Themed collection Flexibility and Disorder in Metal-Organic Frameworks

Welcome to this themed issue of Dalton Transactions entitled ‘Flexibility and Disorder in Metal–Organic Frameworks’.

The wide-ranging properties of metal organic frameworks (MOFs) rely in many cases on the presence of defects within their structures and the disorder that is inevitably associated with such defects.

In the recent past an enormous number of Metal–Organic Framework type compounds (MOFs) have been synthesized.

This article provides a comprehensive review of the nature of catalytic sites in MOFs.

The large reversible flexibility of hybrid crystallized matter is relatively new.

This short review focuses on the flexibility aspect of MOFs based on neutral N-donor ligands with representative examples concerning the structural aspects and the subsequent properties induced by the reorganization of the frameworks.

We demonstrate a theoretical model to describe the behavior of flexible adsorbent materials, or soft porous crystals, when used in practical applications as nanostructured composites such as core–shell particles or mixed matrix membranes.

Single-crystal to single-crystal post synthetic bromination of unsaturated carbon–carbon bonds in two related zirconium metal–organic frameworks leads to structures with lower elastic moduli.

An amorphous and metastable precursor for a Zn two-dimensional coordination framework was synthesised via freeze drying.

This work proposes a general strategy to model the adsorption behavior of phase changing metal–organic framework (MOF) adsorbents during column separations.

Mixed-ligand syntheses and post-synthetic metal exchange performed on the Mn₃L₃ structure type results in site-specific manipulations to the framework structure.

A new approach for the fine tuning of flexibility in MOFs, involving functionalization of the secondary building unit, is presented.

Doping of MIL-53(Fe) with fluoride atoms introduces a polar organization in the structure when guest molecules are present.

The energetic performances of various ZIFs with SOD or RHO topology were evaluated by water intrusion–extrusion experiments under high pressure. The effects of the metal cation nature, the type of linker and the topology are discussed.

Total neutron scattering data suggest new geometries for transient hydrogen bonding in a disordered metal–organic framework.

Counting rules derived from mechanical engineering and rigidity theory are applied to MOFs. Scalar versions fail to predict flexibility, but group-theoretical variant succeed. The algorithm is presented in detail and two examples are solved step-by-step.

Defect engineering has arisen as a promising approach to tune and optimise the adsorptive performance of metal–organic frameworks.

This paper presents a method for the systematic and automated design of flexible organic linkers for construction of metal organic-frameworks (MOFs) in which flexibility, compliance, or other mechanically exotic properties originate at the linker level rather than from the framework kinematics.

We have adapted our genetic algorithm based optimization approach, originally developed to generate force field parameters from quantum mechanic reference data, to derive a first coarse grained force field for a MOF, taking the atomistic MOF-FF as a reference.

The effect of the elastic strain modes of MOFs on the guest diffusivity was presented and analysed.

Changing the ratio of the dicarboxylates, L : L′, in MOFs of the general formula [Zn₂(L)_2–x(L′)_x(dabco)] affords control of the pore geometry, through non-covalent interactions between the ligands.

Addition of small amounts of a second metal cation results in crystal phase competition during the synthesis of solid-solution MOFs.

Electronic energies and elastic constants of four amino functionalized MIL-47(V) supercells were computed using the plane wave density functional theory to determine the influence of the substituent positions on the organic linker.

The hydrostatic behaviour of a cubic dense inorganic–organic framework [DABCOH₂²⁺][K(ClO₄)₃] has been systematically studied via high-pressure synchrotron X-ray powder diffraction. Further first principles calculations of full elastic tensors give full mapping of the Young's moduli, shear moduli and Poisson's ratios of this material.

The structural behaviour under mechanical stimuli of two metal organic frameworks, UiO-66(Zr) and MIL-125(Ti) and their amino-functionalized derivatives has been investigated by high-pressure powder X-ray diffraction up to 3.5 GPa.

We report the results of a series of molecular dynamics simulations on a number of zinc zeolitic imidazolate framework (ZIF) structures together with some lattice dynamics calculations on ZIF-4, providing information about the flexibilities of these structures.

A hypothetical porous network isomeric to MIL-88/MIL-101 has been realized by the introduction of terminal ligands and further stabilized by crosslinking.

Amorphization of zeolitic imidazolate frameworks during ball-milling is much more rapid than that of aluminosilicate zeolites.

Structural flexibility in pillared-layer metal–organic frameworks can be controlled via the concept of mixed-linker solid solutions.

The rate of adsorption to a flexible metal-organic framework is described via generalization of the Avrami theory of phase transition kinetics.

A thermodynamic study of the structural large-pore (LP) to narrow pore (NP) transition in various Metal Organic Frameworks (MOFs) is presented.

We demonstrate that CO₂ gate adsorption behaviour of elastic layer-structured metal–organic framework-11 can be described by a thermodynamic model by free energy analysis with the aid of an adsorption experiment and a molecular simulation.

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).

The cation-dependent phase transition and the relevant dielectric response were demonstrated in a family of cyano-bridged perovskite-like coordination polymers, [(CH₃)_nNH_4−n]₂[KFe(CN)₆] (n = 1–4).

A new breathing Al-MIL-53 framework incorporating adipic acid as linker molecules is reported and characterised in detail.

The flexible MOF, Zn₂(BDC)₂(DABCO) presents unusual guest-dependent structural responses upon temperature changes.

Two series of cationic dyes have been encapsulated in the 1D channel of MOFs, and the tunable second order nonlinear optical properties of these MOF⊃dye materials were observed.

Low temperature adsorption of argon in several conceptual models of IRMOF-1 featuring various types of defects and inclusions has been investigated.

Thermal expansion in ABX₃ formates is correlated to the size and molecular anisotropy of the A- and B-site cations.

The flexibility of eight aluminium hydroxo terephthalates [Al(OH)(BDC–X)] (X = –H, –CH₃, –Cl, –Br, –NH₂, –NO₂, –(OH)₂, –CO₂H) has been investigated upon thermal dehydration, superhydration and methanol adsorption/desorption using in situ powder X-ray diffraction.

The detailed mechanical characteristics of four structurally polymorphic ZIFs have been computed using density functional theory. We elucidate the anomalous elastic behaviour ranging from zero Poisson's ratio and auxeticity, to negative linear compressibility and a remarkably low resistance to shear deformation.

The MOF Cu-MOF-74/Cu-CPO-27 was identified as a candidate for high-volumetric ammonia uptake due to the high density of Cu sites.

A mechanistic model is developed to reproduce concerted changes in the internal coordinates of the coordination helix of a MOF and evaluated using DFT.