Photoluminescent porous modular lanthanide-vanadium-organic frameworks

Abstract

Modularmixedmetal-organicframeworkswithlanthanidecentres, M4[M12V24O24(OH)8(H2hedp)8(Hhedp)16(H2O)64+n]· 88+y(H2O) (M3+ = Y3+, Ce3+, Sm3+, Eu3+, Tb3+, Gd3+, Er3+; H5hedp = etidronic acid), have been reported. The compounds have been prepared by (i) slow evaporation of the solvent to afford large single-crystals of the Y3+, Ce3+ and Er3+compounds and (ii) facile one-pot synthesis (at ambient conditions) overnight to yield microcrystalline Y3+, Ce3+, Sm3+, Eu3+, Tb3+ and Gd3+ solids. Framework construction has been shown to be modular and based on the self-assembly of cyclic trinuclear [V3O3(OH)(H2hedp)(Hhedp)2]6– anionic units with cationic {MO8} or {MO9} aqua-based lanthanide complexes (with dodecahedral, square antiprismatic or tricapped trigonal prismatic coordination geometries), which gives rise to unprecedented trinodal networks (having and 4-connected nodes) with a total Schäfli symbol of {4.83.102}2{42.84}{8}2. The anionic charge of the networks is balanced by highly disordered trivalent lanthanide cations in the channels. The compounds have been studied by singlecrystal and powder X-ray diffraction, vibrational spectroscopy (FTIR), thermogravimetry, optical and scanning electron microscopy and elemental analysis. The photoluminescence properties of selected compounds have been investigated. Intriguingly, the co-existence of V4+ and Eu3+ cations in the same material allows the fine tuning of the photoluminescence emission from white to purplish-blue, by changing the excitation wavelength.