Preparation method of photoelectric catalyst of novel covalent organic framework and photoelectric catalyst thereof

Abstract

The invention belongs to the technical field of chemical engineering, and discloses a novel covalent organic framework photoelectric catalyst preparation method and a photoelectric catalyst thereof, bromophenyl porphyrin and phenylboronic acid are subjected to an addition reaction to obtain an aldehyde group, and biphenyl porphyrin (PP) is obtained. Triptycene (TC) and ceric ammonium nitrate obtain an amino functional group under the action of a palladium-carbon catalyst, namely diamino triptycene (TAT), and the aldehyde group of biphenyl porphyrin (PP) and the amino group of the diamino triptycene (TAT) react with each other under the catalysis of an acidic condition to synthesize a-C = N-bond; and a stable Schiff base structure is formed, so that the novel covalent organic framework photoelectric catalyst capable of effectively and continuously generating urea is prepared. The novel covalent organic framework photoelectric catalyst can photoelectrocatalyze CO2 and nitrite to generate urea, and has the advantages of good physical and chemical stability, good dispersibility, small environmental harm, low cost and the like.

Description

Technical Field

[0001] The invention relates to the technical field of chemical engineering, and in particular to a preparation method of a novel covalent organic framework photoelectric catalyst and the photoelectric catalyst. Background Art

[0002] Humans have built a rich material civilization through excessive consumption of fossil fuels (coal, natural gas and petroleum products), but it has also brought about serious energy shortages, greenhouse effects and other problems. The greenhouse effect is mainly caused by the increase in the level of greenhouse gas carbon dioxide in the environment. The greenhouse effect will cause global temperatures to rise, leading to serious environmental problems such as rising sea levels and ozone layer destruction. Photoelectrocatalytic reduction of carbon dioxide into valuable carbon products is an effective and sustainable solution. Using clean and sustainable light energy and electricity to catalytically reduce carbon dioxide into high-value hydrocarbons can alleviate 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 and more sustainable future for mankind.

[0003] Porphyrin-based photocatalysts are commonly used materials for catalyzing carbon dioxide reduction. Porphyrin has a strong absorption of red and purple light, and its π-π conjugated structure can better transport photoelectrons. However, porphyrin-based photocatalysts still have certain defects when used for photocatalytic reduction: First, porphyrin is not very sensitive to CO 2 The adsorption capacity is poor, and the photoelectrocatalytic process requires the use of ion solutions or corresponding electrolyte solutions with strong storage capacity, which results in low efficiency. Secondly, porphyrin has only one set of 18 π-electron aromatic structures. The symmetrical tetrapyrrole ring and multiple carbon bridges determine that it has a certain electron conduction resistance. Thirdly, the catalytic process requires the use of sacrificial agents, co-catalysts, photosensitizers, etc. to capture photoelectrons and convert them into chemical energy. The subsequent processing of these additional reagents makes the reduction of carbon dioxide cumbersome. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a novel covalent organic framework photoelectrocatalyst and a photoelectrocatalyst thereof, in view of the above-mentioned deficiencies of the prior art. The photoelectrocatalyst is based on a porphyrin group and has a Schiff base structure, and can photoelectrocatalyze CO 2 The generated urea has the advantages of physical and chemical stability, good dispersibility, little harm to the environment and low cost.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: The present invention provides a method for preparing a novel covalent organic framework photoelectrocatalyst, comprising the following steps: S1. mixing bromophenylporphyrin 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 are mixed, potassium carbonate is added, and ultrasonic treatment is performed to obtain solution D, and solution D is heated under reflux in 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; The suspension H is filtered and washed to obtain a filtrate I; the potassium carbonate solution is mixed with the filtrate I to obtain a mixed component J, and after standing and stratification, the mixed components are separated and the organic phases are combined to obtain a solution K, and then anhydrous magnesium sulfate is added to the solution K, and then filtered to obtain a powder L; Powder L is dissolved in ethanol to form solution M; palladium carbon catalyst and hydrazine hydrate are added to solution M, heated to reflux for reaction, and powder N is obtained after filtering, namely diaminotriptycene TAT; S3. The biphenyl porphyrin PP is mixed with dichloromethane to obtain a solution O; the diaminotriptycene TAT is mixed with dichloromethane to obtain a solution P; Acetic acid is mixed with solution O to obtain suspension Q, and then suspension Q is dripped dropwise into solution P under continuous stirring and protective atmosphere to obtain solution R. The solution R is then heated to reflux in an oxygen atmosphere for a certain period of time, filtered and washed to obtain a powder S, namely the photoelectrocatalyst COF_PP-TAT.

[0006] 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, 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.

[0007] Preferably, the ultrasonication time in step S1 is 2 hours; and / or, The heating temperature is 105°C; and / or, The heating reflux reaction time is 72h.

[0008] 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, 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 dosage 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.

[0009] Preferably, 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.

[0010] 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, 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.

[0011] Preferably, 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.

[0012] 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.

[0013] The present invention adopts the above scheme to provide a method for preparing a novel covalent organic framework photoelectric catalyst and a photoelectric catalyst thereof, which is a CO catalyst having photoelectric activity and no metal. 2 Reduction catalyst, no need to add additional sacrificial agent, co-catalyst and photosensitizer, etc., the photoelectric catalyst is a high CO 2 Adsorbent photoactive polymers that promote CO 2 The photocatalyst uses biphenyl porphyrin with high visible light collection and charge separation capabilities as the core, introduces a twisted triptycene scaffold with "internal molecular free volume (IMFV)", creates molecular channels through polymer chains, and enhances the adsorption of gases at active sites, thus obtaining a photoelectrically active, non-metallic covalent organic framework photocatalyst (COF_PP-TAT). This photocatalyst has a large π-π conjugated structure and a unique internal free volume structure, which can achieve CO2 The purpose of specific adsorption is to effectively photoelectrocatalyze CO 2 Reduction synthesis of urea. The photoelectric catalyst preparation process is simple, low energy consumption, and green and environmentally friendly.

[0014] The present invention uses bromophenylporphyrin (TBPP) and phenylboronic acid as raw materials, and prepares biphenylporphyrin (PP) through Suzuki coupling reaction; triptycene reacts with ammonium cerium nitrate (SAN) under acidic conditions for 12 hours to generate dinitrotriptycene, and dinitrotriptycene is reduced to diaminotriptycene (TAT) under the action of palladium carbon catalyst (Pd / C) and hydrazine hydrate. The aldehyde group of biphenylporphyrin (PP) and the amino group of diaminotriptycene (TAT) are used to react under acidic conditions to synthesize a -C=N- bond, and COF_PP-TAT is synthesized through Schiff base reaction, forming a stable Schiff base structure, and preparing a novel covalent organic framework photoelectric catalyst (COF_PP-TAT) that can effectively and continuously generate urea.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of the novel covalent organic framework photoelectric catalyst and the photoelectric catalyst thereof are based on porphyrin and have a Schiff base structure, which can photoelectrocatalyze CO 2 The novel covalent organic framework photoelectrocatalyst (COF_PP-TAT) of the present invention has 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) is unique, and intermediates such as formic acid (HCOOH), carbon monoxide (CO), and ammonia (NH 3 ) and other valuable products with a wide range of applications, green and environmentally friendly synthesis scheme, simple operation and low cost.

[0016] 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

[0017] Figure 1 It is the SEM picture of PP and COF_PP-TAT of the present invention; Figure 2 FT-IR spectra of PP, TAT and COF_PP-TAT of the present invention; Figure 3 XRD patterns of PP, TAT and COF_PP-TAT of the present invention; Figure 4 UV spectra of PP, TAT and COF_PP-TAT of the present invention; Figure 5 It is the UV spectrum of the photoelectrocatalytic sample before and after urease treatment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following is a detailed description in conjunction with 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.

[0019] The specific implementation steps of the present invention are mainly divided into three steps: the first step is to prepare biphenyl porphyrin PP, using bromophenyl porphyrin and phenylboric acid as raw materials, using tetrakis(triphenylphosphine)palladium as a catalyst, and potassium carbonate to provide an alkaline environment, that is, using bromophenyl porphyrin (TBPP) and phenylboric acid such as 4-formylphenylboric acid as raw materials, and preparing biphenyl porphyrin (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 reduce and generate diaminotriptycene (TAT); the third step is to synthesize a novel covalent organic framework photoelectrocatalyst COF_PP-TAT, and the aforementioned PP and TAT are both synthesized by Schiff base reaction under the catalysis of acetic acid to synthesize COF_PP-TAT.

[0020] Example 1

[0021] This embodiment provides biphenyl porphyrin PP and a preparation method thereof, and the specific steps include: 1) Dissolve 1.20 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A; 2) Dissolve 1.40 g of 4-formylphenylboronic acid in 40 mL of pure water to obtain solution B; 3) Dissolve 0.18 g of tetrakis(triphenylphosphine)palladium catalyst in 160 mL of toluene to obtain solution C; 4) Solutions A, B, and C were mixed, and 1.6 g of potassium carbonate was added and ultrasonicated for 2 h to fully dissolve it to obtain solution D; potassium carbonate provides an alkaline environment to catalyze the synthesis of PP.

[0022] 5) Solution D was heated to reflux at 105°C under nitrogen protection for 72 hours to obtain suspension E; 6) Filter the suspension E and wash the filter cake with dichloromethane to obtain biphenyl porphyrin PP.

[0023] Example 2

[0024] 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: 1) Dissolve 1.40 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A.

[0025] Example 3

[0026] 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: 1) Dissolve 1.60 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A.

[0027] Example 4

[0028] 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: 1) Dissolve 1.80 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A.

[0029] Example 5

[0030] 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: 1) Dissolve 2.00 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A.

[0031] Example 6

[0032] 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: 1) Dissolve 2.20 g of bromophenylporphyrin TBPP in 80 mL of N,N-dimethylformamide to obtain solution A.

[0033] In Example 1-6, the amount of bromophenylporphyrin TBPP is changed (1.2-2.2 g). The amount of bromophenylporphyrin TBPP used will cause the yield and purity of PP to change. By appropriately increasing the amount of bromophenylporphyrin, the purity of the product PP will be appropriately improved. 1.20 g-2.20 g of bromophenylporphyrin can produce suitable biphenylporphyrin PP. Examples 15-19 are prepared based on the use of 1.20 g of bromophenylporphyrin. The bromophenylporphyrin PP used in Examples 15-19 is prepared using Example 1.

[0034] Example 7

[0035] This embodiment provides diaminotriptycene TAT and a preparation method thereof, and the specific steps include: 1) Disperse 3.39 g of triptycene TC in 50 mL of dichloromethane to obtain solution F; 2) Add 14.7 g of ammonium cerium nitrate to solution F to obtain suspension G; 3) Add 2.56 mL of sulfuric acid to suspension G, and stir the mixture under nitrogen for 12 h to obtain suspension H; suspension H contains dinitrotriptycene.

[0036] 4) Suspension H was filtered and the filter residue was thoroughly washed with 150 mL of dichloromethane until it became colorless to obtain filtrate I; filtrate I contained dinitrotriptycene.

[0037] 5) adding 100 mL of 10 wt% potassium carbonate solution to the filtrate I to obtain a mixed component J; potassium carbonate provides an alkaline environment, reduces the solubility of dinitrotriptycene in water, and increases the yield of dinitrotriptycene in dichloromethane.

[0038] 6) The mixed component J was allowed to stand for stratification, the aqueous phase was extracted three times with 50 mL of dichloromethane, and the organic phases were combined to obtain solution K; solution K was still dinitrotriptycene.

[0039] 7) Add 20 g of anhydrous magnesium sulfate to solution K, filter and remove the solvent to obtain powder L. Remove water from anhydrous magnesium sulfate and remove the solvent to obtain powder L, i.e., dinitrotriptycene powder.

[0040] 8) Dissolve 2.50 g of powdered L-dinitrotriptycene in 50 ml of ethanol to form solution M; 9) Add 0.2 g of palladium carbon (Pd / C) catalyst and 0.5 mL of hydrazine hydrate to solution M, heat to reflux for 2 h, filter and obtain powder N. Dinitrotriptycene is reduced to diaminotriptycene under the action of Pd / C and hydrazine hydrate catalyst to obtain powder N diaminotriptycene (TAT).

[0041] Example 8

[0042] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as that of Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include: 2) Add 29.4 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0043] Example 9

[0044] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as that of Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include: 2) Add 44.1 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0045] Example 10

[0046] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as that of Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include: 2) Add 58.8 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0047] Embodiment 11

[0048] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as that of Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include: 2) Add 73.5 g of ammonium cerium nitrate to solution F to obtain suspension G.

[0049] Example 12

[0050] This embodiment provides diaminotriptycene TAT and a preparation method thereof, which is basically the same as that of Example 7, except that the amount of ammonium cerium nitrate is changed. The specific steps include: 2) 88.2 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0051] Embodiment 13

[0052] 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: 2) 102.9 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0053] Embodiment 14

[0054] 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: 2) 117.6 g of ammonium cerium nitrate was added to solution F to obtain suspension G.

[0055] In Examples 7-14, by changing the amount of ammonium cerium nitrate (14.7-102.9 g), since the reaction of ammonium cerium nitrate with triptycene may generate mononitrotriptycene, dinitrotriptycene and trinitrotriptycene, appropriately increasing the amount of ammonium cerium nitrate helps to increase the yield of dinitrotriptycene, so that the purity of the subsequently synthesized diaminotriptycene is appropriately high. 14.7 g-102.9 g of ammonium cerium nitrate can obtain suitable diaminotriptycene TAT, and Examples 15-19 use 14.7 g of ammonium cerium nitrate, that is, the diaminotriptycene TAT of Example 7.

[0056] Embodiment 15

[0057] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is specifically implemented as follows 1) 0.31 g of biphenylporphyrin PP was mixed with 50 mL of dichloromethane to obtain solution O; 2) 0.31 g of diaminotriptycene TAT was mixed with 50 mL of dichloromethane to obtain solution P; 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. 4) The suspension Q was added dropwise into the solution P under continuous stirring and nitrogen protection for 24 hours to obtain a solution R; 5) The solution R was heated to reflux at 50°C in an oxygen atmosphere for 72 hours, and then filtered and washed to obtain powder S, i.e., the photoelectrocatalyst COF_PP-TAT. The oxygen atmosphere will accelerate the precipitation of COF_PP-TAT, which is beneficial to the production of COF_PP-TAT.

[0058] Example 16

[0059] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as that of Example 15, except that the amount of acetic acid is changed, and the specific implementation is as follows: 3) Mix 0.1 mL of acetic acid with solution O to obtain suspension Q.

[0060] Embodiment 17

[0061] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as that of Example 15, except that the amount of acetic acid is changed, and the specific implementation is as follows: 3) Mix 1.0 mL of acetic acid with solution O to obtain suspension P.

[0062] Embodiment 18

[0063] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as that of Example 15, except that the amount of acetic acid is changed, and the specific implementation is as follows: 3) Mix 2.0 mL of acetic acid with solution O to obtain suspension P.

[0064] Embodiment 19

[0065] This embodiment provides a photoelectrocatalyst COF_PP-TAT and a preparation method thereof, which is basically the same as that of Example 15, except that the amount of acetic acid is changed, and the specific implementation is as follows: 3) Mix 5.0 mL of acetic acid with solution O to obtain suspension P.

[0066] In Examples 15-19, the amount of acetic acid used was changed (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-5.0 mL. Figure 1 -Attached Figure 5 Photoelectrocatalyst COF_PP-TAT from Example 15.

[0067] 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 subjected to CO 2 Photoelectrocatalytic reduction experimental test.

[0068] By the attached Figure 1 It can be seen that PP presents a flake stacking structure at the microscopic level, and COF_PP-TAT after the 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.

[0069] By the attached Figure 2 It can be seen that 700-1700cm -1 The peaks are characteristic absorption peaks of PP, among which 1700cm -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 peaks at 1613 cm -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 can be attributed to the stretching vibration of the C=N group. -1 The absorption peak intensity of the carbonyl group at the position was weakened, indicating that COF_PP-TAT was successfully synthesized, in which the -NH2 of TAT reacted with -CHO to generate C=N, and a small amount of carbonyl groups of PP were not reacted.

[0070] By the attached Figure 3It 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.

[0071] By the attached Figure 4 It can be seen that, combined with the UV spectrum of COF_PP-TAT, COF_PP-TAT has multiple absorption bands, a strong Soret band at 413nm, and four Q bands at 512nm, 548nm, 589nm and 644nm, which are characteristic absorptions of porphyrin standards. PP and TAT are connected through the Schiff base structure, the stability of the molecular structure increases, the electron cloud density increases, and the energy required for electron transition decreases, causing the Soret band at 413nm to red-shift and red-shift to 445nm, and the Q band is reduced to one (670nm); TAT has a broad absorption peak at 240nm, which is reflected in COF_PP-TAT as a broad ultraviolet absorption peak red-shifted to 275nm. This shows that the COFs material has continuous absorption from 275nm to 670nm, and its light absorption capacity is significantly improved, which is beneficial for its CO 2 Photoelectrocatalytic reduction.

[0072] By the attached Figure 5 It can be seen that the indophenol blue compound has an ultraviolet absorption peak at 650nm. COF_PP-TAT in 0.4MNaNO 2 with 0.5 M NaHCO 3 Photoelectrocatalytic CO 2 Reduction, urea is generated in the system, and after urease treatment, the urea in the system is decomposed into ammonia and reacts with the developer to form indigo blue compound, resulting in an increase in the absorbance at 650nm. Figure 5 The absorbance at 650 nm in the sample indicates the ammonia content in the sample, and the purpose is to demonstrate the presence of urea in the reduction product. The dotted line indicates the ammonia content in the liquid reduction product formed after the electrolyte is photoelectrocatalyzed by the photoelectrocatalyst COF_PP-TAT of Example 15, and the solid line indicates the ammonia content of the liquid reduction product after urease treatment. The increase in absorbance at 650 nm indicates that the ammonia content of the reduction product has increased, because the urea in the reduction product is decomposed into ammonia after urease treatment.

[0073] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs 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 changes to the invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a novel covalent organic framework photoelectrocatalyst, characterized in that: The steps include: S1. mixing bromophenylporphyrin 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 are mixed, potassium carbonate is added, and ultrasonic treatment is performed to obtain solution D, and solution D is heated under reflux in 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; The suspension H is filtered and washed to obtain a filtrate I; the potassium carbonate solution is mixed with the filtrate I to obtain a mixed component J, and after standing and stratification, the mixed components are separated and the organic phases are combined to obtain a solution K, and then anhydrous magnesium sulfate is added to the solution K, and then filtered to obtain a powder L; Powder L is dissolved in ethanol to form solution M; palladium carbon catalyst and hydrazine hydrate are added to solution M, heated to reflux for reaction, and powder N is obtained after filtering, namely diaminotriptycene TAT; S3. The biphenyl porphyrin PP is mixed with dichloromethane to obtain a solution O; the diaminotriptycene TAT is mixed with dichloromethane to obtain a solution P; Acetic acid is mixed with solution O to obtain suspension Q, and then suspension Q is dripped dropwise into solution P under continuous stirring and protective atmosphere to obtain solution R. The solution R is then heated to reflux in an oxygen atmosphere for a certain period of time, filtered and washed to obtain a powder S, namely the photoelectrocatalyst COF_PP-TAT.

2. The method for preparing the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: In the 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, 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 the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: 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 the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: 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 ammonium cerium 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 dosage 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 the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: In the 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 the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: In the 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 the novel covalent organic framework photoelectrocatalyst according to claim 1, characterized in that: 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 novel covalent organic framework photoelectrocatalyst, characterized in that: The novel covalent organic framework photoelectric catalyst is prepared by the preparation method of the novel covalent organic framework photoelectric catalyst according to any one of claims 1 to 7, and is based on biphenyl porphyrin as the core composite triptycene scaffold and forms a Schiff base structure.

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