All compounds in this work were initially prepared in the form of M24(L1)24 metal-organic polyhedra (MOPs), which could be converted into multi-component MOFs via the insertion of a second ligand L2 in a precisely defined lattice position . The metal centers in the MOPs and MOFs occupy paddlewheel (PW) nodes, and are bound to the carboxylate groups of L1, which is a substituted 1,3-benzenedicarboxylic acid (Fig. ). Structomers for which metal intermixing is observed on the PW level are referred to as kofo-1 (for Max-Planck Institut für Kohlenforschung; kofo is used for MOP and KOFO for MOF structures). MOFs in which monometallic PWs share 20 MOP cages are labeled KOFO-2, those for which monometallic cages are intimately intermixed are labelled KOFO-3, and those in which intermixing is only present between extended segments of monometallic MOP cages as KOFO-4. The Cu24(L1)24 MOP can be thought of as a soluble analogue of the mesopore present in HKUST-1 , so that the KOFO-2 series contains mixed-metal pores, and the KOFO-3 series contains different monometallic pores directly adjacent to one another. To access mixing level 1, individual metal centers must be mobile under the framework synthesis conditions, while the use of mobile dimeric building blocks gives rise to mixing level 2. For example, PdCu-kofo-1 could be prepared from Pd(OAc)2 and Cu(OAc)2 and 5-tert-butylisophthalic acid (H2BDC-t Bu, Fig. ) in dimethylacetamide (DMA) because the dative bonds present in the dimeric copper-and trimeric palladium-containing precursors are reversibly cleaved in the presence of the linker. Notably, deliberate preparation of PdCu(OAc)2, which comprises mixed-metal PWs, followed by MOP synthesis with H2BDC-t Bu in DMA likewise furnished PdCu-kofo-1 . Direct MOP synthesis with Cu2(OAc)4 and Mo2(OAc)4, on the other hand, resulted in MoCu-kofo-2 because the strong Mo-Mo quadruple bond is retained throughout the reaction. To verify that a single structomer could be formed over an extended composition range, we prepared kofo-1 with Pd:Cu ratios of 10:90, 18:82, 25:75 and 30:70 as well as kofo-2 with Mo:Cu ratios of 12:18, 24:76, 49:51 and 58:42, for which detailed characterization data is provided in the supplementary information (SI).