Reversible thermosalience of 4-aminobenzonitrile

Crystals of 4-aminobenzonitrile grown by sublimation undergo a reversible thermosalient phase change during cooling and subsequent heating. Single-crystal diffraction studies have been carried out at 20 K intervals during cooling from 300 to 100 K in order to explain the structural change that occurs.

A Fine-Tuned Metal-Organic Framework for Autonomous Indoor Moisture Control

Conventional adsorbents, namely zeolites and silica gel, are often used to control humidity by adsorbing water; however, adsorbents capable of the dual functionality of humidification and dehumidification, offering the desired control of the moisture level at room temperature, have yet to be explored. Here we report Y-shp-MOF-5, a hybrid microporous highly connected rare-earth-based metal-organic framework (MOF), with dual functionality for moisture control within the recommended range of relative humidity (45%-65% RH) set by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Y-shp-MOF-5 exhibits exceptional structural integrity, robustness, and unique humidity-control performance, as confirmed by the large number (thousand) of conducted water vapor adsorption-desorption cycles. The retained structural integrity and the mechanism of water sorption were corroborated using in situ single-crystal X-ray diffraction (SCXRD) studies. The resultant working water uptake of 0.45 g·g^-1 is solely regulated by a simple adjustment of the relative humidity, positioning this hydrolytically stable MOF as a prospective adsorbent for humidity control in confined spaces, such as space shuttles, aircraft cabins, and air-conditioned buildings.

Solvatochromism as a probe to observe the solvent exchange process in a 1-D porous coordination polymer with 1-D solvent accessible channels

A one-dimensional porous coordination polymer possessing pleochroic and solvatochromic properties produces an unexpected double V-shaped discolouration of the crystal upon solvent exchange with acetonitrile and nitromethane. Modelling shows that the origin of this effect is preferential sorption at two faces of the crystal.

Reversible structural switching of a metal–organic framework by photoirradiation

A photoresponsive metal organic framework material undergoes switching of its pore volume and sorption capacity.

Threading the needle: guest transport in a versatile 0D porous molecular crystal

Porous host crystals of the metallocycle [Cu₂(1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene)₂Cl₄]·2CH₃OH are permeable to a series of small organic guests despite their lack of permanent channels.

Molecular recognition and solvatomorphism of a cyclic peptoid: formation of a stable 1D porous framework

Molecular aggregation and the hydrophobic effect explain the solvatomorphism and sorption behavior of a cyclic hexapeptoid.

A five-fold interpenetrated metal–organic framework showing a large variation in thermal expansion behaviour owing to dramatic structural transformation upon dehydration–rehydration

A five-fold interpenetrated MOF has the highest uniaxial negative thermal expansion coefficient reported for any interpenetrated MOF to date. Upon dehydration, the framework shows considerable change in the magnitudes of the thermal expansion coefficients.

Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid

Incorporation of a dithiadiazolyl radical into a dynamic paramagnetic metallocycle yields an unusual paramagnetic hybrid material with exchange coupling between host and guest.

Elucidating the mechanism responsible for anomalous thermal expansion in a metal-organic framework

The previously reported anisotropic thermal expansion of a three-dimensional metal-organic framework (MOF) is examined by means of theoretical calculations. Inspection of the 100, 190, 280 and 370 K single crystal X-ray diffraction (SCD) structures indicated a concerted change in the coordination sphere of the zinc centre leading to elongation of the coordination helix in the crystallographic c direction (the Zn-O(H)-Zn angle expands), while the largely unaltered ligands (the ZnLZn distance remains constant) are pulled closer together in the ab plane. This study develops and evaluates a mechanistic model at the DFT level of theory that reproduces the convergent expansion of the coordination helix of the material. The linear increase in energy calculated for extension of a model consisting of six zinc centres and truncated ligands compares favourably with results obtained from a periodic DFT evaluation of the SCD structures. It was also found that the anisotropic thermal expansion trend could be reproduced qualitatively by Molecular Dynamics (MD) simulations in the NPT ensemble.

Solid-State Conformational Flexibility at Work: Zipping and Unzipping within a Cyclic Peptoid Single Crystal

A peptidomimetic compound undergoes a reversible single-crystal-to-single-crystal transformation upon guest release/uptake with the transformation involving a drastic conformational change. The extensive and reversible alteration in the solid state is connected to the formation of an unprecedented "CH-π zipper" which can reversibly open and close (through the formation of CH-π interactions), thus allowing for guest sensing.

Creation of new guest accessible space under gas pressure in a flexible MOF: multidimensional insight through combination of in situ techniques

Creation of a new guest accessible space under gas pressure in a flexible MOF studied by in situ single crystal diffraction and Pressure Gradient DSC.

Readily prepared inclusion forming chiral calixsalens

Chiral, rigid vase-like calixsalens show unprecedented substituent-driven self-association and provide supermolecules of contrasting character.

Hydration-dependent anomalous thermal expansion behaviour in a coordination polymer

A polar coordination polymer has been synthesised that exhibits anomalous anisotropic thermal expansion. The guest water molecules of the as-synthesised complex can be removed on activation without loss of crystal singularity to yield the fully dehydrated form that shows considerably different thermal expansion behaviour compared to its hydrated analogue.

Anomalous Anisotropic Thermal Expansion in a One-Dimensional Coordination Polymer Driven by Conformational Flexibility

A one-dimensional lithium(I) coordination polymer has been characterized by variable-temperature single-crystal X-ray diffraction and differential scanning calorimetry. This compound possesses an anisotropic packing arrangement that, along with a scissor-like or hingelike movement of the pyridyl ligand side arms, results in an extremely rare combination of positive, negative, and zero thermal expansion. Designing such types of materials and understanding the mechanistic details can facilitate the design of new thermoresponsive materials.