Mind the gap: Embedding green metrics in modern flow chemistry

Abstract: Continuous-flow chemistry is widely regarded as an inherently green technology due to advantages in heat and mass transfer, safety, and process intensification. However, whether these benefits translate into measurable environmental performance is rarely demonstrated quantitatively. Here, we examine how sustainability is framed, inferred, and documented in the modern flow-chemistry literature using a structured, text-mining–assisted review of 113 machine-readable research articles drawn from a larger corpus of 680 publications. We identify a pronounced “metrics gap.” Fewer than 10% of full-text articles report quantitative sustainability metrics such as Process Mass Intensity (PMI), E-factor, solvent intensity, or energy intensity, while more than 80% report sustainability-relevant performance improvements (e.g., higher yields, shorter reaction times, milder conditions, or improved safety). These results indicate that most flow platforms are already “metrics-ready,” but lack standardized pathways for translating existing data into green metrics. To address this gap, we propose a practical, modular framework for embedding PMI, solvent intensity, and energy intensity directly into routine continuous-flow experimentation. This approach emphasizes clear system boundaries, deliberate capture of mass and energy flows, transparent metric calculation, and integration of sustainability objectives into automated optimization workflows.