Mechanistic insights into the stepwise oxidation of methane to methanol and formaldehyde over Cu-exchanged SSZ-13

Abstract

The partial oxidation of methane to methanol is investigated over Cu-exchanged SSZ-13 using grid-based projector augmented wave within density functional theory and FDMNES XANES simulations. CH₄ activation at the Cu–O site proceeds, followed by CH₃OH oxidation to HCHO. Projected density of states analysis shows hybridization of the O 2p, Cu 3d, and H 1s orbitals at the transition states, confirming C–H bond activation at the Cu–O moiety. FDMNES simulations reveal a red shift in the Cu K-edge during both steps, indicating Cu reduction and its participation in the redox cycle. These results demonstrate that Cu–O sites are responsible for both methane activation and methanol oxidation with high selectivity toward partial oxidation products.