Metal‐Organic Frameworks with Novel Catenane‐like Interlocking: Metal‐Determined Photoresponse and Uranyl Sensing

Abstract

The assembly of two tripyridinium‐tricarboxylate ligands and different metal ions leads to seven isostructural MOFs, which show novel 2D→2D supramolecular entanglement featuring catenane‐like interlocking of tricyclic cages. The MOFs show tripyridinium‐afforded and metal‐modulated photoresponsive properties. The MOFs with d10 metal centers (1‐Cd, 1‐Zn, 2‐Cd, 2‐Zn) show fast and reversible photochromism and concomitant fluorescence quenching, 1‐Ni displays slower photochromism but does not fluoresce, and 1‐Co and 2‐Co are neither photochromic nor fluorescent. It is shown here that the network entanglement dictates donor‐acceptor close contacts, which enable fluorescence originated from interligand charge transfer. The contacts also allow photoinduced electron transfer, which underlies photochromism and concomitant fluorescence response. The metal dependence in fluorescence and photochromism can be related to energy transfer through metal‐centered d‐d transitions. In addition, 1‐Cd is demonstrated to be a potential fluorescence sensor for sensitive and selective detection of UO22+ in water.

Confinement of Pyridine Derivatives into a Metal–Organic Framework Host as Electron Acceptors to Achieve Photoinduced Electron-Transfer

“…Detailed structural analysis was further conducted to identify the possible transfer path for the ET process in these compounds. Previous studies have suggested that photoinduced ET in solid-state viologen compounds generally occurs through a short contact between the pyridinium moiety and an electron donor (D), for instance, N pyridinium ···D, − ,, (α-C–H) pyridinium ···D, , and π pyridinium ···π D . , Typically, the appropriate N···O distance for ET is less than 4.0 Å. − ,, In our study, we found that the distances between the carboxylate oxygen atoms and pyridine nitrogen atoms were 3.267–3.327 Å for 1 , 3.044–3.904 Å for 2 , 3.092–3.851 Å for 3 , and 3.204 and 3.360 Å for 4 , which locate at suitable distances for photoinduced ET (Figure ). Therefore, in this work, due to the strong hydrogen-bonding interactions together with other intermolecular interactions, the hydrogen atom in the coordinated H 2 O delocalizes and approaches the nitrogen atoms of the pyridine derivatives, which facilitates photoinduced ET from the carboxylates in the host to the pyridine derivatives, resulting in the formation of photogenerated radicals, similar to the behavior of viologen molecules.…”

Recent Progress in Metal-Organic Framework Based Fluorescent Sensors for Hazardous Materials Detection

“…Chen and Wang obtained a series of 2D isomorphous MOFs [M(HBTC)(BMIOPE)·DMF·H 2 O] n (M = Zn, Zn 0.7 Co 0.3 , Zn 0.5 Co 0.5 , Zn 0.3 Co 0.7 , Co, BMIOPE = 4,4′-bis(2-methylimidazol-1-yl)diphenyl ether, H 3 BTC = 1,3,5-benzenetricarboxylic acid) to discuss the optical detection of UO 2 2+ in an aqueous solution [ 93 ]. Seven isostructural MOFs indicating novel 2D→2D supramolecular entanglement featuring catenane-like interlocking of tricyclic cages by the assembly of two tripyridinium-tricarboxylate ligands and different metal ions were reported by Guo et al, as shown in Figure 12 a [ 94 ]. The tripyridinium-afforded and metal-modulated photoresponsive properties of Cd-MOF allow it to be used as a potential fluorescence sensor for sensitive and selective detection of UO 2 2+ in water, as shown in Figure 12 b.…”

Electrochemical switching in mechanically interlocked molecules (MIMs)

“…[145][146][147] Catenanes are at the forefront of this field to construct artificial molecular machines and take advantage of the dynamics of interlocked structures in polymers, metal/covalent-organic frameworks (M/COFs), and other materials. [148][149][150][151][152] Their research has resulted in significant advancements that have significance for various scientific fields, from biology to soft matter physics, as well as supramolecular chemistry. 153 Like rotaxanes, catenanes have a naming system where the term is preceded by square brackets denoting the number of macrocycles that make up a catenane.…”