Seed-Controlled Gel-to-Single-Crystal Transformation in the Supramolecular Co-assembly of Metal-Organic Polyhedra and...

Rational molecular design is paramount for comprehending hierarchical self-assembly processes. While current approaches have primarily focused on π-chromophore-based systems, there is limited understanding about the self-assembly of metal-organic polyhedra (MOP). In this study, the co-assembly between Ga^III-based metal-organic cubes (Ga-MOCs) ([Ga₈(ImDC)₁₂]^12-) (ImDC = imidazoledicarboxylate) and [Cu(en)₂(H₂O)₂]²⁺ (Cu-en) binder is exploited via charge-assisted hydrogen bonding (CAHB) interactions at low concentration to regulate supramolecular polymerization. Employing a sequential growth control approach, precise tuning over the supramolecular co-assembly is enabled. At higher concentrations, the supramolecular polymer fibers entangle to form a hydrogel. Notably, the kinetically metastable gel state spontaneously transforms into a thermodynamically stable cubic crystal within 17 days, driven by the nanofiber bundling. A seeded approach is utilized to regulate the time scale, accelerating the kinetics and reducing the transformation period from 17 days to 8 h. The excellent processable redox-active GaCu assembly demonstrates notable performance in electrochemical CO₂ reduction, showing high Faradaic efficiency and stability for CO production, supported by in situ spectroscopy and DFT calculations. This study demonstrates unprecedented high-precision control over nanostructure and transition rates from kinetic to thermodynamic assembly in a MOP-based supramolecular system and highlights the pivotal role of redox-active, processable soft materials in CO₂ valorization.