Coupling Reaction Of Carbon Dioxide Research Articles

Turning waste into resources. Efficient synthesis of biopolyurethanes from used cooking oils and CO2

The coupling reaction of carbon dioxide and highly-substituted epoxides derived from renewable resources such as fatty acids and waste vegetable oils (cooking oils derived from olive and sunflower) leads to the synthesis of new bio-derived cyclic carbonates using efficient metal-free bifunctional organocatalysts under mild and solvent-free reaction conditions. Once cyclic carbonates derived from biobased sources were synthesized, the design of non-isocyanate polyurethanes (NIPUs) with different chemical structures was investigated by their reaction with a broad substrate scope of diamines. The NIPUs materials were characterized by spectroscopic techniques (NMR and IR) and their molecular weights and polydispersities were determined by GPC studies. Finally, thermal properties of the polymers were studied by DSC and TGA analyses.

Solvent-Free Coupling Reaction of Carbon Dioxide and Epoxides Catalyzed by Quaternary Ammonium Functionalized Schiff Base Metal Complexes under Mild Conditions.

A series of bifunctional Schiff base metal catalysts (Zn-NPClR, Zn-NPXH, and M-NPClH) with two quaternary ammonium groups were prepared for carbon dioxide (CO2) and epoxide coupling reactions. The effects of the reaction variables on the catalytic activity were systematically investigated, and the optimal reaction conditions (120 °C, 1 MPa CO2, 3 h) were screened. The performances of different metal-centered catalysts were evaluated, and Co-NPClH showed excellent activity. This kind of bifunctional catalyst has a wide range of substrate applicability, excellent stability, and can be reused for more than five runs. A relatively high TOF could reach up to 1416 h-1 with Zn-NPClH as catalyst by adjusting reaction factors. In addition, the kinetic study of the coupling reaction catalyzed by three catalysts (Zn, Co, and Ni) was carried out to obtain the activation energy (Ea) for the formation of cyclic carbonates. Finally, a possible mechanism for this cyclization reaction was proposed.

Functionalized β-Cyclodextrins Catalyzed Environment-Friendly Cycloaddition of Carbon Dioxide and Epoxides

Ammonium, imidazole, or pyridinium functionalized β-cyclodextrins (β-CDs) were used as efficient one-component bifunctional catalysts for the coupling reaction of carbon dioxide (CO2) and epoxide without the addition of solvent and metal. The influence of different catalysts and reaction parameters on the catalytic performance were examined in detail. Under optimal conditions, Im-CD1-I catalysts functionalized with imidazole groups were able to convert various epoxides into target products with high selectivity and good conversion rates. The one-component bifunctional catalysts can also be recovered easily by filtration and reused at least for five times with only slight decrease in catalytic performance. Finally, a possible process for hydroxyl group-assisted ring-opening of epoxide and functionalized group- induced activation of CO2 was presented.

New Co and Mn Catalysts Bearing ONO Ligands Containing Nucleophile for the Coupling of CO2 and Propylene Oxide

A series of novel ONO ligands bearing an ionic pendant-armed (hereinafter indicated as ONONu, where Nu corresponds to an anionic nucleophile) were synthesized, characterized, and successfully coordinated to cobalt and manganese precursors. New air-stable cobalt (III) complexes (1–6) and manganese (II) complexes (7 and 8) were obtained and characterized. Single crystal X-ray diffraction analysis of the Co(III) compound 5 confirmed the presence of two quaternized ligands coordinated to the metal and iodide as counterion. These novel complexes were revealed to be active catalysts in the coupling reaction of carbon dioxide and propylene oxide (PO) in different degrees of success. Among these, the manganese complex 8 afforded the best results towards the formation of propylene carbonate (PC) with a productivity of 256 kg PC/(kg cat·h), achieving a TON of 4860.

Hydroxyl-Imidazolium Ionic Liquid-Functionalized MIL-101(Cr): A Bifunctional and Highly Efficient Catalyst for the Conversion of CO2 to Styrene Carbonate.

Considerable attention has been focused on the development of catalysts for the coupling reaction of carbon dioxide (CO2) and epoxides due to the distinct advantages and importance of this reaction. To develop high-performance and easy-to-recycle catalyst is still a hot topic, especially for candidates with excellent activity under moderate conditions. A new heterogeneous catalyst, MIL-101-ImEtOH, is reported by post-synthesis modification, in which 2-(1-imidazol-1-yl) ethanol (Im-EtOH) is immobilized on MIL-101(Cr). In the absence of solvent and co-catalyst, MIL-101-ImEtOH exhibits high activity for the cycloaddition of CO2 and styrene oxide. A 95.6% yield is achieved under 0.5 MPa CO2 pressure and 90 °C by utilization of 50 mg of catalyst for 3 h. Moreover, MIL-101-ImEtOH is easily separated from the catalytic system by simple filtration. To elucidate the influence of hydroxyl group and porous structure on catalysis, other two supported ionic liquids, MIL-101-EtIm and PS-ImEtOH, are prepared and used to catalyze the title reaction under the same conditions. The contribution of each active component is determined by density functional theory along with noncovalent interaction analysis.

Efficient synthesis of cyclic carbonates under atmospheric CO2 by DMAP-based ionic liquids: the difference of inert hydrogen atom and active hydrogen atom in cation

The coupling reaction of carbon dioxide (CO2) and epoxides is one of the most efficient pathways to achieve the carbon balance. However, to accomplish it under the mild conditions, especially under the atmospheric pressure, is still a perplexing problem. Three novel ionic liquids (ILs), [DMAPBrPC][TMGH], [DMAPBrPC][DBUH], and [DMAPBrPC][BTMA], are designed and synthesized. All of them display the excellent catalytic activity for the title reaction achieving the yield over 96.6% under the atmospheric CO2 pressure at 60 °C. Interestingly, [DMAPBrPC][BTMA] with the inert hydrogen atom in cation exhibits the superior catalytic activity as compared to other two ILs with the protic hydrogen atom in cation along with the same anion. The active hydrogen atom in [DMAPBrPC][TMGH] and [DMAPBrPC][DBUH] would impede the –COO− group to absorb CO2, which is an unfavorable item for the reaction. Moreover, the strong hydrogen bond in [DMAPBrPC][TMGH] and [DMAPBrPC][DBUH] would lessen the nucleophilic ability of Br− anion resulting in the inferior catalytic performance, which is further confirmed by the density functional theory (DFT) calculations. The cation without the active hydrogen atom could also be employed to design the ILs with the excellent catalytic feature when it is combined with the suitable anion.

Design and synthesis of pyridinamide functionalized ionic liquids for efficient conversion of carbon dioxide into cyclic carbonates

Novel and facilely prepared 2-pyridinamide-functionalized ionic liquids 1–4 (PAIL1–4) were explored for the cycloaddition reaction of carbon dioxide with various epoxides to generate cyclic carbonates. The optimum temperature, CO2 pressure, and catalyst dosage of the cycloaddition reaction, are 60 °C, 0.5 MPa, and 5 mol% respectively. The synthesized N, N-dimethyl-N-(2-oxo-2-(pyridin-2-ylamino)ethyl)butan-1-aminium iodide (PAIL-3) exhibited brilliant catalytic activities under mild conditions with nearly quantitative selectivity and conversion in the absence of any solvents, or metal co-catalysts. The catalyst PAIL-3 could be recycled 4 times without obvious loss of its catalytic activity. Moreover, a plausible mechanism is proposed based on the NMR experiments. The designed pyridinamide functionalized ionic liquids integrated pyridine unit, halogen anion and the N-H moiety in amide and they have an excellent synergistic catalytic effect in promoting the coupling reactions of carbon dioxide and epoxides.

One-step preparation of ammonium-specified pyrazolium ionic liquids unveil the more popular pathway for the CO2 fixation: Integrated experimental and theoretical studies

Amino-specified pyrazolium ionic liquid (APEPzBr) is synthesized by two steps. It is interesting that the product of the first step ([EPzPNH3]Br2) could also catalyze the coupling reaction of carbon dioxide (CO2) and epoxides under 70 °C along with 0.5 MPa CO2 pressure, which is even more benign than APEPzBr. It is attributed to the strong ability of [EPzPNH3]Br2 to absorb CO2 along with robust electrophilic activation, which is testified by density functional theory and 13C NMR measurement. The difference between [EPzPNH3]Br2 and APEPzBr is further elucidated by electron localization function (ELF) and atoms in molecules (AIM).

Synthesis and structural characterization of methylindium imino/aminophenolates: Comparison to aluminum analogues and reactivity toward the coupling reactions of carbon dioxide with epoxides

We have synthesized methylindium complexes containing a variety of amino- and iminophenolate ligands for structural comparison to their aluminum analogues. The reaction of Me3In with the corresponding amino-/iminophenols resulted in the formation of MeIn(Et2NCH2CH2-abp) (1), MeIn(PyCH2-abp) (2), [MeIn(iPr-abp)]2 (3), MeIn(Ph-salen) (4), MeIn(Etsalan) (5), MeIn(Cy-ip) (6) and MeIn(Mes-ip) (7) [H2(Et2NCH2CH2-abp) = Et2NCH2CH2N(2-OH-3,5-C6H2tBu2)2, H2(PyCH2-abp) = (2-C5H4N)CH2N(2-OH-3,5- C6H2tBu2)2, H2(iPr-abp) = (CH3)2CHN(2-OH-3,5-C6H2tBu2)2, H2(Ph-salen) = 1,2-(NCH-2-OH-3,5-C6H2tBu2)2C6H4, H2(Et-salan) = 1,2-(NMeCH2-2-OH-3,5- C6H2tBu2)2C2H4, H(Cy-ip) = (2-OH-3,5-tBu2-C6H2)CHN(C6H11), and H(Mes-ip) = (2-OH-3,5-tBu2-C6H2CHN(2,4,6-Me3C6H2)]. X-ray crystallography studies show monomeric structures and five-coordinate indium centres for 1 and 2, a dimeric structure via intermolecular In⋯O interactions and fivecoordinate indium centres for 3, and monomeric structures and fourcoordinate indium centres for 6 and 7. DFT calculations were used to rationalize the observed dimeric structure of 3 and monomeric structures of 6 and 7, and gauge the effect of ligand steric bulk and atomic radius in indium versus aluminum on dimerization. Compounds 2 and 5 are active catalysts for coupling reactions of carbon dioxide and propylene oxide to yield propylene carbonate and carbon dioxide with cyclohexene oxide to yield polycyclohexene carbonate. This work provides insight into controlling intermolecular bonding and hence reactivity in indium and aluminum amino-/iminophenolate complexes, and represents one of the first examples of indium complexes as catalysts for the formation of cyclic- or polycarbonates from carbon dioxide and epoxides.

Influence of ionic liquids microenvironment on the coupling reaction of epoxide and carbon dioxide: DFT and MD

Abstract Theoretical calculation is a powerful tool to uncover the reaction mechanism. Besides it, the theoretical calculation is expected to provide more helpful clues and play more important role for catalysis. Although the calculated barrier height could not be directly compared with the experimental measured activation energy, the range of barrier heights would be the same with that of experimental yields. It would be beneficial to estimating the experimental result and designing the efficient catalysts. For the coupling reaction of carbon dioxide with epoxides catalyzed by ionic liquids, both the interactions among ionic liquids and microenvironment of ionic liquids would affect the calculated barrier heights. They are considered by combination of density functional theory and molecular dynamics in this work. The reliability of calculated barrier heights is improved. More important, this method not only is suitable for the ionic liquids with the similar structures but also be applied to ionic liquids with different structures.

Efficient Solvent-Free Synthesis of Cyclic Carbonates from the Cycloaddition of Carbon Dioxide and Epoxides Catalyzed by New Imidazolinium Functionalized Metal Complexes Under 0.1 MPa

A series of imidazolinium functionalized metal complexes were prepared as efficient and recyclable homogeneous catalysts for the synthesis of cyclic carbonates via the coupling reaction of carbon dioxide and epoxides in the absence of co-catalysts and solvent. Due to the synergistic effect between the metal center as Lewis acid and the imidazolinium groups with halide anions as Lewis base, these catalysts exhibited excellent catalytic capability. Particularly, high turnover frequency (TOF) values of (1174, 1240 and 1262 h−1) for bifunctional catalysts (2c, 2i and 2j, respectively) were achieved via adjusting reaction parameters. These catalysts also showed excellent catalytic performances under atmospheric pressure. Recyclability test showed that this kind of bifunctional catalyst can be easily recovered and reused for at least five times without dramatic loss of activity and selectivity. The optimum reaction conditions were also screened as (120 °C, 1.0 MPa CO2 and 2 h). The catalyst could also be applied to a variety of substrates and be used for a long time with high catalytic activities. We also performed the Kinetic studies, which suggested that the activity of catalysts following the order I− > Br− > Cl−. Moreover, a plausible reaction mechanism by imidazolinium functionalized metal complexes was proposed.

Effect of cluster of quaternary ammonium ionic liquids on catalytic performance for CO2 fixation: ONIOM and MD

Formation of cluster is a popular phenomenon for ionic liquids due to the strong interactions between cation and anion. It would definitely affect the intrinsic properties of ionic liquids and its catalytic activity. Taken the coupling reaction of carbon dioxide and propylene oxide as an example, the effect of quaternary ammonium ionic liquids cluster on its catalytic performance is investigated by combination of ONIOM and molecular dynamics simulations, including quaternary ammonium ionic liquid, hydroxyl functionalized quaternary ammonium ionic liquid, protic quaternary ammonium ionic liquid, and protic hydroxyl functionalized quaternary ammonium ionic liquid. The influence of electrostatic interaction and covalent and non-covalent interactions on the catalytic activity is analyzed by natural bond orbital, electron localization function, and atoms in molecules to explore the critical factors to control the catalytic activity.

Synthesis of Bio-Derived Cyclic Carbonates from Renewable Resources

The coupling reaction of carbon dioxide and terminal, internal, and highly substituted epoxides derived from renewable resources such as furfural, limonene, carvone, carvyl acetate, terpinen-4-ol, ...

Benzothiophene-based complexes mediated formation of cyclic carbonates by cycloaddition of carbon dioxide to epoxides under mild solvent-free conditions

Transition metal complexes of the general formula [(S∩N∩N∩S)MCl2] (M: Cr(II), 2; Fe(II), 3, Co(II); 4; (S∩N∩N∩S): cis-1,2-N1,N2-bis{(benzo[b]thiophen-2-yl)methylene-diaminocyclohexane, S-DACH, 1) were prepared and characterized. The new complexes have been utilized as catalysts for the coupling reaction of carbon dioxide and the epoxides, styrene oxide (SO), and (±)-propylene oxide (PO), in the presence of bis(triphenylphosphoranylidene)imminium bromide (PPNBr) as a co-catalyst. The reactions were carried out under relatively low pressure and solvent-free conditions. The catalyst systems showed to be selective for the formation of cyclic carbonates. In general, the Cr(II)-based catalyst exhibited the highest activity for the coupling reaction of CO2 with both SO and (±)-PO compared with the corresponding iron(II) and cobalt(II) complexes under similar reaction conditions with turnover numbers values of 2445 and 1164 for the production of propylene carbonate and styrene carbonate, respectively.

Effect of cluster of protic pyrazolium ionic liquids or epoxides on the cycloaddition of CO2

The reaction mechanism for the coupling reaction of carbon dioxide with epoxides catalyzed by single-component protic pyrazolium ionic liquids has been extensively elucidated. However, the calculated barrier heights are not accurate enough to predict the catalytic results for a series of ionic liquids with similar structures. The cluster of protic pyrazolium ionic liquids is regarded as catalyst to consider the effect of interactions among ionic liquids on the barrier heights. Moreover, the ionic liquids or epoxides would also affect the barrier heights as the environmental factors, which is also considered by ONIOM method. When the environmental influence is involved, the accuracy is greatly improved. The analysis of interactions between ionic liquid and reactant indicates that the electrophilic attacking plays the more critical role than nucleophilic attacking.

Synergistic effect of carboxylmethyl group and adjacent methylene substitution in pyrazolium ionic liquid promote the conversion of CO2 under benign condition

The carboxyl functionalized ionic liquids normally show better catalytic activity than the corresponding ionic liquids without functional group for the coupling reaction of carbon dioxide and epoxides. However, a long alkyl chain, at least propyl, is required as bridge between carboxyl group and N atom of aromatic heterocycle to ensure the catalytic activity. Inclusion of long alkyl chain indicates the low synthetic yield and harsh synthetic conditions. It is rarely reported that the carboxyl functionalized ionic liquid with methyl would present the high catalytic activity. With the help of ethyl substituted on the other N atom of pyrazolium ring, the carboxylmethyl pyrazolium ionic liquid (CMEPzBr) would present the excellent catalytic activity (yield >99%). Moreover, the product yield still keeps larger than 90% even under 70 °C and 1.0 MPa CO2 initial pressure. The role of methylene appeared on the near N atom is elucidated by density functional theory. The catalytic activity of carboxylmethyl imidazolium ionic liquid is not refined greatly when methylene is substituted on the other N atom of imidazolium ring. The optimal reaction conditions are investigated along with the recyclability and reusability.

Hydroxyl-functionalized pyrazolium ionic liquids to catalyze chemical fixation of CO2: Further benign reaction condition for the single-component catalyst

Lots of ionic liquids have been utilized as catalyst for the coupling reaction of carbon dioxide with epoxides, however, catalyzed conditions could not be regarded as benign, especially when no co-catalyst and/or organic solvent is involved. A series of hydroxyl-functionalized pyrazolium ionic liquids are firstly synthesized. They would efficiently catalyze the cycloaddition of carbon dioxide and propylene oxide under 110°C and 1.0MPa carbon dioxide initial pressure with 1mol% catalyst during 4h resulting in the product yield of 91.2%. The catalytic condition is greatly refined as compared with other single-component ionic liquids with simple anion. Simultaneously, the effect of reaction temperature, amount of catalyst, carbon dioxide initial pressure, and reaction time is explored along with the reusability of catalyst. For most of epoxides with terminal substituted group, HEEPzBr presents acceptable catalytic activity. The difference of HEMPzBr, HEEPzBr, and HPEPzBr is also explored by the density functional theory calculations.

DFT study on coupling reaction of carbon dioxide with ethylene oxide catalyzed by 1,4,6-triaza-bicyclo[3.3.0]oct-4-enium bromide (TBO.HBr)

ABSTRACTChemical fixation of CO2 with epoxides catalyzed by organic-base salts were found to be efficient among the various catalysts tested due to synergetic effects of HBDs and halide-ions for ring-opening. In this study, 1,4,6-Triaza–bicyclo[3.3.0]oct-4-enium bromide catalyzed conversion of CO2 and epoxide into cyclic-carbonate has been studied by using DFT method to understand the reaction mechanism and the catalytic performance of TBO.HBr. Two hypothetical reaction mechanisms were proposed for the coupling reaction. Thermodynamic and kinetic parameters were computed for each steps to determine the more favorable route. Mechanism II is more favorable path whereby Br- ion first interacts with epoxide to form bromo-alcohol, which directed to form carbonate-ion and finally ring-closure step yielded cyclic-carbonate with catalyst-regeneration. Cyclization step is rate-determining step with reaction barrier of 22.696 kcal/mol in gas phase. Ensuing the favorable mechanism, solvent-effects on the reaction barrier has been investigated using water and THF. Mechanism II is still more favorable reaction path in both THF and water. However, the rate-determining step is found to be ring-opening of the epoxide with reaction barrier of 22.658 kcal/mol (wate) and 21.969 kcal/mol (THF). In this study, TBO.HBr exhibited good catalytic activity for the title reaction investigated in both gas phase and solvents.

Iridium-Catalyzed Three-component Coupling Reaction of Carbon Dioxide, Amines, and Sulfoxonium Ylides.

The first iridium-catalyzed three-component coupling reaction of carbon dioxide, amines, and sulfoxonium ylides has been developed, providing an efficient and straightforward method for the construction of a range of structurally diverse O-β-oxoalkyl carbamates in moderate to excellent yields. This novel protocol features the use of readily available substrates, wide substrate scope, and good functional group tolerance. Moreover, the phosgene-free strategy was successfully applied to the synthesis of a potential antitumor agent.

Combination of experimental and theoretical methods to explore the amino-functionalized pyrazolium ionic liquids: An efficient single-component catalyst for chemical fixation of CO2 under mild conditions

Numerous ionic liquids have been developed to catalyze the coupling reaction of carbon dioxide with epoxides without co-catalyst and organic solvent. Although the catalytic activity is satisfied with cyclic carbonate yield over 90%, the reaction condition is still not regarded as benign enough, especially for reaction temperature and carbon dioxide initial pressure. Four new amino-functionalized pyrazolium ionic liquids, AEMPzBr, APMPzBr, AEEPzBr, and APEPzBr, have been firstly synthesized in simple reaction steps with cheap raw materials. Moreover, they would catalyze the coupling reaction of carbon dioxide with propyleneoxide under the optimal reaction conditions, 110 °C, 1.5 MPa carbon dioxide initial pressure as well as 1.0 mol% catalyst amount for 4.0 h, with propylene carbonate yield over 94%. The reaction temperature is decreased by 10–20 °C as compared with other single-component ionic liquids. At the same time, the carbon dioxide initial pressure is not increased to keep 1.5 MPa, which is also superior to lots of other ionic liquids, such as imidazolium, pyrazolium, and guanidinium ionic liquids. The recyclability and suitability of amino-functionalized pyrazolium ionic liquids are also explored. Finally, the catalytic mechanism is investigated by the density functional theory. Moreover, the influence of weak interactions on the reaction is analyzed by atoms in molecules and non-covalent interactions. As compared with other reported ionic liquids, the reaction condition catalyzed by APEPzBr is more benign with comparable product yield. More importantly, there is good balance among various reaction conditions without sacrificing one to ensure others. Amino-functionalized pyrazolium ionic liquids would be a new kind of powerful catalysts for the carbon dioxide fixation.