A porous terephthalaldehyde-aminopyridine polymer and its preparation method and application

Abstract

The present invention relates to a porous terephthalaldehyde-aminopyridine polymer and its preparation method and application. The preparation method comprises the following steps: 1) dispersing 2,6-diaminopyridine in a solution containing a surfactant and an alkali, and performing a polymerization reaction with terephthalaldehyde to obtain a terephthalaldehyde-aminopyridine condensation precursor, wherein the surfactant comprises F127 and sodium dodecylbenzenesulfonate; 2) calcining the terephthalaldehyde-aminopyridine condensation precursor to obtain a porous terephthalaldehyde-aminopyridine polymer. The porous terephthalaldehyde-aminopyridine polymer prepared using the surfactant is used as a catalyst for photocatalytic aquatic production of H2O2. Compared with the prior art, the polymer prepared by the present invention can regulate the band gap structure by adjusting the pore structure, thereby enabling efficient and clean production of H2O2 in pure water without sacrificial agents and under visible light in situ. It has the advantages of simple preparation method and simple equipment, and has good industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysis technology and relates to a polymer photocatalyst and a preparation method and application thereof, and specifically relates to a porous terephthalaldehyde-aminopyridine polymer and a preparation method thereof and application thereof in photocatalytic production of hydrogen peroxide in the absence of an electron donor. Background Art

[0002] Hydrogen peroxide (H2O2) is an important chemical widely used in environmental remediation and disinfection. Conventional anthraquinone production methods are costly and have significant environmental impacts. Given the vulnerability of H2O2 to decomposition and explosion during transportation, there is an urgent need to develop economical and environmentally friendly methods for the clean, in-situ production of H2O2.

[0003] Schiff bases have an electron donor-electron acceptor (DA) structure, and DA structures can also be spatially stacked, resulting in excellent electron-hole separation. Therefore, studies have shown that Schiff base polymers can photocatalytically produce H2O2. However, many Schiff base polymers have a solid nano- or even micron-sized sphere morphology, resulting in a small photocatalytic contact area and a single band gap structure. Different polymer morphologies require different synthetic strategies to precisely control their size, form, and dimensions, making the preparation of polymers with large specific surface areas challenging.

[0004] Chinese patent CN107216605B discloses a porous Schiff base polymer composite material supported by a carbonitride structure and its application. The preparation method comprises the following steps: adding melamine, terephthalaldehyde, and carbonitride to a dimethyl sulfoxide solvent, magnetically stirring and evacuating the mixture at 100°C, continuously introducing nitrogen for 3 hours, and adjusting the synthesis system to an anhydrous and oxygen-free system; adding toluene, heating the mixture to 180°C, and refluxed under condensation for 72 hours to obtain a brown precipitate; adding an appropriate amount of acetone, stirring the mixture for 3 hours, extracting the mixture, and then centrifuging the mixture to obtain a crude product; washing the sample three times with acetone, tetrahydrofuran, and dichloromethane, respectively, and then drying the sample at 100°C under vacuum for 12 hours to obtain a light yellow solid powder of carbonitride / porous Schiff base polymer composite material. Although the prepared polymer has a higher specific surface area and a richer pore structure, the reaction time of this method is too long, making it only suitable for laboratory research, and its industrialization prospects remain to be considered. Summary of the Invention

[0005] The purpose of the present invention is to provide a metal-free semiconductor porous terephthalaldehyde-aminopyridine polymer whose band gap can be regulated by pore structure, as well as a preparation method and application thereof. The band gap structure is regulated by using surfactants to regulate the pore structure, and a porous terephthalaldehyde-aminopyridine polymer with an adjustable DA structure is prepared. The problems of small photocatalytic contact area and single band gap structure of many Schiff base polymers are overcome. The polymer has a wide light absorption range and can produce H2O2 in situ through dual-channel photocatalysis of oxygen reduction and water oxidation in pure water without sacrificial agents.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a porous terephthalaldehyde-aminopyridine polymer, comprising two steps: precursor synthesis and enhanced polymerization. The precursor synthesis mainly refers to the Schiff base condensation of 2,6-diaminopyridine and terephthalaldehyde under heating and surfactant ratio control conditions; the enhanced polymerization mainly refers to the enhanced polymerization of the Schiff base condensation product by low-temperature calcination in an argon atmosphere. Specifically:

[0008] S1: dispersing 2,6-diaminopyridine in an ethanol solution containing a surfactant and an alkali, and performing a polymerization reaction with terephthalaldehyde to obtain a terephthalaldehyde-aminopyridine condensation precursor, wherein the surfactant includes F127 (Pluronic F127);

[0009] S2: calcining the terephthalaldehyde-aminopyridine polycondensation precursor in step S1 in a tube furnace to obtain a porous terephthalaldehyde-aminopyridine polymer.

[0010] Furthermore, the mass ratio of 2,6-diaminopyridine, F127, base, and terephthalaldehyde is (0.4-0.7):(0.4-0.6):(0.07-0.12):(0.4-0.7). Preferably, the mass ratio of 2,6-diaminopyridine, F127, base, and terephthalaldehyde is 0.5:0.5:0.09:0.5.

[0011] Furthermore, in step S1, the surfactant further comprises sodium dodecylbenzene sulfonate, and the mass ratio of sodium dodecylbenzene sulfonate to F127 is (0.0125-0.25):(0.4-0.6). Preferably, the mass ratio of sodium dodecylbenzene sulfonate to F127 is (0.0125-0.25):0.5. Further preferably, the mass ratio of sodium dodecylbenzene sulfonate to F127 is 0.025:0.5.

[0012] Furthermore, in step S1, the solvent in the polymerization reaction is an ethanol solution. In the ethanol solution, the volume ratio of anhydrous ethanol to water is (20-25):(3-5). Preferably, the volume ratio of anhydrous ethanol to water is 20:3.

[0013] Furthermore, in step S1, during the polymerization reaction, the reaction temperature is 40-55° C. Preferably, the reaction temperature is 40° C.

[0014] Furthermore, in step S2, during the calcination, the calcination temperature is 200-300° C., and the calcination time is 2-3 hours. Preferably, the calcination temperature is 250° C., and the calcination time is 2 hours.

[0015] Furthermore, in step S2, during the calcination, the heating rate is 5-8°C / min. Preferably, the heating rate is 5°C / min.

[0016] Furthermore, in step S2, during the calcination, the calcination atmosphere is argon.

[0017] The second aspect of the present invention provides a porous terephthalaldehyde-aminopyridine polymer, which is prepared by the method described in the first aspect.

[0018] The third aspect of the present invention provides a use of the porous terephthalaldehyde-aminopyridine polymer as described in the first and second aspects, wherein the porous terephthalaldehyde-aminopyridine polymer is used as a catalyst for photocatalytic water production of H2O2.

[0019] Furthermore, the method for photocatalytically producing H2O2 from water includes: dispersing the porous terephthalaldehyde-aminopyridine polymer in water under visible light, and photocatalytically producing H2O2 at room temperature (25°C).

[0020] Furthermore, in the photocatalytic water-to-H2O2 reaction, the wavelength of light is 400-700 nm.

[0021] The present invention regulates the synthesis of a porous terephthalaldehyde-aminopyridine polymer with a porous structure by adjusting the ratio of surfactants in the polymerization reaction. After enhanced polymerization, it is found that the band gap structure of the terephthalaldehyde-aminopyridine polymer is essentially regulated, and the formation of the band gap structure enhances the in-situ generation of H2O2. The porous terephthalaldehyde-aminopyridine polymer prepared by the present invention can be used as a catalyst for dual-channel photocatalytic production of H2O2 by oxygen reduction and water oxidation, and can react in a visible light source and pure water without the presence of a sacrificial agent. Its main principle is that the DA structure leads to hybridization of a low HOMO-LUMO gap through conjugation and π stacking, combined with changes in nanometer size, to regulate the narrow band gap and broaden the light absorption range. Most importantly, the pore structure can adjust the band gap, providing more possibilities for the efficient production of H2O2 without sacrificial agents.

[0022] Compared with the prior art, the present invention has the following characteristics:

[0023] 1) The present invention uses surfactants to construct porous spheres and enhance photocatalytic H2O2 production. This method of band gap regulation through pore structure - hollow spheres - is the first reported discovery in the field of Schiff base photocatalytic H2O2 production and can improve the photocatalytic H2O2 production performance compared to solid sphere catalysts.

[0024] 2) The porous terephthalaldehyde-aminopyridine polymer prepared by the present invention photocatalyzes the production of H2O2 from water without the presence of a sacrificial agent and can react in visible light and pure water. It has the advantages of simple preparation method and simple equipment, and has good industrial application prospects;

[0025] 3) The photocatalytic mechanism of the porous terephthalaldehyde-aminopyridine polymer prepared by the present invention is to produce H2O2 through dual-channel photocatalysis of oxygen reduction and water oxidation.

[0026] 4) The porous terephthalaldehyde-aminopyridine polymer prepared by the present invention overcomes the problems of small photocatalytic contact area and single band gap structure of many Schiff base polymers, and has a wide light absorption range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the ultraviolet diffuse reflectance absorption spectrum of the porous terephthalaldehyde-aminopyridine polymer prepared in Example 1;

[0028] Figure 2 is the band gap of the porous terephthalaldehyde-aminopyridine polymer prepared in Example 1;

[0029] Figure 3 TEM spectrum of the porous terephthalaldehyde-aminopyridine polymer prepared in Example 1;

[0030] Figure 4This is a performance diagram of the porous terephthalaldehyde-aminopyridine polymer prepared in Example 1 for photocatalytic production of H2O2 from water;

[0031] Figure 5 The photocatalytic water-to-H2O2 performance graph of the porous terephthalaldehyde-aminopyridine polymer HP s-0.05 prepared in Example 1 and the terephthalaldehyde-aminopyridine condensation precursor HP0-0.05 prepared in Example 2;

[0032] Figure 6 The catalytic stability of the porous terephthalaldehyde-aminopyridine polymer HP-0.05 prepared in Example 1;

[0033] Figure 7 The H2O2 production performance of the porous terephthalaldehyde-aminopyridine polymer HP-0.05 prepared in Example 1 under inhibitor and different gas atmosphere conditions. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercially available products or conventional processing techniques in the art.

[0036] Example 1:

[0037] A porous terephthalaldehyde-aminopyridine polymer, the preparation method of which comprises the following steps:

[0038] S1: Precursor Synthesis

[0039] 0.5 g of 2,6-diaminopyridine, 0.5 g of F127, 0 g to 0.25 g of sodium dodecylbenzenesulfonate (variable amount), and 0.09 g of NaOH were stirred in an ethanol aqueous solution containing 3 mL of anhydrous ethanol and 20 mL of water until clear, and then 0.5 g of terephthalaldehyde was added to carry out a polymerization reaction at 40°C. The reaction was stirred for 2 hours until a milky solution was obtained, and then 1 mL of glacial acetic acid was added and stirred for 30 minutes. After centrifugation, the mixture was washed three times with water and ethanol solution to obtain a terephthalaldehyde-aminopyridine condensation precursor.

[0040] S2: Enhanced Aggregation

[0041] The terephthalaldehyde-aminopyridine polycondensation precursor was heated to 250°C at a rate of 5°C / min in an argon tube furnace and held for 2 hours to obtain porous terephthalaldehyde-aminopyridine polymers with varying pore structures. The prepared porous terephthalaldehyde-aminopyridine polymers were labeled HPs based on the mass ratio of sodium dodecylbenzenesulfonate to F127: HPs-0, HPs-0.025, HPs-0.05, HPs-0.1, HPs-0.25, and HPs-0.5.

[0042] Figure 1 and Figure 2 They are the ultraviolet diffuse reflection absorption spectrum and band gap of the prepared polymer photocatalyst. It can be seen from the figure that the polymer photocatalyst has the ability to absorb visible light, the absorption edge can extend to the near-infrared region, and the band gap structure becomes narrower with the increase of the proportion of surfactant. Figure 3 This is the TEM spectrum of the prepared polymer photocatalyst. It can be seen from the figure that the addition of surfactant can cause a porous structure inside the nanospheres, and it changes with the increase of the proportion of surfactant.

[0043] Example 2:

[0044] A porous terephthalaldehyde-aminopyridine polycondensation precursor is prepared according to the method of Example 1, except that the enhanced polymerization in step S2 is omitted. The remaining steps are the same as in Example 1. The porous terephthalaldehyde-aminopyridine polycondensation precursor obtained by the same method as in Example 1 is labeled HP0-(0-0.5).

[0045] Example 3:

[0046] A solid terephthalaldehyde-aminopyridine polymer is prepared by a method similar to that of Example 1, except that the two surfactants, F127 and sodium dodecylbenzenesulfonate, are omitted in step S1. The remaining steps are the same as those of Example 1. The obtained solid terephthalaldehyde-aminopyridine polymer is labeled HPs.

[0047] Example 4:

[0048] This example is used to investigate the photocatalytic performance of various porous terephthalaldehyde-aminopyridine polymers prepared in Example 1 to produce H2O2 from water. The specific process includes:

[0049] M1: Disperse 10 mg of porous terephthalaldehyde-aminopyridine polymer in 50 mL of water, stir and sonicate until uniform dispersion forms a reaction solution. The sonication time is 15 min, and adsorb in a dark sealed container for 15 min.

[0050] M2: Place the dispersed reaction solution in step M1 under an LED white light source and start visible light irradiation photocatalytic reaction, wherein the light wavelength is preferably 400-700 nm, and react at room temperature (25° C.) for 60 minutes.

[0051] M3: Take samples and filter them at 0min, 10min, 20min, 30min, 40min, 50min and 60min respectively, and use the iodine titration method to detect the H2O2 concentration in the filtrate.

[0052] Test results such as Figure 4 As shown in the figure, a group of catalysts with different surfactant ratios reacted in pure water under visible light for 60 min. When sodium dodecylbenzene sulfonate was not added to the surfactant during the preparation process and only 0.5 g F127 was added, the catalytic efficiency of producing H2O2 was 650.5 μmol g -1 h -1 When the amount of F127 was fixed and the polymer formed by adding trace amounts of sodium dodecylbenzene sulfonate was adjusted to be within the range of 0.0125-0.025 g, the visible light photocatalytic water production of H2O2 increased, and the efficiency of catalytic H2O2 production could reach 998 μmol g -1 h -1 .

[0053] Example 5:

[0054] This example is used to investigate the effect of enhanced polymerization on the photocatalytic aquaculture H2O2 performance of the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 prepared in Example 1 and the terephthalaldehyde-aminopyridine condensation precursor HP0-0.05 prepared in Example 2. Except for the different catalysts, the other processes and conditions are the same as those in Example 4.

[0055] Test results such as Figure 5 As shown in the figure, it can be seen that the enhanced polymerization step can significantly improve the photocatalytic water-to-H2O2 performance of the polymer. When no enhanced polymerization was performed (HP0-0.05 prepared in Example 2), the efficiency of producing H2O2 in pure water under visible light for 60 minutes was 551.5 μmol g -1 h -1 After enhanced polymerization (HPs-0.05 prepared in Example 1), the efficiency of producing H2O2 was increased to 998 μmol g -1 h -1 .

[0056] Example 6:

[0057] This example is used to investigate the effects of surfactants on the photocatalytic aquatic H2O2 production performance of the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 prepared in Example 1 and the solid terephthalaldehyde-aminopyridine condensation precursor HP prepared in Example 3. Except for the catalyst, the other processes and conditions are the same as those in Example 4.

[0058] The test results are shown in Table 1. When the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 was reacted in pure water under visible light for 20, 40, and 60 min, the concentrations of H2O2 produced were 69.1, 129.2, and 199.6 μmol L -1 , which are higher than the concentration of H2O2 produced by solid terephthalaldehyde-aminopyridine condensation precursor HP at the corresponding time. This shows that the pore structure within the nanospheres can significantly improve the photocatalytic H2O2 production performance within a certain range.

[0059] Table 1

[0060]

[0061] Example 7:

[0062] This example is used to investigate the catalytic stability of the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 prepared in Example 1 and explore its long-term photocatalytic water production H2O2 performance. Except for the catalyst and irradiation time, other processes and conditions are the same as those in Example 4.

[0063] Test results such as Figure 6 As shown in the figure, it can be seen that the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 can stably produce H2O2 after long-term irradiation, basically showing a linear growth trend. After extending the irradiation reaction for 6 hours, the concentration of accumulated H2O2 can reach 908.0 μmol L -1 , it can still maintain stable and efficient H2O2 generation efficiency, indicating that the material has stable catalytic efficiency.

[0064] Example 8:

[0065] This example is used to investigate the photocatalytic performance of the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 prepared in Example 1 in producing H2O2 from water under the conditions of inhibitors and different gas atmospheres. Except for the catalyst, inhibitor (benzoquinone BQ), and gas atmosphere (O2, air, N2 at normal pressure, and all examples are carried out under air unless otherwise specified), the other processes and conditions are the same as those in Example 4, wherein the inhibitor is 1 mmol / L.

[0066] Test results such as Figure 7As shown in the figure, after the introduction of oxygen, the photocatalytic performance of the porous terephthalaldehyde-aminopyridine polymer HPs-0.05 in producing H2O2 from water was slightly higher than that of the control group in the air atmosphere due to the enhanced oxygen reduction reaction. After the introduction of nitrogen, the H2O2 production performance was significantly reduced, from 199.6 μmol L -1 reduced to 110.5 μmol L -1 This result indicates that both the oxygen reduction reaction pathway and the water oxidation pathway for producing H2O2 may exist. Benzoquinone BQ, as an inhibitor of superoxide radicals, significantly reduced the performance of H2O2 production, indicating the existence of a two-step single-electron oxygen reduction reaction pathway for producing H2O2. Therefore, the porous terephthalaldehyde-aminopyridine polymer prepared by the present invention produces H2O2 through dual-channel photocatalysis of oxygen reduction and water oxidation.

[0067] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a porous terephthalaldehyde-aminopyridine polymer, characterized in that: The following steps are involved: S1: dispersing 2,6-diaminopyridine in a solution containing a surfactant and an alkali, and polymerizing it with terephthalaldehyde to obtain a terephthalaldehyde-aminopyridine condensation precursor, wherein the surfactant includes F127; S2: calcining the terephthalaldehyde-aminopyridine polycondensation precursor in step S1 to obtain a porous terephthalaldehyde-aminopyridine polymer.

2. The method for preparing the porous terephthalaldehyde-aminopyridine polymer according to claim 1, wherein: In step S1, the mass ratio of the 2,6-diaminopyridine, F127, base, and terephthalaldehyde is (0.4-0.7):(0.4-0.6):(0.07-0.12):(0.4-0.7).

3. The method for preparing the porous terephthalaldehyde-aminopyridine polymer according to claim 1, wherein: In step S1, the surfactant further comprises sodium dodecylbenzenesulfonate, and the mass ratio of sodium dodecylbenzenesulfonate to F127 is (0.0125-0.25):(0.4-0.6).

4. The method for preparing the porous terephthalaldehyde-aminopyridine polymer according to claim 1, wherein: In step S1, during the polymerization reaction, the reaction temperature is 40-55°C.

5. The method for preparing the porous terephthalaldehyde-aminopyridine polymer according to claim 1, wherein: In step S2, during the calcination, the calcination temperature is 200-300° C. and the calcination time is 2-3 hours.

6. The method for preparing the porous terephthalaldehyde-aminopyridine polymer according to claim 1, wherein: In step S2, during the calcination, the calcination atmosphere is argon.

7. A porous terephthalaldehyde-aminopyridine polymer, characterized in that It is prepared by the method according to any one of claims 1 to 6.

8. Use of the porous terephthalaldehyde-aminopyridine polymer according to claim 7, characterized in that: The porous terephthalaldehyde-aminopyridine polymer is used as a catalyst for photocatalytic water production of H2O2.

9. The use of the porous terephthalaldehyde-aminopyridine polymer according to claim 8, characterized in that: The method for photocatalytically producing H2O2 from water comprises: dispersing a porous terephthalaldehyde-aminopyridine polymer in water under visible light, and performing photocatalytic production of H2O2 at room temperature.

10. The use of the porous terephthalaldehyde-aminopyridine polymer according to claim 8, characterized in that: In the photocatalytic water-to-H2O2 reaction, the wavelength of light is 400-700 nm.

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