Enzyme Immobilization in MOF‐derived Porous NiO with Hierarchical Structure: An Efficient and Stable Enzymatic Reactor

Abstract MOF‐derived porous NiO with hierarchical structure (MHNiO) was prepared based on thermolysis of Ni metal organic framework (Ni‐MOF), which was used as carrier for the immobilization of horseradish peroxidase (HRP) and cytochrome C (Cyt c). The pore size of MHNiO was tuned as 11.8 nm to match the size of free enzyme so as to depress the aggregation of the enzymes in the pore. Meanwhile, the hierarchical structure allowed the substrates concentrated in the vicinity of the enzymes. The obtained enzymatic reactors exhibited better thermal stability, storage stability and reusability. For example, over 83 % of its original activity after 1 h incubation at 70 °C could be remained compared to 18.1 % or 38.4 % remained activity of free HRP and Cyt c, respectively; After 12 cycles of use, over 53 % of original catalytic activity of both the enzymatic reactor could be maintain. The enzymatic kinetic data (Km, Vmax, kcat) and thermodynamic data (Ka, ΔH, ΔS and ΔG) indicated that the improved catalytic performance was attributed to the affinity, selectivity and binding of enzyme to substrate. The two enzymatic reactors could be applied in the fast degradation of 2,4‐dichlorophenol and rifaximin in artificial wastewater, a complete degradation of 2 mg ⋅ mL−1 of 2,4‐dichlorophenol or 20 μg ⋅ mL−1 of rifaximin was achieved in only 20 min.