How the Support Defines Properties of 2D Metal–Organic Frameworks: Fe-TCNQ on Graphene versus Au(111)

Abstract

The functionality of 2D metal−organic frameworks (MOFs) is crucially dependent on the local environment of the embedded metal atoms. These atomic-scale details are best ascertained on MOFs supported on well-defined surfaces, but the interaction with the support often changes the MOF properties. We elucidate the extent of this effect by comparing the Fe-TCNQ 2D MOF on two weakly interacting supports: graphene and Au(111). We show that the Fe-TCNQ on graphene is nonplanar with iron in quasi-tetrahedral sites, but on Au(111) it is planarized by stronger van der Waals interaction. The differences in physical and electronic structures result in distinct properties of the supported 2D MOFs. The d z 2 center position is shifted by 1.4 eV between Fe sites on the two supports, and dramatic differences in chemical reactivity are experimentally identified using a TCNQ probe molecule. These results outline the limitations of common onsurface approaches using metal supports and show that the intrinsic MOF properties can be partially retained on graphene.

Emergence of Band Structure in a Two-Dimensional Metal–Organic Framework upon Hierarchical Self-Assembly

“…In this context, a thorough understanding of the interaction between the TM’s 3d states with the π states of the ligand is critical, defining the electronic delocalization effects within the materials and, thus, their functionality. , Specifically, π-conjugated MOFs offer exciting properties from high electrical conductivity and superconductivity to ferromagnetism . Recently, not only have the band structures of on-surface stabilized MOFs been studied, ,,− but ferromagnetic order and Mott metal–insulator transitions have also been reported . Understanding how the band structure emerges in 2D-MOFs upon coupling of the building blocks is crucial for advancing materials’ design, enabling targeted manipulation of electronic properties for tailored applications in electronics and photonics. , …”