A search for all possible stacking modes in the three LCOFs using bulk structural models employing the Density-Functional based Tight-Binding (DFTB) method resulted in five distinct types (Figure , Tables 1, SI-2, 3): i. AA, (hcb and sql); with layers directly above each other. The "eclipsed" stacking mode (AAe) is energetically highly improbable, so the layers shift laterally by about 1.5 Å to AAs. This shift is confirmed theoretically and experimentally. iii. ABC (hcb); layers shifted laterally by [⅓,⅓] UC as in AB and again [⅓,⅓] in the next layer. The interlayer shift is identical to ABs, but a different superlattice appears in projection along layer normal. ABC is known in other hcb COFs. Due to layer corrugation (Figure ) it is the most stable structure for COF-1 and COF-5.