A kind of porphyrin ring branched polybenzimidazole and preparation method of porphyrin ring branched polybenzimidazole proton exchange membrane

Abstract

The invention discloses a method for preparing a porphyrin ring-branched polybenzimidazole and a porphyrin ring-branched polybenzimidazole proton exchange membrane. The porphyrin ring-branched polybenzimidazole is prepared by the following method: in polyphosphoric acid containing phosphorus pentoxide, at least one of the aromatic tetraamine monomers shown in formula I, at least one of the dicarboxylic acid monomers shown in formula II and the tetrakis(4-carboxyphenyl)porphine shown in formula III are subjected to polycondensation reaction to obtain the porphyrin ring-branched polybenzimidazole. The invention provides a method for preparing a homogeneous proton exchange membrane using the porphyrin ring-branched polybenzimidazole. The proton exchange membrane prepared by the invention has good solubility, antioxidant stability, mechanical properties, dimensional stability and high proton conductivity.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell proton exchange membranes and polymer functional membranes, and in particular relates to a porphyrin ring-branched polybenzimidazole and a preparation method of the porphyrin ring-branched polybenzimidazole proton exchange membrane. background

[0002] Fuel cells are a clean and efficient energy technology that can directly convert the chemical energy of fuel into electrical energy. They are mainly composed of an anode, a cathode and an electrolyte. Among them, the proton exchange membrane is the core component of the fuel cell. It acts as a solid electrolyte to provide ion transfer and prevent the fuel from penetrating between the electrodes, which will directly affect the performance and life of the fuel cell. Proton exchange membrane fuel cell technology is considered to be one of the most promising electrochemical technologies for sustainable power generation in the world. Traditional membranes such as Nafion and sulfonated membranes are unstable at higher temperatures and cannot be used as high-temperature proton exchange membranes. By using phosphoric acid as a proton carrier, phosphoric acid-doped polybenzimidazole membranes are used as high-temperature proton exchange membranes, which can have relatively high proton conductivity at high temperatures.

[0003] At present, the proton conductivity of acid-doped polybenzimidazole membranes depends on the acid doping level of the membrane, that is, the number of acid molecules in each repeating unit of the polymer. Branched polymers are composed of dense, three-dimensional macromolecules with covalent bonds, which have good solubility in common solvents and large free volumes similar to cross-linked system structures. The three-dimensional structure of branched polybenzimidazole reduces the entanglement between polymer chains, improves antioxidant stability, and allows the presence of more cavities (free volumes), making it easier to dope a large amount of acid. Secondly, the cavities on the polybenzimidazole membrane can serve as encapsulation sites for doped acids, thereby reducing the leakage of acids from the outside of the membrane due to cathode condensation water.

[0004] Porphyrin is a macrocyclic heterocyclic compound formed by four pyrroles through a methine bridge (=CH-). It has a very stable structure and has the dual functions of electron donation and electron withdrawal. It has broad application prospects in the fields of functional materials, biomedicine, photocatalysis and electrocatalysis. Since porphyrin has both proton acceptors and proton donors, it can undergo a protonation process under the action of acid. The porphyrin ring can also provide a certain free volume, acting as a branching crosslinking agent, increasing the branching degree of the benzimidazole polymer and increasing the acid doping amount.

[0005] The porphyrin star-shaped branched polybenzimidazole of the present invention can absorb more phosphoric acid due to its large branch chain free volume, and the block polybenzimidazole can produce a nano phase separation structure, both of which are conducive to proton transport. By constructing a derived branch core block structure, a new type of membrane with a star-shaped, branched block matrix was successfully prepared. The membrane has a phase separation path, and the dendritic main chain imparts high phosphoric acid doping ability and efficient proton transport. Summary of the invention

[0006] The purpose of the present invention is to provide a porphyrin ring-branched polybenzimidazole and a method for preparing a porphyrin ring-branched polybenzimidazole proton exchange membrane with high proton conductivity and good chemical stability.

[0007] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0008] In a first aspect, the present invention provides a porphyrin ring-branched polybenzimidazole, which is prepared by the following method: in polyphosphoric acid containing phosphorus pentoxide, at least one of the aromatic tetraamine monomers shown in formula I, at least one of the dicarboxylic acid monomers shown in formula II, and meso-tetra(4-carboxyphenyl)porphine shown in formula III are subjected to polycondensation reaction to obtain the porphyrin ring-branched polybenzimidazole; wherein the ratio of the total molar number of the dicarboxylic acid monomer and meso-tetra(4-carboxyphenyl)porphine to the molar number of the aromatic tetraamine monomer is 9-11:10, and the molar amount of meso-tetra(4-carboxyphenyl)porphine accounts for 0.1-3% of the molar amount of the aromatic tetraamine monomer;

[0009]

[0010] In Formula I, -R- is a chemical single bond (i.e., Formula I is a biphenyl structure), -CH2-O-, -O- (ether bond) or -CO- (carbonyl);

[0011] In Formula II, A is selected from one of the chemical structures shown in ① to ⑧:

[0012]

[0013] Where 2≤n≤18;

[0014] In formula III, R is

[0015] Preferably, the mass fraction of the phosphorus pentoxide in the polyphosphoric acid is 1-10%.

[0016] Preferably, the total concentration of all monomers in the polyphosphoric acid containing phosphorus pentoxide is 10-50 mmol / 50 g.

[0017] Preferably, the polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, and then at least one of the aromatic tetraamine monomers shown in formula I, at least one of the dicarboxylic acid monomers shown in formula II and meso-tetrakis(4-carboxyphenyl)porphine shown in formula III are added, stirred until dissolved, the temperature is raised to 140-220° C. and stirred for reaction for 1-12 hours. After the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-branched polybenzimidazole.

[0018] Preferably, the polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, then an aromatic tetraamine monomer A shown in formula I and a dicarboxylic acid monomer A shown in formula II are added, stirred until dissolved, the temperature is raised to 120-160° C. for prepolymerization for 0.5-2h, then the meso-tetrakis(4-carboxyphenyl)porphine shown in formula III is added, stirred until dissolved, the temperature is raised to 140-180° C. and stirred for reaction for 0.5-4h; the system is cooled to 100-140° C., an aromatic tetraamine monomer B shown in formula I and a dicarboxylic acid monomer B shown in formula II are added, stirred for 0.5-2h, the temperature is raised to 140-220° C. and stirred for reaction for 1-24h, and after the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-containing branched polybenzimidazole;

[0019] The dicarboxylic acid monomer A and the dicarboxylic acid monomer B are the same or different, and are independently selected from one of the dicarboxylic acid monomers shown in formula II; the aromatic tetraamine monomer A and the aromatic tetraamine monomer B are the same or different, and are independently selected from one of the aromatic tetraamine monomers shown in formula I.

[0020] As a further preference, in the above-mentioned staged polymerization process, in order to make the reaction of each stage as sufficient as possible, the feeding molar amounts of the aromatic tetraamine monomer A and the dicarboxylic acid monomer A are matched as much as possible, that is, the feeding molar amounts of the aromatic tetraamine monomer A and the dicarboxylic acid monomer A are 1-1.1:0.9-1; similarly, the feeding molar amounts of the aromatic tetraamine monomer B and the dicarboxylic acid monomer B are also matched as much as possible; the feeding molar amounts of the aromatic tetraamine monomer B and the dicarboxylic acid monomer B are 0.9-1:1-1.1.

[0021] As a further preference, the polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, then an aromatic tetraamine monomer A shown in formula I and a dicarboxylic acid monomer A shown in formula II are added, stirred until dissolved, the temperature is raised to 140-160° C. for prepolymerization for 0.5-1h, and then the meso-tetrakis(4-carboxyphenyl)porphine shown in formula III is added, stirred until dissolved, the temperature is raised to 170-180° C. and stirred for reaction for 50-75min; the system is cooled to 100-140° C., and then an aromatic tetraamine monomer B shown in formula I and a dicarboxylic acid monomer B shown in formula II are added, stirred for 1-2h, and the temperature is raised to 180-200° C. and stirred for reaction for 1-5h. After the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-containing branched polybenzimidazole.

[0022] As a further preference, the post-treatment adopts the following operation: pouring the polymer solution into a large amount of saturated NaHCO3 aqueous solution to precipitate the solid, soaking for 24-48 hours, filtering, washing with water and ethanol, and drying to constant weight to obtain porphyrin ring-branched polybenzimidazole.

[0023] In a second aspect, the present invention provides a method for preparing a porphyrin ring-branched polybenzimidazole proton exchange membrane, comprising the following steps:

[0024] The above-mentioned porphyrin ring-branched polybenzimidazole is dissolved in a solvent to obtain a 1-10 wt% homogeneous solution; then the homogeneous solution is poured onto a clean glass plate and vacuum dried at 60-100° C. for 24-48 hours to obtain a porphyrin ring-branched polybenzimidazole proton exchange membrane.

[0025] Preferably, the thickness of the porphyrin ring-branched polybenzimidazole proton exchange membrane is controlled to be 20-100 μm.

[0026] Preferably, the solvent is one or a mixture of two or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dichloromethane, tetrahydrofuran or methanesulfonic acid.

[0027] The porphyrin ring-branched polybenzimidazole proton exchange membrane prepared by the invention can be applied to the field of fuel cells.

[0028] Compared with the prior art, the present invention prepares a new type of polymer - porphyrin ring-branched polybenzimidazole. The homogeneous proton exchange membrane obtained by using the polymer has good solubility, antioxidant stability, mechanical properties, dimensional stability and high proton conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a graph of the oxidation stability of the proton exchange membrane prepared by the present invention.

[0030] Figure 2 It is a proton conductivity diagram of the proton exchange membrane prepared by the present invention.

[0031] Figure 3 This is a cross-sectional morphology of the porphyrin-branched TCPP-OPBI proton exchange membrane prepared in Example 1 of the present invention.

[0032] Figure 4 This is a cross-sectional morphology of the porphyrin-branched TCPP-Py-OPBI proton exchange membrane prepared in Example 2 of the present invention.

[0033] Figure 5 This is a cross-sectional morphology of the non-functionally branched Py-OPBI proton exchange membrane prepared in Comparative Example 5 of the present invention.

[0034] Figure 6 This is a surface morphology of the porphyrin-branched TCPP-OPBI proton exchange membrane prepared in Example 1 of the present invention.

[0035] Figure 7 This is a surface morphology of the porphyrin-branched TCPP-Py-OPBI proton exchange membrane prepared in Example 2 of the present invention.

[0036] Figure 8 This is a surface morphology of the non-functionally branched Py-OPBI proton exchange membrane prepared in Comparative Example 5 of the present invention.

[0037] Fig. 9 The typical structural diagram of the porphyrin ring-containing branched polybenzimidazole prepared by the present invention, wherein the definitions of R and A are the same as those of Formulas I and II, respectively. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme will be further described clearly and completely by examples below. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0039] Embodiment 1:

[0040] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in an 80°C blast drying oven for 0.5h. 2g of phosphorus pentoxide and 50g of polyphosphoric acid were added, the temperature was raised to 120°C and stirred for 0.5h, and then 2.14g (10mmol) of 3,3'-diaminobenzidine was added. After stirring until completely dissolved, 0.79g (0.1mmol) of meso-tetrakis (4-carboxyphenyl) porphine and 2.4g (9.2mmol) of 4,4'-dicarboxy diphenyl ether were added. After mechanical stirring for 2h, the temperature was raised to 210°C. The viscosity of the reaction system gradually increased, and the color deepened. After about 3h, the reaction was completed. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution, and a strip-shaped solid was presented. It was soaked for 48h, filtered, washed with water and ethanol, and dried to constant weight to obtain a porphyrin ring-branched polybenzimidazole TCPP-OPBI polymer.

[0041] 0.5g of polymer was ground into powder, dissolved in N,N-dimethylacetamide, and filtered to obtain a 2.5wt% homogeneous solution. The homogeneous and transparent solution was then poured onto a clean glass plate and dried under vacuum at 80°C for 24h to obtain a proton exchange membrane with high mechanical strength.

[0042] Embodiment 2:

[0043] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in a blast drying oven at 80°C for 0.5h. 2g of phosphorus pentoxide and 50g of polyphosphoric acid were added, the temperature was raised to 120°C and stirred for 0.5h, and then 1.18g (5.5mmol) of 3,3'-diaminobenzidine was added and stirred until completely dissolved, and then 0.83g (5mmol) of 2,6-pyridinedicarboxylic acid was added, and the mixture was stirred for 2h under a nitrogen atmosphere, and the temperature was raised to 150°C for prepolymerization for 0.5h, and then 0.079g (0.1mmol) of meso-tetrakis (4-carboxyphenyl) porphine was added, and the mixture was stirred for 0.5h, and then the temperature was raised to 180°C and reacted for 1h. The system was cooled to 140°C, and 0.96g (4.5mmol) of 3,3'-diaminobenzidine was added, and stirred until dissolved, and then 1.32g (5mmol) of 4,4'-dicarboxyl diphenyl ether was added, and mechanically stirred for 2h, and then the temperature was raised to 200°C. After about 4h, the reaction was completed. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution, and a strip-shaped solid was presented. After soaking for 24h, it was filtered, washed with water and ethanol, dried at 80°C to constant weight, and ground to obtain a black porphyrin branched block polybenzimidazole TCPP-Py-OPBI polymer.

[0044] 0.5 g of the polymer was ground into powder, dissolved in dimethyl sulfoxide, and filtered to obtain a 2.5 wt% homogeneous solution. The homogeneous and transparent solution was then poured onto a clean glass plate and vacuum dried at 80° C. for 24 h to obtain a proton exchange membrane with high mechanical strength.

[0045] Embodiment 3:

[0046] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in a blast drying oven at 80°C for 0.5h. 2g of phosphorus pentoxide and 50g of polyphosphoric acid were added, the temperature was raised to 100°C and stirred for 0.5h, and then 2.14g (10mmol) of 3,3'-diaminobenzidine was added, and after stirring until completely dissolved, 0.79g (0.1mmol) of meso-tetrakis (4-carboxyphenyl) porphine and 1.6g (10mmol) of heptanediol were added, and mechanical stirring was performed for 2h, and then the temperature was raised to 160°C. After about 3h, the reaction was completed. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution, and a strip-shaped solid was presented. It was soaked for 48h, filtered, washed with water and ethanol, and dried to constant weight to obtain a polybenzimidazole TCPP-HPBI polymer containing a branched fatty chain containing a porphyrin ring.

[0047] 0.5g of polymer was ground into powder, dissolved in N,N-dimethylacetamide, and filtered to obtain a 2.5wt% homogeneous solution. The homogeneous and transparent solution was then poured onto a clean glass plate and dried under vacuum at 80°C for 24h to obtain a proton exchange membrane with high mechanical strength.

[0048] Embodiment 4:

[0049] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in a blast drying oven at 80°C for 0.5h. 3g of phosphorus pentoxide and 80g of polyphosphoric acid were added, the temperature was raised to 120°C and stirred for 0.5h, and then 1.11g (5.2mmol) of 3,3'-diaminobenzidine was added and stirred until completely dissolved, and then 0.83g (5mmol) of 2,6-pyridinedicarboxylic acid was added, and the mixture was stirred for 2h under a nitrogen atmosphere, and the temperature was raised to 150°C for prepolymerization for 0.5h, and then 0.079g (0.1mmol) of meso-tetrakis (4-carboxyphenyl) porphine was added, and the mixture was stirred for 0.5h, and then the temperature was raised to 180°C and reacted for 1h. The system was cooled to 100°C, and 2.14g (10mmol) 3,3'-diaminobenzidine was added, stirred until dissolved, and then 1.68g (10.5mmol) heptane dicarboxylic acid was added. After mechanical stirring for 2h, the temperature was raised to 180°C. After about 4h, the reaction was completed. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution to form a strip-like solid. After soaking for 24h, it was filtered, washed with water and ethanol, dried at 80°C to constant weight, and ground to obtain yellow porphyrin branched block fatty chain polybenzimidazole TCPP-Py-HPBI polymer.

[0050] 0.5 g of the polymer was ground into powder, dissolved in dimethyl sulfoxide, and filtered to obtain a 2.5 wt% homogeneous solution. The homogeneous and transparent solution was then poured onto a clean glass plate and vacuum dried at 80° C. for 24 h to obtain a proton exchange membrane with high mechanical strength.

[0051] Comparative Example 5:

[0052] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in an 80°C blast drying oven for 0.5h. 2g of phosphorus pentoxide and 50g of polyphosphoric acid were added, the temperature was raised to 120°C and stirred for 0.5h, and then 1.07g (5mmol) of 3,3'-diaminobenzidine was added, stirred until completely dissolved, and 0.83g (5mmol) of 2,6-pyridinedicarboxylic acid was added, stirred for 2h under nitrogen atmosphere, heated to 150°C, prepolymerized for 0.5h, and then heated to 180°C and reacted for 1h. The system was cooled to 120°C, and 1.07g (5mmol) of 3,3'-diaminobenzidine was added, stirred until dissolved, and then 1.32g (5mmol) of 4,4'-dicarboxyl diphenyl ether was added, mechanically stirred for 2h, and then heated to 200°C. After about 4h, the reaction was completed. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution, and a strip-like solid appeared. After soaking for 24 hours, the mixture was filtered, washed with water and ethanol, dried at 80° C. to a constant weight, and ground to obtain a block polybenzimidazole Py-OPBI polymer.

[0053] Comparative Example 6:

[0054] A nitrogen stream was introduced into the three-mouth reactor, and the polyphosphoric acid was preheated in an 80°C blast drying oven for 0.5h. 2g of phosphorus pentoxide and 50g of polyphosphoric acid were added, the temperature was raised to 120°C and stirred for 0.5h, and then 1.07g (5mmol) of 3,3'-diaminobenzidine was added, stirred until completely dissolved, and 0.83g (5mmol) of 2,6-pyridinedicarboxylic acid was added, stirred for 2h under nitrogen atmosphere, heated to 150°C, prepolymerized for 0.5h, and then heated to 180°C and reacted for 1h. The system was cooled to 120°C, and 1.07g (5mmol) of 3,3'-diaminobenzidine was added, stirred until dissolved, and then 0.8g (5mmol) of heptane dicarboxylic acid was added. After mechanical stirring for 2h, the temperature was raised to 200°C, and the reaction was completed after about 4h. The polymer solution was poured into a large amount of saturated NaHCO3 aqueous solution, and a strip-like solid appeared. After soaking for 24 hours, the mixture was filtered, washed with water and ethanol, dried at 80° C. to constant weight, and ground to obtain a segmented polybenzimidazole Py-HPBI polymer.

[0055] The thickness of the proton exchange membranes prepared in the implementation and comparative examples 1-6 is 50±10 μm, and their performance characteristics are shown in Table 1:

[0056] Table 1

[0057]

[0058] Note:

[0059] 1. Phosphoric acid doping rate ADL and swelling rate: Cut the membrane into strips of 2cm×3cm and record the length, width, thickness and mass. Soak in 85% phosphoric acid solution at 80℃ water bath for 48h, wipe the phosphoric acid on the surface with filter paper, and record the length, width, thickness and mass of the membrane after soaking.

[0060] (1) The formula for calculating the membrane phosphoric acid doping rate is as follows:

[0061]

[0062] ADL is the phosphoric acid doping rate, W d and W o are the mass of PBI membrane after immersion and the mass of PBI membrane before immersion respectively; M PA and M PBI are the molecular weights of phosphoric acid and PBI repeating units, respectively.

[0063] (2) The swelling rate calculation formula is as follows:

[0064]

[0065] Vd and Vo are the volume of the PBI membrane after immersion and the volume of the PBI membrane before immersion, respectively.

[0066] 2. Tensile strength: Cut the sample into 4cm×5mm strips and test it using a universal tensile machine at room temperature at a tensile rate of 2mm / min.

[0067] 3. Proton conductivity test: Place the membrane in 85% phosphoric acid and soak until saturated, then heat it in an oven at 80°C for 4 hours to remove moisture from the membrane. Cut the dry membrane into strips of 1cm×4cm and place them between the two electrodes of the electrochemical workstation. Use the AC impedance method to measure the impedance of the membrane. The frequency scanning range is 1Hz~100kHz; the test temperature range is 100~200°C, the temperature interval is 10°C, and the proton conductivity calculation formula is:

[0068]

[0069] Where, σ is the conductivity of the membrane (S / cm); R is the impedance of the membrane (Q); l is the distance between the two electrodes (cm); A is the effective cross-sectional area of ​​the membrane (cm 2 ). The results are shown in Figure 2 .

[0070] 4. Oxidation stability test: The oxidation stability test mainly uses Fenton reagent (3wt% H2O2, 4ppmFe 2+) Immersion method. The membrane sample was immersed in 50 mL of Fenton's reagent at 80°C for 24 hours, then taken out and repeatedly washed with deionized water, placed in a 120°C vacuum oven to dry completely, and then weighed. Results are shown in Figure 1 .

Claims

1. A porphyrin ring-branched polybenzimidazole, characterized in that: The porphyrin ring-branched polybenzimidazole is prepared by the following method: in polyphosphoric acid containing phosphorus pentoxide, at least one of the aromatic tetraamine monomers shown in formula I, at least one of the dicarboxylic acid monomers shown in formula II and meso-tetra(4-carboxyphenyl)porphine shown in formula III are subjected to polycondensation reaction to obtain the porphyrin ring-branched polybenzimidazole; wherein the ratio of the total molar number of the dicarboxylic acid monomer and meso-tetra(4-carboxyphenyl)porphine to the molar number of the aromatic tetraamine monomer is 9-11:10, and the molar amount of meso-tetra(4-carboxyphenyl)porphine accounts for 0.1-3% of the molar amount of the aromatic tetraamine monomer; In formula I, -R- is a chemical single bond, -CH2-O-, -O- or -CO-; In Formula II, A is selected from one of the chemical structures shown in ① to ⑧: Where 2≤n≤18; In formula III, R is 2. The porphyrin ring-branched polybenzimidazole according to claim 1, wherein: The polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, then at least one of the aromatic tetraamine monomers shown in formula I, at least one of the dicarboxylic acid monomers shown in formula II and meso-tetrakis(4-carboxyphenyl)porphine shown in formula III are added, stirred until dissolved, the temperature is raised to 140-220° C. and stirred for reaction for 1-12 hours. After the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-containing branched polybenzimidazole.

3. The porphyrin ring-branched polybenzimidazole according to claim 1, wherein: The polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, then an aromatic tetraamine monomer A shown in formula I and a dicarboxylic acid monomer A shown in formula II are added, stirred until dissolved, the temperature is raised to 120-160° C. for prepolymerization for 0.5-2h, then the meso-tetrakis(4-carboxyphenyl)porphine shown in formula III is added, stirred until dissolved, the temperature is raised to 140-180° C. and stirred for reaction for 0.5-4h; the system is cooled to 100-140° C., an aromatic tetraamine monomer B shown in formula I and a dicarboxylic acid monomer B shown in formula II are added, stirred for 0.5-2h, the temperature is raised to 140-220° C. and stirred for reaction for 1-24h, and after the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-containing branched polybenzimidazole; The dicarboxylic acid monomer A and the dicarboxylic acid monomer B are the same or different, and are independently selected from one of the dicarboxylic acid monomers shown in formula II; the aromatic tetraamine monomer A and the aromatic tetraamine monomer B are the same or different, and are independently selected from one of the aromatic tetraamine monomers shown in formula I.

4. The porphyrin ring-branched polybenzimidazole according to claim 3, characterized in that: The molar ratio of the aromatic tetraamine monomer A to the dicarboxylic acid monomer A is 1-1.1:0.9-1; the molar ratio of the aromatic tetraamine monomer B to the dicarboxylic acid monomer B is 0.9-1:1-1.

1.

5. The porphyrin ring-branched polybenzimidazole according to claim 3, characterized in that: The polycondensation reaction is carried out according to the following steps: under nitrogen protection, polyphosphoric acid and phosphorus pentoxide are added to a reactor with a stirring paddle, the temperature is raised to 80-120° C. and stirred until melted, then an aromatic tetraamine monomer A shown in formula I and a dicarboxylic acid monomer A shown in formula II are added, stirred until dissolved, the temperature is raised to 140-160° C. for prepolymerization for 0.5-1h, then the meso-tetrakis(4-carboxyphenyl)porphine shown in formula III is added, stirred until dissolved, the temperature is raised to 170-180° C. and stirred for reaction for 50-75min; the system is cooled to 100-140° C., an aromatic tetraamine monomer B shown in formula I and a dicarboxylic acid monomer B shown in formula II are added, stirred for 1-2h, the temperature is raised to 180-200° C. and stirred for reaction for 1-5h, and after the reaction is completed, the obtained polymer solution is post-treated to obtain a porphyrin ring-containing branched polybenzimidazole.

6. The porphyrin ring-branched polybenzimidazole according to any one of claims 1 to 5, characterized in that: The mass fraction of the phosphorus pentoxide in the polyphosphoric acid is 1-10%.

7. The porphyrin ring-branched polybenzimidazole according to any one of claims 1 to 5, characterized in that: The total concentration of all monomers in the polyphosphoric acid containing phosphorus pentoxide is 10-50 mmol / 50 g.

8. A method for preparing a porphyrin ring-branched polybenzimidazole proton exchange membrane, comprising the following steps: The porphyrin ring-branched polybenzimidazole according to any one of claims 1 to 5 is dissolved in a solvent to obtain a 1-10 wt % homogeneous solution; the homogeneous solution is then poured onto a clean glass plate and vacuum dried at 60-100° C. for 24-48 h to obtain a porphyrin ring-branched polybenzimidazole proton exchange membrane.

9. The preparation method according to claim 8, characterized in that: The thickness of the porphyrin ring-branched polybenzimidazole proton exchange membrane is controlled to be 20-100 μm.

10. The preparation method according to claim 8, characterized in that: The solvent is one or a mixture of two or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dichloromethane, tetrahydrofuran or methanesulfonic acid.

Images