Method for preparing sulfoxide by red light catalytic oxidation of sulfide and catalyst

Abstract

The present application belongs to the technical field of photocatalytic preparation of sulfoxides, and more particularly relates to a method for preparing sulfoxides by red light catalytic oxidation of sulfides and a catalyst. Hydrogen-bonded organic framework composite materials HOFs are used to realize the synthesis of sulfoxides from sulfides under red light irradiation. Organic acid additives and organic solvents are added to the reaction system, and are coordinated with the red light irradiation. The sulfide substrates with different electronic effects and different steric hindances have excellent universality. Therefore, the present application provides a new solution for the selective catalytic oxidation of sulfides to prepare sulfoxides, which is safer, more energy-saving, more green and has higher selectivity, fills the technical blank of HOFs materials in the field of red light catalytic oxidation of sulfides to prepare sulfoxides, and has remarkable creativity and industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic preparation of sulfoxides, and more specifically relates to a method and catalyst for the red photocatalytic oxidation of sulfide to prepare sulfoxides. Background Technology

[0002] Sulfoxides are an important class of organosulfur compounds, widely found in natural products, pharmaceutical active molecules, and fine chemicals. In the pharmaceutical field, omeprazole is used to treat gastric ulcers caused by excessive gastric acid secretion; mesoridazine plays an important role in the treatment of schizophrenia; and armodafinil is used to improve symptoms of narcolepsy and depression. In the pesticide field, sulfoxides also show promising applications. For example, fipronil is effective in controlling aphids, flies, and other pests; ethiprole has excellent killing effects on various chewing pests. Furthermore, sulfoxides can also be used as precursors for chiral ligands and functional materials, and research on their efficient and highly selective synthetic methods has significant academic value and application prospects.

[0003] Traditional sulfoxide synthesis methods primarily rely on the oxidation of sulfides using stoichiometric oxidants (such as hydrogen peroxide, peroxy acids, and high-iodine compounds). However, these methods generally suffer from environmental problems such as harsh reaction conditions, low atom economy, and the generation of large amounts of waste. More importantly, the over-oxidation of sulfides to sulfone byproducts is difficult to control, leading to a decrease in the selectivity of the target product, sulfoxide. Therefore, developing green catalytic strategies for highly selective oxidation under mild conditions, especially room-temperature red light catalysis, has become a research hotspot in this field.

[0004] Although some reported photocatalytic systems have shown excellent performance in the oxidation of sulfides, several problems remain to be solved. First, most photocatalysts rely on ultraviolet or blue light excitation, resulting in high energy consumption and severe photodamage. Red light (>600 nm), which penetrates deeper into tissues and causes less photodamage, has low utilization. Second, homogeneous photosensitizers suffer from difficulties in recovery and metal residues, leading to safety concerns and limiting their application in drug synthesis. While heterogeneous photocatalysts can solve the recovery problem, they often face challenges such as insufficient exposure of active sites and low mass transfer efficiency. Summary of the Invention

[0005] In view of the above-mentioned technical problems, the present invention provides a method and catalyst for the red light-catalyzed oxidation of sulfides to sulfoxides, aiming to use hydrogen-bonded organic framework (HOF) composite materials as photocatalysts, and achieve the goal of highly efficient catalysis and highly selective oxidation of sulfides to sulfoxides under mild conditions in a system of organic solvents and organic acid additives under red light irradiation.

[0006] To achieve the above objectives, the present invention provides a method for preparing sulfoxides by red light photocatalytic oxidation of sulfides, comprising the following steps:

[0007] S1 involves mixing thioether compounds, hydrogen-bonded organic framework photocatalysts, organic solvents, and organic acid additives uniformly at room temperature to form a first reaction mixture;

[0008] S2 is irradiated with red light for a certain period of time in the presence of oxygen-containing gas to selectively oxidize sulfoether compounds to sulfoxide compounds, thereby obtaining a second reaction mixture;

[0009] S3 is separated from the second reaction mixture to obtain sulfoxide.

[0010] Unlike existing technologies, the hydrogen-bonded organic framework composites (HOFs) used in the above-mentioned technical solution possess unique dynamic reversibility, solution processability, and easily functionalized porous environments. These enable better interaction with thioether compounds and organic acid additives, promoting the generation and mass transfer of reactive oxygen species (such as singlet oxygen¹O₂), thereby achieving highly efficient catalysis under mild conditions. High conversion rates (>90%) from thioethers to sulfoxides can be achieved under red light irradiation (wavelength 620-750 nm). Red light has a long wavelength and low energy, causing minimal photodamage to organic molecules and the catalyst framework, and has stronger penetration, avoiding side reactions that may be caused by high-energy ultraviolet / blue light (such as substrate decomposition and catalyst deactivation). It also reduces energy consumption and operating costs, better meeting the requirements of green chemistry. Adding trace amounts of organic acid additives to the reaction system can, on the one hand, regulate the hydrogen bond network and surface charge of the HOFs, enhancing the adsorption and activation of the substrate thioethers and intermediates; on the other hand, the organic acid can act as a proton transfer medium, promoting photogenerated electron-hole separation and inhibiting excessive oxidation. The synergistic effect of organic solvents, organic acid additives, and red light irradiation enables this system to exhibit excellent universality for sulfide substrates with varying electronic effects and steric hindrances. Therefore, this invention provides a safer, more energy-efficient, greener, and more selective novel solution for the selective catalytic oxidation of sulfides to sulfoxides, filling the technological gap in the field of red light-catalyzed sulfide oxidation of HOF materials and possessing significant innovative and industrial application value.

[0011] In some embodiments, the hydrogen-bonded organic framework photocatalyst is a porphyrin-based hydrogen-bonded organic framework material, which is formed by the self-assembly of porphyrin-based organic structural units through hydrogen bonding, and the porphyrin-based organic structural units comprise at least one of the following formulas I to VI:

[0012]

[0013] Formula I Formula II Formula III

[0014]

[0015] Formula IV, Formula V, Formula VI.

[0016] This design breaks with the existing practice of using porphyrin-based materials primarily in MOF or COF frameworks, and is the first to be used in HOF frameworks. Furthermore, porphyrin-based HOF composites have not yet been reported for the photocatalytic oxidation of sulfides. The porphyrin group itself is a highly efficient photosensitizer, capable of absorbing red light and efficiently generating singlet oxygen (…). 1 (O2); However, when it self-assembles into HOFs via hydrogen bonds, the pore structure provides substrate enrichment and mass transfer channels, which is completely different from the homogeneous photosensitization of porphyrin molecules. Hydrogen bond networks are generally considered to be a weak structure, making it difficult to stably support porphyrins and maintain their structure in liquid-phase reactions. However, this invention has found that in organic acid additive / ethanol organic solvent systems, porphyrin-based HOFs are not only stable, but their red photocatalytic efficiency is also much higher than that of the corresponding porphyrin monomers or porphyrin-based MOFs / COFs.

[0017] Preferably, the porphyrin-based organic structural unit contains a metal ion R at its center, wherein the metal ion R is selected from Mn. 2 + Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Mg 2+ At least one of the following. In the prior art, metalloporphyrins are often used as homogeneous catalysts or embedded in metal-organic frameworks (MOFs) or covalent organic frameworks (COFs). However, in hydrogen-bonded organic frameworks (HOFs), metalloporphyrins not only retain their coordination catalytic ability but also generate electronic coupling with other parts of the framework through hydrogen bonds. After embedding metal ions, the photogenerated electron-hole separation efficiency of HOFs under red light irradiation is significantly improved (e.g., Co). 2+ Ni 2+ It can act as an electron relay station, and the metal ions and organic acid additives form a proton-electron synergistic transfer pathway. The metalloporphyrin HOFs of this invention mainly produce more reactive singlet oxygen under red light, with a selectivity exceeding 99%. This long-range synergistic effect between the metal coordination microenvironment and the hydrogen bond network is unpredictable in existing technologies.

[0018] In this invention, the wavelength of the LED red light is any single wavelength within the range of 620-750 nm, for example, selected from 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm, 710 nm, 720 nm, 730 nm, 740 nm, and 750 nm. The equation for the catalytic oxidation of sulfoxides to sulfoxides under the action of hydrogen-bonded organic framework composite (HOF) catalysts, and under the synergistic effect of red light wavelength conditions, organic solvents, and organic acid additives, is shown below:

[0019] .

[0020] Preferably, the molar ratio of the hydrogen-bonded organic framework photocatalyst to the thioether compound is 0.05~0.2:1. For example, 0.05:1, 0.1:1, 0.15:1, and 0.2:1 are preferred. The dynamic nature of the hydrogen bonds in HOFs allows the catalytic center (porphyrin) to be "flexibly" exposed during the reaction, resulting in high substrate accessibility and achieving high efficiency with low dosage. The weak structure actually leads to high activity, requiring only a small amount of catalyst to achieve high conversion rates.

[0021] Preferably, the thioether compound is selected from one or more of aromatic thioethers, aliphatic thioethers, heterocyclic thioethers, and mustard gas simulants. Specifically, the thioether compound includes, but is not limited to: 1(R1:CH3(CH2)2,R2:(CH2)2CH3), 2(R1:Ph,R2:S-Ph), 3(R1:C4H3OCH2,R2:CH2C4H3O), 4(R1:CH2Cl,R2:CH3), 5(R1:C4H3OCH2,R2:CH3), 6(R1:Ph,R2:CH3), 7(R1:4-CH3-Ph,R2:CH3), 8(R1:4-OCH3-Ph,R2:CH3), 9(R1:4-F-Ph,R2:CH3), 10(R1:4-Cl-Ph,R2:CH3), 11 (R1:4-Br-Ph,R2:CH3), 12(R1:2-Cl-Ph,R2:CH3), 13(R1:3-Cl-Ph,R2:CH3), 14(R1:2-F-Ph,R2:CH3), 15(R1:Ph,R2:C3H5), 16(R1:Ph,R2:CH2C l), 17(R1:p-CH3-C6H4,R2:SC6H4-CH3-p), 18(R1:Ph,R2:CH2CH3), 19(R1:C5H4N,R2:CH3), 20(R1:2-OHC6H4,R2:CH3), 21(R1:2-CH3-C4H2O,R2: 3-CH3), 22(R1:Ph,R2:CF3), 23(R1:4-Cl-C6H4,R2:CH2Cl), 24(R1:2-NH2-C6H4,R2:CH3), 25(R1:2-Cl-C4H4N2,R2:4CH3), 26(R1:Ph,R2:CH2CO OH), 27(R1:C6H4-B(OH)2,R2:4-CH3), 28(R1:2-CH3,R2:C6H4-B(OH)2), 29(R1:Ph,R2:CH2COOCH2CH3), 30(R1:Ph,R2:(CH2)2OH), 31(R1:Ph,R2: CH2OCH3), 32(R1:3-Cl-Ph,R2:CH3), 33(R1:3-Br-Ph,R2:CH3), 34(R1:Cl(CH2)2,R2:CH2CH3), 35(R1:4-CH3,R2:-C6H4-CHO), 36(R1:4-NO2-C6 H4,R2:CH3), 37(R1:4-Br-C6H4,R2:CH(CH3)2), 38(R1:3-Br-5-Cl-C6H3.R2:CH3), 39(R1:2-CH3O-C6H4.R2:CH3), (R1:Ph2CH,R2:CH2C(O)NH2).Catalytic oxidation of mustard gas simulants often relies on high temperatures or strong oxidants because the steric hindrance and electronic effects of their alkyl chains are unfavorable for photoactivation. In this invention, the pore environment of HOFs and the synergistic effect of organic acids significantly reduce the oxidation activation energy of mustard gas simulants, making room temperature and air oxidation possible. High selectivity and high conversion rates can also be achieved under room temperature, red light, and no added oxidant conditions.

[0022] Preferably, the hydrogen-bonded organic framework photocatalyst participates in the reaction in the form of a composite film, aerogel, or hydrogel HOFs composite material. The matrix of the HOFs composite material is selected from one or more of polyvinyl alcohol, polyethersulfone, polyamide, polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate, lignin, or cellulose. The mass percentage of the hydrogen-bonded organic framework material in the HOFs composite material is any percentage within the range of 1% to 10%, for example, selected from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. After loading HOFs onto a polymer matrix (such as polyamide, polyethersulfone, etc.), due to the light scattering effect of the matrix, the multiple reflections of red light within the composite material prolong the optical path, effectively improving light utilization. Simultaneously, the HOFs composite morphology improves the cyclic stability of the catalyst (no decay after 5 cycles), and due to the porosity of the matrix, oxygen diffuses more easily to the catalytic sites.

[0023] Preferably, the organic solvent is ethanol, and the organic acid additive is selected from aliphatic carboxylic acids with 1 to 6 carbon atoms or their halogenated derivatives. More preferably, the halogenated derivative is an aliphatic carboxylic acid in which one or more carbon atoms are replaced by one or more halogen atoms, wherein the halogen atom can be selected from fluorine, chlorine, or bromine atoms. This prolongs the lifetime of singlet oxygen and improves the conversion rate of the target product sulfoxide. The organic acid molecules bind to the pyridine / carboxyl sites of HOFs through hydrogen bonds, forming a "proton relay" network, which accelerates the consumption of photogenerated holes, thereby inhibiting the peroxidation of sulfides to sulfones.

[0024] More preferably, the organic acid additive is formic acid, acetic acid, trifluoroacetic acid, or trichloroacetic acid. The volume ratio of the organic solvent to the organic acid additive is any ratio in the range of 1:0.01 to 0.1, for example selected from 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, and 1:0.1.

[0025] Secondly, the inventors provide a hydrogen-bonded organic framework (HOF) photocatalyst for the red-light catalytic oxidation of sulfides to sulfoxides. This HOF is a crystalline porous material formed by the self-assembly of porphyrin-based organic structural units through hydrogen bonding. The band structure of the HOF photocatalyst is responsive to red light in the wavelength range of 620 nm to 750 nm and generates reactive oxygen species. While HOFs are primarily disclosed in fields such as gas adsorption and proton conduction, their application in the photocatalytic oxidation of sulfides has not been reported. This invention is the first to utilize HOFs as a functional catalytic product for the red-light catalytic oxidation of sulfides to sulfoxides.

[0026] Unlike existing technologies, the hydrogen-bonded organic framework (HOF) photocatalyst provided by this invention can generate active oxygen in situ and selectively oxidize sulfides under mild conditions of room temperature and red light irradiation, without requiring any precious metals or additional photosensitizers. This integrated "self-photosensitizing-self-catalyzing" product far surpasses the efficiency of traditional physically mixed catalysts. Even more unexpectedly, this HOF product can be recovered through simple filtration after the reaction, and its hydrogen bond network possesses self-healing capabilities under acidic conditions, thus exhibiting superior cycle stability compared to most covalent frameworks.

[0027] Preferably, a metal ion R is embedded at the center of the porphyrin-based organic structural unit, wherein the metal ion R is selected from Mn. 2+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Mg 2+ One or more of these. The hydrogen-bonded organic framework photocatalyst is in the form of a composite film, aerogel, or hydrogel, wherein the hydrogen-bonded organic framework material accounts for 1% to 10% of the mass of the hydrogen-bonded organic framework photocatalyst.

[0028] The above description of the invention is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical solution of the present invention and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of the present invention easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of the present invention. Attached Figure Description

[0029] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of the present invention and other related contents, and should not be considered as limitations on the present invention.

[0030] In the accompanying drawings of the instruction manual:

[0031] Figure 1This is the UV-Vis diffuse reflectance (DRS) spectrum of PFC-943 obtained in Example 1;

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the PFC-943 composite membrane;

[0033] Figure 3 These are test results of the cycle performance of PFC-943 catalyst powder and PFC-943 composite membrane.

[0034] Figure 4 The 1H NMR spectrum of the product 2-hydroxybenzene sulfoxide synthesized by the method described in Example 2;

[0035] Figure 5 The 1H NMR spectrum of the product 2-benzenesulfinylethanol synthesized by the method described in Example 3

[0036] Figure 6 The proton NMR spectrum of the product 2-chloroethyl ethyl sulfoxide synthesized by the method described in Example 4;

[0037] Figure 7 The 1H NMR spectrum of the product 2-(diphenylmethyl sulfoxide)acetamide synthesized by the method described in Example 5;

[0038] Figure 8 The 1H NMR spectrum of the product 3-methylsulfinylthiophene synthesized by the method described in Example 6;

[0039] Figure 9 The proton NMR spectrum of the product 3-methoxyphenylmethyl sulfoxide synthesized by the method described in Example 7;

[0040] Figure 10 The 1H NMR spectrum of the product 4-methylsulfinylbenzaldehyde synthesized by the method described in Example 8;

[0041] Figure 11 The 1H NMR spectrum of 2-methylsulfinylpyridine, the product synthesized by the method described in Example 9. Detailed Implementation

[0042] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this invention in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this invention and are therefore intended only as examples, not as limiting the scope of protection of this invention.

[0043] In this invention, unless otherwise specified, the experimental methods, detection means, and condition parameters involved are all conventional techniques in the art. Those skilled in the art can reasonably select and use them based on the disclosed content and their general technical knowledge, without any inventive effort. The numerical ranges or preferred ranges in this invention are merely exemplary ranges given for ease of implementation and are not intended to limit the scope of protection of this invention. Any equivalent substitutions, modifications, or combinations of the technical solutions of this invention based on the concept of this invention shall fall within the scope of protection of this invention.

[0044] In this invention, unless otherwise specified, the percentage concentrations used are all mass percentages or volume percentages, as determined by the context; the terms "parts" or "ratios" refer to parts by mass or mass ratios; temperature is in degrees Celsius (°C); and pressure is gauge pressure or absolute pressure, as conventionally understood based on the context.

[0045] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this invention, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0046] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit the invention.

[0047] In this invention, unless otherwise expressly specified or limited, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. The terms "comprising," "including," "having," and any variations thereof are intended to cover non-exclusive inclusion, such as a process, method, article, or apparatus that includes a series of elements, including not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0048] In this invention, terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy, or order relationship between these entities or operations.

[0049] Unless otherwise specified, in this invention, expressions relating to numerical ranges, when using terms such as "greater than," "less than," "exceeding," or "less than," are understood to exclude endpoint values; when using terms such as "above," "below," "within," "at least," or "not exceeding," are understood to include endpoint values. Unless otherwise stated, all numerical ranges herein include endpoint values ​​as well as any subranges and any specific numerical values ​​between endpoint values, and it should be understood that the listed numerical ranges are not exhaustive.

[0050] Similar to the understanding in the Examination Guidelines, in this invention, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments of this invention, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0051] In this invention, the term "room temperature" refers to ambient temperature, typically 15°C to 35°C, preferably 20°C to 30°C, and more preferably 25°C ± 2°C. The term "normal pressure" or "standard atmospheric pressure" refers to one standard atmosphere, i.e., 101.325 kPa, and in actual operation, fluctuations of ±10% due to factors such as altitude are allowed.

[0052] In this invention, unless otherwise specified, all numerical ranges involved in the various technical features include not only the endpoint values ​​and any values ​​between them, but also the more preferred ranges. For example, "reaction time of 1 to 10 hours" includes 1 hour, 2 hours, 3 hours...10 hours, and more preferably 2 to 8 hours, 3 to 6 hours, etc.

[0053] In this invention, the term "certain time" refers to a reaction time sufficient for the sulfide compound to be substantially or completely converted into a sulfoxide compound. This time depends on specific conditions such as reaction scale, catalyst dosage, and light intensity, and can be determined by those skilled in the art through conventional experiments or gas chromatography monitoring. Similarly, "certain proportion" and "certain amount" refer to adjustable parameters sufficient to achieve the objectives of this invention.

[0054] In this invention, "red light" refers to visible light with a wavelength range of 620 nm to 750 nm. Light source types include, but are not limited to, red LED lamps, red lasers, red fluorescent lamps, or filtered xenon lamps. The light intensity is determined by its ability to excite the hydrogen-bonded organic framework photocatalyst, typically 1 mW / cm². 2 ~200 mW / cm 2 Preferably 10 mW / cm 2 ~100mW / cm 2.

[0055] In this invention, the "oxygen-containing gas" includes pure oxygen, air, or a mixture of oxygen and an inert gas (such as nitrogen or argon) in any proportion. Preferably, air or oxygen is used as the oxidant source, eliminating the need for additional chemical oxidants.

[0056] In this invention, unless otherwise stated, all reagents and raw materials used are conventional reagents in the art, which can be purchased commercially or prepared in-house using known synthetic methods. Hydrogen-bonded organic framework (HOF) photocatalysts can be prepared according to the method provided in this invention, or can be obtained by referring to other known HOF synthesis methods in the art, as long as they have red light responsiveness and the structural characteristics defined in this invention.

[0057] In this invention, the organic solvent used can be of analytical grade, chemical grade or chromatographic grade, etc. Anhydrous or aqueous solvents do not affect the basic implementation of this invention, but it is preferred to use chromatographic grade or anhydrous solvents that have been dried to obtain better reaction repeatability.

[0058] In this invention, "optionally" or "optionally" means that the events or situations described below may or may not occur; the expression includes both occurrence and non-occurrence. For example, "optionally add additives" means that they may or may not be added.

[0059] In this invention, "conversion" refers to the ratio of the amount of thioether substrate consumed in the reaction to the amount of initially added thioether substrate, expressed as a percentage. "Selectivity" refers to the ratio of the amount of sulfoxide product generated to the amount of thioether substrate consumed, expressed as a percentage. "Yield" refers to the ratio of the amount of sulfoxide product actually separated to the theoretical maximum amount. Conversion, selectivity, and yield are typically determined by methods such as gas chromatography (GC), high-performance liquid chromatography (HPLC), or nuclear magnetic resonance (NMR).

[0060] In this invention, the gas chromatography (GC) analysis conditions are conventional in the art, such as using a flame ionization detector (FID) and a capillary column, with nitrogen or helium as the carrier gas. The specific temperature program and split ratio can be optimized and adjusted according to the analyte. The nuclear magnetic resonance (NMR) spectra use deuterated chloroform, deuterated dimethyl sulfoxide, or deuterated acetone as solvents, and tetramethylsilane (TMS) as an internal standard.

[0061] In the context of this invention, when a class of substances is listed using a phrase such as "organic solvents are selected from: ... or more", it should be understood that it includes "including but not limited to" those listed substances. Those skilled in the art can select other unlisted but functionally equivalent substances based on the same principle, as long as it does not depart from the inventive spirit of this invention.

[0062] Similarly, when describing a structure such as "a porphyrin-based organic structural unit comprises at least one of the following formulas I to VI", it should be understood that the porphyrin-based organic structural unit includes, but is not limited to, these specific structures. Any analogue having the same core photosensitive unit and capable of self-assembling into a framework through hydrogen bonding falls within the scope of this invention.

[0063] Red light possesses characteristics such as low energy, high penetrability, and near-natural light. Therefore, red light photocatalysis can be considered a good choice for visible light-mediated reactions. Hydrogen-bonded organic frameworks (HOFs) are a class of crystalline porous materials constructed from organic structural units linked by intermolecular hydrogen bonds. They exhibit well-defined pore structures, high specific surface areas, structural designability, and good biocompatibility, showing broad application prospects in gas adsorption and separation, proton conduction, molecular recognition, and heterogeneous photocatalysis. In recent years, HOFs have also received increasing attention in the field of photocatalysis. For example, a team from Nanchang University studied the application of HOFs in the photocatalytic reduction of U(VI), discovering that high-speed internal charge carrier separation can occur between the HOF framework and guest molecules. A team from Yantai University constructed a dye-sensitized photocatalyst by combining HOF-TCPB-373 with TiO2 for the degradation of rhodamine B. Huaiyin Institute of Technology reported the application of HOF / CdS heterojunctions in the photocatalytic splitting of water to produce hydrogen. Furthermore, hydrogen-bonded organic frameworks (HOFs) with red light response, as a novel class of coordination polymers, are considered highly attractive heterogeneous catalysts due to their ultra-high porosity, tunable light absorption, large specific surface area, and the presence of multiple catalytic active centers in their structure. However, research on using HOFs as red light photocatalysts for the selective oxidation of sulfides is rarely reported. Therefore, addressing the problems of insufficient utilization of long-wavelength light, difficult catalyst recovery, and the need to improve selectivity in existing photocatalytic sulfide oxidation systems, this invention provides a novel method for preparing sulfides to sulfoxides with high efficiency and high selectivity under red light irradiation using hydrogen-bonded organic framework composite materials as photocatalysts. The method of this invention uses hydrogen-bonded organic frameworks (HOFs) as photocatalysts, forming a crystalline porous structure through intermolecular hydrogen bond self-assembly. Due to the unique dynamic reversibility, solution processability, and easily functionalized pore environment of HOFs, they can better synergize with sulfide substrates, organic acid additives, and ethanol, promoting the activity of reactive oxygen species (such as singlet oxygen). 1 This technology enables efficient catalysis under mild conditions by controlling the generation and mass transfer of O2. This is something that has not been disclosed or implied in existing technologies. It has the advantages of strong red light penetration, tunable catalyst structure, easy recovery, and reusability. Compared with conventional COFs and MOFs, it has higher selectivity and yield, and only requires room temperature conditions. It is green and mild, and has good prospects for industrial application.

[0064] Example 1

[0065] Preparation of Porphyrin-based hydrogen-bonded organic framework (HOF) photocatalyst PFC-943

[0066] This embodiment provides a method for preparing the porphyrin-based HOF photocatalyst shown in Formula VII (denoted as PFC-943).

[0067] S1: TMPP Synthesis: 6-Methoxy-3-pyridinecarboxaldehyde (5.76 g, 42 mmol), pyrrole (3 mL, 43 mmol), and propionic acid (100 mL) were added to a 250 mL round-bottom flask containing a magnetic inlet and wrapped with aluminum foil. The mixture was refluxed at 140°C for 12 hours. After the reaction was complete, the mixture was cooled to room temperature and filtered under reduced pressure. The filter cake was washed several times with acetone and then dried in an oven to obtain a purple powder of TMPP (1.6 g, 2.1 mmol, yield 21%).

[0068] S2: PTTP Synthesis: In a 100 mL pressure-resistant reaction tube, TMPP (0.74 g, 1 mmol), LiCl (0.85 g, 20 mmol), p-toluenesulfonic acid (3.45 g, 20 mmol), and DMF (10 mL) were added sequentially. The reaction system was heated at 120°C for 50 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered under reduced pressure. During filtration, the filter cake was washed repeatedly with DMF until the color changed from green to purple, and then further washed with ethanol. The obtained filter cake was dried in an oven to obtain purple powdered PTTP (580 mg, 0.856 mmol, yield 85%). The above chemical reaction equation is shown below:

[0069]

[0070] S3: Synthesis of PFC-943 Powder: Weigh 150 mg of PTTP and add it to a 250 mL beaker equipped with a magnetic stir bar. Simultaneously add 12 mL of tetramethylammonium hydroxide and 150 mL of ethanol solution. Stir thoroughly until the PTTP is completely dissolved; at this point, the solution is dark green. While stirring, add dropwise a mixed solution prepared with a ratio of V propionic acid:V water = 1:5 until the solution turns purple-red, corresponding to a pH of approximately 6. Filter the resulting purple-red solution; solid PFC-943 remains on the filter cake, while the filtrate is light pink. After drying the filter cake, purple PFC-943 powder is obtained.

[0071] The photocatalyst in this invention is characterized using the following equipment and methods:

[0072] The hydrogen-bonded organic framework (HOF) photocatalyst PFC-943 obtained in this embodiment was characterized by UV-Vis diffuse reflectance spectroscopy. UV-Vis DRS was performed using a PerkinElmer Lambda 950 spectrophotometer (BaSO4 as reference, scan range 200–800 nm). Figure 1 The results showed that the PFC-943 absorption spectrum had three relatively strong absorption peaks in the 450-550 nm range, and an absorption peak appeared near 660 nm. These data indicate that PFC-943 exhibits strong visible light absorption in the 400-700 nm range.

[0073] Example 2

[0074] Preparation of Porphyrin-based hydrogen-bonded organic framework (HOF) photocatalyst PFC-943 composite film

[0075] S1: Polyvinyl alcohol and chitosan (in a ratio of 1:1) are prepared into a solution, stirred evenly at 50 °C, glycerol is added during stirring, and then ultrasonically vibrated for 30 min to obtain a mixed matrix;

[0076] S2: Add PFC-943 to the mixed matrix, stir evenly at 50 ℃, and then sonicate for 30 min to obtain the film-forming solution;

[0077] S3: Pour the film-forming solution into the mold and dry it at 40 ℃ for 6 h; thus, the PFC-943 composite film is obtained.

[0078] The PFC-943 of this embodiment was fabricated into a PFC-943 composite film and characterized by scanning electron microscopy (SEM). SEM analysis was performed using a Zeiss Supra 55 VP field emission scanning electron microscope. The characterization results are described in [reference needed]. Figure 2 The image shown is a scanning electron microscope (SEM) image of the PFC-943 composite film.

[0079] Example 3 Synthesis of 2-hydroxyphenyl sulfoxide

[0080] 42.1 mg of 2-methylthiophenol, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (electrolyte: petroleum ether / ethyl acetate = 3 / 1) yielded a pale yellow powder, 91% (43.5 mg). ¹H NMR (400 MHz, CDCl₃) δ 10.14 (s, 1H), 7.36 (t, J = 7.8 Hz, 1H), 7.15 (d, J = 7.6 Hz, 1H), 6.98 – 6.90 (m, 2H), 2.94 (s, 3H).

[0081] The chemical reaction equation for this embodiment is:

[0082]

[0083] Please refer to the 1H NMR spectrum of the synthesized product 2-hydroxyphenyl sulfoxide in this embodiment. Figure 4 .

[0084] Example 4 Synthesis of 2-Benzenesulfinylethanol

[0085] 46.3 mg of 2-phenylthioethanol, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (evolving solvent: petroleum ether / ethyl acetate = 3 / 1) was performed to give pale yellow oil droplets, with a yield of 84% (42.9 mg). 1H NMR (400 MHz, CDCl3) δ 7.71 – 7.62 (m, 2H), 7.60 – 7.50 (m, 3H), 4.17(ddd, J = 11.9, 8.6, 3.1 Hz, 1H), 4.10 – 3.98 (m, 1H), 3.19 (ddd, J = 12.4,8.6, 3.8 Hz, 1H), 2.87 (ddd, J = 13.6, 5.6, 3.0 Hz, 1H).

[0086] The chemical reaction equation for this embodiment is:

[0087]

[0088] Please refer to the 1H NMR spectrum of the synthesized product 2-benzenesulfonylethanol in this embodiment. Figure 5 .

[0089] Example 5 Synthesis of 2-chloroethyl ethyl sulfoxide

[0090] 37.4 mg of 2-chloroethyl ethyl sulfide, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (electrolyte: petroleum ether / ethyl acetate = 3 / 1) was performed to give a colorless transparent liquid with a yield of 79% (33.7 mg). ¹H NMR (400 MHz, CDCl₃) δ 3.91 (t, J = 6.9 Hz, 2H), 3.40 (t, J = 6.9 Hz, 2H), 3.12 (q, J = 7.4 Hz, 2H), 1.43 (t, J = 7.5 Hz, 3H).

[0091] The chemical reaction equation for this embodiment is:

[0092]

[0093] Please refer to the 1H NMR spectrum of the synthesized product 2-chloroethyl ethyl sulfoxide in this embodiment. Figure 6 .

[0094] Example 6 Synthesis of 2-(diphenylmethane sulfoxide)acetamide

[0095] 77.2 mg of 2-(diphenylthio)acetamide, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 6 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (evolving solvent: petroleum ether / ethyl acetate = 2 / 1) was performed to give a white solid powder in 72% (59.1 mg) yield. 1H NMR (400 MHz, CDCl3) δ 7.56 – 7.31 (m, 10H), 7.05 (s, 1H), 5.60 (s, 1H), 5.19 (s, 1H), 3.49 (d, J = 14.4 Hz, 1H), 3.10 (d, J = 14.4 Hz,1H).

[0096] The chemical reaction equation for this embodiment is:

[0097]

[0098] Please refer to the 1H NMR spectrum of the synthesized product 2-(diphenylmethyl sulfoxide)acetamide in this embodiment. Figure 7 .

[0099] Example 7 Synthesis of 3-methylsulfinylthiophene

[0100] 3-Methylthiothiophene (34.3 mg), 5 mg PFC-943 composite membrane, 50 μL formic acid, and 1 mL ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (electrolyte: petroleum ether / ethyl acetate = 2 / 1) yielded a pale yellow oily liquid, with a yield of 89% (39.1 mg). ¹H NMR (400 MHz, CDCl₃) δ 7.65 (d, J = 5.0 Hz, 1H), 7.50 (s, 1H), 7.13 (s, 1H), 2.94 (s, 3H).

[0101] The chemical reaction equation for this embodiment is:

[0102]

[0103] Please refer to the 1H NMR spectrum of the synthesized product 3-methylsulfinylthiophene in this embodiment. Figure 8 .

[0104] Example 8 Synthesis of 3-methoxyphenylmethyl sulfoxide

[0105] 46.3 mg of 3-methoxyphenyl methyl sulfide, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (evolving solvent: petroleum ether / ethyl acetate = 2 / 1) was performed to give a white solid powder in 93% yield (47.5 mg). 1H NMR (400 MHz, CDCl3) δ 7.40 (t, J = 7.9 Hz, 1H), 7.26 – 7.23(m, 1H), 7.12 (d, J = 7.9 Hz, 1H), 7.00 (dd, J = 8.3, 1.6 Hz, 1H), 3.86 (s,3H), 2.71 (s,3H).

[0106] The chemical reaction equation for this embodiment is:

[0107]

[0108] Please refer to the 1H NMR spectrum of the synthesized product 3-methoxyphenylmethyl sulfoxide in this embodiment. Figure 9 .

[0109] Example 9 Synthesis of 4-Methylsulfinylbenzaldehyde

[0110] 4-Methylthiobenzaldehyde (45.7 mg), 5 mg PFC-943 composite membrane, 50 μL formic acid, and 1 mL ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (electrolyte: petroleum ether / ethyl acetate = 2 / 1) yielded a white solid powder, 90% yield (45.5 mg). ¹H NMR (400 MHz, CDCl₃) δ 10.09 (s, 1H), 8.05 (d, J = 8.3 Hz, 2H), 7.82 (d, J = 8.3 Hz, 2H), 2.78 (s, 3H).

[0111] The chemical reaction equation for this embodiment is:

[0112]

[0113] Please refer to the 1H NMR spectrum of the synthesized product 4-methylsulfinylbenzaldehyde in this embodiment. Figure 10 .

[0114] Example 10 Synthesis of 2-methylsulfinylpyridine

[0115] 37.6 mg of 2-methylthiopyridine, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol were added to a 38 mL thick-walled pressure-resistant tube. The mixture was stirred at room temperature and reacted under a 650 nm LED lamp for 4 h. After the reaction was completed, the reaction was quenched, extracted with ethyl acetate (3 × 2 mL), the organic layer was collected and dried over anhydrous magnesium sulfate, concentrated under reduced pressure, washed with dichloromethane, concentrated under reduced pressure, and column chromatography (electrolyte: petroleum ether / ethyl acetate = 2 / 1) was performed to give a white solid powder in 86% (36.5 mg) yield. ¹H NMR (400 MHz, CDCl₃) δ 8.62 (s, 1H), 8.03 (d, J = 7.9 Hz, 1H), 7.95 (t, J = 7.7 Hz, 1H), 7.42–7.35 (m, 1H), 2.85 (s, 3H).

[0116] The chemical reaction equation for this embodiment is:

[0117]

[0118] Please refer to the 1H NMR spectrum of the synthesized product 2-methylsulfinylpyridine in this embodiment. Figure 11 .

[0119] Example 11

[0120] The PFC-943 composite membrane in Examples 2-9 was replaced with an equal amount of PFC-943 powder.

[0121] Example 12

[0122] Cyclic performance testing of HOFs composite catalysts

[0123] Add 37.2 mg of phenyl methyl sulfide, 5 mg of PFC-943 composite membrane, 50 μL of formic acid, and 1 mL of ethanol to a 38 mL thick-walled pressure-resistant tube. Mix and stir at room temperature, and react under a 650 nm LED lamp for 4 h. After the reaction is complete, quench the reaction, extract with ethyl acetate (3 × 2 mL), and collect the organic layer. Wash and soak the PFC-943 composite membrane with ethanol, air dry, and repeat the operation at least three times.

[0124] Add 37.2 mg of phenyl methyl sulfide, 5 mg of PFC-943 powder, 50 μL of formic acid, and 1 mL of ethanol to a 38 mL thick-walled pressure-resistant tube. Mix and stir at room temperature, and react under a 650 nm LED lamp for 4 h. After the reaction is complete, transfer the reaction mixture to a centrifuge tube for centrifugation. Quench the supernatant with water, wash the solid powder with ethanol, and centrifuge. After three wash-centrifugation cycles, dry the powder in an oven. Extract the supernatant with ethyl acetate (3 × 2 mL) and collect the organic layer. Repeat the operation at least three times.

[0125] Please see Figure 3 The graph shows the cyclic performance test results of catalyst PFC-943 powder and PFC-943 composite membrane. As can be seen from the graph, after 1, 2, and 3 cycles of recycling, both catalyst PFC-943 powder and PFC-943 composite membrane retain the ability to catalyze the oxidation of sulfide compounds to sulfoxide compounds under red light, room temperature conditions, and with the synergistic effect of formic acid and ethanol. Furthermore, the catalytic performance of the PFC-943 composite membrane did not significantly decrease after 3 cycles.

[0126] Example 13

[0127] Following the method of Example 2, with other conditions kept constant, LEDs of different wavelengths were used as light sources (620 nm, 650 nm, 680 nm, 720 nm, 750 nm, and 480 nm blue light control, 365 nm ultraviolet light control) to investigate the effect of light source wavelength on the reaction. The results are shown in Table 1.

[0128] Table 1. Effects of different wavelength light sources on the catalytic oxidation of 2-methylthiophenol

[0129] 620 nm (red light) 94.8 99.0 1.0 650 nm (red light) 94.5 99.2 0.8 680 nm (red light) 91.2 99.5 0.5 720 nm (red light) 85.6 99.6 0.4 750 nm (red light) 76.3 99.7 0.3

[0130] The results in Table 1 show that the sulfoxide selectivity under red light (620–750 nm) irradiation is above 99%, significantly better than that of blue and ultraviolet light. As the wavelength of red light increases, the conversion rate gradually decreases, but the selectivity further improves. Considering both conversion rate and selectivity, the preferred wavelength range is 620–680 nm, more preferably 650 nm.

[0131] Example 14

[0132] Following the method of Example 2, with other conditions unchanged, formic acid, acetic acid, propionic acid, trifluoroacetic acid, and trichloroacetic acid were added in amounts of 50 μL each as additives. A blank control (without added organic acid) was also set up to investigate the effect of the type of organic acid on the reaction. The results are shown in Table 2.

[0133] Table 2. Effects of different organic acid additives on the catalytic oxidation of anisole.

[0134] No additives 74.7 96.4 3.6 Formic acid 94.5 99.2 0.8 Acetic acid 92.6 61.3 38.7 propionic acid 27.8 86.4 13.6 Trifluoroacetic acid 95.8 99.0 1.0 Trichloroacetic acid 94.1 98.8 1.2

[0135] The results in Table 2 show that the addition of organic acid additives can significantly improve the conversion rate and sulfoxide selectivity, with formic acid showing the best effect.

[0136] In summary, this invention, through the synergistic innovation of HOF photocatalysts, red light excitation, organic acid additives, and ethanol solvent, achieves for the first time a highly efficient and selective photocatalytic oxidation of sulfides to sulfoxides under room temperature, air, and without added chemical oxidants. This method boasts comprehensive advantages, including mild conditions (room temperature), low-energy light source (red light), green oxidant (air), excellent selectivity (>99%), broad substrate versatility (aromatic / aliphatic / heterocyclic / mustard gas mimics), recyclable catalyst, and ease of industrial application. These advantages significantly surpass existing technologies, filling the technological gap in red light-catalyzed sulfide oxidation using HOF materials. It possesses significant creative and industrial application value, providing a novel solution for the green synthesis of sulfoxide compounds.

[0137] Finally, it should be noted that although the above embodiments have been described in the description and drawings of this invention, this should not limit the scope of patent protection of this invention. Any technical solutions that are based on the essential concept of this invention, utilize the content described in the description and drawings of this invention to make equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this invention.

Claims

1. A method for preparing sulfoxides by red light photocatalytic oxidation of sulfides, characterized in that, Includes the following steps: S1 involves mixing thioether compounds, hydrogen-bonded organic framework photocatalysts, organic solvents, and organic acid additives uniformly at room temperature to form a first reaction mixture; S2 is irradiated with red light for a certain period of time in the presence of oxygen-containing gas to selectively oxidize sulfoether compounds to sulfoxide compounds, thereby obtaining a second reaction mixture; S3 is separated from the second reaction mixture to obtain sulfoxide.

2. The method according to claim 1, characterized in that, The hydrogen-bonded organic framework photocatalyst is a porphyrin-based hydrogen-bonded organic framework material, which is formed by the self-assembly of porphyrin-based organic structural units through hydrogen bonding. The porphyrin-based organic structural units comprise at least one of the following formulas I to VI: Formula I Formula II Formula III Formula IV, Formula V, Formula VI.

3. The method according to claim 2, characterized in that, The porphyrin-based organic structural unit contains a metal ion R at its center, wherein the metal ion R is selected from Mn. 2+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Mg 2+ At least one of them.

4. The method according to claim 1, characterized in that, The molar ratio of the hydrogen-bonded organic framework photocatalyst to the thioether compound is 0.05~0.2:

1.

5. The method according to claim 1 or 4, characterized in that, The thioether compounds are selected from one or more of aromatic thioethers, aliphatic thioethers, heterocyclic thioethers, and mustard gas simulants.

6. The method according to claim 1, characterized in that, The hydrogen-bonded organic framework photocatalyst participates in the reaction in the form of a composite membrane, aerogel, or hydrogel HOFs composite material, wherein the matrix of the HOFs composite material is selected from one or more of polyvinyl alcohol, polyethersulfone, polyamide, polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate, lignin, or cellulose.

7. The method according to claim 1, characterized in that, The organic solvent is ethanol, and the organic acid additive is selected from aliphatic carboxylic acids or their halogenated derivatives with 1 to 6 carbon atoms.

8. The method according to claim 7, characterized in that, The organic acid additive is formic acid, acetic acid, trifluoroacetic acid, or trichloroacetic acid.

9. A hydrogen-bonded organic framework photocatalyst for the red light-catalyzed oxidation of sulfides to sulfoxides, characterized in that, It is a crystalline porous material formed by the self-assembly of porphyrin-based organic structural units through hydrogen bonding.

10. The hydrogen-bonded organic framework photocatalyst according to claim 9, characterized in that, The porphyrin-based organic structural unit has a metal ion R embedded at its center, and the metal ion R is selected from Mn. 2+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Mg 2+ One or more of them.

Images