Phase transition triggered aggregation-induced emission in a photoluminescent uranyl-organic framework

When exposed to water, the two-dimensional uranyl-organic layered compound [(CH ) NH ][(UO )(BCPBA)]·2DMF·H O (H BCPBA = 3,5-bis (4'-carboxylphenoxy) benzoic acid) gradually undergoes a complete single-crystal-to-single-crystal phase transition to [(CH ) NH ][(UO )(BCPBA)]·3.4H O, resulting in an enhanced ligand-ligand interaction between the adjacent layers. This process gives rise to initial quenching of the uranyl photoluminescence followed by subsequent recovery of the photoluminescence with a much elevated intensity, as a unique case of aggregation-induced emission in an extended solid system, further confirmed by DFT analysis on bonding.