Chiral Metal‐Organic Framework/Polyurea Composite Microreactors From Oil‐In‐Oil Emulsions

An oil‐in‐oil (O/O) emulsion‐templated strategy was developed for the preparation of composite microcapsules comprising a chiral metal‐organic framework (MOF) core and a polyurea shell. In this approach, a polar solvent containing chiral MOF precursors was first emulsified into a nonpolar continuous phase containing a suitable surfactant and an isocyanate monomer. After addition of the diamine monomer, two processes occurred simultaneously: the formation of the chiral MOF within the confined polar droplets and interfacial polymerization at the droplet interface, leading to the formation of a polyurea shell. This concurrent process resulted in well‐defined chiral MOF/polyurea core‐shell microcapsules. The structure and morphology of the composite microcapsules were systematically controlled by varying key parameters, including surfactant type and concentration, polar phase composition, and MOF precursor loading. This methodology was also applied to the fabrication of ruthenium‐based chiral MOF/polyurea microreactors by encapsulating the achiral complex dichlorobis(2‐(diphenylphosphino)ethylamine)ruthenium(II) within the chiral MOF/polyurea framework. Despite the achiral nature of the encapsulated ruthenium complex, the confined chiral microenvironment of the MOF/polyurea microreactors influenced asymmetric induction. In the transfer hydrogenation of acetophenone, the composite microreactors achieved complete conversion and up to 64% enantioselectivity toward (R)‐1‐phenylethanol. These findings reveal the impact of confinement‐induced effects on asymmetric induction and position chiral MOF/polyurea microreactors as promising chiral heterogeneous catalysts.