A Flexible and Porous Ferrocene‐Based Gallium MOF with MIL‐53 Architecture

Abstract

A new gallium based metal-organic framework, denoted as Ga-MIL-53-FcDC, with the chemical formula [Ga(OH)(FeC 12 H 8 O 4)] was synthesized using the ferrocene containing linker molecule 1,1'-ferrocenedicarboxylic acid (H 2 FcDC, FeC 12 H 10 O 4). The porous nature of the compound could be confirmed by nitrogen sorption and a specific surface area of 270 m 2 /g was determined. The persistence of the ferrocene complex inside the structure was confirmed by Mössbauer-, EPR and UV/VIS-spectroscopy. Ga-MIL-53-FcDC shows structural flexibility depending on which guest molecule is located in the pores of the compound. The mechanism of structural flexibility was analyzed by means of powder X-ray diffraction adsorbing pyrazine or iodine. The flexibility of the crystal structure can be attributed to the torsion of the GaO 6 octahedra in the IBU respective to each other and the torsion of the carboxylate groups of FcDC 2À relative to the aromatic ring.

Adsorption of iodine in metal–organic framework materials

“…Iodine sorption in derivatives of MIL-53(Al) with various functional groups [–H, –CH 3 , –NH 2 ,–(OH) 2 , –COOH, –(COOH) 2 , –NO 2 , –Cl, –Br] on the benzene-1,4-dicarboxylate linker has been studied in cyclohexane solutions. 68 These functional groups cover an extensive variety of polarities and electron-donating abilities. MIL-53(Al) adsorbs a negligible amount of iodine, while the amine-functionalised MIL-53-NH 2 (Al) shows an increase in adsorption capacity to 0.18 g g −1 .…”

“…This is due to the poor framework stability of highly porous MOFs as the frameworks often collapse on iodine inclusion due to its caustic nature, thus preventing further investigations of cycling test. 68,75…”

“…The interaction of adsorbed iodine and the framework polarises the I–I bond and leads to blue shifts of the Raman band of typically 5–15 cm −1 . 68,93…”

Flexible metal–organic frameworks for gas storage and separation

“…30 Generally speaking, the dynamic structural changes of flexible MOFs can be divided into two types: (1) crystal phase transition is accompanied by a change in the unit cell volume, (2) with the unit cell volume remaining constant. [31][32][33] The dynamic change of MOFs can be inferred from the analysis of their adsorption isotherm. 34 However, it is not enough to observe the structural transformation directly, so some simulation methods and characterization methods (in situ ETEM (Environmental Transmission Electron Microscopy), EXAFS (Extended X-ray Absorption Fine Structure), and SCXRD (Single Crystal X-ray Diffraction), etc.)…”

Iodine‐Chemisorption, Interpenetration and Polycatenation: Cationic MOFs and CPs from Group 13 Metal Halides and Di‐Pyridyl‐Linkers

“…[26,27] The incorporation of complex anions in the structures is found for cationic coordination polymers and MOFs including group 13 metal halide based compounds constituted together with N-donor ligands. [28][29][30][31][32][33][34][35][36][37][38] Although being less frequent than carboxylate based MOFs and CPs, [39][40][41][42][43][44][45][46] the research concerning N-donor based coordination polymers with group 13 metals has gained growing interest. Until now, only a limited amount of coordination polymers constituted from group 13 metal halides and N-donor ligands have been reported, for example for the linkers pyrazine (pyz), [28,34] 4,4'-bipyridine (bipy), [31][32][33]37,38] 1,2-di(4-pyridyl)ethylene (bpe) [29,35] and 2,4,6-tri(4-pyridyl)-1,3,5triazine (tpt).…”