Spatial localization immobilization of metals and enzymes at Pickering emulsion droplet interfaces for chemo-enzymatic cascade catalysis.

Developing chemo-enzymatic cascade catalysis in catalytic asymmetric synthesis is of utmost significance, but such processes often suffer from low reaction efficiency because of incompatible reaction environments and suppressed intermediate transportation. Herein, a novel compartmentalised metal-enzyme microcapsule nanohybrid, Candida antarctica lipase B@Pd(II)-loaded hydrophobic mesoporous silica nanoparticles (CALB@Pd(II)/HB-MSNs), was fabricated by spatially localizing Pd(II) active sites and CALB at the outer and inner interfacial layers of Pickering emulsion droplets, respectively. Benefiting from the localization of two catalysts in their preferred reaction microenvironments, nanoscale proximity of each other, and interfacial activation of lipase, the CALB@Pd(II)/HB-MSNs exhibited 60-fold higher activity than traditional random co-immobilized metal-enzyme catalysts (Pd(II)/HB-MSNs/CALB). Furthermore, the conversion of rac-1-phenylethanol catalyzed by CALB@Pd(II)/HB-MSNs reached 47.92 %, compared to only 4 % for the randomly co-immobilized catalyst Pd(II)/HB-MSNs/CALB, with a product enantiomeric excess of≥99 % in the cascade reaction of 4-pentynoic acid cycloisomerisation and racemic 1-phenylethanol chiral resolution. Our study offers a platform for the design of efficient chemoenzymatic catalytic cascades for the synthesis of fine chemicals.