2 research outputs found
Understanding the Adsorption of PFOA on MIL-101(Cr)-Based Anionic-Exchange Metal–Organic Frameworks: Comparing DFT Calculations with Aqueous Sorption Experiments
To examine the effects of different
functionalization methods on adsorption behavior, anionic-exchange
MIL-101Â(Cr) metal–organic frameworks (MOFs) were synthesized
using preassembled modification (PAM) and postsynthetic modification
(PSM) methods. Perfluorooctanoic acid (PFOA) adsorption results indicated
that the maximum PFOA adsorption capacity was 1.19 and 1.89 mmol g<sup>–1</sup> for anionic-exchange MIL-101Â(Cr) prepared by PAM
and PSM, respectively. The sorption equilibrium was rapidly reached
within 60 min. Our results indicated that PSM is a better modification
technique for introducing functional groups onto MOFs for adsorptive
removal because PAM places functional groups onto the aperture of
the nanopore, which hinders the entrance of organic contaminants.
Our experimental results and the results of complementary density
functional theory calculations revealed that in addition to the anion-exchange
mechanism, the major PFOA adsorption mechanism is a combination of
Lewis acid/base complexation between PFOA and CrÂ(III) and electrostatic
interaction between PFOA and the protonated carboxyl groups of the
bdc (terephthalic acid) linker
Photoreactivity of Metal–Organic Frameworks in Aqueous Solutions: Metal Dependence of Reactive Oxygen Species Production
Promising applications of metal–organic
frameworks (MOFs)
in various fields have raised concern over their environmental fate
and safety upon inevitable discharge into aqueous environments. Currently,
no information regarding the transformation processes of MOFs is available.
Due to the presence of repetitive π-bond structure and semiconductive
property, photochemical transformations are an important fate process
that affects the performance of MOFs in practical applications. In
the current study, the generation of reactive oxygen species (ROS)
in isoreticular MIL-53s was studied. Scavengers were employed to probe
the production of <sup>1</sup>O<sub>2</sub>, O<sub>2</sub><sup>•–</sup>, and •OH, respectively. In general, MIL-53Â(Cr) and MIL-53Â(Fe)
are dominated by type I and II photosensitization reactions, respectively,
and MIL-53Â(Al) appears to be less photoreactive. The generation of
ROS in MIL-53Â(Fe) may be underestimated due to dismutation. Further
investigation of MIL-53Â(Fe) encapsulated diclofenac transformation
revealed that diclofenac can be easily transformed by MIL-53Â(Fe) generated
ROS. However, the cytotoxicity results implied that the ROS generated
from MIL-53s have little effect on the viability of the human hepatocyte
(HepG2) cell line. These results suggest that the photogeneration
of ROS by MOFs may be metal-node dependent, and the application of
MIL-53s as drug carriers needs to be carefully considered due to their
high photoreactivity