Open versus Interpenetrated: Switchable Supramolecular Trajectories in Mechanosynthesis of a Halogen-Bonded Borromean Network

Complex topologies in co-crystals are attracting the attention of the scientific community due to their often unique properties. However, the design, preparation, and control over the self-assembly process of these systems remain a challenging task. Here, we demonstrate a facile, solvent-free strategy to control the supramolecular trajectory of the self-assembly of a three-component crystalline adduct via mechanosynthesis; i.e., ball milling. Through modification of milling conditions, e.g., by choosing the number and size of milling balls, it is possible to switch topological selectivity between a non-interpenetrated and Borromean-type entanglement. These results pave the way for the controlled solvent-free synthesis of novel materials with complex topologies and unexplored functionalities.