Encapsulation of Microperoxidase‑8 in MIL-101(Cr)‑X Nanoparticles: Influence of Metal–Organic Framework Functionalization on Enzymatic Immobilization and Catalytic Activity

Microperoxidase 8 (MP8) was immobilized within MIL-101­(Cr) bearing terephthalate linkers with functionalized groups (-NH₂ and -SO₃H). A synthesis protocol for MIL-101­(Cr)-SO₃H that avoids the use of toxic Cr­(VI) and HF was developed. The electrostatic interactions between the MP8 molecules and the MOF matrices were found to be crucial for a successful immobilization. Raman spectroscopy revealed the dispersion of the immobilized MP8 molecules in MIL-101­(Cr)-X matrices as monomers without aggregation. The presence of functional groups resulted in higher amounts of immobilized MP8 in comparison to the bare MIL-101­(Cr). The catalytic activity of MP8@MIL-101­(Cr)-NH₂ per material mass was higher than that for MP8@MIL-101­(Cr). The presence of free amino groups can thus improve the immobilization efficiency, leading to a higher amount of catalytically active species and improving the subsequent catalytic activity of the heterogeneous biocatalysts. MP8@MIL­(Cr)-X also successfully catalyzed the selective oxidation of thioanisole derivatives into sulfoxides.