Buckling of Two-Dimensional Covalent Organic Frameworks Under Thermal Stress

Two-dimensional Covalent organic frameworks (2D COFs) are periodic, permanently porous, and lightweight solids that are polymerized from topologically designed monomers. The predictable design and structural modularity of these materials make them promising candidates for applications including catalysis, environmental remediation, chemical separations, and organic electronics, many of which will require stability to mechanical and thermal stress. Based on their reinforced structures and high degradation temperatures as determined by thermal gravimetric analysis (TGA), many reports have claimed that COFs have excellent thermal stability. However, their stability to heat and pressure has not been probed using methods that report on structural changes rather than the loss of volatile compounds. Here we explore two structurally analogous 2D COFs with different polymerization chemistries using in operando X-ray diffraction, which demonstrates the loss of crystallinity at lower temperatures than the degradatio...