Evolution from [Zn9] to a record-high [Zn54] subblock and engineering a hierarchical supramolecular framework for enhanced iodine uptake

Abstract

Hierarchical supramolecular frameworks are being designed and constructed for various applications, yet the controlled assembly and process understanding incorporating giant building blocks remains a great challenge. Here, we report a strategy of “rivet” substitution and “hinge” linkage for the controlled assembly of the hierarchical supramolecular framework. The replacement of two “rivet” ethylene glycol (EG) molecules for triangular prism [Zn₉] (a small block in 1) with a 1,3-propanediol (PDO) provides space for a “hinge” linkage from adjacent ligands, thus providing a hierarchical (from micro- to mesopores, from the internal cavity to external surface) supramolecular framework (2) based on a coordinative subblock with the record number of zinc ions ([Zn₅₄]). Time-dependent powder X-ray diffraction and ESI-MS technology were used to assess the in situ evolution process: logically progressing from [Zn₉] to [Zn₁₈], then to [Zn₂₇], and finally to [Zn₅₄]. The sequential transformation entails two types of half-opening cavities and two types of internal microcages. Further aggregation of [Zn₅₄] in dia topology engenders the formation of a one-dimensional channel (10 Å), and an additional mesocage with a volume of 16 × 16 × 55 ų. The diverse pore system exhibits an impressive uptake capability (3.19 g g⁻¹) for iodine vapor at 75 °C and effective ethylene purification. Our investigations represent a valuable avenue for assembling a giant subblock and hierarchical supramolecular framework, facilitating multi-functional molecular accommodation.