A Diffusion Monte Carlo Study of the Methane-to-Methanol Pathway on a Metal–Organic Framework [Fe2(H2O)2(BTC)4/3]Cl·4.5 DMF

Progress in computation-driven methane-to-methanol catalysis is limited by the difficulty of reliably predicting spin-state ordering and reaction energetics with conventional density functional theory (DFT). We address this issue in the methane-to-methanol pathway on an Fe-based metal–organic framework (MOF), [Fe₂(H₂O)₂(BTC)_4/3]Cl·4.5 DMF (CSD NINVAI), using the fixed-node diffusion Monte Carlo (FNDMC) method. Different from the previous DFT study [1], our FNDMC calculations predict a moderately endothermic O-atom adsorption and a moderately exothermic C–H bond cleavage, with basis-set superposition and incompleteness errors carefully evaluated. Calibration of exchange–correlation functionals shows that MN15 and M06-2X best align with the FNDMC results, although none closely reproduce the C–H bond cleavage energetics. In the talk, we will introduce the background of methane-to-methanol catalysis, the role of Fe-based MOFs, and the suitability of the FNDMC method, followed by a comparison of FNDMC and DFT energy profiles highlighting differences in spin-state ordering and activation energetics.