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The selective fixation of CO2 and epoxides into cyclic carbonates offers an atom-economical approach towards promising utilization of anthropogenic CO2 gas. This work demonstrates the development of recyclable organic–inorganic hybrid TBAI@CuO catalyst containing quaternary ammonium (TBAI) salt as active organic groups and CuO flowers as the inorganic component. Initially, CuO flowers was synthesized using a simple oxidation-precipitation method followed by immobilization of TBAI groups using impregnation method. The impregnated TBAI groups functioned as the active basic centers, whereas CuO flowers with effective surface area provided heterogeneity, Lewis acidic sites, facilitated better dispersion and strong interaction of TBAI. Resultantly, hybrid TBAI@CuO catalyst consisted of dual-active sites which played a decisive role in manipulating catalytic activity without requirement of a co-catalyst. With styrene oxide and CO2 as model substrates, the present catalyst system delivered 95% conversion and 97% selectivity towards styrene carbonate under solvent-free and milder reaction conditions when compared to other single metal oxide catalysts. The homogeneously dispersed TBAI groups in strong interaction with CuO flowers provided simultaneous access to both Lewis acidic as well as basic sites and hence resulted in superior catalytic activity. Meanwhile, hybrid TBAI@CuO catalyst showed catalytic adequacy for various terminal and internal epoxides. This catalytic system also presented good reusability without prominent loss in activity and no leaching of active TBAI groups. Based on characterization results, a plausible reaction mechanism was predicted to support the cycloaddition reaction with hybrid TBAI@CuO catalyst. It was proposed that inorganic Lewis acidic CuO activated the epoxide whereas the immobilized TBAI groups activated the inert CO2 molecule and stabilized the epoxide after ring opening. Therefore, the CuO flowers acting in concert with the immobilized TBAI groups showed exceptional acid–base cooperativity and provided high selectivity towards cyclic carbonates. The hybrid TBAI@CuO catalyst in this effort bridges the gap between homogeneous and heterogeneous catalysis for sustainable transformation of CO2 and epoxides to cyclic carbonates under solvent-free and comparatively mild reaction conditions [ABSTRACT FROM AUTHOR]

Polyoxometalates can be tuned for specific catalytic property by substituting transition metal ions. We report the synthesis of hybrid materials of Cu2+, Co2+ and Ni2+ substituted phosphotungstates and poly(diallyldimethylammonium) chloride polymer (PDDA) for CO2 fixation. The in situ generated transition metal substituted polyoxometalates (TMS-POMs) are analyzed by FTIR, powder XRD, 31P NMR and SEM techniques. The hybrid TMS-POM materials are found to be good catalysts for converting epoxides to cyclic carbonates. Among these, PDDA-PWCo is the most efficient catalyst for cycloaddition of CO2 under solvent-free conditions at room temperature in shortest reaction time. Only 0.2 mol% of PDDA-PWCo is enough to deliver 100% conversion and selectivity to cyclic carbonates. This catalytic approach is employed for conversion of other cyclic, acyclic, and aromatic epoxides without using column purifications. Overall, the method of obtaining cyclic carbonates under green conditions using TMS-POMs-PDDA hybrid materials appears suitable for industrial applications. [ABSTRACT FROM AUTHOR]

The fixation of CO2 into valuable chemicals under mild conditions is of great importance. Here, we reported an efficient and mild method for the cycloaddition of CO2 to cyclic carbonates. Iodized salt of DBU was used as hydrogen-bonding acceptor, 4-methoxyphenol was employed as hydrogen-bonding donor, and deep eutectic solvent was synthesized and characterized by NMR, FI-IR and thermogravimetric analysis. Optimization of the reaction conditions catalyzed by the deep eutectic solvent was performed, a series of epoxides have been converted to the corresponding products with excellent yields under the optimized conditions. The reaction kinetics for the synthesis of cyclic carbonates was investigated, in addition, excellent recovery performance of the catalyst was obtained after recycling for 5 times. Comparing with the literature reported, the method was much milder and efficient simultaneously. This work provides a promising way to the fixation of CO2. [ABSTRACT FROM AUTHOR]

The conversion of atmospheric carbon dioxide (CO2) gas mixtures and epoxides to cyclic carbonates is an environmentally beneficial execution strategy, which is a useful platform chemical. However, this reaction is overly dependent on harsh reaction conditions including temperature and/or CO2 pressure in the traditional conversion process. We report a series of facilely prepared functionalized ionic liquids (ILs) for the one-pot synthesis of styrene carbonate (SC) from pure/diluted CO2 with styrene oxide (SO). Which achieved a yield up to 99% under atmospheric CO2 conditions. In addition, with the assistance of a small amount of catalyst, the product yield remained at 99% under diluted CO2 conditions. This result demonstrates that functionalized ILs could effectively catalyze the cycloaddition reaction of low-pressure CO2 without any co-catalysts such as metals, organic solvents, and active additives. The density functional theory (DFT) calculations combined with experimental results revealed that the highest catalytic ability of Cat.2 was ascribed to the synergic catalysis between positive charge delocalized cations and Br− anions to efficiently activate the substrates. Furthermore, the best ILs catalyst can be reused five times without significant reduction in catalytic activity, which shows its great potential for chemical conversion of atmospheric CO2. [ABSTRACT FROM AUTHOR]

One of the efficient approaches to achieving net-zero greenhouse gas emissions is the 100% atom-economical conversion of the greenhouse gas carbon dioxide (CO2) to cost-effective, less toxic cyclic carbonates that can act as green solvents and abundant C1 synthon in organic synthesis. In this work, we have synthesized an Indium Metal–Organic Framework (MOF), functionalized with triazole MIL-68(In)-NHTr (Tr = 1-methylene-1,2,4-triazole) as a bifunctional catalyst for the synthesis of cyclic carbonates from epoxides with high yield (96%) and selectivity (100%) under solvent-free ambient reaction conditions (CO2 pressure 1 bar, temperature 50 °C, and reaction time 6 h). The synergistic acid–base effect of Indium SBU and the triazole of MIL-68(In)-NHTr make this a better catalyst than the conventional MIL-68(In)-NH2. This new catalyst was non-leachable and was reusable for six consecutive catalytic cycles without appreciable loss in the catalytic efficiency and crystallinity of the MOF framework. [ABSTRACT FROM AUTHOR]

In this study, a new and efficient solvent-less procedure was expanded to synthesize cyclic carbonate derivatives by chemical fixation of CO2 using Cu(II)/hydroxyl terminated triazine-based dendrimer (Cu(II)/TD) as a proficient heterogeneous nano-catalyst. The Cu(II)/TD nano-catalyst was characterized using TEM, TGA, FT-IR, SEM, EDS, and ICP techniques. The application of this new nano-catalyst provides the preparation of assorted cyclic carbonate derivatives in the attendance of 0.045 mol% of nano-catalyst and 0.3 MPa of CO2 pressure at 50 °C under solvent-less situations in outstanding yields. The Cu(II)/TD catalyst was able to be reprocessed and recovered many times without considerable failure of its performance. The findings strongly confirm that Cu(II)/TD can be considered as an environmentally friendly and retrievable catalyst for fixation of CO2 into the valuable products. [ABSTRACT FROM AUTHOR]

A cationic covalent organic polymer with bifunctional active site was synthesized, which was treated by N, N'-bis(5-bromomethylsalicylaldehyde)ethylenediamine (salen ligand) and tris(1H-imidazol-1-yl) triazine (TIT) in the presence of aluminum ethoxide. The bifunctional cationic covalent organic polymer was investigated by various characterization technologies including PXRD, FT-IR, XPS, TG, SEM, EDS, N2-adsorption and CO2-adsorption. In this polymer, aluminum acts as lewis acid site and bromine ion acts as nucleophile, cooperatively catalyzing the cycloaddition reaction of CO2 and epoxides. Due to its cooperative effect, a higher catalytic activity was found to exhibit 98.1% conversion of epichlorohydrin under optimized conditions (Initial pressure 1.0 MPa, 0.57 mol% catalyst of COP-Al, 90 °C, reaction time 18 h, in the absence of a co-catalyst). Notably, the heterogeneous catalyst still showed good activity and stability after five cycles. A salen-based cationic covalent organic polymers (COP-Al) was used as a bifunctional catalyst for the cycloaddition reaction of CO2 and epoxides with high activity under solvent-free and co-catalyst-free conditions. [ABSTRACT FROM AUTHOR]

On the basis of efficient and recyclable criteria for catalytic conversion of CO2 into cyclic carbonates, functionalized polymeric ionic liquids grafted onto the silica (PIL@SiO2) are explored by the polymeric method herein. Among all the prepared PIL@SiO2, the PIL@SiO2 loaded with a high mass fraction (50%) of PIL is the best in catalytic activity, achieving 91% PO conversion, nearly 50% saved than the non-grafted PIL. In addition, the PIL@SiO2 exhibits higher performance than PILs under identical reaction conditions. Subsequent studies concerning recyclability confirm that the as-prepared catalyst is stable after 5 times recycle without obvious loss in activity. This grafting and polymerization process provides an efficient and sustainable way of CO2 conversion in the long term. [ABSTRACT FROM AUTHOR]

An effective direct method for preparing of cyclic carbonates from CO and olefins in the presence of tert-butyl hydroperoxide as an oxidant was provided. The first stage, the epoxidation of olefins, was carried out using MoO(acac) as a catalyst (1h, 100 °C), and the second stage, the cycloaddition of CO to the resulting epoxide, was proceeded in the presence of immobilized tributylmethylammonium chloride on a polystyrene cross-linked with divinylbenzene, and an aqueous solution of ZnBr (100 °C, 0.9 MPa of CO, 4 h). The proposed method allowed to obtain cyclic carbonates with high yields (50-77%) under mild conditions. Moreover, the immobilized catalyst could be reused at least five times without significant loss of its catalytic activity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Synthesis of various cyclic carbonates with yield up to 100% and turn over frequency (TOF) of 351 h−1 using CO2 and epoxides and a cobalt (III) complex of tetraamidomacrocyclic ligand is described. The catalyst was characterized by single crystal X-ray crystallography. A study of reaction conditions indicates that 2 MPa pressure of CO2 without any co-solvent is sufficient to achieve the desired product. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Supported liquid phase catalysts (SLPC) were prepared from high surface area porous silica, polyethylene glycol (PEG), alkali metal halides and used for the synthesis of cyclic carbonates from carbon dioxide and epoxides. These catalysts was found to be highly active and selective for the synthesis of cyclic carbonates. The catalytic activity strongly depends on the nature of the supported alkali metal halide. The amount of alkali metal salt incorporated in the catalyst is one of the most important factor governing the catalytic performance. Effect of various reaction parameters such as pressure, temperature, catalyst loading, surface area of support was also studied in detail. [ABSTRACT FROM AUTHOR]

Metal phthalocyanine complexes (MPc; M = Cu2+, Co2+, Ni2+ and Al3+) encapsulated in zeolite-Y exhibit high catalytic activity for the cycloaddition of CO2 to epichlorohydrin and propylene oxide yielding the corresponding cyclic carbonates. The catalysts could be separated easily from the reaction mixture and reused with little loss in activity. These environmentally benign catalysts are also more efficient than either the “neat” complexes or those obtained by supporting them on solids like silica. [ABSTRACT FROM AUTHOR]