Research on the Mechanism of Aggregation-Induced Emission through Supramolecular Metal–Organic Frameworks with Mechanoluminescent Properties and Application in Press-Jet Printing

This study investigates the mechanism of AIE in the solid state through supramolecular metal–organic frameworks and mechanoluminescent materials for the first time. Herein, four novel differently substituted Schiff base building blocks, SB1–SB4, exhibit typical AIE properties with various fluorescence emissions from yellow to green. SB1–SB4 are linked through C–H···O hydrogen bonding interactions to construct supramolecular metal–organic frameworks (SMOFs): namely, SMOFSB1–SMOFSB4. Particularly, among these SMOFs, SMOFSB3 is observed to have micropores in the 3D supramolecular structure and exhibits mechanoluminescent properties (grinding). An emission turn-on mechanism occurs with destruction of micropores by grinding and blockage of intramolecular rotations of the methyl and acetonitrile in the micropores, resulting in emission turn-on in SMOFSB3. Single-crystal X-ray structures, powder X-ray diffraction, emission spectra at room temperature, temperature-dependent emission spectra, DFT calculations, and a charge separation hypothesis well demonstrate the emission turn-on mechanism, which is consistent with the mechanism of AIE. More importantly, the molecules demonstrated potential application for press-jet printing.