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Ferroelectric Switchable Behavior through Fast Reversible De/adsorption of Water Spirals in a Chiral 3D Metal Organic Framework Xi-Y , Shuang-Quan Zang : zangsqzg@zzu.edu.cn ABSTRACT: A polar homochiral 3D MOF {[Co (L)(bpe)(H O)]⋅5H O} constructed with 2 2 2 n cobalt(II) and a new ligand N-(1,3-di-carboxy-5-benzyl)-carboxymethylglycine (H4L) accommodates ordered helical water streams in its helical grooves. It provides the first example of switchable ferroelectric and optical behavior through two-step reversible single-crystal to single-crystal transformation (SCSC) upon desorption/adsorption of water spirals and coordinated water molecules, respectively. Introduction Metal−organic frameworks (MOFs) have potential applications in gas sorption, separation and storage, catalysis, magnetism and optics.[1] Kobayashi’s group revealed that the chain-like water clusters confined in channels of porous coordination polymer crystals showed ferroelectric behavior at high temperature.[2] Long et al. demonstrated that a (H2O)12n wire confined within a 3D porous MOF, even in a centrosymmetric space group, can elicit a significant FE response.[3] To date, reports on ordered helical water chains confined in homochiral MOFs mainly focus on structural aspects,[4] but their electric polarity has not been extensively investigated. In addition, single-crystal to single-crystal (SCSC) transformation accompanying drastically switchable physical property change has potential applications in molecular devices such as switches and sensors in luminescence, magnetism