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

Graphical Large scalable complex emulsions are developed as innovative one-pot microreactors for multiphasic reactions to overcome the issue of macroscopic phase separation. The reactions achieve 100 % of conversion with controllable reaction kinetics, even for reversible and water-labile esterification and cascade reaction with the reactants in nearly equivalent amounts, at charming conditions of mild temperature and agitating free. These merits fulfill the requirement of atom economy and sustainable chemistry. 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.