CoO Nanoislands as Metal Oxide Precursors for Surface-Supported Co–BDA Coordination Networks

Metal oxide nanoislands offer a localized source of metal centers for the on-surface assembly of coordination networks. Here, we investigate the adsorption and thermal evolution of 4,4'-biphenyldicarboxylic acid (BDA) on CoO nanoislands supported on Au(111) under ultrahigh vacuum using infrared reflection absorption spectroscopy (IRAS), scanning tunneling microscopy (STM), and density functional theory (DFT). At 400 K, BDA forms two coexisting populations: carboxylate species anchored to CoO and a predominantly flat-lying, hydrogen-bonded molecular layer on Au(111). Heating to 500 K removes the IR signatures of intact carboxylic acid groups and changes the relative intensities of the out-of-plane C-H modes. STM reveals a rectangular two-dimensional Co–BDA coordination network, for which DFT supports a structural model containing paired Co centers. These observations support a pathway in which Co species are supplied by partial dissolution of the oxide nanoislands. Annealing to 600 K produces arrays of coordination chains with single-Co nodes, while the IR spectra remain consistent with predominantly flat-lying biphenyl units. These results demonstrate that supported metal oxide nanoislands can serve as precursors for the formation of surface-confined 2D MOFs and provide an alternative route to thermally controlled metal–organic assembly on metal surfaces. TOC Graphic Thermally controlled MOF growth. CoO nanoislands on Au(111) serve as a metal precursor for the formation of a surface-confined Co–BDA network. Annealing at 500 K produces a rectangular 2D MOF with paired Co centers, while further annealing to 600 K induces a transformation into 1D Co–BDA arrays with single-Co nodes. This oxide-mediated approach provides a new route to surface-supported 2D MOF synthesis.