<italic>In situ</italic> catalytic hydrogenation of carbon dioxide

Abstract

Carbon capture and sequestration (CCS) is being explored as potential methods for mitigating CO2 accumulation. However, the high energy input in desorption/compression processes is a barrier. As a nontoxic, abundant, renewable C1 building block, CO2 can be used as an alternative carbonylating reagent to replace phosgene and carbon monoxide in organic synthesis and the chemical industry. The strategy of turning waste gas CO2 into useful compounds and the use of CO2 in the production of high-value-added compounds are important topics, especially the reduction of CO2 to energy products. We describe a strategy involving a combination of CO2 capture and utilization, in which the captured CO2 is considered as the substrate for further in situ catalytic transformations. This process circumvents the desorption and compression steps, and solves the energy penalty problem in CCS. It also avoids the use of high-pressure CO2, which poses safety concerns and is not economically viable. CO2 molecules can also be activated upon adsorption, which is favorable for subsequent in situ conversion under mild conditions. Of the many possible pathways for CO2 use, in situ catalytic hydrogenation is important, and has a wide range of potential application. The CO2 captured as carbamate or carbonic salts can be in situ hydrogenated to formic acid, methanol, and other important energy products. In this review, CO2 adsorption and chemical fixation methods are briefly introduced, and the catalytic systems for CO2 hydrogenation are systematically summarized. In particular, the latest progress on in situ catalytic hydrogenation and mechanistic understanding at the molecular level is discussed in detail.