Preparation method and application of water and organic solvent bistable two-dimensional polymer fullerene film

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a preparation method and application of a water and organic solvent bistable two-dimensional polymer fullerene membrane.The preparation method comprises the following steps that an N-methyl pyrrolidone solvent and a two-dimensional polymer fullerene dispersion liquid are evenly mixed, and a C60 diluent is obtained; placing a substrate filter membrane containing a supporting membrane at the bottom on a filter head of a suction flask, taking a proper amount of N-methyl pyrrolidone solvent to completely wet the substrate filter membrane, starting a suction filtration pump, performing suction filtration for 1-3 minutes, closing the suction filtration pump, and fixing a filter cup at the upper end of the filter head; and starting the suction filtration pump again, and pouring the C60 diluent into the filter cup. The two-dimensional polymer fullerene dispersion liquid and NMP are mixed and subjected to suction filtration and annealing treatment, the two-dimensional polymer fullerene membrane is prepared, the two-dimensional polymer fullerene membrane allows water molecules to pass through and intercepts ions, interlayer bonding is enhanced, the swelling resistance and stability of the membrane are improved, and efficient liquid phase separation is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a preparation method and application of a water and organic solvent bi-stable two-dimensional polymer fullerene film. Background Art

[0002] In recent years, two-dimensional materials such as graphene, transition metal sulfides, and MXene have shown great potential in the field of membrane separation due to their atomic-level thickness, high mechanical strength, and controllable interlayer channel characteristics. The nanochannels of these materials can achieve efficient and selective separation of small molecules, ions, and even water through chemical modification or physical stacking. In 2022, fullerene two-dimensional polymers were first synthesized by the team of Researcher Zheng Jian from the Institute of Chemistry, Chinese Academy of Sciences. As an all-carbon two-dimensional semiconductor, it is a new allotrope in the carbon material family. It is formed by C60 molecules through specific covalent bonding in the plane. It is only one fullerene molecule thick and has a band gap of about 1.6eV. In particular, the quasi-hexagonal two-dimensional fullerene has a native angstrom pore structure, and the equivalent pore diameter is between that of water molecules and hydrated inorganic salt ions, making it an ideal water / salt separation material.

[0003] However, the research on fullerene two-dimensional polymers is still in its infancy, and the existing technology has significant defects. In the existing technology, the prepared two-dimensional fullerene multilayer membrane can only allow gaseous organic molecules to pass through, and is not stable enough in liquid solvents. It will disperse within 10 seconds and cannot be used for liquid phase separation. Other related two-dimensional membranes such as graphene oxide membranes and COF membranes, although attempts have been made to improve stability, have problems such as cross-linker residues leading to structural collapse, poor intercalation stability, and reliance on highly toxic cross-linkers to block channels. They cannot achieve dual stability of aqueous and organic phases, which seriously limits their application in the field of liquid phase membrane separation.

[0004] Therefore, there is an urgent need to develop a mild and pollution-free method for preparing two-dimensional polymer fullerene membranes to solve the problem of their rapid stratification and dispersion in aqueous and organic phases, so that the membrane can maintain the integrity of the intrinsic nanochannels while having both high permeability and high selectivity, and promote its practical application in seawater desalination, organic solvent nanofiltration and other fields. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a water- and organic solvent-bistable two-dimensional polymer fullerene membrane and its application. The method comprises mixing a two-dimensional polymer fullerene dispersion with NMP and filtering the mixture to form a two-dimensional polymer fullerene membrane wet material having an AA-type ordered layered structure on a PTFE filter membrane. The AA-type ordered layered structure is stabilized after annealing, thereby producing a two-dimensional polymer fullerene membrane. The two-dimensional polymer fullerene membrane has a pore diameter of approximately 4.8 Å, allowing water molecules to pass through while retaining ions, and enhancing interlayer bonding, thereby improving the membrane's anti-swelling properties and stability, thereby achieving efficient liquid phase separation.

[0006] The technical solutions adopted by the present invention are as follows: A method for preparing a water-and organic solvent-bistable two-dimensional polymer fullerene film comprises the following steps: St1: uniformly mix N-methylpyrrolidone (NMP) solvent and two-dimensional polymer fullerene dispersion to obtain C60 dilution solution; Step 2: Place the base filter membrane with the support membrane on the filter head of the filtration bottle, take an appropriate amount of N-methylpyrrolidone solvent to completely wet the base filter membrane, start the filtration pump to discharge the N-methylpyrrolidone solvent in the filtration bottle, filter for 1 to 3 minutes, then turn off the pump and fix the filter cup on the upper end of the filter head; St3: Start the filtration pump again and slowly pour the C60 dilution into the filter cup along the wall of the filter cup. After the C60 dilution in the filter cup has completely passed through the base filter membrane, a base filter membrane containing a two-dimensional polymer fullerene membrane wet material is obtained, and the two-dimensional polymer fullerene membrane wet material has an AA-type ordered layered structure. Remove the base filter membrane and place it in a culture dish; St4: Preheat the forced air drying equipment to 150-180°C, place the base filter membrane in a drying oven for annealing treatment and dry it at 150-180°C. The AA-type ordered layered structure is stabilized by annealing treatment. After drying for 0.5-2 hours, take it out to obtain a base filter membrane covered with a two-dimensional polymer fullerene membrane. Peel off the support membrane at the bottom of the base filter membrane to obtain a two-dimensional polymer fullerene membrane containing the base filter membrane.

[0007] In a preferred embodiment, in St1, the volume ratio of the two-dimensional polymer fullerene dispersion and the N-methylpyrrolidone solvent is 1:99.

[0008] In a preferred embodiment, the base filter membrane is a hydrophilic polytetrafluoroethylene (PTFE) filter membrane.

[0009] In a preferred embodiment, the pore size of the hydrophilic polytetrafluoroethylene filter membrane is 0.1 to 0.3 μm. Preferably, the pore size of the hydrophilic polytetrafluoroethylene filter membrane is 0.22 μm.

[0010] In a preferred embodiment, the concentration of the two-dimensional polymer fullerene dispersion is 10 mg / ml.

[0011] In a preferred embodiment, in St5, the blast rate inside the blast drying equipment is 10 to 15 m / s. 3 / h.

[0012] A two-dimensional polymer fullerene membrane is prepared by any of the above-mentioned methods for preparing a water- and organic solvent-bistable two-dimensional polymer fullerene membrane, wherein the two-dimensional polymer fullerene membrane has a native angstrom pore structure with an equivalent pore diameter of approximately 4.8Å, and the two-dimensional polymer fullerene membrane can remain stable in both water and organic solvents.

[0013] In a preferred embodiment, the application of the two-dimensional polymer fullerene membrane described in the present application in liquid phase membrane separation is used to separate small organic molecules, inorganic salt ions or water molecules.

[0014] In a preferred embodiment, the organic small molecules include methylene blue, rhodamine B, methyl orange, methyl blue, and methyl red.

[0015] In a preferred embodiment, the inorganic salt ions include hydrated ions of copper chloride and sodium chloride.

[0016] The technical effects achieved by the present invention are: The present invention prepares a two-dimensional polymer fullerene membrane by mixing a two-dimensional polymer fullerene dispersion with NMP and then filtering the mixture. The two-dimensional polymer fullerene membrane is subjected to a mild annealing treatment. The annealing treatment causes the two-dimensional fullerene to form an AA-type ordered layered structure through π-π stacking. The original pore diameter is about 4.8Å, which is between water molecules and hydrated inorganic salt ions. The efficient permeation of water molecules and ion retention are achieved through size screening. At the same time, the heat treatment strengthens the interlayer covalent bonds and van der Waals forces, improves the membrane's anti-swelling ability in the solvent, and enhances the interlayer interaction and improves the stability of the membrane in the solvent, thereby achieving efficient liquid phase separation and solving the bottleneck of traditional two-dimensional membranes being easily dispersed in the liquid phase. The membrane provides an efficient and stable separation material for seawater desalination, organic solvent nanofiltration, and the like. At the same time, the preparation process does not introduce additional chemical pollution, the operation is simple, and the membrane is easy to scale up, which facilitates the practical application of the two-dimensional polymer fullerene membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic diagram of the stability test results of the two-dimensional polymer fullerene film in water and organic solvents in Test Example 1 of the present invention; Figure 2 Schematic diagram of the change in contact angle of the two-dimensional polymer fullerene film over time in the embodiment and the comparative example in Test Example 2 of the present invention; Figure 3 is a schematic diagram of a scanning electron microscope of a two-dimensional polymer fullerene film in Test Example 3 of the present invention; Figure 4 Schematic diagram of XRD characteristic peaks of the two-dimensional polymer fullerene film in Test Example 3 of the present invention; Figure 5 Schematic diagram of simulated XRD of the two-dimensional polymer fullerene film in different stacking modes in Test Example 3 of the present invention; Figure 6 1 is a schematic diagram of the filterability test results of the two-dimensional polymer fullerene membrane in Test Example 4 of the present invention; Figure 7 Schematic diagram of the methylene blue molecular filtration spectrum of the two-dimensional polymer fullerene film in Test Example 4 of the present invention; Figure 8 1 is a schematic diagram of the filtration spectrum of hydrated copper ions of the two-dimensional polymer fullerene film in Test Example 4 of the present invention; Figure 9 Schematic diagram of the rejection rate of methylene blue molecules and hydrated copper ions of the two-dimensional polymer fullerene membrane in Test Example 4 of the present invention; Figure 10 Schematic diagram of a proton barrier test of a two-dimensional polymer fullerene film in Test Example 5 of the present invention; Figure 11 Schematic diagram of the hydroxide ion barrier test of the two-dimensional polymer fullerene film in Test Example 6 of the present invention; Figure 12 1 is a schematic diagram of the water permeability test results of the two-dimensional polymer fullerene membrane in Test Example 7 of the present invention; Figure 13 Schematic diagram of the water flux test of the two-dimensional polymer fullerene membrane in Test Example 8 of the present invention; Figure 14 Schematic diagram of the filterability test of the PTFE filter membrane in Test Example 9 of the present invention. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive of other embodiments.

[0021] Example Take 198 ml of N-methylpyrrolidone (NMP) solvent and mix it with 2 ml of 10 mg / ml two-dimensional polymer fullerene dispersion, stir it at 300 rpm on a magnetic stirrer for 30 minutes to obtain a 100-fold diluted C60 dilution. Place a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with a diameter of 50 mm, a pore size of 0.22 μm and a support membrane at the bottom on the filter head of the filtration bottle, and evenly drip 2 ml of NMP solvent on the PTFE filter membrane to completely wet it. Turn on the filtration pump to filter for 1 minute and then turn it off to completely drain the liquid. The NMP solvent in the filter bottle is fixed on the filter head with a clip, and the suction pump is turned on again. 35 ml of C60 dilution is slowly poured into the filter cup along the wall of the filter cup. The filtration process is observed until the C60 dilution in the filter cup completely passes through the PTFE filter membrane and no liquid drips. Continue to filter for 30 seconds to ensure that the C60 dilution on the PTFE filter membrane is completely filtered. After the filtration is completed, a PTFE filter membrane containing a two-dimensional polymer fullerene membrane wet material is obtained. The PTFE filter membrane is taken out and placed in a culture dish. The blast drying oven is preheated to 160 ° C and the blast rate is set to 12m 3 / h, and then put the PTFE filter membrane into a drying oven for annealing treatment, dry it at 160°C for 1 hour, take it out, and after naturally cooling to room temperature, peel off the support membrane at the bottom of the PTFE filter membrane to obtain a two-dimensional polymer fullerene membrane with the PTFE filter membrane covering the bottom.

[0022] Furthermore, the hydrophilic polytetrafluoroethylene (PTFE) purchased from the market has its own support membrane at the bottom, which is not added separately. The PTFE and the support membrane are connected to each other at the edges to form a whole with a double-layer membrane structure. After the two-dimensional polymer fullerene membrane is prepared, the support membrane will be peeled off, and the PTFE filter membrane at the bottom will not be peeled off. At the same time, in the actual application process and the various test examples below, only the support membrane is peeled off. The two-dimensional polymer fullerene membrane prepared in the above embodiment has a dried PTFE filter membrane at the bottom that mainly plays a supporting role, and the PTFE filter membrane body does not have a liquid phase separation function (for the test that the PTFE filter membrane body does not have a liquid phase separation function, please refer to Test Example 9).

[0023] It should be noted that, in this embodiment, the specific composition and preparation steps of the two-dimensional polymer fullerene dispersion can be found in Example 1 of Patent Publication No. CN114956053A (paragraphs 91 to 93 of the specification). The composition of the two-dimensional polymer fullerene dispersion in this embodiment is exactly the same as the composition of the polymer C60 dispersion prepared in Example 1 of the above-mentioned reference document. In this embodiment, the concentration of the two-dimensional polymer fullerene dispersion is 10 mg / ml.

[0024] Here, in order to better describe the relevant performance of this product, the bottom of the two-dimensional polymer fullerene membrane in each test example below and without special instructions all contains a PTFE filter membrane.

[0025] It should be noted that in this embodiment, the prepared two-dimensional polymer fullerene film is formed by physical stacking of a single-layer fullerene network (ie, a single-layer nanosheet), rather than being obtained by a chemical reaction.

[0026] Comparative Example This comparative example is based on the embodiment, but the annealing treatment is adjusted to an air-drying treatment. Specifically: Take 198 ml of N-methylpyrrolidone (NMP) solvent and mix it with 2 ml of 10 mg / ml two-dimensional polymer fullerene dispersion, stir it at 300 rpm on a magnetic stirrer for 30 minutes to obtain a 100-fold diluted C60 dilution solution, place a hydrophilic polytetrafluoroethylene (PTFE) filter membrane with a diameter of 50 mm, a pore size of 0.22 μm and a support membrane at the bottom on the filter head of the suction bottle, and evenly drop 2 ml of NMP solvent on the PTFE filter membrane to completely wet it. Turn on the suction pump and filter for 1 minute, then turn it off to completely drain the NMP solvent in the suction bottle, and use Use a clip to fix the filter cup above the filter head, turn on the suction pump again, take 35 ml of C60 dilution and slowly pour it into the filter cup along the wall of the filter cup, observe the filtration process until the C60 dilution in the filter cup completely passes through the PTFE filter membrane and no liquid drips, continue filtration for 30 seconds to ensure that the C60 dilution on the PTFE filter membrane is completely filtered. After the filtration is completed, a PTFE filter membrane containing a two-dimensional polymer fullerene membrane wet material is obtained. Take out the PTFE filter membrane and place it in an air-drying device. After air-drying for 2 hours, use tweezers to carefully peel off the support membrane at the bottom to obtain a two-dimensional polymer fullerene membrane with a PTFE filter membrane covering the bottom.

[0027] Test Example 1 Water, NMP (N-methylpyrrolidone), DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), ethanol, methanol, acetonitrile, and acetone were placed in different containers, and the two-dimensional polymer fullerene films prepared in various examples were immersed in the containers. The dissolution state of the two-dimensional polymer fullerene films was observed and recorded every 24 hours. The dissolution state is shown in Table 1: ; Note: Table 1 shows the dissolution state of two-dimensional polymer fullerene films in different solvents for 72 hours.

[0028] By comparing Table 1 and Figure 1It can be seen that the two-dimensional polymer fullerene films prepared in the examples showed no signs of dissolution or dispersion in water or organic solvents. The test results further confirmed that the two-dimensional polymer fullerene films prepared in the examples were suitable for aqueous and organic solutions and exhibited excellent stability.

[0029] It should be noted that Figure 1 This is a schematic diagram of the dissolution state of two-dimensional polymer fullerene films in different solvents at different dissolution times. The data in Table 1 only shows part of the test data.

[0030] Test Example 2 The two-dimensional polymer fullerene films prepared in the examples and comparative examples were cut into 1 cm × 1 cm squares and fixed to the sample stage of the contact angle measuring instrument. The instrument was adjusted so that the lens was aligned with the center of the sample. The ambient temperature was set to 25°C and the humidity was set to 50%. 5 μL of ultrapure water was drawn up with a microsyringe and slowly dripped onto the film surface at a rate of 0.5 μL / s. The measurement program was immediately started, and the initial contact angle at the moment of dripping was recorded. The change in the contact angle was continuously monitored over 20 seconds. The measurement was repeated three times for each sample and the average value was taken. The contact angle differences of the films under different drying conditions were compared and the results were recorded. The test results showed that the contact angle of the two-dimensional polymer fullerene film in the comparative example, which had been air-dried, started from an initial contact angle of approximately 60°. As time increased, water penetrated, the contact angle gradually decreased, and finally stabilized at nearly 0°. However, the contact angle of the two-dimensional polymer fullerene film annealed at 160°C in the example started from an initial contact angle of approximately 90°, decreased slightly, and then stabilized at approximately 80° (see Figure 2 shown).

[0031] Combine Figure 2 It can be seen that in the comparative example, the two-dimensional polymer fullerene membrane treated by air drying has weak interlayer interaction (relying only on van der Waals forces), a loose structure, and polar sites (such as edge defects) that easily form hydrogen bonds with water, resulting in a sharp drop in the contact angle, indicating that its surface is highly hydrophilic. This is also the reason why traditional fullerene membranes dissolve rapidly in water; while in the example, the two-dimensional polymer fullerene membrane treated by annealing promotes π-π stacking or covalent bond strengthening between the two-dimensional fullerene layers through thermal annealing, reduces the exposure of surface polar groups, and reduces the affinity of the membrane for water molecules. Its surface exhibits strong hydrophobicity, but still allows water molecules to pass through (the contact angle does not reach 180°). The hydrophobic surface prevents solvent molecules from destroying the membrane structure, while the native angstrom pores (4.8Å) ensure efficient penetration of water molecules, achieving the dual goals of "anti-swelling" and "high permeability".

[0032] Test Example 3 The two-dimensional polymer fullerene film prepared in the example was analyzed using a scanning electron microscope, an X-ray diffractometer, and molecular simulation software. The results are shown in Figures 3 to 5 shown.

[0033] Figure 3 In the figure, a is a SEM image at 100 μm, b is a SEM image at 50 μm, and c is a SEM image at 10 μm. Figure 3 、 Figure 4 and Figure 5 It can be seen that the two-dimensional polymer fullerene membrane has good macroscopic continuity and uniformity. The multi-layer physically stacked two-dimensional fullerene nanosheets present a sheet-like overlapping structure. The sheets are closely arranged to form a regular layered network. The sheet thickness is uniform, and a regular angstrom pore structure (pore diameter of about 4.8Å) is formed between the layers. This further illustrates that the two-dimensional polymer fullerene membrane prepared in the embodiment can efficiently intercept ions and allow water molecules to pass through, and has good separation performance.

[0034] Test Example 4 The two-dimensional polymer fullerene membrane prepared in the embodiment was clamped in an H-shaped transparent test cell (inner diameter 40 mm, height 50 mm; inner diameter 15 mm, outer diameter 30 mm of the middle channel). A variety of dye molecules and colored inorganic salts were selected as research objects, including Methy1ene Blue (methylene blue, 2.36 nm), Rhodamine B (rhodamine B, 1.59 nm), Methyl Orange (methyl orange, 1.54 nm), Methyl Blue (methyl blue, 1.40 nm), Methyl Red (methyl red, 0.80 nm), and hydrated copper ions (0.65 nm) in CuCl2 solution. 50 mL of a 50 μg / ml aqueous solution of the dye was placed on the left side of the two-dimensional polymer fullerene membrane, and 50 mL of ultrapure water was placed on the right side. The ability of the dye molecules to pass through the membrane was observed and recorded to evaluate the membrane's filtration ability for small organic molecules. Among them, methyl red dye molecules are not easily soluble in water. 50mL of a 50μg / ml NMP solution of the dye is placed on the left side of the two-dimensional polymer fullerene membrane, and 50mL of NMP solvent is placed on the right side. The ability of the dye molecules to pass through the membrane is observed and recorded to evaluate the membrane's filtration ability for small organic molecules. Similarly, 50mL of a 0.1M CuCl2 aqueous solution is placed on the left side of the two-dimensional polymer fullerene membrane, and 50mL of ultrapure water is placed on the right side. Then, using a UV-visible spectrophotometer, the absorbance of the liquid in the right test tank is recorded within the wavelength range of 350-950nm, and a spectrum is plotted. Similarly, when testing the filtration performance using methylene blue, due to the high content of dye molecules in methylene blue, in this test example, only the concentration of methylene blue is 12.5ug / mL.

[0035] See also Figures 6 to 9As shown, within 5 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of methylene blue molecules; within 12 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of rhodamine B molecules; within 12 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of methyl orange molecules; within 12 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of methyl blue molecules; within 3 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of methyl red molecules in NMP solvent; within 5 days, the two-dimensional polymer fullerene membrane can effectively prevent the penetration of hydrated copper ions. Through the above tests, the two-dimensional polymer fullerene membrane prepared in the embodiment can efficiently intercept ions and allow water molecules to pass through, and has the ability to filter small molecule dyes and inorganic salt ions.

[0036] It should be noted that, in this test example, the retention rate is obtained by automatic calculation using a UV / visible spectrophotometer. Specifically, in this test example, the specific model of the UV / visible spectrophotometer selected is: UV-5500PC produced by Shanghai Precision Instruments Co., Ltd. Of course, the retention rate can also be calculated manually according to the test data using a calculation formula. The specific method of manual calculation can refer to the calculation method disclosed in Hirunpinyopas W, Prestat E, Worrall SD, et al. Desalination and nanofiltration through functionalized laminar MoS2membranes. ACS Nano, 2017, 11: 11082–11090. In this test example, the retention rate is preferably obtained by automatic calculation by the device.

[0037] Further, combined Figure 9 It can be seen that the rejection rate of the two-dimensional polymer fullerene membrane reaches more than 99.7%, so Figure 7 In the figure, the characteristic peak appeared on the permeation side of the methylene blue solution at 24h. Similarly, Figure 8 In the experiment, a characteristic peak appeared on the permeate side of copper chloride solution at 24h.

[0038] Test Example 5 HCl solution (0.50 nm) was used as the research object, and methyl orange was used as the indicator. 0.1 g of methyl orange powder was weighed, added to 50 mL of deionized water, stirred until completely dissolved, and then transferred to a 100 mL volumetric flask. The mixture was then brought to volume and shaken to obtain a 0.1% methyl orange stock solution. A 50 mL solution of 0.1 M HCl (pH ≈ 1) was placed on the left side of the two-dimensional polymer fullerene membrane. Five drops of 0.1% methyl orange solution in 50 mL of ultrapure water (initial pH ≈ 6.5) were added to the right side. The color change of the indicator was observed and recorded to evaluate the proton barrier properties of the two-dimensional polymer fullerene membrane.

[0039] See also Figure 10 As shown, within 5 days, the right side changes from orange to orange-red, indicating that H + Ions pass through the filter membrane from the left to the right, causing the pH value on the right to decrease and the methyl orange indicator to change from orange to orange-red. + The diameter of the ion is basically equal to the equivalent pore size of the original angstrom pore of the two-dimensional polymer fullerene membrane (4.8Å, i.e. 0.48nm). + Ions can slowly penetrate through nanochannels. Although the two-dimensional polymer fullerene membrane has a nearly 100% retention rate for small organic molecules (such as methylene blue, 2.36 nm) and inorganic salt ions (such as hydrated copper ions, 0.65 nm), H + The ions can pass through, indicating that there is a size threshold for separation selectivity, that is, when the ion diameter is close to or slightly exceeds the pore size (H + The theoretical size is slightly larger than 0.48nm), and it is still possible to penetrate through the "sieving effect + ion migration" mechanism, which provides possibilities for the application of membranes in proton conduction, pH regulation and other fields. It also suggests that in strict ion retention scenarios, the precise matching of ion size and pore size must be considered.

[0040] Test Example 6 A NaOH solution (0.35 nm) was used as the research target, and phenolphthalein was used as the indicator. 0.1 g of phenolphthalein was dissolved in 100 mL of 95% ethanol to obtain a 0.1% phenolphthalein ethanol solution. 50 mL of 0.1 M NaOH aqueous solution (pH ≈ 13) was placed on the left side of the two-dimensional polymer fullerene film. Five drops of 0.1% phenolphthalein ethanol solution in 50 mL of ultrapure water (initial pH ≈ 6.5) were added to the right side. The color change of the indicator was observed and recorded to evaluate the ability of the two-dimensional polymer fullerene film to block hydroxide ions.

[0041] See also Figure 11 As shown, the right side changes from colorless to pink within 24 hours. - Ions pass through the filter membrane from the left to the right, causing the pH value on the right to increase, and the phenolphthalein indicator changes from colorless to pink. The two-dimensional polymer fullerene membrane cannot completely block hydroxide under strong alkaline conditions, among which OH - The ion diameter is about 0.35nm, which is significantly smaller than the equivalent pore size of the native angstrom pore of the two-dimensional polymer fullerene membrane.

[0042] Test Example 7 Through the forward osmosis experiment, the permeability of the two-dimensional polymer fullerene membrane to water molecules (0.28nm) was studied. The height difference of the solution on both sides of the membrane was observed to evaluate the water permeability of the membrane. The stable two-dimensional polymer fullerene membrane was clamped in an H-shaped transparent test tank and Cu was selected. 2+Ions are selected as the research object because they are blue and easier to observe. 45 mL of 0.1 M CuCl2 aqueous solution is placed on the left side of the two-dimensional polymer fullerene membrane, and 45 mL of 1 M sucrose aqueous solution is placed on the right side. Observe and record whether there is a height difference between the two sides. If there is a height difference, record the change of the height difference over time to obtain the water flux of the two-dimensional polymer fullerene membrane under this condition, and realize the quantification of the desalination process. At the same time, due to Na + Ions have no color. If you choose Na + When ions were studied, Cu 2+ We can also draw the same conclusion based on the experimental phenomena of similar ions.

[0043] See also Figures 12 to 13 As shown in the experimental results, within 12 days, a height difference of 15.18 mm appeared on both sides of the CuCl2 aqueous solution and the sucrose aqueous solution; within 12 days, a height difference of 14.31 mm appeared on both sides of the NaCl aqueous solution and the sucrose aqueous solution; this shows that the two-dimensional polymer fullerene film blocked the Cu 2+ ions and Na + ions, but allows water molecules to pass through.

[0044] Test Example 8 Due to the size screening of the two-dimensional fullerene membrane, it can block dye molecules and inorganic salt ions, but it requires the passage of water molecules. The following water flux test experiment will be conducted. Take 35ml of C60 dilution solution with different dilution ratios (the two-dimensional polymer fullerene dispersion is diluted 300-1000 times. The two-dimensional fullerene membrane corresponding to the two-dimensional polymer fullerene dispersion diluted 300 times is the thickest, and the two-dimensional fullerene membrane corresponding to the two-dimensional polymer fullerene dispersion diluted 1000 times is the thinnest) to control the thickness of the two-dimensional fullerene membrane. Select a two-dimensional fullerene membrane with a uniform surface and no obvious defects and place it on the filter (the effective area of the two-dimensional fullerene membrane is π). Add 30ml of ultrapure water to the glass funnel, turn on the vacuum filtration pump, and the displayed pressure is 0.08-0.09MPa (the filtration pressure will fluctuate due to different membrane thicknesses. Record the filtration pressure at different membrane thicknesses during the experiment). At the same time, turn on the calculator. When the water content in the glass funnel drops to 20 ml (i.e., the volume of permeated water is 10 ml), turn off the vacuum filtration pump and record the filtration time. Calculate the water flux for each membrane thickness using the water flux calculation formula. Repeat the test three times for each membrane thickness, remove outliers, and average the values. Finally, obtain the water flux data corresponding to different membrane thicknesses for subsequent analysis and plotting.

[0045] The calculation formula of water flux is: Water flux (L / (m²・h / bar)) = permeate volume (L) ÷ (membrane effective area (m²) × operating pressure (bar) × time (h)).

[0046] See also Figure 13 As shown, the experimental results show that in the different film thickness ranges corresponding to the dilution of the two-dimensional polymer fullerene dispersion from 300 to 1000 times, the water flux as a whole shows a trend of first slowly increasing with the increase of the dilution ratio (decreasing the membrane thickness), and then rising sharply when the dilution ratio reaches 1000 times. Among them, the water flux corresponding to the two-dimensional fullerene film corresponding to the 400-fold dilution deviates to a certain extent, because the relationship between membrane thickness and dilution ratio is not linear, but the larger the dilution ratio, the thinner the film is. Secondly, the two-dimensional fullerene film is formed by stacking single-layer fullerene nanosheets, and the interlayer spacing is closely related to the dilution ratio, indicating that the interlayer spacing corresponding to this dilution ratio is more conducive to the passage of water molecules. Therefore, compared with other adjacent dilution ratios, the water flux deviates to a certain extent. For the two-dimensional fullerene film diluted by 1000 times, the water flux rises sharply, indicating that when the two-dimensional fullerene film is thin enough, it will have a large water flux.

[0047] Test Example 9 This test example is mainly to prove that "PTFE filter membrane itself does not have liquid phase separation function" discussed in the embodiment. The specific operation steps of the membrane treatment process are exactly the same as those in the embodiment. The main difference is that 35ml of NMP solvent without C60 is used. The specific operation steps of the filtration process are exactly the same as those in Test Example 4. The main difference is that the membrane sandwiched in the middle is a PTFE blank membrane (i.e., the PTFE filter membrane surface does not contain a two-dimensional fullerene membrane). For the results, please refer to Figure 14 ,pass Figure 14 It can be seen that after 1 hour, the methylene blue molecules in the left test tank penetrated through the PTFE filter into the right test tank, further confirming that the PTFE filter membrane itself does not have the liquid phase separation function. Combined with the experimental results in Test Example 4, it can be clearly seen that the various dye molecules and colored inorganic salts in Test Example 4 cannot penetrate from the left test tank to the right test tank, mainly because the two-dimensional fullerene membrane plays a blocking role.

[0048] In summary, in this application, a two-dimensional polymer fullerene dispersion is mixed with NMP and then filtered, and a two-dimensional polymer fullerene membrane is prepared after mild annealing treatment. The annealing treatment causes the two-dimensional fullerene to form an AA-type ordered layered structure through π-π stacking. The native pore diameter is about 4.8Å, which is between water molecules and hydrated inorganic salt ions. The efficient permeation of water molecules and ion retention are achieved through size screening; at the same time, the heat treatment strengthens the interlayer covalent bonds and van der Waals forces, improves the membrane's anti-swelling ability in the solvent, and at the same time enhances the interlayer effect and improves the stability of the membrane in the solvent, which can achieve efficient liquid phase separation and solve the bottleneck of traditional two-dimensional membranes that are easy to disperse in the liquid phase, providing efficient and stable separation materials for seawater desalination, organic solvent nanofiltration, etc. At the same time, its preparation process does not introduce additional chemical pollution, the operation is simple, and it is easy to scale up, which provides convenience for the practical application of two-dimensional polymer fullerene membranes.

[0049] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. A method for preparing a two-dimensional polymer fullerene film bi-stable in water and organic solvents, characterized by: The following steps are involved: St1: uniformly mix N-methylpyrrolidone solvent and two-dimensional polymer fullerene dispersion to obtain C60 dilution solution; St2: Place the base filter membrane with the support membrane on the filter head of the filtration bottle, take an appropriate amount of N-methylpyrrolidone solvent to completely wet the base filter membrane, start the filtration pump, filter for 1 to 3 minutes, then turn it off, and then fix the filter cup on the upper end of the filter head; St3: Start the filtration pump again and pour the C60 dilution into the filter cup. After the C60 dilution in the filter cup has completely passed through the base filter membrane, remove the base filter membrane. St4: Preheat the forced air drying equipment to 150-180°C, place the base filter membrane in a drying oven for annealing, dry it at 150-180°C for 0.5-2 hours, then take it out to obtain a base filter membrane covered with a two-dimensional polymer fullerene membrane, peel off the support membrane at the bottom of the base filter membrane, and obtain a two-dimensional polymer fullerene membrane containing the base filter membrane.

2. The method for preparing a water-and organic solvent-bistable two-dimensional polymer fullerene film according to claim 1, characterized in that: In St1, the volume ratio of the two-dimensional polymer fullerene dispersion and the N-methylpyrrolidone solvent is 1:

99.

3. The method for preparing a water-and-organic solvent bistably two-dimensional polymer fullerene film according to claim 1, characterized in that: The base filter membrane is a hydrophilic polytetrafluoroethylene filter membrane.

4. The method for preparing a water-and organic solvent-bistable two-dimensional polymer fullerene film according to claim 3, characterized in that: The pore size of the hydrophilic polytetrafluoroethylene filter membrane is 0.1 to 0.3 μm.

5. A two-dimensional polymer fullerene film, prepared by the method for preparing a water-and organic solvent-bistable two-dimensional polymer fullerene film according to any one of claims 1 to 4, characterized in that: The two-dimensional polymer fullerene membrane has a native angstrom pore structure with an equivalent pore diameter of 4.8Å.

6. Use of a two-dimensional polymer fullerene membrane as claimed in claim 5 in liquid phase membrane separation, characterized in that: Used to separate small organic molecules, inorganic salt ions or water molecules.

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