Metal-organic polyhedra (MOPs) or metal-organic cages (MOCs) are assembled through the coordination of organic ligands to metal nodes giving discrete molecules that contain a defined cavity. The shape of this cavity arises from the combination of the bonding preferences of the metal node with the geometry and denticity of the ligand(s) used in the synthesis. Homoleptic cages contain one type of ligand, and examples of this approach include the use of 3,3′-((1,3phenylene)bis(ethyne-2,1-diyl))dibenzoic acid or 1,3bis(pyridin-3-ylethynyl)benzene derivatives to synthesise lantern-type cages; carbazole derivatives to access octahedral cages; and isophthalic acid or 1,3-di(pyridine-4yl)benzene derivatives to synthesise cuboctahedral cages. Alternatively, two or more types of ligand can be used, giving heteroleptic cages, increasing the complexity of the assembly as now the geometry of the cage will be determined by contributions from the bonding angles as well as the relative lengths of the ligands. In the study of self-assembly of metalorganic cages in solution, this approach is used as a way to create more complex micro-environments within the cavity of the cage itself. When MOPs have been investigated for gas sorption in the solid-state, heteroleptic approaches have largely involved the use of two ligands with well-defined, independent structural roles, such as the use of calixarenes to form bowltype arrangements, which are then connected through isophthalates or other carboxylate-based ligands to complete the discrete cage. The above routes focus on the formation of the internal pore environment. However, the porosity of MOPs in the solid state also depends on the surface functionalisation of the cage, as this affects packing and hence, the extrinsic porosity. In this context, heteroleptic MOPs where the ligands used have the same backbone, but different external functionalisation, are less well explored as a means of tuning porosity in the cages. An early example of this type of MOP is [Cu24(OH-bdc)12(bdc)12], which was obtained via solution-phase ligand exchange on the cuboctahedral MOP [Cu24(OH-bdc)24], where OH-bdc and bdc represent 5-hydroxyisophthalate and isophthalate, respectively. In this case the effect of the ligand exchange on the gas sorption properties of the material was not reported. These processes require the MOP to present a high degree of solubility, which is the case for [Cu24(OH-bdc)24], and for the rate of ligand exchange to be favourable. Recent work from von Baeckmann and co-workers described a stepwise strategy based on protection/deprotection strategies available to more robust [Rh2] paddlewheels. If the MOPs are soluble, but no ligand exchange takes place, then pure Please do not adjust margins Please do not adjust margins homoleptic cages can also be blended to obtain alloys. When direct synthesis is employed with ligands of the same length, then the approach is similar to that found in multivariate MOFs, or analogous to the dynamic covalent scrambling that is possible for porous organic cages (POCs). Previous work in this area for porous MOPs is limited to a few examples. Lerma-Berlanga and co-workers used this method to develop a family of MOPs based on mononuclear Ti(IV) nodes, where the different hydrogen bond donor/acceptor capabilities of the MeO-and -NH2 functionalised ligands were found to affect the degree of incorporation of the ligands in the final cages. Antonio and co-workers and Nam and co-workers found that the surface areas of scrambled cages lay between those of pure homoleptic materials for [Mo24(bdc)24]-type cuboctahedra and tetrahedra based on [(Cp3Zr)3] nodes, respectively.