Proton conduction in alkali metal ion-exchanged porous ionic crystals A[CrO(OOCH)(etpy)][α-SiWO]·nHO [I-A] (A = Li, Na, K, Cs, etpy = 4-ethylpyridine) is investigated. Single crystal and powder X-ray diffraction measurements show that I-A possesses analogous one-dimensional channels where alkali metal ions (A) and water of crystallization exist. Impedance spectroscopy and water diffusion measurements of I-A show that proton conductivities are low (10-10 S cm) under low relative humidity (RH), and protons mostly migrate as HO with HO as vehicles (vehicle mechanism). The proton conductivity of I-A increases with the increase in RH and is largely dependent on the types of alkali metal ions. I-Li shows a high proton conductivity of 1.9 × 10 S cm (323 K) and a low activation energy of 0.23 eV under RH 95%. Under high RH, alkali metal ions with high ionic potentials (e.g., Li) form a dense and extensive hydrogen-bonding network of water molecules with mobile protons at the periphery, which leads to high proton conductivities and low activation energies via rearrangement of the hydrogen-bonding network (Grotthuss mechanism).

Borophene and the analogs are attractive 2D-materials showing unique mechanical and electronic properties. In this study, the bottom-up synthesis of an atomic boron network possessing a completely planar skeleton was achieved from KBH 4 . The borophene-analog was stabilized by oxygen atoms positioned on the same plane, providing holes and the anionic state of the layer. Potassium cations between the layers enabled crystalline stacking of the layers, as well as dissolution in solvents as atomically thin layers. The conductivity measurements revealed the electronic feature. Unlike the interplane conducting property, almost zero activation energy like a metal was suggested from the in-plane measurement.

Borophene has been recently proposed as a next-generation two-dimensional material with promising electronic and optical properties. However, its instability has thus far limited its large-scale applications. Here, we investigate a liquid-state borophene analogue with an ordered layer structure derived from two-dimensional borophene oxide. The material structure, phase transition features and basic properties are revealed by using X-ray analysis, optical and electron microscopy, and thermal characterization. The obtained liquid crystal exhibits high thermal stability at temperatures up to 350 °C and an optical switching behaviour driven by a low voltage of 1 V.

Ultra-small metal particles are attractive materials exhibiting unique physical and chemical properties. In this study, we have produced polymer composites of 1-nm sized bismuth particles using phenylazomethine dendrimer templates and linear polymers. The formation of the polymer film with bismuth particles was revealed by STEM measurements. The stability of the ultra-small bismuth particles was demonstrated by XPS measurements. Variations of the protecting polymers were also successfully obtained by using polystyrene and polythiophene.

Proton conduction in crystalline porous materials has received much attention from basic scientific research through to practical applications. Polyoxometalates (POMs) can efficiently transport protons because of their small superficial negative charge density. A simple method for enhancing proton conductivity is to introduce NH4+ into the crystal structure, because NH4+ can form hydrogen bonds and function as a proton carrier. According to these considerations, NH4+ was introduced into the porous structure of A2[Cr3O(OOCH)6(etpy)3]2[α‐SiW12O40]·nH2O (A = Li, Na, K and Cs; etpy = 4‐ethylpyridine) (I‐A+) via topotactic cation exchange. The resulting compound, diammonium tris(4‐ethylpyridine)hexaformatooxidotrichromium α‐silicododecatungstate hexahydrate, (NH4)2[Cr3(CHO2)6O(C7H9N)3]2[α‐SiW12O40]·6H2O, showed high proton conductivity and low activation energy under high relative humidity (RH), suggesting that protons migrate efficiently via rearrangement of the hydrogen‐bonding network formed by the NH4+ cations and the waters of crystallization (Grotthuss mechanism). The proton conductivity and activation energy greatly decreased and increased, respectively, with the decrease in RH, suggesting that protons migrate as NH4+ and/or H3O+ under low RH (vehicle mechanism).