Preparation method and application of a chiral engineered fluorinated covalent organic framework material

Abstract

The present invention discloses a preparation method and application of a chiral engineered fluorinated covalent organic framework material. The present invention prepares a chiral engineered fluorinated covalent organic framework material, directionally controls the direction of electron spin, suppresses the decomposition path of hydrogen peroxide, and improves photocatalytic performance. The preparation method includes dissolving (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine and 1,3,5-triformylphloroglucinol in an organic solvent and refluxing to obtain an intermediate; then dissolving 1,3,5-triformylphloroglucinol and the intermediate TP-R or TP-S with 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene (F) in a mixed solvent and reacting after ultrasonic treatment to obtain a photocatalytic material. The method of the present invention is low in cost, simple to operate, green and pollution-free. The obtained material has good stability in complex water environments and high photocatalytic activity, which solves the defects in the prior art and promotes the development and application of photocatalytic hydrogen peroxide synthesis technology.

Description

Technical Field

[0001] The present invention relates to the technical field of organic porous photocatalytic materials, and in particular to a preparation method and application of a chiral engineered fluorinated covalent organic framework material. Background Art

[0002] Hydrogen peroxide (H2O2), a key cornerstone chemical, is widely used in fields ranging from environmental remediation to pharmaceutical synthesis. Currently, its production relies primarily on the century-old anthraquinone oxidation (AO) process. Although scalable, this process suffers from several significant drawbacks: First, it is energy-intensive; the hydrogenation and oxidation cycles require significant energy consumption and must be performed under high hydrogen pressures, placing high demands on equipment and increasing production costs. Second, the expensive palladium-based catalyst used further increases costs. Third, it generates significant organic waste, such as alkylanthraquinones in benzene / hexane mixtures, requiring complex purification steps to separate the H2O2 from the reaction byproducts.

[0003] In contrast, photocatalytic H2O2 synthesis technology has become a highly promising environmentally friendly alternative due to its many advantages. It uses abundant solar energy to drive the conversion of oxygen and water, enabling on-site, on-demand production of H2O2 without the high energy consumption, complex storage and transportation problems associated with the anthraquinone method. In recent years, continuous progress in photocatalyst design has brought H2O2 production rates close to industrial benchmarks. However, existing photocatalytic technologies still need to be optimized in terms of efficiency, stability, and selectivity. The root cause of these problems lies in the complex interplay between light absorption, charge separation, and surface reaction kinetics.

[0004] Covalent organic frameworks (COFs), an emerging class of crystalline porous polymers, have shown great potential in photocatalysis due to their modular design, high surface area, and tunable optoelectronic properties, potentially overcoming existing technological bottlenecks. Unlike traditional semiconductors such as TiO2 or g-C3N4, COFs enable atomic-level precision in active site engineering, allowing for customized integration of functional groups to meet specific redox reaction requirements. The emergence of chiral COFs has revitalized this field, leveraging stereoelectronic effects to enhance substrate-catalyst interactions and selectively stabilize transition states. In H2O2 synthesis, chiral COFs can manipulate O2 adsorption configurations and influence charge transfer pathways during oxygen reduction reaction (ORR). Fluorinated COFs, in particular, offer not only strong electron-withdrawing properties and enhanced light-harvesting capabilities, but also hydrophobic pores that mitigate H2O2 decomposition, overcoming a key limitation of water-based photocatalytic systems. While chiral COFs have demonstrated promising applications in enantioselective catalysis and sensing, their application in H2O2 production, particularly in the mechanistic control of reaction pathways by stereochemistry, remains underexplored. Summary of the Invention

[0005] To address the technical challenges currently associated with the practical photocatalytic production of hydrogen peroxide using covalent organic frameworks (COFs), this invention provides a method for preparing and applying chirally engineered fluorinated COFs. The resulting photocatalytic materials exhibit unique structures. Compared to achiral FCOFs, R-FCCOF and S-FCCOF samples exhibit significantly enhanced activity in hydrogen peroxide production. R-FCCOF, in particular, effectively inhibits the decomposition pathway of H₂O₂ by directional manipulation of electron spin orientation. Furthermore, the introduction of chirality enhances the material's stability and photocatalytic performance in complex aqueous environments (such as seawater and wastewater).

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing a chiral engineered fluorinated covalent organic framework material comprises the following steps:

[0008] S1. Dissolve (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine and 1,3,5-triformylphloroglucinol in an organic solvent and react under reflux to obtain the intermediate TP-R or TP-S. The chemical reaction formula is shown below:

[0009] ,

[0010] ,

[0011] S2. 1,3,5-triformylphloroglucinol and TP-R or TP-S are dissolved with 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene monomer in a mixed solvent, and an acetic acid solution is added. The mixture is first ultrasonically treated and then reacted at 100-140°C for 40-80 hours to obtain a chiral engineered fluorinated covalent organic framework photocatalytic material.

[0012] Furthermore, in step S1, the molar ratio of 1,3,5-triformylphloroglucinol to (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine is 1:5-9, preferably 1:6-7.

[0013] Furthermore, in step S1, the organic solvent is methanol and / or ethanol, preferably ethanol.

[0014] Furthermore, in step S1, the reflux reaction time is 18-30 hours, preferably 20-26 hours.

[0015] Furthermore, in step S2, the mixed solvent is a mixture of o-dichlorobenzene, mesitylene and ethanol, and the volume ratio of o-dichlorobenzene, mesitylene and ethanol is 0.9-1.1:1-1.1:1-1.1, preferably 1:1:1; the concentration of the acetic acid solution is 4-8 mol / L, preferably 5-7 mol / L.

[0016] Furthermore, in step S2, the molar ratio of 1,3,5-triformylphloroglucinol, the intermediate and 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene (F) is 1:1-4:1, preferably 1:2-3:1.

[0017] Furthermore, in step S2, the ultrasonic treatment time is 10-20 minutes.

[0018] Furthermore, in step S2, the reaction temperature is preferably 110-120° C., and the reaction time is preferably 48-72 hours.

[0019] Furthermore, in step S2, filtration, Soxhlet extraction and drying are performed after the reaction.

[0020] Furthermore, in step S2, the filtered precipitate is first washed with THF 2-5 times, then extracted with THF for 20-40 hours, preferably 20-30 hours, and dried in vacuum at a temperature of 50-80° C. for 15-35 hours, preferably 20-30 hours.

[0021] In step S1 , in the absence of a chiral monomer, an achiral catalytic material is synthesized by the same method using only an amine monomer and an aldehyde monomer at a molar ratio of 1:1.

[0022] The chiral engineered fluorinated covalent organic framework photocatalytic material is used for photocatalytic production of hydrogen peroxide and exhibits excellent photocatalytic activity.

[0023] The beneficial effects of the present invention are:

[0024] (1) The present invention optimizes the oxygen reduction reaction (ORR) pathway by regulating the electron spin direction through chirality, thereby significantly improving the photocatalytic H2O2 yield.

[0025] (2) The fluorinated hydrophobic pores and chiral structures work synergistically to maintain high catalytic activity in complex environments such as seawater.

[0026] (3) The process is simple and low-cost. There are no toxic reagents in the preparation process and the solvent is recyclable. It conforms to the principles of green chemistry and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1This is a scanning electron microscope (SEM) image of the R-FCCOF material obtained in Example 1 at a 2µm scale.

[0028] Figure 2 Element distribution maps of C, N, O, and F elements corresponding to the SEM image of R-FCCOF obtained in Example 1, where (a) corresponds to C element, (b) corresponds to N element, (c) corresponds to O element, and (d) corresponds to F element.

[0029] Figure 3 The graph shows the test results of the photocatalytic hydrogen peroxide production activity of different catalytic materials in seawater and pure water, including the photocatalytic activity of R-FCCOF, S-FCCOF and FCOF.

[0030] Figure 4 This is the photocurrent test result diagram.

[0031] Figure 5 This is the impedance test result diagram. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0033] Example 1

[0034] Step 1, Synthesis of Intermediate TP-R

[0035] 1,3,5-Triformylphloroglucinol (0.081 g, 0.4 mmol) and (R)-(+)-1-phenylethylamine (0.327 g, 2.7 mmol) were dissolved in ethanol (35 ml). The reaction was then carried out under reflux for 24 hours. After cooling to room temperature, the solvent was removed by rotary evaporation. The residue was washed with 9 mol·L -1 The solution was washed several times with HCl aqueous solution and water and dried under vacuum for 24 h to obtain a yellow-green product TP-R.

[0036] Step 2, Synthesis of Photocatalytic COF

[0037] 0.08 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.16 mmol of TP-R, and 0.08 mmol of 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene (F) were placed in a glass container and dissolved in 1.5-3 mL of solvent (o-dichlorobenzene:mesitylene:ethanol, volume ratio 1:1:1). After sonication for 15 minutes, the reaction was maintained at 120°C for 60 hours. The precipitate was filtered, washed with THF (3 × 10 mL), extracted with THF for 24 hours, and dried under vacuum at 60°C for 24 hours to obtain the product, R-FCCOF, with the following structural formula:

[0038] .

[0039] Example 2

[0040] Step 1, Synthesis of Intermediate TP-S

[0041] 1,3,5-Triformylphloroglucinol (0.081 g, 0.4 mmol) and (S)-(-)-α-methylbenzylamine (0.327 g, 2.7 mmol) were dissolved in ethanol (35 ml). The reaction was then refluxed for 24 hours. After cooling to room temperature, the solvent was removed by rotary evaporation. The residue was washed several times with 9 mol / L aqueous HCl and water, and dried under vacuum for 24 hours to obtain the yellow-green product TP-S.

[0042] Step 2, Synthesis of Photocatalytic COF

[0043] 0.08 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.16 mmol of TP-S, and 0.08 mmol of 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene (F) were placed in a glass container and dissolved in 3 mL of solvent (o-dichlorobenzene:mesitylene:ethanol, volume ratio: 1:1:1). After sonication for 15 minutes, the reaction was maintained at 120°C for 60 hours. The precipitate was filtered, washed with THF (3 × 10 mL), extracted with THF for 24 hours, and dried under vacuum at 60°C for 24 hours to obtain the product, S-FCCOF, with the following structure:

[0044] .

[0045] The materials obtained in the above examples were characterized and tested, with Example 1 being a typical example. The experimental results are described as follows:

[0046] Scanning electron microscopy (SEM) of R-FCCOF materials Figure 1 As shown, it can be seen that the prepared R-FCCOF has a nanorod structure morphology.

[0047] The mapping map corresponding to the SEM image of R-FCCOF is as follows Figure 2 As shown, Figure 2 (a), (b), (c), and (d) show the C, N, O, and F elements in the R-FCCOF material, respectively, and the elements are evenly distributed in the structure.

[0048] The test results of photocatalytic hydrogen peroxide production activity of different catalytic materials in seawater and pure water are shown in the figure below. Figure 3As shown in the figure, the photocatalytic activities of R-FCCOF, S-FCCOF and FCOF are shown. The average rate of photocatalytic hydrogen peroxide production of the prepared R-FCCOF in seawater under visible light irradiation is 4967 μmol·g -1 ·h -1 , which exhibits excellent photocatalytic activity.

[0049] The photocurrent test results are as follows Figure 4 As shown, it can be seen that the photocurrent of R-FCCOF is 2.6 times and 8.5 times that of S-FCCOF and FCOF.

[0050] The impedance test results are as follows: Figure 5 As shown, it can be seen that R-FCCOF has the smallest Nernst radius, indicating that the strategy of optimizing fluorinated COF by introducing chirality is relatively successful.

[0051] Comparative Example 1

[0052] Preparation of achiral fluorinated COFs

[0053] The rest is the same as Example 1, except that: no chiral intermediate is added, 0.24 mmol of 1,3,5-triformylphloroglucinol (Tp) and 0.24 mmol of 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene are used for the reaction, and other conditions remain unchanged, as follows:

[0054] 0.24 mmol of 1,3,5-triformylphloroglucinol (Tp) and 0.24 mmol of 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene (F) were placed in a glass container and dissolved in 3 mL of solvent (o-dichlorobenzene:mesitylene:ethanol, 1:1:1 by volume). After sonication for 15 minutes, the reaction was maintained at 120°C for 60 hours. The precipitate was filtered, washed with THF (3 × 10 mL), extracted with THF for 24 hours, and dried under vacuum at 60°C for 24 hours to obtain an achiral FCOF.

[0055] The experimental results show that the H2O2 yield of the obtained achiral FCOF is 2100 µmol·g -1 ·h -1 (pure water) and 800 µmol·g -1 ·h -1 (seawater) (e.g. Figure 3 ), which is significantly lower than R-FCCOF (4967 µmol·g -1 ·h -1 ), indicating that the chiral structure is beneficial to improving the H2O2 yield.

Claims

1. A method for preparing a chiral engineered fluorinated covalent organic framework material, characterized in that: The following steps are involved: S1. Dissolve (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine and 1,3,5-triformylphloroglucinol in an organic solvent and react under reflux to obtain the intermediate TP-R or TP-S. The chemical reaction formula is shown below: ， ， S2. 1,3,5-triformylphloroglucinol, intermediate TP-R or TP-S, and 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene are dissolved in a mixed solvent, and an acetic acid solution is added. The mixture is first ultrasonically treated and then reacted at 100-140°C for 40-80 hours to obtain a chiral engineered fluorinated covalent organic framework photocatalytic material.

2. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, characterized in that: In step S1, the molar ratio of 1,3,5-triformylphloroglucinol to (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine is 1:5-9.

3. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, characterized in that: In step S1, the organic solvent is methanol or ethanol.

4. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S1, the reflux reaction time is 18-30 hours.

5. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S2, the mixed solvent is a mixture of o-dichlorobenzene, mesitylene and ethanol, and the volume ratio of o-dichlorobenzene, mesitylene and ethanol is 0.9-1.1:1-1.1:1-1.1; the concentration of the acetic acid solution is 4-8 mol / L.

6. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S2, the molar ratio of 1,3,5-triformylphloroglucinol, the intermediate and 1,3,5-tris-(2,3,5,6-tetrafluoro-4-aminophenyl)-benzene is 1:1-4:

1.

7. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S2, the ultrasonic treatment time is 10-20 minutes.

8. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S2, the reaction temperature is 110-120° C., and the reaction time is 48-72 hours.

9. The method for preparing a chiral engineered fluorinated covalent organic framework material according to claim 1, wherein: In step S2, after the reaction, filtration, Soxhlet extraction and drying are performed; the precipitate obtained by filtration is first washed with THF 2-5 times, then Soxhlet extraction is performed with THF for 20-40 hours, and drying is performed in a vacuum at a drying temperature of 50-80° C. for 15-35 hours.

10. Use of the chiral engineered fluorinated covalent organic framework material obtained by the preparation method according to any one of claims 1 to 9 in the photocatalytic production of hydrogen peroxide.

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