Complex Droplet Microreactor for Highly Efficient and Controllable Esterification and Cascade Reactions

Abstract A highly efficient complex emulsion microreactor has been successfully developed for multiphasic water‐labile reactions, providing a powerful platform for atom economy and spatiotemporal control of reaction kinetics. Complex emulsions, composing a hydrocarbon phase (H) and a fluorocarbon phase (F) dispersed in an aqueous phase (W), are fabricated in batch scale with precisely controlled droplet morphologies. A biphasic esterification reaction between 2‐bromo‐1,2‐diphenylethane‐1‐ol (BPO) and perfluoro‐heptanoic acid (PFHA) is chosen as a reversible and water‐labile reaction model. The conversion reaches up to 100 % under mild temperature without agitation, even with nearly equivalent amounts of reactants. This efficiency surpasses all reported single emulsion microreactors, i. e ., 84~95 %, stabilized by various emulsifiers with different catalysts, which typically necessitate continuous stirring, a high excess of one reactant, and/or extended reaction time. Furthermore, over 3 times regulation threshold in conversion rate is attained by manipulating the droplet morphologies, including size and topology, e. g ., transition from completely engulfed F/H/W double to partially engulfed (F+H)/W Janus. Addition‐esterification, serving as a model for triple phasic cascade reaction, is also successfully implemented under agitating‐free and mild temperature with controlled reaction kinetics, demonstrating the versatility and effectiveness of the complex emulsion microreactor.