The formation of the ABC -stacking of the 4A2E-PDA-COF is a rare example of this stacking type in the kgm net. Due to the dimethyl core and the methyl benzoate group in ortho position to the aldehyde groups, the 4A2E linker possesses large dihedral angles along its backbone that inhibit efficient πstacking of the linker in the resulting COF. This lack of strong interactions between the layers might be responsible for the formation of the ABC stacked structure. This feature of the linker might also be responsible for the slip stacking of the 4A2E-Bz-COF, where the slip stacking relieves unfavorable close contact of the dimethyl benzene core of the linker. Another reason for the apparent rarity of the ABCstacked kgm structures might be the misassignment of sql nets to ABC stacked kgm structures, as often the position of the reflection with the lowest angle in the PXRD is taken an indication of kgm vs. sql. The absence of the (100) reflection in 𝑅3 ̅ /ABC stacked kgm COFs leads to the first observed reflection (110) to be in approximately the same position as the (100) reflection of a sql lattice based on the same linkers (in the case of the 4A2E-Bz-COF it is the (110) reflection due to the super cell). In the COFs reported here, the differentiation between ABC-stacked kgm and sql is more straightforward, as the methyl benzoate leads to high intensity on reflections at larger angles, and only a very weak reflection at low angles in the sql case. This highlights the importance for TEM measurements to not only verify the d-spacings, but also the symmetries in the crystallites.