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Abstract: The experimental detection and synthesis of pentazole (HN5) and its anion (cyclo‐N5−) have been actively pursued for the past hundred years. The synthesis of an aesthetic three‐dimensional metal–pentazolate framework (denoted as MPF‐1) is presented. It consists of sodium ions and cyclo‐N5− anions in which the isolated cyclo‐N5− anions are preternaturally stabilized in this inorganic open framework featuring two types of nanocages (Na20N60 and Na24N60) through strong metal coordination bonds. The compound MPF‐1 is indefinitely stable at room temperature and exhibits high thermal stability relative to the reported cyclo‐N5− salts. This finding offers a new approach to create metal–pentazolate frameworks (MPFs) and enables the future exploration of interesting pentazole chemistry and also related functional materials. [ABSTRACT FROM AUTHOR]

Three anionic open frameworks, formulated as [Him]2Eu2(ox)4(H2O)2 ·2H2O ( 1), [Him]2Tb2(ox)4(H2O)2 ·2H2O ( 2), and [Hmim]2Eu2(ox)4(H2O)2 ·2H2O ( 3; ox = oxalate, im = imidazole, mim = methylimidazole), have been synthesized by a solvent-free method. In these solvent-free processes, in situ encapsulation of imidazolium in the channels of the anionic open frameworks was successfully achieved. These compounds show 1D channels with extensive hydrogen-bonding networks created between the guest molecules and adjacent oxalate oxygen atoms; the imidazolium or methylimidazolium cations are regularly arranged within the channels. Alternating current (AC) impedance measurements revealed that the three compounds display high proton conductivities (>10-3 S cm-1) at 298 K and 98 % relative humidity, with compound 2 showing the highest proton conductivity of 5.0 × 10-3 S cm-1 at 298 K. The high proton conductivities of compounds 1- 3 may be attributed to the extensive hydrogen-bonding networks existing in the open frameworks, which are constructed by water molecules, protonated imidazole or methylimidazole molecules, and adjacent oxalate oxygen atoms. This work provides an efficient synthetic strategy for the construction of high-performance solid proton conductors. [ABSTRACT FROM AUTHOR]