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.