Niflumic Anion Intercalated Layered Double Hydroxides with Mechano-Induced and Solvent-Responsive Luminescence

Stimuli-responsive luminescent materials play an important role in fluorescent switches, optical storage devices and smart sensors. In this work, we report a mechano-induced and solvent stimuli-responsive luminescent change by the assembly of a typical aggregation-induced-emissive (ALE) molecule, niflumic acid (NFC), into the interlayer region of Zn-Al-layered double hydroxides (LDHs) with heptanesulfonate (HPS) as a cointercalation guest. The structure, chemical composition, and thermostability of the as-prepared NFC-HPS/LDHs composites were characterized by X-ray diffraction, elemental analysis, and thermogravimetry and differential thermal analysis (TG-DTA). Fluorescence spectra demonstrate that the sample with 5% NFC initial molar percentage, with respect to the interlayer guests, exhibits the optimal luminescent intensity. The NFC-HPS/LDH (5%) sample also exhibits the most obvious luminescent mechano-response with a 16 nm blue-shift and increase in the fluorescent intensity after grinding, while the pristine NFC solid shows little to no mechano-responsive behavior. Moreover, the NFC-HPS/LDH (5%) also presents reversible luminescent response to different volatile organic compounds (VOCs) (such as tetrahydrofuran, methanol, acetone, toluene, and chloroform). Therefore, this work not only gives a detailed description on the dual stimuli (mechanics and solvent)-responsive luminescence for future sensor applications but also supplies a deep understanding of the optical properties of the new AIE molecule within the confined LDH layers.