Guiding Photochemical Process Intensification Through Kinetic Diagnostics

Photochemical methodologies are commonly optimized towards yield, yet yield alone provides limited insight into productivity and scalability. Here, we demonstrate how simple kinetic diagnostics can guide photochemical process intensification by identifying the dominant limitations governing reaction performance. Using the photochemical Minisci alkylation of phenanthridine with ethane as a representative gas-liquid transformation, systematic screening of pressure, mixing, light intensity, and temperature revealed the controlling transport and kinetic phenomena, enabling targeted engineering interventions and reactor selection. The resulting workflow guided the transition from batch to continuous flow and ultimately gram-scale synthesis, achieving a production rate of 19 g day^{- 1} while operating under substantially less demanding conditions than the original methodology. Beyond improving productivity and energy efficiency, this work illustrates how integrating kinetic diagnostics into methodology development provides a practical framework for designing scalable photochemical processes.