Pressure-Induced Luminescence Enhancement of Aggregation-Induced Emission Molecules Confined in Two-Dimensional MOF Layers

Confining individual luminescent molecules in nanoscale spaces and investigating the correlation mechanism between molecular structure and luminescent properties under external stimuli is an effective strategy for optimizing their luminescent performance. Herein, 2,2′-biquinoline-4,4-dicarboxylic acid disodium salt (BCA) molecules with significant AIE characteristics were confined within the two-dimensional layers of Ni-MOF, forming a dye-embedded MOF (DE-Ni-MOF). A remarkable pressure-induced luminescence enhancement was observed when the confined BCA was released from high pressure to ambient conditions. In situ experimental and theoretical investigations under high pressure have revealed that the application of pressure compresses the lattice structure of DE-Ni-MOF, ultimately leading to the disruption of its layered framework. A binding interaction was established between the confined BCA molecules and the framework after pressure treatment, effectively restricting the vibrational and rotational motions of the BCA molecules. This binding was maintained to atmospheric pressure, and the pressure treatment significantly enhanced the luminescence of BCA.