Reversible Mechanofluorochromism in a Catechol-Derived Zn-Based Hydrogen-Bonded Coordination Assembly: Structural Origin and Interfacial Studies for Flexible Optical Films

Abstract Hydrogen-bonded coordination assemblies (HBCAs) are an emerging class of supramolecular materials that combine coordination interactions with dynamic hydrogen bonds. However, their mechanoresponsive luminescence has remained relatively unexplored. In this work, we report a crystalline Zn-based hydrogen-bonded coordination assembly (Zn-HBCA) comprising discrete Zn8 coordination clusters that self-assemble into an extended supramolecular architecture through intermolecular hydrogen-bonding interactions. The resulting material exhibits reversible mechanofluorochromism, distinct mechanochromic behavior arising from mechanically induced changes in molecular packing, and excellent thermal robustness. The as-synthesized Zn-HBCA is comprehensively characterized by ATR-IR, TGA, FE-SEM, SCXRD, PXRD, EDAX, and elemental mapping analyses. Furthermore, the crystalline form of Zn-HBCA was incorporated into a poly(vinyl alcohol) (PVA) matrix via a simple drop-casting method to fabricate a luminescent composite film (Zn-HBCA-PVA). The resulting film exhibits bright UV-responsive luminescence (365 nm), enhanced mechanical strength, superior stretchability and flexibility, and high thermal stability. FE-SEM and confocal microscopy confirmed the uniform distribution of Zn-HBCA crystalline particles within the PVA matrix. The luminescent composite films show promising potential for applications in stress sensing, chemosensing, optical displays, and smart packaging.