Semipermeable Organic–Inorganic Hybrid Microreactors for Highly Efficient and Size-Selective Asymmetric Catalysis

A highly efficient and size-selective organic–inorganic hybrid microreactor was fabricated successfully by assembling the semipermeable microporous silica hollow nanospheres at the interface of organic polymers containing an asymmetric transfer hydrogenation catalyst. The small micropores in the silica shells (1.0–1.5 nm) of the microreactors provide short mass-transfer channels for small molecules but prevent the diffusion of large reactants through the shell. At the same time, the combination of the outer microporous silica and inner polymers endows the microreactor with hydrophobic@hydrophilic property, which helps its dispersion in water as well as the adsorption of reactant molecules from water, yielding an ideal microenvironment for water medium catalysis reactions. Such microreactors could efficiently catalyze the aqueous asymmetric transfer hydrogenation (ATH) of small-sized ketones with catalytic activity comparable to the homogeneous Rh-VBSDPEN catalyst (TOF 625 vs 724 h–1). Meanwhile, the microreactors also showed size selectivity toward large-sized reactants. Our studies provide an approach for the construction of artificial bioinspired microreactors with size-selective properties and favorable catalysis microenvironments.