A polymer containing a thiazolo[5,4-d]thiazole structural unit, a preparation method thereof, and applications thereof

Abstract

The present invention discloses a polymer containing a thiazolo[5,4-d]thiazole structural unit, a preparation method thereof, and an application thereof. The polymer containing a thiazolo[5,4-d]thiazole structural unit of the present invention is obtained by polymerizing a thiazolo[5,4-d]thiazole monomer. The thiazolo[5,4-d]thiazole monomer of the present invention has a porous structure and can be well dispersed in various reagents, facilitating the dissociation and transport of photo-generated carriers. As a catalyst for photocatalytic water oxidation to produce hydrogen peroxide, it has a very high hydrogen peroxide production rate and broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of porous organic polymers, and particularly relates to a polymer containing a thiazolo[5,4-d]thiazole structural unit, a preparation method thereof, and an application thereof. Background Art

[0002] Porous organic polymers are a new type of porous materials that have emerged in recent decades. They have the characteristics of high porosity, low framework density, structural designability, framework functionalization, and high stability. Porous organic polymers can be classified into intrinsically microporous polymers (PIMs), hypercrosslinked polymers (HCPs), conjugated microporous polymers (CMPs), covalent organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc. according to their structural characteristics and preparation methods. Porous organic polymers can precisely control the pore size, pore environment, and specific surface area at the atomic scale by utilizing the easy modification characteristics of organic building units, and then obtain an organic porous framework structure with specific structure and specific functions, which has great application value (for example: used in gas storage and separation, catalysis, sensing, energy storage, photoelectric conversion, etc.). However, the application of porous organic polymers is mainly realized in the form of thin films. However, they essentially belong to highly crosslinked macromolecular compounds, and the preparation process is a rapid crosslinking process, which will cause porous organic polymers to usually present in the form of insoluble and infusible powders after the reaction, and it is very difficult to process them into films, which greatly limits their application.

[0003] Hydrogen peroxide (H2O2) is an oxidant that plays an important role in the chemical industry, healthcare, and water treatment, and there is a huge market demand (currently, the annual global demand for H2O2 is about 4 million tons, and it is expected to increase to 5.7 million tons in 2027). Industrial synthesis of H2O2 usually adopts the anthraquinone method. This process involves multi-step hydrogenation and oxidation reactions, is a highly energy-intensive process, and there are side reactions that cause net consumption of anthraquinone. It is necessary to regenerate the solution and catalyst, and the processes of product separation and purification are complex, with high energy consumption and large environmental pollution, and it is not sustainable. Using noble metal-based catalysts (for example: Pd, Au, and Pt) can directly synthesize H2O2 from H2 and O2, but this method has potential explosion risks, and the cost of noble metal-based catalysts is high, and it is not suitable for large-scale industrial production.

[0004] Studies have found that artificial photosynthesis using water and oxygen with semiconductor photocatalysts can be used to prepare H2O2. This method has the advantages of low energy consumption, less pollution, and high safety, and has good application prospects. However, so far, no photocatalyst for producing hydrogen peroxide that can be truly put into large-scale industrial production applications has been found.

[0005] Therefore, it is of great significance to develop a photocatalytic hydrogen peroxide production catalyst with excellent performance and suitable for large-scale industrial production applications. Summary of the Invention

[0006] The object of the present invention is to provide a polymer containing a thiazolo[5,4-d]thiazole structural unit, a preparation method thereof, and an application thereof.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A polymer containing a thiazolo[5,4-d]thiazole structural unit, which is obtained by polymerizing thiazolo[5,4-d]thiazole monomers; the thiazolo[5,4-d]thiazole monomers are

[0009] Preferably, the polymer containing a thiazolo[5,4-d]thiazole structural unit has a repeating unit shown in formula (I) or formula (II):

[0010] Formula (I):

[0011] Formula (II):

[0012] A preparation method of a polymer containing a thiazolo[5,4-d]thiazole structural unit as described above includes the following steps:

[0013] 1) Adding thiazolo[5,4-d]thiazole monomers to trifluoromethanesulfonic acid for a polymerization reaction to obtain a polymer having a repeating unit shown in formula (I);

[0014] 2) Protonating the polymer having a repeating unit shown in formula (I) by adding an acid to obtain a polymer having a repeating unit shown in formula (II).

[0015] Note: The polymer having a repeating unit shown in formula (I) can be protonated by adding an acid to be converted into a polymer having a repeating unit shown in formula (II), and the polymer having a repeating unit shown in formula (II) can also be deprotonated by adding a base to be converted into a polymer having a repeating unit shown in formula (I).

[0016] Preferably, the thiazolo[5,4-d]thiazole monomers in step 1) are prepared by the following method: mixing dithiooxamide and p-cyanobenzaldehyde for a polycondensation reaction to obtain monomers containing a thiazolo[5,4-d]thiazole structural unit.

[0017] Preferably, the polycondensation reaction is carried out at 150 °C to 170 °C.

[0018] Preferably, the time of the polycondensation reaction is 10 h to 15 h.

[0019] Preferably, the polymerization reaction (cyano trimerization reaction) in step 1) is carried out at 50 °C to 70 °C.

[0020] Preferably, the time of the polymerization reaction in step 1) is 5 h to 10 h.

[0021] Preferably, the acid in step 2) is hydrochloric acid.

[0022] Preferably, the mass fraction of the hydrochloric acid is 25% to 35%.

[0023] A photocatalyst comprising the polymer containing the thiazolo[5,4-d]thiazole structural unit described above.

[0024] An application of a polymer containing the thiazolo[5,4-d]thiazole structural unit as described above as a catalyst for photocatalytic water oxidation to hydrogen peroxide.

[0025] The beneficial effects of the present invention are as follows: The polymer containing the thiazolo[5,4-d]thiazole structural unit of the present invention has a porous structure and can be well dispersed in various reagents, facilitating the dissociation and transport of photo-generated carriers. As a catalyst for photocatalytic water oxidation to hydrogen peroxide, it has a very high hydrogen peroxide production rate and broad application prospects.

[0026] Specifically:

[0027] 1) The polymer containing the thiazolo[5,4-d]thiazole structural unit of the present invention reacts significantly to acids and bases. By adding an acid, it can be protonated, and by adding a base, it can be deprotonated to return to its original state. Therefore, it can be well dispersed in various reagents, solving the problem of insolubility of traditional porous organic polymers, and can be processed by solution processing;

[0028] 2) The thiazolo[5,4-d]thiazole structural unit and triazine ring structural unit in the polymer containing the thiazolo[5,4-d]thiazole structural unit of the present invention have excellent photocatalytic properties. As a catalyst for photocatalytic water oxidation to hydrogen peroxide, it has a very high hydrogen peroxide production rate. Description of the Drawings

[0029] Figure 1 1H NMR spectrum of TT-BN.

[0030] Figure 2 Solubility test results of TT-CTF in different solvents.

[0031] Figure 3 Infrared spectra of TT-BN, TT-CTF and TTH-CTF.

[0032] Figure 4 CO2 adsorption - desorption curves of TT - CTF and TTH - CTF.

[0033] Figure 5 UV - Vis diffuse reflectance spectra and corresponding Tauc plots of TT - CTF and TTH - CTF.

[0034] Figure 6 Mott - Schottky curves of TT - CTF and TTH - CTF.

[0035] Figure 7 Schematic diagrams of the energy band structures of TT - CTF and TTH - CTF.

[0036] Figure 8 Photocurrent response test result graphs of TT - CTF and TTH - CTF.

[0037] Figure 9 Test result graphs of the H2O2 production rates of TT - CTF and TTH - CTF under different sacrificial reagents. Detailed implementation manners

[0038] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0039] Embodiment:

[0040] A polymer containing a thiazolo[5,4 - d]thiazole structural unit, and its preparation method includes the following steps:

[0041] 1) Synthesis of TT - BN: Add 720 mg (6 mmol) of dithiooxamide, 1809.6 mg (13.8 mmol) of p - cyanobenzaldehyde, and 20 mL of N,N - dimethylformamide (DMF) into a 100 - mL Schlenk tube. After evacuating the air in the Schlenk tube and filling it with argon for protection, heat it to 160 °C and stir at a constant temperature for 12 h. Then cool it naturally to room temperature and filter by suction. The obtained solid (yellow) is purified by Soxhlet extraction (using ethanol as the solvent) to obtain 1081.21 mg of thiazolo[5,4 - d]thiazole - type monomer (denoted as TT - BN, a yellow - green solid, with a yield of 52.32%);

[0042] The synthesis reaction formula of TT - BN is as follows:

[0043]

[0044] 2) Synthesis of TT-CTF: Add 100 mg of TT-BN into a Schlenk tube with a volume of 10 mL. After evacuating the air in the Schlenk tube, fill it with argon for protection, and then place it in a low-temperature reactor. Slowly add 1 mL of trifluoromethanesulfonic acid dropwise at -10 °C, and finish adding it in 2 min. Then stir at a constant temperature for 1.5 h, transfer it to an oil bath and stir at 60 °C for 10 h. Naturally cool it to room temperature, then add water to quench the reaction, and then add an excessive amount of NaOH solution with a concentration of 2 mol / L and deionized water for washing. Then transfer it to a centrifuge tube and centrifuge with 10 mL of N-methylpyrrolidone (NMP) for 20 min, filter. The obtained solid is successively subjected to Soxhlet extraction with dichloromethane (12 h), tetrahydrofuran (24 h) and ethanol (12 h), and then dried under vacuum at 80 °C to obtain 91 mg of a polymer with a repeating unit shown in formula (I) (denoted as TT-CTF, yellow powder, with a yield of 91%);

[0045] 3) Preparation of TTH-CTF: Add 100 mg of TT-CTF into 3 mL of water, then add 3 mL of hydrochloric acid with a mass fraction of 30%, stir at 30 °C for 4 h, then dilute with water, filter. The obtained solid (orange) is rinsed with water and methanol, and then dried under vacuum to obtain a polymer with a repeating unit shown in formula (II) (denoted as TTH-CTF);

[0046] The synthesis reaction formulas of TT-CTF and TTH-CTF are as follows:

[0047]

[0048] Performance testing:

[0049] 1) The 1H NMR spectrum of TT-BN is as Figure 1 shown.

[0050] It can be seen from Figure 1 that: The present invention has indeed prepared TT-BN( 1 1H NMR (500 MHz, CF3COOD): δ (ppm) = 8.46 (4H, d, J = 8.2 Hz, Ph C2-H), 8.25 (4H, d, J = 8.2 Hz, Ph C3-H)).

[0051] 2) The solubility test results of TT-CTF in different solvents are as Figure 2 (The upper row of samples is irradiated with natural light, and the lower row of samples is irradiated with laser) shown.

[0052] It can be seen from Figure 2 that: TT-CTF has good dispersion performance in various reagents and is suitable for solution processing.

[0053] 3) The infrared spectra of TT-BN, TT-CTF, and TTH-CTF are as follows Figure 3 as shown

[0054] As can be seen Figure 3 from -1 it that the absorption peak at 2238 cm -1 is for the cyano group. TT-BN shows a strong absorption peak at this position, while the cyano absorption peak in TT-CTF has basically disappeared, indicating that most of TT-BN has reacted and the degree of polymerization reaction is very high. The characteristic absorption peaks of the triazine ring appear in TT-CTF at 1466 cm -1 , 1289 cm -1 , and 776 cm

[0055] 4) The carbon dioxide adsorption-desorption curves of TT-CTF and TTH-CTF are as follows Figure 4 (testing instrument: fully automatic three-station specific surface area and pore size distribution analyzer BELSORP-Max).

[0056] As can be seen Figure 4 from 2 it that both TT-CTF and TTH-CTF show rapid adsorption at low pressure (P / P0 < 0.1) and slow adsorption behavior at P / P0 > 0.1. This adsorption curve is a typical type I adsorption curve, indicating that TT-CTF and TTH-CTF are microporous materials. By calculation, the specific surface areas of TT-CTF and TTH-CTF are 387 m 2 / g and 268 m

[0057] 5) The UV-Vis diffuse reflectance spectra and corresponding Tauc plots of TT-CTF and TTH-CTF are as follows Figure 5 (a is the UV-Vis diffuse reflectance spectrum, b is the corresponding Tauc plot) (TT-CTF and TTH-CTF are respectively mixed and ground evenly with barium sulfate, then pressed into tablets with a glass rod, and then tested using a Shimadzu UV-3600 UV-Vis near-infrared spectrophotometer).

[0058] As can be seen Figure 5 from

[0059] it that both TT-CTF and TTH-CTF have good absorption in the wavelength range of 240 nm - 800 nm, and the absorption edges are at 532 nm and 570 nm respectively, indicating that both TT-CTF and TTH-CTF have good light absorption and light trapping capabilities. At the same time, according to the calculation, the optical band gaps of TT-CTF and TTH-CTF are 2.33 eV and 2.18 eV respectively, indicating that TT-CTF and TTH-CTF have light absorption capabilities in a relatively wide spectral range.6) 5 mg of TT-CTF or TTH-CTF and 100 μL of Nafion solution were added to 900 μL of N,N-dimethylformamide (DMF) to prepare a stock solution. Then, 10 μL of the stock solution was drop-coated on a clean FTO glass and dried in a vacuum environment to obtain a CTF-based photoanode. Using the CTF-based photoanode as the working electrode, a platinum sheet with a size of 1.0 cm × 1.0 cm as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a three-electrode system was used for testing. The obtained Mott-Schottky curve is as Figure 6 (a for TT-CTF, b for TTH-CTF) shown. The schematic energy band structure diagram obtained based on the valence band position and band gap width is as Figure 7 shown. The test result graph of photocurrent response is as Figure 8 (in the figure, the curve with large up and down fluctuations is TT-CTF, and the curve with small up and down fluctuations is TTH-CTF) shown.

[0060] It can be seen from Figure 6 that: by intercepting the intersection of the straight line at the maximum slope of the Mott-Schottky curve at frequencies of 0.5 kHz, 1.0 kHz, and 1.5 kHz on the horizontal axis, the flat-band potentials of TT-CTF and TTH-CTF were obtained as -0.53 V and -0.41 V respectively. At the same time, the curve slopes of both CTFs were negative values, indicating that both CTFs are n-type semiconductors. After converting to the standard hydrogen electrode through energy level conversion, the conduction bands (CB) of TT-CTF and TTH-CTF under the reversible hydrogen electrode were -0.33 V and -0.21 V respectively.

[0061] It can be seen from Figure 7 that: combining the band gap widths measured for CTFs, the valence bands (VB) of TT-CTF and TTH-CTF were obtained as +2.00 V and +1.97 V respectively. The conduction band positions of TT-CTF and TTH-CTF are not very different and are both at positions more negative than 0.28 V, meeting the thermodynamic conditions for reducing O2 to H2O2.

[0062] It can be seen from Figure 8 that: under visible light illumination, both TT-CTF and TTH-CTF have obvious transient photocurrent responses, indicating that free carriers are generated by exciton dissociation.

[0063] 7) Add 10 mg of TT-CTF or TTH-CTF into a Schlenk tube with a volume of 50 mL, then add 18 mL of deionized water and 2 mL of sacrificial agent (methanol, ethanol or benzyl alcohol), ultrasonically disperse for 10 min, then replace the atmosphere in the tube with oxygen by means of multiple vacuum-pumping-backfilling oxygen cycles, then use an LED lamp as a light source for illumination for 2 h, then take 5 mL of the reaction solution and filter to obtain a clear solution, then pour it into a volumetric flask with a volume of 25 mL, add 1 mL of color reagent Ti(SO4)2, then make up the volume, then use water as a reference solution, and measure the absorbance at a wavelength of 407 nm with a UV-visible spectrophotometer. Calculate the content of hydrogen peroxide according to the standard curve, and then obtain the production rate of H2O2. The test result graph of the H2O2 production rate under different sacrificial reagents is as shown in Figure 9 shown.

[0064] It can be seen from Figure 9 this that both TT-CTF and TTH-CTF can exhibit the performance of catalyzing the reduction of O2 to H2O2 under the action of three kinds of cocatalysts. Among them, using benzyl alcohol as the cocatalyst has the best effect, and the highest H2O2 production rate can reach 23.1 mmol·g -1 ·h -1 .

[0065] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A polymer containing a thiazolo[5,4-d]thiazole structural unit, characterized in that, Obtained by polymerizing thiazolo[5,4-d]thiazole monomers; the thiazolo[5,4-d]thiazole monomers are The polymer containing a thiazolo[5,4-d]thiazole structural unit has a repeating unit represented by the formula (I) or the formula (II): Formula (I): Formula (II):

2. A method for preparing a polymer containing a thiazolo[5,4-d]thiazole structural unit as described in claim 1, characterized in that, It includes the following steps: 1) Adding thiazolo[5,4-d]thiazole monomers into trifluoromethanesulfonic acid for polymerization reaction to obtain a polymer having repeating units as shown in formula (I); 2) Adding the polymer having repeating units as shown in formula (I) into an acid for protonation to obtain a polymer having repeating units as shown in formula (II).

3. The preparation method according to claim 2, wherein: The thiazolo[5,4-d]thiazole monomers described in step 1) are prepared by the following method: Mixing dithiooxamide and p-cyanobenzaldehyde for polycondensation reaction to obtain monomers containing thiazolo[5,4-d]thiazole structural units.

4. The preparation method according to claim 3, characterized in that: The polycondensation reaction is carried out at 150 °C to 170 °C, and the time of the polycondensation reaction is 10 h to 15 h.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The polymerization reaction described in step 1) is carried out at 50 °C to 70 °C.

6. The preparation method according to claim 5, characterized in that: The time of the polymerization reaction described in step 1) is 5 h to 10 h.

7. The preparation method according to any one of claims 2 to 4, characterized in that: The acid described in step 2) is hydrochloric acid.

8. A photocatalyst, characterized in that, A polymer containing thiazolo[5,4-d]thiazole structural units as claimed in claim 1.

9. Use of a polymer containing thiazolo[5,4-d]thiazole structural units as claimed in claim 1 as a catalyst for photocatalytic water oxidation to hydrogen peroxide.

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