Tunable Crystallinity and Electron Conduction in Wavy 2D Conjugated Metal–Organic Frameworks via Halogen Substitution

Abstract

AbstractCurrently, most reported 2D conjugated metal–organic frameworks (2D c‐MOFs) are based on planar polycyclic aromatic hydrocarbons (PAHs) with symmetrical functional groups, limiting the possibility of introducing additional substituents to fine‐tune the crystallinity and electrical properties. Herein, a novel class of wavy 2D c‐MOFs with highly substituted, core‐twisted hexahydroxy‐hexa‐cata‐benzocoronenes (HH‐cHBCs) as ligands is reported. By tailoring the substitution of the c‐HBC ligands with electron‐withdrawing groups (EWGs), such as fluorine, chlorine, and bromine, it is demonstrated that the crystallinity and electrical conductivity at the molecular level can be tuned. The theoretical calculations demonstrate that F‐substitution leads to a more reversible coordination bonding between HH‐cHBCs and copper metal center, due to smaller atomic size and stronger electron‐withdrawing effect. As a result, the achieved F‐substituted 2D c‐MOF exhibits superior crystallinity, comprising ribbon‐like single crystals up to tens of micrometers in length. Moreover, the F‐substituted 2D c‐MOF displays higher electrical conductivity (two orders of magnitude) and higher charge carrier mobility (almost three times) than the Cl‐substituted one. This work provides a new molecular design strategy for the development of wavy 2D c‐MOFs and opens a new route for tailoring the coordination reversibility by ligand substitution toward increased crystallinity and superior electric conductivity.