Capture and immobilization of gaseous ruthenium tetroxide RuO in the UiO-66-NH metal-organic framework.

Ru is a radioactive isotope usually generated by the nuclear industry within power plant reactors. During a nuclear accident, Ru reacts with oxygen, leading to the production of highly volatile ruthenium tetroxide RuO. The combination of volatility and radioactivity makes RuO, one of the most radiotoxic species and justifies the development of a specific setup for its capture and immobilization. In this study, we report for the first time the capture and immobilization of gaseous RuO within a porous metal-organic framework (UiO-66-NH). We used specific installation for the production of gaseous RuO as well as for the quantification of this gas trapped within the filtering medium. We proved that UiO-66-NH has remarkable affinity for RuO capture, as this MOF exhibited the worldwide highest RuO decontamination factor (DF of 5745), hundreds of times higher than the DF values of sorbents daily used by the nuclear industry (zeolites or activated charcoal). The efficiency of UiO-66-NH can be explained by its pore diameters well adapted to the capture and immobilization of RuO as well as its conversion into stable RuO within the pores. This conversion corresponds to the reactivity of RuO with the MOF organic sub-network, leading to the oxidation of terephthalate ligands. As proved by powder X-ray diffraction and NMR techniques, these modifications did not decompose the MOF structure.