Supramolecular Templating of 3D Metal Halide Perovskites into Noncentrosymmetric Hybrids with High Nonlinear Optical Responses

Lead-based halide perovskites have demonstrated remarkable success in applications such as photovoltaics, photodetectors, and LEDs, owing to their defect tolerance and exceptional optical and electrical properties. However, the major issue of lead toxicity has drawn considerable attention, requiring an appropriate solution for the efficient, sustainable recycling or upcycling of lead halide perovskite precursors. In this study, we present a supramolecular approach to transform 3D perovskites into nonlinear optical hybrid materials by employing crown ethers as symmetry-breaking molecular templates. Robust hydrogen-bonding interactions between the crown ethers and the cationic components of the perovskites enable selective extraction and guided self-assembly of perovskite precursors (lead halides and organic amines) into supramolecular metal-halide hybrid crystals. These hybrids exhibit strong room-temperature nonlinear optical (NLO) responses, as confirmed by polarization-resolved second-harmonic generation (SHG) measurements showing a large modulation depth of ∼68%. In addition, the supramolecular crystals display enhanced photoluminescence and improved environmental stability compared with their parent perovskite phases. Notably, upon thermal annealing, they can be reverted to the pristine 3D perovskite phase with restored crystal structure and emission, completing a reversible and byproduct-free recycling loop. This work establishes a sustainable and reversible pathway that couples perovskite upcycling with emergent nonlinear optical functionality, enabling phase-preserving storage and on-demand regeneration.