Homogeneous Metal-Catalyzed Hydrogenation of CO2 Derivatives: Towards Indirect Conversion of CO2 to Methanol

Abstract

The increase in anthropogenic CO2 concentrations and associated environmental issues have demanded the development of technologies for CO2 utilization. Among various potential solutions to decrease CO2 emissions and achieve carbon neutrality, the recycling of post-combustion CO2 into value-added chemicals and fuels is considered one of the most economically attractive processes. In this regard, due to its large global demand and versatile applications in the chemical and energy sectors, methanol serves as the most appealing target for the chemical utilization of CO2. However, direct hydrogenation of CO2 to MeOH has proved challenging due to selectivity issues and high energy input, mainly dependent on CO2-emitting fossil energy sources. To address these challenges, an alternative indirect CO2-to-MeOH methodology has been proposed, which involves the hydrogenation of CO2 via the intermediate formation of well-known CO2 derivatives, such as formates, carbonates, formamides, carbamates, and urea derivatives. Homogeneous transition metal catalysts have been at the center of this research avenue, potentially allowing for more selective and low-temperature alternative routes from CO2 to MeOH. This review aims to highlight the advances and challenges in homogeneous transition metal-catalyzed hydrogenation of major CO2 derivatives to MeOH. Special attention is paid to the mechanisms of such transformations.