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

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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 (Fe 2 M) 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 N 2 O as the oxidant to understand the reactivity of the oxocentered Fe 2 M 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 N 2 O 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 N 2 O activation but hindering C–H activation. To validate the DFT predictions, we synthesized and tested PCN-250(Fe 2 M) with M = Mn, Fe, Co, and Ni and found that PCN-250(Fe 2 Mn) and PCN-250(Fe 3 ) are more active than PCN-250(Fe 2 Co) and PCN-250(Fe 2 Ni) 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.