Mapping Local Environments in Single-Atom Catalysts

Single-atom catalysts (SACs) offer exceptional structural resolution for investigating how local environments govern catalytic behavior and, ultimately, for controlling these effects through catalyst design. Yet, atomic dispersion does not imply a single or fully defined catalytic environment. The behavior of atomically dispersed active centers is shaped by a hierarchical local environment comprising persistent and transient contributions, while also being influenced by an extended reaction environment that intersects with the local environment in controlling reactivity and can become integrated into it. Establishing these boundaries and understanding how these contributions evolve and interact are central challenges in the interpretation and design of SACs. Here, we critically examine how local environments are generated and controlled, experimentally and theoretically resolved across spatial and temporal scales, transformed from synthesis through operation and deactivation, and linked to catalytic performance through structural, energetic, and electronic descriptors. By integrating aspects that are often considered separately and highlighting those that remain insufficiently addressed, we provide a roadmap toward the predictive, environment-driven design of SACs and a deeper understanding of catalytic phenomena.