Structure–Dynamics-Property Relationship Reveals the Origin of Porous Integrity in Imine-Linked Covalent Organic Frameworks

Normal-mode decomposition and torsional potential energy surfaces show that these coordinates are comparatively stiff in the imine-based frameworks, preserving near-planar linker conformations that support guest-responsive structures. In contrast, COF-300-AR exhibits a shallower, multiwell torsional potential that enables bent linker conformations, favoring collapsed packing. Gas-phase local-mode analysis reproduces this relative trend in torsional softness, suggesting that linker flexibility can be screened before a crystal structure is available.

The negligible gas uptake of COF-300-AR is therefore linked to the coupling of local amine flexibility with packing constraints in the interpenetrated framework. More broadly, these results demonstrate how low-frequency dynamics can identify molecular coordinates governing the structural integrity and porosity in flexible COFs.