Hybrid open-frameworks: synthesis and structures of four vanado-alkyldiphosphonates with occluded potassium cations

Abstract

The ternary systems KVO3:H2O3P(CH2)nPO3H2:H2O (n=1, 2, 3) were hydrothermally investigated. Four phases were obtained and their structures determined by single crystal X-ray diffraction. K4(VIVO)2(VIVO(H2O))4{O3PCH2PO3}4.8H2O or MIL-2K is orthorhombic (S.G. P mmn (n° 59)) with lattice parameters a=13.7642(2) Å, b=15.6796(4) Å, c=4.6902(1) Å, V=1012.23(4) Å3, Z=1. Its three-dimensional framework presents some 14-membered tunnels inserting potassium cations and water molecules. K(VVO(H2O))(VIVO)O{O3P(CH2)2PO3} or MIL-3K is triclinic (S.G. P -1 (n° 2)) with lattice parameters a=7.3807(2) Å, b=7.9984(3) Å, c=10.0641(3) Å, α=75.695(1)°, β=69.178(1)°, γ=80.769(1)°, V=536.37(3) Å3, Z=2. MIL-3K exhibits a pillared structure showing inorganic layers covalently linked by the ethyl chains. Its dehydration is studied. The pillared structures of K(VIVO)2(OH){O3P(CH2)3PO3}3H2O or MIL-7K(HT) and K(V2IV/VO3)(H2O){O3P(CH2)3PO3}H2O or MIL-7K(LT) are closely related, differing only by the neighbouring and the oxidation state of one vanadium atom. Both structures are monoclinic (S.G. C 2/c (n° 15)) with lattices parameters a=14.4939(1) Å, b=10.2595(2) Å, c=18.6782(2) Å, β=98.991(1)°, V=2743.32(6) Å3, Z=8 and a=14.6228(1) Å, b=10.2783(2) Å, c=18.2716(3) Å, β=100.272(1)°, V=2702.16(7) Å3, Z=8 for MIL-7K(HT) and MIL-7K(LT), respectively.