Stepwise guest adsorption with large hysteresis in a coordination polymer {[Cu(bhnq)(THF)2](THF)}n constructed from a flexible hingelike ligand.

Reversible vapochromic behavior of a porous copper(II) coordination polymer {[Cu(bhnq)(THF)2](THF)}n (1; THF = tetrahydrofuran) constructed from a flexible hingelike ligand H2bhnq [2,2'-bis(3-hydroxy-1,4-naphthoquinone)] has been investigated by adsorption measurements. The isotherms show large hysteretic and stepwise profiles, suggesting the occurrence of the guest-induced framework transformation. The dynamic coil-like behavior of 1 can be controlled through the change of the hydrogen-bonding interactions caused by the reversible and selective incorporation of guest molecules.