Enzyme immobilization in highly ordered macro-microporous metal-organic frameworks for rapid biodegradation of hazardous dyes

Enzyme immobilization in hierarchically porous metal-organic frameworks (HP-MOFs) has attracted extensive attention in biocatalysis and contaminant biodegradation. However, the small-dimension mesopores and micropores on the exterior of MOFs are incompatible with large-sized enzymes, thus limiting the further enhancement of mass transfer efficiency and enzyme accessibility. Herein, we encapsulated horseradish peroxidase (HRP) in highly ordered macro-micropore zeolitic imidazolate framework-8, in which the encapsulated enzyme not only fully preserved its catalytic activity, but also exhibited long-term stability, recyclability, low leakage, and resistance to chelating compounds. Through enzyme immobilization, we significantly enhanced the biodegradation process of hazardous dyes probably as a result of the pre-concentration of the dye reactant for the combination of enzymes and MOFs. This work shows the great potential of constructing highly functional biocatalysts in three-dimensional ordered macro-micropore MOFs with enhanced mass diffusion efficiency, which is promising for applications to biodegradation of all sorts of other organic pollutants in water resources.