Multifunctional Metal–Organic Frameworks Based on Redox-Active Rhenium Octahedral Clusters

Abstract

The redox-active rhenium octahedral cluster unit [ReSe(CN)] was combined with Gd ions and dicarboxylate linkers in novel types of metal-organic frameworks (MOFs) that display a set of functional properties. The hydrolytically stable complexes [{Gd(HO)}(L)ReSe(CN)]·nHO (1, L = furan-2,5-dicarboxylate, fdc; 2, L = thiophene-2,5-dicarboxylate, tdc) exhibit a 3D framework of trigonal symmetry where 1D chains of [{Gd(HO)}(L)] are connected by [ReSe(CN)] clusters. Frameworks contain spacious channels filled with HO. Solvent molecules can be easily removed under vacuum to produce permanently porous solids with high volumetric CO uptake and remarkable CO/N selectivity at room temperature. The frameworks demonstrate an ability for reversible redox transformations of the cluster fragment. The orange powders of compounds 1 and 2 react with Br, yielding dark-green powders of [{Gd(HO)}(L)ReSe(CN)]Br·nHO (3, L = fdc; 4, L = tdc). Compounds 3 and 4 are isostructural with 1 and 2 and also have permanently porous frameworks but display different optical, magnetic, and sorption properties. In particular, oxidation of the cluster fragment "switches off" its luminescence in the red region, and the incorporation of Br leads to a decrease of the solvent-accessible volume in the channels of 3 and 4. Finally, the green powders of 3 and 4 can be reduced back to the orange powders of 1 and 2 by reaction with hydrazine, thus displaying a rare ability for fully reversible chemical redox transitions. Compounds 1-4 are mentioned as a new class of redox-active cluster-based MOFs with potential usage as multifunctional materials for gas separation and chemical contamination sensors.

Heavy chalcogenide-transition metal clusters as coordination polymer nodes

“…50 Besides these 1D chains, two novel types of 3D porous MOFs have been reported using [Re 6 Se 8 (CN) 6 ] 4À , Gd 3+ , and dicarboxylate linkers in a three-component framework. 51 These materials exhibit trigonal symmetry which can be viewed as 1D chains of [{Gd(H 2 Fig. 10A and B and serves as a typical example.…”

Supramolecular Frameworks Based on Rhenium Clusters Using the Synthons Approach

“…The resulting literature is abundant and mainly reports on supramolecular networks involving hydrogen bonding and/or π–π stacking interactions between cluster units, and to a lesser extent coordination networks combining, for instance, the porosity of the framework with the intrinsic properties of the clusters [ 11 ]. As examples of functionalization of hexarhenium octahedral clusters with organic moieties or ligands, one can note the use of formate [ 13 ], acetate [ 14 ], phosphine [ 15 , 16 , 17 , 18 ], furan or thiophene dicarboxylate li-gands with Gd cation [ 19 ], and isonicotinate with lanthanide cations [ 20 ]. The last two substitutions lead to 3D frameworks through the Ln additional cations.…”

Zirconium metal–organic frameworks incorporating tetrathiafulvalene linkers: robust and redox-active matrices for in situ confinement of metal nanoparticles

“…They have attracted considerable research interest in the elds of gas storage, 1,2 separations, 2,3 energy storage, 4 catalysis 5 and chemical sensing. 6 While many MOFs remain inert under application conditions, recent studies have highlighted their redox activity potential arising from metal ions, [7][8][9][10][11][12][13][14][15] organic linkers, [16][17][18][19][20][21][22][23][24][25] or the guest molecules. 18,26 Redox-active MOFs represent a unique class of switchable solid materials in which the different redox states with distinct physical properties can be achieved by redox modulation.…”