Sustainable Cyclic Carbonate Production, Utilizing Carbon Dioxide and Azolate Ionic Liquids

Abstract

An efficient protocol is described for producing cyclic carbonates in good to excellent yields under moderate reaction conditions (100.0 °C, 1.0 MPa) by treating epoxides with carbon dioxide, promoted by a series of azolate ionic liquids, which are effective, recyclable, metal-free, and halide-free catalysts.

The Role of Water Revisited and Enhanced: A Sustainable Catalytic System for the Conversion of CO2 into Cyclic Carbonates under Mild Conditions

“…[5] Many highly active and selective metal-based catalysts containing Lewis acid sites have been reported, such as metal complexes [10] and metal-organic frameworks (MOFs). [1,12] Several metal-free organic catalysts have also been investigated, such as ammonium halides, [1,[13][14][15] phosphonium halides, [3,16] and imidazolium-basedi onic liquids, [17][18][19] in which the halidesa re the catalytic speciesa cting as nucleophiles. [1,12] Several metal-free organic catalysts have also been investigated, such as ammonium halides, [1,[13][14][15] phosphonium halides, [3,16] and imidazolium-basedi onic liquids, [17][18][19] in which the halidesa re the catalytic speciesa cting as nucleophiles.…”

Controllable Homogeneity/Heterogeneity Switch of Imidazolium Ionic Liquids for CO2 Utilization

“…Temperature‐assisted homogeneity/heterogeneity switch of IL has been applied to epoxide substrates with a variety of substituents (Figure ). Regardless of the functionalities, the tested substrates have shown quantitative conversion into cyclic carbonates under atmospheric pressure of CO 2 , making mimC 18 [Br] comparable to efficient ILs reported recently,. By virtue of thermal stability of mimC 18 [Br] (Figure S2), reaction temperature could range from 90 °C to 130 °C to yield target products 2 a–2 h in 24 h (See NMR spectra of products in supporting information).…”

“…The CO 2 cycloaddition upon epoxide is often conducted in elevated temperature, and imidazolium IL plays a role as a homogeneous catalyst in the reaction. Therefore, in order to separate out cyclic carbonate product and recycle the IL catalyst, energy‐intensive methods have been utilized such as vacuum distillation and column chromatography, resulting in extra cost. Basic idea of homogeneity/heterogeneity switch resides in phase separation of IL catalyst by temperature change.…”

Azolate Anions in Ionic Liquids: Promising and Under‐Utilized Components of the Ionic Liquid Toolbox

“…(Interestingly, the azolate ILs did not show any change in viscosity after CO 2 capture as is the case and the major challenge with amines and most functionalized ILs.) Very recently, Seddon et al., described the capture and fixation of CO 2 into cyclic carbonate, a key building block for various commodity chemicals . These contributions would seem to point to an important role for azolate ILs in CO 2 capture and reuse, so it is surprising that so few researchers seem to consider azolate ILs in these applications.…”

“…Recycling of the ILs will certainly not be of concern for azolate ILs as hypergolic fuels. However, the recent report noted above on the study of azolate ILs in CO 2 capture applications, specifically highlighted the easy and efficient recycling of the ILs . We believe that once more azolate IL applications are considered, the community will engage in a more concerted effort to study recycle and cost reductions in synthesis.…”