Circular mesostructures: solids with novel symmetry properties

Abstract

Mesoporous structures are more than just materials with pores (2 nm < d_meso < 50 nm) bigger than micropores (d_micro < 2 nm). They show new structures, shapes and symmetries that induce new properties and reveal unexpected applications. This work starts with a comprehensive description of one especially-perfect class of mesoporous structures (circulites), exhibiting circularly arranged pores which represent a novel symmetry behavior. It is shown that these structures are, from a more systematic point of view, strictly-defined hierarchies. They can serve as a prototype for the description and formation of hierarchical structures. Here, coiling is used as a general approach to the assembly of hierarchies. The control and design of hierarchical structures are the ultimate aims and have been achieved for this hierarchy type. We show that surfaces can be used for the selection of the hierarchy type, position control and alignment of the resulting particles. A molecular structuring of the support leads to pixel-like, highly-defined growth of a hierarchical arrangement containing 4 hierarchy levels. Finally, the properties of the hierarchies can be very specific, as shown by the guest transport behavior.