METHOD FOR PREPARING TWO-DIMENSIONAL ORDERED MESOPOROUS NANOSHEETS BY INORGANIC SALT INTERFACE-INDUCED ASSEMBLY

Abstract

A method for preparing two-dimensional (2D) ordered mesoporous nanosheets by inorganic salt interface-induced assembly includes the following steps: carrying out, by using a soluble inorganic salt as a substrate and an amphiphilic block copolymer as a template, uniform mass diffusion of a target precursor solution at an inorganic salt crystal interface through vacuum filtration or low-speed centrifugation; forming a single-layer ordered mesoporous structure by using the solvent evaporation-induced co-assembly (EICA) technology; and promoting, through gradient temperature-controlled Ostwald ripening, the evaporation and induced formation of an organic solvent, and removing the template in N2 to obtain a 2D single-layer ordered mesoporous nanosheet material. The assembled nanosheet material has a large pore size, regular spherical pores and orderly arrangement. By changing the type of the precursor, a variety of mesoporous metal oxides, metal elements, inorganic non-metal nanosheets are synthesized.

Claims

1. A method for preparing two-dimensional (2D) ordered mesoporous nanosheets by inorganic salt interface-induced assembly, comprising the following steps: (1) preparing a nonmaterial precursor solution by using an amphiphilic block copolymer with a high molecular weight as a template; (2) introducing the nanomaterial precursor solution into a soluble inorganic salt serving as a substrate; guiding mass diffusion of the nanomaterial precursor solution in the soluble inorganic salt by a physical means of suction filtration or low-speed centrifugation to realize a single-layer dispersion interface on a surface of the precursor solution, wherein the suction filtration is less than 0.03 MPa, and the low-speed centrifugation is less than 4.000 rpm; (3) based on a principle of solvent evaporation-induced co-assembly (EICA), regulating a volatile organic solvent to evaporate at slow or medium-speed in a gradient temperature-controlled manner, to realize self-assembly of a molecular precursor and the amphiphilic block copolymer on a surface of the soluble inorganic salt; (4) heating up to 300-600° C. in N.sub.2; carrying out high-temperature calcination for 2-3 h to remove the amphiphilic block copolymer and to obtain a layered 2D ordered mesoporous organic/inorganic hybrid composite; heating up to 430-630° C. in air in a muffle furnace; carrying out high-temperature calcination for 2-3 h to remove residual carbon and to obtain a highly ordered mesoporous structure; dissolving the soluble inorganic salt template with a large amount of deionized water to obtain a 2D single-layer ordered mesoporous nanosheet material.

2. The method according to claim 1, wherein the amphiphilic block copolymer is a high-molecular-weight polymer, and the high-molecular-weight polymer is one or more selected from the group consisting of a commercial polyether template, PEO-b-PS, PEO-PPO-PEO and PS-b-P4VP[P]; wherein the commercial polyether template comprises F127; a target nanosheet raw material used is one or more selected from the group consisting of metal alkoxide, metal chloride, metal sulfate, acetylacetonate, inorganic non-metal precursor salt and phenolic formaldehyde resin; the volatile organic solvent used by the nanomaterial precursor solution is one or more selected from the group consisting of tetrahydrofuran (THF) and ethanol.

3. The method according to claim 2, wherein the soluble inorganic salt used is selected from the group consisting of NaCl, KCl and K.sub.2SO.sub.4.

4. The method according to claim 1, wherein when the volatile organic solvent is regulated in the gradient temperature-controlled manner, the solvent is gradiently and continuously evaporated at room temperature for 12-24 h, at 35-40° C. for 15-24 h and at 95-105° C. for 15-24 h.

5. The method according to 4, wherein a heating rate of the high-temperature calcination is 1-5° C./min.

6. The method according to claim 2, wherein a solution-phase assembly system of the 2D single-layer ordered mesoporous nanosheet material comprises 5-20 wt % of the target nanosheet raw material, 1-5 wt % of the amphiphilic block copolymer, 20-80 wt % of the soluble inorganic salt, and the balance being the volatile organic solvent.

7. A 2D ordered mesoporous nanosheet material prepared by the method according to claim 1, wherein a mesoporous size is changeable, the molecular weight of the amphiphilic block copolymer is adjustable within 18-50 nm, and the number of nanosheet layers is adjusted to 1-5 by changing a solubility of the molecular precursor, a suction filtration time or a centrifugation speed.

8. The method according to claim 2, wherein when the volatile organic solvent is regulated in the gradient temperature-controlled manner, the solvent is gradiently and continuously evaporated at room temperature for 12-24 h, at 35-40° C. for 15-24 h and at 95-105° C. for 15-24 h.

9. The method according to claim 3, wherein when the volatile organic solvent is regulated in the gradient temperature-controlled manner, the solvent is gradiently and continuously evaporated at room temperature for 12-24 h, at 35-40° C. for 15-24 h and at 95-105° C. for 15-24 h.

10. The method according to claim 4, wherein a solution-phase assembly system of the 2D single-layer ordered mesoporous nanosheet material comprises 5-20 wt % of a target nanosheet raw material, 1-5 wt % of the amphiphilic block copolymer, 20-80 wt % of the soluble inorganic salt, and the balance being the volatile organic solvent.

11. The 2D ordered mesoporous nanosheet material according to claim 7, wherein the amphiphilic block copolymer is a high-molecular-weight polymer, and the high-molecular-weight polymer is one or more selected from the group consisting of a commercial polyether template, PEO-b-PS, PEO-PPO-PEO and PS-b-P4VP; wherein the commercial polyether template comprises F127; a target nanosheet raw material used is one or more selected from the group consisting of metal alkoxide, metal chloride, metal sulfate, acetylacetonate, inorganic non-metal precursor salt and phenolic formaldehyde resin; the volatile organic solvent used by the nanomaterial precursor solution is one or more selected from the group consisting of tetrahydrofuran (THF) and ethanol.

12. The 2D ordered mesoporous nanosheet material according to claim 11, wherein the soluble inorganic salt used is selected from the group consisting of NaCl, KCl and K.sub.2SO.sub.4.

13. The 2D ordered mesoporous nanosheet material according to claim 12, wherein when the volatile organic solvent is regulated in the gradient temperature-controlled mariner, the solvent is gradiently and continuously evaporated at room temperature for 12-24 h, at 35-40° C. for 15-24 h and at 95-105° C. for 15-24 h.

14. The 2D ordered mesoporous nanosheet material to claim 13, wherein a heating rate of the high-temperature calcination is 1-5° C./min.

15. The 2D ordered mesoporous nanosheet material according to claim 7, wherein a solution-phase assembly system of the single-layer 2D ordered mesoporous nanosheet material comprises 5-20 wt % of a target nanosheet raw material, 1-5 wt % of the amphiphilic block copolymer, 20-80 wt % of the soluble inorganic salt, and the balance being the volatile organic solvent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1: Single-layer ordered mesoporous TiO.sub.2 nanosheet calcinated at 350° C. in N.sub.2, with a scale bar of 100 nm

[0025] FIG. 2: Single-layer ordered mesoporous TiO.sub.2 nanosheet calcinated at 350° C. in N.sub.2, with a scale bar of 50 nm

[0026] FIG. 3: Single-layer ordered mesoporous TiO.sub.2 nanosheet calcinated at 430° C. in air, with a scale bar of 100 nm

[0027] FIG. 4: Single-layer ordered mesoporous TiO.sub.2 nanosheet calcinated at 430° C. in air, with a scale bar of 50 nm

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The technical solutions of the present disclosure are described below with reference to the specific examples, but the protection scope of the present disclosure is not limited thereto. The present disclosure first prepares precursor solutions of different raw materials, and then assembles the precursor solution on the surface of an inorganic salt under the induction of a volatile solvent. The present disclosure is described in further detail below.

EXAMPLE 1

[0029] PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 g.Math.mol.sup.−1, 0.1 g) was dissolved and dispersed into 10.0 g of a tetrahydrofuran (THF) solution, and 2.0 g of a THF-soluble phenolic formaldehyde resin precursor (20 wt %, including 0.25 g of phenol and 0.15 g of fortnaldehyde) was added. Magnetic stirring was continued for 0.5 h at room temperature to generate a unifbrm transparent solution. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 12 h. Then the solvent was transferred to an oven at 35° C. to continuously evaporate for 15 h. The temperature was adjusted to 100° C. to continuously evaporate for 15 h. The solid was taken out and calcinated in a tube furnace at 300° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a two-dimensional (2D) single-layer ordered mesoporous polymer nanosheet with a pore size of 27 nm. If the solid was calcinated in a tube furnace at 600° C. in N.sub.2 for 3 h at a heating rate of 1° C./min, the finally obtained 2D single-layer ordered mesoporous carbon nanosheet had a pore size of 23 nm.

EXAMPLE 2

[0030] PEO.sub.117-h-PS.sub.113 (molecular weight 16,700 g.Math.mol.sup.−1, or F127) and tetrabutyl titanate (TROT, 0.2 g) were dissolved and dispersed into 10 mL of a THF solution. Concentrated hydrochloric acid (0.1 mL, 37%) and acetic acid (0.1 mL, 98%) were added. Magnetic stirring was continued for 0.5 h at room temperature. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 15 h. Then the solvent was transferred to an oven at 40° C. to continuously evaporate for 18 h. The temperature was adjusted to 105° C. to continuously evaporate for 24 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 2 h at a heating rate of 1° C./min so as to decompose the template. The solid was taken out and calcinated in a muffle furnace at 430° C. for 2 h at a heating rate of 1° C./min. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous nanosheet TiO.sub.2 with a pore size of 18 nm.

EXAMPLE 3

[0031] PEO.sub.117-h-PS.sub.113 (molecular weight 16,700 g.Math.mol.sup.−1, 40 mg) and ethyl orthosilicate (TEOS, 0.2 g) were dissolved and dispersed into 4.0 g of a THF solution. 0.1 M hydrochloric acid (0.06 g) was added. Magnetic stirring was continued for 0.5 h at room temperature to generate a uniform solution. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 18 h. Then the solvent was transferred to an oven at 42° C. to continuously evaporate for 18 h. The temperature was adjusted to 95° C. to continuously evaporate for 20 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. The solid was taken out and calcinated in a muffle furnace at 600° C. for 2 h at a heating rate of 1° C./min. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous nanosheet SiO.sub.2 with a pore size of 25 nm.

EXAMPLE 4

[0032] PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 gmol.sup.−1, 0.1 g) was dissolved and dispersed into 10.0 g of a tetrahydrofuran (THF) solution, and 0.5 g of aluminum acetylacetonate was added. Then concentrated nitric acid (0.17 mL) was added, and magnetic stirring was continued for 12 h at room temperature. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 20 h. Then the solvent was transferred to an oven at 45° C. to continuously evaporate for 22 h. The temperature was adjusted to 98° C. to continuously evaporate for 22 h. The solid was taken out and calcinated in a tube furnace at 400° C. in N.sub.2 for 2 h at a heating rate of 3° C./min so as to decompose the template. A resulting product was cooled, and transferred to a muffle furnace to calcinate at 630° C. in air for 3 h at a rate of 1° C./min. The product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous nanosheet Al.sub.2O.sub.3.

EXAMPLE 5

[0033] PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 gmol.sup.−1, 0.1 g) was dissolved and dispersed into 10.0 g of a THF solution, and 0.3 g of zirconium acetylacetonate was added. 0.15 mL of concentrated hydrochloric acid was added, and magnetic stirring was continued for 8 h at room temperature. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 20 h. Then the solvent was transferred to an oven at 38° C. to continuously evaporate for 20 h. The temperature was adjusted to 102° C. to continuously evaporate for 24 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. The solid was taken out and calcinated in a muffle furnace at 450° C. for 2 h at a heating rate of 5° C./min. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous nanosheet ZrO.sub.2.

EXAMPLE 6

[0034] PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 g.Math.mol.sup.−1, 0.1 g) was dissolved and dispersed into 4 mL of an N,N-dimethylformamide/ethanol mixed solution. Then 0.15 g of zirconium acetylacetonate and 0.104 g of TBOT were added. Magnetic stirring was continued for 2 h at room temperature. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 24 h. Then the solvent was transferred to an oven at 40° C. to continuously evaporate for 24 h. The temperature was adjusted to 105° C. to continuously evaporate for 24 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. A resulting product was cooled, and transferred to a muffle furnace to calcinate at 450° C. for 2 h at a heating rate of 1° C./min. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2.1) single-layer ordered mesoporous polymer nanosheet ZrTiO.sub.4.

EXAMPLE 7

[0035] PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 gmol.sup.−1, 0.1 g) was dissolved and dispersed into 10.0 g of a THF solution, and 0.4 g of zirconium acetylacetonate and 0.4 g of CeCl.sub.3.Math.6H.sub.2O were added. Magnetic stirring was continued for 2 h at room temperature. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 24 h. Then the solvent was transferred to an oven at 35° C. to continuously evaporate for 24 h. The temperature was adjusted to 95° C. to continuously evaporate for 24 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. A resulting product was cooled, and transferred to a muffle furnace to calcinate at 450° C. in air for 2 h at a rate of 5° C./min. The product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous polymer nanosheet Ce.sub.0.5Zr.sub.0.5O.sub.2.

EXAMPLE 8

[0036] A CeO.sub.2 nanocrystal with a particle size of <5 nm was synthesized by pyrolysis, and the CeO.sub.2 nanocrystal was subjected to surface hydrophilic treatment with 4-hydroxybenzoic acid to serve as a metal precursor, PEO.sub.117-b-PS.sub.113 (molecular weight 16,700 g.Math.mol.sup.−1, 20 mg) was dissolved and dispersed in 2.0 g of a THF solution. 40 mg of the modified CeO.sub.2 nanocrystal was dispersed in 2.0 mL of an anhydrous ethanol solution. These solutions were mixed uniformly and stirred at room temperature for 2 h. A certain amount of mixed solution was added into a solid crystal powder of inorganic salt NaCl. Lower than 0.03 MPa/30-120 s suction filtration (or 3,000 rpm/3 min centrifugation) was carried out. A small amount of precursor solution was attached to a NaCl crystal surface. A yielded solid was placed in a jar to evaporate the solvent at room temperature for 20 h, Then the solvent was transferred to an oven at 40° C. to continuously evaporate for 24 h. The temperature was adjusted to 100° C. to continuously evaporate for 24 h. The solid was taken out and calcinated in a tube furnace at 350° C. in N.sub.2 for 3 h at a heating rate of 1° C./min so as to decompose the template. The solid was taken out and calcinated in a muffle furnace at 450° C. for 2 h at a heating rate of 5° C./min. A resulting product was cooled, and washed 3-5 times with deionized water to remove the NaCl template, thereby obtaining a 2D single-layer ordered mesoporous nanosheet CeO.sub.2 with a pore size of 27 nm. If the template was replaced with PEO.sub.234-b-PS.sub.266 with a higher molecular weight (molecular weight 39,000 g˜mol−1, 20 mg), the finally obtained nanosheet had a pore size of 35 nm. If the template was replaced with PEO.sub.468-b-PS.sub.307 (molecular weight 51,000 g.Math.mol.sup.−1, 20 mg), the finally obtained nanosheet had a pore size of 48 nm.

[0037] The preferred specific examples of the present disclosure are described in detail above. It should be understood that a person of ordinary skill in the art can make various modifications and variations according to the concept of the present disclosure without creative efforts. Therefore, all technical solutions derived by those skilled in the art through logical analysis, reasoning or finite experiments based on the concept of the present disclosure should fall within the protection scope defined by the appended claims.