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.