Epitaxial transformations of metal–organic frameworks into orientated superparticles

Abstract

Assembly of metal–organic framework (MOF) nanoparticles into ordered superparticles is of great research value, and their collective properties could provide unique performance in a variety of fields. Herein, we successfully prepared well-defined superparticles consisting of highly aligned MOF-74 nanoneedles (with L/D ratios up to 45 and Hermans orientation factors up to 0.91) through the so-called “epitaxial” MOF-to-MOF transformation. The transformation involved dissolution of the precursor MOF and consequent recrystallization into MOF-74 using the crystalline lattice of the precursor as the template. The occurrence of epitaxial transformation was attributed to the close match between the lattices of the precursor and MOF-74 in a certain direction. In addition, the quasi-periodic alignment of the nanoneedles endowed the superparticles with distinct optical properties, demonstrating great potential applications as anti-counterfeiting materials. This discovery provides fresh insights into the MOF-to-MOF transformation and provides a new route to hierarchical architectures.