Nitrogen heterocyclic polyimide photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an N-heterocyclic polyimide photocatalyst and a preparation method and application thereof.The preparation method comprises the steps that nitrogen-rich small organic molecules are subjected to heat treatment to obtain a nitrogen-containing precursor, the nitrogen-containing precursor in the first step is mixed with polybasic anhydride, a polyimide mixture is obtained through a solid-phase reaction, the polyimide mixture in the second step is washed with hot water, and then the nitrogen-heterocyclic polyimide photocatalyst is obtained. And carrying out Soxhlet extraction by using an organic solvent, filtering, and drying the filtered product in a vacuum drying oven to obtain the N-heterocyclic polyimide photocatalyst. According to the preparation method of the azacyclo-polyimide photocatalyst, no solvent is needed in the reaction process, the temperature is low, and different azacyclo-polyimides can be prepared through regulation and control of the precursor and the polybasic anhydride. The photocatalyst has the characteristics of visible light response and oxygen activation.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, and specifically relates to a nitrogen heterocyclic polyimide photocatalyst and a preparation method and application thereof. Background Art

[0002] The controllable extraction of oxygen-containing free radicals (such as hydroxyl radicals, superoxide radicals, etc.) is of great significance to the low-temperature green development of oxidation reactions. However, the bond energy of the O=O bond in the oxygen molecule is as high as 498 kJ / mol, which makes it extremely difficult to achieve bond breaking activation of O=O at low temperatures. In addition, in most oxidation reactions, the substrate or catalyst is in a singlet state, and oxygen is a triplet molecule, and the reaction between the two violates the law of spin conservation. Therefore, high bond energy and spin prohibition have become the key obstacles to low-temperature driven oxidation reactions. In order to reduce the activation energy of the oxidation reaction, it is necessary to study low-temperature activation catalysts for oxygen.

[0003] Oxygen activation catalysts are key to achieving low-temperature oxygen activation, directly determining the apparent activation energy of the reaction as well as the types and content of oxygen-containing free radicals. Numerous studies have confirmed that light-induced oxygen activation at room temperature can be achieved. It can drive oxygen to produce superoxide radicals through single-electron transfer of photogenerated electrons, or it can utilize photogenerated holes to oxidize water to produce hydroxyl radicals. Furthermore, singlet oxygen generation can also be achieved through energy transfer. However, conventional oxide semiconductors face problems such as weak visible light response and severe photogenerated carrier recombination, which reduce their room-temperature oxygen activation capabilities.

[0004] Currently, polymer semiconductor materials, represented by graphitic carbon nitride (GCN), are attracting widespread attention in the field of light-driven oxygen activation. Their diverse unit cell structures, controllable energy distribution, and designable reactive sites hold great promise for photocatalysis. However, GCN is limited by its high exciton binding energy and limited oxygen activation capacity. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a photocatalyst of nitrogen heterocyclic polyimide, which aims to provide a novel, visible light responsive photocatalyst and achieve effective activation of O2.

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

[0007] A method for preparing a nitrogen heterocyclic polyimide photocatalyst comprises the following steps:

[0008] Step 1: heat-treating nitrogen-rich organic small molecules to obtain nitrogen-containing precursors;

[0009] Step 2: mixing the nitrogen-containing precursor in step 1 with a polyacid anhydride, and obtaining a polyimide mixture through a solid phase reaction;

[0010] Step 3: The polyimide mixture in step 2 is first rinsed with hot water, then subjected to Soxhlet extraction and filtration using an organic solvent. The filtered product is placed in a vacuum drying oven and dried to obtain the nitrogen heterocyclic polyimide photocatalyst.

[0011] Among them, the nitrogen-rich organic small molecules described in step 1 include 3,5-diamino-1,2,4-triazole, 3-amino-1,2,4-triazole, and 5-amino-1H-tetrazole.

[0012] Wherein, the heat treatment temperature in step 1 is 225°C to 425°C.

[0013] Wherein, the polyacid anhydride described in step 2 includes pyromellitic anhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride.

[0014] Wherein, the molar ratio of the nitrogen-containing precursor to the polyacid anhydride in step 2 is 1-2:0.5-1.

[0015] Wherein, the solid phase reaction temperature in step 2 is 225°C-525°C.

[0016] Wherein, the solid phase reaction heating rate in step 2 is 5°C / min-15°C / min.

[0017] The hot water rinse in step 3 is warm water at a temperature of 50°C to 70°C;

[0018] The solvent for Soxhlet extraction is tetrahydrofuran or methanol, and the vacuum drying time is 1h-12h.

[0019] A nitrogen heterocyclic polyimide photocatalyst is prepared by the above-mentioned preparation method of the nitrogen heterocyclic polyimide photocatalyst, and the nitrogen heterocyclic polyimide is a bulk aggregated structure.

[0020] An application of a nitrogen heterocyclic polyimide photocatalyst is based on the above-mentioned nitrogen heterocyclic polyimide photocatalyst, wherein the nitrogen heterocyclic polyimide photocatalyst is applied to the photocatalytic activation of oxygen to produce hydrogen peroxide and the oxidation of phenylboric acid to produce phenol.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. The present invention provides a method for preparing a nitrogen-heterocyclic polyimide photocatalyst. The reaction process does not require a solvent and is performed at a low temperature. By regulating the precursors and polyanhydrides, different nitrogen-heterocyclic polyimides can be prepared. This type of photocatalyst exhibits visible light response and oxygen activation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of nitrogen heterocyclic polyimide;

[0024] Figure 2 This is the solid-state NMR image of nitrogen heterocyclic polyimide;

[0025] Figure 3 This is the XPS spectrum of nitrogen heterocyclic polyimide;

[0026] Figure 4 is the UV-visible absorption spectrum of nitrogen heterocyclic polyimide;

[0027] Figure 5 is the XRD spectrum of nitrogen heterocyclic polyimide;

[0028] Figure 6 This is the infrared spectrum of nitrogen heterocyclic polyimide;

[0029] Figure 7 This is a scanning electron microscope image of nitrogen heterocyclic polyimide. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Example 1

[0032] A method for preparing a nitrogen heterocyclic polyimide photocatalyst comprises the following steps:

[0033] Step 1: heat-treating nitrogen-rich organic small molecules to obtain nitrogen-containing precursors;

[0034] Among them, the nitrogen-rich organic small molecule is 5-amino-1H-tetrazole;

[0035] The heat treatment temperature is 325°C.

[0036] Step 2: mixing the nitrogen-containing precursor in step 1 with a polyacid anhydride, and obtaining a polyimide mixture through a solid phase reaction;

[0037] Wherein, the polyacid anhydride is pyromellitic anhydride;

[0038] Wherein, the molar ratio of nitrogen-containing precursor to polyacid anhydride is 1:1;

[0039] Among them, the solid phase reaction temperature is 425℃;

[0040] Among them, the solid phase reaction heating rate is 10℃ / min;

[0041] The solid phase reaction time is 2 h.

[0042] Step 3: The polyimide mixture in step 2 is first rinsed with hot water, then subjected to Soxhlet extraction with an organic solvent, filtered, and the filtered product is placed in a vacuum drying oven for drying to obtain a nitrogen heterocyclic polyimide photocatalyst;

[0043] Among them, hot water flushing is warm water at a temperature of 60°C;

[0044] The solvent for Soxhlet extraction is tetrahydrofuran or methanol, and the vacuum drying time is 2 h.

[0045] Example 2

[0046] A method for preparing a nitrogen heterocyclic polyimide photocatalyst comprises the following steps:

[0047] Step 1: heat-treating nitrogen-rich organic small molecules to obtain nitrogen-containing precursors;

[0048] Among them, the nitrogen-rich organic small molecule is 3,5-diamino-1,2,4-triazole;

[0049] The heat treatment temperature is 225°C.

[0050] Step 2: mixing the nitrogen-containing precursor in step 1 with a polyacid anhydride, and obtaining a polyimide mixture through a solid phase reaction;

[0051] Among them, polyacid anhydrides include 1,4,5,8-naphthalenetetracarboxylic anhydride;

[0052] The molar ratio of the nitrogen-containing precursor to the polyacid anhydride is 2:1;

[0053] Among them, the solid phase reaction temperature is 225℃;

[0054] Among them, the solid phase reaction heating rate is 5℃ / min;

[0055] The solid phase reaction time is 2 h.

[0056] Step 3: The polyimide mixture in step 2 is first rinsed with hot water, then subjected to Soxhlet extraction with an organic solvent, filtered, and the filtered product is placed in a vacuum drying oven for drying to obtain a nitrogen heterocyclic polyimide photocatalyst;

[0057] Among them, hot water flushing is warm water at a temperature of 50°C;

[0058] The solvent for Soxhlet extraction is tetrahydrofuran or methanol, and the vacuum drying time is 5 h.

[0059] Example 3

[0060] A method for preparing a nitrogen heterocyclic polyimide photocatalyst comprises the following steps:

[0061] Step 1: heat-treating nitrogen-rich organic small molecules to obtain nitrogen-containing precursors;

[0062] Among them, the nitrogen-rich organic small molecule is 3-amino-1,2,4-triazole;

[0063] The heat treatment temperature is 425°C.

[0064] Step 2: mixing the nitrogen-containing precursor in step 1 with a polyacid anhydride, and obtaining a polyimide mixture through a solid phase reaction;

[0065] Wherein, the polyacid anhydride is 1,4,5,8-naphthalenetetracarboxylic anhydride;

[0066] Wherein, the molar ratio of nitrogen-containing precursor to polyacid anhydride is 1:1;

[0067] Among them, the solid phase reaction temperature is 525℃;

[0068] Among them, the solid phase reaction heating rate is 15℃ / min;

[0069] Among them, the solid phase reaction time is 4h.

[0070] Step 3: The polyimide mixture in step 2 is first rinsed with hot water, then subjected to Soxhlet extraction with an organic solvent, filtered, and the filtered product is placed in a vacuum drying oven for drying to obtain a nitrogen heterocyclic polyimide photocatalyst;

[0071] Among them, hot water flushing is warm water at a temperature of 70°C;

[0072] The solvent for Soxhlet extraction is tetrahydrofuran or methanol, and the vacuum drying time is 12 h.

[0073] Experimental Example 1

[0074] 10.0g of 5-amino-1H-tetrazole was heated to 325°C in a muffle furnace at a heating rate of 10°C / min for 4 hours. After cooling, a dark yellow precursor was obtained. The precursor was mixed with pyromellitic anhydride at a molar ratio of 1:1 and heated to 425°C in a tube furnace at a heating rate of 10°C / min for 2 hours. After the reaction was completed, the reaction product was washed with 60°C warm water. After Soxhlet extraction with tetrahydrofuran and methanol, the final product was dried under vacuum. 30mg of the catalyst was placed in a reactor and an ethanol-water solution (V ethanol:V water = 3mL:27mL) was added. A xenon lamp was used as the light source and oxygen was used as the oxidant. The reaction was allowed to proceed for 1 hour, resulting in a hydrogen peroxide yield of 576μmol·g⁻¹·h⁻¹.

[0075] Experimental Example 2

[0076] 10.0g of 3,5-diamino-1,2,4-triazole was heated to 325°C in a muffle furnace at a heating rate of 10°C / min for 4 hours. After cooling, a dark yellow precursor was obtained. The precursor was mixed with pyromellitic anhydride at a molar ratio of 1:1 and heated to 425°C in a tube furnace at a heating rate of 10°C / min for 2 hours. After the reaction was completed, the product was washed with 60°C warm water. After Soxhlet extraction with tetrahydrofuran and methanol, the final product was vacuum dried. 30mg of the catalyst was placed in a reactor, and acetonitrile and triethylamine solution and 0.5mmol of phenylboric acid were added. Using a xenon lamp as the light source, the reaction temperature was 60°C, and oxygen was used as the oxidant. The reaction was allowed to proceed for 6 hours, resulting in a phenol yield of 93.4%.

[0077] Experimental Example 3

[0078] 10.0g of 5-amino-1H-tetrazole was heated to 325°C in a muffle furnace at a heating rate of 10°C / min for 4 hours. After cooling, a yellow precursor was obtained. The precursor was mixed with 1,4,5,8-naphthalenetetracarboxylic anhydride in a 1:1 molar ratio and heated to 425°C in a tube furnace at a heating rate of 10°C / min for 2 hours. After the reaction was completed, the product was washed with 60°C warm water. After Soxhlet extraction with tetrahydrofuran and methanol, the final product was dried under vacuum. 30mg of the catalyst was placed in a reactor and an ethanol-water solution (Vethanol:Vwater = 3mL:27mL) was added. A xenon lamp was used as the light source and oxygen was used as the oxidant. The reaction was allowed to proceed for 1 hour, yielding a hydrogen peroxide yield of 373μmol·g⁻¹·h⁻¹.

[0079] It can be seen that the method for preparing nitrogen heterocyclic polyimide photocatalyst provided in this application does not require a solvent during the reaction process and has a low temperature. By regulating the precursor and polyacid anhydride, different nitrogen heterocyclic polyimides can be prepared, which has the characteristics of energy saving and consumption reduction.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen heterocyclic polyimide photocatalyst, characterized in that: The following steps are involved: Step 1: heat-treating nitrogen-rich organic small molecules to obtain nitrogen-containing precursors; Step 2: mixing the nitrogen-containing precursor in step 1 with a polyacid anhydride, and obtaining a polyimide mixture through a solid phase reaction; Step 3: The polyimide mixture in step 2 is first rinsed with hot water, then subjected to Soxhlet extraction and filtration using an organic solvent. The filtered product is placed in a vacuum drying oven and dried to obtain the nitrogen heterocyclic polyimide photocatalyst.

2. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The nitrogen-rich organic small molecules described in step 1 include 3,5-diamino-1,2,4-triazole, 3-amino-1,2,4-triazole, and 5-amino-1H-tetrazole.

3. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The heat treatment temperature in step 1 is 225°C to 425°C.

4. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The polyacid anhydride in step 2 includes pyromellitic anhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride.

5. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The molar ratio of the nitrogen-containing precursor to the polyacid anhydride in step 2 is 1-2:0.5-1.

6. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The solid phase reaction temperature in step 2 is 225°C-525°C.

7. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The solid phase reaction heating rate in step 2 is 5°C / min-15°C / min; The solid phase reaction time in step 2 is 2h-4h.

8. The method for preparing a nitrogen heterocyclic polyimide photocatalyst according to claim 1, wherein: The hot water rinse in step 3 is warm water at a temperature of 50°C-70°C; The solvent for Soxhlet extraction is tetrahydrofuran or methanol, and the vacuum drying time is 1h-12h.

9. A nitrogen heterocyclic polyimide photocatalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Nitrogen heterocyclic polyimide has a bulk aggregated structure.

10. An application of a nitrogen heterocyclic polyimide photocatalyst, based on the nitrogen heterocyclic polyimide photocatalyst according to claim 9, characterized in that: The nitrogen heterocyclic polyimide photocatalyst is used for photocatalytic oxygen activation to produce hydrogen peroxide and phenylboronic acid oxidation to produce phenol.

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