Programmable Self-Sorting within a Library of Metal–Organic Cages

Abstract

Self-sorting exerts a pivotal role in biological self-assembly processes, enabling the hierarchical organization of biomacromolecules with exquisite selectivity. Inspired by nature, we present a programmable supramolecular coordination system where two types of ligands undergo sequential narcissistic and social self-sorting events to assemble either homoleptic or heteroleptic metal–organic cages. Homoleptic cage formation proceeds through the narcissistic self-sorting of either rigid or flexible ligands, depending on their varying sizes, whereas heteroleptic cages emerge through social self-sorting, where flexible ligands undergo adaptive conformational adjustments to achieve geometric complementarity with rigid counterparts. Notably, this social sorting behavior exhibits progressive enhancement with ligand size expansion, facilitating a cascaded sorting when alternating flexible and rigid components along a dimensional gradient are sequentially introduced. Furthermore, the introduction of hydrogen-bonding constraints modifies ligand flexibility and adaptive capacity, thereby redirecting self-sorting pathways toward distinct supramolecular outcomes. This study lays a foundation for advancing the field of systems chemistry, emphasizing the potential for developing multistage assembly cascades.