Chemical reduction preparation method of Pt-loaded PTA (pure terephthalic acid) COFs (covalent organic frameworks) catalyst

Abstract

The invention discloses a chemical reduction preparation method of a Pt-loaded PTA (pure terephthalic acid) COFs (covalent organic frameworks) catalyst, and belongs to the field of preparation of covalent organic framework photocatalytic materials. The COF (covalent organic framework) is used as a common crystal organic polymer photocatalyst and has high porosity and specific surface area, however, photo-induced electrons and holes are easy to recombine, and the original COF photocatalytic CO2 reduction activity is poor. A chemical reduction method easy to manufacture is adopted, and the Pt-loaded PTA COFs photocatalytic material is simply produced, so that the performance of photocatalytic reduction of carbon dioxide is improved. The performance of the prepared sample for photocatalytic reduction of CO2 is 120.2970 [mu] mol.g <-1 >. H <-1 >, the catalytic efficiency is basically unchanged through multiple cycle tests, the problem of combination of COFs and a metal catalyst is effectively solved, and the method is suitable for practical application of photocatalytic reduction of CO2.

Description

Technical Field

[0001] This invention belongs to the field of covalent organic framework (COF) photocatalytic material preparation, specifically involving a chemical reduction preparation method of Pt-supported PTACOF catalyst and its application in photocatalytic reduction of CO2. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of crystalline organic polymer materials with highly ordered porous structures, tunable molecular structural units, and excellent physicochemical stability. These unique characteristics endow COFs with large specific surface areas and fast carrier mobility, making them promising for applications in photocatalysis, adsorption, and sensing, especially in the field of CO2 photocatalytic reduction.

[0003] However, CO2 is a nonpolar linear molecule with high chemical stability and inertness, resulting in limited photocatalytic reduction activity of CO2 in pure COF materials. Introducing coordinating metal sites (such as Co, Pt, Ni, etc.) into the COF framework can significantly improve the affinity for CO2, accelerate mass transport, and enhance photoinduced charge transfer, thereby effectively promoting the photocatalytic reduction reaction of CO2.

[0004] Currently, methods for introducing metal active sites into the COF framework mainly include in-situ synthesis, post-synthetic modification, ligand prefunctionalization, and ion exchange. While these methods can achieve the combination of metals and COFs, they all have drawbacks such as harsh reaction conditions, long production time, and low yield. Furthermore, due to the high reversibility of imine bonds in COFs, the self-correction process of defect structures is easily restricted in aqueous phases, thus affecting the synthesis and crystallization quality of COFs. This makes it difficult for COFs to achieve tight bonding with other photocatalysts synthesized in aqueous phases, limiting further improvement of their photocatalytic performance and practical applications.

[0005] Therefore, developing a simple, mild, and efficient method for combining COFs with metal active sites to prepare high-performance supported metal COF photocatalytic materials is of great significance for promoting the development of CO2 photocatalytic reduction technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the harsh synthesis conditions of Pt-supported PTA COFs materials, insufficient binding between COF and metal catalysts, and limited photocatalytic reduction activity of CO2. This invention provides a simple, mild, and efficient chemical reduction preparation method for synthesizing tightly bound Pt-supported PTA COFs photocatalytic materials, thereby improving their photocatalytic reduction performance of CO2. It also provides a new catalyst composite approach.

[0007] This invention is achieved through the following scheme: a chemical reduction preparation method for Pt-supported PTA COFs catalyst, and a method for preparing Pt catalyst supported on a PTA COFs framework, characterized by comprising the following steps:

[0008] (1) Preparation of PTA COFs materials

[0009] 1) Add 0.2 mmol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.2 mmol of pyromellitic methyl ester to 10 mL of o-dichlorobenzene / n-butanol mixed solvent with a volume ratio of 3:7, and sonicate for 10 minutes;

[0010] 2) Transfer the solution obtained in step 1) to a 20 mL glass reaction tube, add 2 mL of 6 mol / L glacial acetic acid solution, and then sonicate for 10 minutes;

[0011] 3) The reaction tube of the solution obtained in step 2) was flash-frozen in liquid nitrogen. After degassing by three freeze-thaw cycles, the reaction tube was sealed and heated at 120°C for 72 h. The resulting yellow precipitate was filtered and washed with excess methanol, ethanol and water in sequence. After vacuum drying, PTA COFs material was obtained.

[0012] (2) Preparation of Pt@PTA COFs materials

[0013] 4) Disperse 30 mg of PTA COFs material in deionized water and stir for 30 minutes; take a chloroplatinic acid (H2PtCl4) solution with a concentration of 1 g / 100 mL (1 wt%) and mix it with the suspension, and continue stirring for 30 minutes;

[0014] 5) Add the solution obtained in step 4) to ice water, add sodium borohydride (NaBH4) solution with a concentration of 50 mg / mL dropwise, stir for 30 minutes, wash the product with deionized water and anhydrous ethanol several times, and dry it under vacuum to obtain Pt-loaded PTACOFs material; according to the mass ratio of Pt to COFs, the obtained sample is named 1%Pt@PTA COFs.

[0015] All raw materials used in this invention are commercially available conventional products, as detailed below:

[0016] 1. 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, o-dichlorobenzene, n-butanol: supplied by Aladdin;

[0017] 2. Trimethylbenzaldehyde: supplied by Macklin Company;

[0018] 3. Chloroplatinic acid (H2PtCl4): supplied by Rhawn Corporation;

[0019] 4. Sodium borohydride (NaBH4): supplied by Chengdu Kelon Company;

[0020] 5. Deionized water, methanol, ethanol, and glacial acetic acid: all are conventional analytical grade reagents.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention employs a chemical reduction method, which involves reacting at a relatively low temperature. This effectively protects the high porosity and crystallinity of COFs, prevents the destruction of imine bonds and crystal structure in the COFs structure, and ensures the excellent performance of the COFs material itself.

[0023] 2. By directly reducing the metal precursor on the surface of pre-synthesized COFs through chemical reduction, Pt can be anchored in the pores or functional groups of COFs in an atomically dispersed form, forming strong interactions, which solves the problem of insufficient binding between COFs and metal catalysts in the existing technology.

[0024] 3. The entire preparation process is divided into two steps, which are simple and do not require harsh reaction conditions or complex equipment. It is easy to scale up production and reduce preparation costs.

[0025] 4. This method does not depend on specific COFs materials or metal precursors. The metal loading can be controlled by adjusting parameters such as reducing agent concentration and reaction time. It is suitable for loading precious metals or transition metals such as Pt, Pd, and Au, and has broad application prospects.

[0026] 5. Pt-loaded PTA COFs materials exhibit significantly improved photocatalytic CO2 reduction performance compared to unmodified monomeric COFs, and also demonstrate good stability. After multiple cycle tests, the catalytic efficiency remains essentially unchanged, meeting the requirements of practical applications. Attached Figure Description

[0027] Figure 1 Lifetime curve of the 1% Pt@PTA COFs catalyst prepared in Example 2;

[0028] Figure 2 Example 2 shows the performance curve of the product obtained in the photocatalytic reduction of CO2 under simulated sunlight. Detailed Implementation

[0029] The following is combined Figure 1-2 The present invention will be further described, but the scope of protection of the present invention is not limited to the contents described herein.

[0030] Example 1: Preparation of PTA COFs materials

[0031] 1) Add 0.2 mmol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.2 mmol of pyromellitic methyl ester to 10 mL of o-dichlorobenzene / n-butanol mixed solvent with a volume ratio of 3:7, and sonicate for 10 minutes to fully dissolve and mix the reactants.

[0032] 2) Transfer the solution obtained in step 1) to a 20 mL glass reaction tube, add 2 mL of 6 mol / L glacial acetic acid solution, and then sonicate for 10 minutes;

[0033] 3) The reaction tube of the solution obtained in step 2) was flash-frozen in liquid nitrogen. After degassing by three freeze-thaw cycles, the reaction tube was sealed and heated at 120°C for 72 h. The resulting yellow precipitate was filtered and washed sequentially with excess methanol, ethanol and water. After vacuum drying, PTA COFs material was obtained.

[0034] Example 2: Preparation and performance testing of 1%Pt@PTA COFs material

[0035] (1) Preparation of Pt@PTA COFs materials

[0036] 4) Disperse 30 mg of the PTA COFs material prepared in Example 1 in deionized water and stir for 30 minutes; take 63 μL of chloroplatinic acid (H2PtCl4) solution with a concentration of 1 g / 100 mL (1wt%) and mix it with the suspension, and continue stirring for 30 minutes;

[0037] 5) Add the solution obtained in step 4) to ice water, add 6 μL of sodium borohydride (NaBH4) solution with a concentration of 50 mg / mL, stir for 30 minutes, and wash the product with deionized water and anhydrous ethanol several times. After vacuum drying, 1% Pt@PTACOFs material (mass ratio of Pt to COFs is 1%) is obtained.

[0038] (2) Photocatalytic CO2 reduction performance test

[0039] A mixed solution of H2O / CH3CN / TEOA (volume ratio 1:4:1, total volume 6 mL), 5 mg of [Ru(bpy)3Cl2·6H2O], and 5 mg of the 1% Pt@PTA COFs catalyst prepared above were added to a 50 mL quartz tube. The quartz tube was sealed, and CO2 gas was bubbled into it for 30 minutes to completely exchange the air inside the quartz tube (stirring was performed during the bubbling process to ensure the sample was uniformly dispersed in the mixed solution). After the bubbling was completed, the quartz tube was placed under a 300W xenon lamp to simulate sunlight irradiation for 2 hours. After the reaction was complete, 500 μL of the reaction gas was injected into a Panno gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) for quantitative analysis of the products. The test results showed that the photocatalytic reduction efficiency of CO2 by this catalyst was 120.2970 μmol·g⁻¹. -1 ·h -1 .

[0040] (3) Catalyst lifetime test

[0041] Following the performance testing method described above, the 1%Pt@PTA COFs catalyst underwent multiple cycle tests, and the test results are as follows: Figure 1 As shown in the figure, the photocatalytic efficiency of the catalyst does not decrease significantly after multiple cycles, indicating a long service life. This demonstrates that the Pt and PTA COFs in the sample prepared by the chemical reduction method of this invention are tightly bound, chemically stable, and maintain structural integrity during multiple reactions.

[0042] Example 3: Preparation of 0.5% Pt@PTA COFs material

[0043] Steps 1), 2), and 3) are exactly the same as in Example 1; the volume of chloroplatinic acid solution added in step 4) is 31.5 μL, and the volume of sodium borohydride solution added in step 5) is 3 μL. The remaining operations are the same as in Example 2, and finally 0.5% Pt@PTA COFs material (the mass ratio of Pt to COFs is 0.5%) is obtained.

[0044] Example 4: Preparation of 1.5% Pt@PTA COFs material

[0045] Steps 1), 2), and 3) are exactly the same as in Example 1; the volume of chloroplatinic acid solution added in step 4) is 94.5 μL, and the volume of sodium borohydride solution added in step 5) is 9 μL. The remaining operations are the same as in Example 2, and finally 1.5% Pt@PTA COFs material (the mass ratio of Pt to COFs is 1.5%) is obtained.

[0046] Performance Comparison Analysis

[0047] The photocatalytic CO2 reduction performance of Pt@PTA COFs materials with different Pt loadings prepared in Examples 2, 3, and 4 was tested. The test method was the same as in Example 2, and the test results are as follows: Figure 2 As shown in the figure, the Pt loading significantly affects the photocatalytic performance of the catalyst: when the mass ratio of Pt to PTA COFs is in the range of 0.5%-1.5%, the photocatalytic reduction efficiency of CO2 is significantly improved; among them, the catalytic efficiency reaches its highest level of 120.2970 μmol·g when the Pt loading is 1%. -1 ·h -1 It is 5.41 times more efficient than unmodified monomeric COFs.

[0048] The results demonstrate that the chemical reduction method employed in this invention can effectively protect the high porosity and crystallinity of COFs under mild conditions, while simultaneously achieving uniform Pt loading. This significantly enhances the adsorption and activation capacity of COFs for CO2, promotes the separation of photogenerated electron-hole pairs, and thus substantially improves the photocatalytic reduction performance of COFs for CO2. The method provided by this invention has important guiding significance for the combination of COFs with common semiconductor catalysts, offering a new approach and method for the preparation of photocatalytic CO2 reduction materials.

[0049] Although the technical solutions of the present invention have been described and enumerated in detail, it should be understood that modifications to the above embodiments or the adoption of equivalent alternatives are obvious to those skilled in the art. Such modifications or improvements made without departing from the spirit of the present invention are all within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a Pt catalyst supported on a PTA COFs framework, characterized in that, Includes the following steps: (1) Preparation of PTA COFs materials 1) Add 0.2 mmol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.2 mmol of pyromellitic methyl ester to 10 mL of o-dichlorobenzene / n-butanol mixed solvent with a volume ratio of 3:7, and sonicate for 10 minutes; 2) Transfer the solution obtained in step 1) to a 20 mL glass reaction tube, add 2 mL of 6 mol / L glacial acetic acid solution, and then sonicate for 10 minutes; 3) The reaction tube of the solution obtained in step 2) was flash-frozen in liquid nitrogen. After degassing by three freeze-thaw cycles, the reaction tube was sealed and heated at 120°C for 72 h. The resulting yellow precipitate was filtered and washed with excess methanol, ethanol and water in sequence. After vacuum drying, PTA COFs material was obtained. (2) Preparation of Pt@PTA COFs materials 4) Disperse 30 mg of PTA COFs material in deionized water and stir for 30 minutes; take a chloroplatinic acid (H2PtCl4) solution with a concentration of 1 g / 100 mL (1 wt%) and mix it with the suspension, and continue stirring for 30 minutes; 5) Add the solution obtained in step 4) to ice water, add sodium borohydride (NaBH4) solution with a concentration of 50 mg / mL dropwise, stir for 30 minutes, and wash the product with deionized water and anhydrous ethanol several times. After vacuum drying, Pt-supported PTA COFs material is obtained. According to the mass ratio of Pt to COFs, the obtained sample is named 1%Pt@PTA COFs.

2. The method according to claim 1, characterized in that, The 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, o-dichlorobenzene, and n-butanol were provided by Aladdin; the pyromellitic methyl ester was provided by Macklin; the chloroplatinic acid was provided by Rhawn; and the sodium borohydride was provided by Chengdu Kelon.

3. The method according to claim 1, characterized in that, In step 3), the reaction temperature is maintained at 120°C and the heating reaction time is 72 hours.

4. The method according to claim 1, characterized in that, PTA COFs material was added in advance during the preparation process, and Pt was directly loaded onto the PTA COFs during stirring.

5. The method according to claim 1, characterized in that, The method can control the metal loading by adjusting parameters such as reducing agent concentration and reaction time, and is suitable for loading precious metals or transition metals such as Pt, Pd, and Au.

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