Methoxyallyloxy mixed side chain triazacrown alkenyl cofs, methods of making and using the same

Abstract

The application discloses a methoxy allyloxy mixed side chain triazacrown alkene COF and a preparation method and application thereof, relates to the technical field of porous organic polymer materials, and aims to overcome the defect that the active site of a COF photocatalyst is single in the prior art.The COF is connected to an aromatic aldehyde group monomer through an imine bond by a triphenylamine connecting arm, and is prepared by condensation reaction of an amine group monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthrolin-2,6,10-triyl)triphenylamine, an aldehyde group monomer 2,5-dimethoxyterephthaldehyde and an aldehyde group monomer 2,5-bisallyloxyterephthaldehyde under catalysis of acetic acid.The application can realize efficient photocatalytic synthesis of hydrogen peroxide and degradation of organic pollutants in water under visible light, and has excellent chemical stability and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of porous organic polymer materials technology. More specifically, this invention relates to a methoxyallyloxy mixed-side-chain triazacrownenyl COF, its preparation method, and its applications. Background Technology

[0002] Covalent organic frameworks (COFs) are crystalline porous polymer materials composed of organic building blocks connected by covalent bonds. They have advantages such as designable structure, high specific surface area, regular pores, good chemical stability and strong visible light response, making them ideal platform materials for constructing efficient photocatalysts.

[0003] Hydrogen peroxide is an important green oxidant, widely used in chemical, textile, and water treatment industries, with water as the only oxidation byproduct. Industrially, the anthraquinone process for hydrogen peroxide production is energy-intensive and complex. A green and sustainable route for photocatalytic synthesis of hydrogen peroxide, using water and oxygen as raw materials and driven by solar energy, hinges on the development of efficient and stable photocatalysts. Meanwhile, wastewater from industries such as textiles, dyeing, and pharmaceuticals contains large amounts of recalcitrant organic dyes, antibiotics, and phenolic pollutants. Photocatalytic advanced oxidation can oxidize these pollutants to carbon dioxide and water at ambient temperature and pressure, making it an ideal approach for water purification. In 2020, Van Der Voort's research group first reported a COF-based photocatalyst based on a (diarylamino)-benzene linker for the photocatalytic generation of H2O2. This material exhibited excellent photocatalytic activity in the reaction, laying an important foundation for the design, modification, and application of subsequent COF-based photocatalysts.

[0004] However, existing COF-based photocatalysts still suffer from problems such as single active sites, easy recombination of photogenerated electrons and holes, and narrow visible light absorption range, resulting in low yields, low quantum efficiency, and limited mass transfer kinetics in the photocatalytic synthesis of hydrogen peroxide. Although attempts have been made to introduce nitrogen-containing heterocycles, functional groups, and side chain modifications, targeted designs are still lacking, and the overall performance cannot yet meet the needs of practical applications.

[0005] Therefore, it is necessary to design a technical solution that can overcome the above-mentioned defects. Summary of the Invention

[0006] One objective of this invention is to provide a methoxyallyloxy mixed side chain triazacrownenyl COF, its preparation method, and its application, aiming to overcome the problems of existing technologies such as single active site, easy recombination of photogenerated electrons and holes, and narrow visible light absorption range.

[0007] To achieve these objectives and other advantages of the present invention, according to one aspect of the present invention, a methoxyallyloxy mixed-side-chain triazacrownenyl COF is provided, with the following structural formula: .

[0008] According to another aspect of the present invention, a preparation method is also provided, wherein an amino monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine, an aldehyde monomer 2,5-dimethoxyterephthalaldehyde, and an aldehyde monomer 2,5-diallyloxyterephthalaldehyde are condensed under the catalysis of acetic acid to obtain a methoxyallyloxy mixed side chain triazacrownene COF.

[0009] Further, the amino monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine is prepared by the following steps: reacting o-phenylenedimethyl ether in the presence of anhydrous ferric chloride and concentrated sulfuric acid to obtain 2,3,6,7,10,11-hexamethoxytriphenylene; reacting 2... 3,6,7,10,11-Hexamethoxytriphenylene reacts with fuming nitric acid to give 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-trinitro; 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-trinitro reacts with sodium borohydride in the presence of nickel acetate tetrahydrate to give 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-trinitro Amine; 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-triamine was reacted with p-nitrobenzaldehyde in the presence of trifluoromethanesulfonic acid to give 3,4,7,8,11,12-hexamethoxy-2,6,10-tris(4-nitrophenyl)benzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline; 3,4,7,8,11,12-hexamethoxy -2,6,10-tris(4-nitrophenyl)benzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline reacts with hydrogen in the presence of palladium activated carbon to give 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine.

[0010] Further, the aldehyde monomer 2,5-diallyloxy-terephthalaldehyde is prepared by the following steps: reacting 2,5-dimethoxy-terephthalaldehyde with boron tribromide to obtain 2,5-dihydroxy-terephthalaldehyde; reacting 2,5-dihydroxy-terephthalaldehyde with allyl bromide in the presence of potassium carbonate to obtain 2,5-diallyloxy-terephthalaldehyde.

[0011] Further, the aldehyde monomer 2,5-dimethoxy-terephthalaldehyde is prepared by the following steps: reacting 1,4-dimethoxybenzene with liquid bromine to obtain 1,4-dibromo-2,5-dimethoxybenzene; reacting 1,4-dibromo-2,5-dimethoxybenzene with n-butyllithium and then with N,N-dimethylformamide to obtain 2,5-dimethoxy-terephthalaldehyde.

[0012] According to another aspect of the invention, the application of methoxyallyloxy mixed-side-chain triazacrownenyl COF in the photocatalytic synthesis of hydrogen peroxide is provided.

[0013] According to another aspect of the present invention, the application of methoxyallyloxy mixed-side-chain triazacrownene COF in the photocatalytic degradation of organic pollutants in water is provided.

[0014] This invention offers at least the following advantages: Addressing the issues of single active sites and insufficient adsorption and activation capacity, the nitrogen-rich triazacrownene core provides ample active sites for the oxygen reduction reaction, significantly enhancing the adsorption and activation capacity of reactants. The synergistic effect of the methoxy and allyloxy side chains regulates the internal hydrogen bond network and interfacial microenvironment of the material, resulting in superior photocatalytic activity compared to single-side-chain COFs. Addressing the issue of easy recombination of photogenerated electrons and holes, the strong π-conjugation of the core and the well-ordered two-dimensional framework endow the material with excellent photoelectric properties, high charge separation efficiency, and effective suppression of carrier recombination. Addressing the issue of limited visible light absorption, the material exhibits broad absorption in the visible light region, a moderate optical band gap, and band structure that meets the thermodynamic requirements for photocatalytic synthesis of hydrogen peroxide. The material is resistant to strong acids, strong alkalis, and common organic solvents, maintaining stable performance after five cycles.

[0015] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0016] Figure 1 The Fourier transform infrared (FT-IR) spectra of monomer OMe-TAC-NH2, aldehyde monomer DMTA and DATA, and the compound of this invention were compared to confirm the occurrence of the imine condensation reaction.

[0017] Figure 2 This is the PXRD pattern of the compound of the present invention.

[0018] Figure 3 This is a scanning electron microscope (SEM) image of the compound of the present invention.

[0019] Figure 4 The thermogravimetric (TGA) curves of the compounds of this invention under a nitrogen atmosphere are shown.

[0020] Figure 5The N2 adsorption-desorption isotherms and pore size distribution curves of the compounds of this invention are shown.

[0021] Figure 6 This is the UV-vis DRS spectrum of the compound of this invention.

[0022] Figure 7 This is a Tauc curve plotted based on UV-vis DRS in this invention.

[0023] Figure 8 The Mott-Schottky curves of the compounds of this invention at different frequencies (1000 Hz, 1500 Hz, 2000 Hz) are shown.

[0024] Figure 9 The chemical stability test results of the compounds of this invention are shown in (a) FT-IR, (b) PXRD, and (c) comparison of residual mass.

[0025] Figure 10 The time curves for the photocatalytic synthesis of H2O2 by the compounds of this invention in oxygen-saturated pure water systems under oxygen and air atmospheres are shown.

[0026] Figure 11 The figure shows the stability test curve of the compound of this invention in the photocatalytic synthesis of H2O2 in oxygen-saturated pure water after 5 cycles.

[0027] Figure 12 This is a comparison of the FT-IR spectra of the compound of the present invention before and after 5 photocatalytic cycles.

[0028] Figure 13 This is a comparison of the PXRD spectra of the compound of the present invention before and after 5 photocatalytic cycles.

[0029] Figure 14 The images show a comparison of the SEM morphology of the compound before and after five photocatalytic cycles. Detailed Implementation

[0030] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0031] It should be understood that terms such as "having," "comprising," and "including" used in the embodiments of this application do not exclude the presence or addition of one or more other elements or combinations thereof. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. When an element is referred to as "fixed to" or "set on" another element, it can be directly on the other element or may have an intervening element present. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element through an intervening element. Descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0032] It should be noted that the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0033] 1. Compound Description

[0034] The compounds of this invention are constructed by a Schiff base condensation reaction of the triamine monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine (OMe-TAC-NH2) with the dialdehyde monomers 2,5-dimethoxyterephthalaldehyde (DMTA) and 2,5-bis(allyloxy)terephthalaldehyde (DATA). The skeleton is connected by imine bonds (C=N), thus yielding a triazacrownenyl COF with mixed methoxyallyl side chains.

[0035] The structure is as follows:

[0036] , where … represents the periodic repetition and extension of the above structure.

[0037] The compound of this invention exhibits a two-dimensional layered structure with hexagonal symmetry, consisting of stacked AA atoms. The TAC core in the framework retains six methoxy groups, while methoxy and allyloxy side chains are simultaneously introduced onto the benzene ring of the linker, with these two types of side chains alternating. The introduction of mixed methoxy and allyloxy side chains endows the material with a unique porous microenvironment: the methoxy side chains can form a strong hydrogen bond network, and the sp2 hybridized C=C bonds in the allyloxy side chains have strong electronegativity. Their electronic effects influence the p-π conjugation between the oxygen atoms of the side chains and the benzene ring, both of which jointly affect the hydrogen bond interactions and charge carrier dynamics within the material. Intralayer C–H···N and C–H···O hydrogen bonds, as well as interlayer C–H···O hydrogen bonds, still exist within the TAC core unit.

[0038] The compound of this invention has a highly ordered mesoporous structure with a specific surface area of ​​866 m². 2 g -1 The pore size is mainly concentrated at 3.30 nm. The material exhibits excellent crystallinity, thermal stability, and chemical stability, and possesses a suitable band structure. Both its valence and conduction band positions meet the band requirements for the photocatalytic synthesis of H₂O₂, allowing for the simultaneous passage of 2e⁻. − Oxygen reduction reaction (ORR) and 4e − The water oxidation reaction (WOR) pathway is used for the photocatalytic synthesis of H2O2. The three pyridine nitrogen atoms in the TAC core of the framework can serve as active sites for the oxygen reduction reaction, accelerating the photocatalytic generation of H2O2.

[0039] 2. Compound Synthesis

[0040] The synthesis route diagram is as follows:

[0041] (a) Synthesis of monomers

[0042] 1. Synthesis of 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine (OMe-TAC-NH2)

[0043] (1) Synthesis of 2,3,6,7,10,11-hexamethoxytriphenylene (compound 1):

[0044] Add 50 mL of dichloromethane to a dry 250 mL flask, followed by 17.6 g of anhydrous ferric chloride (108.6 mmol), and stir to form a suspension. Place the suspension in an ice-water bath at 0 °C, and add 0.25 mL of concentrated sulfuric acid dropwise. Then, slowly add 25 mL of dichloromethane solution containing 36.2 mmol of o-phenylenediamine (4.6 mL) dropwise to the ferric chloride system over 15 min. After the addition is complete, slowly heat the reaction mixture to room temperature while stirring, and continue the reaction for 3 h. After the reaction is complete, slowly add 75 mL of methanol in portions to terminate the reaction until the system changes from a thick, tarry black slurry to a uniform, turbid yellow suspension. After the methanol is added, continue stirring the reaction system for 30 min, then filter under reduced pressure to obtain a grayish-white solid, wash thoroughly with methanol (5 times, 50 mL each time), and dry under reduced pressure at 60 °C to obtain pure compound 1 (5.03 g, yield 91%). 1 H NMR (400 MHz, DMSO-d6) δ 8.02 (s, 6H), 4.06 (s, 18H).

[0045] (2) Synthesis of 2,3,6,7,10,11-hexamethoxy-1,5,9-trinitrotriphenylene (compound 2):

[0046] 2,3,6,7,10,11-hexamethoxytriphenylene (1, 3.00 g) was suspended in a mixed solvent of 15.0 mL each of acetic acid, diethyl ether, and chloroform. After stirring to ensure uniform dispersion, fuming nitric acid (3.1 mL, density 1.52 g·cm³) was slowly added dropwise. −3 After the addition was complete, the mixture was heated to reflux and stirred continuously for 6 h. After the reaction was complete, most of the mixed solvent was removed by vacuum distillation. The remaining solution was slowly poured into water, followed by vacuum filtration. The filter cake was washed with a large amount of distilled water to obtain an orange-yellow solid, which was then dried under reduced pressure at 60 °C for 8 h. The crude product was purified by silica gel column chromatography (eluent: chloroform). The purified product was then recrystallized from the chloroform / ethanol mixed solvent to finally obtain yellow needle-like crystals 2 (1.06 g, yield 25%).

[0047] (3) Synthesis of 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-triamine (compound 3):

[0048] To a 500 mL round-bottom flask equipped with a magnetic stirrer, add 1,5,9-trinitro-2,3,6,7,10,11-hexamethoxytriphenylene (2, 5.0 g, 9.2 mmol), followed by 200 mL of a tetrahydrofuran / methanol (THF / MeOH, v / v) mixture. Stir until the substrate is fully dissolved. Add nickel acetate tetrahydrate (Ni(OAc)₂·4H₂O, 2.3 g, 9.2 mmol) to the resulting solution and continue stirring for 5 min. Then, add sodium borohydride (NaBH₄, 5.22 g, 138.0 mmol) in portions to the reaction system; a fine black precipitate forms immediately upon addition. Continue stirring the reaction and monitor the reaction progress by thin-layer chromatography (TLC) until the starting material is undetectable. After the reaction was completed, 100 mL of distilled water was added to the system to quench the reaction, and the solvent in the filtrate was evaporated under reduced pressure. The residue was purified by recrystallization from ethanol to obtain a gray solid (4.0 g, 96%). 1 H NMR (400MHz, DMSO-d6) δ 8.11 (s, 3H), 5.13 (s, 6H), 3.92 (s, 9H), 3.80 (s, 9H).

[0049] (4) Synthesis of 3,4,7,8,11,12-hexamethoxy-2,6,10-tris(4-nitrophenyl)benzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline (compound 4):

[0050] 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-triamine (3, 50.0 mg; 0.110 mmol) and p-nitrobenzaldehyde (29.6 mg; 0.165 mmol), 2 mL DMF, and trifluoromethanesulfonic acid (120 μL) were added to a round-bottom flask. The reaction system was stirred at 120 °C for 72 h. The solvent in the system was removed by vacuum filtration. The resulting filter cake was washed repeatedly with deionized water, ethanol, and acetone to thoroughly remove impurities, and then dried under vacuum to finally obtain 31 mg of a yellow solid product. 1 H NMR (400 MHz, Chloroform-d) δ 8.54 (d, J = 8.7 Hz, 6H), 8.10 (d, J = 8.6 Hz, 6H), 4.55 (s, 9H), 3.87 (s, 9H).

[0051] (5) Synthesis of OMe-TAC-NH2:

[0052] Under an argon atmosphere, compound 4 (70 mg), ethanol, and 10% Pd / C were placed into a side-mounted reaction flask and washed three times with H2 until the final pressure reached 60 psi. The reaction system was stirred and heated at 80 °C for 72 h, cooled to room temperature, and then filtered. The black solid was washed successively with ethanol and acetone until the filtrate was clear. The organic phases were combined, and the organic solvent was removed by rotary evaporation to obtain 53 mg of a yellow solid. 1 H NMR (400 MHz, DMSO-d6) δ 7.69 (d, J = 8.3 Hz, 6H), 7.12–6.54(m, 6H), 5.50 (s, 6H), 4.47 (s, 9H), 3.70 (s, 9H).

[0053] 2. Synthesis of Aldehyde Monomers

[0054] (1) Synthesis of 2,5-dimethoxy-terephthalaldehyde (DMTA):

[0055] Under a nitrogen atmosphere, 500 mg of 1,4-dibromo-2,5-dimethoxybenzene (1.67 mmol) was dissolved in 8.5 mL of anhydrous and oxygen-free dry THF. The reaction system was cooled to -78 °C in a cryogenic bath. Then, a 1.6 M n-butyllithium solution (dissolved in hexane, 2.3 mL, 3.68 mmol) was slowly added dropwise. After the addition was complete, the temperature was raised to -60 °C, and the reaction was stirred for 3 h. After the reaction was complete, the system was cooled again to -78 °C, and 0.6 mL of DMF was added. After the addition was complete, the cryogenic bath was closed, and the system was allowed to slowly warm to room temperature while stirring for 1 h. A saturated ammonium chloride solution was added to quench excess n-butyllithium. The THF solvent was removed by rotary evaporation, and the remaining solution was extracted multiple times with dichloromethane. After merging the organic phases, Na2SO4 was added for drying, and the solvent was removed by rotary evaporation to obtain a yellow solid crude product. After separation and purification by silica gel column chromatography, the bright yellow target product DMTA (185 mg, 57%) was finally obtained.

[0056] (2) Synthesis of 2,5-dihydroxyterephthalaldehyde (DHTA):

[0057] Under a nitrogen atmosphere, 900 mg of DMTA (4.64 mmol) was weighed and dissolved in 20 mL of anhydrous dichloromethane. The reaction system was then cooled to -78 °C. Next, a dichloromethane solution containing boron tribromide (BBr3) (1 M, 20 mL, 20 mmol) was slowly added dropwise. After the addition was complete, the temperature of the reaction system was slowly increased to room temperature, and the reaction was continued with stirring for 12 h. Once the reaction reached its endpoint, the reaction mixture was slowly poured into 40 mL of deionized water, and the resulting mixture was extracted three times with dichloromethane. All organic phases were combined, dried over anhydrous MgSO4, and the solvent was removed by rotary evaporation to obtain the yellow-green target product (730 mg, 94.8%). 1 H NMR (400 MHz, DMSO-d6) δ 10.32 (s, 2H), 10.30 (s, 2H), 7.23 (s, 2H).

[0058] (3) DATA synthesis:

[0059] To a 7 mL mixture of anhydrous N,N'-dimethylformamide (DMF) containing dissolved DHTA (300 mg, 1.8 mmol) and potassium carbonate (K₂CO₃, 750 mg, 5.44 mmol), 0.43 mL of allyl bromide (4.0 mmol) was added dropwise. The reaction mixture was heated to 80 °C and stirred overnight. After the reaction was complete, distilled water was added to the mixture to allow the product to precipitate completely. The mixture was then extracted three times with ethyl acetate. The organic phases were combined and dried over anhydrous Na₂SO₄. The organic solvent was removed by rotary evaporation, and the residue was purified by silica gel column chromatography to obtain the yellow target product DATA (323 mg, 77%). 1 H NMR (400 MHz, Chloroform-d) δ 10.54 (s, 1H), 7.45 (s, 1H), 6.40-5.84 (m, 1H), 5.46 (dd, J = 17.3, 1.6 Hz, 1H), 5.37-5.17 (m, 1H), 4.68 (d, J = 5.3 Hz, 1H).

[0060] (II) Synthesis of the compounds of this invention

[0061] Weigh 20.69 mg of OMe-TAC-NH2 (0.03 mmol), 4.4 mg of DMTA (0.028 mmol), and 5.4 mg of DATA (0.028 mmol) and add them to a Pyrex tube. Then add 0.5 mL of o-dichlorobenzene (o-DCB), 0.1 mL of 6 M acetic acid aqueous solution, and 0.5 mL of n-butanol (n-BuOH) sequentially. Sonicate for 15 min. After sonication, the Pyrex tube is subjected to three vacuum freeze-drying treatments for degassing. After degassing, the tube opening is sealed with a flame. Once the sealed Pyrex tube has returned to room temperature, it is placed in an 80 °C oven for 72 h. After the reaction, the Pyrex tube is removed and allowed to cool naturally to room temperature. The sealed tube opening is opened, and the solid product is collected by vacuum filtration. The solid product is then washed repeatedly with tetrahydrofuran (THF) and acetone alternately to thoroughly remove unreacted raw materials and impurities. The washed solid was dried in a vacuum drying oven at 80 °C for 6 h to obtain a yellow, fluffy solid powder of the compound of the present invention, with a separation yield of 96%.

[0062] 3. Characterization of compounds

[0063] To confirm the chemical composition, crystal structure, morphological characteristics, and pore structure of the synthesized compound of the present invention, the following systematic characterization was performed.

[0064] 3.1 Fourier Transform Infrared Spectroscopy (FT-IR)

[0065] like Figure 1 As shown, in the FT-IR spectrum, the N–H stretching vibration peak of the reactant amino monomer OMe-TAC-NH2 (located at 3,300–3,400 cm⁻¹) is... -1 The bimodal distribution of the interval) and DMTA (-CHO at 1,681 cm⁻¹) -1 ) and DATA (-CHO is located at 1,682cm -1 The C=O stretching vibration peak was significantly weakened or almost disappeared; meanwhile, at 1,603 cm⁻¹... -1 The characteristic stretching vibration peak at the C=N imine bond appears. This indicates that an imine condensation reaction occurred between the amine and aldehyde groups, forming a covalent organic framework. The peak is located at 2,800–3,000 cm⁻¹. -1 The CH stretching vibration peak in the region originates from the sp2 hybridized CH vibration of the allyloxy side chain, 1,000–1,300 cm⁻¹. -1 The COC stretching vibration peak in the region originates from both the asymmetric COC bond in DMTA and the COC bond in the allyloxy side chain, proving that both methoxy and allyloxy side chain groups are completely preserved after COF formation.

[0066] solid state 13 C-cross polarized magic angle rotating nuclear magnetic resonance (C-C) 13 CCP / MAS NMR spectroscopy further corroborates the construction of the imine bond: the solid-state of the compound of this invention... 13 The C CP / MAS NMR spectrum showed a characteristic signal peak at 153.0 ppm, which is attributed to the C=N bond, providing direct structural evidence for the successful formation of the imine bond.

[0067] 3.2 Powder X-ray Diffraction (PXRD)

[0068] like Figure 2 As shown, the PXRD pattern reveals sharp and clear diffraction peaks in the compound of this invention, indicating good crystallinity and the formation of a highly ordered porous framework structure. Obvious (100), (110), (200), and (210) crystal plane diffraction peaks are observed in the low-angle region, while diffraction characteristics belonging to the (001) crystal plane are observed in the high-angle region. To clarify the stacking configuration of the material, two typical stacking models, overlapping (AA) and staggered (AB / ABC), were constructed using Materials Studio software, and the experimental PXRD patterns were compared with the simulated patterns. The results show that the experimental PXRD patterns are in high agreement with the simulated patterns of the AA stacking model, confirming that the material adopts an AA-type stacking mode; the minimum difference curve between the experimental and refined patterns further verifies the reliability of the constructed structural model. The crystal structure of the material was refined using the Pawley refinement method, and the resulting lattice parameters were: a=b=72.868 Å, c=3.604 Å, α=β=90°, γ=120°, Rp=2.9%, Rwp=4.36%.

[0069] 3.3 Scanning Electron Microscopy (SEM)

[0070] Characterization results from field emission scanning electron microscopy (FE-SEM) show that the compound of this invention is composed of near-spherical particles, exhibiting a uniform particle aggregate morphology. The particle surfaces are rough and possess rich texture structures, such as... Figure 3 As shown.

[0071] 3.4 Nitrogen adsorption-desorption test and pore structure

[0072] The porosity of the compounds of this invention was characterized using nitrogen adsorption-desorption isotherms. Figure 5 As shown, the nitrogen adsorption-desorption isotherm exhibits typical type IV adsorption-desorption isotherms, indicating that the material belongs to a mesoporous structure. Based on the Brunauer-Emmett-Teller (BET) model, the specific surface area of ​​the compound of this invention is calculated to be 866 m². 2 g-1 The pore size distribution curve based on the nonlocal density functional theory (NLDFT) model shows that the pore size of the compound of the present invention is mainly concentrated at 3.30 nm, which is consistent with the theoretical pore size predicted based on crystallographic parameters. Figure 5 The numerical values ​​of the BET specific surface area and pore size of the compounds of this invention are displayed visually. These two pore structure parameters provide a material basis for subsequent discussions on their photocatalytic performance (such as the migration rate of photogenerated charges within the pores and the enrichment efficiency of reactant molecules at active sites).

[0073] 3.5 Ultraviolet-Vis Diffuse Reflectance Spectroscopy (UV-vis DRS) and Band Structure

[0074] like Figure 6 As shown, the UV-vis DRS spectrum reveals that the compound of this invention exhibits a broad light absorption range in the visible region, attributed to the conjugated π-π* electronic transition between the triazacrownene core and the imine linker; the optical band gap of the compound of this invention is calculated to be 2.40 eV using the Tauc equation. See [link to Tauc equation]. Figure 7 See also Figure 8 Using Mott-Schottky curves measured at different frequencies, the flat band potential was extrapolated to -1.42 V (vs Ag / AgCl). After conversion to NHE, the conduction band position was -1.22 V (vs NHE, pH=6.8). The MS curve showed a positive slope, indicating that the material has n-type semiconductor characteristics. Combining the optical band gap and the MS curve, the valence band position was determined to be 1.18 V (vs NHE, pH=6.8), which meets the band requirements for photocatalytic synthesis of hydrogen peroxide, indicating that it has the thermodynamic feasibility of photocatalytic synthesis of hydrogen peroxide through two-electron oxygen reduction reaction and four-electron water oxidation pathway.

[0075] 3.6 Thermal stability and chemical stability

[0076] like Figure 4 As shown, the thermal stability of the compound of the present invention was tested under a nitrogen atmosphere. The results showed that the material has excellent thermal stability. Its initial decomposition temperature is as high as 400 °C. When the temperature is raised to 800 °C, the remaining mass of the material can still be maintained at about 71% of the initial mass, indicating that it can withstand high temperature environments.

[0077] Chemical stability was investigated through immersion experiments: the compounds of this invention were immersed in common organic solvents tetrahydrofuran, acetonitrile, methanol, N,N-dimethylformamide, and 12 mol / L hydrochloric acid and 12 mol / L sodium hydroxide aqueous solutions for 72 h, respectively. After immersion, the samples were filtered, washed with tetrahydrofuran, and dried, and then characterized by PXRD and FT-IR tests. PXRD results showed that the compounds of this invention maintained their crystallinity well after immersion in different media; FT-IR spectra further confirmed that the chemical structure and composition of the material remained unchanged. (See [link to relevant documentation]). Figure 9 The above test results fully demonstrate that the prepared compounds of this invention possess excellent thermal and chemical stability and are suitable for various aqueous catalytic reaction systems.

[0078] The characterization results consistently indicate that the synthesized material is a two-dimensional ordered crystalline COF with AA-type stacking, and possesses multiple advantages such as high specific surface area, regular channels, visible light absorption, and excellent stability, laying the material foundation for its subsequent photocatalytic applications.

[0079] 4. Applications of compound synthesis of hydrogen peroxide

[0080] Further research in this invention has revealed that the compound exhibits excellent photocatalytic synthesis performance of hydrogen peroxide (H2O2) under visible light irradiation.

[0081] (1) Direct photocatalytic production of H2O2 from pure water / actual water sample: The compound of the present invention (5 mg) was dispersed in pure water (50 mL), and the reactor was placed on a magnetic stirrer under simulated sunlight (AM 1.5G, 100 mW cm⁻¹). -2 The reaction takes place under irradiation at ambient temperature and normal pressure. For example... Figure 10 As shown, in an oxygen-saturated pure water system, the yield of H2O2 of the compound of the present invention is approximately 5.68 mmol g. -1 h -1 When the reaction is carried out in air, the rate of H2O2 formation is approximately 4.73 mmol g. -1 h -1 .

[0082] Furthermore, the effect of catalyst dosage on the photocatalytic synthesis of H2O2 by the compound of the present invention was investigated. When the amount of the compound of the present invention in a 50 mL pure water system was 1 mg, the yield of H2O2 reached approximately 11.2 mmol g. -1 h -1 When the dosage is 3 mg, the yield of H2O2 is approximately 7.95 mmol g. -1 h -1When the dosage is 5 mg, the yield of H2O2 is approximately 5.68 mmol g. -1 h -1 This indicates that under the experimental conditions, reducing the amount of catalyst can enhance the light absorption capacity of individual particles, thereby increasing the yield of H2O2 per unit mass.

[0083] Subsequently, using different actual water samples such as tap water, seawater, and river water instead of pure water, the photosynthetic rate of H2O2 of the compound of this invention in tap water, seawater, and river water was approximately 5.35 mmol g, respectively. -1 h -1 5.6 mmol g -1 h -1 and 5.7 mmol g -1 h -1 The results are comparable to those of a pure water system, demonstrating the feasibility of the compound of this invention performing H2O2 photocatalysis in different types of real water bodies.

[0084] (2) Cascade reaction with hole sacrificial agent: When isopropanol is added as a hole sacrificial agent in an oxygen-saturated system, the yield of H2O2 of the compound of the present invention increases from 5.68 mmol g in the pure water system. -1 h -1 Increased to approximately 7.7 mmol g -1 h -1 When benzyl alcohol is used as the sacrificial reagent, the H2O2 formation rate is further increased to approximately 10.5 mmol g. -1 h -1 Furthermore, the aromatic skeleton of benzyl alcohol enables a strong π-π interaction between it and the π-extended skeleton of the compound of this invention. Introducing benzyl alcohol to form a two-phase catalytic system can effectively avoid the decomposition of H2O2.

[0085] (3) Quantum efficiency and cycle stability: The apparent quantum yield (AQY) of the compound of this invention was tested in a pure water system under four different monochromatic lights (420 nm, 450 nm, 500 nm, and 550 nm). The AQY reached approximately 7.0% under monochromatic light at 450 nm. Five cycles of photocatalytic H2O2 generation experiments were conducted in an oxygen-saturated pure water system. The compound of this invention maintained excellent H2O2 photosynthesis efficiency in all five cycles. See [link to relevant documentation]. Figure 11 The recovered samples were characterized by FT-IR, PXRD, and SEM. The results showed that the recycled material retained the basic morphology of particle aggregates, and the main crystal structure and chemical composition did not change significantly, fully demonstrating that the material possesses excellent photochemical stability during the photocatalytic reaction. (See [link to relevant documentation]). Figure 12 , Figure 13 and Figure 14 .

[0086] The advantages of the compound in photocatalytic H2O2 production in this invention stem from: the strong electronic coupling between the triazacrownene core and the mixed aldehyde groups of 2,5-dimethoxy-terephthalaldehyde / 2,5-bis(allyloxy)-terephthalaldehyde, which effectively promotes the separation of photogenerated charges; the mixed side chains of methoxy and allyloxy on the inner wall of the pores synergistically regulate the pore microenvironment and hydrogen bond interactions at the molecular scale: the methoxy group provides a strong hydrogen bond network, and the sp2 hybrid C=C of the allyloxy group provides a polar channel and excited state stabilization effect, which synergistically improves the reactant transport efficiency and accelerates the oxygen reduction reaction; the AA-type stacked structure provides an efficient channel for the migration of photogenerated electrons to the surface active sites and inhibits charge recombination.

[0087] 5. Application of compounds in the degradation of organic pollutants in water

[0088] Based on the ability of the compound of this invention to generate H2O2 in situ via photocatalysis, it can be further used for the photocatalytic oxidation of organic pollutants in water. The degradation mechanism is as follows: the H2O2 generated by the photocatalytic reaction of the compound of this invention is itself a strong oxidant, which can further oxidize and decompose organic pollutants in water through reactive oxygen species. Simultaneously, the porous, hydrophilic microenvironment constructed by the TAC core, imine linkages, and allyloxy side chains in the compound's framework can effectively adsorb and enrich organic pollutants in water, shortening the interaction distance between H2O2 and its derived reactive oxygen species and pollutants, thus improving degradation kinetics. This strategy of in-situ H2O2 generation and combined use for the degradation of organic pollutants requires no external oxidant, has mild reaction conditions, is green and economical, and can be applied to the removal of various organic pollutants such as dyes, antibiotics, and phenols.

[0089] 6. Conclusion

[0090] In summary, this invention provides a methoxyallyl-containing mixed-side-chain triazacrownenyl covalent organic framework. The compounds of this invention are prepared by an acetic acid-catalyzed imine condensation reaction of an amino node OMe-TAC-NH2 with an aldehyde linker DMTA and DATA (mixed), exhibiting a two-dimensional AA-type stacked layered structure with a BET specific surface area of ​​approximately 866 m². 2 g -1 The aperture is approximately 3.30 nm and the optical band gap is approximately 2.40 eV.

[0091] The inventiveness of this invention is reflected in the following aspects:

[0092] (1) For the first time, a novel two-dimensional COF was constructed by combining a triazacrownene core with a mixed aldehyde group of DMTA and DATA. The strong π-conjugation and multi-site amino reactivity of the triazacrownene core endowed the COF with a regular hexagonal framework and excellent photoelectric properties. The aldehyde linker simultaneously introduced methoxy (electron-withdrawing at the 2,5-position) and allyloxy (electron-donating at the 2,5-position) dual-type side chains, which synergistically regulated the adsorption and activation ability of the material for O2 and organic pollutant molecules, and optimized the reactant transport kinetics through hydrogen bond network and polar channels. This combination strategy of triazacrownene core + methoxy / allyoxy mixed side chain aldehyde linker has not been reported in the published COF literature.

[0093] (2) The compounds of this invention exhibit significant photocatalytic synthesis of H2O2 under visible light: in an oxygen-saturated pure water system, the H2O2 generation rate is approximately 5.68 mmol g. -1 h -1 Under 450 nm monochromatic light, the AQY is approximately 7.0%. These properties are attributed to the visible light absorption and charge transport capabilities of the triazacrownene core, the synergistic regulation of the reactants and interfacial microenvironment by the mixed methoxy and allyloxy side chains, and the promoting effect of the AA-type stacked structure on photogenerated charge migration.

[0094] (3) The compound of the present invention has the dual functions of photocatalytic synthesis of H2O2 and photocatalytic degradation of organic pollutants in water. It exhibits good visible light response performance, good chemical stability and cycle stability in both reactions, and has broad practical application prospects.

[0095] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A methoxyallyloxy mixed-side-chain triazacrownenyl COF, characterized in that, The structure is as follows: 。 2. The method for preparing the methoxyallyl-mixed side-chain triazacrownene COF as described in claim 1, characterized in that, The amino monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine, the aldehyde monomer 2,5-dimethoxyterephthalaldehyde, and the aldehyde monomer 2,5-diallyloxyterephthalaldehyde were condensed under the catalysis of acetic acid to obtain a triazacrownenyl COF with mixed methoxyallyl side chains.

3. The preparation method according to claim 2, characterized in that, The amino monomer 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthidio[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine was prepared by the following steps: Phthalic dimethyl ether was reacted in the presence of anhydrous ferric chloride and concentrated sulfuric acid to give 2,3,6,7,10,11-hexamethoxytriphenylene. 2,3,6,7,10,11-hexamethoxytriphenylene was reacted with fuming nitric acid to give 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-trinitro; 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-trinitro was reacted with sodium borohydride in the presence of nickel acetate tetrahydrate to give 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-triamine; 2,3,6,7,10,11-hexamethoxytriphenyl-1,5,9-triamine was reacted with p-nitrobenzaldehyde in the presence of trifluoromethanesulfonic acid to give 3,4,7,8,11,12-hexamethoxy-2,6,10-tris(4-nitrophenyl)benzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthreneline; 3,4,7,8,11,12-hexamethoxy-2,6,10-tris(4-nitrophenyl)benzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline was reacted with hydrogen in the presence of palladium activated carbon to give 4,4',4''-(3,4,7,8,11,12-hexamethoxybenzo[lmn]phenanthridine[2,1,10,9-defgh][2,8]phenanthroline-2,6,10-triyl)triphenylamine.

4. The preparation method according to claim 2, characterized in that, The aldehyde monomer 2,5-diallyloxy-terephthalaldehyde is prepared by the following steps: 2,5-Dimethoxy-terephthalaldehyde was reacted with boron tribromide to give 2,5-dihydroxy-terephthalaldehyde; 2,5-Dihydroxyterephthalaldehyde was reacted with allyl bromide in the presence of potassium carbonate to give 2,5-diallyloxyterephthalaldehyde.

5. The preparation method according to claim 2, characterized in that, The aldehyde monomer 2,5-dimethoxy-terephthalaldehyde is prepared by the following steps: 1,4-Dimethoxybenzene was reacted with liquid bromine to give 1,4-dibromo-2,5-dimethoxybenzene; 1,4-Dibromo-2,5-dimethoxybenzene was reacted with n-butyllithium and then with N,N-dimethylformamide to give 2,5-dimethoxyterephthalaldehyde.

6. The application of the methoxyallyloxy mixed side chain triazacrownenyl COF as described in claim 1 in the photocatalytic synthesis of hydrogen peroxide.

7. The application of the methoxyallyloxy mixed side chain triazacrownene COF as described in claim 1 in the photocatalytic degradation of organic pollutants in water.

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