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• The synthesis of cyclic carbonates by oxidative carboxylation of olefins and CO 2 is a typical green synthesis reaction. • Olefins as feedstock are cheap and readily available, moreover, the oxidative carboxylation reaction can avoid the separation and purification of intermediates beforehand. • The oxidative carboxylation approaches include: auto oxidative carboxylation, assisted oxidative carboxylation, and oxybromination carboxylation, this review covers the catalysts commonly used in reaction processes and the research progress of catalytic mechanism. Cyclic carbonates are key compounds with high boiling point, low toxicity, good solubility and biodegradability, exhibiting wide applications. The direct synthesis of cyclic carbonates from cheap olefin and CO 2 is a green reaction process, without the separation of intermediate products. Starting from three different organic reaction pathways: auto oxidative carboxylation, assisted oxidative carboxylation, and oxybromination carboxylation, this review covers the catalysts commonly used in reaction processes and the research progress of catalytic mechanism. These catalysts mainly included metal complexes, metal oxides, supported metals, metal-organic frameworks, ionic liquids and molecular sieves. Finally, in order to further improve the efficiency of one-pot oxidative carboxylation reaction, the inspirations for design of catalysts and the optimization of reaction conditions are prospected. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel heterogeneous ionic liquid catalyst was developed for CO 2 conversion to carbonates. • Porous phosphonium bromide-microspheres can be controllably synthesized from flexible monomers. • The catalyst shows high specific surface area, the hierarchical pore structure and excellent CO 2 adsorption capacity. • High catalytic activity (conversion of 99.7 %) with low bromine content (3.03 wt%) was achieved. • Synergistic effect of physisorption and chemical interaction probably assists the CO 2 activation. Heterogeneous ionic liquid (IL) catalysts with multiple active sites can be considered as the highly efficient catalyst for CO 2 conversion to cyclic carbonates. It is extremely challenging to achieve the strategic design and precise control of multi-site polymeric ILs' morphology and properties. In this work, we developed a novel and facile polymerization-ionization method employing flexible brominated monomers as raw materials (e.g. 4‑bromo-1-butene) to successfully synthesize porous hyper-cross-linked phosphonium bromide-microspheres (PBr-microspheres), in order to break through the drawbacks of multi-step preparation and difficulty in microsphere forming. Compared with conventional bromine spheres of the same size, the specific surface area of the new synthetic bromine sphere is 16 times, and the average pore size is one-eighth, with 3-times CO 2 adsorption capacity, with rich microporous structure and exposed active sites, excellent CO 2 adsorption capacity and thermal stability. PBr-microspheres can achieve synergistic effect of physical adsorption and chemical interaction for CO 2 , thus enhancing the catalytic performance in CO 2 conversion process, affording propylene oxide conversion of 99.7 % and propylene carbonate selectivity of 99.9 %, while the catalytic activity did not decrease significantly after reusing 8 runs. This facile controllable synthesis of PBr-microspheres with excellent catalytic performance provides a new idea for heterogeneous ILs-catalyzed CO 2 utilization. [Display omitted] [ABSTRACT FROM AUTHOR]

• Heteronuclear bicentric pyridinium-based ionic liquid catalysts were synthesized. • Heteronuclear bicentric catalysts exhibit more catalytic efficiency than monocentric catalysts under moderate conditions. • Bicentric catalysts can simultaneously activate CO 2 and propylene oxide (PO), while monocentric catalysts can activate only one reactant. • Catalytic efficiencies of alkyl chain-tailored bicentric catalysts have been compared with no alkyl chain catalysts. • Bicentric ILs demonstrated outstanding catalytic performance, yield, and selectivity of up to 99 %. The rapid increase of CO 2 in the environment is causing severe climate catastrophes and rising ocean surfaces. Therefore, its reduction and green utilization into value-added materials is significant. Herein, heteronuclear bicentric pyridinium-based ionic liquids (BILs) tailored with different chain lengths and halogen anions have been synthesized and structurally characterized. These BILs were utilized as thermally stable, metal-free, and homogeneous catalysts to synthesize other cyclic organic carbonates (COCs) using various epoxides and sustainable, economical, and inert CO 2, and their catalytic activity phenomenon has been discussed in detail. The results demonstrated that [TMGH+][ ̶O 2 MPy+][Br ̶] possesses Lewis acid-base bifunctional characteristics with strong nucleophilic active sites, which play an essential synergistic effect on the activation of CO 2 and the ring-opening of epoxides. Various factors affecting the conversion and selectivity of catalysts, including reaction temperature, halide ion, catalyst amount, CO 2 pressure, and reaction time, were further investigated. The results illustrated that under metal and solvent-free conditions, the dual functionalized heteronuclear BILs catalyst ([TMGH+][ ̶O 2 MPy+][Br ̶]) exhibited 99.7 % yield and 99.9 % selectivity at 90 °C temperature and 1 MPa CO 2 pressure up to 4 h for the cycloaddition reaction between CO 2 and propylene oxide (PO). At the same time, the turn-over frequency was as high as 10.2 h−1. Moreover, the versatility and recyclability of the catalyst were studied, and a plausible reaction mechanism was proposed. Compared to previously reported functionalized heteronuclear bicentric catalysts, [TMGH+][ ̶O 2 MPy+][Br ̶] requires moderate reaction conditions without using any metal, solvent, or co-catalyst, which demonstrates the bright prospect of synthesizing pyridinium-based bicentric (BILs) catalysts and its practical use in CO 2 conversion, activation, and utilization. Synopsis Novel bicentric dual-functionalized pyridinium-based ionic liquid catalysts were synthesized and utilized for CO 2 conversion into cyclic carbonates under moderate conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

• A series of deep eutectic solvents (DESs) catalysts with varying ratios were successfully synthesized. • The DES with a composition of [TEA-12][OH]:[Q-COOH]- 0.9: 0.1 had the lowest melting point of 100.17 °C. • The efficiency of the catalysts for CO 2 fixation was evaluated and [TEA-12][OH]:[Q-COOH]−0.9:0.1 proved to be the most effective catalyst with a TOF of 1466 h−1. • Exceptional conversions were observed for epoxides with electron-withdrawing function groups, while electron-donating functional groups showed lower activity. The accumulation of greenhouse gases (GHG) in the atmosphere, with carbon dioxide being the most significant contributor, is a major environmental problem as it impacts significantly on climate change. The development of new catalysts and chemical reactions that incorporate CO 2 are needed to reduce its further emission significantly. Deep eutectic solvents (DES) have garnered increasing attention as environmentally friendly catalysts in the cycloaddition of carbon dioxide (CO 2) with epoxide substrates to produce cyclic carbonates. Their appeal stems from their facile synthesis, cost-effectiveness, low vapour pressure, and thermal stability. In this study, we present a convenient solvent-free synthesis method for nine deep eutectic solvents (DES), utilizing varying compositions of quaternary amine salts (N,N,N -triethyldodecan-1-aminium hydroxide, [TEA-12][OH]) and quinaldic acid [Q-COOH]. These deep eutectic solvents were thoroughly characterized using several techniques, including FTIR, NMR, DSC, and TGA. Moreover, their efficacy for the solvent-free fixation of CO 2 to cyclic carbonates were evaluated. Among the tested compositions, [TEA-12]:[Q-COOH] (0.9:0.1) exhibited the lowest melting point (100.17 °C) and highest catalytic activity, showcasing an optimized Turn-Over Frequency (TOF) of 1466 h−1. This remarkable result represents a significant advancement in the application of DES for CO 2 fixation, exceeding the previous highest catalytic activity observed with TBAB:Citric acid (2.5:1) by more than tenfold. [Display omitted] [ABSTRACT FROM AUTHOR]

A molybdate-incorporated cooperative catalyst CuMo-BPY was synthesized and explored in the highly efficient and atom-economical assisted tandem process for conversion of CO 2 and olefins into value-added cyclic carbonates. [Display omitted] • A molybdenum(VI) oxide incorporated cooperative catalyst, CuMo-BPY , was achieved by a simple and effective way. • The spatial matching of duple catalytic sites provide further compatibility and drive the tandem catalytic proceeded. • CuMo-BPY was explored in the atom-economical assisted tandem process to synthesize cyclic carbonates from olefins and CO 2. • CuMo-BPY has advantages of unambiguous structure, economic chemical reagents and highly stability. • CuMo-BPY will be promising for preparation of practical chemical materials. Currently, substantial interest is focused on developing assisted tandem catalysis to optimize the reaction conditions for each step in the process. By combining a molybdate oxidation catalyst and alkaline μ 3 -OH tricopper (II) cores into a metal-organic framework (MOF), a bifunctional catalyst, Cu 3 (μ 3 -OH) 2 (4,4′-BPY)(MoO 4) 2 (CuMo-BPY , BPY = 4,4′-bipyridine), was achieved and successfully explored for the assisted tandem catalytic conversion of olefins into value-added cyclic carbonates. CuMo-BPY displayed a three-dimensional (3D) extended network of two-dimensional (2D) inorganic CuMo layers interconnected with 4,4′-bipyridine groups. Two potential catalytic sites, Mo(VI) oxide (an oxidant for the epoxidation of olefins) and the alkaline μ 3 -OH of tricopper (II) cores (for the capture and activation of CO 2), exhibit an orderly distribution and spatial matching in the framework, which can provide further compatibility with the Mo=Ot-activated epoxidation intermediate to drive tandem catalysis in a single workup stage. [ABSTRACT FROM AUTHOR]

• Overviews the current research on the fixation of CO 2 to cyclic carbonate by using MOFs-based materials. • Discuss the different strategy for the fixation of CO 2 to cyclic carbonate. • Focused on the various aspects for further designing of MOFs-based materials. The combustion of fossil fuels leads to the significant emission of carbonaceous compounds (e.g. CO 2 , CO), which results in a range of environmental problems (e.g. global warming). Among numerous carbonaceous compounds, although CO 2 is the main culprit causing greenhouse effect, it is also an important carbon resource that can be used as a raw material for the synthesis of other important chemical substances. Among numerous CO 2 activation and conversion processes, CO 2 cycloaddition is an economically efficient transformation method because of its low price of raw materials, no other by-products during the reaction process, and atomic utilization rate of up to 100%, which comply with "green chemistry" and "atom economy". Moreover, the products of cyclic carbonates (e.g. ethylene carbonate, propylene carbonate) play a crucial role in the electric vehicle industry and are widely utilized for their numerous advantages. However, CO 2 is inert and difficult to be activated, so the search for efficient and stable catalysts is crucial for the rapid CO 2 conversion. Metal-organic frameworks (MOFs) have emerged as highly promising materials in the field of CO 2 activation and conversion due to their tremendous potential for development. This review provides a comprehensive analysis of the application of MOFs based catalysts in CO 2 conversion. In addition, this study explores potential techniques for enhancing the catalytic efficiency of novel catalysts based on MOFs while investigating unexplored reactions for CO 2 conversion. Application of metal-organic frameworks (MOFs)-based catalysts for the direct conversion of carbon dioxide (CO 2) to cyclic carbonate. [Display omitted] [ABSTRACT FROM AUTHOR]

• The ionic organic polymeric materials fabricated with urea units are the efficient catalysts for the CO 2 fixation reaction. • The outstanding performance was attributable to the synergistic effect of bromine ion and urea units. • The kinetic experimental was studied and the activated energy was calculated as 48.5 kJ/mol. • A possible mechanism of the cycloaddition reaction catalyzed by ionic organic polymeric material of UIP-2 was proposed. Ionic organic polymeric materials are one of the most promising catalysts for the conversion of carbon dioxide (CO 2) to five-membered cyclic carbonates (5CCs). Herein, a series of urea functionalized ionic organic polymer materials UIPs (UIP-1, UIP-2 and UIP-3) have been prepared by condensation and Menshutkin reaction of three components in one-pot by solvothermal method. After characterization by FT-IR, SEM, 13C CP MAS NMR, TGA, N 2 adsorption and XPS spectroscopy, the UIPs were alternated as competitive catalysts for the CO 2 cycloaddition reaction with epoxides without metal and co-catalyst under solvent-free conditions. In particular, UIP-2, derived from 1,3,5-tribromomethyl benzene, 4-amino pyridine and 4,4′-diphenylmethane diisocyanate, demonstrated excellent catalytic activity in the CO 2 cycloaddition reaction with a high cyclic carbonate yield of 92.6 % under mild conditions: epichlorohydrin (ECH) (10 mmol), UIP-2 (0.10 mmol), reaction at 70 °C for 16 h with 1 bar of CO 2 , and the activated energy was calculated to be 48.5 kJ/mol. Furthermore, a possible catalytic mechanism was proposed by experiments and density functional theory (DFT) calculations. The ionic organic polymeric materials (UIPs) fabricated with urea units as activation sites showed excellent catalytic activity for CO 2 fixation reaction under mild conditions. The outstanding performance was attributable to the synergistic effect of nucleophilic bromine ion and urea unit as hydrogen bonding donor. [Display omitted] [ABSTRACT FROM AUTHOR]

• Development of mesoporosity by post-synthetic acid treatment of microporous SAPO-34 and SAPO-5 materials. • Hierarchical structure of SAPO-5 and SAPO-34 was confirmed by XRD, ICP-OES, 29Si-NMR, N 2 adsorption/desorption, TEM. • Enhanced catalytic activity of post-synthetic treated materials in cycloaddition of carbon dioxide to epoxides. • The conversion of cyclohexene oxide was observed to be 100 % using acid treated SAPO-34. Hierarchical silicoaluminophosphates comprising dual micro/ meso pore structures have been explored, and proven to be effective, robust, and recyclable materials for the production of cyclic carbonates in the absence of co-catalyst. Upon activation at the temperature range of 80–100 °C, treated SAPOs have been examined as catalysts for the reaction. The crystalline structures of the hierarchical SAPO were checked by P-XRD. FE-SEM images confirmed the morphology and TEM measurement showed the periodicity of the framework. The BET analysis revealed the surface modification. In the cycloaddition of CO 2 to epoxide (cyclohexene oxide, and styrene oxide), the hierarchical silicoaluminophosphate materials were explored where the activity of post-synthetic treated materials as catalyst was discovered to be superior. 100 % and 93 % reactant conversion were found for treated SAPO-34 and SAPO-5 catalyst, respectively. [Display omitted] The purpose of this work is to generate mesoporosity in SAPO-34 and SAPO-5 catalysts by post-synthetic acid treatment and use the modified materials in cycloaddition of carbon dioxide to epoxides to check the effectiveness of the materials, the synthesized materials were thoroughly characterized with different physicochemical techniques and the acid-treated SAPOs demonstrated enhanced catalytic activity. [ABSTRACT FROM AUTHOR]

• Immobilization of ZnGlu MOF into hexagonal mesoporous silica SBA-16 to fabricate ZnGlu MOF/SBA-16 hybrid material. • ZnGlu MOF/SBA-16 as a sustainable green nanocomposite for CO 2 epoxidation to cyclic carbonates under solvent-free conditions at low pressure of CO 2. • Improving reactants diffusion and molecular accessibility for suitable interactions in lewis acid centers by mesoporous silica SBA-16. • Convenient separation of the nanocatalyst by simple filtration, and reused for five runs under the optimized reaction conditions. In this study, ZnGlu MOF has been immobilized into hexagonal mesoporous silica SBA-16 to fabricate ZnGlu MOF/SBA-16 hybrid material. The prepared hybrid material was introduced as a sustainable green nanocomposite for CO 2 epoxidation to cyclic carbonates under solvent-free conditions at low pressure of CO 2 (5 bar). The structure of the obtained nanocomposites is authenticated using various analytical techniques like FT-IR, XRD, SAXRD, CO 2 -TPD, NH 3 -TPD, BET, TEM, FE-SEM, EDX, EDX-mapping, and ICP-OES. For making a greener process, ZnGlu MOF/SBA-16 nanocomposite showed remarkable catalytic activity for converting CO 2 with diverse epoxides toward five-membered cyclic carbonates prepared without using any toxic metals and reagents. The presence of the mesoporous silica SBA-16 has improved reactants diffusion and molecular accessibility for suitable interactions in Lewis acid centers, which led to MOFs outperforming in the efficient chemical fixation of CO 2. Also, the essential role of free amino groups in ZnGlu MOF was shown as base sites and H-bonding groups when suggesting a possible reaction mechanism. This efficient, and convenient catalytic system can be separated by filtration, and its original activity was maintained for five successive cycles under the same reaction conditions. The above nanocomposite, with great potential, can be used to catalyze different chemical reactions for industrial purposes. This study reports a solvent-free chemical fixation of carbon dioxide with various epoxides by ZnGlu MOF/SBA-16 nanocomposite as an energy-efficient, reusable, and eco-friendly green catalytic system. [Display omitted] [ABSTRACT FROM AUTHOR]

• Co-Salen complexes containing different groups and bearing potassium iodide (KI) complexed with crown ether (K@SCs) were prepared. • Salen derivative organic polymer as heterogeneous catalyst for CO 2 cycloaddition reaction. • Alkali metal halides and Lewis acids have good synergistic effects in catalytic reactions. Metallosalen presents very important applications in both homogenous and heterogeneous catalysis. Correspondingly, porous polymeric metallosalen combined with the performance of organometallics and heterogeneous polymers possess potential in CO 2 fixation reactions. Herein, a family collection of K@SCs were conceived and obtained by combining cobalt-salen complexes with different groups and diaminobenzene-18-crown-6 complexed with KI, which allows multiphase catalytic immobilization of CO 2 to epoxides. Catalyst K@SC-3 can fix CO 2 into a variety of substituted epoxides in >90% yields to the corresponding cyclic carbonates in co-catalyst-free and solvent-free conditions. Furthermore, K@SC-3 can be recovered and reused at least six times by simple centrifugal separation, demonstrating superior stability. The kinetics experiments were also carried out at varied temperatures catalyzed by K@SC-3. It is concluded that a first-order equation of epoxide was proved and the activation energy was calculated to be 27.13 KJ/mol. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxophilic Zn-N 4 -Schiff bases catalyzed solvent free CO 2 /epoxide direct coupling. • Cyclic carbonates were selectively obtained with high TON up to 4900. • Zn complex combined in only equimolar ratio to TBAI was able to catalyze efficiently. • Two plausible pathways of CO 2 /epoxide coupling were proposed without halide intervention. Tetra-nitrogenated Zn-Schiff-base complexes have been synthetized and studied by X-ray diffraction. The prepared Zn-N 4 -ligands complexes could not follow the 18-electron rule. This property has allowed the complexes to be efficient in the coordination and activation of the substrates. The zinc complex of N,N '-bis(2-p-tosylaminobenzylidene)-1,2-diaminecyclohexane, Zn(Cy-Ts) combined to tetra-butylammonium iodide (TBAI) in a ratio of 1:1, or to triethylamine, catalyzed efficiently the CO 2 /epoxides coupling. These catalytic reactions were carried out without solvent at 120 °C under CO 2 pressure. Cyclic carbonates were selectively obtained with high yield up to 99% (TON up to 4900). Two plausible pathways of CO 2 /epoxide coupling mechanism were proposed without halide intervention, where both reactants are activated by the same Zn metal center. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multisite activation of epoxides for synthesis of cyclic carbonates under mild conditions. • Environmentally friendly and cost-effective CaI 2 /MDEA catalyst was applied. • Large scale synthesis of cyclic carbonates using CO 2 as a reproducible C1 source. • The CaI 2 /MDEA system revealed excellent recyclability after six running. The conversion of CO 2 into valuable products has become the inherent part of green and sustainable chemistry. Here we demonstrated an efficient synthesis of cyclic carbonates from epoxides and CO 2 under mild conditions (at 50 °C for 6 h under a CO 2 atmosphere) via the use of CaI 2 / N -methyldiethanolamine (MDEA) system as the catalyst. The excellent conversions and selectivities for a broad range of epoxides are achieved under solvent-free conditions even at atmospheric CO 2 pressure and in the presence of water. The catalyst can be simply recycled and reused without obvious loss in its activity. A plausible multisite-activation mechanism is proposed involving hydrogen bond site-assisted and Ca2+-promoted ring opening path, in combination with the activation of epoxides by iodide ion. [ABSTRACT FROM AUTHOR]

Nanocrystalline MgO has been synthesized by simple hydrothermal method and it showed excellent catalytic activity and recyclibility for the synthesis of cyclic carbonates by chemical fixation of CO 2 on epoxides and N-formylation of amines by using HCO 2 H as reagent at room temperature. [Display omitted] • Synthesis of magnesium oxide based nanomaterial using precipitation method. • MgO nanomaterial showed good surface basicity. • MgO catalyses cycloaddition of epoxides with CO2.under atmospheric pressure and RT. • MgO nanocatalyst showed good catalytic activity for N-formylation of amines with HCO 2 H at room temperature. • The MgO nanocatalyst is easily recoverable, stable and showing high recycling efficiency. Chemical fixation of CO 2 into fine chemicals is one of the key areas of research today to mitigate greenhouse gas CO 2 and its successful utilization as C1 building block. Nanocrystalline MgO has been synthesized by simple precipitation method followed by calcination at 450 °C. The materials are characterized thoroughly by several instrumental tools, which suggested the presence of mesoscopic void space and excellent catalytic activity for the synthesis of organic cyclic carbonates by chemical fixation of CO 2 on a wide range of epoxides at atmospheric pressure and room temperature within a short reaction time. Maximum product yields upto 99% for the cyclic carbonates are observed. It also displayed a high catalytic activity in the N-formylation of various amines by using formic acid as reagent (acts both as carbon source and reducing agent) at room temperature with excellent product yields upto 99.5%. This nanocrystalline MgO material showed high recycling efficiency for the cycloaddition of CO 2 onto the epoxides and no sign of catalyst deactivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • PVA-KI is a non-toxic, cheap and efficient catalyst system for the cycloaddition of CO 2 under solvent-free condition. • Synergetic catalytic effect occurs between PVA and KI in the reaction. • PVA-KI is stable and usable for multicycle reaction. • The strategy producing cyclic carbonate in an environmentally-friendly manner. In this study, we have for the first time demonstrated that polyvinyl alcohol (PVA) and potassium iodide (KI) can form an efficient catalytic system for synthesis of cyclic carbonates from epoxide and CO 2. The catalytic reaction happens in solvent-free conditions. A synergetic effect occur between PVA and KI which considerably increases the reaction yield. This binary catalytic system is mainly suitable for mono-substituted terminal epoxides. In the optimized reaction condition, over 90% reaction yield can be achieved. The binary catalyst is reusable and can be recycled at least five times without significant loss of the catalytic activity. The PVA hydrolysis degree affect the catalytic activity as well. A possible mechanism of synergetic effect of the binary system was proposed. PVA and KI may form a non-toxic, low cost, recyclable, highly-efficiency catalyst for fixing CO 2 through cycloaddition with epoxides. [ABSTRACT FROM AUTHOR]

• ABbILs catalyst reduces the reaction barriers by activating all reaction substrates through acid-base synergistic effect. • The addition of epoxide breaks the equilibrium limit, which facilitates the cyclic esterification reaction. • Combined with characterization and DFT calculation, the reaction mechanism of acid-base multi-site synergistic catalysis was proposed. In view of the harsh conditions of cyclic esterification reaction of ethylene glycol (EG) and carbon dioxide (CO 2) to synthesize ethylene carbonate (EC), the yield is low and the catalysts are mostly metals, a series of green acid-base bicentric ionic liquids (ABbILs) were developed. Among them, the ABbILs of 1,5,7-Triazabicyclo[4.4.0]dec‑5-ene glutarimide ([TBDH][Glu]) had the best catalytic performance. Under the optimal reaction conditions, the yield of EC reached 29.5%, which was higher than most of the conventional metal-based catalysts. Through activity screening results and DFT calculation, it was found that different cations affect the interaction between N on anion and H proton of EG, and the H on the cation can activate the O on EG, which would affect the ability of ABbILs to activate EG. The acid-base bicentered synergistic catalytic mechanism of Bronsted acid and Lewis base was proposed by characterization and DFT calculation. This study opens up new avenues for the efficient conversion of diols and CO 2 for the preparation of cyclic carbonates. A series of green acid-base bicentric ionic liquids (ABbILs) were developed to catalyze the synthesis of cyclic carbonates from ethylene glycol (EG), CO 2 and styrene oxide (SO). The addition of SO has a promoting effect on the reaction. On the one hand, SO avoids the hydrolysis of ethylene carbonate (EC) by removing H 2 O through reacting with H 2 O, which improves the yield of EC; on the other hand, SO reacts with CO 2 to generate styrene carbonate (SC), which further generates EC by transesterification with EG, which promotes the yield of EC. [Display omitted] [ABSTRACT FROM AUTHOR]

• The Tröger base analogue coordinated with potassium iodide and containing crown ether CATB-KI was fabricated. • The acidified CATB-KIs shown high catalytic efficiency to cyclic carbonates. • The synergistic mechanism has been proved in terms of experimental results and calculation of dynamics. Tröger's bases (TB) containing two steric nitrogen atoms, are alternated as building block for constructing molecular acceptors to form covalent bonds with acids, making TB a promising catalyst. Herein, TB analogs fabricated with crown ethers were knitted by condensation reaction and combined with potassium iodide as a brand-new catalytic system (CATB-KIs), which were characterized using FT-IR, 13C CP MAS NMR, SEM, TGA, and XPS spectroscopy respectively. The generated CATB-KIs exhibited excellent performance for CO 2 fixation reaction with epoxides to produce cyclic carbonates under mild conditions, and the catalytic activity could be further improved by coordinating with acids beforehand, in which HBr performs fascinated activity. After 12 h, the corresponding cyclic carbonate from epichlorohydrin with 95.1% yield was detected at mild conditions with solvent-free in the presence of CATB-KI-2 and HBr. A series of terminal epoxides were converted into desired cyclic carbonates with desirable yields. The catalyst could be recovered successfully and reused six times without significant loss of activity. Finally, dynamics study on catalytic mechanism has been accomplished and the activated energy was calculated as 72.1 kJ/mol. A synergistic catalytic mechanism of hydrogen bonding and I anion has been proposed to account for the excellent catalytic activity of this catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The ionic liquids were found to be single component bifunctional catalysts. • The amino acid ionic liquids show high catalytic efficiency to cyclic carbonates. • Catalytic activity enhances with increasing carbon chain length of anion. • No additional organic solvent required and halogen free. The amino acid ionic liquids of 1-butyl-3-methylimidazolium aspartic acid [bmim][ASP], 1-butyl-3-methylimidazolium glutamic acid [bmim][Glu], N -octyl- N -methylmorpholinium glutamic acid [mor 1,8 ][Glu] and N -hexylisoquinolinium aspartic acid [HiQuin][ASP] have been synthesized and characterized by 1H NMR, 13C NMR and IR spectroscopy. The catalytic performance of the amino acid ionic liquids for the coupling of various epoxides and CO 2 to produce cyclic carbonates was studied. The influence of anion type, catalyst dose, reaction temperature, reaction time and CO 2 pressure on the yields of cyclic carbonates was examined. The synthesized ionic liquids were found to be single component bifunctional catalysts in good yields and selectivity, no additional organic solvent required and halogen free. Furthermore, this system provides a reasonably environmentally benign chemical process in terms of potential industrial application. [ABSTRACT FROM AUTHOR]

• Zn(II)-N4-donor ligands complexes were prepared and fully characterized. • The computational stability predictions agree with X-ray diffraction data. • Cyclic carbonates were selectively obtained with Zn-N-donor/TBAB catalytic systems 1,2-epoxihexane carbonate TOF 565 h−1. • Relation between catalytic activity and structural characteristics of Zn complexes is stablished. Zinc(II) complexes [Zn(L1 - L5)Cl 2 ] with tetra-aza donor ligands bearing phenanthroline and bipyridine bis(aniline) skeleton L1 - L5 have been prepared and characterised. These ligands were selected to analyse the influence on the catalytic activity for the CO 2 -cycloaddition to epoxides of three parameters: the steric hindrance of the orto substituent of the aniline ring, the central skeleton and the nature of the non-aromatic amine. X-ray diffraction characterisation of [Zn(L1)Cl 2 ] and [Zn(L2)Cl 2 ] showed that the geometry is pentacoordinate while in the case of [Zn(L5)Cl 2 ] a four-coordinate tetrahedral complex was formed. Computational calculations using density functional theory methods (DFT) agreed with these results. These complexes combined with tetrabutylammonium bromide (TBAB) are very selective for the CO 2 /terminal epoxides coupling to form cyclic carbonates providing activity up to TOF 565 h−1. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ultrathin metal-porphyrinic MOF nanosheets were prepared. • A substrate-specific strategy for CO 2 cycloaddition was developed. • Cyclic carbonates were obtained in 84-99% yields at ambient and solvent-free conditions. • Insights into Co-TCPP-based cooperative systems were provided. A series of ultrathin (∼1.11–4.80 nm) 2D porphyrinic MOF nanosheets are developed and novel synergistic systems are conveniently constructed for the facile formation of cyclic carbonates. Using n -Bu 4 NBr (TBAB) as a co-catalyst, ultrathin (ca. 2.58 nm) Co-TCPP exhibited high catalytic activity for the solvent-free conversion of styrene oxide to cyclic carbonate, affording 99% yield at ambient conditions (25 °C and 1 atm CO 2). A relatively low energy (19.6 kcal/mol) for the rate-determining step is required for Co-TCPP/TBAB nanosystem as calculated by DFT. Notably, utilizing amino acid ionic liquid (AAIL, [Bmim][Glu] or [Bmim][His]) as the modifier, a substrate-dependent protocol was proposed to fix CO 2 with terminal epoxides or cyclohexene oxide, giving cyclic carbonates in 84–99% yields under mild conditions (solvent-free, 80 °C and 1 atm CO 2). 13C NMR and UV-vis studies provided insights into the vital roles of AAIL during CO 2 capture via carbamate dianion and in situ fabrication of Co-TCPP-AAIL. Moreover, DFT calculations also confirmed the AAIL-regulated substrate-dependent transformation strategy. 2D Co-TCPP-based synergistic systems are developed for the highly efficient synthesis of cyclic carbonates at ambient condition. [Display omitted] [ABSTRACT FROM AUTHOR]

• Photoinduced-polymerized poly(ionic liquid) membranes convert CO 2 into carbonates. • PILMs catalyze the gas state epoxides & CO 2 into cyclic carbonates. • PILMs exhibit almost the same catalytic activity as the IL monomers. • The superb swelling ability of PILMs provide the high activity for CO 2 conversion. Polymeric ionic liquid membranes (PILMs) were prepared by photo-initiated polymerization of DMAEMA-based ionic liquids (ILs) and co-monomers for the conversion of CO 2 into cyclic carbonates. The influences of functional groups and anions were investigated to find the optimal ionic liquid monomer. The PILM based on [DMAEMA-EtOH]Br exhibited the highest propyl carbonate (PC) yield (98%), which was close to that of the [DMAEMA-EtOH]Br monomer. Moreover, the PILMs can catalyze the gas state propylene oxide (PO) and CO 2 into PC with a PO conversion of 87.3%, while the PO conversion of the pure polymeric ionic liquids was only 3.1% for gas state PO. The excellent catalytic activity can be attributed to the highly active catalytic sites and superb swelling ability of PILMs. The dry PILMs could absorb the PO vapor and swell into membranes with abundant pores, which contained plentiful active sites to catalyze PO and CO 2 to PC efficiently. As can be seen in the Figure that the Polymeric ionic liquid membranes (PILMs) can catalyze the gas state propylene oxide (PO) and CO 2 into PC with a PO conversion of 87.3%, while the PO conversion of the pure polymeric ionic liquids was only 3.1% for gas state PO. The excellent catalytic activity can be attributed to the highly active catalytic sites and superb swelling ability of PILMs. The dry PILMs could absorb the PO vapor and swell into membranes with abundant pores, which contained plentiful active sites to catalyze PO and CO 2 to PC efficiently. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ag/TUD-1 catalysts were used for CO 2 fixation to cyclic carbonates. • The solvent free approach resulted in optimum activity in greener route. • The metallic nature of Ag was responsible for effective CO 2 conversion. • Maximum yield of epichlorohydrin to carbonate was 98% in ambient condition. Utilization of abandoned CO 2 that is generated from fossil fuels and industrial sources into valuable chemicals is a smart approach for a greener future. The fixation of CO 2 over epoxides and the production of cyclic carbonates is one of the popular CO 2 utilization techniques. Silica supported silver nanoparticles have been used before in different important reactions like nitrophenol reduction, alcohol oxidation etc., due to the high surface area, pore size of silica and high activity of the Ag0 species. In this study, Technische Universiteit Delft -1 (TUD-1) is used as silica support for stabilizing silver nanoparticles and CO 2 has been converted to cyclic carbonate under solvent less condition. The Lewis acidic nature of the silver particles have aided into the solvent-less CO 2 conversion, resulting into the maximum yield of 98% at 60 °C and 1 MPa pressure. [Display omitted] [ABSTRACT FROM AUTHOR]

• Zn-based complex including iodide was found with the highest catalytic activity. • CO 2 coupling with epoxides can be efficiently enhanced by Zn-based complexes. • 98.62% conversion of ECH and 96.97% selectivity to CPC were observed. • The key step of the coupling reaction was unveiled by DFT calculations. The present work aimed at comparably studying the catalytic performance of Zn (II) complexes applied as the efficient catalysts in accelerating the transformation of CO 2 into cyclic carbonates. The physicochemical properties of the synthesized complexes were determined by XRD, NMR, FT-IR, TGA, NH 3 -TPD, CO 2 -adsorption. The synthesized samples were found to possess the Lewis acid/basic sites derived from the zinc ions and nitrogen-containing ligands, which can synergistically catalyze the coupling reaction. In addition, the sample containing iodide ion ligands showed the highest catalytic performance compared with other Zn (II) complexes, suggesting that the amount and distribution of the Lewis acid sites were not the primary factors for determining the catalytic activity, and the difference in activity of halogen ion ligands (I−, Br−, Cl−) has a larger influence on the coupling process, which made the CO 2 insertion and ring closure of the formed intermediate more easily occur when iodide ion ligands participated. It can be drawn that the catalytic activity of the Zn (II) complexes was simultaneously associated with halide ion ligands and substitution group of the ligand. Moreover, 98.62% conversion of epichlorohydrin (ECH) and 96.97% selectivity to chloropropene carbonate (TOF=56.65 h −1) was achieved at the optimal operation parameters (110 °C, 2.5 MPa, 8 h, 1.25 wt.% catalyst of ECH). Furthermore, the proposed pathway of CO 2 coupling with epoxide was confirmed by DFT calculation, with the result confirming that the process of epoxide ring opening was the key step for the coupling reaction. Chemical fixation of CO 2 into cyclic carbonates over Zn (II) Schiff base complex [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Covalent Organic Framework (COF) was synthesized and Characterized. • COF was successfully used as the active photocatalyst for CO2 fixation to Cyclic Carbonate under Visible Light. • Good yield of the corresponding products (Cyclic Carbonate) were obtained. • Control experiments suggest the light dependency of the reaction. • Mechanistic investigation was carried out with spectrometric analysis. • The catalyst was recycled and reused for five times retaining its activity. We have demonstrated the photo-catalytic fixation of CO 2 over epoxides for the formation of corresponding cyclic carbonates using a mesoporous Covalent Organic Framework (COF) which acts as a potential photocatalyst with TBAB (Tetrabutyl ammonium bromide), 5 mol% as the co-catalyst under atmospheric pressure in visible light. Greater than 86% yield of the isolated product is achieved with the use of 5 mg of catalyst. The use of Catalyst and co-catalyst TBAB controls the reaction cycle. There is no progress of the reaction occurred in the absence of light (445 nm) even on the elevation of reaction temperature. We have also demonstrated that 25% of the isolated product could be obtained with the use of sunlight using the catalytic cycle. These results open the door to an entirely new class of protocol for photo catalytically fixation of CO 2 into cyclic carbonate from epoxide using COF as photocatalyst under visible light. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of triazole organocatalysts were synthesized and fully characterized. • First report of triazole organocatalysts that are active for the cycloaddition of CO 2 under atmospheric pressure. • Solvent-free and cocatalysts-free set up for the CO 2 cycloaddition is significant for a green and sustainable environment. • The catalyst synthesis is facile, cost-effective, reusable, and stable. A general synthesis of triazole-based catalysts remains a significant challenge. Consequently, triazole-based catalysts are rarely studied. Herein, the first report is presented for the construction of cyclic carbonates using triazole-based organocatalysts, which is a crucial technology to a genuinely sustainable and atom-efficient economy. A series of triazole-based organocatalysts was synthesized, entirely characterized by FTIR, NMR, mass spectrometry, and elemental analysis. This work is mainly based on the construction of nucleophilic-electrophilic bifunctional catalysts (N-rich triazole ring-carboxylic group) combined with substituents, which evaluate the vital effect of substituents for the catalytic cycloaddition reaction of CO 2 into epoxide. In general, various systems required the Lewis basic site in the form of cocatalyst or solvent to be optimally effective. However, our designed catalyst contained Lewis basic and acidic sites. It, therefore, can catalyze the reaction proficiently without the aid of solvent, cocatalysts and can perform at ambient pressure of CO 2 (1 bar) to produce different cyclic carbonates. Moreover, the catalyst is reusable, maintaining the same activity along with remarkable catalyst stability. [ABSTRACT FROM AUTHOR]