The cyclic Zn4 clusters tetrahedrally coordinated to Im -or mIm -already resemble seminal core structural features present in most ZIFs. The configurational space of the Zn4 clusters becomes increasingly complex, with various possible configurations for the 4-membered rings (4MRs). We studied two types of 4MRs, namely a 4MR extracted from the SOD crystal structure, of ZIF-8 (labeled 4MR-SOD), and a 4MR extracted from the zni crystal structure, of ZIF-zni (labeled 4MR-zni), as shown in Figure . It is worth noting that ZIF-zni has very low porosity, and is the most stable of the Im-bearing ZIFs, as observed both experimentally, and in periodic DFT calculations. The synthesis of ZIFs with Im -ligands often yields low porosity ZIFs, mainly ZIFzni, and in order to obtain a ZIF with the sodalite topology a post-synthetic ligand exchange process must be undertaken. Indeed, our results show that, for Im-bearing clusters, the 4MR-zni is the most stable of the ring clusters. It is slightly more stable than 4MR-SOD (formation energies of -4.74 eV and -4.70 eV respectively, see in Table ), and, as expected, much more stable than the undercoordinated 4MR (with formation energies of less than 4 eV).