Methane partial oxidation by monomeric Cu active center confined on ZIF-7

Abstract

The monomeric cupric ion (Cu2+) species coordinated to four nitrogen ligands (CuN4) is recognized as a possible active site for particulate methane monooxygenase (pMMO) of the methanotrophic bacteria that convert methane to methanol. Herein, inspired by the active site of pMMO, a copper-doped zeolitic imidazolate framework-7 (Cu/ZIF-7) was prepared, the mononuclear CuN4 centers of which displayed catalytic partial oxidative activity and converted methane to methanol, methyl hydroperoxide, and hydroxymethyl hydroper-oxide without producing the overoxidized product of formic acid. Spectroscopy studies established the mono-nuclear Cu(2+ )center coordinates with four benzimidazole nitrogens. The catalytic activity of Cu/ZIF-7 was scrutinized considering the potential reaction mechanism at the CuN4 center, which substantially reduced the strong acidity of ZIF-7 to afford the partial oxidation of methane without forming formic acid.