From batch to flow plasmon catalysis: revealing mass transport limits in Au@Pd nanocatalysts for Suzuki coupling

Plasmonic catalysis, as a powerful tool for synthetic transformations, has the potential to impact wide-scale applications by converting solar light into energy for chemical reactions. Current studies are limited to mL-scale batch reactors with mg-level nanocatalysts, lacking feasibility in common laboratory and industrial configurations. To overcome this limitation, transition of plasmonic chemistry from batch to flow mode is foreseen; however, there is a lack of understanding of how plasmon-driven processes couple with mass transport. To address this issue, we designed plasmonic catalysts for a flow system at a tens of mL scale employing gram-scale Au@PdNPs-Al₂O₃ nanostructures in a flow reactor. Using Suzuki cross-coupling as a model reaction, we showed that the flow mode for Au@PdNPs-Al₂O₃ increases the reaction rate, the time to full conversion and the apparent quantum yield (AQY) ×3 compared to batch mode and outperforms previously reported examples/cases. Fluid dynamic simulations showed the critical effect of the residence times of nanocatalyst-reactant complexes under illumination on the product yield. This was consistent with photocurrent measurements, revealing that the electron transfer efficiency is enhanced under increased mass transport conditions. Unlike previous studies that primarily emphasized the carrier dynamics within metal-metal/semiconductor heterojunctions (e.g., Au/Pd) in batch mode, our flow system demonstrates that efficient carrier transfer to reactants is critical for achieving high TONs and AQYs. This work provides the first framework for translating plasmonic catalysis into flow, offering design principles for future light-driven chemical processes beyond conventional batch mode.