Photocatalytic oxidation of methane to C1 oxygenates promoted by Fe−N−Ti electron bridge

Abstract

Highly efficient oxidation of methane (CH) to liquid oxygenates with O over non-noble heterogeneous catalysts under mild conditions remains a huge challenge owing to the ultra-inert C−H bond of CH molecule. In this work, we have successfully constructed photocatalysts of N-FeTiO/TiO by thermal treatment of a bimetallic amino-functionalized metal-organic framework, i.e., Fe-NH-MIL-125, aiming at photocatalytic oxidation of CH to one-carbon (C) oxygenates using O at room temperature. Impressively, the optimized photocatalyst of 10 wt%N-FeTiO/TiO exhibited superior activity in photocatalytic oxidation of CH with a formation rate of C liquid oxygenates of 5897 μmol·g·h. The selectivity of the primary products (CHOH and CHOOH) was up to 91.7 % over 10 wt%N-FeTiO/TiO. Mechanistic studies demonstrated that the presence of Fe−N−Ti electron bridge could trigger robust charge redistribution in 10 wt%N-FeTiO/TiO to form electron-deficient Fe sites and electron-rich Ti sites. The formed electron-deficient Fe sites could oxidize HO molecules to ·OH radicals. Meanwhile, electron-rich Ti sites greatly enhanced the chemisorption and activation of CH molecules, thereby synergistically promoting the generation of C liquid oxygenates.