Graphite-supported porphyrin aluminum catalysts, their preparation, and their application in CO2 copolymerization

Abstract

This invention discloses a graphdiyne-supported porphyrin aluminum catalyst and its preparation method. The method provided by this invention successfully immobilizes the porphyrin aluminum catalyst on the surface and interlayer regions of the two-dimensional carbon material graphdiyne, combining the advantages of homogeneous and heterogeneous catalysis. The preparation method of the graphdiyne-supported porphyrin aluminum catalyst provided by this invention cleverly integrates the porphyrin ligand immobilization process into the coupling synthesis process of graphdiyne. The preparation process is simple and straightforward, showing good application prospects and economic value. The graphdiyne-supported porphyrin aluminum catalyst provided by this invention exhibits higher catalytic activity and better selectivity in the copolymerization reaction of carbon dioxide and propylene oxide, resulting in higher quality polypropylene carbonate.

Description

Technical Field

[0001] This invention relates to a graphdiyne-supported porphyrin aluminum catalyst, its preparation method, and its application in CO2 copolymerization. Background Technology

[0002] Against the backdrop of actively promoting a low-carbon circular economy and pursuing a balance between carbon emissions and comprehensive carbon utilization, the chemical conversion technology of carbon dioxide (CO2) has received widespread attention. Among them, the copolymerization technology route using CO2 and propylene oxide as monomers is an important research direction in the field of CO2 chemical resource utilization, which can produce high-value-added biodegradable plastics—polypropylene carbonate (PPC).

[0003] Since Inoue's team first discovered the copolymerization reaction of CO2 and propylene oxide in 1969, researchers have developed a series of catalyst materials aimed at improving the efficiency and selectivity of CO2 copolymerization, as well as improving key performance indicators such as molecular weight and polyester unit of PPC products.

[0004] Currently, heterogeneous catalysts have been applied in the industrial production of PPC, such as rare earth ternary catalysts and zinc glutarate catalytic systems. However, heterogeneous catalysts suffer from drawbacks such as low catalytic activity and poor selectivity, thus requiring a large amount of catalyst to be added during production, leading to high metal residue levels in the final product. To ensure that PPC products meet the environmental requirement of being compostable, post-processing is necessary.

[0005] Homogeneous catalysts, represented by metal Salen complexes, have seen significant improvements in catalytic activity and selectivity through continuous development and refinement. For example, a functionalized Salen-Co complex can achieve a time-to-shift (TOF) frequency of 10882 h⁻¹. -1 The polymer selectivity was 97% [Reference: Journal of the American Chemical Society, 2009, 131(32): 11509-11518]. However, the use of heavy metals such as Co in biodegradable plastic PPC is strictly limited, and separating homogeneous catalysts from polymers is quite difficult, which significantly increases production costs. These factors hinder the application of cobalt-based catalysts in the preparation of PPC by CO2 copolymerization.

[0006] Homogeneous porphyrin aluminum catalysts with Al metal centers have attracted considerable attention from researchers as environmentally friendly catalysts that meet the environmental protection requirements of PPC production. However, this catalytic system still faces challenges such as low catalytic activity and poor selectivity. For example, under the conditions of a reaction temperature of 70℃, 3.0 MPa CO2, and a [propylene oxide] / [catalyst] ratio of 5000 / 1, the TOF of the reaction is only 305 h⁻¹. -1 The polymer selectivity was 88% (Reference: Journal of Polymer Science A: Polymer Chemistry, 2014, 52(16): 2346-2355). Some researchers have attempted to graft porphyrin aluminum onto the side chains of oligomers, and successfully improved the activity and selectivity of CO2 copolymerization by controllably constructing synergistic effects of adjacent aluminum sites. However, the preparation and separation processes of such catalysts are significantly more complex and the production cost is high (Reference: Macromolecular Chemistry and Physics, 2022, 223: 2100403). Summary of the Invention

[0007] In view of the above problems, the present invention is proposed to provide a graphdiyne-supported porphyrin aluminum catalyst and a method for preparing the same, which overcomes or at least partially solves the above problems.

[0008] The graphdiyne-supported porphyrin aluminum catalyst provided by this invention is applied to the copolymerization reaction of CO2 and propylene oxide to improve the selectivity and catalytic activity of the target product polypropylene carbonate (PPC) in the CO2 copolymerization reaction, while achieving high carbonate unit content and high number average molecular weight of the product.

[0009] As one aspect of the present invention, a method for preparing graphdiyne-supported porphyrin aluminum catalysts is disclosed, the method comprising the following steps:

[0010] (1) Porphyrin is added to a mixed solvent of N,N-dimethylformamide and pyridine and stirred at 60-80°C to dissolve it, thereby obtaining a porphyrin solution; stirring is stopped and copper foil is added, wherein the copper foil is submerged below the liquid surface, thereby obtaining a porphyrin solution containing copper foil;

[0011] (2) Dissolve hexaethynylbenzene in a mixed solvent of N,N-dimethylformamide and pyridine to obtain a hexaethynylbenzene solution;

[0012] (3) In a light-proof, nitrogen-protected environment, at 60-80°C for 12-72 hours, add the hexaethynylbenzene solution described in step (2) dropwise to the porphyrin solution containing copper foil described in step (1), remove the copper foil, and obtain a mixture containing porphyrin ligands immobilized with graphynylene; remove the solvent and impurities to obtain porphyrin ligands immobilized with graphynylene.

[0013] (4) Dissolve diethylaluminum chloride in n-hexane to obtain a diethylaluminum chloride solution;

[0014] (5) Under argon protection, the graphdiyne-supported porphyrin ligand obtained in step (3) is dispersed in dehydrated dichloromethane, and the diethylaluminum chloride solution obtained in step (4) is added and stirred to obtain a mixture containing graphdiyne-supported porphyrin aluminum catalyst; the solvent and impurities are removed to obtain the graphdiyne-supported porphyrin aluminum catalyst.

[0015] In a specific implementation, the porphyrin mentioned in step (1) is one of or any combination of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(4-methoxy)porphyrin, 5,10,15,20-tetra(4-bromophenyl)porphyrin, 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 5,10,15,20-tetra(4-fluorophenyl)porphyrin and 5,10,15,20-tetra(4-methylbenzoate)porphyrin.

[0016] In a specific implementation, the structural formula of the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst obtained in step (5) is shown in formula (1):

[0017]

[0018] In formula (1), R is -H, -Cl, -Br, -F, -OCH3 or -COOCH3.

[0019] In a specific implementation, in step (1), the concentration of porphyrin in the porphyrin solution is 0.05 to 0.2 mol / L.

[0020] In a specific implementation, in steps (1) and (2), the volume ratio of pyridine to N,N-dimethylformamide in the mixed solvent of N,N-dimethylformamide and pyridine is (1-5):1.

[0021] In a specific implementation, the molar ratio of hexaethynylbenzene in step (2) to porphyrin in step (1) is (1.6-20):1.

[0022] In a specific implementation, the molar ratio of diethylaluminum chloride in step (4) to porphyrin in step (1) is (0.9-1.1):1.

[0023] As another aspect of the present invention, there is a graphdiyne-supported porphyrin aluminum catalyst prepared by the above method.

[0024] As another aspect of the present invention, a method for preparing polypropylene carbonate by copolymerization of carbon dioxide and propylene oxide is provided, the method comprising:

[0025] Polypropylene carbonate is obtained by mixing propylene oxide, bis(triphenylphosphine)ammonium chloride, and the above-mentioned graphdiyne-supported porphyrin aluminum catalyst in a molar ratio of (2000-20000):(1-1.5):1, wherein the amount of the graphdiyne-supported porphyrin aluminum catalyst is based on the molar mass of aluminum, and maintaining the mixture at 25-80°C for 1-24 hours in an environment filled with carbon dioxide and a pressure of 1.0-5.0 MPa.

[0026] As another aspect of the present invention, it relates to a polypropylene carbonate prepared by the above method.

[0027] Compared with the prior art, the present invention has significant beneficial effects, specifically including the following aspects:

[0028] (1) This invention successfully immobilizes porphyrin aluminum catalyst on the surface and interlayer region of two-dimensional carbon material graphyne (structural schematic diagram shown in Figure 1). Figure 1 (As shown). The graphdiyne-supported porphyrin aluminum catalyst prepared by the method provided in this invention achieves synergistic effects from adjacent metal active centers, while combining the advantages of both homogeneous and heterogeneous catalysis. Compared to unsupported homogeneous porphyrin catalysts, the graphdiyne-supported porphyrin aluminum catalyst provided in this invention exhibits significantly improved activity and selectivity in CO2 copolymerization reactions. Furthermore, the polymer products prepared by CO2 copolymerization using the graphdiyne-supported porphyrin aluminum catalyst provided in this invention also show significant improvements in molecular weight and carbonate unit content, demonstrating superior performance.

[0029] (2) The method for preparing graphdiyne-supported porphyrin aluminum catalyst provided by the present invention cleverly integrates the porphyrin ligand immobilization process into the graphdiyne coupling synthesis process. The preparation process is simple and convenient to operate, without the need for complex processes and equipment, and has high preparation efficiency. It has good application prospects and economic value. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the graphdiyne-supported porphyrin aluminum catalyst of the present invention.

[0031] Figure 2 This is a scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in Example 1.

[0032] Figure 3 The 1H nuclear magnetic resonance spectrum of the purified washing solution from Example 1;

[0033] Figure 4 The 1H nuclear magnetic resonance spectrum of the polypropylene carbonate prepared in Example 1 is shown below.

[0034] Figure 5 The 1H nuclear magnetic resonance spectrum of the polypropylene carbonate prepared in Example 4 is shown below.

[0035] Figure 6 This is a scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in Example 7.

[0036] Figure 7 The image shows the 1H nuclear magnetic resonance spectrum of the polypropylene carbonate prepared in Example 7. Detailed Implementation

[0037] To further illustrate the present invention, the following describes in detail, with reference to examples and comparative examples, the application of the graphdiyne-supported porphyrin aluminum catalyst and its preparation method provided by the present invention in the preparation of polypropylene carbonate (PPC) by copolymerization with CO2-propylene oxide.

[0038] Example 1

[0039] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0040] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetraphenylporphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved, stop stirring, put copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface;

[0041] (2) In a light-proof, nitrogen-protected environment, at 60°C, add dropwise a mixed solution of DMF and pyridine containing 5 mmol of hexaethynylbenzene (the volume ratio of DMF to pyridine is 50 mL: 50 mL). After the addition is complete, keep at 60°C for 48 h. Remove the copper foil from the reaction vessel to obtain a mixture containing solid products.

[0042] (3) Cool the above mixture containing the solid product and remove the solvent from the mixture by rotary evaporation to obtain the solid product; wash the obtained solid product successively with DMF at 60℃, 0.1mol / L hydrochloric acid solution, deionized water and anhydrous ethanol; after each wash, separate the solid and liquid by vacuum filtration, and repeat the washing and vacuum filtration operation until the filtrate obtained by vacuum filtration is colorless and transparent, indicating that the impurities on the surface of the solid have been removed and a clean solid is obtained; after drying, a blackish-purple solid product is obtained, which is the porphyrin ligand supported on graphdiyne;

[0043] (4) Under argon protection, the porphyrin ligand supported by graphdiyne obtained in step (3) and 80 mL of dehydrated dichloromethane were added to the reaction vessel, stirred and dispersed, and 2 mmol of diethylaluminum chloride (the diethylaluminum chloride was dissolved in n-hexane solution) was added. After stirring at room temperature for 3 h, a mixture containing the porphyrin aluminum catalyst supported by graphdiyne was obtained. The mixture containing the porphyrin aluminum catalyst supported by graphdiyne was washed and filtered with dehydrated dichloromethane to remove residual impurities and unreacted substances. Finally, the solvent was removed by rotary evaporation and dried to obtain a blackish-purple product, which is the porphyrin aluminum catalyst supported by graphdiyne.

[0044] Structural analysis:

[0045] Scanning electron microscopy (SEM) analysis: The graphdiyne-supported porphyrin aluminum catalyst prepared above was subjected to scanning electron microscopy (SEM) analysis, and the obtained images are shown below. Figure 2 As shown. By Figure 2 It can be seen that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment exhibits a rough surface morphology, which is consistent with the typical morphology of graphdiyne, preliminarily indicating that the graphdiyne-supported porphyrin aluminum catalyst contains graphdiyne structural components.

[0046] The graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was washed with dichloromethane. During washing, the washing solution initially appeared pale purple, gradually turning colorless and remaining so as washing continued. This color change indicated the presence of loosely bound porphyrin species in the graphdiyne-supported porphyrin aluminum catalyst, which were separated by the dichloromethane washing. The pale purple washing solution was collected and purified by column chromatography. Neutral alumina was used as the stationary phase, and dichloromethane / methanol (volume ratio V / V = 10 / 1) was used as the mobile phase to obtain the purified washing solution. The 1H nuclear magnetic resonance spectrum of the purified washing solution was measured. Figure 3Analysis revealed that the purified washing solution was 5,10,15,20-tetraphenylporphyrin aluminum, with the structural formula shown in formula (1), where R in formula (1) is -H. This result indicates that in the preparation process of this invention, the initially added porphyrin was successfully converted into porphyrin aluminum catalyst.

[0047] Based on the above characterization results, combined with the planar two-dimensional structural characteristics of graphyne and the chemical structural properties of porphyrin aluminum, and referring to subsequent studies on the CO2 copolymerization catalytic performance of this graphyne-supported porphyrin aluminum catalyst, it is inferred that the successful preparation of the graphyne-supported porphyrin aluminum catalyst is as follows: Figure 1 As shown. This invention immobilizes a porphyrin aluminum catalyst on the surface or interlayer of a two-dimensional carbon material, graphyne, to form a catalyst with a stable structure.

[0048] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0049] Polymerization process: In a high-pressure reactor, 1.207 g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example was 22373 mg / kg, and the aluminum equivalent in 1.207 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example was 1 mmol) of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, 5 mol of propylene oxide, and 1 mmol of bis(triphenylphosphine)ammonium chloride (PPNCl) were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5 MPa. The reactor was kept at 70°C for 3 h, cooled to room temperature, and the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0050] Product separation and purification: The crude polypropylene carbonate mixture obtained above was dissolved in dichloromethane (CH2Cl2), and then slowly poured into methanol. At this time, a solid precipitate will be formed. The solid precipitate was collected. The above process of dissolution (in dichloromethane)-precipitation (in methanol) was repeated three times to finally obtain polypropylene carbonate (PPC).

[0051] Performance characterization:

[0052] The 1H nuclear magnetic resonance spectrum of the polypropylene carbonate prepared in this embodiment was tested, and the test results are as follows: Figure 4 As shown. For the copolymerization system of CO2 and propylene oxide (PO), the method in the reference (Zhuo Chunwei. Synthesis of carbon dioxide copolymers under aluminum porphyrin catalyst [D]. University of Science and Technology of China) was compared with... Figure 4 The integral area of ​​the key 1H NMR characteristic peaks can be used to calculate the polymer selectivity and carbonate unit content, and the results are shown in Table 1.

[0053] Number-average molecular weight determination: The polypropylene carbonate prepared in this example was tested by gel permeation chromatography (GPC) to obtain the number-average molecular weight of the polypropylene carbonate prepared in this example. The results are shown in Table 1.

[0054] Time-of-Flight (TOF) calculation: TOF equals the mass of polypropylene carbonate obtained from the CO2 copolymerization reaction divided by the mass of the graphdiyne-supported porphyrin aluminum catalyst in the CO2 copolymerization reaction, and then divided by the reaction time. The TOF of the CO2 copolymerization reaction in this embodiment is shown in Table 1.

[0055] Example 2

[0056] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0057] (1) In a reaction vessel, add 2.5 mmol of 5,10,15,20-tetraphenylporphyrin, 20 mL of DMF and 25 mL of pyridine, heat to 80°C and stir until dissolved. Stop stirring and place copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface.

[0058] (2) In a light-proof, nitrogen-protected environment, at 80°C, add dropwise a mixed solution of DMF and pyridine containing 5 mmol of hexaethynylbenzene (the volume ratio of DMF to pyridine is 50 mL: 50 mL). After the addition is complete, maintain the temperature at 80°C for 72 h. Remove the copper foil from the reaction vessel to obtain a mixture containing solid products.

[0059] (3) Cool the above mixture containing solid products and remove the solvent from the mixture by rotary evaporation to obtain solid products; wash the obtained solid products successively with DMF at 80℃, 0.15mol / L hydrochloric acid solution, deionized water and anhydrous ethanol; after each washing, separate the solid and liquid by vacuum filtration, and repeat the washing and vacuum filtration operations until the filtrate obtained by vacuum filtration is colorless and transparent, indicating that the impurities on the surface of the solid have been removed and a clean solid is obtained; after drying, a blackish-purple solid product is obtained, which is the porphyrin ligand supported on graphdiyne;

[0060] (4) Under argon protection, the porphyrin ligand supported by graphdiyne obtained in step (3) and 100 mL of dehydrated dichloromethane were added to the reaction vessel and stirred to disperse. 2.25 mmol of diethylaluminum chloride (the diethylaluminum chloride was dissolved in n-hexane solution) was added and stirred at room temperature for 3 h to obtain a mixture containing the porphyrin aluminum catalyst supported by graphdiyne. The mixture containing the porphyrin aluminum catalyst supported by graphdiyne was washed and filtered with dehydrated dichloromethane to remove residual impurities and unreacted substances. Finally, the solvent was removed by rotary evaporation and dried to obtain a blackish-purple product, which is the porphyrin aluminum catalyst supported by graphdiyne.

[0061] Structural analysis:

[0062] The graphdiyne-supported porphyrin aluminum catalyst prepared in this example was subjected to structural analysis using the same structural analysis method as in Example 1. The structural analysis results were the same as in Example 1. The porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 5,10,15,20-tetraphenylporphyrin aluminum, and its structural formula is shown in Formula (1), where R is -H.

[0063] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0064] Polymerization process: In a high-pressure reactor, 2.119 g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 25485 mg / kg, and the aluminum equivalent in 2.119 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 2 mmol) of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, 10 mol of propylene oxide, and 2 mmol of PPNCl were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5 MPa, and kept at 70°C for 3 h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0065] Product separation and purification: The crude polypropylene carbonate mixture obtained above was dissolved in dichloromethane (CH2Cl2), and then slowly poured into methanol. At this time, a solid precipitate will be formed. The solid precipitate was collected. The above process of dissolution (in dichloromethane)-precipitation (in methanol) was repeated three times to finally obtain polypropylene carbonate (PPC).

[0066] Performance characterization:

[0067] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0068] Example 3

[0069] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0070] (1) In a reaction vessel, add 5 mmol of 5,10,15,20-tetraphenylporphyrin, 25 mL of DMF and 25 mL of pyridine, heat to 60°C and stir until dissolved. Stop stirring and place copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface.

[0071] (2) In a light-proof, argon-protected environment, at 60°C, add dropwise a mixed solution of DMF and pyridine containing 8 mmol of hexaethynylbenzene (the volume ratio of DMF to pyridine is 50 mL: 80 mL). After the addition is complete, maintain the temperature at 60°C for 72 h. Remove the copper foil from the reaction vessel to obtain a mixture containing solid products.

[0072] (3) Cool the above mixture containing solid products and remove the solvent from the mixture by rotary evaporation to obtain solid products; wash the obtained solid products successively with DMF at 70℃, 0.1mol / L hydrochloric acid solution, deionized water and anhydrous ethanol; after each washing, separate the solid and liquid by vacuum filtration, and repeat the washing and vacuum filtration operations until the filtrate obtained by vacuum filtration is colorless and transparent, indicating that the impurities on the surface of the solid have been removed and a clean solid is obtained; after drying, a blackish-purple solid product is obtained, which is the porphyrin ligand supported on graphdiyne;

[0073] (4) Under argon protection, the porphyrin ligand supported by graphdiyne obtained in step (3) and 80 mL of dehydrated dichloromethane were added to the reaction vessel, stirred and dispersed, and 5.5 mmol of diethylaluminum chloride (the diethylaluminum chloride was dissolved in n-hexane solution) were added. After stirring at room temperature for 3 h, a mixture containing the porphyrin aluminum catalyst supported by graphdiyne was obtained. The mixture containing the porphyrin aluminum catalyst supported by graphdiyne was washed and filtered with dehydrated dichloromethane to remove residual impurities and unreacted substances. Finally, the solvent was removed by rotary evaporation and dried to obtain a blackish-purple product, which is the porphyrin aluminum catalyst supported by graphdiyne.

[0074] Structural analysis:

[0075] The graphdiyne-supported porphyrin aluminum catalyst prepared in this example was subjected to structural analysis using the same structural analysis method as in Example 1. The structural analysis results were the same as in Example 1. The porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 5,10,15,20-tetraphenylporphyrin aluminum, and its structural formula is shown in Formula (1), where R is -H.

[0076] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0077] Polymerization process: In a high-pressure reactor, 3.299 g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example was 16370 mg / kg, and the aluminum equivalent in 3.299 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example was 2 mmol) of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, 5 mol of propylene oxide, and 2 mmol of bis(triphenylphosphine)ammonium chloride (PPNCl) were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5 MPa. The reactor was kept at 70°C for 3 h, cooled to room temperature, and the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0078] Product separation and purification: Same as in Example 1.

[0079] Performance characterization:

[0080] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0081] Example 4

[0082] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0083] Same as Example 1.

[0084] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0085] Polymerization process: In a high-pressure reactor, 1.103 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 24464 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.103 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 1 mmol), 5 mol of propylene oxide, and 1 mmol of bis(triphenylphosphine)ammonium chloride (PPNCl) were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5 MPa, and kept at 80°C for 3 h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0086] Product separation and purification: Same as in Example 1.

[0087] Performance characterization:

[0088] The polypropylene carbonate prepared in this example was characterized using the same method as in Example 1. The 1H NMR spectrum of the polypropylene carbonate prepared in this example is shown below. Figure 5 As shown in Table 1, the polymer selectivity, carbonate unit content, number-average molecular weight, and transition frequency (TOF) of this embodiment were obtained using the same characterization and calculation methods as in the examples.

[0089] Example 5

[0090] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0091] Same as Example 1.

[0092] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0093] Polymerization process: In a high-pressure reactor, 1.541g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 17518mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.541g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 1mmol), 5mol of propylene oxide, and 1mmol of PPNCl were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5MPa, and kept at 70°C for 12h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0094] Product separation and purification: Same as in Example 1.

[0095] Performance characterization:

[0096] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0097] Example 6

[0098] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0099] Same as Example 1.

[0100] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0101] Polymerization process: In a high-pressure reactor, 1.141 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 23671 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.141 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 1 mmol), 10 mol of propylene oxide, and 1.5 mmol of PPNCl were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 5 MPa, and kept at 70°C for 3 h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0102] Product separation and purification: Same as in Example 1.

[0103] Performance characterization:

[0104] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0105] Example 7

[0106] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0107] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetra(4-methoxy)porphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved, stop stirring, put copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface;

[0108] Steps (2), (3) and (4) are the same as in Example 1.

[0109] Structural analysis:

[0110] The graphdiyne-supported porphyrin aluminum catalyst prepared in this example was subjected to structural analysis using the same structural analysis methods as in Example 1. Specifically, the scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is shown below. Figure 6 Analysis revealed that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment contains graphdiyne structural components. According to the 1H nuclear magnetic resonance spectrum analysis of the porphyrin aluminum separated from the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment is 5,10,15,20-tetra(4-methoxy)porphyrin, and its structural formula is shown in formula (1), where R in formula (1) is -OCH3.

[0111] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0112] Except that the graphdiyne-supported porphyrin aluminum catalyst used is the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, and the catalyst mass is 1.038g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 26007mg / kg, and the aluminum equivalent in 1.038g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 1mmol), the rest is the same as in Example 1.

[0113] Performance characterization:

[0114] The polypropylene carbonate prepared in this example was characterized using the same method as in Example 1. Specifically, the performance of the polypropylene carbonate prepared in this example was characterized by testing its 1H nuclear magnetic resonance spectrum (NMR spectrum). Figure 7 Using the same calculation method as Example 1, the polymer selectivity, carbonate unit content, number-average molecular weight, and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0115] Example 8

[0116] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0117] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetra(4-bromophenyl)porphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved, stop stirring, put copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface;

[0118] Steps (2), (3) and (4) are the same as in Example 1.

[0119] Structural analysis:

[0120] The graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was subjected to structural analysis using the same structural analysis method as in Example 1. Specifically, based on the scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment contains graphdiyne structural components; based on the 1H nuclear magnetic resonance spectrum analysis of the porphyrin aluminum separated from the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment is 5,10,15,20-tetra(4-bromophenyl)porphyrin, and its structural formula is shown in Formula (1), where R in Formula (1) is -Br.

[0121] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0122] Except that the graphdiyne-supported porphyrin aluminum catalyst used is the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, and the catalyst mass is 1.370 g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 19714 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.370 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 1 mmol), the rest is the same as in Example 1.

[0123] Performance characterization:

[0124] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0125] Example 9

[0126] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0127] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved. Stop stirring and place copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface.

[0128] Steps (2), (3) and (4) are the same as in Example 1.

[0129] Structural analysis:

[0130] The graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was subjected to structural analysis using the same structural analysis method as in Example 1. Specifically, based on the scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment contains graphdiyne structural components; based on the 1H nuclear magnetic resonance spectrum analysis of the porphyrin aluminum separated from the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment is 5,10,15,20-tetra(4-chlorophenyl)porphyrin, and its structural formula is shown in Formula (1), where R in Formula (1) is -Cl.

[0131] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0132] Except that the graphdiyne-supported porphyrin aluminum catalyst used is the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, and the catalyst mass is 0.850 g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 31779 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 0.850 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 1 mmol), the rest is the same as in Example 1.

[0133] Performance characterization:

[0134] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0135] Example 10

[0136] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0137] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetra(4-fluorophenyl)porphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved, stop stirring, put copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface;

[0138] Steps (2), (3) and (4) are the same as in Example 1.

[0139] Structural analysis:

[0140] The graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was subjected to structural analysis using the same structural analysis method as in Example 1. Specifically, based on the scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment contains graphdiyne structural components; based on the 1H nuclear magnetic resonance spectrum analysis of the porphyrin aluminum separated from the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment is 5,10,15,20-tetra(4-fluorophenyl)porphyrin, and its structural formula is shown in Formula (1), where R in Formula (1) is -F.

[0141] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0142] Except that the graphdiyne-supported porphyrin aluminum catalyst used is the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, and the catalyst mass is 1.073g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 25158mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.073g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 1mmol), the rest is the same as in Example 1.

[0143] Performance characterization:

[0144] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0145] Example 11

[0146] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0147] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetrakis(4-benzoate methyl ester)porphyrin, 20 mL of N,N-dimethylformamide (DMF) and 20 mL of pyridine, heat to 60°C and stir until dissolved, stop stirring, put copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface;

[0148] Steps (2), (3) and (4) are the same as in Example 1.

[0149] Structural analysis:

[0150] The graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was subjected to structural analysis using the same structural analysis method as in Example 1. Specifically, based on the scanning electron microscope image of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment contains graphdiyne structural components; based on the 1H nuclear magnetic resonance spectrum analysis of the porphyrin aluminum separated from the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment, it was found that the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment is 5,10,15,20-tetrakis(4-methylbenzoate)porphyrin, and its structural formula is shown in Formula (1), where R in Formula (1) is -COOCH3.

[0151] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0152] Except that the graphdiyne-supported porphyrin aluminum catalyst used is the graphdiyne-supported porphyrin aluminum catalyst prepared in this example, and the catalyst mass is 1.561g (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 17294mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.561g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 1mmol), the rest is the same as in Example 1.

[0153] Performance characterization:

[0154] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0155] Example 12

[0156] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0157] (1) In a reaction vessel, add 12 mmol of 5,10,15,20-tetraphenylporphyrin, 10 mL of DMF and 50 mL of pyridine, heat to 70°C and stir until dissolved. Stop stirring and place copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface.

[0158] (2) In a light-proof, nitrogen-protected environment, at 70°C, add dropwise a mixed solution of DMF and pyridine containing 240 mmol of hexaethynylbenzene (the volume ratio of DMF to pyridine is 50 mL: 250 mL). After the addition is complete, keep at 60°C for 12 h. Remove the copper foil from the reaction vessel to obtain a mixture containing solid products.

[0159] (3) Cool the above mixture containing the solid product and remove the solvent from the mixture by rotary evaporation to obtain the solid product; wash the obtained solid product successively with DMF at 60℃, 0.1mol / L hydrochloric acid solution, deionized water and anhydrous ethanol; after each wash, separate the solid and liquid by vacuum filtration, and repeat the washing and vacuum filtration operation until the filtrate obtained by vacuum filtration is colorless and transparent, indicating that the impurities on the surface of the solid have been removed and a clean solid is obtained; after drying, a blackish-purple solid product is obtained, which is the porphyrin ligand supported on graphdiyne;

[0160] (4) Under argon protection, the porphyrin ligand supported by graphdiyne obtained in step (3) and 200 mL of dehydrated dichloromethane were added to the reaction vessel, stirred and dispersed, and 12 mmol of diethylaluminum chloride (the diethylaluminum chloride was dissolved in n-hexane solution) was added. After stirring at room temperature for 0.5 h, a mixture containing the porphyrin aluminum catalyst supported by graphdiyne was obtained. The mixture containing the porphyrin aluminum catalyst supported by graphdiyne was washed and filtered with dehydrated dichloromethane to remove residual impurities and unreacted substances. Finally, the solvent was removed by rotary evaporation and dried to obtain a blackish-purple product, which is the porphyrin aluminum catalyst supported by graphdiyne.

[0161] Structural analysis:

[0162] The graphdiyne-supported porphyrin aluminum catalyst prepared in this example was subjected to structural analysis using the same structural analysis method as in Example 1. The structural analysis results were the same as in Example 1. The porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 5,10,15,20-tetraphenylporphyrin aluminum, and its structural formula is shown in Formula (1), where R is -H.

[0163] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0164] Polymerization process: In a high-pressure reactor, 3.537g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 15269mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 3.537g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 2mmol), 40mol of propylene oxide, and 3mmol of PPNCl were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 5MPa, and kept at 80℃ for 1h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0165] Product separation and purification: Same as in Example 1.

[0166] Performance characterization:

[0167] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0168] Example 13

[0169] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0170] (1) In a reaction vessel, add 2 mmol of 5,10,15,20-tetraphenylporphyrin, 20 mL of DMF and 20 mL of pyridine, heat to 60°C and stir until dissolved. Stop stirring and place copper foil into the reaction vessel so that the copper foil is submerged below the liquid surface.

[0171] (2) In a light-proof, nitrogen-protected environment, at 70°C, add dropwise a mixed solution of DMF and pyridine containing 5 mmol of hexaethynylbenzene (the volume ratio of DMF to pyridine is 50 mL: 50 mL). After the addition is complete, keep at 60°C for 72 h. Remove the copper foil from the reaction vessel to obtain a mixture containing solid products.

[0172] (3) Cool the above mixture containing the solid product and remove the solvent from the mixture by rotary evaporation to obtain the solid product; wash the obtained solid product successively with DMF at 60℃, 0.1mol / L hydrochloric acid solution, deionized water and anhydrous ethanol; after each wash, separate the solid and liquid by vacuum filtration, and repeat the washing and vacuum filtration operation until the filtrate obtained by vacuum filtration is colorless and transparent, indicating that the impurities on the surface of the solid have been removed and a clean solid is obtained; after drying, a blackish-purple solid product is obtained, which is the porphyrin ligand supported on graphdiyne;

[0173] (4) Under argon protection, the porphyrin ligand supported by graphdiyne obtained in step (3) and 80 mL of dehydrated dichloromethane were added to the reaction vessel, stirred and dispersed, and 2.1 mmol of diethylaluminum chloride (the diethylaluminum chloride was dissolved in n-hexane solution) were added. After stirring at room temperature for 0.5 h, a mixture containing the porphyrin aluminum catalyst supported by graphdiyne was obtained. The mixture containing the porphyrin aluminum catalyst supported by graphdiyne was washed and filtered with dehydrated dichloromethane to remove residual impurities and unreacted substances. Finally, the solvent was removed by rotary evaporation and dried to obtain a blackish-purple product, which is the porphyrin aluminum catalyst supported by graphdiyne.

[0174] Structural analysis:

[0175] The graphdiyne-supported porphyrin aluminum catalyst prepared in this example was subjected to structural analysis using the same structural analysis method as in Example 1. The structural analysis results were the same as in Example 1. The porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst prepared in this example is 5,10,15,20-tetraphenylporphyrin aluminum, and its structural formula is shown in Formula (1), where R is -H.

[0176] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0177] Polymerization process: In a high-pressure reactor, 2.014 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment (the aluminum content in the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 26808 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 2.014 g of the graphdiyne-supported porphyrin aluminum catalyst prepared in this embodiment was 2 mmol), 4 mol of propylene oxide, and 3 mmol of PPNCl were added; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 1 MPa, and kept at 25°C for 24 h. After cooling to room temperature, the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0178] Product separation and purification: Same as in Example 1.

[0179] Performance characterization:

[0180] The polypropylene carbonate prepared in this example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this example were obtained, and the results are shown in Table 1.

[0181] Comparative Example 1

[0182] This comparative example uses 5,10,15,20-tetraphenylporphyrin aluminum as a catalyst to prepare polypropylene carbonate via CO2-propylene oxide copolymerization.

[0183] Polymerization process: 1 mmol of 5,10,15,20-tetraphenylporphyrin aluminum, 5 mol of propylene oxide, and 1 mmol of PPNCl were added to a high-pressure reactor; the high-pressure reactor was filled with carbon dioxide and the pressure was maintained at 3.5 MPa. The reactor was kept at 70°C for 3 hours, cooled to room temperature, and the carbon dioxide in the high-pressure reactor was released to obtain a crude mixture of polypropylene carbonate.

[0184] Product separation and purification: Same as in Example 1.

[0185] Performance characterization:

[0186] The polypropylene carbonate prepared in this comparative example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this comparative example were obtained, and the results are shown in Table 1.

[0187] Comparative Example 2

[0188] Preparation of graphene oxide (rGO) supported porphyrin aluminum catalyst:

[0189] In a reaction vessel, 2 mmol of 5,10,15,20-tetraphenylporphyrin aluminum, 2 g of reduced graphene oxide powder (rGO), and 150 mL of anhydrous ethanol were added. The mixture was ultrasonically dispersed for 12 h, and then the solvent was removed by rotary evaporation under reduced pressure. The solid product was collected and thoroughly dried to obtain the rGO-supported porphyrin aluminum catalyst, with a theoretical aluminum content of 27000 mg / kg.

[0190] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0191] Except that the catalyst used was the rGO-supported porphyrin aluminum catalyst prepared in this comparative example, and the catalyst mass was 1.073 g (the aluminum content in the catalyst was 25166 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.073 g catalyst was 1 mmol), the rest was the same as in Example 1.

[0192] Performance characterization:

[0193] The polypropylene carbonate prepared in this comparative example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this comparative example were obtained, and the results are shown in Table 1.

[0194] Comparative Example 3

[0195] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0196] In a reaction vessel, 2 mmol of 5,10,15,20-tetraphenylporphyrin aluminum, 2 g of graphyne powder and 150 mL of anhydrous ethanol were added and ultrasonically dispersed for 12 h. The solvent was then removed by rotary evaporation under reduced pressure, the solid product was collected and thoroughly dried to obtain a graphyne-supported porphyrin aluminum catalyst with a theoretical aluminum content of 27000 mg / kg.

[0197] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0198] Except that the catalyst used was the graphdiyne-supported porphyrin aluminum catalyst prepared in this comparative example, and the catalyst mass was 1.027 g (the aluminum content in the catalyst was 26290 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 1.027 g catalyst was 1 mmol), the rest was the same as in Example 1.

[0199] Performance characterization:

[0200] The polypropylene carbonate prepared in this comparative example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this comparative example were obtained, and the results are shown in Table 1.

[0201] Comparative Example 4

[0202] Preparation of graphdiyne-supported porphyrin aluminum catalyst:

[0203] 2 mmol of 5,10,15,20-tetraphenylporphyrin aluminum and 2 g of graphyne powder were mixed and ground in a ball mill reactor using two large stainless steel grinding balls with a diameter of 15 mm at 25 Hz for 5 h to obtain a graphyne-supported porphyrin aluminum catalyst with a theoretical aluminum content of 27000 mg / kg.

[0204] Preparation of polypropylene carbonate by CO2-propylene oxide copolymerization:

[0205] Except that the catalyst used was the graphdiyne-supported porphyrin aluminum catalyst prepared in this comparative example, and the catalyst mass was 0.930 g (the aluminum content in the catalyst was 29046 mg / kg according to inductively coupled plasma mass spectrometry, and the aluminum equivalent in 0.930 g catalyst was 1 mmol), the rest was the same as in Example 1.

[0206] Performance characterization:

[0207] The polypropylene carbonate prepared in this comparative example was characterized and its properties were calculated using the same method as in Example 1. The polymer selectivity, carbonate unit content, number-average molecular weight and transition frequency (TOF) of this comparative example were obtained, and the results are shown in Table 1.

[0208] Table 1

[0209]

[0210]

[0211] As shown in Table 1, the number average molecular weight of polypropylene carbonate prepared in Examples 1-13 was 20.1-35.3 kg / mol, while the number average molecular weight of polypropylene carbonate prepared in Comparative Examples 1-4 was 15.4-20.0 kg / mol. The polypropylene carbonate prepared in Examples 1-13 had a higher number average molecular weight and better quality.

[0212] The polypropylene carbonate prepared in Examples 1-13 had a carbonate unit content of 84-96%, while the polypropylene carbonate prepared in Comparative Examples 1-4 had a carbonate unit content of 79-85%. The carbonate unit content of the polypropylene carbonate prepared in Examples 1-13 was higher or comparable to that in Comparative Examples 1-4, indicating that during the polymer chain growth process of the CO2 copolymerization reaction, the copolymerization reaction of propylene oxide and CO2 is more likely to occur than the homopolymerization reaction of propylene oxide, thus resulting in a higher chemical carbon fixation efficiency.

[0213] As shown in Table 1, the conversion frequency in Examples 1-13 during the CO2 copolymerization reaction was 308–1260 h⁻¹. -1 The switching frequencies of Comparative Examples 1-4 are 266–355 h. -1 Examples 1-13 show higher catalytic activity at their switching frequencies;

[0214] In the CO2 copolymerization reaction, the polymer selectivity of Examples 1-13 was 87-99%, while that of Comparative Examples 1-4 was 72-84%. The higher polymer selectivity of Examples 1-13 indicates that the graphdiyne-supported porphyrin aluminum catalyst prepared in Examples 1-13, when applied to the CO2 copolymerization reaction, yields higher polymer selectivity for polypropylene carbonate. This suggests that in this reaction system, when propylene oxide reacts with CO2, it tends to produce polypropylene carbonate (PPC) polymer products with higher added value, rather than cyclic carbonate byproducts.

[0215] Through comprehensive comparative analysis of the above examples and comparative examples, it can be seen that the graphdiyne-supported porphyrin aluminum catalysts prepared in Examples 1-13 exhibit high polymer selectivity and catalytic activity for polypropylene carbonate in the CO2 copolymerization reaction; the obtained polypropylene carbonate has a high number-average molecular weight, high chemical carbon fixation efficiency, and better quality.

[0216] In summary, this invention successfully obtained a high-performance graphdiyne-supported porphyrin aluminum catalyst through a method for preparing such a catalyst. The graphdiyne-supported porphyrin aluminum catalyst provided in this invention has been effectively applied in the copolymerization reaction of CO2 and propylene oxide, significantly improving the selectivity and catalytic activity of the target product polypropylene carbonate (PPC), while also achieving high carbonate unit content and number-average molecular weight, demonstrating significant technical value and application prospects.

[0217] Examples 1-13 can be summarized as follows:

[0218] A method for preparing graphdiyne-supported porphyrin aluminum catalyst, the method comprising the following steps:

[0219] (1) Porphyrin is added to a mixed solvent of N,N-dimethylformamide and pyridine and stirred at 60-80°C to dissolve it, thereby obtaining a porphyrin solution; stirring is stopped and copper foil is added, wherein the copper foil is submerged below the liquid surface, thereby obtaining a porphyrin solution containing copper foil;

[0220] (2) Dissolve hexaethynylbenzene in a mixed solvent of N,N-dimethylformamide and pyridine to obtain a hexaethynylbenzene solution;

[0221] (3) In a light-proof, nitrogen-protected environment, at 60-80°C for 12-72 hours, add the hexaethynylbenzene solution described in step (2) dropwise to the porphyrin solution containing copper foil described in step (1), remove the copper foil, and obtain a mixture containing porphyrin ligands immobilized with graphynylene; remove the solvent and impurities to obtain porphyrin ligands immobilized with graphynylene.

[0222] (4) Dissolve diethylaluminum chloride in n-hexane to obtain a diethylaluminum chloride solution;

[0223] (5) Under argon protection, the graphdiyne-supported porphyrin ligand obtained in step (3) is dispersed in dehydrated dichloromethane, and the diethylaluminum chloride solution obtained in step (4) is added and stirred to obtain a mixture containing graphdiyne-supported porphyrin aluminum catalyst; the solvent and impurities are removed to obtain the graphdiyne-supported porphyrin aluminum catalyst.

[0224] Wherein, the porphyrin mentioned in step (1) is one of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(4-methoxy)porphyrin, 5,10,15,20-tetra(4-bromophenyl)porphyrin, 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 5,10,15,20-tetra(4-fluorophenyl)porphyrin and 5,10,15,20-tetra(4-methylbenzoate)porphyrin or any combination thereof;

[0225] The structural formula of the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst obtained in step (5) is shown in formula (1), where R is -H, -Cl, -Br, -F, -OCH3 or -COOCH3.

[0226] In step (1), the concentration of porphyrin in the porphyrin solution is 0.05–0.2 mol / L;

[0227] In steps (1) and (2), the volume ratio of pyridine to N,N-dimethylformamide in the mixed solvent of N,N-dimethylformamide and pyridine is (1-5):1.

[0228] The molar ratio of hexaethynylbenzene in step (2) to porphyrin in step (1) is (1.6-20):1;

[0229] The molar ratio of diethylaluminum chloride in step (4) to porphyrin in step (1) is (0.9-1.1):1.

[0230] A method for preparing polypropylene carbonate by copolymerization of carbon dioxide and propylene oxide, the method comprising:

[0231] Polypropylene carbonate is obtained by mixing propylene oxide, bis(triphenylphosphine)ammonium chloride, and the above-mentioned graphdiyne-supported porphyrin aluminum catalyst in a molar ratio of (2000-20000):(1-1.5):1, wherein the amount of the graphdiyne-supported porphyrin aluminum catalyst is based on the molar mass of aluminum, and maintaining the mixture at 25-80°C for 1-24 hours in an environment filled with carbon dioxide and a pressure of 1.0-5.0 MPa.

Claims

1. A method for preparing graphdiyne-supported porphyrin aluminum catalyst, characterized in that, The method includes the following steps: (1) Porphyrin is added to a mixed solvent of N,N-dimethylformamide and pyridine and stirred at 60-80°C to dissolve it, thereby obtaining a porphyrin solution; stirring is stopped and copper foil is added, wherein the copper foil is submerged below the liquid surface, thereby obtaining a porphyrin solution containing copper foil; (2) Dissolve hexaethynylbenzene in a mixed solvent of N,N-dimethylformamide and pyridine to obtain a hexaethynylbenzene solution; (3) In a light-proof, nitrogen-protected environment, at 60-80°C for 12-72 hours, add the hexaethynylbenzene solution described in step (2) dropwise to the porphyrin solution containing copper foil described in step (1), remove the copper foil, and obtain a mixture containing porphyrin ligands immobilized with graphynylene; remove the solvent and impurities to obtain porphyrin ligands immobilized with graphynylene. (4) Dissolve diethylaluminum chloride in n-hexane to obtain a diethylaluminum chloride solution; (5) Under argon protection, the graphdiyne-supported porphyrin ligand obtained in step (3) is dispersed in dehydrated dichloromethane, and the diethylaluminum chloride solution obtained in step (4) is added and stirred to obtain a mixture containing graphdiyne-supported porphyrin aluminum catalyst; the solvent and impurities are removed to obtain the graphdiyne-supported porphyrin aluminum catalyst.

2. The method according to claim 1, characterized in that, The porphyrin mentioned in step (1) is one of or any combination of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(4-methoxy)porphyrin, 5,10,15,20-tetra(4-bromophenyl)porphyrin, 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 5,10,15,20-tetra(4-fluorophenyl)porphyrin and 5,10,15,20-tetra(4-methylbenzoate)porphyrin.

3. The method according to claim 1, characterized in that, The structural formula of the porphyrin aluminum in the graphdiyne-supported porphyrin aluminum catalyst obtained in step (5) is: In the formula, R is -H, -Cl, -Br, -F, -OCH3, or -COOCH3.

4. The method according to claim 1, characterized in that, In step (1), the concentration of porphyrin in the porphyrin solution is 0.05 to 0.2 mol / L.

5. The method according to claim 1, characterized in that, In steps (1) and (2), the volume ratio of pyridine to N,N-dimethylformamide in the mixed solvent of N,N-dimethylformamide and pyridine is (1-5):

1.

6. The method according to claim 1, characterized in that, The molar ratio of hexaethynylbenzene in step (2) to porphyrin in step (1) is (1.6-20):

1.

7. The method according to claim 1, characterized in that, The molar ratio of diethylaluminum chloride in step (4) to porphyrin in step (1) is (0.9-1.1):

1.

8. A graphdiyne-supported porphyrin aluminum catalyst, characterized in that, The graphdiyne-supported porphyrin aluminum catalyst is prepared by the method described in any one of claims 1-7.

9. A method for preparing polypropylene carbonate by copolymerization of carbon dioxide and propylene oxide, characterized in that, The method includes: A mixture of propylene oxide, bis(triphenylphosphine)ammonium chloride, and the graphdiyne-supported porphyrin aluminum catalyst of claim 8, in a molar ratio of (2000–20000):(1–1.5):1, wherein the amount of the graphdiyne-supported porphyrin aluminum catalyst is based on the molar mass of aluminum, is kept at a temperature of 25–80°C for 1–24 hours in an environment filled with carbon dioxide at a pressure of 1.0–5.0 MPa. Polypropylene carbonate is obtained.

10. Polypropylene carbonate, characterized in that, The polypropylene carbonate is prepared by the method described in claim 9.

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