A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

Seo, Joobeom; Matsuda, Ryotaro; Sakamoto, Hirotoshi; Bonneau, Charlotte; Kitagawa, Susumu

doi:10.1021/ja904363b

Cited by 308 publications

(190 citation statements)

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“…Further modeling could reveal interesting behavior arising from features involved in other reported MOFs with dynamic constituents, such as the MOF of Seo et al (29), where rotating ligands reach across the cage to interact with each other. Such different paradigms of moving constituents in porous materials likely need to be built into a specialized model and studied on a case-by-case basis.…”

Section: Discussionmentioning

confidence: 95%

“…Several reported MOFs possess dynamic constituents, e.g., bridging ligands that can rotate, while maintaining an approximately rigid unit cell (18,(24)(25)(26)(27)(28)(28)(29)(30)(31)(32)(33)(34). Nuclear magnetic resonance (NMR) spectroscopy revealed that aromatic rings in the ligands of MOF-5 (26), IRMOF-3 (27), and MIL-47(V) (35) rotate, resembling an ordered assembly of molecular rotors (36).…”

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confidence: 99%

“…When the dominant conformations of these flexible parts in MOFs are different in the evacuated solid than in the presence of gas, the dynamic moieties can qualitatively affect the adsorption behavior, e.g., by inducing inflections (30), steps (29), and hysteresis (18) in the adsorption isotherms. Linkers in ZIF-7 are believed to rotate and cause steps and hysteresis in the adsorption isotherms of several hydrocarbons (39,40).…”

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confidence: 99%

“…18 were shown to rotate upon CO2 adsorption to accommodate more molecules, leading to an inflection and hysteresis in the CO2 adsorption isotherm. Seo et al (29) engineered a framework with rotating pillars bearing side chains that reach across a cage to lock together, serving as a molecular gate. When immersed in a bath of CO2 gas, the locks Significance Some nanoporous, crystalline materials possess dynamic/ flexible constituents, for example, a ligand that can rotate.…”

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confidence: 99%

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Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Simon

Braun

Carraro

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.metal-organic frameworks | flexible metal-organic frameworks | statistical mechanics | porous materials | gas storage M etal-organic frameworks (MOFs) are porous, crystalline materials with very large internal surface areas (1). The consequent adsorption properties of MOFs have demonstrated promise toward solving paramount energy problems (2) such as in gas storage (3) and gas separations (4). MOFs are also being explored for chemical sensing (5), drug delivery (6), and catalysis (7). In the synthesis of MOFs, metal nodes or clusters and organic linker molecules self-assemble (8). Owing to their modular and versatile chemistry, tens of thousands of MOFs have been synthesized (9).Some MOFs are dynamic/flexible and respond to gas molecules adsorbing into their pores by exhibiting structural changes while retaining their crystallinity (reviews in refs. 10-14). Reported modes of guest-induced structural changes in MOFs include breathing (15), swelling (16), and subnetwork displacement (17), as well as less dramatic changes, such as the rotation of a ligand (18) or deformation (19). In molecular recognition and enzyme catalysis in biology, a conformation change of the enzyme is often involved in substrate binding (20,21). Responsive, dynamic constituents thus may endow MOFs with enzymelike selectivities (11) for selective gas adsorption, chemical sensing, and catalysis.In the long run, a more intimate understanding of MOFs with moving parts may enable the construction of molecular machines (22). Because of their crystallinity and tunability, MOFs are an ideal scaffold on which to organize machine subunits and tune their response to stimuli. Notably, Zhu et al. (23) used a [2] rotaxane molecular switch as a building block in a MOF to construct a conceptual molecular machine.Several reported MOFs possess dynamic constituents, e.g., bridging ligands that can rotate, while maintaini...

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Section: Discussionmentioning

confidence: 95%

mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Simon

Braun

Carraro

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The challenge of structural characterisation of breathing MOFs is a pervasive one and, for example, materials that are amenable to the most accurate characterisation by single crystal diffraction throughout their dynamic behaviour are uncommon, but highly sought after. [30][31][32] Here we report a new example of continuous breathing behaviour in the MOF (Me 2 NH 2 )[In(ABDC) 2 ] (SHF-61) (ABDC = 2-aminoterephthalate; SHF = Sheffield Framework), for which full characterization by both single crystal and powder X-ray diffraction offers unusually detailed structural insight into the flexibility. Originally reported as a static MOF with high CO 2 /CH 4 selectivity, 33 we reveal that this MOF exhibits a large breathing behaviour, with a mechanism that differs from that of previously reported flexible MOFs.…”

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confidence: 99%