Band Renormalization in Metal-Organic Framework/Au(111) Epitaxial Heterostructures

TL;DR

This study investigates the interfacial electronic interactions in monolayer M3(HITP)2 metal-organic frameworks grown on Au(111), revealing how the substrate influences band structure, flat bands, and quantum confinement effects relevant for electronic devices.

Contribution

It provides microscopic insight into the interlayer coupling mechanisms in M3(HITP)2/Au(111) heterostructures using synthesis, STM characterization, and tight-binding analysis, advancing understanding of metal-organic framework/metal interfaces.

Findings

Au(111) substrate renormalizes the electronic band structure of M3(HITP)2.

A ligand-derived flat band appears at 0.4 eV, correcting previous orbital character assignments.

Quantum confinement creates a quantum corral network with resonant states within pores.

Abstract

Two-dimensional conjugated metal-organic frameworks hold great promise for applications in chemiresistive sensing, electrocatalysis, and energy storage. Their interfacial interaction with metal electrodes, which has been rarely investigated, exerts a critical influence on the electronic properties and device performance. As a representative material, M3(HITP)2 (M = Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene) exhibits excellent performance in various electronic devices, yet the microscopic mechanism of the interfacial interaction in M3(HITP)2/metal heterostructures remains unclear. Here, we report the synthesis, scanning tunneling microscopic characterization, and tight-binding analysis of monolayer M3(HITP)2 epitaxially grown on Au(111). Scanning tunneling spectroscopic mapping reveals a commensurate kagome-hexagonal-honeycomb triple-lattice architecture. The Au(111) substrate renormalizes the electronic band structure of M3(HITP)2, pinning the Fermi level and generating a ligand-derived flat band at 0.4 eV that corrects prior misassignment of orbital character. Meanwhile, the periodic and microporous M3(HITP)2 lattice strongly modulates the surface electronic state of Au(111) via electron-phonon coupling and quantum confinement, the latter of which gives rise to a quantum corral network exhibiting two resonant states within each pore. The formation of fully dispersive electronic bands and the robust quantum corral network requires crystallites comprising at least ten pores. The atomic-scale investigation of M3(HITP)2/Au(111) epitaxial heterostructures elucidates interlayer coupling mechanisms and advances the understanding of metal-organic framework/metal interfaces that are integral to electronic and energy-storage devices.