The design of inorganic open‐framework materials is of interests because of their architectures/topologies, physical properties, and potential applications in various areas such as ion exchange, industrial catalysis, molecular separation, and proton‐conduction. Zeolites are, so far, the most representative example among these materials. Not much effort has been taken to explore the chemistry of metal‐halide‐based open frameworks. Lead‐halide perovskites (haloplumbates) are an important subclass of these materials which have raised research interests due to their potential applications in optoelectronic devices and to their fascinating structural diversity. However, the majority of reported haloplumbates are low-dimensional polymeric structures, i.e., clusters, ribbons, or 2D layers. Until now, the number of 3D haloplumbate frameworks has been very limited.

Qihua Xiong, Qichun Zhang, and colleagues, Nanyang Technological University, Singapore, have prepared a 3D haloplumbate framework, [H₄TIMM]Pb₇Br₁₈ (TIMM = tetrakis(N‐imidazolemethylene)methane). The team reacted PbBr₂, HBr, and TIMM under hydrothermal conditions and obtained the framework in a yield of 25 %.

The framework was characterized using single‐crystal X‐ray diffraction. It is constructed from [Pb₆Br₂₅]^13– nanoclusters (pictured left), which connect to each other through sharing faces and edges. H₄TIMM acts as a template to direct the assembly of the [Pb₆Br₂₅]^13– nanoclusters into an extended framework. The Pb²⁺ ions in the framework adopt seven‐ and eight-coordinated structures, which are very rare in haloplumbate chemistry. The synthesized framework is the first example of haloplumbates completely made from such highly‐coordinated Pb²⁺ ions.

• A 3D Haloplumbate Framework Constructed From Unprecedented Lindqvist-like Highly Coordinated [Pb₆Br₂₅]^13– Nanoclusters with Temperature-Dependent Emission,
  Xinxiong Li, T. Thu Ha Do, A. Granados del Águila, Yinjuan Huang, Wangqiao Chen, Qihua Xiong, Qichun Zhang,
  Chem. Asian J. 2018.
  https://doi.org/10.1002/asia.201801292