An Adaptive Palladium Single-Atom Catalyst Enabling Reactivity Switching between Borylation and C-C Coupling.

The development of single-atom catalysts (SACs) with site-specific and tunable catalytic functionalities remains a highly desirable yet challenging goal in catalysis. In this study, we report a SAC featuring anisotropic coordination cavities synthesized via a one-step polymerization of 2,6-diaminopyridine and cyanuric chloride. These cavities provide a robust framework for anchoring isolated Pd single atoms with exceptional stability. The unique broken symmetry of the catalyst's local structure enables precise control over reaction pathways, allowing reactivity to be switched between distinct catalytic outcomes. Specifically, under tailored reaction conditions, the catalyst can either halt at the borylation step or proceed seamlessly to Suzuki coupling in a self-cascade process. Mechanistic studies unveil the pivotal role of Pd single atoms in driving key steps, including oxidative addition, base exchange, and reductive elimination. Furthermore, green metrics demonstrate the process's sustainability, with minimized waste generation and reduced reliance on hazardous reagents in the self-cascade transformation. This work establishes an innovative benchmark in the field of single-atom catalysis: by enabling complex, multistep transformations via strategic activation of multiple functional groups, this catalyst exemplifies the potential of self-cascade processes to revolutionize synthetic chemistry via catalysis engineering.