Crystal Sponge Behavior in a Two-Dimensional Rare-Earth Hybrid Coordinate Polymer.

Stimuli-responsive multifunctional materials (SRMMs) have attracted tremendous attention due to their dynamic responses to external stimuli. However, it remains challenging to simultaneously achieve solvent-induced single-crystal to single-crystal (SCSC) transformation and structural phase transition after desolvation. Here, we report a two-dimensional (2D) rare-earth organic-inorganic hybrid coordinate polymer [(CH 3 ) 3 NCH 2 Cl] 2 [Eu·H 2 O] 2 [CH 2 (SO 3 ) 2 ] 4 ·2H 2 O ( 1 ) that exhibits a reversible SCSC transformation by changing to 2 ([(CH 3 ) 3 NCH 2 Cl][Eu·H 2 O][CH 2 (SO 3 ) 2 ] 2 ). Impressively, the SCSC transformation process couples with large changes in quantum efficiency dropped from 33.68% of 1 to 20.07% that of 2 . Furthermore, polymer 2 shows an isomorphic structural phase transition associated with switching dielectric. Notably, the distance of the 2D layers shows reversible change during the two successive transition processes displaying a crystal sponge behavior. This work reveals the potential of rare-earth 2D hybrid coordination polymers in the design of multifunctional responsive materials and opens a new prospect to explore the construction of novel SRMMs.