Metallization defect type porous organic framework, preparation method thereof and application of metallization defect type porous organic framework in catalytic conversion of carbon dioxide

Abstract

The invention belongs to the technical field of material synthesis catalysis, and particularly relates to a metallization defect type porous organic framework, a preparation method of the metallization defect type porous organic framework and application of the metallization defect type porous organic framework in carbon dioxide catalytic conversion. According to the invention, 1, 4-dihydroxy benzaldehyde is subjected to a Schiff alkali condensation polymerization reaction to form a structural unit containing a catechol site, and ferric iron is anchored on the catechol site. The metallization defect type porous organic framework obtained in the invention can catalyze the reaction of carbon dioxide and an epoxy compound under normal pressure and solvent-free conditions, the product is simple to separate and purify, the catalyst is easy to recover, and the metallization defect type porous organic framework has good stability and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis and catalysis technology, specifically relating to a metallized defect-type porous organic framework, its preparation method, and its application in carbon dioxide catalytic conversion. Background Technology

[0002] The accelerated pace of global industrialization has led to a continuous rise in anthropogenic carbon dioxide (CO2) emissions. According to the International Energy Agency (IEA), global annual CO2 emissions have reached 37.5 billion metric tons. The resulting environmental challenges, such as the greenhouse effect and ocean acidification, pose a serious threat to the long-term sustainable development of global ecosystems and human society. Against this backdrop, developing efficient CO2 resource utilization technologies has become one of the core pathways to achieving the "dual carbon" strategic goals (i.e., carbon peaking and carbon neutrality). Utilizing catalytic conversion technology to transform CO2 into low-carbon fuels (such as methanol and formic acid), high-value-added chemicals (such as cyclic carbonates), or high-purity fine chemicals can not only effectively alleviate greenhouse gas emission pressures but also realize the cyclical value-added of carbon resources, providing innovative solutions for building a low-carbon economic system. Among these, the catalytic conversion of CO2 into high-value cyclic carbonates has become a significant research hotspot in the field of green chemistry due to its synergistic effect of reducing carbon emissions while creating economic value.

[0003] Currently, catalyst systems for the cycloaddition reaction of CO2 with epoxides to synthesize cyclic carbonates have been extensively studied. Based on the phase state of the catalytic material, they can be mainly divided into two categories: homogeneous catalytic systems and heterogeneous catalytic systems. Homogeneous catalysts mainly include transition metal complexes and ionic liquids, but they generally suffer from difficulties in product separation and recycling. Heterogeneous catalysts, represented by metal-organic frameworks (MOFs), multifunctional carbon materials, and porous organic polymers (POPs), have attracted widespread attention due to their ease of separation and recycling, but still face problems such as a limited number of active sites, long material preparation cycles, and cumbersome processes. For example, patent CN111889141A discloses an ionic liquid-functionalized bipyridine porous polymer catalyst for catalyzing the cycloaddition reaction of CO2 with epoxides. This catalyst exhibits activity at dosages of 0.01-5.0 mmol%, CO2 pressures of 0.1-6.0 MPa, and reaction temperatures of 25-150 °C. However, its preparation process is lengthy and complex, and the key raw material 4,4'-dihydroxymethyl-2,2'-bipyridine is expensive, resulting in excessively high catalyst costs, which is not conducive to large-scale industrial production and application.

[0004] In summary, developing novel porous organic framework-based heterogeneous catalysts that combine high stability, excellent catalytic activity, and easy recyclability, and achieving their efficient catalytic synthesis of cyclic carbonates from CO2 under mild conditions, still faces significant challenges. Based on this technological background and need, this invention is proposed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a metallized defect-type porous organic framework, its preparation method and its application in carbon dioxide catalytic conversion.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: Technical Topic 1 A metallized defect-type porous organic framework is characterized by being prepared by forming structural units containing catechol sites through a Schiff base condensation reaction of m-phenylenediamine, terephthalaldehyde, and 3,4-dihydroxybenzaldehyde, and then anchoring trivalent iron at the catechol sites.

[0007] Technical Theme Two A method for preparing a metallized defect-type porous organic framework as described in Technical Subject 1, characterized by comprising the following steps: S1: Preparation of defective porous organic frameworks m-phenylenediamine, terephthalaldehyde and 3,4-dihydroxybenzaldehyde were dissolved and dispersed evenly in an alcohol solvent in a certain proportion, acetic acid solution was added, and the mixture was subjected to Schiff polycondensation reaction. After filtration, washing and drying, defective porous organic frameworks were obtained. S2: Preparation of metallized defect-type porous organic frameworks The defective porous organic framework obtained in S1 was dispersed in an alcohol solvent, and then ferric chloride was added. The mixture was stirred at room temperature for 10-14 h, filtered, washed, and dried to obtain the metallized defective porous organic framework.

[0008] As a further improvement of the present invention, in step S1, the molar ratio of intermediate phenylenediamine, terephthalaldehyde and 3,4-dihydroxybenzaldehyde is 1:0.6-0.9:0.1-0.4; in step S2, ferric chloride hexahydrate is selected, and the mass ratio of defective porous organic framework to ferric chloride hexahydrate is 1:0.08-0.12. The ratio of S1 intermediate phenylenediamine to alcohol solvent is 1 mmol: 4-6 mL; In S2, the ratio of defective porous organic framework to alcohol solvent is 0.1 g: 15-25 mL; The ratio of S1 intermediate phenylenediamine to acetic acid is 1 mmol: 6 mmol - 24 mmol.

[0009] As a further improvement of the present invention, the conditions for the Schiff polycondensation reaction in S1 are as follows: first, stir at room temperature for 20-40 min, then transfer to a hydrothermal reactor and statically heat at 30-120°C for 24-96 h.

[0010] As a further improvement of the present invention, the alcohol solvent in S1 and S2 is either methanol or ethanol.

[0011] Technical Theme 3 Application of a metallized defect-type porous organic framework as described in Technical Subject 1 in the catalytic conversion of carbon dioxide under ambient pressure.

[0012] Technical Theme 4 A method for synthesizing cyclic carbonates by reacting carbon dioxide with epoxides under ambient pressure using a metallized defect porous organic framework as described in Technical Subject 1, the key being that a metallized defect porous organic framework is used as a catalyst and tetrabutylammonium bromide is used as a co-catalyst, so that epoxides and carbon dioxide can be synthesized into cyclic carbonates through a cycloaddition reaction.

[0013] As a further improvement of the present invention, the epoxide has the following structural formula: or .

[0014] As a further improvement of the present invention, the amount of the metallized defect-type porous organic framework catalyst is calculated in terms of Fe, and the molar amount of Fe is 0.5% to 1.2% of the molar amount of the epoxide; the reaction temperature is 70-110℃, the reaction pressure is at atmospheric pressure, and the time is 6-10 h.

[0015] As a further improvement of the present invention, the amount of the metallized defect-type porous organic framework catalyst is calculated in terms of Fe, and the molar amount of Fe is 0.8% of the molar amount of the epoxide; the reaction temperature is 90°C, the reaction pressure is at atmospheric pressure, and the reaction time is 8h.

[0016] As a further improvement of the present invention, the metallized defect-type porous organic framework is dPOF-OFe-10.

[0017] As a further improvement of the present invention, the dPOF-OFe-10 is prepared by m-phenylenediamine, terephthalaldehyde and 3,4-dihydroxybenzaldehyde in a molar ratio of 1:0.8:0.2.

[0018] The beneficial effects of adopting the above technical solution are as follows: This invention utilizes m-phenylenediamine, terephthalaldehyde, and 3,4-dihydroxybenzaldehyde to prepare defective porous organic frameworks via Schiff base condensation, and then prepares metallized defective porous organic frameworks through post-modification. These metallized defective porous organic frameworks possess abundant multi-functional active sites, including Lewis acidic Fe... 3+ The site, hydrogen bond donor acetal amine (N−H) group, and Lewis basic free amino (−NH2) group can react with Br in the tetrabutylammonium bromide (TBAB) cocatalyst. – The active sites synergistically activate CO2 and simultaneously promote the activation and ring-opening of epoxides. The synergistic effect among the multiple active sites significantly improves the catalyst activity. This metallized defect-type porous organic framework material is easy to prepare, enables the catalytic reaction of CO2 with epoxides under solvent-free conditions at atmospheric pressure, and features simple product separation and purification, easy catalyst recovery, and good stability, showing promising application prospects in practical production. Attached Figure Description

[0019] Figure 1 These are the FT-IR spectra of the compounds involved in this invention, wherein (a) is the FT-IR spectrum of MPA, TPA monomers and MPA-TPA prepared in Preparation Example 1, and (b) is the FT-IR spectrum of MPA-TPA prepared in Preparation Example 1 and dPOF-OH-5, dPOF-OH-10, dPOF-OFe-10 and dPOF-OH-20 prepared in Examples 1-3; Figure 2 It is the MPA-TPA prepared in Example 1 and the dPOF-OH-10 prepared in Example 2 of this invention. 13 C6 MASNMR spectrum; Figure 3 These are the TGA curves of MPA-TPA prepared in Example 1 and dPOF-OH-10 and dPOF-OFe-10 prepared in Example 2 of this invention; Figure 4 These are the XPS spectra of MPA-TPA prepared in Example 1 of this invention, and dPOF-OH-10 and dPOF-OFe-10 prepared in Example 2, wherein (a) is the total spectrum, (b) is C 1s, (c) is N 1s, (d) is O 1s, and (e) is Fe 2p. Figure 5 These are the XRD spectra of MPA-TPA prepared in Example 1 of this invention, and dPOF-OH-10 and dPOF-OFe-10 prepared in Example 2; Figure 6These are SEM images of the materials prepared according to the present invention, wherein (a) is MPA-TPA prepared in Preparation Example 1, (b) is dPOF-OH-10 prepared in Example 2, (c) is dPOF-OFe-10 prepared in Example 2, (d) is dPOF-OFe-10 prepared in Example 2, (e) is dPOF-OFe-10-1 prepared in Example 4, and (f) is dPOF-OFe-10-2 prepared in Example 5; Figure 7 This is a mapping diagram of dPOF-OFe-10 prepared in Example 2 of the present invention, where (a) is C, (b) is N, (c) is O, and (d) is Fe; Figure 8 This is a graph showing the recycling results of dPOF-OFe-10 prepared in Example 2 of the present invention. (a) is a graph of the number of cycles and the yield, and (b) is the FT-IR spectrum of the recovered dPOF-OFe-10 and the fresh dPOF-OFe-10 after five cycles. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described clearly and completely below in conjunction with specific embodiments.

[0021] A partial structural schematic diagram of the metallized defect-type porous organic framework prepared in this application is shown in Equation I: Formula I Preparation Example 1: Preparation of a porous organic framework of m-phenylenediamine-terephthalaldehyde MPA-TPA was constructed by using m-phenylenediamine (MPA) and terephthalaldehyde (TPA) as monomers via a Schiff base condensation reaction.

[0022] First, MPA (1.0 mmol, 0.108 g), TPA (1.0 mmol, 0.134 g), and 5 mL of anhydrous ethanol were added separately to the lining of a 20 mL high-pressure reactor and sonicated for 10 minutes. Then, 2 mL of acetic acid solution (6 M) was added. The resulting mixture was then stirred at room temperature for another 30 minutes, transferred to a stainless steel high-pressure reactor, and statically reacted at 60 °C for 72 h. After the reaction was complete and cooled, the mixture was filtered to collect the yellow solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove unreacted monomers and other impurities. The product was then dried under vacuum at 100 °C for 6 h to obtain a yellow powder, MPA-TPA. The morphology of MPA-TPA was characterized using SEM, and the results are shown below. Figure 6 As shown in a.

[0023] Example 1 The three monomeric components of MPA (1 mmol), TPA (0.9 mmol), and 3,4-dihydroxybenzaldehyde (3,4-DHA, 0.1 mmol) were dissolved in 5 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 30 min, then transferred to a stainless steel autoclave and statically reacted at 60 °C for 72 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding dPOF-OH-5.

[0024] 0.1 g of dPOF-OH-5 was dispersed in 20 mL of methanol, and then 0.01 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 12 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was dried under vacuum at 50 °C for 12 h to obtain the metallized dPOF-OFe-5 material.

[0025] Example 2 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 5 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. The resulting mixture was then stirred at room temperature for another 30 min, transferred to a stainless steel autoclave, and statically reacted at 60 °C for 72 h. After cooling, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding dPOF-OH-10. The morphology of dPOF-OH-10 was labeled using SEM, and the results are shown below. Figure 6 As shown in b.

[0026] 0.1 g of dPOF-OH-10 was dispersed in 20 mL of methanol, and then 0.01 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 12 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was vacuum dried at 50 °C for 12 h to obtain the metallized dPOF-OFe-10 material. The morphology of dPOF-OFe-10 was labeled using SEM, and the results are as follows. Figure 6 c- Figure 6 As shown in d.

[0027] Example 3 The three monomeric components of MPA (1 mmol), TPA (0.6 mmol), and 3,4-DHA (0.4 mmol) were dissolved in 5 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 30 min, then transferred to a stainless steel autoclave and statically reacted at 60 °C for 72 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent dPOF-OH-20.

[0028] 0.1 g of dPOF-OH-20 was dispersed in 20 mL of methanol, and then 0.01 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 12 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was dried under vacuum at 50 °C for 12 h to obtain the metallized dPOF-OFe-20 material.

[0029] Example 4 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 5 mL of methanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. The resulting mixture was then stirred at room temperature for another 30 min, transferred to a stainless steel autoclave, and statically reacted at 60 °C for 72 h. After cooling, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding dPOF-OH-10-1 prepared in methanol. The morphology of dPOF-OH-10-1 prepared in methanol was labeled using SEM, and the results are shown below. Figure 6 As shown in e.

[0030] Example 5 Take the dPOF-OH-10 prepared in Example 2, disperse 0.1 g of dPOF-OH-10 in 20 mL of ethanol, and then add 0.01 g of FeCl3·6H2O. Stir the resulting suspension at room temperature for 12 h. Subsequently, filter to separate the solid product, wash thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively, and finally vacuum dry at 50 °C for 12 h to obtain the metallized dPOF-OFe-10-2 material prepared using ethanol as a solvent. The morphology of the dPOF-OFe-10-2 prepared using ethanol as a solvent was labeled using SEM, and the results are as follows: Figure 6 As shown in f.

[0031] Example 6 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 4 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (3 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 30 min, then transferred to a stainless steel autoclave and statically reacted at 30 °C for 96 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding the precursor.

[0032] 0.1 g of the precursor was dispersed in 20 mL of methanol, and then 0.01 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 12 h. Subsequently, the solid product was separated by filtration, washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively, and finally dried under vacuum at 50 °C for 12 h to obtain a metallized defect porous organic framework.

[0033] Example 7 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 6 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (12 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 40 min, then transferred to a stainless steel autoclave and statically reacted at 120 °C for 24 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding the precursor.

[0034] 0.1 g of the precursor was dispersed in 20 mL of methanol, and then 0.01 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 12 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was dried under vacuum at 50 °C for 12 h to obtain a metallized defect porous organic framework.

[0035] Example 8 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 5 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 30 min, then transferred to a stainless steel autoclave and statically reacted at 60 °C for 72 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding the precursor.

[0036] 0.1 g of the precursor was dispersed in 25 mL of methanol, and then 0.008 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 14 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was dried under vacuum at 50 °C for 12 h to obtain a metallized defect porous organic framework.

[0037] Example 9 The three monomers of MPA (1 mmol), TPA (0.8 mmol), and 3,4-DHA (0.2 mmol) were dissolved in 5 mL of ethanol. The mixture was sonicated for 10 min, and then 2 mL of acetic acid solution (6 M) was added. Subsequently, the resulting mixture was stirred at room temperature for another 30 min, then transferred to a stainless steel autoclave and statically reacted at 60 °C for 72 h. After the reaction was complete and cooled, the mixture was filtered to collect the solid product, which was washed successively with ethanol (3 × 30 mL) and acetone (3 × 30 mL) to remove impurities, and then dried under vacuum at 100 °C for 6 h to remove residual solvent, yielding the precursor.

[0038] 0.1 g of the precursor was dispersed in 25 mL of methanol, and then 0.012 g of FeCl3·6H2O was added. The resulting suspension was stirred at room temperature for 10 h. Subsequently, the solid product was separated by filtration, and washed thoroughly with methanol (3 × 20 mL) and acetone (3 × 20 mL) successively. Finally, it was dried under vacuum at 50 °C for 12 h to obtain a metallized defect porous organic framework.

[0039] Example 1 The MPA-TPA obtained in Preparation Example 1, and the dPOF-OH-5, dPOF-OH-10, dPOF-OH-20, dPOF-OFe-5, dPOF-OFe-10 and dPOF-OFe-20 obtained in Examples 1-3 were characterized by FT-IR spectroscopy.

[0040] 1. The structural characteristics of monomers (m-phenylenediamine and terephthalaldehyde), dPOF-OH-X (X=5, 10, or 20), and dPOF-OFe-X (X=5, 10, or 20) were studied by FT-IR spectroscopy comparison. Figure 1 As shown in a, the m-phenylenediamine (MPA) monomer at 3400–3200 cm⁻¹ −1 The characteristic double absorption peaks are observed within the range, attributed to the stretching vibration of the amino group (−NH2); while at 1695 cm⁻¹... −1 The strong absorption peak at 1630 cm⁻¹ corresponds to the stretching vibration of the aldehyde group (−CHO) in the terephthalaldehyde (TPA) monomer. After the polymerization reaction, in the FT-IR spectrum of the generated MPA-TPA sample, the stretching vibration peak of −CHO is significantly weakened, the stretching vibration peak of −NH₂ disappears, and the peak at 1630 cm⁻¹ is significantly lower. −1 A new imine bond (C=N) stretching vibration peak appeared at 3445 cm⁻¹, indicating that a Schiff base polymerization reaction occurred between MPA and TPA, forming a new imine bond. Furthermore, compared to the monomer, the MPA-TPA spectrum showed a higher peak at 3445 cm⁻¹. −1 The single absorption peak at the position is attributed to the stretching vibration of the N−H bond of the acetalamine group, indicating that in addition to the formation of imine bonds, a new acetalamine structure is formed through the nucleophilic attack of the amino group on the imine bond during the polymerization process.

[0041] 2. Figure 1 b shows the FT-IR spectra of MPA-TPA, dPOF-OH-X (X = 5, 10, 20), and dPOF-OFe-10. It can be observed that after introducing different amounts of 3,4-DHA during the polymerization process, the prepared defective dPOF-OH-5, dPOF-OH-10, and dPOF-OH-20 exhibit characteristic absorption peaks similar to MPA-TPA, indicating that the introduction of 3,4-DHA did not significantly affect the framework structure of the porous organic framework. With increasing 3,4-DHA content as a terminator, the absorption peaks at 3350 cm⁻¹... −1 The gradually increasing stretching vibration peaks attributed to −NH2 indicate that more free amino groups are exposed, demonstrating the successful preparation of the defective porous organic framework. Furthermore, compared to MPA-TPA, dPOF-OH-X (X = 5, 10, 20) shows a higher peak intensity at 3741 cm⁻¹.−1 A new −OH absorption peak appeared, which can be attributed to the phenolic hydroxyl groups in 3,4-DHA. After post-modification and metal anchoring, the −OH vibration peak disappeared, further confirming the successful preparation of the metallized defect porous organic framework.

[0042] Example 2 The MPA-TPA prepared in Example 1 and the dPOF-OH-10 prepared in Example 2 were subjected to solid-state reaction. 13 CMAS NMR characterization.

[0043] The results are as follows Figure 2 As shown, both MPA-TPA and dPOF-OH-10 exhibit signal peaks at 159.6 and 46.6 ppm, respectively, which are attributed to carbon atoms in the imine and acetal groups, confirming the formation of MPA-TPA and dPOF-OH-10. The peak at 193.2 ppm can be attributed to carbon atoms in the aldehyde terminal group, while the multiple broad peaks observed in the range of 151.4–105.7 ppm are attributed to aromatic carbons in the framework. Furthermore, the signal peaks observed in dPOF-OH-10... 13 The ¹³C MAS NMR spectrum shows a new peak at δ = 68 ppm, which may be due to a carbon atom in 3,4-DHA. 13 ¹³C NMR spectroscopy confirmed the successful preparation of MPA-TPA and dPOF-OH-10 materials. Furthermore, FT-IR and… 13 The 1C MAS NMR spectrum results show that imine and acetal amine bonds are formed simultaneously in MPA-TPA and dPOF-OH-10, indicating that the framework network has a branched network and porous structure.

[0044] Example 3 The thermal stability of MPA-TPA prepared in Example 1, dPOF-OH-10 prepared in Example 2, and dPOF-OFe-10 prepared in Example 2 were investigated by TGA. The results are as follows: Figure 3 As shown, when the temperature reaches 200℃, the weight loss rates of MPA-TPA, dPOF-OH-10, and dPOF-OFe-10 are 1.18%, 2.81%, and 5.12%, respectively. This indicates that MPA-TPA, dPOF-OH-10, and dPOF-OFe-10 possess good thermal stability.

[0045] Example of effect 4 The dPOF-OFe-X (X = 5, 10, 20) materials prepared in Examples 1-3 were characterized by ICP-OES, and the results are shown in Table 1.

[0046] The Fe content in dPOF-OFe-5, dPOF-OFe-10, and dPOF-OFe-20 was 0.43 wt.%, 4.54 wt.%, and 6.32 wt.%, respectively. It can be seen that among the three metallization defect porous organic frameworks, dPOF-OFe-20 had the highest Fe content, while dPOF-OFe-5 had the lowest. This indicates that the introduction of 3,4-DHA as a terminator successfully induced the formation of missing joint defects, and the degree of defect was related to the content of the introduced 3,4-DHA. This further demonstrates the successful preparation of the metallization defect porous organic framework dPOF-OFe-X (X = 5, 10, 20).

[0047] Table 1 Example 5 The structures of MPA-TPA prepared in Example 1, dPOF-OH-10 prepared in Example 2, and dPOF-OFe-10 prepared in Example 2 were further confirmed by XPS characterization.

[0048] A comparison of the XPS total spectra of MPA-TPA, dPOF-OH-10, and dPOF-OFe-10 shows that ( Figure 4 a) Both MPA-TPA and dPOF-OH-10 samples contain C, N, and O, while the dPOF-OFe-10 sample contains C, N, O, and Fe, indicating that Fe... 3+ Successfully introduced into the defective porous organic framework dPOF-OH-10 structure. For example... Figure 4 As shown in b, C 1s analysis of MPA-TPA, dPOF-OH-10, and dPOF-OFe-10 indicates the presence of C−C / C=C (284.8 eV), C−N (286.1 eV), and C=N / C=O (287.6 eV) bonds in MPA-TPA. The presence of O can be attributed to the unreacted aldehyde oxygen at the end of the TPA monomer. Compared to MPA-TPA, dPOF-OH-10 and dPOF-OFe-10 exhibit C−O bonds, and the C−N is shifted. Combined with O 1s spectroscopy ( Figure 4 d) The deconvolution at 533.5 eV and 533.7 eV into new C−OH signal peaks indicates that a reaction occurred after the addition of the end-capping group 3,4-DHA, and the defective porous organic framework was successfully prepared. High-resolution N 1s spectra of dPOF-OH-10 and dPOF-OFe-10 (…) Figure 4In step c), a shift in the C-N bond was detected. Analysis showed that the introduction of the defect exposed more free amino groups (-NH2), further confirming the successful preparation of the defective dPOF-OH-10. Comparing the O 1s spectra of dPOF-OH-10 and dPOF-OFe-10, the absorption peak of C-OH in dPOF-OFe-10 was weakened, indicating that the post-modification successfully anchored Fe. 3+ In the Fe 2p spectrum ( Figure 4 In e), the signal peaks at 711.2 and 726.7 eV correspond to Fe 2p, respectively. 1 / 2 and Fe 2p 3 / 2 It can prove that Fe 3+ The presence of [something] was observed. Combined with XPS spectra, it was found that [something] was a defect. The successful preparation of dPOF-OH-10 and the successful anchoring of Fe by dPOF-OFe-10 were also identified. 3+ It provides strong evidence.

[0049] Example 6 The crystal structures of the MPA-TPA prepared in Example 1, the dPOF-OH-10 prepared in Example 2, and the dPOF-OFe-10 prepared in Example 2 were characterized by XRD. Figure 5 As shown, in 2θ ≈ 24.2 o A broad diffraction peak is observed at the [location], indicating that the prepared catalyst material has an amorphous structure, thus proving its amorphous nature. Compared with MPA-TPA, the crystal planes of dPOF-OFe-10 are wider and weaker, indicating that the introduction of the Fe component promotes the formation of the amorphous structure. Furthermore, the diffraction patterns of the porous organic frameworks show that their crystal structures are largely the same, independent of the missing connectants on the frameworks, suggesting that the introduction of defects does not lead to any structural collapse.

[0050] Example 7 The dPOF-OFe-10 prepared in Example 2 was characterized using SEM-EDS elemental mapping images, and the results are as follows: Figure 7 As shown in a-7d, the elemental diagram not only shows that each element exists and is uniformly distributed in the dPOF-OFe-10 material, but also that the dPOF-OFe-10 material contains Fe, suggesting that metallic Fe is present. 3+ It was successfully anchored to dPOF-OH-10.

[0051] Example 10 The catalysts prepared in Examples 1-5, TBAB, and epichlorohydrin were sequentially added to a 10 mL Schlenk reaction flask connected to a CO2 balloon. The amount of epichlorohydrin was 5 mmol, and the amount of catalyst depended on the Fe content in the catalyst. 3+Calculations are performed on Fe. 3+ The molar amount of the catalyst was 0.8% of the molar amount of epichlorohydrin (the addition of the metal-free catalyst was the same as that of dPOF-OFe-10), and 0.01 g of TBAB was added. The residual air inside was removed under reduced pressure. The reaction flask was connected to a CO2 balloon, and the reaction was carried out for 8 hours at a reaction temperature of 90℃ and a CO2 pressure of 0.1 MPa. After the reaction was completed, the product was quantitatively analyzed by gas chromatography, and the product yield was calculated.

[0052] The results are shown in Table 2. The results showed that the metallized defect dPOF-OFe-X (X = 5, 10, 20) materials exhibited higher catalytic activity than the standalone porous organic framework or the defective dPOF-OH-X (X = 5, 10, 20). Furthermore, the catalytic performance of dPOF-OFe-10 materials prepared using methanol as a solvent was investigated. The product yield was found to be close to that of dPOF-OFe-10 materials prepared using ethanol as a solvent, indicating that the different solvents only altered the catalyst morphology and did not affect the catalytic effect.

[0053] Example 11 Cyclic Stability Cyclic experiments were conducted on the catalyst dPOF-OFe-10 prepared in Example 2. The specific experimental conditions and procedures were the same as in Example 10. After each cycloaddition reaction, the used catalyst was recovered by centrifugation and washed with ethyl acetate before being used in the next catalytic reaction. After 5 cycles, the catalytic activity results are as follows: Figure 8 As shown, Figure 8 The yield of the product cyclochloropropylene carbonate decreased from 93% to 89% on the fifth run, demonstrating that the catalyst prepared in this application has good recycling performance.

[0054] The dPOF-OFe-10 recovered after the fifth catalytic reaction was characterized by FT-IR, and the results are as follows: Figure 8 As shown in b, compared with fresh dPOF-OFe-10, the characteristic peaks in the recycled dPOF-OFe-10 are all retained and are basically consistent with the infrared spectrum of fresh dPOF-OFe-10. This indicates that the framework structure and organic functional groups of dPOF-OFe-10 are not destroyed after multiple cycles, which also reflects the good recycling effect of the catalyst prepared in this application.

[0055] Example 12 The specific experimental process and detection method are the same as in Example 10. Epichlorohydrin was replaced with other epoxides with different substituents and cycloaddition reactions were carried out with carbon dioxide at atmospheric pressure at different temperatures. The results are shown in Table 3.

[0056] Table 3. Cycloaddition reactions of different substituent epoxides with CO2 The results show that dPOF-OFe-10 has good catalytic activity for the cycloaddition reaction of different substituent epoxides with atmospheric pressure CO2.

[0057] Example 13 1. The catalyst prepared in Example 2, TBAB, and epichlorohydrin were sequentially added to a 10 mL Schlenk reaction flask connected to a CO2 balloon. The amount of epichlorohydrin was 5 mmol, and the amount of catalyst depended on the Fe content in the catalyst. 3+ Calculations are performed on Fe. 3+ The molar amount of the reaction flask was 0.5% of the molar amount of epichlorohydrin, and 0.01 g of TBAB was added. The air inside the flask was removed under reduced pressure. The reaction flask was connected to a CO2 balloon and the reaction was carried out for 8 hours at a reaction temperature of 90℃ and a CO2 pressure of 0.1 MPa. After the reaction was completed, the product was quantitatively analyzed by gas chromatography, and the product yield was 85%.

[0058] 2. The catalyst prepared in Example 2, TBAB, and epichlorohydrin were sequentially added to a 10 mL Schlenk reaction flask connected to a CO2 balloon. The amount of epichlorohydrin was 5 mmol, and the amount of catalyst depended on the Fe content in the catalyst. 3+ Calculations are performed on Fe. 3+ The molar amount of the reaction flask was 1.2% of the molar amount of epichlorohydrin, and 0.01 g of TBAB was added. The air inside the flask was removed under reduced pressure. The reaction flask was connected to a CO2 balloon and the reaction was carried out for 8 hours at a reaction temperature of 90℃ and a CO2 pressure of 0.1 MPa. After the reaction was completed, the product was quantitatively analyzed by gas chromatography, and the product yield was 97%.

[0059] 3. The catalyst prepared in Example 2, TBAB, and epichlorohydrin were sequentially added to a 10 mL Schlenk reaction flask connected to a CO2 balloon. The amount of epichlorohydrin was 5 mmol, and the amount of catalyst depended on the Fe content in the catalyst. 3+ Calculations are performed on Fe. 3+The molar amount of the reaction flask was 0.8% of the molar amount of epichlorohydrin, and 0.01 g of TBAB was added. The air inside the flask was removed under reduced pressure. The reaction flask was connected to a CO2 balloon and the reaction was carried out for 10 hours at a reaction temperature of 70°C and a CO2 pressure of 0.1 MPa. After the reaction was completed, the product was quantitatively analyzed by gas chromatography, and the product yield was 86%.

[0060] 4. The catalyst prepared in Example 2, TBAB, and epichlorohydrin were sequentially added to a 10 mL Schlenk reaction flask connected to a CO2 balloon. The amount of epichlorohydrin was 5 mmol, and the amount of catalyst depended on the Fe content in the catalyst. 3+ Calculations are performed on Fe. 3+ The molar amount of the reaction flask was 0.8% of the molar amount of epichlorohydrin, and 0.01 g of TBAB was added. The air inside the flask was removed under reduced pressure. The reaction flask was connected to a CO2 balloon and the reaction was carried out for 6 hours at a reaction temperature of 110℃ and a CO2 pressure of 0.1 MPa. After the reaction was completed, the product was quantitatively analyzed by gas chromatography, and the product yield was 94%.

[0061] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metallized defect-type porous organic framework, characterized in that, It is prepared by forming structural units containing catechol sites through a Schiff base condensation reaction of m-phenylenediamine, terephthalaldehyde, and 3,4-dihydroxybenzaldehyde, and then anchoring trivalent iron at the catechol sites.

2. A method for preparing a metallized defect-type porous organic framework as described in claim 1, characterized in that, Includes the following steps: S1: Preparation of defective porous organic frameworks m-phenylenediamine, terephthalaldehyde and 3,4-dihydroxybenzaldehyde were dissolved and dispersed evenly in an alcohol solvent in a certain proportion, acetic acid solution was added, and the mixture was subjected to Schiff polycondensation reaction. After filtration, washing and drying, defective porous organic frameworks were obtained. S2: Preparation of metallized defect-type porous organic frameworks The defective porous organic framework obtained in S1 was dispersed in an alcohol solvent, and then ferric chloride was added. The mixture was stirred at room temperature for 10-14 h, filtered, washed, and dried to obtain the metallized defective porous organic framework.

3. The preparation method according to claim 2, characterized in that, In step S1, the molar ratio of intermediate phenylenediamine, terephthalaldehyde, and 3,4-dihydroxybenzaldehyde is 1:0.6-0.9:0.1-0.4; in step S2, ferric chloride hexahydrate is selected, and the mass ratio of defective porous organic framework to ferric chloride hexahydrate is 1:0.08-0.

12. The ratio of S1 intermediate phenylenediamine to alcohol solvent is 1 mmol: 4-6 mL; In S2, the ratio of defective porous organic framework to alcohol solvent is 0.1 g: 15-25 mL; The ratio of S1 intermediate phenylenediamine to acetic acid is 1 mmol: 6 mmol - 24 mmol.

4. The preparation method according to claim 2, characterized in that, The conditions for the Schiff polycondensation reaction in S1 are as follows: first stir at room temperature for 20-40 min, then transfer to a hydrothermal reactor and statically heat at 30-120℃ for 24-96 h.

5. The preparation method according to claim 2, characterized in that, The alcohol solvent in S1 and S2 is either methanol or ethanol.

6. The application of a metallized defect-type porous organic framework as described in claim 1 in the catalytic conversion of carbon dioxide under ambient pressure.

7. A method for synthesizing cyclic carbonates by catalytic reaction of carbon dioxide and epoxides under ambient pressure using a metallized defect-type porous organic framework as described in claim 1, characterized in that... Using a metallized defect-type porous organic framework as a catalyst and tetrabutylammonium bromide as a co-catalyst, cyclic carbonates are synthesized from epoxides and carbon dioxide through a cycloaddition reaction.

8. The method for synthesizing cyclic carbonates by catalytic reaction of carbon dioxide and epoxides under ambient pressure using a metallized defect-type porous organic framework according to claim 7, characterized in that... The structural formula of the epoxide is as follows: 。 9. The method for synthesizing cyclic carbonates by catalytic reaction of carbon dioxide and epoxides under ambient pressure using a metallized defect-type porous organic framework according to claim 7, characterized in that... The amount of the metallized defect-type porous organic framework catalyst is calculated in terms of Fe, and the molar amount of Fe is 0.5% to 1.2% of the molar amount of the epoxide; the reaction temperature is 70-110℃, and the time is 6-10h.

10. The method for synthesizing cyclic carbonates by catalytic reaction of carbon dioxide and epoxides under ambient pressure using a metallized defect-type porous organic framework according to claim 7, characterized in that... The amount of the metallized defect-type porous organic framework catalyst is calculated in terms of Fe, and the molar amount of Fe is 0.8% of the molar amount of the epoxide; the reaction temperature is 90℃ and the time is 8h.

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