Recent advances in N-formylation reaction for the chemical recycling of carbon dioxide

Transformation of carbon dioxide into valuable chemicals has been an important goal of green chemistry and sustainable development of chemistry due to its contribution to the carbon cycle in the environment. Currently, many challenges, such as low efficiency and low atom utilization, have been encountered in the direct conversion of CO₂ into energy or chemicals. Notably, application of CO₂ as a carbon source in the synthesis of fine chemicals seems to be a highly efficient strategy to fully utilize it. In this case, the N-formylation reactions of amines and CO₂ toward formamides have attracted attention since formamides are very important intermediates in the synthesis of medicines and various organic compounds and can also be used as solvents. Herein, this review summarizes the recent significant advances in the last decade in the preparation, characterization, and evaluation of various types of catalysts including homogeneous and heterogeneous systems applied in N-formylation reactions. We emphasize the diversity in catalyst performances and the fundamental understanding of catalytic mechanisms. It is anticipated that this review will provide future research perspectives for catalyst design rules for catalytic N-formylation reactions of CO₂ hydrogenation coupled with amines.