A survey of "porous" π-stacked systems including (porphyrin) 2 , (annulene) 2 and (COF1) 2 reveals that a slip-stacked geometry is preferred in all cases, to varying degrees. Amongst various energy components and combinations thereof the vdW interaction potential, which encodes the competition between dispersion and Pauli repulsion, proves to be the best qualitative match for the total interaction potential and provides a physical basis to understand the emergence of offset-or slip-stacking in these systems, just as it does in benzene dimer and other π-stacked aromatic hydrocarbons. Other energy components are simply too small in magnitude or do not generate a potential surface that matches the topography of the total interaction potential surface. As such, we find no compelling rationale for the continued invocation of "Hunter-Sanders" in the context of π-π interactions Examination of (COF1) 2 and related model sys-tems proves to be especially interesting. For (COF1) 2 (mesitylene), where a solvent molecule occupies the pore, steric repulsion severely limits the available lateral offsets, strongly favoring eclipsed-cofacial or AA-type stacking. Upon removing the guest molecule, a ∼ 1.5 Å lateral offset becomes the minimum-energy geometry. This displacement is still best explained by the vdW interaction potential although the role of electrostatics becomes important for quantitative purposes. AB-type stacking geometries involving larger lateral offsets are significantly less stable.