Electronic connection to the interior of a mesoporous insulator with nanowires of crystalline RuO2

Highly porous materials such as mesoporous oxides are of technological interest1 for catalytic, sensing and remediation applications: the mesopores (of size 2–50 nm) permit ingress by molecules and guests that are physically excluded from microporous materials. Connecting the interior of porous materials with a nanoscale or ‘molecular’ wire would allow the direct electronic control (and monitoring) of chemical reactions and the creation of nanostructures for high-density electronic materials2. The challenge is to create an electronic pathway (that is, a wire) within a mesoporous platform without greatly occluding its free volume and reactive surface area3. Here we report the synthesis of an electronically conductive mesoporous composite—by the cryogenic decomposition of RuO4—on the nanoscale network of a partially densified silica aerogel. The composite consists of a three-dimensional web of interconnected (∼4-nm in diameter) crystallites of RuO2, supported conformally on the nanoscopic silica network. The resulting monolithic (RuO2∥SiO2) composite retains the free volume of the aerogel and exhibits pure electronic conductivity. In addition to acting as a wired mesoporous platform, the RuO2-wired silica aerogel behaves as a porous catalytic electrode for the oxidation of chloride to molecular chlorine.