Dynamic and Patternable MOF-Based Liquid Photonic Crystals for Metameric Displays

We present the development of dynamic and patternable liquid photonic crystals (LPCs) based on zeolitic imidazolate framework-8 (ZIF-8) crystals, an approach that exploits the unique optical and structural properties of metal-organic frameworks (MOFs). By utilizing monodisperse ZIF-8 particles with tunable size and morphology, our study demonstrates the formation of vibrant structural colors via reversible electric-field-induced assembly. These LPCs exhibit rapid color modulation, angle-independent coloration, and remarkable stability, surpassing the performance of traditional LPCs. A key finding lies in the observation of metamerism within MOF-based LPCs, where spectrally distinct configurations appear indistinguishable to the human eye, potentially enabling hidden optical encoding. Additionally, our patterned electrophoretic displays showcase the ability to generate dynamic color patterns, further emphasizing their versatility. This work represents the first realization of on-demand structural color control of MOF-based materials, whereby the observed metamerism of the materials could unlock new opportunities for advanced photonic applications such as anti-counterfeiting, optical encoding, and dynamic displays.