Structure and exact stoichiometry of microcrystalline, molecular {CexZr6-xO4(OH)4} clusters with different Ce/Zr ratios will be determined employing Ce and Zr K-edge EXAFS. In addition, their solubility and stability in methanol solvents at elevated temperature will be verified. Combined XRD and Ce-K-edge XAS studies will allow to follow in situ the direct incorporation of the {CexZr6-xO4(OH)4} precursors into the 3D metal-organic frameworks through ligand exchange reactions. The overall goal is to demonstrate that Ce/Zr-MOFs with well-defined stoichiometries can be synthesized with pre-made hexanuclear clusters, which would allow us to tune the electronic and catalytic properties for possible applications in (photo-) catalysis.