Bifunctional multicenter metalloporphyrin complex and use in the preparation of polycarbonates

Abstract

The application provides a preparation method of a bifunctional multicenter metal porphyrin complex and polycarbonate, wherein the bifunctional multicenter metal porphyrin complex has multiple active centers, and the chain end has a quaternary ammonium salt or an organic alkali group which can be used as a cocatalyst. The complex can catalyze the copolymerization of carbon dioxide and an epoxide without adding a cocatalyst, and has high catalytic activity, high thermal stability and good polymer product selectivity. Experimental results show that the number average molecular weight of the copolymerization product of carbon dioxide and an epoxide is 5000-820000 g / mol, the molecular weight distribution is 1.05-3.10, the content of carbonate units in the polymer reaches 10-60%, and the obtained polymer shows the characteristics of a crystalline polymer with a melting point of 58-68 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of catalytic synthesis technology, and particularly relates to a bifunctional multicenter metalloporphyrin complex and its method for catalytic preparation of polycarbonate. Background Technology

[0002] Carbon dioxide is a major greenhouse gas and also a cheap carbon-oxygen resource. As a source of carbon and oxygen, carbon dioxide is used to synthesize basic chemicals, fuels, and polymers, offering a new approach to overcoming the energy, resource, and environmental crises caused by excessive fossil fuel use. This field has thus become a focus of attention for both the scientific and industrial communities. Among these, aliphatic polycarbonate, copolymerized from carbon dioxide and epoxides under catalysis, is a fully biodegradable polymer with good transparency and excellent oxygen and water barrier properties. It can be used in engineering plastics, disposable pharmaceutical and food packaging materials, adhesives, and more.

[0003] Since Inoue first achieved the copolymerization of carbon dioxide and propylene oxide in 1969, a series of catalytic systems have emerged, including alkyl zinc / active hydrogen catalytic systems, zinc carboxylate systems, bimetallic cyanide catalysts, rare earth ternary catalysts, metalloporphyrin catalysts, zinc phenolate catalytic systems, and zinc diimide catalysts. The research and development of these catalytic systems have greatly promoted the synthesis of fully biodegradable aliphatic polycarbonates. Some systems have been used in industrial production. However, most of these catalysts are mononuclear catalytics and rely on the use of co-catalysts, and still suffer from low catalytic activity and poor polymer selectivity. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a method for preparing bifunctional multi-center metalloporphyrin complexes and polycarbonates, wherein the number of active centers and the types of cocatalytic groups such as quaternary ammonium salts in the metalloporphyrin complexes are adjustable, exhibiting high catalytic activity. The technical solution of this invention is as follows:

[0005] A bifunctional multicenter metalloporphyrin complex having the structure of formula (I):

[0006]

[0007] The Z is selected from formula a or formula b:

[0008] The R c Alkyl groups selected from C2 to C12;

[0009] The q is 0 or 1; the R d Alkyl groups selected from C1 to C12;

[0010] The R' is selected from formula c:

[0011] -Rp-L formula c; the R p The L is independently selected from C1 to C12 alkyl or benzene rings; the L is independently selected from quaternary ammonium salts or organic bases;

[0012] The R a and R b Independently selected from hydrogen, halogen, C1-C12 aliphatic group, substituted aliphatic group, substituted heteroaliphatic group, aryl, substituted aryl or substituted heteroaryl;

[0013] The value of m is 2 to 20; It is a linking group;

[0014] The It has the structure of formula (II):

[0015]

[0016] In formula (II), M is a metallic element; R1 to R 19 The group is independently selected from hydrogen, halogen, C1-C12 aliphatic group, substituted aliphatic group, substituted heteroaliphatic group, aryl, substituted aryl or substituted heteroaryl; wherein h is 0 or 1;

[0017] The X is selected from halogens, -NO3, CH3COO-, CCl3COO-, CF3COO-, ClO4-, BF4-, BPh4-, -CN, -N3, p-methylbenzoate, p-methylbenzenesulfonate, o-nitrophenol oxygen anion, p-nitrophenol oxygen anion, m-nitrophenol oxygen anion, 2,4-dinitrophenol oxygen anion, 3,5-dinitrophenol oxygen anion, 2,4,6-trinitrophenol oxygen anion, 3,5-dichlorophenol oxygen anion, 3,5-difluorophenol oxygen anion, 3,5-bis(trifluoromethyl)phenol oxygen anion, or pentafluorophenol oxygen anion.

[0018] The aforementioned bifunctional multicenter metalloporphyrin complex, the It has the structure of formula (III):

[0019]

[0020] The aforementioned bifunctional multicenter metalloporphyrin complex, wherein the metal element is selected from magnesium, aluminum, zinc, chromium, manganese, iron, cobalt, titanium, yttrium, nickel, or ruthenium.

[0021] The bifunctional multicenter metalloporphyrin complex, wherein X is selected from halogens or 2,4-dinitrophenol oxoanions; wherein R1 to R 19 It is independently selected from hydrogen or Cl.

[0022] The aforementioned bifunctional multicenter metalloporphyrin complex is specifically shown in formula (IV), formula (V), formula (VI), or formula (VII):

[0023]

[0024] In formula (VII), Y is 2,4-dinitrophenol.

[0025] The method for preparing polycarbonate by catalysis of the bifunctional multicenter metalloporphyrin complex involves weighing the bifunctional multicenter metalloporphyrin complex and adding it to a high-pressure reactor, then adding an epoxide and introducing carbon dioxide to carry out a copolymerization reaction. After the polymerization reaction is completed, the reactor is cooled to room temperature, the carbon dioxide is slowly released, dichloromethane is added to the reactor to dissolve the product, and then methanol is added to precipitate the product. The precipitate is collected, washed with methanol, and dried to constant weight to obtain polycarbonate.

[0026] The method for preparing polycarbonate by catalysis of the bifunctional multicenter metalloporphyrin complex, wherein the molar ratio of the bifunctional multicenter metalloporphyrin complex to the epoxide is 1:2000-50000.

[0027] The copolymerization reaction temperature is 20℃~150℃; the copolymerization reaction time is 0.1~48h; and the carbon dioxide pressure of the copolymerization reaction is 1~8MPa.

[0028] The epoxide is selected from at least one of ethylene oxide, propylene oxide, 1,2-epoxybutane, cyclohexane oxide, cyclopentane oxide, epichlorohydrin methacrylate glycidyl ether, methyl glycidyl ether, phenyl glycidyl ether, and styrene epoxyalkane.

[0029] This invention has the following advantages and beneficial effects:

[0030] This invention provides a bifunctional, multi-center metalloporphyrin complex with the structure of formula (I). This metalloporphyrin complex possesses multiple active centers, with quaternary ammonium salts or organic bases at the chain ends that can act as co-catalysts. It is a novel metalloporphyrin complex combining bifunctionality and multi-center characteristics. This complex can catalyze the copolymerization of carbon dioxide and epoxides without the need for co-catalysts, exhibiting high catalytic activity, product selectivity, and high-temperature stability. The excellent catalytic activity exhibited by this complex mainly stems from the interactions between the multi-center metals. In particular, the presence of multiple active centers on a single polymer chain allows for local enrichment of the active centers, thereby effectively enhancing the activity. Furthermore, the interaction between the co-catalyst groups at the chain ends and the metal active centers ensures the stability of the metal active centers, thus improving product selectivity and high-temperature stability during polymerization. Experimental results show that the number-average molecular weight of the products from the copolymerization of carbon dioxide and epoxides is 5000–820000 g / mol, with a molecular weight distribution of 1.05–3.10; the carbonate unit content in the polymer reaches 10%–60%. DSC test results showed that the polymer obtained by the complex catalysis unexpectedly exhibited the characteristics of a crystalline polymer, with a melting point between 58 and 68 °C. Attached Figure Description

[0031] Figure 1 This is the 1H NMR spectrum of Oligo-L1, a bifunctional multicenter ligand obtained in Example 3.

[0032] Figure 2 The NMR spectrum of the bifunctional multicenter porphyrin aluminum obtained in Example 3 is shown in Figure 3.

[0033] Figure 3 These are the DSC diagrams of the polymer products obtained in Example 7 (upper curve) and Example 8 (lower curve). Detailed Implementation

[0034] To fully illustrate the present invention, specific embodiments and accompanying drawings are described below. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0035] The catalyst described in this invention preferably comprises the structures shown in formulas (IV), (V), (VI), and (VII):

[0036]

[0037] The specific method for preparing bifunctional multicenter metalloporphyrin complexes involved in this invention is as follows:

[0038] It is mainly divided into two parts: (1) the synthesis of bifunctional multicenter ligands shown in formula (VIII); and (2) the synthesis of bifunctional multicenter metalloporphyrin complexes shown in formula (I).

[0039]

[0040] In formula (VIII), R1 to R 19 Selected from hydrogen, halogen, aliphatic group, substituted aliphatic group, substituted heteroaliphatic group, aryl, substituted aryl or substituted heteroaryl;

[0041] In this invention, the compound having the structure of formula (VIII) is preferably prepared by the following method:

[0042] The compound having the structure of formula (IX) and the ZR' compound were dissolved in toluene, and under the action of RAFT polymerization initiator, the compound having the structure of formula (VIII) was obtained.

[0043]

[0044] The R 21 Selected from -CH2; the R 22 Selected from hydrogen or methyl.

[0045] In this invention, the compound having the structure of formula (IX) is preferably prepared by the following method:

[0046] A compound having the structure of formula (XIII) is subjected to a substitution reaction with acryloyl chloride (or methacryloyl chloride), preferably triethylamine as an acid-binding agent, to obtain a compound having the structure of formula (IX);

[0047]

[0048] In formula (XIII), R1 to R 19 Each is independently selected from hydrogen, halogen, aliphatic group, substituted aliphatic group, substituted heteroaliphatic group, aryl, substituted aryl or substituted heteroaryl;

[0049] In a specific embodiment of the present invention, the ZR' compound is specifically...

[0050] The chemical structures of S-1-dodecyl-S-O-(methylbenzyltriethylammonium bromide) trithiocarbonate (RAFT-NEt3Br), S-1-dodecyl(4-((3,4,7,8-tetrahydro-2H-pyrimidino[1,2-a]pyrimidin-1(6H)-methyl)benzyl)trithiomethyl ester (RAFT-TBD), and S-1-phenyl-S-O-(methylbenzyltriethylammonium bromide) dithiobenzoate (RAFT-PhNEt3Br) are shown in formulas (X), (XI), and (XII), respectively.

[0051]

[0052] The RAFT polymerization initiator is selected from azobisisobutyronitrile (AIBN), 1-1'-azocyclohexanenitrile (ACC), and 1,1,2,2-tetraphenylethylene glycol;

[0053] In this invention, the RAFT polymerization initiator is preferably AIBN.

[0054] In this invention, the metal source compound is preferably cobalt acetate or diethylaluminum chloride (AlEt2Cl).

[0055] In this invention, if the metal in the metal source compound is a divalent metal, it preferably also includes: zinc chloride, zinc acetate, manganese chloride, magnesium chloride, and ferrous chloride.

[0056] The ligand containing a divalent metal is oxidized and then coordinated with a phenoxy anion compound to obtain a bifunctional multicenter metalloporphyrin complex with the structure of formula (I).

[0057] Example 1:

[0058] Preparation of unsaturated porphyrin monomers

[0059] In a 1000 mL three-necked flask, 4.4 g (36.0 mmol) of 3-hydroxybenzaldehyde, 10.94 mL (54.0 mmol) of benzaldehyde, and 500 mL of propionic acid were added, and the mixture was heated to 130 °C and reacted for 0.5 h. Pre-distilled pyrrole (10 mL, 144.0 mmol) was added dropwise to the flask, and the mixture was heated to 165 °C and refluxed for 1 h. After the reaction was complete, the product was transferred to a 1000 mL beaker, 500 mL of methanol was added, and the mixture was placed in a refrigerator and allowed to stand overnight. The mixture was filtered to obtain a purple solid, which was washed with methanol and hot water, and then separated by column chromatography (using DCM as the eluent) to obtain monohydroxyporphyrin in 6% yield. 1H NMR (300MHz, CDCl3) δ = 8.85 (s, 8H), 8.22 (dd, J = 7.3, 1.8, 6H), 8.07 (d, J = 8.4, 2H), 7.76 (d, J = 6.6, 9H), 7.19 (d, J = 8.4, 2H), -2.79 (s, 2H).

[0060] In a 50 mL three-necked flask under argon protection, 1.28 g (2.0 mmol) of monohydroxyporphyrin and 0.33 mL (2.4 mmol) of triethylamine were dissolved in 10 mL of anhydrous tetrahydrofuran. Under ice-water bath conditions, 0.2 mL (2.4 mmol) of acryloyl chloride was slowly added dropwise to the flask. After the addition was complete, the mixture was allowed to return to room temperature and stirred overnight. The tetrahydrofuran was evaporated to dryness using a rotary evaporator. The product was dissolved in dichloromethane and transferred to a separatory funnel. The solution was washed three times with saturated brine, extracted, and the organic phase was dried over anhydrous MgSO4 overnight. The mixture was filtered, and the filtrate was collected and eluented with dichloromethane by column chromatography to obtain the pure unsaturated porphyrin monomer product L1 in 85% yield.

[0061]

[0062] Example 2:

[0063] Preparation of RAFT-NEt3Br

[0064] When the ZR' compound is RAFT-NEt3Br as shown in formula (X), the synthesis process requires the intermediate product Br-Bn-NEt3Br, whose structural formula is:

[0065]

[0066] Following the method described in the literature, 11.4 g (113 mmol) of triethylamine was dispersed in 100 mL of ethyl acetate. Then, 26.4 g (100 mmol) of 1,4-di(bromomethyl)benzene was weighed and dissolved in 200 mL of ethyl acetate. The triethylamine solution was then slowly added dropwise to the reaction substrate, and the mixture was stirred at 50 °C for 48 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed several times with ethyl acetate and dried under vacuum to obtain the intermediate product Br-Bn-NEt3Br.

[0067] Weigh 6.1 g (30.3 mmol) dodecyl mercaptan, 3.6 g (47.4 mmol) carbon disulfide, and 3.4 g (33.6 mmol) triethylamine into a reaction flask containing dichloromethane. Stir at room temperature for 1 h, add 10.9 g (30 mmol) Br-Bn-NEt3Br, and continue the reaction for 24 h. After the reaction is complete, remove the solvent by rotary evaporation, then add toluene to dissolve the solid. Filter to remove insoluble impurities, concentrate the filtrate, and you will get bright yellow RAFT-NEt3Br with a yield of 90%.

[0068] Example 3:

[0069] Preparation of bifunctional oligoporphyrin ligand Oligo-L1 and its complex Oligo-CAT1 (with the structure shown in formula (IV))

[0070] Under argon protection, 0.685 g (1.0 mmol) of unsaturated porphyrin monomer L1, 0.0274 g (0.167 mmol) of AIBN, 0.094 g (0.167 mmol) of RAFT-NEt3, and 7 mL of toluene were added to a 50 mL round-bottom flask. After four cycles of freezing-evacuation-thawing to remove gas, the flask was heated to 60 °C under argon atmosphere. Once the reaction stabilized, the flask was sealed and the reaction was allowed to proceed for 48 h. The reaction was then quenched with liquid nitrogen and precipitated with cold diethyl ether. The precipitated product was dissolved in dichloromethane, and the diethyl ether precipitation was repeated five times to wash away unreacted monomers and AIBN, yielding a purple powder. The powder was characterized by 1H NMR spectroscopy as the target product, the bifunctional oligoporphyrin ligand Oligo-L1 (see attached 1H NMR spectrum). Figure 1 ).

[0071]

[0072] The above ligand was dissolved in dichloromethane, and AlEt2Cl (diethylaluminum chloride) was added dropwise. The mixture was stirred at room temperature for 6 hours. The resulting product was purified by column chromatography and dried to obtain the desired complex. NMR characterization showed that the characteristic peak of hydrogen within the pyrrole ring disappeared, indicating successful metal coordination. Figure 2 ).

[0073] Example 4:

[0074] Bifunctional multicenter metalloporphyrin complex Oligo-CAT2

[0075] Replacing the RAFT reagent in Example 1 with RAFT-TBD (0.074 g, 0.167 mmol), the unsaturated porphyrin monomer L1 (0.685 g, 1.0 mmol), and the initiator AIBN (0.0274 g, 0.167 mmol), while keeping other conditions unchanged, yields Oligo-L2. After coordination with AlEt2Cl, Oligo-CAT2, a complex with the structure of formula (V), is obtained.

[0076]

[0077] Example 5:

[0078] Preparation of bifunctional multicenter metalloporphyrin complex Oligo-CAT3

[0079]

[0080] The bifunctional multicentric porphyrin ligand Oligo-L1 (0.685 g, 1.0 mmol) was dissolved in dichloromethane, and cobalt acetate solution was slowly added dropwise under an argon atmosphere and an ice-water bath. The reaction was stirred at room temperature for 6 h. The crude product was purified by column chromatography using methanol / dichloromethane (1 / 10) as the eluent. Finally, the product was dried under vacuum to constant weight to obtain the complex Oligo-CAT3 with the structure shown in formula (VII), in 80% yield.

[0081] Example 6:

[0082] Preparation of ligand Oligo-L3 and complex Oligo-CAT4

[0083]

[0084] The synthesis steps of Oligo-L3:

[0085] Under argon protection, unsaturated porphyrin monomer L1 (0.685 g, 1.0 mmol), initiator AIBN (0.0274 g, 0.167 mmol), and RAFT reagent RAFT-PhNEt3Br (0.073 g, 0.167 mmol) with the structure shown in formula (XII) were dissolved in 10 mL of dry toluene. After degassing by three freeze cycles, the reaction was heated to 60 °C for 48 h, quenched with liquid nitrogen, and precipitated with cold diethyl ether. The precipitated product was again dissolved in dichloromethane and precipitated with cold diethyl ether, repeated five times to wash away unreacted porphyrin monomer and initiator AIBN, finally yielding the purple bifunctional multicenter porphyrin ligand Oligo-L3 with the structure shown in formula (VI), in 81% yield.

[0086]

[0087] The bifunctional multicenter porphyrin ligand Oligo-L3 (0.685 g, 1.0 mmol) was dissolved in dichloromethane, and AlEt2Cl solution was slowly added dropwise under an argon atmosphere and an ice-water bath. The reaction was stirred at room temperature for 6 h. The crude product was purified by column chromatography using methanol / dichloromethane (1 / 10) as the eluent. Finally, the product was dried under vacuum to constant weight to obtain Oligo-CAT4, as shown in formula (VI), in 78% yield.

[0088] Example 7

[0089] 0.006 mmol of Oligo-CAT1 and 30 mmol of propylene oxide were added to a 10 mL high-pressure reactor that had been pre-treated for dehydration and deoxygenation. CO2 was rapidly introduced into the reactor to a pressure of 3.0 MPa through a CO2 supply line with pressure regulation. The temperature was maintained at 80 °C and the reaction was stirred for 2 hours. After the polymerization reaction was completed, the reactor was cooled to room temperature, and the carbon dioxide was slowly released. Then, a certain amount of dichloromethane was added to the reactor to dissolve the copolymer mixture. A certain amount of methanol was then added to precipitate the polycarbonate. The precipitated polymer was washed with methanol, and the washed copolymer was vacuum dried to constant weight. The number average molecular weight of the polymer was determined to be 16500 g / mol and the molecular weight distribution was 1.19 by gel permeation chromatography. 1 H-NMR analysis showed that cyclic carbonate byproducts were less than 0.05%, the content of carbonate units (CU%) in the polymer was 28.0%, and the melting point measured by DSC was 62℃ (DSC curve shown). Figure 3 ).

[0090] Example 8

[0091] 0.006 mmol of Oligo-CAT1 and 30 mmol of propylene oxide were added to a 10 mL high-pressure reactor that had been pre-treated for dehydration and deoxygenation. CO2 was rapidly introduced into the reactor through a pressure-regulating CO2 supply line to a pressure of 5.0 MPa. The temperature was maintained at 120 °C, and the reactor was stirred for 1 hour. After the polymerization reaction was complete, the reactor was cooled to room temperature, and the carbon dioxide was slowly released. Then, a certain amount of dichloromethane was added to the reactor to dissolve the copolymer mixture. A certain amount of methanol was then added to precipitate the polycarbonate. The precipitated polymer was washed with methanol, and the washed copolymer was vacuum dried to constant weight. Gel permeation chromatography determined that the number-average molecular weight of the polymer was 153,000 g / mol, and the molecular weight distribution was 2.12. 1 H-NMR analysis showed that the cyclic carbonate byproduct was 3%, the carbonate unit content (CU%) in the polymer was 33%, and the melting point measured by DSC was 64℃ (DSC curve shown). Figure 3 ).

[0092] Example 9

[0093] 0.006 mmol of Oligo-CAT2 and 300 mmol of propylene oxide were added to a 100 mL high-pressure reactor that had been pre-treated for dehydration and deoxygenation. CO2 was rapidly introduced into the reactor to a pressure of 2.0 MPa through a CO2 supply line with pressure regulation. The reaction was carried out at 90 °C with stirring for 8 hours. After the polymerization reaction was completed, the reactor was cooled to room temperature, and the carbon dioxide was slowly released. Then, a certain amount of dichloromethane was added to the reactor to dissolve the copolymer mixture. A certain amount of methanol was then added to precipitate the polycarbonate. The precipitated polymer was washed with methanol, and the washed copolymer was vacuum dried to constant weight. The number average molecular weight of the polymer was determined to be 263,000 g / mol and the molecular weight distribution was 1.52 by gel permeation chromatography. 1 H-NMR analysis showed that cyclic carbonate byproducts accounted for 1.2%, and the content of carbonate units (CU%) in the polymer was 45%.

[0094] Example 10

[0095] 0.015 mmol of Oligo-CAT3 and 300 mmol of 1,2-epoxybutane were added to a 100 mL high-pressure reactor that had been pre-treated for dehydration and deoxygenation. CO2 was rapidly introduced into the reactor to 1.0 MPa through a pressure-regulating CO2 supply line, and the reaction was carried out at 60 °C with stirring for 4 hours. After the polymerization reaction was completed, the reactor was cooled to room temperature, and the carbon dioxide was slowly released. Then, a certain amount of dichloromethane was added to the reactor to dissolve the copolymer mixture, followed by the addition of methanol to precipitate the polycarbonate. The precipitated polymer was washed with methanol, and the washed copolymer was vacuum dried to constant weight. Gel permeation chromatography determined that the number-average molecular weight of the polymer was 53,000 g / mol, and the molecular weight distribution was 1.36. 1 H-NMR analysis showed that the cyclic carbonate byproduct was 0.5%, and the carbonate unit (CU%) content in the polymer was 38.5%.

[0096] Example 11

[0097] 0.003 mmol of Oligo-CAT4 and 30 mmol of propylene oxide were added to a 10 mL high-pressure reactor that had been pre-treated for dehydration and deoxygenation. CO2 was rapidly introduced into the reactor through a pressure-regulating CO2 supply line to a pressure of 3.0 MPa. The reaction was carried out at 80 °C with stirring for 6 hours. After the polymerization reaction was completed, the reactor was cooled to room temperature, and the carbon dioxide was slowly released. Then, a certain amount of dichloromethane was added to the reactor to dissolve the copolymer mixture. A certain amount of methanol was then added to precipitate the polycarbonate. The precipitated polymer was washed with methanol, and the washed copolymer was vacuum dried to constant weight. Gel permeation chromatography determined that the number-average molecular weight of the polymer was 467,000 g / mol, and the molecular weight distribution was 2.01.1 H-NMR analysis showed that the cyclic carbonate byproducts were 1.1%, the carbonate unit content (CU%) in the polymer was 38%, and the melting point measured by DSC was 65℃.

Claims

1. A bifunctional multicenter metalloporphyrin complex, characterized in that, The bifunctional multicenter metalloporphyrin complexes are specifically shown in formulas (IV), (V), (VI), or (VII): Formula (IV), Formula (V), Formula (VI), Equation (VII); In formula (VII), Y is 2,4-dinitrophenol.

2. The method for preparing polycarbonate catalyzed by the bifunctional multicenter metalloporphyrin complex according to claim 1, characterized in that, The bifunctional multicenter metalloporphyrin complex was weighed and added to a high-pressure reactor, followed by the addition of propylene oxide or 1,2-epoxybutane, and carbon dioxide was introduced to carry out a copolymerization reaction. After the polymerization reaction was completed, the reactor was cooled to room temperature, the carbon dioxide was slowly released, dichloromethane was added to the reactor to dissolve the product, and then methanol was added to precipitate the product. The precipitate was collected, washed with methanol, and dried to constant weight to obtain polycarbonate.

3. The method according to claim 2, characterized in that, The molar ratio of the bifunctional multicenter metalloporphyrin complex to propylene oxide or 1,2-epoxybutane is 1:2000~50000.

4. The method according to claim 2, characterized in that, The copolymerization reaction temperature is 20℃~150℃; the copolymerization reaction time is 0.1~48 h; and the carbon dioxide pressure of the copolymerization reaction is 1~8 MPa.

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