A ZIF-8 / GO composite membrane, its preparation method and application

Abstract

This invention provides a ZIF-8 / GO composite membrane, its preparation method, and its applications. The ZIF-8 / GO composite membrane is prepared by uniformly dispersing ZIF-8 / GO nanosheets modified with a modifying agent in water or methanol, filtering the resulting filtrate onto a polymer membrane substrate or a positive alumina template, and then drying. The modified ZIF-8 / GO nanosheets are prepared by calcining ZIF-8 / GO nanosheets in air or an inert atmosphere, dispersing the calcined ZIF-8 / GO nanosheets in a first solvent, adding a modifying agent, and then performing a chemical modification reaction. The ZIF-8 / GO composite membrane provided by this invention has adjustable surface properties, such as surface charge, and is easy to assemble into devices, making it widely applicable in fields such as ion selective transport.

Description

Technical Field

[0001] This invention relates to a ZIF-8 / GO composite membrane, its preparation method and application, belonging to the field of composite material preparation and membrane separation technology. Background Technology

[0002] Achieving efficient ion-selective transport is of great significance in fields such as chemical separation, energy conversion, and sensing. Metal-organic frameworks (MOFs) are crystalline framework materials with intramolecular pores formed by the self-assembly of metal ions or clusters with organic ligands through coordination bonds under certain conditions. These materials have advantages such as large specific surface area, high porosity, and tunable pore size and shape, making them ideal materials for preparing ion-selective membranes. However, MOF materials themselves are difficult to form membranes on their own, so it is necessary to combine them with other materials, such as two-dimensional materials (graphene oxide (GO), molybdenum dioxide, and MXene, etc.), to prepare composite membranes of MOF materials (see Chinese Patent CN 111569665 A). Currently, these MOF-based ion-selective membranes mainly achieve high ion selectivity based on their size effect, but they are difficult to effectively select for anions and cations of similar size, which greatly limits the application of MOF-based membranes. To address this problem, a feasible solution is to introduce functional groups into the metal-organic framework materials through post-modification (see Chinese Patent CN107722287A). Post-modification methods for MOFs mainly include covalent modification with organic ligands, coordination covalent modification with metal ions or organic ligands, and ligand exchange. However, existing post-modification methods suffer from problems such as a limited number of reactive sites and low modification efficiency, which restricts the preparation of functionalized metal-organic framework materials.

[0003] Therefore, there is an urgent need to develop new and efficient post-modification techniques to precisely control the chemical environment of MOFs in order to prepare high-performance metal-organic framework composite films. Summary of the Invention

[0004] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide a ZIF-8 / GO nanosheet modified with a modifying reagent.

[0005] Another object of the present invention is to provide a method for preparing ZIF-8 / GO nanosheets modified with the above-described modifying reagents.

[0006] Another object of the present invention is to provide a ZIF-8 / GO composite membrane, which is prepared by using ZIF-8 / GO nanosheets modified with the above-described modifying agents.

[0007] Another object of the present invention is to provide a method for preparing the ZIF-8 / GO composite membrane described above.

[0008] A final objective of this invention is to provide the application of the ZIF-8 / GO composite membrane described above in ion-selective transport.

[0009] To achieve the above objectives, on the one hand, the present invention provides ZIF-8 / GO nanosheets modified with a modifying reagent, wherein the ZIF-8 / GO nanosheets modified with the modifying reagent are prepared by calcining ZIF-8 / GO nanosheets in an air atmosphere or an inert atmosphere, dispersing the calcined ZIF-8 / GO nanosheets in a first solvent, adding a modifying reagent, and then carrying out a chemical modification reaction.

[0010] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the calcination temperature is 200-450℃ and the time is 0.5-7h in an air atmosphere; the calcination temperature is 300-600℃ and the time is 0.5-7h in an inert atmosphere.

[0011] In one specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the inert atmosphere includes a nitrogen atmosphere.

[0012] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the first solvent includes one or a combination of toluene, chloroform, acetone and ethyl acetate.

[0013] In a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the concentration of ZIF-8 / GO nanosheets in the first solvent is 5-30 mg / mL, based on the total volume of the first solvent.

[0014] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the modifying agent includes one of the amine reagents such as ethylenediamine, hexamethylenediamine, or 3-aminopropyltriethoxysilane.

[0015] In a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the concentration of the modifying reagent is 0.01-2 mmol / mL based on the total volume of the first solvent.

[0016] In one specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the temperature of the chemical modification reaction is 60-120°C and the time is 1-24h.

[0017] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the ZIF-8 / GO nanosheets are prepared by a method comprising the following steps:

[0018] Graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole were added to a second solvent to obtain a graphene oxide dispersion, a zinc nitrate hexahydrate solution, and a 2-methylimidazole solution, respectively.

[0019] Zinc nitrate hexahydrate solution was added to graphene oxide dispersion, followed by 2-methylimidazole solution, and then mixed thoroughly to obtain precursor mixture.

[0020] The precursor mixture was reacted at a certain temperature for a period of time to obtain a ZIF-8 / GO suspension. The suspension was then centrifuged, washed, and dried to obtain ZIF-8 / GO nanosheets.

[0021] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the mass ratio of graphene oxide, zinc nitrate hexahydrate and 2-methylimidazole is (1-5):(40-80):(45-90).

[0022] Based on the total volume of the second solvent, the concentration range of the graphene oxide dispersion is 0.2-4 mg / mL, the concentration range of the zinc nitrate hexahydrate solution is 5-50 mg / mL, and the concentration of the 2-methylimidazole solution is 10-100 mg / mL.

[0023] In this invention, the concentrations of the graphene oxide dispersion, zinc nitrate hexahydrate solution, and 2-methylimidazole solution used in the preparation of the ZIF-8 / GO nanosheets are all relatively high. This facilitates the rapid formation of crystal nuclei, which in turn helps the uniform growth of ZIF-8 on the GO surface to obtain the ZIF-8 / GO nanosheets.

[0024] In a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the second solvent includes one or a combination of deionized water, methanol, ethanol, and N,N dimethylformamide.

[0025] In this invention, the second solvent used to prepare the graphene oxide dispersion, zinc nitrate hexahydrate solution, and 2-methylimidazole solution can be the same or different.

[0026] In one specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the precursor mixture is reacted at 25-150°C for 0.5-5 hours.

[0027] As a specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, centrifugation, washing, drying, etc. are all conventional operations in the art. Those skilled in the art can reasonably perform these operations according to actual operational needs, as long as the corresponding purpose of this invention can be achieved.

[0028] In one specific embodiment of the ZIF-8 / GO nanosheets described above in this invention, the drying process is carried out at 60-150°C for 12-48 hours.

[0029] On the other hand, the present invention also provides a method for preparing ZIF-8 / GO nanosheets modified with the above-described modifying reagents, wherein the preparation method includes:

[0030] ZIF-8 / GO nanosheets were calcined in air or an inert atmosphere to obtain calcined ZIF-8 / GO nanosheets.

[0031] The calcined ZIF-8 / GO nanosheets were then dispersed in a first solvent, and a modifying agent was added. The mixture was then subjected to a chemical modification reaction under heating conditions. After the reaction was completed, ZIF-8 / GO nanosheets modified with the modifying agent were obtained.

[0032] In one specific embodiment of the preparation method described above in this invention, the calcination can be carried out in a tube furnace or a muffle furnace.

[0033] This invention uses 2-methylimidazolium zinc salt (ZIF-8) as a typical metal-organic framework material to prepare chemically bonded 2-methylimidazolium zinc salt / graphene oxide (ZIF-8 / GO) nanosheets. After calcination, the ZIF-8 / GO nanosheets are then controllably modified using amine reagents. Specifically, this invention uses one of the amine reagents, such as ethylenediamine, hexamethylenediamine, or 3-aminopropyltriethoxysilane, as the modifying reagent, and grafts the modifying reagent onto the surface of ZIF-8 with the aid of calcination. This alters many properties of the material, including but not limited to surface charge density, and also facilitates the formation of films (i.e., ZIF-8 / GO composite films) from the modified ZIF-8 / GO nanosheets.

[0034] In another aspect, the present invention also provides a ZIF-8 / GO composite membrane, wherein the ZIF-8 / GO composite membrane is prepared by uniformly dispersing ZIF-8 / GO nanosheets modified by the above-mentioned modifying reagent in water or methanol, filtering the resulting filtrate onto a polymer membrane substrate or a positive alumina template, and then drying it.

[0035] In a specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the concentration of the ZIF-8 / GO nanosheets modified by the modifying agent in the filtrate is 0.10-2 mg / mL, based on the total volume of the water or methanol.

[0036] As a specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the polymer membrane includes flexible polymer membranes such as polytetrafluoroethylene membrane, cellulose acetate membrane, or polyvinylidene fluoride membrane.

[0037] In one specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the pore size of the polymer membrane is 0.05-1 μm.

[0038] In one specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the positive alumina template is a rigid anodic alumina membrane (AAO).

[0039] In one specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the pore size of the rigid anodic aluminum oxide membrane is 0.05-0.4 μm.

[0040] In one specific embodiment of the ZIF-8 / GO composite membrane described above in this invention, the drying process is carried out at 60-120°C for 6-24 hours.

[0041] Finally, the present invention also provides the application of the ZIF-8 / GO composite membrane described above in ion selective transport.

[0042] This invention utilizes a calcination-assisted grafting method to prepare ZIF-8 / GO nanosheets modified with a modifying reagent, achieving efficient and homogeneous modification of metal-organic framework materials.

[0043] Meanwhile, the present invention also utilizes the modified ZIF-8 / GO nanosheets to prepare ZIF-8 / GO composite films under relatively mild conditions. The surface properties of the obtained ZIF-8 / GO composite films, such as surface charge, are adjustable and they are easy to assemble into devices, which have broad application value in fields such as ion selective transport. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the preparation process of the ZIF-8 / GO composite membrane provided in an embodiment of the present invention.

[0046] Figure 2 This is a SEM image of the ZIF-8 / GO nanosheets prepared in Example 1 of this invention.

[0047] Figure 3 This is a SEM image of the ethylenediamine-modified ZIF-8 / GO nanosheets prepared in Example 2 of this invention.

[0048] Figure 4 This is a photograph of the ZIF-8 / GO composite membrane prepared in Example 3 of the present invention.

[0049] Figure 5 The graph shows the surface Zeta potential test results of the ZIF-8 / GO composite films prepared in Examples 1-4 of Test Example 1 of this invention.

[0050] Figure 6 This is a schematic diagram of the test apparatus used to test the permeation energy conversion performance of the ZIF-8 / GO composite membrane in Test Example 2 of the present invention.

[0051] Figure 7 This is a schematic diagram showing the voltage output of the ZIF-8 / GO composite membrane prepared in Examples 1-4 of Test Example 2 of the present invention when used for permeation energy power generation. Detailed Implementation

[0052] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail with reference to the following specific embodiments, but this should not be construed as limiting the scope of implementation of the present invention.

[0053] Example 1

[0054] This embodiment provides a ZIF-8 / GO composite membrane, wherein the preparation process of the ZIF-8 / GO composite membrane is shown in the schematic diagram below. Figure 1 As shown, from Figure 1 As can be seen from this, it is prepared by a method including the following steps:

[0055] (1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio of 1:32:18), and add them to methanol to obtain a graphene oxide dispersion with a concentration of 3 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 16 mg / mL, and a 2-methylimidazole solution with a concentration of 30 mg / mL. Add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution and mix well to obtain a precursor mixture. Stir the precursor mixture magnetically at room temperature for 3 h to obtain a suspension. Centrifuge the suspension, wash it, and then dry the solid product at 150 °C in a vacuum oven for 12 h to obtain ZIF-8 / GO nanosheets. The SEM image is shown below. Figure 2 ,from Figure 2 As can be seen, ZIF-8 particles grow uniformly and orderly on the ZIF-8 / GO composite nanosheets prepared in this embodiment;

[0056] (2) The obtained ZIF-8 / GO nanosheets were placed in a muffle furnace and calcined at 300°C for 3 hours under air atmosphere to obtain calcined ZIF-8 / GO nanosheets.

[0057] (3) The calcined ZIF-8 / GO nanosheets were dispersed in chloroform, wherein the concentration of ZIF-8 / GO nanosheets in chloroform was 15 mg / mL. Hexamethylenediamine was added, and the concentration of hexamethylenediamine was 0.5 mmol / mL. The mixture was heated to 80 °C and stirred continuously for 12 h. After filtration and washing, hexamethylenediamine-modified ZIF-8 / GO nanosheets were obtained.

[0058] (4) Disperse the hexamethylenediamine-modified ZIF-8 / GO nanosheets in water to obtain a filtrate with a nanosheet concentration of 1 mg / mL. Filter the filtrate onto a polytetrafluoroethylene membrane (pore size of 0.44 μm) and then vacuum dry it at 60 °C for 12 h to obtain a ZIF-8 / GO composite membrane.

[0059] Example 2

[0060] This embodiment provides a ZIF-8 / GO composite membrane, wherein the preparation process of the ZIF-8 / GO composite membrane is shown in the schematic diagram below. Figure 1 As shown, from Figure 1 As can be seen from this, it is prepared by a method including the following steps:

[0061] (1) Weigh graphene oxide, zinc nitrate hexahydrate and 2-methylimidazole (mass ratio of the three is 1:16:18), and add them to methanol to obtain a graphene oxide dispersion with a concentration of 4 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 30 mg / mL and a 2-methylimidazole solution with a concentration of 48 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 1 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 120℃ for 12 h to obtain ZIF-8 / GO nanosheets;

[0062] (2) The obtained ZIF-8 / GO nanosheets were placed in a muffle furnace and calcined at 350°C for 2 hours under air atmosphere to obtain calcined ZIF-8 / GO nanosheets.

[0063] (3) The calcined ZIF-8 / GO nanosheets were dispersed in toluene at a concentration of 20 mg / mL. Ethylenediamine was added at a concentration of 0.8 mmol / mL. The mixture was heated to 75 °C and stirred continuously for 8 h. After filtration and washing, ethylenediamine-modified ZIF-8 / GO nanosheets were obtained. The SEM image of the nanosheets is shown below. Figure 3 As shown, from Figure 3 As can be seen, compared with the original ZIF-8 / GO nanosheets, the surface morphology of ZIF-8 / GO nanosheets did not change significantly after calcination modification; in addition, from Figure 2 and Figure 3 The SEM images also show that the ZIF-8 / GO nanosheets prepared in this embodiment of the invention are highly regular sheet-like materials with relatively intact layers. In summary, the ZIF-8 / GO nanosheets prepared in this embodiment of the invention are regular sheet-like materials with relatively intact layers, and ZIF-8 particles grow uniformly and orderly on the ZIF-8 / GO composite nanosheets. These characteristics all contribute to the stacking of the ZIF-8 / GO nanosheets prepared in this embodiment of the invention to form a ZIF-8 / GO composite film.

[0064] (4) Disperse the ethylenediamine-modified ZIF-8 / GO nanosheets in water to obtain a filtrate with a nanosheet concentration of 2 mg / mL. Filter the filtrate onto a polytetrafluoroethylene membrane (pore size of 0.22 μm) and then vacuum dry it at 60 °C for 24 h to obtain a ZIF-8 / GO composite membrane.

[0065] Example 3

[0066] This embodiment provides a ZIF-8 / GO composite membrane, wherein the preparation process of the ZIF-8 / GO composite membrane is shown in the schematic diagram below. Figure 1 As shown, from Figure 1 As can be seen from this, it is prepared by a method including the following steps:

[0067] (1) Weigh graphene oxide, zinc nitrate hexahydrate and 2-methylimidazole (mass ratio of the three is 1:8:9), and add them to methanol to obtain a graphene oxide dispersion with a concentration of 3 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 15 mg / mL and a 2-methylimidazole solution with a concentration of 30 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 1 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 140℃ for 20 h to obtain ZIF-8 / GO nanosheets;

[0068] (2) The obtained ZIF-8 / GO nanosheets were placed in a muffle furnace and calcined at 450°C for 6 hours under a nitrogen atmosphere to obtain calcined ZIF-8 / GO nanosheets.

[0069] (3) The calcined ZIF-8 / GO nanosheets were dispersed in chloroform, wherein the concentration of ZIF-8 / GO nanosheets in chloroform was 10 mg / mL. 3-aminopropyltriethoxysilane was added, and the concentration of 3-aminopropyltriethoxysilane was 1 mmol / mL. The mixture was heated to 60 °C and stirred continuously for 15 h. After filtration and washing, ZIF-8 / GO nanosheets modified with 3-aminopropyltriethoxysilane were obtained.

[0070] (4) 3-aminopropyltriethoxysilane-modified ZIF-8 / GO nanosheets were dispersed in methanol to obtain a filtrate with a nanosheet concentration of 1 mg / mL; the filtrate was filtered onto an AAO film (pore size 200 nm), and then vacuum dried at 60 °C for 15 h to obtain a ZIF-8 / GO composite membrane, the actual image of which is shown below. Figure 4 As shown.

[0071] Example 4

[0072] This embodiment provides a ZIF-8 / GO composite membrane, wherein the preparation process of the ZIF-8 / GO composite membrane is shown in the schematic diagram below. Figure 1 As shown, from Figure 1 As can be seen from this, it is prepared by a method including the following steps:

[0073] (1) Weigh graphene oxide, zinc nitrate hexahydrate and 2-methylimidazole (mass ratio of the three is 1:8:9), and add them to methanol to obtain a graphene oxide dispersion with a concentration of 4 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 5 mg / mL and a 2-methylimidazole solution with a concentration of 50 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 5 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 140℃ for 15 h to obtain ZIF-8 / GO nanosheets;

[0074] (2) The obtained ZIF-8 / GO nanosheets were placed in a muffle furnace and calcined at 300°C for 3 hours under air atmosphere to obtain calcined ZIF-8 / GO nanosheets.

[0075] (3) The calcined ZIF-8 / GO nanosheets were dispersed in chloroform, with a concentration of 30 mg / mL in chloroform. Hexamethylenediamine was added with a concentration of 2 mmol / mL. The mixture was heated to 90 °C and stirred continuously for 6 h. After filtration and washing, hexamethylenediamine-modified ZIF-8 / GO nanosheets were obtained.

[0076] (4) Disperse the hexamethylenediamine-modified ZIF-8 / GO nanosheets in water to obtain a filtrate with a nanosheet concentration of 2 mg / mL. Filter the filtrate onto a cellulose acetate membrane (pore size of 1 μm) and then vacuum dry it at 60 °C for 15 h to obtain a ZIF-8 / GO composite membrane.

[0077] Comparative Example 1

[0078] This comparative example provides a ZIF-8 / GO composite film, wherein the ZIF-8 / GO composite film is prepared using unmodified ZIF-8 / GO nanosheets, and is prepared by a method including the following steps:

[0079] 1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio 1:32:18), and add them separately to methanol to obtain a graphene oxide dispersion with a concentration of 3 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 16 mg / mL, and a 2-methylimidazole solution with a concentration of 30 mg / mL. Add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution and mix well to obtain a precursor mixture. Stir the precursor mixture magnetically at room temperature for 3 hours to obtain a suspension. Centrifuge the suspension, wash it, and then dry the solid product at 150℃ in a vacuum oven for 12 hours to obtain ZIF-8 / GO nanosheets. The SEM image is shown below. Figure 2 ,from Figure 2 As can be seen, ZIF-8 particles grow uniformly and orderly on the ZIF-8 / GO composite nanosheets prepared in this embodiment;

[0080] 2) Disperse ZIF-8 / GO nanosheets in water to obtain a filtrate with a nanosheet concentration of 1 mg / mL. Filter the filtrate onto a polytetrafluoroethylene membrane (pore size of 0.44 μm) and then vacuum dry it at 60 °C for 12 h to obtain a ZIF-8 / GO composite membrane, which is an unmodified ZIF-8 / GO composite membrane.

[0081] Comparative Example 2

[0082] This comparative example provides a ZIF-8 / GO composite film, wherein the ZIF-8 / GO composite film is prepared using unmodified ZIF-8 / GO nanosheets, and is prepared by a method including the following steps:

[0083] 1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio of 1:16:18), and add them to methanol to obtain a graphene oxide dispersion with a concentration of 4 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 30 mg / mL, and a 2-methylimidazole solution with a concentration of 48 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, and mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 1 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 120 °C for 12 h to obtain ZIF-8 / GO nanosheets;

[0084] 2) The ZIF-8 / GO nanosheets were dispersed in water to obtain a filtrate with a nanosheet concentration of 2 mg / mL. The filtrate was then filtered onto a polytetrafluoroethylene membrane (pore size of 0.22 μm) and dried under vacuum at 60 °C for 24 h to obtain a ZIF-8 / GO composite membrane, which is an unmodified ZIF-8 / GO composite membrane.

[0085] Comparative Example 3

[0086] This comparative example provides a ZIF-8 / GO composite film, wherein the ZIF-8 / GO composite film is prepared using unmodified ZIF-8 / GO nanosheets, and is prepared by a method including the following steps:

[0087] 1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio of 1:8:9), and add them separately to methanol to obtain a graphene oxide dispersion with a concentration of 3 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 15 mg / mL, and a 2-methylimidazole solution with a concentration of 30 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 1 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 140℃ for 20 h to obtain ZIF-8 / GO nanosheets;

[0088] 2) The ZIF-8 / GO nanosheets were dispersed in methanol to obtain a filtrate with a nanosheet concentration of 1 mg / mL; the filtrate was filtered onto an AAO (pore size of 200 nm) and then vacuum dried at 60 °C for 15 h to obtain a ZIF-8 / GO composite membrane, which is an unmodified ZIF-8 / GO composite membrane.

[0089] Comparative Example 4-1

[0090] This comparative example provides a ZIF-8 / GO composite film, wherein the ZIF-8 / GO composite film is prepared using unmodified ZIF-8 / GO nanosheets, and is prepared by a method including the following steps:

[0091] 1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio of 1:8:9), and add them separately to methanol to obtain a graphene oxide dispersion with a concentration of 4 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 5 mg / mL, and a 2-methylimidazole solution with a concentration of 50 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, and mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 5 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 140℃ for 15 h to obtain ZIF-8 / GO nanosheets;

[0092] 2) The ZIF-8 / GO nanosheets were dispersed in water to obtain a filtrate with a nanosheet concentration of 2 mg / mL. The filtrate was then filtered onto a cellulose acetate membrane (pore size of 1 μm) and dried under vacuum at 60 °C for 15 h to obtain a ZIF-8 / GO composite membrane, which is an unmodified ZIF-8 / GO composite membrane.

[0093] Comparative Example 4-2

[0094] This comparative example provides a ZIF-8 / GO composite membrane, wherein the ZIF-8 / GO composite membrane is prepared by a method comprising the following steps:

[0095] 1) Weigh graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole (mass ratio of 1:8:9), and add them separately to methanol to obtain a graphene oxide dispersion with a concentration of 4 mg / mL, a zinc nitrate hexahydrate solution with a concentration of 5 mg / mL, and a 2-methylimidazole solution with a concentration of 50 mg / mL; add the zinc nitrate hexahydrate solution to the graphene oxide dispersion, then add the 2-methylimidazole solution, and mix well to obtain a precursor mixture; stir the precursor mixture magnetically at room temperature for 5 h to obtain a suspension, centrifuge the suspension, wash it, and then dry the solid product in a vacuum oven at 140℃ for 15 h to obtain ZIF-8 / GO nanosheets;

[0096] 2) The obtained ZIF-8 / GO nanosheets were dispersed in chloroform, wherein the concentration of ZIF-8 / GO nanosheets in chloroform was 30 mg / mL. Hexamethylenediamine was added, and the concentration of hexamethylenediamine was 2 mmol / mL. The mixture was heated to 90 °C and stirred continuously for 6 h. After filtration and washing, hexamethylenediamine-modified ZIF-8 / GO nanosheets were obtained.

[0097] 3) Disperse hexamethylenediamine-modified ZIF-8 / GO nanosheets in water to obtain a filtrate with a nanosheet concentration of 2 mg / mL. Filter the filtrate onto a cellulose acetate membrane (pore size 1 μm) and then vacuum dry it at 60 °C for 15 h to obtain a ZIF-8 / GO composite membrane.

[0098] Test Example 1

[0099] This test example uses conventional methods in the art to test the surface Zeta potential of the ZIF-8 / GO composite films prepared in Examples 1-4 and Comparative Examples 1-3, and Comparative Examples 4-1 to 4-2. The experimental results are as follows: Figure 5 As shown.

[0100] from Figure 5 As can be seen, compared with the unmodified ZIF-8 / GO composite films prepared in Comparative Examples 1-3 and Comparative Examples 4-1, the surface Zeta potential of the ZIF-8 / GO composite films modified with the modification reagent prepared in Examples 1-4 of the present invention is significantly improved.

[0101] Meanwhile, comparing Example 4 with Comparative Examples 4-1 and 4-2, it can be seen that, compared with the unmodified ZIF-8 / GO composite film prepared without calcination in Comparative Example 4-1, the ZIF-8 / GO composite film prepared directly by chemical modification with a modifying agent without calcination in Comparative Example 4-2 shows little change in zeta potential. This indicates that the modification efficiency is low because the chemical modification with the modifying agent is performed directly without calcination in Comparative Example 4-2. However, the surface zeta potential of the ZIF-8 / GO composite films prepared in Comparative Examples 4-1 and 4-2 is significantly lower than that of the ZIF-8 / GO composite film prepared in Example 4 of this invention. This indicates that in Example 4 of this invention, the ZIF-8 / GO nanosheets are first calcined, and then the calcined ZIF-8 / GO nanosheets are chemically modified with a modifying agent. The modifying agent is efficiently grafted onto ZIF-8. That is, this invention utilizes calcination-assisted modification to achieve efficient homogeneous modification of metal-organic frameworks.

[0102] Test Example 2

[0103] This test example examines the permeation energy conversion performance of the ZIF-8 / GO composite membranes prepared in Examples 1-4, Comparative Examples 1-3, and Comparative Examples 4-1 to 4-2. A schematic diagram of the testing apparatus is shown below. Figure 6As shown, the left and right sides of the device contain a 0.001 mol / L NaCl solution (i.e., a low-concentration electrolyte) and a 1 mol / L NaCl solution (a high-concentration electrolyte), respectively. A silver / silver chloride standard electrode is used as the electrode. ZIF-8 / GO composite membranes prepared in Examples 1-4 and Comparative Examples 1-3, 4-1, and 4-2 are used as ion transport membranes. During the test, the output voltage of the device is measured using a multimeter. The results are shown in the figure below. Figure 7 As shown.

[0104] from Figure 7 As can be seen, compared with the unmodified ZIF-8 / GO composite membranes prepared in Comparative Examples 1-3 and Comparative Examples 4-1, the output voltage of the modified ZIF-8 / GO composite membranes prepared in Examples 1-4 of the present invention is significantly improved. This indicates that in Examples 1-4 of the present invention, the ZIF-8 / GO nanosheets were first calcined, and then the calcined ZIF-8 / GO nanosheets were chemically modified with a modifying agent. The modifying agent was efficiently grafted onto ZIF-8, thereby enabling the modified ZIF-8 / GO composite membranes prepared in the examples to have a strong membrane surface charge, which can realize the controllable transport of ions.

[0105] Meanwhile, comparing Example 4 with Comparative Examples 4-1 and 4-2, it can be seen that compared with the unmodified ZIF-8 / GO composite membrane prepared without calcination in Comparative Example 4-1, the output voltage of the ZIF-8 / GO composite membrane prepared directly by chemical modification with the modifying reagent in Comparative Example 4-2 without calcination does not change significantly. This indicates that because the chemical modification with the modifying reagent was performed directly without calcination in Comparative Example 4-2, the modification efficiency was low, and the resulting ZIF-8 / GO composite membrane modified with the modifying reagent had a weaker surface charge. However, The output voltages of the ZIF-8 / GO composite membranes prepared in Comparative Examples 4-1 and 4-2 were significantly lower than those of the ZIF-8 / GO composite membrane prepared in Example 4 of this invention. This indicates that in Example 4 of this invention, the ZIF-8 / GO nanosheets were first calcined, and then the calcined ZIF-8 / GO nanosheets were chemically modified with a modifying agent. The modifying agent was efficiently grafted onto ZIF-8, thereby enabling the ZIF-8 / GO composite membrane prepared in Example 4 to have a strong membrane surface charge, which can realize the controllable transport of ions.

[0106] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A ZIF-8 / GO nanoplatelet modified for ion-selective transport of a modifying agent, characterized in that, The ZIF-8 / GO nanosheet modified by the modification reagent for ion selective transmission is prepared by calcining ZIF-8 / GO nanosheets in an air atmosphere or an inert atmosphere, dispersing the calcined ZIF-8 / GO nanosheets in a first solvent, and then performing a chemical modification reaction after adding a modification reagent. In the air atmosphere, the calcination temperature is 200-450 DEG C, and the time is 0.5-7 h; in the inert atmosphere, the calcination temperature is 300-600 DEG C, and the time is 0.5-7 h.

2. The modification reagent modified ZIF-8 / GO nanoplatelets for ion selective transport according to claim 1, wherein, The inert atmosphere includes a nitrogen atmosphere.

3. The modification reagent modified ZIF-8 / GO nanoplatelets for ion selective transport according to claim 1, wherein, The first solvent includes one or a combination of toluene, chloroform, acetone, and ethyl acetate.

4. The ZIF-8 / GO nanoplatelets modified for ion-selective transport according to claim 1 or 3, wherein, The concentration of the ZIF-8 / GO nanosheets in the first solvent is 5-30 mg / mL based on the total volume of the first solvent.

5. The modification reagent modified ZIF-8 / GO nanoplatelets for ion selective transport of claim 1, wherein, The modification reagent includes one of ethylenediamine, hexanediamine, or 3-aminopropyltriethoxysilane.

6. The ZIF-8 / GO nanoplatelets modified for ion-selective transport according to claim 1 or 5, wherein, The concentration of the modification reagent is 0.01-2 mmol / mL based on the total volume of the first solvent.

7. The ZIF-8 / GO nanoplatelets modified for ion-selective transport of the modifying reagent according to claim 1, characterized in that, The temperature of the chemical modification reaction is 60-120 DEG C, and the time is 1-24 h.

8. The modification reagent modified ZIF-8 / GO nanoplatelets for ion selective transport of claim 1, wherein, The ZIF-8 / GO nanosheet is prepared by a preparation method including the following steps: The graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole are respectively added to a second solvent to obtain a graphene oxide dispersion, a zinc nitrate hexahydrate solution, and a 2-methylimidazole solution; The zinc nitrate hexahydrate solution is added to the graphene oxide dispersion, and the 2-methylimidazole solution is then added and mixed uniformly to obtain a precursor mixture; The precursor mixture is reacted at a certain temperature for a period of time to obtain a ZIF-8 / GO suspension, which is then centrifuged, washed, and dried to obtain ZIF-8 / GO nanosheets.

9. The modification reagent modified ZIF-8 / GO nanoplatelets for ion selective transport of claim 8, wherein, The mass ratio of the graphene oxide, zinc nitrate hexahydrate, and 2-methylimidazole is (1-5):(40-80):(45-90). The concentration of the graphene oxide dispersion is 0.2-4 mg / mL, the concentration of the zinc nitrate hexahydrate solution is 5-50 mg / mL, and the concentration of the 2-methylimidazole solution is 10-100 mg / mL based on the total volume of the second solvent.

10. The modification reagent modified ZIF-8 / GO nanoplatelets for ion- selective transport according to claim 8 or 9, wherein, The second solvent includes one or a combination of deionized water, methanol, ethanol, and N-N dimethylformamide.

11. The ZIF-8 / GO nanoplatelets modified for ion-selective transport according to claim 8 or 9, wherein, The precursor mixture is reacted at 25-150 DEG C for 0.5-5 h.

12. A method for the preparation of ZIF-8 / GO nanoplatelets for ion selective transport modified with the modification reagent of any one of claims 1-11, characterized in that, The preparation method includes: The ZIF-8 / GO nanosheets are calcined in an air atmosphere or an inert atmosphere to obtain calcined ZIF-8 / GO nanosheets; The calcined ZIF-8 / GO nanosheets are dispersed in a first solvent, a modification reagent is added, and a chemical modification reaction is performed under heating, and after the reaction, the ZIF-8 / GO nanosheet modified by the modification reagent for ion selective transmission is obtained.

13. A ZIF-8 / GO composite film, characterized in that, The ZIF-8 / GO composite membrane is prepared by uniformly dispersing the modified ion-selective transport ZIF-8 / GO nanosheets modified by the modifying agent of any one of claims 1-11 in water or methanol, then filtering the obtained filtrate onto a polymer membrane substrate or a positive alumina template, and drying.

14. The ZIF-8 / GO composite film according to claim 13, characterized in that, The concentration of the modified ion-selective transport ZIF-8 / GO nanosheets modified by the modifying agent in the filtrate is 0.10-2 mg / mL, based on the total volume of the water or methanol.

15. The ZIF-8 / GO composite film according to claim 13 or 14, wherein, The polymer membrane comprises a polytetrafluoroethylene membrane, a cellulose acetate membrane, or a polyvinylidene fluoride membrane.

16. The ZIF-8 / GO composite film of claim 15, wherein, The membrane pore size of the polymer membrane is 0.05-1 μm.

17. The ZIF-8 / GO composite film according to claim 13 or 14, wherein, The positive alumina template is a rigid anodic aluminum oxide membrane.

18. The ZIF-8 / GO composite film according to claim 17, characterized in that, The membrane pore size of the rigid anodic aluminum oxide membrane is 0.05-0.4 μm.

19. Use of the ZIF-8 / GO composite membrane of any one of claims 13-18 in ion-selective transport.

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