Atomically precise single-atom cobalt photocatalyst for enhanced decarboxylative cross-couplings

The development of single-atom photocatalysts (SAPs) with superior activity, selectivity and reusability is a promising yet challenging strategy for advancing heterogeneous metallaphotocatalytic organic transformations in sustainable chemical synthesis. In this study, we report the controllable fabrication and application of novel cobalt-based SAPs, a class of atomically dispersed Co/photo bifunctional heterogeneous catalysts, for highly efficient decarboxylative Heck-type coupling reactions of carboxylic acids with olefins. The optimal SAP (Co_SA-K-PHI, containing 1 wt% Co and 11 wt% K), supported on ionic carbon nitride, can be facilely prepared via a mild and straightforward Co/K exchange approach using potassium poly(heptazine imide) (K-PHI) and Co-containing precursors. The close proximity and synergistic interactions between photoactive centers and single-atomic Co sites endow the catalyst with exceptional catalytic performance, enabling remarkable activity even at very low Co loading (0.07-0.34 mol%) and delivering high yields with good selectivity in decarboxylative Heck couplings, surpassing multi-component homogeneous catalyst systems. Furthermore, the integrated catalyst exhibits high stability and can be recycled at least six times without loss of activity and selectivity. This heterogeneous metallaphotocatalytic protocol not only facilitates the efficient synthesis of a diverse array of multi-substituted alkenes with good functional group tolerance, but also allows for the late-stage functionalization of bioactive natural products and the synthesis of pharmaceutically relevant compounds. This work offers new insights into the synergistic effects between atomically dispersed metals and light-harvesting carriers to enhance catalytic activity and selectivity.