Adaptive Hydrogenation of Alkynes Using CO as a Molecular Trigger to Selectively Produce Alkanes or Z-Alkenes

The selective hydrogenation of alkynes to either alkanes or alkenes is an important step in synthetic processes across the entire chemical value chain with a broad range of applications especially for fine chemical and pharmaceutical production. While traditional developments aim at individual catalysts optimized for either one or the other product, catalytic systems capable of adaptively targeting both classes of products with high activity and selectivity could enable flexible production schemes. Here, we show that CO can be used as a molecular trigger to dynamically adjust the selectivity of supported palladium nanoparticles (NPs) in alkyne hydrogenation. In particular, Pd NPs immobilized on an imidazolium-based supported ionic liquid phase (Pd@SILP) hydrogenate a wide range of structurally diverse alkynes, delivering synthetically relevant alkane or Z-alkene products under H₂ or H₂/CO as feed gas, respectively. Reference experiments, kinetic studies including isotope labeling, and near-ambient-pressure XPS studies reveal that the rapid and robust selectivity switch originates from the reversible adsorption of CO competing with alkene at the Pd surface. In contrast to its notorious reputation as a catalyst poison in hydrogenation, these findings establish CO as an effective molecular trigger for adaptive catalysis, paving the way toward even broader applications for reversible selectivity control.