Preparation method of a novel covalent organic framework photoelectrocatalyst and photoelectrocatalyst thereof

Abstract

The present invention belongs to the field of chemical engineering and discloses a method for preparing a novel covalent organic framework photoelectrocatalyst and the photoelectrocatalyst thereof. The method comprises reacting bromophenylporphyrin with phenylboronic acid to obtain an aldehyde group, thereby obtaining biphenylporphyrin (PP). Triphenylene (TC) reacts with ammonium cerium nitrate under a palladium-carbon catalyst to obtain an amino group, thereby obtaining diaminotriptycene (TAT). Under acidic conditions, the aldehyde group of the biphenylporphyrin (PP) and the amino group of the diaminotriptycene (TAT) react with each other to form a -C=N- bond, forming a stable Schiff base structure. This novel covalent organic framework photoelectrocatalyst can photoelectrocatalyze the production of urea from CO2 and nitrite, and exhibits advantages such as physical and chemical stability, good dispersibility, minimal environmental impact, and low cost.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and in particular to a preparation method of a novel covalent organic framework photoelectrocatalyst and the photoelectrocatalyst. Background Art

[0002] Humanity has built a rich material civilization through excessive consumption of fossil fuels (coal, natural gas, and petroleum products), but this has also led to severe energy shortages, the greenhouse effect, and other problems. The greenhouse effect, primarily caused by increased levels of the greenhouse gas carbon dioxide in the environment, leads to rising global temperatures, which in turn causes sea level rise, ozone layer depletion, and other serious environmental problems. Photoelectrocatalytic reduction of carbon dioxide into valuable carbon products is an effective and sustainable solution. Using clean, sustainable light and electricity to catalytically reduce carbon dioxide to high-value hydrocarbons can alleviate the environmental pollution caused by large amounts of carbon dioxide emissions, reduce dependence on non-renewable resources such as fossil fuels, and pave the way for a cleaner, more sustainable future for humanity.

[0003] Porphyrin-based photoelectrocatalysts are commonly used to catalyze carbon dioxide reduction. Porphyrin strongly absorbs red-violet light, and its π-π conjugated structure facilitates the transport of photoelectrons. However, porphyrin-based photoelectrocatalysts still have certain drawbacks when used in photocatalytic reduction. First, porphyrin has a poor CO adsorption capacity, requiring the use of ionic solutions or corresponding electrolyte solutions with strong storage capacity for photoelectrocatalysis, resulting in low efficiency. Second, porphyrin has only one set of 18 π-electron aromatic structures. The symmetrical tetrapyrrole ring and multiple intercalating carbon bridges determine its electron conduction resistance. Third, the catalytic process requires the use of sacrificial agents, co-catalysts, and photosensitizers to capture photoelectrons and convert them into chemical energy. The subsequent processing of these additional reagents makes carbon dioxide reduction cumbersome. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned shortcomings of the prior art and provide a method for preparing a novel covalent organic framework photoelectrocatalyst and its photoelectrocatalyst. The photoelectrocatalyst is based on a porphyrin group and has a Schiff base structure. It can photoelectrocatalyze CO2 to produce urea and has the advantages of physicochemical stability, good dispersibility, low environmental harm, and low cost.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned object is:

[0006] The present invention provides a method for preparing a novel covalent organic framework photoelectrocatalyst, comprising the following steps:

[0007] S1. mixing bromophenylporphyrin with N,N-dimethylformamide to obtain solution A;

[0008] Mixing 4-formylphenylboronic acid with pure water to obtain solution B;

[0009] Tetrakis(triphenylphosphine)palladium and toluene are mixed to obtain solution C;

[0010] Then, solutions A, B, and C were mixed, potassium carbonate was added, and ultrasonic treatment was performed to obtain solution D, and solution D was heated under reflux under a protective atmosphere to obtain suspension E;

[0011] The suspension E is filtered and washed to obtain biphenyl porphyrin PP;

[0012] S2. The triptycene was mixed with dichloromethane to obtain a solution F; ammonium cerium nitrate was mixed with the solution F to obtain a suspension G; sulfuric acid was added to the suspension G, and the reaction was carried out under a protective atmosphere to obtain a suspension H;

[0013] Suspension H was filtered and washed to obtain filtrate I; potassium carbonate solution was mixed with filtrate I to obtain mixed component J, which was allowed to stand for stratification and then separated, and the organic phases were combined to obtain solution K. Anhydrous magnesium sulfate was then added to solution K, and then filtered to obtain powder L;

[0014] Powder L is dissolved in ethanol to form solution M; palladium carbon catalyst and hydrazine hydrate are added to solution M, heated under reflux for reaction, and filtered to obtain powder N, namely diaminotriptycene TAT;

[0015] S3. The biphenyl porphyrin PP was mixed with dichloromethane to obtain a solution O; diaminotriptycene TAT was mixed with dichloromethane to obtain a solution P;

[0016] Acetic acid was mixed with solution O to obtain suspension Q, and then suspension Q was added dropwise into solution P under continuous stirring and protective atmosphere to obtain solution R.

[0017] The solution R is then heated under reflux in an oxygen atmosphere for a certain period of time, filtered, and washed to obtain powder S, namely the photoelectrocatalyst COF_PP-TAT.

[0018] Preferably, in step S1, the amount of bromophenylporphyrin added is 1.2-2.2 g, and the amount of N,N-dimethylformamide added is 80 mL; and / or,

[0019] The amount of 4-formylphenylboronic acid added is 1.40 g, and the amount of pure water added is 40 mL; and / or,

[0020] The amount of tetrakis(triphenylphosphine)palladium added was 0.18 g, and the amount of toluene added was 160 mL;

[0021] The amount of potassium carbonate added was 1.60 g.

[0022] Preferably, the ultrasonication time in step S1 is 2 hours; and / or,

[0023] The heating temperature is 105°C; and / or,

[0024] The heating reflux reaction time is 72h.

[0025] Preferably, in step S2, the amount of triptycene added is 3.39 g, and the amount of dichloromethane added is 50 mL; and / or, the amount of cerium ammonium nitrate added is 14.7-102.9 g; and / or,

[0026] The amount of sulfuric acid added was 2.56 mL;

[0027] and / or, the mass concentration of potassium carbonate solution is 10wt%, and the addition amount is 100mL; and / or,

[0028] The amount of anhydrous magnesium sulfate is 20g; and / or,

[0029] The amount of ethanol used is 50 ml; and / or,

[0030] The amount of palladium carbon catalyst used was 0.2 g, and the amount of hydrazine hydrate used was 0.5 mL.

[0031] Preferably, in step S2, the suspension H is obtained by reacting for 12 hours under a protective atmosphere; and / or,

[0032] Heat to reflux and react for 2 h.

[0033] Preferably, in step S3, the amount of biphenylporphyrin PP added is 0.31 g, and the amount of dichloromethane added is 50 mL; and / or,

[0034] The amount of diaminotriptycene TAT added is 0.31 g, and the amount of dichloromethane added is 50 mL; and / or,

[0035] The concentration of acetic acid is 0.5 mol / L, and the amount added is 0.5-5.0 mL.

[0036] Preferably, the stirring time in step S3 is 24 hours; and / or,

[0037] The heating reflux time is 72h; and / or,

[0038] The heating temperature is 50°C.

[0039] In a second aspect, the present invention also provides the aforementioned novel covalent organic framework photoelectrocatalyst, which is prepared by the aforementioned novel covalent organic framework photoelectrocatalyst preparation method, and is based on biphenyl porphyrin as the core composite triptycene scaffold and forms a Schiff base structure.

[0040] The present invention utilizes the above-mentioned scheme to provide a method for preparing a novel covalent organic framework photoelectrocatalyst and its photoelectrocatalyst. This photoelectrocatalyst is a photoactive polymer with high CO2 adsorption, capable of promoting CO2 mass transfer and inhibiting the HER reaction. Using a biphenylporphyrin core with high visible light harvesting and charge separation capabilities, and incorporating a twisted triptycene scaffold with an internal molecular free volume (IMFV), the polymer chains create molecular channels, enhancing gas adsorption at the active sites. This results in a photoelectroactive, metal-free covalent organic framework photoelectrocatalyst (COF_PP-TAT). This photoelectrocatalyst exhibits a large π-π conjugated structure and a unique internal free volume, enabling specific CO2 adsorption and efficient photoelectrocatalytic CO2 reduction for urea synthesis. The preparation of this photoelectrocatalyst is simple, energy-efficient, and environmentally friendly.

[0041] This method uses bromophenylporphyrin (TBPP) and phenylboronic acid as raw materials to prepare biphenylporphyrin (PP) via a Suzuki coupling reaction. Triptylene reacts with ammonium cerium nitrate (SAN) under acidic conditions for 12 hours to form dinitrotriptycene, which is then reduced to diaminotriptycene (TAT) using a palladium-on-carbon (Pd / C) catalyst and hydrazine hydrate. The aldehyde group of biphenylporphyrin (PP) reacts with the amino group of diaminotriptycene (TAT) under acidic conditions to form a -C=N- bond. This is then followed by a Schiff base reaction to synthesize COF_PP-TAT, forming a stable Schiff base structure. This results in a novel covalent organic framework photoelectrocatalyst (COF_PP-TAT) that efficiently and sustainably produces urea.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The preparation method of the novel covalent organic framework photoelectrocatalyst and the photoelectrocatalyst thereof of the present invention are based on porphyrin and have a Schiff base structure. They can photoelectrocatalyze CO2 to produce urea and have the advantages of physical and chemical stability, good dispersibility, and little harm to the environment. The preparation method of the novel covalent organic framework photoelectrocatalyst (COF_PP-TAT) of the present invention is unique. During the preparation process, intermediates such as formic acid (HCOOH), carbon monoxide (CO), ammonia (NH3) and other valuable products are also formed. It has a wide range of applications, a green and environmentally friendly synthesis scheme, simple operation and low cost.

[0044] The above is an overview of the technical solution of the invention. The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 1 is the SEM image of PP and COF_PP-TAT of the present invention;

[0046] Figure 2 FT-IR spectra of PP, TAT and COF_PP-TAT of the present invention;

[0047] Figure 3 XRD patterns of PP and COF_PP-TAT of the present invention;

[0048] Figure 4 UV spectra of PP, TAT and COF_PP-TAT of the present invention;

[0049] Figure 5 This is the UV spectrum of the photoelectrocatalytic sample before and after urease treatment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following is a detailed description of the 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.

[0051] The specific implementation steps of the present invention are mainly divided into three steps: the first step is to prepare biphenylporphyrin PP, using bromophenylporphyrin and phenylboric acid as raw materials, tetrakis(triphenylphosphine)palladium as a catalyst, and potassium carbonate to provide an alkaline environment, that is, using bromophenylporphyrin (TBPP) and phenylboric acid such as 4-formylphenylboric acid as raw materials, and preparing biphenylporphyrin (PP) through Suzuki coupling reaction; the second step is to synthesize diaminotriptycene (TAT), by first nitrating triptycene, and then nitrating triptycene with ammonium cerium nitrate under acidic conditions for 12 hours, and then reducing the nitro group to an amino group under the action of a palladium-carbon catalyst and a hydrazine hydrate catalyst to generate diaminotriptycene (TAT); the third step is to synthesize a new covalent organic framework photoelectrocatalyst COF_PP-TAT, and the aforementioned PP and TAT are synthesized by a Schiff base reaction under the catalysis of acetic acid to synthesize COF_PP-TAT.

[0052] Example 1

[0053] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, the specific steps comprising:

[0054] 1) Dissolve 1.20 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0055] 2) Dissolve 1.40 g of 4-formylphenylboronic acid in 40 mL of pure water to obtain solution B.

[0056] 3) Dissolve 0.18 g of tetrakis(triphenylphosphine)palladium catalyst in 160 mL of toluene to obtain solution C;

[0057] 4) Solutions A, B, and C were mixed, and 1.6 g of potassium carbonate was added and sonicated for 2 h to fully dissolve the mixture to obtain solution D. Potassium carbonate provides an alkaline environment to catalyze the synthesis of PP.

[0058] 5) Solution D was heated under reflux at 105°C under nitrogen for 72 h to obtain suspension E;

[0059] 6) Suspension E is filtered and the filter cake is washed with dichloromethane to obtain biphenylporphyrin PP.

[0060] Example 2

[0061] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, which is basically the same as that of Example 1, except that the amount of bromophenyl porphyrin TBPP is changed. The specific steps include:

[0062] 1) Dissolve 1.40 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0063] Example 3

[0064] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, which is basically the same as that of Example 1, except that the amount of bromophenyl porphyrin TBPP is changed. The specific steps include:

[0065] 1) Dissolve 1.60 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0066] Example 4

[0067] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, which is basically the same as that of Example 1, except that the amount of bromophenyl porphyrin TBPP is changed. The specific steps include:

[0068] 1) Dissolve 1.80 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0069] Example 5

[0070] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, which is basically the same as that of Example 1, except that the amount of bromophenyl porphyrin TBPP is changed. The specific steps include:

[0071] 1) Dissolve 2.00 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0072] Example 6

[0073] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, which is basically the same as that of Example 1, except that the amount of bromophenyl porphyrin TBPP is changed. The specific steps include:

[0074] 1) Dissolve 2.20 g of bromophenylporphyrin (TBPP) in 80 mL of N,N-dimethylformamide to obtain solution A.

[0075] In Examples 1-6, the amount of bromophenylporphyrin (TBPP) used was varied (1.2-2.2 g). Since the amount of bromophenylporphyrin (TBPP) used can alter the yield and purity of PP, the purity of the product PP can be improved appropriately by increasing the amount of bromophenylporphyrin. Suitable biphenylporphyrin (PP) can be obtained using 1.20 g to 2.20 g of bromophenylporphyrin. Examples 15-19 were prepared using 1.20 g of bromophenylporphyrin. The bromophenylporphyrin (PP) used in Examples 15-19 was prepared using the same method as in Example 1.

[0076] Example 7

[0077] This embodiment provides diaminotriptycene TAT and a preparation method thereof, the specific steps comprising:

[0078] 1) Disperse 3.39 g of triptycene TC in 50 mL of dichloromethane to obtain solution F;

[0079] 2) Add 14.7 g of cerium ammonium nitrate to solution F to obtain suspension G;

[0080] 3) Add 2.56 mL of sulfuric acid to suspension G and stir thoroughly under nitrogen for 12 h to obtain suspension H, which contains dinitrotriptycene.

[0081] 4) Suspension H was filtered and the filter residue was thoroughly washed with 150 mL of dichloromethane until colorless to obtain filtrate I; filtrate I contained dinitrotriptycene.

[0082] 5) Adding 100 mL of a 10 wt% potassium carbonate solution to filtrate I to obtain a mixed component J; the potassium carbonate provides an alkaline environment, reducing the solubility of dinitrotriptycene in water and increasing the yield of dinitrotriptycene in dichloromethane.

[0083] 6) The mixed component J was allowed to stand and separate into layers. The aqueous phase was extracted three times with 50 mL of dichloromethane. The organic phases were combined to obtain solution K. Solution K still contained dinitrotriptycene.

[0084] 7) Add 20 g of anhydrous magnesium sulfate to solution K, filter, and remove the solvent to obtain powder L. Remove water from the anhydrous magnesium sulfate and remove the solvent to obtain powder L, which is dinitrotriptycene powder.

[0085] 8) Dissolve 2.50 g of powdered L-dinitrotriptycene in 50 ml of ethanol to form solution M.

[0086] 9) Add 0.2 g of palladium on carbon (Pd / C) and 0.5 mL of hydrazine hydrate to solution M, heat under reflux for 2 h, and filter to obtain powdered N. Dinitrotriptycene is reduced to diaminotriptycene in the presence of Pd / C and hydrazine hydrate, yielding powdered N-diaminotriptycene (TAT).

[0087] Example 8

[0088] This example provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0089] 2) Add 29.4 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0090] Example 9

[0091] This example provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0092] 2) Add 44.1 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0093] Example 10

[0094] This example provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0095] 2) Add 58.8 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0096] Example 11

[0097] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0098] 2) Add 73.5 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0099] Example 12

[0100] This example provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0101] 2) 88.2 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0102] Example 13

[0103] This example provides TAT ​​and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0104] 2) 102.9 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0105] Example 14

[0106] This example provides TAT ​​and a preparation method thereof, which is basically the same as Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include:

[0107] 2) 117.6 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0108] In Examples 7-14, varying the amount of ceric ammonium nitrate (14.7-102.9 g) helped increase the yield of dinitrotriptycene, thereby ensuring a suitably high purity of the subsequently synthesized diaminotriptycene. Since the reaction of ceric ammonium nitrate with triptycene may produce mononitrotriptycene, dinitrotriptycene, and trinitrotriptycene, appropriately increasing the amount of ceric ammonium nitrate helped increase the yield of dinitrotriptycene. Suitable diaminotriptycene (TAT) was obtained with amounts of ceric ammonium nitrate ranging from 14.7 g to 102.9 g. Examples 15-19 used 14.7 g of ceric ammonium nitrate, i.e., the diaminotriptycene (TAT) prepared in Example 7.

[0109] Example 15

[0110] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is specifically implemented as follows

[0111] 1) Mix 0.31 g of biphenylporphyrin PP with 50 mL of dichloromethane to obtain solution O;

[0112] 2) Mix 0.31 g of diaminotriptycene (TAT) with 50 mL of dichloromethane to obtain solution P;

[0113] 3) Mix 0.5 mL of acetic acid (the concentration of acetic acid is 0.5 mol / L) with solution O to obtain suspension Q.

[0114] 4) Add suspension Q dropwise into solution P under continuous stirring and nitrogen protection for 24 hours to obtain solution R;

[0115] 5) Heat solution R at 50°C under reflux in an oxygen atmosphere for 72 hours. Filter and wash to obtain powder S, the photoelectrocatalyst COF_PP-TAT. The oxygen atmosphere accelerates the precipitation of COF_PP-TAT, favoring its production.

[0116] Example 16

[0117] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as Example 15, except that the amount of acetic acid is changed. The specific implementation is as follows:

[0118] 3) Mix 0.1 mL of acetic acid with solution O to obtain suspension Q.

[0119] Example 17

[0120] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as Example 15, except that the amount of acetic acid is changed. The specific implementation is as follows:

[0121] 3) Mix 1.0 mL of acetic acid with solution O to obtain suspension P.

[0122] Example 18

[0123] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as Example 15, except that the amount of acetic acid is changed. The specific implementation is as follows:

[0124] 3) Mix 2.0 mL of acetic acid with solution O to obtain suspension P.

[0125] Example 19

[0126] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as Example 15, except that the amount of acetic acid is changed. The specific implementation is as follows:

[0127] 3) Mix 5.0 mL of acetic acid with solution O to obtain suspension P.

[0128] In Examples 15-19, the amount of acetic acid used was varied (0.5-5.0 mL). Since a certain amount of H+ is required for catalysis during the synthesis of PP and TAT, too little acetic acid will slow down the reaction and reduce the yield; too much acetic acid will cause PP to acidify and terminate the reaction. The photoelectrocatalyst COF_PP-TAT can be prepared with an acetic acid amount of 0.5 mL to 5.0 mL. Figure 1 -Attached Figure 5 Photoelectrocatalyst COF_PP-TAT from Example 15.

[0129] The COF_PP-TAT obtained in the above example was subjected to a performance test. The COF_PP-TAT was prepared into an ethanol solution of appropriate concentration, and a photoelectrocatalytic reduction experiment of CO2 was carried out under an electrochemical workstation.

[0130] By the attached Figure 1 It can be seen that PP has a sheet-like stacking structure at the microscopic level, and COF_PP-TAT after Schiff base reaction has a rough, porous surface, which indicates that COF_PP-TAT has the advantage of a larger specific surface area compared with PP, which is conducive to the adsorption of gas for photoelectrocatalytic reduction reaction.

[0131] By the attached Figure 2 It can be seen that 700-1700cm -1 The peaks at 1700 cm-1 belong to the characteristic absorption peaks of PP. -1 The absorption peak at 1602 cm is caused by the stretching vibration of the C=O group of the carbonyl group. -1 The absorption peak at 1471 cm -1 The absorption peak at 3340 cm-1 can be attributed to the stretching vibration of the C=N group. -1 3200cm -1 The typical -NH stretching vibration peak and 1613cm -1 -NH bending vibration peak at 1474 cm -1 The absorption peak at 1700 cm-1 can be attributed to the stretching vibration of the C=N group. In COF_PP-TAT, the characteristic peak of -NH completely disappears, and the absorption peak at 1700 cm-1 is -1 The absorption peak intensity of the carbonyl group at the position of COF_PP-TAT was weakened, indicating that COF_PP-TAT was successfully synthesized, in which the -NH2 of TAT reacted with -CHO to form C=N, and a small amount of carbonyl groups in PP remained unreacted.

[0132] By the attached Figure 3 It can be seen that, combining the XRD patterns of PP and COF_PP-TAT, compared with PP, there is a special lattice peak of 12.04° in the XRD pattern of COF_PP-TAT, and the lattice peak is sharper, indicating that when PP is synthesized, new crystal planes that are beneficial to photocatalysis are formed after COF_PP-TAT, and the crystallinity is improved.

[0133] By the attached Figure 4The UV spectrum of COF_PP-TAT reveals multiple absorption bands, including a strong Soret band at 413 nm and four Q bands at 512 nm, 548 nm, 589 nm, and 644 nm, which are characteristic absorption bands of porphyrins. The Schiff base structure connecting PP and TAT increases molecular stability, increases electron cloud density, and reduces the energy required for electron transitions. This red-shifts the 413 nm Soret band to 445 nm, reducing the number of Q bands to just one (670 nm). TAT exhibits a broad absorption peak at 240 nm, which in COF_PP-TAT is reflected as a broad UV absorption peak red-shifted to 275 nm. This indicates that the COF material exhibits continuous absorption from 275 nm to 670 nm, significantly enhancing its light absorption capacity and facilitating photoelectrocatalytic reduction of CO2.

[0134] By the attached Figure 5 Indigo blue exhibits a UV absorption peak at 650 nm. COF_PP-TAT undergoes photoelectrocatalytic CO2 reduction in a mixture of 0.4 M NaNO2 and 0.5 M NaHCO3, generating urea. Urea is then decomposed into ammonia after urease treatment, which reacts with the developer to form indigo blue, resulting in an increase in absorbance at 650 nm. Figure 5 The absorbance at 650 nm indicates the ammonia content in the sample and serves to demonstrate the presence of urea in the reduction product. The dashed line represents the ammonia content in the liquid reduction product formed after photoelectrocatalysis of the electrolyte over the photoelectrocatalyst COF_PP-TAT of Example 15, while the solid line represents the ammonia content of the liquid reduction product after urease treatment. The increase in absorbance at 650 nm indicates an increase in the ammonia content of the reduction product, as the urease treatment decomposes the urea in the reduction product into ammonia.

[0135] Based on the disclosure and teachings of the above description, those skilled in the art may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a covalent organic framework photoelectrocatalyst, characterized in that: The steps include: S1. Mixing bromophenylporphyrin TBPP with N,N-dimethylformamide to obtain solution A; Mixing 4-formylphenylboronic acid with pure water to obtain solution B; Tetrakis(triphenylphosphine)palladium and toluene are mixed to obtain solution C; Then, solutions A, B, and C were mixed, potassium carbonate was added, and ultrasonic treatment was performed to obtain solution D, and solution D was heated under reflux under a protective atmosphere to obtain suspension E; The suspension E is filtered and washed to obtain biphenyl porphyrin PP; S2. The triptycene was mixed with dichloromethane to obtain a solution F; ammonium cerium nitrate was mixed with the solution F to obtain a suspension G; sulfuric acid was added to the suspension G, and the reaction was carried out under a protective atmosphere to obtain a suspension H; Suspension H was filtered and washed to obtain filtrate I; potassium carbonate solution was mixed with filtrate I to obtain mixed component J, which was allowed to stand for stratification and then separated, and the organic phases were combined to obtain solution K. Anhydrous magnesium sulfate was then added to solution K, and then filtered to obtain powder L; Powder L is dissolved in ethanol to form solution M; palladium carbon catalyst and hydrazine hydrate are added to solution M, heated under reflux for reaction, and filtered to obtain powder N, namely diaminotriptycene TAT; S3. The biphenyl porphyrin PP was mixed with dichloromethane to obtain a solution O; diaminotriptycene TAT was mixed with dichloromethane to obtain a solution P; Acetic acid was mixed with solution O to obtain suspension Q, and then suspension Q was added dropwise into solution P under continuous stirring and protective atmosphere to obtain solution R. The solution R is then heated under reflux in an oxygen atmosphere for a certain period of time, filtered, and washed to obtain powder S, namely the photoelectrocatalyst COF_PP-TAT.

2. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: In the step S1, the amount of bromophenylporphyrin TBPP added is 1.2-2.2 g, and the amount of N,N-dimethylformamide added is 80 mL; and / or, The amount of 4-formylphenylboronic acid added is 1.40 g, and the amount of pure water added is 40 mL; and / or, The amount of tetrakis(triphenylphosphine)palladium added was 0.18 g, and the amount of toluene added was 160 mL; The amount of potassium carbonate added was 1.60 g.

3. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: The ultrasonic time in step S1 is 2 hours; and / or, The heating temperature is 105°C; and / or, The heating reflux reaction time is 72h.

4. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: In the step S2, the amount of triptycene added is 3.39 g, and the amount of dichloromethane added is 50 mL; and / or, the amount of cerium ammonium nitrate added is 14.7-102.9 g; and / or, The amount of sulfuric acid added was 2.56 mL; and / or, the mass concentration of potassium carbonate solution is 10wt%, and the addition amount is 100mL; and / or, The amount of anhydrous magnesium sulfate is 20g; and / or, The amount of ethanol used is 50 ml; and / or, The amount of palladium carbon catalyst used was 0.2 g, and the amount of hydrazine hydrate used was 0.5 mL.

5. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: In step S2, the suspension H is obtained by reacting for 12 hours under a protective atmosphere; and / or, Heat to reflux and react for 2 h.

6. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: In step S3, the amount of biphenylporphyrin PP added is 0.31 g, and the amount of dichloromethane added is 50 mL; and / or, The amount of diaminotriptycene TAT added is 0.31 g, and the amount of dichloromethane added is 50 mL; and / or, The concentration of acetic acid is 0.5 mol / L, and the amount added is 0.5-5.0 mL.

7. The method for preparing a covalent organic framework photoelectrocatalyst according to claim 1, wherein: The stirring time in step S3 is 24 hours; and / or, The heating reflux time is 72h; and / or, The heating temperature is 50°C.

8. A covalent organic framework photoelectrocatalyst, characterized in that The covalent organic framework photoelectrocatalyst is prepared by the preparation method of the covalent organic framework photoelectrocatalyst according to any one of claims 1 to 7, and is based on biphenyl porphyrin as the core and a triptycene composite scaffold to form a Schiff base structure.

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