Developing proton–conducting electrolytes that are usable over a wide temperature range (25–150 °C) is highly desirable to enhance the efficiency of fuel cells for on-board automotive applications. Increasing the stability of water above its boiling point is considered one possible method to maintain the hydrogen bond network in composite materials for fast proton conduction. We herein propose an approach to encapsulate LiBr into a negatively charged metal–organic framework of (H3O)­[(UO2)4(2-pmb)3(H2O)3]·0.5H2O (1) [2-pmbH3 = 2-(phosphonomethyl)­benzoic acid] to enhance the water stability at high temperatures and inhibit the migration of Li ions by Coulombic interactions induced by anionic skeletons. The resulting composite shows a superprotonic conductivity of over 10–2 S cm–1 and a low activation energy of less than 0.4 eV in an anhydrous N2 atmosphere from ambient temperature to 110 °C. Diffusion coefficient tests confirm that protons, rather than lithium ions, are the main contributor to conductivity.

Chiral transcription from the molecular level to the macroscopic level by self-organization has been a topic of considerable interest for mimicking biological systems. Homochiral coordination polymers (CPs) are intriguing systems...

Nanotubular materials have garnered considerable attention since the discovery of carbon nanotubes. Although the layer-to-tube rolling up mechanism has been well recognized in explaining the formation of many inorganic nanotubes, it has not been generally applied to coordination polymers (CPs). To uncover the key factors that determine the rolling-up of layered CPs, we have chosen the Co/R-, S-Xpemp [Xpemp = (4-X-1-phenylethylamino)­methylphosphonic acid, X = H, F, Cl, Br] systems and study how the weak interactions influence the formation of layered or tubular structures. Four pairs of homochiral isostructural compounds R-, S-Co­(Xpemp)­(H2O)2 [X = H (1H), F (2F), Cl (3Cl), Br (4Br)] were obtained with tubular structures. The inclusion of 3,3′-azobipyridine (ABP) guest molecules led to compounds R-, S-[Co­(Xpemp)­(H2O)2]4·ABP·H2O with layered structures when X was Cl (5Cl) and Br (6Br), but tubular compounds 1H and 2F when X was H and F. Layered structures were also obtained for racemic compounds meso-Co­(Xpemp)­(H2O)2 [X = F (7F), Cl (8Cl), Br (9Br)] using racemic XpempH2 as the reaction precursor, but not when X = H. A detailed study on R- 6Br revealed that layer-to-tube transformation occurred upon removal of ABP under hydrothermal conditions, forming R- 4Br with a tubular structure. Similar layer-to-tube conversion did not occur in organic solvents. The results demonstrate that weak interlayer interactions are a prerequisite but not sufficient for the rolling-up of the layers. In the present cases, water also provides a driving force in the layer-to-tube transformation. The experimental results were rationalized by theoretical calculations.