H8[PV5Mo7O40] (HPA-5) - a unique polyoxometalate for acid and RedOx catalysis: synthesis, characterization, and modern applications in green chemical processes.

Polyoxometalates (POMs) are a fascinating group of anionic metal-oxide clusters with a broad variety of structural properties and several catalytic applications, especially in the conversion of bio-derived platform chemicals. H8[PV5Mo7O40] (HPA-5) is a unique POM catalyst that ideally links numerous fascinating research fields for the following reasons: a) HPA-5 can be synthesized by rational design approaches; b) HPA-5 can be well characterised using multiple analytical tools explaining its catalytic properties; and c) HPA-5 is suitable for multiple important catalytic transformations of bio-based feedstocks. This review combines the fields of synthesis, spectroscopic, electrochemical and crystallographic characterization of HPA-5 with those of sustainable catalysis and green chemistry. Selected catalytic applications include esterification, dehydration and delignification of biomass as well as selective oxidation and fractionation of bio-based feedstock. We are fascinated from this unique POM and hope that the reader can get deeper insights into the chemistry of HPA-5 and its broad scope for biomass valorisation.