In this study, we investigated how steric interactions through the pores of 2D COFs affect their nets. We achieved the through-pore interactions by rigid attachment of a long and bulky methoxycarbonylterminated phenyl group to a tetraaldehyde linker. Using this modified tetraaldehyde, we synthesized COFs with different linear diamine linkers. We observed a kgm structure with the short pphenylenediamine and a sql structure with the longer benzidine (p-diaminodiphenyl). Our work tackles the challenge of controlling the nets with this sterically demanding linker design. The structural characterization by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) confirmed the selectivity for sql and kgm. Additionally, we found evidence for the rare ABC stacking in the kgm COF. Force field simulations provided evidence for strong steric crowding in the rhombic pore of a hypothetical sql 4A2E-PDA-COF, based on the p-phenylenediamine, that is relieved when forming the hexagonal pores in the kgm net. The longer benzidine linker increases the intrapore distance and decreases the steric demand, thus allowing the formation of a sql net. Our linker design enables sterically demanding functional groups to control the net. This design principle expands the COF synthesis toolbox for inducing the kgm net more reliably.