Pressure-driven interconversion between Ruddlesden-Popper and Dion-Jacobson phases in two-dimensional hybrid perovskites via 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, S-[BPEA]2PbI4 and rac-[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, S-[BPEA]2PbI4 undergoes a nDJ-to-nRP phase transition, while rac-[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 in situ 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 via pressure stimuli, enabling their future use in optoelectronic systems.