Microperoxidase 8 (MP8) was immobilized within MIL-101(Cr) bearing terephthalate linkers with functionalized groups (-NH 2 and -SO 3 H). A synthesis protocol for MIL-101(Cr)-SO 3 H 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)-NH 2 per material mass was higher than for MP8@MIL-101(Cr).The presence of free amino groups can thus improve the immobilization efficiency, leading to higher amount of catalytic active species and improving the subsequent catalytic activity of the heterogeneous biocatalysts. MP8@MIL-101(Cr)/-NH 2 successfully catalyzed as well the selective oxidation of thioanisole derivatives into sulfoxides.