Linker desymmetrisation unlocks new topologies, defective clusters, and catalytic activity in zirconium- and rare-earth metal-organic frameworks

Abstract

Metal–organic frameworks (MOFs) based on highly connected nets continue to expand the landscape of reticular chemistry, with zirconium (Zr) and rare-earth (RE) clusters offering ideal nodes for the construction of robust and structurally diverse materials. While desymmetrisation of tetratopic linkers has recently emerged as a promising approach to accessing new framework topologies, the underlying principles governing cluster connectivity remain poorly understood. Here, we systematically investigate the effect of linker desymmetrisation on the assembly of Zr- and RE-MOFs. A literature survey of planar tetratopic linkers revealed that geometric parameters such as height-to-width ratio and torsion angles play a key role in dictating cluster connectivity. Guided by these insights, we designed two new nanosized tetratopic ligands with enhanced conformational flexibility, enabling the synthesis of six MOFs with diverse cluster types and topologies. These include three Zr-MOFs, two featuring 8-connected (8-c) Zr₆ clusters with csq and scu topologies, and one with a rare 4-c Zr cluster, and three RE-MOFs, including one with an unprecedented heptanuclear RE cluster forming a 4,8L15 net. Finally, we demonstrate that frameworks with accessible metal clusters, such as the csq-Zr-MOF and 4,8L15-RE-MOF, show outstanding catalytic activity in the hydrolysis of P–F bonds in G-type nerve agent simulants. These results highlight linker desymmetrisation as a powerful strategy for tuning both structure and function in MOFs.