Efficient guest exchange: The organic zeolite analogue TPP⋅x(THF) (x=0.35–0.65) takes up I2 quickly when exposed to iodine vapor. The previously colorless crystals (a) color at the ends (b), and after 1–2 days the iodine has permeated all the way through the crystal (c). The conductivity values of the TPP⋅y(I2) crystals are of the same order as those of elemental I2. TPP=tris(o‐phenylenedioxy)cyclotriphosphazene.

Phase-sensitive second-harmonic microscopy is applied to reveal grow-in polarity in topologically centrosymmetric crystals of 4-chloro-4′-nitrostilben. As predicted by the Markow model of layer-by-layer polarity formation, growth along + and −b-direction in P21/c is producing optical nonlinearity in both sectors associated with the b axis. Present experiments show that formation of a pyroelectric symmetry class is a stochastic property of molecular crystals grown from dipolar compounds and near to thermodynamic equilibrium.

Macroscopically polar crystals of an organic zeolite, tris(o‐phenylenedioxy)cyclotriphosphazene, are obtained by partial guest exchange of included THF molecules with nonlinear optical molecules, which enter the channels via a mechanism of surface recognition (4‐amino‐4′‐nitrobiphenyl partially (left) and fully (right) stained crystals are shown in the Figure).

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