1. Institute of Inorganic Chemistry, Department of Chemistry, University of Cologne, Greinstraße 6, Cologne 50939, Germany
2. University of Applied Sciences Upper Austria, Stelzhamerstraße 23, Wels 4600, Austria
3. Department of Aerogels and Aerogel Composites, Institute of Materials Research, German Aerospace Center (DLR), Linder Höhe, Cologne 51147, Germany