Distinct and Selective Amine- and Anion-Responsive Behaviors of an Electron-Deficient and Anion-Exchangeable Metal–Organic Framework

Abstract

Smart materials that respond to chemical stimuli with color or luminescence changes are highly desirable for dailylife and high-tech applications. Here, we report a novel porous metal−organic framework (MOF) that shows multiple, selective, and discriminative responsive properties owing to the combination of different functional ingredients [tripyridinium chromogen, Eu(III) luminophore, cationic framework, and special porous structure]. The MOF contains two interpenetrated three-dimensional cationic coordination networks built of a tetrahedral [Eu 4 (μ 3 -OH) 4 ] cluster and a tripyridinium-tricarboxylate zwitterionic linker. It shows reversible and discriminative chromic response to aliphatic amines and aniline through different host− guest interactions between electron-deficient pyridinium and electron-rich amines. The size-and shape-selective response to aliphatic amines is ascribed to the radical formation through host−guest electron transfer, whereas the response to aniline is ascribed to the formation of sandwich-type acceptor−donor− acceptor complexes. The MOF is capable of reversible anion exchange with various anions and shows selective and discriminative ionochromic response to iodide, bromide, and thiocyanate, which is attributed to charge-transfer complexation. The above chromic behaviors are accompanied by efficient quenching of Eu(III) photoluminescence. The MOF represents a multi-stimuli dual-output responsive system. It can be used for discrimination and identification of anions and amines. The potential use in invisible printing, reusable sensory films, and optical switches was demonstrated by the ink and the membrane made of the MOF and organic polymers.

Recognition and Sequestration of Toxic Inorganic Water Pollutants with Hydrolytically Stable Metal‐Organic Frameworks

“…However, MOFs score over these contemporary materials because of its benefits, such as high detection limits, excellent selectivity in presence of other competing pollutants, ease of device fabrication for real time applicability etc [7,8,10–12] . Furthermore, favorable binding interactions with incoming guest molecules along with uniform pore surface and high stability of the MOFs allow to regenerate/recycle the sorbent material from post treated phase, which is regarded as one of the most important aspect in rational utilization of laboratory performing materials [60–62] …”

Anion binding in metal-organic frameworks

“…Importantly, they satisfy the desired qualities of an optimal sensor which can be quickly and easily detected by their optical response, often luminescent or a color change. [19]…”

Decorating Metal Nitrate with a Coplanar Bipyridine Moiety: A Simple and General Method for Fabricating Photochromic Complexes

“…The crystalline HPMs (CHPMs) feature intrinsic advantages in elucidating the structure‐dependent photoswitchable properties, which has received sustained interest of researchers and been broadly investigated [10] . Although representative results have been obtained during the development of CHPMs, [2–15] the fabrication of CHPMs with tailor‐made photoresponsive performance is still a challenge to chemists.…”

“…Hybrid photochromic materials (HPMs) have gained tremendous attention of researchers for their potential applications in various areas and possibilities for generating other photoresponsive functionality [1–9] . The crystalline HPMs (CHPMs) feature intrinsic advantages in elucidating the structure‐dependent photoswitchable properties, which has received sustained interest of researchers and been broadly investigated [10] .…”