New Frontiers in Single-Atom Catalysis: Active-Site Dynamics and AI-Enabled Design

Single-atom catalysts (SACs) have emerged as a rapidly advancing frontier in heterogeneous catalysis because of their unique electronic structures, maximized atomic efficiency, and tunable catalytic properties. Increasing evidence shows that SACs are inherently dynamic under working conditions with their coordination environment, electronic structure, and spatial configuration continuously adapting in response to reactants, intermediates, or external stimuli. These dynamic properties critically influence catalytic activity, selectivity, and stability, challenging conventional design paradigms and opening new opportunities for performance optimization. This review provides a comprehensive overview of the active-site evolution in SACs under reaction conditions. We discuss the fundamental mechanisms underlying atomic migration, coordination changes, and reaction-induced interconversion of desaturated single-atom states. We also highlight strategies to harness and control these processes through support engineering and coordination modulation, enabling the rational design of desaturated active sites. Finally, we outline major challenges and future directions, including the use of in situ/operando characterization, multiscale modeling, and machine learning, to accelerate the rational design of high-performance SACs. By elucidating the fundamental aspects of SAC active site evolution, this Review provides critical insights and design principles to advance the development of high-performance SACs.