Pressure-driven interconversion between Ruddlesden–Popper and Dion–Jacobson phases in two-dimensional hybrid perovskites <i>via</i> supramolecular interactions

Hybrid lead halide perovskites have emerged as versatile candidates for advanced optoelectronic applications. However, precise control over their phase interconversion remains challenging. Here, we report two structurally distinct 2D perovskites, <i>S</i>-[BPEA]₂PbI₄ and <i>rac</i>-[BPEA]₂PbI₄, featuring near Dion-Jacobson (nDJ) and near Ruddlesden-Popper (nRP) stacking configurations induced by stereospecific organic cations. Under mild hydrostatic pressure, both compounds exhibit significant photoluminescence enhancement (1.97 times at 0.38 GPa, 1.09 times at 0.22 GPa) and tunable emission energies. Notably, <i>S</i>-[BPEA]₂PbI₄ undergoes a nDJ-to-nRP phase transition, while <i>rac</i>-[BPEA]₂PbI₄ evolves toward an ideal RP phase, driven by supramolecular interaction modulation and octahedral distortion. In addition, structural analyses, including Hirshfeld surface mapping, deformation potential modeling, and <i>in situ</i> high-pressure PXRD, quantitatively correlate lattice response with emission behavior. Moreover, both materials exhibit reversible mechanochromic luminescence, underscoring their mechanical robustness and optical responsiveness. These findings establish a supramolecular engineering framework for controlling phase structure and light emission in 2D hybrid perovskites <i>via</i> pressure stimuli, enabling their future use in optoelectronic systems.