Opening the Gate: Framework Flexibility in ZIF-8 Explored by Experiments and Simulations

Fairen‐Jimenez, David; Moggach, Stephen A.; Wharmby, Michael T.; Wright, Paul A.; Parsons, Simon; Düren, Tina

doi:10.1021/ja202154j

Cited by 1,009 publications

(966 citation statements)

References 16 publications

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“…In contrast to many MOFs, which are water soluble or thermal unstable, ZIFs (e.g. ZIF-8) owe a high chemical stability, high specific surface area and excellent porosity [8,9]. ZIF-8 particles, consisting of zinc and 2-methylimidazole (2-Hmim), is a prototypical subclass of ZIFs with a sodalite (SOD) topology similar to some aluminosilicate zeolites, where T-O-T bridges (T = Si, Al, P) are replaced by Zn-Im-Zn [10].…”

Section: Introductionmentioning

confidence: 99%

Highly efficient removal of arsenic(III) from aqueous solution by zeolitic imidazolate frameworks with different morphology

Bao

Jian

Liu

et al. 2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

125

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Section: Introductionmentioning

confidence: 99%

Highly efficient removal of arsenic(III) from aqueous solution by zeolitic imidazolate frameworks with different morphology

Bao

Jian

Liu

et al. 2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

125

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“…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).…”

mentioning

confidence: 99%

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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“…Owing to the framework flexibility of ZIF-8 phase, molecules with a kinetic diameter larger than the pore size of ZIF-8 such as CH 4 (0.38 nm) could also pass through the membrane. 26 In summary, the LDH layer had a positive influence on the gas separation performance of the prepared ZIF-8 membrane, deserving further exploration. For comparison, a pure asymmetric ZIF-8 membrane was also synthesized on a bare a-Al 2 O 3 substrate without LDH network by secondary growth under identical conditions (details are shown in ESI-6 †).…”

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confidence: 94%

MOF membrane synthesis in the confined space of a vertically aligned LDH network

et al. 2014

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MOF membranes have gained widespread attention due to their unprecedented gas separation performance. Relying on physical interactions, we successfully deposited MOF seeds on a substrate modified with a network of vertically aligned LDH walls before secondary growth of the MOF layer. ZIF-8 membranes thus prepared show considerable H 2 permeance with high H 2 -CH 4 selectivity. This approach is in general suitable for the deposition of nanoparticles on solid surface and their subsequent growth into a dense layer.Metal-organic frameworks (MOFs), a new class of crystalline porous materials, are composed of metal ions or metal oxide clusters coordinated by organic linkers to form highly regular porous networks. Since pioneering works on MOFs (also called coordination polymers) in the 1990s, 1 MOFs have had extensive interest due to their unprecedented opportunities for a wide range of applications in gas storage, purification, catalysis and sensing. 2In particular, the flexibility of pore size and sorption behaviour make them ideal candidates as membranes for gas separation. Our concept is shown in Fig. 1. Prior to seeding, the surface of substrate is segmented into micrometer-sized two-dimensional (2D) compartments by vertically aligned layered double hydroxides (LDHs). LDHs, which have the general formula [M 1Àx, and A nÀ represent di-, tri-valent metal ions and n-valent anions, respectively), are representative of layered compounds. LDHs consist of positively charged brucite-like layers and interlayer galleries containing charge compensating anions. LDHs are selected as ''walls'' between the segments due to their high length-towidth ratio. 15 In particular, we find that MgAl-CO 3 LDH crystallites could be easily in situ grown on porous a-Al 2 O 3 substrate to form LDH networks with diverse microstructures by proper manipulation of Fig. 1 Schematic illustration of the ZIF-8 membrane synthesis in the confined space of a vertically aligned layered double hydroxide (LDH) network illustrating the role of the LDH network: a ''perch'' for the seeds.

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Opening the Gate: Framework Flexibility in ZIF-8 Explored by Experiments and Simulations

Cited by 1,009 publications

References 16 publications

Highly efficient removal of arsenic(III) from aqueous solution by zeolitic imidazolate frameworks with different morphology

Highly efficient removal of arsenic(III) from aqueous solution by zeolitic imidazolate frameworks with different morphology

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

MOF membrane synthesis in the confined space of a vertically aligned LDH network

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