Electrocarboxylation of CO_(2) with Organic Substrates:Toward Cathodic Reaction

Electrocarboxylation of carbon dioxide(CO_(2))using organic substrates has emerged as a promising method for the sustainable synthesis of value-added carboxylic acids due to its renewable energy source and mild reaction conditions.The reactivity and product selectivity of electrocarboxylation are highly dependent on the cathodic behavior,involving a sequence of electron transfers and chemical reactions.Hence,it is necessary to understand the cathodic reaction mechanisms for optimizing reaction performance and product distribution.In this work,a review of recent advancements in the electrocarboxylation of CO_(2)with organic substrates based on different cathodic reaction pathways is presented to provide a reference for the development of novel methodologies of CO_(2)electrocarboxylation.Herein,cathodic reactions are particularly classified into two categories based on the initial electron carriers(i.e.,CO_(2)radical anion and substrate radical anion).Furthermore,three cathodic pathways(ENE(N),ENED,and EDEN)of substrate radical anion-induced electrocarboxylation are discussed,which differ in their electron transfer sequence,substrate dissociation,and nucleophilic reaction,to highlight their implications on reactivity and product selectivity.

Recent advances in cycloaddition of CO_(2) with epoxides:halogen-free catalysis and mechanistic insights

The atom-economical cycloaddition of CO_(2) with epoxides to synthesize cyclic carbonates is a promising route for valuable utilization of CO_(2).Halogenide such as alkali metal halides and quaternary ammonium salt have been developed as the efficient catalysts.However,the spilled halogen causes equipment corrosion and affects the product purity.To address these concerns,the halogen-free cycloaddition of CO_(2) with epoxides has always been desired.In this review,we systematically discussed the halogen-free catalysis for cycloaddition of CO_(2) with epoxides from the mechanistic insights,aiming to promote the development of efficient halogen-free catalysts.Two types of catalysts,i.e.,alternatives of halogen nucleophiles for epoxide activation,and bifunctional catalysts with Lewis acid-base sites for synergistic activation of CO_(2) and epoxides are summarized and emphasized.Specially,metal oxides as the potential halogen-free catalysts are highlighted due to their flexible acid-base sites for synergistic activation of CO_(2) and epoxides,facile preparation,and low cost.