A New Type of Supramolecular Compound: Molybdenum-Oxide-Based Composites Consisting of Magnetic Nanocapsules with Encapsulated Keggin-Ion Electron Reservoirs Cross-Linked to a Two-Dimensional Network We thank Prof. Dr. H. U. Güdel (Bern), Dr. L. Cronin (Birmingham), and Dr. E. Diemann (Bielefeld) fo