Solid-State Reversible Nucleophilic Addition in a Highly Flexible MOF

A flexible and porous metal–organic
framework, based on
CoII connectors and benzotriazolide-5-carboxylato linkers,
is shown to selectively react with guest molecules trapped in the
channels during the sample preparation or after an exchange process.
Stimulated by a small crystal shrinking, upon compression or cooling,
the system undergoes a reversible, nonoxidative nucleophilic addition
of the guest molecules to the metal ion. With dimethylformamide, only
part of the penta-coordinated Co atoms transform into hexa-coordinated,
whereas with the smaller methanol all of them stepwise increase their
coordination, preserving the crystallinity of the solid at all stages.
This extraordinary example of chemisorption has enormous implications
for catalysis, storage, or selective sieving.