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Research

Outline

Our goal is to decrease the effects on the environment by removing environmental pollutants, preventing global warming, and saving our energy, toward a sustainable society. To realize it, we work on the synthesis of porous materials based on our original strategies and the evaluation of structures and porous properties by chemical techniques. By repeating this design-synthesis-evaluation cycle, we achieve high-performance and/or unprecedented porous properties and explore the possibility of practical applications.

Separation and Conversion of Carbon Dioxide Using Porous Metal Complexes

Polymeric metal complexes constructed from metal cations and organic bridging ligands are crystalline materials with high structural diversity, controllability, and flexibility. Because of the coexistance of inorganic "metal cation" parts and organic "ligand" parts, polymeric metal complexes can combine features of both parts. Therefore, they have attracted much attention as a variety of functional materials. Especially, polymeric porous metal complexes with regular pores, so called metal-organic frameworks (MOFs) and porous coordination polymers (PCPs), have been energetically studied as next-generation porous materials following zeolites and activated carbons during the last two decades. We are synthesizing unique MOFs/PCPs based on original molecular/structural design and evaluating separation and conversion properties of the global warming gas, carbon dioxide.

    References
  • S. Noro, R. Matsuda, Y. Hijikata, Y. Inubushi, S. Takeda, S. Kitagawa, Y. Takahashi, M. Yoshitake, K. Kubo, T. Nakamura, "High CO2/CH4 Selectivity of a Flexible Copper(II) Porous Coordination Polymer under Humid Conditions" (selected in a front cover) ChemPlusChem 2015, 80, 1517-1524 (DOI: 10.1002/cplu.201500278).
  • S. Noro, R. Ochi, Y. Inubushi, K. Kubo, T. Nakamura, "CH4/CO2 and CH4/C2H6 gas separation using a flexible one-dimensional copper(II) porous coordination polymer" Microporous Mesoporous Mater. 2015, 216, 92-96 (DOI: 10.1016/j.micromeso.2015.03.021).
  • S. Noro, Y. Hijikata, M. Inukai, S. Horike, M. Higuchi, S. Kitagawa, T. Akutagawa, T. Nakamura "Highly Selective CO2 Adsorption Accompanied with Low-Energy Regeneration in a Two-Dimensional Cu(II) Porous Coordination Polymer with Inorganic Fluorinated PF6- Anions" Inorg. Chem. 2013, 52, 280-285.(DOI: 10.1021/ic301949n)

Synthesis of Porous Light Metal Complexes

Generally, sparse and toxic heavy metal cations have been utilized as metal sources of MOFs/PCPs. If ubiquitous and low-toxic light metal cations are embedded in MOFs/PCPs instead of heavy metal cations, the resulting MOFs/PCPs could become inexpensive and have higher biocompatibility. We are trying to synthesize a diversity of light metal MOFs/PCPs using novel organic bridging ligands that have the ability to form stable coordination bonds.

    References
  • R. Ochi, S. Noro, Y. Hijikata, K. Kubo, T. Nakamura, "Structural diversification of light metal coordination polymers using 4-(methylsulfonyl)benzoate with a charge-polarized neutral methylsulfonyl coordination moiety" Eur. J. Inorg. Chem. 2017, 4013-4019 (DOI: 10.1002/ejic.201700627).
  • R. Ochi, S. Noro, Y. Kamiya, K. Kubo, T. Nakamura "Highly water-tolerant magnesium(II) coordination polymer derived from a flexible layered structure" Chem. Eur. J. 2016, 22, 11042-11047. (DOI: 10.1002/chem.201600843).
  • S. Noro, J. Mizutani, Y. Hijikata, R. Matsuda, H. Sato, S. Kitagawa, K.a Sugimoto, Y. Inubushi, K. Kubo, T. Nakamura "Porous coordination polymers with ubiquitous and biocompatible metals and a neutral bridging ligand" Nature Commun. 2015, 6, 5851 (DOI: 10.1038/ncomms6851 (open access)).

Development of Flexible Porous Materials

Traditional porous materials have rigid pores and their pore size and shape are almost unchanged. On the other hand, flexible pores are found in some porous metal complexes, in which pore size and/or shape are changed by the passage of guest molecules. Although such flexible porous metal complexes could afford interesting properties such as highly selective separation, sensors, and actuators, they has been obtained by chance. We are going ahead with rational design and costruction of flexible porous metal complexes using inorganic fluorinated anions in order to develop properties specific to flexible pores.

    References
  • S. Noro, T. Nakamura, "Fluorine-functionalized metal-organic frameworks and porous coordination polymers" (review) NPG Asia Mater. (Nature Publishing Group) 2017, 9, e433 (DOI: 10.1038/am.2017.165 (open access)).
  • K. Takahashi, N. Hoshino, T. Takeda, S. Noro, T. Nakamura, S. Takeda, T. Akutagawa, "Structural Flexibilities and Gas Adsorption Properties of One-Dimensional Copper(II) Polymers with Paddle-Wheel Units by Modification of Benzoate Ligands" Inorg. Chem. 2015, 54, 9423-9431 (DOI: 10.1021/acs.inorgchem.5b01168).
  • K. Takahashi, N. Hoshino, T. Takeda, S. Noro, T. Nakamura, S. Takedad, T. Akutagawa, "Crystal structures, CO2 adsorption, and dielectric properties of [Cu(II)2(R-benzoate)4(pyrazine)]∞ polymers (R = m-F, 2,3-F2, m-Cl, and m-CH3)" Dalton Trans. 2014, 43, 9081-9089 (DOI: 10.1039/c4dt00258j).
  • K. Fukuhara, S. Noro, K. Sugimoto, T. Akutagawa, K. Kubo, T. Nakamura "Porous Coordination Polymer Polymorphs with Different Flexible Pores Using Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand" Inorg. Chem. 2013, 52, 4229-4237 (DOI: 10.1021/ic301949n).
  • S. Noro, K. Fukuhara, K. Sugimoto, Y. Hijikata, K. Kubo, T. Nakamura "Anion-dependent host-guest properties of porous assemblies of co-ordination complexes (PACs), [Cu(A)2(py)4] (A = PF6, BF4, CF3SO3, and CH3SO3; py = pyridine), based on Werner-type copper(II) compound in the solid state" Dalton Trans. 2013, 42, 11100-11110 (DOI: 10.1039/C3DT51104A).
  • S. Noro, T. Ohba, K. Fukuhara, Y. Takahashi, T. Akutagawa, T. Nakamura "Diverse structures adsorption properties of quasi-Werner-type copper(II) complexes with flexible and polar axial bonds" (selected in the 'New Talent: Asia' issue) Dalton Trans. 2011, 40, 2268-2274 (DOI: 10.1039/C0DT01129K).

Evaluation of Gas Saparation Properties under Practical Conditions

Gas separation properties of porous materials have been investigated using single-component gas adsorption measurements. However, in order to determine whether porous materials can indeed separate a targeted gas, it is necessary to evaluate gas separation properties under conditions close to practical use (multi-component gas, near room temperature, humidified atmosphere). We are elucidating true gas separation properties of porous materials using multi-component gas adsorption/separation machines.

    References
  • J. Duan, M. Higuchi, J. Zheng, S. Noro, I.-Y Chang, K. Hyeon-Deuk, S. Mathew, S. Kusaka, E. Sivaniah, R. Matsuda, S. Sakaki, S. Kitagawa "Density Gradation of Open Metal Sites in the Mesospace of Porous Coordination Polymers" J. Am. Chem. Soc. 2017, 139, 11576-11583 (DOI: 10.1021/jacs.7b05702).
  • F. Cheng, Q. Li, J. Duan, N. Hosono, S. Noro, R. Krishna, H. Lyu, S. Kusaka, W. Jin, S. Kitagawa, "Fine-tuning optimal porous coordination polymers by functional alkyl groups for CH4 purification" J. Mater. Chem. A 2017, 5, 17874-17880 (DOI: 10.1039/C7TA02760E).
  • A. Schneemann, Y. Takahashi, R. Rudolf, S. Noro, R. A. Fischer "Influence of Coadsorbates on CO2 Induced Phase Transition in Functionalized Pillared-Layered Metal-organic Frameworks" J. Mater. Chem. A 2016, 4, 12963-12972. (DOI: 10.1039/C6TA03266D).
  • Z. Zhang, M. Sadakane, S. Noro, T. Murayama, T. Kamachi, K. Yoshizawaf, W. Ueda, "Selective carbon dioxide adsorption of ε-Keggin-type zincomolybdate-based purely-inorganic 3D frameworks" J. Mater. Chem. A 2015, 3, 746-755 (DOI: 10.1039/c4ta05496b).