Polymerization-Driven Hierarchical Co-Assembly of Micelles for Access to Mesoporous Hollow Metal Coordination Bio-Polymers

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials. However, the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure. Here, we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy, using phytic acid-based natural compounds as an example, for the spatially controlled fabrication of metal coordination bio-polymers. The aliphatic surfactant pentadecafluorooctanoic acid and block co-polymer of polystyrene-b-poly (ethylene oxide) are assembled into two kinds of the discrete amphiphilic micelles. They evolve into hollow vesicles surrounding with spherical micelles, driven by the strong interaction triggered by coordination polymerization of ferric phytate precursors, which in turn facilitate the growth of precursors in a confined space. Consequently, the synchronous control on morphology and mesoscale structure for bio-compounds was successfully achieved for the first time. The resultant ferric phytate bio-polymer nanospheres feature hollow architecture, ordered meso-channels of ~12 nm, high surface area of 401 m²g^-1, and large pore volume of 0.53 cm³g^-1. As an advanced anode material, this bio-derivative metal coordination polymer delivers a remarkable reversible capacity of 540 mAh g^-1 at 50 mA g^-1, good rate capability and cycling stability for the use in sodium ion batteries. This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.