Microdroplet Cascade Catalysis for Highly Selective Production of Propylene Glycol under Ambient Conditions

Conventional propylene glycol (PG) production relies on an energy-intensive two-step thermocatalytic process, contributing significantly to CO₂ emissions. A sustainable alternative under ambient conditions remains elusive, hindered by challenges in selectivity and energy efficiency. Here, we present a cascade catalysis strategy for efficient and selective PG production within water microdroplets under ambient conditions. Propylene (CH₃CH═CH₂) is converted to PG (CH₃CH(OH)CH₂OH) at the microdroplet/titanium silicalite-1 (TS-1) interface, driven by in situ generated hydrogen peroxide (H₂O₂) via methyl viologen catalysis. This approach harnesses the water microdroplet interface to confine the reaction, enhancing catalytic activity and increasing selectivity. Our system achieves a PG production efficiency of 680 μM and a selectivity of 88%, while minimizing unwanted side products and energy demands. This innovative method offers a sustainable pathway for PG synthesis and highlights the transformative potential of water microdroplet technology in advancing green chemistry and industrial applications.