Promising applications of metal-organic frameworks (MOFs) in various fields, especially biological applications, have raised concern over their environmental fate and safety upon their inevitable discharge into aqueous environments. Currently, no information regarding the transformation process of MOFs has been reported. Due to the presence of a repetitive π-bond structure embedded in MOFs and their semi-conductive 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 MOFs with MIL-53 topology has been studied. Furfuryl alcohol (FFA), tetrazolium salt (NBT2+), and p-chlorobenzoic acid (pCBA) were employed to probe the production of 1O2, O2.-, and .OH, respectively. In general, the amount of ROS generated from ROS-photogeneration reactions mediated by isoreticular MIL-53s are orders of magnitude greater than those of carbon nanotubes (CNTs) tested under similar conditions. In addition, MIL-53(Cr) and MIL-53(Fe) are dominated by type I and II photosensitization reactions, respectively, and MIL-53(Al) appears to be less photoreactive. In addition, the generation of ROS in MIL-53(Fe) may be underestimated due to dismutation. Further investigation of MIL-53-mediated encapsulated diclofenac transformation has been performed as an example of the overall environmental impact, and this study revealed that diclofenac encapsulated in a MOF can be easily transformed by the ROS generated from MIL-53. 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 phototransformed MIL-53s may not pose a significant threat. The application of MIL-53s as drug carriers needs to be carefully considered due to their high photoreactivity.

Photoreactivity of metal-organic frameworks in aqueous solutions: Metal dependence of reactive oxygen species production

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.