Preparation methods and applications of self-photosensitive organic molecular catalysts

Abstract

This invention relates to the field of catalyst technology, and particularly to a method for preparing and applying a self-photosensitive organic molecular catalyst. The method for preparing the self-photosensitive organic molecular catalyst includes the following steps: deprotonating tetrathione with a non-nucleophilic strong base to obtain deprotonated tetrathione; subjecting the deprotonated tetrathione to a nucleophilic substitution reaction to obtain a monotin-substituted tetrathione; subjecting the monotin-substituted tetrathione to a Stille coupling reaction with 5-bromo-isophthalaldehyde to obtain a tetrathione derivative containing multiple aldehyde groups; and reacting the tetrathione derivative containing multiple aldehyde groups with a polyamine via a Schiff base reaction to obtain the self-photosensitive organic molecular catalyst. The self-photosensitive organic molecular catalyst of this invention achieves a synergistic reaction of CO2 reduction and organic molecule oxidation without the need for additional photosensitizers and sacrificial agents.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a method for preparing and applying a self-photosensitive organic molecular catalyst. Background Technology

[0002] The excessive consumption of fossil fuels has triggered a global energy shortage and environmental crisis. The large amounts of CO2 released from their combustion continue to disrupt the Earth's carbon cycle balance, which is a core factor contributing to the exacerbation of the greenhouse effect.

[0003] To alleviate the current situation of fossil fuel depletion and worsening environmental problems, the development of clean and sustainable energy and efficient environmental governance technologies is urgently needed.

[0004] Solar energy is considered an abundant, widely distributed, safe, clean, and infinitely renewable energy source that can meet human energy needs. Utilizing photocatalysis to convert the Earth's abundant and renewable solar energy into chemical energy is an ideal way to solve environmental problems. Photocatalysis reduces CO2 into high-value-added chemicals and is one of the most promising technologies in sustainable carbon cycling. Molecular catalysts have attracted much attention from researchers due to their high atom utilization, well-defined and tunable structure, and easily elucidated catalytic mechanisms.

[0005] However, the photocatalytic reduction of CO2 by molecular catalysts requires the separate addition of photosensitizers (such as noble metal Ru and Ir complexes) and electron sacrificial agents (such as TEA and BIH), resulting in complex system composition, high cost, and the additional components are prone to triggering side reactions and reducing product selectivity. At the same time, the photosensitizer and catalyst are independent dispersed phases, resulting in insufficient intermolecular contact, low electron transfer efficiency, and rapid recombination of photogenerated carriers, which restricts the improvement of catalytic performance.

[0006] Therefore, it is necessary to seek a new catalyst that meets the requirements of photosensitivity. Summary of the Invention

[0007] To address at least one of the aforementioned technical problems, this invention provides a method for preparing and applying a self-photosensitive organic molecular catalyst, which achieves a synergistic reaction of CO2 reduction and organic saturated alcohol molecule oxidation without the need for additional photosensitizers and sacrificial agents.

[0008] In one aspect, the present invention provides a method for preparing a self-photosensitive organic molecular catalyst, comprising: deprotonating tetrathione with a non-nucleophilic strong base to obtain deprotonated tetrathione; subjecting the deprotonated tetrathione to a nucleophilic substitution reaction to obtain a monotin-substituted tetrathione; subjecting the monotin-substituted tetrathione to a Stille coupling reaction with 5-bromo-isophthalaldehyde to obtain a tetrathione derivative containing multiple aldehyde groups; and subjecting the tetrathione derivative containing multiple aldehyde groups to a Schiff base reaction with a polyamine to obtain a self-photosensitive organic molecular catalyst.

[0009] In some embodiments of the present invention, the non-nucleophilic strong base is lithium diisopropylamino.

[0010] In some embodiments of the present invention, the deprotonation reaction is carried out at a temperature of -83 to -70°C for a time of 0.5 to 3 hours.

[0011] In some embodiments of the present invention, the electrophilic reagent in the nucleophilic substitution reaction is a trialkyltin halide.

[0012] In some embodiments of the present invention, the nucleophilic substitution reaction is carried out at a temperature of 20-30°C for a time of 7-22 hours.

[0013] In some embodiments of the present invention, the Stille coupling reaction is carried out at a temperature of 110-130°C for a time of 20-28 hours.

[0014] In some embodiments of the present invention, the polyamine is tris(2-aminoethyl)amine.

[0015] In some embodiments of the present invention, the Schiff base reaction is carried out at a temperature of 20-30°C for a time of 19-28 hours.

[0016] In some embodiments of the present invention, the structural formula of the self-photosensitive organic molecular catalyst is shown in formula (I): Formula (I) In formula (I), the imine N is the catalytic active center for the reduction reaction, and the tetrathiofulvalene group is the catalytic active center for the oxidation reaction.

[0017] In another aspect, the present invention provides an application of the self-photosensitive organic molecular catalyst obtained by the above preparation method in the synergistic reaction of CO2 reduction and saturated alcohol oxidation.

[0018] The technical solution provided by this invention has the following advantages: The self-photosensitive organic molecular catalyst of this invention achieves the synergistic reaction of CO2 reduction and CH3OH oxidation without the need for additional photosensitizers and sacrificial agents, thus simplifying the reaction system.

[0019] Specifically, using CH3OH / H2O as the reaction medium, CO2 reduction occurs at the imine N, the catalytic active center of the reduction reaction in the photosensitive organic molecular catalyst; and CH3OH oxidation occurs at the tetrathiofulvalene group, the catalytic active center of the oxidation reaction. The oxidation of CH3OH provides a continuous electron supply for CO2 reduction, solving the problem of the traditional CO2 reduction system relying on sacrificial agents, and at the same time realizing the oxidation of CH3OH to HCOOH.

[0020] Furthermore, the self-photosensitive organic molecular catalyst of this invention uses CH3OH / H2O as the reaction medium, which can reduce costs while minimizing environmental impact and improving the practicality of the technology. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0023] Figure 1 The 1H NMR spectrum of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention; Figure 2 Comparison of in-situ X-ray photoelectron spectroscopy (XPS) spectra of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention under different conditions; Figure 3 Fourier transform infrared spectrum of L-TTF, a self-photosensitive organic molecular catalyst prepared in Example 1 of this invention; Figure 4 The UV-Vis absorption spectrum of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention; Figure 5 This is a schematic diagram showing the changes in photoreduction of CO2 and oxidation of CH3OH products over time in the catalytic evaluation of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0026] According to an embodiment of the present invention, a self-photosensitive organic molecular catalyst is provided, the structural formula of which is shown in formula (I): Formula (I) In formula (I), the imine N is the catalytic active center for the CO2 reduction reaction, and the tetrathiofulvalene group is the catalytic active center for the saturated alcohol oxidation reaction.

[0027] According to an embodiment of the present invention, a method for preparing a self-photosensitive organic molecular catalyst is provided, characterized by comprising the following steps: (1) Tetrathiofulvalene (TTF) was deprotonated with a non-nucleophilic strong base, lithium diisopropylamino (LDA), to obtain deprotonated tetrathiofulvalene. (2) The deprotonated tetrathionolene was subjected to a nucleophilic substitution reaction with an electrophilic reagent, trialkyltin halide (e.g., Bu3SnCl), to obtain a monotin-substituted tetrathionolene. (3) Tetrathiofulvalene monotin-substituted derivatives were subjected to Stille coupling reaction with 5-bromo-isophthalaldehyde to obtain tetrathiofulvalene derivatives containing multiple aldehyde groups. (4) A tetrathiofulvalene derivative containing multiple aldehyde groups is reacted with tri(2-aminoethyl)amine in a polyamine to obtain a self-photosensitive organic molecule catalyst.

[0028] In some embodiments of the present invention, in step (1), the temperature of the deprotonation reaction is -83 to -70°C (for example, it can be -82°C, -79°C, -76°C, -74°C, -71°C), and the time is 0.5 to 3 hours (for example, it can be 0.9 hours, 1.3 hours, 1.9 hours, 2.4 hours, 2.9 hours, etc.).

[0029] In some embodiments of the present invention, in step (2), the temperature of the nucleophilic substitution reaction is 20~30°C (e.g., it can be 21°C, 23°C, 26°C, 27°C, 29°C, etc.), and the time is 7~22h (e.g., it can be 9h, 13h, 16h, 19h, 21h, etc.).

[0030] In some embodiments of the present invention, in step (2), the electrophilic reagent in the nucleophilic substitution reaction is Bu3SnCl, and the deprotonated tetrathiofulvalene undergoes a nucleophilic substitution reaction with Bu3SnCl to generate mono(tributyltin)tetrathiofulvalene.

[0031] In some embodiments of the present invention, in step (3), under the action of Pd(PPh3)4 catalyst, the tetrathiofulvalene monotin-substituted product reacts with 5-bromo-isophthalaldehyde at 110~130℃ (e.g., 112℃, 118℃, 121℃, 126℃, 129℃, etc.) for 20~28h (e.g., 21h, 23h, 24h, 26h, 27h, etc.) to obtain a tetrathiofulvalene derivative containing multiple aldehyde groups.

[0032] In some embodiments of the present invention, in step (3), under the action of Pd(PPh3)4 catalyst, mono(tributyltin)tetrathiofulvalene reacts with 5-bromo-m-phthalaldehyde to obtain the product 5-(tetrathiofulvalene-4-yl)m-phthalaldehyde.

[0033] In some embodiments of the present invention, the reactions that occur in steps (1) to (3) are as shown in Equation 1. Equation 1 In some embodiments of the present invention, in step (4), the tetrathiofulvalene derivative 5-(tetrathiofulvalene-4-yl)isophthalaldehyde containing multiple aldehyde groups obtained in step (3) undergoes a Schiff base reaction with tris(2-aminoethyl)amine to obtain the self-photosensitive organic molecular catalyst shown in formula (I); the specific reaction equation is shown in formula 2. Equation 2 The technical solution of this application will be further explained and described in more detail below through specific embodiments.

[0034] Example 1 (1) Tetrathiofulvalene TTF (1.98 g, 9.7 mmol) was dissolved in anhydrous tetrahydrofuran (THF) (120 mL) with constant stirring. The resulting solution was cooled to -83°C in a liquid nitrogen bath. Then, lithium diisopropylaminolithium (LDA) (6.5 mL, 11.7 mmol) was added dropwise over 15 minutes, followed by stirring at -83°C for 1 hour.

[0035] (2) Following step (1), tributyltin chloride (Bu3SnCl) (4.8 mL, 17.7 mmol) was slowly added dropwise to the reaction solution obtained in step (1). After stirring for 1 hour, the reaction mixture was slowly heated to room temperature overnight. After the reaction was complete, the reaction mixture was diluted with water (50 mL) and extracted with dichloromethane (50 mL). The lower organic phase was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation under reduced pressure to obtain an orange oily crude product. The product was purified by silica gel column chromatography using petroleum ether as the eluent to obtain a yellow oily compound.

[0036] (3) The yellow oily compound obtained in step (2) was dissolved in 160 mL of toluene, and then Pd(PPh3)4 (0.80 g, 0.69 mmol) and 5-bromo-isophthalaldehyde (1.46 g, 6.86 mmol) were added. The reaction mixture was refluxed at 120 °C for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, then diluted with water (50 mL) and extracted with dichloromethane (100 mL). The resulting organic phase was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation under reduced pressure to obtain a crude product of reddish-black solid. The product was purified by silica gel column chromatography with dichloromethane:petroleum ether (1.5:1) as the eluent to obtain a red solid powder 5-(tetrathiofulvalen-4-yl)-isophthalaldehyde (yield 30%).

[0037] (4) First, under an argon atmosphere, tris(2-aminoethyl)amine (292 mg, 2 mmol) was dissolved in anhydrous methanol (50 mL), and slowly added over half an hour to a solution of dichloromethane (50 mL) containing 5-(tetrathiofulvalen-4-yl)-isophthalaldehyde (840 mg, 2.5 mmol) obtained in step (4). After stirring the mixed solution at room temperature for 24 hours, the solvent was removed by rotary evaporation under reduced pressure to obtain an orange-yellow precipitate. The precipitate was washed three times with anhydrous methanol and dried under vacuum at 50 °C for 12 hours. The self-photosensitive organic molecular catalyst L-TTF (yield 76%) was obtained as an orange-yellow solid powder.

[0038] (5) The orange-yellow solid powder L-TTF obtained in step (4) was subjected to 1H NMR spectroscopy, in-situ X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, and ultraviolet-visible absorption spectroscopy. The specific test results are as follows: Figures 1-4 As shown.

[0039] (6) The self-photosensitive organic molecular catalyst L-TTF, the orange-yellow solid powder obtained in step (4), was reacted in the reaction medium of CH3OH / H2O, and the catalyst was evaluated as follows: In a 17.5 mL quartz tube, with 5 mL of CH3OH / H2O (v / v = 4:1) mixed solvent as the system solution, a light intensity of 300 mW / cm² was used. -2 A high-intensity xenon lamp was used as the irradiation source, and the temperature of the space containing the quartz tube was maintained at around 25°C for 10 hours during the catalytic process. Before the catalytic reaction began, high-purity CO2 gas was introduced into the quartz tube for 30 minutes to purge the air from the reaction tube. After the reaction, the products were analyzed by GC and IC to detect both gaseous and liquid phase products.

[0040] The schematic diagram of the changes in photoreduction CO2 and CH3OH oxidation products of L-TTF catalyst over time is shown below. Figure 5 As shown.

[0041] Results analysis: (1) Figure 1 The above is the 1H NMR spectrum of the self-photosensitive organic molecular catalyst L-TTF obtained in step (4) of Example 1. Figure 1 The specific information for the proton NMR spectrum is as follows: 1 H NMR (400 MHz, CDCl3): δ(ppm):8.20 (s, 6H),7.55 (s, 6H), 6.76 (s, 3H), 6.33 (s, 6H), 5.28 (s, 3H), 3.57 (d, J = 183.9Hz, 12H), 2.85 (d, J = 78.5 Hz, 12H). according to Figure 1 The nuclear magnetic resonance hydrogen spectrum can prove that the self-photosensitive organic molecular catalyst L-TTF was synthesized.

[0042] (2) Figure 2 The image shows a comparison of the in-situ X-ray photoelectron spectroscopy (XPS) characterization of the self-photosensitive organic molecular catalyst L-TTF obtained in step (4) of Example 1 under different conditions. Figure 2 As shown, under dark conditions, the binding energy of imine N in L-TTF exhibits a characteristic peak at 398.46 eV, while after illumination treatment, a slight negative shift (0.13 eV) in the binding energy of imine N is observed. Furthermore, the binding energies of S 2p3 / 2 and S 2p1 / 2 are 163.75 eV and 164.8 eV respectively under dark conditions, and both show a significant positive shift (0.12 eV) under illumination. This phenomenon indicates an increase in electron density on imine N and a decrease in electron density on the tetrathiofulvalene group. From the shift patterns of these characteristic binding energies, it can be concluded that in the photocatalytic reaction process involving L-TTF, the electron transfer direction is from the TTF group to imine N. Based on this electron transfer mechanism, it can be concluded that the CO2 reduction reaction occurs on imine N, while the CH3OH oxidation reaction occurs on the TTF unit.

[0043] (3) Figure 3 The Fourier transform infrared spectrum of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention is shown. Figure 3 As shown, the Fourier transform infrared spectroscopy results indicate that L-TTF is at 1636 cm⁻¹. -1 The presence of a characteristic absorption peak at C=N further confirms the successful preparation of the photosensitive organic molecular catalyst L-TTF.

[0044] (4) Figure 4 The image shows the UV-Vis absorption spectrum of the self-photosensitive organic molecular catalyst L-TTF prepared in Example 1 of this invention. The specific detection conditions were as follows: L-TTF was tested in methanol solution using a UV-3600 UV-Vis spectrophotometer, with a test range of 250–650 nm. Figure 4 The experimental results show that the synthesized L-TTF has good absorption in the visible light range, which provides a basis for the photocatalytic reduction of carbon dioxide.

[0045] (5) Figure 5 This diagram illustrates the changes in photoreduction of CO2 and the oxidation of CH3OH products over time in the catalytic evaluation of the L-TTF catalyst prepared in Example 1 of this invention. Figure 5 As shown, when the catalyst L-TTF concentration was 0.5 μM, the yield of photocatalytic CO2 reduction to HCOOH was 11.43 µmol after 10 hours, with a TON of 4572. Meanwhile, no gaseous products were detected by gas chromatography, and the yield of HCOOH essentially ceased to increase after 10 hours.

[0046] Comparative Example 1 First, under an argon atmosphere, tris(2-aminoethyl)amine (584 mg, 4 mmol) was dissolved in anhydrous methanol (50 mL), and then slowly added over half an hour to an anhydrous methanol solution (50 mL) containing isophthalaldehyde (670 mg, 5 mmol). After stirring the mixture at room temperature for 24 hours, the solvent was removed by rotary evaporation under reduced pressure to obtain a white precipitate. The precipitate was washed three times with anhydrous methanol and dried under vacuum at 50 °C for 12 hours. A white solid powder catalyst was obtained; the specific reaction formula is shown in Equation 3. Equation 3 (2) The white solid powder catalyst obtained in step (1) was evaluated as follows: In a 17.5 mL quartz tube, in a 5 mL CH3OH / H2O (v / v = 4:1) mixed solvent system solution, a light intensity of 300 mW / cm² was used. -2 A high-intensity xenon lamp was used as the irradiation source, and the temperature of the space containing the quartz tube was maintained at around 25°C for 10 hours during the catalytic process. Before the catalytic reaction began, high-purity CO2 gas was introduced into the quartz tube for 30 minutes to purge the air from the reaction tube. After the reaction, the products were analyzed by IC to detect the liquid phase products.

[0047] Analysis of test results: The generated liquid products were analyzed and detected using IC. No HCOOH was detected using the white solid powder catalyst.

[0048] In summary, the self-photosensitive organic molecule catalyst of the present invention achieves the synergistic reaction of CO2 reduction and organic molecule oxidation without the need for additional photosensitizers and sacrificial agents; it solves the problems of complex photocatalytic CO2 reduction systems and insufficient photocatalytic performance of catalysts.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0050] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a self-photosensitive organic molecular catalyst, characterized in that, include: Tetrathionolene was deprotonated by reacting it with a nonnucleophilic strong base to obtain deprotonated tetrathionolene. The deprotonated tetrathionuron was subjected to a nucleophilic substitution reaction to obtain a monotin-substituted tetrathionuronuron. The tetrathiofulvalene monotin-substituted product was subjected to a Stille coupling reaction with 5-bromo-isophthalaldehyde to obtain a tetrathiofulvalene derivative containing multiple aldehyde groups. The tetrathiofulvalene derivative containing multiple aldehyde groups was reacted with a polyamine via a Schiff base reaction to obtain a self-photosensitive organic molecular catalyst.

2. The method for preparing the self-photosensitive organic molecular catalyst according to claim 1, characterized in that, The non-nucleophilic strong base is lithium diisopropylamino.

3. The method for preparing the self-photosensitive organic molecular catalyst according to claim 1 or 2, characterized in that, The deprotonation reaction is carried out at a temperature of -83 to -70°C for a time of 0.5 to 3 hours.

4. The method for preparing the self-photosensitive organic molecular catalyst according to any one of claims 1 to 3, characterized in that, The electrophile in the nucleophilic substitution reaction is a trialkyltin halide.

5. The method for preparing the self-photosensitive organic molecular catalyst according to any one of claims 1 to 4, characterized in that, The nucleophilic substitution reaction is carried out at a temperature of 20-30℃ for 7-22 hours.

6. The method for preparing a self-photosensitive organic molecular catalyst according to any one of claims 1 to 5, characterized in that, The Stille coupling reaction is carried out at a temperature of 110-130°C for 20-28 hours.

7. The method for preparing the self-photosensitive organic molecular catalyst according to any one of claims 1 to 6, characterized in that, The polyamine is tris(2-aminoethyl)amine.

8. The method for preparing a self-photosensitive organic molecular catalyst according to any one of claims 1 to 7, characterized in that, The Schiff base reaction is carried out at a temperature of 20-30°C for 19-28 hours.

9. The self-photosensitive organic molecular catalyst according to any one of claims 1 to 8, characterized in that, The structural formula of the self-photosensitive organic molecular catalyst is shown in formula (I): Formula (I) In formula (I), the imine N is the catalytic active center for the reduction reaction, and the tetrathiofulvalene group is the catalytic active center for the oxidation reaction.

10. The application of a self-photosensitive organic molecular catalyst obtained by the preparation method according to any one of claims 1 to 9 in the synergistic reaction of CO2 reduction and saturated alcohol oxidation.

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