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 via 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 frameworks materials have defects and grain boundaries which make it challenging to describe properties of realistic materials computationally. To approach this issue, we present in this work a coarse-graining model based on elastsc beams representing molecular building units. We show how to easily fit this model based on density functional based tight binding (DFTB) calculations. This allows us to model large scale defective 2D framework materials at low computational cost and paves the way for multiscale modeling.