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Ambient condition-determined chemical CO2 fixation affords great promise for remitting the pressure of CO2 release. The construction of a microporous environment easily captures CO2 molecules around the reactive sites of the catalyst to reinforce the reaction process. Herein, multi-hydroxyl-containing hyper-crosslinked organic polymers (HCPs-OH-n) are synthesized by the polymerization of 1,4-dichlorobenzyl (DCX) and m-trihydroxybenzene in the monosaccharide form in a Friedel–Crafts alkylation hypercrosslinking process (FCAHP). By tuning the DCX ratio in the FCAHP, the structural properties can be regulated to create a more microporous surface in the HCPs-OH-n; meanwhile, the formed multi-hydroxyl species in the microporous environment could induce the easy interaction between hydroxyls and epoxides by forming a hydrogen bond, which improves the activation of epoxides during the cycloaddition reaction to synthesize the cyclic carbonates at ambient conditions. The structural properties suggest that HCPs-OH-n possess a large surface area with appreciable microporous and mesoporous distribution. As expected, the HCPs-OH-3 bearing the most abundant mesoporosity affords the highest reactivity in the chemical CO2 fixation to cyclic carbonates and is endowed with rational recoverability. [ABSTRACT FROM AUTHOR]

2–(1H–1,2,4–Triazol–3–yl)phenol (CAT–1) was used as an organocatalyst for the coupling reaction of CO2 and epoxides at an ambient temperature and atmospheric CO2 pressure (1 bar). This compound has a structure in which a hydrogen bond donor, a hydrogen bond acceptor, and another hydrogen bond donor are adjacent in sequence in a molecule. The binary catalytic system of CAT–1/nBu4NI showed TON = 19.2 and TOF = 1.60 h−1 under 1 bar CO2 at room temperature within 12 h using 2–butyloxirane. Surprisingly, the activity of CAT–1, in which phenol and 1H–1,2,4–triazole are chemically linked, showed a much greater synergistic effect than when simply mixing the same amount of phenol and 1H–1,2,4–triazole under the same reaction conditions. In addition, our system showed a broad terminal and internal epoxide substrate scope. [ABSTRACT FROM AUTHOR]

Porous polymeric frameworks have received great interest over the past few years because of their nonstop growth as crystalline porous polymeric materials connected through covalent bonds and versatile utilities in diverse fields. The production of high-value organic compounds via sustainable and environment-friendly methods is an uphill struggle for researchers. The elegant strategy of using carbon dioxide as a C1 building block is an intriguing platform owing to its non-toxicity, easy accessibility, natural abundance, recyclability, non-flammability, and cheapness. Additionally, CO2 levels are regarded as the main contributor to the greenhouse effect (the most abundant greenhouse gas across the globe) and the aforementioned strategy needs to mitigate CO2 emissions. This present study describes the synthesis of silver nanoparticles (AgNPs) embedded in a porous polymeric framework, a reusable heterogeneous catalyst (recyclable over 5 times), TpMA (MC)@Ag. The synthesized catalyst is characterized by using FT-IR, PXRD, XPS, FE-SEM, TEM, EDAX, TGA DTA, and N2 sorption studies. Additionally, the catalysts can be easily recycled to generate the desired α-alkylidene cyclic carbonates and oxazolidinone compounds under solvent-free conditions. This research demonstrates the potential of nanoporous 2D porous polymeric framework-based materials in the area of catalysis, specially, in CO2 capture and chemical fixation. These findings offer a promising approach for the chemical fixation of CO2 into α-alkylidene cyclic carbonates and oxazolidinones from propargylic alcohols utilizing AgNPs embedded in a 2D catalyst, which functions as a potential heterogeneous catalyst under mild conditions (e.g., solvent-free approach). [ABSTRACT FROM AUTHOR]

Development of an effective catalytic system for the cycloaddition of carbon dioxide to epoxides for the preparation of cyclic carbonates under mild conditions is of great importance. Herein, a mixture of zinc iodide, metal chlorides, and strong organic bases is demonstrated to be a useful catalytic system that works at room temperature under atmospheric pressure. The most efficient combination, zinc iodide-niobium chloride-7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (1.2-0.3-3.0 mol%), gave styrene carbonate (95%) from styrene oxide and CO2 (balloon) at 25 °C for 24 h. Another combination, zinc iodide-zinc chloride-1,8-diazabicyclo[5.4.0]undec-7-ene (1.2-0.8-4.0 mol%), kept the catalytic activity for the preparation of propylene carbonate until the fourth run. Therefore, the reaction system was operationally simple, highly efficient, and proceeded under ambient conditions. The catalyst is composed of readily available reagents and is reusable. Thus, the method presented is a powerful tool for utilizing CO2 as the starting material for the production of valuable chemicals. [ABSTRACT FROM AUTHOR]

A one-pot multicomponent green process is investigated for the synthesis of perfluoroalkylated cyclic carbonate which merges the photo-promoted Atom Transfer Radical Addition (ATRA) of a perfluoroalkyl iodide (Rf-I) onto allyl alcohols with the Lewis-base-promoted carboxylative cyclization. The evolution of the complex mixture during the reaction was monitored by in situ ATR-IR and Raman spectroscopies that provided insights into the reaction mechanism. The effect on the kinetics and the carbonate yields of key parameters such as the stoichiometry of reagents, the nature of the Lewis base and the solvent, the temperature and the pressure were evaluated. It was found that high yields were obtained using strong Lewis bases that played both the role of activating the allyl alcohol for the generation of the allyl carbonate in the presence of CO2 and promoting the ATRA reaction through the activation of C4F9I by halogen bonding. This protocol was also extended to various unsaturated alcohols. [ABSTRACT FROM AUTHOR]

For the production of cyclic carbonates from the cycloaddition of CO2 with epoxides, halogen pollution and product purity are two of the most common problems due to the usage of homogeneous halogen-containing catalysts such as ammonium salt and alkali metal halide. Hence, the development of a novel, halogen-free and efficient catalyst for the synthesis of high-purity cyclic carbonates is significant. Here, a series of acid–base bifunctional Ce1-xZrxO2 nanorods were successfully prepared. The Ce1-xZrxO2 nanorods could catalyze the cycloaddition of CO2 with epoxides efficiently without any halogen addition. Especially for the Ce0.7Zr0.3O2 catalyst, a conversion of 96% with 100% 1,2-butylene carbonate selectivity was achieved. The excellent catalytic performance of Ce1-xZrxO2 nanorods is attributed to the formation of the CeO2-ZrO2 solid solution, which contributes to abundant moderate acidic–basic active sites on the catalyst surface. It is the synergistic effect of moderate acidic–basic sites that dominates the conversion of CO2 with epoxides, which will supply important references for the synthesis of efficient metal oxide catalyst for the cycloaddition of CO2 with epoxides. [ABSTRACT FROM AUTHOR]

In this article, the combination of guanidine hydrochloride with co-catalyst ZnI2 proved to be a highly efficient heterogeneous catalyst for the environmentally benign, solvent-free synthesis of cyclic carbonates under mild reaction conditions. The effects of different co-catalysts as well as reaction parameters including catalyst loadings, CO2 pressure, reaction temperature, and reaction time on the coupling reaction of CO2 to propylene oxide were thoroughly investigated. With the molar ratio of guanidine hydrochloride to ZnI2 at 5:1, excellent yield (94%) and selectivity (≥99%) of propylene carbonate were obtained under 100 °C and at 1 MPa for 1.5 h. Additionally, ZnI2 could be recycled, but because of the washing loss of guanidine hydrochloride, there was a slight decrease in the yield of propylene carbonate. Gratifyingly, the activity of the catalytic system could be restored by adding additional 20 mol% of fresh guanidine hydrochloride, thus exhibiting excellent recyclability of the ZnI2 catalyst. Moreover, the binary catalysts were also versatile when using other epoxides for CO2 cycloaddition. A possible reaction mechanism was proposed wherein guanidine hydrochloride plays a dual role in activating CO2 and epoxide, and ZnI2 activated epoxide, simultaneously. The synergistic effect of guanidine hydrochloride and ZnI2 ensure the reaction proceeds effectively. [ABSTRACT FROM AUTHOR]

This review presents the synergistic effect in the catalytic system of ionic liquids (ILs) for the synthesis of cyclic carbonate from carbon dioxide and epoxide. The emphasis of this review is on three aspects: the catalytic system of metal-based ionic liquids, the catalytic system of hydrogen bond-promoted ionic liquids and supported ionic liquids. Metal and ionic liquids show a synergistic effect on the cycloaddition reactions of epoxides. The cations and anions of ionic liquids show a synergistic effect on the cycloaddition reactions. The functional groups in cations or supports combined with the anions have a synergistic effect on the cycloaddition reactions. Synergistic catalytic effects of ILs play an important role of promoting the cycloaddition reactions of epoxides. The design of catalytic system of ionic liquids will be possible if the synergistic effect on a molecular level is understood. [ABSTRACT FROM AUTHOR]

The effective conversion of carbon dioxide (CO2) into cyclic carbonates requires porous materials with high ionic content and large specific surface area. Herein, we developed a new systematic post-synthetic modification strategy for synthesizing imidazolium-based hypercrosslinked ionic polymers (HIPs) with high ionic content (up to 2.1 mmol g−1) and large specific surface area (385 m2 g−1) from porous hypercrosslinked polymers (HCPs) through addition reaction and quaternization. The obtained HIPs were efficient in CO2 capture and conversion. Under the synergistic effect of high ionic content, large specific surface area, and plentiful micro/mesoporosity, the metal-free catalyst [HCP-CH2-Im][Cl]-1 exhibited quantitative selectivities, high catalytic yields, and good substrate compatibility for the conversion of CO2 into cyclic carbonates at atmospheric pressure (0.1 MPa) in a shorter reaction time in the absence of cocatalysts, solvents, and additives. High catalytic yields (styrene oxide, 120 °C, 8 h, 94% yield; 100 °C, 20 h, 93% yield) can be achieved by appropriately extending the reaction times at low temperature, and the reaction times are shorter than other porous materials under the same conditions. This work provides a new strategy for synthesizing an efficient metal-free heterogeneous catalyst with high ionic content and a large specific surface area from HCPs for the conversion of CO2 into cyclic carbonates. It also demonstrates that the ionic content and specific surface area must be coordinated to obtain high catalytic activity for CO2 cycloaddition reaction. [ABSTRACT FROM AUTHOR]

In this work, the ionic liquid [Aliquat][Cl] was supported into alginate and silica aerogel matrices and applied as a catalyst in the cycloaddition reaction between CO2 and a bio-based epoxide (limonene oxide). The efficiency of the alginate aerogel system is much higher than that of the silica one. The method of wet impregnation was used for the impregnation of the aerogel with [Aliquat][Cl] and a zinc complex. The procedure originated a well-defined thin solvent film on the surface of support materials. Final materials were characterised by Fourier Transform Infrared Spectroscopy, N2 Adsorption–Desorption Analysis, X-ray diffraction, atomic absorption and Field Emission Scanning Microscopy. Several catalytic tests were performed in a high-pressure apparatus at 353.2 K and 4 MPa of CO2. [ABSTRACT FROM AUTHOR]

A set of tetranuclear alkyl aluminum adducts 1 and 2 supported by benzodiimidazole-diylidene ligands L1, N,N'-(1,5-diisopropylbenzodiimidazole-2,6-diylidene)bis(propan-2-amine), and L2, N,N'-(1,5-dicyclohexyl-benzodiimidazole-2,6-diylidene)dicyclohexanamine were synthetized in exceptional yields and characterized by spectroscopic methods. These compounds were studied as catalysts for cyclic carbonate formation (3a–o) from their corresponding terminal epoxides (2a–o) and carbon dioxide utilizing tetrabutylammonium iodide as a nucleophile in the absence of a solvent. The experiments were carried out at 70 °C and 1 bar CO2 pressure for 24 h and adduct 1 was the most efficient catalyst for the synthesis of a large variety of monosubstituted cyclic carbonates with excellent conversions and yields. [ABSTRACT FROM AUTHOR]

Various types of mesoporous silica were used as carriers to synthesize a series of immobilized imidazolium-based ionic liquids. Their activity was tested in the synthesis of styrene carbonate from CO2 and styrene. This is one-pot process, whereby two stages are carried out in one reactor and there is no need to isolate the intermediate product, epoxide. A systematic study on the influence of parameters such as temperature, the reaction time, CO2 pressure, as well as the amount and type of catalyst used was carried out. A strong synergistic catalytic effect of ionic liquid and Lewis acid was observed in promoting this reaction. The addition sequence of regents and amount of immobilized catalyst were considered crucial for the synthesis of styrene carbonate from CO2 and styrene. The tested silica-supported ionic liquids gave an easily-recyclable system which under the most favorable conditions ([mtespim]Cl/@SiO2; ZnBr2, 0.1 mol%; 110 °C, 4 h, 1 MPa) can be reused without a significant loss of catalytic activity nor selectivity. [ABSTRACT FROM AUTHOR]

Coupling of CO2 with epoxides is a green emerging alternative for the synthesis of cyclic organic carbonates (COC) and aliphatic polycarbonates (APC). The scope of this work is to provide a comprehensive overview of metal complexes having sulfur-containing ligands as homogeneous catalytic systems able to efficiently promote this transformation with a concise discussion of the most significant results. The crucial role of sulfur as the hemilabile ligand and its influence on the catalytic activity are highlighted as well. [ABSTRACT FROM AUTHOR]

Based on the ligand H2dpPzda (1), a novel cobalt complex [Co(H2dpPzda)(NCS)2]·CH3OH(2) has been synthesized and characterized. The Complex 2 exhibited excellent catalytic performance for converting CO2 into cyclic carbonates under mild conditions. For propylene oxide (PO) and CO2 synthesis of propylene carbonate (PC), the catalytic system showed a remarkable TOF as high as 29,200 h−1. The catalytic system also showed broad substrate scope of epoxide. Additionally, the catalyst could be recycled to maintain the integrity of the structure and remained equal to the level of its catalytic activity even after seven catalytic rounds. Additionally, a possible catalytic mechanism was proposed due to the high catalytic activity which might be owing to the synergism of Lewis acidic metal centers and N group. [ABSTRACT FROM AUTHOR]

Carbon dioxide produced by human activities is one of the main contributions responsible for the greenhouse effect, which is modifying the Earth's climate. Therefore, post-combustion CO2 capture and its conversion into high value-added chemicals are integral parts of today's green industry. On the other hand, carbon dioxide is a ubiquitous, cheap, abundant, non-toxic, non-flammable and renewable C1 source. Among CO2 usages, this review aims to summarize and discuss the advances in the reaction of CO2, in the synthesis of cyclic carbonates, carbamates, and ureas appeared in the literature since 2017. [ABSTRACT FROM AUTHOR]

The reduction of the representative greenhouse gas, carbon dioxide (CO2), is significantly an important theme for the current research in the modern chemical world. For the last two decades, the development of new metal-organic framework (MOF) systems with highly selective capture of CO2, in the presence of other competing gaseous molecules, has flourished to capture or separate CO2 for environmental protection. Nonetheless, the ultimate resolution to lessen the atmospheric CO2 concentration may be in the chemical or electrochemical conversion of CO2 to other compounds. In this context, the catalytic cycloaddition reaction of CO2 into organic epoxides to produce cyclic carbonates is a more attractive method. MOFs are being proven as efficient heterogeneous catalytic systems for this important reaction. In this review, we collected very recent progress in MOF-based catalytic systems, fully operable under very mild reaction conditions (room temperature and 1 atm CO2). [ABSTRACT FROM AUTHOR]