Two-dimensional nanochannel membrane based on molecular encapsulation technology regulation, preparation and application

Abstract

The application discloses a two-dimensional nanochannel membrane based on regulation of a molecular encapsulation technology, preparation and application, and belongs to the technical field of nanofiltration membrane preparation. The application constructs a graphene oxide membrane based on a method of intercalating by subjecting supramolecular encapsulation of guest metal ions, specifically, first, cross-linking modification is performed on a base film so that a GO selection layer on the base film has good dispersibility and the base film and the GO selection layer have good bonding force; then, a solution of the host-guest complex formed by encapsulation is mixed with a GO dispersion solution to obtain a coating liquid, and the coating liquid is uniformly deposited on the base film by using a pressure-assisted filtration method to obtain a GO nanofiltration membrane. Through interlayer cross-linking, the formation of a more ordered channel is promoted, and the membrane is endowed with good stability and screening performance.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane technology, specifically to a two-dimensional nanochannel membrane based on molecular encapsulation technology, its preparation, and its application in sieving dye molecules. Background Technology

[0002] With the rapid development of the pharmaceutical, petrochemical, and catalysis industries, the demand for organic solvents is increasing daily. Against this backdrop, the large amounts of organic wastewater discharged must be properly treated. Direct discharge into the environment is not only a serious waste of resources but also causes environmental harm. In the long run, the separation and recycling of organic solvents is essential.

[0003] Organic solvent nanofiltration (OSN) is a novel membrane separation technology capable of efficiently separating organic solvents and solutes with relative molecular masses ranging from 200 to 1000. Compared to conventional separation techniques, OSN offers advantages such as low energy consumption, mild operating conditions, and strong solvent recovery capabilities, demonstrating excellent performance in the recovery and purification of organic solvents. However, the main challenge facing OSN membranes in practical applications is their poor stability; they are prone to swelling and compaction in solvents. Developing OSN membranes that are stable in various solvents and possess good retention rates and solvent permeability is a pressing issue that needs to be addressed.

[0004] Graphene oxide (GO) is a two-dimensional material with tunable nanochannels, characterized by good film-forming properties and abundant oxygen-containing functional groups, and is often used to make separation membrane materials. Graphene oxide membranes are formed by the stacking of graphene oxide nanosheets through hydrogen bonding and π–π interactions. However, the interlayer channels are highly susceptible to interference in liquid environments, and the membrane generally exhibits poor stability in polar solvents. This is because the oxygen-containing functional groups dehydrogenate and form negative charges upon solvation, leading to swelling and disintegration of the layered microstructure, significantly reducing the membrane's sieving performance during long-term operation.

[0005] Research has shown that intercalation is an effective strategy for addressing GO swelling and improving its stability. The strong interaction between the intercalator and GO nanosheets adjusts the interlayer spacing while helping to maintain the stability of the GO membrane's interlayer structure, enabling continuous and stable separation. Researchers have attempted to intercalate GO using ions, nanoparticles of different dimensions, and molecules of different sizes, such as metal cations, silica nanoparticles, and polystyrene. Although various intercalating agents added to GO nanosheets can enhance the interlayer channel structure to some extent, thereby improving membrane permeability, the distribution of these intercalating agents is difficult to achieve evenly, resulting in irregular and unstable transport channels. Therefore, we need a crosslinking agent that can effectively regulate the GO interlayer spacing while promoting the formation of regular and ordered channels.

[0006] Cucurbita 6 (CB6) is a cyclic supramolecular compound with polar carbonyl ports and hydrophobic cavities. Its rigid structure and nanoscale molecular size make it suitable as an intercalating agent for regulating GO interlayer channels. Due to its strong host-guest recognition ability, CB6 can bond with cations through ionic dipole interactions. CB6 can be used to encapsulate metal cations, thereby regulating GO interlayer channels and constructing two-dimensional membranes with stable separation performance. In fact, CB6 has demonstrated great potential in improving permeability and precise membrane structure design in membrane applications. For example, Chinese Patent CN 112934004 B discloses a cucurbita / metal ion crosslinked graphene oxide composite membrane, which uses a cucurbita / metal ion supramolecular complex as a crosslinking agent. This not only improves the stability of the graphene oxide membrane in an aqueous environment but also serves as a rapid mass transfer channel for water molecules, enhancing membrane permeability. However, the membrane structure disclosed in this application is essentially a water-permeable membrane rather than a nanofiltration membrane. Although it improves the permeation flux and selectivity for water molecules and can be used for pervaporation of butanol-water solution systems, it has not demonstrated its ability to retain dye solutes. This may be related to the substrate material used and the crosslinked metal ions selected. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art, and to provide a graphene oxide organic solvent nanofiltration membrane and disclose its preparation process. The host-guest complex formed by encapsulating barium ions with supramolecular cucurbituril is used to regulate the GO sieving channels. Through interlayer crosslinking, the formation of more ordered channels is promoted, while endowing the membrane with good stability and sieving performance.

[0008] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution:

[0009] A two-dimensional nanochannel membrane based on molecular encapsulation technology includes a substrate and a selective separation layer on the substrate. The selective separation layer is composed of graphene oxide (GO) nanosheets, and between adjacent GO nanosheets, there are host-guest complexes composed of cucurbita-encapsulated metal ions.

[0010] The cucurbituril mentioned refers to one or more of CB6, CB7, CB8, CB9, and CB10; the metal ion mentioned is Ba. 2+ Ca 2+ Or Cu 2+ One or more of them.

[0011] The substrate is a polyimide material.

[0012] The surface of the substrate has been cross-linked with a polyamine, which is selected from triethylenetetramine, diethylenetriamine, and polyethylenepolyamine.

[0013] The above-mentioned method for preparing two-dimensional nanochannel membranes includes the following steps:

[0014] Metal ion salts and cucurbituril were dissolved in deionized water and encapsulated to form a host-guest complex solution. GO dispersion was added to obtain a coating solution. The coating solution was deposited onto a modified substrate using pressure-assisted filtration to form a uniform coating layer. After heat treatment, a nanofiltration membrane was obtained.

[0015] The substrate is polyimide, which has undergone cross-linking treatment. The cross-linking treatment process is as follows: the PI substrate is immersed in polyethylene polyamine with a mass concentration of 8-15% for 10-20 minutes to complete the cross-linking.

[0016] The metal ion salt is Ba 2+ Ca 2+ Or Cu 2+ Salts, whose anion is Cl. - NO3 - CO3 2- SO4 2- Any one of them.

[0017] The mass percentage of metal ion salts and the mass percentage of cucurbituril in the host-guest complex solution are 0.2–0.5 wt% and 0.6–0.8 wt%, respectively.

[0018] The GO dispersion was obtained by dispersing a GO solution in deionized water and then sonicating it for 100–140 min. The concentration of GO in the resulting GO dispersion was 0.03–0.05 mg / mL. -1 .

[0019] The volume ratio of GO dispersion to host-guest complex solution is 10:1 to 2.5.

[0020] This application also discloses a two-dimensional nanochannel membrane prepared using the above method. The obtained two-dimensional nanochannel membrane is obtained by regulating the GO sieving channels using a host-guest complex formed by encapsulating metal ion salts with cucurbituril. Through interlayer crosslinking, the formation of more ordered channels is promoted, while endowing the membrane with good stability and sieving performance.

[0021] The aforementioned organic solvent nanofiltration membrane can be used in the separation and recovery of organic solvents, such as for the retention of dyes. The dyes mentioned here can be one or more of Reactive Blue 19 (RB19), Aniline Blue (AB), Methyl Blue (MB), Fast Green (FG), and Coomassie Brilliant Blue (BBR).

[0022] The sample prepared in this application achieved 27.23 L m -2 h -1 bar -1It exhibits excellent acetonitrile permeability and achieves 99.21% retention of solid green in acetonitrile while maintaining stable performance after 110 hours of continuous operation.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This application constructs a graphene oxide membrane by encapsulating guest metal ions with a host supramolecular cucurbita and forming a host-guest complex intercalation method. Through interlayer crosslinking, a more ordered channel is formed, which also endows the membrane with good stability and sieving performance.

[0025] 2. The membrane prepared in this application possesses ordered and stable two-dimensional interlayer channels, exhibiting excellent solvent permeability and dye retention performance. Compared with GO membranes, its permeability to organic solvents is nearly doubled, while also demonstrating excellent organic solute removal capability; specifically, it achieves a thickness of 27.23 L / m³. -2 h -1 bar -1 It exhibits excellent acetonitrile permeability and achieves 99.21% retention of solid green in acetonitrile while maintaining stable performance after 110 hours of continuous operation.

[0026] 3. The addition of the host-guest complex formed by encapsulation affects the non-covalent bonding interactions between adjacent GO nanosheets. Specifically, the metal ions in the host-guest complex interact with GO through cation-π interactions, resulting in more ordered nano-stacking of GO sheets during pressure-assisted processing, thus making the membrane surface structure flatter. In addition, the micropore defects caused by loose stacking are reduced, and the more regular channels shorten the solvent molecule transport path, thereby increasing permeability.

[0027] 4. Nanofiltration membranes have controllable interlayer spacing (d), which can be used to achieve effective sieving of dye molecules by utilizing size exclusion.

[0028] 5. The nanofiltration membrane exhibits pressure resistance and long-term separation stability, which is mainly attributed to the rigid structure of CB6, which helps to suppress the swelling of GO nanosheets, thereby enhancing the stability of the membrane.

[0029] 6. This application provides a new material for the intercalation of GO membranes, offering a new approach to constructing GO membranes with ordered and stable nanochannels. Attached Figure Description

[0030] Figure 1 The small figure in the middle (a) shows the UV absorption spectrum of a mixture of 0.025M salt solutions and GO suspension (50 mg / L) at a volume ratio of 1:1; the small figure (b) shows the infrared spectrum of GO and GO cation membrane; the small figure (c) shows the interaction forces between GO and metal ions and between CB6 and metal ions; the small figure (d) shows the ITC isotherm of the complexation of BaCl2 and CB6.

[0031] Figure 2 The smaller image in the middle is GO-CB6-Ba. 2+ Schematic diagram of membrane fabrication process; smaller figure b shows CB6, GO membrane, and GO-Ba membrane. 2+ Membrane and GO-CB6-Ba 2+ FTIR spectra of the membranes; small image c shows the GO membrane and GO-Ba membrane. 2+ Membrane and GO-CB6-Ba 2+ XPS full spectrum of the membrane; the smaller d-plot is GO-CB6-Ba 2+ Ba 3d spectrum of the membrane;

[0032] Figure 3 The smaller images in the middle and lower sections represent the GO membrane and GO-Ba. 2+ Membrane and GO-CB6-Ba 2+ Surface field emission scanning electron microscope (SEM) images of the membranes; the smaller images in df represent the GO membrane and GO-Ba membrane, respectively. 2+ Membrane and GO-CB6-Ba 2+ SEM cross-sectional images of the membranes; the small images in gi represent the GO membrane and GO-Ba membrane, respectively. 2+ Membrane and GO-CB6-Ba 2+ AFM images of the membrane;

[0033] Figure 4 The small image in middle a shows dry and wet GO membranes and GO-Ba. 2+ Membrane and GO-CB6-Ba 2+ Interlayer spacing of the membranes; subplot b shows the changes in relaxation time of different membranes under the action of water molecule probes; subplots ce represent GO membranes and GO-Ba membranes. 2+ Membrane and GO-CB6-Ba 2+ A schematic diagram of membrane channel formation;

[0034] Figure 5 The small image (a) shows the permeability of different membranes in different organic solvents; the small image (b) shows the permeability of GO-CB6-Ba. 2+ The pressure resistance of the membrane in acetonitrile and water; subplot c reflects the relationship between the solvent permeability of different membranes and solvent properties; subplot d shows the surface charge density of different membranes; subplot e shows the dynamic water contact angle of different membranes; subplot f reflects the changes in low-field NMR relaxation time of different membranes under acetonitrile probe.

[0035] Figure 6 The small image in the middle shows GO-CB6-Ba 2+ Separation performance of the membrane for different dyes in acetonitrile; inset b shows GO-CB6-Ba 2+ Long-term separation performance of the membrane for solid green in acetonitrile. Detailed Implementation

[0036] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the invention are within the scope of the present invention.

[0037] To address the issue of irregular transport channels caused by the disordered stacking of GO sheets, this application utilizes the cation-π interaction between metal ions and GO to facilitate more ordered nano-stacking of GO sheets. However, since both CB6 and GO interact with metal cations, the crosslinking ions are first screened.

[0038] 1) Screening of cross-linking ions based on the strength of the interaction between GO and metal cations.

[0039] The UV absorption spectra of GO and GO in LiCl, NaCl, CaCl2, CuCl2 and BaCl2 solutions are shown below. Figure 1 In the small figure (a), the characteristic peak of GO is located at ~230 nm, which is attributed to the π-π* aromatic conjugated double bond. Compared with the UV intensity of GO in pure water, the peak intensity of GO in various salt solutions is significantly reduced, indicating that the π-π* aromatic conjugated double bond of GO is greatly affected by various salt solutions, i.e., there is a cation-π interaction. Figure 1 (Small image in C). See again. Figure 1 In the small image (b), the infrared spectra of both the GO and GO cation membranes show stretching of C=O, carboxyl CO, and aromatic C=C. Compared to the pure GO membrane, the carboxyl CO peak shows a red shift, indicating that the carboxylic acid group is coordinated with the cation, i.e., there is an electrostatic interaction. Figure 1 (See the small image in the middle), and the C=C peak also shows a redshift, indicating that a cation-π interaction occurs between the cation and the GO sheet.

[0040] Different salt solutions were mixed with GO dispersion. After 2 hours, the monovalent cation solution (Li) was... + and Na +The mixture of GO and monovalent cations did not show significant changes. However, GO sheets aggregated in the GO dispersion with the addition of a divalent cation solution. This result is because although smaller ionic cations have a stronger ability to attract the π electron cloud of the benzene ring, their hydration energy in aqueous solution is also much higher than that of larger ionic cations. Higher hydration energy means that the metal cations can be highly solvated in aqueous solution, thus being surrounded by a large number of water molecules, providing a strong shielding effect and preventing metal ions from binding to GO nanosheets. Therefore, it is speculated that the interaction force between divalent cations and GO nanosheets is stronger than that between monovalent cations. Further verification was performed by calculating the binding percentage of GO to metal cations. The mixture of GO and metal cations was centrifuged, and the supernatant was subjected to ICP testing with a reference metal salt solution of consistent concentration. The content of metal ions bound to GO was calculated in reverse. This confirmed that the binding percentage of divalent cations to GO was greater than that with monovalent cations.

[0041] 2) Screening of cross-linking ions based on the strength of the interaction between metal ions and CB6.

[0042] The strength of the binding between CB6 and metal ions is reflected by the binding constant; divalent cations (Cu) 2+ Ca 2+ and Ba 2+ The binding constants of CB6 and Ba showed a trend of increasing from small to large. Then, isothermal titration calorimetry experiments were used to study the binding constants of CB6 and Ba. 2+ Thermodynamics of Interactions Figure 1 (See small graph in d). ΔH < 0 indicates that the reaction is enthalpy-driven. Ba 2+ It interacts with CB6 through hydrogen bonds. -TΔS < 0 indicates an entropy-driven process that results in a conformational change. ΔG < 0 indicates a spontaneous reaction. Furthermore, Ba... 2+ The combination with CB6 is 2:1. Therefore, Ba was ultimately selected. 2+ Crosslinking ions as GO selector layers.

[0043] Example 1

[0044] This embodiment discloses a method for preparing a graphene oxide organic solvent nanofiltration membrane, which introduces CB6 encapsulation of Ba 2+ The formed host-guest complex controls the interlayer structure of GO to address the instability of GO membranes in organic solvents. The membrane preparation process is described in [reference needed]. Figure 2 The specific steps are as follows: (See small image a)

[0045] 1) Preparation of polyimide (PI) substrate by non-solvent-induced phase inversion method: The preparation of PI substrate can refer to existing technology. Specifically, PI is first dried overnight in a vacuum oven at 70°C to remove moisture. Then, it is dissolved in a mixed solution of N-methylpyrrolidone (NMP) and polyethylene glycol (PEG 400) at a certain concentration and stirred until a homogeneous solution is formed. After standing to remove bubbles, a casting solution is formed. The contents of polyimide, PEG 400 and NMP in the casting solution are 30wt%, 20wt%, and 50wt%, respectively. The casting solution is poured onto polyethylene terephthalate nonwoven fabric and coated at a uniform speed using a 100-micron thick doctor blade. Finally, it is immersed in water to complete the phase inversion, thereby obtaining the initial PI substrate.

[0046] 2) PI substrate modification: The PI substrate was immersed in 10% triethylenetetramine (TETA) for 15 min for crosslinking. Polyimide contains a large number of amide groups. Triethylenetetramine is a polyamine containing three amine groups, which can undergo amidation reaction with the amide groups in polyimide to form a crosslinked structure. The crosslinked PI substrate was then soaked in deionized water to remove residual crosslinking agent. Crosslinking is used to give the PI substrate a certain stability in organic solvents, thereby enabling the preparation of a GO composite membrane with certain organic solvent separation performance. The crosslinking time of 15 min was chosen because the PI membrane with a crosslinking time of 15 min has the smallest weight loss ratio in NMP solvent.

[0047] 3) Preparation of GO dispersion: The GO solution was uniformly dispersed in deionized water and ultrasonically treated for 120 min using an ultrasonic cell disruptor to remove large GO aggregates and promote the formation of a uniform GO dispersion. The concentration of GO in the resulting GO dispersion was 0.04 mg / mL. -1 .

[0048] 4) Preparation of GO nanofiltration membrane: BaCl2 (0.0037 g) was dissolved in 100 mL of deionized water, and CB6 (0.0075 g) was added. After complete dissolution, 12.5 mL of GO dispersion was added to obtain the coating solution. Using pressure-assisted filtration, 112.5 mL of the coating solution was deposited on a modified PI substrate (effective membrane area 7.065 cm²) at 4 bar. 2 A uniform coating layer is formed on the surface, and the GO nanofiltration membrane is obtained by heat treatment at 60°C for 1 hour, denoted as GO-CB6-Ba. 2+ The membrane is stored in deionized water or a test solvent for later use.

[0049] Comparative Example 1

[0050] The difference between Comparative Example 1 and Example 1 lies only in step 4): 12.5 mL of GO dispersion was added to 100 mL of deionized water to obtain a coating solution. Using pressure-assisted filtration, 112.5 mL of the coating solution was deposited onto the modified PI substrate (effective membrane area 7.065 cm²) at 4 bar. 2 A uniform coating layer is formed on the substrate, and the film is formed by heat treatment at 60°C for 1 hour. The prepared membrane product is designated as GO membrane, and the membrane is stored in deionized water or a test solvent for later use.

[0051] Comparative Example 2

[0052] The difference between Comparative Example 2 and Example 1 lies only in step 4): BaCl2 (0.0037 g) was dissolved in 100 mL of deionized water. After complete dissolution, 12.5 mL of GO dispersion was added to obtain the coating solution. Using pressure-assisted filtration, 112.5 mL of the coating solution was deposited onto the modified PI substrate (effective membrane area 7.065 cm²) at 4 bar. 2 A uniform coating layer is formed on the substrate, and the film is formed by heat treatment at 60°C for 1 hour. The prepared film product is designated as GO-Ba. 2+ The membrane is stored in deionized water or a test solvent for later use.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 1 lies only in step 4): CB6 (0.0075 g) was dissolved in 100 mL of deionized water. After complete dissolution, 12.5 mL of GO dispersion was added to obtain the coating solution. Using pressure-assisted filtration, 112.5 mL of the coating solution was deposited onto the modified PI substrate (effective membrane area 7.065 cm²) at 4 bar. 2 A uniform coating layer is formed on the substrate, and the film is formed by heat treatment at 60°C for 1 hour. The prepared membrane product is designated as GO-CB6 membrane, and the membrane is stored in deionized water or a test solvent for later use.

[0055] Comparative Example 4

[0056] The difference between Comparative Example 4 and Example 1 is that the PI substrate was not crosslinked modified. All other steps and processes are the same. Experiments have shown that after coating the uncrosslinked PI substrate and the PI substrate crosslinked with TETA with a GO selective layer, the coating layer on the uncrosslinked PI substrate is uneven, while the GO selective layer on the crosslinked PI substrate shows good dispersion, and the two have good bonding force.

[0057] Related performance tests

[0058] 1. GO membranes and GO-Ba prepared in Comparative Examples 1, 2 and 1. 2+ Membrane and GO-CB6-Ba2+ The FTIR spectrum of the membrane is as follows Figure 2 As shown in the small image (b), GO-CB6-Ba 2+ The membrane retains the characteristic peaks of the GO membrane while also containing the characteristic peaks of the CB6 molecule. As can be seen from the figure, the GO membrane exhibits peaks at 3223 cm⁻¹. -1 (-OH), 1726cm -1 (-C=O), 1640cm -1 (C=C), 1364cm -1 (CO, carboxyl group), 1232cm -1 (CO, epoxy group) and 1083cm -1 A distinct absorption peak is observed at (CO, alkoxy) . 1716 cm⁻¹ -1 The vibrational absorption peak of -C=O, 1470 cm⁻¹ -1 The vibrational absorption peak of CN and 955 cm⁻¹ -1 The vibrational absorption peaks at -CH are all characteristic peaks of the CB6 molecule. XPS results further confirm the presence of CB6 and Ba in the membrane. 2+ The successful introduction ( Figure 2 (Small image in C). Experiments have confirmed that GO-Ba 2+ Membrane and GO-CB6-Ba 2+ The membrane surface is uniformly covered with barium, indicating that the membrane contains Ba. 2+ The presence of [something]. And with the addition of the same amount of Ba [something]... 2+ In the case of GO-CB6-Ba 2+ The barium content on the membrane surface is less than that of GO-Ba. 2+ The membrane indicates that CB6 interacts with Ba in the presence of CB6. 2+ The interaction between them makes more Ba 2+ It exists in the interlayer, thus controlling the GO interlayer. In the XPS Ba 3d spectrum of the membrane, the binding energies centered at 779 eV and 795 eV correspond to Ba 3d, further indicating that GO-CB6-Ba 2+ Ba exists in the membrane 2+ ( Figure 2 (Middle d small image).

[0059] 2. The effect of intercalation on the microstructure of GO membranes

[0060] from Figure 3 As can be seen from the small image in Figure 1, Comparative Example 1, Comparative Example 2, and Example 1, the GO membranes and GO-Ba membranes prepared in these examples show... 2+ Membrane and GO-CB6-Ba 2+The membrane surfaces of both GO membranes exhibit the distinctive ridge-like structure characteristic of GO membranes. Furthermore, the GO membranes show larger ridges, while the ridges on the intercalated GO membrane surface become smaller, possibly due to the presence of Ba. 2+ and CB6-Ba 2+ The addition of host-guest complexes influenced the stacking of GO nanosheets to some extent, thus compensating for wrinkles. Cross-sectional images of the three films ( Figure 3 As seen in the small image (df), the membrane exhibits a clear two-dimensional layered structure with highly ordered stacking, and the separation layer has a relatively uniform thickness. With the increase of Ba... 2+ and CB6-Ba 2+ The addition of host-guest complexes increased the film thickness and significantly altered the curvature of the GO nanosheets, further affecting the film roughness. (GO film, GO-Ba) 2+ Membrane and GO-CB6-Ba 2+ AFM images of the membrane ( Figure 3 The small image (in the middle section) further confirms this phenomenon. The image shows that all intercalated GO films exhibit a smoother surface than the original film, with the roughness gradually decreasing. The maximum roughness of the GO films can be attributed to the local hydrogen bonding interactions between numerous oxygen-containing functional groups on the GO nanosheets, leading to the aggregation and folding of certain regions of the GO nanosheets during stacking. Meanwhile, Ba... 2+ and CB6-Ba 2+ The interaction between the complex and GO allows it to insert into the interlayer of GO nanosheets. This weakens the non-covalent bonding interactions between adjacent GO nanosheets, resulting in uniform and ordered stacking during pressure-assisted processing, thus leading to a flatter film surface structure. Specifically, GO-CB6-Ba... 2+ The roughness of the membrane is greater than that of GO-Ba 2+ The reason is that the inherent rigid structure of CB6 prevents the complete stacking of GO nanosheets.

[0061] During the experiment, observation of the surface morphology of the GO films and GO-CB6 films prepared in Comparative Examples 1 and 3 revealed that the GO-CB6 film surface exhibited agglomeration of GO nanosheets, resulting in surface defects. This was attributed to the uneven stacking of the GO nanosheets. Cross-sectional images of the GO-CB6 film further confirmed this conclusion, showing that the GO nanosheets were loosely and chaotically stacked with uneven thickness. This demonstrates that CB6, lacking active sites, cannot function as a standalone interlayer crosslinking agent for GO nanosheets. Therefore, CB6-Ba 2+ The intercalation of host-guest complexes has a significant impact on the microstructure of GO membranes.

[0062] The stacking of GO nanosheets leads to changes in the membrane surface morphology and also affects the formation of membrane channels. To clarify the role of Ba... 2+ and CB6-Ba2+ The changes in GO channels caused by intercalation were characterized by XRD in different membranes under dry and wet conditions. The Bragg equation was used to calculate the GO membrane and GO-Ba membrane. 2+ Membrane and GO-CB6-Ba 2+ Interlayer d-space value of the membrane ( Figure 4 (small image a), due to Ba 2+ The introduction of this technology increases the interlayer spacing of GO layers, but CB6-Ba 2+ The introduction of [a specific ingredient] reduces the interlayer spacing of GO. The d-spacing of the original GO film significantly increases from 1 nm to 1.11 nm. This is because, under wet conditions, the GO nanosheets exhibit strong hydrophilicity due to the presence of oxygen-containing functional groups, causing water molecules to be adsorbed into the interlayer channels, resulting in swelling of the membrane structure. In contrast, GO-CB6-Ba [a specific ingredient]... 2+ The difference in dry and wet d-spacing between the membranes is smaller than that of the original GO membrane, indicating that this is due to the CB6-Ba 2+ The interaction between GO and water molecules improves the anti-swelling properties of the GO membrane. LF-NMR was used with water molecules as a probe. Figure 4 The small figure (b) further analyzed CB6-Ba 2+ The influence of intercalation on the microchannel structure of the membrane. For GO membrane structures, three time domains emerge: the sub-nanometer confinement region (10). -1 The time domain region of -10ms, channel I), and the nanoscale confinement region (10⁻¹⁰ ms). 3 The time domain region of ms (channel II) and the free water region not in the GO membrane (10 3 -10 4 The time-domain region in milliseconds (channel III). Channel I belongs to the nanochannels generated by the interlayer spacing of the GO film, while channel II represents microporous defects constructed from loosely overlapping GO nanosheets. (Compared to GO films and GO-Ba...) 2+ Compared to membranes, GO-CB6-Ba exhibits superior performance in the sub-nanometer confinement region. 2+ The increased relaxation time of water in the medium indicates that water molecules have penetrated the interlayer spacing of GO, making them more easily diffused, and that the interlayer spacing has increased. Compared to GO membranes, GO-CB6-Ba... 2+ The reduced relaxation time of the film within the nanoconfined region indicates a decrease in the size and number of micropore defects, suggesting that CB6 and Ba... 2+ The addition of GO nanosheets makes the stacking more orderly and the channels more regular.

[0063] 3. OSN performance of the membrane

[0064] 3.1 Solvent Transport

[0065] To verify the CB6-Ba package formed 2+Intercalation of the complex can solve the swelling problem of GO. Experiments were conducted using solvents with different polarities. Before the OSN experiment, the stability of the membrane was evaluated by observing the appearance of the membrane after sonication in water and measuring the weight loss ratio in different solvents.

[0066] GO membrane and GO-Ba 2+ After a period of ultrasound treatment, the GO selective layer on the membrane surface began to detach, compared to the GO-CB6-Ba layer. 2+ The base membrane and selective layer exhibited good adhesion, and the GO layer remained intact during subsequent testing. Furthermore, GO-CB6-Ba... 2+ The membrane exhibits a smaller weight loss ratio than the other two membranes in several solvents.

[0067] See Figure 5 Small image a, compared to GO membrane and GO-Ba 2+ Membrane, GO-CB6-Ba 2+ The membrane exhibits superior permeability to common solvents such as N,N-dimethylformamide (DMF), ethanol (EtOH), methanol (MeOH), water, and acetonitrile (ACN). The introduction of CB6 significantly improves the membrane's permeability to solvents, with a particularly noticeable increase in flux for water and acetonitrile.

[0068] For GO-CB6-Ba 2+ The membrane's resistance to compaction in water and acetonitrile was evaluated, and the results showed that ( Figure 5 (See small figure b). The fluxes of water and acetonitrile show an approximately linear increase without slowing down, indicating that the membrane can withstand high pressure. A possible reason is that GO-CB6-Ba... 2+ The addition of CB6 results in a larger interlayer spacing in the membrane, thereby accelerating the permeation of organic solvents. Furthermore, the rigid structure of CB6 may reduce the degree of membrane swelling in organic solvents, thus maintaining the structural stability of the channels and leading to an increase in solvent permeability.

[0069] To further investigate solvent transport within membrane nanochannels and clarify the reasons for increased solvent permeability, we first studied the relationship between solvent properties and membrane permeability. Differences in solvent permeability may be related to solvent physical parameters, such as viscosity, solubility parameters, and kinetic diameter. Experiments revealed that GO-CB6-Ba... 2+ The permeability of the membrane is strongly correlated with the viscosity of the solvent. Figure 5 (See small figure in c), the order of permeability to pure solvents is acetonitrile (27.23 LMH bar). -1 )>Water (11.69LMHbar -1 > Methanol (8.61 LMH bar) -1> Ethanol (3.52 LMH bar) -1 > DMF (0.13 LMH bar) -1 Therefore, it can be shown that solvent viscosity plays an important role in the solvent permeation process of this membrane.

[0070] GO-CB6-Ba 2+ The rapid water permeability of the membrane is attributed to the adsorption of water molecules by the carbonyl groups on the CB6 molecules. The surface charge density σ(α) of the membrane was calculated using the Gouy-Chapmann equation by testing the surface Zeta potential of several membranes. Figure 5 (See small image d). Due to the hydrolysis of oxygen-containing functional groups on the GO nanosheets, the GO film has a negatively charged surface, while Ba... 2+ The addition of CB6 reduces the negative charge density on the film surface. With the addition of CB6, GO-CB6-Ba 2+ The surface charge density of the membrane is comparable to that of the GO membrane; however, its water permeability is nearly four times higher. This indicates that the presence of carbonyl ports on CB6 enhances the hydrogen bonding interaction between CB6 and water molecules, allowing water to readily adsorb onto the membrane surface and thus permeate rapidly. Additionally, the dynamic water contact angle (…) Figure 5 (See the small figure in the middle) Further analysis of solvent transport channels is possible. The three membranes have similar surface hydrophilicity, but at 2 s, GO-CB6-Ba... 2+ The rate of decrease in water contact angle of the membrane is greater than that of the GO membrane and GO-Ba membrane. 2+ The membrane showed that water molecules entered the interlayer space more quickly. After 18 seconds, the contact angles of the various membranes decreased by 7.2%, 13.8%, and 15.3%, respectively. This indicates that the addition of CB6 molecules makes it easier for water molecules to enter the interlayer space of the GO nanosheets, thus facilitating water molecule permeation into the membrane bulk.

[0071] Low-field NMR using acetonitrile molecules as probes further demonstrated the transport of acetonitrile molecules within the channel. Figure 5 (Small figure in f). From the figure, it can be seen that, compared to the GO membrane and GO-Ba... 2+ Compared to membranes, GO-CB6-Ba 2+ The increased relaxation time of ACN in the sub-nanometer confinement region indicates that ACN molecules penetrate the GO interlayer spacing and diffuse more easily (similar to the transport of water molecules). GO-CB6-Ba 2+ The reduced relaxation time of the membrane within the nanoconfined region indicates a decrease in the size and number of micropore defects, suggesting that CB6 and Ba... 2+ The addition of GO nanosheets makes the stacking more orderly, the channels more regular, and the transport path of acetonitrile molecules shorter, thus increasing its permeability.

[0072] 3.2 Separation performance

[0073] Using solutes of different sizes and charges to target GO-CB6-Ba 2+ Preliminary performance of the membrane was evaluated. Experiments revealed that GO-CB6-Ba... 2+ The membrane exhibits higher retention rates for negatively charged dyes than for positively charged dyes, and even higher retention rates for dyes with molecular weights above 600. To further demonstrate the effectiveness of GO-CB6-Ba... 2+ The membrane's separation potential in organic solvent systems was demonstrated by testing its separation performance for several dyes in an acetonitrile system. The membrane maintained a retention rate of over 90% for several dyes (Reactive Blue 19 (RB19), Aniline Blue (AB), Methyl Blue (MB), Fast Green (FG), and Coomassie Brilliant Blue (BBR)), and achieved an acetonitrile flux of 25 LMH / bar. -1 above( Figure 6 (Small image in middle a).

[0074] Meanwhile, the long-term stability of the solid green in acetonitrile was investigated. Figure 6 (small image in b), within 110 hours of testing, GO-CB6-Ba 2+ The membrane consistently maintained a retention rate of over 99% for the solid green dye, while the permeability decreased, which can be attributed to the adsorption of the dye on the membrane surface.

[0075] Compared with the OSN performance in the literature, GO-CB6-Ba 2+ The membrane exhibits good solvent permeability and molecular selectivity. The retention mechanism of the dye molecules can be attributed to size sieving and the Donnan effect. Based on the size and charge of the dye molecules and the zeta potential of the membrane, GO-CB6-Ba 2+ The membrane surface is negatively charged, so the membrane has an electrostatic repulsion effect on negatively charged dyes. At the same time, the membrane pore size and the size of the interlayer channels have different separation effects on molecules of different sizes.

[0076] The above study reveals the influence of intercalation complexes on GO membrane channel formation and provides a new GO intercalation material to improve the stability of GO membranes. This material is expected to be used for intercalation of other two-dimensional material membranes.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. However, the above description is merely a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other embodiments derived by those skilled in the art without departing from the technical solution of the present invention should be covered within the patent scope of the present invention.

Claims

1. An application of a two-dimensional nanochannel membrane based on molecular encapsulation technology in the filtration of organic solvent systems, wherein the filtration of organic solvent systems is for the filtration of negatively charged dyes; the two-dimensional nanochannel membrane is used to improve permeation flux or molecular selectivity, characterized in that, The two-dimensional nanochannel membrane includes a substrate and a selective separation layer on the substrate. The selective separation layer is composed of graphene oxide nanosheets, and between adjacent GO nanosheets are host-guest complexes composed of cucurbitaurea-encapsulated metal ions, wherein the metal ions are Ba. 2+ ; The cucurbituril mentioned refers to one or more of CB6, CB7, CB8, CB9, and CB10; The surface of the substrate has been cross-linked with a polyamine, which is selected from triethylenetetramine, diethylenetriamine, and polyethylenepolyamine. The method for preparing the two-dimensional nanochannel membrane includes the following steps: Metal ion salts and cucurbituril were dissolved in deionized water and encapsulated to form a host-guest complex solution. GO dispersion was added to obtain a coating solution. The coating solution was deposited on a modified substrate using pressure-assisted filtration to form a uniform coating layer. After heat treatment at 60°C, a two-dimensional nanochannel membrane was obtained. The anion of a metal ion salt is Cl. - The mass percentage of metal ion salts and the mass percentage of cucurbituril in the host-guest complex solution are 0.2–0.5 wt% and 0.6–0.8 wt%, respectively.

2. The application according to claim 1, characterized in that, The substrate is a polyimide material.

3. The application according to claim 2, characterized in that, The substrate crosslinking process is as follows: the PI substrate is immersed in polyethylene polyamine with a mass concentration of 8-15% for 10-20 minutes to complete the crosslinking.

4. The application according to claim 1, characterized in that, The GO dispersion was obtained by dispersing a GO solution in deionized water and then sonicating it for 100–140 min. The concentration of GO in the resulting GO dispersion was 0.03–0.05 mg / mL. -1 ; The volume ratio of GO dispersion to host-guest complex solution was 10:1~2.5; per 1 cm 2 For the surface area of ​​the base film, the amount of coating solution used is 5-30 mL.

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