Preparation method and application of chiral engineering fluorinated covalent organic framework material

Abstract

The invention discloses a preparation method and application of a chiral engineering fluorinated covalent organic framework material. By preparing the chiral engineering fluorinated covalent organic framework material, the electron spinning direction is directionally regulated and controlled, the decomposition path of hydrogen peroxide is inhibited, and the photocatalytic performance is improved. The preparation method comprises the following steps: dissolving (R)-(+)-1-phenylethylamine or (S)-(-)-alpha-methylbenzylamine and 1, 3, 5-triformyl phloroglucinol in an organic solvent for reflux reaction to obtain an intermediate; and dissolving 1, 3, 5-triformyl phloroglucinol, the intermediate TP-R or TP-S and amino tetrafluorophenyl (F) in a mixed solvent, carrying out ultrasonic treatment, and reacting to obtain the photocatalytic material. The method is low in cost, easy and convenient to operate, green and free of pollution, the obtained material is good in stability and high in photocatalytic activity in a complex water environment, the defects in the prior art are overcome, and development and application of a photocatalytic hydrogen peroxide synthesis technology are promoted.

Description

Technical Field

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

[0002] Hydrogen peroxide (H2O2), as a key building-block chemical, has extensive applications in many fields such as environmental remediation and pharmaceutical synthesis. Currently, its production mainly relies on the anthraquinone oxidation (AO) process with a history of a hundred years. Although this process is scalable, it has many significant drawbacks: one is the huge energy consumption. Its hydrogenation and oxidation cycles require a large amount of energy and need to be carried out under high hydrogen pressure conditions, which requires high equipment requirements and increases production costs; the second is that the catalyst used is an expensive Pd-based catalyst, further increasing the cost; the third is that a large amount of organic waste will be generated, such as alkyl anthraquinones in benzene / hexane mixtures, etc., and complex purification steps are required to separate H2O2 from reaction by-products.

[0003] In contrast, photocatalytic H2O2 synthesis technology, with many advantages, has become a very promising environmental protection alternative. It uses abundant solar energy to drive the conversion of oxygen and water, and can achieve on-site on-demand production of H2O2, without facing problems such as high energy consumption, complex storage and transportation like the anthraquinone method. In recent years, continuous progress has been made in the design of photocatalysts, making the H2O2 production rate close to the industrial benchmark. 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 interaction between light absorption, charge separation and surface reaction kinetics.

[0004] Covalent organic frameworks (COFs), as a class of emerging crystalline porous polymers, show great potential in the field of photocatalysis due to their modular design, high surface area and tunable optoelectronic properties, and are expected to break through the bottleneck of existing technologies. Different from traditional semiconductors such as TiO2 or g-C3N4, COFs can achieve atomic-level precision in active site engineering and can be custom-integrated with functional groups to meet the needs of specific redox reactions. The emergence of chiral COFs injects new vitality into this field. It uses stereoelectronic effects to enhance the substrate-catalyst interaction and selectively stabilize the transition state. In H2O2 synthesis, chiral COFs can regulate the O2 adsorption configuration and affect the charge transfer pathway during oxygen reduction (ORR). Especially for fluorinated COFs, they not only have a strong electron-withdrawing effect and enhanced light capture ability, but their hydrophobic pores can also reduce H2O2 decomposition, overcoming the key limitations of the water-photocatalysis system. Although chiral COFs have shown their prominence in enantioselective catalysis and sensing, in the field of H2O2 production, especially in the mechanism of stereochemistry controlling the reaction pathway, it is still in the stage of insufficient exploration. Summary of the Invention

[0005] In view of the current technical problems existing in the use of covalent organic framework (COF) materials for actual photocatalytic production of hydrogen peroxide, the present invention provides a preparation method and application of a chiral engineering fluorinated covalent organic framework material. The photocatalytic material prepared by this method has a unique structure. Compared with the achiral FCOF material, the R-FCCOF and S-FCCOF samples have significantly improved activity in the production of hydrogen peroxide. In particular, R-FCCOF can effectively inhibit the decomposition path of H2O2 by directionally regulating the electron spin direction. At the same time, after introducing chirality, the stability and photocatalytic performance of the material in complex water environments (such as seawater, wastewater) are improved.

[0006] The technical solution adopted by the present invention is as follows: A preparation method of a chiral engineering fluorinated covalent organic framework material, comprising the following steps: S1. Dissolve (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine and 1,3,5-triformylphloroglucinol in an organic solvent, and react under reflux conditions to obtain intermediate TP-R or TP-S. The chemical reaction formula is as follows: , , S2. Dissolve 1,3,5-triformylphloroglucinol and TP-R or TP-S and an amino tetrafluorophenyl monomer in a mixed solvent, add an acetic acid solution, first perform ultrasonic treatment, and then react at 100-140 °C for 40-80 hours to obtain a chiral engineering fluorinated covalent organic framework photocatalytic material.

[0007] Further, 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.

[0008] Further, in step S1, the organic solvent is methanol or / and ethanol, preferably ethanol.

[0009] Further, in step S1, the reflux reaction time is 18-30 hours, preferably 20-26 hours.

[0010] Further, in step S2, the mixed solvent is a solvent composed 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.

[0011] Further, in step S2, the molar ratio of 1,3,5-triformylphloroglucinol, the intermediate, and amino tetrafluorophenyl (F) is 1:1-4:1, preferably 1:2-3:1.

[0012] Further, in step S2, the ultrasonic treatment time is 10-20 minutes.

[0013] Further, in step S2, the reaction temperature is preferably 110-120 °C, and the reaction time is preferably 48-72 hours.

[0014] Further, in step S2, filtration, Soxhlet extraction, and drying are carried out after the reaction.

[0015] Further, in step S2, the precipitate obtained by filtration is first washed with THF 2-5 times, then Soxhlet extracted with THF for 20-40 hours, preferably 20-30 hours, and dried by vacuum drying. The drying temperature is 50-80 °C, and the time is 15-35 hours, preferably 20-30 hours.

[0016] In step S1, in the absence of a chiral monomer, a non-chiral catalytic material is synthesized by the same method using only an amine monomer and an aldehyde monomer in a molar ratio of 1:1.

[0017] The above chiral engineering fluorinated covalent organic framework photocatalytic material is used for photocatalytic production of hydrogen peroxide and exhibits excellent photocatalytic activity.

[0018] The beneficial effects of the present invention are as follows: (1) The present invention regulates the electron spin direction through chirality, optimizes the oxygen reduction reaction (ORR) path, and significantly improves the photocatalytic H2O2 yield.

[0019] (2) The fluorinated hydrophobic pores and the chiral structure act synergistically to maintain high catalytic activity in complex environments such as seawater.

[0020] (3) The process is simple and low-cost. There are no toxic reagents in the preparation process, and the solvent can be recycled, which not only conforms to the principles of green chemistry but also is suitable for large-scale production. Description of the Drawings

[0021] Figure 1 It is a scanning electron microscope (SEM) image of the R-FCCOF material obtained in Example 1 at a scale of 2 µm.

[0022] Figure 2 It is the elemental distribution pattern of C, N, O, and F elements corresponding to the SEM image of R-FCCOF obtained in Example 1, where (a) corresponds to the C element, (b) corresponds to the N element, (c) corresponds to the O element, and (d) corresponds to the F element.

[0023] Figure 3It is a test result diagram of the photocatalytic hydrogen peroxide production activities of different catalytic materials under seawater and pure water, including the photocatalytic activities of R-FCCOF, S-FCCOF, and FCOF.

[0024] Figure 4 It is a test result diagram of photocurrent.

[0025] Figure 5 It is a test result diagram of impedance. Detailed implementation manners

[0026] 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.

[0027] Example 1 Step 1, Synthesis of intermediate TP-R Dissolve 1,3,5-triformylphloroglucinol (0.081 g, 0.4 mmol) and (R)-(+)-1-phenylethylamine (0.327 g, 2.7 mmol) in ethanol (35 mL). Then the reaction is carried out under reflux for 24 hours. After cooling to room temperature, the solvent is removed by rotary evaporation. The residue is washed several times with 9 mol·L -1 aqueous HCl solution and water, and dried under vacuum for 24 hours to obtain a yellow-green product TP-R.

[0028] Step 2, Synthesis of photocatalytic COF Put 0.08 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.16 mmol of TP-R, and 0.08 mmol of aminotetrafluorophenyl (F) into a glass container and dissolve them in 1.5 - 3 mL of solvent (the volume ratio of o-dichlorobenzene: mesitylene: ethanol is 1:1:1). After ultrasonic treatment for 15 min, the reaction is maintained at 120 °C for 60 h. Filter the precipitate, wash it with THF (3×10 mL), perform Soxhlet extraction with THF for 24 h, and dry it under vacuum at 60 °C for 24 h to obtain the product R-FCCOF, and its structural formula is as follows: .

[0029] Example 2 Step 1, Synthesis of intermediate TP-S Dissolve 1,3,5-triformylphloroglucinol (0.081 g, 0.4 mmol) and (S)-(-)-α-methylbenzylamine (0.327 g, 2.7 mmol) in ethanol (35 mL). Then the reaction is carried out under reflux for 24 hours. After cooling to room temperature, the solvent is removed by rotary evaporation. The residue is washed several times with 9 mol / L aqueous HCl solution and water, and dried under vacuum for 24 hours to obtain a yellow-green product TP-S.

[0030] Step 2, Synthesis of photocatalytic COF 0.08 mmol of 1,3,5-triformylphloroglucinol (Tp), 0.16 mmol of TP-S and 0.08 mmol of aminotetrafluorophenyl (F) were loaded into a glass container and dissolved in 3 mL of solvent (o-dichlorobenzene: mesitylene: ethanol volume ratio of 1:1:1). After ultrasonic treatment for 15 min, the reaction was maintained at 120 °C for 60 h. The precipitate was filtered, washed with THF (3×10 mL), Soxhlet extracted with THF for 24 h, and dried in vacuo at 60 °C for 24 h to obtain the product S-FCCOF, whose structural formula is as follows: 。

[0031] The materials obtained in the above examples were characterized and tested. Taking Example 1 as a typical representative, the experimental results are described as follows: The scanning electron microscopy (SEM) of the R-FCCOF material is as Figure 1 shown. It can be seen that the prepared R-FCCOF has a nanorod structure morphology.

[0032] The mapping spectrum corresponding to the SEM image of R-FCCOF is as Figure 2 shown, Figure 2 (a), (b), (c), and (d) respectively show the C, N, O, and F elements in the R-FCCOF material, and the elements in the structure are uniformly distributed.

[0033] The test results of the photocatalytic hydrogen peroxide production activity of different catalytic materials in seawater and pure water are as Figure 3 shown, including the photocatalytic activities of R-FCCOF, S-FCCOF, and FCOF. 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 , showing excellent photocatalytic activity.

[0034] The photocurrent test results are as Figure 4 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, respectively.

[0035] The impedance test results are as Figure 5 shown. It can be seen that R-FCCOF has the smallest Nernst radius, indicating that the strategy of introducing chirality to optimize fluorine-containing COF is relatively successful.

[0036] Comparative Example 1 Preparation of achiral fluorinated COF The rest is the same as in Example 1, except that: no chiral intermediate is added, and 0.24 mmol of 1,3,5-triformylphloroglucinol (Tp) and 0.24 mmol of aminotetrafluorophenyl are used for the reaction, and other conditions remain unchanged. The details are as follows: 0.24 mmol of 1,3,5-triformylphloroglucinol (Tp) and 0.24 mmol of aminotetrafluorophenyl (F) were placed in a glass container and dissolved in 3 mL of a solvent (o-dichlorobenzene: mesitylene: ethanol, volume ratio 1:1:1). After sonication for 15 min, the reaction was maintained at 120 °C for 60 h. The precipitate was filtered, washed with THF (3 × 10 mL), Soxhlet extracted with THF for 24 h, and dried under vacuum at 60 °C for 24 h to obtain achiral FCOF.

[0037] The experimental results showed that the H2O2 production rate of the obtained achiral FCOF was 2100 µmol·g -1 ·h -1 (pure water) and 800 µmol·g -1 ·h -1 (seawater) (as Figure 3 shown), significantly lower than that of R-FCCOF (4967 µmol·g -1 ·h -1 ), indicating that the chiral structure is beneficial to improving the H2O2 production rate.

Claims

1. A preparation method of a chiral engineering fluorinated covalent organic framework material, characterized in that, It includes the following steps: S1. Dissolve (R)-(+)-1-phenylethylamine or (S)-(-)-α-methylbenzylamine and 1,3,5-triformylphloroglucinol in an organic solvent, and carry out a reaction under reflux conditions to obtain intermediate TP-R or TP-S. The chemical reaction formula is as follows: ， ， S2. Dissolve 1,3,5-triformylphloroglucinol, intermediate TP-R or TP-S, and amino tetrafluorophenyl in a mixed solvent, add acetic acid solution, first carry out ultrasonic treatment, and then react at 100-140 °C for 40-80 hours to obtain a chiral engineering fluorinated covalent organic framework photocatalytic material.

2. The preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, wherein 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 preparation method of the 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 preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, wherein In step S1, the reflux reaction time is 18-30 hours.

5. The preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, wherein In step S2, the mixed solvent is a solvent composed 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 preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, wherein In step S2, the molar ratio of 1,3,5-triformylphloroglucinol, intermediate, and amino tetrafluorophenyl is 1:1-4:

1.

7. The preparation method of the 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 preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, characterized in that, In step S2, the reaction temperature is 110-120 °C, and the reaction time is 48-72 hours.

9. The preparation method of the chiral engineering fluorinated covalent organic framework material according to claim 1, characterized in that, In step S2, after the reaction, filtration, Soxhlet extraction, and drying are carried out; the precipitate obtained by filtration is first washed with THF 2-5 times, then Soxhlet extracted with THF for 20-40 hours, and the drying is vacuum drying, the drying temperature is 50-80 °C, and the time is 15-35 hours.

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

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