A new member of the UiO-66 series of zirconium metal-organic frameworks (MOFs) is reported, and the postsynthetic bromination of its integral alkene moeities in a single-crystal to single-crystal manner is fully characterised. Nanoindentation is used to probe the bromination of unsaturated carbon-carbon bonds, in it and an analogous Zr MOF, which leads to more compliant materials with lower elastic moduli.