Bismuth-based metal-organic materials: lone-pair-driven structures, single-crystal-mediated synthetic strategies, and emerging applications.

Bismuth-based metal-organic materials (MOMs), including coordination polymers and metal-organic frameworks (MOFs), are gaining momentum in terms of their popularity in the field of materials chemistry. Their biocompatibility and potentially abundant and tunable structures and properties are some of their eye-catching features. The 6s2 lone pair of Bi3+ gives rise to both hemidirected and holodirected coordination environments, which strongly influence the dimensionality, topology, crystallinity, and porosity. This review summarizes the recent progress in Bi-based MOMs with emphasis on their synthetic methods, structural modification strategies, modulating agents, solvent and reaction effects, and the relationship between coordination geometry and framework formation. The review surveys representative dense and porous Bi-MOMs, inclusive of their oxide and sulfide derivatives, highlighting emerging applications in catalysis, sensing, photoluminescence, gas adsorption/separation, energy storage, and biomedicine. Finally, current challenges and future opportunities are outlined, foreseeing Bi-based MOMs with holodirected building units to follow in the footsteps of reticular chemistry-guided transition-metal MOFs. Further developments are required to improve strategies to directly synthesize hemi- and holo-directed building units, balance the degree of connectivity and net's interpenetration, thereby controlling porosity and stability, and develop greener routes for high-quality crystalline materials.