Synthesis and characterization of a series of porous lanthanide tricarboxylates Thomas Devic a,⇑ , Virgile Wagner a , Nathalie Guillou a , Alexandre Vimont b , Mohamed Haouas a , Michele Pascolini c , Christian Serre a , Jérome Marrot a , Marco Daturi b , Francis Taulelle a , Gérard Férey a a Institut Lavoisier, UMR CNRS 8180, Université de Versailles Saint-Quentin-en-Yvelines, 45 avenue des Etats-Unis, 78035 Versailles cedex, France b Laboratoire Catalyse et Spectrochimie, UMR CNRS 6506, ENSICAEN and Université de Caen, 6 boulevard du Maréchal Juin, 14050 Caen cedex, France c Dipartimento di Scienze Chimiche, via Marzolo 1, 35131 Padova, Italy article info Article history: Available online 28 October 2010 Keywords: MOFs Porous solids Lanthanide Thermal behavior XR structure abstract The synthesis of a series of 11 porous lanthanides-based MOFs formulated Ln(C 27 H 15 O 6 )(H 2 O)x(solv) (denoted MIL-103) (Ln = La to Ho, Y), presenting large one-dimensional channels and a high surface area after dehydration, is reported. X-ray diffraction (XRD) reveals that these solids crystallize in the chiral space group R32 (no. 155) with a slight contraction of the cell parameters according to the ionic radii of the rare-earth. Their thermal stability has been characterized concomitantly by thermogravimetric analysis, X-ray thermodiffraction, 1 H solid state NMR, in situ IR spectroscopy and nitrogen sorption mea- surements, revealing that (i) all solids are stable upon dehydration and porous (S BET around 700 m 2 g 1 ); (ii) dehydration is accompanied by a structural rearrangement of the lanthanide cations coordination shell. This rearrangement is reversible upon re-hydration, thus proving the presence of accessible Lewis acid sites within the dehydrated forms, whose strength increases when the ionic radius of the metal decreases. Finally, first photoluminescent properties of the Eu-based material have been investigated. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Porous Coordination Polymers (PCPs) or Metal Organic Frame- works (MOFs) including lanthanide cations are of interest [1–3], due: (i) to the high coordination number (6–12) of the rare-earth cations leading to new and intriguing topologies compared to their transition-metal based counterparts [4,5]; (ii) the presence of sev- eral properties of interest such as heterogeneous catalysis [6–9], solid state luminescence [10–19], magnetism [20–27] or contrast enhancing agent [28,29], which, combined with a permanent porosity, paves the way for the design of multifunctional porous solids. Nevertheless, the lack of directionality of the Ln–O bonds (related to their ionic nature) renders rather difficult the prepara- tion of Ln-based PCPs exhibiting a permanent porosity. First of all, although molecular Ln-based inorganic Secondary Building Units (SBUs) have been proposed [30,31], the preparation of well defined Ln based SBUs stable in the reaction medium is rather difficult, whereas it has been proven to be a powerful tool for the prepara- tion of several porous transition-metal based MOFs based on zinc, copper or iron [32]. Moreover, most of the lanthanide-based solids presenting open frameworks, and thus a potential porosity, [33] collapse or loose their long range order upon guest departure, often as a consequence of sharp structural rearrangements of the coordi- nation shell of the lanthanide cations. Thus, only very few rare- earth-based coordination polymers exhibit a permanent porosity [34–41], and a significant surface area relative to nitrogen [42– 45]. A mesoporous material based on molecular Ln SBUs and ex- tended tritopic linkers has been reported recently [46], as well as solids based on 1-D inorganic SBUs and either 3,5-pyridine-dicar- boxylate [47] or trimesate [48,49] linkers. Some of us also prepared a terbium-based MOF (later denoted MIL-103(Tb), MIL = Material Institut Lavoisier) built up from inorganic rods and benze- netribenzoate linkers exhibiting 1-D cylindrical pores (diame- ter  11 Å) and a BET surface area around 700 m 2 g 1 [50]. As the potential applications of such solids are strongly dependent on the nature of the rare-earth (as already exemplified with the Nd analogue acting as a convenient Ziegler Natta catalyst [9]), the syn- thesis of MIL-103 was extended to other rare-earth cations, leading to a series of eleven isostructural porous Ln-based MOFs denoted MIL-103(Ln)as (as for as-synthesized). Their structural characteris- tics are studied by XRD (both single crystal and powder diffraction data), and their thermal behavior were deeply investigated by a combination of thermogravimetry, thermodiffraction (including the structure solution of the anhydrous MIL-103(Eu)dry structure), 1 H solid state NMR and in situ IR spectroscopy (dehydration). Finally, the presence and strength of metal Lewis acid sites was investigated in relation with the potential use of Ln-based MOFs for chemical sensing [51–57]. 1387-1811/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2010.10.022 ⇑ Corresponding author. Tel.: +33 139254299. E-mail address: devic@chimie.uvsq.fr (T. Devic). Microporous and Mesoporous Materials 140 (2011) 25–33 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso