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Structure-designed squaramide-based IL shows excellent activity as single-component and recyclable catalyst platform for chemical fixation of CO 2 to cyclic carbonates under mild conditions. • Multiple hydrogen bond donors-based squaramide ionic liquids (SAILs) were developed and characterized. • The SAIL showed excellent activity and reusability for transformation of CO 2 into cyclic carbonates. • The protocol solved the problems of cocatalyst leaching and complex separation/purification. • The protocol performed in the absence of toxic transition metal ions and organic solvents. • An insight into the catalytic mechanism deriving from the synergistic interaction of cation-anion was proposed. Novel squaramide-based ionic liquids (SAILs) were first presented through properly molecular structure design. They were successfully applied to the cycloaddition of CO 2 and epoxide to form cyclic carbonate as single-component catalyst. The catalytic behaviors of SAILs with different structures were thoroughly studied for the cycloaddition reaction. The squaramide groups were easy to form strong hydrogen bonds with oxygen atoms of epoxide, leading to an intensive activation of the epoxide. Under the optimum reaction conditions, good to excellent product yields with satisfactory selectivities were obtained. The structure-designed catalyst was easily recovered and showed excellent reusability with no significant loss of catalytic activity after six cycles. An insight into the synergistic catalytic mechanism deriving from the multiple hydrogen bond donors and bromine anions was proposed. The new strategy helps to solve the problems of cocatalyst/nucleophile leaching and complex separation/purification existed in binary organocatalysts. The multiple hydrogen bond catalysis shows a green and promising alternative to Lewis acid catalysis in the relevant CO 2 conversion applications. [ABSTRACT FROM AUTHOR]

Abstract The application of ionic liquids in chemical recycling of waste polycarbonate (PC) via the simple hydrolytic strategy has shown great potential. Herein, a series of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) based ILs were facilely synthesized and characterized, and could efficiently catalyze the hydrolysis of PC in the absence of transition metal and solvent. The catalyst structures and reaction conditions were optimized, and 100% PC conversion with 97% bisphenol A (BPA) yield could be obtained under the conditions of n (H 2 O)/ n (PC) = 3:1, n (Cat.)/ n (PC) = 0.1:1, 140 °C for 3.0 h. Based on the experimental results and in-situ FT-IR analysis of the PC residues and BPA product, a feasible molecular activation and catalytic pathway for [HDBU][LAc] catalyzed hydrolysis of PC was proposed. Highlights • The DBU-based ILs exhibited the higher activity for hydrolysis of polycarbonate compared with the reported catalysts. • The protocol shows great advance for hydrolysis of polycarbonate without solvent and metal ions. • The eco-friendly catalysts were easily recyclable and could keep high stability and activity. • An insight into the molecular activation and catalytic pathway by in-situ FT-IR and NMR analysis was provided. [ABSTRACT FROM AUTHOR]

Different DBU-based ionic liquids (DILs) were facilely synthesized by one-step neutralization and exhibited excellent catalytic activity for CO 2 cycloaddition to epoxides under mild and solvent-free conditions cooperating with ZnI 2. [Display omitted] • The DILs were one-step prepared, low cost and environmentally benign. • The DIL/ZnI 2 showed superior catalytic activity for CO 2 coupling with various epoxides. • The catalytic reaction was performed under mild and cocatalyst-free conditions. • The catalyst was easily recycled and showed good chemical and structural stability. The cycloaddition of CO 2 to epoxides is an important reaction and has got increasing attention. In this work, a series of DBU-based ionic liquids (DILs) were synthesized via facile neutralization of superbase 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) with corresponding hydrogen bond donor acids, such as D(−)-tartaric acid (TA), malic acid (MA) and succinic acid (SA). The DILs cooperated with ZnI 2 were first evaluated in detail for catalyzing the coupling reaction of CO 2 with propylene oxide (PO), and DIL-1 exhibited obviously enhanced catalytic activity under 80 °C, 3 MPa and solvent-free conditions. The effects of reaction parameters on the activity for propylene carbonate (PC) synthesis were thoroughly investigated, and a possible synergistic catalytic mechanism was proposed. The catalytic system reported here could be separated by simple centrifugation from the products after reaction and then reused efficiently. Moreover, the catalytic system showed the advantages of simple synthesis, high catalytic activity, low cost, and substrate versatility for CO 2 conversion to cyclic carbonates. [ABSTRACT FROM AUTHOR]

Novel metal-free tri- s -triazine terminal-linked ionic liquids have been developed from various precursors of urea-derivative-based ionic liquid/urea by a co-condensation method. These were successfully used for the chemical fixation of CO 2 to epoxides producing cyclic carbonates under mild and green conditions in which no co-catalyst and solvent were needed. The tri- s -triazine terminal-linked ionic liquids so prepared possess multiple functionalities of hydrogen bond donor ability, nucleophilicity, and Lewis base property, which are vital to the ring-opening of epoxide and the activation of CO 2 . Reaction parameters (temperature, CO 2 pressure, catalyst loading, time, water content) for cycloaddition of CO 2 with propylene oxide (PO) to propylene carbonate (PC) over tri- s -triazine terminal-linked ionic liquids were optimized. It has been shown that, under the optimal conditions, the catalyst is also versatile to CO 2 cycloaddition with other epoxides, can be reused in up to five consecutive recycles without significant loss of activity, and can still remain active in the presence of moderate amounts of water. A possible reaction mechanism has been proposed. The single-component, metal-free, multifunctional, and easily recyclable tri- s -triazine terminal-linked ionic liquids reported here can be an effective and ecofriendly catalyst for highly efficient CO 2 fixation. [ABSTRACT FROM AUTHOR]

Several urea derivative-based ionic liquids (UDILs) with superior thermal stability were facilely synthesized, structurally analyzed, and applied to CO2 capture and conversion under mild conditions. These UDILs reversibly capture CO2 with double molar CO2 absorption and exhibit outstanding catalytic activity for the conversion of CO2 and various epoxides to cyclic carbonates under metal- and solvent-free conditions. The effects of reaction parameters on the catalytic activity for propylene carbonate (PC) synthesis from propylene oxide (PO) and CO2 were thoroughly investigated. Because water is inevitably contained in real gases requiring treatment, the influence of water on CO2 capture and conversion was also studied. Furthermore, reaction kinetic studies were also undertaken and a cation–anion synergistic catalytic mechanism was proposed. The single-component, metal-free, dual functional, stable, and easily recyclable ionic liquids reported herein are interesting materials, displaying a good performance for both CO2 capture and conversion. [ABSTRACT FROM AUTHOR]

Several environmentally benign eutectic-based ionic liquids (ILs) were developed as novel homogeneous catalysts for efficient conversion of carbon dioxide to cyclic carbonates. Propylene oxide (PO) was selected as a benchmark substrate to optimize the catalytic activity, and on account of the catalytic cooperativity between the cation and anion in the [urea-Zn]I 2 catalyst, excellent yield (95%) and selectivity (98%) to propylene carbonate (PC) was obtained under the optimized reaction conditions of 120 °C and 1.5 MPa for 3.0 h in the absence of cocatalyst and solvent. Also [urea-Zn]I 2 was proved to be an efficient and versatile catalyst, and could realize catalytic conversion of CO 2 with various epoxides. Moreover, the synergistic reaction mechanism involving cation structure and halogen anion for CO 2 conversion was proposed, and the eutectic-based ILs were easily recyclable with high activity. The eutectic-based ILs that possessing low cost, moisture-stability, facile synthesis and efficiently bifunctional properties reported herein displayed the exceptionally outstanding features for efficient conversion of CO 2 to cyclic carbonates. [ABSTRACT FROM AUTHOR]

The combination of pyrrolidine-2,5-dione-derived ionic liquids with silver acetate (AgOAc) were developed as binary catalysts for conversion of simulated flue gas CO 2 and propargylic alcohols to α-alkylidene cyclic carbonates. By tuning different catalyst components, the [HTMG][Pyrro]/AgOAc system was confirmed to be the most efficient and exhibited an excellent synergistic action in facilitating the carboxylic cyclization under room temperature and solvent-free conditions. The influence of reaction parameters on carboxylic cyclization of CO 2 with 2-methylbut-3-yn-2-ol were optimized. Under the determined conditions, the [HTMG][Pyrro]/AgOAc system was stable enough to show durable high activity in eight recycles, and also versatile in carboxylic cyclization of flue gas CO 2 with other propargylic alcohols. Moreover, a thorough comparison of [HTMG][Pyrro]/AgOAc with the reported catalysts was provided and evaluated, the results suggested that the developed catalytic system has significant advantages in practical application. Finally, the mechanistic details for the conversion of CO 2 into α-alkylidene cyclic carbonates catalyzed by [HTMG][Pyrro]/AgOAc was also elucidated on the basis of reactants activation. [Display omitted] • [HTMG][Pyrro]/AgOAc system is developed for direct CO 2 conversion from flue gases. • The system realizes ambient and clean synthesis of α-alkylidene cyclic carbonates. • [HTMG][Pyrro]/AgOAc system shows higher activity than most reported catalysts. • The catalytic system is easily separated and exhibits durable high-activity. • Detailed activation behaviors and synergistic catalytic mechanism are revealed. [ABSTRACT FROM AUTHOR]

Catalytic coupling of carbon dioxide with epoxides to cyclic carbonates is an important reaction that has been receiving renewed interest. In this contribution, the binary catalysts of dicationic ionic liquids mediated metal halide were first evaluated in detail, together we provided an insight into the influence of various dications on catalytic activity to help the understanding and design of catalysts for efficient fixation of CO 2 to epoxides. Among the catalysts, 1,1′-(hexane-1,6-diyl)-bis(3-methylimidazolium) dibromide ( 6a )/ZnI 2 at molar ratio 1:2 showed the best catalytic activity with TOF of 328 h −1 and 96% yield to propylene carbonate under solvent-free condition and 110 °C, 1.5 MPa for 2.0 h. Also the catalytic system was effectively versatile to the cycloadditions of other less active epoxides with CO 2 . Compared with the reported monocationic ionic liquids, the dicationic ionic liquids exhibited the unique features of facile synthesis, easy separation, superior thermal stability and insensitivity to water and/or air, which make them good candidates for further developments and applications in sustainable processes concerned with CO 2 fixation. [ABSTRACT FROM AUTHOR]

Abstract: Three kinds of imidazole based dicationic [C2(Mim)2], [C3(Mim)2], [C4(Mim)2] with traditional counter anion ionic liquids (ILs) were synthesized. Key physicochemical properties, such as thermal stability, solubility in common solvents, acidic property and corrosion of ILs for Austenitic stainless steel 316 were determined. Esterification of alcohols by carboxylic acids has been carried out at room temperature in a group of imidazole dicationic ionic liquid. The catalytic performance was found to be much better than that of conventional non-cation functionalized ionic liquids and the corrosion was five times weaker than sulfuric acid. The esters were easily recovered due to immiscibility with the ionic liquid and reported imidazole dicationic ionic liquids were a promising catalyst for esterification reaction. [Copyright &y& Elsevier]

Rationally designed bio-AILs show exceptional performance for CO 2 activation and conversion into quinazoline-2,4(1 H ,3 H)-diones under mild conditions. [Display omitted] • Novel biocompatible media are developed for CO 2 /2-aminobenzonitrile reaction. • The bio-AILs media are facilely synthesized, highly stable and inexpensive. • The present media realizes the simultaneous activations of CO 2 and substrate. • The [HTMG][Lae] shows superior activity under mild and additive-free conditions. • The [HTMG][Lae] as dual solvent-catalyst is recyclable with excellent reusability. Based on an one-step acid-base neutralization method, several biocompatible anions-derived ionic liquids (bio-AILs) were prepared and characterized. They were first used as dual solvent-catalyst for cyclization of CO 2 and 2-aminobenzonitriles to synthesize quinazoline-2,4(1 H ,3 H)-diones. The influence of different bio-AILs structures on the cyclization reaction were studied, and [HTMG][Lae] was confirmed to be an excellent medium. By optimizing the reaction conditions, the [HTMG][Lae]-mediated cyclization reaction could afford a 96 % quinazoline-2,4(1 H ,3 H)-dione yield at 70 °C, 1.0 MPa CO 2 pressure for 6 h without other additives. The catalytic activities of various homogeneous media for transformation of CO 2 into quinazoline-2,4(1 H ,3 H)-dione were analyzed and compared. In addition, the reusability and general applicability of the [HTMG][Lae] medium were examined, the [HTMG][Lae] could show comparable activity in the fifth experiment, and it had good versatility for cyclization of CO 2 with various 2-aminobenzonitriles. Finally, an insight into the activation behaviors of [HTMG][Lae] to reactants were further investigated, and based on this, a feasible reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

Experimental and theoretical insights into robust PIL-Br@ZIF-8 hetero-frameworks for the selective conversion of CO 2 into cyclic carbonates under mild conditions. [Display omitted] • A novel strategy is developed for fabricating core–shell PILs@ZIF-8 composites. • PIL-Br@ZIF-8 enables simultaneous adsorption and activation of CO 2 and epoxide. • Low-concentration/low-pressure CO 2 conversion into cyclic carbonates was achieved. • PIL-Br@ZIF-8 is recyclable and exhibits good thermal and structural stability. • Valuable insight into the cycloaddition mechanism is theoretically elucidated. The present study, for the first time, reports the fabrication of core–shell poly(ionic liquids)@ZIF-8 nanocomposites through a facile in-situ polymerization strategy. These composites exhibited exceptional structural characteristics including high specific surface areas and the integration of high-density Lewis acid/base and nucleophilic active sites. The structure–activity relationship, reusability, and versatility of the poly(ionic liquids)@ZIF-8 composites were investigated for the cycloaddition reaction between CO 2 and epoxide. By optimizing the composites structures and their catalytic performance, PIL-Br@ZIF-8(2:1) was identified as an exciting catalyst that exhibits high activity and selectivity in the synthesis of various cyclic carbonates under mild or even atmospheric pressure or simulated flue gas conditions. Moreover, the catalyst demonstrated excellent structural stability while maintaining its catalytic activity throughout multiple usage cycles. By combining DFT calculations, we investigated the transition states and intermediate geometries of the cycloaddition reaction in different coordination microenvironments, thereby proposing a synergistic catalytic mechanism involving multiple active sites. [ABSTRACT FROM AUTHOR]

The introduced catalyst can be reused at least four times without significant loss of reactivity. [ABSTRACT FROM AUTHOR]

Several DBU-based protic ionic liquids were facilely synthesized, they were successfully used as solvents and catalysts for alcoholysis of poly(lactic acid) (PLA) to yield lactate esters. The structure of ionic liquids and reaction parameters were optimized. Using [HDBU][AA] as the catalytic medium, which was composed by a 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) cation and an acetate anion, the PLA could be completely depolymerized with a 91% methyl lactate yield under the conditions of 100 °C, 5 mol% catalyst loading for 5 h. The effect of alcohol structures on the catalytic behaviors was studied, and good to excellent product yields were obtained. Moreover, the developed [HDBU][AA] showed excellent recyclability and structure stability. A possible reaction mechanism concerning the synergistic effect of the anion-cation ions was proposed. The DBU-based protic ionic liquids presented herein are low-cost and one-step synthesized, exhibiting great potential as green and efficient platform for direct and selective alcoholysis of PLA. • The facilely obtained DBU-based protic ILs show the higher activity for alcoholysis of poly(lactic acid) compared with the reported catalysts. • The protocol shows great advance for alcoholysis of poly(lactic acid) without additional solvent and metal ions. • The eco-friendly catalysts exhibit excellent stability and can keep durable high-activity after six cycles. • The possible activation and catalytic mechanism concerning the synergistic effect of the anion-cation ions is provided. [ABSTRACT FROM AUTHOR]

Robust Zn-TPMO x @PIL-C n hetero-frameworks are developed and exhibit excellent performance for in-situ flue gas CO 2 capture and transformation. [Display omitted] • Robust Zn-TPMO x @PIL-C n hetero-frameworks with multiple active sites are developed. • The catalyst shows excellent dual functions of in-situ CO 2 capture and conversion. • The optimal Zn-TPMO 20 @PIL-C 6 exhibits excellent recyclability and versatility. • A novel strategy is presented for the effective utilization of low-concentration CO 2. Chemical utilization of CO 2 has garnered significant attention in response to the growing environmental and energy challenges. Novel porous hetero-frameworks, Zn-TPMO x @PIL-C n , are developed herein via in-situ polymerization of [VImC n ]Br (n = 2, 4, 6) onto porphyrin derivative-functionalized organosilicas (Zn-TPMO x , x = 10, 15, 20). The structures of Zn-TPMO x @PIL-C n are characterized and found to possess high specific surface area as well as multiple active sites including Lewis acid/base groups, dual hydrogen bond donors and nucleophilic groups. These hetero-frameworks are then utilized for the synthesis of cyclic carbonates through in-situ capture and conversion of CO 2 from simulated flue gas. The catalytic performance of different Zn-TPMO x @PIL-C n and technological conditions are investigated, revealing that the optimal Zn-TPMO 20 @PIL-C 6 catalyst achieves a 96 % yield of chloropropene carbonate with 99 % selectivity under reaction conditions of 110 °C, 1 MPa flue gas for 6 h. Through an assessment of the recyclability and versatility of Zn-TPMO 20 @PIL-C 6 catalyst, it is observed that the robust Zn-TPMO 20 @PIL-C 6 maintains its high activity even after five cycles. Furthermore, this catalyst exhibits satisfactory performance in promoting reactions between various epoxides and flue gas CO 2. Based on the synergistic activation of multiple active sites, the cycloaddition mechanism between CO 2 and epoxide under the catalysis of Zn-TPMO x @PIL-C n is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Two kinds of alkylimidazolium salts containing dimethyl phosphate or diethyl phosphate were obtained as room temperature ionic liquids synthesized by one step, and both of them have the ability to dissolve untreated cellulose. Especially, 1-ethyl-3-methylimidazolium diethylphosphonate ([EMIM]DEP) could obtain 4wt% cellulose solution within 10min under 90. The effects of dissolution temperature on cellulose dissolution time and degree of polymerization were investigated. As dissolution temperature increased, dissolution time was greatly reduced. Both the original and regenerated cellulose samples were characterized with wide-angle X-ray diffraction, thermogravimetric analysis and scanning electron micrograph. The results showed that the crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose. It was also found that the regenerated cellulose had good thermal stability with [EMIM]DEP ionic liquid. [Copyright &y& Elsevier]

In this paper, several succinimide-based ionic liquids (SIILs) were developed and structurally characterized. They were used as multifunctional and sustainable media for selective conversion of polycarbonate (PC) into bisphenol A (BPA) via methanolysis method. The catalytic behaviors of SIILs to the reaction, including the effects of SIIL structures, effects of reaction parameters, catalyst reusability, and interaction between SIIL and CH 3 OH were studied in detail. The [HDBU][Suc] comprising a 1,8-diazabicyclo[5.4.0]undec-7-ene cation and a succinimide anion exhibited superior performance compared to previous catalysts, and it afforded a complete depolymerization of PC with 96% BPA yield under mild conditions of 70 °C for 2 h in the absence of organic solvents and metal ions. The [HDBU][Suc] was easy to recycle and showed satisfactory reusability. Finally, a plausible mechanism for [HDBU][Suc]-catalyzed methanolysis of PC was presented in depth. Multifunctional succinimide-based IL shows excellent activity as a dual solvent-catalyst for methanolysis of polycarbonate to recover bisphenol A under mild and green conditions. Image 1 • Series of succinimide-based ionic liquids (SIILs) were facilely synthesized and clearly characterized. • The developed media realized the simultaneous activation of PC and CH 3 OH. • The [HDBU][Suc] exhibited superior or comparable activity under the milder and greener conditions. • The [HDBU][Suc] as homogeneous catalyst is easily recyclable with excellent reusability. • The developed media are facilely synthesized, eco-friendly and inexpensive, showing great potential for practical large-scale application. [ABSTRACT FROM AUTHOR]