Bifunctional catalysts for the conversion of CO2 into value-added products – distance as a design parameter for new catalysts

Abstract

More than 1000 CO₂ chemistry publications within the last five years have featured the application of bifunctional catalysts. The majority of these articles investigate hydrogenation reactions of CO₂ for producing alkanes, alcohols, and ethers. Reactions using CO₂ and epoxides as reactants for producing cyclic carbonates or linear polycarbonates have also been extensively researched. For all of these CO₂ chemistries, an informed choice of the combined materials and their arrangement as a bifunctional catalyst is critical to their performance. Herein, we identify the distance between active sites in bifunctional catalysts as an important control parameter for the system performance. We show that a range of optimal distances between the active sites can be identified for each of the interaction mechanisms enabled by bifunctional catalysts, namely steric and electrostatic interactions as well as concentration gradients of intermediate products. For the design of bifunctional core–shell catalysts, a model-based workflow is suggested.