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. Porous β‐cyclodextrin (CD) cubic poles: The first success of using an asymmetric supramolecular building block, β‐CD, for the construction of a covalent organic framework. The framework is built from heptakis(6‐amino‐6‐deoxy)‐β‐CD and terephthalaldehyde under acid catalysis in aqueous ethanol at room temperature. It exhibits a morphology of cubic poles, with an average width of 125 nm. The material has a high surface area, uniform pore size, and abundant β‐CD units, enabling highly selective molecular adsorption in water.