Droplet‐Based Microfluidics Reveals Insights into Cross‐Coupling Mechanisms over Single‐Atom Heterogeneous Catalysts

Single‐atom heterogeneous catalysts (SACs) hold promise as sustainable alternatives to metal complexes in organic transformations. However, their working structure and dynamics remain poorly understood, hindering advances in their design. Exploiting the unique features of droplet‐based microfluidics, we present the first in‐situ assessment of a palladium SAC based on exfoliated carbon nitride in Suzuki–Miyaura cross‐coupling using X‐ray absorption spectroscopy. Our results confirm a surface‐catalyzed mechanism, revealing the distinct electronic structure of active Pd centers compared to homogeneous systems, and providing insights into the stabilizing role of ligands and bases. This study establishes a valuable framework for advancing mechanistic understanding of organic syntheses catalyzed by SACs. Developing recyclable heterogeneous catalysts for organic synthesis requires a deep understanding of active site architectures during surface‐catalyzed reactions. Our approach, combining in‐situ X‐ray absorption spectroscopy and droplet‐based microfluidics, investigates Suzuki–Miyaura coupling over palladium single‐atoms on carbon nitride. The results highlight the need for distinct design criteria compared to traditional homogeneously catalyzed processes.