Isolated Single-Atom Cobalt in the ZnIn2S4 Monolayer with Exposed Zn Sites for CO2 Photofixation

Constructing highly active photocatalysts with rich reactive sites for photofixation of CO2 with organic compounds implements an environmentally friendly route for CO2 valorization and carbon neutralization. Herein, we report the isolated cobalt (Co) single-atom (SA)-decorated two-dimensional (2D) single-layer ZnIn2S4 (ZIS) nanosheet composites (Co-sZIS) with dual active centers of Co and Zn for CO2 fixation with epoxides under visible light. The unique ensemble of Co-sZIS optimizes light harvesting, promotes charge carrier separation, and enriches the bifunctional active sites for the efficient adsorption and activation of the reactants of epoxides and CO2. Consequently, the Co-sZIS exhibits significantly improved CO2-epoxide cycloaddition performance compared to bulk ZIS. In addition, the synergetic photoredox manner of simultaneously exploiting photogenerated electrons and holes efficiently facilitates the activation of CO2 and epoxides, thereby further reducing the energy barrier of CO2 fixation. This work not only provides a paradigm of rationally interfacial engineered SA-onto-2D semiconductors for CO2 valorization but also highlights the structure–activity relationship by the well-defined active sites in this SA-based hybrid platform.