Structural Dynamism and Controlled Chemical Blocking/Unblocking of Active Coordination Space of a Soft Porous Crystal

A three-dimensional
biporous soft porous coordination polymer containing active coordination
space, made of cadmium­(II) and a tripodal carboxylate ligand bearing
ether linkages, was synthesized and characterized. Guest-dependent
dynamic activities in the active coordination space of the soft porous
crystal have been explored. We have demonstrated controlled chemical
blocking and unblocking of active pores of the dynamic framework along
with guest-dependent contraction and expansion of the channels by
single-crystal-to-single-crystal structural transformation studies.
Detailed studies revealed up to 70% contraction of the void volume
and almost a 100 times increase in gas sorption by controlled phases
obtained by guest switching. These types of soft materials with porous
scaffolds, also known as soft porous crystals, may have general implications
in the preparation of intelligent host materials with zeolitic properties
and enzyme-like specificity.