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.