Layer stacking order tunes thermal and mechanical properties in a prototypical imine-linked 2D covalent organic framework
摘要
Layer stacking is a route to structural tuning in two-dimensional covalent organic frameworks (2D COFs) that allows properties to be modified without changing chemical composition. Here, the anisotropic thermal conductivities and Young’s moduli of six distinct stacking arrangements of the 2D COF TAPB-DMPDA are studied using molecular dynamics simulations. The in-plane thermal conductivity (k∥) is maximized in the ABC (1.14 W/m-K) and AB-staggered (1.02 W/m-K) arrangements due to a reduced interlayer spacing that increases the stiffness. The AB-serrated arrangement yields the highest cross-plane thermal conductivity (k⊥, 0.14 W/m-K) as a result of continuous thermal transport pathways. The decoupled mechanisms of in-plane and cross-plane thermal transport lead to anisotropy ratios k∥/k⊥ that span from 5 to 16. The observed thermal transport trends correlate strongly with in-plane and cross-plane Young’s moduli, as well as with key structural and energetic descriptors. Furthermore, a subtle linker modification to a dipole-aligned configuration decreases k∥ by up to 25% while increasing k⊥ by up to 35%, highlighting the potential of side-group chemistry to enhance interlayer coupling. This work demonstrates layer stacking as a powerful design strategy for tailoring the thermal and mechanical performance of 2D COFs.