Enhancing the Fenton catalytic activity of Fe-MOFs by incorporation of carbon nanotubes: The crucial role of C-O-Fe coordination structure

Abstract

Fe-based metal–organic frameworks (MOFs) have garnered significant attention as catalysts for heterogeneous Fenton reactions, while the limited efficiency of the Fe(III)/Fe(II) redox cycle hinders their widespread use in wastewater treatment. Herein, we successfully incorporated carbon nanotubes (CNTs) into MIL-101(Fe) to modulate the coordination environment of Fe for achieving better catalytic activity. The MIL-101(Fe)/CNTs/H2O2 system shows outstanding performance in degrading various pollutants, with the catalytic activity of the MIL-101(Fe)/CNTs composites (98.8%) significantly surpassing that of MIL-101(Fe) alone (26.4%) or CNTs alone (3.5%). Multiple experimental findings suggest that this synergistic effect is primarily attributed to the C-O-Fe bridge bonds resulting from the interaction of surface carboxyl groups on CNTs with Fe in MIL-101(Fe). This unique coordination structure accelerates the redox cycle of Fe(III)/Fe(II), thereby promoting the generation of hydroxyl radicals (HO•). Furthermore, the MIL-101(Fe)/CNTs composites demonstrate excellent reusability and stability, maintaining effectiveness over a wide pH range from 3.0 to 6.5. This study provides new insights into regulating the microstructure of Fe-based MOFs to enhance their Fenton catalytic activity.