Computational Predictions and Experimental Validation of Alkane Oxidative Dehydrogenation by Fe₂M MOF Nodes

The modular structure of metal-organic frameworks (MOFs) makes them promising platforms for catalyst design and for elucidating structure/performance relationships in catalysis. In this work, we systematically varied the composition of the metal nodes (Fe₂M) of the MOF PCN-250 and used density functional theory (DFT) to identify promising catalysts for light alkane C-H bond activation. Oxidative dehydrogenation (ODH) of alkanes was studied using N₂O as the oxidant to understand the reactivity of the oxocentered Fe₂M nodes found in PCN-250, where the Fe ions are in the +3 oxidation state and M is a metal with the oxidation state of +2. We show that the N₂O activation barrier is positively correlated with the oxygen-binding energy at the metal center, and the C-H activation barrier is negatively correlated with this same quantity. For clusters containing early transition metals, oxygen binds strongly, facilitating N₂O activation but hindering C-H activation. To validate the DFT predictions, we synthesized and tested PCN-250(Fe₂M) with M = Mn, Fe, Co, and Ni and found that PCN-250(Fe₂Mn) and PCN-250(Fe₃) are more active than PCN-250(Fe₂Co) and PCN-250(Fe₂Ni) in agreement with the DFT predictions, demonstrating the power of DFT calculations to predict and identify promising MOF catalysts for alkane C-H bond activation in advance of experiments.