Functionalization and post-functionalization of polyoxometalates (POMs) by organic groups or biological moieties can provide versatile platforms for creating novel functional hybrids with synergetic properties. Such materials can easily be envisioned as having many advanced applications in biology and materials science. Nowadays, the organic groups or biological moieties used for conjugation with POMs, can readily become increasingly complicated in terms of structure, size and properties. Accordingly, a major challenge lies in the development of efficient conjugation methods. In this work, we report our application of metal-free Diels–Alder click reactions under mild conditions to covalently link an Anderson-type polyoxomolybdate with some organic groups or biological moieties possessing complex structures or different properties. High coupling efficiencies and facile purification methods guarantee > 90 % yields. Clearly, this is an ideal methodology for the synthesis of the post-functionalized POM hybrids. With this technology now in hand, finding valuable applications for such post-functionalized POM hybrids will be a highly significant focus of future investigations.