The rational design of stimuli-responsive materials requires a deep understanding of the structure–activity relationship. Herein, we proposed an intramolecular conformation-locking strategy─incorporating flexible tetraphenylethylene (TPE) luminogens into the rigid scaffold of a molecular cage─to produce a molecular photoswitch with dual outputs of luminescence and photochromism in solution and in the solid states at once. The molecular cage scaffold, which restricts the intramolecular rotations of the TPE moiety, not only helps to preserve the luminescence of TPE in a dilute solution but facilitates the reversible photochromism on account of the intramolecular cyclization/cycloreversion reactions. Furthermore, we demonstrate assorted applications of this multiresponsive molecular cage, e.g., photo-switchable patterning, anticounterfeiting, and selective vapochromism sensing.

The construction of nanotubes with well-defined structures, although synthetically challenging, offers the prospect of studying novel chemical reactions and transportation within confined spaces, as well as fabricating molecular devices and nanoporous materials. Here we report a discrete molecular nanotube, namely the covalent organic pillar COP-1, synthesized through a [2 + 5] imine condensation reaction involving two penta-aldehyde macrocycles and five phenylenediamine linkers. A pair of enantiomeric nanotubes, obtained in a quantitative and diastereoselective manner, were characterized and resolved readily. NMR spectroscopy, isothermal titration calorimetric and X-ray crystallographic studies revealed that the 2-nm-long and 4.7-Å-wide one-dimensional channel inside COP-1 can accommodate α,ω-disubstituted n-alkyl chains with complementary lengths and electron density distributions. Furthermore, in a length-mismatched host–guest pair, we found that the nonamethylene dibromide thread not only displays a diminished binding constant in solution, but adapts an energetically unfavoured gauche conformation inside COP-1 in the solid state.