On-surface Synthesis of a Semiconducting 2D Metal-Organic Framework Cu₃ (C₆ O₆ ) Exhibiting Dispersive Electronic Bands

A 2D metal-organic framework (2D-MOF) was formed on a Cu(111) substrate using benzenehexol molecules. By means of a combination of scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and density-functional theory, the structure of the 2D-MOF is determined to be Cu₃ (C₆ O₆ ), which is stabilized by O-Cu-O bonding motifs. We find that upon adsorption on Cu(111), the 2D-MOF features a semiconductor band structure with a direct band gap of 1.5 eV. The O-Cu-O bonds offer efficient charge delocalization, which gives rise to a highly dispersive conduction band with an effective mass of 0.45 m_e at the band bottom, implying a high electron mobility in this material.