Jahn–Teller Distortion in the Amino-Functionalized Metal–organic Framework Promotes CH<sub>4</sub> Partial Oxidation with Enhanced in situ H<sub>2</sub>O<sub>2</sub> Utilization Efficiency
Yueyuan Xu, Ning Cao, Yao Shi, Yan Mi, Pengfei Xie
Abstract
The partial CH 4 oxidation by in situ generation of H 2 O 2 from O 2 and H 2 offers a promising strategy to synthesize CH 3 OH from affordable and sustainable substances. However, it remains a grand challenge to efficiently utilize H 2 O 2 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 CH 3 OH productivity of 14.8 mmol·g cat –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 Fe 2+ 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 Fe 2+ facilitates H 2 O 2 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 CH 4 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 CH 3 OH.