Polycatenation-Driven Self-Assembly of Nanoporous Frameworks Based on a 1D Ribbon of Rings: Regular Structural Evolution, Interpenetration Transformation, and Photochemical Modification

A charge-decorated porous framework with polar pores and open O donor sites for CO2/CH4 and C2H2/C2H4 separations

Developing efficient adsorbent materials towards energy gas purification, e.g. CO₂ removal from natural gas or hydrocarbon separation, is an important but extremely challenging task. Herein, taking advantage of a cationic bipyridinium ligand in competition with a multicarboxylate ligand for binding with metal ions, a porous material with open carboxylate oxygen atoms exposed on the pore surface has been demonstrated as an efficient adsorbent for gas separation. The polar environment arising from the cationic pyridinium moiety and the negative carboxylate group endows the title compound with selective affinity to CO₂ over CH₄. Moreover, the rich open O donor sites on the channel surface enable the resultant coordination polymer to selectively adsorb C₂H₂ over C₂H₄ through H-bonding interactions. The separation mechanism has been revealed by theoretical studies. This work provides a specific guidance for the design of applicable porous materials toward energy resource purification.

Multifunctional Viologen-Derived Supramolecular Network with Photo/Vapochromic and Proton Conduction Properties

A supramolecular network [H₄bdcbpy(NO₃)₂·H₂O] (H₄bdcbpy = 1,1′-Bis(3,5-dicarboxybenzyl)-4,4′-bipyridinium) (1) was prepared by a zwitterionic viologen carboxylate ligand in hydrothermal synthesis conditions. The as-synthesized (1) has been well characterized by means of single-crystal/powder X-ray diffraction, elemental analysis, thermogravimetric analysis and infrared and UV-vis spectroscopy. This compound possesses a three-dimensional supramolecular structure, formed by the hydrogen bond and π–π interaction between the organic ligands. This compound shows photochromic properties under UV light, as well as vapochromic behavior upon exposure to volatile amines and ammonia, in which the electron transfer from electron-rich parts to the electron-deficient viologen unit gives rise to colored radicals. Moreover, the intensive intermolecular H-bonding networks in 1 endows it with a proton conductivity of 1.06 × 10⁻³ S cm⁻¹ in water at 90 °C.

A novel multichromic Zn(II) cationic coordination polymer based on a new flexible viologen ligand exhibiting aniline detection in the solid state

In this work, a novel multichromic cationic coordination polymer, named [Zn4(BTC)3(bcbpy)2]·5H2O (1), based on a new flexible viologen ligand 1,1'-bis(3-cyanobenzyl)-[4,4'-bipyridine]-1,1'-diium (H2bcbpy·2Cl), Zn(NO3)2·6H2O and pyromellitic acid (H4BTC) was synthesized. Compound 1 has good photosensitive activity and can respond to sunlight at room temperature. The colour of compound 1 changes rapidly in response to UV light and blue ray irradiation within 5 s. We rarely obtained the crystal structures after irradiation under UV light and blue ray. At the same time, compound 1 shows the hydrochromism phenomenon when heated at 120 °C, and it also shows the ability of detecting aniline and NO2- under low-concentration conditions (10-4 M).

Guest-Selective Recognition in a Flexible Bipyridinium-Based Framework in a Reversible Crystal-to-Crystal Fashion

A flexible bipyridinium-linker-based porous host framework with electron-accepting pore surface, namely, [Zn₂ (L)(pmc)_1.5 ]⋅12 H₂ O (1; L⋅Cl₂ =1,1'-[1,4-phenylene-bis(methylene)]bis(4,4'-bipyridinium) dichloride, H₄ pmc=pyromellitic acid) exhibits recognition of phenol and aromatic amine guests based on adsorbent-adsorbate charge-transfer interactions. Significantly, the resultant guest-encapsulated complexes 1@Guests can all be characterized by single-crystal X-ray diffraction. The host framework undergoes a reversible single crystal-to-single crystal transformation in response to the inclusion of different guests with flexible torsional motions of the hexagonal ring and the trapezoid-shaped bipyridinium groups. Such recognition can be visibly monitored and detected by obvious color changes. The host framework could also be recovered, and this suggested that guest sorption/desorption is reversible and that the host framework could be reused in potential applications. This work may provide an effective way to develop porous materials with special emphasis on applications involving guest recognition.

Photoinduced-electron-transfer-driven surface modification to regulate adsorption behavior in a pyridinium-decorated metal–organic framework

Photoinduced-electron-transfer-driven surface modification was presented in a pyridinium-decorated metal–organic framework and found to be effective to regulate its adsorption behaviors toward polar molecules and halogens.

Tracking the Superefficient Anion Exchange of a Dynamic Porous Material Constructed by Ag(I) Nitrate and Tripyridyltriazole via Multistep Single-Crystal to Single-Crystal Transformations

To avoid the instability and inefficiency for anion-exchange resins and layered double-hydroxides materials, we present herein a flexible coordination network [Ag(L²⁴³)](NO₃)(H₂O)(CH₃CN) (L²⁴³ = 3-(2-pyridyl)-4-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole) with superefficient trapping capacity for permanganate, as a group-7 oxoanion model for radiotoxic pertechnetate pollutant. Furthermore, a high-throughput screening strategy has been developed based on concentration-gradient design principle to ascertain the process and mechanism for anion exchange. Significantly, a series of intermediates can be successfully isolated as the qualified crystals for single-crystal X-ray diffraction. The result evidently indicates that such a dynamic material will show remarkable breathing effect of the three-dimensional host framework upon anion exchange, which mostly facilitates the anion trapping process. This established methodology will provide a general strategy to discover the internal secrets of complicated solid-state reactions in crystals at the molecular level.

A multifunctional Ni(ii) coordination polymer: synthesis, crystal structure and applications as a luminescent sensor, electrochemical probe, and photocatalyst

A new Ni(ii) complex containing 2,5-dichloroterephthalate and rigid bis(imidazole) ligands, which manifests multifunctional properties, has been synthesized and characterized.

Post-cycloaddition modification of a porous MOF for improved GC separation of ethanol and water

An olefin-containing porous framework undergoes [2 + 2] cycloaddition to give post-modified pore space, accompanied by turn-on luminescence upon light irradiation. The photochemical modification reinforces the supramolecular network and improves GC separation performance of ethanol and water.

Dual structure evolution of a Ag(i) supramolecular framework triggered by anion-exchange: replacement of terminal ligand and switching of network interpenetration degree

Dual single-crystal to single-crystal transformations triggered by different anion-exchanges are achieved for a Ag(i) coordination framework, where switching of network interpenetration degree is observed.

I2-induced SC–SC transformation within two-dimensional Zn(ii)-triazole framework: an ideal detector of cyano-containing molecules

A SC–SC transformation process driven by I₂ has been shown to generate a 2D + 1D → 2D interpenetrated architecture from a 2D + 2D → 2D network. For the first time we demonstrate a selective sensor toward cyano-containing molecules.

Multiple single-crystal-to-single-crystal guest exchange in a dynamic 1D coordination polymer

We report on the multiple single-crystal-to-single-crystal exchange of chlorinated volatile organic compounds in a remarkably stable 1D coordination polymer possessing 1D channels.

Dynamic structural transformations of coordination supramolecular systems upon exogenous stimulation

This feature article comments on the dynamic structural transformations of coordination supramolecular systems, which can be triggered by exposure to various exogenous stimuli such as concentration, temperature, light and mechanical force, as well as their synergic effect.

Synthesis of a novel hybrid metal–organic salt and its solid-state transformation

A new adamantanoid metal cluster has been synthesized and its solid-state transformation monitored by X-ray diffraction.

A rare (3,4,5)-connected metal–organic framework featuring an unprecedented 1D + 2D → 3D self-interpenetrated array and an O-atom lined pore surface: structure and controlled drug release

A rare (3,4,5)-connected metal–organic framework has been constructed, which features an unprecedented 1D + 2D → 3D self-interpenetrated array and an O-atom lined pore surface, and shows good controlled release of ibuprofen.