Recyclable Nanoporous Materials with Ordered Tunnels Self-Assembled from alpha- and gamma-Cyclodextrins

A straightforward method to create nanoporous materials via the self-assembly of macrocyclic molecules (MCMs) is proposed and fulfilled by using cyclodextrins (CD) as building blocks. Due to molecular geometry, alpha-CD forms a hexagonal nanoporous crystal, whereas gamma-CD forms a cuboid crystal. The resulting products are confirmed by FTIR, H-1 NMR and solid-state C-13 NMR to be solely built up by CDs. Well-defined and monodisperse nano-tunnels are formed in nanoporous materials by the template-free, face-to-face self-assembly of CDs, with diameters around 0.8 or 0.5 nm equal to the diameter of the CD cavities. Moreover, the nanoporous structure of the CD is reversible controlled simply by switching temperature in DMF, indicating that the nanoporous CDs could be recyclable used and recovered. These characteristic properties and behaviors of the nanoporous CDs made them to be an ideal green material for absorption, separation as well as CD recovery.