Abstract
Multifunctional supramolecular systems are a central research topic in light‐driven solar energy conversion. Here, we report a polyoxometalate (POM)‐based supramolecular dyad, where two platinum‐complex hydrogen evolution catalysts are covalently anchored to an Anderson polyoxomolybdate anion. Supramolecular electrostatic coupling of the system to an iridium photosensitizer enables visible light‐driven hydrogen evolution. Combined theory and experiment demonstrate the multifunctionality of the POM, which acts as photosensitizer/catalyst‐binding‐site[1] and facilitates light‐induced charge‐transfer and catalytic turnover. Chemical modification of the Pt‐catalyst site leads to increased hydrogen evolution reactivity. Mechanistic studies shed light on the role of the individual components and provide a molecular understanding of the interactions which govern stability and reactivity. The system could serve as a blueprint for multifunctional polyoxometalates in energy conversion and storage.
Highlights
Supramolecular systems combine molecular-level control of structure and reactivity with the ability to deploy a range of specific intermolecular interactions to access new function
Over the last decade, pioneering studies have demonstrated the potential of supramolecular catalysis for energy conversion and storage,[7,8] for example in the fields of water oxidation,[9] CO2 reduction,[10] and the hydrogen evolution reaction (HER).[11,12]
In light-driven HER catalysis, pioneering studies have demonstrated how supramolecular systems can be accessed by combining molecular catalysts with molecular photosensitizers
Summary
Supramolecular systems combine molecular-level control of structure and reactivity with the ability to deploy a range of specific intermolecular interactions to access new function. POMs are versatile dyad components, which can act as oxidation and reduction catalysts as well as charge separation[28] and charge-storage sites.[29,30] In addition, their structure and reactivity can be tuned over a wide range by chemical modification.[31,32,33,34,35] This versatility has made POMs a research focus for advanced, light-driven energy conversion and storage.[30,36,37,38] In particular, the covalent organo-functionalization of POMs has paved the way for the design of multifunctional platform molecules,[39,40] where several functions can in principle be incorporated in one POM.[32,33,41,42] This has led to ground-breaking studies in light-driven hydrogen evolution,[27,43] photo-electrochemistry[28] and nanocomposites for reversible electron storage.[44] Building on these pioneering studies, we report the use of POMs as multifunctional redox-active platform molecules capable of charge storage, HER catalyst anchoring as well as supramolecular photosensitizer binding.[45] Using this approach, multiple functions can be combined in one molecular assembly, while independent reactivity tuning would be possible by modification of each component. Experimental and theoretical mechanistic studies show that the POM acts as PS- and catalyst-binding site, facilitating electron transfer under irradiation
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