Preparation method of bionic photosynthetic membrane and method for enhancing ion pump effect by light

Abstract

The invention discloses a preparation method of a bionic photosynthetic membrane and a method for enhancing an ion pump effect by light, and belongs to the technical field of bionic photosynthetic membranes. According to the preparation method, a pyrrole monomer is immersed into pore channels of the MOF porous material through a solution soaking method; the preparation method comprises the following steps: oxidizing a pyrrole monomer into a polypyrrole conductive polymer PPy by adopting a chemical oxidation method so as to construct a PPy / MOF heterogeneous membrane compounded by the PPy and an MOF porous material; and then, the surface of the PPy / MOF heterogeneous film is modified with a TiO2 nano layer through a spin coating method, and a PPy / MOF / TiO2 heterogeneous film, namely the bionic photosynthetic film, is constructed. Different photoresponse molecules are compounded, transmission of photo-induced electrons is promoted, electron-hole recombination is inhibited, and the light-enhanced ion pump effect of the bionic photosynthetic film is achieved. The PPy / MIL-101 (Cr) / TiO2 heterogeneous film disclosed by the invention can be used for manufacturing optical elements, systems or instruments due to excellent light response performance, relatively high electron-hole separation efficiency and photoelectric conversion efficiency and relatively strong ion pump effect.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic photosynthetic membranes, and particularly to a method for preparing a bionic photosynthetic membrane and enhancing the light-induced 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 photosynthetic reaction centers (P680 and P700) in the photosynthetic membrane act in series. Under the action of light stimulation, the reaction center pigment P680 in photosystem II (PSII) is photoexcited to transfer electrons to plastoquinone (PQ). Through the Q cycle, protons are pumped into the thylakoid lumen. The electrons temporarily stored in plastoquinol (PQH2) pass through the cytochrome b 6 f complex, and finally are transferred to P700 in photosystem Ι (PSI) + , reducing it to P700. The photosynthetic electron transport is completed by three transmembrane supramolecular complexes: PSII, cytochrome b 6 f complex, and PSI. The heterogeneous structure composed of transmembrane supramolecular complexes on the photosynthetic membrane promotes the transfer of photo-generated electrons, inhibits the recombination of electrons and holes, improves the photoelectric conversion efficiency, and enhances the efficient conversion of light energy and chemical energy during photosynthesis.

[0003] Inspired by the tandem structure of the light-absorbing molecular complexes on the surface of plant photosynthetic membranes, the construction of bionic photosynthetic membranes containing hybrid nanochannels composed of different membrane materials has attracted extensive attention from all walks of life. For example, the heterogeneous nanochannels composed of TiO2 / Al2O3 generate negative charges on the channel surface under ultraviolet light irradiation, forming an electrostatic potential trap in the nanochannels, which affects the ion transport performance. Light stimulation causes charge separation in MoS2 nanochannels, improving the ion selectivity of the channels and increasing the power generation of salinity gradient power generation. Porphyrin-based nanochannels with conjugated π bonds generate an internal electric field under light excitation, driving ions to transport against the concentration gradient and forming an ion pump effect. However, due to the electrostatic attraction, the photo-generated electron-hole pairs will meet again and recombine, releasing energy and reducing the photoelectric response properties, resulting in low photoelectric conversion efficiency and poor ion pump effect of existing bionic photosynthetic membranes. Therefore, designing a new type of bionic photosynthetic membrane composed of different membrane materials is an important method to improve its performance. Summary of the Invention

[0004] In view of the above prior art, the purpose of the present invention is to provide a method for preparing a bionic photosynthetic membrane and enhancing the ion pump effect by light. In order to solve the problems of low photoelectric conversion efficiency and poor ion pump effect of the existing bionic photosynthetic membrane, the inventors found that modifying the surface of the PPy / MIL-101(Cr) heterogeneous membrane with TiO2 nanoparticles can construct a PPy / MIL-101(Cr) / TiO2 bionic photosynthetic membrane with enhanced light-responsive ion pump effect. 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-responsive performance. In addition, the titanium dioxide photosystem in the heterogeneous membrane is photoexcited to generate separation of electrons and holes. The photo-generated electrons migrate from the valence band (VB) to the conduction band (CB), and photo-generated holes (h + ) are left at the VB position; at the same time, the electrons on the HOMO orbital of the MIL-101(Cr) molecule are photoexcited and transition to the LUMO orbital position. The photoexcited electrons and holes are separated at the two-phase interface of the titanium dioxide and MOF materials, inhibiting the recombination of electrons and holes and improving the charge separation efficiency.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect of the present invention, a method for preparing a bionic photosynthetic membrane is provided. The preparation method includes the following steps: A conductive polymer is prepared on the pores of the MOF porous material, dispersed in a dispersant, and a conductive polymer / MOF coating solution in which the conductive polymer is combined with the MOF porous material is constructed; after drop-coating and drying, a conductive polymer / MOF heterogeneous membrane is obtained; 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, that is, a bionic photosynthetic membrane; The conductive polymer is polyaniline, polypyrrole, polythiophene, polyacetylene, poly(phenylene styrene) or poly(ethylene dioxythiophene); 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 the MOF porous material to the conductive polymer is 0.5-2:1.

[0006] In some embodiments, as a method for preparing the bionic photosynthetic membrane of the present invention, first, by using the methods of surface modification and chemical oxidation, MIL-101(Cr) powder is added to a pyrrole solution to immerse pyrrole (Py) units into the pores of MIL-101(Cr), and a Py / MIL-101(Cr) composite is obtained by centrifugation. Secondly, polypyrrole and MIL-101(Cr) are prepared by chemical oxidation method. An FeCl3 oxidant is added to the composite to obtain a PPy / MIL-101(Cr) composite. Thirdly, a PPy / MIL-101(Cr) heterogeneous membrane is prepared by a drop-coating method. Finally, TiO2 nanoparticles are surface-modified on the surface of the PPy / MIL-101(Cr) heterogeneous membrane by a spin-coating method to obtain a PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0007] Further, the dispersant is a polyvinylidene fluoride coating binder; the ratio of polyvinylidene fluoride to N-methylpyrrolidone is 0.18 g:(3 - 6) mL.

[0008] Further, in the conductive polymer / MOF coating solution, the mass fractions of the conductive polymer and the MOF porous material in the dispersant are 2 - 15%.

[0009] Further, 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 a polypyrrole / MIL-101(Cr) / TiO2 membrane.

[0010] Further, the surface modification method is single-side spin-coating. The rotation rate during spin-coating is 2000 - 8000 revolutions per minute. A 10 - 100 mg / ml nanoparticle hydrogel 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 used nanoparticles is 1 - 20 nm.

[0011] In the second aspect of the present invention, a method for enhancing the ion pump effect by light is provided, including the following steps: preparing a bionic photosynthetic membrane according to the described 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 pump effect.

[0012] Applying light irradiation, the bionic photosynthetic membrane is photoexcited, causing the separation of electrons and holes. The photo-generated electrons migrate from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), and photo-generated holes (h +);Photo-generated electrons migrate from the valence band (VB) to the conduction band (CB), leaving photo-generated holes (h + ) on the VB position. On the PPy / MOF / TiO2 heterojunction film, the photo-generated electrons generated by the photo-excitation of PPy transition to the conduction band energy level of TiO2, and the valence band holes of TiO2 migrate to the HOMO energy level of the PPy conductive polymer, causing the separation of electrons and holes, inhibiting the electron-hole recombination, and further improving the light response performance. At the same time, the electrons on the VB of titanium dioxide are photo-excited and transition to the CB. The photo-generated electrons on the LOMO orbit migrate to the conduction band orbit of TiO2, and the holes on the VB migrate to the HOMO orbit. The photo-excited electron-hole separation inhibits the recombination of electrons and holes again, improving the light response performance. The electrons on the HOMO orbit of MIL-101(Cr) molecules are photo-excited and transition to the LUMO orbit position. The photo-excited electrons and holes are separated at the two-phase interface of titanium dioxide and MOF materials. The electrons on the LUMO orbit migrate to the CB, and the holes on the VB migrate to the HOMO orbit, inhibiting the recombination of electrons and holes and improving the charge separation efficiency.

[0013] Advantages of the present invention: The present invention utilizes the different energy level structures of titanium dioxide, polypyrrole, and MIL-101(Cr) materials, connects the PPy, TiO2, and MIL-101(Cr) photo-responsive molecules in series to form a photo-responsive series complex, namely the PPy / MIL-101(Cr) / TiO2 heterojunction film. By using light illumination to cause electron transitions, the separation of electrons and holes on the surface of the heterojunction film is excited, the charge state on the film surface is changed, and electron-hole pairs are generated. At the heterojunction interface, the electron-hole recombination can be effectively inhibited, the electron-hole separation efficiency of the heterojunction film is improved, and the light response performance is enhanced. In addition, by applying asymmetric light illumination on one side of the film, the asymmetric electric field generated by the light stimulation can form an ion pump effect to achieve the reverse concentration gradient transport of anions. The PPy / MIL-101(Cr) / TiO2 heterojunction film 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 of the drawings

[0014] Figure 1 It is the scanning electron microscope photograph of the PPy / MIL-101(Cr) / TiO2 heterojunction film.

[0015] Figure 2 It is the charge separation state diagram of the PPy / MIL-101(Cr) / TiO2 heterojunction film.

[0016] Figure 3 It is the current-voltage curve graph of the PPy / MIL-101(Cr) / TiO2 heterojunction film under different transmembrane voltages.

[0017] Figure 4 Ion current-time trajectory curve of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane under alternating visible light.

[0018] Figure 5 Ion pump effect diagram of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0019] Figure 6 Photoresponse ion current of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane under different light intensities. Detailed implementation manners

[0020] It should be noted that the following detailed description is exemplary and is 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 of ordinary skill in the technical field to which the present application belongs.

[0021] The "biomimetic photosynthetic membrane" of the present invention refers to a functional membrane material with ion pump performance under illumination. Utilizing the intrinsic optoelectronic properties of the membrane material, an internal electric field formed by uneven charge distribution is generated under illumination, driving the reverse transport of ions. In order to maximize the utilization of clean light energy, titanium dioxide molecules are added to act as light-absorbing wires, expanding the spectral absorption range and increasing the photoelectric conversion efficiency.

[0022] Hereinafter, the production method of the biomimetic photosynthetic membrane of the present invention will be described using polypyrrole as the light-absorbing antenna material. However, those skilled in the art can understand that the present invention is not limited to the following embodiments.

[0023] For the aforementioned biomimetic photosynthetic membrane, a polypyrrole conductive polymer membrane is modified in the porous channels of MIL-101(Cr) by chemical oxidation. The surface of the polypyrrole membrane is positively charged and has anion-selective transport properties. Under illumination, polypyrrole is photoexcited, causing electrons in the HOMO orbital to transition to the LUMO orbital, resulting in electron-hole separation. In addition, under light stimulation, the photogenerated electrons in the valence band of TiO2 migrate to the conduction band, leaving holes in the valence band orbitals at the same time. The electrons in the LOMO orbital of MIL-101(Cr) migrate to the conduction band of TiO2, and the holes in the valence band of TiO2 migrate to the HOMO energy level of MIL-101(Cr). The electron-hole separation at the MIL-101(Cr) / TiO2 composite interface inhibits the electron-hole separation efficiency and improves the photoresponse performance. The photoexcitation of PPy causes electron-hole separation, and the electrons in the LUMO orbital migrate to the conduction band of TiO2, and the holes in the valence band of TiO2 migrate to the HOMO orbital. The electron-hole separation at the PPy / TiO2 composite interface improves the photoresponse performance.

[0024] The tandem structure of the photoreaction complex in the PPy / MOF / TiO2 heterojunction membrane increases the spectral absorption range, enhances the light absorption performance of the membrane, inhibits electron-hole recombination, and improves the charge separation efficiency.

[0025] MIL-101(Cr) is a three-dimensional network structure formed by the coordination bond between terephthalic acid and the inorganic structural unit of chromium trimer Cr3O(CO2)6, with a large surface area and pore space. The most basic unit of MIL-101(Cr) consists of a Cr3O trinuclear chromium cluster and terephthalic acid. Each Cr3O cluster contains one μ3O, four carboxylic acid oxygens, and one F or OH terminal site. The unit cell of MIL-101(Cr) belongs to the Fd-3m space group and is a cubic crystal system. MIL-101(Cr) is composed of two types of mesoporous cage frameworks with diameters of 2.9 nm and 3.4 nm, respectively. The ratio of these two cage frameworks is 2:1. The smaller cage window is a pentagon with a size of 1.2 nm, and the larger cage framework window is a hexagon with a size of 1.4 - 1.6 nm. The large pore size and wide cavity structure of MIL-101(Cr) provide favorable conditions for the entry and in-situ polymerization of polymer monomers. Through chemical oxidation, pyrrole can be oxidized to polypyrrole to obtain PPy / MIL-101(Cr). By dispersing PPy / MIL-101(Cr) in a dispersant, the PPy / MIL-101(Cr) heterojunction membrane can be finally constructed.

[0026] The polypyrrole photosystem in the heterojunction membrane is photoexcited, resulting in the separation of electrons and holes. The photo-generated electrons migrate from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), leaving photo-generated holes (h +) PPy is a p-type semiconductor, forming a p-n heterojunction with the n-type semiconductor TiO2. The p-n junction formed between TiO2 and PPy is conducive to the separation of photoinduced charges. The photogenerated electrons of PPy transfer to the conduction band of TiO2, increasing the surface charge density of the positively charged PPy film and suppressing the recombination of electrons and holes. At the same time, the electrons on the HOMO orbital of the MIL-101(Cr) molecule are excited by light and transition to the LUMO orbital position. Since the LUMO orbital energy level of MIL-101(Cr) (-0.42 eV) is more negative than the conduction band of TiO2 (-0.4 eV), the excited electrons of MIL-101(Cr) transfer to the conduction band of TiO2; the valence band energy level of TiO2 (2.8 eV) is more positive than the HOMO orbital energy level of MIL-101(Cr) (2.16 eV), and the holes on the valence band of TiO2 migrate to the HOMO orbital of MIL-101(Cr). At the same time, the valence band energy level of TiO2 is more positive than the HOMO orbital energy level of PPy (1.75 eV), resulting in the migration of holes on the valence band of TiO2 to the HOMO orbital of PPy. The tandem structure of the photoreaction complex is conducive to the separation of electrons and holes, inhibits the recombination of photogenerated electrons and holes, and improves the light response performance of the heterojunction film ( Figure 2 )。

[0027] Titanium dioxide is an n-type semiconductor material with a wide bandgap. Its bandgap width at room temperature is 3.2 eV. The photon wavelength absorbed by titanium dioxide intrinsically is less than 380 nm, and the light in this region only accounts for 5% of the entire solar spectrum, greatly limiting its application. Titanium dioxide has high chemical stability, non-toxicity, and excellent light stability, with great potential in converting solar energy into electrical energy. The conductive polymer polypyrrole (PPy) is a p-type semiconductor, and TiO2 is an n-type semiconductor. The p-n junction is formed by the combination of p-type and n-type semiconductors. The built-in electric field formed at the interface of the p-n junction can improve the separation of photogenerated electron-hole pairs. By modifying TiO2 nanoparticles on the surface of the PPy / MIL-101(Cr) heterojunction film, a composite heterojunction film of PPy / MIL-101(Cr) / TiO2 can be constructed. Under ultraviolet light irradiation, the electrons on the valence band of titanium dioxide transition to the conduction band, causing uneven charge distribution to form a built-in electric field. This built-in electric field drives the transport of ions against the concentration gradient, forming an ion pump transport performance. Incorporating a PPy light-absorbing antenna with a wide range of light absorption wavelengths can increase 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. Thus, the clean light source is fully utilized and converted into chemical energy, greatly improving the photoelectric conversion efficiency.

[0028] Anion pump transport mechanism of PPy / MIL-101(Cr) / TiO2 heteromembrane. Asymmetric visible light illumination is applied to one side of the heteromembrane, resulting in asymmetric accumulation of surface charges on the membrane and forming an internal electric field. This internal electric field drives the transport of anions against the concentration gradient, forming an ion pump effect.

[0029] In order to enable those skilled in the art to more clearly understand the technical solutions of this application, the technical solutions of this application will be described in detail below in conjunction with specific embodiments.

[0030] The test materials not specifically described used in the embodiments of the present invention are all conventional test materials in the art and can be obtained through commercial channels. The TiO2 sol was purchased from Hengge Nano Technology Co., Ltd. The CAS number of MIL-101(Cr) is 869288-09-5. Example 1: Preparation of biomimetic photosynthetic membrane Preparation of PPy / MIL-101(Cr) heteromembrane The preparation method of the PPy / MIL-101(Cr) heteromembrane is partially derived from "Theoretical Calculation and Iodine Extraction Performance Study of Inorganic-Organic Electroactive Ion Exchange Material MIL-101@PPy" (Taiyuan University of Technology), and is specifically as follows: The PPy / MIL-101(Cr) heteromembrane is prepared by a method of surface modification and chemical oxidation. Add 0.2 g of MIL-101(Cr) powder to a pyrrole (Py) solution with a volume of 3 mL and a concentration of 1 mol / L, and perform ultrasonic treatment to make it evenly dispersed. Soak at room temperature for three days to allow pyrrole units to enter the pores of MIL-101(Cr), and centrifuge to obtain the Py-doped MIL-101(Cr) complex. Add deionized water to the complex and centrifuge and wash four times to wash off the pyrrole solution on the surface of MIL-101(Cr). At this time, the mass ratio of MIL-101(Cr) to Py in it is 1:1.67. Dry at room temperature for 24 h to obtain the cleaned Py / MIL-101(Cr) complex. Then, the PPy / MIL-101(Cr) complex is prepared by chemical oxidation. Add 5 mL of 0.8 mol / L FeCl3 oxidant to the Py / MIL-101(Cr) composite material, and oxidize it at 24 h under ice-water bath conditions to oxidize Py to PPy, obtaining the PPy / MIL-101(Cr) heteromembrane material in which the PPy polymer is combined with MIL-101(Cr). After centrifugation, dry it under an infrared lamp at 40 °C for 12 h to obtain the black powder of PPy / MIL-101(Cr). At this time, the mass ratio of MIL-101(Cr) to PPy in it is 1.26:1.

[0031] The PPy / MIL-101(Cr) heterogeneous membrane was prepared by the drop-casting method. A 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 PVDF coating binder with a mass fraction of 3.75%. 0.05 g of black PPy / MIL-101(Cr) powder was weighed and 2500 μL of the PVDF coating binder was added to obtain a PPy / MIL-101(Cr) coating solution with a mass fraction of 2%. In 0.05 g of PPy / MIL-101(Cr) powder, 625 μL and 333 μL of PVDF binder were added respectively to obtain PPy / MIL-101(Cr) coating solutions with mass fractions of 8% and 15% respectively. 10 μL of each coating solution was taken and drop-cast onto the surface of a glass slide. Due to the surface tension of the coating solution, it would automatically spread on the glass slide surface, and the spreading area was limited to 0.5 cm × 1.5 cm. It was placed in an oven, the oven temperature was adjusted to 60 °C, and dried for 10 min. After drying, the oven was turned off, and the glass slide was taken out of the oven and cooled to room temperature. The membrane was peeled off from the glass slide surface with tweezers to obtain PPy / MIL-101(Cr) heterogeneous membranes with mass fractions of 2%, 8% and 15% respectively. The PPy / MIL-101(Cr) heterogeneous membrane with a mass fraction of 8% was used for subsequent experiments.

[0032] Preparation of PPy / MIL-101(Cr) / TiO2 Heterogeneous Membrane The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was prepared by the spin-coating method to modify TiO2 nanoparticles on the surface of the PPy / MIL-101(Cr) heterogeneous membrane to form a photo-responsive tandem complex, namely the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0033] If the nanoparticles are too large, it is not easy to adsorb onto the membrane surface; if the particles are too small, the ion transport resistance increases. Therefore, the size of the TiO2 nanoparticles used is 5.9 ± 1.2 nm. The rotation rate during spin-coating is 4000 revolutions per minute, and 50 mg / ml TiO2 hydrosol is spin-coated on the surface of the PPy / MIL-101(Cr) membrane for 30 s. Spin-coating is unilateral spin-coating. Using the unilateral spin-coating method helps the asymmetric accumulation of photo-responsive charges to form an internal electric field.

[0034] By adjusting the spin-coating rate and TiO2 concentration, the thickness of the TiO2 layer can be controlled. During spin-coating, it is carried out in multiple steps. After the surface of the PPy / MIL-101(Cr) film is dried, the next spin-coating is carried out. If the spin-coating amount is too much, resulting in an increase in the thickness of the TiO2 layer on the film surface, the ion transport current will be reduced; if the spin-coating amount is too little, it is not conducive to the light absorption performance. The PPy / MIL-101(Cr) film is spin-coated with TiO2 sol 3 times, 4 times, and 5 times respectively to obtain the PPy / MIL-101(Cr) / TiO2 heterojunction film. At this time, the thicknesses of the TiO2 nanoparticle layers on the surface of the PPy / MIL-101(Cr) / TiO2 heterojunction film are 1.2 µm, 1.7 µm, and 2.2 µm respectively. The PPy / MIL-101(Cr) / TiO2 heterojunction film obtained by spin-coating 4 times is scanned, and the scanning electron microscope photos are shown in Figure 1 , and subsequent experiments are carried out using the PPy / MIL-101(Cr) / TiO2 heterojunction film prepared by this method.

[0035] Example 2: Ion current-voltage curve At room temperature, the PPy / MIL-101(Cr) / TiO2 heterojunction film is installed on a self-made double-chamber electrolyzer, and 1 mM KCl electrolyte is injected into the two side chambers of the electrolytic cell. The current-voltage curve measured by passing through the PPy / MIL-101(Cr) / TiO2 heterojunction film is shown in the solid line of Figure 3. Subsequently, the PPy / MIL-101(Cr) / TiO2 heterojunction film is replaced with the PPy / MIL-101(Cr) heterojunction film, and the ion current-voltage curve of this film is shown in the dotted line of Figure 3.

[0036] It can be seen from the results that at the same voltage, the ion current passing through the PPy / MIL-101(Cr) / TiO2 heterojunction film is greater than that of the pure polyvinylidene fluoride film. This is because the incorporation of PPy / MIL-101(Cr) / TiO2 increases the porosity of the film and improves the ion transport current.

[0037] Example 3: Photoresponse ion transport performance test Select the PPy / MIL-101(Cr) / TiO2 heterojunction film as the diaphragm and install it in a self-made double-chamber electrolytic cell, and inject 1 mM KCl electrolyte solution into the double-chamber electrolytic cell. Using a xenon lamp (wavelength range 190 - 1100 nm) as the light source, visible light with an irradiation intensity of 320 mW / cm 2 is passed through a quartz window to irradiate the surface of the heterojunction film. A pair of Ag / AgCl reference electrodes (the black tube is protected from light) monitor the ion current passing through the film, and the ion current-time curve of the PPy / MIL-101(Cr) / TiO2 heterojunction film with the applied light irradiation is recorded.

[0038] The results are as Figure 4 shown. It can be seen that when light is applied, the ionic current passing through the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane increases; when the light is turned off, the ionic current decreases. The light-responsive ionic transport properties of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane were further characterized.

[0039] When light is applied, the ionic current passing through the membrane increases. When the light is turned off, the ionic current passing through the membrane decreases. This demonstrates the light-responsive ionic transport properties of the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane.

[0040] Example 4: Ion pump effect test The light-responsive ionic transport properties of the PPy / MIL-101(Cr) / TiO2 membrane endow it with an ion pump effect. The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was fixed on a two-chamber electrolytic cell. Electrolytes were injected into the two side chambers of the electrolytic cell respectively. The concentration of the electrolyte on the high-concentration side was fixed at 1 mM KCl, and that on the low-concentration side was 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. Using a xenon lamp (wavelength range 190 - 1100 nm) as the light source, visible light with an irradiation intensity of 320 mW / cm 2 was passed through a quartz window and irradiated on the surface of the heterogeneous membrane from the high-concentration electrolyte side. A pair of Ag / AgCl reference electrodes (the black tube was protected from light) monitored the ionic current passing through the membrane. Before illumination, due to the different concentrations of KCl electrolytes on both sides of the membrane, the concentration difference drove Cl - to transport from the high-concentration side to the low-concentration side, generating a negative ionic current of -3 nA. After applying light, the negative ionic current decreased rapidly, and a positive current of 3 nA was generated in about 100 s. When the light was turned off, the ionic current passing through the PPy / MIL-101(Cr) / TiO2 heterogeneous membrane returned to the original negative value state ( Figure 5 ).

[0041] Example 5: Light-responsive ionic current test The PPy / MIL-101(Cr) / TiO2 heterogeneous membrane was selected as the diaphragm and installed in a self-made two-chamber electrolytic cell. A 1 mM KCl electrolyte solution was injected into the two-chamber electrolytic cell. Using a xenon lamp (wavelength range 190 - 1100 nm) as the light source, the irradiation intensities were 120, 220, 320 mW / cm 2Visible light passes through the quartz window and irradiates the surface of the heterojunction film. A pair of Ag / AgCl reference electrodes (protected from light by a black tube) monitor the photocurrent response passing through the film. Subsequently, the PPy / MIL-101(Cr) / TiO2 heterojunction film is replaced with the PPy / MIL-101(Cr) heterojunction film, and the Ag / AgCl reference electrodes (protected from light by a black tube) are used again to monitor the photocurrent response passing through the film.

[0042] Figure 6 The bar chart shows the photocurrent response of the PPy / MIL-101(Cr) / TiO2 heterojunction film and the PPy / MIL-101(Cr) heterojunction film under different light intensities. As can be seen from the figure, under different light intensities, the photocurrent response of the PPy / MIL-101(Cr) / TiO2 heterojunction film is higher than that of the PPy / MIL-101(Cr) heterojunction film, indicating that under light stimulation, the tandem structure of the photoreaction complex in the PPy / MOF / TiO2 heterojunction film increases the spectral absorption range, enhances the light response absorption performance of the film, inhibits electron-hole recombination, and improves the charge separation efficiency.

[0043] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, various modifications and changes can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a bionic photosynthetic membrane, characterized in that, The preparation method described above includes the following steps: Prepare a conductive polymer on the pores of the MOF porous material, disperse it in a dispersant, and construct a conductive polymer / MOF coating solution in which the conductive polymer is combined with the MOF porous material; after drop-coating and drying, obtain a conductive polymer / MOF heterogeneous membrane; modify the surface of the conductive polymer / MOF heterogeneous membrane with an inorganic light-absorbing material to obtain a conductive polymer / MOF / nanoparticle heterogeneous membrane, that is, a biomimetic photosynthetic membrane; The conductive polymer is polyaniline, polypyrrole, polythiophene, polyacetylene, poly(p-styrene) or poly(3,4-ethylenedioxythiophene); 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 the MOF porous material to the conductive polymer is 0.5-2:

1.

2. The preparation method of the bionic photosynthetic membrane according to claim 1, wherein, The dispersant is a polyvinylidene fluoride coating binder; the ratio of polyvinylidene fluoride to N-methylpyrrolidone is 0.18 g:(3-6) mL.

3. The preparation method of the biomimetic photosynthetic membrane 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%.

4. The preparation method of the bionic photosynthetic membrane according to claim 1, characterized in that, 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 a polypyrrole / MIL-101(Cr) / TiO2 membrane.

5. The preparation method of the bionic photosynthetic membrane according to claim 1, characterized in that, The surface modification method is single-sided spin coating. The rotation rate during spin coating is 2000-8000 revolutions per minute. Spin coat the 10-100 mg / ml nanoparticle hydrogel 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 used nanoparticles is 1-20 nm.

6. A method for enhancing the ion pump effect by light, characterized in that, It includes the following steps: Prepare a biomimetic photosynthetic membrane according to the preparation method described in any one of claims 1-5, irradiate the biomimetic photosynthetic membrane with externally applied light, regulate the charge distribution state on the membrane surface, improve the electron-hole separation efficiency of the biomimetic photosynthetic membrane, and realize the light-enhanced ion pump effect.

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