Metal-organic frameworks (MOFs) are regarded as key compounds related to energy storage and conversion, as their unprecedented surface areas make them promising materials for gas storage and catalysis purposes. The proposed research activities explore the modular construction principles of MOFs or molecular coordination cages that may allow the replication of key features of natural enzymes thus demonstrating how cavity size, shape, charge and functional group availability influence the performances in catalytic reactions. The research activities address the question of how such novel, bio-inspired metallo-supramolecular systems can be prepared and exploited for sustainable energy applications. Thus, the investigations take direct inspiration from the key characteristics of the related natural enzyme photosystem II (PSII) which contains a tetranuclear manganese-based {Mn4CaO5} oxo-cluster. A scientific breakthrough that demonstrates the efficient conversion of light into chemical energy would be one of the greatest scientific achievements with unprecedented impact to future generations.
The research project focusses on the following aspects:
a) MOFs, clusters or coordination cages containing novel, catalytically active complexes with labile coordination sites are synthesised using rigid organic ligands that allow us to control the topologies, cavity sizes and surface areas of the materials. We incorporate photosensitizers to develop robust porous materials in which light-absorption initiates electron-transfer events that lead to the activation of a catalytic centre. In addition, photoactive molecules will serve as addressable ligands whereby reversible, photo-induced structural transformations impose changes to porosity and chemical attributes at the active sites on demand.
b) Catalytic studies focus on important oxidations of alkenes and alcohols. These reactions are relevant to H2-based energy concepts as the anodic liberation of protons and electrons can be coupled to their cathodic recombination to produce H2. The studies provide proof-of-concept for the development of photocatalytic systems for the highly endergonic H2O oxidation reaction that will be explored using most stable MOFs/cages. Further, gas storage and magnetic properties that may also be influenced by light-irradiation will be analyzed.
