Silica encapsulated catalase@metal-organic framework composite: A highly stable and recyclable biocatalyst

Abstract Metal-organic frameworks (MOFs) have recently emerged as a promising candidate for the immobilization of enzymes due to their diversified structures and porosity. However, it is difficult to handle and fully recover the enzyme-MOF composites from the reaction medium due to their nanometer size and good dispersity in solvents, which limits their practical applications. Here, a novel enzyme-MOF composite with both highly stable and easily reusable features was prepared via encapsulating catalase/ZIF-8 nanocrystals into large mesoporous silica layer (silica@CAT/ZIF-8). This immobilized system exhibited high activity recovery (81%). The silica layer around the catalase/ZIF-8 particles provided a “shield” to protect from biological and chemical degradation for enzyme. As a result, the silica@CAT/ZIF-8 composites exhibited higher stability against proteolytic agent and extreme conditions (such as low pH) than that of conventional catalase/ZIF-8 composites. More importantly, the micrometer-sized silica@CAT/ZIF-8 can be easily repeatedly used without obvious activity loss. The silica@CAT/ZIF-8 composites still remained 50% of their original activity after 10 cycles, whereas the conventional catalase/ZIF-8 composites only retained 7% of their original activity after 5 cycles. These results demonstrated that this approach could be an efficient strategy to prepare enzyme-ZIF-8 composite with both high stability and excellent recyclability.