COF adsorbent for Pb ions as well as preparation and application of COF adsorbent

Abstract

The invention relates to preparation and application of a COF adsorbent for efficiently and selectively recovering Pb (II), and belongs to the field of efficient adsorbents for adsorbing heavy metals and high-sensitivity electrochemical sensors. Benzo [1, 2-b: 3, 4-b ': 5, 6-b'] trithiophene-2, 5, 8-trialdehyde (BTT) and 3, 3 '-dihydroxybenzidine (DHBD) are subjected to a Schiff base reaction to form BTT-DHBD-COF, the BT-DHBD-COF has excellent adsorption performance on Pd (II), the adsorption capacity can reach 570.7 mg / g after adsorption is carried out for 10 min, and the detection limit of the BTT-DHBD-COF / GCE on Pb (II) is 3 * 10 <-12 > mol L <-1 >.

Description

Technical Field

[0001] The invention relates to a COF adsorbent for efficient selective adsorption and high-sensitivity detection of Pb(II) and a preparation method and application thereof, and belongs to the field of efficient adsorbents for adsorbing heavy metals and high-sensitivity electrochemical sensors. Background Art

[0002] Heavy metal water contamination has attracted great attention from industrialists and scientists and is regarded as a global environmental problem. Heavy metal ions generated by industrialization and mining operations are not only harmful to the environment and non-biodegradable, but can also bioaccumulate in the human body through the food chain. This may have serious impacts on ecosystems and public health. Lead ions (Pb(II)) are considered to be one of the most harmful heavy metal ions to human health. Long-term consumption of drinking water contaminated with Pb(II) can lead to anemia, kidney damage, central nervous system dysfunction, and even possible death.

[0003] At present, the most common technologies for removing heavy metals from wastewater are precipitation, electrolysis, solvent extraction, biological treatment and adsorption. Among these methods, precipitation and electrolysis have poor selective removal of heavy metal ions. Solvent extraction and biological treatment methods cannot be reused, and the treated water quality does not meet people's requirements. Due to its simplicity, flexibility, no toxic byproducts, environmental protection, multifunctionality and easy regeneration, adsorption has become an important technology for capturing harmful metal ions from aqueous solutions. The selection of adsorbent is a basic component of adsorption. Traditional adsorbents (such as activated carbon, nanoparticle adsorbents, etc.) have defects such as poor selectivity and low adsorption performance. Porous adsorbents COFs have become candidate materials for the effective removal of heavy metal ions due to their high specific surface area, rich functional groups, accessible pore structure, adjustable pore size and easy modification. So far, there has been no report on the efficient selective adsorption and high-sensitivity detection of Pb(II) by BTT-DHBD-COF adsorbent. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a preparation and application of a COF adsorbent for efficient selective adsorption and high-sensitivity detection of Pb(II). The present invention synthesizes BTT-DHBD-COF by a solvothermal method to react a carbonyl-containing BTT monomer with a hydroxyl-containing DHBD monomer to undergo a Schiff base reaction, which can achieve efficient selective adsorption and high-sensitivity detection of Pb(II) in water.

[0005] The present invention discloses a COF adsorbent for Pb ions. The adsorbent is synthesized by Schiff base reaction of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde (BTT) and 3,3'-dihydroxybenzidine (DHBD). The obtained adsorbent has a 1624 cm -1A C=N peak is generated at

[0006] The COF adsorbent of Pb ions of the present invention has a -1 The COH peak at 1255 cm -1 A CS peak was generated at .

[0007] The benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde (BTT) contains a carbonyl group and an S group.

[0008] The 3,3'-dihydroxybenzidine (DHBD) contains amino and hydroxyl groups.

[0009] The present invention discloses a COF adsorbent for Pb ions, wherein in its XRD diagram, the diffraction peak intensity appearing at 2.73° is greater than 1000 au.

[0010] The present invention provides a method for preparing a COF adsorbent for Pb ions, comprising the following steps: (1) Dissolve BTT and DHBD in a mixture of o-dichlorobenzene (o-DCB) and n-butanol (n-BuOH), and stir evenly to obtain a standby solution; (2) Add acetic acid (HAc) to the reserve solution; (3) Rapid freezing using a liquid nitrogen bath (77 K), performing N freeze pump-thaw cycles to remove oxygen, and heating at 115-125°C, wherein N is greater than or equal to 2.

[0011] (4) After the reaction is completed, the sample is centrifuged, washed with furan, and vacuum dried to obtain BTT-DHBD-COF.

[0012] Optionally, in step (1), the molar ratio of BTT to DHBD is 1:1.5.

[0013] Optionally, in step (1), the volume ratio of o-dichlorobenzene (o-DCB) to n-butanol (n-BuOH) is 1:1-2.

[0014] Optionally, the volume ratio of the sum of the volumes of o-dichlorobenzene (o-DCB) and n-butanol (n-BuOH) to 6M acetic acid (HAc) is 20:0.8-1.2, preferably 20:1.

[0015] Optionally, in step (3), the heating temperature is 120° C. and the reaction time is 70 to 74 hours.

[0016] Optionally, in step (4), the vacuum drying temperature is 80-120°C and the time is 12-24 h.

[0017] Furthermore, the microstructure of the obtained COF adsorbent is rod-shaped.

[0018] The COF adsorbent designed and prepared by the present invention can be used to adsorb lead ions, preferably divalent lead ions. The COF adsorbent designed and prepared by the present invention can also be used to adsorb other heavy metal ions.

[0019] The COF adsorbent designed and prepared by the present invention is coated on an electrochemical sensor and can be used to detect the concentration of divalent lead ions in a liquid.

[0020] The COF adsorbent designed and prepared by the present invention has a maximum adsorption capacity of 570.7 mg / g for divalent lead ions under the limitation of current technology.

[0021] Under the current technological limitations, the COF adsorbent designed and prepared by the present invention is coated on an electrochemical sensor, which has a high sensitivity detection limit when detecting divalent lead ions in a solution, such as 3×10 -12 mol L -1 .

[0022] Beneficial effects of the present invention: 1. The BTT-DHBD-COF prepared by the present invention has novel morphology, structure and composition, and the preparation process is simple and convenient.

[0023] 2. Through the adjustment of the technical solution of the present invention, the obtained BTT-DHBD-COF adsorbent is used for efficient selective adsorption and high-sensitivity detection of Pb(II), and has excellent selective adsorption performance (maximum adsorption capacity can reach 570.7 mg / g) and high-sensitivity detection limit (3*10 -12 mol L -1 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD pattern of BTT-DHBD-COF prepared in Example 3 of the present invention.

[0025] Figure 2 This is a scanning electron microscope (SEM) image of BTT-DHBD-COF prepared in Example 3 of the present invention.

[0026] Figure 3 This is the FT-IR spectrum of the BTT-DHBD-COF material prepared in Example 3 of the present invention.

[0027] Figure 4 The effect of initial concentration on the adsorption performance of Pb(II).

[0028] Figure 5 This is a study on the adsorption mechanism of Pb(II) according to Example 3 of the present invention.

[0029] Figure 6 The electrochemical sensing performance of the COF material prepared in Example 3.

[0030] Figure 7 DPASV diagram of BTT-DHBD-COF / GCE electrodes prepared with slurries of different concentrations in 0.0001 μM Pb(II) solution.

[0031] Figure 8 This is the FT-IR spectrum of the BTT-DHBD-COF material obtained in Example 1; Fig. 9 This is the FT-IR spectrum of the BTT-DHBD-COF material obtained in Example 2. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention and the accompanying drawings.

[0033] Example 1 This example provides a COF adsorbent preparation and application for efficient selective adsorption and high sensitivity detection of Pb(II), which specifically includes the following steps: (1) BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) were added sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 2:1) and ultrasonicated for 10 min.

[0034] (2) After sonication, add 0.15 mL of 6 M HAc.

[0035] (3) Rapid freezing using a liquid nitrogen bath (77 K) and three freeze-pump-thaw cycles were performed to remove oxygen and heated at 120 °C for 72 h.

[0036] (4) After the reaction, the sample was centrifuged, washed thoroughly with THF several times, and dried under vacuum at 80 °C for 12 h to obtain BTT-DHBD-COF.

[0037] Example 2 This example provides a COF adsorbent preparation and application for efficient selective adsorption and high sensitivity detection of Pb(II), which specifically includes the following steps: (1) BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) were added sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 1:2) and ultrasonicated for 10 min.

[0038] (2) After sonication, add 0.15 mL of 6 M HAc.

[0039] (3) Rapid freezing using a liquid nitrogen bath (77 K) and three freeze-pump-thaw cycles were performed to remove oxygen and heated at 120 °C for 72 h.

[0040] (4) After the reaction, the sample was centrifuged, washed thoroughly with THF several times, and dried under vacuum at 80 °C for 12 h to obtain BTT-DHBD-COF.

[0041] Example 3 This example provides a COF adsorbent preparation and application for efficient selective adsorption and high sensitivity detection of Pb(II), which specifically includes the following steps: (1) BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) were added sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 1:1) and ultrasonicated for 10 min.

[0042] (2) After sonication, add 0.15 mL of 6 M HAc.

[0043] (3) Rapid freezing using a liquid nitrogen bath (77 K) and three freeze-pump-thaw cycles were performed to remove oxygen and heated at 120 °C for 72 h.

[0044] (4) After the reaction, the sample was centrifuged, washed thoroughly with THF several times, and dried under vacuum at 80 °C for 12 h to obtain BTT-DHBD-COF.

[0045] Figure 1 This is the XRD diagram of the COF material prepared in Example 3. The results show that a diffraction peak of COF appears at 2.73° in the composite material (with an intensity of approximately 1345 au), indicating that the COF material is successfully prepared.

[0046] Figure 2 This is the SEM of the COF material prepared in Example 3. It can be seen that the COF is a rod-like structure with a length of 0.5-3 μm and a diameter of 460 nm.

[0047] Figure 3 This is the FT-IR image of the COF material prepared in Example 3. After the synthesis of BTT-DHBD-COF, BTT has a wavelength of 1680 cm -1 The C=O peak at 3382 cm -1 and 3307 cm -1The -NH2 peak at 1624 cm-1 disappears due to the amine-aldehyde condensation reaction. -1 A C=N peak was generated, proving that BTT-DHBD-COF was successfully prepared.

[0048] Adsorption experiment: The BTT-DHBD-COF of Example 3 was added to a wastewater solution containing Pb(II) for adsorption. Figure 4 The adsorption performance of the COF material prepared in the example is shown in Figure 1, and its maximum adsorption capacity for Pb(II) is 570.7 mg / g, which is higher than most of the reported adsorbents, indicating that BTT-DHBD-COF has excellent adsorption performance for Pb(II).

[0049] Adsorption mechanism study: Five possible adsorption models were constructed for BTT-DHBD-COF and Pb(II), and the optimization results and binding energy (ΔE) were shown in Figure 5 These results indicate that the N, O, and S atoms in BTT-DHBD-COF can capture Pb(II) via coordination.

[0050] Electrochemical sensing performance: The BTT-DHBD-COF of this example was prepared into an electrode BTT-DHBD-COF / GCE, and different concentrations of Pb(II) were detected in a PBS buffer solution (pH 5). Figure 6 The electrochemical sensing performance of the COF material prepared in Example 3 is shown in Figure 3. The detection limit for Pb(II) is 3.0×10 -12 mol L -1 μM. This is higher than that of most of the reported electrode materials, indicating that BTT-DHBD-COF has excellent electrochemical sensing performance for Pb(II).

[0051] In addition, during the technical development process, the DPASV of BTT-DHBD-COF / GCE electrode prepared by slurry of different concentrations (1.5 mg BTT-DHBD-COF was added to 1 mL, 0.7 mL, 0.5 mL, and 0.3 mL of water and ethanol mixture (v / v=3:1)) in 0.0001 μM Pb(II) solution was also tried. Figure 7 ), and it was found that the DPASV electrochemical signal of the BTT-DHBD-COF / GCE electrode prepared by adding 1.5 mg BTT-DHBD-COF into 0.3 mL of a mixture of water and ethanol (v / v=3:1) was more obvious.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A COF adsorbent for Pb ions, characterized in that: The adsorbent is synthesized by Schiff base reaction of benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde and 3,3'-dihydroxybenzidine. -1 A C=N peak is generated at 2. The COF adsorbent for Pb ions according to claim 1, characterized in that: The COF adsorbent has a peak at 1438 cm -1 The COH peak at 1255 cm -1 A CS peak was generated at .

3. The COF adsorbent for Pb ions according to claim 1, characterized in that: The benzo[1,2-b:3,4-b':5,6-b']terthiophene-2,5,8-trialdehyde contains a carbonyl group and an S group; The 3,3'-dihydroxybenzidine contains an amino group and a hydroxyl group.

4. A method for preparing a COF adsorbent for Pb ions as claimed in any one of claims 1 to 3, characterized in that: The steps include: (1) Dissolving BTT and DHBD in a mixed solution of o-DCB and n-BuOH, and mixing them evenly to obtain a standby solution; (2) adding acetic acid to the reserve solution; (3) freezing in a liquid nitrogen bath, performing N freeze pump-thaw cycles to remove oxygen, and heating at 115-125° C., wherein N is greater than or equal to 2; (4) After the reaction is completed, the sample is centrifuged, washed with furan, and vacuum dried to obtain BTT-DHBD-COF.

5. The method for preparing a COF adsorbent for Pb ions according to claim 4, characterized in that: In step (1), the molar ratio of BTT to DHBD is 1:1.

5.

6. The method for preparing a COF adsorbent for Pb ions according to claim 4, characterized in that: In step (1), the volume ratio of o-DCB to n-BuOH is 1:1-2.

7. The method for preparing a COF adsorbent for Pb ions according to claim 4, characterized in that: The volume ratio of the sum of the volumes of o-DCB and n-BuOH to 6M acetic acid is 20:0.8-1.2, preferably 20:

1.

8. The method for preparing a COF adsorbent for Pb ions according to claim 4, characterized in that: In step (3), the heating temperature is 120°C and the reaction time is 70-74h. In step (4), the vacuum drying temperature is 80-120°C and the time is 12-24h.

9. Use of the COF adsorbent for Pb ions as claimed in any one of claims 1 to 3, characterized in that: The application includes using it to adsorb lead ions, preferably divalent lead ions; or coating the COF adsorbent on an electrochemical sensor for detecting the concentration of divalent lead ions in a liquid.

10. A use of the COF adsorbent for Pb ions as claimed in claim 9, characterized in that: The maximum adsorption capacity of the COF adsorbent for divalent lead ions is 570.7 mg / g; The obtained COF adsorbent was coated on an electrochemical sensor, and its detection limit was 3×10 -12 mol L -1 .

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