Assembling Polyhedral Metal-Organic Framework Superstructures by Bidirectional Shear

Colloidal superstructures with long-range order offer a gateway to emergent collective properties, yet achieving simultaneous translational and orientational control over anisotropic polyhedral building blocks remains a formidable challenge. Here, we show that bidirectional shear enables the assembly of polyhedral colloidal superstructures. Using Zeolitic Imidazolate Framework-8 (ZIF-8) particles in a polymer matrix, alternating bidirectional shear fields, coupled with dynamic coordination and hydrogen-bonding interactions, generate a viscoelastic regime that aligns particles into facet-specific ordered lattices. This mechanism couples translational and orientational ordering beyond that accessible by conventional shear processing. The resulting large-area composite superstructures exhibit high-saturation structural colors with reflectance intensities approaching 70%. The intrinsic microporosity of ZIF-8 further enables in situ encapsulation of fluorescent guests, yielding films with integrated structural color and fluorescence. These orthogonal optical responses provide a platform for multilevel anticounterfeiting. This work establishes bidirectional shear as a general strategy for assembling anisotropic colloids into multifunctional composite superstructures.