Newly synthesized imidazolium precursors for CO2 utilization and sequestration: aprotic versus protic salts

Abstract

Herein, a first-time, one pot synthesis of 1,3-bis(3-(1,3-dioxoisoindolin-2-yl)propyl)-1H-imidazol-3-ium bromide (7), which can be considered a vital precursor for the facile synthesis of highly pure task specific ionic liquids (TSILs), and other derivatives including unprecedented protic and aprotic systems is reported. Catalyst decoration including: phthalimide effect (protic vs. aprotic), peripheral length, and blocking the head and base of imidazolium active sites was investigated extensively. Single crystal X-ray diffraction (XRD) verified the chemical structure of the ammonium-based precursor, viz., 1,3-bis(3-ammoniopropyl)-1H-imidazol-3-ium bromide (15). Moreover, we report on the overall activity of homogeneous rather than heterogeneous imidazolium-based catalytic systems for cyclic carbonate (CC) production with almost quantitative conversions as achieved by TSIL 3 at 90 °C and 1 bar of CO₂. Also, isolated yields of CCs were obtained and a 5-run recyclability experiment for the homogeneous catalyst 7 was further carried out with high productivity. In addition, 3 was tested for CO₂ capture in DMSO, which resulted in the formation of an ionic carbamate because of a 1 : 2 reaction mechanism. Experimental isolation of some intermediates was achieved and supported via density functional theory (DFT) calculations.