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

Highly efficient oxidation of methane (CH4) to liquid oxygenates with O2 over non-noble heterogeneous catalysts under mild conditions remains a huge challenge owing to the ultra-inert C−H bond of CH4 molecule. In this work, we have successfully constructed photocatalysts of N-Fe2Ti3O9/TiO2 by thermal treatment of a bimetallic amino-functionalized metal-organic framework, i.e., Fe-NH2-MIL-125, aiming at photocatalytic oxidation of CH4 to one-carbon (C1) oxygenates using O2 at room temperature. Impressively, the optimized photocatalyst of 10 wt%N-Fe2Ti3O9/TiO2 exhibited superior activity in photocatalytic oxidation of CH4 with a formation rate of C1 liquid oxygenates of 5897 μmol·gcat.–1·h–1. The selectivity of the primary products (CH3OH and CH3OOH) was up to 91.7 % over 10 wt%N-Fe2Ti3O9/TiO2. Mechanistic studies demonstrated that the presence of Fe−N−Ti electron bridge could trigger robust charge redistribution in 10 wt%N-Fe2Ti3O9/TiO2 to form electron-deficient Fe sites and electron-rich Ti sites. The formed electron-deficient Fe sites could oxidize H2O molecules to ·OH radicals. Meanwhile, electron-rich Ti sites greatly enhanced the chemisorption and activation of CH4 molecules, thereby synergistically promoting the generation of C1 liquid oxygenates. © 2024 Elsevier B.V.