Recent Advances in Carbon Dioxide Capture, Fixation, and Activation by using N‐Heterocyclic Carbenes

Abstract

In the last two decades, CO2 emission has caused a lot of environmental problems. To mitigate the concentration of CO2 in the atmosphere, various strategies have been implemented, one of which is the use of N-heterocyclic carbenes (NHCs) and related complexes to accomplish the capture, fixation, and activation of CO2 effectively. In this review, we summarize CO2 capture, fixation, and activation by utilizing NHCs and related complexes; homogeneous reactions and their reaction mechanisms are discussed. Free NHCs and NHC salts can capture CO2 in both direct and indirect ways to form imidazolium carboxylates, and they can also catalyze the reaction of aromatic aldehydes with CO2 to form carboxylic acids and derivatives. Moreover, associated with transition metals (TMs), NHCs can form NHC-TM complexes to transform CO2 into industrial acid or esters. Non-metal-NHC complexes can also catalyze the reactions of silicon and boron complexes with CO2 . In addition, catalytic cycloaddition of epoxides with CO2 is another effective function of NHC complexes, and NHC ionic liquids perform excellently in this aspect.

Trapping CO2by Adduct Formation with Nitrogen Heterocyclic Carbenes (NHCs): A Theoretical Study

“…Carbon dioxide is simultaneously an environmental problem and an organic synthetic challenge to incorporate carbon from cheap and abundant sources . To address these important issues, a number of methods have been devised to sequestrate and incorporate CO 2 into other molecules . Strong Lewis bases, such as carbenes, guanidines, and phosphines, have been explored for this purpose in recent years.…”

A Theoretical Study on the Mechanism of Methylation of N‐methylaniline with CO2 and Silyl Hydrides

“…Alternatively, because methylamines feature a C1 group, their synthesis by using CO 2 as a synthon would be an attractive strategy (Scheme , reaction 2). This approach is also a green and environmental‐friendly way to reduce CO 2 levels in the atmosphere . Much effort has been, therefore, devoted to developing the efficient methodologies for synthesizing methylamines with high yields and excellent selectivity.…”

Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

“…Later, Louie and coworkers reported a different synthesis, carried out bubbling CO2 into an imidazolium salt and potassium tert-butoxide solution [52]. The various syntheses of NHC-CO2 adducts as well as their chemistry are discussed in both classical and more recent reviews [53][54][55].…”