An ionic conjugated microporous polymer nanochannel composite membrane and its preparation method and application

Abstract

The present invention discloses an ionic conjugated microporous polymer nanochannel composite membrane and its preparation and application. The composite membrane includes a layer of ionic conjugated microporous polymer membrane and a layer of membrane material with a macroporous structure. The ionic conjugated microporous polymer membrane has an ultra-thin membrane thickness and regular charged sub-nanometer channels, and has good ion permeability and good ion selectivity. Some pores of the ionic conjugated microporous polymer membrane correspond to some macropores in the membrane material with a macroporous structure. The composite membrane is prepared by electrochemical in-situ polymerization using a membrane material with a macroporous structure as a substrate. The salinity gradient energy output power density of the composite membrane of the present invention can reach 18W / m 2 The above method is simple to operate, easy to control, requires simple equipment, can be produced on a large scale, and has broad application prospects.

Description

Technical Field

[0001] The invention relates to an ionic conjugated microporous polymer nanochannel composite membrane and preparation and application thereof, belonging to the field of nanochannel composite membranes. Background Art

[0002] Osmotic energy, or salinity gradient energy, also known as "blue energy," is considered a promising renewable energy source due to its abundant reserves and widespread distribution. It offers an attractive solution for transitioning away from fossil fuels and meeting growing energy demands. Over the past few decades, membrane-based reverse electrodialysis (RED) has emerged as a promising technology for capturing this blue energy from natural water. In RED systems, preferential counterion diffusion through ion exchange membranes is crucial for osmotic energy conversion, but their performance is often limited by a trade-off between permeability and selectivity. In recent years, significant research has focused on emerging crystalline porous materials, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, and graphene oxide (GO), as ion-conducting materials. These membranes exhibit excellent ion selectivity due to their highly uniform pore sizes, but processability remains a major challenge. In recent years, a variety of polymer membranes with dense structures and small channel diameters have been developed for selective ion transport. These polymer membranes exhibit high ion selectivity due to size selection and electrostatic interactions. However, the long, discontinuous channels formed by the self-assembly of flexible segments significantly hinder ion transport. Unfortunately, the osmotic energy conversion performance of currently reported polymer membranes remains unsatisfactory. This is mainly due to their insufficient ion permeation selectivity, which increases the Gibbs free energy dissipated by the RED system in the form of Joule heat. Furthermore, the complex preparation process also greatly limits their application. Therefore, porous membranes with tunable pore structures and designable channel surfaces are a promising platform for the production of advanced membranes.

[0003] Conjugated microporous polymers (CMPs), emerging porous organic materials, offer advantages such as high surface area, permanent micropores, extended π-conjugation, and excellent chemical and thermal stability. They hold great promise as ion-exchange membranes for osmotic energy harvesting. However, to our knowledge, CMPs have never been applied to develop ion-selective exchange membranes for osmotic energy harvesting. This is because most CMP membranes reported to date are neutral nanoporous frameworks lacking charge separation capabilities. Ionic CMPs (i-CMPs) are an intriguing class of CMPs because they share the characteristics of CMP materials: integrating ion modules into the CMP framework allows for the formation of charged channels within subnanometer spaces, imbuing them with charge separation capabilities. This allows ion transport to be controlled by both size and charge, further improving selectivity without sacrificing permeability. Therefore, i-CMPs are considered promising candidates for ion conductors and ion separators, potentially breaking the trade-off between ionic conductivity and ion selectivity. However, due to the inherent extremely rigid cross-linked structure of CMPs materials, the processability and control of the film formation process are challenging, and only a few i-CMPs films have been reported. Summary of the Invention

[0004] Purpose of the invention: The first purpose of the present invention is to provide an ionic conjugated microporous polymer nanochannel composite membrane, which has stable performance and is green and environmentally friendly. The second purpose of the present invention is to provide a method for preparing an ionic conjugated microporous polymer nanochannel composite membrane, which is simple to operate, has mild conditions and is easy to implement. The third purpose of the present invention is to provide the application of the ionic conjugated microporous polymer nanochannel composite membrane in salinity gradient energy conversion. The ionic conjugated microporous polymer nanochannel composite membrane can be used for salinity gradient energy conversion, extracting osmotic energy from the salinity gradient, and has the advantages of stable performance, high conversion power, and a wide range of applicable environments.

[0005] Technical solution: The present invention describes an ionic conjugated microporous polymer nanochannel composite membrane, which includes a layer of ionic conjugated microporous polymer membrane and a layer of membrane material with a macroporous structure. Some pores of the ionic conjugated microporous polymer membrane correspond to and communicate with some macropores in the membrane material with a macroporous structure.

[0006] Furthermore, the ionic conjugated microporous polymer membrane has an ultra-thin membrane thickness and regular charged sub-nanopores.

[0007] Furthermore, the ionic conjugated microporous polymer membrane includes 1,3,5-tris(9-carbazolyl)benzene and an ionic carbazole monomer (i-Cbz) and is synthesized by electrochemical polymerization.

[0008] Furthermore, the ionic carbazole monomer is 6-(9H-carbazole-9-yl)-N,N,N-trimethylhexane-1-ammonium bromide (CbzC6-N), 6-(9H-carbazole-9-yl)hexane-1-sodium sulfonate (CbzC6-S) or carbazole (Cbz).

[0009] Furthermore, the membrane material with a macroporous structure is selected from one of anodic aluminum oxide membrane (AAO), titanium dioxide nanotube array membrane (TNT), polycarbonate membrane (PC), cellulose membrane (NC), polytetrafluoroethylene membrane (PTFE) or polyvinylidene fluoride membrane (PVDF), preferably AAO.

[0010] Furthermore, the thickness of the ionic conjugated microporous polymer membrane is 40 to 100 nm, preferably 40 nm, and the diameter of the pores is 0.7 to 0.9 nm.

[0011] Furthermore, the diameter of the pores of the membrane material having a macroporous structure is 50 to 80 nm, preferably 60 nm.

[0012] The method for preparing the ionic conjugated microporous polymer nanochannel composite membrane of the present invention comprises the following steps:

[0013] (1) mixing 1,3,5-tris(9-carbazolyl)benzene, an ionic carbazole monomer, and a supporting electrolyte, and adding dichloromethane and acetonitrile to obtain a mixed solution;

[0014] (2) Using a membrane material with a macroporous structure as a working electrode, an electrochemical polymerization reaction is carried out using cyclic voltammetry;

[0015] (3) After the polymerization reaction is completed, the composite membrane material is taken out, washed with a solvent, and vacuum-dried to obtain an ionic conjugated microporous polymer nanochannel composite membrane.

[0016] Furthermore, in step (1), the supporting electrolyte is tetrabutylammonium hexafluorophosphate.

[0017] Furthermore, in step (1), the molar ratio of 1,3,5-tris(9-carbazolyl)benzene to the ionic carbazole monomer (i-Cbz) is (1-1.2):(1-1.5), preferably 1:1.

[0018] Furthermore, in step (1), the content of the supporting electrolyte in the mixed solution is 0.1 to 0.2 mol / L.

[0019] Furthermore, in step (1), the volume ratio of dichloromethane to acetonitrile is 3-4:2-1, preferably 3:2.

[0020] Furthermore, in step (1), the volume molar ratio of dichloromethane to 1,3,5-tris(9-carbazolyl)benzene is 24:03-0.05 mL / mmol, preferably 24:0.04 mL / mmol.

[0021] Furthermore, in step (2), the window potential of the cyclic voltammetry is -0.6 to +1.23 V, the scan rate is 50 to 100 mV / s, the polymerization time is 0.5 to 6 h, and the reaction temperature is maintained at 20 to 25° C., preferably: the temperature is 20° C. and the polymerization time is 1 h.

[0022] Furthermore, in step (3), the solvent is a mixed solution of dichloromethane and acetonitrile, and the volume ratio of dichloromethane to acetonitrile is 3-4:2-1, preferably 3:2.

[0023] Furthermore, in step (3), the washing method is to soak the composite membrane in the solvent for 10 to 12 hours, preferably for 10 hours.

[0024] Furthermore, in step (3), vacuum drying is performed at 60-100° C. for 6-8 h, preferably at 80° C. for 8 h.

[0025] The invention relates to the application of the ionic conjugated microporous polymer nanochannel composite membrane in the salinity gradient energy conversion process.

[0026] Furthermore, during the application process, a salinity difference is formed between the concentrated salt solution and the dilute salt solution, and the salinity difference energy is converted into electrical energy.

[0027] Furthermore, the molar ratio of the concentrated salt solution to the dilute salt solution is (0.1-5):(0.0001-0.1).

[0028] Furthermore, the concentrated salt solution and the dilute salt solution are both sodium chloride solution, potassium chloride solution, magnesium chloride solution, lithium bromide solution or calcium chloride solution.

[0029] Furthermore, the molar concentration of the concentrated salt solution is 0.1 to 5 mol / L.

[0030] Furthermore, the molar concentration of the dilute salt solution is 0.0001 to 0.1 mol / L.

[0031] Furthermore, the concentrated salt solution and the dilute salt solution contain the same salt type.

[0032] This invention uses 1,3,5-tris(9-carbazolyl)benzene and ionic carbazole monomers as raw materials and prepares an ionic conjugated microporous polymer nanochannel composite membrane through electrochemical polymerization. The ionic conjugated microporous polymer membrane prepared in this invention has an ultrathin membrane thickness and charged sub-nanometer membrane pores; it can simultaneously achieve selective ion transport and exhibit good ion permeability.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0034] (1) The ionic conjugated microporous polymer nanochannel composite membrane of the present invention includes an ionic conjugated microporous polymer membrane with regular charged sub-nanopores. The ionic conjugated microporous polymer nanochannel composite membrane has stable performance, is green and environmentally friendly, and the preparation method is simple to operate under mild conditions and is easy to implement. It overcomes the shortcomings of the prior art that ion selectivity and ion permeability cannot be taken into account at the same time, the process is complex, and the controllability is poor.

[0035] (2) The application of the ionic conjugated microporous polymer nanochannel composite membrane of the present invention in salinity gradient osmotic energy conversion has obvious advantages:

[0036] First, the ionic conjugated microporous polymer membrane serving as the ion-selective layer possesses abundant charged subnanometer pores, endowing it with excellent ion selectivity. The introduction of more electronegative functional groups further increases the surface charge density, further enhancing the membrane's ion selectivity. The ultra-thin membrane and well-organized pore structure significantly reduce resistance to ion transport across the membrane, effectively improving ion permeability through the selective layer.

[0037] Secondly, the inherent surface charge distribution asymmetry and structural asymmetry of the ionic conjugated microporous polymer nanochannel composite membrane make the charge density of the ionic conjugated microporous polymer membrane layer higher than that of the membrane material with a macroporous structure, and the pore size is smaller than that of the membrane material with a macroporous structure, which makes the asymmetric ionic conjugated microporous polymer nanochannel composite membrane have good ion current rectification characteristics, greatly improving the ion selectivity of the osmotic energy conversion system.

[0038] Again, the ionic conjugated microporous polymer nanochannel composite membrane of the present invention successfully converted salinity gradient energy into electrical energy in the salinity gradient osmotic energy conversion. Under the conditions of simulating the salinity gradient of seawater (0.5 mol / L NaCl) and river water (0.01 mol / L NaCl), the maximum output power density reached 18.91 W / m 2 , this is the commercial standard 5W / m 2 Above that, further increasing the salinity gradient (5mol / L NaCl / 0.01mol / L NaCl), the maximum output power density can be increased to 105W / m 2 .

[0039] Finally, the ionic conjugated microporous polymer nanochannel composite membrane of the present invention showed good stability in the application of salinity gradient osmotic energy conversion. After 10 days of performance stability testing, the maximum output power density showed almost no attenuation, laying a solid foundation for subsequent practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the preparation process of the ionic conjugated microporous polymer nanochannel composite membrane prepared in Example 1;

[0041] Figure 2 This is a scanning electron microscope image of the AAO film prepared in Example 1;

[0042] Figure 3 This is a scanning electron microscope image of the Au-AAO film prepared in Example 1;

[0043] Figure 4 This is a scanning electron microscope image of the ionic conjugated microporous polymer nanochannel composite membrane prepared in Example 1;

[0044] Figure 5 Schematic diagram of the salinity gradient osmotic energy conversion device in Example 4;

[0045] Figure 6 The current density and external resistance relationship diagrams and the power density and external resistance relationship diagrams obtained from the salinity gradient osmotic energy conversion of ionic conjugated microporous polymer nanochannel composite membranes of different thicknesses in Example 1 and Example 3;

[0046] Figure 7 The current density-external resistance relationship diagram and the power density-external resistance relationship diagram obtained in salinity gradient osmotic energy conversion of the i-CMPs / AAO composite membrane in Example 1-2 and the CMPs / AAO composite membrane and AAO membrane in Comparative Example 1;

[0047] Figure 8 This is a comparison chart of the energy conversion performance of salinity gradient osmosis of membrane materials reported in relevant literature in Example 2 and Comparative Example 2;

[0048] Figure 9 This is a test chart of salinity gradient osmotic energy conversion of the ionic conjugated microporous polymer nanochannel composite membrane in Example 5 within 10 days. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0050] Example 1 Preparation of ionic conjugated microporous polymer nanochannel composite membrane

[0051] (1) Preparation of anodic aluminum oxide (AAO) membrane: First, the aluminum foil was ultrasonically cleaned with acetone and 1 mol / L NaOH solution for 10 minutes. After the ultrasonication, the residual liquid on the surface of the aluminum foil was rinsed with deionized water. The first anodization was carried out with 0.4 mol / L oxalic acid as the electrolyte at 50 V and 25°C for 40 minutes. In order to eliminate the irregular oxide layer formed, the oxide layer formed on the surface of the aluminum foil after the first anodization was cleaned with a mixed acid solution consisting of 6 wt% H3PO4 and 2 wt% H2CrO4 at 60°C for 30 minutes. Subsequently, the second anodization was carried out for 6 hours, and the other conditions were the same as the first anodization. The aluminum substrate was removed with a saturated CuCl2 solution. The AAO membrane was treated with 5 wt% H3PO4 solution at 30°C for 40 minutes to remove the barrier layer on the top of the anodized aluminum membrane. The AAO membrane was soaked in deionized water overnight and dried. The pore size of the nanochannels in the anodic aluminum oxide membrane can be controlled by adjusting the voltage during anodization. Scanning electron microscopy analysis of the AAO membrane shows that the pore size of the AAO membrane is 60 nm, the thickness is 40 μm, and the pores are evenly distributed. Figure 2 shown. Figure 2 The scanning electron microscope images of the AAO membrane prepared in Example 1, wherein A is the SEM image of the AAO top barrier layer, B is the SEM image of the top cross section, C is the SEM image of the AAO bottom, and D is the SEM image of the bottom cross section. Figure 2 It can be seen that the prepared AAO morphology and structure are regular and orderly.

[0052] (2) Preparation of Au-AAO: A thin Au-AAO film with gold conductive function was plated on one side of the prepared AAO film using magnetron sputtering technology. Scanning electron microscopy analysis of Au-AAO was performed, as shown in Figure 2. Figure 3 shown. Figure 3 The following are scanning electron microscope images of the Au-AAO film prepared in Example 1, wherein A is the SEM image of the top of the Au-AAO and B is the SEM image of the top cross section. Figure 3 It can be seen that the sputtered Au layer has no effect on the surface morphology of AAO.

[0053] (3) Preparation of a mixed reaction solution: 23 mg of 1,3,5-tris(9-carbazolyl)benzene, an equimolar amount of ionic carbazole monomer CbzC6-S (12.45 mg), and 1.55 g of tetrabutylammonium hexafluorophosphate were dissolved in 40 mL of a mixed solution of dichloromethane and acetonitrile (volume ratio 3:2) to obtain a mixed reaction solution.

[0054] (4) Preparation of ionic conjugated microporous polymer nanochannel composite membrane: 40 mL of the mixed reaction solution was placed in an electrolytic cell device, in which an Au-AAO membrane with a lead was fixed. Cyclic voltammetry was used to perform electrochemical polymerization with a window potential of -0.6 to +1.23 V, a scan rate of 50 mV / s, and a polymerization time of 1 h. The ionic conjugated microporous polymer membrane structure was deposited on an area of ​​1.14 cm 2 On the conductive gold surface of the Au-AAO membrane material with a macroporous structure, an ionic conjugated microporous polymer nanochannel (S-CMP / AAO) composite membrane with an AAO nanochannel pore size of 60 nm was obtained. The preparation process is as follows Figure 1 Scanning electron microscopy analysis of the ionic conjugated microporous polymer nanochannel composite membrane prepared in this embodiment shows that the thickness of the ionic conjugated microporous polymer membrane is 40±0.5nm. Figure 4 shown. Figure 4 The scanning electron microscope images of the ionic conjugated microporous polymer nanochannel composite membrane prepared in Example 1, wherein (A) is the top image of the i-CMPs / AAO composite membrane, (B) is the cross-sectional image of the i-CMPs / AAO composite membrane, (C) is the bottom image of the i-CMPs / AAO composite membrane, and (D) is the enlarged cross-sectional top image of the i-CMPs / AAO composite membrane. Figure 4 It can be seen that the ionic conjugated microporous polymer membrane is tightly covered on the top of the AAO nanochannel, indicating the successful preparation of the ionic conjugated microporous polymer nanochannel composite membrane. The pore size of the ionic conjugated microporous polymer membrane layer was measured by nitrogen adsorption experiment at 77K to be 0.78nm.

[0055] Example 2

[0056] The preparation process was the same as in Example 1, except that 15.6 mg of CbzC6-N or 6.69 mg of CbzC6-S was used instead of 12.45 mg. This resulted in two sets of ionic conjugated microporous polymer nanochannel (i-CMPs / AAO) composite membranes, designated N-CMP / AAO and H-CMP / AAO, respectively. Scanning electron microscopy analysis revealed that the thickness of both sets of ionic conjugated microporous polymer membranes was 40 ± 0.5 nm. Nitrogen adsorption experiments at 77 K revealed pore sizes of 0.73 nm and 0.85 nm, respectively. This demonstrates the successful preparation of ionic conjugated microporous polymer nanochannel composite membranes.

[0057] Example 3 Experimental process for preparing ionic conjugated microporous polymer nanochannel composite membranes with different thicknesses

[0058] The preparation process was the same as that of Example 1, except that by changing the electrochemical polymerization time in step (4) of Example 1 to 1.5 h, 2 h, 2.5 h, and 3 h, four groups of clay-based nanofiber nanochannel composite membranes with an anodic aluminum oxide nanochannel pore size of 60 nm were obtained. Scanning electron microscopy analysis showed that the thicknesses of the four groups of ionic conjugated microporous polymer membranes were 50 ± 0.5 nm, 60 ± 0.5 nm, 80 ± 0.5 nm, and 100 ± 0.5 nm, respectively. This indicates that the electrochemical polymerization time can regularly affect the thickness of the ionic conjugated microporous polymer membrane.

[0059] Example 4 Application of Salinity Gradient Osmotic Energy Conversion of Ionic Conjugated Microporous Polymer Nanochannel Composite Membrane

[0060] 1. Salinity gradient osmosis energy conversion device such as Figure 5 As shown, the salinity gradient osmotic energy conversion device consists of a homemade H-2-compartment electrochemical cell. An ionic conjugated microporous polymer nanochannel composite membrane is sandwiched between the two cells, secured by screws. A concentrated salt solution (0.5M NaCl electrolyte solution) is placed on the large-pore side of the ionic conjugated microporous polymer nanochannel composite membrane, i.e., the anodic aluminum oxide side. A dilute salt solution (0.01M NaCl electrolyte solution) is placed on the small-pore side of the ionic conjugated microporous polymer nanochannel composite membrane, i.e., the ionic conjugated microporous polymer membrane side. The two salt solutions are connected via an external electrochemical workstation and a load resistor. By adjusting the external resistance, the relationship between current density and power density and the external resistance can be measured.

[0061] 2. Salinity gradient osmotic energy conversion of ionic conjugated microporous polymer nanochannel composite membranes with different thicknesses

[0062] The salinity gradient osmotic energy conversion device in step 1 was used, and the composite membranes in the salinity gradient osmotic energy conversion device were replaced by the ionic conjugated microporous polymer nanochannel composite membranes prepared in Example 1 and Example 3, respectively. Other conditions remained unchanged, and the effect of the thickness of the ionic conjugated microporous polymer membrane on the salinity gradient osmotic energy conversion performance was tested. The results are shown in FIG. Figure 6 shown.

[0063] Figure 6 The current density and external resistance relationship diagrams and the power density and external resistance relationship diagrams obtained in the salinity gradient osmotic energy conversion of ionic conjugated microporous polymer nanochannel composite membranes of different thicknesses in Example 1 and Example 3, wherein A is the current density and external resistance relationship diagram, and B is the power density and external resistance relationship diagram. Figure 6It can be found that when the thickness of the ionic conjugated microporous polymer membrane is 40±0.5nm, 50±0.5nm, 60±0.5nm, 80±0.5nm and 100±0.5nm, the corresponding external circuit power density is 18.91W / m 2 、13.67W / m 2 、10.7W / m 2 、8.59W / m 2 and 7.05W / m 2 When the thickness of the ionic conjugated microporous polymer membrane is within 40~100±0.5nm, it meets the commercial standard of 5W / m 2 , and when the thickness of the ionic conjugated microporous polymer membrane is 40±0.5nm, its salinity gradient osmotic energy conversion output power is the highest.

[0064] Comparative Example 1

[0065] Preparation of CMPs / AAO membrane: The preparation process is the same as that in Example 1, except that 40 mL of the mixed reaction solution in Example 1 is replaced with 40 mL of 1 mmol / L pure 1,3,5-tris(9-carbazolyl)benzene solution, and the CMPs / AAO membrane is formed on the Au-AAO by electrochemical polymerization.

[0066] The output power density of salinity gradient osmotic energy conversion of pure AAO membrane and CMPs / AAO membrane was tested by replacing the ionic conjugated microporous polymer nanochannel composite membrane in Example 4 with the pure AAO membrane prepared in Example 1 and the CMPs / AAO membrane prepared in this comparative example, respectively. Other conditions remained unchanged. Figure 7 shown.

[0067] Figure 7 The current density-to-resistance relationship diagram and the power density-to-resistance relationship diagram obtained in salinity gradient osmotic energy conversion of the i-CMPs / AAO composite membrane in Example 1-2 and the CMPs / AAO composite membrane and AAO membrane in Comparative Example 1 are shown in Figures A and B. Figure 7 The experimental results show that the external circuit power density of pure AAO membrane and CMPs / AAO membrane under 0.01M:0.5M NaCl gradient is 0.58W / m 2 and 1.41W / m 2, which is far lower than the external circuit power density of the i-CMPs / AAO membrane with a thickness of 40±0.5nm of the present invention. Since the pure AAO membrane does not have the functional layer of ionic conjugated microporous polymer membrane to improve the ion selective transmission performance, the salinity gradient osmosis energy conversion performance of the pure AAO membrane is far inferior to that of the ionic conjugated microporous polymer nanochannel composite membrane.

[0068] Comparative Example 2

[0069] The existing publicly reported:

[0070] Two-dimensional layered transition metal carbide (MXenes) films (see L. Ding, M. Zheng, D. Xiao, et al. Bioinspired Ti3C2T x MXene-Based Ionic Diode Membrane for High-EfficientOsmotic Energy Conversion. Angew. Chem. Int. Ed. 2022, 61, e202206152.);

[0071] Metal organic framework (MOFs) membranes (see C. Chen, L. Meng, L. Cao, et al. Phase Engineering of Zirconium MOFs Enables Efficient Osmotic Energy Conversion: Structural Evolution Unveiled by Direct Imaging. J. Am. Chem. Soc. 2024 146(17), 11855-11865.);

[0072] Covalent organic framework alumina (COFs / AAO) composite membranes (see M. Chen, K. Yang, J. Wang, et al. InSitu Growth of Imine-Bridged Anion-Selective COF / AAO Membrane for Ion Current Rectification and Nanofluidic Osmotic Energy Conversion. Adv. Funct. Mater., 33: 230-2427.);

[0073] Polymer (SPEEKs) membranes (see Y. Sun, T. Dong, C. Lu, et al. Tailoring A Poly (ethersulfone) Bipolar Membrane: Osmotic-Energy Generator with High Power Density. Angew. Chem. Int. Ed. 2020, 59, 17423.)

[0074] The salinity gradient osmotic energy conversion output power density of the above membrane material is compared with the salinity gradient osmotic energy collection performance of the ionic conjugated microporous polymer nanochannel composite membrane (S-CMP / AAO) in Example 1. Figure 8 shown

[0075] Figure 8 This is a comparison chart of the maximum output power density obtained by the ionic conjugated microporous polymer nanochannel composite membrane in Example 1 and the existing membrane material in Comparative Example 2 in salinity gradient osmotic energy conversion. Figure 8 The comparison results show that the external circuit power density of MXenes membrane, MOF membrane, COF membrane and Polymers membrane is 8.6W / m under the salinity gradient of 0.01M:0.5M. 2 、10.08W / m 2 , 2.55W / m 2 and 6.2W / m 2 , which is lower than the external circuit power density of 18.91W / m of the ionic conjugated microporous polymer membrane (S-CMP / AAO) with a thickness of 40±0.5nm of the present invention. 2 The salinity gradient osmotic energy conversion performance of some existing more advanced membrane materials is inferior to that of the ionic conjugated microporous polymer nanochannel composite membrane of the present invention.

[0076] Example 5 Stability Test of Salinity Gradient Osmotic Energy Conversion of Ionic Conjugated Microporous Polymer Nanochannel Composite Membrane

[0077] The ionic conjugated microporous polymer nanochannel composite membranes with a thickness of 40±0.5 nm in Examples 1 and 2 were placed for 2 days, 4 days, 6 days, 8 days, and 10 days to perform salinity gradient osmotic energy conversion tests. The post-test process was the same as in Example 4, with other conditions remaining unchanged. The results are shown in FIG. Figure 9 shown.

[0078] Figure 9 This is a 10-day salinity gradient osmotic energy conversion test of the ionic conjugated microporous polymer nanochannel composite membrane in Example 1 and Example 2. Figure 9The experimental results show that the ionic conjugated microporous polymer nanochannel composite membranes prepared in Examples 1 and 2 exhibit good stability in the application of salinity gradient osmotic energy conversion. After 10 consecutive days of testing, the reduction in output power density was less than 5%, laying a reliable foundation for subsequent practical applications.

Claims

1. An ionic conjugated microporous polymer nanochannel composite membrane, characterized in that: The ionic conjugated microporous polymer nanochannel composite membrane comprises a layer of ionic conjugated microporous polymer membrane and a layer of membrane material with a macroporous structure, wherein some pores of the ionic conjugated microporous polymer membrane are correspondingly connected with some macropores of the membrane material with a macroporous structure; The membrane material with a macroporous structure is selected from anodized aluminum membrane. The ionic conjugated microporous polymer membrane has an ultrathin membrane thickness and regular charged sub-nanopores. The thickness of the ionic conjugated microporous polymer membrane is 40 to 100 nm. The ionic conjugated microporous polymer membrane is synthesized by electrochemical polymerization of 1,3,5-tris(9-carbazolyl)benzene and an ionic carbazole monomer. The ionic carbazole monomer is 6-(9H-carbazol-9-yl)-N,N,N-trimethylhexane-1-ammonium bromide.

2. The ionic conjugated microporous polymer nanochannel composite membrane according to claim 1, characterized in that: The diameter of the pores of the ionic conjugated microporous polymer membrane is 0.7 to 0.9 nm, and the diameter of the pores of the membrane material with a macroporous structure is 50 to 80 nm.

3. The method for preparing the ionic conjugated microporous polymer nanochannel composite membrane according to claim 1 or 2, characterized in that: The following steps are involved: (1) 1,3,5-tris(9-carbazolyl)benzene, ionic carbazole monomer, and supporting electrolyte were mixed, and dichloromethane and acetonitrile were added to obtain a mixed solution; (2) Using a membrane material with a macroporous structure as the working electrode, the electrochemical polymerization reaction was carried out using cyclic voltammetry. The window potential of the cyclic voltammetry was -0.6 ~ +1.23 V and the scan rate was 50~100 mV / s. (3) After the polymerization reaction is completed, the composite membrane material is taken out, washed with a solvent, and vacuum dried to obtain an ionic conjugated microporous polymer nanochannel composite membrane.

4. The method for preparing the ionic conjugated microporous polymer nanochannel composite membrane according to claim 3, characterized in that: In step (1), the supporting electrolyte is tetrabutylammonium hexafluorophosphate, the molar ratio of 1,3,5-tris(9-carbazolyl)benzene to the ionic carbazole monomer is 1-1.2:1-1.5, the content of the supporting electrolyte in the mixed solution is 0.1-0.2 mol / L, the volume ratio of dichloromethane to acetonitrile is 3-4:2-1, and the volume molar ratio of dichloromethane to 1,3,5-tris(9-carbazolyl)benzene is 24:0.03-0.05 mL / mmol.

5. The method for preparing the ionic conjugated microporous polymer nanochannel composite membrane according to claim 3, characterized in that: In step (2), the reaction time is 0.5 to 6 h, and the reaction temperature is maintained at 20 to 25 °C; in step (3), the solvent is a mixed solution of dichloromethane and acetonitrile, and the washing method is to immerse the composite membrane in the solvent for 10 to 12 h; and the vacuum drying is drying at 60 to 100 °C for 6 to 8 h.

6. Use of the ionic conjugated microporous polymer nanochannel composite membrane according to claim 1 or 2 in a salinity gradient energy conversion process.

7. The use according to claim 6, characterized in that During the application process, a salinity difference is formed between the concentrated salt solution and the dilute salt solution, and the salinity difference energy is converted into electrical energy, wherein the molar ratio of the concentrated salt solution to the dilute salt solution is 0.1~5:0.0001~0.1, and the concentrated salt solution and the dilute salt solution are both sodium chloride solution, potassium chloride solution, magnesium chloride solution, lithium bromide solution or calcium chloride solution, and the type of salt in the concentrated salt solution and the dilute salt solution is the same.

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