Integrated electrochemical CO2 reduction and hydroformylation

Abstract

The development of integrated multi-catalyst processes has become of high interest to transform abundant feedstocks or environmental pollutants to commodity chemicals in a one pot, one pass fashion. Specifically, CO₂ poses a large environmental burden and would thus be a desirable, relatively abundant C1 source in multi-step synthetic chemistry. Herein we disclose the synthesis of aldehydes from CO₂via the integration of electrochemical CO₂ reduction (CO₂RR) and hydroformylation, taking advantage of the typically unwanted concomitant hydrogen evolution (HER) to generate the necessary CO and H₂ needed for hydroformylation. Though typical hydroformylation catalysts based on Rh would be deactivated under CO₂RR conditions, we circumvent this limitation by spatially segregating our CO₂RR and hydroformylation systems in a vial-in-vial reactor, while allowing CO and H₂ transport between catalyst sites. In this manner, 97% aldehyde yield from CO₂RR and styrene was achieved selectively using a classic homogeneous hydroformylation catalyst in HRh(CO)(PPh₃)₃, and 43% aldehyde yield was obtained using a heterogenized version of this Rh catalyst onto mesoporous silica. This work not only repurposes undesired HER in CO₂RR and prepares aldehydes from CO₂ without added H₂, but expands the scope of processes that transform feedstocks all the way to commodity chemicals in a one pass manner.