COF / MXene composite membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of new material membrane separation, and relates to a COF / MXene composite membrane and a preparation method and application thereof, the preparation method comprises the following steps: (1) preparing a Ti3C2Tx nanosheet dispersion liquid to obtain an MXene solution; (2) preparing a TpPa-SO3H nanosheet solution, so as to obtain a COF solution; and (3) depositing the TpPa-SO3H nanosheet solution on the nylon porous substrate film through vacuum-assisted self-assembly to form an intermediate porous COF layer, and then depositing the Ti3C2Tx nanosheet dispersion liquid on the COF layer to prepare the COF / MXene composite film. The preparation method disclosed by the invention is simple to operate and high in repeatability, and the obtained composite membrane has excellent separation performance and can efficiently separate organic pollutants such as dye in water.

Description

Technical Field

[0001] The present invention belongs to the field of new material membrane separation and relates to a COF / MXene composite membrane and a preparation method and application thereof. Background Art

[0002] With the rapid growth of population and industrial development, the random discharge of a large number of pollutants has accelerated the deterioration of the environment, and many areas are facing water shortages. Organic dye wastewater is one of the common water pollutants. Some dyes are toxic, so the treatment of organic dye wastewater is of great significance. Membrane separation technology has the advantages of high efficiency, energy saving, no phase change, and high separation efficiency, and has been widely used in the treatment of dye wastewater.

[0003] As a new type of two-dimensional nanomaterial, transition metal carbide / nitride (MXene) has been widely studied in the fields of catalysis, medicine and biology, energy storage, liquid separation, etc. due to its unique physical and chemical properties. The layered structure of MXene membrane can achieve the separation of dye solution; MXene usually forms a dense structure in a face-to-face stacking mode, and the electrostatic repulsion between them produces non-selective defects, which limits the exposed surface area and leads to a decrease in the permeability of the membrane.

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

[0005] In order to solve the above technical problems existing in the prior art, the present invention proposes a COF / MXene composite membrane and a preparation method and application thereof. The preparation method is simple to operate and has strong repeatability. The prepared composite membrane utilizes the interlayer nano-mass transfer channels of the MXene layer and the pore structure vertically penetrating the middle porous COF layer to have excellent separation performance. The specific technical scheme is as follows: A method for preparing a COF / MXene composite film comprises 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) The TpPa-SO3H nanosheet solution was first deposited on the nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then the Ti3C2T xThe nanosheet dispersion was deposited on the COF layer to produce a COF / MXene composite film.

[0006] Furthermore, step (1) is specifically as follows: 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) is mixed with octanoic acid until dissolved to obtain an organic phase solution, and 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and Na2CO3 are mixed with deionized water until dissolved to obtain an aqueous phase solution, and then the organic phase solution is added dropwise to the aqueous phase solution as the top, and reacted at 16°C under static conditions for 7 days. After the reaction is completed, the organic phase solution is removed, and the obtained aqueous phase solution is dialyzed in deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution.

[0007] Further, step (2) is specifically as follows: LiF is added to hydrochloric acid and stirred until dissolved, and then Ti3AlC2 is added and stirred at 45°C for 36 h. After the reaction is completed, the centrifugal precipitate is repeatedly washed with deionized water. During the washing process, combined with manual shaking, 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, and then the supernatant is centrifuged at 1500 rpm for 15 min to remove the unpeeled part to obtain black Ti3C2T x Nanosheet dispersion.

[0008] Further, in step (3), TpPa-SO3H nanosheet solution and Ti3C2T x The nanosheet dispersions were diluted with ethanol before deposition.

[0009] Furthermore, in step (3), the mass ratio of COF to MXene in the prepared COF / MXene composite film is 8:(2~10).

[0010] A COF / MXene composite film, wherein the mass ratio of COF to MXene in the composite film is 4:3.

[0011] An application of a COF / MXene composite membrane as a separation membrane material can be used to conduct separation experimental tests using different dye solutions during the separation of organic dye wastewater, that is, the organic dye solution passes through the COF / MXene composite membrane and the concentration of the organic dye solution before and after passing through the composite membrane is analyzed.

[0012] Beneficial effects of the present invention: The composite membrane of the present invention utilizes the interlayer nano-mass transfer channels of the MXene layer and the pore structure vertically penetrating the middle porous COF layer, so that the composite membrane has good selectivity and high permeability. The COF / MXene composite membrane of the present invention has excellent performance, with a Congo red rejection rate of 99.8% and a water flux of 165.9 L m -2 h -1 bar -1 , which outperforms other current COF membranes and MXene membranes and can efficiently separate organic pollutants such as dyes from water; The COF / MXene composite membrane of the present invention can be successfully prepared by simple vacuum filtration, which is simple to operate and has strong repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the COF / MXene composite membrane of the present invention; Figure 2 is a surface morphology of the COF / MXene composite film of the present invention; Figure 3 Graph showing the separation performance of the COF / MXene composite membranes in Examples 1 to 5 of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and technical effect of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0015] The method for preparing the COF / MXene composite film of the present invention comprises 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) The TpPa-SO3H nanosheet solution was first deposited on the nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then the Ti3C2T x The nanosheet dispersion was deposited on the COF layer to prepare the COF / MXene composite film, e.g. Figure 1 and Figure 2 shown.

[0016] Embodiment 1: In this embodiment, the method for preparing the COF / MXene composite film specifically includes the following steps: (1) Preparation of TpPa-SO3H nanosheets: 21.1 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) was mixed with 20 mL of n-octanoic acid until dissolved 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 mixed with 30 mL of deionized water until dissolved to obtain an aqueous phase solution. The organic phase solution was added dropwise to the aqueous phase solution as the top and reacted at 16°C for 7 days under static conditions. After the reaction was completed, the organic phase solution was removed and the obtained aqueous phase solution was dialyzed in deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution. The concentration of TpPa-SO3H nanosheets can be calculated by freeze drying method.

[0017] (2) Ti3C2T x Preparation of nanosheets: 1 g of LiF was added to 20 mL of hydrochloric acid and stirred until dissolved. Then 1 g of Ti3AlC2 was added and stirred at 45 °C for 36 h. After the reaction was completed, the centrifugal precipitate was repeatedly washed with deionized water. During the washing process, combined with manual shaking, the centrifuge speed was gradually increased from 3500 rpm to 10000 rpm, and the washing was repeated several times until the pH value of the supernatant was greater than 6. Then centrifuged at 1500 rpm for 15 min to remove the unpeeled part and obtain black Ti3C2T x Nanosheet dispersion. The Ti3C2T x Nanosheet concentration.

[0018] (3) Preparation of COF / MXene composite membrane: The TpPa-SO3H nanosheet solution was diluted with ethanol, and then the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on the nylon substrate by vacuum-assisted self-assembly. x The nanosheet solution was diluted with ethanol and then 20 μg Ti3C2T x The diluted solution of nanosheets was deposited on the COF layer to prepare a COF / MXene composite film, in which the mass ratio of COF to MXene was 4:1.

[0019] The COF / MXene composite membrane has a rejection rate of 82.7% for Congo red dye with a concentration of 100 mg / L and a water flux of 572.9 L m -2 h -1 bar -1 .

[0020] Embodiment 2: In this embodiment, the preparation method of the COF / MXene composite film specifically includes the following steps: (1) The preparation of TpPa-SO3H nanosheets is the same as that in Example 1 and will not be described in detail here; (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1 and will not be described in detail here; (3) Preparation of COF / MXene composite membrane: The TpPa-SO3H nanosheet solution was diluted with ethanol, and then the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on the nylon substrate by vacuum-assisted self-assembly. x The nanosheet solution was diluted with ethanol and then 40 μg Ti3C2T x The diluted solution of nanosheets was deposited on the COF layer to prepare a COF / MXene composite film, in which the mass ratio of COF to MXene was 2:1.

[0021] The COF / MXene composite membrane has a retention rate of 96.7% for Congo red dye at a concentration of 100 mg / L and a water flux of 356.6 L m -2 h -1 bar -1 .

[0022] Embodiment 3: In this embodiment, the preparation method of the COF / MXene composite film specifically includes the following steps: (1) The preparation of TpPa-SO3H nanosheets is the same as that in Example 1 and will not be described in detail here; (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1 and will not be described in detail here; (3) Preparation of COF / MXene composite membrane: The TpPa-SO3H nanosheet solution was diluted with ethanol, and then the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on the nylon substrate by vacuum-assisted self-assembly. x The nanosheet solution was diluted with ethanol and then 60 μg Ti3C2T x The diluted solution of nanosheets was deposited on the COF layer to prepare a COF / MXene composite film, in which the mass ratio of COF to MXene was 4:3.

[0023] The COF / MXene composite membrane has a retention rate of 99.8% for Congo red dye at a concentration of 100 mg / L and a water flux of 165.9 L m -2 h -1 bar -1 .

[0024] Embodiment 4: In this embodiment, the COF / MXene composite film preparation method specifically includes the following steps: (1) The preparation of TpPa-SO3H nanosheets is the same as that in Example 1 and will not be described in detail here; (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1 and will not be described in detail here; (3) Preparation of COF / MXene composite membrane: The TpPa-SO3H nanosheet solution was diluted with ethanol, and then the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on the nylon substrate by vacuum-assisted self-assembly. x The nanosheet solution was diluted with ethanol and then 80 μg Ti3C2T x The diluted solution of nanosheets was deposited on the COF layer to prepare a COF / MXene composite film, in which the mass ratio of COF to MXene was 1:1.

[0025] The COF / MXene composite membrane has a rejection rate of 99.9% for Congo red dye at a concentration of 100 mg / L, and a water flux of 87.6 L m -2 h -1 bar -1 .

[0026] Embodiment 5: In this embodiment, the COF / MXene composite film preparation method specifically includes the following steps: (1) The preparation of TpPa-SO3H nanosheets is the same as that in Example 1 and will not be described in detail here; (2) Ti3C2T x The preparation of the nanosheets is the same as in Example 1 and will not be described in detail here; (3) Preparation of COF / MXene composite membrane: The TpPa-SO3H nanosheet solution was diluted with ethanol, and then the diluted solution containing 80 μg of TpPa-SO3H nanosheets was deposited on the nylon substrate by vacuum-assisted self-assembly. x The nanosheet solution was diluted with ethanol and then 100 μg Ti3C2Tx The diluted solution of nanosheets was deposited on the COF layer to prepare a COF / MXene composite film, in which the mass ratio of COF to MXene was 4:5.

[0027] The rejection rate of Congo red dye with a concentration of 100 mg / L using the COF / MXene composite membrane was 99.9%, and the water flux was 88.1 L m -2 h -1 bar -1 .

[0028] like Figure 3 Shown are the results of separation performance tests of the COF / MXene composite membranes prepared in Examples 1 to 5.

[0029] The above description is only a preferred implementation case of the present invention and does not limit the present invention in any form. Although the implementation process of the present invention is described in detail above, for those familiar with the art, they can still modify the technical solutions recorded in the above examples, or replace some of the technical features therein with equivalents. All modifications, equivalent replacements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a COF / MXene composite film, characterized in that: The following steps are involved: (1) Prepare TpPa-SO3H nanosheet solution to obtain COF solution; (2) Preparation of Ti3C2T x Nanosheet dispersion to obtain MXene solution; (3) The TpPa-SO3H nanosheet solution was first deposited on the nylon porous substrate membrane by vacuum-assisted self-assembly to form an intermediate porous COF layer, and then the Ti3C2T x The nanosheet dispersion was deposited on the COF layer to produce a COF / MXene composite film.

2. The method for preparing a COF / MXene composite film according to claim 1, characterized in that: Step (1) is specifically as follows: 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde (Tp) is mixed with n-octanoic acid until dissolved to obtain an organic phase solution, and 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and Na2CO3 are mixed with deionized water until dissolved to obtain an aqueous phase solution, and then the organic phase solution is added dropwise onto the aqueous phase solution as the top, and reacted at 16°C under static conditions for 7 days. After the reaction is completed, the organic phase solution is removed, and the obtained aqueous phase solution is dialyzed in deionized water for 3 days to obtain a TpPa-SO3H nanosheet solution.

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

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

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

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

3.

7. An application of the COF / MXene composite film as claimed in claim 5, characterized in that: As separation membrane material.

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