Porous Crystalline Spherulite Superstructures

Summary Assembly of crystallites into three-dimensional hierarchical superstructures is vital for the design of multicomponent architectures as capsules and reactors for storage, delivery, and catalysis. However, the development of these assemblies, for example, spherulite superstructures, has mainly been hampered by limited control over nucleation, orientational growth, and stability. In this work, we observed a hierarchical evolution from metal-organic framework (MOF) nanofibrils into spherulite superstructures. Under a polarized light, these superstructures exhibited a "Maltese cross" extinction pattern typical of spherulites, which is the first time this has been observed in porous materials. We demonstrated that by tuning the evolution kinetics via a mixed-solvent approach, varying morphologies could be obtained as a result of small-angle branching. Isoreticular expansion of MOF spherulites and incorporation of multiple components could also be achieved. This work provides a fresh avenue to pack porous crystallites into sophisticated superstructures, which are expected to serve applications from catalysis to guest delivery and transportation.