Utilisation of CO 2 as “Structure Modifier” of Inorganic Solids

Utilisation of CO 2 as a chemical reagent is challenging, due to the molecule's inherent chemical stability. However, CO 2 reacts promptly at high temperature (∼1000 °C) with alkaline‐earth oxides to form carbonates and such reactions are used towards capture and re‐utilisation. In this work, this concept is extended and CO 2 is utilised as a reagent to modify the crystal structure of mixed‐metal inorganic solids. Modification of the crystal structure is a “tool” used by materials scientists to tailor the physical property of solids. CO 2 gas was reacted with several isostructural mixed‐metal oxides Sr 2 CuO 3 , Sr 1.8 Ba 0.2 CuO 3 and Ba 2 PdO 3 . These oxides are carefully selected to show anion vacancies in their crystal structure, to act as host sites for CO 2 molecules, leading to the formation of carbonate anions, (CO 3 ) 2− . The corresponding oxide carbonates were formed successfully and the favourable formation of SrCO 3 as secondary phase was minimised via an innovative, yet simple synthetic procedure involving alternating of CO 2 and air. We also derived a simple model to predict the kinetics of the reactions for the cuprates, using first‐principles density functional theory and assimilating the reaction to a gas‐surface process.