Oxygen vacancy-rich Sr${}_2$MgSi${}_2$O${}_7$:Eu${}^{2+}$,Dy${}^{3+}$ long afterglow phosphor as a round-the-clock catalyst for selective reduction of CO${}_2$ to CO

Solar-driven CO${}_2$ conversion to fuels is a central technique for closing the anthropogenic carbon cycle, but to date is limited by the intermittent solar flux. To face this challenge, a catalyst is needed that can work well in both light and dark. Here, surface oxygen vacancies are created in a Sr${}_2$MgSi${}_2$O${}_7$:Eu${}^{2+}$,Dy${}^{3+}$ long-afterglow phosphor with long-time and high charge storage capacity (denoted as Vo-SMSED) as both electron transfer station and active sites for molecule activation. The strong ability for oxygen vacancies to store and extract electrons from charge storage centers enables the Vo-SMSED to work efficiently in both light and dark. As a result, Vo-SMSED manifests nearly 100% selectivity for catalyzing CO${}_2$ reduction by H${}_2$O to CO with high light stability and over 3 h dark activity. These results demonstrate that creating the bifunctional sites as electron-storing/extracting and molecule-activating center is an efficient route to change the long-lived charge into the highly active species for catalysis, thus making the long-afterglow phosphors with high charge storage capacity a highly efficient round-the-clock photocatalyst. (© 2022 Wiley‐VCH GmbH)