Unprecedented 2D-to-1D Reconstructive Phase Transition in Lead Iodide Perovskites

Organic-inorganic hybrid perovskites (OIHPs) demonstrate significant potential for optoelectronic devices and smart materials owing to their exceptional photoelectric properties and tunable stimulus-response characteristics. While their structural instability limits practical applications, this same instability enables unique stimuli-responsive functionalities. This study presents two compounds: (<i>N</i>-isopropylmethylamine)PbI₃ <b>(1)</b> with a 1D structure and (<i>N</i>-isopropylmethylamine)₆Pb₅I₁₆ <b>(2)</b> with a 2D structure. Comprehensive characterization reveals that compound <b>1</b> exhibits a 6/<i>mmm</i>F2/<i>m</i>(s) ferroelastic phase transition and demonstrates stable dielectric switching behavior. From 400 to 460 K, compound <b>2</b> transforms into compound <b>1</b> through an irreversible reconstructive phase transition, which exhibits properties identical to those of the experimentally synthesized compound <b>1</b>. Notably, both compounds exhibit low-temperature photoluminescence, with a 15 nm spectral shift between their emission peak. This study not only provides a new solution to the stability problem of high-dimensional perovskites but also opens up a new paradigm of dimension regulation for the development of new intelligent response materials.