Electronic Structure and Magnetic Property of 2D Open-Shell Covalent Organic Framework

Abstract

Triarylmethyl, a class of long-lived organic radials, is highly attractive open-shell organic molecular building block. In this study, we design two-dimensional (2D) open-shell covalent organic framework (COF) based on perchloro-triarylmethyl radical (PTM) and 1,3,5-tris(4-aminophenyl)benzene (TPB) building blocks. By performing density functional theory calculations, we systematically investigate electronic structure and magnetic property of the 2D open-shell COF while considering several possible stacking modes and contact types between building blocks. The thermodynamic stability of the 2D open-shell COF is found to increase as its interlayer distance decreases, which mainly depend on the contact type between building blocks. The 2D open-shell COF shows a finite band gap. The energy states near Fermi level are mainly occupied by pz orbital of central carbon (αC) atom of PTM building blocks. The magnetization of the 2D open-shell COF is evidenced by asymmetric density of states of each spin. The magnetic moment of αC is found to be in the range of 0.27-0.30, indicating that unpaired electron of αC is delocalized to carbon atoms at ortho- and para- positions of each aryl rings.