Thiophene, triazine functionalized covalent organic semiconductors, methods of making and use thereof

Abstract

The application discloses a thiophene, triazine functionalized covalent organic semiconductor and a preparation method and application thereof, and belongs to the technical field of organic semiconductor materials; the preparation method comprises the following steps: mixing a thiophene halogen precursor, a palladium catalyst, an alkali, 5-bromothiophene-2-carbonitrile and a polar aprotic solvent, and performing a coupling reaction to obtain a thiophene precursor containing double cyano groups; the thiophene precursor containing double cyano groups is subjected to a cyclization reaction in an organic hot solvent containing a Lewis acid, or a cyclization reaction is performed by using trifluoromethanesulfonic acid to obtain the thiophene, triazine functionalized covalent organic semiconductor. The thiophene, triazine functionalized covalent organic semiconductor prepared by the application has good absorption in a visible light range, and a band structure thereof meets the requirement of catalyzing the full decomposition of water to generate oxygen and hydrogen under visible light irradiation, and has the ability of photocatalytic water decomposition for hydrogen and oxygen evolution.

Description

Technical Field

[0001] This invention belongs to the field of organic semiconductor materials technology, specifically relating to thiophene and triazine functionalized covalent organic semiconductors, their preparation methods, and applications. Background Technology

[0002] With the increasing severity of the global energy crisis and environmental problems, the development of efficient and sustainable energy conversion and environmental governance materials has become a research hotspot. Organic semiconductors, due to their advantages such as tunable structure, excellent photoelectric properties, and low preparation cost, have shown broad application prospects in fields such as photocatalytic hydrogen production, CO2 reduction, and pollutant degradation.

[0003] Thiophene compounds possess excellent π-conjugated systems and electron transport properties, while triazine units exhibit strong electron-withdrawing capabilities and stable chemical structures. Combining the two to construct thiophene-triazine organic semiconductors can promote charge separation through donor-acceptor (DA) interactions, thereby enhancing photocatalytic activity.

[0004] However, existing thiophene-triazine materials suffer from problems such as demanding synthesis conditions, insufficient charge separation efficiency, and limited application scenarios, which restrict their practical applications. Therefore, developing a thiophene-triazine organic semiconductor with a simple preparation process, excellent performance, and wide range of applications is of great significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide thiophene and triazine functionalized covalent organic semiconductors, their preparation methods, and applications, thereby solving the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: The structural formula of the thiophene- and triazine-functionalized covalent organic semiconductor is as follows: Where n is an integer from 1 to 6.

[0007] The above-mentioned method for preparing thiophene and triazine functionalized covalent organic semiconductors includes the following steps: A thiophene halogen precursor, a palladium catalyst, a base, 5-bromothiophene-2-carboxynitrile, and a polar aprotic solvent were mixed and coupled to obtain a dicyano-containing thiophene precursor. Thiophene- and triazine-functionalized covalent organic semiconductors are obtained by cyclotrimerization of dicyano-containing thiophene precursors in a solvent containing Lewis acids, or by cyclotrimerization catalyzed by trifluoromethanesulfonic acid.

[0008] The reaction generates thiophene and triazine-functionalized covalent organic semiconductors.

[0009] Furthermore, the general structural formula of the dicyano-containing thiophene precursor is: Where n is an integer from 1 to 6.

[0010] Further, the thiophene halide precursor is: 2,5-dibromothiophene, 2,5-diiodothiophene, 2,5-dichlorothiophene, 5,5'-dibromo-2,2'-bithiophene, 5,5'-diiodo-2,2'-bithiophene, 5,5'-dichloro-2,2'-bithiophene, 5,5''-dibromo-2,2':5',2''-trithiophene, 5,5''-diiodo-2,2':5',2''-trithiophene, 5,5''-dichloro-2,2':5',2''-trithiophene, 5,5'''-dibromo-2,2':5',2'':5'',2'''-tetrathiophene, 5,5'''-diiodo-2,2':5',2'':5'',2'''-tetrathiophene, 5,5'''-diiodo-2,2':5',2'':5'',2'''-tetrathiophene, 5,5''' One or more of -dichloro-2,2':5',2'':5'',2'''-tetrathiophene.

[0011] Further, the base is one or more of the following: potassium carbonate, cesium carbonate, sodium carbonate, potassium phosphate, sodium acetate, potassium acetate, potassium tert-valerate, potassium tert-butoxide, and triethylamine.

[0012] Further, the palladium catalyst comprises a palladium source and a ligand, wherein the palladium source comprises one or more of tetra(triphenylphosphine)palladium (0), palladium acetate (II), palladium chloride (II), bis(benzylnitrile)palladium chloride (II), and allyl palladium chloride (II) dimer; and the ligand comprises one or more of triphenylphosphine, tricyclohexylphosphine, biarylphosphine, phosphine ligand, and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-yl group.

[0013] Further, the molar ratio of the thiophene halide, 5-bromothiophene-2-carboxynitrile, base and palladium catalyst is 1:(1.5-2):(2-2.5):0.05, wherein the concentration of palladium source in the palladium catalyst is 5 mol.

[0014] Furthermore, the methods for generating thiophene and triazine-functionalized covalent organic semiconductors via cyclotrimerization reactions include the following two: Method 1: Dissolve the dicyano-containing thiophene precursor in an anhydrous and degassed solvent, and add Lewis acid catalyst to the solution; place the reaction system under an inert atmosphere and stir and reflux in a heated oil bath; after the reaction is completed, cool, separate, filter, wash and dry to obtain the product. Method 2: In an anhydrous and oxygen-free environment, the thiophene precursor containing dicyano groups is mixed with trifluoromethanesulfonic acid under an inert gas atmosphere, then transferred to room temperature for reaction, followed by heat treatment, then cooling to room temperature to quench the reaction, washing the product, and then purifying and drying it to obtain the final product.

[0015] Furthermore, in Method 1: the Lewis acid is any one of zinc chloride, aluminum chloride, and ferric chloride; the molar ratio of the dicyano-containing thiophene precursor to the Lewis acid is preferably 1:1-30; In Method 2, the molar ratio of the dicyano-containing thiophene precursor to trifluoromethanesulfonic acid is 1:1-10.

[0016] The above-mentioned thiophene and triazine functionalized covalent organic semiconductors are used in photocatalytic water splitting to produce hydrogen and oxygen.

[0017] The beneficial effects of this invention are: 1. The preparation process of the thiophene and triazine functionalized covalent organic semiconductor of the present invention is clear, the synthesis conditions are mild, the raw materials are readily available, and it has the potential for large-scale preparation.

[0018] 2. This invention, through the bifunctionalization of thiophene and triazine, can endow organic semiconductor materials with stronger electron donor and acceptor capabilities, and promote the generation of active intermediates in the reaction.

[0019] 3. The optimized electron transfer characteristics of this invention help enhance the stability and selectivity of the catalyst, thereby improving the efficiency of photocatalytic water splitting for hydrogen production and oxygen generation.

[0020] 4. The thiophene and triazine functionalized covalent organic semiconductors prepared by this invention have good absorption in the visible light range, and their band structure meets the requirements for catalytic water splitting to produce oxygen and hydrogen under visible light irradiation, thus possessing the ability to photocatalytically split water to produce hydrogen and oxygen.

[0021] 5. The Lewis acid-catalyzed cyclotrimerization method for preparing thiophene and triazine functionalized covalent organic semiconductors involved in this invention uses Lewis acids (such as zinc chloride, aluminum chloride, ferric chloride, etc.) as catalysts. The cyclotrimerization reaction is achieved by heating under reflux in an inert atmosphere. It has the advantages of flexible selection of catalysts and solvents, controllable cost, mild and easy-to-control reaction conditions, simple and efficient product separation, strong reaction adaptability, and high fault tolerance. It is suitable for large-scale preparation and low-cost production.

[0022] 6. The low-temperature-heat treatment cyclotrimerization reaction method catalyzed by trifluoromethanesulfonic acid of this invention for preparing thiophene and triazine functionalized covalent organic semiconductors achieves cyclotrimerization in an anhydrous and oxygen-free environment by using trifluoromethanesulfonic acid as a catalyst through "low-temperature mixing-room-room-heat treatment". It has the advantages of high reaction efficiency, short total cycle, strong catalytic activity, high cyclization selectivity, high product purity, stable performance, and low reagent toxicity, and is suitable for preparing high-purity samples. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a synthetic route diagram of a thiophene-triazine functionalized covalent organic semiconductor according to the present invention; Figure 2 This is a schematic diagram of the structure of P-1Th, P-2Th, P-3Th, P-4Th, P-5Th, and P-6Th of the present invention; Figure 3 This is a transmission electron microscope schematic diagram of the thiophene and triazine functionalized covalent organic semiconductors obtained in the examples; Figure 4 These are the visible-near-infrared absorption spectra and band gap diagrams of the thiophene and triazine functionalized covalent organic semiconductors obtained in the examples; Figure 5 This is a schematic diagram illustrating the performance of the thiophene and triazine functionalized covalent organic semiconductors obtained in the examples in the photocatalytic water splitting reaction under a pure water and argon atmosphere. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] like Figure 2 As shown, a thiophene-triazine functionalized covalent organic semiconductor comprises the following steps: its structure is composed of alternating thiophene units and 1,3,5-triazine units. Depending on the polymerization length of the thiophene units, it can be classified into P-1Th, P-2Th, P-3Th, P-4Th, P-5Th, P-6Th, etc.; its general structural formula is: Formula (II); Where n is an integer from 1 to 6.

[0027] The thiophene-triazine functionalized covalent organic semiconductor includes the repeating unit shown in formula (Ⅲ): Formula (Ⅲ); In formula (III), the wavy line represents a repeating unit or repeating segment in a thiophene or triazine functionalized covalent organic semiconductor, which has the same meaning as polymers with wavy lines on both sides that are well known to those skilled in the art; wherein, n is an integer from 1 to 6, preferably an integer from 1 to 4; more preferably 1 or 2, that is, the most preferred thiophene or triazine covalent organic semiconductor shown in formula (III) of the present invention is as shown in formula (VI) or formula (VII): Formula (VI) Formula (VII) This invention also provides a method for preparing the above-mentioned thiophene and triazine functionalized covalent organic semiconductors, such as... Figure 1 The synthetic route shown specifically includes the following steps: S1, the thiophene halogen precursor is coupled in a polar aprotic solvent in the presence of a palladium catalyst, a base, and a co-catalyst (5-bromothiophene-2-carboxynitrile) to obtain a dicyano-containing thiophene precursor, the general structural formula of which is: Equation (I) Wherein, n is an integer from 1 to 6, preferably an integer from 1 to 4; more preferably 1 or 2, that is, the most preferred form of the cyanothiophene-containing small organic molecule shown in formula (I) of the present invention is as shown in formula (IV) or formula (V): Formula (Ⅳ); Formula (V); S2, a dicyano-containing thiophene precursor is generated through a cyclotrimerization reaction to produce a thiophene-triazine functionalized covalent organic semiconductor.

[0028] Specifically, the steps of S1 are as follows: Thiophene halide precursor, 5-bromothiophene-2-carboxynitrile, palladium catalyst, base and polar aprotic solvent are mixed and stirred at a specific temperature. After cooling, quenching, washing, purification, drying and recrystallization, the purified dicyanothiophene-containing precursor is separated. The thiophene halide precursors are: 2,5-dibromothiophene, 2,5-diiodothiophene, 2,5-dichlorothiophene, 5,5'-dibromo-2,2'-bithiophene, 5,5'-diiodo-2,2'-bithiophene, 5,5'-dichloro-2,2'-bithiophene, 5,5''-dibromo-2,2':5',2''-trithiophene, 5,5''-diiodo-2,2':5',2''-trithiophene, 5,5''-dichloro-2,2':5',2''-trithiophene, 5,5'''-dibromo-2,2':5',2''-tetrathiophene, 5,5'''-diiodo-2,2':5',2''-tetrathiophene, 5,5'''-dichloro- One or more of 2,2':5',2'':5'',2'''-tetrathiophene; preferably: 2,5-dibromothiophene, 2,5-diiodothiophene, 5,5'-dibromo-2,2'-bithiophene, 5,5'-diiodo-2,2'-bithiophene, 5,5''-dibromo-2,2':5',2''-trithiophene, 5,5''-diiodo-2,2':5',2''-trithiophene, 5,5'''-dibromo-2,2':5',2''-tetrathiophene, 5,5'''-diiodo- One or more of 2,2':5', 2'':5'', 2'''-tetrathiophene; most preferably one or more of 2,5-dibromothiophene, 5,5''-dibromo-2,2'-bithiophene, 5,5''-dibromo-2,2':5', 2''-trithiophene, and 5,5'''-dibromo-2,2':5', 2'':5'', 2'''-tetrathiophene; The base is one or more of the following: potassium carbonate, cesium carbonate, sodium carbonate, potassium phosphate, sodium acetate, potassium tert-valerate, potassium tert-butoxide, and triethylamine. The palladium catalyst comprises a palladium source and a ligand. The palladium source comprises one or more of tetra(triphenylphosphine)palladium (0), palladium acetate (II), palladium chloride (II), bis(benzylnitrile)palladium chloride (II), and allyl palladium chloride (II) dimer. The ligand comprises one or more of triphenylphosphine, tricyclohexylphosphine, biarylphosphine, phosphine ligand, and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-yl group.

[0029] The polar aprotic solvent is one or more of the following: N-methylpyrrolidone, diethylene glycol butyl ether, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methylformamide, toluene, dioxane, acetonitrile, dimethyl sulfoxide, dimethyl sulfone, sulfolane, pyridine, and piperidine.

[0030] The solvent used for recrystallization includes one or more of the following: a tetrahydrofuran / petroleum ether mixture, a tetrahydrofuran / diethyl ether mixture, an ethyl acetate / petroleum ether mixture, an ethyl acetate / diethyl ether mixture, a dichloromethane / petroleum ether mixture, a dichloromethane / diethyl ether mixture, a chloroform / petroleum ether mixture, and a chloroform / diethyl ether mixture.

[0031] In S1, the ratio of the thiophene halide to 5-bromothiophene-2-carboxynitrile, the base, and the palladium catalyst is preferably 1:(1.0-6.0):(0.5-5):(0.01-0.5); more preferably 1:(1.5-4.0):(1-3):(0.01-0.3); and most preferably 1:3:2:0.05 (5mol%), with a palladium catalyst concentration of 5mol%. In S1, the specific temperature is 65 to 150°C, preferably 80 to 140°C, more preferably 100 to 140°C, and most preferably 110 to 130°C; the stirring time is 12 to 72 hours. In S1, the recrystallization times are preferably 2 to 8 times, more preferably 3 to 6 times, and most preferably 4 times.

[0032] The methods in S2 for generating thiophene- and triazine-functionalized covalent organic semiconductors from dicyano-containing thiophene precursors via cyclotrimerization include the following two: Method 1: Dissolve the dicyanothiophene monomer in an anhydrous and degassed solvent, and add a Lewis acid to the solution for catalysis. Place the reaction system under an inert atmosphere and stir and reflux in a heated oil bath. After the reaction is complete, cool the mixture to room temperature, separate the products by precipitation, and collect the solid precipitate by centrifugation or filtration. The collected solid sample is continuously washed with solvent in a Soxhlet extractor and finally transferred to a vacuum drying oven to obtain the polymer.

[0033] The Lewis acid is zinc chloride, aluminum chloride, ferric chloride, or a sodium chloride / potassium chloride / zinc chloride eutectic salt, preferably zinc chloride, aluminum chloride, or ferric chloride, and most preferably zinc chloride; the concentration of the cyanothiophene monomer is preferably 5 to 50 mM, more preferably 8 to 30 mM, and most preferably 10 to 20 mM; the molar ratio of the monomer to the Lewis acid is preferably 1:1 to 1:30, more preferably 1:3 to 1:10, and most preferably 1:5; the solvent is preferably anhydrous chloroform, anhydrous tetrahydrofuran, anhydrous N,N-dimethylformamide, anhydrous dimethyl sulfoxide, or anhydrous N-methylpyrrolidone, more preferably anhydrous tetrahydrofuran, anhydrous N,N-dimethylformamide, anhydrous dimethyl sulfoxide, or anhydrous N-methylpyrrolidone, and most preferably anhydrous N,N-dimethylformamide or anhydrous dimethyl sulfoxide; the oil bath temperature is preferably 80 to 180°C. The temperature is ℃, more preferably 90 to 150℃, and most preferably 100 to 120℃; the reaction time is preferably 10 to 72 hours, more preferably 20 to 48 hours, and most preferably 24 to 36 hours.

[0034] Method 2: In an anhydrous and oxygen-free environment, the dicyanothiophene monomer shown in formula (I) is mixed with trifluoromethanesulfonic acid under low temperature and inert gas, and then transferred to room temperature for reaction. Subsequently, heat treatment is performed, followed by cooling to room temperature to quench the reaction, washing the product, purifying the product by Soxhlet extraction, and drying to obtain the thiophene and triazine functionalized polymer.

[0035] The preferred molar ratio of the cyanothiophene monomer to trifluoromethanesulfonic acid is 1:1 to 1:20, more preferably 1:1 to 1:10, and most preferably 1:3 to 1:5. The preferred low-temperature conditions are -40°C to 5°C, more preferably -20°C to 5°C, and most preferably -10°C to 0°C. The preferred room-temperature reaction time is 0.5 to 12 hours, more preferably 0.5 to 6 hours, and most preferably 1 to 3 hours. The preferred heat treatment temperature is 45 to 120°C, more preferably 50 to 100°C, and most preferably 70 to 80°C. The preferred heat treatment time is 1 to 96 hours, more preferably 2 to 48 hours, and most preferably 3 to 24 hours. The reaction is preferably quenched with methanol, ethanol, or deionized water, more preferably with deionized water, and most preferably with supercooled deionized water. After quenching, the product is preferably washed with ammonia and methanol. The concentration of the ammonia water is preferably 0.1–1 mol / L; the purification process preferably uses Soxhlet extraction to purify the product, that is, purifying the product with an extraction solvent; Soxhlet extraction with an extraction solvent can remove impurities from the product; the extraction solvents used for Soxhlet extraction are preferably deionized water, ethanol, acetonitrile, and acetone in that order; the extraction time for each solvent is preferably 8 to 24 hours, more preferably 10 to 16 hours, and even more preferably 12 hours; the drying process is preferably vacuum drying; the vacuum drying temperature is preferably 50°C to 80°C, more preferably 55°C to 70°C, even more preferably 60°C to 65°C, and most preferably 60°C; the vacuum drying time is preferably 20 to 30 hours, more preferably 22 to 28 hours, even more preferably 24 to 26 hours, and most preferably 24 hours.

[0036] The thiophene and triazine functionalized covalent organic semiconductors prepared by this invention have good absorption in the visible light range, and their band structure meets the requirements for catalytic total water splitting to produce oxygen and hydrogen under visible light irradiation.

[0037] The present invention also provides an application of the above-mentioned thiophene and triazine functionalized covalent organic semiconductors in photocatalytic water splitting to produce hydrogen and oxygen, more preferably visible light catalysis; in the present invention, the method of photocatalytic water splitting to produce hydrogen and oxygen preferably specifically comprises: dispersing the thiophene and triazine functionalized organic semiconductors in deionized water, continuously purging argon gas to remove the solvent and air in the container, sealing it, and catalytically splitting water to produce hydrogen and oxygen under visible light irradiation with a wavelength greater than 420 nm.

[0038] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a thiophene-triazine functionalized covalent organic semiconductor, its preparation method, and its applications. All reagents used in the following embodiments are commercially available, and some raw materials are sourced as follows: Tetra(triphenylphosphine)palladium(0) (triphenylphosphine): Manufacturer: MP, Homogeneous Catalysts, Monodentate Ligands, Phosphorus Ligands - Achiral, CAS No.: 14221-01-3, MDL No.: MFCD00010012; Ethyl acetate / petroleum ether (volume ratio 1:1) mixture: Manufacturer: Aladdin, Product No.: C485789; 2,5-Dicyanothiophene (1Th): Manufacturer: 18853-40-2, CAS No.: 18853-40-2, Product No.: 18853-40-2.

[0039] Example 1 1Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (216 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120°C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-1Th.

[0040] Example 2 In an anhydrous and oxygen-free environment, 1Th was placed in a reaction vessel, and trifluoromethanesulfonic acid was slowly added dropwise under nitrogen protection from -10°C to 0°C, with a 1:5 molar ratio of 1Th to TfOH. After mixing, the mixture was transferred to room temperature and reacted for 3 hours, followed by heat treatment at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-1Th.

[0041] Example 3 2,5-Dibromothiophene, 5-bromothiophene-2-carboxynitrile, potassium carbonate, and tetrakis(triphenylphosphine)palladium(0) (triphenylphosphine) were mixed in a molar ratio of 1:1.5:2.5:0.05 (5 mol%) (1 mmol, 242 mg : (1.5 mmol, 282.1 mg : (2.5 mmol, 345.5 mg : (0.05 mmol, 57.8 mg)). Dry N,N-dimethylacetamide (5 mL) was added, and the mixture was stirred at 120 °C for 48 hours under argon protection. After the reaction was complete, the mixture was slowly cooled naturally for 12 hours. The reaction solution was then diluted with deionized water, filtered, collected, and concentrated to obtain a solid crude product. The crude product was dissolved in a mixture of ethyl acetate / petroleum ether (1:1, v / v) at room temperature, the supernatant was collected by centrifugation, concentrated, and recrystallized three times. After recrystallization, the product was dried under vacuum at 60°C for 24 hours to obtain a dicyanothiophene compound, 5,5'-dicyano-2,2'-bithiophene, denoted as 2Th.

[0042] Example 4 2Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (216 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120 °C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60 °C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-2Th.

[0043] Example 5 In an anhydrous and oxygen-free environment, 2Th was placed in a reaction vessel, and trifluoromethanesulfonic acid was slowly added dropwise under nitrogen protection from -10°C to 0°C, with a molar ratio of 2Th to TfOH of 1:5. After mixing, the mixture was transferred to room temperature and reacted for 3 hours, followed by heat treatment at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-2Th.

[0044] Example 6 2,5-Dibromothiophene, 5-bromothiophene-2-carboxynitrile, potassium carbonate, and tetrakis(triphenylphosphine)palladium (0) were mixed in a molar ratio of 1:3:2:0.05 (5 mol%) ((1 mmol, 242 mg : (3 mmol, 564.2 mg : (2 mmol, 276.4 mg : (0.05 mmol, 57.8 mg)), and 5 mL of dry N,N-dimethylacetamide was added. The mixture was stirred at 120 °C for 48 hours under argon protection. After the reaction was completed, the mixture was slowly cooled naturally for 12 hours. The reaction solution was then diluted and quenched with deionized water, filtered, collected, and concentrated to obtain a solid crude product. The crude product was dissolved in a mixture of ethyl acetate / petroleum ether (1:1 v / v) at room temperature, and the supernatant was collected by centrifugation. The supernatant was concentrated and recrystallized four times. After recrystallization, the product was dried under vacuum at 60 °C for 24 hours to separate the purified dicyanothiophene precursor, denoted as 3Th.

[0045] Example 7 3Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (324 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120 °C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60 °C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-3Th.

[0046] Example 8 In an anhydrous and oxygen-free environment, 3Th was placed in a reaction vessel, and trifluoromethanesulfonic acid was slowly added dropwise under nitrogen protection at -10°C to 0°C, with a 3Th to TfOH molar ratio of 1:5. After mixing, the mixture was transferred to room temperature and reacted for 3 hours, followed by heat treatment at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-3Th.

[0047] Example 9 5,5''-dibromo-2,2':5',2''-trithiophene, 5-bromothiophene-2-carboxynitrile, potassium carbonate, and tetrakis(triphenylphosphine)palladium (0) were mixed in a molar ratio of 1:3:2:0.05 (5 mol%) ((1 mmol, 406.2 mg : (3 mmol, 564.2 mg : (2 mmol, 276.4 mg : (0.05 mmol, 57.8 mg)), and 10 mL of dry N,N-dimethylacetamide was added. The reaction was carried out under argon protection at 120 °C with stirring for 48 hours. After the reaction was completed, the mixture was slowly cooled naturally for 12 hours. The reaction solution was then diluted and quenched with deionized water, filtered, collected, and concentrated to obtain a solid crude product. The crude product was dissolved in a mixture of ethyl acetate / petroleum ether (1:1, v / v) at room temperature, the supernatant was collected by centrifugation, concentrated, and recrystallized four times. After recrystallization, the product was dried under vacuum at 60°C for 24 hours to separate the purified dicyanothiophene precursor, denoted as 4Th.

[0048] Example 10 4Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (488 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120 °C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60 °C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-4Th.

[0049] Example 11 In an anhydrous and oxygen-free environment, 488 mg (1 mmol) of 4Th monomer was thoroughly mixed with trifluoromethanesulfonic acid (at a molar ratio of 1:5) under argon protection from -10°C to 0°C, and the mixture was transferred to room temperature for 3 hours. Subsequently, the mixture was heat-treated at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then vacuum-dried at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-4Th.

[0050] Example 12 5,5'''-dibromo-2,2':5',2'':5'',2'''-tetrathiophene, 5-bromothiophene-2-carboxynitrile, potassium carbonate, and tetra(triphenylphosphine)palladium (0) were mixed in a molar ratio of 1:3:2:0.05 (5 mol%) ((1 mmol, 488.3 mg):(3 mmol, 564.2 mg):(2 mmol, 276.4 mg):(0.05 mmol, 57.8 mg)), and 15 mL of dry N,N-dimethylacetamide was added. The reaction was stirred at 120 °C for 48 hours under argon protection. After the reaction was completed, the mixture was slowly cooled naturally for 12 hours, then diluted and quenched with deionized water, filtered, collected, and concentrated to obtain a solid crude product. The crude product was dissolved in a mixture of ethyl acetate / petroleum ether (1:1, v / v) at room temperature, the supernatant was collected by centrifugation, concentrated, and recrystallized four times. After recrystallization, the product was dried under vacuum at 60°C for 24 hours to separate the purified dicyanothiophene precursor, denoted as 5Th.

[0051] Example 13 5Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (570 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120 °C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60 °C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-5Th.

[0052] Example 14 In an anhydrous and oxygen-free environment, 5Th was placed in a reaction vessel, and trifluoromethanesulfonic acid was slowly added dropwise under nitrogen protection at -10°C to 0°C, with a 5Th to TfOH molar ratio of 1:5. After mixing, the mixture was transferred to room temperature and reacted for 3 hours, followed by heat treatment at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-5Th.

[0053] Example 15 5,5''''-dibromo-2,2':5',2'':5'',2''':5''',2'''-pentathiophene, 5-bromothiophene-2-carboxynitrile, potassium carbonate, and tetrakis(triphenylphosphine)palladium (0) were mixed in a molar ratio of 1:3:2:0.05 (5 mol%) ((1 mmol, 570.4 mg):(3 mmol, 564.2 mg):(2 mmol, 276.4 mg):(0.05 mmol, 57.8 mg)), and dried N,N-dimethylacetamide (20 mL) was added. The reaction was stirred at 120 °C for 48 hours under argon protection. After the reaction was completed, the mixture was slowly cooled naturally for 12 hours, then diluted and quenched with deionized water, filtered, collected, and concentrated to obtain a solid crude product. The crude product was dissolved in a mixture of ethyl acetate and petroleum ether (1:1, v / v) at room temperature. The supernatant was collected by centrifugation, concentrated, and recrystallized four times. After recrystallization, the product was dried under vacuum at 60°C for 24 hours to separate the purified dicyanothiophene precursor, denoted as 6Th.

[0054] Example 16 6Th was mixed with anhydrous ZnCl2 at a molar ratio of 1:5 (653 mg: 680 mg), placed in a high-vacuum flask, and circulated three times by cooling, evacuation, and nitrogen purging before sealing. 50 mL of anhydrous N,N-dimethylformamide was then injected, and the mixture was reacted at 120 °C for 36 hours. After the reaction, the mixture was allowed to cool naturally to room temperature, and methanol was added to quench the reaction. The solid was collected by filtration, washed with a large amount of methanol, and then collected again. Purification was then performed using Soxhlet extraction. Specifically, the obtained solid was wrapped in filter paper and placed in an extraction apparatus. 180 mL of extraction solvent was added to a 250 mL extraction flask each time, and extraction was performed for 12 hours with each solvent. The extracts were not collected. The extraction solvents were, in order, deionized water, ethanol, acetonitrile, and acetone. After extraction, the solid was dried under vacuum at 60 °C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-5Th.

[0055] Example 17 In an anhydrous and oxygen-free environment, 6Th was placed in a reaction vessel, and trifluoromethanesulfonic acid was slowly added dropwise under nitrogen protection at -10°C to 0°C, with a 6Th to TfOH molar ratio of 1:5. After mixing, the mixture was transferred to room temperature and reacted for 3 hours, followed by heat treatment at 80°C for 24 hours. After heat treatment, the mixture was cooled to room temperature, and the reaction was quenched with supercooled deionized water. The solid was repeatedly washed with 0.1 mol / L ammonia and methanol, and then purified by Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone, respectively, for 12 hours with each solvent. The solid was then dried under vacuum at 60°C for 24 hours to obtain a thiophene-triazine functionalized covalent organic semiconductor, denoted as P-6Th.

[0056] Characterization and testing The morphology of P-1Th, P-2Th, P-3Th, P-4Th, P-5Th, and P-6Th prepared in Examples 1, 4, 7, 10, 13, and 16 was characterized using transmission electron microscopy. The results are as follows: Figure 3 As shown, where, Figure 3 In this context, 'a' represents the P-1Th high-performance organic semiconductor prepared in Example 1. Figure 3 In this context, b represents the P-2Th high-performance organic semiconductor prepared in Example 4; Figure 3 In this context, c represents the P-3Th high-performance organic semiconductor prepared in Example 7; Figure 3 In this context, d represents the P-4Th high-performance organic semiconductor prepared in Example 10; Figure 3 In this context, 'e' represents the P-5Th high-performance organic semiconductor prepared in Example 13. Figure 3 f in the example refers to the P-6Th high-performance organic semiconductor prepared in Example 16.

[0057] Depend on Figure 3 As shown in 'a', P-1Th exhibits a morphological characteristic similar to "thin gauze" or "wrinkled paper," existing as dispersed small clusters without obvious large aggregates, demonstrating good dispersion and sufficient inter-cluster space. The size of individual clusters is approximately 50–150 nm, and the particle packing is relatively loose, indicating that the triazine ring and thiophene unit successfully constructed a layered conjugated framework through polymerization. Electron beams can easily penetrate its layered structure, and the cluster edges exhibit blurred and faint imaging characteristics, indicating that the sample thickness is extremely thin. This helps to shorten the distance photogenerated charge carriers migrate from the material's interior to the surface, thereby effectively suppressing charge recombination and improving photocatalytic efficiency.

[0058] Depend on Figure 3 As shown in b, P-2Th exhibits a fine, loose morphology similar to "silk" or "veil," composed of loose aggregates of even smaller nanoparticles (5–20 nm). The particles are highly dispersed yet finely aggregated, resulting in low overall density and numerous voids, confirming the successful construction of a layered conjugated framework. Its smaller particle size and stronger dispersion allow the electron beam to penetrate the layers without obstruction, while the edge imaging remains faint and blurred, further indicating that the extremely thin sample thickness significantly shortens the carrier migration path and reduces the probability of charge recombination.

[0059] Depend on Figure 3As shown in 'c', P-3Th exhibits a morphology resembling "wrinkled paper" or "stacked gauze," with increased cluster size (~100–300 nm), improved aggregation compared to P-2Th, reduced inter-cluster gaps, and the formation of continuous aggregated regions, while still maintaining a certain degree of looseness. The electron density is slightly higher than P-2Th, and the particle packing density is moderate. Despite the increased cluster size, the electron beam can still penetrate effectively; the faint imaging at the sheet edges indicates that its thickness remains relatively thin, resulting in a short carrier migration distance and maintaining good charge separation efficiency.

[0060] Depend on Figure 3 As can be seen from d, P-4Th exhibits a morphology resembling "wrinkled paper" and "tightly stacked," with large, dense aggregates (~200–500 nm). Agglomeration is significantly intensified, and the layered conjugated framework is retained at higher aggregation levels. The aggregates are dense and blocky, with significantly reduced gaps between aggregates, resulting in tight particle packing and a noticeably deeper grayscale. Electron beam penetration is slightly reduced, but faint, blurred features are still visible at the edges of the sheets, indicating that the sample still maintains a certain thin layered structure, which can shorten the carrier migration path to some extent and suppress charge recombination.

[0061] Depend on Figure 3 As can be seen from the 'e', ​​P-5Th exhibits a dense agglomerate morphology resembling "highly stacked wrinkled paper," with the most significant aggregation forming large, dense clumps (~300–600 nm). There are almost no gaps between particles, and the aggregates are highly dense, irregular blocks. The layered conjugated framework is still preserved even in this tightly aggregated state. It has the darkest grayscale, the highest electron density, a highly enriched structure, and extremely tight particle packing. Although the electron density is significantly increased and the sample thickness is somewhat increased, the presence of the layered structure still reduces the migration distance of charge carriers within the bulk phase, lowering the risk of charge recombination.

[0062] Depend on Figure 3 As can be seen from f, P-6Th exhibits a loose, porous morphology resembling a "thin veil interwoven into a network," composed of fine particles. Its open structure and abundant porosity, coupled with a significantly lighter grayscale compared to P-5Th, confirm the construction of a layered conjugated framework. Electron beams can easily penetrate this framework, not only shortening carrier migration distances but also providing abundant adsorption sites for reactants, further enhancing photocatalytic performance.

[0063] From P-1Th to P-5Th, there is a trend of increasing agglomeration degree and increasing particle packing density, while P-6... Th It has a porous and loose structure, which may be due to the adjustment of the synthesis conditions, which promoted the formation of open aggregates of particles.

[0064] Differences in TEM grayscale also reflect changes in the sample's electron density, indirectly corresponding to the distribution and content of thiophene structures: the darker the grayscale, the higher the enrichment of thiophene structures or the higher the particle packing density (e.g., P-5Th); the lighter the grayscale, the finer the particles or the lower the thiophene content (e.g., P-2Th).

[0065] The P-1Th, P-2Th, P-3Th, P-4Th, and P-5Th bifunctional organic semiconductors prepared in Examples 1, 4, 7, 10, and 13 were characterized by ultraviolet-visible-near-infrared diffuse reflectance spectroscopy. The resulting optical bandgap diagrams are shown below. Figure 4 As shown. Among them, Figure 4 In this diagram, 'a' represents the UV-Vis-NIR diffuse reflectance spectrum of P-1Th in Example 1. Figure 4 b in the figure represents the optical band gap diagram of the 2D nanosheets of the alkynyl-functionalized covalent triazine polymer in Example 1. Figure 4 In the diagram, c represents the UV-Vis-NIR diffuse reflectance spectrum of P-2Th in Example 4. Figure 4 In the figure, d represents the optical band gap diagram of the 2D nanosheets of the alkynyl-functionalized covalent triazine polymer in Example 4; Figure 4 In this context, 'e' represents the UV-Vis-NIR diffuse reflectance spectrum of P-3Th in Example 7. Figure 4 f in Example 7 is the optical band gap diagram of the alkynyl-functionalized covalent triazine polymer two-dimensional nanosheets. Figure 4 In this context, g represents the UV-Vis-NIR diffuse reflectance spectrum of P-4Th in Example 10. Figure 4 In the figure, h represents the optical band gap diagram of the acetylation-functionalized covalent triazine polymer two-dimensional nanosheets in Example 10; Figure 4 In this diagram, i represents the UV-Vis-NIR diffuse reflectance spectrum of P-5Th in Example 13. Figure 4 In the figure, j represents the optical band gap diagram of the two-dimensional nanosheets of the alkynyl functionalized covalent triazine polymer in Example 13.

[0066] Depend on Figure 4 As shown in 'a', P-1Th exhibits strong absorption in the ultraviolet-visible region of 300–600 nm, with the absorption intensity gradually decreasing as the wavelength increases. It still retains some absorption capacity in the near-infrared region of 900–1200 nm, indicating a basic response to ultraviolet-visible light. Its absorption edge is located around 415 nm, and the overall absorption is biased towards the shorter wavelength region.

[0067] Depend on Figure 4 As shown in 'c', P-2Th exhibits a significant redshift in absorption, with strong absorption in the visible light region of 300–800 nm. Its absorption intensity in the near-infrared region (900–1200 nm) is significantly higher than that of P-1Th, broadening its response range to visible light. Its absorption edge redshifts to ~506 nm, enhancing its ability to capture medium- and long-wavelength visible light.

[0068] Depend on Figure 4 As can be seen from the 'e', ​​P-3Th absorption undergoes a further redshift, exhibiting significant absorption in the visible-near-infrared region from 300 to 1000 nm, with continuously enhanced absorption in the near-infrared region, thus improving its response to longer wavelengths of light. Its absorption edge redshifts to ~643 nm, covering more of the visible light spectrum and part of the near-infrared band.

[0069] Depend on Figure 4 As can be seen from g, P-4Th absorption continues to redshift, maintaining high absorption intensity in the 300–1100 nm range, with further enhancement in the near-infrared region, and also exhibiting responsiveness to longer wavelengths of near-infrared light. Its absorption edge redshifts to ~663 nm, and the redshift trend in light absorption continues.

[0070] Depend on Figure 4 As shown in the figure, P-5Th exhibits the most significant redshift in absorption, demonstrating strong absorption across the entire visible-near-infrared region from 300 to 1200 nm. Its near-infrared absorption intensity is the highest among the five groups, indicating the widest range of solar energy utilization. Its absorption edge redshifts to ~713 nm, effectively capturing both visible and near-infrared light.

[0071] Figure 4 The results for b, d, f, h, and j show that the optical band gaps of P-1Th, P-2Th, P-3Th, P-4Th, and P-5Th are 2.98 eV, 2.45 eV, 1.93 eV, 1.87 eV, and 1.74 eV, respectively.

[0072] From P-1Th to P-5Th, the samples exhibit a continuous redshift of the absorption edge and a gradual narrowing of the optical band gap. This trend stems from the extension of the material's conjugated framework, including an increased proportion of thiophene units and improved polymerization degree, which expands the delocalization range of π electrons, thereby reducing the energy required for electronic transitions.

[0073] Narrowing the band gap and widening the absorption range directly improves the material's utilization efficiency of visible and near-infrared light, helps increase the generation of photogenerated carriers, and thus exhibits better performance in applications such as photocatalysis.

[0074] Example 18 50 mg of the thiophene and triazine functionalized covalent organic semiconductor P-1Th obtained in Example 1 was added to a quartz bottle containing 50 mL of deionized water. The dispersion was sonicated in the dark for 30 minutes to achieve good dispersibility in water. Then, argon gas was continuously introduced into the dark for 30 minutes, and the bottle was sealed with a rubber stopper. A 300-watt xenon lamp was used as the light source, and a 420 nm filter was configured to obtain visible light (λ>420 nm). Every hour, 1 mL of the upper gas was extracted from the quartz bottle, and the hydrogen and oxygen yields were determined using a Shimadzu GC-2014C gas chromatograph.

[0075] Example 19 50 mg of the thiophene and triazine functionalized covalent organic semiconductor P-2Th obtained in Example 4 was added to a quartz bottle containing 50 mL of deionized water. The dispersion was sonicated for 5 minutes to achieve good dispersibility in the water. Argon gas was then continuously introduced for 30 minutes, and the bottle was sealed with a rubber stopper. The photocatalytic experiment used a 300-watt xenon lamp as the light source, and a 420 nm filter was used to obtain visible light (λ>420 nm). Every hour, 1 mL of the upper gas layer was extracted from the quartz bottle, and the hydrogen and oxygen yields were measured using a Shimadzu GC-2014C gas chromatograph.

[0076] Example 20 50 mg of the thiophene and triazine functionalized covalent organic semiconductor P-3Th obtained in Example 1 was added to a quartz bottle containing 50 mL of deionized water. The dispersion was sonicated for 5 minutes to achieve good dispersibility in water. Argon gas was then continuously introduced for 30 minutes, and the bottle was sealed with a rubber stopper. A 300-watt xenon lamp was used as the light source, and a 420 nm filter was configured to obtain visible light (λ>420 nm). Every hour, 1 mL of the upper gas was extracted from the quartz bottle, and the hydrogen and oxygen yields were determined using a Shimadzu GC-2014C gas chromatograph.

[0077] Example 21 50 mg of the thiophene and triazine functionalized covalent organic semiconductor P-4Th obtained in Example 4 was added to a quartz bottle containing 50 mL of deionized water. The dispersion was sonicated for 5 minutes to achieve good dispersibility in the water. Argon gas was then continuously introduced for 30 minutes, and the bottle was sealed with a rubber stopper. The photocatalytic experiment used a 300-watt xenon lamp as the light source, and a 420 nm filter was used to obtain visible light (λ>420 nm). Every hour, 1 mL of the upper gas layer was extracted from the quartz bottle, and the hydrogen and oxygen yields were measured using a Shimadzu GC-2014C gas chromatograph.

[0078] Example 22 50 mg of the thiophene and triazine functionalized covalent organic semiconductor P-5Th obtained in Example 4 was added to a quartz bottle containing 50 mL of deionized water. The dispersion was sonicated for 5 minutes to achieve good dispersibility in the water. Argon gas was then continuously introduced for 30 minutes, and the bottle was sealed with a rubber stopper. The photocatalytic experiment used a 300-watt xenon lamp as the light source, and a 420 nm filter was used to obtain visible light (λ>420 nm). Every hour, 1 mL of the upper gas was extracted from the quartz bottle, and the hydrogen and oxygen yields were measured using a Shimadzu GC-2014C gas chromatograph.

[0079] The water splitting performance of P-1Th, P-2Th, P-3Th, P-4Th, and P-5Th in an argon-saturated pure water system was tested, and the cumulative amount of reaction products changed over time as follows: Figure 5 As shown in the figure. The results indicate that the P-5Th prepared in Example 16 had the highest H2 yield, approximately 400 μmolg / g after 4 hours. -1 The H2 yield was significantly better than that of P-1Th prepared in Example 1 (200 μmol / g). -1 Following the principle that "the narrower the band gap, the higher the activity," the overall yield of H2 was significantly lower than that of O2, indicating that the catalytic system has a higher charge utilization efficiency in the oxygen evolution half-reaction. By adjusting the length of the thiophene chain in the polymerization unit, the catalytic performance of the organic semiconductor material can be effectively controlled.

[0080] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A thiophene / triazine functionalized covalent organic semiconductor, characterized in that, Its structural formula is: Where n is an integer from 1 to 6.

2. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 1, characterized in that, Includes the following steps: A thiophene halogen precursor, a palladium catalyst, a base, 5-bromothiophene-2-carboxynitrile, and a polar aprotic solvent were mixed and coupled to obtain a dicyano-containing thiophene precursor. Thiophene- and triazine-functionalized covalent organic semiconductors are obtained by cyclotrimerization of dicyano-containing thiophene precursors in a solvent containing Lewis acids, or by cyclotrimerization catalyzed by trifluoromethanesulfonic acid. The reaction generates thiophene and triazine-functionalized covalent organic semiconductors.

3. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 2, characterized in that, The general structural formula of the dicyano-containing thiophene precursor is: Where n is an integer from 1 to 6.

4. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 2, characterized in that, The thiophene halide precursors are: 2,5-dibromothiophene, 2,5-diiodothiophene, 2,5-dichlorothiophene, 5,5'-dibromo-2,2'-bithiophene, 5,5'-diiodo-2,2'-bithiophene, 5,5'-dichloro-2,2'-bithiophene, 5,5''-dibromo-2,2':5',2''-trithiophene, 5,5''-diiodo-2,2':5',2''-trithiophene, 5,5''-dichloro-2,2':5',2''-trithiophene, 5,5'''-dibromo-2,2':5',2''-tetrathiophene, 5,5'''-diiodo-2,2':5',2''-tetrathiophene, 5,5'''-dichloro- 2,2':5',2'':5'',2'''-one or more of tetrathiophenes.

5. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 2, characterized in that, The alkali is one or more of the following: potassium carbonate, cesium carbonate, sodium carbonate, potassium phosphate, sodium acetate, potassium acetate, potassium tert-valerate, potassium tert-butoxide, and triethylamine.

6. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 2, characterized in that, The palladium catalyst comprises a palladium source and a ligand. The palladium source comprises one or more of tetra(triphenylphosphine)palladium (0), palladium acetate (II), palladium chloride (II), bis(benzylnitrile)palladium chloride (II), and allyl palladium chloride (II) dimer. The ligand comprises one or more of triphenylphosphine, tricyclohexylphosphine, biarylphosphine, phosphine ligand, and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-yl group.

7. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 6, characterized in that, The molar ratio of the thiophene halide, 5-bromothiophene-2-carboxynitrile, base, and palladium catalyst is 1:(1.5-2):(2-2.5):0.05, wherein the concentration of the palladium source in the palladium catalyst is 5 mol.

8. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 2, characterized in that, The methods for generating thiophene and triazine-functionalized covalent organic semiconductors via cyclotrimerization include the following two: Method 1: Dissolve the dicyano-containing thiophene precursor in an anhydrous and degassed solvent, and add Lewis acid catalyst to the solution; place the reaction system under an inert atmosphere and stir and reflux in a heated oil bath; after the reaction is completed, cool, separate, filter, wash and dry to obtain the product. Method 2: In an anhydrous and oxygen-free environment, the thiophene precursor containing dicyano groups is mixed with trifluoromethanesulfonic acid under an inert gas atmosphere, then transferred to room temperature for reaction, followed by heat treatment, then cooling to room temperature to quench the reaction, washing the product, and then purifying and drying it to obtain the final product.

9. The method for preparing thiophene and triazine functionalized covalent organic semiconductors according to claim 8, characterized in that, In Method 1: the Lewis acid is any one of zinc chloride, aluminum chloride, and ferric chloride; the molar ratio of the dicyano-containing thiophene precursor to the Lewis acid is preferably 1:1-30; In Method 2, the molar ratio of the dicyano-containing thiophene precursor to trifluoromethanesulfonic acid is 1:1-10.

10. The application of the thiophene and triazine functionalized covalent organic semiconductor of claim 1 in photocatalytic water splitting for hydrogen production and oxygen evolution.

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