A theoretical prediction of 2D covalent organic frameworks constructed by B-heterocyclic carbenes

Abstract

Using density functional theory, we have designed a family of stable B-heterocyclic carbenes (BHCs) building blocks (a′-f′) with C2 symmetry and obtained six types of novel 2D COFs (COF-BHC-n, n = 1–6) by the condensation reaction of a′-f′. Optimized structures of 0D (Bn), 1D (Cn) and 2D (Dn) porous organic molecules (POMs) obtained by a′-f′ are stable. The stability order of Bn, Cn and Dn is Bn < Cn < Dn. Based on the stability of Bn, Cn and Dn, six novel 2D COFs were designed by extending the 2D POMs. Optimized lattice parameters of COF-BHC-n show that COF-BHC-n are hexagonal lattices and the apertures of their hexagonal channels are between 1.8 and 3.1 nm. Because the geometries of COF-BHC-n and Bn are almost same, calculated molecular electrostatic potential of Bn might be used to molecular modification of COF-BHC-n. Thus, COF-BHC-n are promising in design for functional materials with planar tetracoordinate carbon (ptC) towards its BHC units.