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Nowadays there is an urgent need for mitigating CO2 emissions through clean energy and the development of new carbon capture and utilization (CCU) technologies. Among others, the use of bifunctional ionic liquids (ILs) addressed simultaneously CO2 capture and conversion steps, having applied successfully to the propylene carbonate production case. In this work, a systematic evaluation of all representative cyclic carbonate literature was made, covering ethylene, propylene, butylene, hexylene, cyclohexene, and styrene cyclic carbonates, in order to guide the product role within the integrated CCU (ICCU) concept. The multiscale strategy combining molecular simulation (DFT -Density Functional Theory-, COSMO -COnductor-like Screening MOdel-), process simulation (COSMO/Aspen methodology), and life cycle assessment (LCA) was used to set up, simulate and evaluate the processes. ICCU configuration is the best approach when compared with sequential configuration for energy consumption analysis (reduction of 28, 28, 22, 11 and 6 %, respectively, for ethylene, propylene, butylene, hexylene, and cyclohexene cases) and CO2 emissions associated (reduction of 38, 40, 31 and 14 %, respectively, for ethylene, propylene, butylene, and hexylene cases). The main variable of the results is the boiling point of the cyclic carbonate since heavy products impose technical limitations and even discard ICCU alternative. The ICCU concept works since all cyclic carbonates’ reaction enthalpies are higher than that of the IL-CO2 one, which reduces heating requirements. Finally, energy demand can be slightly further reduced, partially recycling the cyclic carbonate to the capture unit.

The conversion of CO2 with epoxides into the corresponding cyclic carbonates represents a green approach to transform a waste into value-added products. To promote this conversion, a catalyst in needed. This study presents the synthesis of two cross-linked materials composed of magnesium phthalocyanine and imidazolium bromide moieties: MgPc-BIBI-Br and MgPc-SIBI-Br. Magnesium phthalocyanines are cost-effective and versatile catalysts, synthesized in high yield from low-cost precursors and can be easily modified for specific needs. Imidazolium bromide groups play a crucial role as well, acting as a nucleophile source essential to promote the ring-opening process of the epoxide. The materials have been extensively characterized through analytical and spectroscopic techniques and tested as catalysts in the conversion of epichlorohydrin into 4-chloromethyl-1,3-dioxalan-2-one. They both achieved excellent catalytic performance (maximal TON values of 3070 for MgPc-SIBI-Br and 1903 for MgPc-BIBI-Br) and recyclability (both recyclable at least for 4 cycles). The reported results represent an improvement if compared to similar materials already reported in the literature in which the addition of external nucleophilic species (e.g. TBAB, BMIM-Br, etc.) is needed. To the best of our knowledge, this work is the first example in which imidazolium bromide and magnesium phthalocyanine moieties are combined in bifunctional polymeric materials that convert CO2 into cyclic carbonates via heterogeneous catalysis.

This study introduces a straightforward synthesis method for producing a hybrid material composed of halloysite and kojic acid, which catalyzes carbon dioxide (CO2) conversion processes. Kojic acid, derived from malted rice fermentation, exhibits inherent chelating properties that facilitate the introduction of copper ions onto the material’s surface. Copper ions, an economically viable alternative to noble metals, catalyze CO2 conversion reactions effectively. The hybrid catalyst was evaluated for two distinct CO2 conversion pathways: photocatalytic methane production under simulated sunlight and CO2 fixation into cyclic carbonates via epoxide reactions. The hybrid material demonstrates remarkable catalytic activity under mild conditions, achieving high conversion efficiencies at 45 °C for methane production and 70 °C for carbonate fixation at atmospheric pressure. Conversion of 31 % and 89 % were achieved for the photocatalytic CO2 reduction and the carbonate fixation, respectively. FT-IR spectra confirmed the functionalization of the material. Additionally, its organic/inorganic hybrid nature is complemented by excellent thermal stability, as studied by TGA. It enables repeated utilization, maintaining a 25 % catalytic activity for methane production and 70 % for carbonate fixation after the fourth reuse. This research highlights the potential of using naturally derived materials for sustainable CO2 mitigation.

The cycloaddition reaction of CO2 with epoxides such as limonene epoxide (LE) to form cyclic carbonates is considered a promising alternative for reducing CO2 emissions. In this work, CO2 fixation on LE to produce cyclic carbonates was carried out over Zn/SBA-15 with tetrabutylammonium bromide (TBAB) as co-catalyst and over NH3X-Zn/SBA-15 (X= Cl, Br, or I) catalysts. The catalysts were characterized by FT-IR, XRD, N2 adsorption–desorption isotherms, TEM, NH3-TPD, XPS, TGA and Py-FTIR. The Zn/SBA-15 support mainly presents Lewis’s acid sites of medium acidity; the surface area was 512 m2/g and 378 m2/g and the pore size were 9 nm and 7.2 nm, for Zn/SBA-15 and NH3Cl-Zn/SBA-15, respectively. The functionalization of Zn/SBA-15 was verified by FTIR, UV-vis, and XPS analysis. It was found that when Zn/SBA-15 was used as catalyst that reaction time had a significative effect on LE conversion and in the case of limonene carbonate selectivity, co-catalyst concentration variation had the main effect. Zn/SBA-15 catalyst can be reused up to 5 times without significant changes neither in conversion nor in limonene carbonate selectivity. The best LE conversion and limonene carbonate selectivity was 33% and 93%, respectively (1 M LE, 200 mg Zn/SBA-15, 7% TBAB; 30 bar, 18 h, 700 rpm and 20 mL diethyl carbonate). The reported catalytic system is a promising system for obtaining limonene carbonate using a heterogeneous catalyst.

We report on the metal-free and rapid catalytic conversion of carbon dioxide into cyclic carbonates under solventless conditions utilizing novel bifunctional fluoroalcohol-based ionic liquids (FBILs) as catalsyts. In the presence of 2.5 mol% 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl) phenyl trimethylammonium iodide (FBIL-1), under 0.1 MPa and 90 °C, excellent yield of propylene carbonate(>95%) was achieved in 1 h, which significantly shortens the reaction time, compared with the conventional catalysts. DFT calculations reveal that FBILs with fluorine-substituted hydroxyl groups exhibit stronger hydrogen bonding with epoxides compared to ILs lacking fluorine substitutions. The hydrogen bond length for ILF/PO is 1.658 Å, shorter than that for IL/PO (1.813 Å). This characteristic contributes to reducing the activation energy for the ring-opening reaction of epoxides. In the ILF/PO system, the reaction barrier is 88.72 kJ·mol−1, lower than the 101.46 kJ·mol−1 barrier for IL/PO, allowing the former to more rapidly facilitate the fixation of carbon dioxide into cyclic carbonates. Besides high catalytic efficiency, these FBILs have the characteristics of a facile synthesis route and easy post-reaction recovery.

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.

A novel approach is reported to prepare 3D-printed polymers that incorporate metal-organic frameworks (MOFs) through a one-pot growth process, involving covalent grafting and growth onto 3D polymeric surfaces. The resulting hybrid materials were subjected to comprehensive characterization using techniques such as SEM, XRD, FTIR, Raman, and XPS. The findings demonstrated an excellent dispersion of the inorganic units on the polymer matrix while preserving their metal-organic structure. The hybrid materials exhibited the presence of Lewis acid and basic groups within the MOF. The catalytic performance of these hybrid materials was evaluated in the mild cycloaddition reaction of carbon dioxide (CO2) to epoxides. Notably, the polymers incorporating UiO-67 MOFs displayed remarkable activity, even at low CO2 pressures and in the absence of auxiliary co-catalysts or additives. The catalytic activity of these hybrid materials exhibited a significant improvement, up to two orders of magnitude higher than analogous bulk MOFs. This observation highlights the superior performance of the 3D-printed polymer/MOF hybrids in this catalytic transformation.

The present work focuses on developing heterogeneous catalysts for conversion of CO2 and mono-/di-epoxides to mono-/bis-cyclic carbonates. To achieve this purpose, two types of recyclable solid catalysts, namely polyurethane (PU-BTP) and polyurethane modified on silica gel-solid support (SG-AU-BPT), are synthesized. On these catalysts, the key promoter CaI2 is pre-absorbed. Both catalysts show high catalytic activity under mild conditions. For example, phenyl glycidyl ether (PGE) can be converted to 4-(phenoxymethyl)− 1,3-dioxolan-2-one at 60 °C within 6 h under 1 atm pressure of CO2. PU-BTP and SG-AU-BPT can be recollected by suction filtration and reused for eight times with conversion larger than 81% and 95% respectively. These results indicate that the degree of CaI2 leaching out from the catalysts in each cycle and loss is low.

There is a limited number of systematic CO 2 conversion studies that provide a clear understanding of the effect of the active sites of catalysts. Hence, this work examines the catalytic activity of 24 organic salts consisting of chloride, bromide or iodide anions and imidazolium, ammonium, or phosphonium-based cations, in the synthesis of hexylene and styrene carbonates from CO 2 , resulting in a diverse range of yields. The findings revealed that high yields depend heavily on catalyst solubility in the reaction medium, but solubility alone does not guarantee reaction success. This finding supports the new hypothesis that catalyst dissociation, reliant on solubility, is a critical factor in defining the catalytic activity. A strong correlation was observed between carbonate yields and the dissociation constants of catalysts, calculated using the COSMO-RS method. This suggests that greater dissociation, reflecting weaker cation-anion interactions, facilitates the anion nucleophilic attack on the epoxide. Also, the relationship between calculated dissociation constant and experimental ionic conductivity was successfully validated. This highlights the significance of organic salt dissociation on catalytic performance and validates the use of computational tools to predict key operational parameters, enhancing the understanding and optimization of CO 2 conversion into cyclic carbonates. [Display omitted] • Systematic study of 24 organic salts to synthesize hexylene and styrene carbonates from CO 2. • Demonstration of the importance of catalyst solubility and dissociation in the epoxide. • Strong correlation between experimental yields and computationally calculated dissociation constants of catalysts. • Consistency between calculated dissociation constants and experimental ionic conductivity. [ABSTRACT FROM AUTHOR]

Nowadays there is an urgent need for mitigating CO 2 emissions through clean energy and the development of new carbon capture and utilization (CCU) technologies. Among others, the use of bifunctional ionic liquids (ILs) addressed simultaneously CO 2 capture and conversion steps, having applied successfully to the propylene carbonate production case. In this work, a systematic evaluation of all representative cyclic carbonate literature was made, covering ethylene, propylene, butylene, hexylene, cyclohexene, and styrene cyclic carbonates, in order to guide the product role within the integrated CCU (ICCU) concept. The multiscale strategy combining molecular simulation (DFT -Density Functional Theory-, COSMO -COnductor-like Screening MOdel-), process simulation (COSMO/Aspen methodology), and life cycle assessment (LCA) was used to set up, simulate and evaluate the processes. ICCU configuration is the best approach when compared with sequential configuration for energy consumption analysis (reduction of 28, 28, 22, 11 and 6 %, respectively, for ethylene, propylene, butylene, hexylene, and cyclohexene cases) and CO 2 emissions associated (reduction of 38, 40, 31 and 14 %, respectively, for ethylene, propylene, butylene, and hexylene cases). The main variable of the results is the boiling point of the cyclic carbonate since heavy products impose technical limitations and even discard ICCU alternative. The ICCU concept works since all cyclic carbonates' reaction enthalpies are higher than that of the IL-CO 2 one, which reduces heating requirements. Finally, energy demand can be slightly further reduced, partially recycling the cyclic carbonate to the capture unit. [Display omitted] • Sequential and integrated CO 2 capture and conversion processes were evaluated. • Integrated schemes are better in energy consumption in almost all the cases. • Neat emissions are highly improved in integrated processes. • Product's boiling point was found to be the optimization key in all scenarios. [ABSTRACT FROM AUTHOR]

The conversion of CO 2 with epoxides into the corresponding cyclic carbonates represents a green approach to transform a waste into value-added products. To promote this conversion, a catalyst in needed. This study presents the synthesis of two cross-linked materials composed of magnesium phthalocyanine and imidazolium bromide moieties: MgPc-BIBI-Br and MgPc-SIBI-Br. Magnesium phthalocyanines are cost-effective and versatile catalysts, synthesized in high yield from low-cost precursors and can be easily modified for specific needs. Imidazolium bromide groups play a crucial role as well, acting as a nucleophile source essential to promote the ring-opening process of the epoxide. The materials have been extensively characterized through analytical and spectroscopic techniques and tested as catalysts in the conversion of epichlorohydrin into 4-chloromethyl-1,3-dioxalan-2-one. They both achieved excellent catalytic performance (maximal TON values of 3070 for MgPc-SIBI-Br and 1903 for MgPc-BIBI-Br) and recyclability (both recyclable at least for 4 cycles). The reported results represent an improvement if compared to similar materials already reported in the literature in which the addition of external nucleophilic species (e.g. TBAB, BMIM-Br, etc.) is needed. To the best of our knowledge, this work is the first example in which imidazolium bromide and magnesium phthalocyanine moieties are combined in bifunctional polymeric materials that convert CO 2 into cyclic carbonates via heterogeneous catalysis. [Display omitted] • Efficient synthesis of highly cross-linked magnesium phthalocyanine-based catalysts. • New examples of entirely heterogeneous bifunctional catalysts for CO 2 valorisation. • Green and sustainable approach for the synthesis of cyclic carbonates. • Raising Br-/Mg ratio in the catalyst to increment the level of epoxide conversion. [ABSTRACT FROM AUTHOR]

This study introduces a straightforward synthesis method for producing a hybrid material composed of halloysite and kojic acid, which catalyzes carbon dioxide (CO 2) conversion processes. Kojic acid, derived from malted rice fermentation, exhibits inherent chelating properties that facilitate the introduction of copper ions onto the material's surface. Copper ions, an economically viable alternative to noble metals, catalyze CO 2 conversion reactions effectively. The hybrid catalyst was evaluated for two distinct CO 2 conversion pathways: photocatalytic methane production under simulated sunlight and CO 2 fixation into cyclic carbonates via epoxide reactions. The hybrid material demonstrates remarkable catalytic activity under mild conditions, achieving high conversion efficiencies at 45 °C for methane production and 70 °C for carbonate fixation at atmospheric pressure. Conversion of 31 % and 89 % were achieved for the photocatalytic CO 2 reduction and the carbonate fixation, respectively. FT-IR spectra confirmed the functionalization of the material. Additionally, its organic/inorganic hybrid nature is complemented by excellent thermal stability, as studied by TGA. It enables repeated utilization, maintaining a 25 % catalytic activity for methane production and 70 % for carbonate fixation after the fourth reuse. This research highlights the potential of using naturally derived materials for sustainable CO 2 mitigation. [Display omitted] • Hybrid halloysite-kojic acid material efficiently catalyzes CO 2 conversion processes. • Copper ions offer a cost-effective alternative to other metals. • Converts CO 2 to methane under simulated sunlight at 45 °C and atmospheric pressure. • Fixes CO 2 into cyclic carbonates with epoxides at 70 °C. • Facile synthesis and excellent thermal stability enhance practical utility. [ABSTRACT FROM AUTHOR]

The cycloaddition reaction of CO 2 with epoxides such as limonene epoxide (LE) to form cyclic carbonates is considered a promising alternative for reducing CO 2 emissions. In this work, CO 2 fixation on LE to produce cyclic carbonates was carried out over Zn/SBA-15 with tetrabutylammonium bromide (TBAB) as co-catalyst and over NH 3 X-Zn/SBA-15 (X= Cl, Br, or I) catalysts. The catalysts were characterized by FT-IR, XRD, N 2 adsorption–desorption isotherms, TEM, NH 3 -TPD, XPS, TGA and Py-FTIR. The Zn/SBA-15 support mainly presents Lewis's acid sites of medium acidity; the surface area was 512 m2/g and 378 m2/g and the pore size were 9 nm and 7.2 nm, for Zn/SBA-15 and NH 3 Cl-Zn/SBA-15, respectively. The functionalization of Zn/SBA-15 was verified by FTIR, UV-vis, and XPS analysis. It was found that when Zn/SBA-15 was used as catalyst that reaction time had a significative effect on LE conversion and in the case of limonene carbonate selectivity, co-catalyst concentration variation had the main effect. Zn/SBA-15 catalyst can be reused up to 5 times without significant changes neither in conversion nor in limonene carbonate selectivity. The best LE conversion and limonene carbonate selectivity was 33% and 93%, respectively (1 M LE, 200 mg Zn/SBA-15, 7% TBAB; 30 bar, 18 h, 700 rpm and 20 mL diethyl carbonate). The reported catalytic system is a promising system for obtaining limonene carbonate using a heterogeneous catalyst. [Display omitted] • Heterogeneous catalysts for the carbonation reaction of limonene epoxide and CO 2 • Reaction time had a significative effect on limonene epoxide conversion. • Limonene carbonate selectivity was significantly affected by cocatalyst concentration. • Limonene carbonate is selectively obtained over Zn/SBA-15 with TBAB as cocatalyst. • Zn/SBA-15 can be reused up to five times for limonene carbonate synthesis. [ABSTRACT FROM AUTHOR]

We report on the metal-free and rapid catalytic conversion of carbon dioxide into cyclic carbonates under solventless conditions utilizing novel bifunctional fluoroalcohol-based ionic liquids (FBILs) as catalsyts. In the presence of 2.5 mol% 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl) phenyl trimethylammonium iodide (FBIL-1), under 0.1 MPa and 90 °C, excellent yield of propylene carbonate(>95%) was achieved in 1 h, which significantly shortens the reaction time, compared with the conventional catalysts. DFT calculations reveal that FBILs with fluorine-substituted hydroxyl groups exhibit stronger hydrogen bonding with epoxides compared to ILs lacking fluorine substitutions. The hydrogen bond length for ILF/PO is 1.658 Å, shorter than that for IL/PO (1.813 Å). This characteristic contributes to reducing the activation energy for the ring-opening reaction of epoxides. In the ILF/PO system, the reaction barrier is 88.72 kJ·mol−1, lower than the 101.46 kJ·mol−1 barrier for IL/PO, allowing the former to more rapidly facilitate the fixation of carbon dioxide into cyclic carbonates. Besides high catalytic efficiency, these FBILs have the characteristics of a facile synthesis route and easy post-reaction recovery. [Display omitted] • Novel fluoroalcohol-based bifunctional ILs with potent hydrogen bond donors were prepared. • Cyclic carbonates can be obtained with high yield quickly under mild conditions. • These ILs catalyze cyclic carbonate formation faster than similar catalysts. • The fluoroalcohol groups on ILs promote rapid ring-opening of epoxides through strong hydrogen bonding. [ABSTRACT FROM AUTHOR]

• Luffa sponge-supported dendritic imidazolium ionic liquid heterogeneous catalysts with high ionic density were prepared. • A series of cyclic carbonates have been efficiently synthesized in high yields (84–99 %) under mild reaction conditions. • There was a positive dendritic effect on the yields of cyclic carbonates. • Cyclic carbonates could be prepared on a multigram scale. Efficient using of green heterogeneous catalysts from renewable natural sources through chemical modification for the cycloaddition of terminal epoxides with CO 2 is attractive but still challenging. Luffa sponge is a cheap, biodegradable, abundant and renewable source with netting-like three-dimensional porous structure. Herein, we report a simple and facile approach to the preparation of a series of novel luffa sponge-supported dendritic imidazolium ILs heterogeneous catalysts LS-DIL-(G1-G3) with high ionic density from natural luffa sponge fibers. LS-DIL-(G1-G3) were properly characterized by FT-IR spectroscopy, TGA, elemental analysis, and SEM. Among them, LS-DIL-G3 was found to exhibit the highest catalytic activity for the synthesis of cyclic carbonates under metal-free and solvent-free conditions. It was clearly observed that there was a positive dendritic effect on the yields of cyclic carbonates. Furthermore, a wide range of terminal epoxides was converted smoothly to the corresponding cyclic carbonates with high yields (84–99 %). LS-DIL-G3 could be reused for up to six consecutive runs without any obvious decline in catalytic activity. Importantly, the desired cyclic carbonates could be prepared on a multigram scale by using LS-DIL-G3 as a green heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

• Dicationic ionic liquids (DILs) were studied in the cycloaddition of CO 2 to epoxides. • Some of the bromide DILs were partially soluble in model epichlorohydrin. • Solubility issues were overcome by adding 20 mol% of epichlorohydrin carbonate. • Bromide DILs displayed a pseudo-first order kinetic. The cycloaddition of CO 2 to epoxides has attracted a great deal of interest in recent years as an atom efficient way to employ this greenhouse gas as a useful C1 building block. While several ionic liquids have been tested as catalysts for the reaction, little attention has been devoted to dicationic ionic liquids (DILs). Herein, the catalytic activity of a panel of structurally-related DILs has been evaluated in the cycloaddition of CO 2 to epichlorohydrin, in order to study the influence of the DILs' structure on their activity. The solubilities of a series of bromide DILs in epichlorohydrin, featuring various linker lengths and imidazolium substituents, were investigated. The bromide C n (MIM) 2 series displayed a limited solubility in this medium, which particularly affected the performances of C 3 (MIM) 2 2Br. However, the addition of 20 mol% of reaction product to the reactants was found to be an effective way to overcome this issue. This way, it was possible to compare the catalytic activity of both soluble and only partially soluble systems in epichlorohydrin. C 6 (MIM) 2 2Br and C 5 (HIM) 2 2Br were found to be the best performing DILs and have been tested, together with monocation C 4 MIM Br, also on less reactive epoxides. Mono and dicarboxylate (D)ILs instead proved to be less active than the bromide DILs and, when considering their synthesis, thermal stability and moisture sensitivity, ultimately less attractive for the development of future catalysts. Finally, a convenient and operationally simple way of recovering and reusing the bromide DILs at the end of the reaction was also evaluated. [ABSTRACT FROM AUTHOR]

• Investigation of the role of SBA-15 silica on NBu 4 X reactivity. • Rate enhancement is entropically driven through preorganization at the pore surface. • Confinement effect led to improved activity. • Activity promotion applicable to a broad substrate scope. The conversion of CO 2 into cyclic carbonates in the presence of epoxides is one of the most promising methods to valorize this important C 1 building block. Tetrabutylammonium halide salts are known to catalyze this reaction with moderate activity, and often a co-catalyst is added to increase efficiency. Herein, the influence of the addition of ultra-large pore SBA-15 silica on the catalytic activity of tetrabutylammonium halide salts for this reaction has been investigated in detail. Whereas a negative effect of silica was observed for the NBu 4 Cl catalyst, surface silanols were shown to strongly improve the yield of the reaction when NBu 4 Br and NBu 4 I were used as catalysts. The catalytic activity of the NBu 4 I salt could be increased by a factor of ten when a relevant amount of mesoporous silica was added. This latter catalytic system leads to high yields and selectivity for a wide variety of substrates under mild condition (80°C). Measurement of the activation parameters demonstrated that the rate enhancement is entropically driven: the pre-organization of the reactants and catalyst on the surface leads to a marked decrease of the activation energy of the reaction. A direct comparison between yield improvement induced by the addition of either an amorphous or a mesostructured silica highlights the crucial role played by the shape and concavity of the support. [ABSTRACT FROM AUTHOR]

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. [Display omitted] ● Valorization of cooking vegetable oils for the preparation of polymers such as non-isocyanate polyurethanes (NIPUs). ● Highly active metal-free catalysts for the carboxylation of epoxides with CO 2 under solvent-free conditions. ● The catalyst is efficient, inexpensive, and recyclable. [ABSTRACT FROM AUTHOR]

A novel approach is reported to prepare 3D-printed polymers that incorporate metal-organic frameworks (MOFs) through a one-pot growth process, involving covalent grafting and growth onto 3D polymeric surfaces. The resulting hybrid materials were subjected to comprehensive characterization using techniques such as SEM, XRD, FTIR, Raman, and XPS. The findings demonstrated an excellent dispersion of the inorganic units on the polymer matrix while preserving their metal-organic structure. The hybrid materials exhibited the presence of Lewis acid and basic groups within the MOF. The catalytic performance of these hybrid materials was evaluated in the mild cycloaddition reaction of carbon dioxide (CO 2) to epoxides. Notably, the polymers incorporating UiO-67 MOFs displayed remarkable activity, even at low CO 2 pressures and in the absence of auxiliary co-catalysts or additives. The catalytic activity of these hybrid materials exhibited a significant improvement, up to two orders of magnitude higher than analogous bulk MOFs. This observation highlights the superior performance of the 3D-printed polymer/MOF hybrids in this catalytic transformation. • The surface of 3D-printed polymers allowed the growth of MOF-like active phases. • The study of the MOF-polymer interface is done by FTIR, XRD, SEM, Raman, and XPS. • Varying degrees of defects in MOFs are found depending on the growth method. • Compared to bulk MOFs, catalytic activity is increased two orders of magnitude. [ABSTRACT FROM AUTHOR]

Graphical abstract B 2 O 3 was found as an effective metal-free heterogeneous catalyst for the chemical fixation of CO 2 with epoxides. The Lewis acidic "boron" site on B 2 O 3 is essential to promote the ring opening process of epoxides. Highlights • B 2 O 3 was reported as an effective metal-free catalyst for the utilization of CO 2 with epoxides to produce COCs. • Ball milling could enhance the catalytic activity of B 2 O 3 by increasing the adsorption capacity to propylene oxide substrate. • Lewis acidic boron sites of B 2 O 3 are the dominated active sites rather than B-O H. • The ring-opening process of epoxides over B 2 O 3 was tracked by using in situ DRIFT. Abstract Boron trioxide (B 2 O 3), a common and easily available boron oxide, was first reported as an effective metal-free heterogeneous catalyst for the chemical fixation of CO 2 with epoxides to produce cyclic organic carbonates (COCs). The ball-milling treatment of B 2 O 3 significantly enhanced the catalytic activity by increasing the adsorption capacity to propylene oxide substrate. In situ DRIFTS characterization indicated there was a ring opening process of epoxides on the surface of B 2 O 3 , which was induced by the boron sites from B 2 O 3. The recovery test of B 2 O 3 showed that it could be easily recycled and reused for 5 runs without a loss of activity. This kind of Lewis acid catalytic property of B 2 O 3 marks a rare case of a metal-free heterogeneous catalyst mimicking the metal-based catalysts for the COCs production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • C 2 v -symmetric metalloporphyrins were synthesized for the cycloaddition of epoxides and CO 2 at atmospheric pressure. • The catalytic performance is strongly dependent on their coordinated metal species of catalysts. • Detailed kinetic investigations were carried out by three catalysts. • A Lewis acid-base dual cooperative catalytic mechanism was carefully proposed. Abstract A series of C 2 v -symmetric diphenylporphyrin complexes containing a metal ion (Mg, Al, Mn, Fe, Co, Zn) have been synthesized and applied as catalysts for the solvent-free cycloaddition of epoxides and carbon dioxide under atmospheric pressure and mild temperature, in concert with phenyltrimethylammonium tribromide (PTAT) as a co-catalyst. The activity of these catalysts deeply relies on their coordinated metal species. [5,15-Diphenylporphyrin]manganese(III) chloride (DPP-MnCl) has been found to be the most effective catalyst under optimal reaction conditions. It's worth mentioning that the cycloaddition of phenyl glycidyl ether (GPE) and CO 2 proceeded successfully by DPP-MnCl /PTAT even at 25 °C and atmospheric pressure. Moreover, preliminary kinetic investigations of this cycloaddition were carried out by using catalysts DPP-MnCl , DPP-CoCl and DPP-Zn , revealing that the (phenoxymethyl)ethylene carbonate (PEC) formation with the lowest activation energy is catalyzed by DPP-MnCl. Furthermore, a Lewis acid-base dual cooperative catalytic mechanism has been carefully proposed in light of the catalyst systems and the experimental results. [ABSTRACT FROM AUTHOR]

Highlights • High yield (87%) trans -LO synthesis by stereoselective epoxidation of limonene. • 100% selective bio-based cyclic carbonate synthesis by CO 2 cycloaddition to LO. • 3-fold higher reaction rate using trans -enriched LO than commercial LO. • Determination of activation energy and thermodynamic activation parameters. • Proposed reaction mechanism is consistent with the experimental observations. Abstract Bio-derived cyclic carbonates are of significant research interest as building blocks for non-isocyanate polyurethanes (NIPUs). Cyclic carbonates from limonene are bio-renewable monomers for the production of fully bio-based polymers from citrus waste; however, there are currently very few reports on their synthesis. This work reports the synthesis of five-membered cyclic carbonates from bio-based limonene oxide (LO) and CO 2 catalysed by commercially available inexpensive, tetrabutylammonium halides (TBAX). The cycloaddition of CO 2 with commercial LO mixture of cis/trans- isomers (40:60) is highly stereoselective and the trans -isomer exhibits considerably higher conversion than the cis- isomer. Therefore, a stereoselective method of (R)-(+)-limonene epoxidation was performed to achieve a significantly higher yield of the trans -isomer (87 ± 2%) than cis- isomer, which leads to high conversion and yield to the corresponding cyclic carbonates. The catalytic effect of halide anions (X¯) and the influence of operational reaction parameters such as temperature, pressure, and catalyst amount were studied. High conversion (87%) was obtained after 20 h at 120 °C, 40 bar CO 2 using 6 mol% tetrabutylammonium chloride (TBAC) catalyst. A detailed study of the reaction kinetics revealed the reaction to be first-order in epoxide (LO), CO 2 and catalyst (TBAC) concentrations. Moreover, the temperature dependence of the reaction was studied using Arrhenius and Eyring equations. The activation energy (E a) of the reaction was calculated to be 64 kJ mol–1. The high positive value of Gibbs free energy (ΔG‡ = 102.6 kJ mol–1) and negative value of activation entropy (ΔS‡ = –103.6 J mol–1) obtained as result of the thermodynamic study, indicate that the reaction was endergonic and kinetically controlled in nature. [ABSTRACT FROM AUTHOR]

Graphical abstract A range of simple, cost effective and easily available metal carbamates was investigated for the first time in CO 2 catalysis; some earth abundant metal complexes promoted epoxide carbonation to cyclic carbonates with high yield and selectivity, under solventless and ambient conditions. Highlights • The conversion propylene oxide → carbonate is catalyzed by metal carbamates. • High conversion and selectivity are obtained at 25 °C and 1 atm of CO 2 pressure. • MCl 2 (O 2 CNEt 2) 2 reacts with silica through partial release of Cl− and carbamato ligands. • Heterogeneous catalytic systems are less efficient than the homogeneous counterparts. Abstract A series of previously reported homoleptic and non-homoleptic N,N -dialkylcarbamates of a range of non precious metals and N,N -dialkylcarbamate of Al(III) were investigated as easily available and inexpensive catalysts in the solventless synthesis of propylene carbonate (PC) from propylene oxide (PO) and CO 2. By operating at atmospheric CO 2 pressure at ambient temperature, excellent results were achieved using Ti(O 2 CNEt 2) 4, Al(O 2 CNR 2) 3 (R = Et, iPr), Cu(O 2 CNEt 2) 2 and Sn(O 2 CNEt 2) 4 , in combination with NBu 4 X (X = Br or Cl) as a co-catalyst. The reactions of MCl 2 (O 2 CNEt 2) 2 (M = Ti, Zr) with amorphous silica were straightforward through partial release of both chlorido and carbamato ligands, and readily afforded solid materials which were characterized by ICP-OES and EDS analyses, coupled to SEM. These heterogeneous catalytic systems revealed less efficient than the homogeneous counterparts. [ABSTRACT FROM AUTHOR]

The present work focuses on developing heterogeneous catalysts for conversion of CO 2 and mono-/di-epoxides to mono-/bis-cyclic carbonates. To achieve this purpose, two types of recyclable solid catalysts, namely polyurethane (PU-BTP) and polyurethane modified on silica gel-solid support (SG-AU-BPT), are synthesized. On these catalysts, the key promoter CaI 2 is pre-absorbed. Both catalysts show high catalytic activity under mild conditions. For example, phenyl glycidyl ether (PGE) can be converted to 4-(phenoxymethyl)− 1,3-dioxolan-2-one at 60 °C within 6 h under 1 atm pressure of CO 2. PU-BTP and SG-AU-BPT can be recollected by suction filtration and reused for eight times with conversion larger than 81% and 95% respectively. These results indicate that the degree of CaI 2 leaching out from the catalysts in each cycle and loss is low. ● Novel PU-BTP and SG-AU-BPT catalysts enable CO 2 and epoxide conversion. ● High activity at mild conditions: at 60 °C, 1 atm. ● High reusability: Catalysts remain efficient after 8 runs (>80%, >95%). ● Dual role of silica gel: Catalyst carrier and activity enhancer demonstrated. ● Versatile substrate scope: Efficient conversion of various mono-/di-/bio-epoxides showcased. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cyclic carbonates are made in one step from CO 2 and diols. • The method works at ambient temperature and 1 atm of CO 2 pressure. • No strong and moisture sensitive bases are needed, only common lab reagents. • Fifteen 5- to 8-membered cyclic carbonates were synthesised, including twelve known monomers and three novel compounds. • Six 7- and 8-membered cyclic carbonates were made for the first time using CO 2. Abstract 6-, 7- and 8-membered ring cyclic carbonates are of particular interest as monomers for ring-opening polymerisation towards more sustainable polymers. They are traditionally synthesised from diols and phosgene derivatives, and while alternative CO 2 methods exist to make 5- and 6-membered cyclic carbonates, there is no report of the synthesis of 7- and 8-membered cyclic carbonates made directly from CO 2. Herein we report an efficient one-pot synthesis of cyclic carbonates which uses diols, CO 2 , tosyl chloride and mild bases (NEt 3 or TMP), under ambient temperature and 1 atm of CO 2 pressure. Fifteen cyclic carbonates were synthesised, including twelve known monomers, and the first examples of 7- and 8-membered cyclic carbonates made using CO 2. [ABSTRACT FROM AUTHOR]

N,N,N -tributyl- N -propylammonium iodide-functionalized mesoporous silicas (SBA-15 and a silica gel) proved to be efficient, robust and reusable catalysts for the solvent-free synthesis of cyclic carbonates (CCs) from epoxides and CO 2 . The reusability of the catalysts was found to be dependent on the nature of the support and the substrate. In the presence of 1,2-epoxybutane (1,2-EB) as substrate, the SBA-15-based catalyst (PHS-1) exhibited a constant catalytic activity for five reaction cycles (yield > 96.0%) under mild conditions (1.0 MPa CO 2 , 100 °C and 4 h). Conversely, in the presence of styrene oxide, a gradual decrease in yield was observed. Based on textural properties and 13 C CP-MAS NMR measurements, such decline was attributed to the adsorption of solid reaction product (styrene carbonate - SC) on the catalyst surface. Using a chromatographic silica gel as support and an improved catalyst recovery step gave rise to a highly efficient, robust and fully reusable catalyst (PHS-2) for the synthesis of CCs. Notably, PHS-2 led to a 33–50% decrease in reaction time, and maintained an excellent and steady catalytic activity over 5 cycles in the synthesis of SC (yield > 96% and selectivity > 97%). The amount of trapped solid SC product on PHS-2 surface was also significantly reduced. [ABSTRACT FROM AUTHOR]

Porous aromatic polymers functionalized with ethylenediamine (CBAP-1(EDA)) and then complexed with Zn 2+ or Co 2+ ions (CBAP-1(EDA-Zn)) and (CBAP-1(EDA-Co) were synthesized and applied as a catalyst for the solventless synthesis of cyclic carbonates from CO 2 and epoxides. The properties of the catalysts were examined by various analytical techniques. CBAP-1(EDA) alone enabled the high catalytic conversion of epoxides (>98%) to five-membered cyclic carbonates at 130 °C under solvent-, metal-, and co-catalyst-free conditions with high selectivity. The catalytic activity of CBAP-1(EDA) was enhanced in the presence of a nucleophile and Lewis acidic metal ion sites. Thus, CBAP-1(EDA) with tetrabutylammonium bromide (TBAB) had shown 98% conversion of epoxide at 80 °C and 1 MPa CO 2 in 8 h, whereas CBAP-1(EDA-Zn) and CBAP-1(EDA-Co) with TBAB achieved 96% epoxide conversion in 36 h at room temperature (RT). The stability of the catalysts was confirmed by hot-filtering and reusability tests, which demonstrated that the catalysts could be reused for up to five consecutive runs without any noticeable decline in catalytic activity. The synergism between the basic catalytic sites in CBAP-1(EDA) and TBAB and the Lewis metallic sites was explained by the proposed reaction mechanistic pathway covering both high temperature (metal- and halogen-free) and RT conditions (with metal and halogen). [ABSTRACT FROM AUTHOR]

In the present study, the dual amino-functionalised imidazolium ionic liquids of 1-(3-aminopropyl)-3-butylimidazolium glutamic acid [APbim][Glu], 1-(3-aminopropyl)-3-butylimidazolium aspartic acid [APbim][Asp], 1-(3-aminopropyl)-3- butylimidazolium glycine [APbim][Gly], have been synthesized and characterized by 1 H NMR, 13 C NMR spectroscopy and IR spectroscopy. The synthesis of cyclic carbonate by cycloaddition reaction of CO 2 and various epoxides catalyzed by dual amino-functionalized imidazolium ionic liquids, was carried out under no additional organic solvent required and halogen free condition. Simultaneously, the influence of anion type, catalyst dose, reaction temperature, reaction time and CO 2 pressure on the yields of cyclic carbonates was examined. The dual amino-functionalized imidazolium ionic liquids possess good yields and selectivity and provide a reasonably environmentally benign and recycled chemical process. [ABSTRACT FROM AUTHOR]

A newly Zn-doped ZIF-67 has been synthesized in water at room temperature for the first time without the aid of any organic solvent. The textural and physical properties of the material were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), N 2 adsorption-desorption, scanning electron microscopy (SEM) and ICP-AES. The catalyst showed quantitative conversions and selectivity for the synthesis of cyclic carbonates starting from epoxides and carbon dioxide. Compared with different reported MOFs as heterogeneous catalysts used for the cycloaddition of carbon dioxide to epoxides, this catalyst outperforms all the reported ones till now. The coupling reaction was studied at different pressures and temperatures applying different epoxide substrates. Additionally, no co-catalyst and solvent were required to obtain excellent conversions. The heterogeneous nature of the catalyst was maintained at least up to four catalytic cycles with a slight loss of activity. [ABSTRACT FROM AUTHOR]

A variety of zero-valent molybdenum complexes and divalent molybdenum complexes with N -heterocyclic carbenes (NHC)-pyridine ligands were synthesized, and their catalytic activities and performances in the cycloaddition reaction of epoxides and carbon dioxide (CO 2) were investigated. It was found that the divalent molybdenum complexes show high catalytic activity in the synthesis of cyclic carbonates from epoxide and CO 2 in comparison with zero-valent molybdenum complexes. The divalent molybdenum complexes combined with tetrabutylammonium iodide (TBAI) can effectively transform various terminal epoxides and internal epoxides under 30–80 ℃ and 5–10 bar of CO 2 pressure. The mechanic experiments by FT-IR and HRMS spectrometry reveal the reaction pathway of binary system in combination of divalent molybdenum complexes with TBAI. [Display omitted] • A series of zero-valent and divalent molybdenum complexes were synthesized. • Divalent molybdenum complexes show higher activity than zero-valent complexes in synthesis of cyclic carbonates. • Synergetic catalytic mechanism of divalent molybdenum complexes with TBAI is elaborated. [ABSTRACT FROM AUTHOR]

Six ionic liquids-functionalized metallophorphyrins have been designed, prepared and characterized by NMR, MS and elemental analysis. They were applied as efficient bifunctional catalysts to the cycloaddition of epoxides and carbon dioxide without additive and organic solvent yielding cyclic carbonates. 5,15-Di[4-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide ( JB p ) and 5,15-di[3-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide ( JB m ) have been demonstrated excellent activities under optimized conditions. It has been found that both the structure of porphyrin complex cations and the anion moieties would strongly affect their catalytic performance. The catalysts were versatile for the cycloaddition of CO 2 to various terminal epoxides in satisfying yields with excellent selectivities. Moreover, phenoxypropylene carbonate was able to be obtained under atmosphere pressure of CO 2 and in large-scale. Furthermore, a plausible mechanism involving Lewis acid-base synergistic catalysis has been proposed according to our experimental results. [ABSTRACT FROM AUTHOR]

Efficient synthesis of cyclic carbonates from olefins using K 2 S 2 O 8 as oxidant and NaBr as “bromination” reagent has been developed through a reaction sequence involving hydroxybromination of olefins and subsequent carboxylation of the bromohydrin in situ generated with CO 2 . This process provides a novel and convenient access to cyclic carbonates in a one-pot stepwise fashion. Representative olefins with different functional groups could react smoothly under relatively mild (3 MPa, 60 °C) and transition metal-free conditions to afford various cyclic carbonates. [ABSTRACT FROM AUTHOR]

With the continuous emission of greenhouse gases, the rational transformation and utilization of CO 2 is particularly important. Cyclic carbonates are a kind of versatile compounds and have wide applications in Li-ion batteries, pharmaceutical manufacturing and many fine chemicals. Cycloaddition of CO 2 and epoxide to synthesize cyclic carbonates is considered one of the most promising CO 2 conversion routes because of its 100% atomic economy, non-toxicity, as well as a more economic technical route for the utilization of CO 2. In this paper, this review surveys the synthesis of cyclic carbonates employing CO 2 as a building block. The mechanisms of CO 2 activation have been described in detail due to the thermodynamic stability of CO 2 molecule. The reaction mechanism of CO 2 and epoxide is expounded, and seven CO 2 activation methods are summarized and compared, deeply analyzing the research progress of recent years. To reduce the activation energy of the CO 2 conversion, the utilization of catalysts is very crucial. Various types of catalysts suitable for the synthesis of cyclic carbonates derived from CO 2 have been expounded in depth. Finally, the development trend of catalysts is prospected. The development of improved catalysts is strongly demanded for successful commercialization of CO 2 transformation technologies. This review enables researchers to timely seize the current advancements and thus may provide some rewarding insights for future investigations on the synthesis of cyclic carbonates employing CO 2 as the feedstock. It will provide a good reference and guide for scholars to achieve the better improvements. [Display omitted] • The advantages of CO 2 conversion to cyclic carbonates are described. • The most representative mechanism of CO 2 activation is summarized. • The future development trend is obtained by comparing various catalysts. • The performance of very promising catalysts is described in detail. [ABSTRACT FROM AUTHOR]

The styrene oxide to styrene carbonate conversion performed in CO 2 atmosphere, herein selected as a case study, was implemented in microdroplets (aerosol) reactions at the preparative scale (3.5 mmol of the starting material) and mild conditions (1 atm CO 2 pressure), within a custom-made ultrasonic nebulization reactor. Upon optimization of the promoter stoichiometry (1 eq of 4.3 TEG/KI ratio) and methanol (MeOH) dilution (7.5 mL of 2.5 v/v MeOH/TEG), performances under mass transfer-limited conditions of this novel methodological paradigm have been compared at 25 °C and 50 °C with those implemented as: a) no-stirred, b) stirred, and c) sonicated bulk reactions. Complete selectivity and an apparent acceleration factor (AAF) of 1.9 was registered at both temperature for microdroplets reactions in respect with the sonicated counterparts, these latter performing better than the other bulk reactions. These significative efficiency improvements, candidate aerosol reactions as a preferred process intensification approach in the realm of effective CO 2 -utilization strategies and, in general, in the development and exploitation of gas-liquid two-phase reactions. [Display omitted] • Twofold rate acceleration in the direct carbonation of styrene oxide. • Aerosol as an innovative methodological paradigm in biphasic gas-liquid reactions. • Custom-made ultrasonic nebulization reactor for improved performances. [ABSTRACT FROM AUTHOR]

A novel process for efficient conversion of CO 2 to cyclic carbonates under atmospheric pressure in the absence of solvents has been achieved by using cheap and readily available multiple-amine material (PS-PEI) as a catalyst. As a metal-free catalyst, PS-PEI showed excellent catalytic activity and CO 2 absorption capacity. PS-PEI can participate in the cycloaddition of a variety of epoxides and CO 2 with high yields. The structure and catalytic performance of this polymer material do not change significantly after being recycled four times. Based on the results of experiments and characterization, a possible mechanism was proposed, in which the collaboration of amine groups and chloride ion promotes the efficient activation of CO 2 and epoxides. Moreover, the effect of various reaction parameters, temperature, catalyst dosage, and reaction time were investigated to optimize the reaction conditions. [Display omitted] • 95% yield of chloropropane carbonate could be achieve for 14 h under ambient reaction conditions without any metal, solvent and co-catalyst. • PS-PEIs preparation method is simple and promising for industrial production. • The multisite synergistic activation of epoxide is adjusted by varying the ratio between the NH 2 and Cl-. [ABSTRACT FROM AUTHOR]

A new family of dinuclear chromium complexes bearing thioether-triphenolate ligands has been developed for the cycloaddition of CO 2 with epoxides. The catalytic systems resulting from the combination of complexes 1–3 with tetrabutylammonium chloride (TBAC) show high activity and selectivity for the synthesis of cyclic carbonates with a broad range of substrates including terminal and internal epoxides. Notably, in the case of epichlorohydrin, a TOF up to 4650 h-1 (120 °C, 2 MPa) was recorded, showing one of the highest activity for chromium complexes. In the case of internal epoxides, the reaction proceeds with the retention of the substrate configuration highlighting that the mechanism proceeds through two consecutive S N 2 reactions. [Display omitted] • Three dinuclear chromium complexes were synthesized and showed high performance in the synthesis of organic carbonates from CO 2 /epoxides. • Terminal epoxides are converted with good activity with TOF up to 4650 h-1. • Internal epoxides are converted to the corresponding cyclic carbonates with retention of configuration. [ABSTRACT FROM AUTHOR]

A zeolitic imidazolate framework possessing LTA topology is investigated for its catalytic potential in the synthesis of cyclic carbonates from CO 2 and epoxides. The synthesized ZIF-22 was chemically and thermally stable and was analyzed using multiple physico-chemical characterizations such as XRD, FT-IR, FE-SEM, XPS, TGA, ICP-OES and EA. ZIF-22 was found to afford excellent heterogeneous catalysis with high turnover frequencies (TOF) and selectivity, outperforming the activities exhibited by the previously reported ZIF catalysts. Parameter studies were carried out with various temperature, CO 2 pressure, catalyst amount and reaction time and the catalyst was found to have reusable properties over three times with negligible or no loss in catalytic activity. [ABSTRACT FROM AUTHOR]

a series of different substituents-modified C 2 v -symmetric cobaltoporphyrin complexes have been designed, synthesized and applied as efficient catalysts in conjunction with tetrabutylammonium iodide (TBAI) for the cycloaddition of epoxides and carbon dioxide. The porphyrin skeleton architectures with steric and electronic variation would deeply affect their catalytic performance. [5,15-Di(4-methoxyphenyl)porphyrin]cobalt(III) chloride (c-1) is the most effective catalyst under optimal reaction conditions. Foundational kinetic study results catalyzed by catalysts c-1 , c-2 , c-3 and c-4 reveal that the catalytic performance of electron-donating group-modified cobaltoporphyrin is better than it of electron-withdrawing group-modified ones, and high steric hindrance has a minor negative impact to its catalytic performance. [Display omitted] • Efficient C 2 v -symmetric metalloporphyrin catalysts were synthesized for the cycloaddition of epoxides and CO 2. • The catalytic performance is strongly dependent on the porphyrin skeleton with steric and electronic variation. • Detailed kinetic investigations were carried out by four catalysts. [ABSTRACT FROM AUTHOR]

Cyclic carbonates are key compounds with a large scope of applications. Their one-pot synthesis from cheap and available alkenes using CO 2 and oxidants has gained great attention from an economic perspective. Furthermore, their synthesis under relatively low temperature and CO 2 pressure with various oxidants such as alkyl peroxides, H 2 O 2 and O 2 could lead to an increasingly sustainable preparation route. Over the last two decades, some advances have been made in the development of catalytic systems affording the reaction of CO 2 with epoxides under progressively milder conditions which is a prerequisite for the whole process. This review covers the state of art of the one-pot synthesis of cyclic carbonates from alkenes, mainly styrene, CO 2 and oxidants with a focus on catalysts working under moderate temperature and low CO 2 pressure in the presence of green reagents such as O 2 and, to a lesser extent, H 2 O 2. Procedures leading to a step economic pathway will be especially emphasized. Catalytic systems involving the two steps leading to an oxidative carboxylation of alkenes (i.e. auto-tandem vs. orthogonal catalysis or one-pot catalysis) are key issues that will be addressed in this review. • This manuscript is a review on the formation of cyclic carbonates from alkenes, CO 2 and oxidants. • Procedures leading to a step economic pathway were especially emphasized. • We focused on catalytic systems with low temperature and CO 2 pressure and/or using green reagents. [ABSTRACT FROM AUTHOR]

Developing highly efficient, cost-effective and robust heterogeneous catalysts for carbon dioxide (CO 2) fixation into valuable chemicals plays an essential role in carbon emissions reduction. Herein, a family of novel and bifunctional hypercrosslinked polymers, which consist of amide groups (-CONH-) as hydrogen bond donors (HBDs) and Br¯ as nucleophiles, were developed for metal- and co-catalyst free cycloaddition of CO 2 to epoxides. The incorporation of amide units into the polymeric networks not only provided active sites for synergistic activation of epoxides, but it also enhanced their swelling abilities toward epoxide substrates. As a result, the optimal catalyst exhibited high catalytic performance towards the cycloaddition of CO 2 and epoxide to cyclic carbonate, the catalytic activity was comparable to those of the homogeneous analogues and outperformed most of the metal-free polymeric catalysts previously reported. Experimental and density functional theory (DFT) investigations suggested that excellent activity of the catalyst stemmed from the synergistic effect between amide HBDs and Br¯ nucleophiles, as well as its excellent swelling ability toward epoxides. Additionally, the catalyst exhibited excellent structural stability and could be reused at least 10 times without significant activity loss. The present work not only highlights a versatile HBD to construct efficient and robust solid catalysts for CO 2 fixation, but also paves the way to boost the performance of polymeric catalysts by engineering their swelling abilities toward reactant molecules. [Display omitted] • Amide-functionalized organic cationic polymer was facilely prepared by a one-pot method. • Incorporation of amide units endows the polymer with HBDs and excellent swelling ability. • The optimal catalyst exhibited high catalytic performance for CO 2 cycloaddition. • Synergism of dual active sites and excellent swelling property led to high catalytic activity. [ABSTRACT FROM AUTHOR]

As a bioinspired metal-organic framework (MOF) with a unique trigonal pyramidal Cu(I) site in a bowl-shaped pocket, Cu(I)-MFU-4 l has emerged as an advanced single-site heterogeneous catalyst for several important reactions. Herein, we computationally investigate Cu(I)-MFU-4 l combining with tetrabutylammonium bromide (TBAB) as a high-performance catalyst for CO 2 conversion with propylene oxide (PO) into propylene carbonate (PC), a reaction of great significance in achieving carbon neutrality and sustainable development. Four paths are proposed depending on the initial activation of either PO or CO 2 by Cu(I), as well as the ring-opening of PO at C α -O bond or C β -O bond. Density functional theory calculations over a large cluster model reveal that Cu(I) is prone to interact with PO first and the most favorable path (Path 3) involves the sequential ring-opening of PO at C β -O bond, CO 2 insertion and ring closure with Gibbs energy barriers of 8.0, 2.8 and 10.3 kcal/mol, respectively. In view of such low energy barriers, Cu(I)-MFU-4 l /TBAB is predicted to be highly active for CO 2 cycloaddition with PO at ambient conditions. Significant confinement effect is demonstrated in Cu(I)-MFU-4 l by comparing Path 3 over both large and small cluster models. The observed confinement not only stabilizes the intermediates and transition states thermodynamically, but also promotes the ring-opening of PO kinetically, which is mainly attributed to the van der Waals (vdW) interactions between reactive fragments and surrounding frameworks through non-covalent interaction (NCI) analysis. A mechanism of electronic effect competing with steric effect is proposed to rationalize the regioselectivity of ring-opening of PO under different scenarios via natural bond orbital (NBO) charge and NCI analysis. Our results also suggest that Cu(I)-MFU-4 l /TBAB outperforms Cu(II) paddle-wheel MOFs/TBAB reported previously for CO 2 cycloaddition with PO. The structural robustness, the soft electron-rich Cu(I) site and the inherent confinement promote Cu(I)-MFU-4 l to be an appealing candidate catalyst for a wide range of reactions. [Display omitted] • Cu(I)-MFU-4 l /TBAB is computationally predicted to be highly active for CO 2 cycloaddition under ambient conditions. • Significant confinement is demonstrated and the importance of the environment beyond active site is highlighted. • Electronic effect competes with steric effect to dominate the regioselectivity of ring-opening of epoxides. • Cu(I)-MFU-4 l /TBAB outperforms Cu(II) paddle-wheel MOFs/TBAB for CO 2 cycloaddition with propylene oxide. [ABSTRACT FROM AUTHOR]

A sulfonic acid tethered mesoporous silica material (SBA-15-SO 3 H) was successfully synthesized and characterized using SAXS, N 2 physisorption studies, TEM, EA and XPS. This metal-free heterogeneous catalyst with terabutyl ammonium bromide (TBAB) co-catalyst was found to be an efficient catalyst system for styrene carbonate synthesis from CO 2 and styrene oxide. The synergistic mechanistic pathways of SBA-15-SO 3 H with TBAB have been explained by hydrogen bond interactions and nucleophilic effects. A turn over number of 920 was obtained at mild reaction temperature of 80 °C. The catalyst was thermally stable and reused for five times without loss of any significant activity. [ABSTRACT FROM AUTHOR]

Soluble tetrabutylammonium ferrates, [TBA][FeX 3 Y] (TBA = n Bu 4 N) were synthetized by treating ferric salts (FeX 3) with tetrabuthylammoniom halides. Their activity as a stand-alone catalyst in CO 2 cycloaddition reactions to epoxides was assessed under solvent free and quite mild reaction conditions (CO 2 pressures between 0.4 and 0.8 MPa) and TOF up to 428 h-1 (T = 150 °C) were observed. Good yields of cyclic organic carbonates were obtained, especially with terminal epoxides, without the need of any Lewis base as co-catalyst, with a broad reaction scope. A scale-up reaction on 5 mL of styrene oxide was performed and the robustness of the catalyst was proved up to three recycles in the case of propylene oxide (TON = 594). To shed light on the reaction mechanism, an extensive set of theoretical calculations has been carried out. Iron salts almost annihilate the barrier for the epoxide ring opening and stabilize the first reaction intermediate. Along the same reaction path, chloride proved to be more effective as nucleophile than bromide, and preferentially attacks on the more hindered carbon atom. On the other hand, when no Lewis acid (LA) is present, the rate determining step of the reaction becomes the ring opening of the epoxide. A tight correlation with experimental results was observed. Smart ammonium ferrates, [TBA][FeX 3 Y] , as stand-alone catalyst for the transformation of epoxides and CO 2 into cyclic organic carbonates. [Display omitted] • Very simple ammonium ferrates with activity in the CO 2 cycloaddition to epoxides. • No need for a co-catalyst (Lewis base). • High conversions and selectivities under solvent-free and quite mild reaction conditions. • TOF up to 428 h-1 and TONs up to 594. • An extensive set of theoretical calculations has been carried out highlighting the bifunctional nature of the catalyst. [ABSTRACT FROM AUTHOR]

Fixation of CO 2 with epoxides to generate cyclic carbonates is an essential reaction. The co-catalysts free catalytic conversion of CO 2 without metals and solvents is still challenge. Herein, a new series of quaternary ammonium immobilized polyamidoamines (PAMAMs) with hydroxylamino groups were fabricated from reaction of third generation PAMAM dendrimer with glycidyl alkyl dimethylammonium bromide originated from varied tertiary amine with epibromohydrin, which were characterized by FT-IR, TGA, 1H NMR, SEM and XPS, and CO 2 adsorption was also observed. These polymers were considered as efficient catalyst for CO 2 fixation reaction in the absence of co-catalysts and solvent conditions. Catalytic performances demonstrated that the introduced alkyl groups connected on polymers backbone exhibited crucial effect on catalytic activity, especially, [G 3 -PAMAM-HADMAB-C n ]Br could effectively catalyzed CO 2 fixation with various epoxides under optimized conditions, and corresponding cyclic carbonates can reached at excellent yields. Furthermore, a proposed catalytic mechanism was elucidated on the experimental results and density functional theory (DFT), which indicates that hydrogen bonding play a significant role in activating epoxide and CO 2. [Display omitted] • The hydroxylamino quaternary ammonium PAMAMs with alkyl-chain terminals were frabricated. • The functionalized PAMAMs were applied to CO 2 fixation and high cyclic carbonate conversion was obtained. • The synergistic mechanism has been proved in terms of experimental results and DFT. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hybrid materials easily prepared through 100 % atom economical radical polymerization. • The copolymeric network covers the whole surface of the carbon nanotubes. • Enhanced catalytic activity of the nanotube-supported material compared to the unsupported one. • Synergism of the catalytic sites (Al3+ and Br− ions) due to their forced close proximity in the final hybrid material. The increased awareness of the catastrophic consequences caused by the accumulation of greenhouse gases into the atmosphere has generated a large mobilization aimed at CO 2 mitigation. Herein, in the spirit of the transformation of a waste as CO 2 into value added products, we propose an efficient preparation of two different hybrid systems based on aluminum chloride tetrastyrylporphyrin (TSP-Al-Cl) and 1,4-butanediyl-3,3′-bis-1-vinylimidazolium dibromide copolymerized in the presence (MWCNT-TSP-AlCl-imi) and in absence (TSP-AlCl-imi) of multi-walled carbon nanotubes (MWCNTs) for the CO 2 utilization in the synthesis of cyclic carbonates. The so-prepared materials have been thoroughly characterized by means of several spectroscopic and analytical techniques. The MWCNT-TSP-AlCl-imi heterogenous catalyst enabled the highly efficient chemical transformation of CO 2 and epoxides into cyclic carbonates with high turnover number (TON) and frequency (TOF) values at low temperature down to 30 °C in solvent-free conditions. MWCNT-TSP-AlCl-imi proved to be a very stable and reusable heterogeneous catalyst in consecutive cycles without the need of any reactivation procedure and no leaching phenomena. Furthermore, the optimal morphology of MWCNT-TSP-AlCl-imi, with the crosslinked polymer uniformly distributed onto MWCNTs backbone, resulted in a more active catalyst with a TON double than the unsupported one. The enhanced activity of MWCNT-TSP-AlCl-imi can be ascribed to its higher surface area that permits fully accessible catalytic sites. Interestingly, MWCNT-TSP-AlCl-imi also showed a catalytic activity comparable to a reference homogeneous catalytic system, proving that synergism occurred between the metal centers and the nucleophilic sites due to their close proximity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Triethanolamine borate (TEOAB) was as efficient bifunctional catalyst for the cycloaddition of CO 2 with epoxides. • Most cyclic carbonates can be obtained in quantitative yields and high selectivity (99 %). • The catalyst can be easily separated from the product by water washing. Triethanolamine borate (TEOAB) possessing Lewis pair is an environmentally friendly, nontoxic, cheap and water-soluble catalyst for the cycloaddition of CO 2 with epoxides under solvent-free condition. Due to the synergistic effect of Lewis pair, TEOAB exhibits excellent catalytic activity and selectivity (99 %). The catalytic activity can be further improved by using TBAB as co-catalyst. Most cyclic carbonates can be obtained in quantitative yields and can be purified by water washing. [ABSTRACT FROM AUTHOR]

Abstract: Ionic liquids were firstly used as catalysts for one-pot synthesis of 4-(phenylamino)methyl-ethylene carbonate from CO2, epichlorohydrin and aniline without the utilization of any solvents or additives. The effects of the ratio of epichlorohydrin and aniline, catalyst amount, reaction temperature, time and initial CO2 pressure were investigated. The catalytic activity of the reaction was affected by the anions of ionic liquids and followed the order of Cl− >Br− >OAc− >BF4 − >PF6 −. The possible reaction mechanism was proposed based on the reaction results. [Copyright &y& Elsevier]