MXene film with stepped holes as well as preparation method and application of MXene film

Abstract

The invention discloses an MXene membrane with stepped holes and a preparation method and application thereof, and belongs to the technical field of separation membrane materials, and the MXene membrane with the stepped holes comprises a substrate, a super-macroporous MXene membrane layer with the thickness of 0-30 nm and the aperture of 2-5 nm, and a super-macroporous MXene membrane layer with the thickness of 0-30 nm and the aperture of 2-5 nm in sequence from bottom to top; the thickness of the macroporous MXene film layer is 0 to 30 nm, and the aperture of the macroporous MXene film layer is 0.9 to 1.2 nm; the thickness of the mesoporous MXene film layer is 20 to 50 nm, and the aperture of the mesoporous MXene film layer is 0.6 to 0.8 nm; and the thickness of the small-hole MXene film layer is 40 to 60 nm, and the aperture of the small-hole MXene film layer is 0.3 to 0.5 nm. According to the preparation method, the MXene membrane with the stepped holes is prepared by repeatedly spin-coating and plasma irradiation and limiting the irradiation time, and the membrane has high permeability and high selectivity on gas by utilizing abundant stepped hole channels of the MXene membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of separation membrane materials, and in particular relates to a MXene membrane with stepped pores and a preparation method and application thereof. Background Art

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

[0003] However, existing pore-forming methods (such as Cu 2+ / O2, H2SO4 and H2O2 etching) usually involve the introduction of chemicals, and the pore size produced is generally nanometer-sized, which is only a fraction of the kinetic diameter. The screening of small gas molecules is large, which will sacrifice the selectivity of the membrane to a certain extent. If angstrom-level pores can be prepared on MXene nanosheets, it is expected that the MXene membrane can separate gases more efficiently. In addition, a single pore-forming condition will result in a single pore size in the prepared MXene membrane. Either the pores are too large, resulting in high permeability and low selectivity; or the pores are too small, resulting in low permeability and high selectivity; that is, permeability and selectivity are incompatible.

[0004] Therefore, there is an urgent need to develop a new porous MXene membrane that can achieve both high permeability and high selectivity. Summary of the invention

[0005] In response to the above technical problems, the present invention proposes a MXene membrane with stepped pores and a preparation method and application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

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

[0009] Ultra-macroporous MXene membrane layer, with a thickness of 0-30nm and a pore size of 2-5nm;

[0010] Macroporous MXene membrane layer, thickness 0-30nm, pore size 0.9-1.2nm;

[0011] Mesoporous MXene film layer, thickness is 20-50nm, pore size is 0.6-0.8nm;

[0012] Small-pore MXene film layer, thickness 40-60nm, pore size 0.3-0.5nm;

[0013] Among them, the overall thickness of the MXene film layer is 100nm.

[0014] Optionally, the MXene film with stepped pores, in addition to the substrate, comprises, from bottom to top:

[0015] Macroporous MXene film layer, 30nm thick, 0.9-1.2nm pore size;

[0016] Mesoporous MXene film layer, 30nm thick, 0.6-0.8nm pore size;

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

[0018] Optionally, the MXene film with stepped pores, in addition to the substrate, comprises, from bottom to top:

[0019] Macroporous MXene film layer, 10nm thick, 0.9-1.2nm pore size;

[0020] Mesoporous MXene film layer, 30nm thick, 0.6-0.8nm pore size;

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

[0022] Optionally, the MXene film with stepped pores, in addition to the substrate, comprises, from bottom to top:

[0023] Mesoporous MXene film layer, 50nm thick, 0.6-0.8nm pore size;

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

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

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

[0027] The second technical solution of the present invention:

[0028] A method for preparing a MXene film with stepped pores comprises the following steps:

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

[0030] Optionally, the concentration of MXene nanosheets in the MXene nanosheet dispersion is 0.5 mg / mL; the solvent in the dispersion 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° C. for 30 minutes.

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

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

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

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

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

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

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

[0039] Furthermore, 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 macroporous MXene film layer;

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

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

[0043] The third technical solution of the present invention:

[0044] The above-mentioned MXene membrane with stepped pores is used for gas separation.

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

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

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

[0048] (1) The pore-making and film-making processes used in the preparation method disclosed in the present invention are simple and controllable, and a MXene film with stepped pores can be prepared by repeated spin coating + plasma irradiation strategy.

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

[0050] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 This is a flow chart of preparing a MXene film with stepped pores according to Example 1 of the present invention;

[0052] Figure 2 TEM images of MXene nanosheets after different plasma irradiation times in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0054] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0055] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0056] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0057] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0058] The embodiment of the present invention discloses a method for preparing a MXene film with stepped pores, comprising the following steps:

[0059] (1) A MXene film having a certain thickness is loaded on a porous substrate by spin coating a MXene nanosheet dispersion, and after drying, it is subjected to Ar plasma irradiation for a long time (11-15 min), and the above spin coating and irradiation steps are repeated multiple times to obtain a MXene film having an ultra-large porous MXene film layer;

[0060] (2) performing multiple spin coatings on the MXene film with the ultra-large porous layer in step (1), and after drying, performing long-term (6-10 min) Ar plasma irradiation, and repeating the above spin coating and irradiation steps multiple times to obtain a MXene film with a large porous MXene film layer;

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

[0062] (4) Based on step (3), multiple spin coating and short-term (1-2 min) Ar plasma irradiation are continued to obtain a MXene film with stepped pores (super-large pores, large pores, medium pores and small pores MXene film layers).

[0063] The MXene film prepared by the above method has a stepped structure, which includes, from bottom to top, the following in addition to the substrate:

[0064] Ultra-macroporous MXene membrane layer, with a thickness of 0-30nm and a pore size of 2-5nm;

[0065] Macroporous MXene membrane layer, thickness 0-30nm, pore size 0.9-1.2nm;

[0066] Mesoporous MXene film layer, thickness is 20-50nm, pore size is 0.6-0.8nm;

[0067] Small-pore MXene film layer, thickness 40-60nm, pore size 0.3-0.5nm;

[0068] Among them, the overall thickness of the MXene film layer is 100nm.

[0069] In some embodiments, the ultra-macroporous MXene membrane layer and the macroporous MXene membrane layer may be omitted.

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

[0071] The above-mentioned MXene membrane with stepped pores disclosed in the embodiment of the present invention 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 invention are all purchased from the market.

[0073] The technical solution of the present invention is further illustrated by the following embodiments.

[0074] Example 1 (Level 3)

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

[0076] (1) Preparation of pristine MXene (Ti3C2T x) Nanosheet water and ethanol dispersion: 2.5 g lithium fluoride, 2 g Ti3AlC2 powder and 9M 50 mL hydrochloric acid solution were mixed and stirred at 50 ° C for 30 h. The mixed slurry after the reaction was repeatedly centrifuged and washed at 3500-6000 rpm until the pH was ~6. Finally, the solution was centrifuged at 5000 rpm for 30 min, the supernatant was poured out to remove small pieces, and the precipitate was centrifuged at 1500 rpm to collect the supernatant, which was the original Ti3C2T x Nanosheet aqueous dispersion, take the same volume of ethanol and mix it to obtain the original MXene (Ti3C2T x ) nanosheets water and ethanol dispersions;

[0077] (2) A 0.5 mg / mL MXene nanosheet dispersion was spin-coated on a polyethersulfone substrate (pore size: 0.2 μm) to obtain an ultrathin original MXene film (thickness: 10 nm), which was then vacuum dried at 100 °C for 30 min, and then irradiated with Ar plasma for 10 min (irradiation power: 100 W; gas flow rate: 100 mL / min). The above spin coating and irradiation steps were repeated 3 times to obtain a MXene film with a macroporous layer (thickness: 30 nm; pore size: 1.2 nm);

[0078] (3) Repeating the spin coating and irradiation steps on the MXene film with a macroporous layer having a thickness of 30 nm for 3 times (except changing the irradiation time to 5 min, the other conditions are the same as step (2)) to obtain a MXene film with a macroporous layer (thickness: 30 nm) and a mesoporous layer (thickness: 30 nm, pore size 0.6 nm);

[0079] (4) Based on (3), the spin coating and irradiation steps were repeated for 4 times (except that the irradiation time was changed to 2 min, the other conditions were the same as step (2)) to obtain a MXene membrane having a macroporous layer (thickness: 30 nm; pore size: 1.2 nm), a mesoporous layer (thickness: 30 nm, pore size: 0.6 nm), and a microporous layer (thickness: 40 nm, pore size: 0.3 nm), i.e., the MXene membrane having three-level stepped pores (total thickness: 100 nm).

[0080] Example 2 (Secondary)

[0081] A method for preparing a MXene film with stepped pores, which is different from that in Example 1,

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

[0083] Step (3) spin coating and irradiation steps were repeated 5 times, and the resulting mesoporous layer had a thickness of 50 nm and a pore size of 0.6 nm;

[0084] Step (4) The spin coating and irradiation steps were repeated 5 times, and the obtained small pore layer had a thickness of 50 nm and a pore size of 0.3 nm; a MXene membrane with secondary stepped pores consisting only of a mesoporous layer (thickness: 50 nm) and a small pore layer (thickness: 50 nm) was obtained.

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

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

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

[0088] Step (2) spin coating and irradiation steps are performed once, and the obtained macroporous layer has a thickness of 10 nm and a pore size of 1.2 nm;

[0089] Step (3) The spin coating and irradiation steps were repeated three times, and the resulting mesoporous layer had a thickness of 30 nm and a pore size of 0.6 nm;

[0090] Step (4) spin coating and irradiation steps were performed 6 times, and the obtained small pore layer had a thickness of 60 nm and a pore diameter of 0.3 nm; a MXene membrane having a large pore layer (thickness: 10 nm), a medium pore layer (thickness: 30 nm), and a small pore layer (thickness: 60 nm) was obtained.

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

[0092] Embodiment 4 (fourth level)

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

[0094] (1) Preparation of pristine MXene (Ti3C2T x ) Nanosheet water and ethanol dispersion: 2.5 g lithium fluoride, 2 g Ti3AlC2 powder and 9M 50 mL hydrochloric acid solution were mixed and stirred at 50 ° C for 30 h. The mixed slurry after the reaction was repeatedly centrifuged and washed at 3500-6000 rpm until the pH was ~6. Finally, the solution was centrifuged at 5000 rpm for 30 min, the supernatant was poured out to remove small pieces, and the precipitate was centrifuged at 1500 rpm to collect the supernatant, which was the original Ti3C2T x Nanosheet aqueous dispersion, take the same volume of ethanol and mix it to obtain the original MXene (Ti3C2T x ) nanosheets water and ethanol dispersions;

[0095] (2) A 0.5 mg / mL MXene nanosheet dispersion was spin-coated on a polyethersulfone substrate (pore size: 0.2 μm) to obtain an ultrathin original MXene film (thickness: 10 nm), which was then vacuum dried at 100 °C for 30 min, and then irradiated with Ar plasma for 15 min (irradiation power: 100 W; gas flow rate: 100 mL / min). The above spin coating and irradiation steps were repeated once to obtain a MXene film with an ultra-large pore layer (thickness: 10 nm; pore size: 5 nm);

[0096] (3) Repeating the spin coating and irradiation steps once on the MXene film with a super-large pore layer having a thickness of 10 nm (except that the irradiation time is changed to 10 min, the other conditions are the same as step (2)) to obtain a MXene film with a super-large pore layer (thickness: 10 nm; pore size: 5 nm) and a macroporous layer (thickness: 10 nm, pore size: 1.2 nm);

[0097] (4) Repeating the spin coating and irradiation steps twice on a 20 nm thick MXene membrane having an ultra-large pore layer (10 nm) and a macro-pore layer (10 nm) (except that the irradiation time is changed to 5 min, other conditions are the same as step (2)) to obtain a MXene membrane having an ultra-large pore layer (thickness: 10 nm, pore size: 5 nm), a macro-pore layer (thickness: 10 nm, pore size: 1.2 nm) and a meso-pore layer (thickness: 20 nm, pore size: 0.6 nm);

[0098] (5) Based on (4), the spin coating and irradiation steps were repeated for 6 times (except that the irradiation time was changed to 2 min, the other conditions were the same as step (2)) to obtain a MXene membrane having an ultra-large pore layer (thickness: 10 nm), a large pore layer (thickness: 10 nm), a medium pore layer (thickness: 20 nm), and a small pore layer (thickness: 60 nm, pore size 0.3 nm), that is, the MXene membrane with four-level stepped pores (total thickness: 100 nm).

[0099] Comparative Example 1 (Single MXene Film)

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

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

[0102] (2) A 0.5 mg / mL MXene nanosheet dispersion was spin-coated on a polyethersulfone substrate (pore size: 0.2 μm) to obtain an ultrathin original MXene film (thickness: 10 nm), which was then vacuum-dried at 100 °C for 30 min. The above spin coating step was repeated 10 times to obtain a 100 nm thick original MXene film.

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

[0104] A MXene film having only a small pore layer and a preparation method thereof, comprising the following steps:

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

[0106] (2) A 0.5 mg / mL MXene nanosheet dispersion was spin-coated on a polyethersulfone substrate (pore size: 0.2 μm) to obtain an ultrathin original MXene film (thickness: 10 nm), which was then irradiated with Ar plasma for 2 min (irradiation power: 100 W; gas flow rate: 100 mL / min). The above spin coating and irradiation steps were repeated 10 times to obtain a MXene film with only a small pore layer (thickness: 100 nm, pore size 0.3 nm).

[0107] Comparative Example 3 (single-stage, MXene membrane with only mesoporous layer)

[0108] A MXene film having only a mesoporous layer and a preparation method thereof, which is different from Comparative Example 2 in that:

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

[0110] Comparative Example 4 (single-stage, MXene membrane with only macroporous layer)

[0111] A MXene membrane having only a small pore layer and a preparation method thereof, which is different from Comparative Example 2 in that:

[0112] Only the time of single plasma irradiation was changed to 10 min, and a MXene film having only a macroporous layer (thickness: 100 nm, pore size: 1.2 nm) was obtained. The other process steps and parameters were the same as those in Comparative Example 2.

[0113] Comparative Example 5

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

[0115] A step is added between step (1) and step (2): Ar plasma irradiation for 15 minutes, spin coating and irradiation steps are repeated twice; the thickness of the obtained ultra-large pore layer is 20 nm, wherein the pore size of the ultra-large pore is 5 nm;

[0116] Step (2) spin coating and irradiation steps are performed twice, and the obtained macroporous layer has a thickness of 20 nm and a macropore diameter of 1.2 nm;

[0117] Step (3) spin coating and irradiation steps are repeated three times, and the resulting mesoporous layer has a thickness of 30 nm and a mesopore diameter of 0.6 nm;

[0118] Step (4) spin coating and irradiation steps are repeated three times, and the obtained pinhole layer has a thickness of 30 nm and a pinhole diameter of 0.3 nm;

[0119] A MXene membrane with an ultra-large pore layer (thickness: 20 nm), a large pore layer (thickness: 20 nm), a medium pore layer (thickness: 30 nm), and a small pore layer (thickness: 30 nm) was obtained.

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

[0121] Comparative Example 6

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

[0123] Step (2) spin coating and irradiation steps were repeated 5 times, and the obtained macroporous layer had a thickness of 50 nm and a macropore diameter of 1.2 nm;

[0124] Step (3) spin coating and irradiation steps are repeated three times, and the resulting mesoporous layer has a thickness of 30 nm and a mesopore diameter of 0.6 nm;

[0125] Step (4) spin coating and irradiation steps are performed twice, and the obtained small pore layer thickness is 20nm and the small pore diameter is 0.3nm; a MXene film having a large pore layer (thickness: 50nm), a medium pore layer (thickness: 30nm), and a small pore layer (thickness: 20nm) is obtained.

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

[0127] Effect verification

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

[0129] First, 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 stepped pores (Example 1) are compared, as shown in Table 1:

[0130] Table 1

[0131]

[0132] According to Table 1, it can be found that with the extension of irradiation time, 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 both high H2 permeation rate and H2 / CO2 selectivity; however, the MXene membrane with stepped pores prepared in Example 1 has a nearly 5-fold increase in H2 permeation rate (from 320 GPU to 1564 GPU) compared with the original MXene membrane, and the selectivity is basically maintained (from 184 to 164). The macroporous layer (pore size: 1.2 nm) of the membrane can modify the polyethersulfone substrate with micropores. As a supporting layer, it effectively avoids the problem of increased defects in the MXene membrane due to excessive substrate pores. At the same time, since the macroporous layer has a larger pore size, it also contributes to the permeability of the membrane; in addition, the rich vertical multi-angstrom channels and interlayer channels in the mesoporous layer (pore size: 0.6 nm) and the small pore layer (pore size: 0.3 nm) give the MXene membrane an ultra-high H2 permeation rate and excellent H2 / CO2 selectivity.

[0133] Secondly, the present invention also explores the effects of the number of stages (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 stepped 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 when the number of levels in the MXene membrane with stepped pores is 3, and the thickness and irradiation time of each level from top to bottom are 40nm / 2min, 30nm / 5min and 30nm / 10min respectively (ie, Example 1), the optimal H2 / CO2 separation performance is exhibited.

[0137] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A MXene film with stepped pores, characterized in that: In addition to the base, from bottom to top, it includes: Ultra-macroporous MXene membrane layer, with a thickness of 0-30nm and a pore size of 2-5nm; Macroporous MXene membrane layer, thickness 0-30nm, pore size 0.9-1.2nm; Mesoporous MXene film layer, thickness is 20-50nm, pore size is 0.6-0.8nm; Small-pore MXene film layer, thickness 40-60nm, pore size 0.3-0.5nm; Among them, the overall thickness of the MXene film layer is 100nm.

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

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

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

5. A method for preparing a MXene film having stepped pores, characterized in that: The following steps are involved: The MXene nanosheet dispersion is spin-coated on a substrate, dried, and then plasma irradiated. The above operation is repeated to prepare a MXene film with stepped pores as described in any one of claims 1 to 4 by controlling the plasma irradiation time.

6. The method for preparing a MXene film with stepped pores according to claim 5, characterized in that: The concentration of MXene nanosheets in the MXene nanosheet dispersion is 0.5 mg / mL.

7. The method for preparing a MXene film with stepped pores according to claim 5, characterized in that: The drying process is: vacuum drying at 100° C. for 30 minutes.

8. The method for preparing a MXene film with stepped pores according to claim 5, characterized in that: The conditions during the plasma irradiation process are: The irradiation power is 100W; the gas flow rate is 100mL / min; and the irradiation time is 2-15min.

9. The method for preparing a MXene film with stepped pores according to claim 8, characterized in that: When the irradiation time is 11-15 min, it is a super-macroporous MXene film layer; When the irradiation time is 6-10 min, it is a macroporous MXene film layer; When the irradiation time is 3-5 min, it is a mesoporous MXene film layer; When the irradiation time is 1-2 min, it is a small-pore MXene film layer.

10. Use of the MXene membrane with stepped pores as claimed in any one of claims 1 to 4 in gas separation.

Images