“…POMs are synthetic, early transition, metal–oxygen clusters (Pope, ; Pope and Müller, ) known for nearly 200 years (Berzelius, ). According to their chemical composition, POMs are classified as isopolyanions ((M m O y ) p– ) and heteropolyanions ((X x M m O y ) q– ), in which, alongside metal M (most commonly V, Mo or W, and sometimes Nb or Ta), 65 other elements could be present as X heteroatom (P, Si, Ge, Sb, etc.)…”