Side-Arm Sterics Direct Conformation, Topology, and Function in Zirconium Metal–Organic Frameworks

The conformational variability of organic linkers holds significant potential for expanding the structural and topological diversity of metal–organic frameworks (MOFs). Traditional design strategies typically rely on steric tuning of the central linker core using small substituents, such as methyl groups. In this study, we depart from that paradigm by introducing steric control through modular side-arm functionali-zation. Six amide or cyano groups are employed as unconventional steric units to induce isolable con-formational variability. This design enables the linker to flex and twist, guiding the formation of two isostructural Zr-MOFs, AM-Zr-1 and CN-Zr-1, both adopting previously unreported underlying net 6,8-c nuh1 and 3,8-c nuh2 with highly distorted, topologically complex porous architecture. Despite their iden-tical connectivity, AM-Zr-1 generates a geometrically unique amide pocket that enhances CO2 binding and affords higher CO2/N2 and CO2/CH4 selectivity, whereas the less bulky cyano substituents confer a more extended conformation to CN-Zr-1, resulting in higher surface area and H2 uptake. These findings highlight steric side-arm functionalization as a simple yet versatile strategy for tuning Zr-MOF topology and function.