A mxene membrane with stepped holes and a preparation method and application thereof

Abstract

The application discloses a kind of MXene membranes with stepped holes and its preparation method and application, belong to separation membrane material technical field, the MXene membrane with stepped holes, in addition to substrate, from bottom to top also include successively: ultralarge-pore MXene membrane layer, thickness is 0-30nm, pore size is 2-5nm;Large-pore MXene membrane layer, thickness is 0-30nm, pore size is 0.9-1.2nm;Mesoporous MXene membrane layer, thickness is 20-50nm, pore size is 0.6-0.8nm;Small-pore MXene membrane layer, thickness is 40-60nm, pore size is 0.3-0.5nm. That is, the MXene membrane with stepped holes is prepared by repeated spin coating and plasma irradiation, and the irradiation time is limited, so that the membrane has high permeability and high selectivity for gas simultaneously by using the rich stepped hole channel.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of separation membrane materials, and particularly relates to a MXene membrane with stepped pores and a preparation method and application thereof. BACKGROUND

[0002] In recent years, two-dimensional (2D) nanosheets have been widely used as membrane building units for gas and ion separation due to their atomic thickness. The 2D membranes assembled by the nanosheets overcome the trade-off between permeability and selectivity of traditional polymer membranes. MXene (Ti3C2T x ) as a two-dimensional transition metal carbide has been widely used in the manufacture of membrane materials, and its laminated membrane shows great potential in gas and ion sieving, and even has greater application prospects in the future. The MXene nanosheet is in-plane non-porous, so the interlayer channel between adjacent MXene nanosheets dominates the gas transport in the MXene membrane. However, the single interlayer channel will cause the gas diffusion channel to be long and tortuous, resulting in a relatively low permeation rate of the MXene membrane. Therefore, introducing artificial in-plane pores on the two-dimensional non-porous nanosheet is an effective strategy to shorten the mass transfer path and improve the separation performance of the laminated membrane.

[0003] However, the existing pore-making methods (such as Cu 2+ / O2, H2SO4 and H2O2 etching) generally involve the introduction of chemicals, and the pore diameter produced is generally nanoscale. The nanoscale pore diameter is relatively large for the sieving of gas molecules with a kinetic diameter of only , and to some extent, the selectivity of the membrane is sacrificed. If the pore diameter of the MXene nanosheet can be prepared to be microns, it is expected to realize more efficient separation of the MXene membrane for gas. In addition, a single pore-making condition will result in a single pore diameter of the prepared MXene membrane, either too large to cause high permeability and low selectivity, or too small to cause low permeability and high selectivity, that is, the permeability and selectivity cannot be compatible.

[0004] Therefore, there is an urgent need to develop a new porous MXene membrane that can simultaneously realize high permeability and high selectivity. SUMMARY

[0005] In view of the above technical problems, the application provides a MXene membrane with stepped pores and a preparation method and application thereof.

[0006] To achieve the above purpose, the application provides the following technical scheme:

[0007] One of the technical schemes of the application is as follows:

[0008] A MXene membrane with stepped pores, in addition to a substrate, further comprises, from bottom to top:

[0009] A large-pore MXene film layer with a thickness of 0-30 nm and a pore size of 2-5 nm;

[0010] A large-pore MXene film layer with a thickness of 0-30 nm and a pore size of 0.9-1.2 nm;

[0011] A mesoporous MXene film layer with a thickness of 20-50 nm and a pore size of 0.6-0.8 nm;

[0012] A small-pore MXene film layer with a thickness of 40-60 nm and a pore size of 0.3-0.5 nm;

[0013] The overall thickness of the MXene film layer is 100 nm.

[0014] Optionally, the MXene film with a hierarchical pore structure comprises, in addition to the substrate, from bottom to top:

[0015] A large-pore MXene film layer with a thickness of 30 nm and a pore size of 0.9-1.2 nm;

[0016] A mesoporous MXene film layer with a thickness of 30 nm and a pore size of 0.6-0.8 nm;

[0017] A small-pore MXene film layer with a thickness of 40 nm and a pore size of 0.3-0.5 nm.

[0018] Optionally, the MXene film with a hierarchical pore structure comprises, in addition to the substrate, from bottom to top:

[0019] A large-pore MXene film layer with a thickness of 10 nm and a pore size of 0.9-1.2 nm;

[0020] A mesoporous MXene film layer with a thickness of 30 nm and a pore size of 0.6-0.8 nm;

[0021] A small-pore MXene film layer with a thickness of 60 nm and a pore size of 0.3-0.5 nm.

[0022] Optionally, the MXene film with a hierarchical pore structure comprises, in addition to the substrate, from bottom to top:

[0023] A mesoporous MXene film layer with a thickness of 50 nm and a pore size of 0.6-0.8 nm;

[0024] A small-pore MXene film layer with a thickness of 50 nm and a pore size of 0.3-0.5 nm.

[0025] Further, the MXene is Ti3C2T x ; wherein T x is a surface functional group (such as -OH, =O, -F, etc.).

[0026] Further, the material of the substrate is at least one of polyether sulfone, nylon, polyvinylidene fluoride, cellulose acetate, polyacrylonitrile or polysulfone.

[0027] The second technical solution of the present application is:

[0028] A preparation method of an MXene film with hierarchical pores, comprising the following steps:

[0029] The MXene nanosheet dispersion liquid is spin-coated on a substrate, dried, and then subjected to plasma irradiation, and the above operations are repeated to prepare the MXene film with hierarchical pores by controlling the plasma irradiation time.

[0030] Optionally, the concentration of MXene nanosheets in the MXene nanosheet dispersion liquid is 0.5 mg / mL; the solvent in the dispersion liquid is ethanol and water, and the volume ratio of ethanol to water is 0.5-1:1.

[0031] Optionally, the drying process is vacuum drying at 100℃ for 30 min.

[0032] Optionally, the conditions in the plasma irradiation process are:

[0033] The irradiation power is 100 W; the gas flow rate is 100 mL / min; and the irradiation time is 2-15 min.

[0034] Further, the plasma gas used in the plasma irradiation is Ar.

[0035] Further, when the irradiation time is 11-15 min, it is a super-large-pore MXene film layer;

[0036] When the irradiation time is 6-10 min, it is a large-pore MXene film layer;

[0037] When the irradiation time is 3-5 min, it is a medium-pore MXene film layer;

[0038] When the irradiation time is 1-2 min, it is a small-pore MXene film layer.

[0039] Further, when the irradiation time is 15 min, it is a super-large-pore layer;

[0040] When the irradiation time is 10 min, it is a large-pore MXene film layer;

[0041] When the irradiation time is 5 min, it is a medium-pore MXene film layer;

[0042] When the irradiation time is 2 min, it is a small-pore MXene film layer.

[0043] The third technical solution of the present application is:

[0044] Application of the MXene membrane with hierarchical pores in gas separation.

[0045] Optionally, the gas separation is H2 / CO2 gas separation.

[0046] Optionally, the H2 permeation rate of the MXene membrane with hierarchical pores is 980-1600 GPU; and the H2 / CO2 selectivity is 160-180.

[0047] Compared with the prior art, the present application has the following advantages and technical effects:

[0048] (1) The pore-forming and membrane-forming process used in the preparation method disclosed in the present application is simple and controllable, and a MXene membrane with hierarchical pores can be prepared through the strategy of repeated spin coating + plasma irradiation.

[0049] (2) Compared with the MXene membrane with only single interlayer channels, the MXene membrane prepared by the method of the present application has a hierarchical pore structure, which is composed of small pore (0.3-0.5 nm), medium pore (0.6-0.8 nm) and large pore (0.9-1.2 nm) layers. The large pore layer of the MXene membrane can serve as a substrate support layer, and also contributes to the permeability of the membrane; the vertical multi-angstrom channels and effective interlayer channels of the small pore and medium pore layers endow the MXene membrane with both ultra-high H2 permeation rate and excellent H2 / CO2 selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0050] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application should not be limited by the accompanying drawings.

[0051] Figure 1 It is a preparation flow chart of the MXene membrane with hierarchical pores of the present application embodiment 1.

[0052] Figure 2 It is a TEM diagram of the MXene nanosheet after different plasma irradiation times of the present application embodiment 1. DETAILED DESCRIPTION

[0053] Now, various exemplary embodiments of the present application will be described in detail. This detailed description should not be considered limiting of the present application, but rather as an exemplification of certain aspects, features and embodiments of the present application.

[0054] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentrations, solvent amounts, and the like, it is to be understood that each intervening value, to the upper and lower limits of the ranges is also specifically included within the scope of the present application. The upper and lower limits of these intervening values are also specifically included within the scope of the present application. These smaller ranges are not insubstantial as they still maintain a reasonable range in value that one of ordinary skill in the art would understand as being within the scope of the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the present specification will control.

[0056] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative only.

[0057] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0058] The embodiments of the present application disclose a preparation method of an MXene film with stepped pores, comprising the following steps:

[0059] (1) loading the MXene nanosheet dispersion liquid on the porous substrate by spin coating to form a MXene film with a certain thickness, and then drying the MXene film and performing long-time (11-15 min) Ar plasma irradiation, and repeating the above spin coating and irradiation steps for multiple times to obtain a MXene film with a super-large-pore MXene film layer;

[0060] (2) performing multiple spin coating on the MXene film with the super-large-pore layer obtained in step (1), and then drying the MXene film and performing long-time (6-10 min) Ar plasma irradiation, and repeating the above spin coating and irradiation steps for multiple times to obtain a MXene film with a large-pore MXene film layer;

[0061] (3) performing multiple spin coating and medium-time (3-5 min) Ar plasma irradiation on the MXene film with the large-pore layer obtained in step (2) to obtain a MXene film with a medium-pore MXene film layer;

[0062] (4) Continue to perform spin coating and short time (1-2 min) Ar plasma irradiation multiple times on the basis of step (3) to obtain a MXene film with a hierarchical pore (super-large hole, large hole, medium hole and small hole MXene film layer).

[0063] The MXene film prepared by the above method has a hierarchical structure, in addition to the substrate, from bottom to top including:

[0064] a super-large hole MXene film layer with a thickness of 0-30 nm and a pore size of 2-5 nm;

[0065] a large hole MXene film layer with a thickness of 0-30 nm and a pore size of 0.9-1.2 nm;

[0066] a medium hole MXene film layer with a thickness of 20-50 nm and a pore size of 0.6-0.8 nm;

[0067] a small hole MXene film layer with a thickness of 40-60 nm and a pore size of 0.3-0.5 nm;

[0068] wherein the overall thickness of the MXene film layer is 100 nm.

[0069] In some embodiments, the super-large hole MXene film layer and the large hole MXene film layer can be omitted.

[0070] In some optional embodiments, the solvent of the MXene nanoplatelet dispersion liquid is ethanol and water, and the volume ratio of ethanol and water is (0.5-1) : 1.

[0071] The above-mentioned MXene film with hierarchical pores disclosed in the embodiments of the present application can be applied in the field of gas separation; wherein the gas separation is H2 / CO2 gas separation.

[0072] The raw materials used in the present application are all obtained by purchase on the market.

[0073] The technical solutions of the present application are further illustrated by the following examples.

[0074] Example 1 (three stages)

[0075] As shown in Figure 1 , a method for preparing a MXene film with hierarchical pores comprises the following steps:

[0076] (1) Prepare the original MXene (Ti3C2T x) Nanosheet water and ethanol dispersion: 2.5 g of lithium fluoride, 2 g of Ti3AlC2 powder were mixed with 9M 50 mL hydrochloric acid solution, stirred at 50°C for 30 h, and the mixed slurry after reaction was repeatedly centrifuged at 3500-6000 rpm to wash to pH ~ 6, and finally the solution was centrifuged at 5000 rpm for 30 min, the supernatant was discarded to remove small pieces, and the precipitate was centrifuged at 1500 rpm to collect the supernatant, which was the original Ti3C2T x Nanosheet water dispersion, mixed with the same volume of ethanol to obtain the original MXene (Ti3C2T x ) Nanosheet water and ethanol dispersion;

[0077] (2) The 0.5 mg / mL MXene nanosheet dispersion was loaded on a polyether sulfone substrate (pore size: 0.2 μm) by spin coating to obtain an ultra-thin original MXene film (thickness: 10 nm), and it was placed in a vacuum oven at 100°C for 30 min, and then subjected to Ar plasma irradiation for 10 min (irradiation power: 100 W; gas flow rate: 100 mL / min), and the above spin coating and irradiation steps were repeated 3 times to obtain a MXene film with a large pore layer (thickness: 30 nm; pore size: 1.2 nm);

[0078] (3) The spin coating and irradiation steps were repeated 3 times on the 30 nm thick MXene film with a large pore layer (except that the irradiation time was changed to 5 min, and the other conditions were the same as step (2)), to obtain a MXene film with a large pore layer (thickness: 30 nm) and a mesoporous layer (thickness: 30 nm, pore size: 0.6 nm);

[0079] (4) On the basis of (3), the spin coating and irradiation steps were repeated 4 times (except that the irradiation time was changed to 2 min, and the other conditions were the same as step (2)), to obtain a MXene film with a large pore layer (thickness: 30 nm; pore size: 1.2 nm), a mesoporous layer (thickness: 30 nm, pore size: 0.6 nm), and a small pore layer (thickness: 40 nm, pore size: 0.3 nm), i.e. the MXene film with a three-stage hierarchical pore (total thickness: 100 nm).

[0080] Example 2 (two-stage)

[0081] A method for preparing a MXene film with hierarchical pores, which is different from example 1,

[0082] Step (2) is not included, and step (3) is directly performed after step (1);

[0083] Step (3) is repeated 5 times, and the thickness of the mesoporous layer obtained is 50 nm, and the pore size is 0.6 nm;

[0084] Step (4) spin-coating and irradiation for 5 times, the thickness of the small pore layer obtained is 50 nm, and the pore size is 0.3 nm; a MXene film with secondary stepped pores consisting of only a mesopore layer (thickness: 50 nm) and a small pore layer (thickness: 50 nm) is obtained.

[0085] The other process steps and parameters are the same as those in Example 1.

[0086] Example 3 (tertiary, different thickness from Example 1)

[0087] A method for preparing a MXene film with stepped pores, which is different from Example 1 in that,

[0088] Step (2) spin-coating and irradiation for 1 time, the thickness of the macropore layer obtained is 10 nm, and the pore size is 1.2 nm;

[0089] Step (3) spin-coating and irradiation for 3 times, the thickness of the mesopore layer obtained is 30 nm, and the pore size is 0.6 nm;

[0090] Step (4) spin-coating and irradiation for 6 times, the thickness of the small pore layer obtained is 60 nm, and the pore size is 0.3 nm; a MXene film with a macropore layer (thickness: 10 nm), a mesopore layer (thickness: 30 nm), and a small pore layer (thickness: 60 nm) is obtained.

[0091] The other process steps and parameters are the same as those in Example 1.

[0092] Example 4 (quaternary)

[0093] A method for preparing a MXene film with stepped pores, comprising the following steps:

[0094] (1) Preparation of an original MXene (Ti3C2T x ) nanosheet water and ethanol dispersion: 2.5 g of lithium fluoride, 2 g of Ti3AlC2 powder, and 9M 50 mL of hydrochloric acid solution were mixed, stirred at 50°C for 30 h, and the mixed slurry after reaction was repeatedly centrifuged at 3500-6000 rpm until the pH was ~ 6. Finally, the solution was centrifuged at 5000 rpm for 30 min, the supernatant was discarded to remove small pieces, and the supernatant was collected by centrifugation at 1500 rpm to obtain an original Ti3C2T x nanosheet water dispersion. The same volume of ethanol was mixed with it to obtain an original MXene (Ti3C2T x ) nanosheet water and ethanol dispersion;

[0095] (2) 0.5 mg / mL MXene nanosheet dispersion was loaded on a polyether sulfone substrate (pore size: 0.2 pm) by spin coating to obtain an ultra-thin pristine MXene film (thickness: 10 nm), and it was placed under vacuum drying at 100 °C for 30 min, followed by Ar plasma irradiation for 15 min (irradiation power: 100 W; gas flow rate: 100 mL / min), and the above spin coating and irradiation steps were repeated once to obtain a MXene film with a supermacroporous layer (thickness: 10 nm; pore size 5 nm);

[0096] (3) The spin coating and irradiation steps were repeated once on the 10 nm thick MXene film with a supermacroporous layer (except that the irradiation time was changed to 10 min, and the other conditions were the same as step (2)), to obtain a MXene film with a supermacroporous layer (thickness: 10 nm; pore size 5 nm) and a macroporous layer (thickness: 10 nm, pore size 1.2 nm);

[0097] (4) The spin coating and irradiation steps were repeated twice on the 20 nm thick MXene film with a supermacroporous layer (10 nm) and a macroporous layer (10 nm) (except that the irradiation time was changed to 5 min, and the other conditions were the same as step (2)), to obtain a MXene film with a supermacroporous layer (thickness: 10 nm, pore size 5 nm), a macroporous layer (thickness: 10 nm, pore size 1.2 nm) and a mesoporous layer (thickness: 20 nm, pore size 0.6 nm);

[0098] (5) On the basis of (4), the spin coating and irradiation steps were continued to be repeated 6 times (except that the irradiation time was changed to 2 min, and the other conditions were the same as step (2)), to obtain a MXene film with a supermacroporous layer (thickness: 10 nm), a macroporous layer (thickness: 10 nm), a mesoporous layer (thickness: 20 nm), a small pore layer (thickness: 60 nm, pore size 0.3 nm), i.e. the MXene film with four-level hierarchical pores (total thickness: 100 nm).

[0099] Comparative Example 1 (single MXene film)

[0100] A method for preparing a pristine MXene film, comprising the following steps:

[0101] (1) Preparation of pristine MXene (Ti3C2T x ) nanosheet water and ethanol dispersion (the specific preparation conditions are the same as in Example 1);

[0102] (2) 0.5 mg / mL MXene nanoplatelet dispersion was loaded on a polyether sulfone substrate (pore size: 0.2 pm) by spin coating to obtain an ultrathin pristine MXene film (thickness: 10 nm), and it was vacuum dried at 100°C for 30 min, and the above spin coating step was repeated 10 times to obtain a 100 nm thick pristine MXene film.

[0103] Comparative Example 2 (single stage, MXene film with only small pore layer)

[0104] A MXene film with only a small pore layer and a method for preparing the same, comprising the following steps:

[0105] (1) Preparation of a pristine MXene (Ti3C2T x ) nanoplatelet water and ethanol dispersion (specific preparation conditions are the same as in Example 1);

[0106] (2) 0.5 mg / mL MXene nanoplatelet dispersion was loaded on a polyether sulfone substrate (pore size: 0.2 pm) by spin coating to obtain an ultrathin pristine MXene film (thickness: 10 nm), and it was vacuum dried at 100°C for 30 min, and the above spin coating step was repeated 10 times to obtain a 100 nm thick pristine MXene film.

[0107] Comparative Example 3 (single stage, MXene film with only a mesopore layer)

[0108] A MXene film with only a mesopore layer and a method for preparing the same, which is different from Comparative Example 2 in that,

[0109] only the single plasma irradiation time was changed to 5 min to obtain a MXene film with only a mesopore layer (thickness: 100 nm, pore size: 0.6 nm). The other process steps and parameters are the same as in Comparative Example 2.

[0110] Comparative Example 4 (single stage, MXene film with only a macropore layer)

[0111] A MXene film with only a small pore layer and a method for preparing the same, which is different from Comparative Example 2 in that,

[0112] only the single plasma irradiation time was changed to 10 min to obtain a MXene film with only a macropore layer (thickness: 100 nm, pore size: 1.2 nm). The other process steps and parameters are the same as in Comparative Example 2.

[0113] Comparative Example 5

[0114] A method for preparing a MXene film with a hierarchical pore, which is different from Example 1 in that,

[0115] Step (1) and step (2) are added: Ar plasma irradiation for 15 min, spin coating and irradiation step 2 times; the supermacroporous layer thickness is 20 nm, wherein the supermacroporous pore size is 5 nm;

[0116] Step (2) spin coating and irradiation step 2 times, the macroporous layer thickness is 20 nm, and the macroporous pore size is 1.2 nm;

[0117] Step (3) spin coating and irradiation step 3 times, the mesoporous layer thickness is 30 nm, and the mesoporous pore size is 0.6 nm;

[0118] Step (4) spin coating and irradiation step 3 times, the microporous layer thickness is 30 nm, and the microporous pore size is 0.3 nm;

[0119] A MXene film with a supermacroporous layer (thickness: 20 nm), a macroporous layer (thickness: 20 nm), a mesoporous layer (thickness: 30 nm), and a microporous layer (thickness: 30 nm) is obtained.

[0120] The other process steps and parameters are the same as those of Example 1.

[0121] Comparative Example 6

[0122] A MXene film with a stepped pore and a preparation method thereof, which is different from Example 1,

[0123] Step (2) spin coating and irradiation step 5 times, the macroporous layer thickness is 50 nm, and the macroporous pore size is 1.2 nm;

[0124] Step (3) spin coating and irradiation step 3 times, the mesoporous layer thickness is 30 nm, and the mesoporous pore size is 0.6 nm;

[0125] Step (4) spin coating and irradiation step 2 times, the microporous layer thickness is 20 nm, and the microporous pore size is 0.3 nm; a MXene film with a macroporous layer (thickness: 50 nm), a mesoporous layer (thickness: 30 nm), and a microporous layer (thickness: 20 nm) is obtained.

[0126] The other process steps and parameters are the same as those of Example 1.

[0127] Effect verification

[0128] The present application verifies the in-plane pore size change of MXene nanosheets under different Ar plasma irradiation times in the preparation process of Example 1 by spherical aberration transmission electron microscopy, from Figure 2It can be observed that the pore size of MXene nanosheets gradually increases from 0.3 nm to 1.2 nm as the plasma irradiation time is prolonged from 2 min to 10 min. Then the MXene membranes prepared in the examples and comparative examples are put into a gas separation device, and equal volumes of H2 / CO2 mixed gas (both flow rates are 50 mL / min) are introduced into the feed side, argon gas (flow rate is 50 mL / min) is introduced into the purge side, and the gas on the permeation side is introduced into the gas chromatograph for detection.

[0129] Firstly, the gas separation performance of the original MXene membrane (Comparative Example 1), the MXene membrane with single-stage pores (Comparative Examples 2-4) and the MXene membrane with hierarchical pores (Example 1) is compared, as shown in Table 1:

[0130] Table 1

[0131]

[0132] According to Table 1, it can be found that as the irradiation time is prolonged, the H2 permeation rate gradually increases, and the H2 / CO2 selectivity gradually decreases, indicating that the original MXene membrane and the MXene membrane with single-stage pores cannot simultaneously achieve high H2 permeation rate and H2 / CO2 selectivity; but looking at the MXene membrane with hierarchical pores prepared in Example 1, compared with the original MXene membrane, the H2 permeation rate is increased by nearly 5 times (from 320 GPU to 1564 GPU), and the selectivity is basically maintained (from 184 to 164). The macroporous layer of the membrane (pore size: 1.2 nm) can modify the microporous polyether sulfone substrate as a support layer, effectively avoiding the problem of increased defects of the MXene membrane caused by the too large pores of the substrate, and at the same time, the macroporous layer also contributes to the permeability of the membrane due to its large pore size; in addition, the rich vertical mesoporous channels and interlayer channels in the mesoporous layer (pore size: 0.6 nm) and the small pore layer (pore size: 0.3 nm) endow the MXene membrane with ultra-high H2 permeation rate and excellent H2 / CO2 selectivity.

[0133] Secondly, the present application also discusses the effect of the number of hierarchical pores (Example 1, Example 2 and Comparative Example 5) and the thickness of each stage (Example 1, Example 3 and Comparative Example 6) of the MXene membrane with hierarchical pores on the H2 / CO2 gas separation performance, as shown in Table 2:

[0134] Table 2

[0135]

[0136] It can be found from Table 2 that the MXene membrane with stepped pores exhibits the optimal H2 / CO2 separation performance when the number of steps is 3, the thickness of each step from top to bottom is 40 nm / 2 min, 30 nm / 5 min and 30 nm / 10 min, respectively (i.e. Example 1).

[0137] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An MXene membrane with stepped pores, characterized in that, In addition to the substrate, from bottom to top, sequentially comprises: a super-large pore MXene film layer, thickness of 0-30nm, pore size of 2-5nm; a large pore MXene film layer, thickness of 0-30nm, pore size of 0.9-1.2nm; a mesoporous MXene film layer, thickness of 20-50nm, pore size of 0.6-0.8nm; a small pore MXene film layer, thickness of 40-60nm, pore size of 0.3-0.5nm; wherein the overall thickness of the MXene film layer is 100nm.

2. The MXene membrane with stepped pores according to claim 1, characterized in that, The MXene film with hierarchical pores, in addition to the substrate, from bottom to top, sequentially comprises: a large pore MXene film layer, thickness of 30nm, pore size of 0.9-1.2nm; a mesoporous MXene film layer, thickness of 30nm, pore size of 0.6-0.8nm; a small pore MXene film layer, thickness of 40nm, pore size of 0.3-0.5nm.

3. The MXene membrane with stepped pores according to claim 1, characterized in that, The MXene film with hierarchical pores, in addition to the substrate, from bottom to top, sequentially comprises: a large pore MXene film layer, thickness of 10nm, pore size of 0.9-1.2nm; a mesoporous MXene film layer, thickness of 30nm, pore size of 0.6-0.8nm; a small pore MXene film layer, thickness of 60nm, pore size of 0.3-0.5nm.

4. The MXene membrane with stepped pores according to claim 1, characterized in that, The MXene film with hierarchical pores, in addition to the substrate, from bottom to top, sequentially comprises: a mesoporous MXene film layer, thickness of 50nm, pore size of 0.6-0.8nm; a small pore MXene film layer, thickness of 50nm, pore size of 0.3-0.5nm.

5. A method of preparing an MXene membrane with stepped pores, characterized by, comprises the following steps: spinning MXene nanosheet dispersion on the substrate, drying, and then repeating the above operation to prepare the MXene film with hierarchical pores of any one of claims 1-4 by controlling the plasma irradiation time.

6. The method of claim 5, wherein the MXene membrane with stepped pores is prepared by, The concentration of MXene nanosheets in the MXene nanosheet dispersion is 0.5mg / mL.

7. The method of claim 5, wherein the MXene membrane with stepped pores is prepared by, The drying process is vacuum drying at 100℃ for 30min.

8. The method of claim 5, wherein the MXene membrane with stepped pores is prepared by, The conditions in the plasma irradiation process are: irradiation power of 100W; gas flow rate of 100mL / min; irradiation time of 2-15min.

9. The method of claim 8, wherein the MXene membrane with stepped pores is prepared by, When the irradiation time is 11-15min, it is a super-large pore MXene film layer; When the irradiation time is 6-10min, it is a large pore MXene film layer; When the irradiation time is 3-5min, it is a mesoporous MXene film layer; When the irradiation time is 1-2min, it is a small pore MXene film layer.

10. The MXene film with hierarchical pores of any one of claims 1-4 for use in gas separation.

Images