Guest-Specific Function of a Flexible Undulating Channel in a 7,7,8,8-Tetracyano-p-quinodimethane Dimer-Based Porous Coordination Polymer

3-D coordination polymers based on the tetrathiafulvalenetetracarboxylate (TTF-TC) derivative: synthesis, characterization, and oxidation issues

The reactivity of the redox-active tetracarboxylic acid derived from the tetrathiafulvalene (TTF-TC)H(4) with alkaline cations (K, Rb, Cs) is reported. The exploration of various experimental parameters (temperature, pH) led to the formation of four crystalline three-dimensional coordination polymers formulated M(2)(TTF-TC)H(2) (M = K, Rb, Cs), denoted MIL-132(K), MIL-133(isostructural K, Rb), and MIL-134(Cs). Thermogravimetric analysis and thermodiffraction show that all of the solids are thermally stable up to 150-200 degrees C in the air. In order to exploit the possibility of oxidation of the organic linker in TTF-based compounds, they were employed as positive electrodes in a classical lithium cell. A highly reversible cyclability was achieved at high current density (10 C) with a reasonable performance (approximately 50 mAh g(-1)). Finally, combined electro-(sub)hydrothermal synthesis was used to prepare a fifth 3-D coordination polymer formulated K(TTF-TC)H(2) (denoted MIL-135(K)), this time not based on the neutral TTF-TC linker but its radical, oxidized form TTF-TC(+*). This solid is less thermally stable than its neutral counterparts but exhibits a semiconducting behavior, with a conductivity at room temperature of about 1 mS cm(-1).

A rod packing microporous metal-organic framework with open metal sites for selective guest sorption and sensing of nitrobenzene

A microporous MOF [Zn(4)(OH)(2)(1,2,4-BTC)(2)] (1,2,4-BTC = Benzene-1,2,4-tricarboxylate) with two immobilized open metal Zn(2+) sites was obtained by solvothermal reaction, which exhibits highly selective guest sorption and sensing of nitrobenzene.

Syntheses and characterization of new nickel coordination polymers with 4,4'-dipyridylsulfide. Dynamic rearrangements of one-dimensional chains responding to external stimuli: temperature variation and guest releases/re-inclusions

Crystal structures and dynamic rearrangements of one-dimensional coordination polymers with 4,4′-dipyridylsulfide (dps) have been studied. Reaction of Ni(NO₃)₂·6H₂O with dps in EtOH yielded [Ni(dps)₂(NO₃)₂] ·EtOH (1), which had channels filled with guest EtOH molecules among the four Ni(dps)₂ chains. This coordination polymer reversibly transformed the channel structure responding to temperature variations. Immersion of 1 in m-xylene released guest EtOH molecules to yield a guest-free coordination polymer [Ni(dps)₂(NO₃)₂] (2a), which was also obtained by treatment of Ni(NO₃)₂·6H₂O with dps in MeOH. On the other hand, removal of the guest molecules from 1 upon heating at 130 °C under reduced pressure produced a guest-free coordination polymer [Ni(dps)₂(NO₃)₂] (2b). Although the 2a and 2b guest-free coordination polymers have the same formula, they showed differences in the assembled structures of the one-dimensional chains. Exposure of 2b to EtOH vapor reproduced 1, while 2a did not convert to 1 in a similar reaction. Reaction of Ni(NO₃)₂·6H₂O with dps in acetone provided [Ni(dps)(NO₃)₂(H₂O)] ·Me₂CO (4) with no channel structure. When MeOH or acetone was used as a reaction solvent, the [Ni(dps)₂(NO₃)₂] · (guest molecule) type coordination polymer, which was observed in 1, was not formed. Nevertheless, the reaction of Ni(NO₃)₂·6H₂O with dps in MeOH/acetone mixed solution produced [Ni(dps)₂(NO₃)₂]·0.5(MeOH·acetone) (5), which has an isostructural Ni-dps framework to 1.

Selective separation of larger molecules from a Lewis-base mixture by flexible one-dimensional Cu(II) coordination polymer with shape-recognizing space

A flexible one-dimensional Cu(II) coordination polymer with shape-recognizing space shows selective adsorption of larger 2-butanone guests from Lewis-base mixtures containing 2-butanone-EtOH or 2-butanone-MeOH.

Soft porous crystals

The field of host-guest complexation is intensely attractive from diverse perspectives, including materials science, chemistry and biology. The uptake and encapsulation of guest species by host frameworks are being investigated for a wide variety of purposes, including separation and storage using zeolites, and recognition and sensing by enzymes in solution. Here we focus on the concept of the cooperative integration of 'softness' and 'regularity'. Recent developments on porous coordination polymers (or metal-organic frameworks) have provided the inherent properties that combine these features. Such soft porous crystals exhibit dynamic frameworks that are able to respond to external stimuli such as light, electric fields or the presence of particular species, but they are also crystalline and can change their channels reversibly while retaining high regularity. We discuss the relationship between the structures and properties of these materials in view of their practical applications.