Efficient methane to ethane conversion via C–H bond activation catalyzed by a MOF-derived porous PdO/TiO2 nanocomposite

Abstract

The photocatalytic conversion of methane (CH₄) into high-value multicarbon (C₂₊) products under ambient conditions provides a highly promising approach for the transformation of the energy structure and environmental protection. However, the high C–H bond dissociation energy of CH₄ and the overoxidation of methyl radical (˙CH₃) intermediates greatly limit the conversion of CH₄ to C₂₊ products. Herein, we demonstrate a metal–organic framework (MOF) crystal engineering strategy to synthesize a MOF-derived PdO/TiO₂ nanocomposite for photocatalytic nonoxidative coupling of methane (NOCM), achieving high selectivity and activity in the conversion of CH₄ to ethane (C₂H₆). Mechanistic investigations reveal that the spatially separated active sites for C–H bond cleavage and C–C coupling contribute to the efficient conversion of CH₄ to C₂H₆. Specifically, the lattice oxygen captures the photogenerated holes, leading to the formation of oxygen radical anions (˙O⁻), which activate the C–H bond and generate ˙CH₃ intermediates. PdO stabilizes ˙CH₃ intermediates, effectively inhibiting the overoxidation of ˙CH₃, and thereby promoting the C–C coupling process. This work opens a new avenue for the rational design of efficient MOF-derived photocatalysts for NOCM.