Hydrogen-Bonded Open-Framework with Pyridyl-Decorated Channels: Straightforward Preparation and Insight into Its Affinity for Acidic Molecules in Solution.

ABSTRACT

A hydrogen-bonded open framework with pores decorated by pyridyl groups was constructed by off-charge-stoichiometry assembly of protonated tetrakis(4-pyridyloxymethyl)methane and [Al(oxalate)3 ]3- , which are the H-bond donor and acceptor of ionic H-bond interactions, respectively. This supramolecular porous architecture (SPA-2) has 1 nm-large pores interconnected in 3D with large solvent-accessible void (53 %). It demonstrated remarkable affinity for acidic organic molecules in solution, which was investigated by means of various carboxylic acids including larger drug molecules. Competing sorption between acetic acid and its halogenated homologues evidenced good selectivity of the porous material for the halogenated acids. The gathered results, including a series of guest@SPA-2 crystal structures and HRMAS-NMR spectra, suggest that the efficient sorption exhibited by the material relies not only on an acid-base interaction. The facile release of these guest molecules under neutral conditions makes this SPA a carrier of acidic molecules.