Ligation of Carbon Monoxide at Cobalt Single-Metal-Atom Sites in a Surface-Confined Metal-Organic Network: Oxidation State, Anharmonicity, and Long-Range Lateral Interactions

Ligation of carbon monoxide at the single-metal-atom cobalt sites of a surface-confined tetra-pyridyl porphyrin coordination network is investigated under near-ambient pressure conditions at room temperature. It is found that (anti)cooperative effects associated with network-mediated lateral interactions allow tuning of the adduct adsorption energy and of its coverage dependence. The mechanism involves charge and geometric distortions, induced upon ligation, that are transferred to proximal sites of the network as far as a few nanometers away through deformation of the pyridinic residues. Anharmonic contributions to the ligation potential are evidenced via the light-induced population of the vibrational hot band of the internal C-O stretching mode, known to play a role in the C-O dissociation energy barrier and, thus, in the CO activation toward reaction.