Pore Environment Reinforced Laser Dye Fluorescence in an Adenine-Containing Metal-Organic Framework with Pocket-Like Channels

Two novel adenine-containing metal-organic frameworks (MOFs) with the same components but different pore environments and topologies, named ZnTDCA-1 and ZnTDCA-2, were designed and synthesized. The host-guest composites were successfully fabricated by encapsulating a laser dye, 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM), into the MOFs, and their luminescence behaviours were found to be dependent on their different pore shapes, supported by spectral measurements, pore metrics analysis, and periodic density functional theory calculations. Notably, the quantum yield of DSM@ZnTDCA-1 can reach 39.3%, with no obvious decrease when increasing the content of DSM, indicating a favourable pore matching effect between the pocket-like pores of the ZnTDCA-1 host and DSM, which facilitates DSM to be fixed within the frameworks and uniformly dispersed. In contrast, although ZnTDCA-2 has a larger size to adsorb more dye, DSM diffuses along one-dimensional square channels after entering the host framework, resulting in the accumulation of DSM in large and regular channels, leading to fluorescence quenching. The work reveals the influence of pore shape, in particular the pocket-like confinement space, on the luminescence of the DSM@MOF system. Moreover, our preliminary cell culture and cytotoxicity experiments indicate that the DSM@MOF system is biocompatible and can serve as a platform for biological microlasers and various bio-applications. Confinement laser dye into two novel adenine-containing metal-organic frameworks with the same components but different pore environments and topologies exhibited distinct adsorptive luminescence behaviours.