© 2015 American Chemical Society. Metal-organic frameworks with Zr6nodes, UiO-66 and NU-1000, were investigated as supports for Ir(CO)2and Ir(C2H4)2complexes. A single bonding site for the iridium is identified on the nodes of NU-1000, whereas two sites are identified on UiO-66, although at low iridium loadings only one site is occupied. Density functional theory calculations provide structural results that are in good agreement with infrared and X-ray absorption fine-structure spectra. The reactivity of node-supported Ir(CO)2with C2H4and the catalytic activity and selectivity of the species initially present as Ir(C2H4)2for ethylene hydrogenation and dimerization were investigated both experimentally and computationally and shown to be strongly influenced by the node.