Perspective on CO2 Hydrogenation for Dimethyl Ether Economy

The CO2 hydrogenation to dimethyl ether (DME) is a potentially promising process for efficiently utilizing CO2 as a renewable and cheap carbon resource. Currently, the one-step heterogeneous catalytic conversion of CO2 to value-added chemicals exhibits higher efficiency than photocatalytic or electrocatalytic routes. However, typical catalysts for the one-step CO2 hydrogenation to DME still suffer from the deficient space–time yield and stability in industrial demonstrations/applications. In this perspective, the recent development of the one-step CO2 hydrogenation to DME is focused on different catalytic systems by examining the reported experimental results and the reaction mechanism including the catalytic nature of active sites, activation modes and of CO2 molecules under relevant conditions; surface intermediates are comparatively analyzed and discussed. In addition to the more traditional Cu-based, Pd-based, and oxide-derived bifunctional catalysts, a further emphasis is given to the characteristics of the recently emerged In2O3-based bifunctional catalysts for the one-step conversion of CO2 to DME. Moreover, GaN itself, as a bifunctional catalyst, shows over 90% DME selectivity and a reasonably high activity for one-step CO2 hydrogenation, and the direct hydrogenation of CO2 via the unique non-methanol intermediate mechanism is highlighted as an important illustration for exploring new catalytic systems. With these analyses and current understandings, the research directions in the aspects of catalysis and DME economy are suggested for the further development of one-step DME synthesis from CO2 hydrogenation.