Enhanced Activity and Stability of Horseradish Peroxidase via Immobilization on Hierarchical Covalent Organic Frameworks

In this work, hierarchical covalent organic frameworks (H-COF (PS)) were prepared via a hard template strategy using polystyrene spheres (PS) as the template. The H-COF (PS) exhibits high stability in aqueous solution without skeleton collapse. When used as a carrier for enzyme immobilization, the H-COF (PS) shows several outstanding advantages. The well-defined macropores and micropores are distributed throughout the COF. The created macrospores provide sufficient space for distribution of enzyme while the intrinsic micropores can concentrate substrates. The macropores and micropores in H-COF (PS) are adjacent, so the substrate can access to horseradish peroxidase (HRP) with lower diffusion resistance than that in solution, resulting in enhanced enzymatic catalytic activity. The porous skeleton in H-COF (PS) can protect the embedded enzyme from inactivation caused by high temperature and organic solvents, ensuring HRP stability under strict reaction conditions. The prepared HRP immobilized H-COF (PS) (HRP@H-COF(PS)) demonstrates high efficiency in dye decolorization applications. This work provides a new platform to design enzyme-nanomaterials composites with both high activity and stability.