A Porphyrin‐Based Porous rtl Metal–Organic Framework as an Efficient Catalyst for the Cycloaddition of CO2 to Epoxides

A porous rtl metal–organic framework (MOF) [Mn₅L(H₂O)₆?(DMA)₂]?5DMA?4C₂H₅OH ( 1? Mn) (H₁₀L=5,10,15,20‐tetra(4‐(3,5‐dicarboxylphenoxy)phenyl)porphyrin; DMA=N,N′‐dimethylacetamide) was synthesized by employing a new porphyrin‐based octacarboxylic acid ligand. 1? Mn exhibits high Mn^II density in the porous framework, providing it great Lewis‐acid heterogeneous catalytic capability for the cycloaddition of CO₂ with epoxides. Strikingly, 1? Mn features excellent catalytic activity to the cycloaddition of CO₂ to epoxides, with a remarkable initial turnover frequency 400 per mole of catalyst per hour at 20 atm. As‐synthesized 1? Mn also exhibits size selectivity to different epoxide substrates on account of their steric hindrance. The high catalytic activity, size selectivity, and stability toward the epoxides on catalytic cycloaddition of CO₂ make 1? Mn a promising heterogeneous catalyst for fixation and utilization of CO₂.     

A Pyridinium-Pyridinium Zinc(II) Porphyrin Ion Porous Organic Polymer as Efficient Heterogeneous Catalyst for Cycloaddition of Epoxides with CO2

A zinc(II)porphyrin-based ion porous organic polymer (ZnTPyPBr₄-iPOP) is successfully synthesized from newly designed pyridinium-functionalized cationic Zn-porphyrin monomer (ZnTPyPBr₄) by free radical self-polymerization, and is employed as an efficient bifunctional heterogeneous catalyst for CO₂ cycloaddition reaction with epoxides. The ZnTPyPBr₄-iPOP exhibits excellent catalytic performance and good substrate expansion in CO₂ cycloaddition reaction under solvent-free and cocatalyst-free conditions with a TOF as high as 15,500 h⁻¹ for the cycloaddition of CO₂ and epichlorohydrin. The synergistic effect of zinc(II)porphyrin as the Lewis acidic site and the Br⁻ anion as the nucleophile in ZnTPyPBr₄-iPOP responds to the high catalytic activity. Moreover, ZnTPyPBr₄-iPOP can easily be recovered and reused at least seven times without the loss of activity. This work provides a valuable approach for the synthesis of novel and efficient heterogeneous catalyst for CO₂ cycloaddition.     

Cycloaddition of epoxide and CO2 to cyclic carbonate catalyzed by VO(IV) porphyrin

The cycloaddition of epoxide and CO₂ to synthesize cyclic carbonate catalyzed by VO(IV) porphyrin was achieved under 1.4 MPa at 150°C. The effects of reaction temperature, time, CO₂ pressure, co‐catalyst and porphyrin framework were investigated. The catalytic results showed that moderate to high yields of cyclic carbonates were obtained under the optimal reaction conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

An Efficient Catalyst System at Mild Reaction Conditions Containing Rare Earth Metal Complexes

An efficient rare earth metal complex‐catalyzed cycloaddition reaction of CO₂ with propylene oxide using Hdpza (di(2‐pyrazyl)amine) as a N‐donor ligand has been accomplished in good to excellent yields with high selectivity. The effects of different rare earth metal salts, ligands and reaction conditions were examined. Catalytic reaction tests demonstrated that the incorporation of ErCl₃ and Hdpza can significantly enhance the catalytic reactivity of the TBAB (nBu₄NBr, tetra‐n‐butyl ammonium bromide) towards cycloaddition reaction of CO₂ and propylene oxide that produce cyclic carbonates under mild conditions without any co‐solvent.     

Synergetic activation of carbon dioxide molecule using phenylazomethine dendrimers as a catalyst

Phenylazomethine dendrimers bearing a cobalt porphyrin core act as catalysts for CO₂ reduction in the presence of a strong Lewis acid such as lanthanide trifluoromethanesulfonate (Ln(OTf)₃). We investigated the catalytic activity using electrochemical measurements (cyclic voltammetry) on a glassy carbon electrode in a DMF solution. Dissolving CO₂ gas into the solution, the cyclic voltammograms displayed an irreversible increase of the cathodic current. This result suggests the catalytic reduction of CO₂. The redox potential (–1.3 V versus Fc/Fc⁺) at which the catalytic behavior was observed is 1.1 V higher than that catalyzed by cobalt tetraphenylporphyrin (CoTPP). The generation number (n) dependence of the dendrimer catalysts showed the maximum activity at n = 3. A significant decrease of the activity for the largest dendrimer (n = 4) indicates a steric effect, which prevents transmission of the substrate (CO₂ molecule) and electrons to the catalytic center (cobalt porphyrin core). For more efficient catalysis, a novel open-shell dendrimer having a pocket on one side of the molecule was designed and synthesized. Because the accessibility to the core in the opened shell improved, this dendrimer exhibited the highest catalytic activity. These results suggest that tuning of the local domain around the cobalt porphyrin center would lead to a decisive solution for further activation of the CO₂ molecule. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5229–5236, 2006     

Pyridinium-functionalized metalloporphyrins as bifunctional catalysts for cycloaddition of epoxides and carbon dioxide

New pyridinium-functionalized metalloporphyrins MEtPpBr₄ (M = Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺; EtPp = 5, 10, 15, 20-tetra(4-(3-(N-ethyl-4-pyridyl)pyrazolyl)phenyl)porphyrin) were synthesized as bifunctional catalysts for the cycloaddition reactions of epoxides and CO₂. The effects of catalyst loading, CO₂ pressure, reaction temperature and time on catalytic activity were investigated. ZnEtPpBr₄ ( 1 ) and CoEtPpBr₄ ( 2 ) exhibited efficient activities in the cycloaddition reactions of various epoxides with CO₂ as at 120 °C under 2 MPa of CO₂ pressure without solvent. Most of corresponding cyclic carbonates could be obtained in almost quantitative yields and > 99.9% selectivity with molar ratio of epoxide/catalyst 2222 after 8 hr of reaction.     

Preparation of polystyrene-supported Lewis acidic Fe(III) ionic liquid and its application in catalytic conversion of carbon dioxide

A polystyrene-supported Lewis acidic iron-containing ionic liquid was proved to be recyclable and efficient heterogeneous catalyst for converting CO₂ into cyclic carbonate without utilization of any organic solvent or additive. Excellent yields and selectivity were obtained under mild reaction conditions. Notably, the catalyst could be readily recovered and reused over five times without appreciable loss of catalytic activity. A possible catalytic cycle was proposed. The present protocol has successfully been applied to reactions of aziridines/propargyl amines with CO₂. This kind of the catalyst presented herein would have great potential in industrial application thanks to its featured advantages.     

Environmentally benign chemical fixation of CO2 catalyzed by the functionalized ion-exchange resins

Basic ion-exchange resins, one kind of polystyryl-supported tertiary amine, were demonstrated to be highly efficient and recyclable catalysts for the fixation of carbon dioxide with aziridines under mild conditions, leading to the formation of 5-aryl-2-oxazolidinone with excellent regio-selectivities. Notably, neither solvents nor any additives were required, and the catalyst could be recovered by simple filtration and directly reused at least five times without significant loss of catalytic activity and selectivity. The present protocol has been applied to reactions of epoxides/propargyl amines with CO₂/CS₂. This solvent-free process thus represents environmentally friendly catalytic conversion of CO₂ into value-added chemicals and may have potential in various continuous flow reactors in industry.     

Highly Porous Metalloporphyrin Covalent Ionic Frameworks with Well-Defined Cooperative Functional Groups as Excellent Catalysts for CO2 Cycloaddition

The development of multifunctional heterogeneous catalysts with high porosity and remarkable catalytic activity still remains a challenge. Herein, four highly porous metalloporphyrin covalent ionic frameworks (CIFs) were synthesized by coupling 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (TNPP) with 3,8-diamino-6-phenylphenanithridine (NPPN) or 5,5′-diamino-2,2′-bipyridine (NBPy) followed by ionization with bromoethane (C₂H₅Br) or dibromoethane (C₂H₄Br₂) and then metalization with Zn or Co. The resulting CIFs showed high efficiency in catalyzing the cycloaddition of propylene oxide (PO) with CO₂ to form propylene carbonate (PC). All of the Zn-containing CIF catalysts were able to catalyze the cycloaddition reaction with a PC yield greater than 97 %. The TNPP/NBPy (CIF2) catalyst ionized with C₂H₄Br₂ and metalized with Zn (Zn-CIF2-C₂H₄) exhibited the highest catalytic activity among the synthesized catalysts. The high catalytic performance of Zn-CIF2-C₂H₄ is related to its high porosity (577 m² g⁻¹), high Br:metal ratio (1:3.89), and excellent synergistic action between the Lewis acidic Zn sites and the nucleophilic Br⁻ ions. Zn-CIF2-C₂H₄ is sufficiently stable that greater than 94 % PC yield could be obtained even after six cycles. In addition, Zn-CIF2-C₂H₄ could catalyze the cycloaddition of several other epoxides with CO₂. These highly porous materials are promising multifunctional and efficient catalysts for industrially relevant reactions.     

Two Stable Heterometal‐MOFs as Highly Efficient and Recyclable Catalysts in the CO2 Coupling Reaction with Aziridines

Two stable heterometal‐organic frameworks, {Na[LnCo(DATP)₂(Ac)(H₂O)](NO₃)?DMA?11 H₂O}_n (Ln=Er( 1 ) and Yb( 2 )), have been prepared with H₂DATP (4′‐(3,5‐dicarboxyphenyl)‐2,2′:6′,2′′′‐terpyridine) as organic building block. These two isostructural compounds featuring two‐dimensional layer architectures possess outstanding thermal stabilities and excellent chemical stabilities in common organic solvents and different acid/base solutions with pH range changing from 1 to 13. Moreover, compounds 1 and 2 serving as heterogeneous catalysts can efficiently catalyse the CO₂ fixation reaction with various aziridines to result in corresponding oxazolidinones at 70 °C. Importantly, a good recyclable performance of 1 for at least 10 cycles is observed based on the experimental results, which are further confirmed by PXRD, TGA and ICP analyses.     

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble‐Metal‐Free [Zn116] Nanocages

The reaction of propargylic amines and CO₂ can provide high‐value‐added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco‐friendly noble‐metal‐free MOFs catalysts. Here, a giant and lantern‐like [Zn₁₁₆] nanocage in zinc‐tetrazole 3D framework [Zn₂₂(Trz)₈(OH)₁₂(H₂O)₉?8 H₂O]_n Trz=(C₄N₁₂O)^4? ( 1 ) was obtained and structurally characterized. It consists of six [Zn₁₄O₂₁] clusters and eight [Zn₄O₄] clusters. To our knowledge, this is the highest‐nuclearity nanocages constructed by Zn‐clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO₂, exclusively affording various 2‐oxazolidinones under mild conditions. It is the first eco‐friendly noble‐metal‐free MOFs catalyst for the cyclization of propargylic amines with CO₂. DFT calculations uncover that Zn^II ions can efficiently activate both C≡C bonds of propargylic amines and CO₂ by coordination interaction. NMR and FTIR spectroscopy further prove that Zn‐clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1 .     

Photocatalytic CO2 Reductions Catalyzed by meso-(1,10-Phenanthrolin-2-yl)-Porphyrins Having a Rhenium(I) Tricarbonyl Complex

We have prepared Zn and free-base porphyrins appended with a fac-Re(phen)(CO)₃Br (where phen is 1,10-phenanthroline) at the meso position of the porphyrin, and performed photocatalytic CO₂ reduction using porphyrin–Re dyads in the presence of either triethylamine (TEA) or 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. The Zn porphyrin dyad showed a high turnover number for CO production compared with the free-base porphyrin dyad, suggesting that the central Zn ion of porphyrin plays an important role in suppressing electron accumulation on the porphyrin part and achieving high durability of the photocatalytic CO₂ reduction using both TEA and BIH. The effect of acids on the CO₂ reduction was investigated using the Zn porphyrin–Re dyad and BIH. Acetic acid, a relatively strong Brønsted acid, rapidly causes the porphyrin's color to fade upon irradiation and dramatically decreases CO production, whereas proper weak Brønsted acids such as 2,2,2-trifluoroethanol and phenol enhance the CO₂ reduction.     

Zirconyl chloride: an efficient recyclable catalyst for synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 under solvent-free conditions

Zirconyl chloride was found to be an efficient catalyst for the cycloaddition reaction of aziridines with CO₂, thus leading to the preferential formation of 5-aryl-2-oxazolidinones under solvent-free conditions. The methodology could be extended to various substituted aziridines with high conversion and chemo-, regio-, and stereoselectivity. Furthermore, the catalyst could be reused over five times without significant loss in activity. Interestingly, the recovered catalyst showed higher activity in comparison with the fresh catalyst, presumably due to its morphological variation. The use of this cheap and moisture stable catalyst make this protocol practical, environmentally benign, and economically attractive.     

A Rapid and Simple Method for Quantitative Aziridination from Aminobrominated Derivatives of Olefins under Solvent‐free and Mild Conditions

The urea‐catalyzed aziridination of 1,2‐vicinal haloamines derived from aminohalogenation of olefins has been developed. This rapid and simple method was carried out by simply grinding the solid mixture of the substrate, K₂CO₃ and catalytic amount of urea at room temperature in air. The reaction provides a protocol for quantitative preparation of aziridines in a large scope of aminohalogenated derivatives of olefins including α,β‐unsaturated ketones, α,β‐unsaturated esters and simple olefins. The possible mechanism involving an H‐bond promoting deprotonation has been suggested for this reaction.     

A One‐Pot Synthesis of N‐Aryl‐2‐Oxazolidinones and Cyclic Urethanes by the Lewis Base Catalyzed Fixation of Carbon Dioxide into Anilines and Bromoalkanes

The multicomponent assembly of pharmaceutically relevant N‐aryl‐oxazolidinones through the direct insertion of carbon dioxide into readily available anilines and dibromoalkanes is described. The addition of catalytic amounts of an organosuperbase such as Barton's base enables this transformation to proceed with high yields and exquisite substrate functional‐group tolerance under ambient CO₂ pressure and mild temperature. This report also provides the first proof‐of‐principle for the single‐operation synthesis of elusive seven‐membered ring cyclic urethanes.     

Regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines using BrPh3PPEG600PPh3Br as an efficient, homogenous recyclable catalyst at ambient conditions

Polyethylene glycol functionalized phosphonium salt (Br⁻Ph₃⁺PPEG₆₀₀P⁺Ph₃Br⁻) was found to be an efficient, homogenous, recyclable catalyst for coupling of CO₂ with a variety of aziridines producing corresponding 5-aryl-2-oxazolidinones with good yields and excellent regioselectivity under relatively mild and solvent free conditions. Furthermore, the catalyst was effectively recycled for four consecutive cycles without any significant loss in its catalytic activity and selectivity.     

离子液体功能化金属有机骨架材料催化CO2环加成反应研究进展

金属有机骨架(Metal-organic frameworks, MOFs)材料因具有超大比表面积、可修饰的化学结构、可调的孔隙形状和大小、开放的金属位点等独特的结构优越性而被广泛用于催化CO₂环加成反应的研究中。然而,大部分MOFs材料在此反应中往往需要在助催化剂或溶剂的存在下才能发挥其催化性能,这也导致了产物分离困难、资源浪费等问题。因此,开发能够单独催化CO₂环加成反应的MOFs材料成为当前科学家们研究的热点。在MOFs骨架上或孔腔内修饰离子液体是构筑此类催化体系的一种重要途径。本文对近年来这类MOFs的构筑策略、催化CO₂环加成反应的性能以及催化机理进行了总结,同时还对MOFs组成、形貌以及催化反应条件等因素对催化活性的影响进行了探讨。     

Proline-Catalyzed Synthesis of 5-Aryl-2-oxazolidinones from Carbon Dioxide and Aziridines Under Solvent-Free Conditions

Natural α-amino acids were proven to be ecofriendly and recyclable catalysts for the carboxylation of aziridines with CO₂ without utilization of any organic solvents or additives. Notably, a series of 5-aryl-2-oxazolidinones were obtained in good yield together with excellent chemo- and regioselectivity under mild conditions using proline as the catalyst. Notably, the catalyst could be recycled more than five times after a simple separation procedure without appreciable loss of catalytic activity. This process represents a promising strategy for homogeneous catalyst recycling.     

Cu‐Catalyzed Selective Oxy‐Cyanoalkylation of Allylamines with Cycloketone Oxime Esters and CO2

The radical‐initiated carboxylative cyclization of allylamines with CO₂ represents an efficient and highly promising strategy to afford valuable 2‐oxazolidinones. However, the radical precursors and pathways to generate radicals in such processes are still limited. Herein, we report the first Cu‐catalyzed selective oxy‐cyanoalkylation of allylamines with cycloketone oxime esters and CO₂ via C—C bond cleavage. Many cyanoalkyl‐substituted 2‐oxazolidinones are obtained in moderate to good yields with high regio‐ and chemo‐selectivities. The utility of this redox‐neutral and cyanide‐free method is demonstrated with mild conditions, broad substrate scope, good functional group tolerance and easy scalability.     

Synthesis of substituted imidazolines via [3+2]-cycloaddition of aziridines with nitriles

An efficient synthesis of 2,4-disubstituted 1H-imidazolines from aziridines and nitriles in the presence of BF₃-Et₂O or triethyloxonium tetrafluoroborate has been described. The reaction proceeds via a [3+2]-cycloaddition reaction. Most of the nitriles successfully underwent cycloaddition reactions with aziridines even at room temperature in a very short time.