Jahn-Teller Distortion in the Amino-Functionalized Metal-organic Framework Promotes CH4 Partial Oxidation with Enhanced in situ H2O2 Utilization Efficiency.

The partial CH4 oxidation by in situ generation of H2O2 from O2 and H2 offers a promising strategy to synthesize CH3OH from affordable and sustainable substances. However, it remains a grand challenge to efficiently utilize H2O2 for the exclusive production of methanol. Herein, we report a tandem catalyst by encapsulating Pd nanoparticles in an amino-functionalized Fe-based metal-organic framework, delivering a CH3OH productivity of 14.8 mmol·gcat-1·h-1 with a selectivity of 98.6%. The spectroscopy characterizations suggest that the modification of the ligand by amino groups not only increases the electron density of the triiron motif through ligand-to-metal charge transfer but also induces the Jahn-Teller distortion of Fe2+ coordination, giving rise to the unpaired electrons at a high occupancy state, evidenced by theoretical calculations as well. Mechanism studies reveal that this unique electron configuration of Fe2+ facilitates H2O2 decomposition, resulting in an asymmetrical Fe-O octahedron with further enhanced Jahn-Teller distortion and more unpaired electrons in the σ* antibonding orbitals. This structural evolution promotes CH4 activation with a reduced barrier of 0.35 eV for the amino-functionalized catalyst, compared to 0.47 eV for the nonfunctionalized counterpart, enabling selective formation of CH3OH.