Electrostatically Dominated Pre‐Organization in Cyclodextrin Metal–Organic Frameworks

Abstract Electrostatic interactions between oppositely charged entities play a key role in pre‐organizing substrates and stabilizing transition states of reactions in enzymes. The use of electrostatic interactions to pre‐organize ions in nanoconfined pores, however, has not been investigated to its full potential. Herein, we describe how carboxylate anions can be pre‐organized at the behest of their electrostatic interactions with K + cations in nanoconfined tunnels present in γ‐cyclodextrin metal–organic frameworks, i.e., CD‐MOFs. Several carboxylate anions, which are all much smaller than the cavities of the tunnels, were visualized by X‐ray crystallography when nanoconfined in CD‐MOFs, despite the large voids present in the tunnels. These anions were found to be aligned within a planar array defined by four K + cations, positioned around the periphery of the tunnels. The strong electrostatic interactions between the carboxylate anions and the K + cations dictate the orientation of the anions and override the influence of all other possible noncovalent bonding interactions between them and the tunnels. Consequently, the aligned pairs of γ‐cyclodextrin rings constituting the tunnels become distorted, resulting in them having lower symmetry and fewer disordered carboxylate anions in the solid state. Our findings offer a transformative strategy for controlling the packing and orientation of ions in nanoconfined environments.