MIL-100(V) – A mesoporous vanadium metal organic framework with accessible metal sites

The large pore vanadium(III) trimesate MIL-100(V), i.e. V3O(H2O)2X[C9H3O6]2·yH2O with X=(Cl-)1-z(C9H5O6)z-, y ≈ 3 and z ≈ 0.3, has been synthesized under hydrothermal conditions (MIL stands for Materials from Institute Lavoisier). Its structure, which crystallizes in the space group Fd-3m (No. 227) with a = 73.0286(2) Å, V = 389474.4(2) Å3, exhibits a zeotype architecture with mesoporous cages of approx. 25 and 29 Å diameter, accessible through microporous windows of 5.5 and 8.9 Å diameter. Synchrotron X-ray powder diffraction analysis confirms its isostructural character with previously reported MIL-100(Cr, Fe, Al) solids. Its thermal stability under O2 and N2, up to 523 K (250 °C), is comparable to that of MIL-100(Fe). Preliminary gas adsorption experiments and in situ IR-spectroscopy after NO exposure reveal that MIL-100(V) combines high sorption capacities and co-ordinatively unsaturated vanadium sites in different oxidation states (+III and +IV). With these properties this material could be a promising candidate for specific sorption or redox catalytic applications.