Topology Exploration in Highly Connected Rare-Earth Metal–Organic Frameworks via Continuous Hindrance Control

Abstract

The structural diversity of highly connected metal–organic frameworks (MOFs) has long been limited due to the scarcity of highly connected metal clusters and the corresponding available topology. Herein, we deliberately chose a series of tritopic linkers with multiple substituents to construct a series of highly connected rare-earth (RE) MOFs. The steric hindrance of these substituents can be systematically tuned to generate various linker rotamers with tunable configurations and symmetries. For example, the methyl-functionalized linker (L-CH3) with C 2v symmetry exhibits larger steric hindrance, forcing two peripheral phenyl rings perpendicular to the central one. The combination of C 2v linkers and 9-connected RE6 clusters leads to the formation of a new fascinating (3,9)-c sep topology. Unlike Zr-MOFs exhibiting Zr6 clusters in various linker configurations and corresponding different structures, the adaptable RE6 clusters can undergo metal insertion and rearrange into new RE9 clusters when connected to an unfunctionalized linker (L–H) with C 1 symmetry, giving rise to a new (3,3,18)-c ytw topology. More interestingly, by judiciously combining the linkers with both small and bulky substituents through mixed-linker strategies, an RE9-based MOF with an engaging (3,3,12)-c flg topology could be obtained as a result of continuous steric hindrance control. In this case, the two mixed linkers adopt configurations with moderate steric hindrances. Molecular simulation demonstrates that the combination of substituents with various steric hindrances dictates the resulting MOF structures. This work provides insights into the discovery of unprecedented topologies through systematic and continuous steric tuning, which can further serve as a blueprint for the design and construction of highly complicated porous structures for sophisticated applications.

Molecular Pivot‐Hinge Installation to Evolve Topology in Rare‐Earth Metal–Organic Frameworks

“…[19] Enhancing Diversity of RE-MOFsb yLinker Installation This result is consistent with our previous study on the steric effect of various functional groups,where -CH 3 groups tend to induce alarger torsion angle than -NH 2 .…”

“…Fore xample,b ya ltering the positions of linker substituents, the formation of Zr-tetratopic carboxylate MOFs with various topologies can be controlled (Figure 1c). [19] Yeti na ll the aforementioned highly connected MOF examples,t he structural diversity,f lexibility and the resulting component tunability are highly limited by the rigid ligand backbone. [19] Yeti na ll the aforementioned highly connected MOF examples,t he structural diversity,f lexibility and the resulting component tunability are highly limited by the rigid ligand backbone.…”

Metal–Organic Frameworks Based on Group 3 and 4 Metals

“…To further study the relationship between steric hindrance of linkers and the resulting MOF topologies, Zhou and coworkers studied a series of RE-MOFs based on a tritopic linker [1,1′:3′,1′′-terphenyl]-4,4′′,5′-tricarboxylate (L) and its derivatives. [115] By altering functional groups on the central benzene ring, the linker symmetries were adjusted, leading to the [116] Later, Eddaoudi and co-workers reported a series of RE-MOFs with different topologies based on the 12-connected [RE 9 (μ 3 -OH) 12…”

Multifunctional NaLnF4@MOF-Ln Nanocomposites with Dual-Mode Luminescence for Drug Delivery and Cell Imaging

“…This type of materials can be self-assembled directly by organic linkages and metal centers [15,16,17]. Rare-earth MOF (MOF-Ln) is a type of hybrid porous materials composed of lanthanide metal ion clusters and organic ligands through coordination bonds, which is an important branch of metal–organic framework materials [18,19,20,21]. The versatile functions of MOFs have been widely used in many fields such as heterogeneous catalysis, chemical sensors, proton conduction, gas separation, bioimaging, and drug delivery [22,23,24,25].…”