β-Cyclodextrin Covalent Organic Framework for Selective Molecular Adsorption.

Covalent organic frameworks (COF) are complex functional systems constructed with atomic precision by linking well-defined building blocks through robust covalent bonds. β-cyclodextrin (β-CD) is a most employed supramolecule which bears a hydrophobic cavity guiding molecular specific recognitions. Building COF with asymmetric β-CD linkers is challenging and has never been reported. Here, β-CD COF is grown with heptakis(6-amino-6-deoxy)-β-CD and terephthalaldehyde in green solvents of water and ethanol at room temperature. The COF is characterized by powder X-ray diffraction, which matches well with the simulated crystal structure. Weaving β-CD into a framework through reticular chemistry allows the integration of a large amount of β-CD units (50 mol %), much higher than β-CD polymers. The β-CD COF has larger surface area, more uniform pore size, and higher thermal stability than the non-crystalline β-CD polymer produced by the same reagents. Finally, the β-CD COF holds abundant specific interaction sites enabling selective molecular adsorption.