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International audience; The reactivity of aryl monocarboxylic acids (benzoic, 1- or 2-naphtoic, 4’-methylbiphenyl-4-carboxylic and anthracene-9-carboxylic acids) has been investigated as complexing agent toward the ethoxide niobium(V) (Nb(OEt)5 precursor. A total of 8 coordination complexes has been isolated with distinct niobium(V) nuclearities as well as carboxylates complexation states. The use of benzoic acid gives to a tetranuclear core Nb4(μ2-O)4(L)4(OEt)8] (L = benzoate (1)) exhibiting four Nb-(μ2-O)-Nb linkages in a square plane configuration. A similar tetramer (7) is obtained with 2-naphtoic acid by using a 55% humidity atmosphere synthetic route. Two types of dinuclear bricks has been identified with one central Nb-(μ2-O)-Nb linkages, and differ by the complexation state, with one bridging carboxylate ([Nb2(μ2-O)(μ2-OEt)(L)(OEt)6], with L = 1-naphtoate (3) & L = anthracene-9-carboxylate (5)) or two bridging carboxylate groups ([Nb2(μ2-O)(L)2(OEt)6], with L = 4’-methylbiphenyl-4-carboxylic (4) & L = anthracene-9-carboxylate (6)). An octanuclear moiety [Nb8(μ2-O)12(L)8(η1-L)4-x(OEt)4+x] (with L = 2-naphtoate, x = 0 or 2; 8) has been obtained by using solvothermal route in acetonitrile, and possesses a cubic configuration with niobium centers at each node, linked through 12 μ2-O groups. The formation of the niobium oxo clusters has been characterized by infrared and liquid 1H NMR spectroscopy in order to analyze the esterification reaction, which induce the release of water molecule, which further reacts through oxolation process with niobium atoms, in different {Nb2O}, {Nb4 O4} and {Nb8O12} nuclearities.; a réactivité des acides aryl monocarboxyliques (acides benzoïque, 1- ou 2-naphtoïque, 4'-méthylbiphényl-4-carboxylique et anthracène-9-carboxylique) a été étudiée comme agent complexant vis-à-vis de l'éthoxyde niobium(V) (Nb(OEt) 5 précurseur. Au total, 8 complexes de coordination ont été isolés avec des nucléarités distinctes du niobium(V) ainsi que des états de complexation des carboxylates. L'utilisation de l'acide benzoïque donne à un noyau tétranucléaire Nb4(μ2-O)4(L)4(OEt) 8] (L = benzoate (1)) présentant quatre liaisons Nb-(μ2-O)-Nb dans une configuration de plan carré. Un tétramère similaire (7) est obtenu avec l'acide 2-naphtoïque en utilisant une voie de synthèse en atmosphère à 55 % d'humidité Deux types de briques dinucléaires ont été identifiées avec une liaison centrale Nb-(μ2-O)-Nb, et diffèrent par l'état de complexation, avec un carboxylate pontant ([Nb2(μ2-O)(μ2-OEt)(L) (OEt)6], avec L = 1-naphtoate (3) & L = anthracène-9-carboxylate (5)) ou deux groupes carboxylate pontants ([Nb2(μ2-O)(L)2(OEt)6], avec L = 4'-méthylbiphényl-4-carboxylique (4) & L = anthracène-9-carboxylate (6)). Une fraction octanucléaire [Nb8(μ2-O)12(L)8(η1-L)4-x(OEt)4+x] (avec L = 2-naphtoate, x = 0 ou 2 ; 8) a été obtenue par utilisant la voie solvothermique dans l'acétonitrile, et possède une configuration cubique avec des centres de niobium à chaque nœud, liés par 12 groupes μ2-O. La formation des agrégats oxo de niobium a été caractérisée par spectroscopie RMN 1H infrarouge et liquide afin d'analyser la réaction d'estérification, qui induit la libération de la molécule d'eau, qui réagit ensuite par le processus d'oxolation avec les atomes de niobium, dans différents {Nb2O}, {nucléarités Nb4O4} et {Nb8O12}.

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International audience; Xenon and krypton are noble gases produced by fission reactions in nuclear fuel. In accident situations, these potential gas releases can lead to significant radioactive doses in the short and medium term, particularly for on-site operators. These radioactive isotopes have various half-life, from several years (10.8 years for Kr-85) to several days (5.3 days for Xe-133, short term nuclear accident tracer). Almost chemically inert, these gases are difficult to trap (nuclear mitigation) and separate (industrial applications). Until recently, the trapping of these rare gases had never been deeply investigated because only complex and expensive methods or processes existed, difficult to implement in industry. However, for more than a decade, new porous materials named MOF (Metal-Organic Framework) have demonstrated efficient trapping capacities towards volatile compounds such as the capture of fission products I2 or RuO4[1] as well as trapping of CO2. Indeed, these hybrid metal-ligand materials, organized in a network, are flexible with very variable pore diameters. They also have an unlimited functionalization linked to the organic part which can promote a selective adsorption of gases.So, the objective of this PhD work (2020-2023) is to study the feasibility of rare gas trapping by innovative porous materials such as MOFs in a nuclear context. This will contribute to better characterize the efficiency of filtration or purification devices in order to reduce radioactive releases in normal and accidental operation.Based on recent works[2][3], a first study has been carried out on promising MOFs. Synthesized by hydrothermal process at UCCS (Lille), the influence of doping MOFs with silver, copper or palladium nanoparticles on the adsorption of noble gases (static conditions at room temperature) has been investigated. The MOFs are also tested under dynamic conditions on the SAFARI experimental bench of IRSN under thermohydraulic conditions representative of accidental situations (flow velocity, temperature, humidity...). Some preliminary results will be presented.

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