Water-driven Successive Structural Transformation in a Two-Dimensional (2D) Lead-Free Hybrid Double Perovskite

Hybrid organic-inorganic halide perovskites (HOIPs) have received continued interest for their structure diversity and potential application in optoelectronic, solar cells, nonlinear optics (NLO), and ferroelectrics. Structural symmetry breaking induced by water molecules in single-crystal-to -single-crystal (SCSC) transformations is beneficial to develop ferroelectrics or second-harmonic generation (SHG) materials. Along this line, a water-containing two-dimensional (2D) double perovskite, (C6H16N2)2AgBiBr8 center dot H2O (1), was prepared. Acentric 1 suffered a twice SCSC transformation when subjected to dehydration and rehydration, where the new centric (C6H16N2)2AgBiBr8 (2) and acentric (C6H16N2)2AgBiBr8 center dot 0.5H2O (3) were generated. In contrast to the irreversible transformation from 1 to 2 (symmetry: P21 -> Pmna), it is prominent that the reversible conversion of centric 2 to acentric 3 (symmetry: Pmna <-> P21212). The result validated the effect of guest water on inducing structural transformation and symmetry breaking of 2D perovskites, inspiring further explorations on water-involved 2D materials.

Automated summary

Hybrid organic-inorganic halide perovskites have received interest for their structure diversity and potential application in optoelectronic, solar cells, NLO, and ferroelectrics. Water molecules can induce structural symmetry breaking and transformation, which inspire further explorations on water-involved 2D materials.