  Two-dimensional covalent organic frameworks (2D COFs) are an interesting
class of 2D materials since their reticular synthesis allows the tailored
design of structures and functionalities. For many of their applications the
mechanical stability and performance is an important aspect. Here, we use a
computational approach involving a density-functional based tight-binding
method to calculate the in-plane elastic properties of about 40 COFs with a
honeycomb lattice. Based on those calculations, we develop two coarse-grained
descriptions: one based on a spring network and the second using a network of
elastic beams. The models allow us to connect the COF force constants to the
molecular force constants of the linker molecules and thus enable an efficient
description of elastic deformations. To illustrate this aspect, we calculate
the deformation energy of different COFs containing the equivalent of a
Stone-Wales defect and find very good agreement with the coarse-grained
description.
