Hierarchically open-capsule metal–organic frameworks via controlled etching for enzyme encapsulation

Abstract

Nanocapsules with large accommodation interior space and exterior shell present a wide range of potential applications for storage, catalysis and drug delivery. However, conventional nanocapsules feature enclosed shells, which reduce the available surface areas for target molecule loading and pose mass transfer resistance. Here, we present a facile strategy for fabrication of hierarchically open-capsule metal–organic frameworks by utilizing a controlled self-etching process. Benefiting from the exposed surface of the openings on the wall and intrinsic stability of the MOFs, this open-capsule MOF (ocMOF) exhibits remarkably higher loading efficiency for lipase (3 times higher than unmodified MOFs). With commercialized lipase product Novozym 435 (N435) as bench mark, the obtained CALB@ocMOF showed 11.3-fold higher catalytic efficiency, with kcat/Km of 186 mM−1·s−1 and comparable stability under hostile conditions. As a proof-of-concept, the prepared CALB@ocMOF was used for non-aqueous enzymatic synthesis of retinyl palmitate, bioavailable substances beneficial for human health, with 3.2-times higher catalytic activity than N435. This study would afford prospects for developing MOFs capsule for biotechnology application.