). These facets on the top and bottom parts of the pyramids are indexed as {122}, {122 % }, {121} and {121 % }. They gradually curve inward at the apices. The continuous evolution of these facets is indicated by the curving edges, highlighted in Fig. in a rainbow of tangent line segments. The AdDB ligand in other MOFs shows a tendency to form unusual shapes with decidedly curved edges; segmented tubes, 9 flower-like, yo-yo-like , and brain-like morphologies. The gradual tapering of MOFs using this ligand and different nickel salts was well characterized previously. The aforementioned morphological subtleties are consistent with the appearance of additional facets {3 % 2 % 3 % } that appear on only the bottom pyramid and results in curved pyramidal edges in some instances (Fig. ). Over 100 crystals from different batches were collected for single crystal X-ray analysis at 100K. The unit cell best fits a hexagonal cell: a = b = 14.9799(2) Å, c = 18.3087(3) Å. The resolution is poor; the scattering drops off quickly at 2q > ca. 23°. A MOF was constructed with the space group P622 using a crystal with a counterclockwise sense: a left (L) arrangement of the principal facets (Fig. ). The Cd ions are coordinated by six pyridyl ligands and sit on sites of D3 symmetry, corresponding to Wyckoff positions d (1/3, 2/3, 1/2) and (2/3, 1/3, 1/2); the metal sits on a threefold axis. The crystal has a chiral (left-handed) hexagonal channels with a dimension of approximately 7.87 Å. In the absence of definite X-ray data, enantiomorph assignment by anomalous dispersion, we turned to complete polarimetry. The differential scattering of circular polarized light is in principle sensitive to the crystallographic enantiomorphism. For most crystals, intrinsic optical activity or circular birefringence (CB = 𝑛 ! -𝑛 " ) is given as the difference between the refractive indices for left (𝑛 ! ) and right (𝑛 " ) circularly polarized light. This difference is typically much smaller than the linear birefringence (LB = n// -n^), the refractivity differences between orthogonally polarized linear vibrations. It is for this reason that Pasteur never tried to measure the optical activity of his transparent crystals along low symmetry directions.