Oxygen Vacancy‐Rich Sr2MgSi2O7:Eu2+,Dy3+ Long Afterglow Phosphor as a Round‐the‐Clock Catalyst for Selective Reduction of CO2 to CO

Abstract 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.