Figure 1: Structures of POM and POMds.

(a) Wells–Dawson structure; (b) Wells-Dawson POMds with defined histidine-chelating metals (such as Ni, Co, Cu, Fe and Mn). The PO4 and WO6 polyhedra are shown in blue and light pink, respectively. The histidine-chelating metal is shown as a purple ball. The O, C, N and H atoms are shown as red, grey, dark blue and white balls, respectively.