Light driven chemical fixation and conversion of CO2 into cyclic carbonates using transition metals: A review on recent advancements

Carbon dioxide (CO2) is an abundantly available, attractive, and renewable C1 feedstock that can be used for the production of specialty and industrial chemicals. The synthesis of cyclic carbonates from the cycloaddition of CO2 with epoxides is an important, atom economical, and green synthesis than the conventional phosgene based process. So far, numerous catalysts including transition metal complexes, metal oxides, heterogeneous catalysts, ionic liquids, and, more recently metal free systems have been emerged. However, an extensive amount of energy is required for CO2 activation and conversion because of its chemical inertness and higher thermodynamic stability. In order to overcome these limitations and perform the CO2 fixation reactions at ambient conditions, photocatalysis has attracted significant attention. Similarly, photo-induced thermal methods owing to the synergistic effect between photocatalysis and thermocatalysis have shown considerable improvement in the photo-induced CO2 cycloaddition reaction. This particular review is concerned with the recent work (mainly in the last few years) on the photo- and photothermal catalytic synthesis of cyclic carbonates from the coupling of CO2 with epoxides under mild conditions. The reaction parameters and the proposed mechanistic pathways of the reported methods have also been summarized. Furthermore, approximated cost analysis of the best selected photo-/ photothermal methods and a summary of the known catalytic methods for cyclic carbonate synthesis are presented for clarity and better understanding.