Protic Pyrazolium Ionic Liquids: An Efficient Catalyst for Conversion of CO₂ in the Absence of Metal and Solvent

Abstract

A series of novel protic pyrazolium ionic liquids are first synthesized and utilized as catalysts for cycloaddition of carbon dioxide and epoxides to form cyclic carbonates under metal-and solvent-free conditions. The new developed protic pyrazolium ionic liquids present excellent catalytic activity toward the fixation of carbon dioxide. More importantly, they would be prepared by a facile two-step reaction from cheap raw starting materials with a yield more than 90%. The influence of catalyst dosage, reaction temperature, carbon dioxide pressure, and reaction time on the synthesis of cyclic carbonates is investigated to identify the optimal reaction conditions. Under the optimum conditions, the catalyst suitability is studied. Additionally, the possible reaction mechanism is investigated by the double-IL model to elucidate the synergistic effects of electrostatic and weak interaction in the catalytic process.

Efficient transformation of CO2 to cyclic carbonates using bifunctional protic ionic liquids under mild conditions

“…22,23 To date, various catalysts have been developed for the synthesis of useful cyclic carbonates from CO2 and epoxides, such as metal-based catalysts, [24][25][26][27][28][29][30][31][32][33][34] organocatalysts, [35][36][37][38][39][40][41][42][43][44] and ionic liquids etc. [45][46][47][48][49][50][51][52][53] Although most of the catalyst systems show a good yield to produce carbonates, high temperatures (>100 °C) and/or high CO2 pressures are always needed in these studies. Hence, great efforts have been focused on the development of efficient and sustainable catalyst systems that can be carried out chemically converting CO2 at relatively mild reaction conditions.…”

Pyridinium‐functionalized metalloporphyrins as bifunctional catalysts for cycloaddition of epoxides and carbon dioxide

“…Development of efficient catalysts for cycloaddition of epoxides with CO 2 is an attractive topic for the industrial application. Various catalysts have been developed, such as organocatalysts, inorganic salt and organic salt catalysts, quaternary ammonium salts, ionic liquid catalysts and metal complex catalysts et al…”

Supported Polyhedral Oligomeric Silsesquioxane‐Based (POSS) Materials as Highly Active Organocatalysts for the Conversion of CO2

“…On this basis, the better catalytic activity of 5 a could be explained by a higher local concentration of imidazolium modified POSS units which resulted in improved intermolecular interactions. Both 5 a and 6 a showed competitive and higher performances in comparison with other catalytic systems recently reported in literature (Table ) such as 1‐butyl‐3‐methylimidazolium chloride (BmImCl), or pyrazolium bromide (HEPzBr) unsupported ionic liquids (entries 3,4), and heterogeneous catalysts based on polymer supported ammonium chloride salts (PSCQNCl), imidazolium chloride and tetrafluoroborate active sites supported onto silica (SiO 2 ImCl, SiO 2 ImBF 4 ), or imidazolium salts bearing bromide as counterion grafted onto carbon nanohorns (CNHsImBr), and benzyl chloride polymer (BCPImBr) (entries 5–9). The above catalytic systems do not present other co‐catalytic species with Brønsted or Lewis acid functionalities.…”