A cof / mxene composite film and a preparation method and application thereof

Abstract

The application belongs to the field of new material membrane separation, and relates to a COF / MXene composite membrane and a preparation method and application thereof. x nanosheet dispersion solution to obtain an Mxene solution; (2) a TpPa-SO3H nanosheet solution is prepared to obtain a COF solution; (3) the TpPa-SO3H nanosheet solution is first deposited on a nylon porous base membrane through vacuum-assisted self-assembly to form an intermediate porous COF layer, and then the Ti3C2T x nanosheet dispersion solution is deposited on the COF layer to prepare the COF / MXene composite membrane. The preparation method is simple in operation and high in repeatability, and the obtained composite membrane has excellent separation performance and can efficiently separate organic pollutants such as dyes in water.

Description

Technical Field

[0001] This invention belongs to the field of new material membrane separation, and relates to a COF / MXene composite membrane, its preparation method and application. Background Technology

[0002] Organic dye wastewater is a common water pollutant, and some dyes are toxic, making its treatment significant. Membrane separation technology, with its advantages of high efficiency, energy saving, no phase change, and high separation efficiency, has been widely used in the treatment of dye wastewater.

[0003] Transition metal carbides / nitrides (MXenes), as novel two-dimensional nanomaterials, have been extensively studied in catalysis, biomedicine, energy storage, and liquid separation due to their unique physicochemical properties. The layered structure of MXene membranes can achieve the separation of dye solutions; however, MXenes typically form a dense structure through face-to-face stacking, and the electrostatic repulsion between them generates non-selective defects, limiting the exposed surface area and leading to decreased membrane permeability.

[0004] Covalent organic frameworks (COFs) are a novel type of crystalline porous polymer material formed by organic monomers linked by covalent bonds. Due to their advantages such as high porosity, regular pore structure, high thermal stability, and chemical stability, they are widely used in energy storage, catalysis, and molecular separation. In particular, the abundant pores of COFs can provide excellent permeation channels for molecular separation. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this invention proposes a COF / MXene composite membrane, its preparation method, and its application. The preparation method is simple to operate and highly reproducible. The prepared composite membrane utilizes the interlayer nano-mass transfer channels of the MXene layer and the vertically penetrating pore structure of the intermediate porous COF layer to achieve excellent separation performance. The specific technical solution is as follows:

[0006] A method for preparing a COF / MXene composite membrane includes the following steps:

[0007] (1) Prepare TpPa-SO3H nanosheet solution to obtain COF solution;

[0008] (2) Preparation of Ti3C2T x Nanosheet dispersion to obtain Mxene solution;

[0009] (3) First, TpPa-SO3H nanosheet solution was deposited on a nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then Ti3C2T xA COF / MXene composite membrane was prepared by depositing a nanosheet dispersion onto a COF layer.

[0010] Further, step (1) specifically involves: mixing 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) with octanoic acid until dissolved to obtain an organic phase solution; then mixing 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and Na2CO3 with deionized water until dissolved to obtain an aqueous phase solution; then adding the organic phase solution dropwise onto the aqueous phase solution as a top layer; reacting at 16°C under static conditions for 7 days; after the reaction is complete, removing the organic phase solution; and dialysis the resulting aqueous phase solution in deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution.

[0011] Further, step (2) specifically involves: adding LiF to hydrochloric acid and stirring until dissolved, then adding Ti3AlC2 and stirring at 45°C for 36 h. After the reaction is complete, the centrifuged precipitate is repeatedly washed with deionized water. During the washing process, the centrifuge speed is gradually increased from 3500 rpm to 10000 rpm, combined with manual shaking. The washing is repeated multiple times until the pH of the supernatant is greater than 6. Then, the precipitate is centrifuged at 1500 rpm for 15 min to remove the unpeeled portion, resulting in black Ti3C2T. x Nanosheet dispersion.

[0012] Furthermore, in step (3), the TpPa-SO3H nanosheet solution and Ti3C2T x The nanosheet dispersions were diluted with ethanol before deposition.

[0013] Furthermore, in step (3), the mass ratio of COF to MXene in the prepared COF / MXene composite membrane is 8:(2~10).

[0014] A COF / MXene composite membrane, wherein the mass ratio of COF to MXene in the composite membrane is 4:3.

[0015] An application of a COF / MXene composite membrane as a separation membrane material is disclosed. In the process of separating organic dye wastewater, separation experiments can be conducted using different dye solutions. Specifically, the organic dye solution is passed through the COF / MXene composite membrane, and the concentration of the organic dye solution before and after passing through the composite membrane is analyzed.

[0016] The beneficial effects of this invention are:

[0017] The composite membrane of this invention utilizes the interlayer nano-mass transfer channels of the MXene layer and the vertically penetrating pore structure of the intermediate porous COF layer, giving the composite membrane good selectivity and high permeability.

[0018] The COF / MXene composite membrane of this invention exhibits excellent performance, with a Congo red rejection rate of 99.8% and a water flux of 165.9 L / m³. -2 h -1 bar -1 Its performance is superior to other current COF membranes and MXene membranes, and it can efficiently separate organic pollutants such as dyes in water;

[0019] The COF / MXene composite membrane of the present invention can be successfully prepared by simple vacuum filtration, which is simple to operate and highly repeatable. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the COF / MXene composite membrane of the present invention;

[0021] Figure 2 This is a surface morphology diagram of the COF / MXene composite film of the present invention;

[0022] Figure 3 These are separation performance diagrams of the COF / MXene composite membranes in Examples 1-5 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] The method for preparing the COF / MXene composite membrane of the present invention includes the following steps:

[0025] (1) Prepare TpPa-SO3H nanosheet solution to obtain COF solution;

[0026] (2) Preparation of Ti3C2T x Nanosheet dispersion to obtain MXene solution;

[0027] (3) First, TpPa-SO3H nanosheet solution was deposited on a nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then Ti3C2T x Nanosheet dispersions were deposited on a COF layer to prepare a COF / MXene composite film, such as... Figure 1 and Figure 2 As shown.

[0028] Example 1:

[0029] In this embodiment, the preparation method of the COF / MXene composite membrane specifically includes the following steps:

[0030] (1) Preparation of TpPa-SO3H nanosheets:

[0031] 21.1 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) was dissolved in 20 mL of n-octanoic acid to obtain an organic phase solution. 28.3 mg of 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and 23.8 mg of sodium carbonate (Na2CO3) were dissolved in 30 mL of deionized water to obtain an aqueous phase solution. The organic phase solution was added dropwise onto the aqueous phase solution as a top layer, and the reaction was carried out at 16 °C under static conditions for 7 days. After the reaction was complete, the organic phase solution was removed, and the resulting aqueous phase solution was dialyzed against deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution. The concentration of TpPa-SO3H nanosheets can be calculated using the freeze-drying method.

[0032] (2) Ti3C2T x Preparation of nanosheets:

[0033] 1 g of LiF was added to 20 mL of hydrochloric acid and stirred until dissolved. Then, 1 g of Ti3AlC2 was added, and the mixture was stirred at 45 °C for 36 h. After the reaction was complete, the precipitate was repeatedly washed with deionized water. During the washing process, the centrifuge speed was gradually increased from 3500 rpm to 10000 rpm, and the washing was repeated several times until the pH of the supernatant was greater than 6. Then, the precipitate was centrifuged at 1500 rpm for 15 min to remove the unpeeled portion, yielding black Ti3C2T. x Nanosheet dispersion. The Ti3C2T content can be calculated using the freeze-drying method. x Nanosheet concentration.

[0034] (3) Preparation of COF / MXene composite membrane:

[0035] First, the TpPa-SO3H nanosheet solution was diluted with ethanol. Then, through vacuum-assisted self-assembly, the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on a nylon substrate film. Finally, Ti3C2T... x The nanosheet solution was diluted with ethanol, followed by a solution containing 20 μg Ti3C2T x A diluted solution of nanosheets was deposited on a COF layer to prepare a COF / MXene composite film. The mass ratio of COF to MXene in the prepared COF / MXene composite film was 4:1.

[0036] Using this COF / MXene composite membrane, the rejection rate for Congo red dye at a concentration of 100 mg / L was 82.7%, and the water flux was 572.9 L / m³. -2 h -1 bar -1 .

[0037] Example 2:

[0038] In this embodiment, the preparation method of the COF / MXene composite membrane specifically includes the following steps:

[0039] (1) The preparation of TpPa-SO3H nanosheets is the same as in Example 1, and will not be repeated here;

[0040] (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1, and will not be repeated here;

[0041] (3) Preparation of COF / MXene composite membrane:

[0042] First, the TpPa-SO3H nanosheet solution was diluted with ethanol. Then, through vacuum-assisted self-assembly, the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on a nylon substrate film. Finally, Ti3C2T... x The nanosheet solution was diluted with ethanol, followed by a solution containing 40 μg Ti3C2T x A diluted solution of nanosheets was deposited on a COF layer to prepare a COF / MXene composite film. The mass ratio of COF to MXene in the prepared COF / MXene composite film was 2:1.

[0043] Using this COF / MXene composite membrane, the rejection rate of Congo red dye at a concentration of 100 mg / L was 96.7%, and the water flux was 356.6 L / m³. -2 h -1 bar -1 .

[0044] Example 3:

[0045] In this embodiment, the preparation method of the COF / MXene composite membrane specifically includes the following steps:

[0046] (1) The preparation of TpPa-SO3H nanosheets is the same as in Example 1, and will not be repeated here;

[0047] (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1, and will not be repeated here;

[0048] (3) Preparation of COF / MXene composite membrane:

[0049] First, the TpPa-SO3H nanosheet solution was diluted with ethanol. Then, through vacuum-assisted self-assembly, the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on a nylon substrate film. Finally, Ti3C2T... x The nanosheet solution was diluted with ethanol, followed by a solution containing 60 μg Ti3C2Tx A diluted solution of nanosheets was deposited on a COF layer to prepare a COF / MXene composite film. The mass ratio of COF to MXene in the prepared COF / MXene composite film was 4:3.

[0050] Using this COF / MXene composite membrane, the rejection rate of Congo red dye at a concentration of 100 mg / L was 99.8%, and the water flux was 165.9 L / m³. -2 h -1 bar -1 .

[0051] Example 4:

[0052] In this embodiment, the method for preparing the COF / MXene composite membrane specifically includes the following steps:

[0053] (1) The preparation of TpPa-SO3H nanosheets is the same as in Example 1, and will not be repeated here;

[0054] (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1, and will not be repeated here;

[0055] (3) Preparation of COF / MXene composite membrane:

[0056] First, the TpPa-SO3H nanosheet solution was diluted with ethanol. Then, through vacuum-assisted self-assembly, the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on a nylon substrate film. Finally, Ti3C2T... x The nanosheet solution was diluted with ethanol, followed by a solution containing 80 μg Ti3C2T x A diluted solution of nanosheets was deposited on a COF layer to prepare a COF / MXene composite film. The mass ratio of COF to MXene in the prepared COF / MXene composite film was 1:1.

[0057] The COF / MXene composite membrane achieved a 99.9% rejection rate for Congo red dye at a concentration of 100 mg / L, with a water flux of 87.6 L / m³. -2 h -1 bar -1 .

[0058] Example 5:

[0059] In this embodiment, the method for preparing the COF / MXene composite membrane specifically includes the following steps:

[0060] (1) The preparation of TpPa-SO3H nanosheets is the same as in Example 1, and will not be repeated here;

[0061] (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1, and will not be repeated here;

[0062] (3) Preparation of COF / MXene composite membrane:

[0063] First, the TpPa-SO3H nanosheet solution was diluted with ethanol. Then, through vacuum-assisted self-assembly, the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on a nylon substrate film. Finally, Ti3C2T... x The nanosheet solution was diluted with ethanol, followed by a solution containing 100 μg Ti3C2T x A diluted solution of nanosheets was deposited on a COF layer to prepare a COF / MXene composite film. The mass ratio of COF to MXene in the prepared COF / MXene composite film was 4:5.

[0064] The COF / MXene composite membrane achieved a 99.9% rejection rate for Congo red dye at a concentration of 100 mg / L, with a water flux of 88.1 L / m³. -2 h -1 bar -1 .

[0065] like Figure 3 The results of separation performance tests on the COF / MXene composite membranes prepared in Examples 1-5 are shown.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a COF / MXene composite membrane, characterized in that, Includes the following steps: (1) Prepare TpPa-SO3H nanosheet solution to obtain COF solution; (2) Preparation of Ti3C2T x Nanosheet dispersion to obtain MXene solution; (3) First, TpPa-SO3H nanosheet solution was deposited on a nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then Ti3C2T x A COF / MXene composite membrane was prepared by depositing a nanosheet dispersion onto a COF layer. Step (1) is as follows: 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) is mixed with octanoic acid until dissolved to obtain an organic phase solution. Then, 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and Na2CO3 are mixed with deionized water until dissolved to obtain an aqueous phase solution. The organic phase solution is then dropped onto the aqueous phase solution as a top layer. The reaction is carried out at 16°C under static conditions for 7 days. After the reaction is completed, the organic phase solution is removed, and the resulting aqueous phase solution is dialyzed in deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution.

2. The method for preparing the COF / MXene composite membrane according to claim 1, characterized in that, Step (2) is as follows: LiF is added to hydrochloric acid and stirred until dissolved, then Ti3AlC2 is added and stirred at 45℃ for 36 h. After the reaction is completed, the precipitate is repeatedly washed with deionized water. During the washing process, the centrifuge speed is gradually increased from 3500 rpm to 10000 rpm, and the washing is repeated several times until the pH value of the supernatant is greater than 6. Then, the precipitate is centrifuged at 1500 rpm for 15 min to remove the unpeeled part and obtain black Ti3C2T. x Nanosheet dispersion.

3. The method for preparing the COF / MXene composite membrane according to claim 1, characterized in that, In step (3), the TpPa-SO3H nanosheet solution and Ti3C2T x The nanosheet dispersions were diluted with ethanol before deposition.

4. The method for preparing the COF / MXene composite membrane according to claim 1, characterized in that, In step (3), the mass ratio of COF to MXene in the prepared COF / MXene composite membrane is 8: (2~10).

5. A COF / MXene composite membrane prepared by the preparation method according to any one of claims 1 to 4, characterized in that, The mass ratio of COF to MXene in this composite membrane is 4:

3.

6. An application of the COF / MXene composite membrane as described in claim 5, characterized in that, As a separation membrane material.

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