Cluster nuclearity control over the secondary building units (SBUs) of zirconium MOFs provides an alternative avenue to tune the material and chemical properties of these highly stable frameworks. The isolation of Zr 6-based and Zr 12-based phases is demonstrated for the zirconium terephthalate (Zr-BDC) system using a modulated hydrothermal synthesis method with tolerance to functionalized linkers. Phases with diff erent nuclearity SBUs possess distinct sorption and catalytic behaviours.