π-Electron Conjugation Strategy for Regulating the Band Structure of Metal-Organic Structure

Abstract

This study investigates the role of π-electron delocalization in tuning the electronic band structures of two-dimensional metal-organic frameworks (2D MOFs), using 9,10-dicyanoanthracene (DCA) on different metal surfaces. While hydrogen-bonded assemblies form on Ag(111), distinct coordination networks emerge on Cu(111) and Au(111): a Kagome-based 2D framework (DCA₃Cu₂) with flat bands and Dirac cones, and a quasi-one-dimensional chain structure (DCA₃Au₂), respectively. Density functional theory (DFT) calculations reveal a clear correlation between the extent of π-delocalization and the electronic properties. As delocalization evolves from localized (DCA₃Cu₁) to quasi-1D (DCA₃Au₂) characters, the bandgap narrows from 0.07 eV to 0.03 eV. Even in localized and quasi-1D systems, weak inter-unit hydrogen-bonding interactions contribute to electronic band formation, indicating the synergy between coordination and non-covalent interactions in shaping band structures. These findings demonstrate that coordination-controlled π-delocalization offers a precise pathway to tailor the electronic properties of 2D MOFs.