Increasing the Distance of Adjacent Palladium Atoms for Configuration Matching in Selective Hydrogenation.

Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof-of-concept study on the atomically sites-tailored pathway in Pd-catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (d Pd-a-Pd ) for configuration matching in acetylene semi-hydrogenation against coupling. d Pd-a-Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased d Pd-a-Pd prefers the semi-hydrogenation pathway due to simultaneously promoted C 2 H 4 desorption and the destabilized transition state of the C 2 H 3 * coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing d Pd-a-Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.