Electronic Conductivity in a Porous Vanadyl Prussian Blue Analogue upon Air Exposure.

Exposure to humid O2 or ambient air affords a 5-order-of-magnitude increase in electronic conductivity of a new Prussian blue analogue incorporating CoII and VIV-oxo units. Oxidation produces a mixed-valence framework, where the O2 exposure time controls the VIV/VV ratio and thereby the material's conductivity. The oxidized framework shows an intervalence charge-transfer band at ca. 4200 cm-1, consistent with mixed valence. The mixed-valence frameworks show semiconducting behavior with conductivity values of 10-5 S·cm-1 at room temperature and 10-4 S·cm-1 at 100 °C and activation energies of ca. 0.3 eV. N2 adsorption measurements at 77 K show that these materials possess permanent porosity before and after oxidation with Brunauer-Emmett-Teller surface areas of 340 and 370 m2·g-1, respectively.