Elastic Properties in Monolayer Covalent-Organic Frameworks

Covalent-Organic Frameworks (COFs) are crystalline porous materials that are based on organic monomeric units, so called building blocks. As a multitude of different building blocks can be combined in reticular chemistry, manifold different porous structures with tailored properties have been synthesized in recent years. Through current experimental progress, monolayer COF materials have been synthesized, providing a new class of 2D materials. However, these materials have defects and grain boundaries which make it challenging to describe properties of realistic materials computationally. To approach this issue, we show in this work how to use a surrogate model to calculate elastic properties of 2D COFs based on density functional based tight binding (DFTB) calculations. This allows us to model defective systems at low computational cost and paves the way for multiscale modeling. Furthermore, this approach enables us to predict elastic properties from the properties of the monomeric building blocks.