Compartmentalized Liquid Microenvironments of Pickering Emulsion Droplets for Continuous-Flow Catalysis

Transitioning catalysis from batch to continuous flow remains a key objective of sustainable chemistry, yet the effective retention of homogeneous catalysts and enzymes under flow conditions is a persistent challenge. This Perspective highlights Pickering emulsion droplet (PED)-based fixed-bed reactors as a modular strategy that enables continuous-flow catalysis by confining homogeneous catalysts and enzymes within particle-stabilized liquid microdomains that can be directly packed into column reactors. Owing to the high structural stability of droplets under flow, their strong confinement capability, and favorable liquid microenvironments that preserve catalytic activity, as well as the near-plug-flow behavior of the packed-bed, PED-based systems fundamentally differ from conventional solid-supported fixed-bed reactors and exhibit enhanced catalytic efficiency and long-term operational stability. We summarize the evolution of PED architectures from simple Pickering emulsion droplets to shell-engineered microcapsules, multicompartmentalized biomimetic microreactors, and mechanically reinforced supraparticles. Applications in enzymatic catalysis, enzyme-cofactor systems, chemoenzymatic cascades, homogeneous catalysis, and photo- and electrocatalysis are discussed. Finally, we outline future directions toward establishing a theoretical framework for PED-based continuous-flow systems, advancing operando characterization, expanding applications in pharmaceutical continuous manufacturing, and constructing PED-based biomimetic cell factories for carbon upgrading. PED-based fixed-bed systems thus emerge as a versatile platform for sustainable chemical manufacturing.