scholarly journals Complex Phase Behaviour and Structural Transformations of Metal-Organic Frameworks with Mixed Rigid and Flexible Bridging Ligands

2018 ◽  
Vol 25 (5) ◽  
pp. 1353-1362 ◽  
Author(s):  
Hayder D. J. Arkawazi ◽  
Rob Clowes ◽  
Andrew I. Cooper ◽  
Takumi Konno ◽  
Naoto Kuwamura ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Structural Transformations ◽  
Phase Behaviour ◽  
Bridging Ligands ◽  
Complex Phase ◽  
Metal Organic

Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

2019 ◽  
Author(s):  
Andrew Rosen ◽  
M. Rasel Mian ◽  
Timur Islamoglu ◽  
Haoyuan Chen ◽  
Omar Farha ◽  
...  
Keyword(s):  
Density Functional ◽  
Metal Organic Frameworks ◽  
Redox Activity ◽  
Screening Methods ◽  
Bridging Ligands ◽  
Metal Centers ◽  
Computational Screening ◽  
Open Metal Sites ◽  
Metal Organic ◽  
Unsaturated Metal Sites

<p>Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O<sub>2</sub> and N<sub>2</sub> adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the O<sub>2</sub> adsorbate.</p>

scholarly journals Skyrmion Lattices in Chiral Metal–organic Frameworks

2020 ◽  
Author(s):  
Emma Wolpert ◽  
François-Xavier Coudert ◽  
Andrew Goodwin
Keyword(s):  
Simple Model ◽  
Data Storage ◽  
Guest Molecule ◽  
Metal Organic Frameworks ◽  
Orientational Order ◽  
Phase Behaviour ◽  
Smart Devices ◽  
Winding Number ◽  
Metal Organic ◽  
Dynamics Simulations

<p>Skyrmions are knot-like topologically-protected objects of use in data storage and low-energy smart devices. They can be generated by applying a magnetic field to certain chiral ferromagnets, with the knotted state involving a curling of the underlying magnetisation to give a nonzero winding number. Here we explore the possibility that chiral metal–organic frameworks (MOFs) might in principle host skyrmionic phases—realised not through the winding of magnetic spins but through that of guest molecule orientations. We propose a simple model for the interactions governing guest orientational order in chiral MOFs, with uniaxial strain acting as conjugate field. Using Monte Carlo simulations we show that this model gives a rich phase behaviour that includes molecular skyrmion crystals. <i>Ab initio</i> molecular dynamics simulations carried out for a candidate chiral MOF of tractable complexity demonstrate that our simple model effectively captures its underlying energetics. Our results suggest that skyrmionic states may indeed be realisable in MOFs and related porous media and may even arise spontaneously in thin-film samples.</p>

Supramolecular Assembly of Calcium Metal−Organic Frameworks with Structural Transformations

2011 ◽  
Vol 11 (3) ◽  
pp. 699-708 ◽  
Author(s):  
Po-Ching Liang ◽  
Hsin-Kuan Liu ◽  
Chun-Ting Yeh ◽  
Chia-Her Lin ◽  
Vítězslav Zima
Keyword(s):  
Metal Organic Frameworks ◽  
Supramolecular Assembly ◽  
Structural Transformations ◽  
Metal Organic ◽  
Calcium Metal

scholarly journals Exact matrix treatment of an osmotic ensemble model of adsorption and pressure induced structural transitions in metal organic frameworks

2016 ◽  
Vol 45 (10) ◽  
pp. 4213-4217 ◽  
Author(s):  
Lawrence J. Dunne ◽  
George Manos
Keyword(s):  
Metal Organic Frameworks ◽  
Structural Transformations ◽  
Ensemble Model ◽  
Structural Transitions ◽  
One Dimensional ◽  
Metal Organic ◽  
Statistical Mechanical ◽  
Exact Matrix

Here we present an exactly treated quasi-one dimensional statistical mechanical osmotic ensemble model of pressure and adsorption induced breathing structural transformations of metal–organic frameworks (MOFs).

Metal-Organic Frameworks for Asymmetric Catalysis and Chiral Separations

MRS Bulletin ◽  
2007 ◽  
Vol 32 (7) ◽  
pp. 544-548 ◽  
Author(s):  
Wenbin Lin
Keyword(s):  
Asymmetric Catalysis ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Metal Organic Frameworks ◽  
Building Blocks ◽  
Chiral Separations ◽  
Bridging Ligands ◽  
Guest Molecules ◽  
Pure Compounds ◽  
Metal Organic

Metal-organic frameworks (MOFs) are an interesting class of molecule-based hybrid materials built from metal-connecting points and bridging ligands. MOFs have received much attention, owing to their potential impact on many technological areas, including gas storage, separation, and heterogeneous catalysis. The modular nature of MOFs endows them with facile tunability, and as a result, properly designed MOFs can yield ideal heterogeneous catalysts with uniform active sites through judicious choice of the building blocks. Homochiral MOFs, which can be prepared by numerous approaches (construction from achiral components by seeding with a chiral single crystal, templating with coordinating chiral co-ligands, and building from metal-connecting nodes and chiral bridging ligands), represent a unique class of materials for the economical production of optically pure compounds, whether through asymmetric catalysis or enantioselective inclusion of chiral guest molecules in their porous frameworks. As such, homochiral MOFs promise new opportunities for developing chirotechnology. This contribution provides a brief overview of recent progress in the synthesis of homochiral porous MOFs and their applications in asymmetric catalysis and chiral separations.

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