Immobilization of horseradish peroxidase on hierarchically porous magnetic metal-organic frameworks for visual detection and efficient degradation of 2,4-dichlorophenol in simulated wastewater

Immobilization of enzymes onto solid carrier is an important way to improve the stability and reusability of enzymes. However, the enzymatic activity and catalytic efficiency are severely hampered due to enzyme leaching and increased substrate mass transfer resistance. Herein, for the first time, we reported a novel strategy of co-regionalization for enzyme immobilization using hierarchically porous magnetic metal-organic frameworks (HP-Zr-MOF@Fe3O4). The HP-Zr-MOF@Fe3O4 integrate magnetic characteristics and hierarchical porous structure for supporting horseradish peroxidase (HRP) via metal-ion affinity interaction, in which the mesoporous pores are suitable for entrapping enzyme while the microporous can be used to concentrate substrate to reduce the mass transfer resistance. Significantly, the prepared HRP@HP-Zr-MOF@Fe3O4 can efficiently suppress enzyme leaching from the HP-Zr-MOF@Fe3O4 skeleton and remain superior recovered activity (96.8 %) of the initial activity of free HRP, which exhibited excellent stability and reusability. Interestingly, the HRP@HP-Zr-MOF@Fe3O4 was used efficiently in the colorimetric detection and catalytic degradation of 2,4-dichlorophenol in simulated wastewater. The excellent property of HRP@HP-Zr-MOF@Fe3O4 was investigated through the analyses of kinetics and thermodynamics, demonstrating that the HRP@HP-Zr-MOF@Fe3O4 had significant specificity and binding affinity for the substrate compared with free HRP.