Functional Bi-MOFs and Their Derivatives: From Structural Engineering to Multifunctional Applications in Energy, Catalysis, and Biomedicine.

Bismuth-based metal-organic frameworks (Bi-MOFs) are emerging as a distinctive class of functional porous materials that combine structural tunability, biocompatibility, and unique physicochemical characteristics of Bi(III). In contrast to conventional transition-metal-based MOFs, however, their assembly is strongly governed by the stereochemically active 6s2 lone pair, variable coordination environments, and the pronounced hydrolytic tendency of Bi(III), which together complicate the realization of predictable structures, permanent porosity, and operational stability. This review provides a systematic analysis of the structure-property relationships of Bi-MOFs, focusing on how Bi(III) coordination chemistry governs framework design, topology evolution, and stability. The influence of major ligand families, including carboxylates, phosphonates, and phenolates, is critically discussed, and the representative strategies for transforming Bi-MOFs into functional derivatives, such as porous carbons, oxides, sulfides, and phosphides, are summarized. Their applications in photocatalysis, electrocatalysis, energy storage, biomedicine, and environmental remediation are also highlighted, with particular attention to the relationship between precursor structure and functional performance. Key challenges, including green synthesis, rigorous evaluation of porosity and stability, and the development of multivariate and application-oriented systems, are further discussed. Rather than viewing Bi-MOFs as universal substitutes for established MOFs, this review identifies them as specialized functional platforms and provides a critical perspective for the rational development of next-generation Bi-MOF-based materials.