title: Order-disorder in the super-sodalite Zn3Al6(PO4)12, 4tren, 17H2O (MIL-74): a combined XRD-NMR assessment.
abstract: A new mixed zinc-aluminum phosphate Zn(3)Al(6)(PO(4))(12), 4tren, 17H(2)O (MIL-74) has been hydrothermally synthesized with the tris(2-aminoethyl)amine (tren) as a structure-directing agent (453 K, 36 h, autogenous pressure). The solid was characterized by a nonclassical method combining single-crystal X-ray diffraction and several solid-state NMR experiments, RFDR, C7 double quantum ((31)P), and 3QMAS ((27)Al). Its crystal structure is cubic, a = 16.7942(1) A, but the choice of the space group does not follow usual routes of structure determination, due to some "disorder" between Zn and Al. It can be assigned as well to I-43m or to P-43n. The open-framework is built up from an enneameric unit (T = Zn, Al) containing five TO(4) and four PO(4) tetrahedra (one of the P-O bonds is terminal). A central TO(4) tetrahedral unit shares all of the corners with four phosphates groups. Two phosphate groups are connected to two other peripheral TO(4) units. It results in the formation of a "pseudo" planar building block T(5)P(4) consisting of four square 4-rings. The connection of the T(5)P(4) units generates a three-dimensional framework, which defines a super-sodalite topology. The resulting cavities (diameter of 10 A) are bound by 12-ring windows in which are located the tren species in interaction with the phosphate groups (mainly terminal P-O bonds) through hydrogen bonds. A cluster of 17 water molecules occupies the center of the super-sodalite cage. The cationic (Zn, Al) occupancy is discussed for this specific topology.
authors.affiliation: Contribution from the Institut Lavoisier (UMR CNRS 8637) and Institut Universitaire de France, Université de Versailles St Quentin en Yvelines, 45 Avenue des Etats Unis, 78035 Versailles, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Beitone
authors.forename: Clarisse
authors.initials: C
authors.lastname: Huguenard
authors.forename: Axel
authors.initials: A
authors.lastname: Gansmüller
authors.forename: Marc
authors.initials: M
authors.lastname: Henry
authors.forename: Francis
authors.initials: F
authors.lastname: Taulelle
authors.forename: Thierry
authors.initials: T
authors.lastname: Loiseau
authors.forename: Gérard
authors.initials: G
authors.lastname: Férey