Preparation and modification method of sp2 carbon conjugated organic framework adsorbent

Abstract

The invention belongs to the technical field of covalent organic frameworks, and particularly relates to a preparation method and a modification method of an sp2 carbon conjugated organic framework adsorbent, and the preparation method comprises the following steps: adding TFPPy, PDAN, trimethylbenzene, 1, 4-dioxane and a NaOH aqueous solution into a quartz tube, and ultrasonically dispersing uniformly; after degassing treatment is conducted through freezing-pumping-unfreezing circulation, heating is conducted for 3 days at the temperature of 90 DEG C under the vacuum sealing condition; after the reaction is completed, cooling to room temperature, centrifugally collecting precipitate, washing with water and THF in sequence, and then performing Soxhlet extraction in THF for 2 days; and finally, carrying out vacuum drying on the product to obtain the red crystal COF material TFPPy-PDAN. The surface amino modification method comprises the following steps: adding TFPPy-PDAN into absolute ethyl alcohol to react for a certain time, then adding NH2OH. HCl and N (CH2CH3) 3, and magnetically stirring at 85 DEG C; and carrying out vacuum drying, so as to finally obtain the orange amination modified COF material (TFPPy-PDAN-AO). The covalent organic framework (COF) material has excellent catalytic performance and modification function, and can remove short-chain perfluorinated compounds in water.

Description

Technical Field

[0001] The present invention relates to the technical field of covalent organic frameworks, and specifically relates to a preparation and modification method of a sp 2 carbon-conjugated organic framework adsorbent. Background Art

[0002] Due to their excellent chemical stability, thermal stability, and hydrophobicity, short-chain perfluorinated compounds (PFCs) have been widely used in industrial production and consumer products. However, these properties also make short-chain PFCs difficult to decompose in the environment, easily accumulate in water bodies and soil, and are transmitted through the food chain, posing a potential risk to human health. As a major producer and user of short-chain PFCs, China faces severe environmental and health challenges. Research has shown that short-chain PFCs have been detected in aquatic products, meats, eggs, and vegetables, presenting certain health risks to humans. Therefore, effectively treating and recycling short-chain PFCs to reduce their negative impacts on the environment and human health has become an urgent problem to be solved.

[0003] Although there are various technologies for treating short-chain PFCs in water bodies, including adsorption, photochemical oxidation, zero-valent iron reduction, photocatalysis, and electrochemical oxidation, traditional conventional technologies have limited removal effects on short-chain PFCs. The adsorption technology has received attention due to its high efficiency and rapidity, but the adsorption performance of the adsorbent is affected by various factors, including the interaction between the adsorbent and PFCs, the types of PFCs, the properties of the adsorbent, and the hydrochemical conditions. In particular, due to the strong hydrophilicity of short-chain PFCs, conventional adsorbents have unsatisfactory removal effects on them. Covalent organic framework (COF) materials have shown great potential in the adsorption and enrichment of short-chain PFCs due to their ordered porous structure, high specific surface area, and easy functionalization, but most COFs are prone to hydrolysis or cleavage under harsh environments, limiting their practical applications.

[0004] There is an urgent need for a preparation and modification method of a sp 2 carbon-conjugated organic framework adsorbent to solve the problem of poor treatment effects of existing short-chain perfluorinated compounds. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation and modification method of a sp 2 carbon-conjugated organic framework adsorbent, which can solve the problem of poor treatment effects of existing short-chain perfluorinated compounds.

[0006] The technical solution adopted by the present invention is specifically as follows:

[0007] In the first aspect, the present invention provides a preparation method of a sp 2 carbon-conjugated organic framework adsorbent, including the following steps:

[0008] Step 1: Put TFPPy, PDAN, mesitylene, 1,4-dioxane and an aqueous solution of NaOH into a container and ultrasonically mix them until they are well mixed.

[0009] Step 2: Degas the well-mixed materials in the above step through 1 - 3 freeze-pump-thaw cycles and then vacuum seal them.

[0010] Step 3: After vacuum sealing, heat the mixture for reaction. After completion, cool it to room temperature, wash it, vacuum dry it, and collect the red crystal TFPPy-PDAN.

[0011] In a preferred embodiment, the mass ratio of TFPPy to PDAN in Step 1 is 15:8.

[0012] In a preferred embodiment, the volume ratio of mesitylene, 1,4-dioxane, and the aqueous solution of NaOH is 5:25:3.

[0013] In a preferred embodiment, Step 2 includes the following steps: Put the well-mixed materials in Step 1 into a quartz tube, degas them through 1 - 3 freeze-pump-thaw cycles, and then vacuum seal them.

[0014] In a preferred embodiment, the heating temperature in Step 3 is 90 °C and the time is 2 - 3 days.

[0015] In a preferred embodiment, the drying temperature in Step 3 is 100 °C - 120 °C and the time is 12 - 24 hours.

[0016] In a second aspect, the present invention provides a method for modifying a sp 2 carbon-conjugated organic framework adsorbent, comprising the following steps:

[0017] Step 1: Swell TFPPy-PDAN in absolute ethanol, and then add NH₂OH·HCl and N(CH₂CH₃)₃.

[0018] Step 2: Heat the well-mixed materials in the above step for reaction.

[0019] Step 3: After the heated reaction material is cooled, filter it, wash it with excess water, and vacuum dry it to obtain the orange-red solid TFPPy-PDAN-AO.

[0020] In a preferred embodiment, the swelling time of absolute ethanol in Step 1 is 20 min.

[0021] In a preferred embodiment, the mass ratio of TFPPy-PDAN, NH₂OH·HCl, and N(CH₂CH₃)₃ is 4:10:15.

[0022] In a preferred embodiment, step two includes the following steps: connecting the materials mixed in step one to a heat-collecting magnetic stirrer for heating. The temperature is 85 °C and the time is 24 hours.

[0023] The technical effects achieved by the present invention are: sp 2 The carbon conjugate structure enhances the framework stability through π-π interactions and provides rich electron delocalization channels, which is beneficial to charge transfer during the adsorption process and helps capture and remove organic pollutants. The modified COF adsorbent retains the covalent organic framework structure and has amidoxime groups. TFPPy-PDAN-AO has excellent hydrophilicity, chemical stability and is easy to separate from aqueous solutions, and can be used to efficiently adsorb short-chain perfluorinated compounds in water from solutions. Moreover, this COF material has strong recycling ability.

[0024] The preparation method and modification method of the adsorbent of the present invention are simple, flexible and low-cost; and they are non-toxic, have high performance, are easy to separate, and will not cause secondary pollution to the environment; BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of a method for preparing a sp 2 carbon conjugate organic framework adsorbent proposed by the present invention;

[0026] Figure 2 A schematic flow chart of a method for modifying a sp 2 carbon conjugate organic framework adsorbent proposed by the present invention;

[0027] Figure 3 For the sp of the present invention 2 SEM image of the carbon conjugate organic framework adsorbent;

[0028] Figure 4 For the sp of the present invention 2 TEM image of the carbon conjugate organic framework adsorbent;

[0029] Figure 5 For the sp of the present invention 2 N1s comparison chart of XPS of the carbon conjugate organic framework adsorbent;

[0030] Figure 6 For the sp of the present invention 2 O1s comparison chart of XPS of the carbon conjugate organic framework adsorbent;

[0031] Figure 7 For the sp of the present invention 2 XRD pattern of the carbon conjugate organic framework adsorbent;

[0032] Figure 8 For the sp of the present invention 2FT-IR diagram of carbon-conjugated organic framework adsorbent.

[0033] Figure 9 For the sp of the present invention 2 Reaction diagram of the modification method of carbon-conjugated organic framework adsorbent;

[0034] Figure 10 For the sp of the present invention 2 Orange-red solid diagram obtained by the modification method of carbon-conjugated organic framework adsorbent. Detailed implementation manners

[0035] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention will be made in conjunction with the accompanying drawings of the specification.

[0036] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The "in a preferred embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selectively exclusive embodiment from other embodiments.

[0038] Example 1

[0039] Please refer to the attached Figure 1 As shown, it is the first embodiment of the present invention. A method for preparing a sp 2 carbon-conjugated organic framework adsorbent of the present invention embodiment includes the following steps:

[0040] Step 1: Put TFPPy, PDAN, mesitylene, 1,4-dioxane and NaOH aqueous solution into a container, and ultrasonically mix them;

[0041] Step 2: Degas the mixed materials in the above step through 3 freeze-pump-thaw cycles, and vacuum seal;

[0042] Step 3: After vacuum sealing, heat and react, then cool to room temperature, wash, vacuum dry, and collect the red crystal TFPPy-PDAN.

[0043] Among them, in the above step 1, the mass ratio of TFPPy to PDAN is 15:8. The volume ratio of mesitylene, 1,4-dioxane and NaOH aqueous solution is 5:25:3.

[0044] Among them, the above-mentioned container uses a 10 mL quartz tube.

[0045] Among them, the above-mentioned step two includes the following steps: putting the materials mixed in step one into the quartz tube, and performing 3 freeze-pump - thaw cycles for degassing, and then vacuum sealing.

[0046] Among them, the heating temperature in the above-mentioned step three is 90 °C and the time is 3 days. The drying temperature is 120 °C and the time is 12 hours.

[0047] The above-mentioned sp 2 A specific implementation method of the preparation method of the carbon-conjugated organic framework adsorbent, including:

[0048] Step one, weigh 15 mg of TFPPy, 7.58 mg of PDAN, 0.167 ml of mesitylene, 0.835 ml of 1,4-dioxane and 0.1 ml of NaOH aqueous solution.

[0049] Step two, put the materials mixed in step one into a 10 mL quartz tube, perform 3 freeze-pump - thaw cycles for degassing, and then vacuum seal.

[0050] Step three, heat at 90 °C for 3 days after vacuum sealing, cool to room temperature after completion, wash, dry at 120 °C under vacuum, and collect the red crystal TFPPy-PDAN.

[0051] Determination of the adsorption performance of the COF adsorbent TFPPy-PDAN before modification of the product in this example for pure perfluorobutyric acid (PFBA):

[0052] At room temperature, add TFPPy-PDAN (3 mg) and PFBA solution (20 mL, 10 mg / L) into a 50 mL centrifuge tube, and oscillate at a speed of 250 r / min on an oscillator for 20 h; centrifuge to separate the adsorbent and obtain the supernatant, and use HPLC-MS to measure the remaining PFBA concentration in the supernatant to be 1.80 mg / L. The adsorption capacity of the COF adsorbent TFPPy-PDAN before modification for pure PFBA is 54.67 mg / g, and the adsorption efficiency is 82.0%;

[0053] Example 2:

[0054] A kind of sp 2 A modification method of the carbon-conjugated organic framework adsorbent, the specific steps are as follows:

[0055] Step one, expand TFPPy-PDAN in absolute ethanol, and then add NH2OH·HCl and N(CH2CH3)3;

[0056] Step two, heat and react the materials mixed in the above step;

[0057] Step 3: After cooling, filter, wash with excess water, and dry under vacuum to obtain the orange-red solid TFPPy-PDAN-AO.

[0058] Among them, in the above Step 1, the swelling time in absolute ethanol is 20 min. The mass ratio of TFPPy-PDAN, NH2OH·HCl, and N(CH2CH3)3 is 4:10:15.

[0059] Among them, the above container uses a 50 mL round-bottom flask.

[0060] Among them, please refer to Figure 9 , the above Step 2 includes the following steps: Connect the materials mixed in Step 1 to a heating mantle with magnetic stirring and heat. The temperature is 85 °C and the time is 24 hours.

[0061] Among them, the drying temperature in the above Step 3 is 60 °C.

[0062] The above modified sp 2 A specific implementation method for preparing the carbon-conjugated organic framework adsorbent includes:

[0063] Step 1: Weigh 0.4 g of TFPPy-PDAN, put it into a round-bottom flask containing absolute ethanol and swell for 20 min, then add 1.0 g of NH2OH·HCl and 1.5 g of N(CH2CH3)3.

[0064] Step 2: Connect the materials mixed in Step 1 to a heating mantle with magnetic stirring at 85 °C and heat for 24 hours.

[0065] Step 3: After cooling, filter, wash with excess water, and dry under vacuum at 60 °C to obtain the orange-red solid TFPPy-PDAN-AO, as Figure 10 shown.

[0066] Combining the above steps, (a) TFPPy-PDAN and (b) TFPPy-PDAN-AO are obtained as shown in the above figure.

[0067] As Figure 3 (a) is the SEM image of TFPPy-PDAN. A banded microstructure is observed, and the structures are closely packed together, and the C and N elements are also evenly dispersed on the surface of TFPPy-PDAN. At the same time, it can be seen that the crystallinity increases with the formation of the banded material, indicating that π-π interactions promote the interlayer stacking along the Z-axis, thus confirming the formation of TFPPy-PDAN. Figure 3 In (b) as shown in Figure 4The TEM image shows a typical two-dimensional layered structure with a nearly transparent feature, indicating that the prepared sample has an ultra-thin nature. This ultra-thin layered structure is conducive to exposing active sites.

[0068] Figure 5 The N1s spectra of (a) TFPPy-PDAN and (b) TFPPy-PDAN-AO further reveal the changes in chemical bonds: in a, only a single peak appears at 399.7 eV, which is attributed to the C≡N bond in the cyano group; while the N1s spectrum of b can be fitted into two peaks at 400.1 eV (C=N) and 403.6 eV (CN), corresponding to the imine nitrogen and amine nitrogen in the amidoxime group, respectively. This splitting phenomenon confirms the chemical transformation of the cyano group to the amidoxime group. In addition, the O 1s spectrum shows that Figure 6 The N-OH peak area at 531.7 eV in (b) increases by 23.5% compared with (a), indicating that the introduction of hydroxyl groups further enhances the surface polarity of the material and provides more active sites for the adsorption of short-chain PFCs. Figure 7 ) It can be seen that the obvious diffraction peak at 2θ = 26.9° corresponds to the presence of interlayer π-π stacking on the (001) reflection plane, indicating the formation of a COF structure. Both COFs have high-periodic structures and crystal characteristics. In addition, the crystal structure of COFs did not change after aminoximation treatment.

[0069] FT-IR spectra of TFPPy-PDAN and TFPPy-PDAN-AO are shown in Figure 2. Figure 8 The amidoxime group (C=N at 1655 cm -1 NO at 980cm -1 The characteristic peaks of -1 The broad vibration peaks in the range correspond to OH and NH, further indicating that the amidoximation was successful.

[0070] The adsorption performance of TFPPy-PDAN-AO after 50% modification of the product of this example to pure PFBA is measured:

[0071] TFPPy-PDAN-AO (50%, 3 mg) and PFBA solution (20 mL, 10 mg / L) were added to a 50 mL centrifuge tube at room temperature and oscillated at 250 r / min for 20 h on an oscillator. The adsorbent was separated by centrifugation and the supernatant was obtained. The remaining PFBA concentration in the supernatant was determined by HPLC-MS to be 0.92 mg / L. The adsorption capacity of 50% modified TFPPy-PDAN-AO for pure PFBA was 60.53 mg / g, and the adsorption efficiency was 90.8%.

[0072] Embodiment 3:

[0073] A kind of sp 2 Modification method of carbon conjugated organic framework adsorbent, the specific steps are as follows:

[0074] Step 1: Expand TFPPy-PDAN in absolute ethanol, and then add NH2OH·HCL and N(CH2CH3)3;

[0075] Step 2: Heat and react the materials mixed in the above step;

[0076] Step 3: After cooling, filter, wash with excess water, and dry in vacuum to obtain the orange-red solid TFPPy-PDAN-AO.

[0077] Among them, in the above step 1, the expansion time of absolute ethanol is 20 min. The mass ratio of TFPPy-PDAN, NH2OH·HCL and N(CH2CH3)3 is 4:10:15.

[0078] Among them, the above container uses a 50 mL round-bottom flask.

[0079] Among them, the above step 2 includes the following steps: Connect the materials mixed in step 1 to a heating mantle magnetic stirrer for heating. The temperature is 85 °C and the time is 24 hours.

[0080] Among them, in the above step 3, the drying temperature is 60 °C.

[0081] The above modified sp 2 A specific implementation method of the preparation method of carbon conjugated organic framework adsorbent, including:

[0082] Step 1: Weigh 0.4 g of TFPPy-PDAN, put it into a round-bottom flask filled with absolute ethanol and expand for 20 min, and then add 1.0 g of NH2OH·HCL and 1.5 g of N(CH2CH3)3.

[0083] Step 2: Connect the materials mixed in step 1 to a heating mantle magnetic stirrer at a temperature of 85 °C and heat for 24 hours.

[0084] Step 3: After cooling, filter, wash with excess water, and dry in vacuum at 60 °C to obtain the orange-red solid TFPPy-PDAN-AO.

[0085] Determination of the adsorption performance of the product 100% modified TFPPy-PDAN-AO in this example for pure PFBA:

[0086] At room temperature, TFPPy-PDAN-AO (100%, 3 mg) and PFBA solution (20 mL, 10 mg / L) were added to a 50 mL centrifuge tube and shaken at a speed of 250 r / min on a shaker for 20 h; the adsorbent was centrifuged and the supernatant was obtained. The remaining PFBA concentration in the supernatant was measured by HPLC-MS to be 0.86 mg / L. The adsorption capacity of TFPPy-PDAN-AO modified by 100% for pure PFBA was 60.93 mg / g, and the adsorption efficiency was 91.4%;

[0087] Example 4:

[0088] A kind of sp 2 Modification method of carbon conjugated organic framework adsorbent, the specific steps are as follows:

[0089] Step 1: Expand TFPPy-PDAN in absolute ethanol, and then add NH2OH·HCL and N(CH2CH3)3;

[0090] Step 2: Heat and react the materials mixed in the above step;

[0091] Step 3: After cooling, filter, wash with excess water, and dry in vacuum to obtain the orange-red solid TFPPy-PDAN-AO.

[0092] Among them, in the above step 1, the expansion time of absolute ethanol is 20 min. The mass ratio of TFPPy-PDAN, NH2OH·HCL and N(CH2CH3)3 is 4∶10∶15.

[0093] Among them, the above container uses a 50 mL round-bottom flask.

[0094] Among them, the above step 2 includes the following steps: Connect the materials mixed in step 1 to a heating mantle magnetic stirrer for heating. The temperature is 85 °C and the time is 24 hours.

[0095] Among them, in the above step 3, the drying temperature is 60 °C.

[0096] The above modified sp 2 A specific implementation method of the preparation method of carbon conjugated organic framework adsorbent, including:

[0097] Step 1: Weigh 0.4 g of TFPPy-PDAN, put it into a round-bottom flask containing absolute ethanol and expand for 20 min, and then add 1.0 g of NH2OH·HCL and 1.5 g of N(CH2CH3)3.

[0098] Step 2: Connect the materials mixed in step 1 to a heating mantle magnetic stirrer at a temperature of 85 °C and heat for 24 hours.

[0099] Step 3: Filter after cooling, wash with excess water, and dry under vacuum at 60° C. to obtain orange-red solid TFPPy-PDAN-AO.

[0100] The adsorption performance of the product of this example after 200% modification of TFPPy-PDAN-AO to pure PFBA was measured:

[0101] TFPPy-PDAN-AO (200%, 3 mg) and PFBA solution (20 mL, 10 mg / L) were added to a 50 mL centrifuge tube at room temperature and oscillated at 250 r / min for 20 h on an oscillator. The adsorbent was separated by centrifugation and the supernatant was obtained. The remaining PFBA concentration in the supernatant was determined by HPLC-MS to be 0.63 mg / L. The adsorption capacity of 200% modified TFPPy-PDAN-AO for pure PFBA was 62.47 mg / g, and the adsorption efficiency was 93.7%.

[0102] In summary, the present invention provides a large number of adsorption sites through the particularity of the conjugated structure, which is helpful to capture and remove organic pollutants. The modified COF adsorbent maintains the covalent organic framework structure and has an amidoxime group. TFPPy-PDAN-AO has excellent hydrophilicity and chemical stability and is easy to separate from aqueous solution. It can be used to efficiently adsorb short-chain perfluorinated compounds in water from the solution. The COF material has a strong recycling ability, especially after modification, the adsorption capacity and efficiency are significantly enhanced.

[0103] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A sp 2 The preparation method of the carbon conjugated organic framework adsorbent comprises the following steps: Step 1, TFPPy, PDAN, trimethylbenzene, 1,4-dioxane and NaOH aqueous solution are placed in a container and ultrasonicated to mix them evenly; Step 2, degas the mixed materials in the above step 1 through 1-3 freeze pump-thaw cycles and vacuum seal; Step 3: vacuum seal and heat to react, cool to room temperature after completion, wash, vacuum dry, and collect to obtain red crystal TFPPy-PDAN.

2. A sp according to claim 1 2 A method for preparing a carbon conjugated organic framework adsorbent, characterized in that: The mass ratio of TFPPy to PDAN in step 1 is 15:

8.

3. A sp according to claim 1 2 A method for preparing a carbon conjugated organic framework adsorbent, characterized in that: The volume ratio of the trimethylbenzene, 1,4-dioxane, and the NaOH aqueous solution is 5:25:

3.

4. A sp according to claim 2 2 A method for preparing a carbon conjugated organic framework adsorbent, characterized in that: The step 2 comprises the following steps: placing the mixed material in the step 1 into a quartz tube, degassing through 1-3 freeze pump-thaw cycles, and vacuum sealing.

5. A sp according to claim 3 2 A method for preparing a carbon conjugated organic framework adsorbent, characterized in that: The heating temperature in step 3 is 90° C. and the time is 2-3 days.

6. A sp according to claim 3 2 A method for preparing a carbon conjugated organic framework adsorbent, characterized in that: The vacuum drying temperature in step 3 is 100° C.-120° C., and the time is 12-24 hours.

7. A sp 2 A method for modifying a carbon conjugated organic framework adsorbent, characterized in that: The steps include: Step 1: TFPPy-PDAN is swollen in anhydrous ethanol, and then NH2OH·HCl and triethylamine (N(CH2CH3)3) are added to introduce the amidoxime group through amidoximation reaction; Step 2, heating the mixed materials in the above step to react; Step 3: After the material after the heating reaction is cooled, it is filtered, washed with excess water, and vacuum dried to obtain an orange-red solid TFPPy-PDAN-AO.

8. A sp according to claim 7 2 A method for modifying a carbon conjugated organic framework adsorbent, characterized in that: The anhydrous ethanol expansion time described in step 1 is 20 minutes.

9. A sp according to claim 7 2 A method for modifying a carbon conjugated organic framework adsorbent, characterized in that: The mass ratio of the TFPPy-PDAN, NH2OH·HCl and N(CH2CH3)3 is 4:10:

15.

10. A sp according to claim 7 2 A method for modifying a carbon conjugated organic framework adsorbent, characterized in that: The step 2 comprises the following steps: connecting the mixed material in the step 1 to a heat collecting magnetic stirrer and heating the material at a temperature of 85° C. for 24 hours.

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