Cationic modified covalent cobalt porphyrin polymer, preparation method thereof and application of the polymer in electrocatalytic oxygen reduction reaction

Abstract

The application discloses a kind of cation modified covalent cobalt porphyrin polymer and its preparation method and the application of electrocatalytic oxygen reduction reaction, the cation modified covalent cobalt porphyrin polymer is by introducing cation functional group in cobalt porphyrin complex Form cation modified cobalt porphyrin-5,15-dibromo-10,20-di (2-benzyl trimethyl hexafluorophosphoric acid ammonium) cobalt porphyrin, again with tetra (4-ethynylphenyl) methane linker, by son head coupling reaction chemical bond cross coupling formation.The application carries out quaternary ammonium salt cation functional group modification of cobalt porphyrin complex in molecular level, and then positive charge electrostatic effect is successfully introduced into the active center near of covalent polymer by chemical bond coupling mode, and it is applied to electrocatalytic oxygen reduction reaction as cathode catalyst, with better electrocatalytic oxygen reduction reaction performance.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology such as zinc-air batteries and hydrogen-oxygen fuel cells. Specifically, it relates to a cationic modified covalent cobalt porphyrin polymer formed by coupling a cobalt porphyrin complex with a cationic electrostatic interaction group to a tetraphenylmethane linker through a stalk coupling reaction, and its application in the electrocatalytic oxygen reduction reaction. Background Technology

[0002] In recent decades, the demand for renewable and environmentally friendly energy has been increasing. Fuel cells and metal-air batteries using the oxygen reduction reaction (ORR) as the cathode have become key technologies for solving the energy problem due to their high energy density and reliability (Coord. Chem. Rev., 2023, 474, 214854). Since the ORR involves a four-electron, four-proton reduction process, its kinetics are slow, requiring highly efficient catalysts. However, highly efficient noble metal catalysts are scarce and expensive, making them unsuitable for widespread application. Therefore, developing efficient and stable non-noble metal-based ORR catalysts is essential.

[0003] Metalloporphyrin / carboxylated catalysts are widely used in ORR (Organic Reaction Ratio) due to their well-defined and tunable molecular structures and the ability of the macrocyclic center to stabilize high-valence metal ions. They are also frequently used to study structure-activity relationships and catalytic reaction mechanisms (Chem. Rev., 2017, 117, 3717-3797). The promoting effect of cationic electrostatic interactions in metal complex CO2RR has been demonstrated. Introducing cationic electrostatic groups can stabilize CO2 intermediate products and improve catalytic performance, making it a very important performance regulation strategy (J. Am. Chem. Soc., 2016, 138, 16639-16644; Angew. Chem. Int. Ed., 2022, 61, e202209602; Chin. J. Catal., 2022, 43, 3089-3094; eScience, 2022, 2, 623-631). Similarly, it has been reported in the literature that modifying porphyrin with auxiliary electrostatic interaction groups can also stabilize the metal-superoxide negative intermediate that combines the central metal with O2, thereby improving the ORR performance of the catalyst (J.Am.Chem.Soc.,2020,142,13426-13434; J.Am.Chem.Soc.,2021,143,11423-11434; Chem.Sci.,2019,10,9692-9698; Inorg.Chem.,2020,59,17402-17414; Phys.Chem.Chem.Phys.,2023,25,4604-4610).

[0004] Porphyrin-based covalent polymer materials (POFs) possess unique advantages such as periodic topological structures, high specific surface areas, tunable pore sizes, and chemical stability. Furthermore, they can regulate the electronic structure and conjugated systems of the metal-active catalytic centers through microenvironment modulation, making them active in the fields of efficient and environmentally friendly energy conversion and catalysis (Chem. Soc. Rev., 2021, 50, 2540-2581; Energy Environ. Sci., 2018, 11, 1723-1729; Adv. Funct. Mater., 2019, 29, 190130; Adv. Sci., 2023, 10, 2206239; Coord. Chem. Rev., 2022, 464, 214563). In recent years, researchers have successfully modified polymers based on the catalytic properties of cationic electrostatic interactions, demonstrating excellent performance in CO2RR and ORR (J. Mater. Chem. A, 2022, 10, 22781-22790; Nat. Commun., 2023, 14, 3800; Adv. Mater., 2022, 34, 2110496; Angew. Chem. Int. Ed., 2022, 61, e202212162; Angew. Chem. Int. Ed., 2023, 62, e202215687). However, in this method of covalent polymer coupling followed by modification, most of the cationic electrostatic interaction groups formed are located on the linker of the covalent polymer. On the one hand, it cannot guarantee that the modification reaction will proceed completely (i.e., all sites on the linker will be introduced with cationic groups). On the other hand, the modified cationic groups are far from the catalytic active center of the polymer, resulting in weak electrostatic interaction, which cannot improve the catalytic reaction performance of the catalytic active center. Summary of the Invention

[0005] The purpose of this invention is to provide a cationic electrostatically modified Co porphyrin compound, and to cross-couple it with the corresponding tetraphenylmethane to form a cationic modified covalent cobalt porphyrin polymer (N + -COP), and also provides an application for electrocatalytic oxygen reduction reaction.

[0006] To achieve the above objectives, the structural formula of the cationic modified covalent cobalt porphyrin polymer provided by the present invention is as follows:

[0007]

[0008] In the formula, n represents the number of anions, which is the same as the number of cations.

[0009] The synthetic route and specific preparation method of the above-mentioned cationic modified covalent cobalt porphyrin polymer are as follows:

[0010]

[0011] Step 1: 2-(bromomethyl)benzaldehyde and 2,2'-dipyrrolithium methane were added to dichloromethane and stirred at room temperature for 15-20 minutes under argon atmosphere in the dark. Trifluoroacetic acid was added and reacted for 30-40 minutes. Then, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was added and stirred for 30-40 minutes. Triethylamine was added for neutralization, and the mixture was purified by rapid column chromatography to obtain the 5,15-bis(2-benzylbromo)porphyrin ligand with the following structural formula.

[0012] Step 2: Add the 5,15-bis(2-benzylbromo)porphyrin ligand and zinc acetate dihydrate from Step 1 to tetrahydrofuran, reflux at 65-75°C in the dark for 3-4 hours, and then purify by rapid column chromatography to obtain 5,15-bis(2-benzylbromo)zinc porphyrin;

[0013] Step 3: Under anhydrous and oxygen-free conditions, the 5,15-bis(2-benzylbromo)zinc porphyrin from Step 2 was dissolved in chloroform. Pyridine and N-bromosuccinimide were added at 0°C. After reacting for 30–40 minutes, methanol was added to quench the reaction. The solvent was then evaporated by rotary evaporation, followed by rapid column chromatography to obtain a purple solid. The purple solid was dissolved in acetone, hydrochloric acid was added, and the mixture was stirred at room temperature for 2–3 hours. After the solvent was evaporated by rotary evaporation, the mixture was extracted with pure water and dichloromethane, followed by rapid column chromatography to obtain the 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand.

[0014] Step 4: Add the 5,15-dibromo-10,20-di(2-benzylbromo)porphyrin ligand from Step 3 and cobalt acetate tetrahydrate to a mixed solvent of chloroform and methanol, and reflux at 60-70°C in the dark for 3-4 hours. After rapid column chromatography separation and purification, 5,15-dibromo-10,20-di(2-benzylbromo)cobalt porphyrin is obtained.

[0015] Step 5: Under nitrogen conditions in an anhydrous and oxygen-free environment, the 5,15-dibromo-10,20-di(2-benzylbromo)cobalt porphyrin from Step 4 was dissolved in tetrahydrofuran, trimethylamine was added, and the mixture was stirred at room temperature for 20–24 hours. The precipitate was collected by filtration, dissolved in N,N-dimethylformamide, and then added dropwise to a saturated aqueous solution of ammonium hexafluorophosphate. After stirring for 4–6 hours, the mixture was filtered, and the precipitate was washed with diethyl ether and dried under vacuum to obtain a purple-red solid, 5,15-dibromo-10,20-di(2-benzyltrimethylammonium hexafluorophosphate)cobalt porphyrin, i.e., a cationic cobalt porphyrin monomer.

[0016] Step 6: Under nitrogen atmosphere, the cationic cobalt porphyrin monomer from step 5 and tetrakis(4-ethynylphenyl)methane were dissolved in N,N-dimethylformamide. Triethylamine, palladium dichloride of bis(triphenylphosphine)phosphine and cuprous iodide were added. The mixture was stirred at 65-75°C for 45-50 hours. After filtration, the mixture was washed with N,N-dimethylformamide and then with methanol. After vacuum drying, the cationic modified covalent cobalt porphyrin polymer was obtained.

[0017] In step 1 above, the molar ratio of 2-(bromomethyl)benzaldehyde, 2,2'-dipyrrolithane, trifluoroacetic acid, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1:1 to 1.2:2 to 6:2 to 4.

[0018] In step 2 above, the molar ratio of the 5,15-bis(2-benzylbromo)porphyrin ligand to zinc acetate dihydrate is 1:10 to 20.

[0019] In step 3 above, the molar ratio of 5,15-bis(2-benzylbromo)zinc porphyrin to N-bromosuccinimide and pyridine is 1:2-3:1-5.

[0020] In step 4 above, the molar ratio of the 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand to cobalt acetate tetrahydrate is 1:10-20.

[0021] In step 5 above, the molar ratio of 5,15-dibromo-10,20-bis(2-benzylbromo)cobalt porphyrin to trimethylamine is 1:1 to 8.

[0022] In step 6 above, the molar ratio of the cationic cobalt porphyrin monomer, tetra(4-ethynylphenyl)methane, triethylamine, palladium dichloride of bis(triphenylphosphine)phosphine and cuprous iodide is 1:0.3-0.7:20-50:0.02-0.1:0.02-0.1.

[0023] The cationic modified covalent cobalt porphyrin polymer of the present invention can be used for electrocatalytic oxygen reduction reaction. Specifically, the cationic modified covalent cobalt porphyrin polymer is composited with carbon material as a catalyst and loaded on an electrode as the cathode of the electrocatalytic reaction device, with a carbon rod or platinum sheet as the anode, and the electrocatalytic oxygen reduction reaction is carried out in a 1.0 mol / L KOH solution.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention utilizes molecular design principles to controllably synthesize cobalt porphyrin molecules modified with quaternary ammonium salt cationic groups at the meso site, ingeniously designing them as monomeric structures and matching them with corresponding linkers. Employing a stalk cross-coupling reaction, the cobalt porphyrin monomer with cationic electrostatic interaction is coupled to a tetraphenylmethane linker via alkyne bonding to form a covalent organic polymer, clearly and successfully modifying the polymer with cationic electrostatic effects. This design method is the first to explicitly and successfully introduce cationic electrostatic effects closer to the catalytic active center of the covalent polymer. Compared with previously reported polymer materials, the cationic polymer synthesized by this method has a more defined structure and a more pronounced cationic electrostatic effect, while ensuring catalyst stability. It exhibits greater stability in the catalytic oxygen reduction reaction, demonstrating superior catalytic performance and achieving high efficiency and high stability in the electrocatalytic oxygen reduction reaction of metalloporphyrin-based covalent organic polymers. This invention successfully applies molecular design principles to polymer materials, verifying the rationality of molecular catalyst design concepts in heterogeneous systems. Attached Figure Description

[0026] Figure 1 This is the infrared spectrum of the cationic modified covalent cobalt porphyrin polymer prepared in Example 1.

[0027] Figure 2 This is a partial X-ray photoelectron spectrum of the cationic modified covalent cobalt porphyrin polymer prepared in Example 1.

[0028] Figure 3 This is a scanning electron microscope image of the cationic modified covalent cobalt porphyrin polymer prepared in Example 1.

[0029] Figure 4 This is the infrared spectrum of the phenylcobalt porphyrin polymer prepared in Comparative Example 1.

[0030] Figure 5 This is a partial X-ray photoelectron spectrum of the phenylcobalt porphyrin polymer prepared in Comparative Example 1.

[0031] Figure 6 This is a scanning electron microscope image of the phenylcobalt porphyrin polymer prepared in Comparative Example 1.

[0032] Figure 7 This is a graph showing the electrocatalytic oxygen reduction reaction performance of the cationic modified covalent cobalt porphyrin polymer prepared in Example 1.

[0033] Figure 8 This is a graph showing the electrocatalytic oxygen reduction reaction performance of the phenylcobalt porphyrin polymer prepared in Comparative Example 1.

[0034] Figure 9 This is a stability graph of the cationic modified covalent cobalt porphyrin polymer prepared in Example 1. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0036] Example 1

[0037] Step 1: 396 mg (2 mmol) of 2-(bromomethyl)benzaldehyde and 292 mg (2 mmol) of 2,2'-dipyrrolithium methane were added to a 1 L round-bottom flask containing 500 mL of dichloromethane. The mixture was stirred at room temperature for 15 minutes under argon atmosphere in the dark. 0.594 mL (8 mmol) of trifluoroacetic acid was added, and the mixture was stirred for 30 minutes. Then, 1.362 g (6 mmol) of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was added, and the mixture was stirred for 30 minutes. 1 mL of triethylamine was added for neutralization, and the mixture was stirred for another hour. The mixture was then separated by rapid column chromatography using a 1:1 volume ratio of petroleum ether and dichloromethane as the developing solvent. The solvent was removed by rotary evaporation under reduced pressure to obtain a purple solid, which was 5,15-bis(2-benzylbromo)porphyrin ligand, with a yield of 32%. The structure was characterized as follows:

[0038] 1 H NMR (400MHz, Chloroform-d) δ10.32(s,2H),9.38(d,J=4.5Hz,4H),8.89(d,J=4.4Hz,4H),8.16(d,J=7.0Hz,1H),8.10(d,J =7.1Hz, 1H), 7.98 (t, J = 7.7Hz, 2H), 7.89 (t, J = 7.7Hz, 2H), 7.72 (q, J = 6.8Hz, 2H), 4.36 (s, 2H), 4.29 (s, 2H), -3.14 (s, 2H).

[0039] High-resolution mass spectrometry (HRMS(ESI)) m / z:C 34 H 25 Br2N4,[M+H] + Theoretical value: 649.0423; Measured value: 649.0426.

[0040] Step 2: 32.3 mg (0.05 mmol) of 5,15-bis(2-benzylbromo)porphyrin ligand and 109.8 mg (0.5 mmol) of zinc acetate dihydrate were added to 20 mL of tetrahydrofuran. After reflux at 70 °C in the dark for 3 hours, the solvent was rotary evaporated. The mixture was extracted three times with pure water and dichloromethane. Using a 1:1 volume ratio of petroleum ether and dichloromethane as the developing solvent, rapid column chromatography was performed for separation and purification. The solvent was then removed by rotary evaporation under reduced pressure to obtain a purple solid, which is 5,15-bis(2-benzylbromo)zinc porphyrin, with a yield of 96%. The structure is characterized as follows:

[0041] 1 H NMR(400MHz,Chloroform-d)δ10.31(d,J=1.5Hz,2H),9.41(d,J=4.4Hz,4H),8.95(s,4H),8.16(d,J=7.5Hz,1H),8. 09(t,J=7.6Hz,1H),7.94(t,J=7.0Hz,2H),7.85(t,J=7.6Hz,2H),7.53(q,J=5.7Hz,2H),4.26(s,2H),4.22(s,2H).

[0042] High-resolution mass spectrometry (HRMS(ESI)) m / z:C 34 H 23 Br2N4Zn,[M+H] + Theoretical value: 712.9526; Measured value: 712.9526.

[0043] Step 3: Under anhydrous and oxygen-free conditions, 35.6 mg (0.05 mmol) of 5,15-bis(2-benzylbromo)zinc porphyrin was dissolved in 20 mL of chloroform. The mixture was stirred at 0 °C in the dark for 10 minutes. Then, 0.01 mL (0.124 mmol) of pyridine and 18.16 mg (0.102 mmol) of N-bromosuccinimide were added. After reacting for 30 minutes, 0.5 mL of methanol was added to quench the reaction. The solvent was removed by rotary evaporation under reduced pressure. The mixture was then purified by rapid column chromatography using dichloromethane as the developing solvent. The solvent was removed by rotary evaporation under reduced pressure to obtain a purple solid. The purple solid was then dissolved in 20 mL of acetone, and 2 mL of concentrated hydrochloric acid was added. The mixture was stirred at room temperature for 2 hours. The solution was extracted three times with pure water and dichloromethane. Using a 20:1 (v / v) mixture of petroleum ether and dichloromethane as the developing solvent, the mixture was purified by rapid neutral alumina column chromatography. The solvent was removed by rotary evaporation under reduced pressure to obtain a purple-red solid, which is the 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand, with a yield of 98%. The structure is characterized as follows:

[0044] 1 H NMR(400MHz,Chloroform-d)δ9.60(d,J=4.8Hz,4H),8.69(d,J=4.6Hz,4H),8.06(d,J=7.4Hz,1H),8.00(d,J=7.3Hz ,1H),7.92(t,J=3.9Hz,2H),7.85(t,J=7.6Hz,2H),7.69(q,J=6.4Hz,2H),4.24(s,2H),4.18(s,2H),-2.64(s,2H).

[0045] High-resolution mass spectrometry (HRMS(ESI)) m / z:C 34 H 23Br4N4,[M+H] + Theoretical value: 806.8611; Measured value: 806.8614.

[0046] Step 4: 40.3 mg (0.05 mmol) of 5,15-dibromo-10,20-di(2-benzylbromo)porphyrin ligand and 124.5 mg (0.5 mmol) of cobalt acetate tetrahydrate were added to a mixed solvent of 10 mL chloroform and 10 mL methanol. The mixture was refluxed at 65 °C for 3 hours under light-protected conditions. After removing the solvent by rotary evaporation under reduced pressure, the mixture was extracted three times with pure water and dichloromethane. The mixture was purified by rapid neutral alumina column chromatography using a 1:2 volume ratio of petroleum ether and dichloromethane as the developing solvent. After further purification by rotary evaporation under reduced pressure, a red solid was obtained, which was 5,15-dibromo-10,20-di(2-benzylbromo)cobalt porphyrin, with a yield of 96%. The structure was characterized as follows:

[0047] High-resolution mass spectrometry (HRMS(ESI)) m / z:C 34 H 21 Br4N4Co,[M+H] + Theoretical value: 863.7795; Measured value: 863.7789.

[0048] Step 5: Under anhydrous and oxygen-free argon conditions, 43.2 mg (0.05 mmol) of 5,15-dibromo-10,20-di(2-benzyl bromide)cobalt porphyrin was dissolved in 20 mL of tetrahydrofuran. 0.1 mL of 2 M trimethylamine methanol solution was added, and the mixture was stirred at room temperature for 24 hours. After filtration, the precipitate was collected and dissolved in 2 mL of N,N-dimethylformamide. This solution was then slowly added dropwise to a saturated aqueous solution of ammonium hexafluorophosphate. After stirring for 5 hours, the mixture was filtered, and the precipitate was washed with diethyl ether and dried under vacuum to obtain a purple-red solid, 5,15-dibromo-10,20-di(2-benzyltrimethylammonium hexafluorophosphate)cobalt porphyrin, i.e., the cationic cobalt porphyrin monomer, with a yield of 65%. Its structure is characterized as follows:

[0049] High-resolution mass spectrometry (HRMS) (ESI) m / z: [C 40 H 38 Br2N6Co] 2+ [M] 2+ Theoretical value: 410.5413; Measured value: 410.5415.

[0050] Step 6: Under nitrogen atmosphere, 82 mg (0.1 mmol) of cationic cobalt porphyrin monomer and 20.8 mg (0.05 mmol) of tetrakis(4-ethynylphenyl)methane were dissolved in 10 mL of N,N-dimethylformamide. 0.2 mL (2.23 mmol) of triethylamine was added, followed by 5.6 mg (8 μmol) of bis(triphenylphosphine)palladium dichloride and 1.5 mg (8 μmol) of cuprous iodide. The mixture was stirred at 70 °C for 48 hours. After filtration, the precipitate was washed three times with N,N-dimethylformamide and then three times with methanol. It was then dried under vacuum at 60 °C. The resulting black solid was the cationic modified covalent cobalt porphyrin polymer.

[0051] Infrared spectroscopy was used to study tetra(4-ethynylphenyl)methane (TEPM) and the resulting cationic cobalt porphyrin monomer (N... + -Co), cation-modified covalent cobalt porphyrin polymers (N + Characterized by -COP, such as Figure 1 As shown, the connector TEPM is at 3283cm. -1 and 2108cm -1 The characteristic peak of the terminal hydrogen of the alkynyl group, when combined with N + -Co chemically coupled to form N + -COP, the characteristic peak of the terminal hydrogen of the alkynyl group disappears, and N + -COP infrared spectrum and N + The characteristic peaks in the infrared spectrum of -Co correspond one-to-one with those in other locations, proving that N + -COP synthesis successful. In N + In the X-ray photoelectron spectroscopy analysis of -COP, N + The -COP catalyst exhibits two characteristic peaks for divalent Co ions in the Co 2p region, which are attributed to the Co 2p region. 3 / 2 (780.2 eV) and Co 2p 1 / 2 (795.5 eV)(CCS Chem.,2022,4:2959-2967), such as Figure 2 As shown, this is consistent with the coordination and electronic structure of Co in the monomeric cobalt porphyrin. In the N1s spectrum, the cationic modified covalent cobalt porphyrin polymer exhibits a characteristic peak at 398.5 eV attributed to Co-N, and an additional characteristic peak at 402.5 eV attributed to the N atom in the quaternary ammonium salt (Adv. Mater., 2022, 34: 2110496; Angew. Chem. Int. Ed., 2022, 61: e202212162), thus proving that the N-N coordination and electronic structure are consistent with the structure of the monomeric cobalt porphyrin. + The presence of quaternary ammonium salt cations in -COP indicates that the cationic groups can still be retained in the cobalt porphyrin structure after coupling polymerization. N was measured using scanning electron microscopy. +Microscopic images of -COP, such as Figure 3 As shown, N + -COP was displayed as uniform 400 nm microspheres, demonstrating the successful synthesis of the polymer.

[0052] Comparative Example 1

[0053]

[0054]

[0055] Step 1: 252.1 mg (2 mmol) of 3-trimethylsilylpropynaldehyde and 444.6 mg (2 mmol) of 5-phenyldipyrrolemethane were added to a 1 L round-bottom flask containing 600 mL of redistilled DCM. Argon gas was passed through for 15 minutes to remove oxygen. Then, 0.594 mL (8 mmol) of trifluoroacetic acid was added in the dark, and the mixture was stirred at room temperature for 30 minutes. Next, 681 mg (3 mmol) of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was added, and the mixture was stirred for another 30 minutes. The solvent was removed by vacuum distillation, and the crude product was separated. Using PE:DCM = 1:1 as eluent, the crude product was purified by column chromatography. The solvent was removed by vacuum distillation, and the crude product was recrystallized from methanol. Filtering yielded a dark purple solid, which was 5,15-di(phenyl)-10,20-di(trimethylsilylethynyl)porphyrin ligand, with a yield of 22%. The structure was characterized as follows:

[0056] 1 H NMR (CDCl3, 400MHz): δ = 9.61 (d, 4H), 8.82 (d, 4H), 8.18 (d, 4H), 7.78 (q, 6H), 0.60 (s, 18H), -2.20 (s, 2H).

[0057] HRMS(ESI)m / z:C 42 H 39 N4Si2,[M+H] + Theoretical value: 655.2708; Measured value: 655.2721.

[0058] Step 2: 32.7 mg (0.05 mmol) of 5,15-di(phenyl)-10,20-di(trimethylsilylethynyl)porphyrin ligand and 124.5 mg (0.5 mmol) of cobalt acetate tetrahydrate were added to a 100 mL flask, along with 15 mL of chloroform and 15 mL of methanol. The resulting mixture was heated to 70 °C and reacted for 5 hours. After removing the solvent by vacuum distillation, the mixture was extracted three times with water and DCM to obtain the crude product. Using a PE:DCM mixture of 1:1 as the developing solvent, the crude product was purified by rapid column chromatography. After removing the solvent by vacuum distillation, a purple solid was obtained, which was 5,15-di(phenyl)-10,20-di(trimethylsilylethynyl)cobalt porphyrin, with a yield of 98%. The structure was characterized as follows:

[0059] HRMS(ESI)m / z:C 42 H 37 CoN4Si2,[M+H] + Theoretical value: 712.1883; Measured value: 712.1882.

[0060] Step 3: Under nitrogen protection, 35.6 mg (0.05 mmol) of 5,15-di(phenyl)-10,20-di(trimethylsilylethynyl)cobalt porphyrin and 10 mL of anhydrous THF were added to a 50 mL Schlenk flask. Then, 180 μL of a 1 M tetrabutylammonium fluoride (TBAF) THF solution was slowly added. The resulting solution was stirred at room temperature for 3 hours. After the reaction was complete, 10 mL of water was added, and a precipitate formed. The precipitate was collected by filtration and dried under vacuum to obtain a purple-black solid, 5,15-di(phenyl)-10,20-di(ethynyl)cobalt porphyrin, which is the phenylcobalt porphyrin monomer, with a yield of 96%. The structure is characterized as follows:

[0061] HRMS(ESI)m / z:C 36 H 21 CoN4,[M+H] + Theoretical value: 568.1093; Measured value: 568.1094.

[0062] Step 4: Under nitrogen protection, 56.8 mg (0.1 mmol) of phenylcobalt porphyrin monomer, 31.8 mg (0.05 mmol) of tetrakis(4-bromophenyl)methane (TBPM), and 10 mL of N,N-dimethylformamide (DMF) were added to a 50 mL Schlenk flask. 3 mL of triethylamine (TEA) was added, followed by 5.6 mg (8 μmol) of bis(triphenylphosphine) palladium dichloride and 1.5 mg (8 μmol) of cuprous iodide. After sealing the flask, the mixture was heated to 70 °C and stirred for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered, and the precipitate was collected and washed three times with DMF, followed by three washes with methanol (MeOH). Finally, the solid was dried under vacuum at 60 °C to obtain a black solid, which is the phenylcobalt porphyrin polymer.

[0063] Infrared spectroscopy was used to characterize the linker tetra(4-bromophenyl)methane (TBPM), the obtained phenylcobalt porphyrin monomer (Co-H), and the phenylcobalt porphyrin polymer (COP), such as... Figure 4 As shown, Co-H at 3265cm -1 and 2101cm -1 The characteristic peak of the terminal hydrogen of the alkynyl group is present. When COP is chemically coupled with the linker TBPM to form COP, the characteristic peak of the terminal hydrogen of the alkynyl group disappears. Furthermore, the infrared spectrum of COP corresponds one-to-one with the characteristic peaks of the infrared spectrum of Co-H in other regions, proving the successful synthesis of COP. In X-ray photoelectron spectroscopy analysis of COP, the COP catalyst shows two characteristic peaks of divalent Co ions in the Co 2p region, which are attributed to Co 2p... 3 / 2 (780.2 eV) and Co 2p 1 / 2 (795.5 eV)(CCS Chem.,2022,4:2959-2967), such as Figure 5 As shown, the coordination and electronic structure of Co in the monomeric cobalt porphyrin are consistent. In the N1s spectrum, the phenylcobalt porphyrin polymer exhibits a characteristic peak at 398.5 eV belonging to Co-N, thus proving that cobalt porphyrin is completely preserved in COP. Microscopic images of COP were obtained using scanning electron microscopy, as shown below. Figure 6 As shown, COP appears as uniform 400 nm microspheres, demonstrating the successful synthesis of this polymer.

[0064] Example 2

[0065] Cationic modified covalent cobalt porphyrin polymer (N + Applications of COP (electrocatalytic oxygen reduction reaction)

[0066] Because cobalt porphyrin polymer materials have poor electrical conductivity, carbon materials are needed to increase the conductivity of the catalyst for electrocatalytic testing. Take 2 mg of N... +-COP and 2 mg of carbon nanotubes (CNTs) were added to a mixed solution of 0.48 mL isopropanol and 0.48 mL water, followed by 40 μL of 0.5% Nafion solution. The mixture was sonicated for 30 minutes. 20 μL of the resulting suspension was then uniformly drop-coated onto a clean glassy carbon electrode (0.125 cm²). 2 On the surface, air dry at room temperature to obtain N. + - A COP-loaded CNT electrode was prepared. A COP-loaded CNT electrode was also prepared for comparative experiments.

[0067] In the electrocatalytic oxygen reduction test, N was used respectively + - Using a COP-loaded CNT electrode as the working cathode, and a carbon rod electrode and a saturated Ag / AgCl electrode as the counter and reference electrodes, respectively, and a 0.1M KOH solution as the electrolyte, electrochemical oxygen reduction tests were performed. Figure 7 As shown, the left figure shows N under argon and oxygen conditions respectively. + Cyclic voltammetry (CV) tests of -COP show that under oxygen saturation conditions, N + -COP demonstrates electrocatalytic oxygen reduction performance, with a peak potential of 0.78V (vs RHE); the right figure shows the rotating disk electrode test (RRDE) under oxygen saturation conditions, at 1600 rpm, N... + -COP exhibits good performance in the electrocatalytic oxygen reduction reaction, with a half-wave potential of 0.81V (vs RHE). Figure 8 The left figure shows the cyclic voltammetry (CV) tests of COP under argon and oxygen conditions, respectively. It can be seen that under oxygen saturation, COP exhibits electrocatalytic oxygen reduction performance, with a peak potential of 0.74 V (vs RHE). The right figure shows the rotating disk electrode (RRDE) test under oxygen saturation conditions. At 1600 rpm, COP shows good electrocatalytic oxygen reduction performance, with a half-wave potential of 0.78 V (vs RHE). Therefore, the cationic modified covalent cobalt porphyrin polymer (N... + -COP performs better than phenyl cobalt porphyrin polymer (COP) and is also superior to most simple cobalt porphyrin molecular catalysts.

[0068] like Figure 9 As shown in the left figure, after 2000 cycles of the electrocatalytic oxygen reduction reaction test, N... + - The performance of the COP catalyst remains at a high level; in the electrocatalytic oxygen reduction electrolysis experiment shown in the right figure, N + -COP was electrolyzed at a constant potential of 0.36V (vs RHE) for 10 hours. The current decreased to only 94% before and after electrolysis, and it still maintained good performance.

[0069] In summary, N +-COP not only exhibits high catalytic performance within the cobalt porphyrin system in the electrocatalytic oxygen reduction reaction, but also possesses good stability.

Claims

1. A cationic-modified covalent cobalt porphyrin polymer, characterized in that... The structural formula of the polymer is shown below: In the formula, n represents the number of anions, which is the same as the number of cations.

2. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 1, characterized in that... The method includes the following steps: Step 1: 2-(bromomethyl)benzaldehyde and 2,2'-dipyrrolithium methane were added to dichloromethane and stirred at room temperature for 15-20 minutes under argon atmosphere in the dark. Trifluoroacetic acid was added and reacted for 30-40 minutes. Then, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was added and stirred for 30-40 minutes. Triethylamine was added for neutralization, and the mixture was purified by rapid column chromatography to obtain the 5,15-bis(2-benzylbromo)porphyrin ligand with the following structural formula. Step 2: Add the 5,15-bis(2-benzylbromo)porphyrin ligand and zinc acetate dihydrate from Step 1 to tetrahydrofuran, reflux at 65-75°C in the dark for 3-4 hours, and then purify by rapid column chromatography to obtain 5,15-bis(2-benzylbromo)zinc porphyrin with the following structural formula; Step 3: Under anhydrous and oxygen-free conditions, the 5,15-bis(2-benzylbromo)zinc porphyrin from Step 2 was dissolved in chloroform. Pyridine and N-bromosuccinimide were added at 0°C. After reacting for 30–40 minutes, methanol was added to quench the reaction. The solvent was then evaporated by rotary evaporation, followed by rapid column chromatography to obtain a purple solid. The purple solid was dissolved in acetone, hydrochloric acid was added, and the mixture was stirred at room temperature for 2–3 hours. After rotary evaporation, the mixture was extracted with pure water and dichloromethane, followed by rapid column chromatography to obtain the 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand with the following structural formula. Step 4: The 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand from Step 3 and cobalt acetate tetrahydrate were added to a mixed solvent of chloroform and methanol and refluxed at 60-70°C in the dark for 3-4 hours. After rapid column chromatography separation and purification, the following structure 5,15-dibromo-10,20-bis(2-benzylbromo)cobalt porphyrin was obtained. Step 5: Under nitrogen conditions in an anhydrous and oxygen-free environment, dissolve 5,15-dibromo-10,20-di(2-benzylbromo)cobalt porphyrin from Step 4 in tetrahydrofuran, add trimethylamine, stir at room temperature for 20-24 hours, filter to collect the precipitate, dissolve it in N,N-dimethylformamide, and add it dropwise to a saturated aqueous solution of ammonium hexafluorophosphate. After stirring for 4-6 hours, filter, wash the precipitate with diethyl ether, and vacuum dry to obtain a purple-red solid, which is 5,15-dibromo-10,20-di(2-benzyltrimethylammonium hexafluorophosphate)cobalt porphyrin with the following structural formula, i.e., cationic cobalt porphyrin monomer; Step 6: Under nitrogen atmosphere, the cationic cobalt porphyrin monomer from step 5 and tetrakis(4-ethynylphenyl)methane were dissolved in N,N-dimethylformamide. Triethylamine, palladium dichloride of bis(triphenylphosphine)phosphine and cuprous iodide were added. The mixture was stirred at 65-75°C for 45-50 hours. After filtration, the mixture was washed with N,N-dimethylformamide and then with methanol. After vacuum drying, the cationic modified covalent cobalt porphyrin polymer was obtained.

3. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 1, the molar ratio of 2-(bromomethyl)benzaldehyde, 2,2'-dipyrrolithane, trifluoroacetic acid, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1:1 to 1.2:2 to 6:2 to 4.

4. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 2, the molar ratio of the 5,15-bis(2-benzylbromo)porphyrin ligand to zinc acetate dihydrate is 1:10 to 20.

5. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 3, the molar ratio of 5,15-bis(2-benzylbromo)zinc porphyrin to N-bromosuccinimide and pyridine is 1:2-3:1-5.

6. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 4, the molar ratio of the 5,15-dibromo-10,20-bis(2-benzylbromo)porphyrin ligand to cobalt acetate tetrahydrate is 1:10-20.

7. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 5, the molar ratio of 5,15-dibromo-10,20-bis(2-benzylbromo)cobalt porphyrin to trimethylamine is 1:1 to 8.

8. The method for preparing the cationic modified covalent cobalt porphyrin polymer according to claim 2, characterized in that: In step 6, the molar ratio of the cationic cobalt porphyrin monomer, tetra(4-ethynylphenyl)methane, triethylamine, palladium dichloride of bis(triphenylphosphine)phosphine and cuprous iodide is 1:0.3-0.7:20-50:0.02-0.1:0.02-0.

1.

9. The use of the cationic modified covalent cobalt porphyrin polymer of claim 1 in the electrocatalytic oxygen reduction reaction.

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