Method for preparing a biomimetic photosynthetic membrane and light-enhanced ion pump effect

Abstract

The present invention discloses a method for preparing a biomimetic photosynthetic membrane and a light-enhanced ion pump effect, belonging to the technical field of biomimetic photosynthetic membranes. The present invention uses a solution immersion method to immerse pyrrole monomers into the pores of a MOF porous material; a chemical oxidation method is used to oxidize the pyrrole monomers to a polypyrrole conductive polymer PPy, thereby constructing a PPy / MOF heterogeneous membrane composite of PPy and a MOF porous material; subsequently, a TiO2 nanolayer is modified on the surface of the PPy / MOF heterogeneous membrane by a spin coating method to construct a PPy / MOF / TiO2 heterogeneous membrane, i.e., a biomimetic photosynthetic membrane. The present invention compounds different light-responsive molecules to promote the transfer of photogenerated electrons, inhibit electron-hole recombination, and achieve the light-enhanced ion pump effect of the biomimetic photosynthetic membrane. The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane of the present invention can be used to manufacture optical components, systems or instruments due to its excellent light response performance, high electron-hole separation efficiency and photoelectric conversion efficiency, and strong ion pump effect.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic photosynthetic membranes, and in particular to a method for preparing a bionic photosynthetic membrane and light-enhanced ion pump effect. Background Art

[0002] Photosynthesis is the main way for organisms on Earth to obtain solar energy safely and efficiently. The place where photosynthesis occurs is the photosynthetic membrane with a complex and delicate structure. The two photoreaction centers (P680 and P700) in the photosynthetic membrane work in series. Under the action of light stimulation, the electrons generated by the reaction center pigment P680 in photosystem II (PSⅡ) are transferred to plastoquinone (PQ) by light excitation. Through the Q cycle, the protons are pumped into the thylakoid cavity, and the electrons temporarily stored in plastoquinol (PQH2) are transported to the cytochrome P680. b 6 f complex, and ultimately transmits it to P700 in photosystem I (PSI) + , reducing it to P700. Photosynthetic electron transport is carried out by PSⅡ, cytochrome b 6 f The heterogeneous structure of the transmembrane supramolecular complex on the photosynthetic membrane promotes the transfer of photogenerated electrons, inhibits the recombination of electrons and holes, improves the photoelectric conversion efficiency, and enhances the efficient conversion of light energy to chemical energy during photosynthesis.

[0003] Inspired by the tandem structure of light-absorbing molecular complexes on the surface of plant photosynthetic membranes, the construction of biomimetic photosynthetic membranes containing hybrid nanochannels composed of different membrane materials has attracted widespread attention. For example, heterogeneous nanochannels composed of TiO2 / Al2O3 generate negative charges on the channel surface under UV irradiation, forming electrostatic potential traps within the nanochannels, affecting ion transport performance. Light-stimulated charge separation in MoS2 nanochannels improves channel ion selectivity and increases salinity-induced power generation. Porphyrin-based nanochannels with conjugated π bonds generate a built-in electric field upon photoexcitation, driving ion transport against the concentration gradient, creating an ion pumping effect. However, due to electrostatic attraction, photoexcited electron and hole pairs reunite and recombine, releasing energy, reducing the photoelectric response properties. This results in low photoelectric conversion efficiency and poor ion pumping performance in existing biomimetic photosynthetic membranes. Therefore, designing new biomimetic photosynthetic membranes composed of different membrane materials is an important approach to improving their performance. Summary of the Invention

[0004] In view of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a bionic photosynthetic membrane and light-enhanced ion pumping effect. In order to solve the problems of low photoelectric conversion efficiency and poor ion pumping effect of existing bionic photosynthetic membranes, the inventors found that by modifying TiO2 nanoparticles on the surface of PPy / MIL-101(Cr) heterogeneous membranes, a PPy / MIL-101(Cr) / TiO2 bionic photosynthetic membrane with light-responsive enhanced ion pumping effect can be constructed. Doped polypyrrole molecules are used as light-absorbing antennas and adsorbed on the surface of the MIL-101(Cr) porous material to enhance its light response performance. In addition, the titanium dioxide photosystem in the heterogeneous membrane is excited by light, resulting in the separation of electrons and holes, and the photogenerated electrons migrate from the valence band (VB) to the conduction band (CB), leaving photogenerated holes (h + ); at the same time, electrons in the HOMO orbital of the MIL-101(Cr) molecule are excited by light and jump to the LUMO orbital position. The photoexcited electrons and holes separate at the interface between the titanium dioxide and MOF material, inhibiting electron-hole recombination and improving charge separation efficiency.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A first aspect of the present invention provides a method for preparing a biomimetic photosynthetic membrane, the method comprising the following steps:

[0007] A conductive polymer is prepared on the pores of a MOF porous material and dispersed in a dispersant to construct a conductive polymer / MOF coating solution composite of the conductive polymer and the MOF porous material; the coating solution is drop-coated and then dried to obtain a conductive polymer / MOF heterogeneous membrane; an inorganic light-absorbing material is modified on the surface of the conductive polymer / MOF heterogeneous membrane to obtain a conductive polymer / MOF / nanoparticle heterogeneous membrane, i.e., a biomimetic photosynthetic membrane;

[0008] The conductive polymer is polyaniline, polypyrrole, polythiophene, polyacetylene, poly(p-styrene) or polyethylenedioxythiophene;

[0009] The MOF porous material includes at least one of MIL-101 (Cr), ZIF-8, and ZIF-67;

[0010] The inorganic light-absorbing material includes at least one of titanium dioxide, silicon carbide or zinc oxide;

[0011] The mass ratio of MOF porous material to conductive polymer is 0.5-2:1.

[0012] In some embodiments, as a method for preparing the biomimetic photosynthetic membrane of the present invention, first, MIL-101(Cr) powder is added to a pyrrole solution using surface modification and chemical oxidation methods, so that the pyrrole (Py) unit is immersed in the MIL-101(Cr) pores, and centrifugation is performed to obtain a Py / MIL-101(Cr) complex. Secondly, polypyrrole and MIL-101(Cr) are prepared by chemical oxidation, and FeCl3 oxidant is added to the complex to obtain a PPy / MIL-101(Cr) complex. Thirdly, a drop coating method is used to prepare a PPy / MIL-101(Cr) heterogeneous membrane. Finally, TiO2 nanoparticles are modified on the surface of the PPy / MIL-101(Cr) heterogeneous membrane by spin coating to obtain a PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0013] Furthermore, the dispersant is a polyvinylidene fluoride coating binder; wherein the ratio of polyvinylidene fluoride to N-methylpyrrolidone is 0.18 g: (3-6) mL.

[0014] Furthermore, in the conductive polymer / MOF coating solution, the mass fraction of the conductive polymer and the MOF porous material in the dispersant is 2-15%.

[0015] Furthermore, the conductive polymer is polypyrrole, the MOF porous material is MIL-101 (Cr), the inorganic light-absorbing material is TiO2 nanoparticles, and the conductive polymer / MOF / nanoparticle heterogeneous membrane is polypyrrole / MIL-101 (Cr) / TiO2 membrane.

[0016] Furthermore, the surface modification method is single-sided spin coating, with a rotation rate of 2000-8000 rpm during spin coating. 10-100 mg / ml nanoparticle hydrosol is spin-coated on the surface of the conductive polymer / MOF heterogeneous membrane for 10-60 s, and the thickness of the nanoparticle layer is 1.2-2.2 µm; the size of the nanoparticles used is 1-20 nm.

[0017] The second aspect of the present invention provides a method for light-enhanced ion pumping effect, comprising the following steps: preparing a bionic photosynthetic membrane according to the preparation method, irradiating the bionic photosynthetic membrane with externally applied light, regulating the charge distribution state on the membrane surface, improving the electron-hole separation efficiency of the bionic photosynthetic membrane, and realizing the light-enhanced ion pumping effect.

[0018] When light is applied, the biomimetic photosynthetic membrane is excited by light, causing the separation of electrons and holes. The photogenerated electrons migrate from the highest occupied orbital (HOMO) to the lowest unoccupied orbital (LUMO), leaving photogenerated holes (h +); Photogenerated electrons migrate from the valence band (VB) to the conduction band (CB), leaving behind photogenerated holes (h + ). On the PPy / MOF / TiO2 heterogeneous film, the photogenerated electrons generated by PPy under light excitation transition to the conduction band energy level of TiO2, and the holes in the valence band of TiO2 migrate to the HOMO energy level of the PPy conductive polymer, causing the separation of electrons and holes, inhibiting the electron-hole combination, and further improving the photoresponse performance. At the same time, the electrons on the titanium dioxide VB are excited by light and transition to the CB. The photogenerated electrons on the LOMO orbital migrate to the TiO2 conduction band orbital, and the holes on the VB migrate to the HOMO orbital. The photoexcited electron-hole separation inhibits the electron-hole recombination again, thereby improving the photoresponse performance. The electrons on the HOMO orbital of the MIL-101(Cr) molecule are excited by light and transition to the LUMO orbital position. The photoexcited electrons and holes are separated at the interface between titanium dioxide and MOF materials, the LUMO orbital electrons migrate to the CB, and the VB holes migrate to the HOMO orbital, inhibiting the recombination of electrons and holes and improving the charge separation efficiency.

[0019] Beneficial effects of the present invention:

[0020] The present invention utilizes the different energy level structures of titanium dioxide, polypyrrole, and MIL-101 (Cr) materials to connect PPy, TiO2, and MIL-101 (Cr) photoresponsive molecules in series to form a photoresponsive series complex, namely a PPy / MIL-101 (Cr) / TiO2 heterogeneous membrane. Light is used to induce electron transitions, stimulate the separation of electrons and holes on the surface of the heterogeneous membrane, change the charge state of the membrane surface, and generate electron-hole pairs. Electron-hole recombination can be effectively suppressed at the heterogeneous interface, improving the electron-hole separation efficiency of the heterogeneous membrane and enhancing the photoresponsive performance. In addition, asymmetric light is applied to one side of the membrane, and the asymmetric electric field generated by the light stimulation can form an ion pump effect, realizing the transport of anions against the concentration gradient. The PPy / MIL-101 (Cr) / TiO2 heterogeneous membrane of the present invention can be used to manufacture optical components, systems, or instruments due to its excellent photoresponsive performance, high electron-hole separation efficiency and photoelectric conversion efficiency, and strong ion pump effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope photo of PPy / MIL-101(Cr) / TiO2 heterogeneous film.

[0022] Figure 2 This is the charge separation state diagram of PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0023] Figure 3 The current-voltage curve of PPy / MIL-101(Cr) / TiO2 heterogeneous membrane under different transmembrane voltages.

[0024] Figure 4 This is the ion current-time trajectory curve of PPy / MIL-101(Cr) / TiO2 heterogeneous film under alternating visible light.

[0025] Figure 5 This is the ion pump effect diagram of PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0026] Figure 6 The photoresponsive ion current of PPy / MIL-101(Cr) / TiO2 heterogeneous membrane under different light intensities. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0028] The "bionic photosynthetic membrane" of this invention is a functional membrane material that exhibits ion pumping properties when exposed to light. Leveraging the membrane's intrinsic photoelectric properties, illumination generates a built-in electric field, created by uneven charge distribution, driving reverse ion transport. To maximize the use of clean light energy, titanium dioxide molecules are added to act as light-absorbing wires, expanding the spectral absorption range and increasing photoelectric conversion efficiency.

[0029] Hereinafter, the method for producing the biomimetic photosynthetic film of the present invention will be described using polypyrrole as the light-absorbing antenna material. However, those skilled in the art will appreciate that the present invention is not limited to the following embodiments.

[0030] The aforementioned biomimetic photosynthetic membrane utilizes a chemical oxidation method to modify a polypyrrole conductive polymer film within the porous channels of MIL-101(Cr). The polypyrrole film possesses a positive surface charge, exhibiting anion-selective transport properties. Under illumination, the polypyrrole is photoexcited, causing electrons in the HOMO orbital to transition to the LOMO orbital, resulting in electron-hole separation. Furthermore, under light stimulation, photogenerated electrons in the TiO2 valence band migrate to the conduction band, leaving holes in the valence band orbital. Electrons in the LOMO orbital of MIL-101(Cr) migrate to the TiO2 conduction band, while holes in the TiO2 valence band migrate to the HOMO energy level of MIL-101(Cr). This leads to electron-hole separation at the MIL-101(Cr) / TiO2 composite interface, suppressing electron-hole separation efficiency and improving photoresponse performance. Photoexcitation of PPy induces electron-hole separation, with electrons in the LUMO orbital migrating to the TiO2 conduction band and holes in the TiO2 valence band migrating to the HOMO orbital. Electron-hole separation at the PPy / TiO2 composite interface improves photoresponse performance.

[0031] The tandem structure of the photoreaction complex in the PPy / MOF / TiO2 heterogeneous membrane increases the spectral absorption range, enhances the light absorption performance of the membrane, inhibits electron-hole recombination, and improves the charge separation efficiency.

[0032] MIL-101(Cr) is a three-dimensional network structure composed of inorganic structural units of terephthalic acid and the chromium trimer Cr3O(CO2)6, linked by coordination bonds. This structure possesses a large surface area and pore space. The basic unit of MIL-101(Cr) consists of a Cr3O trinuclear chromium cluster and terephthalic acid. Each Cr3O cluster contains a μ3O, four carboxylic acid oxygens, and a F or OH terminal site. The unit cell of MIL-101(Cr) belongs to the Fd-3m space group and is cubic. MIL-101(Cr) is composed of cage frameworks with two mesopore sizes, with diameters of 2.9 nm and 3.4 nm, respectively. The cage frameworks have a 2:1 ratio, with the smaller cage windows consisting of 1.2 nm pentagons and the larger cage framework windows consisting of 1.4-1.6 nm hexagons. The large pore size and expansive cavity structure of MIL-101(Cr) provide favorable conditions for monomer entry and in-situ polymerization. Pyrrole can be oxidized to polypyrrole by chemical oxidation to obtain PPy / MIL-101(Cr), which is then dispersed in a dispersant to finally construct a PPy / MIL-101(Cr) heterogeneous membrane.

[0033] The polypyrrole photosystem in the heterogeneous film is excited by light, generating electrons and holes, and the photogenerated electrons migrate from the highest occupied orbital (HOMO) to the lowest unoccupied orbital (LUMO), leaving photogenerated holes (h +). PPy is a p-type semiconductor that forms a pn heterojunction with the n-type semiconductor TiO2. The pn junction formed between TiO2 and PPy is conducive to photoinduced charge separation. The photogenerated electrons of PPy are transferred to the conduction band of TiO2, increasing the surface charge density of the positively charged PPy film and inhibiting the recombination of electrons and holes. At the same time, the electrons in the HOMO orbit of the MIL-101(Cr) molecule are excited by light and jump to the LUMO orbit position. Since the LUMO orbital energy level of MIL-101(Cr) (-0.42eV) is more negative than the conduction band of TiO2 (-0.4eV), the excited electrons of MIL-101(Cr) are transferred to the conduction band of TiO2; the valence band energy level of TiO2 (2.8eV) is more positive than the HOMO orbital energy level of MIL-101(Cr) (2.16eV), and the holes in the valence band of TiO2 migrate to the HOMO orbit of MIL-101(Cr). At the same time, the TiO2 valence band energy level is more positive than the HOMO orbital energy level of PPy (1.75eV), causing the holes on the TiO2 valence band to migrate to the HOMO orbital of PPy. The tandem structure of the photoreaction complex is conducive to the separation of electrons and holes, inhibiting the recombination of photogenerated electrons and holes, and improving the photoresponse performance of the heterogeneous film ( Figure 2 ).

[0034] Titanium dioxide (TiO2) is a wide-bandgap n-type semiconductor with a band gap of 3.2 eV at room temperature. TiO2 intrinsically absorbs photons with wavelengths less than 380 nm, a region that accounts for only 5% of the solar spectrum, significantly limiting its application. Titanium dioxide exhibits high chemical stability, non-toxicity, and excellent photostability, offering significant potential for converting solar energy into electrical energy. The conductive polymer polypyrrole (PPy) is a p-type semiconductor, while TiO2 is an n-type semiconductor. A pn ​​junction is formed by the combination of p-type and n-type semiconductors. The built-in electric field at the pn junction interface can improve the separation of photogenerated electron-hole pairs. By modifying the surface of a PPy / MIL-101(Cr) / TiO2 heterojunction with TiO2 nanoparticles, a PPy / MIL-101(Cr) / TiO2 composite heterojunction can be constructed. Under UV irradiation, electrons in the valence band of TiO2 transition to the conduction band, causing an uneven charge distribution and generating a built-in electric field. This built-in electric field drives ion transport against the concentration gradient, resulting in ion pumping properties. Incorporating PPy light-absorbing antennas with a broad absorption wavelength range can extend the spectral absorption range from the ultraviolet region to the visible light region, constructing a PPy / MOF / TiO2 photosynthetic film that responds to visible light. This fully utilizes clean light sources and converts them into chemical energy, greatly improving the photoelectric conversion efficiency.

[0035] Anion pumping mechanism of the PPy / MIL-101(Cr) / TiO2 heterostructure. Asymmetric visible light illumination on one side of the heterostructure leads to asymmetric charge accumulation on the membrane surface, creating a built-in electric field. This built-in electric field drives anion transport against the concentration gradient, resulting in an ion pumping effect.

[0036] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to specific embodiments.

[0037] All experimental materials used in the examples of the present invention that are not specifically described are conventional experimental materials in the art and can be purchased through commercial channels. TiO2 hydrosol was purchased from Hengge Nanotechnology Co., Ltd. The CAS number of MIL-101(Cr) is 869288-09-5.

[0038] Example 1: Preparation of biomimetic photosynthetic membrane

[0039] Preparation of PPy / MIL-101(Cr) heterogeneous membrane

[0040] The preparation method of the PPy / MIL-101(Cr) heterogeneous membrane is partly derived from "Theoretical Calculation and Iodine Extraction Performance Study of Inorganic-Organic Electroactive Ion Exchange Material MIL-101@PPy" (Taiyuan University of Technology), as follows:

[0041] A PPy / MIL-101(Cr) heterostructured membrane, composed of a conductive polymer PPy and a porous MIL-101(Cr) material, was prepared by surface modification and chemical oxidation. 0.2 g of MIL-101(Cr) powder was added to a 3 mL volume of a 1 mol / L pyrrole (Py) solution and ultrasonicated for uniform dispersion. The mixture was then allowed to soak at room temperature for three days to allow the pyrrole units to incorporate into the pores of the MIL-101(Cr). The Py-doped MIL-101(Cr) composite was then centrifuged to obtain the Py-doped MIL-101(Cr) composite. Deionized water was added to the composite, and the mixture was washed by centrifugation four times to remove the pyrrole solution from the MIL-101(Cr) surface. At this point, the mass ratio of MIL-101(Cr) to Py was 1:1.67. The composite was dried at room temperature for 24 hours to obtain a clean Py / MIL-101(Cr) composite. Next, a chemical oxidation method was used to prepare the PPy / MIL-101(Cr) composite. 5 mL of 0.8 mol / L FeCl3 was added to the Py / MIL-101(Cr) composite. The mixture was oxidized in an ice-water bath for 24 hours to convert Py to PPy, yielding a PPy / MIL-101(Cr) heterogeneous membrane. After centrifugation, the mixture was dried under an infrared lamp at 40°C for 12 hours to obtain a black PPy / MIL-101(Cr) powder. At this point, the mass ratio of MIL-101(Cr) to PPy was 1.26:1.

[0042] PPy / MIL-101(Cr) heterogeneous membranes were prepared by drop coating. PVDF coating binder was prepared. 0.18 g of polyvinylidene fluoride (PVDF) powder was dissolved in 4.8 mL of N-methylpyrrolidone (NMP) solution to prepare a 3.75% PVDF coating binder. 0.05 g of PPy / MIL-101(Cr) black powder was weighed and 2500 μL of PVDF coating binder was added to obtain a 2% PPy / MIL-101(Cr) coating solution. To 0.05 g of PPy / MIL-101(Cr) powder, 625 μL and 333 μL of PVDF binder were added, respectively, to obtain 8% and 15% PPy / MIL-101(Cr) coating solutions. A 10μL droplet of the coating solution was applied to the surface of a glass slide. Due to the surface tension of the coating solution, it automatically spread across the surface, limiting the spreading area to 0.5 cm × 1.5 cm. The slide was then placed in an oven at 60°C and dried for 10 minutes. After drying, the oven was closed, the slide was removed from the oven, and cooled to room temperature. The film was peeled from the glass slide using a nickel rod, yielding PPy / MIL-101(Cr) heterogeneous films with mass fractions of 2%, 8%, and 15%, respectively. The 8% mass fraction PPy / MIL-101(Cr) heterogeneous films were used for subsequent experiments.

[0043] Preparation of PPy / MIL-101(Cr) / TiO2 Heterogeneous Film

[0044] TiO2 nanoparticles were modified on the surface of PPy / MIL-101(Cr) heterogeneous film by spin coating to form a photoresponsive tandem complex, namely PPy / MIL-101(Cr) / TiO2 heterogeneous film.

[0045] Because nanoparticles that are too large are difficult to adsorb onto the membrane surface, while particles that are too small increase ion transport resistance, the TiO2 nanoparticle size used was 5.9±1.2 nm. A 50 mg / ml TiO2 aqueous solution was spin-coated on the PPy / MIL-101(Cr) membrane surface at a spin rate of 4000 rpm for 30 s. Single-sided spin coating facilitates asymmetric accumulation of photoresponsive charges, forming a built-in electric field.

[0046] The thickness of the TiO2 layer can be controlled by adjusting the spin coating rate and TiO2 concentration. Spin coating is carried out in batches, and the next spin coating is carried out after the surface of the PPy / MIL-101(Cr) film is dried. If the spin coating amount is too much, the thickness of the TiO2 layer on the surface of the film will increase, reducing the ion transport current; if the spin coating amount is too little, it will be detrimental to the light absorption performance. The obtained PPy / MIL-101(Cr) film was spin coated with TiO2 aqueous sol 3 times, 4 times and 5 times respectively to obtain the PPy / MIL-101(Cr) / TiO2 heterogeneous film. At this time, the thickness of the TiO2 nanoparticle layer on the surface of the PPy / MIL-101(Cr) / TiO2 heterogeneous film was 1.2µm, 1.7µm and 2.2µm respectively. The PPy / MIL-101(Cr) / TiO2 heterogeneous film obtained by spin coating 4 times was scanned, and the scanning electron microscope photo is shown in FIG. Figure 1 , and subsequent experiments were conducted using the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane prepared using this method.

[0047] Example 2: Ionic Current-Voltage Curve

[0048] At room temperature, the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was mounted on a homemade dual-chamber electrolyzer. 1 mM KCl electrolyte was injected into the chambers on both sides of the electrolytic cell. The current-voltage curve across the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was measured, and the measured current-voltage curve is shown in the solid line in Figure 3. Subsequently, the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was replaced with the PPy / MIL-101(Cr) heterogeneous membrane, and the ionic current-voltage curve of this membrane is shown in the dotted line in Figure 3.

[0049] The results show that at the same voltage, the ion current through the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane is greater than that of the pure PVDF membrane. This is because the incorporation of PPy / MIL-101(Cr) / TiO2 increases the membrane's porosity and improves the ion transport current.

[0050] Example 3: Photoresponsive ion transport performance test

[0051] The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was selected as the diaphragm and installed in a self-made double-chamber electrolytic cell. 1mM KCl electrolyte solution was injected into the double-chamber electrolytic cell. A xenon lamp (wavelength range 190-1100nm) was used as the light source with an irradiation intensity of 320 mW / cm 2Visible light passes through a quartz window, illuminating the heterostructured membrane surface. A pair of Ag / AgCl reference electrodes (black tubes protected from light) monitor the ionic current through the membrane, recording the ionic current-time curve of the PPy / MIL-101(Cr) / TiO2 heterostructured membrane as it is irradiated with applied light.

[0052] The results are as follows Figure 4 As shown in the figure, it can be seen that when light is applied, the ion current through the PPy / MIL-101(Cr) / TiO2 heterostructure increases; when the light is turned off, the ion current decreases. This further characterizes the photoresponsive ion transport performance of the PPy / MIL-101(Cr) / TiO2 heterostructure.

[0053] When light is applied, the ion current through the membrane increases. When light is turned off, the ion current through the membrane decreases, demonstrating the photoresponsive ion transport properties of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0054] Example 4: Ion Pump Effect Test

[0055] The photoresponsive ion transport properties of the PPy / MIL-101(Cr) / TiO2 membrane give it an ion pump effect. The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was fixed on a double-chamber electrolytic cell. Electrolytes were injected into the two side chambers of the electrolytic cell respectively, and the electrolyte concentration on the high concentration side was fixed at 1 mM KCl and that on the low concentration side was fixed at 0.85 mM. The KCl electrolyte on the high concentration side was fixed as the anode, and the KCl electrolyte on the low concentration side was fixed as the cathode. A xenon lamp (wavelength range 190-1100 nm) was used as the light source, and the irradiation intensity was set to 320 mW / cm 2 Visible light passes through the quartz window and illuminates the heterogeneous membrane surface from the high-concentration electrolyte side. A pair of Ag / AgCl reference electrodes (black tubes protected from light) monitor the ion current passing through the membrane. Before illumination, due to the different concentrations of KCl electrolyte on both sides of the membrane, the concentration difference drives Cl - Transport from the high-concentration side to the low-concentration side, generating a negative ion current of -3nA. After applying light, the negative ion current drops rapidly, and a positive current of 3nA is generated in about 100s. When the light is turned off, the ion current through the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane returns to its original negative state ( Figure 5 ).

[0056] Example 5: Photoresponsive ion current test

[0057] The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was selected as the diaphragm and installed in a self-made double-chamber electrolytic cell. 1mM KCl electrolyte solution was injected into the double-chamber electrolytic cell. A xenon lamp (wavelength range 190-1100nm) was used as the light source, and the irradiation intensity was set to 120, 220, and 320 mW / cm 2 Visible light was passed through a quartz window onto the heterostructured film surface. A pair of Ag / AgCl reference electrodes (protected from light by a black tube) monitored the photoresponse current through the film. Subsequently, the PPy / MIL-101(Cr) / TiO2 heterostructured film was replaced with a PPy / MIL-101(Cr) heterostructured film, and the photoresponse current was again monitored using an Ag / AgCl reference electrode (protected from light by a black tube).

[0058] Figure 6 The bar graph shows the photoresponsive ion currents of the PPy / MIL-101(Cr) / TiO2 heterofilm and the PPy / MIL-101(Cr) heterofilm under different light intensities. As can be seen from the graph, the photoresponsive ion current of the PPy / MIL-101(Cr) / TiO2 heterofilm is higher than that of the PPy / MIL-101(Cr) heterofilm under different light intensities. This indicates that under light stimulation, the tandem structure of the photoreactive complex in the PPy / MOF / TiO2 heterofilm increases the spectral absorption range, enhances the film's light-responsive absorption properties, suppresses electron-hole recombination, and improves charge separation efficiency.

[0059] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a biomimetic photosynthetic membrane, characterized in that: The preparation method comprises the following steps: A conductive polymer is prepared on the pores of a MOF porous material and dispersed in a dispersant to construct a conductive polymer / MOF coating solution composite of the conductive polymer and the MOF porous material; the coating solution is drop-coated and then dried to obtain a conductive polymer / MOF heterogeneous membrane; an inorganic light-absorbing material is modified on the surface of the conductive polymer / MOF heterogeneous membrane to obtain a conductive polymer / MOF / nanoparticle heterogeneous membrane, i.e., a biomimetic photosynthetic membrane; The conductive polymer is polyaniline, polypyrrole, polythiophene, polyacetylene, poly(p-styrene) or polyethylenedioxythiophene; The MOF porous material includes at least one of MIL-101 (Cr), ZIF-8, and ZIF-67; The inorganic light-absorbing material includes at least one of titanium dioxide, silicon carbide or zinc oxide; The mass ratio of MOF porous material and conductive polymer is 0.5-2:1; The dispersant is a polyvinylidene fluoride coating binder; wherein the ratio of polyvinylidene fluoride to N-methylpyrrolidone is 0.18 g: (3-6) mL.

2. The method for preparing the biomimetic photosynthetic film according to claim 1, wherein: In the conductive polymer / MOF coating solution, the mass fraction of the conductive polymer and the MOF porous material in the dispersant is 2-15%.

3. The method for preparing the biomimetic photosynthetic film according to claim 1, wherein: The conductive polymer is polypyrrole, the MOF porous material is MIL-101 (Cr), the inorganic light-absorbing material is TiO2 nanoparticles, and the conductive polymer / MOF / nanoparticle heterogeneous membrane is polypyrrole / MIL-101 (Cr) / TiO2 membrane.

4. The method for preparing the biomimetic photosynthetic film according to claim 1, wherein: The surface modification method is single-sided spin coating with a rotation rate of 2000-8000 rpm. 10-100 mg / ml nanoparticle hydrosol is spin-coated on the surface of the conductive polymer / MOF heterogeneous membrane for 10-60 s. The thickness of the nanoparticle layer is 1.2-2.2 µm. The size of the nanoparticles used is 1-20 nm.

5. A method for light-enhanced ion pumping effect, characterized in that: The method comprises the following steps: preparing a bionic photosynthetic membrane according to the preparation method according to any one of claims 1 to 4, irradiating the bionic photosynthetic membrane with externally applied light, regulating the charge distribution state on the membrane surface, improving the electron-hole separation efficiency of the bionic photosynthetic membrane, and realizing a light-enhanced ion pump effect.

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