Method for preparing hydrogen peroxide by using synthetic melanin-coated porphyrin-based supramolecule

Abstract

The application discloses a preparation method of a synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst, and discloses a method for preparing hydrogen peroxide by using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst. The synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst can be prepared by adding a basic porphyrin solution into a solution of a synthetic melanin precursor, fully mixing, and then reacting under an acidic condition. The method for preparing hydrogen peroxide has mild reaction conditions and simple operation. The synthetic melanin-coated porphyrin-based supramolecular photocatalyst is mixed with ultrapure water, oxygen is introduced and stirred under an atmospheric environment, and then high-concentration hydrogen peroxide can be obtained by reacting under visible light. The method for preparing hydrogen peroxide has the advantages of high yield, high and stable catalytic performance, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing hydrogen peroxide by using a porphyrin-based supermolecular photothermal catalyst coated with synthetic melanin, and belongs to the field of supermolecular chemistry. BACKGROUND

[0002] Hydrogen peroxide (H2O2) is a mild and environmentally friendly oxidant, and is an important raw material for organic synthesis and environmental remediation. It is widely used for sterilization and disinfection and is increasingly attracting people's attention. At present, there are two main methods for preparing hydrogen peroxide in industry: anthraquinone oxidation (AQ) method and direct synthesis method. The anthraquinone oxidation (AQ) method has the disadvantages of high energy consumption and high pollution. Chinese patent CN107176593A proposes a new process of oxidation and extraction coupling production and a new tower equipment for producing H2O2 by the anthraquinone method, and discloses a method for preparing hydrogen peroxide using the equipment. The method improves the extraction rate of H2O2 and simplifies the process, but fundamentally speaking, the method is still a high-energy consumption and high-pollution method. The direct synthesis method is to synthesize H2O2 from H2 and O2 in the presence of a palladium or bimetallic gold palladium catalyst. In this process, the ratio of hydrogen and oxygen needs to be accurately controlled because H2 / O2 mixed gas is explosive in a wide concentration range. Chinese patent CN104379502A proposes a method for reacting hydrogen and oxygen in the presence of a noble metal catalyst and a free radical scavenger. Although the introduction of the free radical scavenger improves the yield of hydrogen peroxide, the use of a noble metal catalyst increases the production cost, and the problem of removing the free radical scavenger from the hydrogen peroxide solution has not been solved. Compared with the anthraquinone oxidation and direct synthesis processes, the photocatalytic method only needs water and oxygen as raw materials, renewable sunlight as energy supply, and a semiconductor as a photocatalyst to complete the preparation of hydrogen peroxide. And there is no pollutant emission in the whole process. However, the photocatalysts currently used for preparing hydrogen peroxide require the addition of a sacrificial agent during the reaction process, and the utilization rate of visible light is low, and the yield of hydrogen peroxide is not high.

[0003] Porphyrin-based supermolecular photocatalysts have strong light absorption capacity (absorbing full visible wavelength), have a special structure that can promote the separation and transmission of photo-generated charges, and have the advantages of being green and non-toxic, and are widely studied as one of the potential high-efficiency photocatalysts for preparing hydrogen peroxide. Zhang et al. proposed a method for preparing hydrogen peroxide by porphyrin-based supermolecular photocatalytic photothermal, and the yield of hydrogen peroxide under visible light irradiation was 1.7 mM / h. However, this method has low hydrogen peroxide yield, low photo-thermal conversion efficiency, and requires an external heat source (Zhang, Y. et al., Nat Energy 2023, 8, 361). Therefore, it is of great significance to study a catalyst that can further improve the yield of hydrogen peroxide and avoid the use of an external heat source.

[0004] Synthetic melanin is a highly efficient electron transfer intermediate (Kim, J. H. et al. Angew Chem Int Ed 2014, 53, 6364), and it has a suitable bandwidth and strong absorption of infrared light, and excellent light-heat conversion ability (Yang, F. et al. J Colloid Interface Sci 2022, 613, 775; Bai, W. et al. Macromolecules 2022, 55, 3493), and is expected to be used as a modifier in the production of hydrogen peroxide by photo-thermal catalysis. SUMMARY

[0005] The present application aims to provide a catalyst for efficient photo-thermal catalytic production of hydrogen peroxide and a preparation method thereof, using synthetic melanin and porphyrin-based supramolecules as raw materials to synthesize photo-thermal catalysts, and using synthetic melanin-coated porphyrin-based supramolecules as photo-thermal catalysts, O2 as a reaction raw material, and visible light as an energy source to produce hydrogen peroxide, which improves the yield of H2O and O2 to generate H2O2, and has high practical significance and actual value.

[0006] To achieve the above-mentioned purpose, the present application first provides a preparation method of synthetic melanin-coated porphyrin-based supramolecular photo-thermal catalyst, comprising the following steps:

[0007] (1) Pretreatment of porphyrin monomer: ultrasonic dispersion of porphyrin monomer in solvent to obtain a porphyrin dispersion, and adjusting the pH of the porphyrin dispersion to 8.0-10.0 using an alkaline pH adjuster to obtain an alkaline porphyrin dispersion;

[0008] (2) Preparation of synthetic melanin-coated porphyrin-based supramolecule: dissolving synthetic melanin precursor in deionized water to form a synthetic melanin precursor aqueous solution, adding the alkaline porphyrin dispersion prepared in step (1) to the synthetic melanin precursor aqueous solution, stirring to fully mix, adjusting the pH of the dispersion to 3-4 using an acidic pH adjuster, centrifuging to collect the precipitate, washing and drying to obtain a synthetic melanin-coated porphyrin-based supramolecular photo-thermal catalyst.

[0009] In the present application, the alkaline porphyrin dispersion is added to the synthetic melanin precursor aqueous solution, and fully mixed, and in the alkaline environment, the synthetic melanin precursor will be oxidized in the air to obtain synthetic melanin, and after adding the acidic pH adjuster, the porphyrin monomer will self-assemble into porphyrin supramolecules under acidic conditions. In the preparation process of the synthetic melanin-coated porphyrin-based supramolecular photo-thermal catalyst, the synthetic melanin precursor and the porphyrin monomer will be converted into synthetic melanin and porphyrin supramolecules, and the synthetic melanin will be coated on the surface of the lamellar porphyrin supramolecule.

[0010] In an embodiment of the present application, in step (1), the porphyrin monomer comprises at least one of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin (THPP), 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP), and 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP).

[0011] In an embodiment of the present application, in step (1), the mass-volume ratio of the porphyrin monomer and the solvent is 1.0-3.0 g / L, and the solvent comprises at least one of anhydrous ethanol, acetone, and water.

[0012] In an embodiment of the present application, in step (1), the power during ultrasonic dispersion is 180-360 W, and the ultrasonic time is 10-30 min.

[0013] In an embodiment of the present application, in step (1), the basic pH regulator comprises at least one of tris(hydroxymethyl)aminomethane, sodium hydroxide, and ammonia.

[0014] In an embodiment of the present application, in step (2), the synthetic melanin precursor comprises at least one of tyrosine (Tyr), dopamine (DA), and 1,3,4-dihydroxyphenylalanine (L-DOPA).

[0015] In an embodiment of the present application, in step (2), the concentration of the synthetic melanin precursor in the aqueous synthetic melanin precursor solution is 30-50 g / L, and the volume ratio of the aqueous synthetic melanin solution to the basic porphyrin solution is 1:5-1:10.

[0016] In an embodiment of the present application, in step (2), the acidic pH regulator comprises at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0017] In an embodiment of the present application, in step (2), the concentration of the added acidic pH regulator is 0.1 mol / L, and the volume of the added acidic pH regulator is 30 mL.

[0018] In an embodiment of the present application, in step (2), the mass ratio of the synthetic melanin to the porphyrin-based supramolecule is 1:0.1-1:10.

[0019] In an embodiment of the present application, in step (2), the stirring speed is 650 rpm, and the stirring time is 24-48 h.

[0020] The present application also provides a synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst prepared by the above method.

[0021] The application further provides application of the above-mentioned synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst in catalytic preparation of hydrogen peroxide.

[0022] The application further provides a method for preparing hydrogen peroxide by using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst, comprising the following steps:

[0023] (1) ultrasonic dispersion of the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst in water to obtain a synthetic melanin-coated porphyrin-based supramolecular dispersion liquid;

[0024] (2) continuously passing O2 with a flow rate of 50-200 mL / min into the synthetic melanin-coated porphyrin-based supramolecular dispersion liquid obtained in step (1) and stirring, and promoting the reaction by visible light irradiation;

[0025] (3) filtering the reaction solution obtained in step (2) to obtain a hydrogen peroxide aqueous solution.

[0026] In an embodiment of the application, in step (1), the concentration of the synthetic melanin-coated porphyrin-based supramolecular dispersion liquid is 2.0-5.0 g / L, preferably 4.0 g / L.

[0027] In an embodiment of the application, in step (1), the power for ultrasonic dispersion is 180-360 W, and the ultrasonic time is 10-30 min.

[0028] In an embodiment of the application, in step (2), the flow rate of oxygen is 50-200 mL / min, preferably 100 mL / min.

[0029] In an embodiment of the application, in step (2), the intensity of visible light irradiation is 100-300 mW / cm 2 , preferably 200 mW / cm 2 , and the irradiation time is 1-20 h.

[0030] In an embodiment of the application, in step (2), the visible light is from a xenon lamp with an additional 420 nm cut-off filter (λ≥420 nm).

[0031] In an embodiment of the application, in step (2), the stirring speed is 500-2000 rpm.

[0032] In an embodiment of the application, in step (3), the method further comprises a concentration step for the filtrate after filtration. Specifically, the concentration of the filtrate can be performed by means of reduced pressure distillation.

[0033] In an embodiment of the application, the temperature for reduced pressure concentration is 55-65℃.

[0034] In an embodiment of the present application, the centrifuge has a rotation speed of 7800 rpm.

[0035] In an embodiment of the present application, step (3) further comprises washing the filtered filter cake with ultrapure water, drying, and recovering the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst.

[0036] In an embodiment of the present application, the drying of the filter cake in step (3) is performed by freeze-drying or vacuum drying at 60°C.

[0037] Advantages of the present application

[0038] (1) The method for preparing hydrogen peroxide using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst provided by the present application avoids the need for an external heat source for the porphyrin-based supramolecular photocatalyst, and greatly improves the yield of hydrogen peroxide.

[0039] (2) The method for preparing hydrogen peroxide using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst provided by the present application uses O2 as the oxygen source and sunlight (visible light) as the energy source under normal pressure. Compared with the industrial anthraquinone method (AQ) for synthesizing hydrogen peroxide, the method of the present application has low energy consumption, a simple process, and high safety.

[0040] (3) The method for preparing hydrogen peroxide using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst provided by the present application does not use noble metals, which is more economically valuable than directly preparing hydrogen peroxide from a mixture of oxygen and hydrogen. Compared with the traditional photocatalytic preparation of hydrogen peroxide, the method does not use organic sacrificial agents and the separation and concentration of hydrogen peroxide are simpler. The raw materials used in the present application have a lower cost, which improves the efficiency of hydrogen peroxide preparation while reducing the preparation cost.

[0041] (4) The present application uses the photothermal catalytic hydrogen peroxide production performance of the porphyrin-based supramolecule prepared from 5,10,15,20-tetra(4-hydroxyphenyl) porphyrin (THPP), 5,10,15,20-tetra(4-carboxyphenyl) porphyrin (TCPP), 5,10,15,20-tetra(4-aminophenyl) porphyrin (TAPP), and other porphyrin monomers. At the same time, the synthetic melanin is used as an efficient electron transfer intermediate and has excellent light-thermal conversion ability. Compared with the photocatalytic hydrogen peroxide production technology scheme of the porphyrin-based catalyst with an external heat source, the yield of hydrogen peroxide per unit time obtained by the method of the present application can be as high as 3 mM / L.

[0042] (5) The method for preparing hydrogen peroxide has mild reaction conditions and simple operation, only needs to uniformly mix the synthetic melanin coated porphyrin-based supramolecular photocatalyst and ultrapure water, passes in oxygen and stirs under the condition of visible light, and high-concentration hydrogen peroxide can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 Performance comparison chart of different synthetic melanin coated TCPP supramolecular catalysts for photo-thermal catalytic preparation of hydrogen peroxide;

[0044] Figure 2 The electron microscope chart of the polydopamine (PDA) coated 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin (TCPP) supramolecular catalyst, wherein (a) is a scanning electron microscope chart, and (b) is a transmission electron microscope chart;

[0045] Figure 3 The concentration of hydrogen peroxide generated by the polydopamine (PDA) coated TCPP supramolecular photo-thermal catalysis and the ratio of the amount of TCPP monomer and DA in the synthesis process chart;

[0046] Figure 4 The concentration of hydrogen peroxide generated by the polydopamine (PDA) coated TCPP supramolecular photo-thermal catalysis and the ratio of the amount of TCPP monomer and DA in the synthesis process chart;

[0047] Figure 5 The concentration of hydrogen peroxide generated by the polydopamine (PDA) coated TCPP supramolecular photo-thermal catalysis and the ratio of the amount of TCPP monomer and DA in the synthesis process chart;

[0048] Figure 6 The concentration of hydrogen peroxide generated by the polydopamine (PDA) coated TCPP supramolecular photo-thermal catalysis and the ratio of the amount of TCPP monomer and DA in the synthesis process chart. DETAILED DESCRIPTION

[0049] The concentration test method of hydrogen peroxide:

[0050] The potassium titanium oxalate solution and hydrogen peroxide form a yellow complex (yellow solution), the absorbance at 400 nm is determined by the ultraviolet spectrophotometer, and the concentration of hydrogen peroxide is calculated by the Lambert-Beer law. Specifically, 1 mL of reaction solution is taken every 1 h after the reaction starts, a 0.45 mu m filter membrane is used to filter the catalyst, 1 ml of 0.02M potassium titanium oxalate solution and 3 mL of deionized water are added, the solution is yellow, and the absorbance of the yellow solution at 400 nm is determined by the ultraviolet spectrophotometer to calculate the concentration of hydrogen peroxide.

[0051] The source of porphyrin and synthetic melanin in the application:

[0052] Sources of porphyrin monomers:

[0053] 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin (THPP): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 97%.

[0054] 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 97%.

[0055] 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 97%.

[0056] Sources of melanin precursors:

[0057] Dopamine hydrochloride (DA·HCl): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 98%.

[0058] 1,3,4-dihydroxyphenylalanine (L-DOPA): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 98%.

[0059] Tyrosine (Tyr): purchased from Beijing InoKai Technology Co., Ltd., with a purity of 98%.

[0060] Example 1

[0061] A method for preparing a polydopamine-coated TCPP supramolecular photothermal catalyst, comprising the following steps:

[0062] (1) Pretreatment of TCPP supramolecule: 200 mg of TCPP monomer was dispersed in a mixture of 40 mL of anhydrous ethanol and 60 mL of deionized water, and after ultrasonic dispersion for 30 min, tris(hydroxymethyl) aminomethane was used to adjust the pH of the dispersion to 8.5, to obtain an alkaline TCPP dispersion;

[0063] (2) Preparation of polydopamine-coated TCPP supramolecule: 500 mg of dopamine hydrochloride was dissolved in 10 mL of deionized water to form a dopamine aqueous solution, and the alkaline TCPP dispersion prepared in step (1) was added to the dopamine aqueous solution, and stirred at 650 rpm for 48 h. The pH of the dispersion was adjusted to 3 with 0.1 mol / L hydrochloric acid, and the precipitate was collected by centrifugation, washed with deionized water three times, and dried at 60°C under vacuum overnight to obtain a polydopamine-coated TCPP supramolecular photothermal catalyst (PDA@TCPP supramolecule).

[0064] Example 2

[0065] The method for producing hydrogen peroxide by using TCPP supramolecular photothermal catalysis coated with polydopamine (PDA) includes the following steps:

[0066] In a 50 mL flask, 120 mg of TCPP supramolecular photothermal catalyst coated with polydopamine and 30 mL of deionized water were added, the mouth plug was sealed, and an oxygen inlet pipe was inserted into the mouth plug. Oxygen was continuously introduced, and after ultrasonic treatment for 30 min, the flask was placed on a magnetic stirring table for stirring at a magnetic stirring speed of 800 rpm. The O2 flow rate was maintained at 100 mL / min during the whole process, and a xenon lamp (λ≥420 nm) with a light intensity of 200 mW / cm2was used for illumination for 4 h. The preparation method of the TCPP supramolecular photothermal catalyst coated with polydopamine was the same as that in Example 1. 2

[0067] Every 1 h, 1 mL of the reaction solution was taken with a needle tube, and after removing the catalyst with a 0.45 μm filter membrane, 1 mL of a titanium potassium oxalate solution (0.02 M) and 3 mL of ultrapure water were added to the reaction solution. The absorbance of the reaction solution at 400 nm was measured using a UV spectrophotometer, and the concentration of hydrogen peroxide was calculated by the Lambert-Beer law.

[0068] Example 3

[0069] Example 3 is different from Example 2 in that the type of catalyst is changed. Specifically, the TCPP supramolecular photothermal catalyst coated with polydopamine is replaced by a TCPP supramolecular (Tyr@TCPP supramolecular) photothermal catalyst coated with polytyrosine. The preparation method of the TCPP supramolecular photothermal catalyst coated with polytyrosine is different from that of Example 1 in that the dopamine hydrochloride in step (3) is replaced by tyrosine.

[0070] Example 4

[0071] Example 4 is different from Example 2 in that the type of catalyst is changed. Specifically, the TCPP supramolecular photothermal catalyst coated with polydopamine is replaced by a TCPP supramolecular (L-DOPA@TCPP supramolecular) photothermal catalyst coated with poly-1,3,4-dihydroxyphenylalanine. The preparation method of the TCPP supramolecular photothermal catalyst coated with poly-1,3,4-dihydroxyphenylalanine is different from that of Example 1 in that the dopamine hydrochloride in step (3) is replaced by 1,3,4-dihydroxyphenylalanine.

[0072] Figure 1 The performance comparison chart of the different melanin-coated TCPP supramolecular catalysts in Examples 2-4 for producing hydrogen peroxide by photothermal catalysis. The illumination time is 4 h. From the chart, it can be seen that the TCPP supramolecular photothermal catalyst coated with polydopamine has the best performance for producing hydrogen peroxide by photothermal catalysis. Figure 1 ​It can be seen that the cumulative production of hydrogen peroxide after 4h of photothermal reaction is used as an index to evaluate the ability of the synthesized melanin-coated porphyrin-based supramolecular catalyst to produce hydrogen peroxide by photothermal catalysis. Among the several synthesized melanin-coated porphyrin-based supramolecular catalysts, the PDA-coated TCPP supramolecular photocatalyst has the best ability to produce hydrogen peroxide by photothermal catalysis, with a hydrogen peroxide concentration as high as 102mM / g (i.e. 0.32wt%); the catalytic activity of the poly-1,3,4-dihydroxyphenylalanine-coated TCPP supramolecular (L-DOPA@TCPP supramolecular) is second, with a hydrogen peroxide concentration of 90mM / g, and the poly-tyrosine (Tyr@TCPP supramolecular)-coated TCPP supramolecular has a hydrogen peroxide concentration of 82mM / g.

[0073] The PDA@TCPP supramolecular photocatalyst in Example 1 was subjected to morphological characterization. Figure 2 (a) is the SEM image of the PDA@TCPP supramolecular catalyst. The SEM image shows that the PDA@TCPP supramolecular has a sheet structure, i.e. the main material is TCPP supramolecular; and there are a large number of particles on the nanosheet, i.e. PDA. This particle accumulation mode on the sheet surface is conducive to the transfer of electrons from TCPP to PDA, promotes the separation of photo-generated carriers, and the heat generated by PDA photothermal is fully transferred to the TCPP sheet. Figure 2 (b) is the TEM image of the PDA@TCPP supramolecular. The TEM image shows the same PDA and TCPP combination mode as the SEM.

[0074] Example 5

[0075] The difference between Example 5 and Example 2 is that the amount of TCPP monomer is adjusted from 200mg to 100mg when preparing the polydopamine-coated TCPP supramolecular photocatalyst.

[0076] Example 6

[0077] The difference between Example 6 and Example 2 is that the amount of TCPP monomer is adjusted from 200mg to 300mg when preparing the polydopamine-coated TCPP supramolecular photocatalyst.

[0078] The effect of the amount of DA and TCPP monomer in the PDA-coated TCPP supramolecular photocatalyst in Example 2, Example 5 and Example 6 on the photothermal hydrogen peroxide production performance is shown in Figure 3

[0079] The PDA@TCPP supramolecular photocatalyst in Example 1 was subjected to morphological characterization. Figure 3 ​Data comparison shows that when the catalyst dosage is 120 mg, the deionized water dosage is 30 mL, the oxygen flow rate is 100 mL / min, and the light exposure time is 4 h, the hydrogen peroxide yield obtained by photothermal catalysis with a DA to TCPP ratio in the range of 5:1 to 5:3 is compared, and the optimal DA to TCPP ratio is found to be 5:2.

[0080] Example 7

[0081] The difference between Example 7 and Example 2 is that the amount of catalyst used was adjusted from 120 mg to 90 mg.

[0082] Example 8

[0083] The difference between Example 8 and Example 2 is that the amount of catalyst used was adjusted from 120 mg to 150 mg.

[0084] The effect of the amount of PDA-coated TCPP supramolecular photothermal catalyst used in Examples 2 and 7-8 on the photothermal hydrogen peroxide production performance is as follows: Figure 4 As shown. By Figure 4 Data comparison shows that when the ratio of PDA to TCPP is 5:2, the amount of deionized water is 30 mL, the oxygen flow rate is 100 mL / min, and the light exposure time is 4 h, the hydrogen peroxide yield obtained by comparing the catalyst dosage range of 90-150 mg is found to be 120 mg.

[0085] Example 9

[0086] A method for sacrificial agent-free photothermal catalytic production of hydrogen peroxide based on PDA-coated TCPP supramolecular molecules includes the following steps:

[0087] In a 50 mL flask, add 90 mg of PDA-coated TCPP supramolecular photothermal catalyst and 30 mL of deionized water. Seal the flask with a reverse stopper and insert an oxygen-filled tubing into the stopper, continuously introducing oxygen. After sonicating for 30 min, place the flask on a magnetic stirrer at 800 rpm, maintain an O2 flow rate of 100 mL / min, and use a light intensity of 200 mW / cm². 2 The solution was irradiated with a xenon lamp (λ≥420nm) for 4 hours. The temperature of the solution was measured every 15 minutes. The preparation method of the polydopamine-coated TCPP supramolecular photothermal catalyst was the same as in Example 1.

[0088] Example 10

[0089] The difference between Example 10 and Example 9 is that the catalyst polydopamine-coated TCPP (PDA@TCPP) supramolecule is replaced by poly-1, 3, 4-dihydroxyphenylalanine-coated TCPP (L-DOPA@TCPP) supramolecule. Among them, the preparation method of the poly-1, 3, 4-dihydroxyphenylalanine-coated TCPP supramolecule photothermal catalyst is different from that of Example 1 in that the dopamine hydrochloride in step (3) is replaced by 1, 3, 4-dihydroxyphenylalanine.

[0090] Example 11

[0091] The difference between Example 11 and Example 9 is that the catalyst PDA@TCPP is replaced by poly-tyrosine-coated TCPP (Tyr@TCPP) supramolecule. Among them, the preparation method of the poly-tyrosine-coated TCPP supramolecule photothermal catalyst is different from that of Example 1 in that the dopamine hydrochloride in step (3) is replaced by tyrosine.

[0092] Example 12

[0093] The difference between Example 12 and Example 9 is that the catalyst PDA@TCPP is replaced by TCPP supramolecule. Among them, the preparation method of the TCPP supramolecule is that 500 mg of TCPP monomer is dissolved in 10 mL of 0.5M KOH solution, then 100 mL of deionized water is added, stirred at room temperature for 0.5 h, then 0.1M HCl is added dropwise with a constant pressure dropping funnel until the pH is 4, the obtained TCPP supramolecule solution is centrifuged at 8000 rpm, and washed with water three times, the collected solid is vacuum dried at 353K, and finally the purple powder obtained is TCPP supramolecule.

[0094] The relationship between temperature change and light time in the reaction solution of different synthetic melanin-coated TCPP supramolecules in Examples 9-12 is as shown in Figure 5 As shown in the data comparison of Figure 5 It can be seen that in the same time, the solution containing the catalyst PDA@TCPP supramolecule has the highest temperature, and the solution temperature tends to be stable at 60 min. The order of photothermal conversion ability is: PDA@TCPP supramolecule>L-DOPA@TCPP supramolecule>Tyr@TCPP supramolecule>TCPP supramolecule; the experiment proves that the introduction of synthetic melanin can improve the photothermal conversion ability of the catalyst.

[0095] Example 13

[0096] The difference between Example 13 and Example 2 is that the light time is adjusted from 4h to 1h.

[0097] Example 14

[0098] The difference between Example 14 and Example 2 is that the illumination time is adjusted from 4 hours to 2 hours.

[0099] Example 15

[0100] The difference between Example 15 and Example 2 is that the illumination time was adjusted from 4 hours to 3 hours.

[0101] Example 16

[0102] The difference between Example 16 and Example 2 is that the illumination time was adjusted from 4 hours to 6 hours.

[0103] Example 17

[0104] The difference between Example 17 and Example 2 is that the illumination time was adjusted from 4 hours to 8 hours.

[0105] Example 18

[0106] The difference between Example 18 and Example 2 is that the illumination time was adjusted from 4 hours to 10 hours.

[0107] The relationship between the concentration of polydopamine (PDA)-coated TCPP supramolecular photothermal catalysis and reaction time in Examples 2 and 13-18 is as follows: Figure 6 As shown, by Figure 6 It can be seen that after 1, 2, 3, 4, 6, 8 h and 10 h of reaction, hydrogen peroxide aqueous solutions with concentrations of 28 mM / g (0.09 wt%), 54 mM / g (0.17 wt%), 79 mM / g (0.24 wt%), 102 mM / g (0.32 wt%), 143 mM / g (0.44 wt%), 184 mM / g (0.57 wt%) and 225 mM / g (0.70 wt%) were obtained, respectively. Observing the trend of the curves in the figure, it can be found that the hydrogen peroxide production rate remained basically unchanged within 10 h of reaction, indicating that the photocatalyst PDA@TCPP has a stable and efficient photothermal catalytic ability to prepare hydrogen peroxide.

Claims

1. A method for preparing a synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst, characterized in that, The method comprises the following steps: (1) Pretreatment of porphyrin monomer: ultrasonic dispersion of porphyrin monomer in a solvent to obtain a porphyrin dispersion, adjustment of the pH of the porphyrin dispersion to 8.0-10.0 using a basic pH adjuster to obtain a basic porphyrin dispersion, the mass-volume ratio of the porphyrin monomer and the solvent being 1.0-3.0 g / L; the porphyrin monomer comprising at least one of 5, 10, 15, 20-tetrakis(4-hydroxyphenyl) porphyrin, 5, 10, 15, 20-tetrakis(4-carboxyphenyl) porphyrin and 5, 10, 15, 20-tetrakis(4-aminophenyl) porphyrin; (2) Preparation of a synthetic melanin-coated porphyrin-based supramolecular: dissolving a synthetic melanin precursor in deionized water to form a synthetic melanin precursor aqueous solution, adding the basic porphyrin dispersion prepared in step (1) to the synthetic melanin precursor aqueous solution, stirring to fully mix, adjusting the pH of the dispersion to 3-4 using an acidic pH adjuster, centrifuging to collect the precipitate, washing and drying to obtain a synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst; wherein the concentration of the synthetic melanin precursor in the synthetic melanin precursor aqueous solution is 30-50 g / L, and the volume ratio of the synthetic melanin precursor aqueous solution to the basic porphyrin dispersion is 1:5-1:10; the synthetic melanin precursor comprises at least one of tyrosine, dopamine and 1, 3, 4-dihydroxyphenylalanine.

2. The production method according to claim 1, characterized by, In step (1), the solvent comprises at least one of anhydrous ethanol, acetone and water, and the basic pH adjuster comprises at least one of tris(hydroxymethyl) aminomethane, sodium hydroxide and ammonia water.

3. The preparation method according to claim 1, characterized in that, In step (2), the acidic pH adjuster comprises at least one of hydrochloric acid, sulfuric acid and nitric acid.

4. The synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst prepared by the preparation method according to any one of claims 1-3.

5. The use of the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst according to claim 4 in the catalytic preparation of hydrogen peroxide.

6. A method for preparing hydrogen peroxide by using the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst according to claim 4, characterized in that, The method comprises the following steps: (1) ultrasonic dispersion of the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst in water to obtain a synthetic melanin-coated porphyrin-based supramolecular dispersion; (2) continuously introducing O2 into the synthetic melanin-coated porphyrin-based supramolecular dispersion obtained in step (1) at a flow rate of 50-200 mL / min, stirring, and promoting the reaction using visible light irradiation; (3) filtering the reaction solution obtained in step (2), taking the filtrate to obtain an aqueous hydrogen peroxide solution.

7. The method of claim 6, wherein, In step (1), the concentration of the synthetic melanin-coated porphyrin-based supramolecular dispersion is 2.0-5.0 g / L, the ultrasonic dispersion power is 180-360 W, and the ultrasonic dispersion time is 10-30 min.

8. The method of claim 6, wherein, In step (2), the flow rate of oxygen is 50-200 mL / min, the light intensity of visible light is 100-300 mW / cm 2 , and the light exposure time is 1-20 h.

9. The method of claim 6, wherein, In step (2), the visible light is from a xenon lamp with an externally added λ≥420 nm cut-off filter.

10. The method of claim 6, wherein, In step (3), further comprising the steps of washing the filter cake after filtration with ultrapure water and drying to recover the synthetic melanin-coated porphyrin-based supramolecular photothermal catalyst, and concentrating the filtrate after filtration.

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