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A series of amino acid-paired dipyridine polymers were synthesized and firstly used as metal- and halogen-free heterogeneous organocatalysts for chemical fixation of CO 2 into cyclic carbonates. Glutamic acid (Glu)-paired dipyridine polymer (Pbpy-Glu) possesses the highest catalytic efficiency for cycloaddition reaction under solvent-free conditions, and provides a reasonable recycled process. The mechanism investigation based on the FTIR analysis of catalyst intermediates suggests that the intermolecular synergistic effect involving the -N + ions in pyridine, COO – groups in Glu, as well as the COO ⋯ H 3 N ion pairs contributes to the good catalytic performance of Pbpy-Glu. [ABSTRACT FROM AUTHOR]

Eco-friendly and facile biomass-derived DESs show excellent activity for conversion of CO 2 into cyclic carbonates under mild and additive-free conditions. [Display omitted] • Novel eco-friendly and facile biomass-derived DESs are developed and characterized. • The ChI/CA is optimized to be an efficient catalyst for CO 2 cycloaddition reaction. • The cycloaddition reaction is performed under mild and additive-free conditions. • The ChI/CA is easily separated and shows excellent stability and reusability. Chemical fixation of CO 2 to produce high value-added chemicals is one of the important measures to effectively control carbon emission. In this paper, novel biomass-derived deep eutectic solvents (BDESs) with multiple active sites were developed as green media for chemical conversion of CO 2 and epoxides into cyclic carbonates. The coupling of propylene oxide (PO) and CO 2 was selected as a model reaction to evaluate the catalytic activity. By screening various BDESs structures and reaction parameters, the iodide choline/citric acid (ChI/CA) with a molar ratio of 2:1 was proved to be an efficient catalytic medium, and it could afford 98 % propylene carbonate (PC) yield with 99 % selectivity under mild (70 °C, 0.5 MPa, 3 h) and additive-free conditions. Moreover, the catalyst reusability and versatility were examined. The ChI/CA could be reused in up to five consecutive runs without loss of activity, and the ChI/CA showed excellent activity to various terminal epoxides/CO 2 coupling reaction. Finally, the activation behaviors of the ChI/CA to the CO 2 and epoxide were studied respectively, and a synergistic catalytic mechanism was provided. [ABSTRACT FROM AUTHOR]

Heterogeneous Co@PTPOFs with multiple Lewis acid/basic sites are developed and show excellent activity for cycloaddition of CO 2 and epoxides. [Display omitted] • Novel M@PPOFs with multiple Lewis acid/basic active sites are prepared facilely. • The M@PPOFs exhibit high specific surface area and good structural stability. • The 1.0Co@PPOFs-mediated CO 2 coupling reaction can conduct under mild conditions. • The optimum catalyst shows excellent reusability and broad substrate scope. • An insight into the M@PPOFs-catalyzed cycloaddition mechanism is proposed. A series of metal-decorated porous organic frameworks (M@PTPOFs) with cross-linked pyridyl and triazinyl were fabricated through a two-step method. The structures of the PTPOFs and M@PTPOFs were systematically characterized. As heterogeneous catalysts with Lewis acid/basic sites, the M@PTPOFs were applied to catalyze the model cycloaddition of CO 2 and epoxides. The optimal catalytic system and reaction parameters were investigated in detail. It was found that 1.0Co@PTPOF-400-15 cooperating with tetrabutylammonium iodide (TBAI) achieved the best catalytic performance, with a 96% product yield and 99% selectivity under mild conditions of 60 °C and 2.0 MPa CO 2 for 5.0 h. Moreover, 1.0Co@PTPOF-400-15 could be easily recycled by centrifugation and reused multiple times with nearly unchanged catalytic activity. Finally, the product yield and reaction parameters were compared with those of reported heterogeneous catalysts, and the possible synergistic catalytic mechanism of 1.0Co@PTPOF-400–15/TBAI was proposed. The multiple Lewis acid/basic active sites, robust structure and excellent catalytic performance are useful for the development of other high-efficiency heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Robust ZPOFs with multiple active sites are facilely constructed and show remarkable CO 2 adsorption and conversion performance under mild/green conditions. [Display omitted] • Novel ZPOFs with multiple active sites are prepared via ionothermal polymerization. • The ZPOFs show exciting dual-functions for CO 2 adsorption and conversion. • The ZPOF-mediated CO 2 coupling reaction can proceed under mild/green conditions. • The present ZPOF is easily separated and shows good stability and reusability. • The optimum catalyst exhibits excellent broad substrate scope. Porous organic frameworks fabricated by well-defined monomeric compounds with different active sites have been regarded as the promising nano-materials for improving the efficiency of CO 2 capture and utilization. In this study, novel zwitterionic porous organic frameworks (ZPOFs) alternately connected by benzimidazole, triazine and imidazolium modules were prepared facilely via ZnCl 2 -catalyzed bi-component polymerization. The influences of different monomer concentration and polymerization temperature on structural properties of the ZPOFs were discussed in detail. It indicates that the ZPOFs present attractive structure characteristics of high specific surface area and hierarchical pore structure, and have abundant hydrogen bond donors, Lewis bases and nucleophilic groups, respectively. The ZPOFs as-obtained were applied to CO 2 adsorption and conversion into cyclic carbonate by coupling with epoxide. The experiment results showed that the ZPOFs could afford the highest CO 2 adsorption capacity of 2505 μmol/g at 273 K and 1.0 bar CO 2 pressure. The effects of ZPOFs structures and reactions conditions on the catalytic performance were investigated. Under the optimized conditions of 70 °C, 2.0 MPa CO 2 for 2.0 h, and cooperating with tetrabutylammonium iodide (TBAI) cocatalyst, the ZPOF-450–30 could efficiently and selectively catalyze the CO 2 /epoxides cycloaddition reaction to yield corresponding cyclic carbonates. Moreover, the ZPOF-450–30 catalyst could be simply separated with durable high stability and activity. Finally, we compared the catalytic behaviors with reported similar heterogeneous catalysts and proposed a feasible ZPOFs-catalyzed mechanism. [ABSTRACT FROM AUTHOR]

Robust TUF-PMOs with excellent structural features are facilely constructed and exhibit enhanced CO 2 adsorption and conversion performance under mild and green conditions. [Display omitted] • Novel functionalized TUF-PMOs with excellent structural features are developed. • The TUF-PMOs show exceptional dual-functions for CO 2 adsorption and conversion. • The TUF-PMO-catalyzed coupling reaction conducts under mild and green conditions. • The catalyst is easily separated and exhibits durable high-activity. The development of advanced multifunctional nanomaterials for selective CO 2 conversion remains a major challenge. Herein, novel triazine- and urea-functionalized periodic mesoporous organosilicas (TUF-PMOs) were constructed and structurally characterized by a facile hydrothermal self-assembly method. The obtained TUF-PMOs integrate multiple hydrogen bond donor and Lewis base sites, and have high surface area and well-ordered mesoporous channel. They were used for CO 2 adsorption and catalyzing CO 2 /epoxide cycloaddition reaction. The effects of active group contents, various cocatalysts and reaction conditions on the cycloaddition reaction were examined. The optimum TUF-PMO-20 displays good bifunctionality for CO 2 adsorption and conversion when combining with tetrabutylammonium iodide (TBAI) cocatalyst under mild and green conditions. Moreover, the TUF-PMO-20 catalyst shows exciting reusability and versatility. Finally a cooperating catalytic mechanism of TUF-PMO/TBAI system in CO 2 cycloaddition reaction was provided. The present work provides a new avenue for the application of task-specific hybrid organosilicon materials in CO 2 activation and conversion. [ABSTRACT FROM AUTHOR]