Mohan Chen,Yichao Wang,Ziwen Fan,Yue Wang,Zheng Niu,Jianping Lang
Graphical We prepared a series of fluorinated MOFs through the post- synthesis modification of the classic Zr-based MOF-808. The fluorinated alkane pores within MOFs can enhance the forces between the framework and C 2 H 2 , therefore, the difference in the adsorption capacity to C 2 H 2 and C 2 H 4 making it possible to effectively separate the C 2 H 2 /C 2 H 4 mixture at room temperature. The separation of ethylene (C 2 H 4 ) and acetylene (C 2 H 2 ) is challenging due to their similar molecular dimensions and boiling points, making conventional methods like cryogenic distillation and solvent extraction inefficient and environmentally harmful. Fluorinated metal-organic frameworks (MOFs) have been proven to be an effective material for the separation of C 2 H 4 and C 2 H 2. However, their direct synthesis is relatively expensive and challenging. In this study, we report a facile post-synthetic modification strategy to introduce fluorinated alkane pores into a zirconium-based MOF, MOF-808. The construction of fluorine-containing pores within the MOFs prefers adsorption for C 2 H 2 attributed to the interaction between the fluorine atoms and C 2 H 2 . This series of fluorinated MOFs demonstrates potential for gas separation processes, with the highest separation ratio reaching 2.67 (1 : 99) at 298 K. Breakthrough experiments for C 2 H 2 /C 2 H 4 mixtures confirmed that fluorinated MOF is capable of separating C 2 H 2 /C 2 H 4 , making it a potential candidate for industrial application. Moreover, the simplicity of the post-synthetic modification method suggests a viable strategy for the synthesis of fluorinated MOFs.
Xiaodan Li,Xiaoqing Liu,Xinyu Hu,Rui He,Hongyu Liu
A fluorine-functionalized zirconium-based metal organic framework (F 4 -UiO-66) was successfully synthesized via the reflux method, and the F 4 -UiO-66/BT nanocomposites of F 4 -UiO-66 modified bismaleimide-triazine resin (BT resin) were prepared. The effects of F 4 -UiO-66 on the crosslinking structure and properties of BT resin were evaluated for the first time. The investigations showed that the active H in F 4 -UiO-66 effectively catalyzed the self-polymerization of cyanate ester and promoted the formation of more rigid triazine rings which increased the initial storage modulus of nanocomposites. But the steric hindrance effect of F 4 -UiO-66 reduced the crosslinking density, which increased the free volume of nanocomposites. So, the dielectric constants of the nanocomposites were significantly reduced with the increase of F 4 -UiO-66 for the reduction of molecular polarization due to triazine rings and C–F bonds, and the decrease of polarization density caused by the nanopores and free volume. In addition, F 4 -UiO-66 was evenly dispersed in BT resin. On the basis of maintaining the thermal stability, the toughness and hydrophobic properties of nanocomposites were also enhanced. This study provided a novel approach for low-dielectric materials with hydrophobic property through the synergy between the nanopores and the C–F bonds.
Liangdi Jiang,Zhouyang Huang,Jiacan Xu,Liqiu Zhang,Ziwen Du
Selectivity is the key for adsorption or recovery of per- and polyfluoroalkyl substances (PFAS) from aqueous environments. In this study, the fluorinated metal–organic frameworks (MOFs) with different fluorine contents were prepared and investigated to evaluate the selective adsorption of an emerging PFAS, sodium p‑perfluorous nonenoxybenzenesulfonate (OBS). Adsorption of OBS increased with the increasing fluorine content of MOFs, and the best fluorinated MOFs showed an excellent selective adsorption capacity. The influence of various co-existing hydrocarbon substances on OBS adsorption was slight. The adsorption amount of OBS was 15-fold to that of the hydrocarbon surfactants (n-caprylic acid). The selectivity was attributed to the fluorinated structures of MOFs whose oil contact angle was up to 101°, and thus the oleophobicity of fluorinated structures made MOFs repel hydrocarbon compounds. Molecular dynamics simulations and density functional theory calculations indicated that the fluorinated structures were able to capture OBS molecules from the long distances (roughly 1–100 nm) via hydrophobic interaction, and then formed a F–F non-covalent interaction which was highly probable to be driven by a dispersion force to further attract OBS fluorinated tails within shorter distances (less than 3.5 Å). The combination of oleophobic and fluorophilic effects contribute to the exclusive selectivity of fluorinated MOFs for OBS molecule.
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