Impact of the Flexible Character of MIL-88 Iron(III) Dicarboxylates on the Adsorption of n-Alkanes

Abstract

Adsorption of n-alkane vapors was performed to probe the unusual highly flexible character of a series of iron­(III) dicarboxylate materials of the MIL-88 structure type. In agreement with the presence of strong intraframework interactions within the dried closed pores form of MIL-88, it appears first that an increase of the size and aromaticity of the spacer makes it more difficult to adsorb alkanes at room temperature. Thus, this led to a high level of adsorption in the iron fumarate MIL-88A and poor levels in the terephthalate and naphthalenedicarboxylate based MIL-88­(B and C, respectively). Second, upon increase in the length of the alkane, diffusion limitations of the guest occur within the very narrow pores, also illustrated through kinetics of adsorption measurements, which result in an overall decrease in the adsorption capacity. Noteworthy, the swelling of the flexible non modified MIL-88 solids occurs only for the MIL-88A sample, because of the number and orientation of aromatic rings that are arranged in trimers within the MIL-88 structures and, therefore, making those more difficult to open than those where the rings are arranged in dimers such as the metal terephthalate MIL-53 structures. Interestingly, modification of the organic linkers by grafting several bulky functional groups (2CF3, 4CH3) makes the adsorption of n-alkanes easier because of a strong decrease in interactions within these trimers associated with a lower pore contraction upon drying, while the substitution of a hydrogen atom by a bromine one on the spacer proved to be not sufficient for an improvement of the adsorbed amounts.

A Complete Separation of Hexane Isomers by a Functionalized Flexible Metal Organic Framework

“…This compound possesses a structure (Figure S1, SI) built up from another type of inorganic sub‐unit, that is, oxocentered trimers of iron(III) octahedra, resulting in a highly flexible architecture with a 3D (micro‐) pores system. It was shown previously that this type of MOFs, despite its very narrow pore form once dried associated with a low nitrogen surface area, could adsorb significant amounts of linear alkanes at 313 K, with in some cases a slight increase in the pore opening (e.g., pentane) . In a first step, adsorption isotherms of the pure components were performed at 313 K resulting into differences in terms of shape of isotherms and amounts of adsorbed guests (Figure S8, SI), much more significant and over a much larger pressure range compared to MIL‐53(Fe)‐(CF 3 ) 2 , with a clear‐cut n HEX>3MP>22DMB order of selectivity.…”

Fe/Fe3C/N‐Doped Carbon Materials from Metal–Organic Framework Composites as Highly Efficient Oxygen Reduction Reaction Electrocatalysts

“…[12] Briefly, FeCl 3 ·6 H 2 O (2.56 g, 0.01 mol) and 2,6-naphthalenedicarboxylic acid (2.08 g, 0.01 mol) were dispersed in dimethylformamide (DMF; 100 mL). The mixture was loaded into a 250 mL round-bottomed flask and heated at 130 8C under continuous stirring for 18 h. The orange powder product was collected by centrifuge, washed three times with pure DMF, and dried under vacuum for further usage.…”

“…The simulated PXRD pattern of MIL-88c-Fe is also presented to confirm the successful synthesis of this MOF. [12] After mixing and drying, the PXRD peaks from both MOF and DCDA are still preserved in the PXRD pattern of the composite, which suggests the intact structures of both MOF and DCDA in the composite. Scanning electron microscopy (SEM) images indicate that the smooth surface of the MOF particles is covered with an additional coarse granular layer after the introduction of DCDA (Figure 1a, b), thus indicating strong coalition between these two phases.…”

Binary metal organic framework derived CoxFe3−xO4/C for lithium ion batteries

“…The formation mechanism of binary Co x Fe 3 À x O 4 /C hybrid (illustrated in Fig. 2c) was as following: metal ions were first coordinated with organic ligands to form the binary Fe(Co)-BDC [11,14]. Generally, Fe(Co)-BDC consisted a metal-oxygen coordinated layer (A) and an organic hydrocarbon layer (B).…”