Synthesis of Cyclic Carbonate Catalyzed by DBU Derived Basic Ionic Liquids

Abstract

In this work, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), 1,5‐diazabicyclo[4.3.0]‐5‐nonene (DBN), and imidazole (MIM)‐derived bromide ionic liquids (ILs) were synthesized and used to catalyze the cycloaddition reactions of carbon dioxide (CO2) with several kinds of epoxides to form cyclic carbonates. The DBU derived bromide ionic liquid system was found to have the best catalytic activity among all the tested ILs. The influences of reaction conditions (including temperature, pressure and reaction time) on the reaction of CO2 to propylene oxide (PO) were studied to show the best conditions of 120 °C, 1 MPa, 2.5 h catalyzed by 2 mol% DBU‐derived bromide ionic liquid, with the conversion of PO and the selectivity of propylene carbonate (PC) reaching 99% and 99%, respectively. Under the optimum reaction conditions, the ionic liquid system could be reused at least five times without decrease in selectivity and conversion. NMR spectroscopy and DFT calculations were used to reveal the hydrogen‐bond interaction between ionic liquids and reagent, based on which the reaction mechanism was proposed.

Regulation of Novel Multi‐Center Ionic Liquids for Synergetically Catalyzing CO2 Conversion into Cyclic Carbonates

“…There are a multitude of catalysts that are investigated for cycloaddition, such as metal complexes, [9] metal‐organic frame material, [10] hydrogen bond donors, [11] ILs [12] and nonmetallic material [13] . For all these catalysts, ILs have been widely studied for its structure tunability and thermal stability, which therefore have many applications in various fields, such as oxidation, [14] cycloaddition, [15] alkylation, [16] hydrogenation [17] . Furthermore, designing ILs with specific structures of cations and anions can promote cycloaddition effectively and ideally.…”

CO2 fixation into cyclic carbonates catalyzed by single-site aprotic organocatalysts

“…31 The utilization of CO 2 can be accomplished either through hydrogen bond donors (HBDs) which are capable of coordinating with epoxides, 32 viz., hydroxyl and amine groups, or through electrostatic interaction between the oxygen atom of epoxide and a quaternary onium center 33 which includes a broad range of the major four families of imidazolium, 34 ammonium, 35 phosphonium, 36 and pyridinium 37 materials. Moreover, ionic liquids (ILS), 38,39 Lewis acid-base motifs, 40,41 functionalized carbon nanotubes, 42,43 covalent-organic frameworks, 44,45 graphene oxides, 46,47 pyrazolium, 48 amidinium, 49 guanidinium, 50 and N-heterocyclic carbene precursors 51 were reported in the literature for the purpose of CO 2 cycloaddition to epoxides.…”

Nanoconfinement Ionic Liquid Membranes for Efficient Flow Catalytic CO2 Cycloaddition

“…In detail, the structure and performance of the hybrid system can be tuned by changing the geometry, pore size distribution, and surface function of porous hosts and the structure, viscosity, and loading fraction of ILs, as well as external conditions such as vacuum, functional groups, electric field, temperature, etc., and enhance the interaction of ILs with supports to satisfy specific application requirements. , Quaternary ammonium-derived ILs were used as catalytically active species, and the reaction cycle performance showed excellent results, especially the cyclic amidine derivative 1,8-diazabicyclo [5.4.0]-undec-7-ene (DBU) is involved in the host of proton-derived ILs . The merits of DBU as an IL precursor are associated with properties such as large size, strong charge delocalization ability, and low cationic symmetry on the N–CN structure, and organic superbase DBU has a highly reactive nitrogen atom in the heterocyclic framework; therefore, efficient quaternization can form stable cationic structures without chemically active hydrogen protons . After the synthesis of proton-derived Lewis basic ionic liquids, the quaternary ammonium cation becomes electron-withdrawing groups that allow the presence of hydrogen-bond donor contributions in the functional group.…”