Herein the novel tetraphenylethylene (TPE) derivative 1 was designed with an integration of aggregationinduced emission (AIE), multi-state mechanochromism and self-recovery photochromism. The molecule was susceptible to grinding,heating and vapor fuming and showed corresponding transition of its emission colors.T he heated powder or single crystal of 1 exhibited reversible photochromism. After ashort period of UV irradiation, it showed ab right red color,b ut recovered to its original white appearance within 1min. The photochromism is due to the formation of photocyclization intermediates upon UV irradiation, while the eversible mechanochromism is attributed to the weak molecular interactions derived from head-to-tail stacking of the molecules.T his reversible multi-state,h igh-contrasted and rapid responsive mechanochromic and photochromic property cooperatively provided ouble enhancement of am ultimode guarantee in advanced anti-counterfeiting.

Transferring the solution-state chemistry of organic-based molecular switches (OMS) into the solid state usually faces several fatal problems, such as spatial confinement or inefficient conversion. As a result, their switching behavior usually cannot be maintained. Herein, we report a redoxswitchable metal−organic framework (MOF) that can undergo a reversible single-crystal-to-single-crystal (SCSC) transformation through a hydroquinone/quinone redox reaction. The redox-triggered transformation is quantitatively reversible while maintaining the crystallinity of the MOF scaffold. In addition, the transformation occurs gradually in the MOF backbone and from the outsurface of MOF to the inside. This study represents a general strategy to enable efficient conversion of the functionality of an OMS from solution into solid state, by incorporation of OMS into the framework of MOF. Furthermore, the material exhibits interesting changes in spectroscopic properties through reversible SCSC transformation and, thus, may be a starting point for the use of such materials in memory storage or redox-based electronic devices.

The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water-stable anthracene and maleimide appended zirconium-based-metal-organic framework (Zr-MOF; UiO-68-An/Ma) is reported. Unlike the regular intramolecular "fluorophore-spacer-receptor" format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo-intramolecular fluorescent PET process, resulting in UiO-68-An/Ma with very weak fluorescence. Interestingly, after Diels-Alder reaction or thiol-ene reaction of maleimide groups, the pseudo-intramolecular fluorescent PET process in UiO-68-An/Ma fails and the solid-state fluorescence of the crystals is recovered. In addition, UiO-68-An/Ma shows an interesting application as solid-state fluorescent turn-on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET-based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli-responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.