Double Twisted Photonic Honeycomb Frameworks with Mesoporous Structures

Abstract In nature, materials such as shell, bone, silk, and wood are assembled with hierarchical structures that span lengths from nanometers to centimeters. These biological materials are fascinating targets for replication and mimicry, often owing to their remarkable properties. The intricate and periodic structure of the snow crab (Chionoecetes opilio) exoskeleton that renders it iridescent is described here. It is discovered that the snow crab has a double twisted photonic honeycomb structure constructed by left‐handed rotation of chitin nanofibrils around cavities throughout its shell. This new chiral framework provides a foundation for exploring chiral photonics and materials. With the goal of mimicking this intricate network, the iridescent mineralized chitin shell is successfully transferred to calcite, carbon, apatite, and fluorapatite/chitin materials with structural replication. It is shown that the sophisticated organization of the iridescent crab shell leads these new materials to have a distinctive macroscopic combination of multilevel chirality, honeycomb channels, and mesoporosity. These solid‐state transformations of snow crab exoskeletons will open the path to making complex hierarchical frameworks of functional porous materials through bioinspired templating.