Photoresponsive ionic covalent organic framework composite membrane as well as preparation method and application thereof
By preparing a photoresponsive ionic covalent organic framework composite membrane, the problem of ion transport regulation in complex aquatic environments for permeation power generation membrane materials was solved, the permeation power generation efficiency was improved, and the efficient extraction of light energy and permeation energy was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-03-13
AI Technical Summary
Existing permeation power generation membrane materials are difficult to actively and intelligently control ion transport behavior when facing complex and variable aquatic environments, resulting in low permeation power generation efficiency.
Ionic covalent organic framework materials were synthesized via a hydrothermal method. A protonation gradient was formed by acid exfoliation and pH adjustment. Combined with carboxymethyl cellulose as a flexible suture agent, a photoresponsive ionic covalent organic framework composite membrane was prepared by layer-by-layer filtration, enabling the directional migration of charge carriers under illumination.
The energy conversion efficiency of osmotic power generation is improved. By promoting the acquisition of ion flow energy under light irradiation through a photoresponsive membrane, active control of ion transport is achieved, thereby improving the extraction efficiency of osmotic energy.
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Figure CN121648766A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane materials technology, and in particular to a photoresponsive ionic covalent organic framework composite membrane, its preparation method, and its application. Background Technology
[0002] Osmotic energy, also known as salinity gradient energy, is a vast, clean, and renewable "blue energy" found at the interface between river and seawater. Osmotic power generation based on reverse electrodialysis technology is an effective way to capture this energy. Its core lies in using a selective separation membrane, utilizing the salt concentration gradient across the membrane to drive the directional migration of ions, thereby generating electricity. Therefore, the performance of the separation membrane directly determines the efficiency and output power of osmotic power generation.
[0003] Currently, membrane materials used for osmotic power generation mainly include traditional polymer ion exchange membranes (such as Nafion membranes) and emerging nanoporous membranes (such as MOF membranes and graphene membranes). However, these materials still face significant challenges in practical applications. Traditional polymer membranes typically suffer from low ion selectivity, high internal resistance, and limited power density. While emerging nanoporous membranes exhibit advantages in ion selectivity, their pore structure and surface physicochemical properties remain fixed once fabricated. This static characteristic makes them difficult to adapt to complex and variable real-world aquatic environments (such as salinity fluctuations and pollutant accumulation), hindering active and intelligent regulation of ion transport behavior and limiting their application in unsteady, high-efficiency osmotic power generation.
[0004] Covalent organic frameworks (COFs) are a class of novel porous crystalline materials formed by organic building blocks linked by strong covalent bonds, exhibiting a regular pore structure and excellent stability. COF membranes prepared from COFs possess advantages such as uniform pore size, ordered pore arrangement, and customizable surface chemistry, making them the preferred choice for high-performance ion separation membranes. However, current research on COF membranes in osmotic power generation largely focuses on their static ion selectivity, lacking research on the dynamic and intelligent control of their transport behavior.
[0005] Therefore, it is necessary to develop a new type of photoresponsive separation membrane that can maintain the inherent high selectivity of COF membranes and combine it with the utilization of light energy to achieve active control of ion transport flux and selectivity, realize the effective output of osmosis power generation, and improve energy conversion efficiency. Summary of the Invention
[0006] Therefore, this invention proposes a photoresponsive ionic covalent organic framework composite membrane, its preparation method, and its application.
[0007] The technical solution of this invention is implemented as follows: A method for preparing a photoresponsive ionic covalent organic framework composite film includes the following steps: S1. Hydrothermal synthesis of ionic covalent organic framework materials The monomers saffron T and 1,3,5-tricarboxymethyl phloroglucinol were added to acetic acid, heated to react, filtered, and the solid product was extracted to obtain an ionic covalent organic framework material. S2, acid-exfoliated ionic covalent organic framework materials The ionic covalent organic framework material obtained in S1 was added to an organic solvent and subjected to acid exfoliation to obtain an initial acid exfoliation solution. S3. Adjust the pH of the acid stripping solution. The pH value of the initial acid stripping solution was adjusted by alkaline solution to obtain acidic acid stripping solution a, neutral acid stripping solution b, and alkaline acid stripping solution c, respectively. S4, blending Acidic acid stripping solution a, neutral acid stripping solution b, and alkaline acid stripping solution c are respectively blended with carboxymethyl cellulose solution to obtain blended solution a, blended solution b, and blended solution c. The initial acid stripping solution is then blended with carboxymethyl cellulose solution to obtain blended solution d for later use. S5. Preparation of photoresponsive ionic covalent organic framework composite membranes The photoresponsive ionic covalent organic framework composite membrane was obtained by adding the blend solution c, blend solution b, blend solution a, and blend solution d in sequence and then filtering.
[0008] Furthermore, in step S1, the mass ratio of the monomer saffron T and 1,3,5-tricarboxymethyl phloroglucinol is 140-180:58-70; The solid-liquid ratio of the monomer saffron T to acetic acid is 140-180:24-30 mg / mL, and the concentration of acetic acid is 17-18 mol / L. Acetic acid is used not only as a solvent but also as a reaction catalyst to synthesize ionic covalent organic framework materials.
[0009] The heating reaction is carried out at 70-75°C for 72-96 hours; The solubilizer is prepared by refluxing at 105-108°C for 72-96 hours using ethanol as a solvent.
[0010] Saffron T, chemical formula C 20 H 19 ClN4, molecular weight 350.85, CAS number 477-73-6, structural formula is:
[0011] The hydrothermal synthesis route for ionic covalent organic framework materials of this invention is as follows:
[0012] Furthermore, in step S2, the organic solvent is acetonitrile, tetrahydrofuran and trifluoroacetic acid in a volume ratio of 7:3:2; trifluoroacetic acid is used to protonate the enamine bonds, increase the interlayer repulsion, and cause the ionic covalent organic framework material to be exfoliated into smaller nanosheet structures in the solution. The solid-liquid ratio of the ionic covalent organic framework material to the organic solvent is 0.1:22-25 g / mL; The acid stripping treatment is performed at a speed of 700-800 rpm for a duration of 72-96 hours. The initial acid stripping solution has a pH value of less than 0.5.
[0013] Furthermore, the acidic acid stripping solution a has a pH of 3.0, the neutral acid stripping solution b has a pH of 7.0, and the alkaline acid stripping solution c has a pH of 9.0. Step S3 is as follows: Take three equal portions of the initial acid stripping solution. First, add the alkali solution to the initial acid stripping solution according to the volume ratio of alkali solution to initial acid stripping solution of 24:45-47. Stir at 700-800 rpm for 5-8 minutes. Then, gradually add the alkali solution dropwise until the three portions of initial acid stripping solution are adjusted to pH=3.0, pH=7.0 and pH=9.0 respectively. Stir at 700-800 rpm for 2-4 hours.
[0014] Furthermore, the alkaline solution is a sodium hydroxide solution with a concentration of 1.0-1.2 mol / L; Furthermore, in step S4, the volume ratio of the acidic acid stripping solution a, the neutral acid stripping solution b, and the alkaline acid stripping solution c to the carboxymethyl cellulose solution is 2:5, the rotation speed is 700-800 rpm, and the time is 6-8 hours. The initial acid stripping solution and carboxymethyl cellulose solution were mixed in a volume ratio of 1:5, at a rotation speed of 700-800 rpm, for a time of 6-8 hours. The concentration of the carboxymethyl cellulose solution is 0.13-0.15 mg / mL.
[0015] Furthermore, in step S5, the filtration specifically involves: first filtration of the blended solution c, then adding the blended solution b after the solution has dried, then adding the blended solution a after the solution has dried, and finally adding the blended solution d for filtration.
[0016] Furthermore, the volume ratio of the blended solution c, blended solution b, blended solution a, and blended solution d is 7-10.5:7-10.5:7-10.5:8-12.
[0017] A photoresponsive ionic covalent organic framework composite membrane is prepared by any of the above-described preparation methods.
[0018] Application of a photoresponsive ionic covalent organic framework composite membrane or a photoresponsive ionic covalent organic framework composite membrane prepared by any of the above methods in water resource permeation energy extraction materials.
[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention regulates the protonation degree of ionic organic framework nanosheets by adjusting the pH to acidic, neutral, and alkaline levels. Carboxymethyl cellulose, a flexible suture agent, is used to maintain material stability. A layer-by-layer vacuum-assisted self-assembly of ionic covalent organic framework nanosheets with different protonation degrees (alkaline, neutral, and acidic) is employed using a layer-by-layer filtration method to obtain an ionic organic framework composite membrane with a protonation gradient. The band shift caused by the protonation gradient results in a type II heterojunction structure, enabling carrier separation and directional migration under illumination. In solution, it generates a photoresponsive ion current, allowing the use of a photogenerated electric field to promote ion current energy acquisition and improve permeation energy extraction efficiency. The photoresponsive ionic covalent organic framework composite membrane of this invention exhibits excellent photoresponsive performance, providing a promising strategy for photoresponsive coupled permeation energy extraction with excellent application prospects. Attached Figure Description
[0020] Figure 1 This is a synthetic route diagram for the ionic covalent organic framework material in the examples.
[0021] Figure 2 The image shown is an atomic force microscopy (AFM) image of the ionic covalent organic framework material after acid exfoliation treatment in this embodiment.
[0022] Figure 3 As an example, photographs of the ionic covalent organic framework composite membranes prepared in Comparative Examples 1-2 are shown.
[0023] Figure 4 The images show X-ray diffraction patterns of ionic covalent organic framework materials with different pH adjustments in the examples. COF represents an ionic covalent organic framework material, COF-TFA represents an initial acid-exfoliated ionic covalent organic framework material, COF-pH 3 represents an acid-exfoliated ionic covalent organic framework material at pH 3, COF-pH 7 represents an acid-exfoliated ionic covalent organic framework material at pH 7, and COF-pH 9 represents an acid-exfoliated ionic covalent organic framework material at pH 9.
[0024] Figure 5 The images show the infrared spectra of ionic covalent organic framework materials with different pH adjustments in the examples, where COF pH 3 -CMC is a blended solution a, COF pH 7-CMC is the blended solution b, COF pH 9 -CMC is the c of the blended solution, COF TFA -CMC represents the blended solution d.
[0025] Figure 6 The image shows a scanning electron microscope (SEM) image of the cross-section of the photoresponsive ionic covalent organic framework composite membrane used in this embodiment.
[0026] Figure 7 This is a comparison of the zeta potentials of the ionic covalent organic framework material and carboxymethyl cellulose before and after blending under different pH adjustments in the examples.
[0027] Figure 8 The image shows a comparison of the surface potential changes of the ionic covalent organic framework composite film before and after light irradiation, as an example.
[0028] Figure 9 The photo-driven current response test diagrams of the ionic covalent organic framework composite membrane COFdp-CMC of Example 1 and the ionic covalent organic framework composite membrane COFpn-CMC of Comparative Example 3 in 0.1M potassium chloride solution are shown.
[0029] Figure 10 The image shows a comparison of the IV curves of the ionic covalent organic framework composite membrane before and after light irradiation, as an example.
[0030] Figure 11 The permeation energy extraction power diagrams of the ionic covalent organic framework composite membrane COFdp-CMC of Example 1 and the ionic covalent organic framework composite membrane COFpn-CMC of Comparative Example 3 before and after light irradiation. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0032] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.
[0033] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.
[0034] The layer-by-layer filtration method of this invention uses the filter membrane brand Lanjing, with a filtration accuracy of 50,000 and a filter membrane diameter of 5 cm.
[0035] Example S1. Hydrothermal synthesis of ionic covalent organic framework materials 58 mg of monomeric saffron T and 140 mg of 1,3,5-tricarboxymethyl phloroglucinol were dissolved in 24 mL of 17.4 mol / L acetic acid by sonication for 30 min. The solution was then transferred to an oven and reacted at 70 °C for 72 h. After the reaction was completed, the solution was filtered and the solid product was placed in a Soxhlet extractor. Extraction was performed using 400 mL of ethanol as solvent at 105 °C under reflux for 72 h. Excess reactants were removed and the product was dried to obtain an ionic covalent organic framework material. S2, acid-exfoliated ionic covalent organic framework materials Weigh 100 mg of ionic covalent organic framework material and add it to 24 mL of organic solvent (acetonitrile, tetrahydrofuran and trifluoroacetic acid in a volume ratio of 7:3:2). Perform acid exfoliation treatment at 750 rpm for 72 h to obtain an initial acid exfoliation solution with a pH value of less than 0.5. S3. Adjust the pH of the acid stripping solution. Take 24 mL of each of the three initial acid stripping solutions, and add 47 mL of 1.0 mol / L sodium hydroxide solution to each solution. Stir at 750 rpm for 5 min, and then gradually add 1.0 mol / L sodium hydroxide solution dropwise. Measure the pH of the solution during this process until the three initial acid stripping solutions are adjusted to pH=3, pH=7 and pH=9, respectively. Stir at 750 rpm for 4 h to obtain the following solutions: pH=3 acid stripping solution a, pH=7 acid stripping solution b and pH=9 acid stripping solution c. S4, blending Weigh out 20 mL of acid stripping solution a (pH=3), acid stripping solution b (pH=7), and acid stripping solution c (pH=9), and mix them with 50 mL of 0.15 mg / mL carboxymethyl cellulose solution. Stir at 750 rpm for 8 h to obtain blended solutions a, b, and c. Weigh out 10 mL of the initial acid stripping solution and mix it with 50 mL of 0.15 mg / mL carboxymethyl cellulose solution. Stir at 750 rpm for 8 h to obtain blended solution d. S5. Preparation of photoresponsive ionic covalent organic framework composite membranes First, filter 10.5 mL of the blend solution c. After the solution is dried, add 10.5 mL of the blend solution b. After the solution is dried, add 10.5 mL of the blend solution a. After the solution is dried, add 12 mL of the blend solution d and filter to obtain a photoresponsive ionic covalent organic framework composite membrane, denoted as COFdp-CMC.
[0036] Comparative Example 1 The difference from the example is that acid stripping in S2 was not performed; otherwise, it is the same as the example.
[0037] Comparative Example 2 The difference from the example is that blending in step S4 was not performed; otherwise, it is the same as the example.
[0038] Test case See Figure 2 The atomic force microscopy images of the ionic covalent organic framework material after acid exfoliation in the examples show that the thickness of the ionic covalent organic framework nanosheets is less than 80 nm after acid exfoliation.
[0039] See Figure 3 The images of the ionic covalent organic framework composite membranes prepared in Comparative Examples 1-2 show that in Comparative Example 1, the solution pH was directly adjusted without acid stripping, resulting in the COF remaining granular and unable to form a dense and uniform COF composite membrane structure. The structure was loose and easily detached, and it could not exhibit photoresponsiveness. In Comparative Example 2, the membrane structure was not blended with the flexible suture agent carboxymethyl cellulose, resulting in a loose membrane structure and poor stability after filtration. The COF membrane cracked and easily detached from the substrate.
[0040] See Figure 4 The X-ray diffraction patterns of the ionic covalent organic framework materials with different pH adjustments in the examples show that pH adjustment does not destroy the crystallinity of the material itself.
[0041] See Figure 5 The infrared spectra of ionic covalent organic framework materials with different pH adjustments in the examples show that, under different pH adjustments, the ionic covalent framework material at 1650 cm⁻¹... -1 CN at the location + The intensity of the characteristic peak signal gradually decreases as pH increases.
[0042] See Figure 6 The scanning electron microscope image of the cross-section of the photoresponsive ionic covalent organic framework composite film in the embodiment shows that the thickness of the composite film is 9.1 µm and the nanosheets are tightly stacked.
[0043] See Figure 7 The comparison diagram of zeta potential of ionic covalent organic framework materials before and after blending with carboxymethyl cellulose under different pH adjustments in the examples shows that before the addition of carboxymethyl cellulose, the higher the degree of protonation of the nanosheets, the stronger the positive potential. After the addition of carboxymethyl cellulose, the overall zeta potential decreases because carboxymethyl cellulose carries a negative charge.
[0044] Comparative Example 3 The difference from the example is that the pH of the acid stripping solution in S3 was adjusted to pH=3, pH=5 and pH=7, while the rest was the same as the example. The resulting ionic covalent organic framework composite membrane is denoted as COFpn-CMC.
[0045] Test case See Figure 8 The comparison of surface potential changes of the ionic covalent organic framework composite film before and after illumination in the embodiment is shown in the figure. The left figure is under dark conditions and the right figure is under illumination conditions. It can be seen that the surface potential of the ionic covalent organic framework composite film with protonation gradient shows a significant positive shift after illumination, indicating that it achieves the separation and migration of charge carriers under illumination, resulting in the accumulation of more holes on the surface.
[0046] See Figure 9 The photo-driven current response test diagrams of the ionic covalent organic framework composite membrane COFdp-CMC of Example 1 and the ionic covalent organic framework composite membrane COFpn-CMC of Comparative Example 3 were performed in 0.1M potassium chloride solution. It can be seen that a periodic response current appeared when the illumination was switched every 60 s. The photoresponse current of COFdp-CMC of Example 1 was 61 nA, which was greater than the 23 nA current of COFpn-CMC of Comparative Example 3. This indicates that the protonation gradient distribution of the present invention has a good promoting effect on the photoresponsibility of the membrane.
[0047] See Figure 10 The comparison of the IV curves of the ionic covalent organic framework composite film before and after illumination in the embodiment shows that the open circuit potential and short circuit current measured after illumination were both improved.
[0048] The ionic covalent organic framework composite membranes prepared in Examples 1 and 2 (Comparative Example 3) were placed in an H-type electrolytic cell, with a 0.5 M sodium chloride solution on the left and a 0.01 M sodium chloride solution on the right, for permeation power testing; see [link to relevant documentation]. Figure 1 The permeation energy extraction power diagrams of the ionic covalent organic framework composite membranes in Examples 1 and 2 (Comparative Example 3) before and after illumination show that the permeation power of the composite membranes in Examples 1 and 2 (Comparative Example 3) was effectively improved under illumination. The output power of the COFdp-CMC ionic covalent organic framework composite membrane in Examples 1 and 2 (Comparative Example 3) before and after illumination was higher than that of the COFpn-CMC ionic covalent organic framework composite membrane in Comparative Example 3. This indicates that the photoresponsive ionic covalent organic framework composite membrane with protonation gradient prepared in the examples of this invention has a good effect of light energy synergistic permeation energy extraction. The distribution of the protonation gradient also affects the permeation energy conversion efficiency of the membrane.
[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a photoresponsive ionic covalent organic framework composite film, characterized in that, Includes the following steps: S1. Add the monomers Saffron T and 1,3,5-tricarboxymethyl phloroglucinol to acetic acid, heat to react, filter, and extract the solid product to obtain an ionic covalent organic framework material. S2. The ionic covalent organic framework material obtained in S1 is added to an organic solvent and subjected to acid exfoliation to obtain an initial acid exfoliation solution. S3. Adjust the pH value of the initial acid stripping solution with alkaline solution to obtain acidic acid stripping solution a, neutral acid stripping solution b and alkaline acid stripping solution c respectively; S4. Acidic acid stripping solution a, neutral acid stripping solution b, and alkaline acid stripping solution c are respectively mixed with carboxymethyl cellulose solution to obtain blended solution a, blended solution b, and blended solution c. The initial acid stripping solution is then mixed with carboxymethyl cellulose solution to obtain blended solution d for later use. S5. The mixture is filtered sequentially according to the order of adding the blend solution c, blend solution b, blend solution a and blend solution d to obtain a photoresponsive ionic covalent organic framework composite membrane.
2. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 1, characterized in that, In step S1, the mass ratio of the monomer saffron T and 1,3,5-tricarboxymethyl phloroglucinol is 140-180:58-70; The solid-liquid ratio of the monomer saffron T to acetic acid is 140-180:24-30 mg / mL, and the concentration of acetic acid is 17-18 mol / L. The heating reaction is carried out at 70-75°C for 72-96 hours; The solubilizer is prepared by refluxing at 105-108°C for 72-96 hours using ethanol as a solvent.
3. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 1, characterized in that, In step S2, the organic solvent is acetonitrile, tetrahydrofuran and trifluoroacetic acid in a volume ratio of 7:3:2; The solid-liquid ratio of the ionic covalent organic framework material to the organic solvent is 0.1:22-25 g / mL; The acid stripping treatment is performed at a speed of 700-800 rpm for a duration of 72-96 hours. The initial acid stripping solution has a pH value of less than 0.
5.
4. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 1, characterized in that, The acidic acid stripping solution a has a pH of 3.0, the neutral acid stripping solution b has a pH of 7.0, and the alkaline acid stripping solution c has a pH of 9.
0. Step S3 is as follows: Take three equal portions of the initial acid stripping solution. First, add the alkali solution to the initial acid stripping solution according to the volume ratio of alkali solution to initial acid stripping solution of 24:45-47. Stir at 700-800 rpm for 5-8 minutes. Then, gradually add the alkali solution dropwise until the three portions of initial acid stripping solution are adjusted to pH=3.0, pH=7.0 and pH=9.0 respectively. Stir at 700-800 rpm for 2-4 hours.
5. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 4, characterized in that, The alkaline solution is a sodium hydroxide solution with a concentration of 1.0-1.2 mol / L.
6. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 1, characterized in that, In step S4, the volume ratio of the acidic acid stripping solution a, the neutral acid stripping solution b, and the alkaline acid stripping solution c to the carboxymethyl cellulose solution is 2:5, the rotation speed is 700-800 rpm, and the time is 6-8 hours. The initial acid stripping solution and carboxymethyl cellulose solution were mixed in a volume ratio of 1:5, at a rotation speed of 700-800 rpm, for a time of 6-8 hours. The concentration of the carboxymethyl cellulose solution is 0.13-0.15 mg / mL.
7. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 1, characterized in that, In step S5, the filtration specifically involves: first filtration of the blended solution c, then adding the blended solution b after the solution has dried, then adding the blended solution a after the solution has dried, and finally adding the blended solution d for filtration.
8. The method for preparing a photoresponsive ionic covalent organic framework composite film as described in claim 7, characterized in that, The volume ratio of the blended solution c, blended solution b, blended solution a, and blended solution d is 7-10.5:7-10.5:7-10.5:8-12.
9. A photoresponsive ionic covalent organic framework composite membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of the photoresponsive ionic covalent organic framework composite membrane according to claim 9 or the photoresponsive ionic covalent organic framework composite membrane prepared by any one of claims 1-8 in water resource permeability extraction materials.