Using variable temperature 2H static NMR spectra and 13C spin‐lattice relaxation times (T1), we show that two different porous organic cages with tubular architectures are ultra‐fast molecular rotors. The central para‐phenylene rings that frame the “windows” to the cage voids display very rapid rotational rates of the order of 1.2–8×106 Hz at 230 K with low activation energy barriers in the 12–18 kJ mol−1 range. These cages act as hosts to iodine guest molecules, which dramatically slows down the rotational rates of the phenylene groups (5–10×104 Hz at 230 K), demonstrating potential use in applications that require molecular capture and release.
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