Hiroshi Kitagawa

Solid-state proton conductors (SSPCs), which are a key component for the safety and efficiency of fuel cells, have received much attention due to their broad application in electrochemical devices. In particular, the development of new materials with high conducting performance and an understanding of the conduction mechanism have become critical issues in this field. Porous metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) have recently emerged and have been extensively stu

Coordination polymers (CPs) have large degrees of freedom in framework compositions and in the structures and environment of the inner pores. This review focuses on the recent significant progress achieved by controlling these degrees of freedom. Two breakthroughs are reviewed for constructing sophisticated structures of CP frameworks, especially in dimensional crossover regions. The first is the synthesis of quasi one-dimensional halogen-bridged coordinative tubes by applying state-of-the-art t

Porous crystalline metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) are emerging as a new class of proton conductors with numerous investigations. Some of the MOFs exhibit an excellent proton-conducting performance (higher than 10^-2 S cm^-1) originating from the interesting hydrogen(H)-bonding networks with guest molecules, where the conducting medium plays a crucial role. In the overwhelming majority of MOFs, the conducting medium is H₂O bec

Since the transition of energy platforms, proton-conducting materials have played a significant role in broad applications for electrochemical devices. In particular, solid-state proton conductors (SSPCs) are emerging as the electrolyte in fuel cells (FC), a promising power generation technology, because of their high performance and safety for operating in a wide range of temperatures. In recent years, proton-conductive porous metal-organic frameworks (MOFs) exhibiting high proton-conducting pr

Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising between the component ions. Metal-organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs <i>via</i> the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorpora

Controlling the dynamics of ionic liquids (ILs) is a significant issue for widespread use. Metal-organic frameworks (MOFs) are ideal host materials for ILs because of their small micropores and tunable host-guest interactions. Herein, we demonstrate the first example of an IL incorporated within the micropores of a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (composed of Zn(MeIM)2 ; H(MeIM)=2-methylimidazole) as the IL a

The charge-ordering states with lattice distortions of a halogen-bridged binuclear-metal mixed-valence complex (called MMX chain), Pt2(dta)4I (dta = CH3CS2-), have been investigated by transport, magnetic, and optical measurements. This complex is a binuclear unit-assembled conductor containing metal−metal bonds. It exhibits metallic conduction above room temperature, representing the first example of a metallic halogen-bridged one-dimensional transition-metal complex. Below 300 K it shows semic