Two other local minima, with E int = -42.7 kcal/mol and E int = -42.4 kcal/mol, are evident in Fig. at coordinates (10.0 Å, 6.0 Å) and (0.0 Å, 12.0 Å), respectively, corresponding to radial displacement along polar angles of 30 • and 90 • . The vdW potential (Fig. ) picks up all of these features, with semiquantitative energetics albeit not as attractive as the E int surface. As in the case of the [18]annulene dimer, the difference is electrostatics, and a two-dimensional E elst surface is shown in Fig. , with a close-up view of small lateral displacements in Fig. . The E elst surface does display some structure that is not unlike E int (or E vdW ), although the potential wells are much shallower and and E vdW is a much better match to E int . For (COF1) 2 , we thus conclude that dispersion provides the dominant stacking interaction, albeit significantly enhanced by electrostatics, and that the competition between dispersion and Pauli repulsion (i.e., the vdW interaction) is sufficient to explain offset-stacking. (See Figs. S13f and S14b for closeup views of E vdW .)