Controllable Photoluminescence Modulation of 2D Hybrid Materials Based on (DFCBA) ₂ PbX ₄ (X = I, Br) via Halogen Regulation

Two-dimensional (2D) organic-inorganic hybrid halide materials have garnered significant research attention due to their tunable structural features and versatile photophysical properties. However, the significant enhancement of photoluminescence (PL) performance by modulating the composition of inorganic frameworks has rarely been reported, despite great efforts. Herein, we have successfully prepared two novel 2D hybrid lead halide compounds by regulating the halogen cation, namely, (DFCBA)₂PbX₄ (<b>1</b> and <b>2</b>, DFCBA = 3,3-difluorocyclobutylamine, X = I and Br). Interestingly, a blue shift of PL with giant quantum yield enhancement ratio of ∼4900% in these homologs was observed from <b>1</b> to <b>2</b>. Optical characterization reveals that their experimental band gap increases from 2.37 to 3.07 eV, which is consistent with the observed changes in PL emission. In addition, Compounds <b>1</b> and <b>2</b> crystallize in the polar <i>Cc</i> space group at room temperature, and both undergo temperature-induced reversible structural phase transitions, with transition temperatures of 331 and 336 K, respectively. These results demonstrate that the halogen modulation strategy can controllably tune the evolution of structure and optical properties in 2D organic-inorganic hybrid halides, highlighting the potential of these materials for applications in tunable optoelectronic devices.