Unveiling photoinduced electron transfers in photosensitized polyoxometalates for solar energy conversion.

Artificial photosynthesis faces the challenge of developing visible-light-driven strategies for converting and storing solar energy in the form of fuels and high-value chemicals. In such an approach, selective fuel production often depends on the accumulation of multiple electrons at a catalytic site. However, this process is constrained by the rapid recombination of photogenerated charges and the inherently slow kinetics of multi-electron catalytic reactions, which hinder efficient charge buildup and utilization. Polyoxometalates (POMs), a tunable class of nanoscale metal oxides, have emerged as promising multi-electron acceptors due to their redox versatility and stability. Their electron storage capabilities make them attractive as both reservoirs and catalysts. In most cases, their UV-limited absorption necessitates pairing of the POM with visible-light-absorbing antennas. Advances in photosensitized POM derivatives-via electrostatic assembly, covalent bonding, or band-gap engineering-are herein detailed. Covalent hybrids, in particular, allow precise control over electron transfer. Still, a detailed understanding of photoinduced electron transfer kinetics remains limited. This perspective article explores the potential applications of POMs in solar fuel generation, emphasizing the need for kinetic insight to design efficient, visible-light-driven photocatalysts and photoelectrochemical devices.