Electrochemical carboxylation is an organic electrosynthesis technique where CO2 is coupled with one or more organic molecules to form carboxylic acids. Here, we show that process intensification and selectivity enhancements are simultaneously achieved by performing electrochemical carboxylation in CO2-eXpanded electrolytes (CXE)a class of media that accommodates multimolar concentrations of CO2 in organic solvents at modest pressures. We observed that electrochemical carboxylation of acetophenone does not occur at ca. 1 atm (0.2 MPa) CO2 headspace pressure. Instead, acetophenone hydrogenation was dominant, producing the undesired 1-phenylethanol as the major product. However, in the CXE media (at 1.4–4.2 MPa CO2 headspace pressure), (±)-atrolactic acid was the major product with a maximum faradaic efficiency of 72% observed at 2.8 MPa. Achieving the pressure-tunable carboxylation results from the high liquid-phase CO2 concentrations afforded by the CXE media. At CO2 pressures exceeding 2.8 MPa, we observed a lower rate of carboxylation, which is attributed to the decreased electrolyte polarity at progressively greater liquid-phase CO2 concentrations present at higher pressures.

[Ru(tpy)(pyalk)Cl]Cl (pyalk = 2-(2'-pyridyl)-2-propanol) was synthesized and characterized crystallographically and electrochemically. Upon dissolution in water and acetonitrile, [Ru(tpy)(pyalk)Cl]Cl was found to form [Ru(tpy)(pyalk)Cl]+ and [Ru(tpy)(pyalk)(OH)]+, respectively. The Ru(ii/iii) couple of [Ru(tpy)(pyalk)Cl]+ was found to be relatively low compared to that of other Ru complexes in acetonitrile, but the Ru(iii/iv) couple was not significantly different than other Ru complexes bearing anionic ligands. Pourbaix diagrams were generated for [Ru(tpy)(phpy)(OH2)]+ (phpy = 2-phenylpyridine) and [Ru(tpy)(pyalk)(OH)]+ in water, and it was found that [Ru(tpy)(pyalk)(OH)]+ has a lower Ru(ii/iii) potential than [Ru(tpy)(phpy)(OH2)]+ under neutral to alkaline pH. [Ru(tpy)(pyalk)(OH)]+ was found to catalyze C-H bond hydroxylation of secondary alkanes and epoxidation of alkenes using cerium(iv) ammonium nitrate as the primary oxidant.