Isotopes of fission products (FP) such as iodine and ruthenium, usually 131I, 103Ru and 106Ru, are usually produced in large amount by nuclear fissions. After a nuclear accident, these elements can be quickly disseminated since they may generate very volatile species such as molecular iodine (I2) or ruthenium tetroxide (RuO4). In order to limit their dispersion, filters made of porous materials are used or could be used in nuclear plants for FP mitigation. However, such pure inorganic porous solids exhibit many limitations in the case of a nuclear accident, especially in the presence of poisoning species (e.g. NOx, H2O, COx) or for the capture of large molecules such as RuO4. Based on these limits, a relative new class of porous materials called Metal-Organic Framework (MOFs) could be an effective substitute. Indeed, MOFs are hybrid materials, composed of inorganic clusters linked to each other by organic ligands. This low-dense organization allows important porosity and records in specific surface (up to 7000 m².g-1). Another advantage of MOFs over zeolites and activated carbons, is the possibility to easily functionalize their frameworks through the organic sub-network. This strategy allows to adjust the size of the pores, as well as to attach specific chemical groups improving the capture of the desired molecules. So far, the efficiency of MOFs for the capture of radioactive gaseous species is not well documented and many questions remain. For example, this family of materials was never tested for the capture of volatile RuO4. Furthermore, the shaping and the contribution of functional groups was not yet examined for the capture of iodine. Therefore, this work deals with the capture of volatile I2 and RuO4 in MOFs. In this communication, we will highlight the importance of MOF functionalization and shaping for the capture of gaseous radionuclides; especially under accidental conditions. The capture of the different species was realized in homemade installations, allowing constant flow of I2 and RuO4, and the quantification of species trapped within the porous structure. The capture of gaseous molecular iodine I2 is studied in the isoreticular series of stable Zr based MOFs called UiO-66, UiO-67, and UiO-68. This particular family of compounds gives an access to a wide range of functional groups (-H, -Cl, CH3, -NH2, etc.) and pore diameters (up to 17 Å). Especially, we showed the formation of charge transfer complexes between amino group attached to the MOFs and iodine, leading to very high uptake (more than 1 gram of I2 per gram of MOFs). This particular interaction was characterized by a set of techniques (XRD, Raman spectroscopy, etc.) and confirmed by modelling calculation. For the capture of RuO4, we focused our work on MOF-808-(Zr), which exhibits a very good stability under drastic conditions, as well as very large cages (size 18 Å) able to trap big molecules such as RuO4. Indeed, this MOF reaches a decontamination factor up to 200, and contains 33 %wt Ru after trapping. When RuO4 is trapped in MOF, it decomposes into its most stable and nonvolatile oxide RuO2. This last species remains permanently trapped into the MOFs cage as nanoparticles. These results were, inter alia, confirmed by transmission electronic microscopy.