Preparation method and application of a double porphyrin-based organic semiconductor photocatalyst

Abstract

The application provides a preparation method and application of a double-porphyrin-based organic semiconductor photocatalyst. The application belongs to the technical field of photocatalysis, and can realize efficient conversion of coenzyme NADH under weak light without relying on special strong light equipment and rhodium complex electronic mediators. The technical scheme comprises the following steps: (1) dissolving porphyrin A in water to assemble the porphyrin A, and obtaining a porphyrin self-assembly solution A; (2) dissolving porphyrin B in water to obtain a porphyrin solution B; (3) adding the porphyrin solution B into the porphyrin self-assembly solution A to obtain a double-porphyrin assembly solution; and (4) adding a potassium tetrachloroplatinate solution and an electron donor reagent solution into the double-porphyrin assembly solution, and obtaining the double-porphyrin-based organic semiconductor photocatalyst after light irradiation. The double-porphyrin-based organic semiconductor photocatalyst obtained by the application can be used for synthesis of NADH under weak light, and can be used for subsequent photocatalytic reduction of CO2 by coupling with enzymes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalysis, and particularly relates to a preparation method and application of a double-porphyrin-based organic semiconductor photocatalyst. TECHNICAL BACKGROUND

[0002] The large use of traditional fossil energy not only drives the rapid development of economy, but also brings serious energy and environmental problems. Especially in countries with not rich energy reserves, the dependence on imported petrochemical resources also brings pressure to China's energy security strategy. Therefore, the development and utilization of new energy are imminent. Among many new energies, solar energy is favored due to its unlimited reserves, no geographical restrictions, and cleanliness. Through photoelectric, photothermal, photochemical conversion and other reactions, it is converted into more easily used forms of electric energy, thermal energy and chemical energy, etc., which has become the main way of current solar energy utilization. Especially, the use of photocatalytic technology to convert greenhouse gas CO2 into chemical fuels or organic chemicals, etc. has attracted widespread attention from governments and scientific researchers around the world, because it is expected to solve the problems of energy shortage and environmental pollution at the same time.

[0003] However, CO2 is stable in nature, and a high energy supply is required to convert it. Moreover, the reduction of CO2 is a multi-electron process, for example, 2 electrons are required to convert CO, 4 electrons are required to convert formaldehyde, 6 electrons are required to convert methanol, and 8 electrons are required to convert methane (see Wang et al. J. Am. Chem. Soc. 2014, 4, 962-972). The multi-electron reduction pathway leads to a variety of photocatalytic products, which brings great difficulty to subsequent purification. How to improve the selectivity of photocatalytic reduction of CO2 is a bottleneck. It is well known that biological enzyme catalytic reactions have the characteristics of high efficiency and specificity. By simulating the mechanism of photosynthesis in nature, the coupling of photoenzymes and catalytic reactions provides a unique solution to achieve specific conversion of CO2. The photo reaction stores energy in coenzyme NADH, and then catalyzes the reduction of CO2 in the enzyme reaction. Therefore, the supply of NADH is the key to determining whether the coupling of photoenzymes and catalytic reactions can be successfully implemented.

[0004] From the existing research, photocatalytic production of NADH generally requires strong light irradiation (>30000 lux), and some semiconductor materials (such as titanium dioxide) also require special ultraviolet light irradiation (see Wang et al. Chemical Engineering Journal, 2023, 466, 143219), and there are few reports of weak light (<1000 lux) sensitive photocatalysts that do not depend on light irradiation equipment. Moreover, many photocatalytic systems currently reported require additional electron mediators (such as rhodium complexes) to match the energy levels between light capture and photocatalysis, increasing costs and making industrial promotion more difficult (see Kim et al. Angewandte Chemie International Edition, 2012, 51, 517-520). Porphyrin molecules have a conjugated macrocyclic structure similar to chlorophyll, are sensitive to sunlight, and are easy to regulate their light absorption and photophysical properties through peripheral group modification or core metalation (see Zhang et al. Chinese Chemical Letters, 2022, 33, 33-60). Studies by researchers using peptide assemblies to induce porphyrin aggregation have shown that by using specific aggregation methods, such as J-aggregation, the electron delocalization is expanded from a single molecule to the entire aggregate, which can greatly improve the charge separation / transport properties (see Wang et al. Materials Chemistry A, 2017, 5, 24612-24616). However, the introduction of organic templates that do not absorb light or conduct electricity in the catalytic system will to some extent reduce the photocatalytic properties of the system, making the conversion rate of NADH under weak light still very low. Therefore, constructing an efficient photocatalytic system to achieve high-efficiency conversion of NADH without strong light irradiation and additional electron mediators has become a key problem that needs to be urgently addressed. SUMMARY

[0005] In view of the problems of low photocatalytic efficiency, dependence on strong light irradiation and additional need for electron mediators in the current light enzyme coupling catalytic process, the present application provides a preparation method and application of a double porphyrin-based organic semiconductor photocatalyst. By assembling one porphyrin molecule on the surface of another porphyrin aggregate, a porphyrin organic semiconductor with a heterojunction structure is constructed, and then by in-situ reduction of platinum salt, platinum metal nanoparticles are introduced on the surface of the porphyrin-based organic semiconductor, which further improves the charge separation effect and serves as a catalytically active center to obtain a high-activity photocatalytic system. The specific application contents are as follows:

[0006] A preparation method of a double porphyrin-based organic semiconductor photocatalyst, characterized in that it comprises the following steps:

[0007] S1: A certain amount of porphyrin A is weighed and added to pure water, the pH value is adjusted to dissolve it, and it is left to assemble to obtain a porphyrin self-assembly solution A;

[0008] S2: A certain amount of porphyrin B is weighed and added to pure water, the pH value is adjusted to dissolve it, and a porphyrin solution B is obtained;

[0009] S3: Freshly prepared porphyrin solution B is gradually added dropwise to porphyrin self-assembly solution A under stirring, and after uniform stirring, assembly is allowed to occur by standing, to obtain a double porphyrin assembly solution;

[0010] S4: A certain amount of potassium tetrachloroplatinate is dissolved in water to prepare a solution of a certain concentration, to obtain a potassium tetrachloroplatinate solution, which is used after being placed for 24 hours;

[0011] S5: A certain amount of double porphyrin assembly solution is measured, a certain amount of potassium tetrachloroplatinate solution and an electron donor reagent are added, and water is added to dilute to a certain volume, and a gray-green solution is obtained after light irradiation for a certain time, and a double porphyrin-based organic semiconductor photocatalyst is obtained after centrifugation, water washing and drying.

[0012] Optionally, porphyrin A and porphyrin B are one of tetraaminophenyl porphyrin, tetracarboxyphenyl porphyrin, tetraphenylsulfonic acid porphyrin and tetrahydroxyphenyl porphyrin.

[0013] Preferably, the concentration of porphyrin A in the porphyrin self-assembly solution A is 50-200 μmol / L, and the concentration of porphyrin B in the porphyrin solution B is 10-50 μmol / L.

[0014] Preferably, the pH value of the porphyrin self-assembly solution A is 1-3, and the pH value of the porphyrin solution B is 4-6.

[0015] Preferably, the mixing ratio of the porphyrin solution B to the porphyrin self-assembly solution A is 0.5-3.

[0016] Preferably, the concentration of potassium tetrachloroplatinate in the potassium tetrachloroplatinate solution is 1-5 mmol / L.

[0017] Preferably, the electron donor reagent is one of triethanolamine, ascorbic acid, glucose and disodium ethylenediaminetetraacetate, and the concentration thereof is 0.1-0.6 mol / L.

[0018] The application provides a double porphyrin-based organic semiconductor photocatalyst prepared according to any one of the preparation methods.

[0019] The application provides an application of the double porphyrin-based organic semiconductor photocatalyst prepared according to the preparation method in photocatalytic synthesis of NADH.

[0020] The double porphyrin-based organic semiconductor photocatalyst prepared by the application has no external electron mediator and does not need a special light-emitting device, and the conversion rate of NADH is more than 75% after reaction for 1 hour under weak light (<1000 lux), which is much higher than the reported efficiency of photocatalysts.

[0021] Compared with the prior art, the application has the following advantages and positive effects:

[0022] 1. Constructing a porphyrin-based organic semiconductor with a heterojunction by using a double porphyrin assembly technique, and reducing platinum nanoparticles in situ on the surface thereof, thereby expanding the single porphyrin absorption spectrum, inhibiting the recombination of electrons and holes through the introduction of a heterojunction and the formation of platinum catalytic active centers, improving the charge separation / transport efficiency, and greatly improving the activity of the photocatalyst, so that the photocatalyst can realize efficient conversion of NADH without relying on an electronic medium and strong light irradiation.

[0023] 2. The double porphyrin organic semiconductor photocatalyst provided by the application has a simple preparation method, and the catalytic process does not require a special strong light source or an external rhodium complex electronic medium, thereby saving cost and reducing the complexity of the subsequent purification process, and facilitating further industrial production and commercial promotion. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A transmission electron microscope (TEM) photo of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0025] Figure 2 An ultraviolet-visible absorption spectrum of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0026] Figure 3 An ultraviolet diffuse reflectance spectrum of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0027] Figure 4 A Mott-Schottky curve of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0028] Figure 5 A band structure schematic diagram of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0029] Figure 6 A photocurrent-time curve of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0030] Figure 7 An electrochemical impedance curve of the double porphyrin-based organic semiconductor photocatalyst prepared in Example 1 of the application;

[0031] Figure 8 A concentration-absorbance standard working curve of NADH;

[0032] Figure 9 A relationship curve between the conversion rate of NADH generated by the double porphyrin-based organic semiconductor photocatalyst and the reaction time when the double porphyrin-based organic semiconductor photocatalyst and a single porphyrin aggregate are used as photocatalysts. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0034] The embodiment of the present application provides a preparation method of a double-porphyrin-based organic semiconductor photocatalyst, characterized in that the method comprises the following steps:

[0035] A certain amount of porphyrin A is weighed and added into pure water, the pH value is adjusted to dissolve the porphyrin A, and the porphyrin A is allowed to stand to assemble, to obtain a porphyrin self-assembly solution A;

[0036] A certain amount of porphyrin B is weighed and added into pure water, the pH value is adjusted to dissolve the porphyrin B, to obtain a porphyrin solution B;

[0037] The freshly prepared porphyrin solution B is gradually added dropwise into the porphyrin self-assembly solution A under stirring, and the mixture is stirred uniformly and allowed to stand to assemble, to obtain a double-porphyrin assembly solution;

[0038] A certain amount of potassium tetrachloroplatinate is weighed and dissolved in water to prepare a solution with a certain concentration, to obtain a potassium tetrachloroplatinate solution, which is used after being placed for 24 hours;

[0039] A certain amount of the double-porphyrin assembly solution is measured, a certain amount of the potassium tetrachloroplatinate solution and an electron donor reagent are added, water is added to dilute to a certain volume, the mixture is irradiated for a certain time, a gray-green solution is obtained, and the double-porphyrin-based organic semiconductor photocatalyst is obtained through centrifugation, water washing and drying.

[0040] The principle of the method disclosed in the above embodiment is to construct a double-porphyrin-based organic semiconductor photocatalyst through sequential assembly of double porphyrin and in-situ reduction of platinum salt. Each porphyrin molecule has its own unique absorption spectrum, and the use of double porphyrin can make it have a wider light absorption range, which is one of the important factors affecting the activity of the photocatalyst. The sequential assembly of two kinds of porphyrin introduces a heterojunction in the double-porphyrin organic semiconductor. Through the design of the band structure of the organic semiconductor, the excitation and charge separation / transport properties of the photocatalyst can be regulated, and the photoelectric conversion efficiency of the photocatalyst and the inhibition of the recombination of photo-generated electrons and holes can be improved. The role of platinum nanoparticles in the photocatalytic system is similar to that of plastoquinone in the natural photosynthetic system, which can effectively promote charge separation, and at the same time play the role of catalytic active center in the photocatalytic process. In summary, the special structure of the double-porphyrin-based organic semiconductor photocatalyst and the enhanced light absorption and improved charge separation / transport properties endow it with excellent photocatalytic properties, so that it can realize efficient conversion of NADH under weak light and without electron mediators.

[0041] In an optional embodiment, porphyrin A, porphyrin B are the one in tetraaminophenylporphyrin, tetracarboxylphenylporphyrin, tetraphenylsulfonylporphyrin, tetrahydroxyphenylporphyrin.Every kind of porphyrin molecule has separate absorption spectrum, and after forming ordered J-aggregate, absorption spectrum can red-shift, closer to the strongest region of sunlight, is conducive to the absorption of visible light, and more importantly, the ordered aggregation of porphyrin can promote the delocalization of photogenerated electrons, improves the separation / transmission efficiency of charge.In addition, the energy band structures of different porphyrin aggregates are different, affect the energy band structure of formed double porphyrin-based organic semiconductor, thus affect its light absorption, photoelectric conversion and photocatalytic performance when as catalyst.Through special design, the structure of double porphyrin-based organic semiconductor can be further optimized, and obtain excellent photocatalytic performance.

[0042] In a preferred embodiment, the concentration of porphyrin A in porphyrin self-assembly solution A is 50-200 μmol / L, and the concentration of porphyrin B in porphyrin solution B is 10-50 μmol / L. We want porphyrin molecules to assemble in an orderly manner in an aqueous solution, and their concentration must be at least higher than their critical aggregation concentration. Different porphyrin molecules have different solubilities in water, that is, different critical aggregation concentrations. Therefore, when designing a bi-porphyrin-based semiconductor photocatalyst, porphyrin concentration is also an important influencing factor. In the embodiment of the present invention, the concentration of porphyrin A is preferably 50-200 μmol / L, and the concentration of porphyrin B is 10-50 μmol / L, to obtain an ordered bi-porphyrin-based organic semiconductor.

[0043] In a preferred embodiment, the pH value of porphyrin self-assembly solution A is 1-3; the pH value of porphyrin solution B is 4-6. Different porphyrin molecules have different peripheral groups, and in particular, the peripheral groups of the porphyrin molecules selected in the present invention are pH-sensitive, that is, at different pH values, the charge of the peripheral groups of the porphyrin molecules is different, which not only affects their solubility in water, but also affects the interaction between molecules, that is, affects the self-assembly of the porphyrin molecules, thereby affecting the structure and photoelectric properties of the formed biporphyrin organic semiconductor. In an embodiment of the present invention, the pH value of porphyrin self-assembly solution A is preferably 1-3; the pH value of porphyrin solution B is 4-6, so that an ordered biporphyrin-based organic semiconductor can be obtained.

[0044] In a preferred embodiment, the mixing ratio of porphyrin solution B to porphyrin self-assembly solution A is 0.5-3. The addition of porphyrin B into the self-assembly solution of porphyrin B will cause the porphyrin B to gather on the surface of the self-assembly of porphyrin A due to the change of pH value of the solution, forming a porphyrin A / porphyrin B core-shell assembly. On the other hand, the addition of porphyrin B will also affect the aggregation / dispersion dynamic balance on the surface of the self-assembly of porphyrin A. Therefore, the ratio of porphyrin solution B to porphyrin self-assembly solution A has an important influence on the structure of the bi-porphyrin-based organic semiconductor and further exerts an influence on its properties. In the present embodiment, the mixing ratio of porphyrin solution B to porphyrin self-assembly solution A is 0.5-3, and an ordered bi-porphyrin-based organic semiconductor can be obtained.

[0045] In a preferred embodiment, the concentration of potassium tetrachloroplatinate in the potassium tetrachloroplatinate solution is 1-5 mmol / L. In the present embodiment, potassium tetrachloroplatinate is used to prepare platinum nanoparticles, and therefore the concentration of potassium tetrachloroplatinate is related to the size and structure of the platinum nanoparticles. In the present embodiment, the purpose of introducing platinum nanoparticles is to further improve the charge separation / transport effect of the photocatalyst, and the structure and size of the platinum nanoparticles are closely related to the catalytic performance of the catalyst. When the concentration of potassium tetrachloroplatinate is 1-5 mmol / L, the prepared bi-porphyrin-based organic semiconductor photocatalyst has good catalytic performance.

[0046] In a preferred embodiment, the electron-donating reagent is one of triethanolamine, ascorbic acid, glucose, and disodium ethylenediaminetetraacetate, and the concentration thereof is 0.1-0.6 mol / L. In the reaction of in-situ photocatalytic reduction of platinum nanoparticles, the platinum salt needs to receive 2 electrons, and therefore a suitable electron-donating reagent is needed to provide electrons. In the present embodiment, triethanolamine, ascorbic acid, glucose, and disodium ethylenediaminetetraacetate are suitable electron-donating reagents, which can help the reaction of reduction of platinum salt to proceed smoothly, and the structure of the prepared bi-porphyrin-based organic semiconductor photocatalyst is as shown in Figure 1 A large number of platinum nanoparticles are deposited around the bi-porphyrin assembly with a diameter of about 50 nm.

[0047] The present embodiment provides a bi-porphyrin-based organic semiconductor photocatalyst prepared according to any one of the preparation methods described above. It has a relatively strong light absorption near the strongest spectral region of sunlight (about 500 nm) Figure 2 ), and a band gap of about 1.71 eV Figure 3 ). Through the Mott-Schottky curve Figure 4 , it can be obtained that the conduction band potential thereof is about -1.28 V, and therefore it can be inferred that the valence band potential thereof is 0.43 V Figure 5 . Meanwhile, it exhibits good photoelectric conversion behavior under visible light irradiation Figure 6 , and has a relatively small electrochemical impedance when coated on the surface of an electrode as an electrode materialFigure 7 ), indicating that the prepared double porphyrin-based organic semiconductor photocatalyst has good light absorption and photoelectrochemical properties.

[0048] The application provides an application of the double porphyrin-based organic semiconductor photocatalyst prepared by the preparation method in photocatalytic synthesis of NADH. In the reaction of photocatalytic synthesis of NADH, the oxidized compound NAD + NADH needs to accept one proton and two electrons to be converted, which belongs to a photocatalytic reduction reaction, and whether the reaction can be carried out depends on the reduction potential of the photocatalyst, that is, the conduction band position. The rate and degree of the reaction are related to the effective current density generated during light irradiation, the surface properties of the photocatalyst and the kinetic diffusion of the reactants and reaction products. In the embodiment of the application, whether NADH is generated is judged by using ultraviolet absorption at 340 nm, and the conversion rate can be determined by using a concentration-absorbance working curve (). Figure 8 The prepared porphyrin-based organic semiconductor photocatalyst has a controllable energy band structure and a porphyrin heterojunction structure for promoting charge separation, can promote photo-generated electrons to have sufficient reduction potential and current density, and further improves the separation / transmission rate of charges in combination with the presence of the platinum nanoparticle surface cocatalyst, so that the reduction reaction of NADH near the platinum nanoparticle can be smoothly carried out.

[0049] The prepared double porphyrin-based organic semiconductor photocatalyst does not need an external electron mediator and a special light-emitting device, and the conversion rate of NADH is more than 75% after 1 hour of reaction under weak light (<1000 lux), which is much higher than that of a single porphyrin aggregate and the reported photocatalyst efficiency. Most of the previously reported photocatalytic NADH synthesis reactions occur in the presence of strong light irradiation and an electron mediator-rhodium complex, and the reason mainly lies in that the used photocatalyst has poor weak light sensitivity and cannot effectively undergo photoelectric / photochemical conversion. In the embodiment of the application, the prepared double porphyrin-based organic semiconductor photocatalyst has good light absorption, excellent photoelectric conversion and charge separation / transmission efficiency, and has excellent weak light sensitivity and photocatalytic efficiency in combination with the cocatalytic effect of the platinum nanoparticle, does not need an external electron mediator and a special light-emitting device, and the conversion rate of NADH is more than 75% after 1 hour of reaction under weak light (<1000 lux) (). Figure 9 ), which is much higher than the reported photocatalyst efficiency.

[0050] In order to more clearly and specifically introduce the preparation method and application of the double porphyrin-based organic semiconductor photocatalyst provided in the embodiment of the application, the following will be described in combination with specific embodiments.

[0051] Embodiment 1

[0052] Take a certain amount of tetraphenylsulfonate-based porphyrin, add pure water, adjust to pH 1 to dissolve it, and let it assemble to obtain a tetraphenylsulfonate-based porphyrin self-assembly solution with a concentration of 200 μmol / L;

[0053] Take a certain amount of tetracarboxyphenyl porphyrin, add pure water, and adjust to pH 4 to dissolve it to obtain a tetracarboxyphenyl porphyrin solution with a concentration of 50 μmol / L;

[0054] The freshly prepared tetracarboxyphenyl porphyrin solution is gradually added dropwise to the tetraphenylsulfonate-based porphyrin self-assembly solution under stirring, and the volume ratio of the two is 1:3. After stirring uniformly, it is left to assemble to obtain a double porphyrin assembly solution;

[0055] A certain amount of potassium tetrachloroplatinate is dissolved in water to prepare a solution with a concentration of 5 mmol / L to obtain a potassium tetrachloroplatinate solution, which is used after being placed for 24 hours;

[0056] 100 mL of the double porphyrin assembly solution is measured, 10 mL of the potassium tetrachloroplatinate solution and 10 mL of ascorbic acid (0.6 mol / L) are added, and water is added to dilute to 1 L. After being irradiated for a certain time, a gray-green solution is obtained. After centrifugation, water washing, and drying, a double porphyrin-based organic semiconductor photocatalyst 1 is obtained.

[0057] Example 2

[0058] A certain amount of tetracarboxyphenyl porphyrin is taken, added to pure water, and adjusted to pH 3 to dissolve it. After being left to assemble, a tetracarboxyphenyl porphyrin self-assembly solution with a concentration of 50 μmol / L is obtained;

[0059] A certain amount of tetracarboxyphenyl porphyrin is taken, added to pure water, and adjusted to pH 3 to dissolve it. After being left to assemble, a tetracarboxyphenyl porphyrin self-assembly solution with a concentration of 50 μmol / L is obtained;

[0060] The freshly prepared tetracarboxyphenyl porphyrin solution is gradually added dropwise to the tetraphenylsulfonate-based porphyrin self-assembly solution under stirring, and the volume ratio of the two is 1:3. After stirring uniformly, it is left to assemble to obtain a double porphyrin assembly solution;

[0061] A certain amount of potassium tetrachloroplatinate is dissolved in water to prepare a solution with a concentration of 5 mmol / L to obtain a potassium tetrachloroplatinate solution, which is used after being placed for 24 hours;

[0062] 100 mL of the double porphyrin assembly solution is measured, 10 mL of the potassium tetrachloroplatinate solution and 10 mL of ascorbic acid (0.6 mol / L) are added, and water is added to dilute to 1 L. After being irradiated for a certain time, a gray-green solution is obtained. After centrifugation, water washing, and drying, a double porphyrin-based organic semiconductor photocatalyst 1 is obtained.

[0063] Example 3

[0064] A certain amount of tetraamino phenyl porphyrin was weighed and added to pure water, adjusted to pH 2 to dissolve it, and allowed to assemble to obtain a self-assembled solution of tetraaminophenyl porphyrin with a concentration of 100 μmol / L;

[0065] A certain amount of tetraaminophenyl porphyrin was weighed and added to pure water, adjusted to pH 2 to dissolve it, and allowed to assemble to obtain a self-assembled solution of tetraaminophenyl porphyrin with a concentration of 100 μmol / L;

[0066] The freshly prepared tetraaminophenyl porphyrin solution was gradually added to the self-assembled solution of tetraaminophenyl porphyrin under stirring, and the volume ratio was 1:1. After uniform stirring, it was allowed to assemble to obtain a double porphyrin assembly solution.

[0067] A certain amount of potassium tetrachloroplatinate was weighed and dissolved in water to prepare a solution with a concentration of 3 mmol / L, and the solution was used after being placed for 24 hours.

[0068] 100 mL of the double porphyrin assembly solution was weighed, 10 mL of the potassium tetrachloroplatinate solution and 10 mL of glucose (0.3 mol / L) were added, and water was added to dilute to 1 L. After light irradiation for a certain time, a gray-green solution was obtained. After centrifugation, water washing and drying, a double porphyrin-based organic semiconductor photocatalyst 3 was obtained.

[0069] Example 4

[0070] The instrument is a JEOL-2100UHR high-resolution transmission electron microscope, and the instrument manufacturer is JEOL.

[0071] The above material obtained in the above example is taken as an example for illustration. The double porphyrin-based organic semiconductor photocatalyst sample was dispersed with ultrapure water, and a copper mesh covered with a carbon support film was placed on an absorbent paper with the front face upward. Then, an appropriate amount of sample dispersion liquid was dropped on the surface of the copper mesh, and adsorbed for about 10 min. Then, the copper mesh was placed under a transmission electron microscope for characterization, and the transmission electron microscope picture of the sample was obtained.

[0072] Figure 1 The picture shown is a high-resolution transmission electron microscope picture of the sample. In the picture, there are mainly two kinds of structures, one is a long rod structure with a diameter of about 50 nm, and the other is a nanoparticle structure with a size of about 3 nm. According to the contrast and the structure of the porphyrin assembly, it can be known that the long rod structure is a double porphyrin-based organic semiconductor, and the particulate matter is a platinum nanoparticle. Their organic combination and synergistic effect are of great significance to the improvement of their light absorption and charge separation / transmission performance.

[0073] Example 5

[0074] The following tests were performed at an experimental temperature of 25°C using a UV- visible spectrophotometer, model UV-1700PharmaSpec, using the materials obtained in the above examples as examples.

[0075] The adopted porphyrin molecules have absorption in the UV-visible spectrum, and after aggregation, their absorption spectrum will shift to a certain extent, for example, H-aggregation has a blue shift, and J-aggregation has a red shift, so the aggregation form can be judged by the shift of the absorption peak in the UV-visible spectrum. As shown in Figure 2 The absorption peak at 490 nm on the UV-visible spectrum of the bis-porphyrin organic semiconductor 1 indicates the presence of J-aggregates of tetraphenylsulfonate porphyrin, and the J-aggregates still exist after in-situ reduction of the metal platinum in the bis-porphyrin-based organic semiconductor photocatalyst.

[0076] NADH has absorption at 260 nm and 340 nm in the UV-visible spectrum, while its oxidized state molecule NAD + Only at 260 nm, the intensity is linearly related to its concentration (as shown in Figure 8 This embodiment combines the intensity of the absorption peak at 340 nm in the UV-visible spectrum to judge the content of NADH in the system.

[0077] First, prepare NADH solutions with different concentrations, then measure their UV absorption at 340 nm, and plot the standard curve of NADH using the absorption peak intensity of NADH aqueous solution at 340 nm as the abscissa and the corresponding concentration as the ordinate, as shown in Figure 8 The data points have a good linear relationship, and the linear equation is: y = 0.22132x - 0.00478. By measuring the UV-visible absorption intensity at 340 nm in different reaction systems, the concentration of NADH in the system can be calculated according to this relationship, and the conversion rate of NADH can be further calculated.

[0078] Example 6

[0079] The following tests were performed at an experimental temperature of 25°C using a UV- visible spectrophotometer, model UV-1700PharmaSpec, using the materials obtained in the above examples as examples.

[0080] The absorption of the bis-porphyrin-based organic semiconductor photocatalyst in the visible region was measured by diffuse reflectance UV-visible spectrophotometry. Specifically, ultrafine barium sulfate was used as a reference, the sample was pressed onto the barium sulfate sheet and then measured, and the measurement range was 200-800 nm.

[0081] The obtained UV diffuse reflectance spectrum was appropriately converted to obtain its energy band structure relationship curve, as shown in Figure 3As shown, through fitting, the band gap is obtained to be 1.71 eV, indicating that the bi-porphyrin-based organic semiconductor photocatalyst prepared in the embodiment of the present invention has excellent light absorption ability under visible light, which is undoubtedly very beneficial for improving its weak light sensitivity.

[0082] Example 7

[0083] The following tests were performed using an electrochemical analyzer, model: CHI 1660E, at an experimental temperature of 25° C., and the materials obtained in the above embodiment were used as an example for illustration.

[0084] The sample was fixed on ITO conductive glass to make an electrode. Usually, 1 mg of sample was dispersed in 200 μL of aqueous solution and ultrasonicated for 10 minutes. Then, the solution was dropped on a 1×1 cm 2 On ITO glass and dried at 50 ° C overnight. Then, 0.1% Nafi on was dropped on the conductive glass deposited with the sample and allowed to dry naturally. All photoelectrochemical measurements were carried out in a three-electrode system, in which a saturated calomel electrode was used as a reference electrode, a platinum sheet was used as a counter electrode, and the sample was used as a working electrode. A xenon lamp (filter > 400nm) was used as the light source, and a CHI 1660E electrochemical analyzer was used for detection, and the sample was subjected to Mott-Schottky curve, photocurrent curve and electrochemical impedance spectroscopy using a three-electrode system. The electrolyte solution was 1M sodium sulfate solution. The parameter setting of the Mott-Schottky curve diagram centered on the open circuit voltage for the Mott-Schottky test set the starting potential and the ending potential in the range of -1.5-1.5V, the amplitude was set to 0.01V, and the frequency was 1500 and 2000.

[0085] The Mott-Schottky curve of the bi-porphyrin-based organic semiconductor prepared in the embodiment of the present invention is as follows: Figure 4 As shown, the slope is positive, indicating that the sample is an n-type semiconductor with a flat band potential of -0.98V. Based on the relationship between the conduction band and the flat band potential of an n-type semiconductor, it is inferred that its conduction band potential is about -1.28V, while the redox potential of NADH is -0.33V, which means that there is a larger potential difference between the conduction band of the photocatalyst and the acceptor, which can accumulate more energy for electron transfer to the acceptor, thereby showing higher catalytic activity. In addition, based on the band gap width and the conduction band potential, the valence band potential of the photocatalyst can be calculated, thereby giving the band structure of the biporphyrin-based organic semiconductor photocatalyst provided in the embodiment of the present invention, as shown in FIG. Figure 5 shown.

[0086] The photocurrent curve of the biporphyrin-based organic semiconductor prepared in the embodiment of the present invention is as follows: Figure 6 As shown in the figure, compared with the double porphyrin assembly without platinum nanoparticles, the photocurrent intensity increased by nearly 2 times, indicating that the introduction of platinum nanoparticles can effectively promote the conversion of light energy into current. The electrochemical impedance spectroscopy of the sample (Figure 7 ) shows that after the introduction of platinum nanoparticles, the electrochemical impedance value is reduced from 60.4 ohms to 36.8 ohms, indicating that the charge transfer resistance is reduced, which may be related to the promotion of charge separation / transmission after the introduction of platinum nanoparticles.

[0087] Example 8

[0088] The effects of the double porphyrin-based organic semiconductor photocatalyst provided by the embodiment of the present application and the double porphyrin organic semiconductor without the introduction of platinum nanoparticles and the single porphyrin aggregate material photocatalysis are compared, and the specific experimental method is as follows:

[0089] The photocatalyst, NAD + , and the electron donor triethanolamine are mixed in a certain proportion and placed under indoor light (<1000 lux). Samples are taken at intervals, and the supernatant is tested on the ultraviolet-visible spectrum after centrifugation. The concentration of NADH is determined by the ultraviolet absorption at 340 nm during the reaction and the standard working curve of concentration-absorbance.

[0090] Figure 9 The relationship curves between the product NADH and the reaction time when the double porphyrin-based organic semiconductor photocatalyst provided by the embodiment 1 of the present application and the single porphyrin aggregate are used as catalysts are given. As can be seen from the figure, the double porphyrin-based organic semiconductor provided by the embodiment of the present application has excellent weak light sensitivity and exhibits excellent catalytic activity under ordinary indoor light (<1000 lux). The conversion rate of NADH is more than 75%, which is much higher than that of the single porphyrin aggregate and the double porphyrin organic semiconductor without the introduction of platinum nanoparticles, further proving the synergistic effect between the porphyrin organic semiconductor and the platinum nanoparticles, and further promoting the industrialization process of the photoenzyme coupled catalysis.

Claims

1. A method for preparing a bisporphyrin-based organic semiconductor photocatalyst, characterized in that: The following steps are involved: Weigh a certain amount of porphyrin A, add it to pure water, adjust the pH value to 1-3 to dissolve it, and let it stand to assemble, to obtain porphyrin self-assembly solution A; Weigh a certain amount of porphyrin B, add it into pure water, adjust the pH value to 4-6 to dissolve it, and obtain porphyrin solution B; Wherein, porphyrin A and porphyrin B are one of tetraaminophenylporphyrin, tetracarboxyphenylporphyrin, tetraphenylsulfonate porphyrin and tetrahydroxyphenylporphyrin; The freshly prepared porphyrin solution B is gradually added dropwise to the porphyrin self-assembly solution A under stirring, and then stirred evenly and allowed to stand for assembly to obtain a bi-porphyrin assembly solution; Weigh a certain amount of potassium tetrachloroplatinate and dissolve it in water to prepare a solution of a certain concentration to obtain a potassium tetrachloroplatinate solution, which is then allowed to stand for 24 hours before use; A certain amount of bisporphyrin assembly solution is measured, a certain amount of potassium tetrachloroplatinate solution and an electron-donating reagent are added, and the solution is diluted with water to a certain volume. The solution is irradiated with light for a certain time to obtain a gray-green solution. The solution is centrifuged, washed with water, and dried to obtain a bisporphyrin-based organic semiconductor photocatalyst.

2. The method according to claim 1, characterized in that The concentration of porphyrin A in the porphyrin self-assembly solution A is 50-200 μmol / L, and the concentration of porphyrin B in the porphyrin solution B is 10-50 μmol / L.

3. The method according to claim 1, characterized in that The mixing molar ratio of the porphyrin solution B to the porphyrin self-assembly solution A is 0.5-3.

4. The method according to claim 1, characterized in that The concentration of potassium tetrachloroplatinate in the potassium tetrachloroplatinate solution is 1-5 mmol / L.

5. The method according to claim 1, characterized in that: The electron-donating reagent is one of triethanolamine, ascorbic acid, glucose, and disodium edetate, and its concentration is 0.1-0.6 mol / L.

6. A bisporphyrin-based organic semiconductor photocatalyst prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the bisporphyrin-based organic semiconductor photocatalyst according to claim 6 in photocatalytic NADH synthesis.

8. The use according to claim 7, characterized in that There is no need for external electron mediators or special light-emitting equipment. The conversion rate of NADH is above 75% after one hour of reaction under weak light of less than 1000 lux.

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