The energetic and structural features outlined in Sec. 3.1 provide a computational framework to now consider a pool of Zn z Im n N m building blocks relevant to the nucleation of ZIF materials. Figure depicts the most stable conformations of clusters with up to four Zn 2+ cations, which constitutes the largest cluster size explored in previous ab initio computational studies of works. The characterization of these clusters allows us to assess the potential routes leading to the simplest Zn-Im cyclic networks. We observe that nitrate anions incorporated into the clusters build two-or three-fold coordination units with Zn 2+ sites, thus stabilizing the imidazolate-poor clusters. We summarize now the fundamental trends derived from the cluster configurations compiled in Figure . From here onwards, energies are given in eV per Zn cation.