limitations such as small surface area, poor selectivity, and difficulty in recovery. Therefore, the development of new, high-performance adsorbents is crucial.

[0003] Covalent organic frameworks (COFs) are a class of nanoporous materials with large surface areas. Their lightweight, high thermal stability, predictable network structure, and tunable pore size make them ideal for adsorption applications. However, due to the weak affinity between carbon atoms and gold atoms and the limited adsorption sites in many COFs, selective adsorption of gold ions is difficult to achieve. Summary of the Invention

[0004] In response to the current problems that the affinity between carbon atoms and gold atoms in covalent organic frameworks (COFs) is weak and the adsorption sites in COFs are limited, making it impossible to achieve selective adsorption of gold ions, the present invention proposes a preparation method and application of a nitrogen-oxygen co-doped COF adsorbent. The present invention utilizes 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine to react to generate the adsorbent N-PTBT, i.e., a functionalized nitrogen-oxygen co-doped COF adsorbent; the functionalized nitrogen-oxygen co-doped COF adsorbent is used for efficiently adsorbing gold ions in solution, has high adsorption selectivity and adsorption capacity, and is reusable.

[0005] A nitrogen-oxygen co-doped COF adsorbent is prepared by reacting 2,3,4-trihydroxybenzaldehyde with 2,4,6-triaminopyrimidine to form a functionalized nitrogen-oxygen co-doped COF adsorbent, the structural formula of which is:

[0006] .

[0007] Preferably, the molar ratio of nitrogen to oxygen elements in the nitrogen-oxygen co-doped COF adsorbent is 2-12:5.

[0008] The preparation method of the nitrogen and oxygen co-doped COF adsorbent comprises the following specific steps:

[0009] (1) dissolving 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine in an acetic acid-water solvent to obtain a 2,3,4-trihydroxybenzaldehyde solution and a 2,4,6-triaminopyrimidine solution;

[0010] (2) The 2,3,4-trihydroxybenzaldehyde solution and the 2,4,6-triaminopyrimidine solution were mixed evenly, and then stirred at a temperature of 130-150°C for 67-77 hours. The mixture was cooled to room temperature, and the solid-liquid separation was performed. The solid was washed and soaked with methanol and deionized water, and vacuum dried to obtain the nitrogen and oxygen co-doped COF adsorbent N-PTBT. The chemical reaction formula is:

[0011] .

[0012] Preferably, the molar ratio of 2,3,4-trihydroxybenzaldehyde to 2,4,6-triaminopyrimidine in step (1) is 3:1.7-2.2.

[0013] Preferably, the volume ratio of acetic acid to water in the acetic acid-water solvent in step (1) is 1:1.7-2.

[0014] The nitrogen and oxygen co-doped COF adsorbent of the present invention can be used to selectively capture gold ions in a solution.

[0015] The mechanism of efficient gold ion adsorption by nitrogen-oxygen co-doped COF adsorbents: The N-PTBT adsorbent design incorporates numerous nitrogen- and oxygen-containing functional groups, providing ample binding sites for gold ion adsorption. The hydroxyl, carboxyl, and amino groups in the N-PTBT adsorbent successfully capture gold ions, engaging in electrostatic attraction and chelation. Experimental calculations show that the distribution coefficient of the nitrogen- and oxygen-loaded N-PTBT adsorbent for gold ions is 7.782 L / g, significantly higher than that for other metal ions. This demonstrates the selective adsorption of gold ions by N-PTBT. The Au=O bond can be cleaved using a combined solution of thiourea and hydrochloric acid, making the N-PTBT adsorbent recyclable.

[0016] The beneficial effects of the present invention are:

[0017] (1) The functionalized nitrogen-oxygen co-doped COF adsorbent of the present invention maintains a covalent organic framework structure and has aldehyde, hydroxyl, amino, and pyrimidine functional groups. The molar ratio of nitrogen and oxygen elements in the functionalized nitrogen-oxygen co-doped COF adsorbent is 2-12:5. It can efficiently and selectively adsorb gold ions from the solution, and the COF material has a strong recycling and regeneration ability.

[0018] (2) The preparation method of the nitrogen-oxygen co-doped COF adsorbent of the present invention is simple, flexible, and low-cost; it is non-toxic, has high performance, is easy to separate, has good selectivity and recycling capabilities, and will not cause secondary pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM image of the functionalized nitrogen and oxygen co-doped COF adsorbent of Example 1;

[0020] Figure 2 This is the EDS image of the functionalized nitrogen and oxygen co-doped COF adsorbent of Example 1;

[0021] Figure 3 This is the XPS graph of the functionalized nitrogen and oxygen co-doped COF adsorbent in Example 1 before and after adsorption of gold ions;

[0022] Figure 4 This is the XRD pattern of the functionalized nitrogen and oxygen co-doped COF adsorbent of Example 1;

[0023] Figure 5 This is the FT-IR image of the functionalized nitrogen and oxygen co-doped COF adsorbent in Example 1. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0025] The nitrogen and oxygen co-doped COF adsorbent of the present invention is prepared by reacting 2,3,4-trihydroxybenzaldehyde with 2,4,6-triaminopyrimidine to form a functionalized nitrogen and oxygen co-doped COF adsorbent, the structural formula of which is:

[0026] ;

[0027] The nitrogen-oxygen co-doped COF adsorbent maintains a covalent organic framework structure and has aldehyde, hydroxyl, amino, and pyrimidine functional groups; the molar ratio of nitrogen to oxygen elements in the nitrogen-oxygen co-doped COF adsorbent is 2-12:5.

[0028] Example 1: A method for preparing a nitrogen and oxygen co-doped COF adsorbent, the specific steps are as follows:

[0029] (1) dissolving 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine in an acetic acid-water solvent (the volume ratio of acetic acid to water is 1:1.9) to obtain a 2,3,4-trihydroxybenzaldehyde solution and a 2,4,6-triaminopyrimidine solution; the molar ratio of the 2,3,4-trihydroxybenzaldehyde to the 2,4,6-triaminopyrimidine is 3:2;

[0030] (2) The 2,3,4-trihydroxybenzaldehyde solution and the 2,4,6-triaminopyrimidine solution were mixed evenly, and then stirred at 140°C for 72 hours. The mixture was cooled to room temperature, and the solid and liquid were separated. The solid was washed and soaked with methanol and deionized water, and vacuum dried to obtain the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT. The chemical reaction formula is:

[0031] ;

[0032] The SEM, EDS, XPS, XRD and FT-IR images of the functionalized nitrogen and oxygen co-doped COF adsorbent of this embodiment are shown in Figure 1-5 As can be seen from the figure, the functionalized nitrogen and oxygen co-doped COF adsorbent is mainly composed of elements C, N and O, and the weight percentages of C, N and O are 52.02%, 16.58% and 31.40%, respectively. From the XRD spectrum, it can be seen that the obvious diffraction peak at 2θ = 27.15° corresponds to the presence of interlayer π-π stacking on the (001) reflection surface, indicating the formation of a COF structure. In the FT-IR spectrum, 1403.5 cm -1 1465.1cm -1 The stretching vibration peak of CN appeared at 1649.3 cm -1 and 1714.4 cm -1 corresponding to C=O and aldehyde groups, at 3283.3 ~3662.7 cm -1 The wide vibration peaks within the range correspond to OH and NH, further confirming the successful synthesis of the functionalized nitrogen-oxygen co-doped COF adsorbent. XPS analysis of the functionalized nitrogen-oxygen co-doped COF adsorbent before and after adsorption revealed that the Au(4f) peak appeared in the spectrum of N-PTBT after adsorption of gold ions, confirming that the functionalized nitrogen-oxygen co-doped COF adsorbent successfully adsorbed gold ions.

[0033] The selective adsorption performance of Au(III) by the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example is measured:

[0034] N-PTBT and a solution to be adsorbed (pH = 4, 40 mL) were added to a 50 mL centrifuge tube at room temperature. The solution to be adsorbed contained 456.24 mg / L Au(III), 225.91 mg / L Mg(II), 371.79 mg / L Co(II), 399.00 mg / L Ni(II), 449.61 mg / L Cr(III), and 492.51 mg / L Ca(II). The mixture was shaken at 200 rpm for 24 hours. The adsorbent was separated by centrifugation and the supernatant was obtained. The residual metal ion concentration in the supernatant was determined by ICP-OES.

[0035] The calculated removal rates of Au(III) were 97.27%, Mg(II) was 11.96%, Co(II) was 3.76%, Ni(II) was 8.25%, Cr(III) was 5.44%, and Ca(II) was 7.00%.

[0036] It can be seen that the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this embodiment has extremely strong selectivity for Au(III);

[0037] The adsorption performance of the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example product on pure Au(III) was measured:

[0038] N-PTBT (10 mg) and a 500 mg / L Au(III) solution (pH 4, 10 mL) were added to a 15 mL centrifuge tube at room temperature and shaken at 200 rpm for 20 h. The adsorbent was separated by centrifugation, and the supernatant was obtained. ICP-OES analysis revealed a residual gold ion concentration of 4.60 mg / L in the supernatant. The adsorption capacity of the functionalized nitrogen-oxygen co-doped COF adsorbent for Au(III) was 495.40 mg / g, with an adsorption efficiency of 99.08%. The adsorbent was eluted with a desorption solution (40 mL) consisting of 1% concentrated hydrochloric acid and 10% thiourea for 20 h. After centrifugation, the adsorbent was washed with distilled water until the solution was neutral, completing the regeneration of the N-PTBT adsorbent. After five repeated experiments, the adsorption efficiency of Au(III) in the fifth adsorption was 90.20%.

[0039] Example 2: A method for preparing a nitrogen and oxygen co-doped COF adsorbent, the specific steps are as follows:

[0040] (1) dissolving 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine in an acetic acid-water solvent (the volume ratio of acetic acid to water is 1:1.8) to obtain a 2,3,4-trihydroxybenzaldehyde solution and a 2,4,6-triaminopyrimidine solution; the molar ratio of the 2,3,4-trihydroxybenzaldehyde to the 2,4,6-triaminopyrimidine is 3:2.2;

[0041] (2) The 2,3,4-trihydroxybenzaldehyde solution and the 2,4,6-triaminopyrimidine solution were mixed evenly, and then stirred at 145°C for 70 hours, cooled to room temperature, and the solid-liquid separation was performed. The solid was washed and soaked with methanol and deionized water, and vacuum dried to obtain the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT;

[0042] The selective adsorption performance of Au(III) by the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example is measured:

[0043] N-PTBT and a solution to be adsorbed (pH = 4, 40 mL) were added to a 50 mL centrifuge tube at room temperature. The solution to be adsorbed contained 384.98 mg / L Au(III), 317.52 mg / L Mg(II), 254.20 mg / L Co(II), 265.69 mg / L Ni(II), 324.38 mg / L Cr(III), and 196.78 mg / L Ca(II). The mixture was shaken at 200 rpm for 24 hours. The adsorbent was separated by centrifugation and the supernatant was obtained. The residual metal ion concentration in the supernatant was determined by ICP-OES.

[0044] The calculated removal rates of Au(III) were 96.82%, Mg(II) were 9.5%, Co(II) were 4.29%, Ni(II) were 9.12%, Cr(III) were 5.62%, and Ca(II) were 6.84%.

[0045] It can be seen that the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this embodiment has extremely strong selectivity for Au(III);

[0046] The adsorption performance of the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example product on pure Au(III) was measured:

[0047] N-PTBT (10 mg) and a 500 mg / L Au(III) solution (pH 4, 10 mL) were added to a 15 mL centrifuge tube at room temperature and shaken at 200 rpm for 20 h. The adsorbent was separated by centrifugation, and the supernatant was obtained. ICP-OES analysis revealed a residual gold ion concentration of 7.02 mg / L in the supernatant. The adsorption capacity of the functionalized nitrogen-oxygen co-doped COF adsorbent for Au(III) was 492.98 mg / g, with an adsorption efficiency of 98.59%. The adsorbent was eluted with a desorption solution (40 mL) consisting of 1% concentrated hydrochloric acid and 10% thiourea for 20 h. After centrifugation, the adsorbent was washed with distilled water until the solution was neutral, completing the regeneration of the N-PTBT adsorbent. After five repeated experiments, the adsorption efficiency of Au(III) in the fifth adsorption was 89.41%.

[0048] Example 3: A method for preparing a nitrogen and oxygen co-doped COF adsorbent, the specific steps are as follows:

[0049] (1) dissolving 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine in an acetic acid-water solvent (the volume ratio of acetic acid to water is 1:2) to obtain a 2,3,4-trihydroxybenzaldehyde solution and a 2,4,6-triaminopyrimidine solution; the molar ratio of the 2,3,4-trihydroxybenzaldehyde to the 2,4,6-triaminopyrimidine is 3:1.8;

[0050] (2) The 2,3,4-trihydroxybenzaldehyde solution and the 2,4,6-triaminopyrimidine solution were mixed evenly, and then stirred at a temperature of 135°C for 75 hours, cooled to room temperature, and the solid-liquid separation was performed. The solid was washed and soaked with methanol and deionized water, and vacuum dried to obtain the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT;

[0051] The selective adsorption performance of Au(III) by the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example is measured:

[0052] N-PTBT and a solution to be adsorbed (pH = 4, 40 mL) were added to a 50 mL centrifuge tube at room temperature. The solution to be adsorbed contained 466.89 mg / L Au(III), 218.41 mg / L Mg(II), 343.18 mg / L Co(II), 349.05 mg / L Ni(II), 440.88 mg / L Cr(III), and 443.03 mg / L Ca(II). The mixture was shaken at 200 rpm for 24 hours. The adsorbent was separated by centrifugation and the supernatant was obtained. The residual metal ion concentration in the supernatant was determined by ICP-OES.

[0053] The calculated removal rates of Au(III) were 95.61%, Mg(II) was 11.76%, Co(II) was 3.00%, Ni(II) was 10.58%, Cr(III) was 4.48%, and Ca(II) was 4.73%.

[0054] It can be seen that the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this embodiment has extremely strong selectivity for Au(III);

[0055] The adsorption performance of the functionalized nitrogen and oxygen co-doped COF adsorbent N-PTBT of this example product on pure Au(III) was measured:

[0056] N-PTBT (10 mg) and a 500 mg / L Au(III) solution (pH = 4, 10 mL) were added to a 15 mL centrifuge tube at room temperature and shaken at 200 rpm for 20 h. The adsorbent was separated by centrifugation, and the supernatant was obtained. ICP-OES analysis revealed a residual gold ion concentration of 5.82 mg / L in the supernatant. The adsorption capacity of the functionalized nitrogen-oxygen co-doped COF adsorbent for Au(III) was 494.18 mg / g, with an adsorption efficiency of 98.84%. The adsorbent was eluted with a desorption solution (40 mL) consisting of 1% concentrated hydrochloric acid and 10% thiourea for 20 h. After centrifugation, the adsorbent was washed with distilled water until the solution was neutral, completing the regeneration of the N-PTBT adsorbent. After five repeated experiments, the adsorption efficiency of Au(III) in the fifth adsorption was 88.96%.

[0057] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A nitrogen and oxygen co-doped COF adsorbent, characterized in that: The functionalized nitrogen and oxygen co-doped COF adsorbent was generated by reacting 2,3,4-trihydroxybenzaldehyde with 2,4,6-triaminopyrimidine, and its structural formula is: 。 2. The nitrogen and oxygen co-doped COF adsorbent according to claim 1, characterized in that: The molar ratio of nitrogen to oxygen elements in the nitrogen-oxygen co-doped COF adsorbent is 2-12:

5.

3. The method for preparing the nitrogen and oxygen co-doped COF adsorbent according to claim 1, characterized in that: The specific steps are as follows: (1) dissolving 2,3,4-trihydroxybenzaldehyde and 2,4,6-triaminopyrimidine in an acetic acid-water solvent to obtain a 2,3,4-trihydroxybenzaldehyde solution and a 2,4,6-triaminopyrimidine solution; (2) The 2,3,4-trihydroxybenzaldehyde solution and the 2,4,6-triaminopyrimidine solution were mixed evenly, and then stirred at a temperature of 130-150 °C for 67-77 hours. The mixture was cooled to room temperature, and the solid-liquid separation was performed. The solid was washed and soaked with methanol and deionized water, and vacuum dried to obtain the nitrogen-oxygen co-doped COF adsorbent N-PTBT.

4. The method for preparing the nitrogen and oxygen co-doped COF adsorbent according to claim 3, characterized in that: In step (1), the molar ratio of 2,3,4-trihydroxybenzaldehyde to 2,4,6-triaminopyrimidine is 3:1.7-2.

2.

5. The method for preparing the nitrogen and oxygen co-doped COF adsorbent according to claim 3, characterized in that: The volume ratio of acetic acid to water in the acetic acid-water solvent in step (1) is 1:1.7-2.

6. Use of the nitrogen and oxygen co-doped COF adsorbent according to any one of claims 1 to 2 in the selective capture of gold ions in a solution.

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