Tunable Hydro/Dicarboxylation of Ethylene with CO₂ via a Barrierless Radiolytic Free-Radicals Pathway

The hydro/dicarboxylation of ethylene (C₂H₄) feedstock with CO₂ to produce high-value carboxylic acids is an industrially relevant yet challenging reaction due to their extremely low reactivities. Herein, we present an effective strategy to synthesize propionic acid and succinic acid from a mixture of CO₂ and C₂H₄ catalyzed by high-energy water radiolysis. The process involves the generation of CO₂ radical anions via the barrierless attachment of hydrated electrons to CO₂, facilitating an ambient, continuous carboxylation of C₂H₄ with an efficiency of 81.4%. Utilizing easily available electron beam irradiation, we achieved a combined production rate of 0.34 mmol L^-1 min^-1 for carboxylic acids, which is unattainable by the existing methods. Notably, product selectivity between hydro- and dicarboxylation was dose-rate/beam intensity-dependent: high-dose-rate irradiation favored succinic acid formation with a proportional yield of up to 65.4%, while milder conditions resulted in an 85.1% yield of propionic acid. We suggested that the simplicity and efficiency of the present carboxylation approach promote circular carbon in the sustainable chemical industry.