Sub-Nanoconfined Aggregation-Induced Emission Molecules via Stacked Layers of Microtubular Covalent Organic Frameworks for Enhanced Fluorescence

Functionalizing aggregation-induced emission molecules (AIEs) by confining them in porous materials is attracted extensive attention. Here stacked layers of hollow microtubular covalent organic frameworks (HT-COFs) are introduced as sub-nanoconfined sites (0.37 nm) to confine AIEs. The spacious hollow channels allow unimpeded entry for AIEs, while the interlayers perpendicular to the channels partially incarcerate the AIEs within the COFs layers. This effectively restricts the intramolecular rotation of AIEs and facilitates its radiative processes. Through exchanging of various AIEs, the versatility of the COFs interlayer as a restriction site is demonstrated. Furthermore, the sub-nanoconfined fluorescence in AIEs@HT-COFs displays reversible temperature dependence. Based on this, a temperature-tunable fluorescent Micro-QR code device is fabricated, wherein the encoded information disappears at a high-temperature and reemerges at a low-temperature. This work offers novel insights into confined fluorescence within functional materials and the fabrication of AIEs-COF multiplex frameworks. Hollow microtubular COFs (HT-COFs) with 0.37 nm subnanometer confinement sites are used to confine AIEs. The hollow channel allows easy access to the AIEs, while the interlayers partially trap AIEs, restricting their rotation and aiding the radiative processes. Besides, through exchanging of various AIEs, the versatility of the HT-COFs interlayer as a restriction site is demonstrated.image