Bismuth-Based Metal–Organic Frameworks Derived from Multi-Carboxylate Organic Linkers

Bismuth is the safest nonradioactive heavy metal to humans. Bi3+ ion possesses a stereoactive lone pair, i.e., lone pair of the 6s subshell, which allows the flexibility/hemi-directed coordination geometry of its complexes. Bismuth-based materials have attracted great interest in many potential applications, such as photoluminescence, metallurgical applications, and catalysis. From a biological standpoint, bismuth is not only deemed a nontoxic but also an antibacterial agent that aids in the treatment of multi-resistant bacterial strains. In addition, bismuth-based materials were used as a contrast agent. Metal–organic frameworks (MOFs) constructed from metal clusters connected to multitopic organic linkers assembled into multidimensional periodic lattices. Owing to their enhanced crystallinity, permanent porosity, and tunable pore functionality, MOFs have been evaluated for a variety of applications, including gas separation and storage, drug delivery, catalysis, and others. Despite the existence of plentiful well-established bismuth (III) complexes and more than 20-year development, there is still only a small number of reported bismuth (III) MOFs compared to other metal ions. In bismuth (III) MOFs, the Bi3+ ion exhibits high coordination numbers, i.e., from 6 to 12 and flexible coordination geometries, which results in unique SBUs (secondary building units) resulting in MOF structural diversity. Coupled with biocompatible organic linkers, Bi-MOFs can be produced with interesting potential applications, such as drug delivery and contrast agents for CT imaging. This chapter reviews the development of bismuth (III) MOFs based on multi-carboxylate organic linkers.