One classical approach is the linkage of molecular photosensitizer (e.g. Ru- or Ir-complexes) and metal complex catalysts (e.g. Pt-, Pd-, Rh- or Co-based ) using ditopic bridging ligands for charge transfer. This has led to unique models, where insights into the photophysical and electronic properties as well as HER activity have become possible using combined experiment and theory. This concept has been significantly expanded by recent studies where several photosensitizers were linked to HER catalytic sites, leading to operational supramolecular HER systems. Component optimization by chemical modification demonstrated the tunability of these systems, leading to in-depth understanding of function and reactivity limitations. In recent years, the concept of supramolecular dyads has been expanded to the field of molecular metal oxides, or polyoxometalates (POMs). POMs are versatile dyad components, which can act as oxidation and reduction catalysts as well as charge separation 27 and charge-storage sites. In addition, their structure and reactivity can be tuned over a wide range by chemical modification. This versatility has made POMs a research focus for advanced, light-driven energy conversion and storage. In particular, the covalent organo-functionalization of POMs has paved the way for the design of multifunctional platform molecules, where several functions can in principle be incorporated in one POM. This has led to ground-breaking studies in light-driven hydrogen evolution, photo-electrochemistry 27 and nanocomposites for reversible electron storage. Building on these pioneering studies, we now propose the use of POMs as multifunctional redox-active platform molecules capable of charge storage, HER catalyst anchoring as well as supramolecular photosensitizer binding. Using this approach, multiple functions can be combined in one molecular assembly, while independent reactivity tuning would be possible by modification of each component.