Template‐Encoded Assembly and Adaptive Function in Selenium‐Based Molybdenum Chalcoxide Rings

ABSTRACT Controlling both structure and function in inorganic self‐assembly remains a major challenge. Here we establish a programmable strategy for constructing selenium‐based molybdenum chalcoxides using the [Mo 2 O 2 Se 2 ] 2+ dimer as a universal building block. The template‐directed assembly process produces a complete family of ring architectures ( n = 8–16), with nuclearity encoded by the template's geometry and acidity. Selenium incorporation introduces electronic softness that imparts unusual structural flexibility and enables adaptive behaviour. NMR titration experiments reveal host–guest exchange in solution, demonstrating dynamic recognition in these purely inorganic rings. This family of clusters also displays tuneable electrocatalytic hydrogen evolution activity (HER), following the trend Mo 8 > Mo 12 > Mo 10 and consistently outperforming their sulphur analogues. Together, these results define a design framework in which modular assembly, dynamic function, and catalytic activity arise from a common chalcogen‐dependent structural logic, opening new avenues for responsive inorganic molecular materials.