title: The Role of a Three Dimensionally Ordered Defect Sublattice on the Acidity of a Sulfonated Metal-Organic Framework.
abstract: Understanding the role that crystal imperfections or defects play on the physical properties of a solid material is important for any application. In this report, the highly unique crystal structure of the metal-organic framework (MOF) zirconium 2-sulfoterephthalate is presented. This MOF contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material. The partially occupied ligand positions give rise to a continuum of pore sizes within this highly porous MOF, supported by N2 gas sorption and micropore analysis. Furthermore, this MOF is lined with sulfonic acid groups, implying a high proton concentration in the pore, but defective zirconium clusters are found to be effective proton trapping sites, which was investigated by a combination of AC impedance analysis to measure the proton conductivity and DFT calculations to determine the solvation energies of the protons in the pore. Based on the calculations, methods to control the pKa of the clusters and improve the conductivity by saturating the zirconium clusters with strong acids were utilized, and a 5-fold increase in proton conductivity was achieved using these methods. High proton conductivity of 5.62 × 10(-3) S cm(-1) at 95% relative humidity and 65 °C could be achieved, with little change down to 40% relative humidity at room temperature.
authors: Division of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.|JST CREST, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan.
authors: Jared M
authors: JM
authors: Taylor
authors: Division of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
authors: Tokutaro
authors: T
authors: Komatsu
authors: Division of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
authors: Shun
authors: S
authors: Dekura
authors: Division of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.|JST CREST, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan.
authors: Kazuya
authors: K
authors: Otsubo
authors: Japan Synchrotron Radiation Research Institute (JASRI) , SPring-8 1-1-1 Kouto, Say-gun, Hyogo 679-5198, Japan.|RIKEN, SPring-8 Center, Koto 1-1-1, Sayo-cho, Sayo, Hyogo 679-5148, Japan.
authors: Masaki
authors: M
authors: Takata
authors: Division of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.|JST CREST, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan.|INAMORI Frontier Research Center, Kyushu University , Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.|Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
authors: Hiroshi
authors: H
authors: Kitagawa