A Robust Open Framework Formed by Decavanadate Clusters and Copper(II) Complexes of Macrocyclic Polyamines: Permanent Microporosity and Catalytic Oxidation of Cycloalkanes

The
first decavanadate-based microporous hybrid, namely, [Cu­(cyclam)]­[{Cu­(cyclam)}2­(V10O28)]·10H2O (1, cyclam = 1,4,8,11-tetraazacyclotetradecane) was
prepared by reaction of (VO3)− anions
and {Cu­(cyclam)}2+ complexes in NaCl (aq) at pH 4.6–4.7
and characterized by elemental analyses, thermogravimetry, and X-ray
diffraction (powder, single-crystal) techniques. Compound 1 exhibits a POMOF-like supramolecular open-framework built of covalent
decavanadate/metalorganic layers with square-like voids, the stacking
of which is aided by interlamellar cementing complexes and generates
water-filled channels with approximate cross sections of 10.4 ×
8.8 Å2. The framework is robust enough to remain virtually
unaltered upon thermal evacuation of all water molecules of hydration,
as demonstrated through single-crystal X-ray diffraction studies on
the anhydrous phase 1a. This permanent microporosity
renders interesting functionality to 1, such as selective
adsorption of CO2 over N2 and remarkable activity
as heterogeneous catalyst toward the H2O2-based
oxidation of the highly-stable, tricyclic alkane adamantane.